Bichectomy Surgery and EMG Masticatory Muscles Function in Adult Women: A Longitudinal Study.

AIM: This longitudinal study aimed to evaluate the electromyographic activity of the masseter and temporal muscles in adult women who underwent buccal fat removal. MATERIALS AND METHODS: The sample consisted of 20 healthy adult women with no temporomandibular dysfunction and normal occlusion, who were assessed before, 30, and 60 days after the surgery. The electromyographic signal of the masseter and temporal muscles was captured through mandibular tasks including rest, protrusion, right and left laterality, and maximum voluntary contraction with and without parafilm. The results obtained were tabulated and the Shapiro-Wilk normality test was performed, which indicated a normal distribution. Statistical analysis was performed using the repeated measures test (p < 0.05). RESULTS: Significant differences were observed between time periods in maximum voluntary contraction for the left masseter muscle (p = 0.006) and in maximum voluntary contraction with parafilm for the right temporal (p = 0.03) and left temporal (p = 0.03) muscles. CONCLUSION: Bichectomy surgery did not modify the electromyographic activity of the masseter and temporal muscles during the rest task but may have influenced variations in the electromyographic signal during different mandibular tasks after 60 days of surgery, suggesting compensatory adaptations and functional recovery. CLINICAL SIGNIFICANCE: Understanding the impact of buccal fat removal surgery on the stomatognathic system function provides insights into postoperative functional recovery and potential compensatory adaptations, guiding clinical management and rehabilitation strategies for patients undergoing such procedures. How to cite this article: Cardoso AHDLS, Palinkas M, Bettiol NB, et al. Bichectomy Surgery and EMG Masticatory Muscles Function in Adult Women: A Longitudinal Study. J Contemp Dent Pract 2024;25(3):207-212.

EMG-assisted forward dynamics simulation of subject-specific mandible musculoskeletal system.

Assessment of mandibular dynamics is essential for examining stomatognathic functions, and many kinds of stomatognathic diseases, such as temporomandibular joint (TMJ) disorder and jaw tumors, require individual diagnosis and rehabilitation treatments. Musculoskeletal models of the mandible system provide an efficient tool for fulfilling these tasks, but most existing models are generic, without direct correlation to subject-specific data. For this reason, the objective of this study was to establish a subject-specific mandible modeling framework based on clinical measurements, including medical imaging, jaw kinematics, and electromyographic (EMG) acquisition. First, a non-rigid iterative closest point method was performed to register muscle insertion sites. A flexible multibody approach was introduced to describe the large deformation behavior of jaw muscles. The EMG signals of the temporalis and masseter muscles were then utilized to determine their active forces. Meanwhile, a feedback loop for tracking desired mandibular kinematics was presented to calculate the activations of jaw opening and pterygoid muscles. The subject-specific muscle forces and TMJ joint loading during jaw opening-closing movements were then calculated based on forward-inverse coupling dynamics procedure. As a validation of the proposed framework, the mandible trajectories of seven healthy subjects were predicted and compared with experimental data. The results demonstrated unintentional movement of the head-neck complex together with the activation patterns of jaw opening and lateral pterygoid muscles for different people. The proposed framework combines musculoskeletal modeling with dental biomechanical testing, providing an efficient method of predicting and understanding the dynamics of subject-specific mandible systems.

Biomechanical characterization of human temporal muscle fascia in uniaxial tensile tests for graft purposes in duraplasty.

The human temporal muscle fascia (TMF) is used frequently as a graft material for duraplasty. Encompassing biomechanical analyses of TMF are lacking, impeding a well-grounded biomechanical comparison of the TMF to other graft materials used for duraplasty, including the dura mater itself. In this study, we investigated the biomechanical properties of 74 human TMF samples in comparison to an age-matched group of dura mater samples. The TMF showed an elastic modulus of 36 ± 19 MPa, an ultimate tensile strength of 3.6 ± 1.7 MPa, a maximum force of 16 ± 8 N, a maximum strain of 13 ± 4% and a strain at failure of 17 ± 6%. Post-mortem interval correlated weakly with elastic modulus (r = 0.255, p = 0.048) and the strain at failure (r = - 0.306, p = 0.022) for TMF. The age of the donors did not reveal significant correlations to the TMF mechanical parameters. Compared to the dura mater, the here investigated TMF showed a significantly lower elastic modulus and ultimate tensile strength, but a larger strain at failure. The human TMF with a post-mortem interval of up to 146 h may be considered a mechanically suitable graft material for duraplasty when stored at a temperature of 4 °C.

