Translucency of human dental enamel

Validation of the pink esthetic score/white esthetic score at single tooth-supported prostheses in the esthetic zone: A randomized clinical trial

OBJECTIVES

To validate the reproducibility and inter/intra-observer variability of the Pink Esthetic Score/White Esthetic Score (PES/WES) of single tooth-supported prostheses in the maxillary esthetic zone (13-23).

MATERIALS AND METHODS

Forty-five patients were randomly assigned to one of the three treatment options (15 patients per group) receiving each one a different crown type: Porcelain fused to metal (PFM), monolithic zirconia, and lithium disilicate. Eight observers from each of four different specialties (Prosthodontists, Orthodontists, Periodontists, and Oral Surgeons) were recruited and assessed twice and four weeks apart (i.e., T1 and T2) 45 photographs of the single tooth-supported prosthesis using PES/WES and compared them with contralateral teeth.

RESULTS

According to the ANOVA and post hoc tests, the zirconia crown type obtained the highest mean score by all observers, with a mean value of 16.70 ± 2.94. The prosthodontists and oral surgeons assigned the lowest mean score to PFM crowns, 13.03 ± 3.47 and 13.80 ± 3.17, respectively. Notably, the prosthodontists awarded the highest scores, specifically 17.50 ± 2.81 for the zirconia crowns. Intraobserver agreement was calculated utilizing the paired t-test. Pairwise comparisons between observers of different specialties revealed significant intraobserver agreement. Interclass correlation coefficient (ICC) scores were statistically significant among four specialties. No difference was detected concerning the interobserver agreement.

CONCLUSIONS

The PES/WES index remains consistent across various observers from different specializations, yielding uniform results in the overall esthetic evaluation. Consequently, in light of the presented preliminary positive results, its use might also be considered for the esthetic assessment of single-tooth-supported prostheses.

CLINICAL SIGNIFICANCE

The PES/WES index may be employed clinically to evaluate single tooth-supported prostheses as it emerged as a reproducible esthetic scoring system.

Color and translucency of enamel in vital maxillary central incisors

STATEMENT OF PROBLEM

Limited data, especially in vivo data, exist regarding translucency parameter (TP) values for vital anterior nonrestored dentition. Additionally, published information on the CIELab values of vital enamel at a theoretical infinite thickness is lacking. Obtaining TP and CIELab values in a population that varies in terms of ethnicity, age, and sex would be useful to inform the development and placement of esthetic dental restorations that more accurately capture the complex optical qualities of enamel.

PURPOSE

The purpose of this clinical study was to investigate in vivo the TP and CIELab values of vital anterior incisor enamel at a theoretical infinite thickness in a diverse pool of participants who varied in age, ethnicity, and sex.

MATERIAL AND METHODS

Spectral reflectance measurements (380 to 780 nm at 2-nm intervals) of the mid-incisal region of vital, unrestored maxillary anterior teeth were made in 120 participants, equally divided into 2 sexes, 4 racial or ethnic groups, and 5 age ranges. Instruments were oriented to achieve 0-degree observation and 45-degree illumination, and spectral measurements were made with white and black silicone backgrounds. Reflectance spectra of the incisal enamel from both the black and white silicone backing were used to fit to the Kubelka-Munk (K-M) reflectance theory. The CIEDE2000 color difference formula was used to determine TP, and data were compared among participant demographics. CIELab color coordinate values for enamel at an infinite thickness were calculated by using a D65 illumination and CIE standard human (2-degree) observer. To determine value ranges and significant differences among participant groups, CIELab values were analyzed with a 4-way ANOVA, and TP values were analyzed with a generalized linear mixed model. Pairwise comparisons of interest were evaluated with Bonferroni-corrected Student t tests.

RESULTS

For maxillary central incisor enamel, the average TP was 10.1 ±3.6, and the average CIELab color coordinates were L∗=73.5 ±7.6, a∗=2.2 ±1.8, b∗=11.9 ±8.4. TP values of incisal enamel significantly differed among specific age and ethnic groups, with general significant interactions of age and sex (P=.009), as well as ethnicity and age (P=.042). CIE color coordinates of enamel at an infinite thickness were found in the L∗ coordinate among different age groups with the same sex and ethnicity, specifically when comparing CIELab direction with the population characteristics of age (P=.011) and the interaction between age, sex, and ethnicity (P=.035).

CONCLUSIONS

In vivo L∗ values and TP values of incisal enamel differed significantly among groups determined by ethnicity, age, and sex.

Does irradiation of the tooth structure interfere with oxygen saturation measured by pulse oximetry?-An ex vivo laboratorial study

The effect of tooth structure subjected to ionising radiation on oxygen saturation levels (SpO2 ) measured by pulse oximetry was investigated. Fifty-four extracted human third molars were sectioned mesiodistally. Pulse oximeter diodes were placed in prefabricated silicone moulds, secured on a vise with tooth surfaces placed between the diodes and the participant's finger, and SpO2 levels were measured. After that, the tooth surfaces were subjected to ionising radiation in fractionated doses of up to 70 Gy, and SpO2 was measured according to the protocol described. The Kolmogorov-Smirnov test was used for the analysis of normality of the quantitative variables, and Student's t-test compared mean SpO2 levels before and after irradiation. Mean SpO2 after irradiation was 94.6 ± 0.9%, without a statistically significant difference from SpO2 before irradiation, which was 94.7 ± 0.6%. Irradiation of the tooth structure did not interfere with SpO2 levels measured by pulse oximetry.

"Enamel layering" using double-layered enamel-shade resin composites: The strategy to simulate the optical characteristics of human enamel

OBJECTIVE

To evaluate the optical match between enamel and resin composites fabricated using mono-layered and double-layered techniques.

MATERIALS AND METHODS

Enamel slabs were prepared from human upper incisors and canines. Mono-layered composite replicas were prepared from seven Filtek Z350XT and Estelite Sigma shades using silicone molds prepared from the respective enamel surfaces. Translucent and enamel shades (A2 or A3) of the two materials were produced from incisor molds for double-layered replicas, and the groups with the best results underwent accelerated aging. Spectrophotometric evaluation was performed using CIE color system. The differences in translucency (ΔTP) and color (ΔE00 ) between the enamel and paired composite replicas were calculated and analyzed using parametric statistics (α = 0.05).

RESULTS

For the mono-layered composites, white enamel and translucent shades of Filtek yielded the lowest ΔTP for canines (4.6) and incisors (8.9), respectively. The ΔE00 of mono-layered replicas ranged from 5.1 to 11.8. Double-layered Filtek replicas displayed a better 1-day optical match with the lowest ΔTP (3.4-4.0) and ΔE00 (4.2-4.6), irrespective of each layer's thickness.

CONCLUSIONS

For canines, the lowest ΔTP of Filtek white enamel was close to the acceptable threshold (4.43). For incisors, the thicker translucent double-layered Filtek composites demonstrated the greatest optical match before and after aging.

