Surface EMG of jaw-elevator muscles and chewing pattern in complete denture wearers

The effect of food supplements on completely edentulous women rehabilitated with complete dentures: A randomized controlled trial

Aim

Neglected oral health is a major issue, especially in women of developing countries, leading to early loss of teeth which may further lead to malnutrition, degradation of overall health, and increased chances of osteoporosis. Thus, the aim of this study was to assess the effect of food supplement on masticatory performance, nutritional status, electromyography (EMG) (masseter and temporalis), and bone mineral density (BMD) among women rehabilitated with complete denture.

Settings and Design

Hospital based randomized controlled trial.

Materials and Methods

A randomized controlled trial with 106 women of 45-65 years rehabilitated with complete denture (56 received food supplement and 50 did not receive food supplement) and 52 healthy control was conducted. The outcomes were assessed at baseline and 3 and 6 months of follow up (after complete denture fabrication). Outcomes were measured via masticatory performance, nutritional status (hemoglobin, serum calcium, albumin, and Vitamin D level), EMG of masseter and temporalis muscles, and BMD.

Statistical Analysis Used

Friedman's analysis of variance test was used as a nonparametric test, and the Statistical Package for the Social Sciences version 21.0 at a significance level of 0.05 was used for statistical analysis.

Results

A statistically significant change was observed during follow up for the group with food supplement for BMD, EMG, and masticatory performance. When biochemical parameters were assessed during follow up, no statistically significant change was observed for both groups (with and without food supplement), except for serum calcium level in group which received food supplement.

Conclusion

It was found that the magnitude of effect was remarkably meager in food supplement group which could be perhaps due to less time given for follow up period. Longer duration of trials would yield better results.

Wearable Orofacial Technology and Orthodontics

Wearable technology to augment traditional approaches are increasingly being added to the arsenals of treatment providers. Wearable technology generally refers to electronic systems, devices, or sensors that are usually worn on or are in close proximity to the human body. Wearables may be stand-alone or integrated into materials that are worn on the body. What sets medical wearables apart from other systems is their ability to collect, store, and relay information regarding an individual's current body status to other devices operating on compatible networks in naturalistic settings. The last decade has witnessed a steady increase in the use of wearables specific to the orofacial region. Applications range from supplementing diagnosis, tracking treatment progress, monitoring patient compliance, and better understanding the jaw's functional and parafunctional activities. Orofacial wearable devices may be unimodal or incorporate multiple sensing modalities. The objective data collected continuously, in real time, in naturalistic settings using these orofacial wearables provide opportunities to formulate accurate and personalized treatment strategies. In the not-too-distant future, it is anticipated that information about an individual's current oral health status may provide patient-centric personalized care to prevent, diagnose, and treat oral diseases, with wearables playing a key role. In this review, we examine the progress achieved, summarize applications of orthodontic relevance and examine the future potential of orofacial wearables.

Oral Health-Related Quality of Life Changes after Clinical Remounting of Existing Dentures

The clinical remount is an accurate and efficient way to reset the occlusion of delivered removable dentures if major occlusal correction is required. Although previous studies have reported that clinical remounting of existing dentures enhances patients’ oral function, little subjective feedback is available. This retrospective study reports short-term changes in oral-health-related quality of life (OHRQoL) and masticatory function after clinical remounting of existing dentures. Three time points were defined: before adjustment (T0), immediately after adjustment (T1), and 1 week after adjustment (T2). The medical records of seven patients were analyzed. The mean age of participants was 77.71 years, and the mean service period of their prostheses was 9.43 months. The mean scores of the OHIP-EDENT-J questionnaire at the respective time points were 35, 21.14, and 22.14. The mean readings of masticatory function at the respective time points were 76.71, 89.29, and 111.86. Significant differences in the OHIP-EDENT-J were found between T0 and T1, and T0 and T2; and in masticatory function between T1 and T2, and T0 and T2. The results indicated that after rebalancing of the occlusion of the existing dentures, the patient-reported OHRQoL was improved immediately and maintained at least for a short time, and masticatory function was enhanced over a 1-week period.

