Implant stability in relation to osseointegration: an experimental study in the Labrador dog

OBJECTIVE: Resonance frequency analysis (RFA) is supposed to determine implant stability. The relation between RFA and the degree of bone-to-implant contact (BIC), however, is unclear. The objective of the present experiment was to evaluate RFA values in relation to osseointegration. MATERIAL AND METHODS: In 20 Labrador dogs, all mandibular premolars were extracted bilaterally. After 3 months, four transmucosal screw-shaped experimental implants were placed in each mandibular premolar region. The implants (12 mm length, slashed circle 4.1mm, insertion depth 9 mm) were either SLA surface or turned surface implants. The animals were divided into four groups (five dogs in each group) to study healing following implant installation at 2 h, 4 days, 1, 2, 4, 6, 8 and 12 weeks. Two experimental implants of each type were installed in each edentulous premolar region. A plaque control program was initiated 2 weeks after each implant installation. RFA assessments were performed at the time of implant installation, at one to three occasions during the monitoring period and at the termination of the experiment. At the end of the experiment, the dogs were sacrificed and each implant site was dissected and processed for histological analysis. The results of the histological analysis, i.e. marginal bone level, degree of osseointegration (BIC%) and bone density, were compared with the corresponding Implant Stability Quotient (ISQ) values of the RFA assessment. RESULTS: No correlations between histological parameters of osseointegration and ISQ values could be identified. Marginal bone level changes, differences in BIC% and bone density were not reflected in the RFA at any time-point during the 12-week monitoring period. CONCLUSION: The value of RFA to predict implant stability over time and to determine at which time-point an implant may be exposed to functional load has to be questioned.