title: A retrospective analysis of mandibular bone height changes associated with 81 screw-retained implant-supported prostheses with distal cantilevers: a long-term follow-up analysis.
abstract: OBJECTIVE
  The aims of this study were (1) to evaluate long-term changes in bone height beneath mandibular screw-retained implant-supported prostheses with distal cantilevers and (2) to determine whether the reversal of residual ridge resorption in the posterior mandible is temporary or continues over the long term.
  
  
  METHODS
  Panoramic radiographs, obtained at surgery and at two follow-up visits, of 81 patients rehabilitated with mandibular screw-retained implant-supported prostheses with distal cantilevers supported by four, five, or six implants were followed for 5 to 19 years (overall mean follow-up, 9.00 years. Changes and trends in bone height adjacent to the most distal implant were evaluated between each follow up visit as well as from time of surgery (baseline) to the final visit using two-way analysis of variance, a two-sample t test, and piecewise linear regression.
  
  
  RESULTS
  Average bone height distal to the distal most implant at placement was 10.34 ± 6.87 mm. From baseline to the first follow-up exam, a mean bone gain of 0.68 mm was noticed, and a mean gain of 0.26 mm was observed from baseline to the second follow-up exam. A statistically significant bone gain (0.92 mm) was noticed in women (n = 49) between the first and second exams, compared to 0.33 mm in men (n = 32). Individuals experienced both bone gain and loss during the study, with an overall gain. Patients with lower initial bone height experienced greater growth, but this was not statistically significant.
  
  
  CONCLUSIONS
  Bone growth is associated with mandibular screw-retained implant-supported prostheses with distal cantilevers, and both bone loss and bone growth may occur in the same patient over time. Within the diverse population of this study, women experienced 2.5 times more gain in bone height than men. No correlation could be established between initial bone height and overall bone height changes.
authors.affiliation: University of Pennsylvania School of Dental Medcine, Philadelphia, Pennsylvania, USA.
authors.forename: Matilda
authors.initials: M
authors.lastname: Dhima
authors.forename: Thomas
authors.initials: T
authors.lastname: Balshi
authors.forename: Glenn
authors.initials: G
authors.lastname: Wolfinger
authors.forename: Vicki C
authors.initials: VC
authors.lastname: Petropoulos
authors.forename: Stephen
authors.initials: S
authors.lastname: Balshi
mesh_terms: D000328:Adult; D000368:Aged; D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D000704:Analysis of Variance; D001863:Bone Screws; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D008875:Middle Aged; D009929:Organ Size; D010012:Osteogenesis / Q000502:physiology*; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D012737:Sex Factors; D013997:Time Factors
chemical_list: D015921:Dental Implants