CLINICAL SIGNIFICANCE

Upper incisors and canines have distinct enamel optical properties. Enamel layering using specific double-layered resin composites could achieve a better optical match with upper incisor enamel.

Performance of two-flux and four-flux models for predicting the spectral reflectance and transmittance factors of flowable dental resin composites

OBJECTIVE

To evaluate the prediction accuracy of the Kubelka-Munk Reflectance Theory and other more innovative two-flux and four-flux models for predicting the reflectance and transmittance factors of two flowable dental resin composites of various thicknesses within clinically acceptable color difference.

METHODS

Cylindrical samples of Aura Easy Flow resin composite (Ae1, Ae2, Ae3, Ae4 shades) and Estelite Universal Flow SuperLow resin composite (A1, A2, A3, A3.5, A4, A5 shades) were prepared with thicknesses ranging from 0.3 mm to 1.8 mm. Their reflectance and transmittance factors were measured with a spectrophotometer based on an integrating sphere, and were also predicted by 3 different two-flux models and 2 different four-flux models. The accuracy of reflectance and transmittance factor predictions was assessed using the CIEDE2000 color distance metric and 50:50% acceptability and perceptibility threshold criteria.

RESULTS

Eymard's four-flux model is found to be the most accurate for predicting the spectral reflectance and transmittance factors, with 85% (resp. 100%) of all color deviations below the acceptability threshold, and below the perceptibility threshold for 40% (resp. 57%) of the samples with thickness ranging from 0.3 to 1.8 mm in reflectance (resp. transmittance) mode. The Kubelka-Munk Reflectance Theory is found to be the least accurate model for predicting the spectral reflectance and transmittance factors of dental resin of thickness ranging from 0.3 to 1.8 mm.

SIGNIFICANCE

Eymard's four-flux model enables to predict the color of slices of dental materials within acceptable color differences. Eymard's four-flux model's optical parameters thus describe light-matter interactions in dental materials more accurately than state of the art Kubelka-Munk Reflectance Theory.

Tooth Shade and Blood Type: A Descriptive Cross-sectional Study in Tunisia

AIM

The aim of the study was to assess the prevalence of tooth shade and its correlation with blood type.

MATERIALS AND METHODS

This study analyzed 312 blood donors at the university Hospital in Monastir between November 2021 and June 2022. Both male and female subjects were included, with ages ranging from 18 to 60 years old. Patients with certain dental conditions or habits were excluded from the study. The study recorded various information about blood donors, including gender, age, governorate of origin, tooth shade, and blood type. The tooth shade values were recorded using A-D shade guide. Data input and tabulation were carried out using Microsoft Excel 2016 and SPSS (version 25.0).

RESULTS

The study included 312 participants, with 85.58% males and 14.42% females. Tooth shade value B was the most prevalent (43%), and D was the least prevalent (7%). The statistical analysis showed that there was no significant link between tooth shade and blood type. However, there were three statistically significant categories: Blood type B/Tooth shade B, Blood type O/Tooth shade C, and Blood Type O/Tooth shade D.

CONCLUSION

The study examined the link between tooth color and blood type but did not find a significant link. However, significant values were found in different subgroups. A wider selection of subjects and a more rigorous measurement equipment might lead to more favorable results.

CLINICAL SIGNIFICANCE

By considering the patient's blood type alongside other relevant factors, clinicians can enhance the accuracy and precision of tooth shade selection, resulting in harmonious and natural-looking dental restorations. This approach improves patient satisfaction and acceptance.

Analysis of Dental Enamel Remineralization: A Systematic Review of Technique Comparisons

The demineralization process conditions the structure of the enamel and begins with a superficial decalcification procedure that makes the enamel surface porous and gives it a chalky appearance. White spot lesions (WSLs) are the first clinical sign that can be appreciated before caries evolves into cavitated lesions. The years of research have led to the testing of several remineralization techniques. This study's objective is to investigate and assess the various methods for remineralizing enamel. The dental enamel remineralization techniques have been evaluated. A literature search on PubMed, Scopus, and Web of Science was performed. After screening, identification, and eligibility processes 17 papers were selected for the qualitative analysis. This systematic review identified several materials that, whether used singly or in combination, can be effective in the process of remineralizing enamel. All methods have a potential for remineralization when they come into contact with tooth enamel surfaces that have early-stage caries (white spot lesions). From the studies conducted in the test, all of the substances used to which fluoride has been added contribute to remineralization. It is believed that by developing and researching new remineralization techniques, this process might develop even more successfully.

Does Age Have a Role in Color and Whiteness Variations After Dehydration and Rehydration in Maxillary Anterior Teeth? An In Vivo Study

OBJECTIVE

To determine the influence of in vivo dehydration and rehydration on color and whiteness variations in maxillary anterior teeth of younger, middle-aged, and older individuals.

METHODS AND MATERIALS

The spectrophotometric shade of maxillary anterior teeth from younger (20 to 30 years, n=20), middle-aged (50 to 60 years, n=20) and older (65 to 80 years, n=20) participants were assessed at baseline and every 10 minutes for 30 minutes after rubber dam isolation (dehydration). The teeth were then allowed to rehydrate, and shade values were assessed every 10 minutes for 30 minutes, after 24 hours, and after 48 hours. Data were collected as International Commission on Illumination (CIE) L*a*b* color coordinates. Color differences (ΔE*ab) and whiteness differences (ΔWID) were evaluated. Statistical analysis was performed using one-way analysis of variance with the Tukey Honest Significant Difference test.

RESULTS

The color and whiteness changes of maxillary anterior teeth in older individuals after dehydration for 30 minutes were significantly lower than that of younger and middle-aged individuals. In younger participants, after 10 minutes of dehydration, mean ΔE*ab values of maxillary anterior teeth were above the acceptability threshold (AT), while mean ΔWID values were above AT only in maxillary canines. In middle-aged participants, mean ΔE*ab values were above AT, and mean ΔWID values were above the perceptibility threshold (PT) and below AT after 10 minutes of dehydration. In older participants, mean ΔE*ab values were above PT and below AT at 20 minutes of dehydration, while mean ΔWID values were above PT at 10 minutes of dehydration, and both were above AT at 30 minutes of dehydration. The mean ΔE*ab values were above AT after 20 minutes of rehydration in younger and middle-aged participants, while they were below AT in older participants after 10 minutes of rehydration. Mean ΔWID values were below AT for older participants after 20 minutes of rehydration. All mean ΔWID values were below AT and above PT after 30 minutes of rehydration except central incisors of younger participants. After 24 hours of rehydration, mean ΔE*ab and mean ΔWID values of participants in all age groups were below AT. After 48 hours of rehydration, mean ΔE*ab and ΔWID values of participants in all age groups were below PT except mean ΔE*ab values of canines and mean ΔWID values of central incisors in younger participants. L*, a*, and b* values were significantly different between age groups at 30 minutes of dehydration and after 48 hours of rehydration (p<0.05).

