Is surface roughness of direct resin composite restorations material and polisher-dependent? A systematic review

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.

Knoop microhardness, surface roughness, and cytotoxicity analysis of arginine-modified experimental orthodontic resins: An in vitro study

AIM

The study aimed to evaluate the impact of incorporating 2.5%, 5%, and 7% arginine on the hardness, roughness, and cytotoxicity of 3M™ Transbond™ XT.

MATERIAL AND METHODS

A total of 48 samples were divided into four groups (n=12): G1 - commercial resin 3M™ Transbond™ XT (TXT); G2 - TXT+2.5% arginine; G3 - TXT+5% arginine; and G4 - TXT+7% arginine. The hardness analysis was performed by a microhardness tester. The measurements of roughness were performed by a surface roughness measuring instrument. The surface morphology analysis was analyzed by digital images obtained with a scanning electron microscope (SEM). For the in vitro cytotoxicity test, dental pulp mesenchymal cells underwent a cell viability reduction assay. For statistical analysis, ANOVA (one-way/two-way) was used, followed by Tukey's test post hoc (P<0.05).

RESULTS

There was a reduction in the hardness of experimental resins compared to 3M™ Transbond™ XT commercial resin (P < 0.05). There was no difference between concentrations of 2.5% and 5%, but there was the largest reduction in resin with 7% arginine (P < 0.05). Surface roughness analysis showed there was no statistical difference between the samples (P ≥ 0.05). SEM also did not demonstrate changes in the surface roughness of the resins. All groups exhibited good cell viability at each timepoint. After 48h, an increase was observed for groups contaning arginine (P < 0.05).

CONCLUSION

Surface hardness was modified with when arginine incorporation - to the Transbond™ XT resin formulation. No differences were observed for surface roughness. Due to the initial cytotoxicity of the resins, precautions regarding satisfactory photopolymerization and the distance of application in relation to the gingival tissues must be adopted.

Development of a smoking simulation machine to evaluate the effects of smoking on the color change of dental restorative materials

To develop a smoking simulation machine, the study evaluated the effects of conventional and electronic cigarette smoke on the color stability of resin-based composites. Two types of nanohybrid resin-based composites were divided into two groups based on the material and subgroups according to the kind of exposure: electronic cigarettes, conventional cigarettes, and control. The exposure was by using a newly developed smoking simulation machine, and color change was the primary outcome, measured with a spectrophotometer and calculated using ΔEab. The results showed significant differences in color change were observed between the groups and subgroups (p < 0.001). Specimens exposed to conventional cigarettes exhibited more significant discoloration compared to those exposed to electronic cigarettes and control. The custom-made machine demonstrated the ability to simulate smoking conditions and their effects on dental materials. The machine provides a standard and controlled method for evaluating smoke's effects on restorative materials, while not all materials exhibited similar reactions under the same smoking conditions. The machine impacts dental materials testing and accurately simulates the oral environment, providing insights into material performance that helps formulate materials that resist tobacco smoke, improve restoration durability with esthetics, enhance patient outcomes, and guide material selection.

Effect of polishing systems on the roughness, color, and staining of conventional and bulk-fill resin composites with and without S-PRG filler

OBJECTIVE

To evaluate the effect of polishing systems on the color and roughness of conventional and bulk-fill nanofilled resins, compared to conventional and bulk-fill nano-hybrid resins with S-PRG fillers.

MATERIALS AND METHODS

Discs (n = 12) were fabricated from the following resin composites: conventional nanofilled resin (Filtek Z350 XT, 3 M), bulk-fill nanofilled resin (Filtek One Bulk-Fill, 3 M), conventional nano-hybrid resin with S-PRG fillers (Beautifil II LS, Shofu), and bulk-fill nano-hybrid resin with S-PRG filler (Beautifil Bulk Restorative, Shofu). Polishing was conducted using multi-grit aluminum oxide abrasive discs (Sof-Lex Pop On, 3 M) or a single-grit aluminum oxide tip (OneGloss, Shofu). Roughness (Ra) and color (CIEL*a*b*, ΔEab and ΔE00) were assessed at baseline, post-polishing, and post-coffee staining. Surface micromorphology was analyzed using scanning electron microscopy (SEM).

