Page 576 - IJB-10-6

International Journal of Bioprinting Biomechanical analysis of mandibular implants

1. Introduction mandibular implants, 15,16 with several successful cases
reported in the literature. 17–19
Mandibular segmental defects often result from trauma,
congenital disorders, and benign or malignant tumors. Although multiple studies have investigated the
If left untreated, these defects may lead to difficulties biomechanical characteristics of porous mandibular
in daily activities such as speaking or eating. Currently, implants, the impact of internal lattice design – specifically
vascularized and non-vascularized bone grafting are the shapes, sizes, and rod diameters – on the biomechanics
regarded as primary surgical techniques for repairing of these implants remains unclear. Therefore, the present
mandibular segmental defects. However, these techniques study determined the effects of different lattice shapes,
require the surgeon to manually shape the grafted bone and sizes, and rod diameters on mandibular implants and
subsequent transplantation into the patient’s oral cavity. identified good design parameters. To facilitate the
Likewise, these procedures are associated with prolonged attachment of dental crowns postoperatively and restore
surgical duration and carry the risk of complications biting function, we designed a mandibular implant with
related to bone transplantation. 1,2 an abutment structure on its top. Selected porous lattice
structures with suitable elastic modulus were used to
Advancements in additive manufacturing technology improve the stress distribution of the titanium alloy
have enabled the customization of facial reconstruction mandibular implant and surrounding bone, providing
for patients with facial defects through the integration insights into its biomechanical design while reducing its
of images from computed tomography and magnetic overall weight.
resonance imaging. This approach not only enables greater
customization of reconstruction but also mitigates the 2. Methods
likelihood of errors occurring during surgery, thereby
increasing the success rate of these procedures. 3,4 2.1. Design of a 3D lattice model
The solid models of lattice structures with four porous
Titanium alloys have excellent mechanical properties, shapes, namely tetrahedron, hex-star, hex-vase, and
corrosion resistance, and biocompatibility. These alloys quad-diametral-cross, were designed in accordance
5
20
are used to manufacture complex geometric shapes with the specifications of ASTM F2077 by SolidWorks
that match anatomical structures, and they are used to 2024 (Dassault Systèmes SolidWorks Corporation, United
construct porous titanium scaffolds with mechanical States of America [USA]) and other related software. As
properties similar to those of trabecular bone. Utilizing presented in Figure 1a, these models were compared based
the pore characteristics of titanium alloys can enhance on three lattice sizes (2.5, 3.0, and 3.5 mm) and three rod
the integration of implants with surrounding bone and diameters (0.5, 0.7, and 0.9 mm). Each lattice model is 10
thereby enhance the long-term stability of the implants. mm in length, 10 mm in width, and 10 mm in height.
6,7
Therefore, porous titanium alloys are regarded as a suitable
8,9
option for the repair of mandibular defects. In particular, 2.2. Finite element analysis of lattice model
Ti6Al4V not only possesses the advantages of titanium After the porous lattice models were imported into the
alloys but also features a high strength-to-weight ratio, finite element analysis (FEA) software Ansys 2021 R2
excellent fatigue resistance, and a lower elastic modulus. (Ansys, USA), they were placed within a 3D model with
This makes it more capable of simulating the elastic upper and lower platens with a length of 12 mm, a width
modulus of human bone in medical implants, reducing of 12 mm, and a height of 2 mm for computer-simulated
the stress-shielding effect between the implant and the compression experiments. Boundary conditions were
established with zero displacement in the x-, y-, and
surrounding bone, which contributes to more effective and z-directions on the lower plane, and the interface between
durable implant outcomes. 10
the lattice model and the upper and lower platens was
Multiple studies have indicated that designing defined as a bonding interface.
mandibular implants with porous structures can reduce As indicated in Figure 1b, the loading conditions
the weight of the implants and promote their long-term involved the application of an axial downward force
integration with surrounding tissues, thereby facilitating with a displacement of 0.1 mm on the upper plane. The
inward bone growth. 11–13 In lattice structures, adjusting material properties were uniformly set as linear elastic,
the rod diameter of the tetrahedron unit cell enables the homogeneous, and isotropic (Table 1). 21
porous structures to achieve higher mechanical strength.
14
However, the use of porous structures alone may not 2.3. In vitro experiments of the lattice model
fully restore biting function. Therefore, many researchers Based on the stress distribution results, two sets of lattice
have attempted to integrate abutment structures into shapes and sizes with more favorable stress distribution

Volume 10 Issue 6 (2024) 568 doi: 10.36922/ijb.3943