title: In vitro assessment of retention and resistance failure loads of two preparation designs for maxillary anterior teeth.
abstract: BACKGROUND
  Parallel labiolingual walls and the preservation of the cingulum in anterior tooth preparations have been advocated. However, their contribution to retention and resistance form has not been evaluated.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the retention and resistance failure loads of 2 preparation designs for maxillary anterior teeth.
  
  
  METHODS
  Forty metal restorations were fabricated and paired with 40 cobalt-chromium prepared tooth analogs. Twenty of the specimens had parallel buccolingual walls at the cervical part (group PBLW; the control group), whereas the remaining 20 had converging buccolingual walls (group CBLW; the experimental group). The restorations were cemented to the tooth analogs with a resin-modified glass ionomer luting agent. Ten specimens from each group were subjected to tensile loading with a universal testing machine; the rest were subjected to compression loading until failure. Descriptive statistics and the independent t test (α=.05) were used to determine the effect of failure loads in the tested groups.
  
  
  RESULTS
  The independent t test revealed statistically significant differences between the tested groups in tensile loading (P<.001) and in compressive loading (P<.001). The PBLW group presented a higher tensile failure load than the CBLW. On the contrary, the PBLW group presented a smaller compression failure load than the CBLW.
  
  
  CONCLUSIONS
  Parallelism of the buccolingual axial walls in anterior maxillary teeth increased the retention form but decreased the resistance form.
authors.affiliation: Resident, Division of Removable Prosthodontics, Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University, Thessaloniki, Greece.
authors.forename: Aimilia
authors.initials: A
authors.lastname: Bintivanou
authors.affiliation: Professor, Division of Removable Prosthodontics, Department of Prosthodontics, Faculty of Health Sciences, School of Dentistry, Aristotle University, Thessaloniki, Greece.
authors.forename: Argirios
authors.initials: A
authors.lastname: Pissiotis
authors.affiliation: Associate Professor, Department of Prosthodontics, Faculty of Health Sciences, School of Dentistry, Aristotle University, Thessaloniki, Greece; and Adjunct Associate Professor, Division of Graduate and Postgraduate Prosthodontics, Tufts University School of Dental Medicine, Boston, Mass. Electronic address: kmichalakis@hotmail.com.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Michalakis
mesh_terms: D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000009:adverse effects / Q000379:methods; D003799:Dental Stress Analysis; D006801:Humans; D007180:Incisor / Q000601:surgery; D008437:Maxilla; D016474:Weight-Bearing