Study Of Microleakage And Fracture Resistance Of Weakende Root Rehabilitated With Resin Composite

Restoration of weakened root is frequently a challenge to dentists. Weakened rootoccurs with canal instrumentation, inadequate post removal, caries, fractures, orinternal resorption. These problems result in loss of tooth structure and consequentreduction in tooth resistance to force. Currently, weakened roots are restorated withdowel-post-crown, and the retention is provided by the post cemented with lutingagent. However, tooth fracture often occurs, which is one of the most seriousproblems with weakened root restored with post. How to improve the fractureresistance of the teeth has been the research interest nowadays. The suggestedtechnique for restoring weakened root is to increase fracture resistance byrehabilitating weakened root with resin composite that is elastically compatible withdentine.Freshly extracted teeth were prepared simulating flared root canal and the teethwere rehabilitated with resin composites. The research is composed of two parts. PartⅠis to evaluate microleakage between resin composites and wall of root canal usingtotal- and self- etch system. PartⅡis to evaluate the fracture resistance of flared rootrestored with fiber post and metal post after rehabilitation.PartⅠStudy of microleakagebetween resin composite and flared root canalObjective: To evaluate microleakage between resin composite and flared root canalwith total- and self- etch system MethodMethods: Sixteen extracted endodontically treated mandibular first premolars wereselected, and flared root canals were prepared. Specimens were randomly divided into2 groups. Group A: Flared root canals were rehabilitated with Prime&bond NT andcomposite; Group B: Flared root canals were rehabilitated with XenoⅢandcomposite. After thermal cycling, all specimens were immersed in Indian ink for oneweek. After using clearing technique, the penetration depth was examined understereomicroscope．Results: Microleakage of self-etch group was less than that of total-etch group. Astactically significant difference(p<0.05) was observed between 2 groups．Conclusion: Sealing ability of self-etch adhesive combining with resin composite asrehabilitating method was better than that of total-etch system in this study.PartⅡResearch of fracture resistance of flared rootrestored with fiber post and casting postObjective:To compare the fracture resistance of flared root restored with fiber postand casting post after rehabilitation.Methods:Sixteen extracted central incisors were selected and flared root canals wereprepared. Specimens were randomly divided into two groups (n=8) and rehabilitatedwith resin composites. After rehabilitation, specimens of group A were restored withcasting post-core; specimens of group B were restored with fiber post and resin core.All teeth were restored with Ni-Cr alloy complete crowns. Each specimen wasembedded in self-cured acry1ic resin and secured in a universal testing machine. At anangle of 135°, load was applied at a crosshead speed of 2 mm/min until fractureoccurred. Failure loads and fracture modes (repairable or catastrophic) were recorded.Results: The failure load of group A was 0.591±0.094KN and the failure load ofgroup B was 0.489±0.081KN. A statistically significant difference(p<0.05) wasobserved between the two groups. Percentage of catastrophic fracture mode of group A was 75%, whereas fracture modes of group B were totally repairable. Asignificance level of P<0.05 was detected between two groups.ConclusiConclusion: Using fiber post is better in preventing rehabilitated flared root fromfracture.