Acceptability and perceptibility thresholds in dentistry: A comprehensive review of clinical and research applications

Long-Term Whitening Stability in Combined In-Office and At-Home Whitening Protocols: A Randomized Controlled Clinical Trial

OBJECTIVE

This clinical study assessed the color stability of combined whitening protocols for up to 2 years when using prefilled at-home whitening trays during intervals between in-office whitening sessions.

MATERIALS AND METHODS

In-office whitening containing 35% hydrogen peroxide was used. A prefilled tray with 6% hydrogen peroxide was used for at-home whitening. Sixty-six participants were randomly assigned to three groups: group I, at-home whitening was performed 10 times between three in-office whitening sessions; group II, at-home whitening was performed five times between three in-office whitening sessions; group III, only in-office whitening (three sessions) was performed. Tooth color was assessed before whitening treatment and at 1-day, 3-month, 6-month, 1-year, and 2-year follow-ups using a spectrophotometer. The color differences between the color before whitening and at each follow-up measurement were evaluated based on CIELAB ΔE*ab, CIE DE2000 ΔE 00, and ΔW ID.

RESULTS

Although the ΔE*ab and ΔE 00 in all groups gradually decreased over time, the color stabilities vary in different whitening techniques. Groups II and III showed significantly decreased ΔW ID (p < 0.05) in the early follow-up periods when compared with that of group I.

CONCLUSIONS

The use of both in-office whitening and at-home whitening using prefilled trays resulted in longer-lasting whitening efficacy than in-office whitening alone.

The color of natural teeth: A scoping review of In-Vivo studies

OBJECTIVES

This review aimed to analyze and present information on the color of natural teeth and its distribution based on color measurement methods, types of studies, and research areas. Additionally, it identified knowledge gaps in dental color science and suggested areas for future research.

DATA

This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) Checklist.

SOURCES

An electronic search was conducted in Medline/Pubmed, Scopus, and Web of Science - all databases using the keywords: human, tooth, color, color difference, spectrophotometer, colorimeter, spectroradiometer. The review included exclusively English-written research articles published after 1979, focusing on those in-vivo protocols that instrumentally evaluated the color of natural human teeth and provided CIEL*a*b*, CIEL*C*h° color coordinates, and/or shade guide designation.

STUDY SELECTION

The initial database search yielded 2501 results: Medline/Pubmed: n = 482; Scopus: n = 334; and Web of Science All databases: n = 1685. After selection, 53 research articles were included in the review.

CONCLUSION

Dental color is a complex phenomenon to objectively record, communicate, and reproduce. Although studies have reported color coordinates based on age, gender, ethnicity, and tooth type, there is no consensus within the scientific community. Most studies are cross-sectional, limiting the understanding of tooth color changes over time. Longitudinal studies involving diverse cultures with adequate sample sizes and consistent methodologies are necessary for objective color recording.

CLINICAL SIGNIFICANCE

Studies assessing the color of in-vivo natural teeth show a high level of heterogeneity due to the diversity in the type of measurement devices used, experimental conditions, illuminant, number of teeth used, area of measurement, and color coordinates reported. Future research must consider more extensive and representative population samples, with standardized reporting of demographic characteristics (age, gender, ethnicity), and more detailed inclusion and exclusion criteria. It is crucial to prioritize the standardization of measurement conditions, using a non-contact instrument, calibration, and detailed reporting of color.

Simple post-curing methods to optimize the depth of cure and physicochemical properties of 3D printed resin

OBJECTIVES

This in vitro study evaluated the effect of different post-curing methods on the degree of conversion, mechanical properties, and color change of a 3D printing resin.

METHODS

Specimens of a 3D printing resin were subjected to different post-curing processes: CONo post-curing; PCC-Post-curing in a violet light chamber; VA-Post-curing with VALO; HC-Post-curing in an oven; HP-Post-curing in an autoclave; PCC+HC-Post-curing in a violet light chamber associated with an oven; PCC+HP-Post-curing in a light chamber associated with an autoclave. The 3D printing accuracy, flexural strength, flexural modulus, Knoop microhardness and degree of depth conversion, surface hardness before and after immersion in solvent, gloss and roughness before and after brushing cycles, and color change after aging in UV light were evaluated.

RESULTS

PCC+HC showed a significant reduction in length and no significant difference was detected in width. CO and VA showed higher distortion in thickness and PCC, HC and PCC+HP were statistically similar. PCC+HP had greater flexural strength and flexural modulus. All groups showed significantly decreased hardness after immersion in the solvent. The groups that associated PCC and heat had greater depth curing efficiency. PCC showed the lowest color change followed by PCC+HC and PCC+HP.

CONCLUSIONS

3D printed resins require additional polymerization methods for optimal physicochemical properties. Post-curing combining violet light and a heat source, oven, or autoclave significantly enhances the depth of cure and improves the optical and physicochemical properties of a 3D resin for indirect restoration.

CLINICAL SIGNIFICANCE

Post-curing methods that combine violet light and a heat source can increase the durability and performance of 3D printed resins for indirect restorations, potentially improving clinical outcomes by providing more reliable and durable restorations.

Analysis of Aesthetic Preferences Regarding Gingival-Dental Color Combinations

STATEMENT OF PROBLEM

It is our view that the color of teeth and gingiva needs to be analyzed conjointly, given their close anatomical interrelation and the lack of research on perceptions of this chromatic combination.

OBJECTIVE

To determine aesthetic preferences concerning the chromatic combination of ceramic gingival specimens and acrylic teeth and analyze the influence of age and sex.

MATERIAL AND METHODS

A sample of 120 participants responded to a survey, in which each participant first selected the three "ad hoc" ceramic gingival specimens whose color they considered the most attractive from seven Vita Lumex AC Gingiva colors (231-237). Each participant then allocated a score from 1 to 10 for the chromatic combination of each of the three ceramic gingival specimens chosen in combination with each of the three acrylic teeth (maxillary central incisor, maxillary lateral incisor, and maxillary canine) in the three most frequent colors in the reference population (1M1, 3M1, and 2L1.5). The questionnaire also collected data on age and sex. Statistical analysis of the results was conducted using SPSS (v.28) software.

RESULTS

Participants most frequently chose gingival shade 232 as their first preference (80.8%), shade 233 was most frequently placed in second position (75%), and most participants selected shade 235 as their third preference (58.3%). The highest rated gingiva-tooth shade combination was 232-1M1 (mean score 7.9), followed by 232-3M1 (mean score 7.3). The only significant difference (p < 0.05) between men and women was between the mean scores allocated for the 232-3M1 combination, which was rated higher by women than men. Statistically significant differences were found between the mean scores allocated by different age groups for the 233-3M1, 233-2L1.5, and 235-1M1 combinations. Younger participants scored the first two shade combinations lower, while the opposite was true for the last combination.

CONCLUSIONS

When establishing aesthetic preferences, gingival color takes priority over dental color when both structures are visible in combination. Preferences regarding the most attractive gingival shades are focused on only two colors (232 and 233). A substantial majority of participants rated the 232-1M1 gingival-dental shade combination most highly. Practically no significant differences were identified between the mean scores allocated for gingival-dental color combinations according to sex. Age made a greater difference to results, although both variables had only a modest impact.

CLINICAL SIGNIFICANCE

Producing a combined gingival-dental shade guide would be useful, enabling the patient to provide their complete aesthetic vision, particularly in clinical situations where gingival tissue needs to be restored in patients with high smile lines. Manufacturers need to improve their gingival shade ranges, due to the limited number available, their disparity with natural gingival color, and the fact that patients do not like most shades on offer. A large percentage of aesthetic preferences focused on a limited number of gingival-dental color combinations, with lighter dental shades combined with the gingival shades that best approximate natural gingival color considered the most aesthetic. Age has more influence on gingival-dental color preferences than sex, although both factors have only a modest impact. For high smile lines, patients prioritize gingival color within the gingival-dental chromatic combination, since the preference for a certain shade of gingival specimen is maintained, irrespective of tooth color, indicating a stable chromatic hierarchy.

Long-term tooth discoloration induced by apical plugs with hydraulic calcium silicate-based cements in bovine teeth with open apices - a 6-year in-vitro study

OBJECTIVES

To investigate the long-term tooth discoloration induced by different hydraulic calcium silicate-based cements (HCSCs), depending on blood contamination and placement method in-vitro.

MATERIALS AND METHODS

Eighty bovine teeth, sliced to a length of 18 mm (crown 8 mm, root 10 mm), were randomly assigned to 10 groups (n = 8), receiving ortho- or retrograde apical plug treatment (APT). Apical plugs were 4 mm in length and made of ProRoot MTA (Dentsply), Medcem MTA (Medcem), TotalFill BC RRM Fast Set Putty (Brasseler), or Medcem Medical Portland Cement (Medcem) plus bismuth oxide (Bi2O3) with and without bovine blood. Orthograde (with or without preoperative adhesive coronal dentin sealing) and retrograde APT were compared. Teeth were root-filled with gutta-percha and sealer, adhesively restored, and stored in distilled water. Tooth color was measured on apical plug, gutta-percha/sealer, and crown surface before treatment, after 24 h, and up to 72 months after treatment by spectrophotometry. Color difference (ΔE) values were calculated and analyzed by ANOVA with post-hoc-tests, Shapiro-Wilk-test, Friedman-test, Mann-Whitney-U-test, t-test, and post-hoc-tests with Bonferroni correction (α = 0.05).

RESULTS

The increase of tooth discoloration occurred in all groups with no significant differences between HCSCs (p >.05). After six years, color changes were strongly marked on roots but insignificant on crowns. The color differences on the measuring surface of the apical plug were statistically significant between 24 and 72 months (p <.001). Blood had a more relevant impact on tooth color than Bi2O3. There were no substantial long-term effects of retrograde placement (p >.05) or preoperative dentin sealing (p >.05).

CONCLUSIONS

Apical plugs of the tested HCSCs cause ongoing discoloration of bovine roots, but no discoloration of bovine tooth crowns within a six-year period.

CLINICAL RELEVANCE

Apical plugs should be carefully placed. If direct contact with the coronal dentin is avoided, long-term aesthetic impairments are unlikely to occur.

The effects of a carbonated beverage on the optical properties and microhardness of preheated bulk-fill composite resin restorations

Introduction

Preheating the high-viscosity forms of bulk-fill resin composites is recommended to enhance their flow and adaptability. Nevertheless, the impact of preheating on their characteristics upon exposure to carbonated beverages remains unclear. This study aims to evaluate the effect of a Cola beverage on the properties of preheated and non-preheated high-viscosity bulk-fill composite resins in vitro.

Methods

Forty disc-shaped specimens were prepared from each of BEAUTIFIL-Bulk Restorative (BB) and Filtek One Bulk-fill (FOB) composite resin, then divided into two groups (n = 20), either preheated to 68°C for 15 min or kept at room temperature before polymerization, then specimens were immersed in Alkozay Cola beverage for 30 days (3 periods of 15 min/day). Color stability (ΔE00), surface gloss (GU) and Vickers Microhardness (VHN) were recorded before and after the Cola immersion. The data was analyzed with Two-way ANOVA, Three-way ANOVA and Tukey's HSD post hoc test using SPSS software at 95% significance level.

Results

The color change was significantly higher in BB than FOB in all groups (P < 0:001), FOB had a significant reduction in color change after preheating (P < 0.05) while BB had no significant change (P > 0.05). Preheating significantly increased the gloss of BB and reduced that of FOB (P < 0.001), however, Cola beverage significantly reduced the gloss of all the groups (P < 0.001). Preheating significantly increased the microhardness of both materials (P < 0.001), however, Cola beverage significantly reduced the microhardness of all the groups (P < 0.001).

