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Assessing the relationship between mini-screw implant shape and primary stability: An experimental study in
Mahmood R Al Mallah1, Sarmad S Salih Al Qassar1, Ibrahim B Badran1
1Department of Pedodontics, Orthodontics and Prevention, College of Dentistry, University of Mosul, Mosul, Iraq.
Objectives:
Mini-screw implants (MSI) are widely used in orthodontics as temporary anchorage device. Implant geometry, including shape and diameter, is a major contributor to their mechanical retention, and osseointegration. This study aimed to evaluate the influence of MSI shape (cylindrical vs. tapered), and diameter (1.2 vs. 1.4 mm) on peak removal torque (PRT) over different subsequent periods with 7 mm length for all used MSI.
Material And Methods:
A total of 160 titanium mini-screws were inserted into the tibiae of three adult sheep. Implants were divided into four groups according to shape and diameter, further subdivided by different post-insertion removal intervals: immediate, 2 weeks, 4 weeks, and 6 weeks. As eight implants per animal multiple by three animals result in 24 implants per group per time. A standardized surgical protocol was used, and PRT was measured using a digital torque driver. Statistical analysis was conducted using three-way ANOVA, where P ≤ 0.05.
Results:
PRT values increased significantly across all groups over time. Larger diameter implants (1.4 mm) exhibited significantly higher torque values compared to 1.2 mm implants at all time points. Cylindrical MSI generally outperformed tapered implants at 4 and 6 weeks. The highest torque values were recorded at 6 weeks in all groups.
Conclusion:
Implant diameter and shape significantly affect MSI stability. Larger diameters provide superior mechanical retention, while cylindrical shapes may offer advantages in later healing stages. These findings support selection of MSI geometry to optimize clinical outcomes in orthodontic anchorage.
