RESUMO
PURPOSE: This study assessed the physical and mechanical properties of interim crown materials fabricated using various digital techniques after accelerated aging. MATERIALS AND METHODS: Three groups of interim dental restorative materials (N = 20) were tested. The first group (CO) was fabricated using a conventional manual method. The second group (ML) was prepared from prefabricated resin blocks for the milling method and cut into specimen sizes using a cutting disc. The third group (3D) was additively manufactured using a digital light-processing (DLP) 3D printer. Aging acceleration treatments using toothbrushing and thermocycling simulators were applied to half of the specimens corresponding to three years of usage in the oral environment (N = 10). Surface roughness (Ra), Vickers microhardness, 3-point bending, sorption, and solubility tests were performed. A 2-way analysis of variance (ANOVA) and Fisher's multiple comparison test were used to compare the results among the groups. RESULTS: The mean surface roughness (Ra) of the resin after accelerated aging was significantly higher in the CO and ML groups than that before aging, but not in the 3D group. All groups showed reduced hardness after accelerated aging. The flexural strength values were highest in the 3D group, followed by the ML and CO groups after accelerated aging. Accelerated aging significantly reduced water sorption in the ML group. CONCLUSION: According to the tested material and 3D printer type, both 3D-printed and milled interim restoration resins showed higher flexural strength and modulus, and lower surface roughness than those prepared by the conventional method after accelerated aging.
RESUMO
BACKGROUND: The racial and ethnic disparities in tooth morphology and alignment indicate the need for different orthodontic prescriptions. PURPOSE: This study aimed at utilizing the 3D digital models to measure the teeth prominence of Saudi adults and compare the results to previously published data. MATERIALS AND METHODS: The sample included 60 sets of 3D digital dental models of subjects who presented with non-orthodontic normal occlusion and balanced profile. Rhinoceros™ 3D modeling software was used to mark the midpoint of the clinical crown (LA) and the embrasure line and then to measure the prominence of the teeth. The collected data was analyzed using SPSS (IBM SPSS Inc., version 20, Chicago, IL, USA). The mean and SD scores were obtained for each measurement. Independent t-test, paired t-test, and student t-test were used for the comparison at a significant level of P ≤ 0.05. RESULT: Comparison between the right and the left sides, and between the male and female showed no significant differences, and hence the result data were combined. However, further comparison with the published data of the North American whites, Japanese, Indian, African and Italian showed significant differences in most of the teeth. CONCLUSION: Racial differences influence the teeth prominence values that should be considered in presenting orthodontic bracket prescriptions. More research in this field is needed.