Evaluation of temporal muscle trophism in relation to the manipulation time and infiltration of 0.5% isobaric bupivacaine through a pterional approach. / Evaluación del trofismo del músculo temporal posquirúrgico en relación con el tiempo de manipulación y la infiltración transoperatoria de bupivacaína isobárica al 0,5% en pacientes sometidos a craneotomía pterional.

INTRODUCTION: There are different techniques for the reconstruction of the temporal muscle (TM) in the pterional approach (PA) in order to avoid and reduce atrophy, it has not been able to avoid it in its entirety. The administration of bupivacaine generates regeneration of muscle fibres. There are no studies in the medical literature that evaluate the time of TM manipulation and the use of bupivacaine for the treatment of atrophy after pterional approach, the present investigation aim is to describe the effects of these variables. PATIENT AND METHODS: Longitudinal study, including patients from 18-80 years old with pterional approach at 2016-2017. We evaluated the effects of the TM manipulation times and the administration of 0.5% bupivacaine on the trophism and function of TM. RESULTS: Twenty-nine patients underwent a PA; 16(55.17%) count with criteria for 0.5% bupivacain infiltration. We found a negative correlation between manipulation times and trophism, with no statistically significance (p>.05). We evaluated presurgical and postsurgical index of Helkimo and Fonseca's index, finding an increase of disfunction with statistically significance (p<.05). In patients who were infiltrated with 0.5% bupivacaine we observed a mean difference in the TM's trophism of 0.275±1.18mm, in contrast with no infiltrated which was 2.39±1.30mm (t[27] = -5.118, p=.0001). CONCLUSIONS: The manipulation of the TM during a pterional approach conditioned an impact on the quality of life according to the disfunction indexes, due to atrophy. This investigation exhibits that de administration of 0.5% bupivacaine during surgery offers a decrease in the TM atrophy.

Evaluation of Temporomandibular Joint Movement After Mandibular Reconstruction.

Mandibular head dislocation and problems with mouth opening may develop after mandibular reconstruction. The authors investigated dislocation of the mandibular head and amount of protrusive sliding (excursion) and their effect on mouth opening. The authors divided 55 mandibular reconstruction patients into 3 groups on the basis of the extent of masticatory muscle and mandibular resection and investigated mandibular head dislocation. On the other hand, the authors focused on mandibular head protrusive excursion as a function of a reconstructed mandible. Protrusive excursion was measured by plain radiography in 29 patients. The extent of mouth opening was measured between the central incisors. Fluoroscopy was performed in 9 patients and the motions of the mandible were analyzed with video-analysis software. Mandibular head dislocation was observed in 15 patients (27.2%) who underwent resection of the mandibular ramus and coronoid process. The extent of mouth opening did not vary significantly among the 3 groups but was lower than that in healthy persons. Mandibular excursion was restricted in patients with conserved temporalis and lateral pterygoid muscles. Protrusive excursion was correlated with the extent of mouth opening. Structural problems involving dislocation of the mandibular head are caused by severing the coronoid process and protrusive excursion disorders are important factors causing mouth opening problems. Physiological sliding and other motions were observed in reconstructed models. The authors believe that when the ramus is resected, there is a greater chance of articular head dislocation. These findings suggest that dislocation of the mandibular head and protrusive excursion disorders arise from imbalances of the remaining masticatory muscles.

Investigation of the activation of the temporalis and masseter muscles in voluntary and spontaneous smile production.