RESULTS

Roughness increased after polishing with the aluminum oxide tip for all materials (p < 0.0001; Mann-Whitney). Bulk-fill nanofilled resin showed increased roughness, while conventional nano-hybrid resin with S-PRG filler showed decreased roughness after multi-grit disc polishing (p < 0.0001; Mann-Whitney). Coffee staining significantly increased the roughness in resin composites with S-PRG filler (p < 0.0001; Mann-Whitney). All resin composites exhibited reduced L* and b* (p < 0.05; generalized linear mixed models for repeated measures) and increased a* (p < 0.05; Friedman and Nemenyi) values after coffee staining. ΔEab and ΔE00 were significantly higher for bulk-fill nano-hybrid containing S-PRG filler, irrespective of polishing type (p < 0.0001; Friedman and Nemenyi). SEM analysis revealed surface degradation and/or particle loss in resin composites with S-PRG filler (conventional and bulk-fill) post-polishing. Single-grit polishing resulted in greater surface irregularities across all resins.

CONCLUSION

Polishing systems significantly influence resin composite roughness based on their composition, with single-grit polishing causing the highest roughness. Bulk-fill nano-hybrid resin composite with S-PRG filler exhibited the greatest color and roughness changes post-staining.

CLINICAL RELEVANCE

Bulk-fill resin composite with S-PRG filler demonstrated lower color and surface stability. Importantly, these changes were significantly mitigated when polished using a multi-stage polishing system.

Enhancing surface energy and characterizing optical properties of ultra-high translucency zirconia via an innovative heat treatment process

PURPOSE

Ultra-high translucency zirconia (UT-Zr) is known for its high esthetic quality; however, its inert surface results in low hydrophilicity and surface energy (SE). To address this limitation, this study proposes an innovative zirconia heat treatment process (ZHTP) and aims to evaluate the effects of ZHTP on the surface characteristics of UT-Zr, offering a novel and practical approach for surface pretreatment in dental practice.

MATERIAL AND METHODS

The plate-shaped UT-Zr samples were fabricated. After sintering, the samples without additional staining or polishing were divided into the following nine groups: NT (no additional pretreatment), AB (airborne-particle abrasion), PL (nonthermal plasma), PO (polishing), HPO (fine-polishing), NTH (treat with ZHTP), POPL (PL followed by PO), POH (ZHTP followed by PO), and HPOH (ZHTP followed by HPO). The surface roughness (Ra), microstructure, transmittance, glossiness, wettability, and SE of the samples (n = 10), and statistical analyses were conducted.

RESULTS

AB showed the highest Ra and lowest glossiness (P < 0.05), while HPO and HPOH yielded the smoothest surfaces, with HPOH achieving the highest glossiness (P < 0.05). Although the ZHTP approach slightly improved transmittance, it did not affect the microstructure. PO reduced hydrophilicity and SE (P < 0.05), and HPO slightly increased them. PL significantly enhanced both properties (P < 0.05), and ZHTP also increased them (P < 0.05) to levels similar to PL. Notably, hydrophilicity in nonthermal plasma and ZHTP-treated samples decreased similarly after 24 h.

CONCLUSIONS

The ZHTP approach enhances UT-Zr wettability and SE, with slight transmittance improvement. HPOH achieves hydrophilicity and SE comparable to PL, validating ZHTP as a promising strategy for UT-Zr surface optimization in dental applications.

Analysis of Mechanical Properties and Printing Orientation Influence of Composite Resin for 3D Printing Compared to Conventional Resin

This study aimed to compare the flexural strength, surface roughness, and microhardness of a resin for three-dimensional (3D) printing and a conventional composite resin and to evaluate whether the printing orientation influences these properties. To evaluate the flexural resistance, test specimens were produced and divided into four groups: three groups of resins for 3D printing with inclinations of 0°, 45°, and 90° and one group of conventional composite resin. Forty discs were produced and subjected to a sandpaper-polishing sequence, and the surface roughness was measured using a roughness meter. The Vickers microhardness (HV) test was performed at three different points, and the average was obtained. The results were subjected to ANOVA statistical analysis and Tukey's test. There were statistical differences in the flexural strength and microhardness between the conventional resin and the resin used for 3D printing. No statistical difference in surface roughness was observed. The resin for 3D printing exhibited lower flexural strength and microhardness than conventional composite resins. We concluded that the resin for 3D printing had lower flexural strength and HV than the conventional composite resin but similar surface roughness. The printing orientation did not affect the flexural strength, whereas the hardness increased as the printing angle increased.

