Generalizability of splint therapy for temporomandibular joint disorders in the era of precision medicine.

Abstract

We read with great interest the randomized controlled trial by Poorna et al.1 on the efficacy of soft and hard splints for the symptomatic management of temporomandibular joint (TMJ) disorders, in which the severity of TMJ disorders, as measured by the modified Helkimo index, was compared between patients undergoing soft and hard splint treatments. The authors reported that soft and hard splints are equally effective during a follow-up period of 3 months, but hard splints exerted an earlier symptom-relieving effect in the first month.1 As splint therapy is an integral part and the foundation of a comprehensive TMJ treatment plan,1 several aspects are worth further research. In the study by Poorna et al., patients with certain baseline characteristics were excluded to ensure that the efficacy of splint therapies was not biased by external factors.1 Nonetheless, there were several confounders. For instance, given that female individuals are more likely to have TMJ disorders than male individuals,2 and that there are sex differences in pain perceptions,3 subgroup analysis based on stratification by sex may facilitate our understanding of populations in which splint therapies are more applicable. Moreover, although patients with a history of several rheumatic, psychiatric, or dental comorbidities were excluded, it was unclear whether the participants had osteoporosis or low bone mineral density of the maxilla and mandible, malocclusion, periodontitis,4-6 or a history of receiving orthognathic surgeries.7 Because the above-mentioned diseases or treatments may result in TMJ overloading thus leading to structural changes in TMJ,8 inclusion of these records may allow us to ascertain the safety and efficacy of splint therapies for TMJ disorders as a disease of multifactorial etiology. Likewise, future studies including patients with a history of TMJ-involving diseases such as osteoarthritis,9, 10 rheumatoid arthritis,11 or juvenile idiopathic arthritis7, 12 may allow for the generalization of splint therapies. On the other hand, further consideration of predictor variables of preferable clinical outcomes, including patient compliance to splint therapies or splint-wearing behaviors and outcomes other than the Helkimo index that can indicate observable symptoms of TMJ disorders,1 such as the visual analogue scale (VAS) and measures of quality of life, may augment our knowledge on the treatment outcomes of splint therapies more comprehensively. It was indicated in the article by Poorna et al. that panoramic radiographs were used to measure TMJ space produced following splint therapies.1 In the era of precision medicine, in addition to panoramic radiographs that provide two-dimensional information, the precise diagnosis and evaluation of TMJ disorders have largely benefited from advanced imaging modalities including cone-beam computed tomography and high-resolution magnetic resonance imaging, for which the morphological assessment of TMJ spaces, condylar volume in different planes, and glenoid fossa roof thickness has been realized.13 Furthermore, as kinematic parameters and trajectory-tracking technology have been widely applied to delineate TMJ functions and occlusion, studies incorporating these modalities can precisely determine morphological and functional changes before versus after splint treatments.14 In addition to anatomical changes, because it has been demonstrated that the severity and symptoms of TMJ disorders are associated with inflammatory biomarkers in the synovial fluid of TMJ,15 studies including synovial fluid analysis with respect to splint therapies or other treatments for TMJ disorders may expand our understanding of the management of TMJ disorders through a targeted approach. In conclusion, given the multifactorial etiology of TMJ disorders, more studies are needed to generalize the efficacy of splint therapies in patients with concurrent comorbidities. Moreover, as novel imaging modalities and diagnostic biomarkers for TMJ disorders have been proposed, future studies incorporating these technologies may strengthen our knowledge on the efficacy of treatments for TMJ disorders. None.