Staining- and aging-dependent changes in color and translucency of 3D-printed resin-modified ceramics.

PURPOSE: To evaluate staining- and aging-dependent changes in the color and translucency of 3D-printed resin-modified ceramics (RMC). METHODS: Specimens (n= 5 per condition and material) were fabricated from test materials: Permanent Crown Resin (PCR), Crowntec (CT), Vita Enamic (VE) and Tetric CAD (TC). Specimens were stained in wine, coffee, tea, and water (control) and exposed to artificial accelerated aging (AAA). Color measurements were obtained using a spectrophotometer at baseline (T0) and at 3.5 (T1) and 7 (T2) days after immersion. For AAA, measurements were obtained at baseline (T0) and after exposure to controlled irradiance of 150 kJ/m² (T1) and 300 kJ/m² (T2). Mean and standard deviations were calculated on CIEDE2000 color differences (ΔE00), translucency parameter (TP00) and treatment-dependent changes in the translucency parameter (ΔTP0 0). Differences between materials and test conditions were tested by one-way ANOVA (α= 0.05). Results were additionally interpreted using visual color difference thresholds in dentistry ΔE00= 0.8 for the 50:50 perceptibility threshold (PT) and ΔE00= 1.8 for the 50:50 acceptability threshold (AT). ΔTP00 values were interpreted using 5058;50 TPT00= 0.6 and 50:0% TAT00= 2.6. RESULTS: Statistically significant differences were found among the materials when exposed to the different test conditions. At the T0-T1 time interval, the highest color difference was found with wine (0.1-2.2) on all materials except CT, which showed the highest ΔE00 with AAA (2.5). The second highest color differences were obtained upon exposure to AAA (0.2-2.5) and tea (0.5-1.1). The TP00 at baseline ranged from 5.1 to 9.8. Significant differences in ΔTP00 were found among the tested materials and staining/aging conditions, but no significant differences were found among the staining/aging intervals (T0-T1, T0-T2 and T1-T2). CLINICAL SIGNIFICANCE: Staining- and artificial aging-dependent changes of 3D-printed and milled resin modified ceramics used for definitive restorations could represent a challenge in terms of restoration acceptability or dissatisfaction. Staining and aging conditions produced significant color changes, while translucency changes were not significant.

Instrumental and visual evaluation of the color adjustment potential of resin composites.

OBJECTIVE: To evaluate the instrumental and visual color adjustment potential (CAP-I, CAP-V), of resin composites. METHODS: Resin composites tested were Omnichroma, Filtek Supreme Ultra, TPH Spectra, Herculite Ultra, and Tetric EvoCeram. Two types of specimens, "dual" and "single" were evaluated. For dual specimens, class I preparations (4 mm-diameter, 2 mm-depth), were created in denture teeth and restored with test resin composites. For single specimens, replications of denture teeth were created using the test resin composites (n = 5) and compared with unrestored denture teeth. Reflectance values were obtained using a spectroradiometer. CAP-I and CAP-V were calculated. Fisher PLSD intervals for comparison of means were calculated at the 0.05 level of significance. RESULTS: CAP-I ranged between 0.02 and 0.67. The Fisher PLSD interval for comparisons between single/dual color differences was 0.09 (P < .0001, power 1.0) and for comparisons between materials and shades 0.18 and 0.33, respectively (P < .0001, power 1.0). CAP-V ranged between 0.16 and 0.60. The Fisher PLSD interval for comparisons between single/dual visual color differences was 0.05 (P < .0001, power 1.0) and 0.08 and 0.14 for comparisons between materials and shades, respectively (P < .0001, except Herculite Ultra-Tetric EvoCeram and certain shade pairs). CONCLUSIONS: Instrumental color differences and visual rating of single specimens were the greatest for Omnichroma, indicating the largest mismatch, while the instrumental and visual color differences of dual specimens were the smallest. Omnichroma had the most pronounced CAP-I followed by Tetric EvoCeram>TPH Spectra = Filtek Supreme Ultra >Herculite Ultra. Similarly, Omnichroma exhibited the most pronounced CAP-V followed by Tetric EvoCeram>TPH Spectra = Herculite Ultra = Filtek Supreme Ultra. CLINICAL SIGNIFICANCE: Resin composites with pronounced CAP blends with surrounding enamel and dentin, resulting in reduced color differences and therefore improving the esthetic appearance of the restoration, simplifying the shade matching and compensating for any color mismatch.

Whitening-dependent changes of fluorescence of extracted human teeth.

OBJECTIVE: To evaluate in vitro the fluorescence properties of extracted human teeth whitened with 40% hydrogen peroxide. MATERIALS AND METHODS: A total of 28 extracted human teeth were pumiced for 1 minute using a low-speed dental handpiece and a disposable rubber cup. Pre-whitening fluorescence measurements (T0), maximum excitation (Exmax ), maximum emission (Emmax ), and maximum intensity (Imax 108 ), were performed using a spectrofluorometer. After T0 measurements, the teeth were whitened using the in-office method with 40% hydrogen peroxide, three times for 20 minutes. The fluorescence parameters were measured under the same conditions 7 and 14 days after bleaching (T1 and T2, respectively). RESULTS: Exmax exhibited a broader range 7 days after whitening and decreased after 14 days. The Emmax and Imax 108 displayed a narrower range after whitening. The mean Exmax differed significantly between the time points (F = 20.09. P < .001). The corresponding analysis for the mean Emmax differed significantly between the time points (F = 16.69, P < .001). The same was true for the mean Imax 108 (F = 9.69, P < .001). CONCLUSIONS: Within the limitations of this study, whitening provoked statistically significant changes in fluorescence of the intact teeth in vitro. CLINICAL SIGNIFICANCE: The appearance of human teeth and dental materials and their changes upon aging and exposure to different agents (staining, whitening) is a topic of great relevance to esthetic dentistry. While some appearance parameters, such as color, translucency, and gloss, have been thoroughly studied, fluorescence and its influence on overall tooth appearance is still not well understood, yet it has influenced the development of fluorescence emitting restorative materials.