ABSTRACT
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.