CONCLUSION

Color and whiteness changes due to dehydration were less pronounced in older participants. Dehydration for 10 minutes in most maxillary anterior teeth of younger and middle-aged participants led to perceptible and clinically unacceptable color and whiteness changes. Maxillary anterior teeth of older participants showed color and whiteness changes that were perceptible at 10 minutes of dehydration but clinically acceptable up to 30 minutes of dehydration. After 30 minutes of dehydration, a 10- and 20-minute rehydration was needed, respectively, for color and whiteness changes to be clinically acceptable in maxillary anterior teeth of older individuals, while a 30-minute rehydration was recommended for the middle aged group and for maxillary laterals and canines of the younger group. Color and whiteness changes in most maxillary anterior teeth were imperceptible only after 48 hours of rehydration.

Effects of shade and thickness on the translucency parameter of anatomic-contour zirconia, transmitted light intensity, and degree of conversion of the resin cement

STATEMENT OF PROBLEM

Anatomic-contour zirconia prostheses are usually cemented with resin cement. However, information regarding the effects of the zirconia shade and thicknesses on the translucency of the prosthesis, the intensity of the transmitted light beneath the prosthesis, and the subsequent degree of conversion in the resin cement is sparse.

PURPOSE

The purpose of this in vitro study was to investigate the translucency parameter in 3 anatomic-contour zirconia specimens of 2 shades at 5 different thicknesses and to investigate the transmitted light intensity and degree of conversion of the resin cement beneath the ceramic specimens by using a traditional zirconia and a lithium disilicate glass-ceramic as controls.

MATERIAL AND METHODS

Ceramic specimens from 1 anatomic-contour zirconia in a generic shade (CAP FZ) and 2 anatomic-contour zirconias in A2 shade (Zirlux and Luxisse) were used. Lithium disilicate in HT A2 shade (IPS e.max CAD) and traditional zirconia in a generic shade (CAP QZ) were used as controls. A total of 125 ceramic specimens (n=25) were fabricated to a final specimen dimension of 12×12 mm and in thicknesses of 1.0, 1.25, 1.5, 1.75, and 2.0 mm according to the manufacturers' recommendations. The CIELab color space for all specimens placed against a white and black background was measured with a spectrophotometer (CM-2600D), and the translucency parameters were calculated for the materials at various thicknesses. A light-polymerizing unit (DEMI LED) was used to polymerize the resin cement (Variolink II) placed beneath the ceramic specimens. Transmitted light intensity from the polymerization unit beneath the ceramic specimens was measured by using a spectrophotometer (MARC Resin Calibrator), and the transmittance of each specimen was calculated. The coefficient of absorption of each material was calculated from the regression analysis between the natural log of transmittance and specimen thickness. The degree of conversion of resin cement was measured by using a Fourier transformation infrared (FTIR) spectrophotometer. The results were analyzed by using 2-way ANOVA (α=.05). The relationship between the transmittance and the translucency parameter was evaluated by plotting the transmittance against the translucency parameter value of each specimen.

RESULTS

The translucency parameter decreased with increasing thickness in all 5 material groups. All anatomic-contour zirconia had lower translucency parameters than e.max CAD (P<.001). The same results were found for the intensity of the transmitted light (P<.001). Both A2 shade anatomic-contour zirconia (Zirlux and Luxisse) showed significantly lower light transmittance than a generic shade anatomic-contour zirconia (CAP FZ) (P<.001). The coefficients of absorption were found to range from 0.63 to 1.72 mm^-1, and reflectance from 0.10 to 0.25. The results from the degree of conversion of resin cement after polymerization through 1 to 2 mm of specimens showed a significantly higher degree of conversion in the e.max group than in all other groups (P<.001). The correlation between translucency parameter and the intensity of the transmitted light suggested that the relationship was shade dependent.

CONCLUSIONS

The translucency parameter and the transmitted light intensity of ceramic material were influenced by the type of ceramic and the shade and thickness of the ceramic. The combined effects of layer thickness and the intensity of the transmitted light in the A2 shade anatomic-contour zirconia (Zirlux and Luxisse) resulted in a lower degree of conversion in resin cement than in a generic shade anatomic-contour zirconia (CAP FZ) at layer thicknesses of 1.75 and 2 mm.

Tooth Shade Relationship with Age, Gender, and Skin Color in a Saudi Population: A Cross-Sectional Study

Objectives: The aim of this study was to assess the relationship between tooth shade among different groups of patients according to their age, gender, and skin color in a Saudi population. Materials and methods: Participants were divided based on age into Group 1 (10–20 years), Group 2 (21–30 years), Group 3 (31–40 years), and Group 4 (41+ years), and according to gender. Tooth shade was measured by Vita easyshade, Shade scanner, 3D Master shade system. The skin color was determined according to the Firzpatrick Scale. It consists of six shades, namely: I, II, III, IV, V, and VI. The skin complexion of the participants was divided into six categories: white/very fair, fair, light brown, moderate brown, dark brown, and black. Results: One hundred and ninety-eight individuals were recruited. Around 70% were males. Females had 25.4% A2 followed by 22% A1, and 22% A3 shade types, while males had B3 shade (18%) followed by A2 and A3 (15.8%). A statistically significant difference was observed between shade and gender (p < 0.05). A statistically significant difference was observed between shade and age group (p < 0.05), where increased age was correlated with darker teeth shades. Shade A1 was correlated with type I skin color in 57.1% of individuals. Skin color type II had A2 as a dominant shade by 34.1%. A2 and A3 shades were equally observed in skin color III by 20.3%. Overall, statistically significant differences were observed between shade and skin color groups (p < 0.05). Conclusions: In conclusion, the most frequent classical shade noted among male and female participants was shade type A, which represents reddish brownish. Group 2 (21–30 years) had the B3 shade as the most prominent shade type among age groups. Gender, age, and skin types all showed a significant relation with the tooth shade.

Influence of restorative material translucency on the chameleon effect

Blending of artificial restoration materials to the natural tooth is challenging. Beyond just color, optical properties, particularly translucency, substantially influence the final appearance. The more chameleon effect that the restorative materials exhibit, the more natural looking restorations. The purpose of this study is to investigate the influence of restorative material translucency on the chameleon effect. Five types of resin composite in three different shades as well as one shade of conventional glass ionomer cement were fabricated into disks. To analyze the chameleon effect, glass ceramic blocks were milled to create four wells in each block. The restorative materials were filled into the wells. The color was measured with CIE L*a*b* every 6 months. Statistical analysis was conducted using Two-Way Repeated Measures ANOVA. The material with the highest translucency was flowable resin composite. The high translucency materials exhibited an immediate chameleon effect, as did the bulk-fill resin composites, which are low translucency. Both high and low translucency materials exhibited a delayed chameleon effect for 3 years, except for the bulk fill resin composites. The translucency of the restorative materials had a 68% positive correlation with their chameleon effect. The age of the restoration is one important factor influencing the color blending.

