Objective

Despite the increased use of monolithic crowns, their performance has yet to be determined when the minimal tooth preparation (MTP) principle is considered. The goal of this study was to evaluate the effect of MTP on the mechanical behavior, reliability and translucency of posterior monolithic ceramic crowns.

Methods

Dentin analogues were machined using two preparation designs (0.5 or 1 mm reduction) to receive first molar crowns in order to evaluate the monolithic crown performance. Next, 126 crowns were divided (21/g) according to the material (High translucent zirconia – YZHT, Zirconia reinforced lithium silicate – ZLS and Hybrid ceramic – HC) and thickness (0.5 or 1 mm). Tensile stress concentration was calculated using the finite element method. The crowns were adhesivelly cemented and step stress fatigued to calculate reliability for missions at 600 and 1000 N. Translucency was analyzed in 10 discs of each material and thickness.

Results

Higher stress concentration was found in thinner crowns and those with higher elastic modulus. YZHT crowns were suspended when fatigue reached 1500 N load, thus 1-parameter Weibull was used to analyze the data. Reliability was only affected by thickness at 1000 N. ZLS.5 showed lower survival than HC.5, which was similar to the groups that presented 100% survival. YZHT showed the highest strength and data scattering. ZLS1 (22.3 ± 1.4) presented higher translucency than HC1 (19.2 ± 0.6) and YZHT1 (12.0 ± 2.9), whereas ZLS.5 and HC.5 were similar to each other (26.5 ± 2.3, 26.7 ± 2.2) and superior to YZHT.5 (12.7 ± 1.2).

Significance

HC.5 combined high reliability and translucency with low stress concentration, yielding better crown performance and tooth preservation.

中文翻译：

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后整块陶瓷牙冠的最少牙准备：对机械性能，可靠性和半透明性的影响

客观的

尽管增加了整体式牙冠的使用，但在考虑最小牙准备（MTP）原理时，尚未确定其性能。这项研究的目的是评估MTP对后整块陶瓷冠的力学行为，可靠性和半透明性的影响。

方法

使用两种制备设计（减小0.5毫米或1毫米）对牙本质类似物进行加工，以接收第一颗磨牙冠，以评估整体冠的性能。接下来，根据材料（高半透明氧化锆– YZHT，氧化锆增强硅酸锂– ZLS和混合陶瓷– HC）和厚度（0.5或1毫米）划分126冠（21 / g）。使用有限元方法计算拉伸应力集中。胎冠采用胶粘剂粘合，并对步应力进行疲劳处理，以计算600和1000 N时任务的可靠性。在每种材料和厚度的10个圆盘中分析半透明度。

结果

在较薄的胎冠和具有较高弹性模量的胎冠中发现较高的应力集中。当疲劳达到1500 N载荷时，YZHT胎冠被悬挂，因此使用1参数的Weibull分析数据。可靠性仅受厚度在1000 N时的影响。ZLS.5的存活率低于HC.5，这与存活率100％的组相似。YZHT显示出最高的强度和数据分散性。ZLS1（22.3±1.4）的半透明性高于HC1（19.2±0.6）和YZHT1（12.0±2.9），而ZLS.5和HC.5彼此相似（26.5±2.3，26.7±2.2），优于YZHT .5（12.7±1.2）。

意义

HC.5将高可靠性和半透明性与低应力集中结合在一起，从而获得更好的牙冠性能和牙齿保护性能。