Conclusion

Although the preheating of high-viscosity bulk-fill composites significantly improved their microhardness and improved the surface gloss of FOB, it did not protect both composites against the Cola drink attack. Preheated FOB showed improved color stability after the Cola immersion, but not to a clinically acceptable limit.

Effects of types of air polishing powders on roughness, microhardness, color, and gloss of gingiva-colored resin-based composites

BACKGROUND

This study aimed to evaluate the effects of air polishing powders on the roughness, microhardness, color, and gloss of two types of gingiva-colored resin-based composites (GCRBCs).

METHODS

Disc-shaped specimens were prepared from two GCRBCs (Gradia Plus Gum, GC: Group G; Crea.lign, Bredent: Group C). Specimens subjected to air polishing were divided into two subgroups (n = 16): erythritol (Group G-e, Group C-e) and sodium bicarbonate (Group G-s, Group C-s). The roughness (Ra), microhardness (VHN), color (ΔE*ab and Δ E00), and gloss (GU) values of all samples were measured before and after the applications. The data were analyzed by dependent t-test and two-way ANOVA.

RESULTS

Surface roughness showed statistically significant differences between initial and final measurements across all groups (G-s: p < 0.001; C-s: p = 0.002; G-e: p = 0.003; C-e: p = 0.011), with final Ra values being consistently higher than initial ones. Group C-e did not show significant differences (p = 0.294) in terms of microhardness after treatment, while hardness decreased in all other groups. In the final measurements, significant differences in color values were observed based on the type of powder applied (p = 0.026 for ΔEab; p = 0.048 for ΔE00), with sodium bicarbonate causing more pronounced changes compared to erythritol. Significant differences were observed in initial and final gloss values for all subgroups (p = 0.00).

CONCLUSION

It was observed that air polishing, particularly with sodium bicarbonate, can lead to significant roughness and discoloration in GCRBCs. Consequently, it is crucial to employ air-polishing devices correctly, limit their use on resin-based composite restorations, and opt for less abrasive polishing powders. These practices are essential to prevent increased surface roughness and surface microhardness and preserve color and gloss in GCRBCs.

Effect of aging on optical behavior and color of 3D printing resin-based dental restorative materials

OBJECTIVES

To evaluate the influence of aging on color and optical properties of 3D printing resin-based dental restorative materials.

METHODS

Four 3D printing resin-based dental restorative materials (DFT- Detax Freeprint Temp; FT- Formlabs Temporary CB; FP- Formlabs Permanent Crown; and GCT- GC TempPrint) were evaluated. The structures were printed using digital light processing (DLP) (DFT and GCT groups) and stereolithography (SLA) (FT and FP groups) technologies. Samples (10 × 10 × 1 mm; n = 3) were printed in light (L) and medium (M) shades and at 0° and 90° and then polished to a thickness of 1.00 ± 0.01 mm with silicon carbide (SiC) sandpapers under water cooling. Artificial aging followed the ISO 4892-2 standard. 1) Color differences were evaluated using CIEDE2000 and perceptibility and acceptability thresholds (PT00 and AT00), 2) spectral reflectance (R%) and transmittance (T%) were measured and scattering (S) and absorption (K) coefficients, light reflectivity (RI), infinite optical thickness (X∞) pre- and post-aging were calculated using Kubelka-Munk method and Root Mean Square Error (RMSE) and Goodness of Fit (GFC) were used as performance optical behavior.

RESULTS

1) All 3D-printed dental resins evaluated, irrespectively of the printed angles, showed mean ΔE00 values above AT00 (.ΔE00>1.8), and FT-M and FP-M showed the least color changes among the evaluated materials, 2) GFC<0.999 and RMSE >2 % values were found between pre and post aging for R%, T%, S, K, RI and X∞ properties.

CONCLUSIONS

This study showed poor spectral match and comparative spectral values of R%, T%, S, K, RI and X∞ between after and before aging, resulting in unacceptable color changes. Printing orientation does not influence the change of the optical behavior of the evaluated materials after aging.

CLINICAL SIGNIFICANCE

Aging causes significant changes on the spectral optical behavior for the 3D-printed resin-based restorative materials studied, resulting in clinically unacceptable color changes.

Is at-home bleaching more effective on the upper arch than the lower arch? A prospective cohort study

OBJECTIVE

Teeth bleaching is one of the most popular aesthetic dental treatments, uses to address both extrinsic and intrinsic tooth discoloration. However, variations in bleaching efficacy between the upper and lower dental arches are commonly observed. Sublingual salivary glands may play a role in these differences by increasing saliva contamination of bleaching trays, which accelerates the degradation of bleaching gel and may reduce its effectiveness in the lower arch. This study aims is to evaluate and compare the effectiveness of bleaching treatments in the upper and lowe arches.

METHODS

This study employed a prospective observational cohort design with a split-mouth approach. Thirty-two participants completed a three-week bleaching regimen using 16 % carbamide peroxide. Color changes were assessed using the CIELAB, CIEDE2000, and Whiteness Index for Dentistry (WID) formulas, with spectrophotometric measurements taken at baseline and weekly intervals.

RESULTS

No statistically significant differences (p > 0.5) in bleaching efficacy for incisors between the two arches. However, upper canines demonstrated significantly greater bleaching effectiveness than lower canines by the second and third weeks (p < 0.05), as indicated by the CIELAB and CIEDE2000 formulas. No significant differences (p > 0.05) were observed using the WID formula.

CONCLUSION

While the lower canines exhibited slightly reduced bleaching effectiveness, these differences were not clinically noticeable, affirming the overall efficacy of the treatment for both arches.

CLINICAL SIGNIFICANCE

At-home bleaching treatment demonstrates equivalent effectiveness in both dental arches. While the lower canines may achieve a slightly reduced degree of bleaching, these differences are not clinically noticeable. Consequently, extending the duration of the bleaching treatment for the lower arch is unnecessary.

Masking Ability of Subtractively and Additively Manufactured Dental Ceramic Restorations: A Systematic Review

OBJECTIVE

To conduct a systematic review on the masking ability of subtractively and additively manufactured dental ceramics.

MATERIALS AND METHODS

The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The electronic search was carried out through MEDLINE, Scopus, and Website of Science databases with a date restriction being from 2001 onwards. Publications in English, in vitro studies, and studies regarding the evaluation of the masking ability of crown materials that were subtractively and additively manufactured were included.

RESULTS

Out of 619 eligible articles, 13 were included. A thickness of 1.5 mm for lithium disilicate (LD) resulted in a dramatic decrease in ∆E ab/∆E 00 across all substrates compared to a 1 mm thickness. Low-translucent LD appeared to have the best masking ability regardless of the shade of the try-in paste. Layering flowable composite over the substrates improved masking ability. Darker substrates were the hardest to mask no matter the type of restorative material, try-in paste used, and layering technique. Bilayered restorative materials proved to be superior to monolithic materials regarding masking ability.

CONCLUSION

Increasing the thickness of subtractively manufactured ceramics materials improves the masking ability. 1.5 mm thickness is found to provide the best masking ability for most ceramic materials. Darker substrates prove to be difficult to mask in comparison to lighter substrates and require either thicker materials and/or more opaque cements. Bilayered crowns are recommended for achieving optimal masking while preserving tooth structure. Despite the increasing demand, there is no study available on 3D-printed (additively manufactured) restoration's masking ability.

CLINICAL SIGNIFICANCE

This review provides a comparison of masking abilities of multiple subtractively manufactured ceramic materials and highlight the lack of current knowledge on additively manufactured crown materials. It also emphasizes the importance of having a universal approach to interpreting and communicating color changes between collaborative dental professionals to ensure the same shade predictions. In addition, when masking darker shades, clinicians should be aware that alternative material choice or clinical and technical procedures are essential.

The Effect of Plaque Detectors on the Color Stability of Two Types of Restorative Materials

OBJECTIVE

To investigate the color stability of a one-shade resin-based composite material (RC) and a glass-ionomer cement (GIC) after staining with plaque detectors (PDs) with different formulations and delivery forms.

MATERIALS AND METHODS

Rectangular-shaped specimens (7 × 3 × 2 mm) were produced with RC (Venus Diamond One, Kulzer) and GIC (Fujy IX GP, GC) (n = 30). Further, the following PDs were used on the specimens: (1) tablets (T; Plaq-Search, TePe); (2) mouthwash (M; Plaque Agent, Miradent); and (3) light-curing liquid (L; Plaque test, Ivoclar). The PDs were removed with dedicated toothbrushes (T1) and the specimens were repolished (T2). The protocol was repeated after 1 week of storage in artificial saliva (staining-T3 and repolishing-T4). Color measurement were performed at baseline (T0) and all testing times (T1-T4) using a recently introduced digital colorimeter (SmartColor, Smart Vision). Color changes (ΔE ab) compared to T0 were automatically recorded by the digital instrument. The data were statistically analyzed (p < 0.05).

RESULTS

The type of PD, the polishing procedure and their interactions influenced the color stability of both restorative materials (p < 0.05). Particularly, after the second PDs application, M and L produced the highest color changes (p < 0.05), with GIC showing higher color variability than RC. Although repolishing reduced the color changes of RC (p < 0.05), it could not reestablish the initial color of GIC, irrespective of the PD used (p < 0.05). Except for RC associated with T, all materials exhibited discoloration above the clinical perceptibility (1.77) and acceptability (2.66) thresholds.

CONCLUSIONS

The influence of PDs on the color stability of RC and GIC was material-dependent. GIC showed higher color instability than RC. Repolishing could not reestablish the original color of GIC and only attenuated the color changes of the one-shade RC. The newly introduced digital colorimeter was an important tool to standardize and simplify color measurement evaluations.

CLINICAL SIGNIFICANCE

PDs can pose a potential risk to the color stability of restorative materials. Dental practitioners should be careful when recommending the frequency of at-home application of PDs, taking into consideration the material properties and the position of the restorations of each patient.

Total sodium replacement by calcium in trimetaphosphate and its incorporation into dental whitening gels: A novel strategy for in-office treatment

OBJECTIVES

The aim of this study was to synthesize a cyclophosphate with total sodium replacement (CaTMP) and to evaluate, in vitro, its incorporation into hydrogen peroxide (HP) whitening gels.

MATERIALS AND METHODS

CaTMP was synthesized through column chromatography using ion-exchange resin and calcium hydroxide solution. Bovine enamel/dentin discs (n = 150) were divided into five groups: 1) negative control (no treatment), 2) 35 % HP whitening gel (positive control), 3) 35 % HP + 1 % CaTMP, 4) 17.5 % HP, and 5) 17.5 % HP + 1 % CaTMP. Whitening gels were applied weekly for three 40-minute sessions. Color change was measured using ΔE, ΔWID, and ΔE00. Transamelodentinal HP diffusion was determined, as well the mineral content of dental substrates by μ-CT (gHAp × cm-3 × µm). Data were analyzed with ANOVA and Student-Newman-Keuls test (p < 0.05).

RESULTS

All whitening gels caused significant color changes (p < 0.001), with no differences between groups in ΔE, ΔE00, and ΔWID (p > 0.05). The highest transamelodentinal HP diffusion occurred in the 35 % HP group (p < 0.001), but adding 1 % CaTMP reduced this diffusion in both HP concentrations (p < 0.05), with a greater reduction in the 17.5 % HP gel. Conventional gels (17.5 % and 35 % HP) caused greater mineral loss (gHAp × cm-3 × µm), while CaTMP protected against these changes.

CONCLUSIONS

Incorporating 1 % CaTMP into whitening gels (17.5 % and 35 % HP) significantly reduced HP diffusion and preserved the mineral content of enamel and dentin, while providing whitening results similar to conventional gels.

