Objectives

To compare stress distribution and failure probability in maxillary premolars restored by simple occlusal veneer (SOV) and buccal-occlusal veneer (BOV) with 3 different CAD/CAM materials.

Materials and methods

A maxillary premolar was digitized by a micro-CT scanner. Three-dimensional dynamic scan data were transformed, and finite element models of 2 different models (SOV and BOV restored teeth) were designed. Three different CAD/CAM materials, including lithium disilicate glass ceramic (LD) IPS e.max CAD, polymer-infiltrated ceramic-network (PICN) Vita Enamic, and resin nano-ceramic (RNC) Lava Ultimate, were designated to both veneers. Maximum principle stresses were determined by applying a 300-N axial load to the occlusal surface. Weibull analyses were performed to calculate the failure probability of the models.

Results

LD-restored teeth showed the highest stress in the veneer, lowest stress in substrate teeth, and lowest failure probability for the overall system; RNC-restored teeth showed the lowest stress in the veneer, highest stress in substrate teeth, and highest failure probability. No significant differences were found in the cement layer among the different models. No significant differences of stress and failure probability existed between SOV and BOV preparations.

Conclusions

CAD/CAM composite resin occlusal veneers bear lower maximum stress than ceramic veneers. Teeth restored by composite veneers are more prone to failure than those restored by ceramic veneers. Additional reduction of the buccal surface did not increase the stress on the occlusal veneer under axial load.

Clinical relevance

Both occlusal veneers could be used under physiological masticatory force. CAD/CAM glass ceramic was safer than composite resins.

中文翻译：

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用不同的CAD / CAM材料和制备设计估算咬合贴面修复的上颌前磨牙的应力分布和失败风险。

目标

比较3种不同的CAD / CAM材料通过简单的咬合贴面（SOV）和颊-咬合贴面（BOV）修复的上颌前磨牙的应力分布和破坏可能性。

材料和方法

用微型CT扫描仪将上颌前磨牙数字化。转换了三维动态扫描数据，并设计了两种不同模型（SOV和BOV修复牙齿）的有限元模型。两种贴面均指定了三种不同的CAD / CAM材料，包括二硅酸锂玻璃陶瓷（LD）IPS e.max CAD，聚合物渗透陶瓷网络（PICN）Vita Enamic和树脂纳米陶瓷（RNC）Lava Ultimate。最大主应力是通过在咬合面上施加300 N的轴向载荷来确定的。进行威布尔分析以计算模型的失效概率。

结果

LD修复的牙齿在单板中显示出最高的应力，基材的牙齿中显示出最低的应力，并且整个系统的失效概率最低；RNC修复的牙齿在饰面中的应力最低，在基体牙齿中的应力最高，并且失效概率最高。在不同模型之间的水泥层中没有发现显着差异。SOV和BOV制剂之间没有明显的应力和失效概率差异。

结论

CAD / CAM复合树脂咬合贴面承受的最大应力低于陶瓷贴面。用复合贴面修复的牙齿比用陶瓷贴面修复的牙齿更容易失效。在轴向载荷下，颊面的进一步减小不会增加对牙合板的应力。

临床相关性

两种咬合贴面均可在生理咀嚼力下使用。CAD / CAM玻璃陶瓷比复合树脂更安全。