The effect of surface macrotexture on the mechanical and histologic characteristics of hydroxylapatite-coated dental...

The interface attachment strength and histology of HA-coated endosseous dental implants with surface texturing added to allow for mechanical interlocking of the implant to bone were evaluated in the canine mandibular model. Twenty-two adult mongrel dogs received eight implants (four per side) placed into healed extraction sites. Fifteen weeks post-implantation, the implants were evaluated mechanically by axial pull-out and torsional testing. Following testing, the specimens were evaluated quantitatively for histologic parameters of bone apposition, HA-coating thickness, and mode of interface failure. The addition of surface macrotexture (threads, grooves, and dimples) was not found to have a significant effect on axial pull-out strength compared with smooth implant controls. Similarly, mechanical testing in torsion failed to reveal any significant effect on implant-bone interface attachment due to surface macrotexture. Interface failure occurred primarily at the HA/substrate interface in all implant designs. Examination of HA-coating thickness revealed non-uniform coatings, particularly in the surface-textured designs. Although bone growth into the surface textures was observed in some cases, often only minimal or a thin osseous layer on the HA coating was observed. This factor most likely contributed to the lack of significant additional interface attachment strength in the textured designs. The reduction in areas of complete implant incorporation may also have exposed the HA coating to high interfacial loads and may be responsible for the greater HA coating break-up and presence of particles observed in the textured designs.