Reliability of the color measurement of resin composites using images obtained using a stereoscopic loupe.

This study assessed the reliability of a color measurement method using images obtained from a charge-coupled device (CCD) camera and a stereoscopic loupe. Disc-shaped specimens were created using the composite Filtek Z350 XT (shades DA1, DA2, DA3, and DA4) (n = 3). CIELAB color coordinates of the specimens were measured using the spectrophotometer SP60 over white and black backgrounds. Images of the same specimens were taken using a CCD camera attached to a stereoscopic loupe. The color of the image was measured (red-green-blue [RGB]) using an image processing software and converted to CIELAB coordinates. For each color coordinate, data from images were adjusted using linear regressions predicting those values from SP60. The whiteness index for dentistry (WID) and translucency parameter (TP00) of the specimens as well as the color differences (ΔE00) among pairwise shades were calculated. Data were analyzed via repeated-measures analysis of variance and Tukey's post hoc test (α = 0.05). Images obtained using the loupe tended to be darker and redder than the actual color. Data adjustment resulted in similar WID, ΔE00, and TP00 values to those observed for the spectrophotometer. Differences were observed only for the WID of shade DA3 and ΔE00 for comparing DA1 and DA3 over the black background. However, these differences were not clinically relevant. The use of adjusted data from images taken using a stereoscopic loupe is considered a feasible method for color measurement.

Over-the-counter products in tooth bleaching: A scoping review.

OBJECTIVE: To map and summarize the current scientific evidence concerning the active ingredients, effectiveness, and adverse effects of over-the-counter (OTC) bleaching products. DATA AND SOURCE: This study was conducted according to the PRISMA-ScR guidelines for scoping reviews and registered on the Open Science Framework platform. STUDY SELECTION: Database searches were conducted in PubMed/MEDLINE, Embase, and Scopus up to January 2024. All in vitro, in situ, and clinical studies evaluating the effectiveness and adverse effects of OTC bleaching products were included. A descriptive analysis of the included studies was performed. RESULTS: A total of 88 studies were included. Most of them were in vitro studies (n = 49), followed by randomized clinical trials (n = 28). The main OTC bleaching products identified were whitening or stain-removing toothpastes (n = 42), followed by whitening strips (n = 39). Most clinical studies indicate that whitening strips are effective in improving tooth color and providing whitening benefits. In contrast, the bleaching effectiveness of toothpastes, mouth rinses and whitening trays was mainly supported by in vitro studies. The main adverse effects associated with OTC bleaching agents were tooth sensitivity and gingival irritation. CONCLUSION: A wide variety of OTC bleaching products is available for consumer self-administered use. Clinical studies have mainly confirmed the bleaching effectiveness of whitening strips, while the validation for toothpastes, mouth rinses and whitening trays has mainly relied on in vitro studies. Nevertheless, the use of OTC bleaching products may result in adverse effects, including tooth sensitivity, gingival irritation, and enamel surface changes. CLINICAL SIGNIFICANCE: Some over-the-counter bleaching products may have whitening properties supported by clinical studies, particularly those containing hydrogen or carbamide peroxide. Nonetheless, clinicians must be aware of the potential risks associated with excessive self-administration of these products, which may result in adverse effects.

Optical properties of dental zirconia, bovine dentin, and enamel-dentin structures.

