Altan Varol

End-stage temporomandibular joint (TMJ) disorders often necessitate total joint replacement, and the selection of biomaterial directly impacts long-term outcomes. Ti6Al4V and CoCrMo are commonly used alloys, yet their biomechanical performance in patient-specific prostheses remains insufficiently compared. This study aimed to evaluate the mechanical response of custom TMJ prostheses fabricated from these alloys using finite element analysis (FEA). A three-dimensional mandibular model was created from computed tomography data, and a patient-specific prosthesis was designed in SolidWorks (Dassault Systèmes, SolidWorks Corp., Waltham, MA, USA) and analyzed in ANSYS Workbench 2022 R1 (Ansys Inc., Canonsburg, PA, USA). Physiological loading was simulated by applying forces at the insertion sites of the temporalis, masseter, and medial pterygoid muscles. In the Ti6Al4V model, maximum von Mises stresses reached 192.18 MPa on the mandibular component and 92.004 MPa on the fossa prosthesis, whereas the CoCrMo model demonstrated higher stresses of 204.31 MPa and 94.182 MPa, respectively. Both alloys exhibited similar stress distributions, but Ti6Al4V generated lower stress magnitudes, indicating more favorable load transfer and a reduced risk of mechanical overload on articulating components. These findings underscore the significance of alloy selection in optimizing TMJ prostheses and demonstrate the value of FEA as a tool for guiding future patient-specific designs.

Objectives: Various types of fixation systems have been developed to stabilize the fractured fragments in their original position. The purpose of this ex vitro study was to compare the biomechanical properties of 2 fixation units provided by different types of second-generation headless cannulated compression screws (SG-HCCS) using a servo-hydraulic testing unit (STU) and finite element analysis (FEA). Materials and Methods: 14 fresh frozen sheep cadaveric mandibles were divided into 2 groups randomly(n=7). 3.0 milimeters (mm) diameter, 20mm length partially threaded Herbert screws were used in Group 1 and 2.8mm diameter, 20mm length fully threaded HCCS were used in Group 2 for the fixation of the fragments that was made by a vertical osteotomy at the midline. 2 screws were placed in each model, parallel to each other but in opposite directions. All models were examined biomechanically for the stability of fixation by using STU and FEA. Results: Both FEA and STU analysis revealed that the forces required to fail the fixation system provided by HCCS were significantly higher than Herbert screws. Conclusions: Within the limits of this experimental study, the findings suggest that the biomechanical adequacy provided by second-generation compression screws may be a promising alternative in the treatment of mandibular symphysis fractures, aided by the favorable anatomy of the region. The study may also be useful for further studies in terms of evaluating and comparing different fixation systems in virtual environments using FEA.

Objectives: Mandibular osteotomies and resection of the temporomandibular joint (TMJ) ankylosis are the mostly performed surgical procedures in the infratemporal fossa, which is in close proximity with the main trunk of the maxillary artery (MA). It is imperative to avoid the trunk or branches of the maxillary artery, otherwise, massive intraoperative or postoperative hemorrhage may develop. The goal of the study was to investigate the position of the maxillary artery in the infratemporal fossa and the lingula of the mandible.Methods: Significant landmarks were selected on the mandibles of formalin fixed cadavers, and the distances were measured between the maxillary artery and the bony landmarks with a digital caliper.Results: The average distances between the MA and the articular eminence, the medial cortex of the mandibular ramus, the inferior border of the pterygoid fovea and the mandibular notch were 1.67±0.48 mm, 5.38±2.47 mm, 16.84±1.74 mm, 2.94±0.52 mm, respectively. Course pattern of the MA at the subcondylar level was also mapped. In order to determine the position of the lingula, the average distances between the tip of the lingula and the mandibular notch, the inferior border of the ramus, the anterior margin of the ramus and posterior margin of the ramus were measured and found as 15.4±2.1 mm, 49.5±4.3 mm, 18.1±2.7 mm, 16.6±2.5 mm, respectively. No significant differences were found between the right and left sides, for all parameters.Conclusions: The studied parameters will assist and navigate clinicians to determine the anatomic proximity to the maxillary artery, and, minimize the risk of damaging the vessel. (Eur J Dent 2010;4:166-169)