INTRODUCTION: Masticatory muscles or their nerve supply are options for facial reanimation surgery, but their ability to create spontaneous smile has been questioned. This study assessed the percentage of healthy adults who activate the temporalis and masseter muscles during voluntary and spontaneous smile. METHODS: Healthy volunteer adults underwent electromyography (EMG) studies of the temporalis and masseter muscles during voluntary and spontaneous smile. Responses were repeated three times and recorded as negative, weakly positive, or strongly positive according to the activity observed. The best response was used for analysis. RESULTS: Thirty healthy adults (median age: 34 years, range: 25-69 years) participated. Overall, 92% of the masseter muscles were activated during voluntary smile (22% strong, 70% weak). Seventy-seven percent of the masseter muscles were activated in spontaneous smile (12% strong, 65% weak). The temporalis muscle was activated in 62% of responses in voluntary smile (15% strong, 47% weak) and in 45% of responses in spontaneous smile (13% strong, 32% weak). No significant difference was found for males vs females or closed vs open mouth smiles. There was no significant difference in responses between voluntary and spontaneous smiles for the temporalis and masseter muscles, and their use in voluntary smile did not predict activity in spontaneous smile. CONCLUSIONS: Our study has shown that masseter and temporalis are active in a high proportion of healthy adults during voluntary and spontaneous smiles. Further work is required to determine the relationship between preoperative donor muscle activation and postoperative spontaneous smile, and whether masticatory muscle activity can be upregulated with appropriate training.

Masseter and temporalis muscle electromyography findings after lower third molar extraction.

BACKGROUND: The main clinical application of electromyography is to detect abnormalities in muscle function, to assess muscle activity for purposes of recruitment, and in the biomechanics of movement. OBJECTIVES: To analyze electromyography (EMG) findings for masticatory muscles during chewing following surgical extraction of lower third molars, and to determine any correlation between pain, inflammation, trismus, and the EMG data registered. MATERIAL AND METHODS: This prospective study included 31 patients. Surface EMG was used to study masseter and temporalis muscle function before lower third molar extraction and 72 hours and seven days after surgery. Clinical variables, pain, inflammation, and trismus were registered before and after surgery. RESULTS: Studying the area and size of the masticatory muscles, higher values were found for temporalis than masseter muscles, regardless of the surgical side, which points to the greater involvement of the temporalis muscle in mastication. Comparing the side where surgery had been performed with the non-surgical side, a sharp and statistically significant reduction in amplitude and area were noted on the surgical side reflecting major functional affectation. One week after surgery, amplitude and area had almost returned to base-line values, indicating almost complete recovery. While pain decreased progressively after surgery, inflammation peaked at 72 hours, while mouth opening reached a minimum at this time, returning to normality within the week. CONCLUSIONS: Surgical extraction of lower third molars produces changes to electromyography activity that are more evident during the first hours after surgery and closely related to the intensity of pain suffered and the patient's inflammatory responses, although they are not related to mouth opening capacity.

Immediate effects of temporary bite-raising with light-cured orthodontic band cement on the electromyographic response of masticatory muscles

Abstract Objective: To assess the immediate effects of temporary bite-raising using light-cured orthodontic band cement on the superficial masseter and anterior temporalis electromyography (EMG) activity in healthy adults. Materials and Methods: Surface EMG signals were recorded bilaterally from the superficial masseter and anterior temporalis muscles of 30 volunteers with a normal occlusion, before and after having temporary bite-raising. The bite-raising was done by adding light-cured orthodontic band cement (3x5x2 mm WxLxH) on the lingual cusps of both upper first molars. The measurements were recorded (i) at rest, (ii) while clenching in centric occluding position and (iii) while chewing on an artificial test food. The EMG activity at rest and during clenching, the maximum voltage, and the duration of the identified EMG signal burst while chewing the artificial test food before and after temporary bite-raising were statistically compared using the paired t-test or the Wilcoxon signed-rank test based on the normality of the variables. The significance level was set at 5%. Results: After temporary bite-raising, we found no significant change in integral EMG activity at rest position for the superficial masseter (mean difference (MD)=7.5 μVs) and for the anterior temporalis muscle (MD=36.8 μVs); however, the integral EMG activity during clenching was significantly reduced for the superficial masseter (MD=201.2 μVs) and for the anterior temporalis muscle (MD=151.8 μVs). During mastication, the maximum voltage of the identified burst was significantly reduced on the preferred chewing side of the superficial masseter and anterior temporalis muscles (MD=127.9 and 47.7 μV, respectively), while no significant change was found for the duration of the identified burst (MD=-34.1 and 3.4 ms, respectively) after temporary bite-raising. Conclusion: The results point to an altered neuromuscular behavior during clenching and chewing immediately after temporary bite-raising with light-cured orthodontic band cement. This information is relevant for orthodontists to inform their patients what will happen to their masticatory muscle activity when this bite-raising method is used.