CLINICAL RELEVANCE

CaTMP may act as a protective agent against peroxide-induced oxidative damage in dental tissues. While these findings are based on in vitro data, they support a promising direction for future translational research aimed at enhancing the safety and effectiveness of in-office whitening procedures.

Color Stability, Surface Gloss, Surface Roughness, and Wettability of Material Jetting 3D-Printed Denture Material Under Various Surface Treatments

Objectives: To examine the effects of surface treatments on the color stability, surface roughness, surface gloss, and wettability of monolithic polychromatic material jetting (MJT) 3D-printed denture material. Material and Methods: Twenty-one color variants of the same denture material (TrueDent; Stratasys, Eden, MN, USA) underwent two surface treatments (polishing only or polishing and glazing), creating 42 study groups with a total of 420 samples (n = 10 per group). The samples were manufactured using a PolyJet 3D printer (J5 DentaJet; Stratasys, Eden, MN, USA), a type of MJT 3D printer. Color measurements were taken with a digital spectrophotometer before and after the surface treatments, and quantitative color differences (ΔE00 and ΔC*) were calculated using the CIE2000 system. Comparisons of ΔE00 were made against the 50%:50% acceptability threshold (AT) of 1.8 and the 50%:50% perceptibility threshold (PT) of 0.8 for tooth shade, as well as the 50%:50% PT of 1.72 and the 50%:50% AT of 4.08 for gingival (pink) shade. After surface treatment, the gloss was measured using a glossmeter, surface roughness was measured with optical profilometry, and wettability was measured by contact angle measurements using an optical tensiometer. The significance of surface treatment on color changes for each color variant was evaluated using one-sided, one-sample t-tests against the AT and PT. The effects of surface treatment on surface gloss, surface roughness, contact angle, and ΔC* were analyzed using t-tests for each color variant. Pairwise comparisons between groups were made using Fisher's Protected Least Significant Differences (α = 0.05). Results: In most cases, glazing caused the color change (ΔE00) to exceed the AT and PT, with a few exceptions. Most materials exhibited a more vibrant (more saturated) appearance and statistically higher chroma, with glazed surface treatments compared to polished ones, though there were some exceptions. For all materials, the glazed samples had significantly higher gloss units than the polished ones (p < 0.0001). Additionally, all materials showed significantly higher surface roughness in glazed samples compared to polished ones (p < 0.0001 for most). The polished samples had significantly higher contact angles (p < 0.0001 for most). Conclusions: Surface treatments significantly influenced the color, surface gloss, surface roughness, and wettability of MJT 3D-printed denture materials. Glazing led to increased chroma and gloss and produced more hydrophilic surfaces, although it also increased surface roughness. These results highlight the importance of surface treatment selection in optimizing the clinical performance of MJT-fabricated dentures.

Bleaching efficacy and tooth sensitivity using violet LED - single-blind randomized controlled trial

This study aims to conduct a single-blind randomized controlled trial to evaluate the bleaching efficacy and tooth sensitivity (TS) following the use of violet LED associated or not with 35% hydrogen peroxide. Eighty-four participants were randomly allocated into three groups according to bleaching treatments (n = 28): 35% hydrogen peroxide (HP) only, Violet LED only (VLED), and an association of 35% HP with violet LED (HP + VLED). Three sessions were performed, with an interval of seven days between each one. Changes in the objective (ΔEab and ΔE00) and subjective (ΔSGU) color and the Whiteness Index for Dentistry (ΔWID) were calculated based on before, and seven and thirty days after treatment using colorimetric measurements. Participants self-reported the risk and intensity of TS on a visual analogue scale (VAS). The color assessments seven and 30 days after bleaching were analyzed by two-way ANOVA and Tukey's test. The absolute TS risk was analyzed by Fisher's exact test. The significance level adopted was α = 0.05. HP and HP + VLED treatments showed higher and significant bleaching values (ΔEab, ΔE00, ΔSGU, and ΔWID) compared to VLED. The HP + VLED and HP groups presented a higher risk and intensity of TS compared to the VLED group (p < 0.05). The bleaching efficacy of VLED alone was lower compared to the HP and HP + VLED protocols both seven and 30 days after the end of treatments.

The Impact of Prophylactic Polishing Pastes on the Surface Roughness, Color, and Stain Resistance of CAD/CAM Restorative Materials

Background: Prophylactic polishing pastes (PPPs) are widely used to clean teeth and dental restorations; however, their effects on restorative materials are crucial for clinical outcomes. This study investigates the impact of PPPs on the susceptibility of CAD/CAM restorative materials to staining and the relationship between surface roughness and discoloration. Methods: Samples of tested materials (resin nanoceramic, hybrid ceramic, feldspathic ceramic, and lithium disilicate-reinforced glass ceramic) were treated with various PPPs (Cleanic, CleanJoy, Detartrine, Proxyt). Surface roughness and color parameters were recorded before and after the PPP application and following coffee immersion for 12 days. Initial measurements of surface roughness (Ra1) and color were taken. The specimens were divided into groups based on the PPP applied. After PPP application, secondary roughness (Ra2) and color values were measured. Changes in roughness (ΔRa), color (ΔE*ab, ΔE00), and whiteness index (ΔWID) were calculated post-application and after coffee immersion. Data normality was tested with the Shapiro-Wilks test. Two-way ANOVA evaluated the effects of material type and PPP on ΔE, ΔWID, and ΔRa. One-way ANOVA, Tukey HDS test, and Pearson correlation were used for further analysis, with significance set at p < 0.05. Results: The Vita Enamic-Detartrine group showed the highest ΔEab 1 and ΔE001 values, while Cerasmart-control showed the lowest. The Vita Enamic-Proxyt group had the lowest ΔWID1, and Vita Enamic-Cleanjoy exhibited the highest values of ΔEab 2, ΔE002, and ΔWID2. The E.MAX-control group had the lowest values for these metrics. No significant correlation was found between ΔRa and color changes (ΔE*ab 2, ΔE002, ΔWID2); however, a moderate positive correlation was found between values of ΔE1 and ΔE2. Conclusions: These findings indicate that PPPs significantly affect the discoloration and surface features of CAD/CAM materials, with both types of PPPs and materials.

Shade variability and stability in interim and definitive tooth-colored resin-based restorative materials: Comparing manufacturer-claimed shades to a universal shade guide

PURPOSE

To evaluate the shade variability and stability of interim and definitive tooth-colored restorative materials by comparing manufacturer-claimed shades to a universal shade guide before and after thermocycling.

MATERIALS AND METHODS

Eight commercially available tooth-colored restorative materials were tested, including conventional, milled, and 3D-printed types. Each material was categorized into three shade subgroups (A1, A2, and A3), with 10 samples per subgroup. The color differences (ΔE00) between the materials' shades and a universal shade guide (VITA classical A1-D4) were measured using a digital spectrophotometer before (ΔE00-R1) and after (ΔE00-R2) thermocycling. A higher ΔE00 indicated higher variability between the manufacturer-claimed shade and a corresponding universal shade guide. The ΔE00 was analyzed using the CIEDE2000 formula, and statistical analysis was performed to evaluate the effects of materials, shades, and thermocycling. In addition, the ΔE00 was compared against 50%:50% perceptibility threshold (PT) and 50%:50% acceptability threshold (AT) using one-sample t-tests (α = 0.05).

RESULTS

The observations from descriptive statistics showed that the milled Aidite group exhibited the lowest ΔE00. In addition, shade A1 showed higher ΔE00 than A2 and A3 within each group; however, the ΔE00 between shade types A2 and A3 was similar. The three-way interaction among materials, shades, and thermocycling was significant (p < 0.0001), highlighting their combined effect on ΔE00. No significant interaction between shade and thermocycling was observed (p = 0.6239), suggesting that thermocycling did not significantly affect ΔE00 among shade subgroups. Comparison of ΔE00-R1 and ΔE00-R2 against 50%:50% PT (0.8) and 50%:50% AT (1.8) revealed significant color differences beyond both thresholds for most study groups.

CONCLUSIONS

Color variability in dental restorative materials is influenced by material, shade, and thermocycling. Most samples showed significant discrepancies from manufacturer-specified shades (A1, A2, and A3) when compared to the VITA classical A1-D4 guide. Clinicians might consider using a custom shade guide that is fabricated from the same material as the prostheses to improve shade matching outcomes.

Effect of staining techniques and repeated firing cycles on translucency, color and biaxial flexural strength of advanced lithium disilicate containing Virgilite crystals

BACKGROUND

The repeated firings can enhance shade matching, translucency, and strength; however, they may also lead to color shifts. Previous research suggests that multiple firings enhance these properties to a certain extent; however, the impact of staining techniques remains underexplored. The aim of this study is to investigate the effect of staining techniques and multiple firings on the translucency, color and biaxial flexural strength of advanced lithium disilicate ALD containing Virgilite crystals.

METHODS

Sixty-three discs of ALD (CEREC Tessera®) were divided into 3 groups based on staining techniques (n = 21); group CO (glaze only), group SC (single-step characterization), and group DC (double-step characterization). The discs were then subjected to either 2, 4, or 6 firing cycles, resulting in 9 groups (n = 7): COII, COIV, COVI, SCII, SCVI, DCII, DCIV, and DCVI. Relative translucency parameter (RTP), color change (ΔE), and biaxial flexural strength were measured, then discs were analyzed using SEM. Data were statistically analyzed using ANOVA, Bonferroni correction, and Spearman's correlation (α = 0.05).

RESULTS

Repeated firing and staining techniques significantly affected translucency, color change, and biaxial flexural strength (p < 0.001). Translucency increased with firings, highest in CO and lowest in DC. ΔE increased with firings, highest for DC and lowest in CO. The biaxial flexural strength of the CO group remained stable across firing cycles, with no significant changes. The SC group, initially the weakest, showed a significant increase, reaching its peak after six cycles. The DC group had high strength in the fourth cycle, with a significant difference observed between the second and fourth cycles. By the sixth cycle, all groups showed comparable strength with no significant differences.

CONCLUSIONS

Within the limitation of this study, firing cycles and staining techniques impact the properties of ALD. More firing cycles enhance translucency but increase color change. Repeated firing, particularly with the double-step characterization technique, significantly improved biaxial flexural strength up to the fourth cycle, demonstrating its superior performance over the single-step characterization technique.

Comparative Evaluation of Color Stability and Surface Roughness of Bulk-Fill and Nanohybrid Composites Following Long-Term Mouthrinse Exposure: An In Vitro Study

INTRODUCTION

Composite resin restorations are widely used in restorative dentistry; however, their long-term aesthetic success depends on color stability and surface integrity. Daily exposure to mouthwashes may influence these properties. This study aimed to evaluate and compare the effects of different mouthwash formulations on the color stability and surface roughness of Tetric N-Ceram Nanohybrid (Ivoclar Vivadent, Schaan, Liechtenstein) and Tetric N-Ceram Bulk-Fill (, Ivoclar Vivadent, Schaan, Liechtenstein) composites.

