da Costa Rogério Goulart, Freire Andrea, Caregnatto de Morais Eduardo Christiano, Machado de Souza Evelise, Correr Giselle Maria, Rached Rodrigo Nunes
Dental Prosthesis, Federal Institute for Science and Technology of Parana, Curitiba, PR, Brazil.
Graduate Program in Dentistry, School of Life Sciences, Pontifícia Universidade Católica do Parana, Curitiba, Parana, Brazil.
Am J Dent. 2017 Feb;30(1):3-8.
To investigate the fracture resistance of weakened roots restored with prefabricated or CAD/CAM-customized posts and cores as well as the thickness of the cement film and the presence of voids in the cement.
The roots of 40 human premolars were weakened by removing internal dentin with a diamond bur (2.5 mm in the coronal third and 1.5 mm in the apical third) and restored with prefabricated posts (PPs) or customized posts (CPs) with or without a zirconia crown (n= 10). Posts and crowns were cemented with resin cement. Microtomography was used to determine the thickness of the cement film and whether voids were present. After fatigue testing (1 million cycles, 50 N, 5 Hz, 36.5°C), the specimens underwent compression testing with an oblique load (30°, 1 mm/minute) and fracture strengths were recorded (N). Fracture strength and film thickness were analyzed with ANOVA and the Games-Howell test; the variable presence of voids was analyzed with the Mann-Whitney test (α= 5%).
Mean fracture strengths varied between 640.4 and 792.9 N and did not differ significantly between groups. The CP group had a thinner cement film and fewer voids than the PP group. There was a positive, statistically significant correlation (Spearman, R=0.488, P= 0.029) between these variables.
CAD/CAM-manufactured glass-fiber posts and cores do not affect the fracture strength of flared root canals or cause catastrophic failure of the root when used with zirconia crowns.
研究用预成桩或计算机辅助设计/计算机辅助制造（CAD/CAM）定制桩核修复的薄弱牙根的抗折性，以及粘结剂膜的厚度和粘结剂中孔隙的存在情况。
用金刚砂车针去除40颗人前磨牙的内部牙本质以削弱牙根（冠方三分之一处为2.5mm，根尖三分之一处为1.5mm），并用预成桩（PPs）或定制桩（CPs）修复，有或没有氧化锆全冠（n = 10）。桩和全冠用树脂粘结剂粘结。使用显微断层扫描来确定粘结剂膜的厚度以及是否存在孔隙。在疲劳测试（100万次循环，50N，5Hz，36.5°C）后，对标本进行斜向加载（30°，1mm/分钟）的压缩测试，并记录抗折强度（N）。用方差分析和Games-Howell检验分析抗折强度和膜厚度；用Mann-Whitney检验分析孔隙的可变存在情况（α = 5%）。
平均抗折强度在640.
