Machado A C, Soares C J, Reis B R, Bicalho A A, Raposo Lha, Soares P V
Oper Dent. 2017 May/Jun;42(3):253-265. doi: 10.2341/14-195-L. Epub 2017 Mar 13.
Noncarious cervical lesions (NCCLs) are characterized by a loss of dental structure at the cementoenamel junction (CEJ) caused by stress, biocorrosion, and attrition. Variations in occlusal loading can promote different stress and strain patterns on the CEJ. Restoration of NCCLs is part of lesion management; however, there is still no conclusive restorative protocol for NCCLs. This study aimed to evaluate the stress and strain distribution of maxillary premolars with NCCLs according to three factors: 1) restorative technique; 2) direction of occlusal loading; and 3) mechanical fatigue. Three-dimensional (3D) finite element analysis (FEA) and strain gauge testing were used to assess stress and strain, respectively. 3D-FEA orthotropic, linear, and elastic models were generated: sound tooth (SO); unrestored NCCL; or NCCL restored with glass ionomer; flowable composite resin; nanofilled composite resin (CR); lithium disilicate ceramic; and nanofilled composite resin core associated with a lithium disilicate laminate (CL). A 150-N compressive static load was applied in two conditions: axially in both cusps (Al); and at a 45° angle to the long axis of the tooth applied to the palatine cusp (Ol). For the experimental tests, specimens were treated as described previously, and one strain gauge was attached to the buccal surface of each tooth to record tooth strains before and after cyclic loading (200,000 cycles, 50 N). FEA showed that the association of NCCL and Ol resulted in higher stress values. CR and CL restorations showed the closest biomechanical behavior to SO for both loading types. Loaded Al or Ol specimens showed higher strain values after mechanical fatigue. Lower stress and strain were observed with Al when compared with Ol. The restoration of NCCLs with composite resin only or associated with ceramic laminates seems to be the best approach because the results for those groups were similar in biomechanical behaviors to sound teeth.
非龋性颈部病变（NCCLs）的特征是由于应力、生物腐蚀和磨损导致牙骨质釉质界（CEJ）处牙体结构丧失。咬合负荷的变化可促使CEJ上出现不同的应力和应变模式。NCCLs的修复是病变管理的一部分；然而，目前仍没有针对NCCLs的确切修复方案。本研究旨在根据三个因素评估患有NCCLs的上颌前磨牙的应力和应变分布：1）修复技术；2）咬合负荷方向；3）机械疲劳。分别使用三维（3D）有限元分析（FEA）和应变片测试来评估应力和应变。生成了3D-FEA正交各向异性、线性和弹性模型：健康牙齿（SO）；未修复的NCCL；或用玻璃离子体、可流动复合树脂、纳米填充复合树脂（CR）、二硅酸锂陶瓷修复的NCCL；以及与二硅酸锂层压板相关的纳米填充复合树脂核（CL）。在两种情况下施加150-N的压缩静载：在两个牙尖轴向施加（Al）；以及与牙齿长轴成45°角施加于腭尖（Ol）。对于实验测试，标本按先前所述进行处理，并且在每个牙齿的颊面附着一个应变片，以记录循环加载（200,000次循环，50 N）前后的牙齿应变。FEA显示，NCCL与Ol的组合导致更高的应力值。对于两种加载类型，CR和CL修复体显示出与SO最接近的生物力学行为。加载Al或Ol的标本在机械疲劳后显示出更高的应变值。与Ol相比，Al时观察到更低的应力和应变。仅用复合树脂或与陶瓷层压板联合修复NCCLs似乎是最佳方法，因为这些组的结果在生物力学行为上与健康牙齿相似。