MATERIALS AND METHODS

80 disc-shaped specimens (n = 40/group) of nanohybrid (Tetric N-Ceram), and bulk-fill composite (Tetric N-Ceram) were fabricated and polished according to the manufacturer's instructions. Each group was further divided into four subgroups (n = 10): control (distilled water), Listerine Cool Mint® (alcohol-based mouthwash, Johnson & Johnson, New Brunswick, USA), Phos-Flur® (fluoride-based mouthwash, Colgate-Palmolive, New York, USA), and Rexidine® (0.2% chlorhexidine-based mouthwash, Indoco Remedies Ltd., Mumbai, India). Specimens were immersed in 30 mL of the respective solution for five min per cycle, three times daily, for 60 days, simulating one year of clinical exposure. The color change (ΔE) was measured using a VITA Easyshade® V spectrophotometer (VITA Zahnfabrik, Bad Säckingen, Germany), and the surface roughness (Ra) was assessed using a contact profilometer (Zeiss, Oberkochen, Germany). Scanning electron microscopy (SEM) (Zeiss, Oberkochen, Germany) analysis with 3D surface plots using ImageJ software (National Institutes of Health, Bethesda, Maryland, USA) provided a complementary morphological evaluation. Data were analyzed using one-way analysis of variance (ANOVA) and post-hoc Tukey's test (p < 0.05).

RESULTS

Significant color changes were observed in both composites, with Listerine causing the highest ΔE values, particularly in the bulk-fill group. Rexidine caused notable discoloration, whereas Phos-Flur had minimal effects. The surface roughness increased significantly in both materials after exposure, with the nanohybrid composites showing greater sensitivity to surface alterations.

CONCLUSION

The mouthwash formulation significantly affected the aesthetic and surface characteristics of composite resins. Nanohybrid composites demonstrated better color stability, but were more susceptible to surface roughness changes than bulk-fill composites.

Effects of post-polymerization on stainability and surface roughness of 3D printed composite resin

STATEMENT OF PROBLEM

Although the post-polymerization is a necessary step to attain the final properties and color of the 3-dimensionally (3D) printed composite resins, research on its effects on color change and surface roughness is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of post-polymerization time and additional placement in boiling water on the color change and surface roughness of 3D printed composite resins after exposure to coffee for 30 days.

MATERIAL AND METHODS

Sixty disk-shaped specimens (Ø10×2 mm) were 3D printed with composite resin (Crowntec). The specimens were randomly divided into 6 groups (n=10), according to the post-polymerization process at 3 different times (2×5, 2×10, and 2×20 minutes) and depending on subsequent placement in boiling water. The color differences (ΔE00) between the baseline and each aging period (1, 7, 15, and 30 days) were determined by using a spectrophotometer. After 30-day aging period, ΔL*, Δa*, and Δb* values were calculated. The surface roughness (Ra) was measured at various aging periods (initial, 7, 15, and 30 days) by a 3D noncontact optical profilometer. The data were analyzed using 2-way repeated measures ANOVA and 1-way ANOVA tests for each aging period followed by Tukey tests (α=.05).

RESULTS

As the post-polymerization time increased, a significant decrease was found in ΔE00 values (P<.001), while no significant difference was found in Ra values (P=.554). The values of ΔE00 and Ra increased with the aging period (P<.001). Additional placement in boiling water resulted in a statistically significant decrease in both ΔE00 and Ra values (P<.001). As the post-polymerization time increased, the Δa* and Δb* values decreased, while the negative ΔL* values increased (P<.001), except for Δa* between 2×10 and 2×20 (P=.175). Additional placement in boiling water resulted in a significant decrease in Δa* and Δb* values and an increase in the negative ΔL* values (P<.001), except for Δa* in 2×20 (P=.379).

CONCLUSIONS

An increase in post-polymerization time resulted in reduced stainability, while additional placement in boiling water led to reduced stainability and roughness. When subsequently placed in boiling water, the post-polymerization time had no effect on either stainability or roughness.

Characterization and effects on enamel of low-concentration bleaching gels containing hyaluronic acid, NF_TiO2 nanoparticles and irradiated with violet LED light

OBJECTIVE

To characterize and evaluate experimental in-office bleaching gels containing hyaluronic acid (HA) or carbomer 940 (CAR), enriched with NF_TiO₂ nanoparticles and irradiated with a violet LED, assessing their effects on the physicochemical properties of enamel.

MATERIALS AND METHODS

Bovine enamel-dentin discs were treated according to the parameters: thickener (HA or CAR), HP concentration (1.5% or 6%), and irradiation (with or without LED), resulting in 9 experimental groups (n = 10/group). An additional control group (35%HP-commercial) was adopted, and three sessions were conducted (30 min each, with a 7-day interval). Gels were evaluated for pH, particle size, polydispersity index, zeta potential and rheological behavior. Samples were assessed for color change (ΔE00), whiteness index (ΔWID), Ca/P ratio (EDS), surface microhardness (KHN), roughness (ΔRa), and surface morphology (SEM). Data were analyzed using ANOVA three-way and Tukey/Bonferroni (α = 5%).

RESULTS

pH remained stable above 6.0. Hyaluronic-based gels exhibited higher particle size and polydispersity, but lower zeta potential and less viscous rheological behavior compared to the carbomer-based ones (p < 0.05). LED light significantly increased ΔE00 and ΔWID for all gels, with HA-1.5%HP and HA-6%HP + LED achieving comparable ΔWID to 35%HP-commercial (p > 0.05). Hyaluronic-based gels groups irradiated with LED increased Knoop microhardness (p < 0.05). No significant changes were found in ΔRa, Ca/P ratio, or enamel morphology (p > 0.05).

CONCLUSION

Experimental hyaluronic or carbomer bleaching gels incorporated with NF_TiO2 nanoparticles and irradiated with violet LED showed minimal variations in physicochemical properties, effective bleaching even at low HP concentrations, and no enamel damage.

CLINICAL RELEVANCE

Innovative bleaching gel formulations incorporating hyaluronic acid, NF_TiO₂ nanoparticles, and violet LED light irradiation exhibit high efficacy even at low hydrogen peroxide concentrations, thereby minimizing enamel damage and potentially mitigating post-operative sensitivity.

Effect of Quercetin-Doped Hydrogen Peroxide Gels on Enamel Properties: An In Vitro Study

This in vitro study evaluated the effects of incorporating quercetin (QC) at varying concentrations (0.25%, 0.5%, and 1%) into a 35% hydrogen peroxide (H2O2) bleaching gel on esthetic outcomes, enamel hardness and roughness, and H2O2 transamelodentinal diffusion. Bovine enamel/dentin discs (n = 180; 12/per group for each analysis) were allocated into five groups: (1) negative control (NC), (2) 35% H2O2 (HP), (3) HP + 0.25% QC, (4) HP + 0.5% QC, and (5) HP + 1% QC. Treatments were applied for 40 min per session across three sessions with 7-day intervals. Color changes were evaluated using the CIELab* color system (ΔEab), with further analysis performed using the CIEDE2000 formula (ΔE00) and the whitening index (ΔWID). Enamel surface hardness, roughness, cross-sectional hardness, and H2O2 diffusion were also evaluated. Data were analyzed using ANOVA, followed by the Student-Newman-Keuls test, with statistical significance set at p < 0.05. All experimental gels resulted in significant color changes (p < 0.001), with similar ΔEab, ΔE00, and ΔWID across QC groups. The HP group showed greater reductions in hardness and increased roughness compared to others (p < 0.0001), while the HP/1%QC group resulted in no statistically significant alterations under the tested conditions. H2O2 diffusion was significantly greater in the HP group, while it was notably lower in the HP/1%QC group (p < 0.05). The incorporation of 1% quercetin into a 35% H2O2 gel maintains its bleaching efficacy while protecting enamel properties and reducing hydrogen peroxide diffusion. Quercetin-enriched H2O2 gels may enhance bleaching safety by protecting dental tissues while maintaining esthetic benefits.

The effect of UV aging on the color stability and translucency of luting agents cemented to different CAD/CAM materials

BACKGROUND

The color stability and translucency of dental restorations are influenced by several factors, including the type of cement used, the chemical composition of the materials, and their thickness. This study aims to assess the color stability and translucency of various adhesive systems and CAD/CAM materials after exposure to UV aging.

METHODS

A total of 140 specimens were prepared using five different CAD/CAM materials: CEREC (CE), Cerasmart (CS), Vita Enamic (VE), Lava Ultimate (LU), and Grandio (GR), with thicknesses of 0.5 mm and 1 mm. The specimens were randomly divided into two cementation techniques: Dual Cure (DC) and Light Cure (LC). The relative translucency parameter (RTP) was measured initially and after UV aging using the RTP00 formula, and (∆RTP) was calculated. The specimens' color change (∆E00) was determined using the CIEDE2000 formula. Statistical analysis was conducted using Three-Way ANOVA with a significance level of 0.05.

RESULT

CE exhibited the least color change (∆E00), while LU displayed the highest ∆E00 across all parameters. There was no significant difference between the DC and LC cementation techniques, except for CS, CE, and VE at a thickness of 0.5 mm, and for CS and CE at 1 mm. Most color changes observed in the groups, were out of clinically acceptable ranges, except for the CE group with a thickness of 1 mm and DC cementation technique. The lowest ∆RTP was noted in specimens with a thickness of 1 mm and DC cementation across all groups.

CONCLUSION

The material structure had the most significant impact on ∆E00, while thickness significantly affected the ∆RTP. The cementation technique had the least influence on ∆E00 and no effect on ∆RTP. New-generation cement materials, whether Light Cure or Dual Cure, showed similar effects on ∆RTP (p < 0.05).

CLINICAL TRIAL NUMBER

None.

Evaluating visual thresholds and color metrics in dental research: An exploratory study

OBJECTIVES

This study aimed to evaluate perceptibility (PT) and acceptability thresholds (AT) for multiple color measurement devices and assess the performance of three color difference equations (∆E*ab, ∆E00, and ∆E94) using a visual dataset from expert observers.

METHODS

A visual dataset previously published was extended by adding the x-rite MetaVue spectrophotometer and ∆E94 to the analysis. Visual scaling was performed on 26 sample pairs of teeth using magnitude estimation. Observers answered PT and AT questions to determine thresholds. Threshold estimation was conducted using a model-free method, and device performance was analyzed using the standardized residual sum of squares (STRESS) index and visual instrument agreement scale (VIAS).

RESULTS

The PT and AT thresholds varied across devices and color difference equations. For ∆E00, STRESS values ranged from 23 to 32 (mean 29, sd 2.9), with VIAS scores between 68 % and 77 % (mean 71 %, sd 2.9). ∆E94 showed higher STRESS values (24-42, mean 34, sd 5.5) and lower VIAS scores (58-76 %, mean 66 %, sd 5.5). ∆E*ab demonstrated excellent visual-instrumental agreement with STRESS values from 18 to 36 (mean 24, sd 5.9) and lower VIAS scores (82-64 %, mean 76 %, sd 5.9) outperforming ∆E94 and ∆E00. The x-rite MetaVue achieved excellent results under controlled conditions but it is unsuitable for clinical research due to its design.

SIGNIFICANCE

This study highlights the variability in PT and AT across devices, suggesting the need for device-specific thresholds. It also demonstrates the effectiveness of ∆E*ab in dental colorimetry compared to more complex color difference metrics.

Color and Translucency Compatibility Among Various Resin-Based Composites and Layering Strategies

(1) Background: Natural-looking dental restorations require careful selection of the restorative material, with color and translucency characteristics similar to the natural dental structures. (2) Objectives: This research aimed to evaluate if there is compatibility regarding the color and translucency between different commercial RBCs in different layering recipes. (3) Methods: Sixty 1 mm thick disk specimens were produced from three different RBCs: ESS (Essentia-GC), BEG (Brilliant Ever Glow-Coltene), and IPS (IPS Empress Direct-Ivoclar Vivadent). Three different opacities and translucencies (enamel, dentin, and opaque shades) from each system were used in four recipes (R1-enamel, R2-dentin, R3-enamel and dentin, R4-enamel, dentin, and opaque) to obtain single-, double-, and triple-layered samples, respecting the anatomical layering technique. CIE L*, a*, b*, C*, h0 coordinates were recorded, and the relative translucency parameter (RTP00) was calculated. Further, the color differences (ΔE00) and the difference in translucencies ΔRTP00 were analyzed between the materials and between the layered recipes. (4) Results: The CIE L* and h° color coordinates and RTP00 showed significant differences among all three RBCs for all four recipes (p < 0.001). The decreasing order of translucency for each recipe was R1: ESS > BEG > IPS, R2 and R3: BEG > IPS > ESS, R4: BEG > ESS > IPS. Important differences were found in color and translucency among the recipes for each of the three RBCs tested (p < 0.001). The decreasing order of translucency for the tested RBCs was ESS: R1 > R3 > R4 > R2, BEG and IPS: R1 > R3 > R2 > R4. (5) Conclusions: No significant compatibility was observed in color and translucency among different layering recipes of the same composite materials nor between similar layering recipes when using different composites. The color differences between materials were more significant than the differences in translucency for each recipe.

