The Application And Efficacy Evaluation Of BTX-A In Temporomandibular Joint Disorders

[Objectives](1) To explore whether intramuscular injection of Botulinum toxin A(BTX-A) into masticatory muscles can alleviate symptoms of temporomandibular joint disorders(TMD) patients with masticatory muscle hyperfunction, and improve the patient's joint movement or not.(2) Three clinical treatments to TMD patients along with masticatory muscle hyperfunction was compared by clinical observation to evaluate the clinical value of BTX – A.(3) To explore whether there is influence on TMJ in normal adult individuals after carrying out the masticatory muscle intramuscular injection of BTX-A through animal experiments, and whether masticatory muscle intramuscular injection of BTX-A will affect the normal joint movement and cause irreversible damage to the muscles and joints.[Methods](1) 30 patients with TMD from the department of stomatology in Shanghai Sixth People's Hospital was selected into the study according to the inclusion criteria, and they were divided into three groups at random: BTX- A group(n = 10); Splint group(n = 10); Functional training group(n = 10). Three groups adopted relevant therapy by group strictly, and each study object related indicators was measured respectively before the test, 1 month, 3 months and 6 months after treatment, including clinical symptoms indicators(VAS, degree of mouth opening and style of mouth opening), electromyography(masseter and temporal muscle), bite force measurement and condylar path trace(the edge of the range in various functional motion, sagittal displacement, horizontal displacement and vertical displacement); research on each object implementation of nuclear Magnetic Resonance Imaging(Magnetic Resonance Imaging, MRI) monitoring before test and 6 months after test.(2) Choosing 24 healthy adult-rabbits(12 male, 12 female), randomly grouping: group A: blank control group(n = 8); Group B: normal saline control group(n = 8); Group C: masseter muscle injection of BTX- A group(n = 8). All adult rabbits are no exception after injection. To test masticatory muscle electricity and weight of the rabbits in 2 weeks and 4 weeks after injection, then executing rabbits to weight chewing muscles. Taking joint and masseter muscle specimen to manufacture pathological specimen by HE dye, then observing the changes of masseter muscle fibers, joint condylar collagen fibers, and articular cartilage cell level.[Results](1) Preliminary selected six subjects showed that intramuscular injection of BTX – A, splint treatment and function training treatment have reduced patients' pain level, and had the trend of reducing the masticatory muscle strength and improving bite jaw force.(2) The clinical research which explores the curative effect evaluation of different treatment methods of TMD shows that: according to the longitudinal comparison, VAS, myodynamia of masseter muscle, maximum bite jaw force and condylar movement of BTX- A group before and after the treatment exist significant change(P < 0.05); according to the horizontal comparison, the indicators of BTX- A group were significantly different compared with splint group and functional training group(P < 0.05), in addition, the curative effect is lasting.(3) Animal experiments showed that rabbit weight of three groups has no significant difference in the whole process of the experiment(P > 0.05), masseter muscleelectricity peak amplitude and masseter weight of rabbits in group C was significantly lower than the other two groups(P < 0.05), and pathological result showed the masseter muscles of rabbits in group C appeared atrophy and lipid, meanwhile articular cartilage occurred damaging change.[Conclusion](1) Masticatory muscle intramuscular injection of BTX- A can ease the clinical subjective symptoms of TMD patients along with masticatory muscle hyperfunction, reduce the myodynamia of masticatory muscles, reduce the biting force, coordinate muscle function in the pain region and improve condylar movement.(2) Masseter muscle intramuscular injection of BTX- A treatment has a significant advantage of curative effect and the effect of maintaining time compared with self-function training and splint treatment. So it can be used as an effective therapeutic treatment of TMD.(3) Normal adult rabbits treated by bilateral masseter muscle injection of BTX – A occurred the myoelectric amplitude reduce of masseter muscle, meanwhile bilateral masseter atrophic change and articular cartilage injury were observed.