OBJECTIVE: To evaluate the optical properties and the relative translucency parameter of Ceramill ZI White (3Y-TZP) and Ceramill Zolid FX White (5Y-PSZ) zirconia ceramic systems and compare them with those of the bovine dentin and enamel/dentin structures. MATERIALS AND METHODS: 3Y-TZP and 5Y-PSZ zirconia ceramic systems were evaluated. A 0.5-mm-thick 3Y-TZP (3Y-NC.5), 0.5-mm-thick (5Y-NC.5), and 1.4-mm-thick (5Y-C.14) were used. A 0.5-mm-thick dentin specimens and 1.4-mm-thick enamel/dentin specimens (n = 5) were obtained from anterior bovine maxillary teeth. Scattering, absorption, transmittance, and albedo coefficient were calculated using Kubelka-Munk's model. Data were statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (p < 0.001), and goodness-of-fit coefficient (GFC). Relative translucency parameter differences were evaluated using translucency thresholds. RESULTS: Reflectance, scattering, absorption, and transmittance properties were wavelength dependent. Good matches (GFC ≥ 0.999) in spectral reflectance were observed between 0.5-mm-thick dentin and 1.4-mm-thick enamel/dentin, and 3Y-NC.5 and 5Y-NC.5. Scattering was the main optical extinction process during light interaction with zirconia and dental structures, as indicated by albedo coefficient. Translucency differences were acceptable only for 3Y-NC.5 and the dentin structure, and 5Y-C.14 and the enamel/dentin structure. CONCLUSIONS: Optical properties of 3Y-TZP and 5Y-PSZ dental zirconia differed from each other and from bovine dental structures. Nevertheless, 3Y-TZP showed similar relative translucency parameter to bovine dentin. CLINICAL SIGNIFICANCE: To achieve the best esthetic results in restorative dentistry, it is crucial for clinicians to know about the optical properties of 3Y-TZP and 5Y-PSZ and to be able to compare these properties with those of dental structures.

Reliability of the color measurement of resin composites using images obtained using a stereoscopic loupe

Abstract This study assessed the reliability of a color measurement method using images obtained from a charge-coupled device (CCD) camera and a stereoscopic loupe. Disc-shaped specimens were created using the composite Filtek Z350 XT (shades DA1, DA2, DA3, and DA4) (n = 3). CIELAB color coordinates of the specimens were measured using the spectrophotometer SP60 over white and black backgrounds. Images of the same specimens were taken using a CCD camera attached to a stereoscopic loupe. The color of the image was measured (red-green-blue [RGB]) using an image processing software and converted to CIELAB coordinates. For each color coordinate, data from images were adjusted using linear regressions predicting those values from SP60. The whiteness index for dentistry (WID) and translucency parameter (TP00) of the specimens as well as the color differences (ΔE00) among pairwise shades were calculated. Data were analyzed via repeated-measures analysis of variance and Tukey's post hoc test (α = 0.05). Images obtained using the loupe tended to be darker and redder than the actual color. Data adjustment resulted in similar WID, ΔE00, and TP00 values to those observed for the spectrophotometer. Differences were observed only for the WID of shade DA3 and ΔE00 for comparing DA1 and DA3 over the black background. However, these differences were not clinically relevant. The use of adjusted data from images taken using a stereoscopic loupe is considered a feasible method for color measurement.

Analysis of topography, flexural strength, and microstructure of a lithium-disilicate glass-ceramic after surface finishing.

Glass-ceramic restorations often require adjustments using coarse diamond burs (D) which have the potential to introduce critical defects at the surface from which a crack can initiate and propagate until fracture. Surface finishing using fine and ultra-fine burs (F), polishing (P), or glazing (G) have the potential to reduce or eliminate these defects. PURPOSE: This study investigated the influence of finishing, polishing, and glazing on the roughness, flexural strength, and microstructure of a lithium disilicate glass-ceramic (LD). MATERIALS AND METHODS: LD CAD-CAM blocks were cut into 96 discs (1.2 mm x 12 mm). After crystallization, a layer of glaze was applied to the discs surface. The specimens were randomly divided into eight groups (n=12) for different surface treatments: G- glaze (control), GD, GDG, GDP, GF GFG, GFP, and GDFP. Mean roughness (Ra), mean square height (Rq) and maximum roughness (Rz) were measured. The biaxial flexural strength test was performed in a universal testing machine at 0.5 mm/min. Microstructural analysis was performed using X-ray diffraction patterns (XRD). Differences on the roughness obtained in distinct groups was analyzed by Kruskal-Wallis and Bonferroni tests (α = 0.05). The flexural strength tests were compared by one-way ANOVA. RESULTS: Glazed groups (G, GDG and GFG) presented the lowest surface roughness, lower crystallinity, and higher flexural strength than the other groups. Although polishing and glaze presented similar surface roughness, polishing protocol decreased the flexural strength compared to the control group G. CONCLUSION: clinically adjusted LD glass-ceramic restorations should be reglazed whenever possible to improve strength.

