铸造桩核冠修复上颌中切牙模拟力学模型的建立和初步应用

Establishment and preliminary application of simulated mechanical model of maxillary central incisors restored with cast post-core-crown with complete ferrule

目的:采用密胺材质人工牙建立具有完整牙本质肩领的铸造桩核冠修复上颌中切牙的模拟力学模型,并初步用于研究加载位置与角度对修复后患牙抗折性能的影响。方法:采用密胺材料人工牙经机械加工制备48个拟铸造桩核冠修复的上颌中切牙预备体试件,用随机数法随机将其分为A、B两组,A组:加载力方向与牙长轴的夹角为45°,B组:加载力方向与牙长轴的夹角为60°,每组再随机分为1、2、3三个亚组,每亚组8个试件,加载位置分别位于舌面切缘下3mm、5mm、7mm。所有试件行铸造桩核冠修复后,用特制夹具固定于万能材料试验机加载平台上,以1mm/min的速率静态加载至试件发生破坏,并记录试件破坏时的载荷和折裂方式。结果:6组样本的折裂载荷如下:A1组754.82±94.75N,B1组556.12±35.90N,A2组1228.56±162.11N,B2组817.11±135.81N,A3组1682.34±251.96N,B3组1097.00±156.89N,加载位置和加载角度均会显著影响试件的折裂载荷,且两者之间存在明显的交互效应(P<0.05)。所有试件均表现为低于树脂包埋平面的不可修复性折裂,各组试件之间的折裂方式没有统计学差异(P>0.05)。结论:在牙本质肩领充足的条件下,加载位置和加载角度会对铸造桩核冠修复上中切牙的抗折性能产生显著影响,且两者之间存在交互作用。

Objective:A simulated mechanical model of artificial teeth with complete ferrule made of melamine was established in order to investigate the effect of loading position and angulation on fracture resistance of maxillary central incisors restored with cast post-core-crown.Methods:Forty-eight standardized analogues made of melamine simulated tooth preparations of maxillary central incisors restored with cast post and core were randomly divided into 2 main groups,Groups A and B.The angles between the loading direction and the long axis of specimens in both groups were 45°and 60°respectively.Each group was then randomly divided into 3 subgroups marked as 1,2 and 3,with 8 specimens in each.The loading positions were 3 mm,5 mm and 7 mm below the incisal edge on lingual surface,respectively.After standardized restorative procedure,all the samples were mounted on the loading platform of the universal testing machine.Static load at the cross-head speed of 1 mm/min was applied until the specimen fracture occurred and force at fracture as well as fracture mode was recorded.Results:The mean fracture load of six groups were as follows:754.82±94.75 N for Group A1,556.12±35.90 N for Group B1,1228.56±162.11 N for Group A2,817.11±135.81 N for Group B2,1682.34±251.96 N for Group A3,1097.00±156.89 N for Group B3.Loading position and loading angulation both have significant effect on the fracture resistance of the specimens,and there was a significant interaction between them(P<0.05).All the specimens showed unrestorable fracture pattern,with crack lines under the embedded acrylic resin,but no significant difference was found in the fracture mode among all groups(P>0.05).Conclusion:With sufficient ferrule,loading position and angulation may have impacts on the fracture resistance of maxillary central incisors restored with cast post and core.And there exists a significant interaction between them.