Developing a protocol for a preventive oral health exam for elderly people (EDePAM) using E-Delphi methodology.

The aim of this study was to develop a Preventive Oral Health Exam for Elderly People (EDePAM), using the e-Delphi technique, to diagnose oral health problems in people 65 or older. The e-Delphi technique was used with experts in multiple stages, and in a final workshop, where an agreement on an examination protocol was reached for diagnosing dental caries, oral mucosa lesions, periodontal diseases, and masticatory function disorders. Quantitative analyses of all the rounds of the e-Delphi method were conducted. It was agreed that the International Caries Detection and Assessment System (ICDAS) should be used together with a modified version of the Nyvad criteria to detect and assess caries lesions. It was also agreed that an assessment was needed of the different factors involved in determining caries risk, namely socioeconomic level, access to fluoride, level of dependence/functionality, salivary flow, history of head and neck cancer treatment, use of medications that decrease salivary flow, diet, use of removable dental prostheses, exposure of root surfaces, and caries history. Furthermore, patients would be required to undergo an examination of the oral mucosa, where any existing lesion should be described in terms of its clinical appearance, location, and risk potential. It was also agreed that an assessment of masticatory function should be performed using the Leake index, together with chewing-gum combined with a color scale to categorize masticatory performance. The number of pairs of occluding antagonist teeth was considered as the best predictor of masticatory function. The 2018 classification by the American Academy of Periodontology (AAP) / European Federation of Periodontology (EFP) was accepted as the standard to assess periodontal status, and it was agreed that this assessment should include an evaluation of clinical attachment loss and bleeding on probing. The novel EDePAM was considered as appropriate for conducting a functional assessment of oral health by providing a comprehensive diagnosis of oral diseases.

Effect of laterotrusive occlusal scheme on chewing duration, external intercostal muscular activity, heart rate, and oxygen saturation.

Objective: To evaluate the effect of the laterotrusive occlusal scheme on chewing duration, external intercostal (EIC) electromyographic (EMG) activity, heart rate (HR), and oxygen saturation (OS) during different tasks in the upright seated position.Methods: Fifty young participants, 25 with canine guidance and 25 with group function, were included. Chewing duration, bilateral EIC EMG activity, HR, and OS were recorded during the following tasks: 1) chewing until swallowing threshold; 2) laterotrusive teeth grinding.Results: Chewing duration, bilateral EIC EMG activity, HR, and OS showed no significant differences between the two laterotrusive occlusal schemes during the tasks studied.Conclusion: These results suggest that chewing duration, EIC muscle activity, HR, and OS were not significantly influenced by the laterotrusive occlusal scheme. Therefore, when a modification of the laterotrusive occlusal scheme is needed during oral rehabilitation or orthodontic treatment, canine guidance or group function should not significantly change EMG activity of EIC muscles.

Do subjects with forced lip closure have different perioral and jaw muscles activity?

Objective: To evaluate the activity of mentalis (MN), buccinator (BC), and suprahyoid (SH) muscles among participants with different lip competence..Methods: Sixty-three participants were classified clinically and assigned to the following groups of 21 each: 1) competent lips (competent), 2) incompetent lips (incompetent), or 3) forced lip closure (forced). Activity was recorded at rest, swallowing, speaking, reciprocal compression of the lips, and chewing.Results: MN activity in incompetent was significantly higher than competent at rest, and it was significantly higher in incompetent and forced when compared with competent during swallowing (p< .05). No differences among incompetent and forced were observed (p> .05). During speaking, reciprocal compression of the lips, and chewing, MN activity did not show significant differences among groups. BC and SH activity did not show significant differences (p> .05).Conclusion: MN activity during swallowing can be considered a relevant biomarker to differentiate between forced and competent participants.

Developing a protocol for a preventive oral health exam for elderly people (EDePAM) using E-Delphi methodology

