ALTERATION OF MUSCULAR ACTIVITY DURING DIFFERENT PHASES OF COMBINED TREATMENT IN PATIENTS WITH SKELETAL CLASS III

Mesial occlusion is found in 8-16% of Russian population. Patients often neglect the symptoms and search help when it is too late for conventional orthodontics and the combined orthodontic and surgical treatment is the only option. In these cases, the esthetics is not the only problem but the disorders in the muscular tonus of the m.masseter, m. orbicularis oris, body posture and mandible movements.
Aim: To investigate the muscular activity, body posture, movements of the lower jaw in patients with skeletal class III during different phases of the combined treatment.
Material and methods: 36 patients (10 male and 26 female), age 18-44-years-old have been studied before and after phase I (orthodontic preparation of the arches), phase II (orthognatic surgery) and phase III (orthodontic improvement of the occlusion). The functional activity of the masseter and orbicularis oris muscles has been studied. Myotonometry was carried out with the aid of original program, developed at the Department of Orthodontics of The Moscow State University of Medicine and Dentistry. Kynesiography and computer optical topography (COT) was performed in every patient at each of the phases.
Results: Pretreatment the tonus of m. masseter dexter in Class III patients was lower than in Class I patients: at rest - less than 34,88  3,01 myotones (40% less than in Class I patients, P 0,001), during maximum contraction - less than 27,89  3,77 myotones (28% less than in Class I patients, P 0,001). The tonus of m. orbicularis oris has decreased during phase I and II of the combined treatment (55,68  7,82 myotones pretreatment and 41,45  3,33 myotones after the orthognatic surgery) and slowly normalized towards the end of the treatment (up to 44,26  4,02 myotones during the III phase – post surgical orthodontics). The results of COT show statistically significant posture disorders in all patients at the beginning of the treatment. In the frontal plane scoliosis was found in 47,22% of all patients. In the horizontal plane – rotation in 38,89%. In the sagittal plane – rounded back in 30,56%. At the end of phase I the posture statistically got worse in 11,12% of all patients (scoliosis I degree, kyphosis and round back). In the end of phase III the posture improved in 38,88% and the number of patients with scoliosis I degree decreased from 50% to 33,33%. Patients with vertebral disorders decreased from 19,44% to 8,33%.
During phase I, there was improvement in the vertical and sagittal movement of the mandible while in the transversal way (left and right) it was worse. After phase II and in the end of the combined treatment, improvement in the sagittal and transversal movements was registered. The vertical movements were limited by 5,75-8,64 mm.
Conclusion: The tonus of all muscles has decreased during phase I and II of the combined treatment and has increased during phase III, still remaining less than norm at the end of the treatment. Therefore, rehabilitation is indicated after the combined treatment in order to normalize the movement of the mandible and the muscular tonus. The use of COT is essential for the further orthodontic retention, normalization of the posture and the function of the muscles, as well as for the general treatment plan.
Key words: muscular activity, function, posture, computer optical topography, kynesiography, myotonometry, skeletal Class III
References: 1. Toll D.E. The use of MRI diagnostics in orthognatic surgery^prevalence of TMJ pathologies in Angle Class I, II, III patients/ D.E.Toll, N.Popovich, N.Drinkuth// Journal of Orofacial Orthopedics=Fortschritte Der Kieferorthopadie: Organ/Official Journal Deuttsche Gesellschft Fur Kieferorthopadie.-2010.-Vol.71.-№1.-P.68-80.
2. Yagublu I.A. Otsenka dvizheniy nizhney chelyusti I sostoyania osanki patsiyentov 12-15 let s sagittalnymi animaliyami okklyuzii: Diss. kand.med.nauk/ I.A.Yagublu.-Moskva.2016/-125s
Address for correspondence:
Moscow 125206, Vucheticha str 9a, MGMSU, Department of orthodontics Dr Alimova AV
E-mail: happysmiles@abv.bg Dr Stoichkova V

Vesela Stoichkova

Orthodontist, DDS, MSD, PhD, Happy Smiles Dental Clinic, Sofia, Bulgaria