Color formulation algorithm of self-curing acrylic resin for the fabrication of facial prostheses

PURPOSE

This study investigated the law of color formation in various color mixtures of dental acrylic resin powder, with the aim of realizing quick and accurate color matching of facial prostheses.

METHODS

Self-curing acrylic resin in crown, gingival, and clear colors was used to prepare 62 disk-shaped specimens (diameter, 30 mm; thickness, 5 mm). For each specimen, 2 g of different colored powders were mixed with 1 g of liquid and polymerized. Color values (L*, a*, and b*) were measured using a spectrophotometer. First-order linear (M1), second-order quadratic (M2S), second-order interactive (M2I), and complete second-order (M2C) models were applied to predict the relationship between component concentrations and color values. Multiple linear regression analysis was performed to assess the fitness of the observed and predicted colors. Differences in fitness were evaluated using repeated measures analysis of variance.

RESULTS

M2C showed a significantly better fit between the observed and predicted values compared with the other models.

CONCLUSION

The new model satisfied the requirements for clinical application. Using this formula, the mixing ratio of the powder of self-curing acrylic resin can easily be calculated to match skin colors. This formula will contribute to the fabrication of facial prostheses with suitable color, using dental material.

Evaluation of a 3D-printed nanohybrid resin composite versus a milled resin composite for flexural strength, wear and color stability

BACKGROUND

Controversial properties and performance of commercially available 3D-printed resin composite for permanent restorations. So, the purpose of this study was to assess the flexural strength, microhardness, wear, and color stability of 3D-printed versus milled nanohybrid resin composites for permanent restoration.

METHODS

A total of 70 samples of nanohybrid resin composites were used; 38 bar-shaped (14 mm ⋅ 2 mm ⋅ 2 mm) and 32 disc-shaped samples (10 mm ⋅ 2 mm) of Tetric CAD™ blocks (TC) and Flexcera Smile Ultra plus™ (FSU) were fabricated (n = 35). Flexural properties were tested using 3-point bending test. The Vickers test was used for microhardness evaluation. Volumetric wear analysis and color changes were assessed after simulated aging via Geomagic Control X software and a Vita Easyshade spectrophotometer, respectively. Color changes were calculated via the CIEDE2000 formula. A paired t-test was used for dependent variable analysis, and the Mann‒Whitney U test was used for independent variables (α = 0.05).

RESULTS

TC resulted in significantly higher flexural strength (247.7 ± 29.1 MPa) and microhardness (94.6 ± 3 gf/um2) than did FSU (97.2 ± 10.2 MPa and 31 ± 4.6 gf/um2, respectively) (P < 0.0001). Compared with FSU (-36.3 mm3), TC resulted in significantly lower wear rates (-17.6 mm3)(P < 0.0001). TC had a ΔE00 value of 2.4 ± 0.5, whereas FSU had a value of 2.1 ± 0.7 (P = 0.532), with no significant difference between the groups, but both values were above the acceptability limit (1.8).

CONCLUSIONS

Compared with 3D-printed nanohybrid resin composites, milled nanohybrid resin composites have better flexural strength, microhardness and wear properties.

CLINICAL RELEVANCE

Milled nanohybrid resin composites exhibit superior flexural strength, microhardness, and wear resistance, making them potentially more durable for clinical dental restorations compared to 3D-printed nanohybrid resin composites.

Use of a Silicone Mask Improves the Reproducibility of Tooth Color Assessment for Whitening Clinical Trials

Objective: This study aimed to investigate the reproducibility of tooth color assessment by dentists using two different spectrophotometers, Rayplicker and Vita Easyshade Advance 4.0, with or without a silicone mask developed to place its tip in the same position. Methods: Twenty subjects participated in this cross-over study. Multiple color coordinates and correlated whitening index measurements were performed to compare the variability with Vita Easyshade, with or without the mask, or the Rayplicker. The intrasubject variability was evaluated in consecutive measures and over time. Results: In consecutive measures, each subject's variance and the percentage of the coefficient of variation (CV) were minimal for each score. Bartlett's test resulted in a more significant variance for Vita Easyshade with a mask compared with either Vita Easyshade without a mask or Rayplicker. The comparison of the values obtained before and after 2'30" indicated complete reproducibility in variance and %CV data. p Values associated with the Bartlett test resulted in >0.90 for all the pre-post score comparisons, and no difference in pre-post %CV values was detected. Bartlett's test indicated that the measures with Vita Easyshade without the mask had significantly greater CV for L and b scores than those obtained with the mask or Rayplicker, which were similar among them. Conclusion: This study indicates that the silicone mask improves the precision of Vita Easyshade, and Rayplicker can be a valid alternative for studies measuring the changes in tooth color after whitening treatments.

Influence of depth and translucency on the color matching of single-shade resin composites: An in vitro study

To evaluate whether the depth and translucency of the restoration influence the color matching of single-color resin composites, cylindrical cavities (2-and-4 mm depths) were prepared in acrylic teeth 62 shade (n=10). Restorations were performed with single-shade resin composites (OC: Omnichroma, Tokuyama; VU: Vittra APS Unique, FGM) and a control multi-shade (EO: Estelite Omega, Tokuyama). The color matching was measured in instrumental analysis (CIEDE2000 color difference formula (ΔE00)) and visual analysis (0 to 4 scale). The translucency of discs (2-and-4mm thickness) was obtained by color difference (ΔE00) between black and white background. Two-way ANOVA followed by the post-hoc Tukey's test was used to evaluate instrumental analysis, and Kruskal-Wallis followed by the post-hoc Tukey's test to evaluate color matching with a significance level of 5%. Restoration depths affected the ΔE00 values of OC and VU (p<0.05) (higher ΔE00 values for 4-mm depth and higher for OC and VU (p< 0.05)). The restoration depths did not influence the color matching in the visual analysis. VU and OC showed higher translucency scores than EO. At 2 mm, OC showed higher translucency values and there was no difference between OC and VU at 4 mm (p <0.05). The color matching of OC and VU was influenced by depth (instrumental analysis). While the OC had a similar color matching to EO at both depths, VU had the best color matching in both depths in the visual analysis. Single-shade materials had greater translucency than EO at different depths, and the translucency decreased with increasing depth.

Strengthening effect of flavonoid antioxidant on resin-enamel bond strength following tooth bleaching

This study aimed to assess the impact of flavonoid-based antioxidant application after in-office bleaching with 35% hydrogen peroxide on the shear bond strength of resin to bovine enamel, comparing it with 10% sodium ascorbate. Bovine enamel blocks (n = 10) were randomly assigned to one of five pretreatments: (i) no bleaching, (ii) bleaching without antioxidant application, and (iii) bleaching followed by a 1-min application of 10% sodium ascorbate, (iv) 5% naringin, or (v) 10% naringin. Color analysis was conducted using a digital spectrophotometer. Shear bond strength was assessed on two, 2-mm-diameter resin cylinders per block using a universal testing machine at 0.5 mm/min until fracture. Enamel surface morphology was analyzed using scanning electron microscopy. Shear bond strength values and color parameters (ΔEab, ΔE00, and ΔWID) were analyzed using one-way ANOVA, while t-tests were used for the individual color parameters lightness (L*), green-red (a*), blue-yellow (b*), and chroma (C*) . None of the antioxidants resulted in bond strength values as high as those observed without bleaching. However, application of sodium ascorbate and 5% naringin after bleaching significantly increased bond strength compared with bleached enamel without antioxidant. Antioxidants had no significant impact on color. The predominant failure modes were adhesive between the adhesive and enamel, and mixed.

Which Whitening Mouthwash With Different Ingredients Is More Effective on Color and Bond Strength of Enamel?

OBJECTIVE

To examine the effects of six whitening mouthwashes on tooth color and immediate bond strength to the enamel.

MATERIALS AND METHODS

Human incisors were divided into seven groups (n = 10) according to mouthwashes (R.O.C.S Black Edition White, Splat White Plus, Colgate Plax White Charcoal, Signal White Now, Listerine Advanced White, Colgate Optic White, and distilled water). After the initial color measurements, the teeth were exposed to mouthwash for 4 weeks. Then, the color measurements were repeated. Then, cylindrical composite resin blocks were immediately applied to the enamel surfaces and subjected to shear bond strength tests. Data were analyzed using Kruskal-Wallis and Bonferroni tests (α = 0.05).

RESULTS

Δ𝑏, Δ𝐿, and ΔE 00 values did not present significant differences among the groups. Significant differences among the groups were determined for Δ𝑎 and ΔWI D values (p < 0.05). R.O.C.S Black Edition White and Splat White Plus produced clinically acceptable color changes. Signal White Now, Splat White Plus, and Listerine Advanced White created acceptable whiteness changes. The mouthwashes did not statistically affect the bond strength compared to the distilled water (p > 0.05).

CONCLUSIONS

Whitening mouthwash containing blue covarine revealed more acceptable color and whitening changes. Mouthwash containing charcoal led to the lowest enamel bond strength values.

CLINICAL SIGNIFICANCE

The content of whitening mouthwashes affected the degree of tooth whitening and shear bond strength to enamel.

Effect of 2-ethylhexyl salicylate incorporation on the color stability of different maxillofacial silicone elastomers after outdoor weathering

STATEMENT OF PROBLEM

Silicone elastomers are considered the most favorable materials for the prosthetic rehabilitation of facial defects. However, color change, because of the ultraviolet (UV) light, limits the life of facial prostheses. The addition of 2-ethylhexyl salicylate as a UV-protective may improve the color stability of different maxillofacial silicone elastomers.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of 2-ethylhexyl salicylate on the color stability of 3 different maxillofacial silicone elastomers after outdoor weathering.

MATERIAL AND METHODS

Three different ratios of UV-protective 2-ethylhexyl salicylate (UV-ES) were incorporated into 3 different types of maxillofacial silicones (M511, TechSil S25, and A-2000) in 1%, 2%, and 5% ratios, and a control group for each silicone was generated. A total of 120 Ø15×2-mm disk-shaped specimens were prepared from 3 different silicone elastomers according to the 4 different UV-ES ratio groups (n=10). The specimens were subjected to outdoor weathering in Ankara, Türkiye, from June 2021 to June 2022. Color differences in the specimens were measured at 3 months and 1 year of weathering. The color change values (ΔE) were statistically analyzed by using repeated measures of 3-way ANOVA. The differences were compared by using the Tukey honest significant difference test (α=.05).

RESULTS

No interaction was found among the factors (silicone type, UV-ES ratio, and aging) (P=.29). The highest ΔE values were found in TechSil S-25 (P<.001), while the results were not significantly different between the M511 and A2000 groups (P=.324) The higher ΔE values were found in the control group when compared with those of the UV-ES added group of each material, while the results were not significantly different among the 1%, 2%, and 5% groups (P>.05).

