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cortical bone damage. The drilling depth was 6 mm, and the bone fragments that were producedwere removed by irrigating with normal saline. When inserting the specimens, the sequence wasdecided by random sampling for statistical reliability, and the specimens were press-fitted (Fig.2A).After the surgery, cefazolin, 25 mg/kg, was intramuscularly injected for one week to preventinfection, and acetachlorphenac sodium, 0.5 mg/kg, was intramuscularly injected for 24 hourspostoperative to minimize pain. The eight beagles were sacrificed 24 weeks postoperative, andradiologic examination and push-out tests were carried out (Fig. 2B).3. Push-out Biomechanical Analysis of the Interfacial Shear StrengthThe soft tissue sample was removed from the femur 24 weeks postoperative; the proximalcontact tissue including the metal material was amputated 20 mm of the major axis. Theamputated sample was inferiorly fixated with the bone cement. The substance tester, INSTRON6022 (Instron, Canton, MA), was used to assess and to prevent the dry-out of the sample;normal saline was applied during the tests. After placing the specimen on the test strip, anintrusion/extrusion velocity of 0.5 mm/hr was applied. The bone – metal interfacial shearstrength was measured from the load – displacement curve.4. Histomorphometric AnalysisThe soft tissues were removed to expose the edentulous areas of the femur, with four integratedimplants per side. The details of the histological processes have been described previously. 13The block specimens with the implants were immersed in a solution of formaldehyde (4%)combined with CaCl 2 (1%). The specimens were dehydrated and embedded inmethylmethacrylate. Using a low-speed diamond saw with coolant (Leco Corporation, St.Joseph, MI, USA), the specimens were cut in the bucco-lingual direction and parallel to the axisof the implants, resulting in three 500-mm-thick undecalcified sections per implant.Subsequently, the sections were glued with acrylic cement to opaque Plexiglas, ground to afinal thickness of 80 μm, and stained superficially with toluidine blue followed by basic fuchsin.The specimens from each implant were analyzed by determining the percentage of directcontact between mineralized bone and the Ti surface from intersection counting, using anintegrative eyepiece with parallel sampling lines at a magnification of 100.5. Statistical AnalysisWe compared the mean interfacial shear strength and bone-to-implant contact percentage of thefour different surfaces using a Wilcoxon signed-rank test. Statistical analysis was performedusing SPSS® 11.5 software (SPSS, Inc., Chicago, IL.).Results1. Radiologic ExaminationThrough the radiologic study performed at 24 weeks postoperative, there was no finding ofosteoporosis, bone resorption, or osteolysis around the implants. There was no significantdifference among the four groups of surface modifications (Fig. 3).2. HistomorphometryUsing phase contrast microscopy, new bone formation could be seen around the metal surfaceregions, and lamellar bone formation and peri-implant osseointegration were observed from thedye sample. The mean bone-to-implant contact percentages were 22.1% for the machinedgroup, 52.7% for the grit-blasted group, 61.3% for the SLA group, and 64.5% for the MAOgroup (Fig. 4). The difference between the machined group and other three groups wasstatistically significant (P < 0.01); however, no statistically significant differences between thegrit-blasted, SLA, and MAO groups were found (P > 0.05).file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]