Anatomy and Function of the Mandible - The mandible is the largest and lowest bone in the facial skeleton. - It is the only movable bone of the skull. - It is connected to the temporal bones by the temporomandibular joints. - The jawbone can articulate side to side as well as forward and back. - The mandible consists of the body and two rami. - The body of the mandible curves anteriorly and gives structure to the chin. - The mental protuberance, or chin, is raised on both sides to form the mental tubercle. - The mandible has a mental spine, mylohyoid line, and various depressions and attachments for muscles. - The superior or alveolar border is hollowed into cavities for the teeth. - The buccinator muscle attaches to the outer lip of the superior border. - The inferior border is rounded and longer than the superior border. - The posterior border is thick, smooth, rounded, and covered by the parotid gland. - The ramus is flat on the outside and gives attachment to the masseter muscle. - The mandibular foramen is located on the inside of the ramus. - The lingula of the mandible gives attachment to the sphenomandibular ligament. - The mandibular canal runs obliquely downward and forward in the ramus, containing the inferior alveolar vessels and nerve. - The coronoid process is a thin, triangular eminence. - The condyloid process consists of the mandibular condyle and the neck. - The mandible has the mandibular foramen above the mandibular angle. - The mandible also has other foramina, such as the mental foramen. - The mandible forms the lower jaw and holds the lower teeth in place. - It articulates with the left and right temporal bones at the temporomandibular joints. - The condyloid process makes the temporomandibular joint with the temporal bone. - The coronoid process provides attachment to the temporal muscle. - The mandible plays a role in mastication, speech, yawning, kissing, and breathing.

Nerves - The inferior alveolar nerve is a branch of the mandibular nerve. - It enters the mandibular foramen and runs forward in the mandibular canal. - The nerve supplies sensation to the gums and teeth. - The nerve divides into two terminal branches: incisive and mental nerves. - The incisive nerve supplies the anterior teeth, while the mental nerve supplies sensation to the chin and lower lip.

Variation and Development - Males generally have squarer, stronger, and larger mandibles than females. - The mental protuberance is more pronounced in males. - Rarely, a bifid inferior alveolar nerve may be present, resulting in a doubled mandibular canal on a radiograph. - There is variation in the shape and size of the mandible among individuals. - The mandible can be visualised and palpated in both males and females. - The mandible of vertebrates evolved from Meckel's cartilage. - In recent human evolution, the oral cavity and jaws have shrunk due to the shift towards agriculture and settlement. - This has led to orthodontic malocclusions. - The mandible has undergone changes throughout evolution to adapt to different dietary habits. - The shape and size of the mandible can vary among different species. - The mandible forms as a bone from Meckel's cartilage. - The two sides of the jawbone fuse at the mandibular symphysis during the first year of life. - The cartilage of the ramus is replaced by fibrous tissue, forming the sphenomandibular ligament. - Ossification takes place in the membrane covering the outer surface of Meckel's cartilage. - Accessory nuclei of cartilage appear in different parts of the mandible during development. - At birth, the mandible is a mere shell with sockets for teeth. - The two segments of the bone become joined at the symphysis in the first year of life. - The body of the mandible elongates and deepens to accommodate additional teeth. - In adults, the alveolar and subdental portions of the body are usually of equal depth. - In old age, the bone can become greatly reduced in volume due to tooth loss and resorption of the alveolar process.

Dislocation, Displacement, and Resorption - Mandible can be dislocated anteriorly and inferiorly, but rarely posteriorly. - The articular disk of the temporomandibular joint prevents posterior movement. - Fractures in the condylar neck are common due to vulnerability. - Temporomandibular joint dysfunction can occur due to jawbone damage. - Symptoms include pain and inflammation. - Mandibular alveolar process can undergo resorption when completely edentulous. - Mental foramen may shift from the anterior surface to the superior border. - Alveolar process absorption can bring the mandibular canal closer to the superior border. - Excessive absorption may lead to the disappearance of the mandibular canal. - Inferior alveolar nerve remains protected by soft tissue.

Mandibulectomy, Regeneration, and Forensic Medicine - Surgical removal of all or part of the jawbone is known as mandibulectomy. - Partial mandibulectomy involves the removal of a small portion. - Segmental mandibulectomy involves the removal of a larger portion. - Mandibulectomy is performed to remove tumors, combat cancer, and treat infections, osteonecrosis, or injuries. - Replaced portions can be made of metal plating or bone from other parts of the body. - Bone grafting can mitigate bone loss in the jawbone, such as in osteoporosis. - Bone grafting is sometimes performed to support dental implants