Effects of textured food masticatory performance in older people with different dental conditions

BACKGROUND

Physiological deterioration (aging, poor dental status, and reduced tongue pressure) makes chewing difficult. This study aimed to investigate the chewing patterns of older people with or without dentures, evaluate the textural and masticatory properties of texture-modified radish Kimchi, and investigate the correlation between dental status and tongue pressure. Additionally, differences in the subjective-objective concordance of texture-modified Kimchi were investigated using the preference test.

METHODS

This study included 32 Korean women aged between 65 and 85 years. Masticatory behavior was recorded by electromyography, and tongue pressure was measured using the Iowa Oral Performance Instrument. A preference test, with hardness as the relevant textural property, determined the participants' preferences among the test samples (food with a homogeneous structure-radish Kimchi). To assess preference differences, a questionnaire suitable for older people was designed. The preference for cooked radish Kimchi with various blanching times based on overall acceptability and self-reporting of preference was investigated to develop elderly-friendly food. The subjective scores indicated whether the sample (radish Kimchi) was hard or soft based on the chewing ability of the participants. Dental status, muscle activities, and tongue pressure were considered for the food design with optimized texture. The relationship between subject score and mastication properties were examined using multiple regression analysis.

RESULTS

The number of chews and chewing time increased with hardness, significantly activating the masseter and temporalis muscles. The evaluation of masseter muscle activity, particularly for level-6 radish Kimchi, showed that older people with complete dentures chewed less actively than those with natural teeth (p < 0.05). The older people with natural teeth (18.94 ± 10.27 kPa) exhibited higher tongue pressure than those with complete dentures (10.81 ± 62.93 kPa), and the difference was statistically significant (p < 0.01). Older people preferred food with familiar tastes and textures. An association was found between the subjective hardness score and the objective hardness level. The perceived hardness intensity was linked to the chewing ability of the participant. Denture wearers exhibited a lower chewing ability, and at level 6, they perceived greater hardness of food than those with natural teeth.

CONCLUSIONS

Developing food with a modified texture can bridge the gap between physiological and psychological aspects of food texture; texture-modified radish Kimchi, with limited blanching time, may be favorable for older people.

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 influ ence on the attention, verbal skills, and visual memory.

Comparing the Electromyographic Features of the Masseter and Temporal Muscles in Patients with full Mouth Implant-supported FDPs and Natural Dentition

BACKGROUND

Due to increasing demands for a full mouth implant reconstructions and the fact that the most failures are associated with biomechanical complications, determining the effect of different occlusal patterns on these complications seems inevitable. The aim of this study is to compare affection of different occlusal designs in full mouth implant reconstructed patients on electromyographic activity of temporal and masseter muscles compared to natural dentition.

METHODS

Thirty-two patients were included in this study, considering that 16 patients had natural dentition and the other 16 were full mouth implant reconstruction patients. In both groups, the participants were divided into two subgroups: 8 patients had canine guidance occlusal pattern and the other eight had a group function occlusal pattern. Muscle contractions were studied during both maximum intercuspation and lateral excursions to the point of intercanine contact using an electromyography device.

RESULTS

The average percentages of masseter muscle contraction in lateral excursions relative to maximum intercuspation were as follows: 72.20% in full mouth implant reconstruction patients with group function occlusion 69.49% in natural dentition with group function occlusion 58.85% in full mouth implant reconstruction patients with canine guidance occlusion 30.91% in natural dentition with canine guidance occlusion. The average percentages of temporal muscle contraction in lateral excursions relative to maximum intercuspation were as follows: 70.87% in full mouth implant reconstruction patients with group function occlusion 78.57% in natural dentition with group function occlusion 51.99% in full mouth implant reconstruction patients with canine guidance occlusion 31.55% in natural dentition with canine guidance occlusion.

