title: The effect of opposing structures, natural teeth vs. implants on crestal bone levels surrounding single-tooth implants.
abstract: OBJECTIVE
  To evaluate the effect of opposing structures in crestal bone levels around single-tooth implants.
  
  
  METHODS
  A retrospective cohort study design was conducted. Descriptive statistics, univariate and multifactor mixed-effects regression models, adjusted for multiple implants in the same patient were utilized to evaluate the effect of opposing structures in crestal bone levels after insertion of single-tooth replacements.
  
  
  RESULTS
  Eighty-one subjects who received 320 Bicon implants were included in the present study. Two hundred and thirty-one implant restorations were opposing natural teeth, 75 implants were opposing implant-supported restorations, 10 implants had no opposing structure and four implants were opposed by a complete denture. The average change in crestal bone levels overtime (AvBL) on implants opposing natural teeth and implant-supported restorations was -0.20 and -0.62 mm, respectively. Hydroxyapatite-coated (HA) mandibular implants opposing natural teeth demonstrated AvBL of +0.01 (indicating bone gain), whereas titanium-plasma sprayed (TPS)-coated mandibular implants opposing implants restored with composite abutment bases demonstrated AvBL of -1.95 mm. When the structure opposing an HA-coated mandibular implant was a natural tooth, it was a predictor of peri-implant bone gain (P = 0.007). While TPS-coated mandibular implants, which had been restored with composite abutment bases, were correlated with peri-implant bone loss when opposed by implant-supported restorations (P = 0.003).
  
  
  CONCLUSIONS
  This study suggests that the type of opposing structure plays a significant role in mandibular crestal bone levels surrounding single-tooth implants following crown insertion but this effect differ around implants with dissimilar surface coatings and can be exacerbated by local irritating factors.
authors.affiliation: Private Practice, Implant Dentistry Centre, Boston, MA, USA.
authors.forename: Rainier A
authors.initials: RA
authors.lastname: Urdaneta
authors.forename: Joseph
authors.initials: J
authors.lastname: Leary
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Panetta
authors.forename: Sung-Kiang
authors.initials: SK
authors.lastname: Chuang
mesh_terms: D016301:Alveolar Bone Loss; D020099:Coated Materials, Biocompatible; D000044:Dental Abutments; D019250:Dental Implants, Single-Tooth; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000601:surgery; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D014025:Titanium; D016896:Treatment Outcome
chemical_list: D020099:Coated Materials, Biocompatible; D014025:Titanium
keywords: crestal bone; dental implants; opposing structures; risk factors; single-implant crowns