Masseter Muscle Activity Research Articles

Textural properties and muscle activities during mastication of normal and ultrasonically softened sticky rice aimed for consumers with swallowing disorder: A pilot study.

Ultrasonication was used to develop softer sticky rice for elder adults. Textural properties of original sticky rice (oSR) and ultrasonically modified sticky rice (mSR) were determined. In addition, jaw muscle activities during mastication of both oSR and mSR were investigated. Twenty-seven healthy elderly subjects, age 68.9 ± 7.6 years, were asked to masticate both types of sticky rice in random sequence for three times with a 5-min rest between each test. Activities of bilateral masseter and suprahyoid muscles were recorded. Root mean square (RMS) and mastication duration were analyzed. After mastication trials, subjects were asked to rate preference and softness of the samples. mSR exhibited significantly lower hardness than oSR, while cohesiveness and adhesiveness values of the two samples were not significantly different. Interestingly, all the muscle activities were not significantly different between masticating oSR and mSR, whereas the number of chewing cycles while chewing the mSR was larger. However, 92% of the subjects preferred mSR and felt that it was softer. mSR may therefore be regarded as having potential for elder people who have difficulty masticating hard solid foods based on its lower hardness and higher level of preference compared to oSR.

Malocclusion with posterior unilateral crossbite affects superficial masseter and anterior temporal muscle activity during mastication

Background: Mastication patterns due to malocclusion with unilateral posterior crossbite may permanently change. Purpose: This study aimed to examine the effect of malocclusion with unilateral posterior crossbite of the superficial masseter and anterior temporal muscles on the crossbite and non-crossbite sides during mastication. Methods: Thirty subjects (8 males and 22 females) between the ages of 17 and 30 years who were students of the 2017–2019 Dentistry and Dental Hygiene Study Program, Faculty of Dentistry, UGM and who had at least two posterior teeth with unilateral posterior crossbite were divided into 10 subjects with Angle’s class I, 10 subjects with class II and 10 subjects with class III malocclusions. The amplitude of the superficial masseter and temporal anterior muscles was performed during mastication using surface electromyography (sEMG). The mean difference between the groups of malocclusion on the crossbite and non-crossbite sides of the superficial masseter and temporal anterior was analysed by a two-way analysis of variance (ANOVA). Results: The results indicated a difference in amplitude mean between the malocclusion types on the crossbite sides and non-crossbite sides of the superficial masseter and temporal anterior muscles (p<0.05). This study confirmed there was a decrease in superficial masseter and anterior temporal muscle activity on the crossbite side rather than in the non-crossbite side in Angle’s class I and class II. However, there was an increase in activity of the superficial masseter and anterior temporal muscles on the crossbite side for class III. Conclusion: Malocclusion with unilateral posterior crossbite affects masticatory activity of the superficial masseter and temporal anterior muscles on the crossbite side.

The Relationship between Stress and Masticatory Muscle Activity in Female Students.

The aim of the study was to analyze the relationship between stress measured by the perceived stress scale (PSS-10) questionnaire and masticatory muscle activity. Experimental design assumed the study of healthy young women without temporomandibular disorders, dividing them into three groups depending on the result of the stress level and then comparing these groups in terms of bioelectrical activity of the masticatory muscles. After the exclusion criteria were applied, 63 female students (mean age: 22.3 ± 2.4 years) from Medical University of Lublin were included in the study. The subjects were then divided into 3 groups: with low (n = 18), medium (n = 18) and high stress level (n = 27), according to PSS-10 results. Resting and functional activity of temporalis anterior (TA) and masseter (MM) muscles were measured by electromyograph BioEMG III. There were statistically significant effects of group on the absolute value of asymmetry index (AsI) of TA and MM during maximum voluntary clenching on dental cotton rollers (both p = 0.02). Post hoc analysis shows that there were statistically significant differences between medium and high stress groups in AsI TA (p = 0.01) and between low and high stress groups in AsI MM (p = 0.02). Perceived stress measured by PSS-10 questionnaire seems to be associated with changes in muscular asymmetry in functional clenching activity.

