Aim: To investigate the effect of implant-abutment angulation and crown material on stress distribution of central incisors. Finite element method was used to simulate the clinical situation of a maxillary right central incisor restored by two different implant-abutment angulations, 15° and 25°, using two different crown materials (IPS E-Max CAD and zirconia). Methods: Two 3D finite element models were specially prepared for this research simulating the abutment angulations. Commercial engineering CAD/CAM package was used to model crown, implant abutment complex and bone (cortical and spongy) in 3D. Linear static analysis was performed by applying a 178 N oblique load. The obtained results were compared with former experimental results. Results: Implant Von Mises stress level was negligibly changed with increasing abutment angulation. The abutment with higher angulation is mechanically weaker and expected to fail at lower loading in comparison with the steeper one. Similarly, screw used with abutment angulation of 25° will fail at lower (about one-third) load value the failure load of similar screw used with abutment angulated by 15°. Conclusions: Bone (cortical and spongy) is insensitive to crown material. Increasing abutment angulation from 15° to 25°, increases stress on cortical bone by about 20% and reduces it by about 12% on spongy bone. Crown fracture resistance is dramatically reduced by increasing abutment angulation. Zirconia crown showed better performance than E-Max one.
Purpose: Objectives of this study were to assess and compare the impact of coloring beverages and surface finishing on color stability and surface roughness of dental ceramics.Material and methods: Twenty-eight identical cuboids (14*12*1mm) were cut from zirconiareinforced lithium silicate blocks (suprinity) using a precision cutting machine. Another 28 identical cuboids with the same dimensions were milled from high translucent zirconia ceramic blank (zolid fx). The specimens of each ceramic material were divided into 2 main groups (n=14) according to the finishing technique used; group G: specimens were glazed. group P: specimens were polished. Each subgroup was subdivided into 2 subgroups (n=7) according to the immersion solution used; Tea or Cola. Color measurements and surface roughness of all specimens were measured at the beginning and after 28 days of immersion in the staining beverages.Results: Tea possessed the highest color changes in all tested groups, and these changes were statistically significant compared with those of Cola in both surface finishing groups and in both types of ceramics. The color changes of Tea were not clinically acceptable in the zirconia ceramic groups (ΔE ˃3.3).While Cola possessed the highest mean Ra in all tested groups, and these changes were statistically significant compared with those of Tea in both surface finishing groups and in both types of ceramics.
Conclusions:Tea showed the highest impact on color of polished and glazed types of used ceramics, while Cola significantly increased the surface roughness of both polished and glazed types of used ceramics.
Objectives: To study the outcome of different surface treatments on X ray diffraction analysis (XRD) and flexural strength of super translucent zirconia.Materials and Methods: Forty identical discs were milled from presintered super translucent zirconia blank (VITA YZ ST, VITA Zahnfabrik, Germany). Specimens were classified into 4 groups according to the surface treatment used: Group C: no treatment (control group), Group S: discs were airborne particle, Group P: discs were treated with primer and Group SP: discs were airborne particle then, they were treated with primer. All specimens were subjected to XRD analysis and biaxial flexural strength test.
Results:The highest biaxial flexural strength recorded value was for the C group (462.11±17.33 MPa) while the lowest one was recorded for S group (310.33±7.78 MPa). Applying one way ANOVA and Tukey test revealed a statistically significant difference among all tested groups. The XRD analysis of specimens that were treated with different surface treatments revealed the evolution of monoclinic phase transformation in groups S and SP.
Conclusions:The airborne particle abrasion resulted in the evolution of tetragonal to monoclinic phase transformation on the zirconia surface which in turn negatively affected the flexural strength of super translucent zirconia.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.