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Reverse torque failure of screw-shaped implants in baboons: baseline data for abutment torque application
A B Carr1, P E Larsen, E Papazoglou
1Section of Restorative and Prosthetic Dentistry, Ohio State University College of Dentistry, Columbus 43210-1241, USA.
Summary
Hydroxyapatite-coated (HA) implants showed superior torque removal strength compared to metallic implants in baboon jaws. This suggests current abutment fastening torque levels may offer a safety margin for similar dental implants.
Area of Science:
- Biomaterials Science
- Dental Implantology
- Biomechanics
Background:
- Torque failure is a biomechanical measure of endosseous implant anchorage, but its clinical significance is not fully understood.
- Understanding implant-tissue interface torque resistance is crucial for determining appropriate torque for abutment screw fastening during stage 2 surgery.
Purpose of the Study:
- To measure and compare the torque failure levels of commercially pure (CP) titanium, Ti-6Al-4V, and hydroxyapatite-coated (HA-coated) screw-shaped implants in baboon maxillae and mandibles.
Main Methods:
- Screw-shaped implants of identical size were surgically placed into the posterior edentulous maxillae and mandibles of six baboons.
- Reverse-torque data were collected at 3–4 months postinsertion using a counterclockwise torque driver.
- Data were analyzed using repeated measures ANOVA to assess differences related to time, biomaterial, and jaw.
Main Results:
- HA-coated implants demonstrated significantly higher torque removal values (186.0 Ncm) compared to Ti-6Al-4V (78.6 Ncm) and CP titanium (74.0 Ncm) implants.
- No significant interaction between torque and jaw type was found, but the mandible exhibited greater torque resistance than the maxilla across all implant types.
- The mandible showed higher torque resistance compared to the maxilla for all tested implant groups.
Conclusions:
- Hydroxyapatite coating significantly enhances the torque removal strength of dental implants compared to metallic counterparts.
- The mandible provides a more robust torque resistance environment than the maxilla for dental implants.
- A clinical abutment fastening torque of 35 Ncm appears to provide a sufficient safety margin for implants similar in design and material to those studied.