CONCLUSION

A canine guidance occlusal pattern in both, natural dentition and full mouth implant-supported FDP, patients resulted in decreased muscle contraction. This decreasing is more significant in natural dentition and it is better to establish a canine guided occlusion in a full mouth reconstruction patient.

Portable auricular device for real-time swallow and chew detection

Monitoring a person’s nutritional consumption is costly and complex. To solve this problem a new technique is proposed to draw conclusions of a person’s food intake. The air pressure signal, recorded in the external acoustic meatus, is used to detect swallow and chew events. A portable device has been developed to record this pressure signal. Due to the constraint of running on a low-power microcontroller, real-time algorithms, used in pattern and speech recognition, were used to develop methods to automatically detect swallow and chew events. A binary classifier was trained by means of manually annotated data sets. Direct comparisons with state of the art technology and tests with several subjects are provided for evaluation purposes.

The Effect of Reading Aloud Exercises for Complete Denture Patients during the Functional Rehabilitation Period

PURPOSE

The focus of this study was to evaluate the effect of reading aloud on masticatory performance and patient satisfaction of patients rehabilitated with conventional complete dentures for the first time.

MATERIALS AND METHODS

Sixty-two edentulous patients who received conventional complete denture treatment for the first time were randomly divided into two equal groups. After insertion of the dentures, patients in group I were asked to read a news report three times per day for 4 weeks, while those in group II did not read. The reading duration increased by 5 minutes per week, from 5 minutes in the first week to 20 minutes in the fourth week. The patients' mouth opening during reading aloud was advised to gradually increase throughout the training project. Two and four weeks after insertion of the dentures, masticatory performance was assessed using the sieving method, and patient satisfaction was measured using a visual analogue scale, which combined the patient's perceptions in relation to comfort, esthetics, stability, ability to talk, and ability to chew.

RESULTS

There were significant improvements in masticatory performance with reading aloud exercises after the insertion of complete dentures (p < 0.001) at the 2- and 4-week follow-up visits. Masticatory performance also showed significant improvement within each group in the follow-up periods (p < 0.001). No significant differences were found between the two groups in patient satisfaction (p > 0.05) at 2 weeks, but at 4 weeks, patient satisfaction regarding stability, ability to talk, and ability to chew was significantly higher for group I (p < 0.001).

CONCLUSIONS

The results of this study suggest that reading aloud exercises significantly improved early masticatory performance and patient satisfaction for denture wearers who were treated with conventional complete dentures for the first time, and may be a useful clinical application for more effective denture treatment.

Motor behavior during the first chewing cycle in subjects with fixed tooth- or implant-supported prostheses

OBJECTIVES

Appropriate sensory information from periodontal mechanoreceptors (PMRs) is important for optimizing the positioning of food and adjustment of force vectors during precision biting. This study was designed to describe motor behavior during the first cycle of a natural chewing task and to evaluate the role of such sensory input in this behavior.

MATERIAL AND METHODS

While 10 subjects with natural dentition, 11 with bimaxillary fixed tooth-supported prostheses (TSP) and 10 with bimaxillary fixed implant-supported prostheses (ISP) (mean age 69 [range 61-83]) chewed a total of five hazelnuts, their vertical and lateral jaw movements were recorded. Data obtained during the first chewing cycle of each hazelnut were analyzed.

RESULTS

The amplitude of vertical and lateral mandibular movement and duration of jaw opening did not differ between the groups, indicating similar behavior during this part of the chewing cycle. However, only 30% of the subjects in the natural dentate group, but 82% of those in the TSP and 70% in the ISP group exhibited slippage of the hazelnut during jaw closure in at least one of five trials. The TSP and ISP groups also exhibited more irregular and narrower patterns of motion (total lateral/vertical movement = 0.15 and 0.19, respectively, compared to 0.27 for the natural group).

