Babaeianfar Amirmohammad, Neshandar Asli Hamid, Babaee Hemmati Yasamin, Falahchai Mehran
School of Dentistry, Guilan University of Medical Sciences, Rasht, Iran.
Department of Prosthodontics, Dental Sciences Research Center, School of Dentistry, Guilan University of Medical Sciences, Rasht, Iran.
J Prosthodont. 2025 Jul 1. doi: 10.1111/jopr.14091.
To assess the effect of crown-to-abutment (C/A) height ratio on fracture resistance (FR) of full-coverage anterior restorations.
In this in vitro study, 66 human maxillary central incisors were assigned to six groups according to their abutment height (n = 11): control (sound tooth), V4 (prepared vital tooth with 4 mm height), V4e (4 mm abutment with 4 mm height gain through elective endodontic treatment, fiber post, and core build-up), V6 (prepared vital tooth with 6 mm height), V6e (6 mm abutment with 2 mm height gain through elective endodontic treatment, fiber post, and core build-up), and V8 (prepared vital tooth with 8 mm height). Zirconia crowns with 10 mm height were fabricated for all teeth and cemented. After thermomechanical loading, the FR and fracture mode were assessed. Data were analyzed by independent t test, analysis of variance (ANOVA) with James-Howell test for pairwise comparisons, and Fisher's exact test (α = 0.05).
Among the experimental groups, V8 showed a significantly lower FR than other groups (p < 0.05). The FR of V6 was significantly lower than V4 (p < 0.001). V4 had a significantly higher FR than V4e (p < 0.001). However, the difference in FR was not significant between V6 and V6e (p = 0.408). V6e had the highest frequency of unfavorable fractures, and V4 had the highest frequency of favorable fractures.
In the same restorative space, the minimum tested abutment height resulted in the highest FR in full-coverage anterior restorations, eliminating the need for invasive procedures to increase the abutment height.
评估全冠修复体的冠根比（C/A）对前牙全冠修复体抗折性（FR）的影响。
在这项体外研究中，66颗人上颌中切牙根据其基牙高度分为六组（每组n = 11）：对照组（健康牙）、V4组（制备后的活髓牙，基牙高度4mm）、V4e组（4mm基牙，通过选择性根管治疗、纤维桩和核桩增加4mm高度）、V6组（制备后的活髓牙，基牙高度6mm）、V6e组（6mm基牙，通过选择性根管治疗、纤维桩和核桩增加2mm高度）和V8组（制备后的活髓牙，基牙高度8mm）。为所有牙齿制作高度为10mm的氧化锆全冠并粘结。在进行热机械加载后，评估抗折性和骨折模式。数据采用独立t检验、方差分析（ANOVA）及James-Howell检验进行两两比较，并采用Fisher精确检验（α = 0.05）。
在实验组中，V8组的抗折性显著低于其他组（p < 0.05）。V6组的抗折性显著低于V4组（p < 0.001）。V4组的抗折性显著高于V4e组（p < 0.001）。然而，V6组和V6e组之间的抗折性差异不显著（p = 0.408）。V6e组出现不利骨折的频率最高，V4组出现有利骨折的频率最高。
在相同的修复空间内，全冠修复体中最小的基牙高度测试值导致了最高的抗折性，无需进行侵入性操作来增加基牙高度。
