Structural optimization of patient-specific temporomandibular joint replacement implants for additive manufacturing : novel metrics for safety evaluation and biomechanical performance

Total temporomandibular joint (TMJ) replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements. Several stock and custom-made TMJ implants have been made available; however, retrospective and comparative studies were unable to find significant differences between the two types of solutions. The introduction of additive manufacturing (AM) techniques in medical practice allows for a greater freedom of design and a higher degree of device customisation. The combination of AM with structural optimisation may streamline development and provide the key for fabricating biomechanically enhanced TMJ implants. In this study, structural optimisation techniques were applied to develop and numerically validate a patient-specific TMJ implant. The biomechanical behaviour of each intermediate TMJ design was assessed under four different nominal and maximum biting tasks using finite element analyses. In addition, a new set of metrics were proposed to compare each design regarding biomechanical performance and implant safety. The results suggest that 55-82% of the natural/intact strain patterns can be recovered with the finally selected TMJ implant. This represents an increase of 15% in biomechanical performance for incisor biting, 15% for right molar biting, 17% for left molar biting and a decrease of 2% for left group biting compared with the initial design. The results also suggest that load transfer at the proximal ramus reduces the implant's impact on the mandible's strain patterns. Finally, structural optimisation allows for a volume reduction of up to 44% with a minimum loss of implant safety and biomechanical performance. [GRAPHICS]

Publication year:2022

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