ABSTRACT
STATEMENT OF PROBLEM: Bidirectional leakage through the implant-abutment interface still constitutes a major concern in implant-supported restorations. PURPOSE: The purpose of this in vitro study was to evaluate the marginal fit, before and after loading simulation, of 3-unit fixed partial prostheses supported by external hexagon or Morse cone implants and to identify and quantify up to 43 microbial species penetrating through the implant-abutment interface after loading. MATERIAL AND METHODS: Forty-eight dental implants with external hexagon (EH; n=24) or Morse cone (MC; n=24) connections were investigated. Experimental specimens were made from 2 implants restored with a 3-unit fixed partial prosthesis and divided into 2 groups (n=12) according to platform connection EH or MC. Vertical misfit at the implant-abutment interface was measured before and after loading (150 Ncm during 500,000 cycles at 1.8 Hz). checkerboard DNA-DNA hybridization was used to identify and quantify up to 38 bacterial and 5 Candida species colonizing the internal parts of the implants after loading. Generalized estimating equations were used for statistical analysis (α=.05). RESULTS: The mean values (mm, ±SD) of vertical misfit for EH were 0.0131 ±0.002 before loading and 0.0138 ±0.002 after loading and for MC were 0.0132 ±0.003 before loading and 0.0137 ±0.001 after loading. Twenty-one bacterial species, including periodontal pathogens and C. albicans, were found colonizing the inner surfaces of EH implants after loading. None of the target species were detected in the internal parts of MC implants. CONCLUSIONS: EH implants showed higher microbial counts than MC implants, in which microbial colonization was not found after loading. Detected species included nonpathogens and microorganisms related to periodontal/periimplant diseases. Further studies are needed to evaluate the effect of loading simulation on the marginal misfit of 3-unit fixed partial prostheses supported by EH or MC implants, because no significant differences could be found either before or after loading.