Masking ability of CAD/CAM monolithic ceramics: effect of ceramic type and thickness, and try-in paste shade.

OBJECTIVE: This in vitro study evaluated the color differences when discolored tooth substrates were restored with CAD/CAM monolithic ceramics depending on ceramic type and thickness, and the try-in paste shade. METHOD AND MATERIALS: Six ceramic types were tested: high-translucent lithium disilicate (LD-HT); medium-translucent lithium disilicate (LD-MT); low-translucent lithium disilicate (LD-LT); low-translucent leucite (LC-LT); feldspathic ceramic (FC); and BL1 low-translucent lithium disilicate, stained to A1 shade (LD-BL1-LT). The ceramics were tested in disk-shaped specimens with 0.5-, 1.0-, and 1.5-mm thickness (n = 10; N = 180; shade A1). The try-in pastes were tested to simulate luting materials and corresponded to colors A1 and Opaque White. Six substrates were used: A1 (reference), B2, B3, A3, C2, and C3. Color differences (∆E00) and translucency parameter (TP00) were assessed with the CIEDE2000 formula. The results were compared with acceptability (1.77) and perceptibility (0.81) thresholds. RESULTS: Ceramic type, thickness, and the try-in paste shade influenced the color differences. LD-LT and LC-LT ceramics and Opaque White try-in paste provided, in general, lower ∆E00 values. The most adequate ceramic thickness varied according to the substrate discoloration. With 1.0 mm of ceramic thickness, it was possible to obtain ∆E00 lower than the perceptibility threshold for substrates C2 and A3, and ∆E00 lower than the acceptability threshold for C3 and B3. ∆E00 lower than the acceptability threshold were obtained with 0.5 mm of ceramic thickness for B2, A3, and C2. CONCLUSION: The use of low-translucent glass-ceramics and Opaque White try-in paste are useful to reduce color differences. The most adequate ceramic thickness depends on the substrate discoloration.

The influence of smoking on the effectiveness of at-home bleaching: A prospective clinical study.

OBJECTIVES: To evaluate the effect of smoking on tooth whitening and color change after at-home bleaching. MATERIALS AND METHODS: This prospective clinical study evaluated two groups of participants: NS-non-smokers (n = 24) and S-smokers (n = 16). All subjects were treated with at-home bleaching using 22% carbamide peroxide (CP) for 1 h/day for 14 days. Color coordinates (L*-luminosity, a*-red-green axis and b*-yellow-blue axis) were obtained before bleaching (D0-baseline), 1 day (D1), 15 days (D15), and 1 month (D30) after bleaching. The whiteness index (WID ) and CIEDE2000 color differences (ΔE00 ) were calculated for S and NS. Color changes between S and NS subjects for specific teeth (CI-Central Incisors, LI-Lateral Incisors, and C-Canines) were analyzed using the Mann-Whitney test (α = 0.05). RESULTS: There was no significant difference in WID between S and NS subjects at baseline. NS participants showed higher WID than S at D1, D15, and D30 (p < 0.05). NS showed higher ΔWID for CI and C between D0 and the other evaluation times (D1, D15, and D30) compared to S. Smokers showed higher darkening of CI than NS in ΔWID D30-D1 (p < 0.05). Color changes showed similar overall behavior for ΔWID . For all evaluation times, ΔWID and ΔE00 values were below the corresponding acceptability thresholds. CONCLUSION: At-home bleaching was effective on smokers and nonsmokers. Smoking negatively affected color stability after bleaching. ΔE00 and ΔWID were acceptable for both groups. CLINICAL SIGNIFICANCE: Although smoking negatively affected color stability after bleaching, the observed changes were clinically acceptable.

Masking ability of resin composites: A scoping review.