CONCLUSIONS

Subjects with fixed tooth- or implant-supported prostheses in both jaws show altered behavior, including inadequate control of the hazelnut, during the first chewing cycle. We propose that these differences are due to impairment or absence of sensory signaling from PMRs in these individuals.

The relationship between facial morphology and the structure of the alveolar part of the mandible in edentulous complete denture wearers. A preliminary study

OBJECTIVE

Although the effect of involutional processes that occurs in the maxilla and mandible of edentulous subjects is obvious, the problem of factors definitely determining the direction of changes still remains unsolved. This study was aimed at determining the relationship between facial morphology and the structure of the alveolar part and the body of the mandible in edentulous complete denture wearers.

MATERIALS AND METHODS

Twenty-five healthy edentulous Caucasian patients in the 70.5 ± 9 years of age group were examined. All patients underwent tele-X-ray examination with the presence of currently used dentures in the oral cavity. To assess morphological parameters of the facial skeleton, cephalograms were analyzed according to Ricketts and Mc Namara method. To assess the mandible morphology, the films were measured using the method of Tallgren.

RESULTS

The period of edentulism was found to be negatively correlated with the anterior segment of the body of the mandible within its symphysis. The parameter corresponding to the location of the first lower molar showed a directly proportional correlation with G'-Sn', G'-Me', Sn'-Me', N-Ans, N-Me, Ans-Me, Co-Gn and Co-Go. Positive correlations were found between the parameters describing contour of the alveolar part of the body of the mandible and mandibular symphysis and G'-Me', Sn'-Me', N-Me, Ans-Me describing the height of the occlusal vertical dimension.

CONCLUSION

The study showed a directly proportional correlation between the vertical occlusal dimension of the lower face conditioned by prosthetic rehabilitation and the height of the alveolar part in the lateral regions of the mandible.

Conventional Versus Implant-Retained Overlay Dentures: A Pilot Study of Masseter and Anterior Temporalis Electromyography

Implant-supported overlay dentures (ISODs) have been widely accepted among patients using conventional removable complete dentures (CRCDs). The present study aimed to comparatively study conventional and ISODs in terms of function and coordination of masticatory muscles using electromyograms. Included were 10 patients with ISODs (each with 2 implants in the intercanine area). The mean wave range (MWR) and frequency (MWF) of masseter and temporalis were recorded with (ISOD) and without (CRCD) ball attachments while maximum clenching on cotton rolls (cotton roll clenching), maximum intercuspal clenching (clenching), and unilateral gum chewing (chewing) using electromyography. Data were analyzed in SPAW using t-paired for matched groups and independent-sample t tests for unmatched ones. The MWF differences were not statistically significant with or without attachments (P &gt; .05). Without attachments in place, the MWF of both masseter and temporalis muscles significantly decreased when patients clenched on cotton rolls (P = .01 and .02, respectively) and when chewing unilaterally (both P = .01). With attachments present, the right and left temporalis muscles did not show identical mean wave ranges while chewing (P = .01). Without attachments, this disharmony was seen in the left and right masseter muscles (P = .03). The MWR of masseter was higher in men while chewing with attachments (P = .02). Without attachments, the MWR of temporalis was higher in women while cotton roll clenching (P = .03) and chewing (P = .02). These findings are seemingly in favor of improved masticatory function and coordination in edentulous patients with the application of ISODs.

3-Dimensional Physiologic Postural Range of the Mandible: A Computerized-Assisted Technique—A Case Study

Previous studies demonstrated that while the mandible assumes its resting position in space, antagonistic muscles should assume minimal muscle activity within a spatial range. This zone of mandibular rest has been mapped using physiologic parameters of muscle activity and incisal spatial kinematics. This case study expands on previous research by monitoring incisal and posterior jaw position and includes lateral pterygoid muscle activity, thus allowing for determining the spatial range including additional relevant coordinates and muscle activity. Four positions were evaluated: a maximum physiologic open position, a maximum physiologic closed position, physiologic rest position, and maximum physiologic protrusion position. Within the physiologic zone of rest formed by these 4 positions, the vertical and anterior borders of the envelope of function may be documented for the incisal and posterior mandible in true 3-dimensional fashion to assist the clinician in determining a physiologic interocclusal freeway space and vertical dimension of occlusion. Advantages and limitations are discussed.

