Fracture Resistance of Endodontically Treated premolar Teeth Restored With CAD/CAM Lithium Disilicate Endocrowns and H-shaped post: In Vitro Study

Aim: This study was conducted to compare the fracture resistance of lithium disilicate endocrowns with circular post and endocrowns with H-shaped short post when bonded to endodontically treated premolar teeth.
Materials and Methods: A twenty two extracted single rooted premolars (specimens), were divided into two equal groups (11 specimens in each group). Group H : restored with endocrowns with H- shaped post. Group C : restored with endocrowns with circular post. Teeth were scanned with DOF scanner and restorations were designed with EXOCAD software. All restorations were milled with imes-icore machine. The endocrowns were cemented on their corresponding teeth using BisCem (Bisco Inc., Schaumburg, IL, USA) dual-cure adhesive resin cement following total etch technique protocol. All samples were subjected to fracture resistance testing using universal testing machine. After facture testing, fracture patterns and failure mode of all samples were examined visually and photographically by digital camera. Data were collected and statistically analysed.
Results: Independent t test revealed that endocrowns with H-shaped post (Group H) showed higher fracture resistance values (1374.6 ±313 N), compared with endocrowns with circular post (Group C) (1107.9 ± 205 N). Chi square test showed no statistically significant difference between groups in mode of failure.
Conclusion : Lithium disilicate endocrowns with H-shaped post provide promising design in premolar region. Design of post of endocrown has no effect on mode of failure.