Abstract The aim of this study was to develop a Preventive Oral Health Exam for Elderly People (EDePAM), using the e-Delphi technique, to diagnose oral health problems in people 65 or older. The e-Delphi technique was used with experts in multiple stages, and in a final workshop, where an agreement on an examination protocol was reached for diagnosing dental caries, oral mucosa lesions, periodontal diseases, and masticatory function disorders. Quantitative analyses of all the rounds of the e-Delphi method were conducted. It was agreed that the International Caries Detection and Assessment System (ICDAS) should be used together with a modified version of the Nyvad criteria to detect and assess caries lesions. It was also agreed that an assessment was needed of the different factors involved in determining caries risk, namely socioeconomic level, access to fluoride, level of dependence/functionality, salivary flow, history of head and neck cancer treatment, use of medications that decrease salivary flow, diet, use of removable dental prostheses, exposure of root surfaces, and caries history. Furthermore, patients would be required to undergo an examination of the oral mucosa, where any existing lesion should be described in terms of its clinical appearance, location, and risk potential. It was also agreed that an assessment of masticatory function should be performed using the Leake index, together with chewing-gum combined with a color scale to categorize masticatory performance. The number of pairs of occluding antagonist teeth was considered as the best predictor of masticatory function. The 2018 classification by the American Academy of Periodontology (AAP) / European Federation of Periodontology (EFP) was accepted as the standard to assess periodontal status, and it was agreed that this assessment should include an evaluation of clinical attachment loss and bleeding on probing. The novel EDePAM was considered as appropriate for conducting a functional assessment of oral health by providing a comprehensive diagnosis of oral diseases.

Overexpression of MMPs, cytokines, and RANKL/OPG in temporomandibular joint osteoarthritis and their association with joint pain, mouth opening, and bone degeneration: A preliminary report.

OBJECTIVE: This study aimed to determine the expression of distinct matrix metalloproteinases, cytokines, and bone resorptive factors in temporomandibular joint osteoarthritis (TMJ-OA) patients and their association with joint pain, mouth opening, and subchondral bone degeneration. MATERIALS AND METHODS: Twelve patients affected with TMJ-OA (n = 5), disk displacement without reduction (DDWoR) (n = 3), or disk displacement with reduction (DDWR) (n = 4) were selected. Joint pain was quantified by using visual analog scale, mouth opening was quantified at the maximum pain-free aperture, and bone degeneration was quantified using joint imaging. Synovial fluid samples were collected and immediately processed for cell and synovial fluid recovering. From cells, the MMP-1, MMP-2, MMP-8, MMP-13, IL-6, IL-23, and TNF-α expression was quantified by qPCR. From synovial fluid, the RANKL and OPG levels were quantified by ELISA. RESULTS: Higher levels of MMP-1, MMP-8, MMP-13, IL-6, IL-23, TNF-α, and RANKL/OPG ratio were detected in TMJ-OA compared with DDWoR and DDWR patients (p < .05). Joint pain significantly correlated with TNF-α levels (r = .975, p = .029). Besides, imaging signs of bone degeneration significantly correlated with RANKL/OPG ratio (r = .949, p = .042). Conversely, mouth opening did not correlate with any of the analyzed mediators. CONCLUSION: During TMJ-OA, a pathological response characterized by the overexpression of TNF-α and RANKL/OPG could be involved in joint pain and subchondral bone degeneration.

Mandibular border movements: The two envelopes of motion.

BACKGROUND: The envelope of motion is a diagrammatic representation of the mandibular border movements. Classically, those movements are carried out eccentrically; starting from the position of maximal intercuspation, the mandible describes an excursion movement until reaching maximal mouth opening. Reverse movements would describe a different path, but up to now concentric development of mandibular border movements has not been considered. Literature states that beyond mandibular border movements limits, no movement is possible. Therefore, it is of great interest to compare both paths-both envelopes of motion-and define the actual limits of mandibular movement. OBJECTIVE: The aim of this study was to compare the geometric characteristics of mandibular border movements carried out eccentrically and concentrically by healthy subjects. METHODS: Sixteen individuals aged between 18 and 27 years, molar class I and with no temporomandibular disorders, participated in the study. Eccentric and concentric mandibular movements were recorded using a 3D electromagnetic articulograph. Data were processed with computational scripts developed in MATLAB. Maximum mouth opening, trajectories, displacement ranges, polygon areas and chewing cycle area/ mandibular border movements area ratio were analysed. RESULTS: The frontal plane showed significant differences in all the parameters evaluated. Higher values were registered in the concentric area of the border movement envelope (P = .008) and in the trajectories on both sides. Statistical differences were observed in polygon areas (P = .006) in the sagittal plane and right ranges (P = .046) in the horizontal plane. CONCLUSION: Concentric mandibular movements revealed significant differences in three-dimensional trajectories in the frontal plane.

Awake teeth grinding in participants with canine guidance or group function: Effect on diaphragm EMG activity, heart rate, and oxygen saturation.

