Biomechanical evaluation of three dimensional titanium miniplates in mandibular fracture fixation

The unique position of mandible on the face makes it one of the most commonly fractured facial bones and considered  the most common fractures treated by oral and maxillofacial surgeon. There are a number of methods used till date for the treatment of mandibular fractures. Traditionally, the treatment modalities have ranged from conservative measures such as maxillomandibular fixation by means of wiring , splints or arch bar fixation to open reduction with fixation. Most authorities today, advise open reduction and fixation by plates and screws which is necessary for most of the mandibular fractures. 
The purpose of this study was to biomechanically evaluate the  properties of the 3 dimensional titanium mini plates in mandibular fractures fixation.20 sheep hemi mandibles were selected, prepared and randomly  divided into 2 groups: 1). Bending test group (compression group) : 10 hemimandibles with induced body fracture and 2). Tensile test group (tension group): 10 hemimandibles with induced body fracture. The specimens of both groups were treated with the same fixation system (plates & screws) and prepared for mechanical testing using universal testing machine. A specifically designed custom made 4-point biomechanical test jig was fabricated to be adapted to universal testing machine. A load range of 0-400 Newtons was progressively applied by the machine at a constant head speed of 10 mm/min. The progression of loading and displacement either vertically or laterally was followed on the machine monitor, and the load value data in Newton, and extent in millimeters (mm) of any resulting displacement or fixation loosening observed between the two fractured segments during the experiment were noted. The experimental end point was defined as permanent deformation (twisting/fracture) of the plate and/or looseness of mini-screws. The load\displacement data were recorded and the yield load and yield displacement and stiffness were observed and transmitted to a computer that generated a data spreadsheet of force versus displacement. The data referring to the maximum force needed to bring instability and failure to the system were collected and subjected to statistical analysis. In the present study ,the results of the mean yield compression and tension stresses revealed that the used fixation system proofed to be highly efficient for supporting the fracture during the period of osteosynthesis , as their point of deformation under load is far away from the reported maximum forces suitable for normal osteosynthesis processes. Three dimensional miniplates are easy to adjust, requires minimal tissue dissection thus least disturbance to the tissues. Its low profile design and space between plate holes permits excellent revascularization. Comparing the three dimensional plating system with conventional systems, only fewer plates and screws are needed to stabilize the bone fragments.