Influence of different glaze firing protocols on the mechanical properties of CAD-CAM ceramic materials.

STATEMENT OF PROBLEM: The influence of different glaze firing protocols and cooling on the behavior of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics is unclear. PURPOSE: The purpose of this in vitro study was to investigate the influence of different glaze firing protocols on the abrasion resistance, surface roughness, microhardness, and brittleness index of CAD-CAM ceramics. MATERIAL AND METHODS: Rectangular specimens of IPS e.max CAD (MAX), IPS Empress CAD (PRE), and CEREC Blocs (CER) were obtained and divided into 5 groups according to the glaze firing protocol (n=8): control (CO), 1 conventional glaze firing (GF), 2 conventional glaze firings (GF2), 1 extended glaze firing (EG), and 2 extended glaze firings (EG2). The coefficient of friction (µ) was determined with the pin-on-disk test, and specimens were analyzed with an optical interferometer to calculate volume loss and roughness. Vickers microhardness and the brittleness index were obtained with a microdurometer. Microhardness data were evaluated by 2-way ANOVA and the Sidak tests (α=.05). Data from other tests were assessed with nonparametric ANOVA and Bonferroni tests (α=.05). RESULTS: Groups GF2, EG, and EG2 of MAX and PRE and all groups of CER presented higher levels of coefficient of friction. Groups EG and EG2 of MAX and CER showed high volume loss and surface roughness. Groups EG and EG2 of MAX and PRE showed lower hardness, as did all groups of CER. MAX-CO and groups GF and EG of PRE showed a lower brittleness index (P<.05), while CER groups showed no significant differences (P>.05). CONCLUSIONS: Ceramic specimens with conventional glaze firing presented less surface wear than those with extended glaze firing. The number of firings did not have a statistically significant influence.

Effect of a Bioactive Glass Ceramic on the Control of Enamel and Dentin Erosion Lesions.

This study evaluated the effect of a bioactive glass ceramic for the control of erosion and caries lesions. Fragments (n=10) of bovine enamel and root dentin received daily application of different treatments (Biosilicate; Acidulated Phosphate Fluoride- APF; Untreated - control) during the performance of erosive cycles. Surfaces were analyzed with 3D optical profilometry to quantify the superficial loss in four periods (1, 7, 14 and 21 days), as well as the lesion depth with confocal laser scanning microscopy. For caries progression assessment, initial Knoop microhardness was measured on enamel bovine fragments. Initial carious lesions were developed and specimens were divided into three groups (n=10), according to the daily topical application (Biosilicate; APF; no application - control), during the de-remineralization cycles for 14 days. Final microhardness was obtained to calculate the change of surface microhardness. Subsurface demineralization was analyzed using cross-sectional microhardness (depths 10, 30, 50, 70, 90, 110 and 220 µm). Data were tested using ANOVA and Tukey's test (a=5%). Results of erosive evaluation showed that Biosilicate promoted the lowest (p<0.05) values of surface loss, regardless of time, for both enamel and dentin; APF promoted lower (p<0.05) surface loss than control; analyzing different periods of time, APF did not show difference (p>0.05) between 14 and 21 days of demineralization. Results of enamel caries assessment showed that Biosilicate resulted in higher (p<0.05) surface and subsurface microhardness than both APF and control-applications. It may be concluded that Biosilicate application showed a higher potential to reduce surface loss and development of erosion and caries lesions.

Effect of a Bioactive Glass Ceramic on the Control of Enamel and Dentin Erosion Lesions

Abstract This study evaluated the effect of a bioactive glass ceramic for the control of erosion and caries lesions. Fragments (n=10) of bovine enamel and root dentin received daily application of different treatments (Biosilicate; Acidulated Phosphate Fluoride- APF; Untreated - control) during the performance of erosive cycles. Surfaces were analyzed with 3D optical profilometry to quantify the superficial loss in four periods (1, 7, 14 and 21 days), as well as the lesion depth with confocal laser scanning microscopy. For caries progression assessment, initial Knoop microhardness was measured on enamel bovine fragments. Initial carious lesions were developed and specimens were divided into three groups (n=10), according to the daily topical application (Biosilicate; APF; no application - control), during the de-remineralization cycles for 14 days. Final microhardness was obtained to calculate the change of surface microhardness. Subsurface demineralization was analyzed using cross-sectional microhardness (depths 10, 30, 50, 70, 90, 110 and 220 µm). Data were tested using ANOVA and Tukey's test (a=5%). Results of erosive evaluation showed that Biosilicate promoted the lowest (p<0.05) values of surface loss, regardless of time, for both enamel and dentin; APF promoted lower (p<0.05) surface loss than control; analyzing different periods of time, APF did not show difference (p>0.05) between 14 and 21 days of demineralization. Results of enamel caries assessment showed that Biosilicate resulted in higher (p<0.05) surface and subsurface microhardness than both APF and control-applications. It may be concluded that Biosilicate application showed a higher potential to reduce surface loss and development of erosion and caries lesions.

Resumo Este estudo avaliou o efeito de uma vitrocerâmica bioativa para o controle de lesões de erosão e cárie. Fragmentos (n=10) de esmalte bovino e dentina radicular receberam aplicação diária de diferentes tratamentos (Biosilicato; Fluoreto de Fosfato Acidulado - APF; não tratado - controle) durante a realização de ciclos erosivos. As superfícies foram analisadas com profilometria óptica 3D para quantificar a perda superficial em quatro períodos (1, 7, 14 e 21 dias), bem como a profundidade da lesão com microscopia confocal de varredura a laser. Para a avaliação da progressão de cárie, foi obtida a microdureza Knoop inicial de fragmentos de esmalte bovino. As lesões cariosas iniciais foram desenvolvidas e os espécimes foram divididos em três grupos (n =10), de acordo com a aplicação tópica diária (Biosilicato; APF; sem aplicação - controle) durante os ciclos de desmineralização por 14 dias. A microdureza final foi obtida para calcular a perda da microdureza superficial. A desmineralização sub-superficial foi analisada utilizando microdureza transversal (profundidades 10, 30, 50, 70, 90, 110 e 220 μm). Os dados foram testados utilizando ANOVA e teste de Tukey (α=5%). Os resultados da avaliação erosiva mostraram que o Biosilicato promoveu os menores valores (p <0,05) de perda superficial, independente do tempo, tanto para o esmalte como para a dentina; APF promoveu menor (p <0,05) perda de superfície do que controle; analisando os períodos de tempo, APF não mostrou diferença (p>0,05) entre 14 e 21 dias de desmineralização. Os resultados da avaliação da cárie no esmalte mostraram que o Biosilicato resultou em maiores (p<0,05) valores de microdureza superficial e subsuperficial do que as aplicações APF e controle. Pode-se concluir que a aplicação de Biosilicato apresentou maior potencial de redução da perda superficial e desenvolvimento de lesões de erosão e cárie.