Objective: To compare the effect of canine guidance or group function on diaphragm activity, heart rate, and oxygen saturation during awake teeth grinding at different body positions. Methods: Fifty healthy participants, 25 with canine guidance and 25 with group function, were included. Bilateral electromyographic (EMG) recordings of the diaphragm (DIA) during awake teeth grinding were performed in standing, seated upright, and right lateral decubitus positions. Simultaneously, heart rate and oxygen saturation were measured. Results: EMG activity of the DIA muscle was similar in the working side and non-working side between participants with canine guidance and group function in the different body positions studied. The heart rate and oxygen saturation showed no significant differences between the two groups. Conclusion: EMG activity of the DIA muscle, the heart rate, and oxygen saturation during teeth grinding are not significantly influenced by the type of laterotrusive occlusal scheme.

Effect of breathing type on electromyographic activity of respiratory muscles during tooth clenching at different decubitus positions.

OBJECTIVE: To compare the effect of breathing type on electromyographic (EMG) activity of respiratory muscles during tooth clenching at different decubitus positions. METHODS: Forty young men participants were included, 11 with upper costal, 9 with mixed, and 20 with costo-diaphragmatic breathing type. EMG recordings of diaphragm (DIA), external intercostal (EIC), sternocleidomastoid (SCM), and latissimus dorsi (LAT) muscles during tooth clenching in the intercuspal position were performed in dorsal, left lateral, and ventral decubitus positions. RESULTS: DIA EMG activity was higher in subjects with upper costal or mixed than with costodiaphragmatic breathing type (p = 0.006; 0.021, respectively), whereas it was similar between upper costal and mixed breathing types. EIC, SCM, and LAT activity was similar among breathing types. CONCLUSION: Higher DIA activity would be a risk factor to exceed the adaptive capability of healthy subjects with upper costal or mixed breathing type.

Assessment of electromyographic activity in patients with temporomandibular disorders and natural mediotrusive occlusal contact during chewing and tooth grinding.

OBJECTIVES: The aim of this study was to investigate whether the presence of a natural mediotrusive contact influences electromyographic (EMG) pattern activity in patients with temporomandibular disorders (TMDs). METHOD: Bilateral surface EMG activity of the anterior temporalis (AT), masseter (MM), and sternocleidomastoid (SCM) muscles was recorded in 43 subjects during unilateral chewing and tooth grinding. Thirteen patients had TMD and a natural mediotrusive contact (Group 1), 15 had TMD without a natural mediotrusive contact (Group 2), and 15 were healthy subjects without mediotrusive contacts (Group 3). All subjects were examined according to the Research Diagnostic Criteria for TMD (RDC/TMD). All EMG values were standardized as the percentage of EMG activity recorded during maximum isometric contraction on cotton rolls. RESULTS: EMG activity from all muscles measured showed no significant differences between groups during chewing and grinding. Overall, in all groups, the EMG activity during chewing was higher in the working side than the non-working side in AT and MM muscles. During grinding, these differences were only found in masseter muscles (mainly in eccentric grinding). SCM EMG activity did not show significant differences during chewing and grinding tasks. Symmetry, muscular balance, and absence of lateral jaw displacement were common findings in all groups. DISCUSSION: EMG results suggest that the contribution of a natural mediotrusive occlusal contact to EMG patterns in TMD patients is minor. Therefore, the elimination of this occlusal feature for therapeutic purposes could be not indicated.

Natural mediotrusive contact: does it affect the masticatory and neck EMG activity during tooth grinding?

OBJECTIVES: There is scarce knowledge regarding the influence of a natural mediotrusive contact on mandibular and cervical muscular activity. The purpose of this study was to analyze the EMG activity of the anterior temporalis (AT) and sternocleidomastoid (SCM) muscles during awake grinding in healthy subjects with or without a natural mediotrusive occlusal contact. METHOD: Fifteen subjects with natural mediotrusive occlusal contact (Group 1) and 15 subjects without natural mediotrusive occlusal contact (Group 2) participated. Bilateral surface EMG activity of AT and SCM muscles was recorded during unilateral eccentric or concentric tooth grinding tasks. EMG activity was normalized against the activity recorded during maximal voluntary clenching in intercuspal position (IP) for AT muscles and during maximal intentional isometric head-neck rotation to each side, for SCM muscles. RESULTS: EMG activity of AT and SCM muscles showed no statistical difference between groups. EMG activity of AT muscle was higher in the working side (WS) than in the non-WS (NWS) in Group 1 during concentric grinding (0.492 vs 0.331, p = 0.047), whereas no difference was observed in Group 2. EMG activity of SCM was similar between working and NWSs in both groups and tasks. Asymmetry indexes (AIs) were not significantly different between groups. DISCUSSION: These findings in healthy subjects support the assumption that during awake tooth grinding, central nerve control predominates over peripheral inputs, and reinforce the idea of a functional link between the motor-neuron pools that control jaw and neck muscles.