Caracterización de la Función Masticatoria en Estudiantes Universitarios / Characterization of the Masticatory Function in University Students

RESUMEN: La masticación es una función orofacial aprendida y de relevancia para el desarrollo armónico del sistema estomatognático y craneofacial. Métodos no instrumentales para la evaluación de la masticación y antecedentes de caracterización de la función masticatoria en Chile son escasos. El objetivo de este estudio es caracterizar la función masticatoria en adultos jóvenes, específicamente el patrón masticatorio más prevalente, número promedio de ciclos masticatorios, así como el tiempo masticatorio promedio, empleando un alimento sólido. Fueron evaluados 92 sujetos, estudiantes universitarios, con edades de entre 18 y 26 años, sin distinción de sexo, con dentición permanente completa o solo ausencia del tercer molar. Los sujetos evaluados presentan mayor prevalencia de patrón masticatorio alternado (62 %), 15,1 ciclos masticatorios en promedio y un tiempo masticatorio promedio de 11,9 s. Nuestros resultados podrían ser considerados valores de referencia para la evaluación clínica de la masticación en Chile.

ABSTRACT: Chewing is an orofacial function learned and relevant to the harmonic development of the stomatognathic system and craniofacial. Non-instrumental methods for the evaluation of chewing and registers of characterization of masticatory function in Chile are limited. The aim of this study is to characterize the masticatory function in young adults, specifically the most prevalent masticatory pattern, the mean masticatory cycles, as well as the mean masticatory time, using a solid food. Ninety-two subjects were evaluated, university students, with ages between 18 and 26 years, without distinction of sex, with complete permanent dentition or only absence of the third molar. The subjects evaluated showed a higher prevalence of alternate masticatory pattern (62%), 15.1 masticatory cycles and masticatory time of 11.9 s on mean. Our results can be considered as reference values for the clinical evaluation of mastication in Chile.

Bite force and electromyography evaluation after cranioplasty in patients with craniosynostosis.

OBJECTIVE: This long-term follow-up investigation aimed to assess masticatory muscle function in 15 patients with craniosynostosis with detachment of the temporal muscle during fronto-orbital advancement 6 years after cranioplasty compared with a non-operative stomatognathic healthy cohort in the same age group (n = 25). STUDY DESIGN: The follow-up assessment for the operated children occurred on average 5.2 ± 1.7 years after surgery at the age of 7 ± 1.6 years. The maximum bite force was assessed, in addition to the bilateral function of both temporal and masseter muscles, which were analyzed using superficial electromyography. RESULTS: The maximum bite force was 257 ± 89 N 255 ± 88 N (right/left), respectively, in the group of operated children and 212 ± 61 N and 203 ± 57 N (right/left), respectively, in the control group, without clinical relevant difference between groups. The surface electromyography signal of the temporal muscle correlated positively with the bite force and showed a slightly lower average resting tone activity in the control group, whereas muscle fatigue occurred slightly faster in the operated children in both muscles without statistically significant difference between the 2 groups. CONCLUSIONS: There was no measurable dysfunction in the temporal muscle after the operative correction of craniosynostosis compared with a healthy population of children.

The Relationship of the Temporal Branch of the Facial Nerve to the Fascial Planes of Temporal Region in Human Fetuses.