The effect of osteoporosis on residual ridge resorption and masticatory performance in denture wearers

AIM

To compare masticatory performance, masticatory efficiency and residual ridge resorption (RRR) in osteoporotic and non-osteoporotic edentulous subjects after rehabilitation with complete dentures.

METHOD

Thirty subjects fulfilling the inclusion criteria were enrolled from the patients visiting the Department of Prosthodontics for complete denture fabrication. Two groups consisting of control subjects (group I; N = 15) and osteoporotic subjects (group II; N = 15) were formed. Complete dentures satisfying certain criteria were fabricated for both groups. Masticatory performance and efficiency were measured 6 months after denture insertion. Areal measurements were taken on lateral cephalograms before and 6 months after denture fabrication. The data were then computed to analyse differences between groups I and II using SPSS statistical software version 15.0.

RESULTS

Six months after denture fabrication, the masticatory performance and efficiency were significantly higher (p < 0.001) for group I, with a significant decrease in maxillary and mandibular sagittal area seen in both groups. The rate of bone loss was more in group II compared with group I.

CONCLUSION

Greater masticatory function was demonstrated by the non-osteoporotic group, and the rate of RRR was more in the osteoporotic group compared with the normal group. In this pilot study, osteoporosis leads to greater RRR, decreased masticatory performance and efficiency in edentulous subjects 6 months after denture insertion. Screening for osteoporosis is suggested as a routine procedure for all edentulous subjects undergoing rehabilitation. Recall check-ups for osteoporotic patients should be more frequent, and these patients may require more frequent denture remakes.

The influence of the occlusal vertical dimension on masticatory muscle activities and hyoid bone position in complete denture wearers

PURPOSE

Long lasting usage of complete dentures causes lower occlusal vertical dimension, producing potential detrimental consequences. The aim of this study was to investigate how changes in vertical dimension during denture exchange affect muscular activity and hyoid bone position.

MATERIAL AND METHODS

Twenty-five edentulous, otherwise healthy patients (14 females, 11 males) aged 70.5 +/- 9 years, wearing their dentures over 5 years but no longer than 15 years (mean 9.8 +/- 5.2), were studied. New dentures were fabricated and the occlusal vertical dimension was recorded on cephalometric radiographs. Cephalograms were analyzed according to Ricketts. The relation of the hyoid bone position to the mandible was estimated. An evaluation of muscular activity was performed using the Biopak Electromyography Recording System synchronized with the T-Scan II Occlusal Analysis System.

RESULTS

The occlusal vertical dimension was higher with the new dentures compared with the old dentures. The transition to new dentures was accompanied by a change of the vertical position of the hyoid bone. Digastric muscle activity was lower with the new dentures in comparison with the old dentures.

CONCLUSIONS

Increase of the occlusal vertical dimension in complete denture wearers affects the hyoid bone position and masticatory muscle activity.

Electromyographic evaluation of mastication and swallowing in elderly individuals with mandibular fixed implant-supported prostheses

This study evaluated the effect of implant-supported oral rehabilitation in the mandible on the electromyographic activity during mastication and swallowing in edentulous elderly individuals. Fifteen patients aged more than 60 years were evaluated, being 10 females and 5 males. All patients were edentulous, wore removable complete dentures on both dental arches, and had the mandibular dentures replaced by implant-supported prostheses. All patients were submitted to electromyographic evaluation of the masseter, superior orbicularis oris muscles, and the submental muscles, before surgery and 3, 6 and 18 months postoperatively, using foods of different textures. The results obtained at the different periods were analyzed statistically by Kruskal-Wallis non-parametric test. Statistical analysis showed that only the masseter muscle had a significant loss in electromyographic activity (p<0.001), with a tendency of similar response for the submental muscles. Moreover, there was an increase in the activity of the orbicularis oris muscle during rubber chewing after treatment, yet without statistically significant difference. Mandibular fixed implant-supported prostheses in elderly individuals revealed a decrease in electromyographic amplitude for the masseter muscles during swallowing, which may indicate adaptation to new conditions of stability provided by fixation of the complete denture in the mandibular arch.

