title: Stability of endodontically treated teeth with differently invasive restorations: Adhesive vs. non-adhesive cusp stabilization.
abstract: OBJECTIVE
  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 3mm; 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. 100N 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<0.05), this effect was more pronounced after MOD preparations. Cast gold PC exhibited the highest fracture strengths (p<0.05), inlays the lowest (p<0.05). IPS Empress was generally inferior to the other bonded materials under investigation (p<0.05) which as PC almost reached the level of control specimens. Amalgam fillings showed the worst outcome (p<0.05).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Operative Dentistry and Endodontics, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, D-35039 Marburg, Germany. Electronic address: frankbg@med.uni-marburg.de.
authors.forename: Roland
authors.initials: R
authors.lastname: Frankenberger
authors.affiliation: Department of Operative Dentistry and Endodontics, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, D-35039 Marburg, Germany.
authors.forename: Inka
authors.initials: I
authors.lastname: Zeilinger
authors.affiliation: Department of Operative Dentistry and Endodontics, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, D-35039 Marburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Krech
authors.affiliation: Department of Operative Dentistry and Endodontics, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, D-35039 Marburg, Germany; Private Practice, Düsseldorf, Germany.
authors.forename: Gernot
authors.initials: G
authors.lastname: Mörig
authors.affiliation: Department of Prosthetic Dentistry, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Naumann
authors.affiliation: Department of Operative Dentistry and Endodontics, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, D-35039 Marburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Braun
authors.affiliation: Department of Pediatric Dentistry, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Giessen, Schlangenzahl 14, D-35392 Giessen, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Krämer
authors.affiliation: Department of Operative Dentistry and Endodontics, Medical Center for Dentistry, University Medical Center Giessen and Marburg, Campus Marburg, Georg-Voigt-Str. 3, D-35039 Marburg, Germany.
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Roggendorf
mesh_terms: D003188:Composite Resins; D003738:Dental Cements; D003776:Dental Porcelain; D007284:Inlays; D008963:Molar; D019279:Resin Cements; D019553:Tooth, Nonvital
chemical_list: D003188:Composite Resins; D003738:Dental Cements; D019279:Resin Cements; D003776:Dental Porcelain
keywords: Amalgam; Cast gold; Cuspal stabilization; Endodontically treated teeth; Leucite-reinforced glass ceramic; Lithium disilicate ceramic; Resin composites; Resin nano ceramic