CHAPTER 14
Oral Cavity
275
Name of
Tissue
Productive
Cells
Inorganic
(Mineral) %
Organic %
Water % Sequence
of Hard
Tissue
Formation
Sequence
of
Productive
Cell
Formation
Activity
Embryological
Origin
Dentin
Odontoblasts
70
20
10
First
Odonto-
blasts second
Lifetime
Dental papilla
(mesoderm)
Enamel
Ameloblasts
96
3
1
Second
Amelo-
blasts ± rst
Before
tooth
eruption
Enamel organ
(ectoderm)
Cementum
Cementoblasts
65
23
12
Third
Cemento-
blasts third
Lifetime
Dental sac/
follicle
(mesoderm)
Alveolar
bone
Osteoblasts
60
25
15
Lifetime;
respond
to stresses
and
tensions
Mesoderm
TABLE 14-3
Dental
Hard
Tissue
CLINICAL CORRELATIONS
Figure 14-16A.
Vitamin D–Resistant Rickets.
H&E,
3
476
Vitamin D–resistant rickets
, commonly known as
X-linked
hypophosphatemic rickets
, is characterized by resistance to con-
ventional vitamin D treatment, decreased reabsorption of phos-
phate by the renal tubules, abnormalities in bones and teeth,
osteomalacia
, and
hypocalcemia
. It is an X-linked autosomal
dominant disorder. Patients with these rickets disorders do not
respond to high-dose vitamin D treatment. Signs include rickets,
short stature, bowing of lower limbs, seizures, congestive cardiac
failure, and tooth defects including
calcif
cation de±ects in dentin
,
enlarged pulp chambers
,
pulpitis
, and
pulp necrosis
. Treatment
with 1, 25-vitamin D (which is not dependent on normal hor-
monal mechanisms or organ systems to activate) plus controlled
phosphate therapy may improve the condition.
Figure 14-16B.
Dentin Dysplasia.
H&E,
3
35; inset
3
7
Dentin dysplasia
is an autosomal-dominant tooth disorder. Teeth
in this disorder are sometimes called
rootless teeth
, because they
often have very short and conical roots. Dentin dysplasia can be
classi±
ed into
types
I
and
II
.
Type I
, also called the
radicular type
,
is characterized by
short roots
and
pulp obliteration
.
Type II
, also
called the
coronal type
, is characterized by a “
thistle tube
pulp
.
Radiographically, extension of the pulp chamber into the root is
usually observed in dentin dysplasia. Pulp stones and sudden con-
striction of the pulp chamber are common. Dentin dysplasia type
II shares some similarities with
dentinogenesis imper±ecta
type II,
but in dentin dysplasia the permanent dentition has normal color
or only slight discoloration. Histologically,
globules o± dentin
and
disorganized dentinal tubules
are characteristic of this condition.
The
left image
shows globules of dentin; the
right image
shows a
low-power photograph of a dentin dysplasia.
Calcification
defect in dentin
A
Dentin
Dentin
Broad
root
Globules
of dentin
Dentin
B
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