title: Evaluation of resistance form of different preparation features on mandibular molars.
abstract: OBJECTIVE
  Resistance form of full metal-ceramic crown is an important feature that determines longevity of these restorations. This study evaluated the resistance form of full metal-ceramic prepared with four different design features.
  
  
  METHODS
  An acrylic tooth was prepared with 20° total occlusal convergence (TOC) angle, 2.5 mm of occlusocervical dimension and a shoulder finishing line. This design lacked resistance form. The crown preparation was subsequently modified by preparing Mesial Occlusal Distal isthmus, placing occlusal inclined plane, and reducing TOC. Four metal dies from these designs were constructed by lathe machine and then 10 metal copings were fabricated for each preparation. Metal coping were cemented on metal dies with temp-bond cement. Force was applied at 45° from lingual to buccal direction with universal testing machine.
  
  
  METHODS
  The data were evaluated by Kruskal-Wallis and non-parametric Mann-Whitney test.
  
  
  RESULTS
  All features increased resistance form when compare to control group. However, reduce TOC group showed greatest value of resistance.
  
  
  CONCLUSIONS
  Within the limitation of this study, reducing the tapering of occlusocervival dimension is the most effective way in increasing resistance form, although, other features were also effective.
authors: Department of Fixed Prosthodontics, Faculty of Dentistry, Esfahan University of Medical Sciences, Iran.
authors: Bajoghli
authors: B
authors: Farshad
authors: Ghasemi
authors: G
authors: Ehsan
authors: Sabouhi
authors: S
authors: Mahmoud
authors: Khodadadi
authors: K
authors: Reza
authors: Behdarvand
authors: B
authors: Mozhdeh
mesh_terms: D002484:Cementation / Q000379:methods; D003442:Crowns; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D003794:Dental Restoration, Temporary / Q000379:methods; D003799:Dental Stress Analysis / Q000295:instrumentation; D005054:Eugenol / Q000737:chemistry; D006801:Humans; D008334:Mandible; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008963:Molar / Q000473:pathology*; D013314:Stress, Mechanical; D013499:Surface Properties; D019237:Tooth Cervix / Q000473:pathology; D019228:Tooth Crown / Q000473:pathology; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D016876:Metal Ceramic Alloys; D005054:Eugenol; C076899:Temp-Bond; D015034:Zinc Oxide