Ultrasonographic assessment of local cross-sectional dimensions of masseter muscle sites: a reproducible technique?

Probable bruxism effects on masseter muscle thickness in children: ultrasonographic evaluation

OBJECTIVE

To compare the masseter muscle thickness (MMT) of patients with probable sleep/awake bruxism and controls without bruxism in mixed dentition as measured with ultrasonography (USG), and to calculate the correlation of MMT with body mass index (BMI).

STUDY DESIGN

The diagnosis of probable bruxism was established based on the parents' reports of the children's behavior, habits, and discomfort, and the presence of clinical signs and symptoms such as attrition-type wear on the teeth and the presence of discomfort, fatigue, and/or pain in the jaw muscles on palpation during clinical examination. The bruxist study group and the control group each included 28 children. MMT was measured separately in relaxed and contracted positions in both groups using USG. The height and weight of the patients were recorded in order to calculate BMI. Statistical analysis was performed with significance established at P < .05.

RESULTS

MMT was found to be significantly larger in the study patients than in controls on the right and left sides in the relaxed and contracted positions (P < .001). No statistically significant correlation was found between MMT and BMI (P ≥ .134).

CONCLUSIONS

MMT as measured with USG can be a beneficial approach in diagnosing bruxism in children. The lack of correlation between MMT and BMI indicates that BMI would not be helpful in diagnosing bruxism.

Local anaesthesia decreases nerve growth factor induced masseter hyperalgesia

The aim of this investigation was to evaluate the effects of local anaesthesia on nerve growth factor (NGF) induced masseter hyperalgesia. Healthy participants randomly received an injection into the right masseter muscle of either isotonic saline (IS) given as a single injection (n = 15) or an injection of NGF (n = 30) followed by a second injection of lidocaine (NGF + lidocaine; n = 15) or IS (NGF + IS; n = 15) in the same muscle 48 h later. Mechanical sensitivity scores of the right and left masseter, referred sensations and jaw pain intensity and jaw function were assessed at baseline, 48 h after the first injection, 5 min after the second injection and 72 h after the first injection. NGF caused significant jaw pain evoked by chewing at 48 and 72 h after the first injection when compared to the IS group, but without significant differences between the NGF + lidocaine and NGF + IS groups. However, the mechanical sensitivity of the right masseter 5 min after the second injection in the NGF + lidocaine group was significantly lower than the second injection in the NGF + IS and was similar to the IS group. There were no significant differences for the referred sensations. Local anaesthetics may provide relevant information regarding the contribution of peripheral mechanisms in the maintenance of persistent musculoskeletal pain.

Association between Lipoprotein Lipase Polymorphism and the Risk of Stroke: A Meta-analysis

BACKGROUND

Several studies have studied the relationship between lipoprotein lipase (LPL) HindIII gene polymorphism and stroke susceptibility. However, the conclusions remain controversial. To clarify the association of LPL gene HindIII polymorphism and stroke susceptibility, we therefore conducted a comprehensive meta-analysis.

MATERIALS AND METHODS

The PubMed, Web of Science, EMBASE, and Google Scholar databases were systemically searched to indentify available studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated under the allelic, dominant, homozygous, heterozygous, and recessive models. The data were analyzed by using Stata 12.0 (StataCorp, College Station, TX).

RESULTS

Ten studies were enrolled, including a total of 2122 cases and 2235 controls. The overall results showed that LPL HindIII variants were associated with a decreased risk of stroke (G versus T: OR = .78, 95% CI = .70-.87, P < .001; GG + TG versus TT: OR = .76, 95% CI = .67-.87, P < .001; GG versus TT: OR = .69, 95% CI = .53-.90, P = .006; TG versus TT: OR = .78, 95% CI = .68-.90, P <.001; GG versus TG + TT: OR = .74, 95% CI = .57-.95, P = .02). Stratified analysis by ethnicity (Asian and non-Asian) indicated that LPL HindIII variants were associated with a decreased risk of stroke in the Asian population, but not in the non-Asian population. In the subgroup analysis by stroke subtype, the results suggested that LPL HindIII variants contributed to a decrease in both ischemic stroke and hemorrhagic stroke risks.

CONCLUSION

Our meta-analysis suggested that LPL HindIII variants were associated with a decreased risk of stroke in the Asian population, but not in the non-Asian population.

Management of myofascial pain by therapeutic ultrasound and transcutaneous electrical nerve stimulation: A comparative study

OBJECTIVE

The present comparative study was aimed to determine the effectiveness of Th US and TENS in the management of myofascial pain in TMD patients.

