Biomechanical properties of orthodontic miniscrews. An in-vitro study.

OBJECTIVE: Comparing five commercially-available miniscrew types for skeletal anchorage with regard to the biomechanical properties influencing their primary stability. MATERIAL AND METHODS: Included in this study was a total of 196 self-tapping and self-drilling miniscrews having a diameter of 2 mm (or the largest possible diameter of the manufacturer in question), a thread shaft length of 10 mm, or the longest miniscrew supplied by the manufacturers. The screw types tested were the FAMI 2, Orlus mini-implant, T.I.T.A.N. Pin, tomas-pin and Vector TAS. Insertion and loosening torque measurements, and pullout tests in axial (0 degrees), 20 degrees and 40 degrees directions, as well as test series with and without pilot hole drilling were performed. Bovine femoral heads having the same bone mineral density (BMD) were used as bone-testing material. RESULTS: Higher insertion torques were found for the cylindrical FAMI 2 screw, the conical Orlus mini-implant and the Vector TAS screw (with mean values of 39.2 Ncm, 32.1 Ncm and 49.5 Ncm) than for the cylindrical T.I.T.A.N. pin and tomas-pin. Insertion without predrilling led the insertion torques of all five screws to rise significantly. We noted statistically significant differences among the five screws in the pullout tests. Those highly significant differences at axial (0 degrees) and 20 degrees angles were not apparent at the 40 degrees pullout angle. Compared with the pullout forces (load) in the axial direction, the cylindrical screws' load values decreased markedly according to the angle (by up to -46.6%). The reduction in pullout force in conjunction with an increasing angle was much less pronounced in the conical screws (-0.8% to -29.0%). The tomas-pin demonstrated the highest pullout force and stiffness values throughout the tests. A total of five tomas-pins, two Orlus mini-implants and one FAMI 2 screw fractured during the pullout tests. CONCLUSIONS: Results from our insertion torque measurements suggest that a conical screw design will provide greater primary stability than cylindrical screw types. The cylindrical screw design's superiority was evident in the pullout tests. All the miniscrews' primary stability rose after drill-free insertion. The tomas-pin screws, although biomechanically superior to the other screws, were most prone to fracture.

Atypical cyst formation following chin augmentation using a nasal osteocartilaginous graft.

The purpose of this paper is to present a case of an intraosseous mucocele that was detected 5 years after chin augmentation using a nasal osteocartilaginous graft. Although complications of this technique have been described as negligible, the surgeon must be aware of possible long-term side effects and should remove all nasal mucosa from the graft prior to implantation.

Vertical distraction osteogenesis of fibula transplants for mandibular reconstruction--a preliminary study.

INTRODUCTION: When reconstructing the mandible after tumour resection with a fibular graft, the mandible is often vertically deficient, making placement of dental implants impossible. PATIENTS: Segmental vertical distraction of the reconstructed mandible was performed in nine patients following tumour surgery between February 1998 and 2001. Their age was 14-65 years (average 46.3); all underwent radiotherapy with a dose of up to 55.6 Gy prior to tumour resection. Mandibular discontinuity was repaired with a microvascular fibular bone graft. All grafts had a vertical bone deficit ranging from 9 to 12 mm when compared with the non-resected part of the mandibles. METHODS: All patients underwent segmental vertical distraction of the transplants. The distraction devices were applied intraorally. Distraction of 1.0 mm/day was performed using a Martin distractor (TRACK 1.5) followed by 12 weeks retention time. RESULTS: The increase of vertical bone height was stable and enabled placement of dental implants without any complications. CONCLUSION: Vertical distraction osteogenesis may become a common procedure in the treatment of alveolar ridge deficiency resulting from transplanting fibulae for mandibular reconstruction following tumour surgery.