The alveolar process is that part of the mandible and maxilla which supports the
teeth. It is the bone that forms the tooth sockets and surrounds the teeth. See figure
3-4. It fulfills the functional demand of supporting the teeth, but it partially disappears
when the teeth are lost and the functional demand ceases to exist. The structure of the
alveolar process is basically the same as that of other bone tissue. Because of
variations in its structural arrangement, however, the alveolar process may be divided
into three parts for descriptive purposes. These parts are called the cortical plate, the
spongiosa, and the lamina dura.
a. The Cortical Plate. The cortical plate is the hard, dense, outer surface of the
bone. The bone is the alveolar process. It varies in thickness and is generally thicker
on the tooth surfaces facing the tongue and the palate.
b. The Spongiosa. The spongiosa is a type of bone which is softer and more
sponge-like than ordinary bone. It occupies the space between the inner and outer
cortical plates. The spongiosa is also called cancellous bone because of the lattice-like
structure of the bony tissue. This structure makes up the central mass of the alveolar
c. The Lamina Dura. The lamina dura is a thin layer of cortical bone that lines
the tooth socket. It is connected to the tooth by the periodontal ligament. The lamina
dura has many sieve-like openings which pierce it and provide passage for blood
vessels and nerves that communicate with the periodontal ligament.
The periodontal ligament is a thin, fibrous ligament connecting a tooth to the
lamina dura of the bony socket. Normally, teeth do not contact bone directly. A tooth is
suspended in its socket by the fibers of the ligament. Because of this arrangement,
each tooth is capable of limited individual movement. The fibers act as shock absorbers
to cushion the force of chewing impacts. The periodontal ligament also supplies
nutrition to the alveolar process. It supports and attaches the gingiva. It registers
sensations of heat, cold, pressure, pain, and touch. In dental radiographs, the ligament
appears as a thin, dark line around the root. The lamina dura, in contrast, appears as a
thin, white line around the ligament.