The Effect of Different Light Curing units and Tip Distances on Translucency Parameters of Bulk Fill Materials

Objectives

To evaluate the effect of light curing unit (LCU) types and distance from light curing unit tip on the translucency parameters (TP) of bulk fill composite materials.

Materials and Methods

Two bulk-fill resin composites and one nanohybrid composite were used in this study. The specimens were divided into groups based on the type of curing unit used, and further subdivided based on the distance of the curing source to the surface of the resin composite. Translucency was evaluated at 4 mm thickness (for the bulk-fill) and 2 mm thickness (for nanohybrid) after curing using two different light curing units at zero, 2 mm, and 4 mm distance. The results were analyzed using two-way ANOVA at the significance level of a p-value of < 0.05.

Results

Among all the tested materials, Filtek Bulk Fill Posterior RBC showed the highest TP at 0 mm distance when cured with Blue phase G2 LED LCU and it was the least affected by the differences in distances. However, Filtek Z350 nanohybrid composite had no significant differences between the three distances when cured with Blue phase G2 LCU.

Conclusion

Translucency values among the studied bulk-fill materials are affected by material composition, curing units and the distance of the tip of the light source to the restoration surface.

Comparison of optical and crystal properties of three translucent yttria-stabilized tetragonal zirconia polycrystals with those of lithium disilicate glass-ceramic material

Background/purpose

Among the ceramic materials used for all-ceramic crowns, zirconia has high biocompatibility and favorable mechanical properties, but its main drawbacks include low translucency and stress-induced phase transformation. To stabilize high-strength tetragonal zirconia polycrystal (TZP), 3–5 mol% yttria is usually added to prepare yttria-stabilized TZP (Y-TZP). In this study, the optical properties of three commercial Y-TZP ceramics were compared with those of the clinically available glass-ceramic material of lithium disilicate, and the relationship between translucency and crystal properties was analyzed in vitro.

Materials and methods

Twelve 5-mm-thick standardized disks were prepared from three Y-TZP ceramics and one lithium disilicate block. Absolute translucency was measured using a spectrophotometer with an integrating sphere. X-ray diffraction was used to quantify the main structural parameters (i.e., preferred plane, quantitative phase, and grain size) of Y-TZP crystals.

Results

The product-dominated phase of Y-TZP exhibited a tetragonal lattice pattern, and the preferred planes had minor variations. The diffraction patterns of the three Y-TZP ceramics demonstrated minor effects on translucency, without significant differences (p > 0.05). The grain size of 54–70 nm was negatively related to translucency in Y-TZP. Lithium disilicate specimens had significantly higher translucency than the three Y-TZP specimens (p < 0.001).

Conclusion

Grain size reduction played an essential role in developing highly translucent Y-TZP ceramics. The three Y-TZP ceramics were essentially opaque but exhibited poorer translucency than lithium disilicate in terms of esthetics.

Objective shade matching, communication, and reproduction by combining dental photography and numeric shade quantification

OBJECTIVE

The subject of this case report is the application of a newly developed workflow for objective shade communication sans visual shade assessment or the use of shade guides.

CLINICAL CONSIDERATIONS

Clinical complications stemming from issues relating to esthetic integration can present a burden on the restorative team, often resulting in strenuous relationships among its members. The faithful imitation of the optical appearance of dental hard tissues with direct- and indirect restorations has been at the center of interest in a great number of publications from the realm of esthetic dentistry over the past 40 years. The present report describes a new approach to objective shade communication, by transcending the role of dental photography from its purely descriptive purpose to the level of quantification, thus abandoning the use of the established shading regimes and replacing them with a patient personal shade recipe based on the CIELAB color space instead.

CONCLUSIONS

Objective shade communication is possible with the eLAB system by combining numeric shade quantification with dental photography.

CLINICAL SIGNIFICANCE

The eLAB system presents a viable alternative to the traditional approach to shade communication and shade matching in dentistry.

A Comparative Study of Light Transmission by Various Dental Restorative Materials and the Tooth Structure

CLINICAL RELEVANCE

Light transmission through dental materials and tooth structure has direct clinical implication on such factors as selecting an appropriate curing technique during a restorative process.

SUMMARY

Clinical effects of dehydration on tooth color: How much and how long?

OBJECTIVE

To evaluate effects of dehydration on tooth color determine whether color returns to baseline after 30 min or 24 h.

MATERIALS AND METHODS

Thirty participants with intact maxillary central and lateral incisors were recruited for the study. Color measurements were performed with a spectrophotometer (SpectroShade Micro) at baseline and at 10, 20, and 30 min of dehydration, as well as 30 min and 24 h of rehydration. CIEDE2000 color parameters were used to calculate color difference. The data were analyzed for color changes over time by repeated-measures analysis of variance (ANOVA), and the Bonferroni-Tukey test was used for post-ANOVA comparisons (P < .05).

RESULTS

After 30 min of dehydration, all the tested teeth were above the perceptibility threshold (ΔE₀₀ = 0.8), and 85% of the teeth were above the acceptability threshold (ΔE₀₀ = 1.8). After 30 min of rehydration, 78.3% of the tested teeth were above the perceptibility threshold, and 31.6% of the teeth were above the acceptability threshold. After 24 h of rehydration, 99.2% of the teeth were below the acceptability threshold, and 90% of the values were below the perceptibility threshold.

CONCLUSIONS

Thirty-minute tooth dehydration can result in a clinically significant color change. After a 24-h rehydration period, reliable color assessment can be performed.

CLINICAL SIGNIFICANCE

Tooth dehydration causes significant color change, thus assessment of final color or clinical success should be considered after tooth rehydration for esthetic restorations and tooth bleaching.

A Pilot Study About the Effect of Laser-Induced Fluorescence on Color and Translucency of Human Enamel During Tooth Bleaching

Objective: To probe into the effect of laser-induced fluorescence (LIF) on color and translucency of human enamel during tooth bleaching. Materials and methods: Twenty enamel slabs were randomly assigned to be whitened by acidic 30% hydrogen peroxide (HP), neutral 30% HP, alkaline 30% HP, and distilled water, respectively, monitored by a colorimeter and Raman spectrometer simultaneously. Afterward, the parameter differences of color, translucency, Raman relative intensity, and LIF intensity between baseline and post-treatment of each bleaching cycle were calculated. Results: The results demonstrated that the three bleaching groups resulted in increasingly prominent whitening outcome over time compared with control group, and no statistical difference was detected between them. Accordingly, the bleaching groups also engendered a same decrease tendency in fluorescence intensity (FI). However, less demineralization effect occurred on the enamel surface in neutral HP group. The correlation analysis further excluded the effect of demineralization on all the optical parameters (p > 0.05). Besides, various degrees of dependency were detected between FI and translucency parameter (TP), masking effect (ME), C*ab, W*, b*. In addition, ΔFI was associated with parameters of ΔC*ab, ΔW*, Δb*, ΔE, Δa*, and ΔME. ΔFI% was correlated with ΔC*ab, Δb*, ΔW*, and ΔE values. Conclusions: Thirty percent HP with different pH values could result in same variation tendency of enamel color, translucency, and FI. Plus, FI showed a strong association with enamel color and translucency alteration, which is promising for future application as a nondestructive testing method to evaluate bleaching effect and might be a novel way to investigate tooth bleaching mechanism.

