不同角度根管桩核对上颌中切牙抗折能力的影响

摘要

背景:临床上,往往会碰到一些患者上前牙唇倾而影响美观的情况,患者因治疗周期过长等多种因素不愿接受正畸治疗情况下,可以采取改向桩核冠的美学修复方式进行治疗.目的:比较3种材料桩核在不同角度改向下修复唇向倾斜上颌中切牙的抗折裂强度以及折裂模式.方法:将75颗上颌中切牙随机分为3组,钴铬合金桩核组行Co-Cr合金桩核加铸造冠修复;金合金桩核组行50％金合金桩核加铸造冠修复;everStick可塑性纤维桩核组行可塑性everstick纤维桩加树脂核加铸造冠修复.每组再根据桩核与牙长轴的角度分0°,10°,20°,30°,40°5个亚组.所有试件均由自凝塑料包埋,固定在电子万能测试机上,加载直至试件任何一处发生断裂,记录折裂时最大载荷值和折裂模式.结果与结论:①everStick可塑性纤维桩核组抗折裂强度明显高于钴铬合金桩核组和金合金桩核组,差异有显著性意义(P＜0.05);钴铬合金桩核组和金合金桩核组差异无显著性意义(P＞0.05);②随改向角度增大,3种材料最大负荷值均呈现递减趋势.everStick可塑性纤维桩核组多发生在根颈1/3折裂;钴铬合金桩核组、金合金桩核组多发生在根中和根尖1/3折裂;③结果表明,everStick纤维桩改向修复唇向倾斜的上颌中切牙的抗折裂强度和折裂模式均优于钴铬合金和金合金桩核,临床改向修复唇倾上前牙时,可以优先考虑everStick纤维桩,以减少不可修复性根折的发生概率,为防止牙根折断,应避免改向角度过大.%BACKGROUND:In clinical practice,there are some patients with labial inclined anterior teeth which influence their appearance,but they refuse orthodontic treatment because of many factors such as long-term treatment.Alternatively,these patients can receive aesthetics restoration with re-directional post-core and crown.OBJECTIVE:To investigate the influence of three kinds of post-core materials on fracture resistant ability of labial inclined maxillary central incisor with different changed angles.METHODS:Seventy-five maxillary central incisors were randomly divided into three groups:group Ⅰ was restored with Co-Cr post-core and porcelain-fused-to-metal (PFM) crown,group Ⅱ was restored with 50％ gold alloy post-core and PFM crown,group Ⅲ was restored with everStick fiber post and composite resin core and PFM crowns.Each group then was divided into five subgroups based on angles between the post-core and long axis of the tooth (0°,10°,20°,30°,40°).All specimens were embedded in acrylic resin and fixed in electronic universal testing machine.Force was loaded to each specimen until fracture occurred,and the maximum load values of fracture and the fracture mode were recorded.RESULTS AND CONCLUSION:The fracture resistance of group Ⅲ was superior to groups Ⅰ and Ⅱ (P ＜ 0.05),but there was no significant difference between group Ⅰ and group Ⅱ (P ＞ 0.05).The maximum load value of the three groups decreased as the changed angle increased.The fracture of group Ⅲ mostly appeared on the 1/3 of the root neck,while the fracture of groups Ⅰ and Ⅱ mostly appeared on the 1/3 of root central or the 1/3 of the root neck.So,the fracture resistance and fracture mode of central incisor under changed angles restored with everStick fiber post were superior to that with cast metal post-core.During re-directional restoration of labial inclined maxillary anterior teeth,everStick fiber post is recommended as a better choice to reduce the risk of catastrophic fractures.Also it suggests that excessive changed angle should be avoided to prevent root fracture.