Changes in Masticatory Muscles following orthognathic surgery (BSSO for correction of skeletal class III deformity )

Aim: To evaluate the postoperative electromyographic changes of temporalis and masseter muscles activity, in patients with orthognathic surgery BSSO,for correction of mandibular prognathism. Material and Methods: Eight adult patients,their ages ranged from 22-45 years,five females and three males ,suffering from mandibular prognathism. underwent BSSO,for performing mandibular setback . EMG examinations(peak to peak amplitude,for detection of the strength of contraction of both temporalis and masseter muscles) were done presurgical and twelve months postoperatively. Results: Significant increase in peak-to-peak amplitude values of both temporalis muscles was founded. Moreover, an increase in peak-to-peak amplitude values of both masseter muscles was found,.No significant differences were found in the mean frequency score (as one of the variables of the EMG measurement) of the masseter muscles before bilateral sagittal split osteotomy and that undertaken 12 months after bilateral sagittal split osteotomy (P = 0.06). An increase in the mean peak to peak amplitude score for the right and left temporalis muscle was found, with significant differences between the measurement found 12 months after bilateral sagittal split osteotomy, and that measured before bilateral sagittal split osteotomy fig (6) (P = 0.002,0.0001 respectively) Conclusion: No change in the strength of contraction of both temporalis and masseter muscle had detected after performing BSSO for correction of mandibular prognathism ,as detected by EMG examination.

Clinical and Instrumental TMJ Evaluation in Children and Adolescents with Juvenile Idiopathic Arthritis: A Case—Control Study

To investigate temporomandibular joint (TMJ) involvement signs such as muscle pain, the ratio of masseter and temporal muscle activity, mouth opening width and jaw deviation during mouth opening in children and adolescents with juvenile idiopathic arthritis (JIA), a group of 32 subjects with JIA and a control group of 32 healthy subjects were evaluated. Data were collected clinically by muscle palpation (masseters, anterior temporalis and sternocleidomastoids) and instrumental analysis (electromyography and kinesiography). Higher pain was registered in the masseter and sternocleidomastoid muscles on both sides and in the right anterior temporalis in the JIA group compared to the control group (p < 0.05). Electromyography showed no statistically significant difference in the frequency of the pathological ratio of masseter and temporal muscle activity (MM/TA < 1) both in the JIA group and in the control group. Kinesiography showed a statistically significant difference in mouth opening width and jaw deviation during mouth opening between the groups (p < 0.05): JIA subjects showed lower mouth opening values and wider deviation on mouth opening; 29 out of 32 JIA subjects showed jaw deviation towards the right side. JIA affects the TMJ, causing myalgia in the head and neck muscles, a reduction in mouth opening width and an increase in jaw deviation during mouth opening.

Electromyographic features and efficacy of orofacial myofunctional treatment for skeletal anterior open bite in adolescents: an exploratory study

BackgroundDue to the multifactorial aetiology and unpredictable long-term stability, skeletal anterior open bite (SAOB) is one of the most intractable conditions for orthodontists. The abnormal orofacial myofunctional status (OMS) may be a major risk factor contributing to the development and relapse of SAOB. This study is aimed at evaluating the OMS and the efficacy of orofacial myofunctional therapy (OMT) alone for SAOB subjects.MethodsEighteen adolescents with SAOB (4 males, 14 females; age: 12–18 years) and eighteen adolescents with normal occlusion (2 males, 16 females; age: 12–18 years) were selected. The electromyographic activity (EMGA) associated with mastication and closed mouth state was measured. Lateral cephalography was used to evaluate craniofacial morphology. Wilcoxon signed rank tests and t-tests were performed to evaluate myofunctional and morphological differences. Pearson or Spearman correlation analysis was used to investigate the correlations between EMGA and morphological characteristics. SAOB subjects were given OMT for 3 months, and the EMGA was compared between before and after OMT.ResultsDuring rest, anterior temporalis activity (TAA) and mentalis muscle activity (MEA) increased in SAOB subjects, but TAA and masseter muscle activity (MMA) decreased in the intercuspal position (ICP); and upper orbicularis activity (UOA) and MEA significantly increased during lip sealing and swallowing (P < 0.05). Morphological evaluation revealed increases in the FMA, GoGn-SN, ANS-Me, N-Me, L1-MP, U6-PP, and L6-MP and decreases in the angle of the axis of the upper and lower central incisors and OB in SAOB subjects (P < 0.05). TAA, MMA and anterior digastric activity (DAA) in the ICP were negatively correlated with vertical height and positively correlated to incisor protrusion. MEA was positively correlated with vertical height and negatively correlated with incisor protrusion; and the UOA showed a similar correlation in ICP, during sealing lip and swallowing. After SAOB subjects received OMT, MEA during rest and TAA, MMA and DAA in the ICP increased, while UOA and MEA decreased (P < 0.05).ConclusionSAOB subjects showed abnormal OMS features including aberrant swallowing patterns and weak masticatory muscles, which were interrelated with the craniofacial dysmorphology features including a greater anterior facial height and incisor protrusion. Furthermore, OMT contributes to OMS harmonization, indicating its therapeutic prospect in SAOB.

