Effect of erosive conditions on different sealant materials used in paediatric dentistry.

To evaluate the effect of acidic challenge on erosion depth and topographic characteristics of different materials used as occlusal sealants. Two hundred specimens of five sealant materials (Fuji IX, Ketac Molar, Fuji II, Equia and Clinpro) and forty bovine teeth enamel samples (control) were prepared and exposed to acidic challenge. The specimens were immersed in four different solutions (orange juice, coke drink, citric acid or distilled water) under mildly shaken conditions for 3 days. The erosion depth profiles were measured using a profilometer and Scanning Electron Microscope (SEM). Two-way ANOVA with Tukey post-hoc test was performed to evaluate the interactions. Sealant material and acidic challenge had significant effects on erosion depth. Among the materials, Fuji II presented the highest mean of erosion depth after immersion in orange juice, coke drink, and citric acid. All materials groups presented higher erosion depth values after immersion in the citric acid solution, except Clinpro. Bovine enamel presented higher erosion depth values compared to all materials when submitted to erosive challenge. Sealant materials submitted to the acidic challenge presented different degrees of erosion and topographic modification; however, they are less susceptible to erosion than bovine teeth enamel.

Effect of erosive conditions on different sealant materials used in paediatric dentistry

Abstract To evaluate the effect of acidic challenge on erosion depth and topographic characteristics of different materials used as occlusal sealants. Two hundred specimens of five sealant materials (Fuji IX, Ketac Molar, Fuji II, Equia and Clinpro) and forty bovine teeth enamel samples (control) were prepared and exposed to acidic challenge. The specimens were immersed in four different solutions (orange juice, coke drink, citric acid or distilled water) under mildly shaken conditions for 3 days. The erosion depth profiles were measured using a profilometer and Scanning Electron Microscope (SEM). Two-way ANOVA with Tukey post-hoc test was performed to evaluate the interactions. Sealant material and acidic challenge had significant effects on erosion depth. Among the materials, Fuji II presented the highest mean of erosion depth after immersion in orange juice, coke drink, and citric acid. All materials groups presented higher erosion depth values after immersion in the citric acid solution, except Clinpro. Bovine enamel presented higher erosion depth values compared to all materials when submitted to erosive challenge. Sealant materials submitted to the acidic challenge presented different degrees of erosion and topographic modification; however, they are less susceptible to erosion than bovine teeth enamel.

Translucency and masking ability of a translucent zirconia with different thicknesses over dark backgrounds / Translucidez e capacidade de mascaramento de uma zircônia translúcida com diferentes espessuras sobre substratos escuros

ABSTRACT Objectives: To evaluate the translucency, contrast ratio and masking ability of a translucent zirconia with different thicknesses. Methods: Disc shaped specimens (n= 3) with 10 mm (Ø) x 1.5 mm, 1 mm and 0.7 mm (thickness) were manufactured simulating all-ceramic simplified restorations. Substrate discs (n= 2; Ø: 10 mm; thickness: 2 mm) were simulated with composite resin shades: A2 (positive control) and C4; and metal alloys: silver (Ni-Cr) and golden (Cu-Al). Optical properties of the 9 translucent zirconia specimens placed on the 3 different substrates were analyzed by a spectrophotometer. The color variation (ΔE00) between each ceramic structure over the positive control substrate (A2) and over the dark backgrounds (C4, silvery, golden) were obtained as to their ceramic masking ability and subjected to non-parametric Kruskal Wallis test (5%). The translucency parameter (TP00) and contrast ratio (CR) of the different thicknesses of the ceramic discs were also collected and analyzed by one-way ANOVA and the Tukey test (5%). Results: The translucent zirconia showed greater opacity in the thickness of 1.5 mm, although it was not statistically different between 0.7 and 1.0 mm. All dark backgrounds significantly affected the final color of the simplified restoration in all evaluated thicknesses. However, the increase in ceramic thickness showed a decrease in ΔE00 values for all substrates. Conclusion: The translucent zirconia was not able to mask the dark substrates, independent of the evaluated thickness.

RESUMO Objetivos: Avaliar a translucidez, razão de contraste e capacidade de mascaramento de uma zircônia translúcida com diferentes espessuras. Métodos: Espécimes em forma de disco (n= 3) com 10 mm (Ø) x 1,5 mm, 1 mm e 0,7 mm (espessura) foram confeccionados simulando restaurações simplificadas em cerâmica pura. Discos de substrato (n= 2; Ø: 10 mm; espessura: 2 mm) foram simulados com as cores de resina composta: A2 (controle positivo) e C4; e ligas metálicas: prata (Ni-Cr) e ouro (Cu-Al). As propriedades ópticas dos 9 espécimes de zircônia translúcida posicionados nos 3 substratos diferentes foram analisadas por um espectrofotômetro. A variação de cor (ΔE00) entre cada espécime cerâmico sobre o substrato controle positivo (A2) e sobre os fundos escuros (C4, prateado, dourado) foi calculada quanto à capacidade de mascaramento da cerâmica e submetida ao teste não paramétrico de Kruskal Wallis (5%). O parâmetro de translucidez (TP00) e a razão de contraste (CR) das diferentes espessuras dos discos cerâmicos também foram coletados e analisados por ANOVA de uma via e teste de Tukey (5%). Resultados: A zircônia translúcida apresentou maior opacidade na espessura de 1,5 mm, embora não tenha sido estatisticamente diferente entre 0,7 e 1,0 mm. Todos os fundos escuros afetaram significativamente a cor final da restauração simplificada em todas as espessuras avaliadas. No entanto, o aumento da espessura da cerâmica mostrou uma diminuição nos valores de ΔE00 para todos os substratos. Conclusão: A zircônia translúcida não foi capaz de mascarar os substratos escuros, independente da espessura avaliada.

