Bone Union Quality after Fracture Fixation of Mandibular Head with Compression Magnesium Screws

Two-screw osteosynthesis of the mandibular condylar head with different screw materials: a finite element analysis

This study compared the biomechanical behavior of titanium, magnesium, and polylactic acid screws for two-screw osteosynthesis of mandibular condylar head fractures using finite element analysis. Von Mises stress distribution, fracture displacement, and fragment deformation were evaluated. Titanium screws performed the best in terms of carrying the highest load, resulting in the least fracture displacement and fragment deformation. Magnesium screws showed intermediate results, while PLA screws were found to be unsuitable with stress values exceeding their tensile strength. These findings suggest that magnesium alloys could be considered a suitable alternative to titanium screws in mandibular condylar head osteosynthesis.

Current Frequency of Mandibular Condylar Process Fractures

There are significant discrepancies in the reported prevalence of condylar process fractures among all mandibular fractures (16.5-56%) in the available literature. In addition, it seems that the actual number of difficult-to-treat fractures of the mandibular head is unknown. The purpose of this study is to present the current incidence of the different types of mandibular process fractures with a special focus on mandibular head fractures. The medical records of 386 patients with single or multiple mandibular fractures were reviewed. Of the fractures found, 58% were body fractures, 32% were angle fractures, 7% were ramus fractures, 2% were coronoid process fractures, and 45% were condylar process fractures. The most common fracture of the condylar process was a basal fracture (54% of condylar fractures), and the second most common fracture was a fracture of the mandibular head (34% of condylar process fractures). Further, 16% of patients had low-neck fractures, and 16% had high-neck fractures. Of the patients with head fractures, 8% had a type A fracture, 34% had a type B fracture, and 73% had a type C fracture. A total of 89.6% of the patients were surgically treated with ORIF. Mandibular head fractures are not as rare as previously thought. Head fractures occur twice as often in the pediatric population than in adults. A mandibular fracture is most likely related to a mandible head fracture. Such evidence can guide the diagnostic procedure in the future.

Biomechanical Comparison of WE43-Based Magnesium vs. Titanium Miniplates in a Mandible Fracture Model in Sheep

In fractures of the mandible, osteosynthesis with titanium plates is considered the gold standard. Titanium is an established and reliable material, its main disadvantages being metal artefacts and the need for removal in case of osteosynthesis complications. Magnesium, as a resorbable material with an elastic modulus close to cortical bone, offers a resorbable alternative osteosynthesis material, yet mechanical studies in mandible fracture fixation are still missing. The hypothesis of this study was that magnesium miniplates show no significant difference in the mechanical integrity provided for fracture fixation in mandible fractures under load-sharing indications. In a non-inferiority test, a continuous load was applied to a sheep mandible fracture model with osteosynthesis using either titanium miniplates of 1.0 mm thickness (Ti1.0), magnesium plates of 1.75 mm (Mg1.75), or magnesium plates of 1.5 mm thickness (Mg1.5). No significant difference (p > 0.05) was found in the peak force at failure, stiffness, or force at vertical displacement of 1.0 mm between Mg1.75, Mg1.5, and Ti1.0. This study shows the non-inferiority of WE43 magnesium miniplates compared to the clinical gold standard titanium miniplates.

Measures of Corticalization

After the insertion of dental implants into living bone, the condition of the peri-implant bone changes with time. Implant-loading phenomena can induce bone remodeling in the form of the corticalization of the trabecular bone. The aim of this study was to see how bone index (BI) values behave in areas of bone loss (radiographically translucent non-trabecular areas) and to propose other indices specifically dedicated to detecting corticalization in living bone. Eight measures of corticalization in clinical standardized intraoral radiographs were studied: mean optical density, entropy, differential entropy, long-run emphasis moment, BI, corticalization index ver. 1 and ver. 2 (CI v.1, CI v.2) and corticalization factor (CF). The analysis was conducted on 40 cortical bone image samples, 40 cancellous bone samples and 40 soft tissue samples. It was found that each measure distinguishes corticalization significantly (p < 0.001), but only CI v.1 and CI v.2 do so selectively. CF or the inverse of BI can serve as a measure of peri-implant bone corticalization. However, better measures are CIs as they are dedicated to detecting this phenomenon and allowing clear clinical deduction.

The Osteosynthesis of the Mandibular Head, Does the Way the Screws Are Positioned Matter?

Currently, an increasing number of medical centers are treating mandibular head fractures surgically. Dedicated screws for compression osteosynthesis have been developed. However, due to the very limited size of the fractured bones and the considerable technical difficulties accompanying the execution of the fixation, there is little room for correction of the positioning and reinsertion of the screws. Therefore, knowing the optimal position of the fixation material is crucial for therapeutic success. The aim of this study is the evaluation of fixation screw position on the mandibular ramus height obtained in the treatment of the condylar head fracture. A total of 57 patients were included in this study. The loss of mandibular ramus height on computed tomography twelve months after mandibular head osteosynthesis was evaluated in relation to the initial distance of the screws from the fracture line, the angle of insertion of the screw into the bone, and the size of the protrusion to the inner side of the condyle. The relationship of the proximity of the screw to the fracture line, angulation, and the size of the protrusion with the loss of ramus height was confirmed. Conclusions: the optimal location for the superior screw is approx. 4 mm below the fracture line (with any angulation), inferior screw is approx. 8 mm (with any angulation), and anterior screw position is approx. 4-5 mm distant from fracture line with the best angulation of 130 degrees to the lateral mandible ramus surface in the coronal plane.