Temporomandibular disorder (TMD) is a common orofacial pain condition and major cause of non-dental orofacial pain.^1,2 Associated clinical problems involve the temporomandibular joint (TMJ), masticatory muscles, adjacent structures and TMJ-related headache conditions.^3-5 The main signs and symptoms involve TMJ pain, muscle pain, sound (clicking, popping, crepitus), jaw movement limitations, and headache.^5-7 The etiologies of TMD are not clear, but associated factors include occlusal abnormalities, orthodontic treatment, bruxism, orthopedic instability, psychological/psychobiological factors and macro/microtrauma.^8,9 TMD is thus a complex and multidimensional disease which if untreated can easily develop into a chronic disease, significantly reducing quality of life.¹⁰ Treatment options for TMD include occlusal splint therapy, manual therapy, physical therapy, medication, and surgery.^11,12 Among these, occlusion splint therapy is most commonly used as it decreases TMD symptoms ranging from internal derangements to myofascial pain.⁶ There have been many studies on the indications and efficacy of splint therapy for patients with TMD.^5,6,13-18 In clinical practice, it seems to be effective in regarding to TMD symptoms improvement if patients received splint therapy. But there are not clear standards for the number of days per week and duration of wearing the splint, so it is difficult for clinician to determine how to end splint treatment. In general, abrupt discontinuation of drug during medication treatment may aggravate the existing disease, so it is better to avoid abrupt discontinuation of splint treatment as much as possible. In other words, during splint treatment, it is necessary to gradually reduce the number of splint use (“weaning”) and end the treatment. However, there have been no studies on the splint weaning method in terms of tapering period of splint use in relation to TMD symptom improvement. This study was performed to analyze an appropriate splint weaning method in patients with TMD based on efficacy of symptom relief.

One hundred thirty patients who were treated with splint as a conservative treatment of TMD at the Department of Orofacial Pain and Oral Medicine in Yonsei University Dental Hospital from 2015 to 2020 were collected for this study (previous chart review). The patients were classified according to the Diagnostic Criteria for TMDs (DC/TMD) axis I. Diagnoses were classified into TMJ disorders, masticatory muscle disorders, and other conditions. TMJ disorders accounted for 45% of cases, masticatory muscle disorders 32%, and other conditions 23% (Fig. 1). All patients wore the splint only at night. This study was approved by the IRB committee (IRB number: 2-2019-0017).

When these subjective symptoms (e.g., visual analog scale (VAS)) and objective signs (e.g., maximal mouth opening (MMO), tenderness) improved, we began weaning, with the patient’s consent, the frequency of splint use per week step by step. The mean splint therapy period was 29.0 months (about 2.5 years), during which patients wore splints 7 days a week for 8.4 months, 3 - 4 days a week for 9.5 months (a total of 17.9 months, about 1.5 years), and finally 1 - 2 days a week for 11.1 months (a total of 29.0 months, about 2.5 years) (Fig. 2, Table 2).

Fig. 2 correlates the number of days per week wearing the splint for each patient and period of splint use. Patients who wore a splint every day are marked at 7, patients who wore a splint 3 - 4 days a week are marked at 3.5, and patients who wore a splint 1 - 2 days a week are 1.5. The denser the distribution of dots, the more it can be confirmed that many patients wore the splint in the corresponding period.

The mechanism that the splint reduces the symptoms associated with TMD remains unclear. Various types of splint have been used to treat TMD over the past half century due to their ease of use and broad indications.^5,15 The splint is widely suggested as an effective treatment modality for patients with signs and symptoms of TMD for a variety of reasons.¹⁵ The splint can maintain the masticatory muscles in the most relaxed position.¹³ Wearing a splint is generally thought to alter the peripheral sensory input for receptors in the masticatory muscles, periodontal tissues, and oral mucosa. Moreover, the splint can decrease the intra-articular pressure in the TMJ.^2,13,19 It is effective in treating for TMJ arthralgia and myalgia, protecting teeth from attrition, and achieving a stable occlusal contact pattern. It also increases MMO with a MMO < 45 mm and reduces VAS pain intensity as well as the frequency of painful episodes for patients with TMJ clicking.⁵ One study found that relative to a placebo group, a group treated with splint could more easily open the mouth without pain and showed a practical treatment effect after 6 months.²⁰ However, some side effects can occur including occlusal changes, dental/myofascial discomfort, TMJ pain, xerostomia, and excess salivation. The occlusal changes can be significant. Several studies have described occlusal changes such as palatal inclination of maxillary incisors, labial inclination of the mandibular incisors, slight mesial shift of the mandibular molars and loss of contact between the posterior teeth or posterior open bite (POB).²¹

Based on patients’ signs and symptoms, splint therapy must be gradually phased out to prevent this side effect. However, few studies have proposed guidelines for weaning of splint therapy in relation to symptoms of TMD.

This study was conducted to investigate the weaning method and duration of splint therapy in TMD patients. We analyzed the frequency of splint use per week in 130 TMD patients in relation to symptom improvement after splint delivery through a retrospective study (chart review). The authors found that it is possible to minimize splint side effects in TMD patients when proper weaning is applied rather than simple splint delivery. The period of splint therapy is associated with a range of factors, usually related to the amount of time necessary for the retrodiscal tissues to adapt adequately. When the main etiologic factor of TMD is macrotrauma, the duration and success of splint therapy depends on four conditions: acuteness of the injury, extent of the injury, age, and general health of the patient. Patients must be treated individually according to their unique circumstances. In general, when patients wear a splint for shorter periods, fewer complications occur.²² In the present study, most patients gradually adapted to the symptoms and conditions. It is desirable to wean the patient from the splint when symptoms have improved.²³ Based on the weaning method and depending on symptom improvement, the splint therapy consisted of 8.4 months of daily splint use, 9.5 months of 3 - 4 days a week, then 11.1 months wearing the splint 1-2 days a week. Therefore, if TMD patients’ symptoms improve, it is recommended that after splint delivery, they should wear the splint 7 days a week for the first 6 months, followed by 3 - 4 days a week for 6 to 18 months, and finally 1 - 2 days a week after 18 months (Fig. 3).

When patients suffer from side effects such as temporary occlusal changes, we prevent permanent occlusal changes by recognizing these symptoms early and weaning frequency of splint use per week or recommending the patients temporarily not wear the splint.

The main limitations of this study are the small sample size and the lack of correlation between side effects and outcomes when splint weaning was not performed properly.

Further studies should include frequency and duration of splint use, the weaning for the type of splint used, and TMD classification as well as a prospective study comparing larger samples of patients in which the weaning was not properly applied.

Conclusions drawn from our retrospective study of splint weaning method in patients with TMD based on symptom improvement are as follows: it is recommended that patients wear a splint 7 days a week for the first 6 months, followed by 3 - 4 days a week for the next 6 to 18 months, and finally 1 - 2 days a week thereafter.