School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
Clin Exp Dent Res. 2023 Jun;9(3):518-525. doi: 10.1002/cre2.726. Epub 2023 Mar 22.
The purpose of this experimental in vitro study was to assess the effect of having one or two intact axial walls on the improvement of the fracture resistance, and marginal and internal adaptation of computer-aided design/computer-aided manufacturer fabricated ceramic endocrowns.
Thirty-six endodontically treated mandibular molars were divided into three groups (n = 12). Group A, represented teeth that all of their axial walls were reduced till they all had 3 mm height. In group B, the buccal wall had 5 mm height and the others were reduced to 3 mm. Specimens of the group C had 5-mm-height buccal and one 5 mm-height proximal wall, with all other walls of 3 mm height. All teeth were scanned using intraoral scanner, and endocrowns were milled from zirconia lithium silicate ceramics blocks. The marginal and internal discrepancy of restorations were evaluated with the replica technique. Fracture resistance was also measured after cementation and modes of failure were observed. One-way analysis of variance and Tukey HSD multiple comparisons were used to analyze the data (α = .5).
Significant differences were observed within the groups in terms of the axial discrepancy (p = .022); group A had significantly higher amounts of axial discrepancy compared to group B (p = .001) and group C (p = .003). Preservation of the intact axial walls did not result in a statistically significant decrease in marginal (p = .21) and pulpal (p = .31) discrepancy values. Also, concerning the fracture resistance no significant difference was observed among the groups (p = .51).
Preservation of at least one of the axial walls could reduce the amount of the axial discrepancy and, therefore, improves the adaptation of the restoration. However, based on this study, it did not improve fracture resistance.
本实验体外研究旨在评估保留一个或两个完整轴壁对提高计算机辅助设计/计算机辅助制造陶瓷嵌体冠的抗折强度、边缘和内部适合性的影响。
将 36 颗下颌磨牙分为三组（n=12）。组 A 代表所有轴壁均被降低至 3mm 高度的牙齿。组 B 的颊壁高度为 5mm，其余壁降低至 3mm。组 C 的标本颊壁和近中壁各有 5mm 高，其余壁均为 3mm 高。所有牙齿均使用口腔内扫描仪扫描，并使用氧化锆锂硅陶瓷块铣削嵌体。采用复制技术评估修复体的边缘和内部差异。在粘结后测量抗折强度，并观察失效模式。采用单因素方差分析和 Tukey HSD 多重比较进行数据分析（α=0.5）。
在轴向差异方面，各组内存在显著差异（p=0.022）；与组 B（p=0.001）和组 C（p=0.003）相比，组 A 的轴向差异明显更大。保留完整的轴壁并不会导致边缘（p=0.21）和牙髓（p=0.31）差异值的统计学显著降低。此外，就抗折强度而言，各组之间没有观察到显著差异（p=0.51）。
保留至少一个轴壁可以减少轴向差异的量，从而改善修复体的适应性。然而，根据本研究，它并没有提高抗折强度。