СРАВНИТЕЛЬНАЯ ОЦЕНКА ПОКАЗАТЕЛЕЙ БИОЭЛЕКТРИЧЕСКОЙ АКТИВНОСТИ МЫШЦ У ПАЦИЕНТОВ СО СЪЕМНЫМИ ПОКРЫВНЫМИ ПРОТЕЗАМИ С ОПОРОЙ НА ИМПЛАНТАТЫ ПРИ ПОЛЬЗОВАНИИ В ТЕЧЕНИЕ 12 МЕСЯЦЕВ

Subject. A comparative assessment of the state of the stomatognathic system on the example of the bioelectrical activity of temporal and masticatory muscles in patients who used removable implant-supported overdentures with bar fixation system, made by two different methods: traditional and using digital methods of treatment planning and manufacturing was carried out.&#x0D; Objectives. To compare the changes of bioelectrical activity of temporal and masticatory muscles in patients with removable implant-supported overdentures made by two different methods: traditional and digital, who used dentures for a long time (12 months).&#x0D; Methods. Bioelectrical activity and symmetry of temporal and masseter muscles were investigated clinically by surface electromyography. Electromyography was performed in five probes: Rest, Light CO, Natural Swallowing, Maximal Volitional Clench (MVC) and Clench on Cotton Rolls (MVCCR).&#x0D; Results. In patients using overdentures produced in traditional way, no normal values of muscle activity were observed in any of the probes at the end of the study. In patients who used overdentures, made with the use of digital technologies, we noted a decrease of bioactivity of the muscles in the probes of Rest and Light CO, and an increase of biopotentials in the probes of MVC and MVCCR. The values obtained at the end of the study were characterized as normal or acceptable.&#x0D; Conclusions. The application of a digital method of treatment planning and fabrication of removable implant-supported overdentures with a bar fixation system allows to achieve more physiological values of temporal and masticatory muscles biopotentials, which can be interpreted as recovery of the functional integrity of the stomatognathic system.

Surface Electromyography (sEMG) Activity of Masticatory Muscle (Masseter and Temporalis) with Three Different Types of Orthodontic Bracket.

Objective This pre-post study is aimed at determining the effects of masticatory muscle activity (masseter and temporalis) measured via sEMG between conventional, self-ligating, and ceramic bracket after six months of orthodontic treatment. Methods A total of eighteen (18) malocclusion patients were identified. Malocclusion patients were subdivided into 3 groups based on the bracket selection (conventional, self-ligating, and ceramic bracket) with 6 patients for each group. sEMG of muscles were done using a two-channel electromyography device, where pregelled and self-adhesive electrodes (bilateral) were applied. Chewing and clenching of masseter and temporalis muscle activity were recorded for 20 s pre and 6 months of orthodontic treatment using sEMG (frequency 60 Hz). The data were analysed by using repeated measures ANOVA in IBM SPSS Statistics Version 24.0. Results Chewing and clenching for masseter muscle showed no significant difference (P > 0.05) in sEMG activity of three types of the brackets. However, for temporalis muscle, there was a significant difference found in sEMG activity during chewing (P < 0.05) and clenching (P < 0.05) between these three brackets. Conclusion The activity of temporalis muscle showed significant changes in chewing and clenching, where the conventional group demonstrated better muscle activity pre and at six months of fixed appliances.

