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Angle Orthod. 2012 Jul;82(4):603-10. doi: 10.2319/070111-427.1.

Effects of screw and host factors on insertion torque and pullout strength.

Author information

1
Department of Orthodontics, Orthodontic Department, St Louis University, St Louis, MO, USA.

Abstract

OBJECTIVE:

To experimentally study the effects of altering implant length, outer diameter, cortical bone thickness, and cortical bone density on the primary stability of orthodontic miniscrew implants (MSIs).

MATERIALS AND METHODS:

Maximum insertion torque (IT) and pullout strength (POS) of 216 MSIs were measured in synthetic bone with different cortical densities (0.64 g/cc or 0.55 g/cc) and cortical thicknesses (1 mm or 2 mm). Three MSIs were evaluated: 6-mm long/1.75-mm outer diameter, 3-mm long/1.75-mm outer diameter, and 3-mm long/2.0-mm outer diameter. To test POS, a vertical force was applied at the rate of 5 mm/min until failure occurred.

RESULTS:

The 6-mm MSIs displayed significantly (P < .001) higher IT and POS than the 3-mm MSIs did. The 3-mm MSIs with 2.0-mm outer diameters showed significantly higher (P < .001) IT and POS than the 3-mm MSIs with 1.75-mm outer diameters. The IT and POS were significantly (P < .001) greater for the MSIs placed in thicker and denser cortical bone.

CONCLUSION:

Both outer diameter and length affect the stability of MSIs. Increases in cortical bone thickness and cortical bone density increase the primary stability of the MSIs.

PMID:
22149542
DOI:
10.2319/070111-427.1
[Indexed for MEDLINE]

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