d. External and Internal Resorption. Resorption of a tooth may develop
externally or internally. Internal resorption is usually caused by inflammatory pulpal
stimulation. External resorption may be caused by inflammatory stimulation of
resorptive cells or through stimulation of resorptive cells associated with the pressure
exerted by developing pathology or impacted teeth. This can cause resorption of tooth
structure and surrounding alveolar bone. The cell responsible for the active resorptive
process in bone is an osteoclast just as the cementoclast is for cementum. The
osteoclast is developed from connective tissue cellular components in the pulp or area
adjacent to an inflammatory stimulus outside the tooth.
Section III. DENTAL CARIES
Dental caries is a term for the process commonly referred to as decay of the
teeth. Thus, a decayed tooth is properly termed a carious tooth. Dental caries or dental
decay is a specific disease that causes dissolution and disintegration of the hard
structures of the tooth, that is, enamel, cementum and dentin. (The word caries or
decay refers to the disease; the word cavity refers to the lesion or hole in the tooth.)
Dental caries is the most widespread disease affecting the human race. The incidence
of caries is greatest during childhood and young adulthood. It attacks deciduous teeth
the same as it attacks permanent teeth. Dental caries is progressively destructive. It
usually begins in a minute area on the enamel or cementum and, if untreated,
progresses to the dentin. The next step is penetration to involve the dental pulp.
Infection and death of the pulp may follow, with possible extension of the infection into
the tissues surrounding the apical portion of the root and the formation of an abscess.
The control of dental caries is a very important problem that is receiving much attention
in the fields of research and prevention.
In general, dental caries occurs because of improper or poor oral hygiene. The
destruction of dental tissue by caries, however, is governed somewhat by the
susceptibility of the teeth. Little is known about susceptibility or resistance to caries, but
the degree of susceptibility may be influenced by certain factors including diet, oral
hygiene, and some systemic diseases. Study of the direct cause of dental caries is very
complex. Only two theories of its cause are considered here.
a. Acidogenic Concept. According to the acidogenic (producing acid) concept,
bacteria and their products accumulate in mucinous plaques, which are often invisible
and adhere tightly to the teeth. The bacteria in the plaques metabolize (feed upon)
carbohydrates in the diet and convert them to organic acids. These acids dissolve the
enamel and allow deeper bacterial penetration into the tooth. The lesion is progressive.