During the early stages of erosion, the eroded areas
are very sensitive to heat and cold, acid foods, and
toothbrushing, but sensitivity may decrease when
secondary dentin is formed.
Man has suffered the effects of dental caries for
centuries, and much study and research have been
devoted to their causes and prevention. The disease is
caused by a microbial process that starts on the surface
of the teeth and leads to the breaking down of the
enamel, dentin, and cementum, in some cases causing
pulp exposure. This pathologic break that is produced
on or in the tooth surface is called acarious lesion (fig.
5-4) or commonly called a cavity. The process that
destroys the hard surfaces of the tooth is called decay.
The cause of tooth decay has been linked to a group
of bacteria called streptococci and other acid
producing bacteria that are in the oral cavity.
Decalcification of the enamel, the first step in the
decay process, is caused by:
Bacterial plaque adhering to the smooth surfaces
of the teeth
Acid, produced by bacteria in food debris, being
trapped in pits and fissures
Dental caries usually appear first as a chalky white
spot on the enamel, which indicates the decalcification
process. If proper oral hygiene is not maintained, the
lesion may become stained and take on a dark
appearance. In pit and fissure caries, the area of
decalcification at the surface is normally small, and the
white spot is less noticeable than in smooth surface
caries. In either type of caries, the surface becomes
roughened, as can be noted by passing a dental
explorer point over it. If the tooth surface has an area
that has not progressed past the decalcification stage,
this type of carious lesion is called incipient. As the
decay spreads in the enamel, it may stop. If this occurs,
the process is called an arrested carious lesion (fig.
5-5). These areas in which dental caries have been
arrested are dark and, in some instances, hollowed out.
A dental explorer passed over or in these areas will feel
hard to the touch. If the area still has active decay, the
explorer may sink in the soft decay.
Dental caries can progress further into the dentin
of the tooth, and spread out laterally widely
undermining the enamel and dentin. If this occurs,
often there may be no visible changes until extensive
destruction has taken place. The condition of the caries
if not arrested or restored with operative dentistry
(filling) will spread through the dentin into the pulp of
the tooth, thus requiring endodontic treatment (root
Figure 5-4.Carious lesions.