title: Impact of crestal and subcrestal implant placement in peri-implant bone: A prospective comparative study.
abstract: BACKGROUND
  To assess the influence of the crestal or subcrestal placement of implants upon peri-implant bone loss over 12 months of follow-up.
  
  
  METHODS
  Twenty-six patients with a single hopeless tooth were recruited in the Oral Surgery Unit (Valencia University, Valencia, Spain). The patients were randomized into two treatment groups: group A (implants placed at crestal level) or group B (implants placed at subcrestal level). Control visits were conducted by a trained clinician at the time of implant placement and 12 months after loading. A previously established standard protocol was used to compile general data on all patients (sex and age, implant length and diameter, and brushing frequency). Implant success rate, peri-implant bone loss and the treatment of the exposed implant surface were studied. The level of statistical significance was defined as 5% (α=0.05).
  
  
  RESULTS
  Twenty-three patients (8 males and 15 females, mean age 49.8±11.6 years, range 28-75 years) were included in the final data analyses, while three were excluded. All the included subjects were non-smokers with a brushing frequency of up to twice a day in 85.7% of the cases. The 23 implants comprised 10 crestal implants and 13 subcrestal implants. After implant placement, the mean bone position with respect to the implant platform in group A was 0.0 mm versus 2.16±0.88 mm in group B. After 12 months of follow-up, the mean bone positions were -0.06±1.11 mm and 0.95±1.50 mm, respectively - this representing a bone loss of 0.06±1.11 mm in the case of the crestal implants and of 1.22±1.06 mm in the case of the subcrestal implants (p=0.014). Four crestal implants and 5 subcrestal implants presented peri-implant bone levels below the platform, leaving a mean exposed treated surface of 1.13 mm and 0.57 mm, respectively. The implant osseointegration success rate at 12 months was 100% in both groups.
  
  
  CONCLUSIONS
  Within the limitations of this study, bone loss was found to be greater in the case of the subcrestal implants, though from the clinical perspective these implants presented bone levels above the implant platform after 12 months of follow-up.
authors.affiliation: Universidad de Valencia, Clínica Odontológica, Unidad de Cirugía Bucal, Calle Gascó Oliag 1, 46021 Valencia, Spain, miguel.penarrocha@uv.es.
authors.forename: Hilario
authors.initials: H
authors.lastname: Pellicer-Chover
authors.forename: María
authors.initials: M
authors.lastname: Peñarrocha-Diago
authors.forename: David
authors.initials: D
authors.lastname: Peñarrocha-Oltra
authors.forename: Sonia
authors.initials: S
authors.lastname: Gomar-Vercher
authors.forename: Rubén
authors.initials: R
authors.lastname: Agustín-Panadero
authors.forename: Miguel
authors.initials: M
authors.lastname: Peñarrocha-Diago
mesh_terms: D000328:Adult; D000368:Aged; D003758:Dental Implantation, Endosseous / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D011446:Prospective Studies; D013997:Time Factors