Anodization increases early integration of Osstem implants in sheep femurs.

Background: Spark discharge anodic oxidation forms a porous TiO2 film on the surface of titanium oral implants, increasing surface roughness and concentrations of calcium and phosphate ions. In this study, anodic-treated oral implants were placed in an animal model and analysed using clinical, micro-computerized tomographic (micro-CT) and histometric techniques.

Methods: Pairs of 3.5 mm x 8.5 mm long titanium implants (Osstem Implant Co., Ltd. Seoul, Korea), with blasted (control) or blasted and oxidized surfaces (test), were placed into the right femoral condyles of 10 sheep. Animals were sacrificed after 1 month unloaded healing. Resonant frequency analysis (RFA) was measured in implant stability quotient (ISQ) using the Mentor II device. Specimens were scanned using medium resolution micro-CT (Skyscan 1172). Mean percent bone-to-implant contact (%BIC) was calculated from two images per implant by three different operators, using Image J software. Inter- and intra-examiner differences were calculated. Specimens were then embedded in methacrylate and undemineralized ground sections were digitized. Mean %BIC was measured using Image J at x 20 magnification for the best-three consecutive threads from the most central section.

Results: Mean micro-CT %BIC was similar for control and test (57.2 +/- 0.05% versus 56.4 +/- 0.03%, p = 0.5). There was considerable inter-examiner variability (interclass correlation coefficient = 0.44). RFA showed no clinically-detectable difference between the two groups (control ISQ: 75.2 +/- 4.2; test ISQ: 76.3 +/- 1.7; p = 0.48). However, histometric analysis found a marked and highly statistically-significant difference (%BIC Test 72.5 +/- 8.6%, Control 46.2 +/- 12.1%, p = 0.01).

Conclusions: The novel anodic oxidation technique increased early ossointegration of rough-surfaced implants by 157%. Neither clinical testing with resonant frequency analysis nor radiographic analysis using micro-CT had sufficient resolution to detect this improvement. Whether this gain in early bone-implant contact is clinically significant in the context of early occlusal loading is the subject of subsequent experiments.