Retention of different CAD/CAM endocrowns bonded to severely damaged endodontically treated teeth: An in vitro study

Aim: Assess the retention of endocrowns fabricated of different CAD/CAM materials. Settings and Design: In vitro - comparative study. Material and Methods: Root canal treated mandibular first molars were prepared in a standardized method. Standardized endocrowns were manufactured using four CAD-CAM blocks: resin infiltrated ceramic (Vita Enamic), partially stabilized tetragonal zirconia (Katana), lithium disilicate ceramic (IPS e.max CAD), and polyether-ether-keton (PEEK, BioHPP). After proper surface treatment, the restorations were cemented using a resin cement (Panavia F2.0) and were connected to a special attachment unit and secured to a universal testing machine. The amount of axial load required to dislodge the restoration from the tooth structure was measured (n = 12, alpha = 0.05). Failures were classified as adhesive debonding from the tooth structure without damaging the supporting tooth structure and cohesive fracture of the supporting tooth structure Statistical Analysis Used: One-way analysis of variance,Tukey's post hoc test. Results: The retention of Vita Enamic (61 +/- 11 N) and IPS e.max CAD (58 +/- 9 N) was significantly higher (F = 123, P < 0.01) than Katana (33 +/- 13) and Peek restorations (23 +/- 11). Vita Enamic and IPS e.max CAD were associated with fractured tooth segments during debonding while Katana and PEEK specimens were adhesively debonded from the remaining tooth structure. Conclusions: Within the limitations of this study, using lithium disilicate ceramics and resin infiltrated ceramics as restorative materials to fabricate endocrowns to restore severely damaged endodontically treated teeth, recorded significantly higher retention values. Meanwhile, using yttrium partially stabilized zirconia and polyether ether ketones for the same purpose recorded a favorable mode failure which avoided the possibility of tooth fracture.