Effect of occlusal splint design and thickness on temporomandibular joint loading: a finite element study

Occlusal splints are a mainstay in the management of temporomandibular disorders, but the mechanical influence of design and thickness variations on joint and dental structures remains unclear. This study compared the stress and strain distributions within the temporomandibular joint (TMJ) and adjacent tissues produced by Michigan (stabilization) and non-permissive splints of 3-mm and 5-mm thicknesses using finite element analysis.

Three-dimensional models of the maxilla, mandible, teeth, periodontal ligament, and articular disc were reconstructed from the Visible Human Project dataset. Michigan and non-permissive splints were modeled with occlusal thicknesses of 3 mm and 5 mm. Functional muscle forces were applied to simulate mandibular movements, and linear static analyses were performed in OptiStruct under defined boundary conditions.

The splint-free model showed the highest stress levels in all structures. Non-permissive splints significantly reduced mandibular stress (32.3 MPa) but increased loading on the periodontal ligament. Michigan splints resulted in lower periodontal ligament stresses and a more even stress distribution within the articular disc. Increasing splint thickness improved stress reduction only in the non-permissive model.

Occlusal splints lowered peak stresses in the TMJ and related structures. Non-permissive splints provided greater joint protection, while Michigan splints achieved a more balanced distribution of occlusal forces.

Splint design and thickness affect how loads are transferred through the temporomandibular system. Non-permissive splints, particularly at 5 mm, reduced joint stress but increased periodontal ligament loading. Splint selection should consider the main treatment goal, with attention to using the minimal effective thickness.