The aim of this study was to obtain information by assessing the relationship between temporal region fascial structures, fat pads, and temporal branches of facial nerve in human fetuses to use the knowledge on treatment of early childhood period surgeries. This anatomic dissection study was conducted on 40 hemifaces with no visible external abnormalities on their faces. Fascial layers and related fat pads of temporal region were dissected layer by layer beginning from superficial to deep. The relations of temporal branches of facial nerve and temporoparietal fascia and the structures of these fascial layers were evaluated. Temporoparietal fascia showed continuity below zygomatic arc with superficial musculoaponeurotic system. Temporal branches of facial nerve showed a multiple branching. Parotid-masseteric fascia became very thin on the superficial of zygomatic arch and ran with superficial layer of temporal fascia above without attaching to periosteum. Temporal branches of facial nerve entered between multilayered layers of temporoparietal fascia. Temporoparietal fascia became thicker on anterior and middle parts because of the localization of superficial temporal fat pad. Temporal fascia was a 2-layered thick and fibrous tissue enveloping intermediate fat pad. Deep layer connected to periosteum of zygomatic arch and superficial layer continued passing superficial of zygomatic arch and connected to the parotid-masseteric fascia. Deep temporal fat pad was found on the deep to deep layer of temporal fascia and surface of temporal muscle. The findings of this study may contribute to the knowledge of the topographical localization of temporal branches of facial nerve with temporal region fascial structures and fat pads in fetuses.

Actividad y fuerza de maseteros y temporales de pacientes rehabilitados con sobredentadura vs pacientes dentados / Masseter and temporalis muscles activity and strength in rehabilitated patients with overdentures versus dentate patients

La investigación de los músculos de la masticación, ayuda a un mejor entendimiento de la función oral al permitir un análisis cuantitativo de su actividad y fuerza. Comparar la actividad y fuerza de los músculos maseteros (M) y temporales (T) derechos (D) e izquierdos (I) de pacientes rehabilitados con sobre-dentaduras inferiores (RSI), con la de pacientes dentados con oclusión funcional (PD). Estudio de corte transversal , con muestreo intencional de 28 adultos RSI y 28 adultos PD .Se analizó la actividad muscular de M y T durante la masticación y contracción voluntaria máxima (CMV) mediante electromiografía de superficie; y la fuerza, mediante mioescanografía. La comparación de promedios se realizó mediante la prueba U de Mann Whitney. Los promedios de la CVM en el grupo ISD en micro-voltios (mV) fue: MD: 418,93 MI: 456,26 ; TD: 439,47 mV; TI: 505,54 mV; actividad en masticación: 198, 56 mV; la fuerza en libras fue: MD: 0,38 lb; MI: 0,37lb. En el grupo control los promedios de la CVM en mV: MD: 829,45; MI: 793,53 ; TD: 830,76; TI: 887,82 ; Masticación MD: 172,79; MI: 182,89; fuerza en lb : MD: o,53lb; MI:0,53 .La diferencia fue estadísticamente significativa en la fuerza, la CVM de M y T ; y en la masticación en el T y M derechos (p<0.05). Hay diferencias en la fuerza y la actividad durante contracción voluntaria máxima y la masticación en maseteros y temporales de pacientes PRSI comparados con pacientes PD.

Mastication muscles research help a better understanding of the patient's oral function by allowing quantitative monitoring of their activity and strength. To compare the masseter (M) and the right (RT) and left (LT) temporalis muscles activity and strength in rehabilitated patients with implant overdentures with functional occlusion dentate patients. Cross sectional study, that examined a convenience sample of 28 edentulous lower jaw adults (group) who had undergone an overdenture rehabilitation treatment on two unsplinted implants and 28 dentate adults with stable occlusion (control group). M and T muscle activity was analyzed during mastication. A surface electromyography served to analyze maximum voluntary contraction (MVC) and a mioescanography served to analyze strength. The Mann-Whitney U test was used to compare average results. The MVC average results of the ISD group in microvolts (mV) were RM: 418.93, LM: 456.26; RT: 439.47 mV; LT: 505.54 mV; mastication activity: 198.56 mV; strength in pounds was RM: 0.38 lbs; LM: 0.37 lbs. The control group showed MVC average results in mV: RM: 829.45; LM: 793.53; RT: 830.76; LT: 887,82; mastication RM: 172.79; LM: 182, 89; strength in pounds: RM: 0.53 lbs; LM: 0,53 lbs. Strength exhibited a statistically significant difference of MVC in M and T muscles; and mastication in RT and RM (p <0.05). There are strength and activity muscle differences during maximum voluntary contraction (MVC) and mastication on both masseter and temporalis muscles of rehabilitated patients with implant overdentures compared to dentate patients.

