Objective

To evaluate the residual stress (nanoindentation based on hardness) of fatigued porcelain-fused to zirconia 3-unit fixed dental prostheses (FDP) with different framework designs.

Methods

Twenty maxillary 3-unit FDP replacing second-premolar (pontic) were fabricated with conventional framework-design (even-thickness of 0.5 mm and 9 mm² connector area) and modified framework-design (thickness of 0.5 mm presenting lingual collar connected to proximal struts and 12 mm² connector area). Connector marginal ridges were loaded and the fractured and suspended FDPs were divided (n = 3/each) into: (1) Fractured zirconia even-thickness (ZrEvenF); (2) Suspended zirconia even-thickness (ZrEvenS); (3) Fractured zirconia with modified framework (ZrModF); (4) Suspended zirconia with modified framework (ZrModS); (5) Non-fatigued FDP with conventional framework design (Control). The FDPs were nanoindented at 0.03 mm (Region of Interest (ROI) 1), 0.35 mm (ROI 2) and 1.05 mm (ROI 3) distances from porcelain veneer outer surface with peak load 4000 μN. The Linear Mixed Analysis of Variance (ANOVA) Model on ranks and Least Significant Difference Test on ranks (95%) were used.

Results

Highest rank hardness values were found for Control group and ZrModS, whereas the lowest values were found in ZrModF. Statistical differences (p = 0.000) were found among all groups except for comparison between ZrModS and Control group (p = 0.371). Hardness between ROIs were statistically significant different (p < 0.001) where ROI 1 presented the lowest values.

Significance

Framework-design modification did not influence the residual stress of porcelain-fused to zirconia fatigued 3-unit FDP. Whereas fractured FDPs showed the highest residual stress compared to suspended and control FDPs. Residual stress increased as nanoindented away from framework.

中文翻译：

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纳米压痕法测量瓷熔合氧化锆3单元固定义齿的残余应力

客观的

为了评估疲劳瓷器与不同框架设计的氧化锆3单元固定义齿（FDP）融合后的残余应力（基于硬度的纳米压痕）。

方法

用传统的框架设计（厚度均匀的0.5 mm和9 mm ^2的连接器区域）和改进的框架设计（厚度0.5 mm的舌环连接至近端）制造二十个上颌3单元FDP替代第二前磨牙（桥状）撑杆和12 mm ²连接器区域）。加载连接器边缘脊，将断裂和悬浮的FDP分为（n = 3 /每个）：（1）断裂的氧化锆均匀厚度（ZrEvenF）；（2）悬浮的氧化锆均匀厚度（ZrEvenS）；（3）具有改良框架的易碎氧化锆（ZrModF）；（4）具有改良框架的悬浮氧化锆（ZrModS）；（5）具有传统框架设计（控件）的无疲劳FDP。FDP的纳米压痕距瓷贴面外表面的距离为0.03 mm（感兴趣区域（ROI）1），0.35 mm（ROI 2）和1.05 mm（ROI 3），峰值载荷为4000μN。使用等级的线性混合方差分析（ANOVA）模型和等级的最小显着性检验（95％）。

结果

对照组和ZrModS的硬度等级值最高，而ZrModF的硬度值最低。 除ZrModS与对照组之间的比较外（p  = 0.371），所有组之间均存在统计学差异（p = 0.000 ）。ROI之间的硬度在统计学上有显着差异（p  <0.001），其中ROI 1呈现最低值。

意义

框架设计的修改不会影响与氧化锆疲劳的3单元FDP融合的烤瓷的残余应力。而断裂的FDP与悬浮FDP和对照FDP相比，显示出最高的残余应力。随着纳米压痕远离框架，残余应力增加。