Effect of Thermocycling, Surface Treatments and Microstructure on the Optical Properties and Roughness of CAD-CAM and Heat-Pressed Glass Ceramics

Dental ceramic restorations are widely spread nowadays due to their aesthetics and biocompatibility. In time, the colour and structure of these ceramic materials can be altered by aging processes. How does artificial aging affect the optical and surface roughness of ceramics? This study aims to assess the effect of thermocycling, surface treatments and microstructure upon translucency, opalescence and surface roughness on CAD-CAM and heat-pressed glass-ceramic. Forty-eight samples (1.5 mm thickness) were fabricated from six types of A2 MT ceramic: heat-pressed and milled glass-ceramic (feldspathic, lithium disilicate and zirconia reinforced lithium silicate). The samples were obtained respecting the manufacturer’s instructions. The resulted surfaces (n = 96) were half glazed and half polished. The samples were subjected to thermocycling (10,000 cycles) and roughness values (Ra and Rz), colour coordinates (L*, a*, b*) and microstructural analyses were assessed before and after thermocycling. Translucency (TP) and opalescence (OP) were calculated. Values were statistically analysed using ANOVA test (one way). TP and OP values were significantly different between heat-pressed and milled ceramics before and also after thermocycling (p < 0.001). Surface treatments (glazing and polishing) had a significant effect on TP and OP and surface roughness (p < 0.05). The heat-pressed and milled zirconia reinforced lithium silicate glass-ceramic experienced a loss in TP and OP. Ra and Rz increased for the glazed samples, TP and OP decreased for all the samples after thermocycling. Microstructural analyse revealed that glazed surfaces were more affected by the thermocycling and especially for the zirconia reinforced lithium silicate ceramic. Optical properties and surface roughness of the chosen ceramic materials were affected by thermocycling, surface treatments and microstructural differences. The least affected of the ceramics was the lithium disilicate ceramic heat-pressed polished and glazed.

Improving 3D photogrammetry models through spectral imaging: Tooth enamel as a case study

Reflective or translucent materials are a challenge to digitize in 3D. Results are better with a matt coating although objects from museum collections are often too fragile or too valuable to be treated in this way. It is therefore essential that alternative solutions are found. This study analyzed spectral photogrammetry as a possible solution. Spectral photogrammetry is an emerging technique which uses images at different wavelengths to create 3D models. Tooth enamel is a challenging material to digitize. Six sets of teeth were photographed at different wavelengths. The results showed that the quality of the models enamels parts improved when taken with ultraviolet wavelengths whilst models were less accurate when photogrammetry was performed with the red and infrared spectrum. This can be explained by the optical properties of enamel. This study demonstrates that knowing the optical properties of a material beforehand could help future photogrammetric digitization of challenging materials.

Effects of Light Attenuation through Dental Tissues on Cure Depth of Composite Resins

Objective

Polymerization of light-cured resin-based materials is well documented; however, the intensity of the activating light can be reduced by passage through air, dental structure, or restoration compromising the physical properties of the restoration. The aim of this study was to evaluate the depth of cure of different light cured composite resins polymerized directly or transdental, through enamel and enamel/dentin tissues.

Material and methods

Five composite resins were selected for this experiment: SureFil SDR, Dentsply (SDR), Filtek Supreme Plus, 3M ESPE (FSP), Aelite LS, Bisco (ALS), Filtek LS, 3M ESPE (FLS), and TPH, Dentsply (TPH). Thirty specimens of each material were prepared with 2- or 4-mm thickness. The specimens were light-cured (Elipar 2500, 3M ESPE) for 40 sec using three different protocols: direct or transdental, through a disc of enamel with 1 mm of thickness, and a disc of enamel and dentin with 2 mm of thickness. Eight Vickers microhardness (VH) measurements were taken from each specimen, four on top and four on bottom surface (Micromet, Buehler, 100 g per 15 sec). Data was analyzed with ANOVA three-way, Tukey HSD post-hoc (α = .05).

Results

Bottom surfaces of specimens exhibited statistically significant lower Vickers microhardness than the top surfaces for all composite resin evaluated, regardless of the curing conditions, except for the SDR when direct light-cured. Transdental light curing through enamel/dentin layer, significantly decreased VH (P<0.05) on the bottom surface of all composite groups.

Conclusion

The results of this study showed that light-curing attenuation of dental structures negatively affect the micro-hardness of composite resins.

Effect of a coating material containing surface reaction-type pre-reacted glass-ionomer filler on prevention of primary enamel demineralization detected by optical coherence tomography

We used optical coherence tomography to examine the effect of a coating material containing surface reaction-type pre-reacted glass-ionomer (S-PRG) filler on primary enamel demineralization in 18 extracted human primary teeth. The pulp was removed, and each tooth was ultrasonically cleaned with distilled water. Six teeth were treated with 0.1-M lactic acid buffer solution (De group). In the second group (n = 6), a thin film of coating material was applied before demineralization (PRG group). A third group (Control group; n = 6) was maintained in artificial saliva. Using optical coherence tomography, we measured peak signal intensity (dB) and width at 1/e² (µm) at predetermined locations on the enamel surface and calculated integrated values. All data were analyzed with ANOVA and the Tukey-Kramer test (α = 0.05). Although changes in integrated values differed between groups, there was a small but significant increase in the Control group and a small but significant decrease in the De group. In the PRG group, integrated values were significantly higher at 7 days after the start of the experiment and significantly increased thereafter. Our findings indicate that a coating material containing S-PRG fillers may prevent primary enamel demineralization.

Mechanisms of Staining with Demeclocycline and Doxycycline Root Canal Medicaments

Tetracyclines are a unique class of antibiotics which also have additional effects including anti-inflammatory, anti-resorptive and substantive within the root canal. There has been a long-held view that tetracycline medicaments discolour teeth and should be avoided. The evidence base around this topic was explored, including a review of the methodology used in laboratory studies. A search of PubMed, Medline and Scopus databases was conducted to identify studies of demeclocycline and doxycycline medicaments used in root canal therapy. An analysis of the methodology used in these studies was performed to determine if these replicate current clinical practice. The related literature on mechanisms of tetracycline stability and the effects of light, oxidation, moisture and chemical interactions was examined. Studies investigating the effects of Ledermix paste on segments of bovine dentine and avulsed or reimplanted teeth as well as combinations with other antibiotics were excluded from this review. Even though demeclocycline medicament pastes were introduced in 1962, the first laboratory studies of discolouration were not done until 2000. All later studies followed a similar approach, which included exposure to sodium hypochlorite for up to 30 minutes and storage in moist conditions with 100% humidity. Staining during dark storage and enhanced staining on exposure to light were reported, indicating multiple pathways of degradation of demeclocycline and its reaction products. Light, moisture and oxidation are the key factors which drive discolouration from demeclocycline. Clinical issues from tooth staining can be prevented by removal of medicament pastes from the access cavity, and placement of a sound interim restoration. Use of a doxycycline paste obviates concerns of staining. Laboratory assessments of the potential for staining should replicate in vivo conditions.