MATERIALS AND METHODS

The present randomized comparative study was on 90 patients who were further assigned in three different groups each having 30 patients; Group I was healthy control patients, Group II was receiving Th US therapy, and Group III was receiving TENS therapy. All the 90 patients were further evaluated for maximum inter incisor subjective evaluation regarding muscle pain, impediment to daily life, massage impression on visual analog scale (VAS) scale, and intensity and duration used in Th US massage.

RESULTS

The masseter muscle thickness in control group was 12.00 (standard deviation [SD] ±1.1) mm when compared with TMD patient of 13.00 (SD ± 1.1) mm before treatment. Statistical significant findings on VAS score of muscle pain, impediment to daily life, and massage impression were observed in Th US. After treatment, the anechoic areas disappeared or were reduced in Th US group by 95.6% and in TENS by 74.4%.

CONCLUSION

Th US appeared to be subjectively better which was related to VAS score of massage impression, muscle pain, and impediment to daily life after treatment as well as sonographically related to existence of anechoic areas.

Assessment of cross-sectional thickness and activity of masseter, anterior temporalis and orbicularis oris muscles in oral submucous fibrosis patients and healthy controls: an ultrasonography and electromyography study

OBJECTIVES

Oral submucous fibrosis (OSMF) is an insidious chronic disease that is associated with significant functional morbidity and an increased risk for malignancy. It initially affects the lamina propria of the oral mucosa, and, as the disease progresses, it involves the submucosa and deeper tissue, including muscles of the oral cavity, resulting in loss of fibroelasticity. OSMF is a pre-malignant condition mainly caused by areca nut chewing. The aim of this study was to find out the involvement of muscles of mastication and facial expression in patients with OSMF by assessing the cross-sectional thickness and activity of the masseter, anterior temporalis and orbicularis oris muscles by ultrasonography and electromyography and comparing with healthy controls and also to find out any correlation between the ultrasonographic cross-sectional thicknesses of the masseter, anterior temporalis and orbicularis oris muscles with electromyographic activity.

METHODS

40 patients with OSMF were included in the study group, and the patients were divided into four groups on the basis of interincisal mouth opening, i.e. Group I (mouth opening >35 mm), Group II (mouth opening between 30 and 35 mm), Group III (mouth opening between 20 and 30 mm) and Group IV (mouth opening <20 mm). Ultrasonographic cross-sectional thickness and electromyographic activity (amplitude and duration) of the masseter, anterior temporalis and orbicualris oris muscles were recorded in patients with OSMF and 20 controls. Intergroup comparison of ultrasonographic cross-sectional thickness and activity (amplitude and duration) was done, and Pearson's correlation coefficient was applied to find out any relation between ultrasonographic and electromyographic findings.

RESULTS

Thickness and activity of the masseter muscle was significantly reduced in Group IV (mouth opening <20 mm) when compared with the control group. The anterior temporalis and orbicularis oris muscles remained unaffected. A positive correlation was observed between the thicknesses of the masseter muscle and the amplitude in Groups I, II and III; the anterior temporalis muscle in Group II and the control group; and the orbicularis oris muscle in Groups II, III and IV.

CONCLUSIONS

It was concluded that, among the muscles studied, there was an early involvement of the masseter muscle in patients with OSMF compared with that of other muscles.

Caracterização eletromiográfica e ultrassonográfica da função mastigatória em indivíduos com oclusão normal

OBJETIVO: Caracterizar o controle motor dos músculos masseter e temporal e a morfologia do músculo masseter em atividades da função mastigatória em indivíduos com oclusão normal; verificar a compatibilidade entre os exames de eletromiografia de superfície (EMGs) e ultrassonografia (USG). MÉTODOS: Participaram 22 indivíduos adultos, de ambos os gêneros, sem alterações no sistema miofuncional orofacial. Os procedimentos adotados para avaliação dos participantes foram: EMGs dos músculos masseteres (MM) e temporais (MT); e USG dos MM, na realização de três tarefas - repouso muscular, apertamento dentário com algodão, apertamento dentário sem algodão. RESULTADOS: Para análise estatística dos dados foram utilizados os testes de Kolmogorv-Smirnov, teste-T pareado e Correlação de Spearman, com nível de significância de 5%. Na EMGs observou-se diferença entre a ativação de MM e MT no apertamento dentário com e sem algodão, sendo MT mais ativo que MM em ambas as tarefas. Não foram observadas diferenças entre as hemifaces, tanto na EMGs quanto na USG. Observou-se também correlação positiva entre os exames na condição de apertamento dentário sem algodão esquerdo e na condição de apertamento dentário esquerdo com algodão, e tendência à significância no apertamento dentário direito sem algodão. CONCLUSÃO: A associação da EMGs e USG na investigação da funcionalidade muscular traz importantes informações sobre fisiologia da musculatura esquelética. Os resultados do presente estudo indicam haver correlação entre a EMGs e a USG, ou seja, o aumento da atividade elétrica e o aumento correspondente da espessura do músculo.

