278
UNIT 3
Organ Systems
T. Yang
Horizontal fibers
Alveolar crest fibers
Gingival fibers
Oblique fibers
Apical fibers
Alveolar
bone proper
Supporting
bone
Fig. 14-18A
Fig. 14-18B
Fig. 14-18B
Fig. 14-18B
Fig. 14-18B
Fig. 14-19A,B
PDL
Sharpey fibers
Sharpey fibers
in alveolar bone
in alveolar bone
Sharpey fibers
in alveolar bone
Dentin
Dentin
Dentin
Alveolar bone
Alveolar bone
Alveolar bone
Cementum
Cementum
Cementum
PDL
PDL
PDL
A
Figure 14-19A.
PDL and alveolar bone, tooth root.
H&E,
3
68; inset
3
408
The
cementum
and
PDL
are derived from the dental sac. During root formation, some F bers from the PDL are trapped within the
cementum and the alveolar bone. These
Sharpey f bers
bridge the space between the cementum and the alveolar bone and serve to
suspend the tooth within the alveolar socket. The principal F bers of the PDL are organized in several groups based on their orientation
and location:
apical
,
oblique
,
horizontal
,
alveolar crest
,
interradicular
, and
gingival f bers
. The interradicular F bers are only present
between multirooted teeth. The gingival F bers attach the gingiva to the hard tissue of the tooth. The
alveolar bone
provides support
and protection for the tooth root. The alveolar bone includes the
alveolar bone proper
and
supporting bone
. The
alveolar bone proper
is a thin layer of compact bone which lines the tooth socket and has Sharpey F bers embedded in it; it is remodeled constantly to adapt
to stresses and tensions. The
supporting bone
is composed of
compact bone
and
cancellous bone
. The
compact bone
forms the cortical
plate, which provides surface strength. The
cancellous bone
makes up the central core of the alveolar bone and contains bone marrow.
CLINICAL CORRELATION
Figure 14-19B.
Tooth
Ankylosis.
H&E,
3
68
Tooth ankylosis
is the fusion of a mineralized root surface to its surround-
ing alveolar bone. It is characterized by a typical metallic percussion sound
and loss of the
PDL
space
in radiographs. Periapical infl ammation and
subsequent tissue repair are believed to be the cause of ankylosis. Ankylo-
sis is more common in
deciduous teeth
and usually results in
impaction
of
a subjacent
permanent tooth
. Impaction of incisors is much less common
than it is in the mandibular third molars. This slide shows impaction of a
central incisor
with focal loss of the PDL the incisor.
SYNOPSIS 14-1
Pathological and Clinical Terms for the Oral Cavity
Microdontia
: disproportionately small teeth (disturbances occur at bud stage).
Macrodontia
: disproportionately large teeth (disturbances occur at bud stage).
Dens invaginatus (dens in dente)
: developmental anomaly in tooth formation at cap stage in which the epithelium invaginates
into the pulp space to form enamel and dentin, creating a “tooth within a tooth” as shown in the radiographic imaging.
Misalignment
: a condition in which teeth are too crowded and incorrectly positioned.
Tooth decay (caries)
: bacterial destruction of teeth, including erosion of the enamel and damage to the pulp tissue.
Hypersensitivity
: a painful condition, especially to touch, sweetness, and cold drinks caused by exposed dentin.
Periodontal disease
: a chronic infl ammatory condition of gingival and surrounding periodontal tissues. Calculus and
plaque are the major causes of the disease.
Gingivitis
: infection and infl ammation of the gingival tissue.
Periodontitis
: infection and infl ammation affecting the periodontium, characterized by gingivitis, destruction of the
alveolar
bone and periodontal ligament, and the formation of periodontal pockets.
Pulpitis
: an infl ammation of the pulpal tissue of a tooth.
White lesions
: lesions on the mucosa of the oral cavity that have a white coating such as leukoplakia.
Red lesions
: chronic red oral mucosal lesions in which underlying vascular structures become more visible (as in
erythroplakia).
Alveolar
Alveolar
bone
bone
Alveolar
bone
Dentin
Dentin
Dentin
Junction between
alveolar bone
and dentin
(absence of PDL)
B
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