残冠剩余侧壁数对纤维桩冠修复动态加载抗折性能的影响

Effects of residual coronal walls on the fracture resistance under dynamic loading in fiber post-core and crown system

目的在模拟口腔咬合的动态加载条件下,研究不同残留侧壁数对纤维桩冠修复抗折性能的影响。方法将正畸拔除的25颗下颌单根管前磨牙随机分为五组,每组按照剩余侧壁数由0到4进行制备,所有离体牙行石英纤维桩复合树脂核+金属全冠修复。用循环加载机对所有试件进行30万次载荷为50N,频率为2Hz的动态加载,然后将试件置于万能材料实验机上,用速率为1mm/min的30°角行静态加载直至试件断裂。结果各组试件抗折力值的大小顺序为4个侧壁组>3个侧壁组>2个侧壁组>1个侧壁组>0个侧壁组。0个侧壁和1个侧壁组的牙体抗折性能显著低于2个侧壁,3个侧壁和4个侧壁组,差异有统计学意义(P<0.05)。所有试件中可修复性折裂占92%(23/25),不可修复性折裂占8%(2/25)。结论当剩余2个侧壁时,修复体的抗折性能与对照组无明显差异。用纤维桩修复残冠残根时,要尽量保留牙体侧壁,以提高修复成功率。

Objective To evaluate the influence of residual coronal walls on the fracture resistance under dynamic loading. Methods Twenty-five extracted single-rooted mandibular premolars from orthodontic patients were divided into 5 groups randomly, and each group was prepared depending on the number of residual coronal walls that ranged from 0 to 4. Each tooth was restored with quartz-fiber post-core and full metal crown system. All specimens were subjected to dynamic loading in a masticatory simulator for 300000 loading cycles with a nominal load of 50N at 2Hz. Then specimens were quasi-statically loaded at a 30° angle with a crosshead speed of lmm/min in a universal testing machine until fracture. Results The order of fracture resistance of all groups were as follows： 4-wall group 〉3-wall group 〉2-wall group 〉l-wall group 〉0-wall group. And the failure load of 0-wall and 1-wall group was significantly lower than that of 2-wall, 3-wall and 4-wall group, the differences were statistically significant （P〈0.05）. The favorable mode accounted for 92% （23/25） of all specimens and unfavorable pattern was 8% （2/25）. Conclusion When 2 coronal walls remained, the difference of fracture resistance is not significant comparing to the control group. When a fiber post is used to restore residual roots and crowns, more dentin walls need to be retained clinically in order to get high success rate.