title: Microbiological assessment of the implant-abutment interface in different connections: cross-sectional study after 5 years of functional loading.
abstract: OBJECTIVE
  To evaluate the bacterial microflora present inside the implant connection and in the peri-implant sulcus fluid of healthy implants, and to analyze the relationships between these harboring sites for four different implant systems after at least 5 years of functional loading.
  
  
  METHODS
  A cross-sectional study was performed involving 40 patients treated with metal-ceramic cemented bridges supported by at least two healthy implants functionally loaded for 5 years. Four different implant-abutment connections were studied: external hexagon (control group), double internal hexagon (test group 1), internal hexagon with external collar (test group 2), and conical connection (test group 3). Samples for microbiological analysis were obtained from three types of sites: peri-implant sulci, connections' inside and abutments surface and, as control, gingival sulci of neighboring teeth. Quantitative real-time PCR was carried out for Total Bacterial Count and for 10 microorganisms: Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Prevotella intermedia, Peptostreptococcus micros, Fusobacterium nucleatum, Campylobacter rectus, Eikenella corrodens, and Candida albicans. The response variables were percentage of positive sites and absolute bacterial load. The relations of the response variables with the type of connection and of sampling site were assessed using generalized estimating equations.
  
  
  RESULTS
  Regarding the analysis of positivity to bacteria in the peri-implant sulcus no significant differences were observed. Analyzing the connection's inside, none of the connection designs had the capacity to prevent microbiological leakage through the implant/abutment microgap. Test group 3 presented the lowest mean values for red complex bacteria and control group the highest, although differences were non-significant. Statistical significance was only reached for Treponema denticola in the bacterial load analysis inside the connection. Test groups 1 and 2 yielded lower values for orange complex bacteria but only for Peptostreptococos micros the differences resulted significant. Test groups 2 and 3 had significantly lower total bacterial counts in the peri-implant sulcus and inside the connection.
  
  
  CONCLUSIONS
  Outcomes suggested that all the analyzed connections resulted contaminated after 5 years of functional loading. However, the connection design might influence bacterial activity levels qualitatively and quantitatively, especially inside the implant connection.
authors.affiliation: Rome, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Canullo
authors.affiliation: Oral Surgery and Implantology, Stomatology Department, University of Valencia, Valencia, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Penarrocha-Oltra
authors.affiliation: Vicenza, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Soldini
authors.affiliation: Padua, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Mazzocco
authors.affiliation: Department of Oral Surgery, University of Valencia, Valencia, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Penarrocha
authors.affiliation: Department of Prosthodontics, University of Pisa, Pisa, Italy.
authors.forename: Ugo
authors.initials: U
authors.lastname: Covani
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D005260:Female; D005883:Gingival Crevicular Fluid / Q000382:microbiology*; D006801:Humans; D008297:Male; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants
keywords: clinical study; implant connection; implant-abutment microgap; microbial leakage