Effect of natural mediotrusive contact on electromyographic activity of jaw and cervical muscles during chewing.

OBJECTIVE: This study evaluated the effect of a natural mediotrusive contact on the electromyographic (EMG) activity of the anterior temporalis and sternocleidomastoid muscles during chewing in healthy subjects. MATERIALS AND METHODS: The study sample included two groups of 15 subjects each (Group 1: with natural mediotrusive contact; Group 2: without natural mediotrusive contact). Bilateral surface EMG activity was recorded on anterior temporalis and sternocleidomastoid muscles during unilateral chewing of a half cookie and unilateral chewing of a piece of apple. Anterior temporalis and sternocleidomastoid muscle activity was normalized against activity recorded during maximal voluntary clenching in intercuspal position and maximal intentional isometric head-neck rotation to each side, respectively. The partial and total asymmetry indexes were also calculated. Data were analyzed using Mann-Whitney, Wilcoxon and unpaired t-test. RESULTS: EMG activity of anterior temporalis and sternocleidomastoid muscles showed no significant difference between the groups. EMG activity of anterior temporalis was similar between working and non-working sides during chewing in both groups. EMG activity of sternocleidomastoid muscle was higher in the working side than in the non-working side in Group 2 subjects. Asymmetry indexes were not significantly different between groups. CONCLUSIONS: The similar EMG pattern and asymmetry indexes observed suggest the predominance of central nervous control over peripheral inputs on anterior temporalis and sternocleidomastoid motor neuron pools.

Electromyographic activity during awake tooth grinding tasks at different jaw posture in the sagittal plane.

OBJECTIVE: The goal of this study was to evaluate the electromyographic (EMG) activity of the anterior temporalis, suprahyoid, infrahyoid and trapezius muscles during tooth grinding at different jaw posture tasks. MATERIALS AND METHODS: Participants were 30 healthy subjects with natural dentition, bilateral molar support and incisive protrusive guidance. Bipolar surface electrodes were located on the right side of the subject. EMG recordings were performed in the following tasks: (A) Eccentric grinding from intercuspal position to protrusive edge-to-edge contact position; (B) concentric grinding from protrusive edge-to-edge contact position to intercuspal position; (C) eccentric grinding from intercuspal position to the maximum voluntary retrusive position; and (D) concentric grinding from the maximum voluntary retrusive position to intercuspal position. The results were analyzed statistically by Friedman test and Wilcoxon signed rank-sum test. RESULTS: EMG activity in the anterior temporalis and infrahyoid muscles was significantly higher during task C than the other tasks. EMG activity in the suprahyoid muscles was significantly higher during task C than task D. EMG activity in the trapezius muscle was significantly higher during task C than tasks A and B. CONCLUSIONS: The higher EMG activity recorded in task C could become important when its frequency, duration and magnitude are enough to exceed the adaptation capability of the individual.

Anterior temporalis and suprahyoid EMG activity during jaw clenching and tooth grinding.

The aim of this study was to evaluate the anterior temporalis and suprahyoid electromyographic (EMG) activity during jaw clenching and tooth grinding at different jaw posture tasks. The study included 30 healthy subjects with natural dentition and bilateral molar support, incisive protrusive guidance and bilateral laterotrusive canine guidance. Bipolar surface electrodes were located on the right anterior temporalis and suprahyoid muscles. Three EMG recordings in the standing position were performed in the following tasks: C. clenching in the intercuspal position (IP); P1. eccentric grinding from IP to protrusive edge-to-edge contact position; P2. clenching in protrusive edge-to-edge contact position; P3. concentric grinding from protrusive edge-to-edge contact position to IP; L1. eccentric grinding from IP to laterotrusive edge-to-edge contact position; L2. clenching in laterotrusive edge-to-edge contact position; L3. concentric grinding from laterotrusive edge-to-edge contact position to IP. EMG activity during protrusive and laterotrusive tasks was lower than intercuspal position in the anterior temporalis, whereas an opposite EMG pattern was observed in the suprahyoid muscles activity, excepting recorded activity in L2 (mixed model with unstructured covariance matrix). Anterior temporalis activity was higher during P3 than P1 and P2 tasks and during L3 than L1 and L2 tasks, whereas in the suprahyoid muscles, activity was higher during P1 than P2 tasks and during L1 than L2 and L3 tasks. These results could support the idea of a differential modulation of the motor neuron pools of anterior temporalis and suprahyoid muscles of peripheral and/or central origin.