Ultrasound measurements of the masseter muscle as predictors of cephalometric indices in orthodontics: a pilot study

This study investigated the potential of ultrasound measurements of the masseter muscle to accurately predict indices normally derived from cephalograms. Masseter muscle measurements on 11 adults (22 to 30 y) were made using lateral cephalometrics and extended field-of-view ultrasound. The ultrasound technique was validated in a simulation pilot study using 12 dry skulls and raw chicken breasts. Twenty cephalometric variables were analyzed against four ultrasound measurements of the masseter muscle. Highly significant correlations (r = 0.81-0.85, p = 0.001-0.002) between ultrasound measurements of the masseter muscle and cephalometric measurements representing the length of the superficial masseter muscle, the length and shape of the mandible and vertical facial proportions were demonstrated. Predictive equations from regression analyses were constructed to deduce ramus length and shape from the ultrasound measurements. The results provide pilot data suggesting that ultrasound is a potential clinical tool for sequential evaluation of masseter muscle length in orthodontics and facial muscle growth studies.

Age and gender influence on maximal bite force and masticatory muscles thickness

The present study aimed investigate the age and gender influence on maximal molar bite force and at outlining the criteria for normal masticatory muscle development in a sample of 177 Brazilian Caucasian dentate individuals aged 7-80 years divided into five age groups: I (7-12 years), II (13-20 years), III (21-40 years), IV (41-60 years), and V (61-80 years). Except for Group V, which comprised nine women and eight men, all groups were equally divided in respect to gender (20 M/20 F). Bite force was recorded with a mouth-adapted 1000N dynamometer and the highest out of three records was regarded as the maximal bite force. The data were submitted to multivariate statistical analysis (SPSS 17.0 p<0.05). Effects of group and gender were found, but no interactions between them. The ANOVA showed significant differences between groups bilaterally. Bonferroni's test showed that group I had significantly lower bite force means at both sides as compared to all groups, except group V. No differences were found between the left and right sides. In all the groups, gender was found to be a significant factor associated with maximal bite force. A global comparison including all the subjects and measures showed that the means of men were approximately 30% higher than those of women. Within-group comparisons yielded similar results in all groups. Muscle thickness was measured with a SonoSite Titan ultrasound tool using a high-resolution real-time 56mm/10MHz linear-array transducer. Three ultrasound images were obtained from the bilateral masseter and temporal muscles at rest and at maximal voluntary contraction. The means of the three measures in each clinical condition were analyzed with multivariate statistical analysis (SPSS 17.0 p<0.05). A gradual increase in thickness of the masseter and temporal muscles was found both at rest and maximal voluntary contraction for groups I to IV, whereas a decrease in muscle thickness was observed in group V. Multivariate analysis showed that in both conditions there was an effect of group and gender. The study of the development of the stomatognathic system in relation to age and gender can provide useful data for the identification of normal and impaired functioning patterns. The results of this study indicate that age and gender are associated with structural and functional alterations in the muscles of the stomatognathic system.

Avaliação eletromiográfica e ultrassonográfica do músculo masseter em indivíduos normais: estudo piloto

TEMA: estudos recentes utilizaram a ultrassonografia com o objetivo de medir cortes musculares. OBJETIVO: caracterizar o controle motor e a morfologia do músculo masseter em indivíduos normais, verificando a compatibilidade entre a eletromiografia de superfície e a ultrassonografia. MÉTODO: cinco indivíduos adultos, sem alterações no sistema estomatognático. Os procedimentos adotados para a avaliação dos participantes foram: 1. Eletromiografia de Superfície; 2. Ultrassonografia. RESULTADOS: houve alta correlação apenas para a comparação entre hemifaces direita e esquerda no exame de ultrassonografia (repouso 0,95; máxima intercuspidação dentária 0,86). CONCLUSÃO: os resultados indicam não haver correlação entre os métodos testados, sugerindo que os exames são complementares e não excludentes.

Electromyographic activity and thickness of masticatory muscles in children with unilateral posterior crossbite

The aim of this study was to assess the electromyographic (EMG) activity and thickness of the masseter and anterior temporalis muscles in children with unilateral posterior crossbite (PCB). Thirty-six children (22 boys, 14 girls, and mean age of 8.8 +/- 1.1 years) were divided into the following groups: The case group with 20 PCB patients (10 on the left side, 10 on the right side); the control group with 16 normal occlusion (NOccl) subjects. EMG activity was recorded with bipolar surface electrodes at rest and during maximal clenching. The muscle thickness was measured with real-time ultrasound. Data were compared between groups and between sides. The correlation between EMG activity and muscle thickness was also evaluated. The data were analyzed using the Shapiro-Wilks test, Pearson's correlation and Spearman as appropriate, paired and unpaired t- test, and Mann-Whitney test. The results revealed that the masseter of the crossbite side was more active than that of the non-crossbite side in PCB group during maximal clenching. The comparisons of EMG activity between PCB and NOccl groups revealed some variability in the results, depending on the crossbite side. The ultrasonographic evaluation did not show statistically significant differences between groups, nor between sides in the PCB and NOccl groups. Significant correlation between EMG activity and thickness was observed only in the left masseter in the NOccl group. In conclusion, these findings showed that asymmetric muscle activity of the masticatory muscles was not related to the thickness of these muscles in children with PCB.

