Abstract
Clinically, a reconstruction plate can be used for the facial repair of patients with mandibular segmental defects, but it cannot restore their chewing function. The main purpose of this research is to design a new three-dimensionally (3D) printed porous titanium mandibular implant with both facial restoration and oral chewing function reconstruction. Its biomechanical properties were examined using both finite element analysis (FEA) and in vitro experiments. Cone beam computed tomography images of the mandible of a patient with oral cancer were selected as a reference to create 3D computational models of the bone and of the 3D-printed porous implant. The pores of the porous implant were circles or hexagons of 1 or 2 mm in size. A nonporous implant was fabricated as a control model. For the FEA, two chewing modes, namely right unilateral molar clench and right group function, were set as loading conditions. Regarding the boundary condition, the displacement of both condyles was fixed in all directions. For the in vitro experiments, an occlusal force (100 N) was applied to the abutment of the 3D-printed mandibular implants with and without porous designs as the loading condition. The porous mandibular implants withstood higher stress and strain than the nonporous mandibular implant, but all stress values were lower than the yield strength of Ti-6Al-4V (800 MPa). The strain value of the bone surrounding the mandibular implant was affected not only by the shape and size of the pores but also by the chewing mode. According to Frost’s mechanostat theory of bone, higher bone strain under the porous implants might help maintain or improve bone quality and bone strength. The findings of this study serve as a biomechanical reference for the design of 3D-printed titanium mandibular implants and require confirmation through clinical investigations.
Highlights
Mandibular segmental defects typically result from jaw trauma, tumor resection, or osteoradionecrosis
The study protocol was approved by the Institutional Review Board (IRB) of China
After the uneven surface of the model was smoothed, the model was imported into a computer-aided design software (Solidworks, Dassault Systemes SE, France), with the x-axis corresponding to the tongue and the buccal direction, the y-axis corresponding to the mesial and distal direction, and the z-axis corresponding to the bite direction
Summary
Common clinical treatments for segmental defects of the mandible include autologous bone grafting and bone plate reconstruction. Autologous bone grafting typically involves one of two types of implants, nonvascularized bone grafts and vascularized bone flaps, which commonly use the fibula, ilium, or ribs as donor sites [1,2]. Patients indicated for such procedures typically undergo a preoperative evaluation through which factors such as age and the location and severity of the defect are considered [3]. If the area of a segmental mandibular defect is small, a nonvascularized bone flap graft or a bone plate is employed
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