Evaluation and Diagnosis of Sleep Bruxism

Bruxism is the masticatory muscle activities involving grinding or clenching the teeth, which is divided into sleep and awake bruxism. Methods for evaluating sleep bruxism include clinical methods to investigate symptoms and signs and the use of supplementary tests such as intra-oral devices, electromyography, and polysomnography. Portable electromyography monitoring the masseter muscle activity is useful for clinical application.Polysomnography is the most accurate method for diagnosing sleep bruxism.

Masticatory performance is influenced by masticatory muscle activity balance and the cumulative occlusal contact area

ObjectiveTo investigate the influence of masticatory muscle activity balance, occlusal contact area balance and the area of occlusal contact on masticatory performance in healthy dentate adults. DesignThis cross-sectional study included ninety-three healthy subjects with complete dentition. Surface electromyography (sEMG) was used to record bilateral anterior temporalis activity and masseter muscle activity during maximum voluntary clenching and while chewing a test food. Seven levels of area of occlusal contact and near contact (ACNC) were registered and calculated cumulatively. The percentage overlapping coefficients were calculated for both muscle groups at maximum voluntary clenching and chewing and all levels of ACNC. Masticatory performance was measured by determining the median particle size of frankfurter sausage after 15 chewing cycles. Pearson’s correlation and stepwise multiple linear regression analyses were used to assess the correlations between variables and the influence of the variables on masticatory performance, respectively, at the 0.05 level of significance. ResultsMuscle balance during clenching and chewing, all near contact levels of cumulative ACNC and ACNC balance correlated negatively with median particle size (P < 0.05). The model based on stepwise multiple linear regression analysis showed muscle balance during clenching and cumulative ACNC at < 250 μm influenced median particle size. ConclusionMasticatory muscle activity balance during maximum voluntary clenching and the cumulative amount of near contact area were associated with masticatory performance, suggesting the amount of occlusal contact area—as well the balance of masticatory muscle activity—play a role in masticatory performance.

Electromyographic Patterns of Masticatory Muscles in Relation to Active Myofascial Trigger Points of the Upper Trapezius and Temporomandibular Disorders.

The presented study aimed to analyze and compare the electromyographic patterns of masticatory muscles in subjects with active myofascial trigger points (MTrPs) within upper trapezius, patients with temporomandibular disorders (TMDs) and healthy adults. Based on the diagnostic criteria of MTrPs according to Travell & Simons and the Research Diagnostic Criteria for Temporomandibular Disorders, 167 people were qualified for the study. Subjects were divided into 3 groups: with active MTrPs in the upper trapezius, with diagnosed temporomandibular disorders (TMDs) and healthy adults. Measurements of the bioelectric activity of the temporalis anterior (TA) and masseter muscle (MM) were carried out using the BioEMG III ™. Based on statistical analysis, significantly lower values of TA resting activity were observed among controls in comparison to MTrPs (1.49 μV vs. 2.81 μV, p = 0.00) and TMDs (1.49 μV vs. 2.97 μV, p = 0.01). The POC index values at rest differed significantly between MTrPs and TMDs (86.61% vs. 105%, p = 0.04). Controls presented different electromyographic patterns within AcI in comparison to both MTrPs (4.90 vs. −15.51, p = 0.00) and TMDs (4.90 vs. −16.49, p = 0.00). During clenching, the difference between MTrPs and TMDs was observed within MVC TA (91.82% vs. 116.98%, p = 0.02). TMDs showed differences within AcI in comparison to both MTrPs group (−42.52 vs. 20.42, p = 0.01) and controls (−42.52 vs. 3.07, p = 0.00). During maximum mouth opening, differences between MTrPs and TMDs were observed within the bioelectric activity of masseter muscle (16.45 μV vs. 10.73 μV, p = 0.01), AsI MM (0.67 vs. 11.12, p = 0.04) and AcI (13.04 vs. −3.89, p = 0.01). Both the presence of MTrPs in the upper trapezius and TMDs are related to changes in electromyographic patterns of masticatory muscles.

