title: Experimental conical-head abutment screws on the microbial leakage through the implant-abutment interface: an in vitro analysis using target-specific DNA probes.
abstract: OBJECTIVE
  The aim of this in vitro study was to identify and quantify up to 38 microbial species from human saliva penetrating through the implant-abutment interface in two different implant connections, external hexagon and tri-channel internal connection, both with conventional flat-head or experimental conical-head abutment screws.
  
  
  METHODS
  Forty-eight two-part implants with external hexagon (EH; n = 24) or tri-channel internal (TI; n = 24) connections were investigated. Abutments were attached to implants with conventional flat-head or experimental conical-head screws. After saliva incubation, Checkerboard DNA-DNA hybridization was used to identify and quantify up to 38 bacterial colonizing the internal parts of the implants. Kruskal-Wallis test followed by Bonferroni's post-tests for multiple comparisons was used for statistical analysis.
  
  
  RESULTS
  Twenty-four of thirty-eight species, including putative periodontal pathogens, were found colonizing the inner surfaces of both EH and TI implants. Peptostreptococcus anaerobios (P = 0.003), Prevotella melaninogenica (P < 0.0001), and Candida dubliniensis (P < 0.0001) presented significant differences between different groups. Means of total microbial count (×104, ±SD) for each group were recorded as follows: G1 (0.27 ± 2.04), G2 (0 ± 0), G3 (1.81 ± 7.50), and G4 (0.35 ± 1.81).
  
  
  CONCLUSIONS
  Differences in the geometry of implant connections and abutment screws have impacted the microbial leakage through the implant-abutment interface. Implants attached with experimental conical-head abutment screws showed lower counts of microorganisms when compared with conventional flat-head screws.
authors.affiliation: Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, 14040-904, São Paulo, SP, Brazil.
authors.forename: Murillo S
authors.initials: MS
authors.lastname: Pita
authors.affiliation: Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, 14040-904, São Paulo, SP, Brazil.
authors.forename: Cássio
authors.initials: C
authors.lastname: do Nascimento
authors.affiliation: Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, 14040-904, São Paulo, SP, Brazil.
authors.forename: Carla G P
authors.initials: CGP
authors.lastname: Dos Santos
authors.affiliation: Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, 14040-904, São Paulo, SP, Brazil.
authors.forename: Isabela M
authors.initials: IM
authors.lastname: Pires
authors.affiliation: Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, 14040-904, São Paulo, SP, Brazil.
authors.forename: Vinícius
authors.initials: V
authors.lastname: Pedrazzi
mesh_terms: D015342:DNA Probes; D059605:Dental Implant-Abutment Design; D015921:Dental Implants / Q000382:microbiology*; D003763:Dental Leakage; D006801:Humans; D009693:Nucleic Acid Hybridization; D012463:Saliva / Q000382:microbiology*
chemical_list: D015342:DNA Probes; D015921:Dental Implants
keywords: microbiology; periodontology; prosthodontics