OBJECTIVE: To map the existing evidence regarding the masking ability of resin composites. OVERVIEW: The literature search was conducted electronically, based on the PRISMA Extension for Scoping Reviews-online protocol at https://osf.io/m2h67/ with no language or time restrictions. Two independent reviewers conducted the screening, and a third reviewer was consulted in case of disagreement. Studies that evaluated resin composite masking ability regardless of background, application technique, thickness, or number of layers were selected. The search found 2995 potentially eligible studies. After removal of duplicates (657), irrelevant articles (2323), 15 citations met the eligibility criteria based on title and abstract, and eight studies were included based on full text analysis (seven in vitro, and one case report). Acceptable masking ability is obtained by one layer of opaque shade resin composite or by the layering technique. A black background is masked with 1.0- to 2.0 mm-thick layers of opaque shade resin composites. Masking of the C4 background is achieved with one layer of 0.5- to 1.5 mm-thick opaque shade resin composite or by the layering technique using different combinations of enamel body and dentin shades with a final thickness of 1.5 mm. CONCLUSIONS: Acceptable masking of C4 shade background is achieved with one layer of opaque shade composite at least 0.5 mm-thick or by different combinations of the layering technique, with a final thickness of 1.5 mm. Acceptable masking of the black background of the oral cavity is achieved with a resin composite of at least 1.0 mm opaque shade. CLINICAL SIGNIFICANCE: The thickness of the resin composite layer required to achieve adequate masking is variable and depends on the translucency/opacity of the tested resin composites and the background shade.

Comparison of visual shade matching and photographic shade analysis.

OBJECTIVE: To compare the performance of a standardized photographic shade analysis (PSA) and visual shade matching (VSM) using two color difference formulas. MATERIALS AND METHODS: Fifty observers (35 undergraduate and 15 graduate students) evaluated the color of two upper left central incisors (LT-light tooth, and DT-dark tooth). VSM was performed using the VITA 3D Master (3D) shade guide in a controlled clinical environment. For PSA, a cross-polarized filter and a gray card (Whibal) were used to standardize the photographs taken (target teeth and shade tabs from 3D). From the pictures obtained, the CIELAB coordinates, and color differences ( Δ E ab * and ΔE00 ) were obtained. The shade tabs selected by two experienced researchers were conducted as part of the pilot study, and finally used as a standard for the analysis. Data were analyzed using descriptive statistics and the chi-square test (p ≤ 0.05). RESULTS: Shade tabs selections of VSM and PSA agreed only for LT. The best "Match" selected by the researchers agreed with data from PSA using ΔE00 . PSA using ΔE00 showed higher total percentages of "Match" and higher percentage of agreement among observers. A relationship was found for LT performing the PSA (p < 0.05). CONCLUSIONS: The performance of the PSA was better than the VSM, but only when the CIEDE2000 color difference formula was used. Therefore, the color difference formulas influenced on the performance of PSA. Finally, the PSA improved the precision of the VSM. CLINICAL SIGNIFICANCE: To use a standardized PSA to improve the VSM and shade communication in clinical esthetic dentistry.

Applications of artificial intelligence in dentistry: A comprehensive review.

OBJECTIVE: To perform a comprehensive review of the use of artificial intelligence (AI) and machine learning (ML) in dentistry, providing the community with a broad insight on the different advances that these technologies and tools have produced, paying special attention to the area of esthetic dentistry and color research. MATERIALS AND METHODS: The comprehensive review was conducted in MEDLINE/PubMed, Web of Science, and Scopus databases, for papers published in English language in the last 20 years. RESULTS: Out of 3871 eligible papers, 120 were included for final appraisal. Study methodologies included deep learning (DL; n = 76), fuzzy logic (FL; n = 12), and other ML techniques (n = 32), which were mainly applied to disease identification, image segmentation, image correction, and biomimetic color analysis and modeling. CONCLUSIONS: The insight provided by the present work has reported outstanding results in the design of high-performance decision support systems for the aforementioned areas. The future of digital dentistry goes through the design of integrated approaches providing personalized treatments to patients. In addition, esthetic dentistry can benefit from those advances by developing models allowing a complete characterization of tooth color, enhancing the accuracy of dental restorations. CLINICAL SIGNIFICANCE: The use of AI and ML has an increasing impact on the dental profession and is complementing the development of digital technologies and tools, with a wide application in treatment planning and esthetic dentistry procedures.

