Evaluation of in vitro resistance of different 2.0-mm titanium plates on the mandibular angle sectioning

Assessment of CAD/CAM Customized V Pattern Plate Versus Standard Miniplates Fixation in Mandibular Angle Fracture (Randomized Clinical Trial)

Background

Mandibular angle is the most common site for fractures, accounting for 23-42% of all cases of mandibular fractures. A customized fixation system is designed directly for a specific patient, which reduces the time spent bending and fixing the plate during the operation. This study was designed to assess the effect of CAD/CAM customized V pattern plate versus standard miniplates fixation in mandibular angle fracture.

Materials and Methods

This prospective randomized clinical trial included 26 patients suffering from mandibular angle fracture. Patients were selected from Oral and Maxillofacial Surgery Department, Faculty of Dentistry, Cairo University and Ahmed Maher Teaching Hospital. Study group (13) needed open reduction and internal fixation by using CAD/CAM V plate with surgical guide, while control group (13) needed open reduction and internal fixation by using standard superior-inferior miniplate fixation. The patients were then followed up for one year postoperatively.

Results

It showed that there was a statistical difference between the study group and the control group regarding postoperative pain, occlusion, and maximal interincisal opening (p value < 0.05%). There was no statistical difference (p value > 0.05%) in the postoperative panoramic radiograph that was taken within the postoperative 1st week in both groups, while the increase in mean bone density was statistically significant (p value < 0.05%) from 6 months to one year postoperatively.

Conclusion

CAD/CAM customized V pattern plate is a suitable plate design because it offers sufficient stability for normal bone healing, the creation of an ideal occlusion, an early return to function, and adequate postoperative radiographic outcomes.

Trial Registration

It was registered at ClinicalTrials.gov. Registration number: NCT03761524. Registration date: 03.12.2018.

Photoelastic analysis of conventional and locking system for treatment of mandibular angle fractures with a single plate

Background

This photoelastic analysis evaluated stress distribution in different osteosynthesis systems, conventional and locking, used for treatment of mandibular angle fractures with a single plate.

Material and Methods

Angle fractures were simulated in mandibles made of photoelastic resin. Following Champy’s method, plate osteosynthesis was performed. The samples were divided into five groups: Group 1, non-fractured mandible; Group 2, two screws were installed in each segment using a conventional system; Group 3, two screws were installed in each segment using a locking system; Group 4, three screws were installed in the proximal segment and four screws in the distal segment using a conventional plate; Group 5, three screws were installed in the proximal segment and four screws in the distal segment using a locking plate. In an universal testing machine coupled to a polariscope, a load was applied to the first molar 10 times. The 50 images were randomly numbered and analyzed qualitatively and quantitatively by two raters.

Results

The locking system promoted better stress distribution along the osteosynthesis. The locking system reduced stress magnitude in the distal segment, with a significant between-group difference (P≤ 0.001).

Conclusions

The locking plate/screw system can distribute stress more evenly throughout the osteosynthesis, especially when long seven-hole plates are used.

Key words:Internal fracture fixation, osteosynthesis, mandibular fracture, bone plates.

A customized fixation plate with novel structure designed by topological optimization for mandibular angle fracture based on finite element analysis

Background

The purpose of this study was to design a customized fixation plate for mandibular angle fracture using topological optimization based on the biomechanical properties of the two conventional fixation systems, and compare the results of stress, strain and displacement distributions calculated by finite element analysis (FEA).

Methods

A three-dimensional (3D) virtual mandible was reconstructed from CT images with a mimic angle fracture and a 1 mm gap between two bone segments, and then a FEA model, including volume mesh with inhomogeneous bone material properties, three loading conditions and constraints (muscles and condyles), was created to design a customized plate using topological optimization method, then the shape of the plate was referenced from the stress concentrated area on an initial part created from thickened bone surface for optimal calculation, and then the plate was formulated as “V” pattern according to dimensions of standard mini-plate finally. To compare the biomechanical behavior of the “V” plate and other conventional mini-plates for angle fracture fixation, two conventional fixation systems were used: type A, one standard mini-plate, and type B, two standard mini-plates, and the stress, strain and displacement distributions within the three fixation systems were compared and discussed.

Results

The stress, strain and displacement distributions to the angle fractured mandible with three different fixation modalities were collected, respectively, and the maximum stress for each model emerged at the mandibular ramus or screw holes. Under the same loading conditions, the maximum stress on the customized fixation system decreased 74.3, 75.6 and 70.6% compared to type A, and 34.9, 34.1, and 39.6% compared to type B. All maximum von Mises stresses of mandible were well below the allowable stress of human bone, as well as maximum principal strain. And the displacement diagram of bony segments indicated the effect of treatment with different fixation systems.

Conclusions

The customized fixation system with topological optimized structure has good biomechanical behavior for mandibular angle fracture because the stress, strain and displacement within the plate could be reduced significantly comparing to conventional “one mini-plate” or “two mini-plates” systems. The design methodology for customized fixation system could be used for other fractures in mandible or other bones to acquire better mechanical behavior of the system and improve stable environment for bone healing. And together with SLM, the customized plate with optimal structure could be designed and fabricated rapidly to satisfy the urgent time requirements for treatment.

In vitro evaluation of the resistance of three types of fixation to treat fractures of the mandibular angle

The purpose of this study was to compare the mechanical resistance of three different plates used to treat fractures of the mandibular angle: a regular 4-hole plate, a longer 4-hole plate (both positioned using the Champy technique), and a 3-dimensional plate positioned over the oblique line. Three equal groups of replicas of human dentate mandibles made out of polyurethane resin were used (n=21 in each group). The force was applied perpendicular to the occlusal plane at a rate of 2mm/minute at three different points: the first molar on the sectioned side; the first molar on the contralateral side; and between the central incisors. This was followed by a resistance-to-load test. The two varying factors (type of plate and site-of-load application) were tested by analysis of variance, and probabilities of less than 0.05 were accepted as significant. There were no significant differences between the subgroups, or between the mean values of the different types of plates (p=0.925). The three types of plates showed similar mechanical behaviour, which showed that the 3-dimensional plates positioned over the oblique line can produce mechanical scores similar to those of conventional plates.