title: Influence of cusp coverage on the fracture resistance of premolars with endodontic access cavities.
abstract: OBJECTIVE
  To assess the influence of cusp reduction and coverage with composite resin on the fracture resistance of premolars with prepared access cavities.
  
  
  METHODS
  Endodontic access cavities were prepared in 60 premolar teeth that were divided into four test groups: R1, R2, R3 and NR (n=15). In all test groups, MOD cavities were prepared and extended towards one of the cusps. The remaining cusp-wall thickness was: 1-1.5 mm in R1, 1.5-2 mm in R2 and 2-3 mm in both R3 and NR groups. In addition, in group R1, R2 and R3 the same cusp was reduced in height to 3.5 mm. Cuspal coverage and MOD restorations were performed using composite resin. Ten intact premolars served as positive controls and another ten MOD-prepared unrestored premolars as negative controls. Teeth were submitted to cyclic fatigue of 1.2 million cycles. A compressive load was applied 30° to the long axis of the teeth until fracture. Fracture loads were recorded and the means and the Confidence Intervals were compared.
  
  
  RESULTS
  The mean fracture resistance of each of the cusp-reduced groups R1, R2 and R3 (603, 712 and 697 N, respectively) was significantly higher than the non-reduced cusp group (305 N) and was comparable to the intact-premolar group (653 N).
  
  
  CONCLUSIONS
  Cusp reduction and coverage with composite resin significantly increased the fracture resistance of premolar teeth with MOD and endodontic access cavities.
authors.affiliation: Department of Conservative Dentistry, School of Dental Medicine, University of Tübingen, Tübingen, Germany. ashraf.elayouti@med.uni-tuebingen.de
authors.forename: A
authors.initials: A
authors.lastname: ElAyouti
authors.forename: M I
authors.initials: MI
authors.lastname: Serry
authors.forename: J
authors.initials: J
authors.lastname: Geis-Gerstorfer
authors.forename: C
authors.initials: C
authors.lastname: Löst
mesh_terms: D001641:Bicuspid / Q000293:injuries*; D003188:Composite Resins / Q000627:therapeutic use*; D003737:Dental Cavity Preparation / Q000009:adverse effects*; D003793:Dental Restoration, Permanent / Q000379:methods; D006801:Humans; D012390:Root Canal Therapy / Q000009:adverse effects*; D019228:Tooth Crown / Q000033:anatomy & histology / Q000293:injuries*; D014082:Tooth Fractures / Q000209:etiology / Q000517:prevention & control*
chemical_list: D003188:Composite Resins