Activities of masticatory muscles in patients before orthognathic surgery.

AIM: To compare the influence of occlusal versus craniofacial characteristics on the functionality of the stomatognathic apparatus. MATERIALS AND METHODS: Two groups of subjects were selected: 27 patients (13 women and 14 men), 18 to 42 years old, all candidates for orthognathic surgery, 7 with prognathic syndrome and 20 with progenic syndrome; and 26 healthy young adults (13 women and 13 men) of corresponding age (control group). To verify the neuromuscular equilibrium induced by occlusion, the electromyographic activities of both right and left masseter and anterior temporal muscles were recorded and analyzed, calculating the percentage overlapping coefficient (an index of the symmetric distribution of the muscular activity determined by the occlusion) and TORS (index of the presence of mandibular torque). Data were compared with Student t-test for independent samples. RESULTS: Between the 2 groups of patients, no statistically significant differences were found, whereas the statistical analysis showed differences between patients and control subjects (P < 0.05): overall, the control subjects had a better neuromuscular stability than the patients who were candidates for orthognathic surgery. CONCLUSIONS: The electromyographic evaluations revealed that there was a neuromuscular imbalance determined by an occlusal instability in the patients candidates for orthognathic surgery, thus indicating that occlusion plays a more important role than any possible mechanical disadvantages due to altered craniofacial morphology.

Longitudinal effects of rapid maxillary expansion on masticatory muscles activity.

BACKGROUND: To investigate the modifications induced by rapid maxillary expansion (RME) on the electromyographic (EMG) activities of the anterior temporal and superficial masseter muscles, in patients without pre-treatment EMG alterations. MATERIAL AND METHODS: Twenty-one patients with unilateral posterior cross-bite selected from the orthodontic department of the University of L'Aquila (Italy), were enrolled. There was no control group in this study since each subject acted as a control of her/himself. Two surface EMG recordings were taken: T0 (before RME) and at T1 (3 month after the end of expansion). To verify the neuromuscular equilibrium, the EMG activities of both right and left masseter and anterior temporal muscles were recorded during a test of maximum clench. EMG indexes were compared by paired Student's t-test. RESULTS: In both occasions, all indices showed a good symmetry between the right and left side masticatory muscles. No statistically significant differences were found between the two recordings. CONCLUSIONS: In children without pre-treatment EMG alterations, no variations in standardized muscular activity after RME were found. The treatment did not alter the equilibrium of the masseter and temporal muscles. Key words:Rapid maxillary expansion, electromyography, masticatory muscles.

Effects of the functional orthopaedic therapy on masticatory muscles activity.

BACKGROUND: The purpose of this study was to examine surface electromyographic (sEMG) activity of masticatory muscles before and after functional orthopaedic therapy with Sander appliance. MATERIAL AND METHODS: Ten adolescents (5 girls, 5 boys) with an Angle Class II, division I malocclusion, 9-13 years old, were submitted to sEMG before and after functional orthopaedic therapy. To verify the neuromuscular equilibrium, the standardized EMG activities of right and left masseter and anterior temporal muscles were recorded during maximum voluntary clench, and analysed calculating: POC (index of the symmetric distribution of the muscular activity determined by the occlusion); TC (index of presence of mandibular torque) and Ac (index suggesting the position of occlusal barycentre). The total muscular activity was also calculated. Pre- and post- functional therapy data were compared with Wilcoxon Signed-Rank Test. RESULTS: Before treatment, all subjects had a good neuromuscular equilibrium, which was not altered by treatment. CONCLUSIONS: sEMG evaluations allow to quantify the impact of occlusion on masticatory muscle activity and to control that the functional orthopaedic therapy maintain a good muscular coordination. Key words:Functional appliance, Sander appliance, electromyography, masticatory muscles.

Orthodontic management of bilateral maxillary canine-first premolar transposition and bilateral agenesis of maxillary lateral incisors: a case report.

INTRODUCTION: Maxillary canine-first premolar transposition (Mx.C.P1) is an uncommon dental positional anomaly that may create many orthodontic problems from both esthetic and functional points of view. OBJECTIVE: In this report we show the orthodontic management of a case of Mx.C.P1 associated with bilateral maxillary lateral incisor agenesis and unilateral mandibular second premolar agenesis METHODS: The patient was treated with a multibracket appliance and the extraction of the lower premolar. RESULTS: treatment was completed without the need for any prosthetic replacement.

Activities of masticatory muscles in patients after orthognathic surgery.

AIM: To evaluate left and right masseter and anterior temporalis muscle activity in patients before and after orthognathic surgery. PATIENTS: Nineteen patients were enrolled, 9 males and 10 females, aged 17-34 years. Four patients were suffering from a prognathic syndrome (skeletal class II with mandibular retrusion) and were candidates for surgical correction involving a mandibular Bilateral Sagittal Split Osteotomy (BSSO), whereas the other 15 patients showed a progenic syndrome (skeletal class III with mandibular protrusion) and were selected for bimaxillary surgery with maxillary advancement and mandibular retrusion. METHODS: Electromyographic examinations were carried out on all subjects presurgically and 6-8 months postoperatively. To verify the neuromuscular equilibrium, the electromyographic activities of both the right and left masseter and anterior temporalis muscles were registered and analysed calculating: percentage overlapping coefficient (POC, index of the symmetric distribution of the muscular activity determined by the occlusion) and torque coefficient (TC, index of presence of mandibular torque). RESULTS: After surgery, a trend in the improvement of POC and TC indices was found, with a reduced intragroup variability. CONCLUSION: The electromyographic evaluation allowed the impact of occlusion on neuromuscular equilibrium to be quantified, and showed that improvements gained by surgical intervention are primarily due to better occlusal stability and not to biomechanical advantages.