Impact of Insertion Depth and Predrilling Diameter on Primary Stability of Orthodontic Mini-implants

Abstract

Objective: To test the hypothesis that the impact of the insertion depth and predrilling diameter have no effect on the primary stability of mini-implants. Materials and Methods: Twelve ilium bone segments of pigs were embedded in resin. After implant site preparation with different predrilling diameters (1.0, 1.1, 1.2, and 1.3 mm), Dual Top Screws 1.6 ϫ 10 mm (Jeil, Korea) were inserted with three different insertion depths (7.5, 8.5, and 9.5 mm). The insertion torque was recorded to assess primary stability. In each bone, five Dual Top Screws were used as a reference to compensate for the differences of local bone quality. Results: Both insertion depth and predrilling diameter influenced the measured insertion torques distinctively: the mean insertion torque for the insertion depth of 7.5 mm was 51.62 Nmm (Ϯ25.22); for insertion depth of 8.5 mm, 65.53 Nmm (Ϯ29.99); and for the insertion depth of 9.5 mm, 94.38 Nmm (Ϯ27.61). The mean insertion torque employing the predrill 1.0 mm was 83.50 Nmm (Ϯ33.56); for predrill 1.1 mm, 77.50 Nmm (Ϯ27.54); for the predrill 1.2 mm, 61.70 Nmm (Ϯ28.46); and for the predrill 1.3 mm, 53.10 (Ϯ32.18). All differences were highly statistically significant (P Ͻ .001). Conclusions:The hypothesis is rejected. Higher insertion depths result in higher insertion torques and thus primary stability. Larger predrilling diameters result in lower insertion torques. (Angle Orthod. 2009;79:609-614.)

Microdamage generation by tapered and cylindrical mini-screw implants after pilot drilling

“…[8][9][10] At placement, success is indicated by ''primary'' stability. 11 While some recommend 5-10 Ncm insertion torques, 12 in general, higher insertion torque would produce greater primary stability. 13,14 But, excessive insertion torque produces potential failure due to bone necrosis, 15 microdamage, 16,17 or MSI fracture during insertion.…”

Measurement of mini-implant stability using resonance frequency analysis

“…The basic requirement is sufficient primary stability. 12 To ensure this, different aspects of implant design [13][14][15][16] and insertion protocol [17][18][19][20] should be considered.…”

Future Advances in Robotic Dentistry

“…An implant surgery system built by the University of Duesseldorf consists of a robot arm, angle sensors, torque sensors, an accuracy potentiometer, driver shafts and mini implants in bone. It is primarily concerned with the effect of insertion angle and depth and stability and predrilling diameter of the mini implant [21,22].…”