Title: How could the thickness of the occlusal splint for temporomandibular joint disc derangement be measured?
Internal derangement of the temporomandibular joint (TMJ) has been defined as an abnormal positional relationship of the disk relative to the condylar head, fossa, and/or articular tubercle and is the major cause of jaw pain, clicking, and/or crepitation and limitation of opening .Different treatment modalities have been proposed for the management of internal derangement of the TMJ, including occlusal splints, physiotherapy, psychological treatment, medications, and surgical procedures. Of these modalities, splint therapy is considered a reversible nonsurgical treatment modality for the management of internal derangement (6) because it reduces the pain in the TMJ caused by excessive occlusal pressure from external forces. Thus, the splint restores blood circulation to the TMJ by maintaining a wide gap between the mandibular condyle and the mandibular fossa. While the effectiveness of occlusal splints for treating temporomandibular internal derangement remains debated, the use of splints is presently considered the most common treatment modality for temporomandibular disorders (TMDs). However, the effect of occlusal splint therapy on the disk-condyle relationship is still controversial. Published studies have described different vertical thicknesses varying from 1 mm to 8 mm. The best method to measure and select the accurate vertical thickness of the occlusal splint is still unsettled. Therefore, it is possible that improvement of the internal derangement of the TMJ after the application of a splint might vary between patients and among different studies. Hence, the selection of the vertical thickness of the occlusal splint should be based on scientific evidence. To our knowledge, no existing studies have thoroughly investigated changes in the disk-condyle relationship with different vertical thicknesses of the occlusal splint by using magnetic resonance imaging (MRI) to select the most accurate and effective vertical thickness for the treatment of disk displacement with and without reduction. The present study aimed to investigate a new method of using MRI to assess the most effective vertical thickness of the occlusal splint for the management of TMJ internal derangement.