Department of Dental Materials and Prosthesis, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
Department of Restorative Dentistry, Faculty of Pharmacy, Dentistry and Nursing, Federal University of Ceará, Fortaleza, CE, Brazil.
Braz Dent J. 2021 Sep-Oct;32(5):67-76. doi: 10.1590/0103-6440202104453.
This study evaluated the vertical misfit, passivity, and stress distribution after tightening the screws of different prosthesis. Two implants were used to simulate the rehabilitation of partially edentulous mandible space from the second premolar to the second molar. 40 three-element screw-retained fixed dental prosthesis with distal cantilever were fabricated and divided into four groups according to the method of production of framework (n = 10): G1 = conventional casting one-piece framework, G2 = conventional casting sectioned and laser welding, G3 = conventional casting sectioned and tungsten inert gas (TIG) welding and G4 = framework obtained by CAD/CAM (computer-aided design/computer-aided manufacturing) system. The vertical misfits (both screws tightened) and the passive fit (one screw tightened) were measured under a comparator optical microscope. The data was submitted to Shapiro-Wilk test to enable comparison with ANOVA followed by Tukey with Bonferroni adjust (α = .05). The qualitative analysis of the stress distribution was performed by the photoelastic method. The vertical misfit (both screws tightened) of the G2 (24 μm) and G3 (27 μm) were significantly higher than G4 (10 μm) (p = 0,006). The passive fit (for the non-tightened) of the G1(64 μm) and G3 (61 μm) were significantly higher than the G4 (32 μm) (p=0,009). G1 showed high stress between the implants in the photoelastic analysis and G4 presented lower stress. In conclusion, CAD/CAM method results in less vertical misfit, more passivity, and consequently better stress distribution to the bone.
本研究评估了不同修复体在拧紧螺丝后垂直不匹配、被动贴合和应力分布情况。使用两个种植体模拟从第二前磨牙到第二磨牙的部分缺牙下颌间隙的修复。制作了 40 个带有远中悬臂的三单位螺丝固位固定义齿，并根据框架制作方法分为四组（n = 10）：G1 = 常规铸造整体式框架，G2 = 常规铸造分段式激光焊接，G3 = 常规铸造分段式钨极惰性气体（TIG）焊接，G4 = CAD/CAM（计算机辅助设计/计算机辅助制造）系统获得的框架。使用比较显微镜测量垂直不匹配（两个螺丝拧紧）和被动贴合（一个螺丝拧紧）。数据采用 Shapiro-Wilk 检验进行正态性检验，然后进行方差分析，随后采用 Tukey 检验进行多重比较（α =.05）。采用光弹法对应力分布进行定性分析。G2（24μm）和 G3（27μm）的垂直不匹配（两个螺丝拧紧）显著高于 G4（10μm）（p = 0.006）。G1（64μm）和 G3（61μm）的被动贴合（非拧紧）显著高于 G4（32μm）（p=0.009）。光弹分析显示 G1 种植体之间的应力较高，而 G4 则呈现较低的应力。综上所述，CAD/CAM 方法可减少垂直不匹配、提高被动贴合度，从而改善骨的应力分布。