CONCLUSIONS

Incorporating 2-ethylhexyl salicylate into the tested maxillofacial silicones reduced color change.

Comparative Analysis of Translucency in Different Thicknesses of Monolithic Zirconia Crowns

OBJECTIVES

Achieving optimal esthetics in dental restorations remains challenging, particularly with zirconia crowns, which, despite their durability, often exhibit less translucency than natural teeth. This study aimed to evaluate how varying thicknesses of monolithic zirconia crowns affect their translucency.

MATERIALS AND METHODS

In this experimental laboratory study, an initial model (a brass die) was scanned, and two dies, one black (9005 RAL), and one white (9010 RAL), were created from Resin according to the scanned file. Next, 30 zirconia crowns (ZrO2, Arum, High Translucent) were fabricated in three thicknesses: 0.5, 0.8, and 1.5 mm. The color and translucency of the samples were assessed under standard lighting conditions (D65) using a spectroradiometer, and the color parameters L*, b*, and a* were recorded. The translucency of each sample was measured using the CIEDE2000 and CIE-Lab formulae. Data were analyzed using one-way ANOVA and the Tamhane test.

RESULTS

Statistically significant changes in the color and translucency of the samples were observed with varying thicknesses (p < 0.001). Specifically, the translucency parameter (TP), L*, and b* values decreased as the thickness increased, whereas a* values remained relatively stable. The average TP values for CIE-Lab ranged from 11.51 at 0.5 mm to 6.54 at 1.5 mm, and for CIEDE2000, they ranged from 8.19 at 0.5 mm to 4.82 at 1.5 mm.

CONCLUSION

Within the limitations of this in vitro study, it can be concluded that reducing the thickness of monolithic zirconia restorations increases their translucency. Thinner zirconia restorations demonstrate a higher TP, which may offer improved esthetic integration in clinical applications.

Translucency of Enamel and Dentin: A Biomimetic Target for Esthetic Dental Materials

OBJECTIVE

This study aimed to assess the relative translucency parameter (RTP) of human enamel and dentin and set target RTP values for dental material development. Additionally, it seeks to validate the spectral RTP concept as supplementary quantitative information.

MATERIALS AND METHODS

Slides of extracted human teeth, 1 and 2 mm thick enamel or dentin slides, were evaluated. RTP was calculated using CIEDE2000 (RTP00) and CIELAB (RTPab) color difference formulas. Spectral RTP (SPECTRAL RTP) curves were also generated from differences between spectral reflectance values obtained against white and black backgrounds. Statistical analyses included multifactorial ANOVAs for each RTP and spectral RTP, and Pearson correlations between RTP and spectral RTP.

RESULTS

Significant correlations were observed between the RTP and spectral RTP values (p < 0.001) at all studied wavelengths. RTP00 and RTPab values were significantly different (p < 0.001). Enamel showed more translucency than dentin (p < 0.001), and 1 mm slices were more translucent than 2 mm slices (p < 0.001).

CONCLUSIONS

Spectral RTP values were influenced by the type of tissue (enamel, dentin), thickness (1 mm, 2 mm), and color difference formula (CIELAB2000, CIELAB). RTP curve values were influenced by tissue type, thickness, and wavelength. Spectral RTP and RTP curve values were correlated.

Synthesis and application of calcium cyclotriphosphate in bleaching formulations: Effects on dental enamel properties

OBJECTIVES

This study aimed to synthesize and evaluate the in vitro effects of varying concentrations (0.25%, 0.5%, and 1%) of calcium-substituted sodium trimetaphosphate (CaNaTMP) incorporated into 17.5% and 35% hydrogen peroxide (HP) whitening formulations on enamel color change, microhardness, morphology, surface roughness, mineral content, and transamelodentinal diffusion of HP.

MATERIALS AND METHODS

Enamel/dentin discs (N = 288) were allocated into eight groups according to the bleaching gel: (1) 35% HP; (2) 35% HP + 0.25% CaNaTMP; (3) 35% HP + 0.5% CaNaTMP; (4) 35% HP + 1% CaNaTMP; (5) 17.5% HP; (6) 17.5% HP + 0.25% CaNaTMP; (7) 17.5% HP + 0.5% CaNaTMP; and (8) 17.5% HP + 1% CaNaTMP. Gels were applied for 40 min across three weekly sessions. Evaluated parameters included total color change according to CIELab (ΔE), CIEDE2000 equation (ΔE00), whiteness index (ΔWID), surface hardness (SH), surface roughness (Ra), enamel mineral content (gHAp × cm⁻³ × µm), and transamelodentinal of HP. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses were used to assess enamel surface characteristics. Data were analyzed using ANOVA and the Student-Newman-Keuls test (p < 0.05).

RESULTS

All bleaching gels caused significant color changes after treatment (p < 0.001), with similar ΔE, ΔE00, and ΔWID values among them. Mineral loss (SH, gHAp × cm⁻³ × µm), Ra, and HP diffusion were highest with the 35% HP gel (p < 0.001) and lowest in groups containing CaNaTMP, particularly at 1% (p < 0.001). SEM/EDX analysis revealed no visible surface alterations in the 17.5% HP group, with prominent amorphous apatite precipitation in the 1% CaTMP-containing group. Incorporating CaNaTMP, particularly at 0.5% and 1%, into the 35% HP gel reduced surface changes.

CONCLUSIONS

This study demonstrated that the addition of CaNaTMP to bleaching gels with 17.5% and 35% HP reduces mineral loss, changes in roughness, and surface morphology of enamel, as well as decreasing trans-amelodentinal diffusion of H₂O₂, without compromising the bleaching efficacy. The incorporation of 1% CaNaTMP was particularly more effective in protecting the dental enamel.

CLINICAL RELEVANCE

The incorporation of CaNaTMP to 17.5% and 35% HP bleaching gels enhances safety and biocompatibility by reducing enamel damage. The lower HP concentration (17.5%) combined with 1% CaNaTMP provides a safer whitening option, maintaining effectiveness while minimizing adverse enamel changes, aimed at improving patient comfort during treatment.

Effects of toothbrush abrasion on color, gloss, and surface roughness, and thermal cycling on bond strength of CAD-CAM composite resin block with light-cured resin coating restoration materials

This study aimed to evaluate the usefulness of light-cured resin coating restoration materials (RCs) on anterior composite resin blocks by quantifying the color, gloss, and surface roughness before and after toothbrush abrasion test and to evaluate the shear bond strength before and after thermal cycling test. Four types of RCs were used in the experiments. The application of RCs to composite resin blocks resulted in color changes and a decrease in gloss after the toothbrush abrasion test; however, both were within clinically acceptable limits. The surface roughness was at a value that made bacterial adhesion difficult both after the application of RCs and after the toothbrush abrasion test. The shear bond strength also had clinically acceptable bond strength. Therefore, the application of RCs to composite resins in the oral cavity is considered effective in terms of maintaining esthetics, gloss, and surface properties, as well as the durability of RCs.

Color stability of frequently used aesthetic restorative materials following in vitro exposure to chlorhexidine- and octenidine-based mouthrinses

BACKGROUND

Long-term color match is one of the most important characteristics of aesthetic restorative materials as discoloration constitutes a primary reason for otherwise unnecessary replacements. The aim of the present in vitro study was to evaluate the color stability of frequent dental materials (ceramic, composite, orthodontic adhesive) induced by common antiseptic mouthrinses taking into account black tea consumption and mechanical cleaning.

METHODS

Twenty-four disc-shaped specimens (8 × 2 mm) were made of the materials Ceram.x Spectra™ ST HV, Ceram.x Spectra™ flow, Ceramill® Zolid HT+ PS and Unitek™ Transbond™ LR. Each of the following solutions was tested on six pieces per material: Chlorhexamed forte (CHX), octenident® (OCTD), octenimed® (OCTM) and artificial saliva (control). Dental samples underwent a total of 30 discoloration cycles in which they were alternatively placed into artificial saliva, black tea and respective mouthrinse or only in artificial saliva. After every 10 cycles, discs were mechanically cleaned with toothbrush and toothpaste. After 30 cycles, dental specimens were submitted to professional polishing. Color shifts were measured at different time-points using the VITA Easyshade® V spectrophotometer and displayed as total color difference ∆E (mean ± standard error). A post-hoc Tukey test (⍺ = 0.05) was applied to the mean ∆E values after 30 cycles to determine discoloration discrepancies between various mouthrinses as well as the control. Moreover, photos of individual discs were taken at all measurement times to visualize potential color changes by eye.

RESULTS

All mouthrinses showed major color shifts in the clinically visible range compared to the control on all different dental materials tested. However, CHX caused significantly more discoloration than OCTM and OCTD. Established color changes could be almost completely removed by simple brushing and even further by professional polishing to clinically acceptable levels on all tested materials.

CONCLUSIONS

Prolonged application of antiseptic mouthrinses may cause discoloration on different restorative materials. To maintain aesthetically satisfying conditions, patients should be educated about the importance of daily mechanical tooth brushing and regular professional polishing.

Influence of curing light irradiance and ceramic thickness on color stability and translucency of cemented ceramic laminate veneers

This in vitro study aimed to evaluate the effects of curing light irradiance and ceramic thickness on the color stability and translucency of cemented laminate veneers after accelerated aging. Eighty ceramic disks were fabricated using shade A3 IPS e.max Press HT specimens of 0.50-mm and 1.00-mm thickness. Specimens of each thickness were randomly divided into four groups, and the A3 shade of Variolink N resin cement was used for bonding in three groups with light irradiances of 700 mW/cm2, 900 mW/cm2, and 1100 mW/cm2. The CIE L*a*b* parameters were measured before and after 5,000 thermal cycles of 5 °C and 55 °C. Changes in the color and translucency were measured through spectrophotometry and analyzed using two-way analysis of variance. Results both ceramic thickness and curing light irradiance caused statistically significant differences in color after aging (P < 0.01). The greatest color changes were observed in samples of thickness 0.50 mm that received a light irradiance of 700 mW/cm2. Samples with varying thicknesses and curing light irradiances showed statistically significant differences in the extent of decrease in translucency after aging (P < 0.01). The results of this study demonstrated that cemented ceramic laminate veneers tended to become darker and yellower after aging. The light irradiance and ceramic thickness clearly affected the color stability of the veneers. The translucency of the veneers was significantly related to their thickness, and aging clearly decreased the translucency of the veneers.

Color Matching and Stability of Single-Shade Chameleon Dental Composites: A Systematic Review

OBJECTIVE

This systematic review evaluates the color-matching ability (ΔE00 values) and chromatic stability of single-shade chameleon dental resin composites in restorative dentistry.

METHODS

A comprehensive search of PubMed, Scopus, Web of Science, Embase, and Cochrane Library was conducted following PRISMA guidelines. Studies assessing color adaptation and stability of single-shade composites in vitro, in clinical trials, and in retrospective analyses were included.

RESULTS

Seven studies (four in vitro, two clinical trials, one retrospective study) reported ΔE00 values within clinically acceptable thresholds (< 3.3). Clinical trials showed that single-shade composites (e.g., Omnichroma, Vittra APS Unique) achieved comparable aesthetic outcomes to multi-shade composites over 12-18 months. Factors such as staining agents and cavity depth influenced color stability, with coffee exposure causing the most discoloration. Bleaching procedures induced minimal color shifts. Study heterogeneity limited meta-analysis.

CONCLUSION

Single-shade chameleon resin composites provide reliable color adaptation and stability, streamlining shade selection and reducing clinical time. However, staining susceptibility and restoration depth must be considered for long-term aesthetic success.

CLINICAL SIGNIFICANCE

Single-shade chameleon composites simplify shade selection, reducing chair time and enhancing efficiency in restorative dentistry. However, clinicians should consider staining susceptibility and restoration depth to ensure long-term aesthetic stability.

