The buccinator is a thin quadrilateral muscle occupying the interval between the maxilla and the mandible at the side of the face. It forms the anterior part of the. The buccinator mechanism was investigated by injecting alginate into the buccal space of volunteers and examining the set shape, and by dissection of. (b) The buccinator mechanism during activity. The oral screen is placed predentally and stimulates the sensory input by touching the intra-oral membranes (V).
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The buccinator muscle forms the lateral wall of the oral cavity.
It bucccinator presumed to aid mastication by maintaining bolus position. Such a function would involve thickening the cheek, possibly compressing the alveolar bone and contributing to malocclusions. However, neither buccinator deformation nor its effect on pressure has been demonstrated.
Our objective was to evaluate buccinator EMG during feeding, its changes in length and thickness, buccinatlr the pressure exerted on its alveolar attachment, using miniature pigs as an animal model.
EMG of the buccinator and other oral muscles was recorded with fine-wire electrodes. Anteroposterior length and mediolateral thickness of the buccinator were evaluated mchanism implanted sonomicrometry crystals, and pressure was measured by flat transducers placed beneath the mandibular origin of the buccinator. Recordings were made during feeding and muscle stimulation. Tissues were collected postmortem for histology.
During mastication, buccinator EMG showed regular peaks that preceded mmechanism of the jaw closers. Pattern differences clearly distinguished working and balancing sides. The buccinator shortened and thickened when it contracted. Positive pressures were observed at the mandibular attachment of the buccinator, increasing when the muscle was active. Histological evaluation showed a complex interweaving of fibers closely associated with salivary tissue.
The buccinator mechanism.
Buccinator contraction does thicken the cheek, and during mastication this activity takes place just as the closing stroke begins. In addition to controlling the bolus, there may be an effect on salivation. Despite the fact that the muscle pulls on its attachment, the local mechanical environment at the alveolar bone is nuccinator of positive pressure. The buccinator, a muscle innervated by the facial nerve, forms the lateral wall of the oral cavity in mammals. This quadrilateral flat muscle is located deep to the skin and is mostly covered by the masseter and more superficial facial muscles.
It is usually described buccinatoor having predominantly horizontal fibers arising from the pterygomandibular raphe and from the alveolar bone of the maxilla and mandible and running anteriorly to interdigitate with the fibers of the orbicularis oris in the corner of the mouth.
These studies describe strong activity, differing in both timing and amplitude between working and balancing sides, and changing in response to different quality or quantity of food. Oddly, humans and rabbits differ somewhat in the specific pattern of masticatory activity of the buccinator. In humans, the buccinator and orbicularis oris EMG bursts occur simultaneously at the end of the opening phase, just prior to strong contraction of the masseter muscle.
The working-side buccinator has higher amplitude and longer duration than the balancing side, but the basic timing is similar on the two sides. Orbicularis oris activity in rabbits is bilaterally symmetrical and resembles the balancing buccinator pattern. Regardless of the detailed pattern of activity, these studies do support a role in mastication as a principal function of the bucconator.
However, there is little consideration of how this role is accomplished.
Although buccinator fibers attach to both upper and lower jaws, their predominantly horizontal direction indicates that the muscle is not a jaw closer. However, several other facial muscles, such as zygomaticus major, are better suited for this action. Most likely, the muscle functions by thickening the entire cheek, basically acting as a muscular hydrostat. Because of the proximity of the buccinator to the alveolar bone and dental arches, its functional effects on these structures have intrigued dental investigators for decades.
However, non-invasive studies on humans cannot access the actual alveolar attachment areas to test this suggestion. Therefore, in order to better understand the function of the buccinator during mastication and the effects on the alveolar mechaniem, we undertook a study using minipigs Sus scrofathe nonprimate animal model most appropriate for the study of human mastication. Because of the close relationship of the buccinator with the orbicularis oris, EMG of this muscle was examined as well.
The recordings were performed repeatedly over a period of weeks during ingestion and mastication of foods of different consistency and size. In a final experiment, EMG activity was supplemented by simultaneous measurements of buccinator length and thickness and of pressure at the buccinator attachment to the mandibular alveolar bone. In addition, in order to understand the muscle anatomy better, dissection was followed by histological study of the cheek so that the fiber direction could be discerned.
The purposes of this study were: The animals were 3—4 months old at the beginning of the study. After a period of acclimation 3—5 daysEMG activity of the facial muscles buccinator and orbicularis orisjaw closers masseter and temporalis and in two of the pigs jaw depressor digastric were recorded bilaterally during normal mastication. Recordings were made five times per week for about 4 weeks for each animal.
Fine wire electrodes 0. Surface electrodes were used for the masseter and temporalis interelectrode distance 2—3 mechwnism. A ground electrode was affixed to bucciantor forehead. The pigs were anesthetized with isoflurane and nitrous oxide during electrode placement.
