Early endosseous integration enhanced by dual acid etching of titanium: a torque removal study in the rabbit

Textured implant surfaces are thought to enhance endosseous integration. To rque removal forces have been used as a biomechanical measure of anchorage, or endosseous integration, in which the greater forces required to remove implants may be interpreted as an increase in the strength of bony integrat ion. The purpose of this study was to compare the torque resistance to remo val of screw-shaped titanium implants having a dual acid-etched surface (Os seotite (R)) with implants having either a machined surface, or a titanium plasma spray surface that exhibited a significantly more complex surface to pography. Three custom screw-shaped implant types - machined, dual acid-etc hed (DAE), and titanium plasma sprayed (TPS) - were used in this study. Eac h implant surface was characterized by scanning electron microscopy and opt ical profilometry. One DAE implant was placed into each distal femur of eig hteen adult New Zealand White rabbits along with one of the of her implant types. Thus, each rabbit received two DAE implants and one each of the mach ined, or TPS, implants. All implants measured 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Eighteen rab bits were used for reverse torque measurements. Groups of six rabbits were sacrificed following one, two and three month healing periods. implants wer e removed by reverse torque rotation with a digital torque-measuring device . Three implants with the machined surface preparation failed to achieve en dosseous integration. All other implants were anchored by bone. Mean torque values for machined, DAE and TPS implants at one, two and three months wer e 6.00 +/-0.64 N-cm, 9.07 +/-0.67 N-cm and 6.73 +/-0.95 N-cm; 21.86 +/-1.37 N-cm, 27.63 +/-3.41 N-cm and 27.40 +/-3.89 N-cm; and 27.48 +/-1.61 N-cm, 4 4.28 +/-4.53 N-cm and 59.23 +/-3.88 N-cm, respectively. Clearly, at the: ea rliest time point the stability of DAE implants was comparable to that of T PS implants, while that of the machined implants was an order of magnitude lower. The TPS implants increased resistance to reverse torque removal over the three-month period. The results of this study confirm our previous res ults that demonstrated enhanced bony anchorage to dual acid-etched implants as compared to machined implants. Furthermore, the present results indicat e that dual acid etching of titanium enhances early endosseous integration to a level which is comparable to that achieved by the topographically more complex TPS surfaces.