The use of ultrasound in the investigation of the muscles of mastication

The aim of this article was to review the literature concerning ultrasonography imaging (US) of the muscles of mastication and to discuss its use, advantages and disadvantages and the findings of the authors. A web search was performed using the terms "ultrasound" and "muscles". US has been shown to be a reliable method of great utility in the field of diagnosis of alterations in the muscles of mastication and for the study of changes during growth and aging. It should be preferred in comparison to computerized axial tomography (CT) and magnetic resonance imaging (MRI) because of its safety and cost advantages since it is as reliable and precise as these other techniques. Although various techniques have been used in ultrasonographic scanning, this article discusses those techniques most commonly adopted by the authors.

Masseter muscle thickness and mechanical advantage in relation to vertical craniofacial morphology in children

OBJECTIVE

To investigate the relationship between vertical craniofacial morphology and masseter muscle thickness and mechanical advantage in children.

MATERIAL AND METHODS

The sample comprised 72 children (36 F, 36 M), 8.5-9.5 years of age, with various malocclusions and no previous orthodontic treatment. The thickness of the masseter was measured bilaterally by means of ultrasonography, and the recordings were performed both in relaxation and under contraction. Mechanical advantage was measured on the lateral cephalograms as the ratio between the masseter moment and the bite force moment arms. Two linear ratios and three angular measurements were used to describe vertical craniofacial morphology.

RESULTS

The mean masseter thickness was greater in the male group (p<0.05) in both relaxed and contracted conditions. There were no significant sex differences for the mechanical advantage or for the measurements of vertical craniofacial morphology. In females, there is a positive association between masseter muscle thickness and its mechanical advantage. Multiple regression analysis showed a positive association between posterior to anterior facial height ratio in both genders and a negative association between masseter thickness and the intermaxillary angle in females.

CONCLUSIONS

There is a significant association between posterior to anterior facial height and the masseter muscle in children. The importance of the masseter muscle is more evident in the vertical facial morphology of females.

Ultrasonography and electromyography of masticatory muscles in a group of adolescents with signs and symptoms of TMD

The thickness and electrical activity of masseter and anterior temporalis muscles were compared in adolescents with and without signs and symptoms of TMD. Forty individuals were selected using the Cranio Mandibular Index and a questionnaire. There was no significant correlation between thickness and activity (p > 0.05). However, there were correlations between thickness and weight and height (p < 0.05). The effect of signs and symptoms on muscle thickness and activity was weak, considering the low CMI scores found.

Comparative data on facial morphology and muscle thickness using ultrasonography

The purpose of this investigation was to measure the thickness of the masseter, levator labii superioris, and zygomaticus major muscles; to examine the reproducibility of ultrasonographically measured muscle thickness; to evaluate the association between facial and masticatory muscle thickness and vertical facial pattern; and to test whether the variation in muscle thickness is related to the variation in the body mass index (BMI) of different individuals. The thickness of the masseter, levator labii superioris and zygomaticus major muscles was measured bilaterally by ultrasonography in 47 (23 females, 24 males) healthy, fully-dentate young adults who volunteered for the study. The measurements for each individual were performed twice for the masseter muscle: during relaxation and during maximal clenching. Standardized lateral cephalograms of the subjects were traced to determine their facial morphology. The data obtained from the lateral cephalograms were used to divide the subjects into three groups according to their vertical facial pattern: low angle (n = 14), high angle (n = 17) and normal (n = 16). In the low angle group, the mean masseter muscle thickness was 15.20 (+/- 1.90) mm under relaxed conditions and 16.31 (+/- 2.18) mm during maximal clenching. In the high angle group, the respective measurements were 13.29 (+/- 2.52) mm and 14.72 (+/- 2.63) mm. In the vertically normal group, they were 13.56 (+/- 1.95) mm and 14.57 (+/- 1.83) mm. There was no relationship between vertical growth of the face and the thickness of the investigated muscles of facial expression. Masseter muscle thickness was found to be significantly correlated to vertical facial pattern and BMI, showing that individuals with a thick masseter had a vertically shorter facial pattern, whereas the muscles of facial expression showed no relationship with vertical facial pattern.