Electromyographic activity of masticatory muscles in women with osteoporosis

The purpose of this study was to analyze the electromyographic (EMG) activity and the maximal molar bite force in women diagnosed with osteoporosis in the maxillary and mandibular regions, considering the habits and conditions that lead to development of generalized skeletal bone loss, including on face bones, can disturb the functional harmony of the stomatognathic system. Twenty-seven women with mandibular and maxillary osteoporosis and 27 healthy controls volunteered to participate in the study. A 5-channel electromyographer was used. Muscle activity was evaluated by means of EMG recordings of the masticatory musculature (masseter and temporalis muscles, bilaterally) during the following clinical conditions: rest (5 s); right and left lateral excursions (5 s); protrusion (5 s); maximal dental clenching on Parafilm™ (4 s) and maximal voluntary contraction (4 s). This latter clinical condition was used as the normalization factor of the sample data. It was observed that individuals with osteoporosis presented greater EMG activity when maintaining mandible posture conditions and less activity during dental clenching and when obtaining maximal molar bite force. It may be concluded that facial osteoporosis can interfere on the patterns of masticatory muscle activation and maximal bite force of the stomatognathic system.

Verificação e análise morfofuncional das características da mastigação em usuários de prótese dentária removível

OBJETIVO: verificar as características da mastigação em indivíduos usuários de prótese dentária removível parcial e total, analisando prováveis fatores interferentes associados à função mastigatória. MÉTODOS: participaram 53 indivíduos, ambos os sexos, entre 42 anos e 67 anos, divididos em dois grupos: 32 indivíduos usuários de prótese dentária total e/ou parcial removível estável (G1) e 21 indivíduos com dentição natural (G2). Foram critérios de exclusão: deficiência neurológica ou cognitiva, deformidades dentofaciais, disfunção temporomandibular e qualquer lesão bucal que pudesse interferir na mastigação. A avaliação foi realizada com pão de sal, solicitando-se mastigação habitual. Foram analisados: características das estruturas e da musculatura, tipo de corte, manutenção de vedamento labial, tempo de mastigação, número de ciclos mastigatórios, e tipo de mastigação: se uni ou bilateral, considerando-se predomínio unilateral em mais de 66% dos ciclos mastigatórios em um único lado. RESULTADOS: foram verificadas alterações quanto à característica do músculo masseter e ao tipo de corte para G1 com diferenças estatisticamente significantes, quando comparado à G2. As demais estruturas orofaciais, lábios, língua, bochechas, mentual, e postura de lábios durante a mastigação apresentaram-se normais para ambos os grupos. Não houve diferença significante entre os grupos quanto aos movimentos mandibulares, ao tipo, tempo e número de ciclos mastigatórios e caracterização da deglutição. CONCLUSÃO: a mastigação em usuários de prótese dentária removível caracteriza-se por alterações no corte do alimento, indefinição de tipo mastigatório, vedamento labial satisfatório, média do tempo e de ciclos mastigatórios semelhantes àqueles obtidos para indivíduos com dentição natural.

