Effect of Anchor Length on the Pullout Strength of Palatal Mini Implants

PURPOSE: The aim of this study was to evaluate the pullout strength of 3 different orthodontic mini implants. MATERIALS AND METHODS: Twenty-seven mini implants (diameter: 2 mm, length: 7 mm) were implanted into artificial bone (Sawbones; Pacific Research Laboratories Inc.) at depths of 3, 4, and 5 mm. The insertion torque (IT), resonance frequency (RF), pullout strength (PS), and anchor length (AL) were measured. One-way analysis of variance with Tukey honest significant difference (HSD) postcomparison were used to detect intergroup differences. The null hypothesis was that IT, RF, and PS would significantly correlate in the same brand. RESULTS: In the implantation depths (ID) (5 and 4 mm), IT of Types C (16.67 and 14.33 N·cm) and Type B (14 and 13.33 N·cm) were significantly higher than Type A (10.33 and 9.33 N·cm). Type A had a largest AL and PS at the IDs (5 and 4 mm). In the IDs (3 mm), PS was no different. Type C had no correlation among the RF, IT, and PS. Therefore, null hypothesis was rejected. CONCLUSION: AL exerted crucial effects on the PS of the mini implants.