Head and neck posture influences masticatory muscle electromyographic amplitude in healthy subjects and patients with temporomandibular disorder: a preliminary study.

Despite the association of masticatory function with head posture and mandible movement, the impact of head posture on masseter muscle electrical activity remains unclear. This study aimed to investigate the electrical activity of the anterior temporal, masseter, superior trapezius, and sternocleidomastoid muscles in temporomandibular disorder (TMD) patients in three different head positions and compare the findings with those for healthy subjects. The study included 16 TMD patients and 17 healthy subjects. Surface electromyography (sEMG) was used to assess the bilateral anterior temporalis, masseter, superior trapezius, and sternocleidomastoid muscle activities. The maximal voluntary contraction (MVC) and root mean square (RMS) sequence of each muscle were measured in three head positions. Mixed analysis of variance was used to evaluate the effects of head posture on muscle electrical activity in each group. The group differences for the bilateral masseter muscles were significant in the relaxation position, neutral head position (NHP), and relaxation position with tooth contact (P<0.05). In both groups, the basal RMSs of the bilateral anterior temporalis muscle in the relaxation position with tooth contact was significantly higher than that in the NHP (P<0.05). In both groups, the basal RMSs of the bilateral masseter muscles in the relaxation position with tooth contact was higher than that in the relaxation position and NHP, with significant differences (P<0.05). During the management of TMD patients, physical therapists should focus on patient education regarding maintenance of a relaxed position and establish appropriate rehabilitation programs to reduce muscle activity.

Short-Term Effect of Orthodontic Treatment with Clear Aligners on Pain and sEMG Activity of Masticatory Muscles.

Background and objectives: The aim of this study is to evaluate mandibular elevator muscles activity and pain on palpation in the early stages of orthodontic treatment with clear aligners using surface electromyography (sEMG). Materials and methods: Surface electromyography (sEMG) activity and pain level on muscle palpation of masseter and anterior temporalis muscles were recorded in a sample of 16 adult subjects (aged 18–32 years; mean 22.5 +/− 3.5 SD) undergoing orthodontic treatment with clear aligners before the treatment (T0), after 1 month of treatment (two clear aligners) (T1), and after 3 months of treatment (T2) (six clear aligners). A chi-square test for nominal data, a Friedman test, and a Wilcoxon-signed rank test as post hoc analysis were applied. Results: No statistically significant differences in muscular pain were observed. At T1, the sEMG activity of masseter muscles at mandibular rest position showed a statistically significant reduction, but after 3 months (T2), the data appeared similar to T0 (p = 0.03 and p = 0.02). Conclusions: During the treatment with clear aligners, subjects could experience an initial reduction in the masseter basal activity after 1 month of treatment. This effect tends to decrease to baseline levels after 3 months of therapy.

Masseter muscle activity of conventional denture, fixed prosthesis, and milled bar overdenture used for All-on-4 implant rehabilitation: A within-subject study.

to examine the electromyographic (EMG) activity of the masseter muscles in patients with conventional dentures and compare it to EMG activity of fixed prosthesis, and milled bar overdentures used to rehabilitate mandibular atrophied ridges according to the All-on-4 concept. Eighteen edentulous subjects with atrophied mandibles received complete dentures (CD, control). After 3months, four implants were installed between the mental foramina according to the "All-on-4" protocol and loaded immediately. After osseointegration, fixed prostheses (FPD) or milled bar overdentures (MBO) were given to the patients in random order. Primary (amplitude), and secondary (chewing rate, time of the masticatory cycle, time of masticatory burst, and masticatory time) outcomes were evaluated 3months after using CD, FPD, and MBO. The evaluations were made during mastication of carrot (hard) and cake (soft) foods. FPD and MBO were associated with a significantly higher (amplitude, time of masticatory cycle, and time of masticatory burst), and significantly lower (chewing rate and masticatory time) compared with conventional dentures. Primary and secondary outcomes did not differ between FPD and MBO. Carrot had significantly higher amplitude, chewing rate, time of masticatory burst, and masticatory time than cake, while cake had a significantly higher time of masticatory cycle than carrot. Within limitations of this study, milled bar overdentures for All-on-4 implant rehabilitation of atrophied mandible is not less efficient than fixed prostheses in terms of electromyographic activity of the masseter muscle. Both prostheses significantly improve muscle activity, chewing rate, time of masticatory cycle, time of masticatory burst, and masticatory time compared with conventional dentures.

