Chewing or Mastication

1. Mastication process or chewing is one of the step in digestion of food when we eat meals. Mastication helps to reduces a size of food and therefore to increase surface area of enzyme of saliva to act with food particles to absorb more nutrients into the body
2. There are 4 muscles of mastication which mainly originated from skull bone and attached onto the bone of mandible. These muscles namely as
a)temporalis muscle
b)masseter muscle
c)medial pterygoid
d)lateral pterygoid
3. Although most of facial muscle supplied by cranial nerve of Facial nerve (CN VII), but there is exception of all of these muscles of mastication which are supplied by cranial nerve of Trigeminal nerve (CN V) specifically mandibular branch (V3). This is because due to embryogenic derivative was different whereby CN V is derived from 1st branchial arch while CN VII is derived from 2nd branchial arch
4. The function of muscle of mastication is either to elevate,depress or retract the mandible or jaw. The mandible is the main bone used in mastication, it moves up and down to crunch and grind a food by the teeth.
5. Temporalis, masseter and medial pterygoid help in elevate or close the jaw except lateral pterygoid which help in depress or open the jaw
6. Clinical important of muscle of mastication is it is can manifest with infection of mastication muscle. the source of infection to these muscles usually from dental origin such as premolar or molar caries. Patient with masseter abscess usually presents with cheek swelling, limited mouth opening (trismus), toothache and fever. An airway of the patient is vital in managing this like of patient.
7. Surgical intervention need to be carried out if medical treatment with intravenous antibiotic is not adequate. Incision and drainage can be done via intraoral or skin incision depends on the limitation of mouth opening as well as patient condition.