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

Area of Science:

• Orthodontics and Dental Implantology
• Biomaterials Science
• Surgical Techniques

Background:

• Mini-screw implants (MSIs) are crucial for orthodontic anchorage.
• Understanding factors influencing MSI insertion-related microdamage is vital for clinical success.
• Previous research has not fully elucidated the impact of MSI diameter and shape on bone microdamage.

Purpose of the Study:

• To investigate the relationship between mini-screw implant (MSI) diameter (1.6 vs 2.0 mm) and shape (tapered vs cylindrical) and the amount of microdamage generated during insertion.
• To determine optimal MSI characteristics for minimizing bone trauma.

Main Methods:

• Thirty-six cylindrical and 36 tapered MSIs (1.6 and 2.0 mm diameter, 6 mm length) were inserted into cadaveric canine maxillae and mandibles after pilot drilling.
• Bone blocks were sectioned, and epifluorescent microscopy quantified cortical thickness, crack length, and number adjacent to the MSI.
• Crack density and total microdamage burden were calculated; three-way ANOVA analyzed the effects of jaw, MSI shape, and diameter.

Main Results:

• Larger diameter (2.0 mm) cylindrical MSIs significantly increased microcrack numbers, lengths, densities, and total microdamage burden compared to 1.6 mm.
• Cylindrical and tapered MSIs of the same diameter produced similar crack numbers and lengths.
• 2.0-mm cylindrical MSIs generated more total microdamage burden than 2.0-mm tapered MSIs.

Conclusions:

• Pilot drilling effectively reduces microdamage during tapered MSI insertion.
• To minimize excessive bone microdamage, clinicians should avoid using large diameter and cylindrical MSIs.
• MSI design (diameter and shape) significantly influences the degree of insertion-related bone trauma.