Masking ability of implant abutment substrates by using different ceramic restorative systems.

STATEMENT OF PROBLEM: Information regarding the masking ability of ceramic crowns over different implant abutment materials is scarce. PURPOSE: The purpose of this in vitro study was to evaluate the masking ability of different monolithic or bilayer ceramic materials with different thicknesses over substrates indicated for implant restorations by using opaque and translucent evaluation pastes. MATERIAL AND METHODS: Disk-shaped specimens, shade A1 (VITA Classic; Ø10×1.5 to 2.5 mm), of different ceramics (a bilayer system [yttria-stabilized zirconia infrastructure+porcelain veneer: Zir+Pc] and monolithic systems [lithium disilicate under low, medium, or high translucency: LtLD, MtLD, or HtLD, respectively, and a high-translucent yttria-stabilized zirconia: HtZir]) were made (n=4). The color difference (ΔE00) was assessed by using the CIEDE2000 formula and considering the different ceramic systems over 5 implant abutment materials (A1 shade Zir [Zir A1]; white Zir [White Zir]; A1 low-translucency lithium disilicate [LD]; polyetheretherketone [PEEK]; and titanium [Ti]) when using 2 different evaluation pastes (translucent or opaque). The control comparison was the restorative material positioned over the Zir A1 substrate with a translucent evaluation paste. Statistical analysis was made by using a 2-way ANOVA and Tukey post hoc tests (α=.05) for ΔE00 data considering the restorative material and luting agent factors as their association. Additionally, ΔE00 data were qualitatively analyzed considering the acceptability and perceptibility thresholds. The translucency parameter (TP00) of each restorative material was evaluated, and data were submitted to 1-way ANOVA and Tukey post hoc tests (α=.05). RESULTS: The most predictable masking ability was seen with Zir+Pc regardless of the evaluation paste used. Nevertheless, under 1.5-mm thickness, Zir+Pc did not adequately mask Ti (ΔE00>1.77). Most monolithic ceramics did not mask discolored substrates (PEEK or Ti, ΔE00>1.77). The exception was HtZir, which presented acceptable masking ability over PEEK at 2.5-mm thickness with both evaluation pastes (ΔE00<1.77). Regardless of the restorative material thickness, Zir+Pc showed the lowest (P<.05) TP00 values (TP00=3.45 at 1.5-mm thickness; TP00=2.00 at 2.5-mm thickness), and HtLD presented the highest (P<.05, TP00=23.50 at 1.5-mm thickness; TP00=13.36 at 2.5-mm thickness). HtZir showed similar TP00 to MtLD at 1.5-mm thickness and similar TP00 to Zir+Pc when used at 2.5-mm thickness (P>.05). CONCLUSIONS: Monolithic ceramics should be used with caution over discolored implant abutments. Bilayer systems (Zir+Pc) were the most predictable approach to adequately masking discolored substrates such as PEEK or Ti. An increased restoration thickness provided higher masking ability for all restorative materials tested.

Fatigue performance of adhesively luted glass or polycrystalline CAD-CAM monolithic crowns.

STATEMENT OF PROBLEM: Data comparing the fatigue performance of adhesively luted glass or polycrystalline ceramic systems for computer-aided design and computer-aided manufacturing (CAD-CAM) are scarce. PURPOSE: The purpose of this in vitro study was to evaluate and compare the fatigue performance of monolithic crowns manufactured from glass or polycrystalline CAD-CAM ceramic systems adhesively luted to a dentin analog. MATERIALS AND METHODS: Fifty-four pairs of standardized preparations of dentin analog (NEMA Grade G10) and simplified ceramic crowns of 1.5-mm thickness were obtained with 3 ceramic materials: lithium disilicate (LD) glass-ceramic (IPS e.max CAD); zirconia-reinforced lithium silicate (ZLS) glass-ceramic (Vita Suprinity); and translucent yttrium fully stabilized polycrystalline zirconia (Trans YZ) (Prettau Anterior). The simplified crowns (n=15) were adhesively cemented onto the preparations and subjected to step-stress fatigue test (initial load of 400 N, 20 Hz, 10 000 cycles, followed by 100-N increment steps until failure). Collected data (fatigue failure load [FFL] and cycles for failure [CFF]) were submitted to survival analysis with the Kaplan-Meier and Mantel-Cox post hoc tests (α=.05) and to Weibull analysis (Weibull modulus and its respective 95% confidence interval). Failed crowns were submitted to fractography analysis. The surface characteristics of the internal surface (roughness, fractal dimension) of additional crowns were accessed, and the occlusal cement thickness obtained in each luted system was measured. RESULTS: Trans YZ crowns presented the highest values of FFL, CFF, and survival rates, followed by ZLS and LD (mean FFL: 1740 N>1187 N>987 N; mean CFF: 149 000>92 613>73 667). Weibull modulus and cement thickness were similar for all tested materials. LD presented the roughest internal surface, followed by ZLS (mean Ra: 226 nm>169 nm>93 nm). The LD and ZLS internal surfaces also showed higher fractal dimension, pointing to a more complex surface topography (mean fractal dimension: 2.242=2.238>2.147). CONCLUSIONS: CAD-CAM monolithic crowns of Trans YZ show the best fatigue performance. In addition, ZLS crowns also showed better performance than LD crowns.