Effect of bolus hardness on the chewing pattern and activation of masticatory muscles in subjects with normal dental occlusion

The aim of the study was to evaluate the effect of bolus hardness on the kinematic of mastication and jaw-elevator muscle activity in subjects with normal dental occlusion and function. The mandibular motion and the surface EMG envelope of the masseter and temporalis anterior muscles were assessed in twelve subjects during mastication of a soft and hard bolus of the same size. When chewing the hard bolus, the chewing pattern in the frontal plane was significantly higher and wider, with smaller closure angle and higher peak velocity than when chewing the soft bolus. EMG peak amplitude of both the masseter and anterior temporalis muscles was higher for the side of the bolus but the contralateral side increased its activity significantly more than the ipsilateral side when the hardness of the bolus increased (for the masseter, mean+/-SD: 130.4+/-108.1% increase for the contralateral side and 29.6+/-26.9% for the ipsilateral side). Moreover, the peak EMG activity for both muscles occurred more distant from the closure point with hard bolus. The increased activity of the contralateral side may help maintaining the mandibular equilibrium, with indirect participation to the power stroke generated by the chewing-side masseter. The results provide kinematic and EMG adaptations to bolus hardness in healthy subjects and can be used as normative data in the development of methods for early diagnosis of impaired chewing function.

Electromyographic activity of the mandible muscles at the beginning and end of masticatory cycles in patients with complete dentures

The aim of this study was to assess the electrical activity of the masseter and anterior temporal muscles in subjects with severe bone resorption at two different times: (a) the initial period, with the complete dentures they had worn for over 10 years, and (b) the final period, 5 months after having new dentures put into place. Twelve asymptomatic subjects were asked to respond to the questionnaire, according to the research diagnostic criteria for temporomandibular disorders, before denture rehabilitation and 5 months after the new dentures were put in place. The electrical activity of the muscles was recorded during mastication in the initial and final period, using artificial food (Optocal). The operator monitored the 35 chewing cycles that were repeated to grind the artificial food. After wearing the new dentures for 5 months, the right anterior temporal muscle showed a statistical difference before and after denture rehabilitation at the beginning and end of mastication. Muscular capacity and ability reduced the electrical activity in the masseter muscles after rehabilitation.

Bite force in temporomandibular dysfunction (TMD) and healthy complete denture wearers

The signs and symptoms of temporomandibular dysfunction (TMD) may contribute to reduce bite force and muscular activity. The aims of this study were to compare bite force in complete denture wearers with TMD (TMD group) and without TMD (healthy group).The TMD group consisted of 9 individuals, who had worn a maxillary and a mandibular complete removable denture for more than 10 years. The healthy group consisted of 9 participants who wore dentures and had satisfactory interocclusal and maxillomandibular relationship. Helkimo Index was used to analyze the dysfunction level. Maximum bite force was measured using a digital dynamometer with capacity of 100 kgf and adapted to oral conditions.The TMD group presented smaller mean bite force values than the healthy group, though without statistical significance (p>0.05). This outcome suggests that the TMD signs and symptoms and the structural conditions of the dentures did not affect the maximal bite force of complete denture wearers.

Mastication of model products in complete denture wearers

OBJECTIVE

The aim of this study was to define the characteristics of muscular activity in complete denture wearers and in dentate subjects during mastication of model foods differing in hardness but similar in terms of rheologically properties.

MATERIAL AND METHODS

The foodstuffs used in this study were laboratory-developed gumdrops demonstrating viscoelastic properties. The test foods cover a range of four hardness levels. The group of complete denture wearers included 15 subjects, while the control group included 9 subjects with normal dentition. Electromyograph (EMG) recordings were taken from the masseter and temporal muscles during mastication of the test foods. The results were evaluated by one-way and two-way ANOVA followed by means comparisons using a Student-Newman-Keuls post hoc test (alpha=0.05).

RESULTS

Preparing the same food bolus for swallowing required a greater number of masticatory cycles and a longer duration of mastication for complete denture wearers than for dentate subjects. In addition, complete denture wearers failed to increase EMG activity per cycle in response to hardness of the food.

CONCLUSION

Denture wearers experienced difficulties during mastication, as indicated by a decreased masticatory rate and the observed failure to increase EMG activity per cycle in response to increased food hardness. The increases in number of cycle and masticatory duration appear to be a response to this impaired masticatory function.