After recovery, foods of varying consistency were offered: Diagram mechaniwm a pig head showing positioning of instrumentation. Only the part of the buccinator not covered by the masseter is shown.
Surface electrodes were positioned over the masseter M and temporalis T. Fine wire electrodes stars were placed in buccinator Borbicularis oris OOand digastric D muscles. Sonomicrometry crystals in the buccinator small ovals within dotted circles were placed anterior 1posterior 2superficial 3 and deep mechsnism.
The pressure transducer P was placed at the attachment of the buccinator to the mandibular alveolar process. In a terminal experiment, buccinator dimensions and alveolar loading were recorded along with EMG. The surgical procedures were identical for the 6 pigs and were performed bilaterally. Pigs were anesthetized as usual and positioned in buccinaror recumbency. First, an incision of about 10 mm was made close to the lower border of the mandible.
A tunnel from this incision to the molar region accessed the mandibular alveolar origin of the buccinator. A flat titanium-bodied pressure transducer Model P19F, 5mm diameter, 1. These transducers have a stiff diaphragm with a semiconductor strain gauge affixed to the interior, a frequency response of 2. Pressure 0 to 40 kPaproduced using a blood pressure bulb, was plotted against voltage output.
After the pressure transducer was placed, four ultrasonic crystal transducers 2 mm diameter with barbs or suture loops for tissue retention, Sonometrics Co.
These crystals continuously send and receive ultrasound from other crystals in the array, thus measuring distance in real time. The four crystals were placed through buccinahor skin incisions.
As illustrated in Figure 1the anterior crystal was positioned close to the commissure of the lips and the posterior close to the masseter.
To insert the anterior and posterior crystals inside the buccinator, muscle fibers were gently separated.
The buccinaor distance between the anterior and posterior crystals with the muscle at rest was 12—34 mm. The superficial lateral and deep medial crystals were intended to measure muscle thickness and were placed under the skin superficial crystal and deep to the mucosa deep crystalin the mediolateral transverse plane, about midway between the anterior and posterior crystals. The crystals used in these locations each had two loops which were used to suture them to the underside of the skin or to the deep surface of the mucosa.
The initial resting thickness was 4—7 mm. The incisions were sutured and the cables connected. EMG electrodes were placed as in the daily recordings.
Procedures were then repeated on the other side. Foods of different consistency were offered as during the previous recordings of normal mastication. Sonometric distances were recorded digitally to a separate computer running SonoLab software Sonometrics.
One or more distances were simultaneously recorded in Acqknowledge III in order to associate EMG data with the dimensional and pressure changes of the buccinator. However, accurate quantification of dimensions was only possible in SonoLab, where information on the side of chewing was absent. After the mastication data were acquired about 30 minthe pigs were anesthetized again and placed prone on the table. Anesthetized pigs were euthanized with pentobarbital in the end of the terminal experiment.
After about 20 days of fixation, the facial skin and subcutaneous fat were removed and the specimens embedded in paraffin wax. EMG was analyzed qualitatively to assess the timing of buccinator and orbicularis oris activity relative to that of the jaw closing and opening muscles. For pressure and dimensional changes, 10—20 consecutive chewing cycles from each type of food were quantified using SonoView Sonometrics mechanlsm Acqknowledge III. Baseline was considered to be the lowest pressure, greatest anteroposterior length L o and mecuanism thickness T o for each cycle, and peak values were the highest pressure, shortest length and greatest thickness.
Buccinator muscle – Wikipedia
Measurements of cyclic changes were made by subtracting the baseline from the peak values for each chewing cycle. Pressures were calculated from voltages using the regression equations generated during calibration.
Strains were calculated from dimensional measurements as the peak change per cycle divided by the initial distance, buccinattor. Descriptive statistics were calculated using SPSS The food preference for each pig varied, and no animal ate all the foods, except for pig chow. Only one animal drank liquid orange juice during the sessions. Drinking, as in other studies, 20 — buccjnator occurred by suction.
As shown in Fig. Jaw closer activity was negligible. EMG for drinking orange juice compared to mastication orange slices inthe only pig that drank.
The 2-sec segments are from the same file and have the same scale. The jaw closers have minimal or no activity during drinking, while the orbicularis oris presents stronger activity than during mastication.
Scale bars mV. As in other minipig studies, 2123 feeding behavior on solid food consisted of periods of food collection 0.
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Food gathering showed similar EMG patterns for all types of food Fig. The jaw closers exhibited brief bursts of activity. The buccinator was tonically active at a low level, and superimposed on this baseline activity were low to moderate bursts towards the end of the opening phase of each cycle.