A Comparative In Vitro Study to Evaluate Two Designs of Endocrowns in Restoring Endodontically Treated Premolars

Our study's objective was to compare resistance to fracture and failure types betweena new design of endocrown and a conventional endocrownwhen subjected to shear force. Materials and Methods: Twenty human maxillary first premolars without cracks or caries that had been extracted for orthodontic purposes were collected.The crown portion of the specimens was removedup to 2 mm above the cementoenamel junction (CEJ). Afterward, these were endodontically treatedand then randomly divided into two groups and restored using two different methodsas follows: Group H: (n = 10) – teeth were restored with H-shaped endocrowns; Group EC: (n = 10) – teeth were restored with conventional endocrowns. All crowns were made from IPS e.max ceramic. Shear forces were applied to these restorations using a test machine until breakage. Results: No significant difference was observed in resistance to fracture between the two groups. However, a greater number of favorable fractures were observed in the conventional endocrowns'group, whereas most of those in the H-shaped endocrowns were unfavorable. Conclusion: Under the conditions of this study, it can be concluded that the new endocrown design shows a higher fracture resistance than conventional endocrowns. but it causes more unfavorable fracture types than the latter.