A comparative study of polishing systems on optical properties and surface roughness of additively manufactured and conventional resin based composites

This study aimed to compare polishing systems on color stability, surface roughness, and gloss of additively manufactured permanent and conventional resin composites. Totally 250 disc specimens (6 mm*2 mm) were prepared from resin-based materials [G-ænial Posterior (GP), Clearfil Majesty Esthetic (CME), SonicFill-2 (SF), Tescera (Tes), and Crowntec (CT)]. Following baseline color (ΔE00), gloss (GU), and surface roughness (Ra) measurements, the specimens were randomly divided into 5 groups (n = 10/group) according to polishing systems: Control (mylar strips); OneGloss; OneGloss + Platina Hi-Gloss; OptiDisc; and OptiDisc + Platina Hi-Gloss. Specimens were immersed in coffee for 144 h following polishing. ΔE00, GU, and Ra measurements were repeated. Atomic force microscopy images were taken in all groups. Spearman's rho correlation coefficient, Robust ANOVA, and Bonferroni correction were used for statistical analysis. Significance level was taken as p < 0.050. Significant differences in ΔE00 values were found among resin-based materials, polishing systems, and their interactions (p < 0.001,p < 0.01, and p = 0.001). Regardless of polishing system, the lowest ΔE00 values were observed in CT, while lowest gloss (GU) values were found in Tes. The lowest surface roughness (Ra) values were detected at OptiDisc group (p < 0.001). A single type of polishing system may not be sufficient to achieve optimal results in resin-based materials.

Can wheel polishers improve surface properties and color stability of monochromatic resin composites?

BACKGROUND

To overcome the color layering procedure, monochromatic resin composites have been introduced. However, little is known about their polishability, gloss and color stability. This study aimed to investigate the surface roughness, gloss, and color change of monochromatic resin composites polished with wheel systems after being immersed in coffee.

MATERIALS AND METHODS

Omnichroma, Zenchroma, Essentia Universal, Charisma Diamond One and NeoSpectra ST were used to obtain 120-disc samples of 8 × 2 mm. Only one side of the sample was polished with Twist Dia (TWD) or Nova Twist (NOV). The samples were examined for surface roughness, gloss, and color (ΔE and ΔE00) before and after 7 days of immersion in coffee and subsequent repolishing. The discs were examined via SEM. Surface roughness and gloss values were analyzed using ANOVA, Tukey and Pearson correlation tests. ΔE and ΔE00 values were evaluated using T tests, multivariate ANOVA, and Dunnett's post-hoc tests.

RESULTS

For TWD groups, the smoothest material was Omnichroma (p < 0.05), while for NOV groups, it was Omnichroma and Zenchroma. Omnichroma was the glossiest, while Charisma Diamond One was the least glossy. In TWD groups, Charisma Diamond One and Essentia Universal were the most discolored, while Zenchroma and Omnichroma were the least. For NOV groups, Essentia Universal and Charisma Diamond One were the most discolored, while NeoSpectra ST, Omnichroma and Zenchroma were the least. After repolishing, Charisma Diamond One did not reach the level of ΔE < 2, while the other groups showed values below. Color evaluation with the CIELab and CIEDE2000 systems revealed similar results for the TWD groups after post-staining.

CONCLUSIONS

Smooth and glossy surfaces could be achieved with the wheel system regardless of the composite resin. Repolishing after discoloration ensures that the color recovery is below the acceptable limit. Color evaluations with CIELab and CIEDE2000 yielded similar results.

Three-year clinical performance of direct restorations using low-shrinkage Giomer vs. nano-hybrid resin composite

Objectives

The objective of this investigation was to compare the clinical performance of a nano-hybrid resin composite and a low-shrinkage Giomer resin composite.

Material and methods

In total, 35 pairs of restorations were performed using either low-shrinkage Giomer (Beautifil II LS, Shofu Inc.) or nano-hybrid (Clearfil Majesty Posterior) resin composite in 35 patients by two operators using the relevant adhesives, i.e., FL-Bond II (Shofu Inc.) and Clearfil SE Bond (Kuraray), with the self-etching technique according to each manufacturer's instructions. Two clinicians assessed the restorations 2 weeks (baseline); 6 months; and 1, 2, and 3 years after the restorative procedures using FDI (World Dental Federation) criteria (Scores 1-5). Data were analyzed using the marginal homogeneity and McNemar tests. The survival rate was calculated using Kaplan-Meier survival analysis and the survival of the two groups was compared with the log-rank test (p = 0.05).

Results

The mean observation period was 37.7 ± 6.8 months. All restorations completed their 3-year follow-up. The criteria were mainly rated with high (1 or 2) scores for quality in both groups. Only one restoration in the low-shrinkage Giomer resin composite group was accepted as a failure at the 2-year recall due to retention loss.

