Effect of recombinant human bone morphogenetic protein-2 in dehiscence defects with non-submerged immediate implants: an experimental study in Cynomolgus monkeys.
BACKGROUND
Alveolar ridge aberrations commonly compromise optimal dental implant installation. To offset any variance between an aberrant alveolar ridge and prosthetic designs, bone augmentation procedures become necessary. The objective of this study was to evaluate bone formation and osseointegration at alveolar dehiscence defects following augmentation of the defect site with recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) at dental implant installation including transmucosal positioning of the dental implant.


METHODS
Four adult male Cynomolgus monkeys received dental implants in contralateral extraction socket sites with surgically created 6 x 4 mm buccal dehiscence defects following elevation of mucoperiosteal flaps. Contralateral sites received rhBMP-2/ACS (rhBMP-2 at 1.5 mg/ml; 0.1 mg/defect) or served as sham-surgery controls. The flaps were adapted and sutured around the healing abutments leaving the implants in a transmucosal position. The animals were sacrificed at 16 weeks postsurgery and block sections of the implant sites were harvested and prepared for histometric analysis.


RESULTS
One dental implant from each treatment group failed to osseointegrate. Another 3 dental implants (sham-surgery controls) failed to osseointegrate with newly-formed bone in the defect area. Thus, 7 of 8 defect sites (4/4 animals) receiving rhBMP-2/ACS compared to 4 of 8 sites (2/4 animals) receiving sham-surgery exhibited evidence of osseointegration with newly formed bone in the defect area. Mean +/- SD defect height amounted to 5.3 +/- 0.2 and 5.4 +/- 0.1 mm for the rhBMP-2/ACS and sham-surgery sites, respectively. Vertical bone gain in rhBMP-2/ACS treated defects (3.9 +/- 0.3 mm) did not differ significantly from that in the sham-surgery control (3.7 +/- 0.4 mm; P > 0.05; paired t-test, N = 4). There were also no significant differences noted for coronal bone-implant contact (3.0 +/- 0.6 versus 3.6 +/- 0.5 mm), and bone-implant contact within the defect site (28.5% +/- 15.1% versus 27.4% +/- 31.7%) and within resident bone (46.9% +/- 26.8% versus 47.8% +/- 39.4%) for the rhBMP-2/ACS and control sites, respectively.


CONCLUSIONS
The observations in this study point to a substantial native osteogenic potential of the alveolar process that has previously not been explored and show that surgical reentry observations of new bone formation may not necessarily indicate that osseointegration has occurred. Bone formation in control defects was substantially greater than predicted, limiting the value of adding an osteoinductive biologic construct.
Hanisch
Oliver
O
Department of Prosthodontics, University of Aachen, Aachen, Germany.
Sorensen
Rachel G
RG
Kinoshita
Atsuhiro
A
Spiekermann
Hubertus
H
Wozney
John M
JM
Wikesjö
Ulf M E
UM
D020341:Absorbable Implants; D016301:Alveolar Bone Loss / Q000601:surgery*; D000539:Alveolar Process / Q000473:pathology; D000540:Alveolar Ridge Augmentation / Q000379:methods*; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000627:therapeutic use*; D003094:Collagen; D000044:Dental Abutments; D015921:Dental Implants; D004195:Disease Models, Animal; D004337:Drug Carriers; D006801:Humans; D008252:Macaca fascicularis; D008297:Male; D016555:Matched-Pair Analysis; D016348:Osseointegration; D010012:Osteogenesis; D011994:Recombinant Proteins; D013499:Surface Properties; D020390:Tooth Socket / Q000601:surgery; D016212:Transforming Growth Factor beta / Q000627:therapeutic use*
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D015921:Dental Implants; D004337:Drug Carriers; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D003094:Collagen