Experimental methodologies to evaluate the masking ability of dental materials: A systematic review.

OBJECTIVE: To conduct a systematic review on the masking ability of discolored substrates, analyzing the capacity and quality of the response produced by the different methodologies and techniques applied to overcome this clinical challenge. MATERIALS AND METHODS: The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The electronic search was conducted in MEDLINE/PubMed, Scopus and Web of Science databases, without date restriction. In vitro studies, written in English, applying different methodologies to evaluate masking ability were included. The variables of interest were: type, color and thickness of the restorative and/or cement material; use of pigments in the restorative material and/or cement; color of the substrate; and background color used for the evaluations. RESULTS: Database search retrieved 307 eligible papers with a final inclusion of 47 published papers. Approximately 98% of the studies used ΔE, 36% used TP, and only 6% used CR to evaluate the masking ability of restorative materials. CONCLUSIONS: The most appropriate methodology to evaluate the masking ability is using color difference equations (ΔE) associated with the perceptibility and acceptability thresholds. CLINICAL SIGNIFICANCE: As different methodologies have been used to evaluate the masking ability of esthetic restorative materials on colored substrates, there is an urgent need to reach a consensus and propose a method, which is suggested by the present systematic review.

Influence of background color on color perception in dentistry.

OBJECTIVE: To evaluate the influence of neutral color backgrounds on the perception of color differences in dentistry. METHODS: A software was developed for this study that calculated the perceptibility (PT) and acceptability (AT) thresholds of color differences between a pair of computer-simulated incisor samples (n = 60 pairs) over three neutral color (white, gray and black) backgrounds. CIELAB and CIEDE2000 color difference formulas were used. Five groups of volunteer observers (N = 100) participated in the psychophysical experiment (n = 20): Dentists; Dental students; Dental auxiliaries; Dental technicians; and Laypersons. The psychophysical experiment was performed in a dark environment on a calibrated high-resolution screen. To determine PT and AT values, the 60 pairs of samples were randomly presented to each observer over the different backgrounds. The data were adjusted (TSK Fuzzy) and analyzed statistically using Student t-test and ANOVA (α = 0.05). RESULTS: Regardless of the metric and the background used, the PT values showed no difference among different observers (p > 0.05). Dentists showed the lowest PT values. Dental technicians showed the lowest AT (p ≤ 0.05) and similar values for the three backgrounds (p > 0.05), regardless of the metric used. The other groups of observers showed the lowest and the highest AT values when using black and white backgrounds, respectively (p ≤ 0.05). CONCLUSIONS: The lowest AT values using a black background indicates that the use of this background allows for the evaluation of slight color differences, and should be used for challenging color differences in esthetic dentistry. This study showed the influence of the observer experience on color evaluation in dentistry. CLINICAL SIGNIFICANCE: There was no influence of the background color on the perceptibility threshold. However, dentists and dental technicians showed greater ability to perceive slight color differences compared to other groups of observers.

Influence of a glycolic acid-based final irrigant for photosensitizer removal of photodynamic therapy on the microhardness and colour change of the dentin structure.

INTRODUCTION: This study aimed to evaluate the influence of glycolic acid-based final irrigant for photosensitizer removal of photodynamic therapy on the microhardness and colour change of the dentin structure. METHODS: Eighty extracted single-rooted human incisors were used. Sample preparation and root split resulted in 160 samples, 80 samples being used for microhardness and 80 samples for colour change evaluation. In the first, PDT protocol was performed and 80 samples were randomly divided into 4 groups (n = 20), according to the final irrigation protocol: distilled water (DW); 17 % ethylenediaminetetraacetic acid (EDTA); QMix; 17 % glycolic acid (GA). Microhardness was evaluated using the Vicker tester, before and after, PDT and final irrigation protocols, calculating the percentage of microhardness reduction. In the second evaluation, PDT and final irrigation protocols were performed in the same way. Colour change was evaluated using digital spectrophotometer before and after these protocols, calculating the ΔE colour change using the CIELAB system (L*a*b* values). Specific statistical analysis was performed for both evaluations (α = 5%). RESULTS: The highest percentage of microhardness reduction was observed in 17 % EDTA, QMix and 17 % GA groups, with no significant difference among them (p > 0.05). Furthermore, none of these protocols was effective in photosensitizer removal, and all final irrigation protocols were statically similar to control group (p > 0.05). CONCLUSIONS: GA promotes microhardness reduction and also contributes to the colourization of dentin structure during the photosensitizer removal process, followingPDT .

