全瓷冠与高嵌体用于修复邻面缺损根管治疗后下颌磨牙抗折强度对比研究

Effect comparison of all-ceramic crowns and onlays in restoring endodontically treated mandibular molar with mesio-occlusal defect

目的探究修复根管治疗后下颌磨牙的邻面牙体缺损时,与全瓷冠相比,保留更多牙体组织的全瓷高嵌体是否有足够的抗折强度。方法收集2015年8—10月在华西口腔医院牙槽外科拔除的32颗下颌磨牙,按照牙体大小配伍后分为4组,分别记为G1、G2、G3、G4组,每组8颗离体牙。将所有离体下颌磨牙预备成邻面缺损洞型并完成根管治疗后,各组进行以下处理。G1组:IPS e.max CAD全瓷冠修复,无机械及冷热循环,模拟修复后的即刻状态;G2组:IPS e.max CAD全瓷冠修复+120万次机械循环和1000次冷热循环,模拟修复后5年状态;G3组:IPS e.max CAD全瓷高嵌体修复,无机械及冷热循环;G4组:IPS e.max CAD全瓷高嵌体修复+120万次机械循环和1000次冷热循环。测试并记录4组的破坏载荷力值,观察并记录试件的破坏模式。结果全冠与高嵌体这两种修复方式的即刻破坏载荷力值分别为(2269.49±281.68)N和(2357.91±342.64)N,差异无统计学意义(P>0.05)。经过机械及冷热循环后,全冠和高嵌体的破坏载荷力值虽均下降[(1738.30±230.21)N和(2096.75±216.75)N],但仍远高于平均咀嚼力和最大力值(100~250 N和200~540 N);高嵌体破坏载荷力值高于全冠,差异有统计学意义(P<0.05)。结论对于邻面缺损行根管治疗后的下颌磨牙,IPS e.max CAD高嵌体与全冠均具有良好的即刻抗折强度,机械及冷热循环模拟口腔内使用5年后仍有足够的抗折强度,且高嵌体表现优于全冠修复。

Objective To explore whether IPS e.max CAD onlays with more sound tissue preserved had enough fracture resistance and better restoration effect compared with all-ceramic crowns when mandibular molars were in mesio-occlu- sal cavities after endodontic treatment. Methods From August to October of 2015, totally 32 extracted mandibular mo- lars were collected in West China Hospital of Stomatology. All teeth were divided into four groups after being made pairs, which were G1, G2, G3 and G4. Subsequently, mesio-occlusal cavities were prepared with the same dimension, and end- odontic treatment was conducted in all specimens. According to the restoration type and whether being exposed to ther- momeehanical cycles or not, the next process was as follows. GI ： IPS e.max CAD crowns, no thermomechanical cycles, to simulate immediate state after restoration; G2 ： IPS e.max CAD crowns, with 1.2 million dynamic loadings and 1000 ther- mal cycles, to simulate 5-year functional state after restoration; G3 ： IPS e.max CAD onlays, no thermomechanical cycles; G4： IPS e.max CAD onlays, with 1.2 million dynamic loadings and 1000 thermal cycles. After that, all the specimens were loaded to failure, and failure modes were inspected and recorded. Results The immediate fracture resistance of crowns and onlays was （2269.49 ± 281.68） N and （2357.91 ±342.64）N, respectively, and there was no significant differ- ence between them （P 〈 0.05）. After thermomechanical cycles, although the fracture resistance of both crowns and on-lays decreased [ （1738.30 ± 230.21）N and （2096.75± 216.75） N] , they were higher than the mean masticatory force （100-250 N） and the maximum biting force（200-540 N）. The fracture resistance of onlays was higher than that of crowns and there was a significant difference be- tween them （P 〈 0.05）. Conelusion For mandibular molars with mesio-occlusal defect, both onlays and crowns achieve excellent immediate flexural strength. After thermomechanical cycles to simulate 5-year functional movement, they still have sufficient fracture resistance and onlays show better result than crowns.