[Olfactory sensory perception]. / Sensopercepción olfatoria: una revisión.

The five senses have had a fundamental importance for survival and socialization of human beings. From an evolutionary point of view the sense of smell is the oldest. This sense has a strong representation within the genome, allowing the existence of many types of receptors that allow us to capture multiple volatile odor producing molecules, sending electrical signals to higher centers to report the outside world. Several cortical areas are activated in the brain, which are interconnected to form an extensive and complex neural network, linking for example, areas involved with memory and emotions, thus giving this sense of perceptual richness. While the concept of flavor is largely related to the sense of taste, smell provides the necessary integration with the rest of the senses and higher functions. Fully understanding the sense of smell is relevant to health professionals. Knowing the characteristics of the receptors, the transduction processes and convergence of information in the higher centers involved, we can properly detect olfactory disorders in our patients.

Influence of jaw clenching and tooth grinding on bilateral sternocleidomastoid EMG activity.

This study compares the effect of tooth clenching and grinding on sternocleidomastoid electromyographic (EMG) activity during different laterotrusive jaw posture tasks. The study included 28 healthy subjects with natural dentition and bilateral molar support, 14 with bilateral canine guidance and 14 with bilateral group function. Bipolar surface electrodes were located on the left and right sternocleidomastoid muscles. EMG activity was recorded during the following tasks: (A) eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; (B) clenching in right edge-to-edge lateral contact position; (C) concentric grinding from right lateral edge-to-edge contact position to intercuspal position. On the working side, activity in the task C was significantly higher than in tasks A and B in subjects with canine guidance, whereas no significant differences were observed between tasks in subjects with group function. On the nonworking side, activity was significantly lower during task A than in tasks B and C, in both occlusal schemes (mixed model with unstructured covariance matrix). When comparing by side, EMG activity was significantly lower during task B on the working side than on the nonworking side. However, there were no significant differences during tasks A and C. The EMG activity was significantly lower with canine guidance than group function on the working side during tasks A, B, and C, and on the nonworking side during tasks B and C. These results could explain muscular symptoms in the sternocleidomastoid muscles if the subject is experiencing parafunctional habits while awake and/or during sleep that exceed the individual's adaptation capability.

Sensopercepción olfatoria: una revisión / Olfactory sensory perception

The five senses have had a fundamental importance for survival and socialization of human beings. From an evolutionary point of view the sense of smell is the oldest. This sense has a strong representation within the genome, allowing the existence of many types of receptors that allow us to capture multiple volatile odor producing molecules, sending electrical signals to higher centers to report the outside world. Several cortical areas are activated in the brain, which are interconnected to form an extensive and complex neural network, linking for example, areas involved with memory and emotions, thus giving this sense of perceptual richness. While the concept of fl avor is largely related to the sense of taste, smell provides the necessary integration with the rest of the senses and higher functions. Fully understanding the sense of smell is relevant to health professionals. Knowing the characteristics of the receptors, the transduction processes and convergence of information in the higher centers involved, we can properly detect olfactory disorders in our patients.

Sensopercepción gustativa: una revisión / Gustatory sensory perception: a review

Los órganos de los sentidos confieren a los seres humanos la capacidad de percibir y responder a una gran gama de estímulos que provienen del entorno, lo cual nos brinda la facultad de elaborar respuestas con el fin de adaptarnos a los cambios medioambientales, cubrir nuestras necesidades básicas y sobrevivir. Para nutrirnos, el sentido del gusto posee un rol primordial que nos permite seleccionar dentro de una amplia variedad de alimentos, las sustancias que son necesarias para nuestro metabolismo, protegiéndonos a su vez de compuestos potencialmente nocivos, debido a su toxicidad o grado de descomposición. Este sentido también es capaz de brindarnos la capacidad de seleccionar y discriminar alimentos que nos permitan sentir agrado y placer. Para los dentistas es fundamental comprender adecuadamente los complejos procesos del sentido del Gusto, identificar las estructuras involucradas tanto a nivel periférico (papilas, receptores y vías nerviosas) como a nivel central (núcleos y cortezas cerebrales); además de conocer las modalidades básicas del gusto y sus respectivos mecanismos de transducción. Este conocimiento aportará los elementos necesarios para enfrentar de manera correcta una situación en la cual un paciente presente una alteración gustativa, siendo capaz de identificar las posibles causas y adoptar medidas adecuadas para resolverla y/o tolerarla en el caso de ser provocada en forma transitoria por un procedimiento que forme parte o no de nuestro tratamiento.

