牙本质肩领与桩核类型对牙体抗折能力的影响

Influence of ferrule designs and posts on the fracture resistance

目的观察冷热循环条件下,不同种类桩核冠修复不同类型牙本质肩领缺损的前磨牙的抗折能力。方法将64颗离体下颌第一前磨牙按照牙本质肩领的位置形态分为4组:A组:360°;B组:180°颊侧;C组:180°舌侧;D组:180°颊+舌侧。然后将各组随机采用纤维桩树脂核或铸造金属桩核修复再分成两组。所有离体牙行铸造钴铬金属全冠修复,人工老化处理(5℃/55℃)5000次。设置电子万能试验机工作端为1 mm/min,并选择加载位置为颊尖顶,加力至样本任何一处出现断裂。统计分析各组的折裂力值和折裂模式。结果抗折力值最高值(A1:(1424.6±383.9) N、A2:(2081.6±419.6) N)都出现在牙本质肩领为360°组(P<0.05)。相对于纤维桩树脂核组,铸造金属桩核组的抗折力值较高(P<0.05)。纤维桩树脂核组(23例)可修复性折裂例数明显高于铸造金属桩核组(4例)(P<0.05)。结论牙本质肩领对于牙体抗折性能有显著影响,但牙本质肩领的位置、形态对其影响不显著;在保护牙根方面,纤维桩显示出明显的优势。

Objective To investigate the influence of ferrule designs and posts on the fracture resistance of mandibular first premolars after artificial aging.Methods Sixty-four mandibular premolars were collected and divided into four groups,group A:360°ferrule,group B:180°ferrule in the buccal region,group C:180°ferrule in the lingual region,group D:180°ferrule in the buccal and lingual region,which then were divided into two groups repaired with fiber posts and casting posts,respectively.All samples were restored with Co-Cr crown and subjected to artificial aging 5000 times(5℃-55℃).Loads were applied on buccal cusps by the electrical universal machine.The maximum loading value and failure mode were analyzed.Results Compared with the other three groups,the loading force of(1424.6±383.9)N and(2081.6±419.6)N were higher(P<0.05).The fracture resistance of casting posts was higher than that of fiber posts.Conclusions The ferrule location may not influence the fracture resistance,while the 360°ferrule can improve the fracture resistance.Fiber post is a better choice to protect the tooth root.