Relações entre potenciais elétricos dos músculos temporais e masseteres, força de mordida e índice morfológico da face / Relationship between electrical activity of the temporal and masseter muscles, bite force, and morphological facial index

RESUMO Objetivo Verificar e analisar possíveis correlações entre a atividade elétrica dos músculos temporais e masseteres, a força de mordida e os índices morfológicos da face, em indivíduos adultos. Método Participaram 43 indivíduos, adultos jovens de ambos os gêneros, entre 18 e 37 anos, submetidos à mensuração da face para cálculo do Índice Morfológico da Face (IMF), Eletromiografia de Superfície (EMGs) de Masseteres Direitos e Esquerdos (MD e ME), Temporais Direitos e Esquerdos (TD e TE) e obtenção da Força de Mordida (FM) nas regiões de pré-molares direitos, pré-molares esquerdos e incisivos. As provas eletromiográficas realizadas foram em repouso, Contração Voluntária Isométrica Máxima (CVIM) e mastigação habitual de uva-passa. Foi realizada análise estatística pelo coeficiente de correlação de Spearman com significância no nível de 5%. Resultados Os valores de repouso em TD e TE foram significativamente maiores que os de MD e ME. Foi encontrada correlação direta significativa entre IMF e a EMGs na prova de CVIM para o TE (rs=36, p=0,017). Observou-se correlação direta significativa entre o IMF com a EMGs durante a FM em Incisivos para os músculos TD, TE e Masseter Direito (MD). Durante as provas de força, foi possível observar correlação direta significativa entre a FM em pré-molares direitos com a EMGs do TE, MD, ME. Conclusões Não foi verificada correlação entre as respostas elétricas dos músculos temporais e masseteres, a força de mordida e os índices morfológicos da face, em indivíduos adultos a partir das provas realizadas. A atividade elétrica dos músculos temporais e masseteres parece associar-se apenas à força de mordida. Como dado de característica postural habitual, a atividade elétrica dos músculos temporais é maior que a atividade de masseteres, também independente do IMF.

ABSTRACT Purpose To analyze possible correlations between the electrical activity of masseter and temporal muscles, Bite Force (BF), and Morphological Facial Indices (MFI). Methods The study involved 43 young adults, both genders, 18 to 37 years old. The individuals were submitted to: face measurement to calculate MFI; Masseter and Temporal Surface Electromyography (sEMG) and BF measurements on right and left premolars and incisors. The following electromyographic tests were conducted: at rest position; Maximal Voluntary Isometrical Contraction (MVIC) and usual chewing of raisins. Statistical analysis was conducted using the coefficient of Spearman correlation with significance level of 5%. Results The values at rest in the temporal muscles were significantly higher than those in the masseter muscles. A meaningful correlation was found between MFI and sEMG in the MVIC test for the Left Temporal (rs=36, p=0.017). A significant correlation was observed between FMI and sEMG during BF in incisors for temporal muscles and the Right Masseter. During the force tests, it was possible to observe a meaningful correlation between BF in right premolars and the sEMG of the Left Temporal and Masseters. Conclusion No correlation was found between the sEMG of temporal and masseter muscles, BF, and FMI in adult individuals based on the tests performed. The SEMG of temporal and masseter muscles seems to be associated only with BF. As a datum of habitual postural characteristic, the electrical activity of temporal muscles is higher than the activity of masseters, also regardless of MFI.

Functional evaluation in orthodontic surgical treatment: long-term stability and predictability.

BACKGROUND: The introduction of electromyographic and kinesiographic technology in orthodontics allows to obtain objective data regarding the functional aspects of the mandibular movements and the masticatory muscular activity. It is then important to be able to correlate the data obtained by instrumental activity with the clinical ones. The aim of this study consists to analyse the post ortodontic surgical stability through instrumental evaluation of the masticatory muscles and mandibular movements. METHOD: 30 patients undergo electromyographic and kinesiographic evaluations through all the surgical orthodontic iter and were than followed during other 4 years. JMP software was used to analyze and correlate the electromyographic and knesioographic data during treatment and during the follow up. RESULTS: A linear correlations between some functional objective values collected from the examinations at the beginning and during therapy and the follow up one has been demonstrated. CONCLUSION: It is important to submit patients in surgical ortodontic treatment to instrumental analysis which can evidence how masticatory function and mandibular movements are performed. It is also important to highlight some functional values also from the beginning of the treatment because an alteration of such values can be related to a better or worse postsurgical rehabilitation.

