Macroscopic Analysis of Human Masseter Compartments Assessed by Magnetic Resonance Imaging

Cioffi, Iacopo; Gallo, Luigi M.; Palla, Sandro; Erni, Stefan; Farella, Mauro

doi:10.1159/000329503

Cited by 24 publications

(11 citation statements)

References 76 publications

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“…Some of these complex aponeuroses attaching to the inferior border of the mandible appeared similar to the DIT observed in the present study, although the previous authors did not report on the morphology of the aponeuroses. There were more aponeuroses in the deeper part than in the superficial part of the masseter muscle (Cioffi et al, ). However, in the present study the DIT was a deep tendon structure forming part of the superficial muscle belly of the superficial part of masseter muscle.…”

Section: Discussionmentioning

confidence: 99%

Ultrasonography of the internal architecture of the superficial part of the masseter muscle in vivo

et al. 2019

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It is unclear whether the deep inferior tendon (DIT) is equally present in vivo, and little anatomical information is available regarding the existence and morphology of the DIT in healthy young subjects. The aim of this study was to characterize the DIT of the masseter muscle in healthy young subjects using ultrasonography and to compare the morphology of this tendon with previously reported data for healthy young subjects in order to provide the most-effective injection methods for botulinum neurotoxin treatments of masseteric hypertrophy. This study investigated two fresh cadavers and 30 healthy subjects. Ultrasonography scanning in both longitudinal and transverse directions was applied to the masseter muscle. The DIT within the superficial part of the masseter was observed in both the fresh cadavers and the living subjects. The posterior region of the masseter muscle was compartmentalized (entirely covered) by the DIT in 26.7% of the specimens. The superficial part of the masseter muscle was divided by the DIT transversely and longitudinally into the superficial and deep muscle bellies in 35% and 38.3% of the specimens, respectively. The present findings suggest applying a DIT-based injection technique under guidance by ultrasonography prior to treating masseteric hypertrophy. Clin. Anat. 32:446-452, 2019.

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Section: Discussionmentioning

confidence: 99%

Ultrasonography of the internal architecture of the superficial part of the masseter muscle in vivo

et al. 2019

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“…The strategy of altering MU recruitment in a similar manner, by generating forces in different directions or for different vertical jaw distances, may be essential for optimum adaptation of the bite force during chewing. This behaviour might be supported by the complex distribution of the several small aponeuroses with their different spatial orientations and dense interconnections in the multipinnate masseter muscle which is probably stiffened by the multimodal MUs to enable appropriate intra‐muscular force transmission.…”

Section: Discussionmentioning

confidence: 99%

Small vertical changes in jaw relation affect motor unit recruitment in the masseter

Terebesi

Giannakopoulos

Brüstle

et al. 2015

J of Oral Rehabilitation

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Strategies for recruitment of masseter muscle motor units (MUs), provoked by constant bite force, for different vertical jaw relations have not previously been investigated. The objective of this study was to analyse the effect of small changes in vertical jaw relation on MU recruitment behaviour in different regions of the masseter during feedback-controlled submaximum biting tasks. Twenty healthy subjects (mean age: 24·6 ± 2·4 years) were involved in the investigation. Intra-muscular electromyographic (EMG) activity of the right masseter was recorded in different regions of the muscle. MUs were identified by the use of decomposition software, and root-mean-square (RMS) values were calculated for each experimental condition. Six hundred and eleven decomposed MUs with significantly (P < 0·001) different jaw relation-specific recruitment behaviour were organised into localised MU task groups. MUs with different task specificity in seven examined tasks were observed. The RMS EMG values obtained from the different recording sites were also significantly (P < 0·01) different between tasks. Overall MU recruitment was significantly (P < 0·05) greater in the deep masseter than in the superficial muscle. The number of recruited MUs and the RMS EMG values decreased significantly (P < 0·01) with increasing jaw separation. This investigation revealed differential MU recruitment behaviour in discrete subvolumes of the masseter in response to small changes in vertical jaw relations. These fine-motor skills might be responsible for its excellent functional adaptability and might also explain the successful management of temporomandibular disorder patients by somatic intervention, in particular by the use of oral splints.

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“…The polymodal behaviour might be related to biomechanical requirements. Indeed, recent anatomical studies using magnetic resonance imaging revealed highly variable inner muscle structure consisting of multiple small aponeuroses with different spatial orientations and dense interconnections . Such a complex structure requires stabilizing elements between the aponeuroses, especially during differential activation of the muscle.…”

Section: Discussionmentioning

confidence: 99%

Localised task‐dependent motor‐unit recruitment in the masseter

Schindler

Hellmann

Giannakopoulos

et al. 2014

J of Oral Rehabilitation

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Localised motor-unit (MU) recruitment in the masseter was analysed in this study. We investigated whether differential activation behaviour, which has already been reported for distant masseter regions, can also be detected in small muscle subvolumes at the level of single MUs. Two bipolar fine-wire electrodes and an intra-oral 3D bite-force transmitter were used to record intra-muscular electromyograms (EMG) resulting from controlled bite-forces of 10 healthy human subjects (mean age 24.1 ± 1.2 years). Two-hundred and seventeen decomposed MUs were organised into localised MU task groups with different (P < 0.001) force-direction-specific behaviour. Proportions of MUs involved in one, two, three or four examined tasks were 46%, 31%, 18% and 5%, respectively. This study provides evidence of the ability of the neuromuscular system to modify the mechanical output of small masseter subvolumes by differential control of adjacent MUs belonging to distinct task groups. Localised differential activation behaviour of the masseter may be the crucial factor enabling highly flexible and efficient adjustment of the muscle activity in response to complex local biomechanical needs, for example, continually varying bite-forces during the demanding masticatory process.

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Macroscopic Analysis of Human Masseter Compartments Assessed by Magnetic Resonance Imaging

Cited by 24 publications

References 76 publications

Ultrasonography of the internal architecture of the superficial part of the masseter muscle in vivo

Ultrasonography of the internal architecture of the superficial part of the masseter muscle in vivo

Small vertical changes in jaw relation affect motor unit recruitment in the masseter

Localised task‐dependent motor‐unit recruitment in the masseter

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