In vitro study of white spot lesion: Maxilla and mandibular teeth

Aim

The aim of the study was to evaluate the effect of resin infiltration on colour changes and surface roughness of artificial white spot lesions (WSLs) on maxillary and mandibular premolar.

Materials and methods

Sixty (60) extracted sound Maxilla (Mx) and Mandibular (Mn) premolars were randomly divided into 2 groups (test and control). Artificial WSLs were produced on buccal surface of teeth and were immersed in artificial saliva for 8 weeks. Colour components (L^∗, a^∗, b^∗) and surface roughness (Sa^∗) were assessed on 40 teeth using colour difference meter RD-100 and Alicona® Infinite Focus profilometer respectively. The measurements were done at baseline (T1), directly after artificial WSLs (T2), after 24 hours immersed in saliva and application of resin (T3) and immersion in artificial saliva for 1 (T4), 2 (T5), 4 (T6), 6 (T7) and 8 (T8) weeks. SEM images analysis were carried out on 20 teeth in four time points.

Results

The values of L^∗ (lightness), b^∗ (yellow/blue) and Sa^∗ (surface roughness) are gradually reduced to the baseline value. Whereas, the value of a^∗ gradually increased with distinct treatment time to achieve the baseline value. The higher value of L^∗ and Sa^∗, the whiter the lesion suggesting higher degree of enamel demineralization and surface roughness. Lower L^∗ values suggest a masking colour effect.

Conclusion

The material produced favorable esthetics on colour and the surface roughness of teeth at distinct treatment times. It is recommended to be used to improve WSL post orthodontic treatment.

Translucency of Zirconia Ceramics before and after Artificial Aging

PURPOSE

The aging of zirconia ceramics (Y-TZP) is associated with tetragonal to monoclinic phase transformation. This change in microstructure may affect the optical properties of the ceramic. This study examines the effect of aging on the translucency of different zirconia materials.

MATERIALS AND METHODS

120 disc-shaped specimens were fabricated from four zirconia materials: Cercon ht white, BruxZir Solid Zirconia, Zenostar T0, Lava Plus (n = 30 per group). Accelerated aging was performed in a steam autoclave (134°C, 0.2 MPa, 5 hours). CIELab coordinates (L*, a*, b*) and luminous reflectance (Y) were measured with a spectrophotometer before and after aging. Contrast ratio (CR) and translucency parameter (TP) were calculated from the L*, a*, b*, and Y tristimulus values. The general linear model (Bonferroni adjusted) was used to compare both parameters before and after aging, as well as between the different zirconia materials (p ≤ 0.05).

RESULTS

CR and TP differed significantly before and after aging in all groups tested. Before aging, Zenostar T showed the highest and Lava Plus showed the lowest translucency. After aging, Cercon ht and Zenostar T showed the highest and BruxZir and Lava Plus the lowest translucency.

CONCLUSIONS

Aging reduced the translucency in all specimens tested. Furthermore, translucency differed between the zirconia brands tested. Nevertheless, the differences were below the detectability threshold of the human eye. The aging process can influence the translucency and thus the esthetic outcome of zirconia restorations; however, the changes in translucency were minimal and probably undetectable by the human eye.

[Analysis of the color changes in teeth at different depths preparation]

Spectrophotometric analysis of the extract and intact teeth revealed the color characteristic of teeth ranged from the cervical area to the cutting edge, as well as by preparation of dental hard tissue to 0.3 mm, 0.6 mm, 0.9 mm depth. Lightness increased as preparation approached dentine. The intensity of the Lightness was more pronounced in the cervical region which is associated with a thin layer of enamel performing the lens function. It is found that Hue values weakly depend on the depth and location of the preparation, the tooth reflecting a relatively constant range of visible wavelengths. During preparation of the hard tissue at different depths the color difference δE* was greater than 2.6 meaning that the color must be registered before and after preparation.

Difference in Striae Periodicity of Heilongjiang and Singaporean Chinese Teeth

Striae periodicity refers to the number of cross-striations between successive lines of Retzius in tooth enamel. A regular time dependency of striae periodicity, known as the circaseptan interval, has been proposed. Previous studies on striae periodicity have been carried out on both modern and early humans given its potential applications in forensic age estimations and anthropology. Nevertheless, research comparing striae periodicities across gender groups and populations in different geographical locations, particularly in Asia, is lacking. In this study, we compared the striae periodicities of Heilongjiang and Singaporean Chinese, as well as that of Singaporean Chinese males and females. Results showed that while the median striae periodicity counts of Heilongjiang Chinese and Singaporean Chinese teeth are both 7, Heilongjiang Chinese tend to have lower striae periodicity counts than Singaporean Chinese (p < 0.01). No significant gender difference was observed between the median striae periodicity of Singaporean Chinese Female and Singaporean Chinese Male teeth (p = 0.511). We concluded that the median striae periodicity may statistically differ with geographical location, but not gender, provided that ethnicity and geographical location are held constant. Further studies are required to examine the causes for variation in striae periodicities between geographical locations, as well as to verify the other bio-environmental determinants of striae periodicity.

Quantitative Swept-Source Optical Coherence Tomography of Early Enamel Erosion in vivo

Swept-source optical coherence tomography (SS-OCT) shows potential for the in vivo quantitative evaluation of micro-structural enamel surface phenomena occurring during early erosive demineralization. This randomized controlled single-blind cross-over clinical study aimed to evaluate the use of SS-OCT for detecting optical changes in the enamel of 30 healthy volunteers subjected to orange juice rinsing (erosive challenge) in comparison to mineral water rinsing (control), according to wiped and non-wiped enamel surface states. Participants were randomly allocated to 60 min of orange juice rinsing (pH 3.8) followed by 60 min of water rinsing (pH 6.7) and vice versa, with a 2-week wash-out period. In addition, the labial surfaces of the right or left maxillary incisors were wiped prior to SS-OCT imaging. An automated ImageJ algorithm was designed to analyse the back-scattered OCT signal intensity (D) after orange juice rinsing compared to after water rinsing. D was quantified as the OCT signal scattering from the 33 µm sub-surface enamel, normalised by the total OCT signal intensity entering the enamel. The back-scattered OCT signal intensity increased by 3.1% (95% CI 1.1-5.1%) in the wiped incisors and by 3.5% (95% CI 1.5-5.5%) in the unwiped incisors (p < 0.0001). Wiping reduced the back-scattered OCT signal intensity by 1.7% (95% CI -3.2 to -0.3%; p = 0.02) in comparison to the unwiped enamel surfaces for both rinsing solutions (p = 0.2). SS-OCT detected OCT signal changes in the superficial sub-surface enamel of maxillary central incisor teeth of healthy volunteers after orange juice rinsing.