Efficacy of color discrimination tests used in dentistry.

OBJECTIVE: To evaluate the efficacy of visual discrimination tests used for color research in dentistry. MATERIALS AND METHODS: Volunteers (N = 120) were divided in three groups of observers (n = 40; gender-balanced): S-dental students; D-dentists; and L-laypersons. Two general color discrimination tests (I-Ishihara and FM-Farnsworth-Munsell 100 Hue) and the test of color discrimination competency in dentistry using the VITA Classical shade guide (VC) were performed and data were recorded according to manufacturers' or literature recommendations. Data were statistically analyzed using Mann-Whitney U test for the gender influence and Kruskal-Wallis test for the observer influence, and Bonferroni as post-hoc test (α = 0.05). Pearson (α = 0.05) was used to examine the correlation among visual tests (I, FM, and VC). RESULTS: Observers and visual tests were not influenced by gender (P > .05). Different observer groups had no influence on I test (P > .05). S and D showed similar level of color perception using FM and VC (P > .05), but these observers showed greater color perception than L (P ≤ .05). FM and VC also showed significant correlation (P ≤ .05) for the overall D observers (r = -0.362), male D (r = -0.594) and female S (r = -0.457). CONCLUSION: Observer experience significantly influenced on color perception, irrespective of gender. FM test showed greater correlation to color correspondence in dentistry (VC) than I test. CLINICAL SIGNIFICANCE: Observer experience is more relevant than gender for the color selection process in dentistry. Considering the visual discrimination tests for color research in dentistry, the Farnsworth-Munsell 100 Hue test seems to be more efficacious than the Ishihara test.

Effect of substrate and cement on the final color of zirconia-based all-ceramic crowns.

OBJECTIVE: To evaluate the influence of the substrate and the cement on the final color of ceramic crowns. METHODS: Prosthetic crowns (framework + porcelain) were fabricated using two all-ceramic systems (YZ, 3 mol% yttria-stabilized tetragonal zirconia; IZ, alumina-based zirconia-reinforced glass-infiltrated ceramic) and a metal-ceramic system (MC; n = 8). Metal (M) and resin (R) were used as substrate abutments. For R substrate, crowns were evaluated as seated (R) and after cementation (R-C). CIELAB color coordinates were obtained using a dental spectrophotometer with D65 light illumination. CIELAB, CIEDE2000 (1:1:1) and CIEDE2000 (2:1:1) color difference metrics were used. Data were analyzed using 95% confidence intervals and compared to perceptibility (PT) and acceptability (AT) thresholds. RESULTS: The ∆Eab* , ∆E00 (1 : 1 : 1), and ∆E00 (2 : 1 : 1) values of the restorative systems evaluated using different substrates (M.R) were similar to the AT values of each metric. When non-cemented and cemented crowns were evaluated (R.R-C), MC had color difference values at PT and below AT; while YZ and IZ showed similar values to AT, for ∆Eab* and ∆E00 (1 : 1 : 1) metrics. CONCLUSION: The substrate and cement affected the final color of zirconia-based all-ceramic crowns, but the color differences corresponded to an acceptable match. CLINICAL SIGNIFICANCE: As both substrate and cement influence the final color of multi-layered ceramic prosthesis, dentists and dental technicians should understand the optical properties of dental ceramics to reproduce the natural appearance of dental structures and maximize the chance for excellent color matches.

Does background color influence visual thresholds?

