Comparison of Stability on Screw Placement with or without Polymethyl Methacrylate Filling in Porcine Mandible

Objective: To compare the stability of screw placement with or without Polymethyl Methacrylate (PMMA) in the porcine mandible.

Materials and Methods: A total of 13 porcine hemimandibles underwent Cone-beam 3D computed tomography for screw hole selection. One screw hole was determined on each hemimandible without overlapping vital structures. A 1.6 mm-diameter drill operated to a depth of 3 mm. Subsequently, 13 miniscrews (2.0 mm diameter, 5.5 mm length) were tightened. A dental implant stability meter (AnyCheck) recorded the IST values at the medial, distal and inferior sides of each miniscrew. To investigate loosened miniscrew stability, they were removed, and the 1.8 mm-diameter drill and miniscrews were used. IST values were recorded again. Lastly, after miniscrew removal, Haraeus Palacos® R+G PMMA was applied (1 ml per screw hole). Miniscrews were inserted and IST was recorded after 5 minutes for PMMA setting. All PMMA specimens were scanned.

Results: The median IST in the PMMA group significantly exceeded the loosening miniscrews group in all measured directions (p<0.05). There were no significant differences between the PMMA group and the tightened miniscrews group in all measured directions (p>0.05). Additionally, PMMA spread locally through cancellous bone from 1.3 mm to 3.3 mm using radiograph.

Conclusion: PMMA effectively restored primary stability of loosening miniscrews in the porcine mandible.