Purpose: This study was conducted to evaluate the effect of two different preparation extensions(4mm,6mm) On fracture resistance of endo-crowns restoring Maxillary premolar teeth under loading using Vita Enamic.
Methods&Materials: 14 non-carious, human premolar teeth without obvious crack lines, were removed for orthodontic treatment were all randomly assigned to two groups of 7 teeth, where a dental-surveyor was used to ensure upright positioning of teeth in epoxy-resin molds, placing the margin below the cemento-enamel junction by 1mm and parallel to it. Then the crown portion of all premolars were removed to within 3 mm above the CEJ Mesio-Distally. Specimens were divided into two groups according to the type of preparation extensions done, Group A(4 mm extension into the pulp chamber),Group B(6 mm extension into the pulp chamber). After Cementation fracture resistance test was performed and failure modes were observed
Results: There was a significant difference between samples regarding different depths of preparation extension were the highest value of fracture resistance was found in samples with 6 mm extension depth (1617.43±733.46) followed by samples with 4 mm depth (1422.21±659.89).
Conclusion: From the results obtained from this study, it could be concluded that endodontically treated premolars can be restored with endocrowns, moreover, the increase of the preparation depth of the endocrowns showed a massive increase in fracture resistance