Analysis of masseter and temporal muscles during surgical extraction of impacted third molars.

With the aim of contributing to the discussion on stomatognathic system dysfunction after surgical procedures, this study compared the electromyographic activity of the superficial masseter and temporal masticatory muscles before, during, and after impacted mandibular third molar extractions. Muscular activity was recorded presurgery, transsurgery, immediately postoperatively, and on postoperative days 7, 15, and 30. Twenty patients requiring extraction of impacted mandibular third molars were selected and evaluated. In 20 patients who underwent mandibular third molar extractions, electromyography showed no alterations in muscle tone, and no statistically significant differences were observed in the left and right temporal and masseter muscles at any of the experimental periods at either mandibular rest or isometric contraction position. However, the degree of mouth opening increased 11.76% from pretreatment to 30 days after surgery. These results may reflect the shorter, careful extraction procedure performed by the surgeon.

[Masticatory performance and assessment of life quality of children with ectodermal dysplasia after prosthetic rehabilitation].

OBJECTIVE: To evaluate masticatory performance and life quality of children with ectodermal dysplasia (ED) after prosthetic rehabilitation. METHODS: Six children with ED received denture restoration and 18 healthy children were involved in this study. The surface electromyography (EMG) of masseter (MM) and anterior temporalis (TA) during clenching and chewing movement were recorded. The EMG amplitude, area, asymmetry index of total and activity index of MM/TA were compared at each stage. The masticatory efficiency was measured with spectrophotometer. The life quality was assessed using visual analogue scale questionnaire. RESULTS: The EMG amplitude of MM and TA during chewing in ED Group were 41.7% and 45.6% of the control group respectively, the area were 35.9% and 36.0% respectively. Significant difference in asymmetry index of total during clenching was observed between the two groups (P < 0.05) but not during chewing (P > 0.05). The differences of activity index of MM/TA during clenching and chewing between the two groups were not detected (P > 0.05). The masticatory efficiency of ED group was 67.2% of the control group. The score of chewing function in children with ED after prosthetic rehabilitation was three times higher than before, and no difference was present between the two groups (P > 0.05). CONCLUSIONS: Early prosthetic rehabilitation can significantly improve the masticatory performance and life quality of children with ED.

Electromyographic Evaluation of Temporalis Muscle Following Temporalis Tendon Transfer (Facial Reanimation) Surgery.

UNLABELLED: Facial paralysis is a significant functional and aesthetic handicap. Many techniques have been defined for facial reanimation. The aim of the study was to evaluate postoperative electromyographical (EMG) activity of temporalis muscle to assess the potential neural impairments related to the surgical procedure. METHODOLOGY: Four patients with facial paralysis were operated with the temporalis muscle tendon transfer technique. Simultaneous surface electromyographic (sEMG) activity at first postoperative year from the bilateral temporalis and masseter muscles was obtained at mandibular rest position and then during maximal clenching. RESULTS: Patients were followed for a minimum period of 18 months. Surface electromyographic evaluations during passive state revealed similar values for the operated and contralateral side. Measurements during active "clench-smiling" of the jaw revealed similar amplitudes for both muscles of the operated side in all cases except case #2. Case #2 revealed lower values for both measurements of temporalis and masseter muscles of the operated side compared with the contralateral side. Dissonant results of case #2 can be the consequence of impaired temporalis muscle activity because of the tension on the muscle as a consequence of overcorrection. CONCLUSION: Temporalis muscle transfer to the perioral region does not hinder contractility of the muscle as long as the facial deformity is not overcorrected.

Prediction at long-term condyle screw fixation of temporomandibular joint implant: A numerical study.

