Expression of bone matrix proteins during the osseus healing of topical conditioned implants: an experimental study.
OBJECTIVE
Osseointegration of implants depends on time and local bone conditions regarding quality and quantity. This led to the bone classification by Lekholm et al. The aim of the present study was to follow the expression of bone matrix proteins during the phase of osseointegration after conditioning of the bone bed by means of immunohistochemistry.


METHODS
In the porcine frontal skull, implant beds of identical size were created. Before placement of the implants (Ankylos 4 x 3.5 mm), the implant beds were conditioned using bone condensation (cond), an osteoinductive collagen (Co) and platelet-rich plasma (PRP). These conditioning methods were compared with standard procedure. The animals were sacrificed after 2, 4 and 8 weeks. The specimens were then analyzed by light microcopy and immunohistochemistry for expression of bone morphogenic proteins (BMP)2, procollagen I and osteocalcin (OC).


RESULTS
Light microscopy revealed an initial effect of condensation and the bovine collagen at 2 weeks in comparison with the standard group. The PRP did not achieve a significant effect. At 8 weeks, the results of the standard, bone condensation and the bovine collagen group had aligned. The PRP group showed a significantly lower bone-implant contact (BIC) (P=0.003) compared with the standard group. BMP2 expression was significantly higher in all evaluated test groups at 4 and 8 weeks, as well as at 2 weeks in the condensation group. The procollagen I expression at 2 weeks was significantly increased for PRP and lower in the collagen and condensation group compared with standard procedure. Values for 4 and 8 weeks were slightly higher than in the standard group. No significant differences were obvious in the OC group at any time.


CONCLUSIONS
During the initial healing phase, an effect of the evaluated methods of topical bone conditioning can be demonstrated by differences in the expression of BMP2 and procollagen I. These findings had leveled at 8 weeks and were, in contrast, not detectable in the expression of OC or by means of light microscopy.
Schlegel
Karl Andreas
KA
Department of Oral & Cranio-Maxillofacial Surgery, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Germany. andreas.schlegel@yahoo.de
Thorwarth
Michael
M
Plesinac
Alexandra
A
Wiltfang
Joerg
J
Rupprecht
Stephan
S
D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D024042:Collagen Type I / Q000378:metabolism*; D003758:Dental Implantation, Endosseous / Q000379:methods*; D005260:Female; D016348:Osseointegration / Q000502:physiology; D015675:Osteocalcin / Q000378:metabolism; D053657:Platelet-Rich Plasma; D011347:Procollagen / Q000378:metabolism*; D012886:Skull / Q000378:metabolism; D013552:Swine
D019485:Bone Morphogenetic Proteins; D024042:Collagen Type I; D011347:Procollagen; D015675:Osteocalcin