1-13. ABRASION AND ATTRITION
Abrasion is considered to be an abnormal or excessive wearing away of tooth
substance by a mechanical process. It can be seen clinically. In abrasion, one or more
teeth may show the effects of wear. The wearing of the tooth substance may be caused
by biting some foreign substance such as a pipe stem or a bobby pin, by faulty tooth
brushing techniques, or by nervous biting habits. Attrition is the wearing away of tooth
structure because of contact with an opposing tooth. It involves all the teeth with the cusps
and contact points of all the teeth showing uniform wear. Abrasion and attrition differ in
that attrition is considered a normal, gradual loss of tooth substance from the chewing of
food and it involves all of the teeth, which will show uniform wear. If the loss of tooth
substance is excessive, it is called abrasion. In both cases, the dentinal tubules may
become calcified and secondary or irregular dentin may be deposited in the pulp
immediately below them. Secondary cementum may be laid down about the roots.
1-14. RESORPTION
a. General. In resorption, there is the dissolving (removal) of body tissues by
body fluids or cellular activity. Osteoclasts (cells that destroy bone) and cementoclasts
(cells that destroy cementum) are the cells active in the resorption of bone and
cementum. The condition is evident most often in the alveolar process and in the roots
of teeth. Certain types of resorption may be considered normal. Other types may be
the result of abnormal conditions. Healthy bone is constantly being remodeled.
Resorption and deposition of bone is a normal physiological process and the principle
that allows orthodontic movement of teeth. Stimulation of resorptive cellular activity
through excessive mechanical or occlusal forces or through the normal shedding of the
primary dentition is also within normal resorptive function. The effects of resorption can
often be seen on a radiograph. Pathological resorption may be initiated through
inflammatory stimulation or as the result of pressure exerted by developing neoplasms
or cysts.
b. Normal Resorption. The roots of deciduous teeth are resorbed just before
the eruption of the permanent teeth. There is also normal resorption of bone in
edentulous areas where permanent teeth have been extracted. Healthy bone is
constantly being remodeled. Resorption and deposition of bone is the basis for the
treatment applied by the orthodontist who moves malposed teeth slowly into proper
position. Resorption is also important in the repair of a fracture and the healing of a
tooth socket.
c. Abnormal Resorption. There are other types of resorption that may not be
considered normal. Resorption of the roots of permanent teeth may be the result of
many factors involving disease and trauma. For example, systemic (endocrine)
disturbances and some neoplasms are characterized by bone and root resorption.
Impacted teeth may impose upon the roots of other teeth to cause areas of resorption.
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