Changes in stability after healing of immediately loaded dental implants.

Purpose: To investigate the parameters that affect primary stability of dental implants, to determine how primary stability influences posthealing stability, and to ascertain the effect of primary stability and insertion parameters on marginal bone loss.

Materials And Methods: A total of 940 immediately loaded implants were considered. Using resonance frequency analysis, primary stability (primary implant stability quotient [pISQ]) and stability after 4 months (tISQ) were recorded. When the differences between pISQ and tISQ exceeded 5 units, marginal bone loss was measured. The implants were placed into three groups based on their primary stability: high (pISQ > 72), moderate, and low (pISQ < 68). Changes in stability after 4 months of loading were evaluated. The relationships between pISQ, insertion parameters, DISQ (ie, tISQ - pISQ), and marginal bone loss were analyzed. The Student t test, one-way analysis of variance, and Spearman nonparametric correlation coefficient were employed for statistical evaluation.

Results: Of the 940 implants, tISQ was recorded in 526 implants and marginal bone loss was measured in 76 implants. There was no statistical relationship between pISQ and insertion torque. Primary stability was influenced by implant diameter but not by implant length. There was a significant relationship between implant insertion torque and bone type. The low primary stability group showed a significant increase in stability during healing. However, high primary stability implants demonstrated a significant reduction in their stability. The linear regression analysis demonstrated that at a pISQ of 69.2, tISQ value would equal pISQ value. Correlations between marginal bone loss and final insertion torque and between marginal bone loss and DISQ values were observed.

Conclusions: Stability of immediately loaded implants with high pISQ decreased significantly during the initial 4 months of healing. However, stability of implants with low primary stability increased significantly. DISQ and insertion torque showed correlation with marginal bone loss.