The fixation of commercial temporomandibular joint (TMJ) implant is accomplished by using screws, which, in some cases, can lead to loosening of the implant. The aim of this study was to predict the evolution of fixation success of a TMJ. Numerical models using a Christensen TMJ implant were developed to analyze strain distributions in the adjacent mandibular bone. The geometry of a human mandible was developed based on computed tomography (CT) scans from a cadaveric mandible on which a TMJ implant was subsequently placed. In this study, the five most important muscle forces acting were applied and the anatomical conditions replicated. The evolution of fixation was defined according to bone response methodology focused in strain distribution around the screws. Strain and micromotions were analyzed to evaluate implant stability, and the evolution process conduct at three different stages: start with all nine screws in place (initial stage); middle stage, with three screws removed (middle stage), and end stage, with only three screws in place (final stage). With regard to loosening, the implant success fixation changed the strains in the bone between 21% and 30%, when considering the last stage. The most important screw positions were #1, #7, and #9. It was observed that, despite the commercial Christensen TMJ implant providing nine screw positions for fixation, only three screws were necessary to ensure implant stability and fixation success.

The correlation between surface electromyography and bite force of mastication muscles in Asian young adults.

BACKGROUND: Mastication function is related to mandible movement, muscle strength, and bite force. No standard device for measuring bite force has been developed. A linear relationship between electromyographic activity and bite force has been reported by several investigators, but data on the reliability of this relationship remain limited in Asian young adults. AIM AND OBJECTIVES: The purpose of this study was to develop a clinically applicable, reliable, quantitative, and noninvasive system to measure the kinetic mastication function and observe the correlation between surface electromyography (sEMG) and bite force. MATERIALS AND METHODS: The study group consisted of 41 young healthy adults (24 men and 17 women). Surface electromyography was used to evaluate bilateral temporalis and masseter muscle activities, and an occlusal bite force system was used concurrently to measure the bite force during maximal voluntary biting. Bilateral symmetry was compared, and the correlation between EMG and bite force was calculated. RESULTS: The sEMG signals were 107.7±55.0 µV and 106.0±56.0 µV (P=0.699) on right and left temporalis muscles and 183.7±86.2 µV and 194.8±94.3 µV (P=0.121) on right and left masseter muscles, respectively. The bite force was 5.0±3.2 kg on the right side and 5.7±4.0 kg on the left side (P=0.974). A positive correlation between sEMG and bite force was observed. The correlation coefficient between the temporalis muscle and bite force was 0.512, and that between the masseter muscle and bite force was 0.360. CONCLUSION: No significant difference between the bilateral electromyographic activities of the temporalis and masseter muscles and bilateral bite force was observed in young healthy adults in Taiwan. A positive correlation between sEMG signals and bite force was noted. By combining sEMG and bite force, we developed a clinically applicable, quantitative, reliable, and noninvasive system for evaluating mastication function by using characteristics of biofeedback.

Effect of surgical treatment of mandibular fracture: electromyographic analysis, bite force, and mandibular mobility.

This study aimed to examine individuals undergoing surgery for the treatment of the fractured mandibular angle, using bite force, mandibular mobility, and electromyographic (EMG) analysis in many different clinical conditions, after 2 months postoperatively. Bite force was recorded with a digital dynamometer, model IDDK. The EMG activity (Myosystem-Br1) included the analysis of the masseter and temporal muscles. Mandibular mobility was measured using a digital pachymeter. The subjects were divided into 3 groups: G1, mandibular angle fracture (n = 7); G2, condylar process fracture (n = 5); and G3, control (n = 12). Data were tabulated and submitted to statistical analysis using the repeated-measure test carried out over time and the Student's t-test (P < 0.05), using the Statistical Package for the Social Sciences software, version 19 (SPSS Inc, Chicago, IL). G1 and G2 had an increase in bite force. In G1, there was a regular decrease in the EMG activity in the second postoperative month. G2 presented an irregular pattern in EMG data during the period tested. Regarding the mandibular mobility, both groups obtained amplitude of all mandibular movements with a high percentage, when compared with control. A good functional recovery was achieved by the individuals who had a mandible angle fracture or condylar process fracture, after 2 postoperative months.