No abstract

The increased patients demand to improve their dental esthetics has led to the development of new tooth-colored ceramic restorations; however, accurate color matching of the restoration to the adjacent teeth and the subsequent dentist-laboratory communication remain one of the most critical procedures in clinical dentistry. (1,2) Several factors influence the esthetic success of dental ceramic restorations, (3) such as surface or substrate characteristics, (4,5) marginal accuracy, (6) ceramic thickness, (7) translucency, (8) underlying

To assess the effect of nano-modification of two CAD/CAM monolithic Zirconia systems (wet and dry-milled) on microstructural changes and fracture resistance upon aging. Twenty monolithic Zirconia discs (10mm x1.5mm) were divided into 2 groups (n=10) according to fabrication system;wet-milled (Incoris TZI) and dry-milled (CeramillZolid). Each group was subdivided into two subgroups (n=5), whether subjected to aging or not. Aging proceduresincluded accelerated hydrothermal aging and cyclic loading. Microstructural changes were assessed quantitatively and qualitatively using x-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Discs were subjected to fracture resistance test usinguniversal testing machine. Meansandstandard deviations were recorded for phase transformation (t-m)of Zirconia and repeated ANOVA was used to correlate phase transformation with fracture resistance results (p≤0.05). For aged subgroups, XRD analysis revealed significantly higher phase transformation of wet-milled than dry-milled (p≤0.05) and SEM analysis revealed wide zone phase transformation for wet-milled zirconia and minimal zone for dry-milled. For both systems, no significant difference between the mean flexural strength values ofnon-agedand aged zirconia (p≤0.05). Nanocrystalline microstructure of monolithic zirconia improved its resistance to aging. The fracture resistance of the two systems was not affected by aging.

No abstract

No abstract

No abstract

Objective: to assess wear behavior and surface roughness of CAD-CAM restorative materials and their opposing enamel antagonists. Materials and methods: Rectangular-shaped specimens (n=22) (14×12×1.5 mm) were prepared; 3D printed VarseoSmile Crown plus (VS) (n=11) and milled brilliant crios (BC) (n=11). Both groups were finished with composite polishing kit. Wear testing was performed in chewing simulator with twenty-two freshly extracted mandibular premolars antagonists. The wear of specimens and opposing enamel antagonists was calculated by weight loss. The surface roughness (Ra) of the specimens and their opposing enamel antagonist was analyzed by using a digital image analysis software at baseline and after chewing simulation then inspected by SEM. Data were statistically analyzed using Paired t-test, Independent t-test, and Chi square test (p = 0.05). Results: A significant weight loss in tested groups and their opposing enamel antagonists after chewing simulation was noticed by Paired t-test (p < 0.05) where insignificant percentage change of weight between tested groups (p = 0.93) and between their antagonists (p = 0.79) was noticed by Chi square test. Also, A significant difference in Ra value after chewing simulation between tested groups was noticed (p < 0.05) where insignificant percentage change in Ra value between tested groups (p =0.74) and between their antagonists (p = 0.88) was noticed by Chi square test. Conclusions: Based on their properties, each material was affected by chewing simulation at different intensities; The tested CAD-CAM restorative materials and their opposing enamel antagonists showed wear demonstrated by weight loss and difference in surface roughness.

Objective: To evaluate an innovative approach, Crown Margin Shifting (CMS), for its ability to re-establish the biological width (BW) or supracrestal tissue attachment. Clinical considerations:Seven patients aged between 25-45 years old, presented with bilateral maxillary premolars with deep interproximal caries violating the BW were recruited for this study. Both study sites received monolithic zirconia crowns with heavy chamfer finish line. The heavy chamfer is thicker and with bevel on the deepest part of experiment site. Clinical parameters were evaluated at baseline, 6 and 12 months after. Radiographic evaluation using CBCT was done to measure marginal bone loss (MBL) and the established BW at the deep proximal finish line.Results revealed significant improvement in Modified Plaque Index (MBI) and Gingival Index (GI) parameters in both sites at the end of the study. The Periodontal Probing Depth (PPD) increased significantly in the first 6 months only for both. The marginal bone loss (MBL) was present in control site throughout the 12 months, whereas in CMS site, it took place only in the first 6 months. Conclusions:The results support that CMS approach had less radiographic marginal bone loss without a negative influence on the clinical parameters up to one year follow-up.