Parafunctional masseter muscle activity during waking is related to periodontitis progression: A pilot prospective cohort study.

The purpose of this pilot prospective cohort study was to investigate the effects of parafunctional masseter muscle activity on periodontitis progression among patients receiving supporting periodontal therapy (SPT). We collected data of patients treated at Okayama University Hospital from August 2014 to September 2018. The progression group was defined as patients with ≥2 teeth demonstrating a longitudinal loss of proximal attachment of ≥3mm during the 3-year study period and/or at least one tooth extraction due to periodontitis progression. Surface electromyography of masseter muscles at baseline was continuously recorded while patients were awake and asleep. We analysed 48 patients (36 females) aged 66.8±9.1years (mean±SD). The rate of parafunctional masseter muscle activity during waking hours and sleeping hours at baseline was 60.4% and 52.1%, respectively. Cox's proportional hazards regression model showed that the incidence of periodontitis progression was significantly associated with number of teeth present (p=0.001) and parafunctional masseter muscle activity during waking hours (p=0.041). Our results suggest that parafunctional masseter muscle activity during waking hours is a risk factor for periodontitis progression among patients receiving SPT.

Evaluating the Efficacy of the Occlusal Splint on the Muscle Activity with the Transducer in Patients with Temporomandibular Joint Dysfunction Syndrome.

A prospective study was designed to evaluate the effectiveness of occlusal splint therapy for the management of temporomandibular joint disorder. This study recorded the activity of anterior temporalis and masseter muscles in patients with TMD using a transducer before and after conservative management with splint therapy. The results suggested that VAS mean dropped from 21.2 to 11% for temporalis and from 12.6 to 7% for masseter. The study concludes that the occlusal splints has a prominent action on muscles of mastication and can be effectively used in early stages of TMD.

Comparative Evaluation of Masseter and Buccinator Muscle Activity using Electromyography in Denture Wearer and Nondenture Wearer by Fabricating Dentures with Neutral Zone Technique – An In vivo Study

Introduction: The objective of this study was to analyze buccinator and masseter muscle activity in previous denture wearer and nondenture wearer wherein dentures were constructed with neutral zone technique; however, complete dentures for patients with no history of previous dentures can be made with a neutral zone technique for improved stability. Methodology: A total of 50 patients were included in this study among which, Group A consisted of a total of 25 patients, who were old denture wearer and for whom a new denture was fabricated with the neutral zone technique. Group B consisted of 25 patients who were first-time denture wearer for whom a new denture was fabricated with a neutral zone technique. Results: The muscle activity does not significantly differ in previous denture and nondenture wearers. However, complete dentures for patient with no history of previous dentures can be made with a neutral zone technique for improved stability. Conclusions: Buccinator and masseter muscle activities significantly differ due to morphological changes that occurred in denture wearers and nondenture wearers.

Increase in masseter muscle activity by newly fabricated complete dentures improved brain function.

Purpose To reveal effects of improvement of masseter muscle activity on brain function in elderly people wearing complete dentures.Methods Subjects were 14 edentulous patients with a chief complaint of the inconvenience of their complete dentures. The surface electromyographic (EMG) activity of the masseter muscles was measured. Brain activities were analyzed with functional magnetic resonance imaging (fMRI), employing chewing gum as the task program. Cognitive functions were evaluated with Trail Making Test Part A (TMT-A), Rey Auditory Verbal Learning Test (RAVLT) and Rey-Osterrieth Complex Figure Test (R-OCFT). Those evaluations were performed in which subjects wore their old dentures (OD) or newly fabricated dentures (ND).Results We compared ND condition with OD condition. The masseter muscle activity significantly increased in ND condition (p < 0.05, Wilcoxon signed rank test). The brain activity increased significantly in the superior frontal gyrus, precentral gyrus, putamen, inferior parietal lobule, cerebellum, inferior frontal lobe, and middle frontal gyrus under the ND condition than under the OD condition (p < 0.01, uncorrected, cluster size > 10 voxels). Results of TMT-A, RAVLT, and R-OCFT were also significantly improved (p < 0.05, Wilcoxon signed rank test).Conclusions In the edentulous elderly, the brain activity was increased following the improvement of the masseter muscle activity. Consequently, it is possible that the improvement of the masseter muscle activity might influence on the attention, verbal skills, and visual memory.

