title: The influence of bone thickness on facial marginal bone response: stage 1 placement through stage 2 uncovering.
abstract: BACKGROUND
  Various causes of facial bone loss around dental implants are reported in the literature; however, reports on the influence of residual facial bone thickness on the facial bone response (loss or gain) have not been published. This study measured changes in vertical dimension of facial bone between implant insertion and uncovering and compared these changes to facial bone thickness for more than 3,000 hydroxyapatite (HA)-coated and non-HA-coated root-form dental implants.
  
  
  METHODS
  Subjects were predominantly white males, 18 to 80+ years of age (mean 62.9 years), who were patients at 30 Department of Veterans Affairs Medical Centers and two university dental clinics. Alveolar ridges ranged from normal to resorbed with intact basal bone. Following preparation of the osteotomy site, direct measurements with calipers were made of the residual facial bone thickness, approximately 0.5 mm below the crest of the bone. The distance from the top of the implants to the crest of the facial bone was also measured using periodontal probes. Implants were uncovered between 3 to 4 months in the mandible and 6 to 8 months in the maxilla after insertion. Facial bone response was the difference between the height of facial bone at Stage 1 (insertion) and Stage 2 (uncovering).
  
  
  RESULTS
  The mean facial bone thickness after osteotomies were made was 1.7 +/- 1.13 mm. When a mean facial bone thickness of 1.8 +/- 1.41 mm or larger remained after site preparation, bone apposition was more likely to occur. The mean facial bone response for 2,685 implants was -0.7 +/- 1.70 mm. For implants integrated at uncovering, the mean bone response was -0.7 +/- 1.69 mm, and -2.8 +/- 1.57 mm for implants mobile at uncovering. Bone quality-4 had the least facial bone response, -0.5 +/- 2.11 mm. Bone responses were similar for both HA-coated and non-HA-coated implants.
  
  
  CONCLUSIONS
  Significantly greater amounts of facial bone loss were associated with implants that failed to integrate. As the bone thickness approached 1.8 to 2 mm, bone loss decreased significantly and some evidence of bone gain was seen. There was no statistically or clinically significant difference in bone response between HA-coated and non-HA-coated implants.
authors.affiliation: Central Arkansas Veterans Healthcare System, Little Rock, AR, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Spray
authors.forename: C G
authors.initials: CG
authors.lastname: Black
authors.forename: H F
authors.initials: HF
authors.lastname: Morris
authors.forename: S
authors.initials: S
authors.lastname: Ochi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000209:etiology*; D000539:Alveolar Process / Q000473:pathology; D000704:Analysis of Variance; D016723:Bone Remodeling / Q000502:physiology; D001862:Bone Resorption / Q000473:pathology / Q000503:physiopathology; D020099:Coated Materials, Biocompatible; D016001:Confidence Intervals; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D017886:Durapatite; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008334:Mandible / Q000473:pathology* / Q000601:surgery; D008437:Maxilla / Q000473:pathology* / Q000601:surgery; D008875:Middle Aged; D016348:Osseointegration; D010012:Osteogenesis / Q000502:physiology; D010027:Osteotomy; D013223:Statistics as Topic; D013499:Surface Properties; D016019:Survival Analysis
chemical_list: D020099:Coated Materials, Biocompatible; D015921:Dental Implants; D017886:Durapatite