Influence of a gray background and the illuminant on tooth shade selection.

STATEMENT OF PROBLEM: Visual shade selection in dentistry may be influenced by factors that include the background color and the illuminant. PURPOSE: The purpose of this clinical study was to evaluate the influence of using a gray background and a light-correcting device on visual shade selection. MATERIAL AND METHODS: Two experienced clinicians assessed the incisor color of 30 volunteers using the VITA 3D-MASTER shade guide. Visual analyses were carried out using or not (control) a gray background, with and without (control) a light-correcting device (Smile Lite). Furthermore, the use of a polarizing filter was evaluated. Data from a clinical spectrophotometer were defined as the standard instrumental analysis. The agreement and the similarity (based on the whitening indexes of tabs) were evaluated between instrumental and visual analyses. Statistical testing was conducted through ordinal logistic regression and repeated-measures ANOVA. The Shapiro-Wilk test was used to confirm the data distribution, and homogeneity of variance was assessed with the Levene test (α=.05) RESULTS: The use of Smile Lite resulted in lighter tabs than indicated by the instrumental analysis, and the opposite was observed in its absence. The polarizing filter did not affect the results (P>.05). For similarity, the illuminant improved the results (P<.001). The gray background reduced the differences between visual and instrumental analysis only in the absence of the Smile Lite (P<.001). CONCLUSIONS: The color similarity between visual and instrumental analysis improved with the use of a light-correcting device with or without a polarization filter. A gray background was useful only without the light-correcting device.

Luting laminate veneers: Do resin-composites produce less polymerization stress than resin cements?

OBJECTIVES: Regular composites could produce less polymerization stress than resin cements when luting laminate veneers but there is no proper evidence to support this theory. The current study aimed to determine the degree of conversion, volumetric shrinkage, polymerization stress and the resultant elastic moduli of materials currently used for adhesive cementation and to determine possible correlations. METHODS: The study considered (i) regular resin composites (Admira Fusion, Gradia, Grandioso, Palfique, Sirius Z, Viscalor and Z100) at room and pre-warmed (PW) at 69ºC, (ii) flowable composites (Sigma Flow and Grandioso Flow); (iii) solely light-activated cements (AllCem Veneer, Variolink Esthetic and RelyX Veneer); and (iv) one dual-activated resin cement (SpeedCEM). Degree of conversion (DC, n = 3) was accessed with FTIR 1 h after irradiation. Bonded-disk and Bioman II instruments were used to access polymerization shrinkage strain and shrinkage stress, respectively, for 60 min at 23 ± 1◦C (n = 3). The elastic modulus was determined by 3-point bending flexural test (n = 6). The results were submitted to analyse s of variance, Tukey's, and correlation tests. RESULTS: For regular composites, the pre-warming did not affect DC, shrinkage and modulus but significantly increased the stress magnitude. Correlation tests indicated a significant relationship only between stress and polymerization shrinkage (r = 0.811343). SIGNIFICANCE: Regular composites can produce less polymerization stress than resin cements when luting laminate veneers. Polymerization stress was dependent on the shrinkage magnitude, but not on the degree of conversion nor the elastic modulus.

Adhesion and optics: The challenges of esthetic oral rehabilitation on varied substrates-Reflections based on a clinical report.

Patients with challenging prosthodontic conditions require rehabilitation with a biological, functional, and esthetic approach. When one or more teeth are badly discolored, their restoration is problematic because poor appearance affects not only the crown but also the periodontal tissues. This clinical report describes a complex esthetic rehabilitation with conservative tissue management and ceramic restorations. Subepithelial connective tissue graft surgery and the replacement of a cast metal post with a glass fiber post addressed the problem of a discolored maxillary central incisor. The discolored right maxillary incisor was restored with a combination of a medium-opaque, lithium-disilicate ceramic coping to mask the dark root and to approximate the color of the other incisors. Subsequently, 6 ceramic veneers were placed. A knowledge of the materials' optical properties and adhesion possibilities helped solve this complex problem.

Curing potential and color stability of different resin-based luting materials.

PURPOSE: To determine the curing potential and color stability of resin-based luting materials for aesthetic restorations. MATERIAL AND METHODS: Four resin-based luting agents were tested: traditional dual-activated resin cement (RelyX ARC, ARC), amine-free dual-activated resin cement (RelyX Ultimate, ULT), light-activated resin cement (RelyX Veneer, VEN), and pre-heated restorative resin composite (Filtek Supreme, PHC). Degree of C=C conversion was determined by infrared spectroscopy (n=3) with direct light exposure or with interposition of 1.5-mm-thick ceramic (e.max Press HT) between the luting material and light. The curing potential considered the ratio between these two scenarios. Color difference (n=6) was determined by CIELAB (ΔEab) and CIEDE2000 (ΔE00) methods, by spectrophotometer measurements made 24h after photoactivation and 90 days after storage in water. Data was submitted to ANOVA and Tukey's test (α=0.05). RESULTS: The luting agents affected both conversion and color stability. With ceramic, ARC produced the highest conversion among the tested groups (75±1%) and the pre-heated composite (PHC) the lowest one (51±3%), but the curing potential was similar for all materials. ULT produced lower ΔEab than ARC. PHC presented the lowest color difference when considered both CIELAB and CIE2000 methods (ΔEab 2.1±0.4; ΔE00 1.6±0.2). SIGNIFICANCE: All luting strategies presented high curing potential. Amine-free dual-activated material was able to reduce color difference than that formulated with the amine component. Pre-heated composite produced the least color variation after storage.