Enamel remineralization effect of a dentifrice containing calcium sodium phosphosilicate: an optical coherence tomography observation

OBJECTIVE

The purpose of this study was to examine the effects of a dentifrice containing 5% calcium sodium phosphosilicate (CSP) on the remineralization of the enamel using optical coherence tomography (OCT).

MATERIALS AND METHODS

Bovine incisors were sliced and shaped in a rectangular form. One group of five specimens was treated with undersaturated 0.1 M lactic acid buffer solution (pH 4.75) for 10 min and then placed in artificial saliva (pH 7.0) (De group). Other specimens were stored in solutions of toothpaste containing CSP for 10 min, followed by 10-min immersion in the lactic acid buffer solution twice a day before storage in artificial saliva (CSP group). An additional group was stored in only artificial saliva (control group). OCT imaging on the selected location of the enamel surface was performed. The peak intensity and width at 1/e² were recorded in each of the six areas on the sample and averaged, and the sample size of each group was six. The integrated value in units (dB × μm) was calculated in the area of peak intensity. The data for each group was subjected to one-way repeated-measures ANOVA and Tukey HSD tests (α = 0.05).

RESULTS

The changes in integrated values of each group were different. A slight but significant increase in the integrated value was observed in the control group, whereas a slight but significant decrease in the value was observed the De group. Integrated values increased in the CSP group.

CONCLUSIONS

Remineralization occurred upon immersion in the toothpaste containing CSP.

A Preliminary Research into Clinical Semi-permeability Tolerance in the Field of Dental Rehabilitation

Objective

To study clinical semi-permeability tolerance level in the field of dental restoration.

Method

Vita 95 enamel porcelain powder was adopted and 6.0% used as the control transmissivity. Discoid porcelain plates with different transmissivity, namely increasing transmissivity (0.25%, 0.5%, 1.0%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% and 4.5%) and decreasing transmissivity (-0.25%, -0.5%, -1.0%, -1.5%, -2%, -2.5%, -3% and -3.5%) were made. Forty observers judged these according to six grades: same, similar, slightly different, visibly different, recognizable and significantly different, and under the observation conditions of a neutral grey background and 45^°/0^° lighting. The judgment results were analysed statistically.

Results

When the transmissivity of the control porcelain plates was 6.032%, and the transmissivity of test porcelain plates decreased by 1% or increased by 3%, observers could find slight differences between the test samples and the control samples. When transmissivity of test samples decreased by 2.5% or increased by 4.5%, observers thought that the two porcelain plates belonged to different orders of magnitude.

Conclusions

Under the experimental conditions, the upper and lower limits of clinical semi-permeability tolerance were 3% and 1%, respectively.

Transmission of Curing Light through Moist, Air-Dried, and EDTA Treated Dentine and Enamel

Objective. This study measured light transmission through enamel and dentin and the effect of exposed dentinal tubules to light propagation. Methods. Light attenuation through enamel and dentin layers of various thicknesses (1 mm, 2 mm, 3 mm, and 4 mm) was measured using specimens that were (1) moist and (2) air-dried (n = 5). Measurements were repeated after the specimens were treated with EDTA. Specimens were transilluminated with a light curing unit (maximum power output 1869 mW/cm(2)), and the mean irradiance power of transmitting light was measured. The transmission of light through teeth was studied using 10 extracted intact human incisors and premolars. Results. Transmitted light irradiance through 1 mm thick moist discs was 500 mW/cm(2) for enamel and 398 mW/cm(2) for dentin (p < 0.05). The increase of the specimen thickness decreased light transmission in all groups (p < 0.005), and moist specimens attenuated light less than air-dried specimens in all thicknesses (p < 0.05). EDTA treatment increased light transmission from 398 mW/cm(2) to 439 mW/cm(2) (1 mm dentin specimen thickness) (p < 0.05). Light transmission through intact premolar was 6.2 mW/cm(2) (average thickness 8.2 mm) and through incisor was 37.6 mW/cm(2) (average thickness 5.6 mm). Conclusion. Light transmission through enamel is greater than that through dentin, probably reflecting differences in refractive indices and extinction coefficients. Light transmission through enamel, dentin, and extracted teeth seemed to follow Beer-Lambert's law.

Criteria for clinical translucency evaluation of direct esthetic restorative materials

The purpose of this review was to suggest practical criteria for the clinical translucency evaluation of direct esthetic restorative materials, and to review the translucency with these criteria. For the evaluation of reported translucency values, measuring instrument and method, specimen thickness, background color, and illumination should be scrutinized. Translucency parameter (TP) of 15 to 19 could be regarded as the translucency of 1 mm thick human enamel. Visual perceptibility threshold for translucency difference in contrast ratio (ΔCR) of 0.07 could be transformed into ΔTP value of 2. Translucency differences between direct and indirect resin composites were perceivable (ΔTP > 2). Universal and corresponding flowable resin composites did not show perceivable translucency differences in most products. Translucency differed significantly by the product within each shade group, and by the shade group within each product. Translucency of human enamel and perceptibility threshold for translucency difference may be used as criteria for the clinical evaluation of translucency of esthetic restorative materials.

Laser light passage through restored and carious posterior teeth

Laser Doppler flowmetry (LDF) has been used to investigate pulpal blood flow as a means of pulp vitality testing. Transmission of laser light from the tooth surface to the pulp space may be influenced by caries and restorations. One hundred and twenty-two first and second molars that had caries into dentine, restorations or significant loss of coronal tissue were sectioned in half axio-bucco-lingually. The two sections were illuminated with a laser from their buccal and lingual aspects 2 mm coronal to the amelocemental junction. Light reaching the pulp space was recorded. Buccal and lingual illumination sites were equally effective for 67 teeth (55%). Buccal sites alone were effective for 35 teeth (29%), despite over one-third of these surfaces being restored or featuring enamel or dentine caries. A lingual position alone was effective for 20 teeth (16%). Caries affected light transmission, but for over half the teeth, the pulp could be illuminated from all four probe positions. No effect was found when the influence of mesial and distal restorations on transmission into the corresponding tooth section was examined. The pulp spaces of most (84%) restored, and carious posterior teeth could be illuminated by laser light from their buccal aspect and these teeth could potentially be vitality tested using LDF.

