This study investigated bite force changes after botulinum toxin type A (BoNT-A) injection into different masticatory muscles. Thirty-five male participants were divided into three groups: masseter only (M), masseter and temporalis (MT), and masseter, temporalis, and medial pterygoid (MTP). Bite force was measured before and up to 6 months after injection with the Dental Prescale II system. Baseline values showed no significant group differences. Group M exhibited significant reduction at 1 and 2 weeks, with recovery within 1 month. Group MT showed a similar transient decrease, also recovering after 1 month. In contrast, Group MTP demonstrated a more pronounced and prolonged reduction, persisting up to 4 months before recovery. These results indicate that the extent and duration of BoNT-A effects depend on the number of muscles injected. Multi-muscle injections, including the medial pterygoid, provide more durable suppression. However, further research involving patient populations is needed to clarify whether multi-muscle injection strategies provide therapeutic benefits in clinical conditions such as temporomandibular disorders or oromandibular dystonia.

Kun-Hwa Kang│Ji-Rak Kim│Jae-Kwang Jung│Jin-Seok Byun. JOMP 2025;50:57-62. https://doi.org/10.14476/jomp.2025.50.2.57

Kun-Hwa Kang, Jin-Seok Byun, Jae-Kwang Jung, Jae-Kap Choi. JOMP 2021;46:63-8. https://doi.org/10.14476/jomp.2021.46.2.63

Age-related differences in temporomandibular joint osteoarthritis (TMJ OA) have been suggested; however, age-specific patterns of functional recovery following occlusal splint therapy remain insufficiently characterized. This retrospective observational study evaluated longitudinal changes in bite force across different age groups in patients with unilateral TMJ OA undergoing stabilization splint therapy. Thirty-two patients diagnosed according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) were categorized into three age groups (20–39, 40–59, and ≥60 years). Maximum bite force was measured repeatedly from baseline to 2 weeks and up to 6 months during the observation period following splint application. Patients aged 60 years and older exhibited significantly lower baseline maximum bite force compared with younger groups (p = 0.011), but demonstrated a gradual and statistically significant increase over the observation period (p = 0.011). In contrast, patients aged 20–39 years showed a significant improvement in bite force asymmetry after 2 weeks of treatment (p = 0.047), which was maintained throughout follow-up. These findings suggest that functional recovery patterns in unilateral TMJ OA may vary according to age, with younger patients showing earlier improvement and older patients demonstrating slower but progressive functional gains. Bite force assessment may serve as a complementary functional parameter for characterizing age-related differences in functional change in patients with unilateral TMJ OA.

We thank the authors for their thoughtful comments

Kun-Hwa Kang│Ji-Rak Kim│Jae-Kwang Jung│Jin-Seok Byun. JOMP 2025;50:6-15. https://doi.org/10.14476/jomp.2025.50.1.6