Effect of ferrule on the fracture resistance of teeth restored with parapost xp and parapost fiber lux under tangential load-an in vitro study

Introduction: Endodontically treated teeth are at higher risk of fracture than vital teeth due to the decreased moisture content in dentin and most of the times, compromised structural integrity. The cast post and core technique has been advocated as the gold standard restoration for decades, but the traditional technique is time consuming and involves great laboratory and material costs. Introduction of prefabricated metallic post systems and esthetic post systems such as fiber-reinforced and zirconia ceramic posts have improved the results significantly. A dental ferrule is an encircling band of cast metal around the coronal surface of the tooth. The availability of 2.0 mm of coronal tooth structure between the shoulder of the crown preparation and the tooth/core junction has been shown to enhance fracture resistance and preventing fracture and dislodgement of the post. Objective: To assess the effect of ferrule on the fracture resistance of teeth restored with Parapost XP and Parapost Fiber Lux under tangential load. Methodology: Forty Human maxillary central incisors extracted within three months were stored in saline solution. Coronal sections of teeth to be restored were sectioned with carborundum discs 2mm occlusal to cementoenamel junction. Forty maxillary central incisors specimen collected were divided into two groups. Group 1 included 20 central incisors without ferrule and were further divided into two subgroups, ‘a’ with Parapost XP and ‘b’ with Parapost Fiber Lux. Group 2 included 20 central incisors with 2mm ferrule and were further divided into two subgroups, ‘a’ with Parapost XP and ‘b’ with Parapost Fiber Lux. The teeth were then endodontically instrumented and root canals were obturated using gutta percha. After root canal treatment, teeth were prepared for post space by means of preparation drills. Self adhesive resin cement was used to cement these posts. After removal of excess cement, resin cement was allowed for 5 minutes to polymerise followed by core build up using Paracore, followed by full coverage crowns. Finally, all the specimens were embedded in the acrylic resin block to a depth of 2mm below the cementoenamel junction. The mounted specimens were secured in a universal testing machine and a force was applied at a crosshead speed of 1mm/min until fracture occurred. The fracture load was recorded in Newtons. Results: When tangential loads were applied to the samples, it was seen that the teeth restored with posts having ferrule withstood higher amounts of force before fracture when compared to those without ferrule. Conclusion: Within the limitation of the present study, it can be concluded that the ferrule effect plays a key role in increasing the fracture resistance of teeth restored with post and core.