The sense organs give to humans the ability to perceive and respond to a wide range of stimuli from the environment. This allows us the power to shape responses in order to adapt to environmental changes, control our basic needs and survive. The sense of taste has a key role in nurture. Enable us to select from a wide variety of foods, elements that are necessary for metabolism and also protecting from potentially harmful compounds, as of its toxicity or degree of decomposition. This sense of taste is also capable of giving us the ability to select and discriminate food that allow us to feel enjoy and pleasure. For dentists is critical to understand adequately the complex processes of taste, identify the structures involved peripheral (papillae, nerve pathways and receptors) and central (nuclei and cerebral cortices), besides knowing the basic modalities of taste and their respective transduction mechanisms. This knowledge will provide the basis to address properly a situation in which a patient has an altered taste, being able to identify possible causes and take appropriate action to resolve it and / or tolerate if temporary caused by a procedure that may be part of our dental treatment.

The effect of tooth clenching and grinding on anterior temporalis electromyographic activity in healthy subjects.

The aim of this study was to determine the effect of tooth clenching and grinding on anterior temporalis electromyographic (EMG) activity. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance and 15 with bilateral group function. An inclusion criterion was that subjects have to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right anterior temporalis muscles. EMG activity was recorded during the following conditions: A. eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; B. clenching in right edge-to-edge lateral contact position; and C. concentric grinding from right lateral edge-to-edge contact position to intercuspal position. On the working side, EMG activity was not significantly different between conditions in both occlusal schemes. On the nonworking side, EMG activity was significantly higher during condition C than condition B in both occlusal schemes (mixed model with unstructured covariance matrix). When comparing by side, EMG activity was significantly higher during conditions A and B on the working side than on the nonworking side. However, there was no significant difference during condition C. EMG activity was significantly lower with canine guidance than group function on the working side (in all conditions) as well as during concentric grinding on the nonworking side. These results could explain muscular symptoms in the anterior temporalis muscles if the subject is experiencing parafunctional habits either while awake and/or sleep that exceed the individual's adaptation capability.

Clenching and grinding: effect on masseter and sternocleidomastoid electromyographic activity in healthy subjects.

This study compares the effect of clenching and grinding on masseter and sternocleidomastoid electromyographic (EMG) activity during different jaw posture tasks in the sagittal plane. The study included 34 healthy subjects with natural dentition, Class I bilateral molar Angle relationship, and absence of posterior occlusal contacts during mandibular protrusion. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the right masseter and sternocleidomastoid muscles. EMG activity was recorded while the subjects were in standing position, during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge protrusive contact position; C. maximal clenching in the edge-to-edge protrusive contact position; D. grinding from edge-to-edge protrusive contact position to intercuspal position; E. grinding from retrusive contact position to intercuspal position. EMG activities in tasks B, C, D, and E were significantly lower than in task A in both muscles (mixed model with unstructured covariance matrix). EMG activity among tasks B, C, D, and E did not show significant differences in both muscles, except between tasks D and E in the masseter muscle. A higher effect was observed on the masseter than on the sternocleidomastoid muscle to avoid excessive muscular activity during clenching and grinding. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.

Influence of laterotrusive occlusal scheme on bilateral masseter EMG activity during clenching and grinding.

This study was designed to determine the effect of the occlusal scheme on masseter EMG activity at different jaw posture tasks. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance, and 15 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right masseter muscles. EMG activity was recorded during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge lateral contact position; C. maximal clenching in the edge-to-edge lateral contact position; D. grinding from edge-to-edge lateral contact position to intercuspal position. EMG activity in tasks B, C, and D was lower than in task A (mixed model with unstructured covariance matrix). EMG activity was not significantly different with canine guidance or group function. EMG activity recorded on the nonworking side was higher than the working side during task C, and no different between tasks B or D. On the nonworking side, EMG activity in task B was significantly lower than C and D, and similar between task C and D. On the working side, EMG activity was significantly higher in task D than C and B, and in task B significantly higher than task C. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.