Department of Restorative Science, Faculty of Dentistry, Kuwait University, Kuwait.
Department of Community Medicine and Behavioral Science, Faculty of Medicine, Kuwait University, Kuwait.
J Prosthodont. 2021 Feb;30(2):183-188. doi: 10.1111/jopr.13252. Epub 2020 Sep 21.
To assess whether the occlusion of metal-ceramic crowns, as received from the laboratory, and the time taken to adjust the occlusion of crowns not deemed acceptable, can be reduced by fabricating the crowns with controlled amounts of infra-occlusion during the laboratory phase.
An opposing set of typodonts, articulated in maximum intercuspal position served as the patient in an in vitro simulation. Seventy-five metal-ceramic crowns were fabricated for the mandibular right second molar with three different occlusal contact specifications: A, control group had occlusal contacts shared evenly by the crown and the neighboring teeth (n = 25); B, first experimental group had the occlusion relieved until 2 shimstock foils were able to be pulled from between the crown and the opposing tooth without tugging (n = 25); C, second experimental group had the occlusion relieved until 4 shimstock foils were able to be pulled from between the crown and the opposing tooth without tugging (n = 25). The occlusion of each crown, as received from the laboratory, was assessed using one of three categories (Excellent, Acceptable, and Poor). Chi-square analysis was used to test the differences in occlusal outcomes between the three study groups. For all of those rated "Acceptable," the time taken to adjust each crown to proper occlusion was recorded. One-way analysis of variance (ANOVA) and Bonferroni tests were carried out to compare the adjustment times across the three study groups.
The 2-shim group had the best outcome, with 56% of the crowns rated as "Excellent" (p = 0.001). In addition, there were statistically significant differences in adjustment times between the control group (A) and the 2-shim (B) and the 4-shim (C) groups (p = 0.0001), but not between the 2-shim (B) and 4-shim (C) groups (p = 0.08).
Metal-ceramic crowns fabricated with controlled interocclusal relief of 2- and 4-shims each required less time for chairside occlusal adjustment than crowns fabricated in the laboratory to conventional occlusal contact. However, the overall superior outcome, in terms of the possibility for immediate insertion as received from the laboratory as well as favorable chairside adjustment time, for the 2-shim prespacing suggests that this dimension is the preferred option over 4-shim prespacing to reduce occlusal inaccuracies of indirect restorations.
评估在实验室阶段制造具有一定程度的亚覆颌的冠时，是否可以减少从实验室收到的金属陶瓷冠的咬合以及调整被认为不可接受的冠的咬合所需的时间。
一副咬合架，在最大牙尖交错位上被铰接，作为一个体外模拟中的患者。为下颌右侧第二磨牙制作了 75 个金属陶瓷冠，有三种不同的咬合接触规格：A 组为对照组，冠与邻牙均匀接触（n=25）；B 组为第一实验组，直到可以从冠和对颌牙之间拉出 2 片箔片而不拉扯为止，减轻咬合（n=25）；C 组为第二实验组，直到可以从冠和对颌牙之间拉出 4 片箔片而不拉扯为止，减轻咬合（n=25）。从实验室收到的每个冠的咬合情况使用三个类别之一进行评估（优秀、可接受和差）。卡方检验用于检验三组研究之间的咬合结果差异。对于所有被评为“可接受”的患者，记录了调整每个冠至适当咬合所需的时间。进行单因素方差分析（ANOVA）和 Bonferroni 检验，以比较三组研究之间的调整时间。
2 片箔组的结果最好，56%的冠评为“优秀”（p=0.001）。此外，对照组（A）与 2 片箔（B）和 4 片箔（C）组之间的调整时间存在统计学差异（p=0.0001），但 2 片箔（B）和 4 片箔（C）组之间的调整时间无统计学差异（p=0.08）。
与实验室制造的具有常规咬合接触的冠相比，用 2 片和 4 片箔片制造的金属陶瓷冠需要更少的椅旁咬合调整时间。然而，就从实验室收到的即刻插入的可能性以及有利的椅旁调整时间而言，2 片箔预间距的整体优异结果表明，与 4 片箔预间距相比，这一尺寸是减少间接修复体咬合不准确的首选方案。
