title: Clinical wear of posterior metal-free polymer crowns. One-year results from a randomized clinical trial.
abstract: OBJECTIVE
  The purpose of this randomized clinical trial was to evaluate the clinical wear behavior of posterior, metal-free polymer crowns, with and without a glass-fiber framework, and to compare it with that of metal-ceramic crowns.
  
  
  METHODS
  Eighty single crowns manufactured from a newly designed polymer composite were set in posterior teeth. Half of these received a glass-fiber framework (group 1) whereas half were prepared without framework stabilization (group 2). All polymer crowns were adhesively luted with resin cement. As the control group, 40 conventional metal-ceramic crowns were inserted with hybrid cement. Wear was measured, by use of gypsum replicas, at baseline and after 12 months, by use of a 3D laser scanner. Statistical analysis was performed using mixed-effects regression model analyses.
  
  
  RESULTS
  The mean total wear of posterior single crowns was -8.1 microm (+/-9.7 microm) in group 1, -7.0 microm (+/-9.1 microm) in group 2, and -3.4 microm (+/-6.3 microm) in the control group. Statistical analysis revealed wear behavior was significantly different from the control group for group 1 (p=0.014) and group 2 (p<0.01). No significant difference was detected between groups 1 and 2. Age, gender, and opposing teeth had no significant effect on wear behavior.
  
  
  CONCLUSIONS
  Within a 12-month observation period mean total wear of posterior polymer crowns with and without a glass-fiber framework was significantly greater than for metal-ceramic crowns. The selection of restorative materials should be based on knowledge of clinical wear in order to preserve occlusal stability.
authors.affiliation: Department of Prosthodontics, University of Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. Brigitte_Ohlmann@med.uni-heidelberg.de
authors.forename: Brigitte
authors.initials: B
authors.lastname: Ohlmann
authors.forename: Jan
authors.initials: J
authors.lastname: Uekermann
authors.forename: Jens
authors.initials: J
authors.lastname: Dreyhaupt
authors.forename: Marc
authors.initials: M
authors.lastname: Schmitter
authors.forename: Katrin
authors.initials: K
authors.lastname: Mussotter
authors.forename: Peter
authors.initials: P
authors.lastname: Rammelsberg
mesh_terms: D000328:Adult; D000368:Aged; D002133:Calcium Sulfate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D019554:Dental Restoration Wear / Q000145:classification*; D005260:Female; D005500:Follow-Up Studies; D005898:Glass / Q000737:chemistry; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008689:Methacrylates / Q000737:chemistry; D018613:Microscopy, Confocal; D008875:Middle Aged; D011140:Polyurethanes / Q000737:chemistry; D011446:Prospective Studies; D016628:Replica Techniques; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D016876:Metal Ceramic Alloys; D008689:Methacrylates; D011140:Polyurethanes; D019279:Resin Cements; C485630:Vectris Pontic; C009753:fiberglass; D003776:Dental Porcelain; C029824:urethane dimethacrylate luting resin; D002133:Calcium Sulfate