OBJECTIVE: To evaluate the influence of neutral color backgrounds on visual thresholds using three color difference metrics: CIELAB, CIEDE2000(1:1:1) and CIEDE2000(2:1:1). METHODS: Sixty observers (dentists and laypersons; n = 30) from three countries participated in the study. A psychophysical experiment based on visual assessments of simulated images of teeth on a calibrated display was performed. Images of simulated upper central incisors (SUCI) were consecutively displayed in pairs (60) on 3 neutral color backgrounds (black, grey and white). Three color difference metrics (CIELAB, CIEDE2000(1:1:1), and CIEDE2000(2:1:1)) were used to calculate the visual thresholds (PT- perceptibility threshold; and AT- acceptability threshold) with 95 % confidence intervals (CI) and a Takagi-Sugeno-Kang (TSK) Fuzzy Approximation model was used as fitting procedure. Data was statistically analyzed using paired t-test (p = 0.05). RESULTS: The50:50 % PT values were significantly lower over white background than over black background. The 50:50 % AT values were significantly greater over white background than over grey and black backgrounds. In most cases, the thresholds (PT and AT) values were significantly different for each color different metric over each background color (p ≤ 0.05). No difference was found between observers for PT and AT values. CONCLUSIONS: The perceptibility and acceptability thresholds in dentistry are affected by the color difference metrics and by the background color. SIGNIFICANCE: Dental color mismatches are more difficult to be accepted over a white background.

Influence of the photoactivation distance on the color and whiteness stability of resin-based composite after bleaching and aging.

OBJECTIVES: To evaluate the influence of photoactivation distance on color stability and whiteness changes after bleaching and water storage of a resin-based composite (RBC). METHODS: Twenty disc-shaped specimens (12 mm x 1 mm; n = 5) from a nanofilled RBC (Filtek Z350 XT) were photoactivated from two distances (0 and 8 mm) and bleached using either an at-home (HB) or an in-office (OB) bleaching protocol. Specimens were stored in distilled water up to 6 months (aged specimens). A spectrophotometer (Vita Easyshade) was used to measure CIE L*a*b* coordinates. Color stability was calculated using CIEDE2000 (ΔE00) metric, and whiteness variations using the whiteness index for dentistry (ΔWID). The 50:50 % visual thresholds were used to analyzed ΔE00 values (PT- perceptibility, and AT- acceptability) and ΔWID values (WPT- whiteness perceptibility, and WAT- whiteness acceptability). Color parameters L*, a*, b* and ΔWID were analyzed using repeated measures two-way ANOVA. RESULTS: After bleaching, RBC specimens photoactivated from 0 mm showed ΔE00 values below AT and the ones from 8 mm had values above AT. After OB, ΔWID values were below WPT, but all other comparisons were above WAT. CONCLUSIONS: Bleaching protocol did not influence on color change, but water storage (aging) did influence on color (ΔE00) and whiteness (ΔWID) changes. However, RBC specimens photoactivated from 8 mm showed color changes above AT after bleaching. CLINICAL SIGNIFICANCE: Color instability is one of the major causes for replacing esthetic restorations. The whiteness index for dentistry (WID) was able to show the "whiter-darker" effect on RBC after bleaching and aging. Dentists should be aware that RBC may appear darker after HB. Regardless of the photoactivation distance, OB did not show a perceptible difference immediately after bleaching. However, OB and HB showed a darker effect after aging procedure.

Intraoral repair of a chipped porcelain-zirconia restoration.

OBJECTIVE: Ceramic fracture is an undesirable outcome of the rehabilitation with fixed partial dentures (FPD), mainly because it may involve additional cost and clinical time for intraoral repair or replacement of the restoration. This clinical report describes a 5 years survival intraoral repair of a chipped porcelain veneered zirconia framework restoration using a resin-based composite. CLINICAL CONSIDERATIONS: A FPD of porcelain veneered zirconia was made. After 18 months, the FPD presented a porcelain chip (porcelain fracture without exposure to the zirconia structure) on the buccal side of the pontic. An epoxy resin replica of the fractured surface was obtained and was examined under scanning electron microscopy. Fracture origin was found at the cervical area of the pontic. Intraoral repair by bonding the chipped fragment back in place was performed. After 15 days, the porcelain fragment debonded without patient knowledge and the fragment was lost. Then, intraoral repair using composite resin to restore the fractured area was performed and is still in function to date. CONCLUSIONS: Based on the 5-years survival of the performed intraoral repair, the composite resin reconstruction technique has shown to be an adequate alternative treatment for fractured FPD. CLINICAL SIGNIFICANCE: A resin composite repair of the fracture site can be performed in one clinical session, using much less time and cost than for the replacement of FPD. This clinical case survived 5 years to date.

