Are Magnesium Screws Proper for Mandibular Condyle Head Osteosynthesis?

Abstract

Recently, magnesium alloys have gained a significant amount of recognition as potential biomaterials for degradable implants for craniofacial bone screws. Purpose: The aim of this work was to compare screws made specifically for mandibular head osteosynthesis from different materials. Materials and Methods: Screws measuring 14 mm made by one manufacturer specifically for mandibular head osteosynthesis out of the following materials were selected: magnesium (MgYREZr), titanium (Ti6Al7Nb), and polymer (PLGA). The axial pull-out strength and torsional properties were investigated. Results: Each type of screw presented different pull-out forces (Kruskal–Wallis test, p < 0.001). The magnesium screw had the highest pull-out force of 399 N (cracked without the screw out being pulled out), followed by the titanium screw, with a force of 340 N, and the PLGA screw, with a force of 138 N (always cracked at the base of the screw head without the screw being pulled out). ANOVA was performed for the maximal torques before damage to the screw (torsional properties), revealing that the maximal torque of the magnesium screw was 16 N·cm, while that of the titanium screw was 19 N·cm. The magnesium screw was significantly weaker than the titanium screw (p < 0.05). The measured torque and pull-out force were not related to each other (p > 0.05). Conclusion: Among the screws compared, the metal biodegradable magnesium screw seems to be the most suitable material for multiscrew mandibular head osteosynthesis, considering the condition of the fragile screwdriver socket.

Change in Pull-Out Force during Resorption of Magnesium Compression Screws for Osteosynthesis of Mandibular Condylar Fractures

“…The rate of this decrease was lower for polymer screws, but it should be noted that the initial pull-out force was also significantly lower for PLGA screws than for magnesium screws ( p < 0.01). This effect has already been observed previously [ 43 ]. It is necessary to comment on the observation of increased pull-out force in the twelfth week of the magnesium alloy experiment.…”

“…The research presented here is a continuation of experiments published in 2020 [ 43 ]. The same method and the same measuring station were used for axial pull-out tests after the resorption time was added.…”

“…This process leads to the resorption of the implant with the formation of gaseous hydrogen and ionized hydroxyl groups [ 46 ]. It seems that with the accumulation of hydrogen around the relatively small volumes of magnesium alloy, the screws dedicated to the fixation of the mandible head [ 43 ] would be less of a clinical problem with particles and molecules persisting in the surrounding soft tissue after degradation of the main mass of the PLGA screw [ 18 , 25 ].…”

“…This difference is distinct from the use of standard low profile screws made of titanium alloys [ 57 , 64 ]. This issue is reduced and slightly supported by a modification that raises the diameter of magnesium screws to 2.2 mm [ 43 ], which improves the mechanical properties of the screw. Nothing stands against the application of a thicker screw with additional 2–3 narrower screws (1.7 mm).…”

“…Nothing stands against the application of a thicker screw with additional 2–3 narrower screws (1.7 mm). It is still suggested that the screwdriver socket should be handled gently because of the fragile construction of the cruciform design [ 43 ].…”