3D phase-shifting fringe projection system on the basis of a tailored free-form mirror

Phase-shifting fringe projection is an effective method to perform 3D shape measurements. Conventionally, fringe projection systems utilize a digital projector that images fringes into the measurement plane. The performance of such systems is limited to the visible spectral range, as most projectors experience technical limitations in UV or IR spectral ranges. However, for certain applications these spectral ranges are of special interest. We present a wideband fringe projector that has been developed on the basis of a picture generating beamshaping mirror. This mirror generates a sinusoidal fringe pattern in the measurement plane without any additional optical elements. Phase shifting is realized without any mechanical movement by a multichip LED. As the system is based on a single mirror, it is wavelength-independent in a wide spectral range and therefore applicable in UV and IR spectral ranges. We present the design and a realized setup of this fringe projection system and the characterization of the generated intensity distribution. Experimental results of 3D shape measurements are presented.

Crown discoloration induced by endodontic sealers: spectrophotometric measurement of Commission International de I'Eclairage's L*, a*, b* chromatic parameters

Despite the improvement of endodontic materials, crown discoloration induced by root canal sealers remains a concerning clinical issue. The aim of this study is the measurement of the alterations in CIE L*, a*, b* chromatic parameters of tooth crowns after placement of commonly used and new-generation endodontic sealers in pulp chambers. Eighty intact, fully developed third mandibular molars were randomly assigned in five groups. Crowns were cross-sectioned from the root complex 1 mm below the cement-enamel junction. The internal axial walls of the pulp chambers were debrided and coated with endodontic sealers (Roth-811, AH-26, Guttaflow, Epiphany SE). The apical access was sealed with glass-ionomer cement. The control group was only debrided. Crowns were stored in individually marked vials in standard conditions (100% humidity, 37°C). The spectral reflectance lines were recorded with a UV-Vis spectrophotometer in the visual spectrum. The CIE L*a*b* parameters were obtained by a linked computer software before sealer placement (baseline), after one week, one, three, and six months, respectively. Statistical analysis was performed with two-way mixed ANOVA models. The level of statistical significance was set at p<0.05. With the exception of the control group, experimental groups presented varying chromatic alterations. Among all experimental groups, Roth-811 sealer induced the most severe alterations in CIE L*, a*, b* chromatic parameters, during all observation periods. After root canal obturation, the clinician should be aware of the presence of remaining root canal filling materials. Thorough debridement of the pulp chamber is essential for the prevention of sealer-induced discoloration.

Effects of refractive index solutions on the color of different luting cements

PURPOSE

The purpose of this study is to determine the effects of refractive index solutions on the color of different luting cements at different periods.

MATERIALS AND METHODS

Fourteen disc-shaped specimens were prepared for three different universal shade luting cements. All specimens were divided into two groups and a phthalate ester and glycerol refractive index solution was applied to the specimens at different periods. Color differences (ΔE*) were calculated for before and after 5, 15, 60 min and 24 h periods of applying refractive index solutions. Data were analyzed with multiple analysis of variance (ANOVA) and mean values were compared by the Tukey HSD test (α = 0.05).

RESULTS

Periods and periods-cement interaction were statistically significant (p ≤ 0.05). There was no statistically significant difference between the mean ΔE values of refractive index solutions and cement groups (p > 0.05).

CONCLUSION

Refractive index solutions affected the color of luting cements.

Validation and spectrophotometric analysis of crown discoloration induced by root canal sealers

OBJECTIVES

A major cause of crown discoloration is root canal sealer remnants in the pulp chamber, after root canal obturation. The aim of this study was the evaluation of the chromogenic effect of common and new-generation root canal sealers. The tested null hypothesis was that none of the sealers induced clinically perceptible crown discoloration, ex vivo (H(0): CIE color difference ∆Ε < 3.7).

METHODS

The crowns of 80 intact, fully developed third mandibular molars were cross-sectioned 1 mm below the cementoenamel junction and stored in standard conditions (100 % humidity, 37 °C). The pulp chambers were chemomechanically debrided with hand files and sodium hypochlorite (NaOCl) and the specimens were randomly assigned into four experimental (1-4) and one control (5) groups. In the experimental groups, the internal axial walls of the pulp chambers were coated with sealers (Group 1; Roth 811, Group 2; AH26, Group 3; GuttaFlow, Group 4; Epiphany SE). The pulp chambers of the control group (Group 5) remained unfilled. The spectral reflectance lines of the crowns were recorded by a UV-Vis spectrophotometer. CIE total color differences [Formula: see text] were calculated after 1 week, 1 month, 3 months, and 6 months, respectively. A pilot study was also conducted for the validation of the experimental model. Two-way mixed ANOVA models were used for statistical data analysis.

RESULTS

The experimental model presented values of ∆Ε < 1 unit and high positive correlation values, after repeated measurements (p < 0.05). Roth 811 sealer (Group 1) induced clinically perceptible crown discoloration (∆Ε > 3.7, p < 0.05) and presented statistically significant differences from Groups 2-5 in all examination intervals (p < 0.05). In Groups 2-5, clinically perceptible crown discoloration was not observed (∆Ε < 3.7, p < 0.05).

CONCLUSIONS

Roth 811 sealer exhibited severe discoloration effects. Within the limitations of this study, it can be concluded that any sealer remnants should be removed from the pulp chamber after root canal obturation and before placement of a final restoration.

CLINICAL RELEVANCE

The chromogenic potential may play an important role in selecting proper root canal sealers.

Imaging in vivo secondary caries and ex vivo dental biofilms using cross-polarization optical coherence tomography

OBJECTIVE

Conventional diagnostic methods frequently detect only late stage enamel demineralization under composite resin restorations. The objective of this study is to examine the subsurface tooth-composite interface and to assess for the presence of secondary caries in pediatric patients using a novel Optical Coherence Tomography System with an intraoral probe.

METHODS

A newly designed intraoral cross polarization swept source optical coherence tomography (CP-OCT) imaging system was used to examine the integrity of the enamel-composite interfaces in vivo. Twenty-two pediatric subjects were recruited with either recently placed or long standing composite restorations in their primary teeth. To better understand how bacterial biofilms cause demineralization at the interface, we also used the intraoral CP-OCT system to assess ex vivo bacterial biofilm growth on dental composites.

RESULTS

As a positive control, cavitated secondary carious interfaces showed a 18.2dB increase (p<0.001), or over 1-2 orders of magnitude higher, scattering than interfaces associated with recently placed composite restorations. Several long standing composite restorations, which appeared clinically sound, had a marked increase in scattering than recently placed restorations. This suggests the ability of CP-OCT to assess interfacial degradation such as early secondary caries prior to cavitation. CP-OCT was also able to image ex vivo biofilms on dental composites and assess their thickness.

SIGNIFICANCE

This paper shows that CP-OCT imaging using a beam splitter based design can examine the subsurface interface of dental composites in human subjects. Furthermore, the probe dimensions and acquisition speed of the CP-OCT system allowed for analysis of caries development in children.