Strategies for Masking Metal Show-Through in Disilicate Dental Ceramics: A Systematic Evaluation Using Different Assessment Techniques

OBJECTIVES

The aim of this study was to assess the masking effect of two lithium disilicate ceramics at various thicknesses, when bonded to opaqued and nonopaqued silvery metallic core buildups, using spectrophotometry and digital photocolorimetric analysis.

MATERIALS AND METHODS

Sixty bis-acrylic blocks in A2 shade were fabricated to serve as control unrestored substrates, and 120 blocks were prepared (8.0 mm × 8.0 mm × 3.0 mm, W × L × H) and restored with amalgam. Sixty amalgam-restored blocks were treated with 0.65 mm (±0.10 mm) resin-based opaquer. Low-translucency (LT) lithium disilicate CAD/CAM blocks from two different manufacturers (Ivoclar IPS e.max CAD and GC Initial LiSi) were sectioned, crystallized (e.max), and polished, then divided into three subgroups according to their thickness (1.0, 1.5, and 2.0 mm, n = 30). The ceramic slices were treated and bonded to the three substrate types (control, opaqued amalgam, and nonopaqued amalgam) using a resin-luting cement. The masking effect of the resulting ceramic-substrate assemblies was investigated using a spectrophotometer and polarized digital photocolorimetric (PDPC) analysis. CIE L*a*b* coordinates were measured, and color difference analysis (ΔE00) was performed using the CIE ΔE00 formula. Acceptability and perceptibility thresholds were set at ΔE00 ≤ 1.8 and ΔE00 ≤ 0.8, respectively. The data were statistically analyzed using three-way and two-way ANOVA, followed by Tukey's test (α ≤ 0.05).

RESULTS

Spectrophotometric analysis showed that, for nonopaqued amalgam substrate, IPS e.max achieved ΔE00 mean (SD) of 4.2(0.4), 2.8(0.3), and 2.1(0.2), for 1.0, 1.5, and 2.0 mm thicknesses, respectively. Initial LiSi achieved ΔE00 mean (SD) of 3.8 (1.1), 2.8(0.9), and 2.7(0.4) for 1.0, 1.5, and 2.0 mm thicknesses, respectively. When the substrate was opaqued amalgam, IPS e.max and LiSi both resulted in a mean ΔE00 of 2.3(0.7). As the thickness increased to 1.5 and 2.0 mm, IPS e.max achieved an acceptable (ΔE00 = 1.3(0.4)) and an excellent (ΔE00 = 0.8(0.3)) masking, respectively. Initial LiSi achieved a moderately unacceptable color difference (ΔE00 = 2.0(0.8)) at 1.5 mm and an acceptable masking (ΔE00 = 1.5(0.6)) at 2.0 mm. PDPC analysis presented similar trends for both ceramic types and substrates, except for LiSi on opaqued amalgam. Individual CIE L*a*b* color coordinates, however, showed significant differences between the two analysis methods.

CONCLUSIONS

The use of opaquer proved to be an effective strategy for masking silvery metallic core buildups in preparation for lithium disilicate-based restorations. IPS e.max CAD provided a superior masking effect compared to Initial LiSi when used in conjunction with a resin opaquer.

CLINICAL SIGNIFICANCE

This study shows the potential of resin-based opaquers to mask metallic restorations when combined with lithium disilicate at different thicknesses. Providing knowledge in this aspect may emphasize conservative dental practices by preventing the replacement of metallic restorations and the accompanying unnecessary removal of tooth structure.

Impact of Glazing, Coating, and Polishing on the Color Stability and Surface Properties of a 3D Printed Resin and Two Veneering Composite Resins

OBJECTIVE

To analyze the impact of various surface treatments on color stability and surface properties of a 3D printed and two veneering composite resins.

MATERIALS AND METHODS

Specimens were manufactured from a 3D printed (VarseoSmile CrownPlus) or two veneering composite resins (GRADIA PLUS; VITA VM LC flow) and underwent varnishing (OPTIGLAZE; VITA AKZENT LC), coating, polishing (goat hair brush; silicone polisher) or remained untreated. For 14 days, specimens were stored in red wine, curcuma, cress, or water. Individual and, for ΔE00 > 1.8, professional prophylaxis was performed. Color (ΔE00), surface free energy (SFE), and surface roughness (SR) were measured longitudinally. Mann-Whitney U, Kruskal-Wallis, Friedman, and Wilcoxon tests were computed (α = 0.05).

RESULTS

For the 3D printed resin, varnishing, coating, or goat hair brushing minimized discoloration, while untreated surfaces showed the highest discoloration. Veneering composite resins benefited from goat hair brushing. Individual and professional prophylaxis improved surface properties and partially reversed discolorations. Solely goat hair brushed veneering composite resins achieved surface roughness values ≤ 0.2 μm.

CONCLUSIONS

To prevent discoloration, varnishing and goat hair brushing can be recommended for all materials. Individual prophylaxis was most effective for veneering composite resin 1, whereas professional prophylaxis significantly reduced discoloration on 3D printed resin. Only veneering composite resins treated with goat hair brushing achieved surface roughness values of ≤ 0.2 μm.

CLINICAL SIGNIFICANCE

As 3D printed resins tend to discolor easily, it is important to understand how different surface treatments may impact their color stability. Applying treatments such as varnishing, coating, and polishing can improve the color stability and surface properties, ensuring better esthetic results over time.

Comparative chromatic study of the interdental gingival papillae

STATEMENT OF PROBLEM

Data are lacking on interdental papillae color, including the effect of sociodemographic or behavioral factors, and which ceramic gingival specimens best match it.

PURPOSE

The purpose of this clinical study was to determine the color coordinates of healthy gingival papillae and compare them according to sex, age, dental hygiene, and smoking habits, to compare the color coordinates of the papillae to other gingival zones, and to present a valid set of pink ceramic specimens for use in subjective color selection with the gingival papillae.

MATERIAL AND METHODS

Color coordinates of the attached gingiva and interdental papillae adjacent to the maxillary incisor were recorded by using spectrophotometry (Spectroshade; MHT Optic Research) in 62 White participants (124 papillae). To determine which color specimens best represented the interdental papillae, according to the acceptability thresholds (AT), 2 published databases were used: 15 validated ceramic gingival specimens and 133 ceramic gingival specimens. MANOVA was used for comparisons of color coordinates, and the coverage error was calculated to evaluate the guide.

RESULTS

The color-coordinate ranges of the interdental papillae were: L*: 42.2 to 57.5; a*: 16.8 to 30.6; and b*: 11.2 to 18.1. Statistically significant differences were found between all gingival zones for all color coordinates (P<.05). The interdental papillae were less yellow than the middle zone of attached gingiva and the free gingival margin, and redder than the mucogingival line. Using the Euclidean formula, the coverage error of the 15-specimen gingival guide was 2.71.

CONCLUSIONS

The gingival papillae of women were significantly lighter than of men, and the b* coordinate was higher in the papillae of smokers than non-smokers. Age or dental hygiene did not significantly affect interdental papillae color coordinates. Color differences exceeding the AT between the interdental papillae and each of the 3 attached gingival zones were found in a large part of the population. The 15 specimens were useful for subjective shade selection with the interdental papillae.

Effect of an experimental pregabalin gel on dental sensitivity and color change after bleaching with 35% hydrogen peroxide: a randomized clinical trial

OBJECTIVE

This clinical study evaluated an experimental pregabalin (PG) gel in reducing dental sensitivity (DS) and color change after dental bleaching.

MATERIALS AND METHODS

Seventy-five volunteers were selected and randomized into three groups: GPG (10% pregabalin gel), GKF (5% potassium nitrate and 2% sodium fluoride), and GP (placebo gel). Prior to the bleaching treatment, GPG and GKF received applications of the respective desensitizing gels for 10 min. The GP group received an application of placebo gel, similar to the other groups. The bleaching was performed with 35% hydrogen peroxide in 3 sessions, with a 7-day interval between sessions. Post-bleaching DS was assessed using the visual analog scale (VAS) over 21 days of follow-up. Color Assessment (ΔE00, ΔWID, and ΔEab) and luminosity (L) were measured at baseline (T0) and 7 days after the third session (T1). Friedman, Kruskal-Wallis, one-way ANOVA, and Tukey tests were used, with α = 5%.

RESULTS

Intergroup analysis showed that on the 1st, 8th, and 15th days, DS was higher for GP (p < 0.006; p = 0.004; p < 0.001) and did not differ between GKF and GPG (p = 0.203; p = 0.178; p = 0.09). In the intragroup analysis, GP showed a significant increase in DS on the 15th day (p < 0.001).

CONCLUSIONS

The experimental 10% pregabalin gel reduced dental sensitivity and did not interfere with bleaching results.

CLINICAL SIGNIFICANCE

The topical application of 10% pregabalin gels and NKF was effective in reducing tooth sensitivity 24 hoursafter whitening with 35% hydrogen peroxide.

TRIAL REGISTRATION

ClinicalTrials.gov trial registry with the identifier NCT06180707.

Efficacy and safety of peroxide-based mouthrinse on whitening treatment: A randomized controlled clinical trial

OBJECTIVES

This randomized controlled clinical trial evaluated the efficacy and safety of peroxide-based mouthrinse on whitening treatment. The patient's satisfaction and treatment longevity were also assessed.

MATERIAL AND METHODS

Participants (N = 45) were randomly allocated to three different groups: WM (Whitening mouthrinse - 2.5% hydrogen peroxide); PM (Placebo mouthrinse - 0% hydrogen peroxide); and WG (Whitening gel - 10% carbamide peroxide). The treatment was performed twice daily for 30 s over 90 days for WM and PM and once daily for 2 h over 14 days for WG. Tooth color was evaluated with shade guides (ΔSGU) and with a spectrophotometer (ΔE00 and WID) after 14, 30, 60, 90, 120 days, and 2 years. Tooth sensitivity, gingival condition, and patient satisfaction were also evaluated.

RESULTS

WG resulted in the highest color change over time for visual (ΔSGU) and objective (ΔE00 and WID) analyses. With WM, significant visual color alteration was detected in the 60-day assessment compared with PM. After 2 years, no color rebound was observed for the treatments. A very low intensity of sensitivity was found for WM and WG. No gingival irritation was detected. All the participants were satisfied with the whitening treatment outcomes.

CONCLUSIONS

The peroxide-based mouthrinse effectively changed tooth color, with relevant effect detected after 60 days of use. However, the whitening result obtained with the conventional carbamide peroxide gel treatment was more pronounced. No relevant adverse effects were observed, and the outcomes were maintained for 2 years.

CLINICAL SIGNIFICANCE

Peroxide-based mouthrinse is an effective alternative whitening treatment, although it promotes less color change compared with the conventional at-home technique without inducing significant adverse effects. Patients should be warned about the prolonged treatment and the need for compliance.

Effect of whitening pens on hydrogen peroxide permeability in the pulp chamber, color change and surface morphology

OBJECTIVE

To evaluate hydrogen peroxide (HP) permeability into the pulp chamber, color change, and surface morphology promoted by different whitening pens.

MATERIAL AND METHODS

Fifty premolars were divided into five groups (n = 10): untreated control; Colgate Optic White Express Whitening Pen (OE-C), Colgate Optic White Overnight Whitening Pen (OW-C), Equate Teeth Whitening Kit (TK-E) and Zimba Teeth Whitening Pen (TW-Z), applied daily for 15 minutes over ten days. HP permeability (μg/mL) was measured using UV-VIS spectroscopy, and color change (ΔEab, ΔE00, and WID) by a digital spectrophotometer at baseline (T0), after one (T1), five (T5) and ten days (T10). Initial HP concentration (%), pH and surface morphology were determined through titration, pH meter, and scanning electron microscopy, respectively. Statistical analysis included one-way and two-way ANOVA with Tukey's and Dunnett's tests (α = 0.05).

