title: The effect of rhBMP-2 around endosseous implants with and without membranes in the canine model.
abstract: BACKGROUND
  Bone morphogenetic protein (BMP) is a potent differentiating agent for cells of the osteoblastic lineage. It has been used in the oral cavity under a variety of indications and with different carriers. However, the optimal carrier for each indication is not known. This study examined a synthetic bioabsorbable carrier for BMP used in osseous defects around dental implants in the canine mandible.
  
  
  METHODS
  Twelve canines had their mandibular four premolars and first molar teeth extracted bilaterally. After 5 months, four implants were placed with standardized circumferential defects around the coronal 4 mm of each implant. One-half of the defects received a polylactide/glycolide (PLGA) polymer carrier with or without recombinant human BMP-2 (rhBMP-2), and the other half received a collagen carrier with or without rhBMP-2. Additionally, one-half of the implants were covered with a non-resorbable (expanded polytetrafluoroethylene [ePTFE]) membrane to exclude soft tissues. Animals were sacrificed either 4 or 12 weeks later. Histomorphometric analysis included the percentage of new bone contact with the implant, the area of new bone, and the percentage of defect fill. This article describes results with the PLGA carrier.
  
  
  RESULTS
  All implants demonstrated clinical and radiographic success with the amount of new bone formed dependent on the time and presence/absence of rhBMP-2 and presence/absence of a membrane. The percentage of bone-to-implant contact was greater with rhBMP-2, and after 12 weeks of healing, there was approximately one-third of the implant contacting bone in the defect site. After 4 weeks, the presence of a membrane appeared to slow new bone area formation. The percentage of fill in membrane-treated sites with rhBMP-2 rose from 24% fill to 42% after 4 and 12 weeks, respectively. Without rhBMP-2, the percentage of fill was 14% rising to 36% fill, respectively.
  
  
  CONCLUSIONS
  After 4 weeks, the rhBMP-2-treated sites had a significantly higher percentage of contact, more new bone area, and higher percentage of defect fill than the sites without rhBMP-2. After 12 weeks, there was no significant difference in sites with or without rhBMP-2 regarding percentage of contact, new bone area, or percentage of defect fill. In regard to these three outcomes, comparing the results with this carrier to the results reported earlier with a collagen carrier in this study, only the area of new bone was significantly different with the collagen carrier resulting in greater bone than the PLGA carrier. Thus, the PLGA carrier for rhBMP-2 significantly stimulated bone formation around dental implants in this model after 1 month but not after 3 months of healing. The use of this growth factor and carrier combination appears to stimulate early bone healing events around the implants but not quite to the same degree as a collagen carrier.
authors.affiliation: Department of Periodontics, Dental School, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
authors.forename: Archie A
authors.initials: AA
authors.lastname: Jones
authors.forename: Daniel
authors.initials: D
authors.lastname: Buser
authors.forename: Robert
authors.initials: R
authors.lastname: Schenk
authors.forename: John
authors.initials: J
authors.lastname: Wozney
authors.forename: David L
authors.initials: DL
authors.lastname: Cochran
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage*; D003094:Collagen; D003758:Dental Implantation, Endosseous / Q000009:adverse effects; D015921:Dental Implants / Q000009:adverse effects*; D004285:Dogs; D004337:Drug Carriers; D016557:Guided Tissue Regeneration, Periodontal / Q000379:methods*; D006801:Humans; D020007:Implants, Experimental; D019344:Lactic Acid; D008297:Male; D008567:Membranes, Artificial; D023421:Models, Animal; D016348:Osseointegration / Q000187:drug effects; D010518:Periodontitis / Q000188:drug therapy / Q000209:etiology / Q000601:surgery*; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D011138:Polytetrafluoroethylene; D011994:Recombinant Proteins / Q000008:administration & dosage; D018709:Statistics, Nonparametric; D016212:Transforming Growth Factor beta / Q000008:administration & dosage*
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D015921:Dental Implants; D004337:Drug Carriers; D008567:Membranes, Artificial; D011108:Polymers; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D011138:Polytetrafluoroethylene; D003094:Collagen