The influence of recent adhesive onlay fabrication techniques on the fracture resistance of endodontically treated premolars (An in vitro study)

Abstract

Background: Endodontically treated teeth have low resistance to fracture against occlusal forces. The strengtheningeffect of bonded esthetic onlay restoration on weakened tooth has been reported. This study aimed to assess thefracture resistance of endodontically treated premolars restored with composite with and without cuspal coverageby using direct and indirect techniques. Indirect technique done by CAD/CAM system (computer aided design –computer aided manufacturer) and laboratory processing.Material and methods: Forty human extracted maxillary premolars of approximately comparable sizes were dividedinto four groups: Group (A): Ten endodontically treated teeth directly filled with Filtek Z250xt without cuspalcoverage. Group (B): Ten endodontically treated teeth prepared with onlay cavities and restored directly with FiltekZ250 XT. Group(C): Ten endodontically treated teeth prepared with onlay cavities and restored indirectly with FiltekZ250 XT. Group (D): Ten endodontically treated teeth prepared with onlay cavities and restored indirectly withParadigm MZ100 CAD/CAM blocks. Fracture strength of the samples was measured by using universal testingmachine (an axial compression test). Data were analyzed statistically by one way ANOVA test and least significantdifference test,Results showed that Group A has the lowest fracture resistance value than all experimental Groups and thedifference are highly significant. While Group B has a high significant fracture resistant value than the indirectlyrestored groups. Group C and Group D showed an approximate fracture resistant result (1.13KN and 1.07KNrespectively) and the difference is statistically not significant.Conclusion All CAD/CAM composite onlay, indirect Filtek z250 XT and direct cuspal coverage survived maximumbiting force for posterior single tooth, so these types of onlays provide good reinforcement in an extensive MODcavities in premolars The mode of fracture for Group D was 90% restorable which is higher than group C (80%)restorable and group B (30%) restorable type of fracture