RESULTS

OE-C and OW-C exhibited higher pH, lower HP concentrations, reduced HP penetration (p < 0.05), and a similar surface morphology pattern compared to TK-E and TW-Z. Bleaching efficacy showed no significant differences among the whitening pens (p > 0.05). For ΔEab and ΔE00, OE-C and OW-C showed similar color changes across all time points, whereas the TK-E and TW-Z exhibited greater changes from T0 to T5 and T0 to T10 (p < 0.05). WID values significantly increased at T5 and T10 across all groups (p < 0.05).

CONCLUSIONS

Whitening pens vary in pH, initial hydrogen peroxide concentration, and hydrogen peroxide penetration; however, these differences do not significantly impact their surface morphology and bleaching effect.

CLINICAL SIGNIFICANCE

The use of whitening pens appears promising for achieving effective teeth bleaching after five days of application. However, the detection of hydrogen peroxide within the pulp chamber may increase the risk of tooth sensitivity.

Influence of image file and white balance on photographic color assessment

STATEMENT OF PROBLEM

How the color parameters obtained from digital photographs may be influenced by illumination, file format, and subject color is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate color differences (ΔE00) and CIELab color coordinates among different types of file formats of dental shade tab images with and without white balance.

MATERIAL AND METHODS

Different shade tab colors (n=10) were photographed with a digital camera under standard conditions. The photographs were stored in RAW, JPEG, and TIFF file formats and evaluated with and without white balance (WB) adjustment by using an image software program and a gray reference card with known color coordinates. CIEDE2000 color differences between each image file format and the control group (RAW WB) were calculated, and interpreted by the visual perceptibility (PT00=0.8) and acceptability (AT00=1.8) thresholds. The ΔE00 color shift was defined according to CIEDE2000 lightness, chroma, and hue and interpreted by the following respective visual acceptability thresholds: 2.92, 2.52, and 1.90. The differences among the color coordinates were analyzed by Kruskal-Wallis and Bonferroni post hoc tests (α=.05).

RESULTS

The color coordinates presented statistically significant differences between the file formats and control group (P<.001). Excellent matches (ΔE00 ≤0.8) were observed on TIFF and JPEG saved from RAW-WB. Images without WB presented unacceptable mismatches (ΔE00 >5.4). ΔE00 color shift of images without WB were predominantly influenced by ΔH00, while JPEG, WB, and TIFF WB were mostly influenced by ΔC00.

CONCLUSIONS

Only compressed JPEG or TIFF files of dental shade tabs derived from original RAW WB photographs were able to achieve color differences within the limits of the 50:50% perceptibility threshold, providing excellent color matches with the RAW WB files.

Influence of sintering temperature and aging on the color and translucency of zirconia

STATEMENT OF PROBLEM

Translucent zirconias are promising materials for monolithic prostheses. However, information on their optical behavior after sintering and aging protocols is scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the color and translucency of zirconia subjected to different sintering temperatures and aging.

MATERIAL AND METHODS

A total of 180 1.5-mm-thick disks were produced from translucent zirconia blocks: DD cubeX2 white, DD cubeX2 A2 shade, DD Bio ZX2 white (Dental Direkt GmbH), and Lava Plus white (3M ESPE). White and A2 shade disks were made for each zirconia. DD Bio ZX2 and Lava Plus were colored by immersion in dyeing liquids. All disks were divided according to the sintering temperature: 1400 ºC, 1450 ºC, and 1500 ºC (T0). Subsequently, the disks were subjected to an aging protocol in an autoclave for 5 (T1) and 20 hours (T2). The L*a*b* coordinates were measured with a spectrophotometer. ∆E00, ∆L', ∆C', ∆H', and TP were calculated using CIEDE2000, and CR was obtained using CIEXYZ. Repeated measures ANOVA and the Tukey HSD test were used for statistical analysis (α=.05).

RESULTS

The 1400 ºC temperature produced the greatest ΔE00 (5.25). A progressive increase in ΔE00 was found after aging (especially in T2), with a reduction in lightness and an increase in saturation in most groups (P<.001). The DD cubeX2 white (DCW) and A2 (DCC) groups presented the highest TP00 values, mainly at 1500 °C. The highest CR values were observed in the Lava Plus colored (LPC) group (1400 °C) (P<.001).

CONCLUSIONS

Sintering at a lower temperature than that recommended by the manufacturer can reduce lightness and increase saturation and opacity, especially after aging.

Effects of post-polymerization conditions on color properties, surface roughness, and flexural strength of 3D-printed permanent resin material after thermal aging

PURPOSE

To evaluate the color, surface properties, and flexural strength of 3D-printed permanent crown resin subjected to different post-polymerization conditions after artificial aging.

MATERIALS AND METHODS

Ninety (10 × 2 mm) disc-shaped specimens were printed by using permanent crown resin with SLA technology. Specimens were divided into nine different groups, subject to post-polymerization conditions at three different times (15, 20, and 30 min) and three different temperatures (40, 60, and 80°C) (n = 10). Color and surface roughness measurements were repeated pre-post thermal aging (5.000 cycles, 5-55°C) and a flexural strength test was carried out. Data were analyzed with Shapiro-Wilk, Kruskal-Wallis, ANOVA, Tukey HSD, and Dunn tests (α < 0.05).

RESULTS

ΔE00 values showed results below the acceptable color threshold, except for the 30 min 40°C group (ΔE00 <1.8). No difference was found between the relative translucency parameter and surface roughness values of the 20 min 60°C group recommended by the manufacturer and the other groups. A significant difference was found between the flexural strength values of the groups (p < 0.001).

CONCLUSIONS

The color properties, surface topography, and mechanical properties of the printed permanent crown material were affected by different post-polymerization conditions: polymerized at different times and temperatures. Although the flexural strength and color change values showed promising results, more studies are required to evaluate its suitability for clinical use.

Effectiveness and one-year whiteness stability of different in-office bleaching agents and alternative protocols

STATEMENT OF PROBLEM

In-office bleaching has been widely researched. However, few studies have evaluated alternative protocols for this procedure. Moreover, information on the long-term stability of in-office whitening is limited.

PURPOSE

The purpose of this in vitro study was to evaluate the effectiveness and 1-year stability of in-office bleaching with 35% hydrogen peroxide (35%HP) and 37% carbamide peroxide (37%CP) using traditional and alternative protocols.

MATERIAL AND METHODS

Forty human third molars were stained with tea and allocated to groups (n=10). Traditional protocols consisted of 3 applications of 35%HP for 15 minutes and 1 application of 37%CP for 45 minutes. Alternative protocols consisted of 1 application of 35%HP for 45 minutes and 3 applications of 37%CP for 45 minutes. Protocols were applied for 3 weeks. CIELab color coordinates were measured at baseline and weekly during treatment and at 1-week, 6-month, and 1-year follow-ups. Effectiveness and stability of the bleaching treatments were interpreted using 50:50% perceptibility and acceptability thresholds. CIELab, chroma, hue angle, and whiteness index were analyzed using the Wilcoxon signed-rank test (α=.05).

RESULTS

All protocols showed improvement in bleaching after the first week (P≤.005). All bleaching procedures presented excellent whitening outcomes. Alternative protocols showed a larger rebound effect after 1 year, indicating less stability. For the whiteness index, no differences between the completion of the treatments and 1-year follow-up was found for the bleaching treatments and protocols (P>.05), except for the 37%CP alternative protocol (P=.005).

CONCLUSIONS

All tested protocols presented excellent effectiveness in bleaching. Traditional protocols exhibited a greater whiteness stability, while the alternative protocols showed a greater rebound effect after 1 year.

Mechanical and optical properties of additively manufactured denture base resin in different colors modified with antimicrobial substances: An in vitro study

STATEMENT OF PROBLEM

Acrylic denture base resins are subject to colonization by oral and nonoral bacteria, contributing to the onset of denture stomatitis. However, how the addition of antimicrobial substances affects the mechanical and optical properties of additively manufactured denture base resin remains unclear.

PURPOSE

The purpose of this in vitro study was to investigate the surface roughness, color stainability, and flexural strength of antimicrobial-modified, additively manufactured polymethyl methacrylate (PMMA) denture base resin in tooth and gingiva colors.

MATERIAL AND METHODS

Three antibacterial agents, e-poly-L-lysine+ methacryloyloxyethyl phosphorylcholine (e-MP), silver nanoparticles (AG-P), quaternized ammonium monomer (QA-P) synthesized via the reaction of octyl bromide and DMAEMA, were separately incorporated into tooth- or gingiva-colored 3-dimensionally (3D) printable PMMA specimens, simulating an implant-supported overdenture base or the artificial teeth (n=80). Unaltered specimens served as controls. Autopolymerizing acrylic resin was used to attach titanium matrix housings to gingiva-colored specimens. All specimens underwent coffee thermal cycling (CTC) comprising 10 000 cycles between 5 °C and 55 °C, and their color coordinates were measured. Surface roughness, color change (ΔE00), and flexural strength were calculated before and after CTC. The results were analyzed and compared by using ANOVA and the Tukey post hoc test (α=.05).

RESULTS

All antibacterial agent-incorporated specimens showed lower ΔE00 values than the control (P=.001), with eM-P exhibiting the least color change (P=.001). The control group had the highest post-CTC roughness (Ra) values (P<.001), while all test groups demonstrated higher flexural strength than the control (P=.001). CTC had no significant effect on flexural strength (P>.115).

CONCLUSIONS

The addition of antimicrobial agents to 3D printable implant overdenture base resin in tooth and gingiva color affected the materials' surface properties, color stainability, and flexural strength. Smoother surface, lower color stainability, and higher flexural strength were observed with the addition of eM-P.

Effects of Detox Juices on Color Stability and Surface Roughness of Universal Chromatic Resin Composites

This study investigated the color stability and surface roughness of universal chromatic resin-based composites (RBCs) after immersion in detox juices. One hundred seventy-six disc-shaped specimens (8 mm in diameter and 2 mm in thickness) were prepared using four universal chromatic RBCs: NeoSpectra ST (NS), Omnichroma (OM), Charisma Topaz One (CO), and G-ænial Universal Injectable (GI). Specimens of each material were randomly divided into four subgroups (n=11) and immersed in either the assigned detox juices (red, green, or yellow) or distilled water (control). Color and surface roughness measurements were taken at baseline, 15 and 30 days of immersion. Scanning electron microscopy (SEM) was used to evaluate the surface topography of the composites. The color change [CIEDE2000 (ΔE00)] and surface roughness (Ra) values were analyzed using generalized linear models and multiple comparison tests with Bonferroni correction. Correlation analysis was performed using Spearman rank correlation test. The main variable effects of "composite and immersion media" were significant for both color change and surface roughness parameters (p<0.001). Additionally, the main effect of the "evaluation period" was significant only for surface roughness (p=0.001). The highest discoloration occurred in the GI group immersed in a red beverage, while the CO group immersed in yellow beverage had the highest Ra values. In SEM analysis, OM demonstrated a more homogeneous filler structure with clearly visible nano-spherical fillers and nanoclusters, contributing to its superior smoothness. Conversely, a significant increase in rough areas was observed, especially in NS exposed to the green beverage and CO exposed to the yellow beverage, after 30 days. While the immersion of resin composites in detox juices induced an acceptable color alteration except for OM and GI groups immersed in the red beverage, all tested materials exhibited clinically admissible results regarding surface roughness.