Stability of endodontically treated teeth with differently invasive restorations: Adhesive vs. non-adhesive cusp stabilization.

Abstract Objectives Aim of the present study was to evaluate fracture strength of endodontically treated molars with different preparations/restorations after thermomechanical loading in vitro. Methods 264 extracted human third molars were used. Beside the control group, 256 teeth in 32 test groups ( n  = 8) received root canal treatment (MTwo #40/.6) and root canal obturation with AH Plus and Guttapercha. After postendodontic sealing and build-up (Syntac, SDR), specimens were additionally prepared MO or MOD. Postendodontic restorations were: Direct restorations (Tetric EvoCeram Bulk Fill bonded with Syntac; as filling or direct partial crown (PC) after reducing the cusps 3 mm; amalgam as filling or direct pin-retained partial crown (PC)), vs. indirect adhesive restorations (I: Inlay vs. PC; IPS Empress I/PC; Celtra Duo I/PC; e.max CAD I/PC; Lava Ultimate I/PC; Enamic I/PC – all inserted with Syntac/Variolink) vs. cemented cast gold I/PC. After 300,000 thermocycles (5/55 °C) and 1.2 Mio. 100 N load cycles, specimens were loaded until fracture. Results Whereas IPS Empress showed no difference between I and PC ( p  > 0.05), in all other groups PC were significantly more stable than fillings/inlays ( p p p p p Significances Less invasive preparation designs were not beneficial for the stability of postendodontic restorations. Except for IPS Empress, PC were generally more successful in restabilization of weakened cusps after endodontic treatment and preparation. Cast gold PC remain the ultimate stabilization tool for ETT in terms of fracture resistance.