A Study On The Effect Of SH Composite Of RhBMP-2 On The Stability Of Micro-implant Anchorage

Purpose:The purpose of this study was to estimate the effect of rhBMP-2 composite of SH on the stability of the micro-implant which was inserted into the tibiae of the rabbits, through revealing progressive changes of implant-bone interfaces with the routine H.E. staining, measuring the shear bond strength of interface between the micro-implants and bones, observing the interface of the micro-implants and bones with scanning electronic microscope(SEM).Methods:12 New Zealand white rabbits were randomly divided into 3 groups: the two weeks, four weeks and eight weeks one. Two micro-implants (one included rhBMP-2/SH) were inserted into each tibiae of these rabbits which were sacrificed in 2, 4, and 8 weeks. The progressive changes of implant-bone interfaces was revealing with the routine H.E. staining. The shear bond strength of interface between the micro-implant and bone was measured with push-test. The surface of the micro-implants and bones was observed with scanning electronic microscope after measuring the shear bond strength.Results:For 2 weeks, 4 weeks and 8 weeks after operation, there was new bone formation observed in the surface of the tibiacs of the rabbits around micro-implants which included rhBMP-2/SH. The ossoinductive activity was more intensive around the micro-implants with rhBMP-2/SH than simply the micro-implants. The micro-implants with rhBMP-2/SH maximal pull-out loads were (124.32±18.25) N,(175.63±23.45) N and (201.07±33.49) N, the micro-implants without rhBMP-2/SH maximal pull-out loads were (121.52±20.32) N,(213.78±25.30) N and (252.15±36.96) N for 2 weeks, 4 weeks and 8 weeks after operation. The thickness of the cortical bones raised in 2, 4, and 8 weeks because of the new bone formation in the surface of the tibiacs of the rabbits around micro-implants which included rhBMP-2/SH. The bone cohered the surface of micro-implants which included rhBMP-2/SH was more than the surface of simply micro-implants in 4, 8 weeks. Conclusions:Within 8 weeks after operation, the stability of the micro-implants was significantly correlated with healing time. The use of rhBMP-2 composite of SH can obviously raise the thickness of the cortical bones and improve the implant-bone regeneration and increase the stability of the micro-implants.