In vivo evaluation of hydroxyapatite coatings of different crystallinities.
OBJECTIVE
The influence of calcium phosphate (CaP) and hydroxyapatite (HA) crystallinity on bone-implant osseointegration is not well established. In this study, the effect of HA crystallinity and coating method on bone-implant osseointegration was investigated using a rat tibia model.


METHODS
HA coatings 1 to 5 microm thick were produced using a supersonic particle acceleration (SPA) technology. The HA crystallinities used for this study were weight ratios of 30%, 50%, 70%, and 90%. A total of 128 HA-coated implants were placed into the tibiae of 64 male Sprague-Dawley rats. Bone-implant interfaces were evaluated using histology and push-out strength testing at 3 and 9 weeks after implantation.


RESULTS
The 70% crystalline coatings exhibited significantly greater interfacial strength (5 implants/time point/treatment) than the 30%, 50%, and 90% crystalline coatings at 3 and 9 weeks following implantation. The implants with coatings of 70% crystallinity also had the greatest bone contact length. In addition, the HA coatings produced with SPA demonstrated greater interfacial strength and bone contact length than plasma-sprayed HA coatings (except for the HA coating with 30% crystallinity).


CONCLUSIONS
HA coatings of different crystallinities exhibited different dissolution and re-precipitation properties which may enhance early bone formation and bone bonding.


CONCLUSIONS
This study suggested that coating crystallinity and coating methods can influence the bone-implant interface.
Oh
Sunho
S
University of Tennessee Health Science Center, Department of Biomedical Engineering, Memphis, TN 38163, USA.
Tobin
Eric
E
Yang
Yunzhi
Y
Carnes
David L
DL
Ong
Joo L
JL
D000704:Analysis of Variance; D000818:Animals; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D003460:Crystallization; D015921:Dental Implants; D003799:Dental Stress Analysis; D017886:Durapatite / Q000737:chemistry*; D020007:Implants, Experimental; D008297:Male; D008422:Materials Testing; D016348:Osseointegration; D051381:Rats; D017207:Rats, Sprague-Dawley; D033081:Shear Strength; D013718:Tensile Strength; D013977:Tibia
D020099:Coated Materials, Biocompatible; D015921:Dental Implants; D017886:Durapatite