A comparison between visual, intraoral scanner, and spectrophotometer shade matching: A clinical study.

STATEMENT OF PROBLEM: Visual shade matching is subjective and a cause of concern for clinicians. Different measurement devices have been developed to assist in tooth color selection and to achieve better esthetic results. However, consensus is lacking as to which method of tooth shade selection provides more predictable results. PURPOSE: The purpose of this clinical study was to compare the reliability of different visual and instrumental methods for dental shade matching. MATERIAL AND METHODS: Visual shade matching was performed by 3 experienced clinicians using 2 different shade guides (VITA Classical A1-D4 and VITA Toothguide 3D-MASTER with 29 tabs; VITA Zahnfabrik) with and without the aid of a light-correcting device (Smile Lite; Smile Line). An intraoral scanner (TRIOS; 3Shape A/S) and a spectrophotometer (VITA Easyshade Advance 4.0; VITA Zahnfabrik) were also used for color shade matching. The instrumental methods were repeated 3 times to determine repeatability. Shade-matching sessions for each method were performed under controlled lighting on the middle third of the maxillary right central incisor of 28 participants. The Fleiss' kappa statistical test was used to assess the reliability of each method. The weighted kappa statistical test was used to assess the agreement between the shades matched by different methods (α=.05). RESULTS: Instrumental methods were more accurate than visual methods. The best performance was found for the intraoral scanner configured for the 3D-MASTER scale (Fleiss' kappa value of .874) and for the spectrophotometer configured for the VITA Classical scale (Fleiss' kappa value of .805). The best visual shade-matching method was the VITA Classical scale associated with the light-correcting device (Fleiss' kappa value of .322). The Classical scale without the light-correcting device showed the poorest reliability (Fleiss' kappa value of .177) (P<.05). CONCLUSIONS: Instrumental methods for color shade matching were more reliable than the visual methods tested.

Análise comparativa da desadaptação obtida por diferentes sistemas usados para a fabricação de coroas cerâmicas suportadas por implantes / Comparative evaluation on the misfits of different all-ceramic implant-supported crown systems

Objetivo: comparar a precisão da adaptação de infraestruturas para coroas unitárias implantossuportadas, em zircônia e alumina, fabricadas por dois diferentes sistemas de fabricação. Material e métodos: implantes cone-morse Neodent foram utilizados, associados a componentes protéticos em zircônia (4,5 x 6 mm). Foram fabricadas 15 infraestruturas e divididas em três grupos (n=5): G1 – Zircônia (Neodent Digital); G2 – Alumina (Neodent); e G3: Zircônia (Zirkonzahn M5). Foram analisadas as discrepâncias horizontal e vertical em microscópio ótico (25x). Os resultados foram submetidos à Anova e teste de Tukey-Kramer (α=0,05). Resultados: os valores médios de desadaptação encontrados foram: Horizontal – G1 - 25,2 ± 12,86 μm, G2 - 79,5 ± 12,76 μm, e G3 - 130,0 ± 8,42 μm; Vertical – G1 - 4,1 ± 2,46 μm, G2 – 12,8 ± 9,62 μm, e G3 – 153,5 ± 83,92 μm. Na comparação estatística entre os grupos, o G3 apresentou os maiores valores de desadaptação (p < 0,05), enquanto que os outros grupos não apresentaram diferenças entre si (p > 0,05). Conclusão: dentro das limitações deste estudo, podemos concluir que as infraestruturas em zircônia fabricadas pelo sistema CAD/CAM Neodent Digital apresentaram adaptação adequada, seguida pelas infraestruturas em alumina e zircônia fabricadas pelo sistema CAD/CAM Zirkonzahn M5.

Objective: the purpose of this in vitro study was to compare the precision of fi t of implant-supported copings milled from semi-sintered Zirconia blocks fabricated by two different computer-assisted designs (CAD)/computer-assisted manufacturing (CAM) systems and using a suspension plasma spray Alumina injection process. Material and methods: the Neodent Morse Cone implant system (Neodent, Brazil) was used in the study associated with Zirconia implant-abutments (4.5 x 6 mm). Fifteen standardized copings were fabricated for the 3 test groups (n=5): G1 – Neodent Digital Zr copings; G2 – Neodent Alumina coping; and G3 – Zirkonzahn M5 copings. Horizontal and vertical discrepancies were measured and the misfi t values were evaluated in an optical microscope (25x). Data were submitted to Anova and Tukey-Kramer’s test (α=0.05). Results: the average misfi t levels found for the groups were: Horizontal – G1 - 25.2 ± 12.86 μm, G2 – 79.5 ± 12.76 μm, and G3 – 130 ± 8.42 μm; Vertical – G1 – 4.1 ± 2.46 μm, G2 - 12.8 ± 9.62 μm, and G3 - 153.5 ± 83.92 μm. In the statistical comparison between groups, G3 presented signifi cantly higher misfi t levels than the other groups (p < 0.05). The other groups had no signifi cant differences between each other (p > 0.05). Conclusion: Within the limitations of this study, it can be concluded that zirconia copings fabricated by Neodent Digital CAD/CAM system presented adequate fit followed by alumina and zirconia copings fabricated by the Zirkonzahn M5 CAD/CAM system.