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Made available in DSpace on 2022-04-28T17:22:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-07-01 Little is known about the impact of bleaching on the optical properties of computer-aided design and computer-aided manufactured (CAD-CAM) monolithic materials. The aim of the present study was to evaluate the effect of one session of in-office bleaching on stain removal, staining susceptibility, translucency, and whiteness variations of CAD-CAM monolithic materials. Disks were fabricated from Lava Ultimate (LU), Vita Enamic (VE), Vita Suprinity (VS), and IPS e.max CAD (IPS). A spectrophotometer was used to register Commission Internationale de l'Eclairage L*a*b* coordinates. For stain removal, 80 specimens from each material were assessed at baseline (R-0) and after immersion in deionized water or coffee for 36.5 days followed or not by bleaching with 40% hydrogen peroxide (R-1). For staining susceptibility, 80 specimens from each material were analyzed at baseline (R-0'), and after having been bleached or not and immersed in deionized water or coffee (R-1'). Both analyses were calculated as the color difference (Delta E-00) between R-1-R-0 and R-1'-R-0', respectively. Differences in translucency (Delta TP00) and whiteness (.WID) between R-1-R-0 and R-1'-R-0' were also calculated. Data were analyzed by three-way ANOVA and the Games-Howell post hoc test (alpha=0.05). Clinical significance was based on 50%:50% perceptibility and acceptability thresholds for Delta E-00, Delta TP00 and Delta W-ID, respectively. Surfaces were analyzed by scanning electron microscopy. Coffee increased Delta E-00 in LU, VE, and VS, and decreased their translucency and whiteness, whereas the IPS had only its whiteness affected. Bleaching after immersion in coffee decreased Delta E-00 in LU and VE, and increased translucency and whiteness of LU, VE, and VS. No effect was observed on IPS. Bleaching before immersion in coffee decreased translucency of LU, but within the acceptable interval, while VE exhibited lower Delta E-00, and became more translucent and less dark. Both VS and IPS were not affected. One session of in-office bleaching benefited optical properties of the previously stained LU, VE, and VS, without increasing their susceptibility to staining or adversely providing clinically unacceptable variations in their translucency and whiteness. All variations exhibited by the IPS were below the perceptible threshold. Sao Paulo State Univ UNESP, Dept Dent Mat & Prosthodont, Sch Dent, Araraquara, SP, Brazil Sao Paulo State Univ UNESP, Sch Dent, Araraquara, SP, Brazil Sao Paulo State Univ UNESP, Sch Dent, Dept Social Dent, Araraquara, SP, Brazil Sao Paulo State Univ UNESP, Dept Dent Mat & Prosthodont, Sch Dent, Araraquara, SP, Brazil Sao Paulo State Univ UNESP, Sch Dent, Araraquara, SP, Brazil Sao Paulo State Univ UNESP, Sch Dent, Dept Social Dent, Araraquara, SP, Brazil

Objective To investigate the influence of surface treatments conducted in presintering and postsintering stages on flexural strength and optical properties of zirconia. Materials and methods Specimens were milled from partially sintered zirconia blocks in different geometries and divided into three main groups as presintered, postsintered, and control groups. Test groups were further divided into three subgroups (n = 10) according to the surface treatments conducted (grinding, Er,Cr:YSGG laser irradiation, air-borne particle abrasion [APA]). Four-point flexural strength (σ) test and Weibull analysis were conducted. Color differences (ΔE00 ) and translucency parameter (TPab ) were calculated with a spectrophotometer. Surfaces of specimens were scrutinized under FESEM. Data were statistically analyzed. Results Postsintered groups exhibited higher σ values (P 0.8). Higher TPab values were obtained and deeper scratches were observed in presintered groups. Conclusions Surface treatments performed at postsintering stage had a favorable effect on the flexural strength of all specimens. Surface treatments performed before sintering increased translucency and caused higher ΔE00 values. Clinical significance Surface treatments performed at different sintering stages can alter mechanical and optical properties of zirconia.

This study evaluated the masking ability of different porcelain thicknesses and combination of enamel and/or dentin porcelain layers over simulated background dental substrates with higher (A2) and lower (C4) color values. Combination of the enamel (E) and dentin (D) monolayer porcelain disks with different thicknesses (0.5 mm, 0.8 mm, and 1 mm) resulted in the following bilayer groups (n=10): D1E1, D1E0.8; D1E0.5; D0.8E0.8; D0.8E0.5, and D0.5E0.5. CIELAB color coordinates were measured with a spectrophotometer. The translucency parameter of mono and bilayer specimens and the masking ability estimated by color variation (ΔE*ab) of bilayer specimens over simulated dental substrates were evaluated. Linear regression analysis was used to investigate the relationships translucency parameter × ΔE*, translucency parameter × porcelain thickness, and ΔE* × porcelain thickness. Data were analyzed statistically (α= 0.05). Thinner porcelain disks were associated with higher translucency. Porcelain monolayers were considerably more translucent than bilayers (enamel + dentin). Dentin porcelain was less translucent than enamel porcelain with same thickness. ΔE* was always lower when measured over A2 background. Higher ΔE* was observed for the C4 background, indicating poorer masking ability. Increased ΔE* was significantly associated with increased translucency for both backgrounds. Decreased translucency and ΔE* were associated with increased total porcelain thickness or increased dentin thickness for both backgrounds. In conclusion, increased porcelain thickness (particularly increased dentin layer) and increased porcelain opacity resulted in better masking ability of the dental backgrounds.

Statement of problem The influences of coloring and sintering procedures on the optical and mechanical properties of monolithic zirconia have not been thoroughly investigated. Purpose The purpose of this in vitro study was to investigate the effects of the coloring procedure and of varying final sintering temperatures on the translucency parameter (TP) and biaxial flexural strength (BFS) of monolithic zirconia. Material and methods Disk-shaped specimens (N=210) of 2 different monolithic zirconia brands (Vita YZ HT White [VYZa]; Vita YZ HT Color A2 [VYZb]; Prettau Zirkonzahn [PZ]; Prettau Anterior Zirkonzahn [PZA]) with a diameter of 15 mm and a thickness of 1.0 ±0.05 mm were prepared. Half of the specimens prepared from noncolored blocks (VYZa, PZ, and PZA) received coloring liquid application. Then, the specimens were divided into 3 subgroups (n=10) according to the final sintering temperatures (1350°C, 1450°C, and 1600°C). The TP was determined by using a reflection spectrophotometer, and the BFS was tested with the piston-on-3-ball method in a universal testing machine. Data were statistically analyzed by multivariate multiple regression and Bonferroni tests (α=.05). Results Significant differences were obtained among the groups based on the results of the TP and BFS ( P P P >.05). Conclusions Increased sintering temperature leads to increased translucency with minimal impact on the BFS. The coloring procedure should be considered at the time of material selection to avoid possible reduction in translucency.

Although the glass-ionomer cements were developed in the 1970s, it is only recently that their clinical use has expanded internationally. Improvements in formulation have resulted in better mechanical strengths, increased translucency and, more importantly, faster setting times. Their use as ‘dentine substitutes’ has expanded the versatility of laminate restorations in anterior and posterior teeth and the introduction of the silver-cermet ionomers provided materials with increased abrasion resistance. Glass-ionomer cements have a number of unique properties, including adhesion to moist tooth structure, biological compatibility, and anticariogenic properties due to their fluoride release. One of their major roles is the treatment of early carious lesions using microcavity preparation. However, like all materials, glass-ionomer cements have their weaknesses, the prime ones being lack of toughness, early water sensitivity, and porosity leading to poor surface polish. Future research should concentrate on correcting these deficiencies.