Temporary anchorage device insertion variables: effects on retention.

OBJECTIVE: To quantify the influence of temporary anchorage device (TAD) insertion variables on implant retention. MATERIALS AND METHODS: Three hundred thirty TADs from three companies were placed in synthetic bone replicas at variable depths and angulations and compared. Clinically relevant forces were applied to the TADs until failure of retention occurred. RESULTS: In all three implants, increased insertion depth increased implant retention. As the distance from the abutment head to the cortical plate increased, the retention of all three implants decreased. A significantly greater force to fail was required for a 90 degrees insertion angle than for 45 degrees or 135 degrees insertion angles. No significant difference was found between the 45 degrees and 135 degrees insertion angles. A significant reduction in force to fail occurred when comparing 90 degrees and 45 degrees oblique insertion angles. CONCLUSIONS: Increasing penetration depth of TADs results in greater retention. Increased abutment head distance from cortical plate leads to decreased retention. Placement of TADs at 90 degrees to the cortical plate is the most retentive insertion angle. Insertion at an oblique angle from the line of force reduces retention of TADs.