The impacts of prosthetic interventions on mastication predominance in Kennedy Class Ⅱ patients.

Purpose The purpose of this study was to investigate the effects of prosthetic interventions in patients with Kennedy Class Ⅱ (unilateral missing posterior teeth) on mastication predominance.Methods The subjects comprised patients with Kennedy Class II and healthy dentate volunteers (HD group). The subjects were asked to freely chew the test foods (chewing gum, beef jerky, and peanuts). Electromyographic activity of the bilateral masseter muscles was recorded twice (before and after prosthetic intervention). The chewing side (right or left) was judged by the level of the root mean square electromyographic amplitude. Mastication predominance was assessed using the mastication predominance index (MPI; range 0-100%). Each patient was restored with a removable partial denture (RPD) or an implant-supported fixed prosthesis (IFP). The effects of prosthetic interventions were statistically evaluated by the differences between MPI before and after prosthetic interventions (pre-MPI and post-MPI , respectively).Results There was a significant difference between pre-MPI of patients with Kennedy Class II and MPI of the HD group (HD-MPI) for all test foods (P < 0.0001). Statistical analysis also demonstrated a significant difference between pre-MPI and post-MPI measured with each of the three food items in both the RPD and IFP groups (P < 0.0001). Multiple comparisons revealed that post-MPI in the IFP group, but not in the RPD group, was statistically comparable with HD-MPI, although there were no significant differences among the three groups when MPIs were calculated using peanuts.Conclusions Prosthetic interventions improved mastication predominance in patients with Kennedy Class Ⅱ patients. Depending on the food type, IFP might contribute to better improvement of mastication predominance than RPD depending on food.

Effect of two occlusal Patterns of Implant Retained Overdenture by Two Attachment Systems on the Electromyographic Activity

Purpose: To assess the effect of two attachment systems ball and socket and locator attachments and two occlusal patterns; bilateral balanced and monoplane occlusion on the electromyographic activity of temporalis and masseter muscles in mandibular implant retained overdenture. Material and Methods: Twelve male completely edentulous patients were selected from the outpatient clinic, Prosthodontic department, Faculty of Dental Medicine for Girls, Al-Azhar University. The patients were divided into two different groups: Group I received the Locator attachment and Group II received ball and socket attachment. All patients in both groups were divided equally into two subgroups: In subgroup 1: Patients received complete dentures with bilateral occlusal pattern and subgroup 2 the patients received complete denture with monoplane occlusion. Electromyographic activity for masseter and temporalis muscles were made after one month and three months for soft food and hard food. In subgroup 1 the dentures were replaced by the dentures with monoplane occlusion while in subgroup 2 the dentures were replaced by the denture with bilateral balanced occlusion. In group I and II attachments were switched and the same steps were followed for subgroups. The data were collected. Results: When using denture with bilateral balanced occlusion with locator attachment showed low electromyographic activity on the masseter and temporalis muscle than the denture with monoplane occlusion and there was no significant difference when using soft food during the first month while after 3 months there were significant difference. When using ball & socket attachments there were significant difference when using soft and hard food when using hard food there are significant difference between the subgroups. Conclusion: The two implant retained mandibular overdenture with the locator attachment showed relatively low electromyographic activity of the masticatory muscles (masseter and temporalis) than with ball and socket attachment and high electromyographic activity of the masticatory muscles (masseter and temporalis) with monoplane occlusion than with bilateral balanced occlusion.