Masking ability of indirect restorative systems on tooth-colored resin substrates.

OBJECTIVE: To evaluate the masking ability of different indirect restorative systems (IRS) on tooth-colored resin substrates. METHODS: A1-shaded specimens from 5 IRS (LDC-IPS e.max® CAD; YZW-Zenostar Zr Translucent; PICN-Enamic; YLD-T-IPS e.max® ZirCAD + IPS e.max Ceram; CAD-on-Zenostar Zr Translucent + Crystall./Connect + IPS e.max® CAD) were fabricated. Specimens (n = 5) were cemented with a resin luting agent (Variolink® N; shade White) on three different shades (ND3, ND8 and ND9) of a tooth-colored resin substrate (IPS Natural Die Material). Spectral reflectance and color coordinates were measured using a spectroradiometer under standardized lighting conditions (CIE D65 illumination) and optical geometry 0/45°. Color differences (ΔEab* and ΔE00) from cemented specimens and CIELAB- and CIEDE2000-based translucency parameter (TP and TP00) from non-cemented specimens were calculated. Data was statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). ΔE values were also analyzed using perceptibility (PT = 1.22 ΔEab* units; 0.81 ΔE00 units) and acceptability (AT = 2.66 ΔEab* units; 1.77 ΔE00 units) thresholds. RESULTS: The cemented specimens of CAD-on, LDC, YZW and PICN on different substrates (ND3-ND8, ND3-ND9 and ND8-ND9) showed different ΔEab* and ΔE00 values (p ≤ 0.05), which were above AT. YLD-T showed ΔEab* and ΔE00 values below AT for all comparisons. Lowest and highest TP and TP00 values were obtained for YLD-T and PICN, respectively (p ≤ 0.05). SIGNIFICANCE: Resin-cemented YLD-T on different tooth-colored substrates showed less translucency as well as smaller color differences (below acceptability threshold), indicating the best masking ability among evaluated systems.

Optical and colorimetric evaluation of a multi-color polymer-infiltrated ceramic-network material.

OBJECTIVE: To evaluate color, translucency parameter and optical properties (scattering (S), absorption (K) and transmittance (T)) of a multi-color polymer-infiltrated ceramic-network (PICN) material. METHODS: Samples of shades 1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT from VITA ENAMIC® multiColor (E-MC) High Translucent were fabricated (n = 3). CAD-CAM blocks were cut and polished to 1.00 ± 0.01 mm of thickness. Diffuse reflectance and color coordinates were measured against white and black backgrounds, using a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45°/0° geometry. Color and translucency differences were evaluated using 50:50% perceptibility (PT and TPT) and 50:50% acceptability (AT and TAT) thresholds. S and K coefficients and T were calculated using Kubelka-Munk's equations. Data was statistically analyzed using Kruskal-Wallis, Mann-Whitney tests, and VAF coefficient. RESULT: Mean C* and b* values increased from incisal to cervical layers with statistically significant differences (p < 0.05). In general, ΔE00 between sequential layers were above PT for all shades. In addition, translucency parameter (TP) increased from cervical to incisal and ΔTP00 values were greater than TPT00 and lower than TAT00 between all sequential layers. Layers from all shades showed similar spectral behavior for S (97.4% ≤ VAF), K (85.0% ≤ VAF) coefficients and T (95.3% ≤ VAF). However, these values presented significant differences (p < 0.05) from cervical to incisal layers. SIGNIFICANCE: The gradient in color and translucency of this novel CAD-CAM multi-color PICN material can assist dental technicians and dentists to reach greater esthetics than the pre-existing CAD-CAM monolithicmaterials.