title: Retrospective study of short and extra-short implants placed in posterior regions: influence of crown-to-implant ratio on marginal bone loss.
abstract: OBJECTIVE
  The aim of this study is to evaluate the influence of crown-to-implant (CI) ratio as well as other surgical, prosthetic and biomechanical variables on marginal bone loss (MBL) and on the survival rates of implant-supported prostheses in short implants (≤8.5 mm in length) placed in posterior areas of maxilla and mandible.
  
  
  METHODS
  This was a retrospective study based on clinical charts and follow-up recordings from a single private practice over a period of 10 years. Patients rehabilitated in the posterior region of the jaws by means of prostheses supported by implants of ≤8.5 mm length were included. Patients-related, surgery-related. and implant-related variables, as well as other prosthetic and biomechanical variables. were registered. The data were split into two groups according to the value of CI ratio (CI < 2 and CI ≥ 2). MBL was measured from radiographs using an image analysis software. Implant and prosthesis survival rates were recorded.
  
  
  RESULTS
  One hundred twenty-eight short implants placed in 63 patients were evaluated. The mean follow-up period was 21.88 months (standard deviation (SD): 22.9, range 7-113 months). Eighty-six implants (67.2%) had a CI ratio of <2, whereas it was ≥2 in 42 implants (32.8%). The mean value of CI ratio was 1.82 (SD: 0.42; range 1.04-3.31). The average MBL after 1 year of follow-up was 0.35 (SD: 0.50), and it was 0.45 (SD: 0.46) mm for subsequent evaluations. Survival rates of implants and prosthesis were 100%. The presence of a cantilever had a negative influence on the first year MBL (p < .05).
  
  
  CONCLUSIONS
  The CI ratio had not a significant influence on MBL in Biotechnology Institute (BTI; Vitoria, Spain) short implants humidified with PRGF-Endoret and placed in posterior areas. The only variable that showed a significant negative influence on first year postloading MBL was the use of cantilever for rehabilitations.
authors: Implantology and Oral Rehabilitation, Vitoria, Spain; Biotechnology Institute (BTI), Vitoria, Spain.
authors: Eduardo
authors: E
authors: Anitua
authors: Laura
authors: L
authors: Piñas
authors: Gorka
authors: G
authors: Orive
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000209:etiology; D001696:Biomechanical Phenomena; D003442:Crowns; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D007576:Jaw, Edentulous, Partially / Q000534:rehabilitation; D008297:Male; D008875:Middle Aged; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D015921:Dental Implants
keywords: extra-short implants; implant survival; marginal bone loss; retrospective; short implants