Rami of the Mandible
The rami of the mandible (rami mandibulae; singular: ramus mandibulae) are the extensions of the mandibular body rising vertically in a dorsal direction.The constructive foundation is the basal arch, from which the functionally oriented parts such as the angle of the mandible and the condylar and coronoid processes arise (Figs 6-26 and 6-27).
The angle of the mandible (angulus mandibulae; submaxillary angle) joins the posterior border of the ramus to the inferior margin of the mandibular body. The large masticatory muscle (musculus masseter) attaches to the external surface of the angle of the mandible. Here it produces the masseteric tuberosities (tuberositates massetericae), whereas on the internal surface the middle pterygoid muscle (musculus pterygoi-
deus) produces the pterygoid tuberosities (tuberositas pterygoidea).
The shape of the angle of the mandible is characterized by the function of these two strong muscles of mastication. In newborn babies, these muscles are not yet fully active so that the angle of the mandible is still not very pronounced. The angle is around 120 degrees in adults and between 140 and 160 degrees in neonates and the elderly (Fig 6-28). In elderly or edentulous patients, the muscles are only under slight stress, which means that the bony tissue of the attachment is resorbed and the angle of the mandible loses its pronounced shape. It looks as if the angle between the body and the ramus has changed, but in reality it is the bone mass that is altered.
The rami divide into two processes, the condylar process posteriorly and the coronoid process anteriorly. The condylar process (processus ar-ticularis = articular process; also processus condylaris) comprises the neck of the mandible (col-lum mandibulae), on which the condyle of the TMJ sits. The articular condyle is also known as the head of the mandible (caputmandibulae). It is made up of a kidney-shaped roll of tissue whose longitudinal axis meets up with the axis of the condyle on the opposite side in front of the occipital foramen.
The coronoid process (processus coronoideus) is actually the ossified insertion tendon of the large temporal muscle (musculus temporalis).
The mandibular notch (incisura mandibulae) is a roundish notch between the two processes of the mandibular rami.This relatively narrow rim of bone broadens on the condylar process to a small depression directly below the condyle. The lateral pterygoid muscle attaches in this small depression, which is why it is called the pterygoid fovea (fovea pterygoidea).
The mandibular foramen (foramen mandibulae) is located in the middle on the internal surface of the mandibular ramus roughly level with the occlusal surfaces of the molars.The mandibular foramen serves as an entry point into the mandibular canal for the third branch of the trigeminal nerve. The position of the mandibular foramen changes during growing and aging processes. A complete half of the jaw can be anaesthetized by injecting anesthetic into the immediate vicinity of the mandibular foramen.
During mandibular movements, this mandibular foramen is in a relative resting state, which is why it is often interpreted as the pivotal point of the mandible. This interpretation is also justified by the fact that an opening at a nonresting point would endanger the vessels entering at that point and would therefore have been selected against during evolution.
The lingula mandibulae is found at the mandibular foramen as a small bony projection to which a tendon attaches, namely the sphenomandibular ligament. This tendon holds the mandible at the same distance from the base of the skull during movement because it cannot stretch. This means, of course, that the mandibular foramen is only able to perform slight relative movements.
The mylohyoid sulcus (sulcus mylohyoidea) is a shallow groove running forward and downward from the mandibular foramen into the floor of the mouth and carrying nerves and blood vessels for the floor of the mouth (nervus and arteria mylo-hyoidea).
The mandibular torus (torus mandibulae) is a pronounced bony bulge on the internal surface of the body of the mandible in the region of the premolars, which is seen in roughly 3% of patients examined. In extreme cases, the torus may interfere with the seating of a mandibular denture, in which case it must be surgically removed.