Conclusion

At the 3-year follow-up, the performance of the restorations using the Giomer and the nano-hybrid resin composite were similar and clinically acceptable.

Clinical relevance

The low-shrinkage Giomer resin composite exhibited a similar clinical performance to the nano-hybrid resin composite after 3 years in service with both materials displaying minor surface deteriorations at the 3-year recall.

Clinical Trial Registration

https://clinicaltrials.gov, identifier: NCT02823769.

Awareness of possible complications associated with direct composite restorations: A multinational survey among dentists from 13 countries with meta-analysis

OBJECTIVES

Resin-based composites (RBCs) evolved into favoured materials for teeth restorations, marking a significant change in dental practice. Despite many advantages, RBCs exhibit various limitations in their physical and chemical properties. Therefore, we assessed the dentists' awareness of possible complications after direct composite restorations and their opinions about this material.

METHODS

The online questionnaire was created in English in May 2023. A 16-item survey was dedicated to general dentists and specialists. The first section included four questions related to demographic characteristics. The second section comprised twelve questions and focused on awareness of potential side effects of composite restorations, the most crucial advantages and disadvantages of composite resins, and the frequency of experienced clinical complications after the application of composite materials.

RESULTS

A total of 1830 dentists from 13 countries took part in the survey. Dentists most often declared awareness of low adhesion to the dentine (77.5 %) and, most rarely, solubility in oral fluids (42.6 %). Aesthetics was identified as the main advantage of composite fillings (79 %), followed by the possibility of repair (59 %) and adhesion to enamel (57 %). Polymerisation shrinkage was a major disadvantage for most countries (70 % overall). Analysing the declared potential clinical complications for all countries, statistically significant findings were obtained for marginal discolouration (OR=2.982, 95 % CI: 1.321-6.730, p-value=0.009) and borderline significance for secondary caries (OR=1.814, 95 % CI: 0.964-3.415, p-value=0.065).

CONCLUSIONS

Dentists value aesthetics and repairability but are aware of shrinkage and experience discolouration. The issue of toxicity and solubility seems to be the least known to dentists.

CLINICAL SIGNIFICANCE

Dentists should use RBCs with critical caution due to possible side effects. Despite the undoubted aesthetics of direct composite restorations, it is necessary to remember potential clinical complications such as marginal discolouration or secondary caries.

In vitro comparison of one-step, two-step, and three-step polishing systems on the surface roughness and gloss of different resin composites

OBJECTIVES

This laboratory study evaluated the effect of three polishing systems on the surface roughness and gloss of resin composites.

MATERIALS AND METHODS

Thirty specimens (6 mm Ø × 8 mm) were fabricated from each of three resin composites: Z 350 XT (nanofill), Harmonize (nanohybrid), and Estelite Omega (supranonofill). All specimens were photopolymerized using a multi-peak LED curing unit (VALO-Standard mode), having a exitance irradiance of approximately 1000 mW/cm2 against a polyester strip (PS). 2 mm was then removed from the irradiated end (finished) using #320 abrasive paper (F). Specimens were then randomly polished (P) using a one-step (1S) (OneGloss), two-step (2S) (EVE Diacomp Twist Basic CA), or 3-step (3S) (Astropol P) system (n = 10). For PS, F, and P groups, surface roughness (Ra) was measured using a surface roughness tester, and surface gloss was measured with a glossmeter. For each specimen, the percent recovery to the PS value (%R) of surface roughness and surface gloss were calculated. Data were analyzed using two-way ANOVA, followed by Tukey's test. Surface roughness and gloss values were submitted to Pearson's correlation test (α = 0.05). All statistical testing was performed using a pre-set alpha of 0.05.

RESULTS

The interaction term [resin composite × polishing system] was significant for both surface roughness (p = 0.001) and gloss (p = 0.0001). For all resin composites, the 2S and 3S systems provided a higher %R of surface roughness and gloss compared to those of the 1S system. There was a negative correlation between surface roughness and gloss, but only a few combinations showed strong correlations.

CONCLUSIONS

The 2S and 3S polishing systems provided surfaces having greater smoothness and gloss compared to the 1S system. The ability to recover surface roughness and gloss was dependent on type of resin composite filler classification.

CLINICAL SIGNIFICANCE

The 3S and 2S polishing systems were more effective in achieving PS values than was the 1S system for all tested resin composites. However, individual polishing systems performed differently depending on type of resin composite.