title: Fracture resistance of soft tissue level implants after cyclic loading and external modification.
abstract: BACKGROUND
  The exposure of the implant collar in the esthetic zone is a challenging complication of implant dentistry. The preparation of the exposed implant collar to create room for restorative material may decrease the strength of the abutment/implant assembly.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the effect on the failure load of preparing a 0.5-mm chamfer finish line on an implant collar at various apical depths.
  
  
  METHODS
  Thirty solid abutments and 30 implants were screwed into a customized metal mold at a 30-degree angle to the vertical axis. An intact group (IN) (control) (n=10) had no preparation, experimental group P1 had a 0.5-mm chamfer margin placed 1 mm apical to the implant/abutment interface, and experimental group P2 had the margin placed 2 mm apical. The specimens were subjected to a fatigue loading of 200 N for 1 000 000 cycles. Unfractured specimens were then loaded until failure. Mean fracture load (MFL) values were compared with 1-way ANOVA, and the Tukey test was used to identify differences among groups (α=.05).
  
  
  RESULTS
  One specimen from both the IN and P1 groups and 2 specimens from the P2 group failed after fatigue loading. Significant differences in the MFL values were found between the IN group (3825) and P1 group (2944), P<.001 and between the IN group and the P2 group (2553), P<.001.
  
  
  CONCLUSIONS
  The mean load required to fracture the abutment/implant assembly decreased significantly after various amounts of implant collar preparation.
authors: Department of Restorative Dentistry, New Jersey Dental School, University of Medicine and Dentistry of New Jersey, Newark, NJ, USA.
authors: Louis
authors: L
authors: DiPede
authors: Abdulmohsin
authors: A
authors: Alhashim
authors: T K
authors: TK
authors: Vaidyanathan
authors: Robert
authors: R
authors: Flinton
mesh_terms: D000704:Analysis of Variance; D001732:Bite Force; D019245:Compressive Strength; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous / Q000009:adverse effects / Q000379:methods*; D015921:Dental Implants; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005889:Gingival Recession; D006801:Humans; D012307:Risk Factors; D018709:Statistics, Nonparametric; D019415:Torque
chemical_list: D015921:Dental Implants