Degradation effects of dietary solvents on microhardness and inorganic elements of computer-aided design/computer-aided manufacturing dental composites.

BACKGROUND: Computer-aided design/computer-aided manufacturing (CAD/CAM) dental composites were introduced with superior mechanical properties than conventional dental composites. However, little is known on effects of dietary solvents on microhardness or inorganic elemental composition of CAD/CAM composites. OBJECTIVES: The objectives of this study were to evaluate the degradation effects of each dietary solvent on the microhardness of the different CAD/CAM dental composites and to observe the degradation effects of dietary solvent on the inorganic elements of the dental composites investigated. METHODS: Fifty specimens with dimensions 12 mm x 14 mm x 1.5 mm were prepared for direct composite (Filtek Z350 XT [FZ]), indirect composite (Shofu Ceramage [CM]), and three CAD/CAM composites (Lava Ultimate [LU], Cerasmart [CS], and Vita Enamic [VE]). The specimens were randomly divided into 5 groups (n = 10) and conditioned for 1-week at 37°C in the following: air (control), distilled water, 0.02 N citric acid, 0.02 N lactic acid and 50% ethanol-water solution. Subsequently, the specimens were subjected to microhardness test (KHN) using Knoop hardness indenter. Air (control) and representative postconditioning specimens with the lowest mean KHN value for each material were analyzed using energy dispersive X-ray spectroscopy (EDX). Statistical analysis was done using one-way ANOVA and post hoc Bonferroni test at a significance level of p = 0.05. RESULTS: Mean KHN values ranged from 39.7 ± 2.7 kg/mm2 for FZ conditioned in 50% ethanol-water solution to 79.2 ± 3.4 kg/mm2 for VE conditioned in air (control). With exception to LU, significant differences were observed between materials and dietary solvents for other dental composites investigated. EDX showed stable peaks of the inorganic elements between air (control) and representative postconditioning specimens. CONCLUSIONS: The microhardness of dental composites was significantly affected by dietary solvents, except for one CAD/CAM composite [LU]. However, no changes were observed in the inorganic elemental composition of dental composites between air (control) and 1-week postconditioning.

Dietary pattern and oral cancer risk--a factor analysis study.

OBJECTIVES: The role of diet in cancer risk has mainly been investigated based on intake of individual food items. However, food consumption is made up of a combination of various food items. This study aims to determine the association of dietary patterns with oral cancer risk. METHODS: A total of 306 matched cases and controls were recruited in this study. Data on dietary intake were obtained using food frequency questionnaire (FFQ). Factor analysis (FA) was performed to identify dietary patterns based on the intake of nine major food groups, resulting in four factors/components being retained. The odds ratio (OR) was computed for each component using conditional logistic regression. RESULTS: The first pattern labelled as 'modern' was loaded with processed foods and snacks, whereas the second pattern termed as 'prudent' was characterized by intake of fruits and vegetables. The third pattern labelled as 'traditional' consisted of beverages and starches, while the fourth pattern termed as 'combination' was loaded with intakes of dairy, fermented/salted and meat/by-products. A significant reduced risk was found for 'prudent' (OR 0.53, 95% CI = 0.28-0.98), whereas an increased risk was found for both 'combination' (OR 2.43, 95% CI = 1.33-4.45) and 'traditional' (OR 2.32, 95% CI = 1.23-4.25) patterns. However, after adjusting for risk habits of tobacco smoking, alcohol consumption and betel quid chewing, only 'combination' (aOR 2.99, 95% CI = 1.55-5.75) and 'traditional' (aOR 2.08, 95% CI = 1.09-3.97) patterns remained significant. CONCLUSION: Consumption in the highest tertile of 'traditional' and 'combination' patterns may induce twice and thrice the risk of oral cancer, respectively.