The bulk of a tooth is formed of dentine, which is sensitive to ternperature
change and other stimuli. In the centre of the tooth crown,
and down the root to the tooth apex, is a hollow space occupied by
the pulp, which is soft tissue containing nerves and vessels. The
crown projects from the gingiva and is protected by a layer of
and hard, like ivory (= elephant enamel) but is susceptible to
caries. Beyond the crown there is a thin layer of cementum covering
the dentine of the root, and this layer forms the anchorage for the
Dental eruption is .
Caries is a bacterial invasion of the tooth which first liquefies a
narrow track through the enamel and then causes more extensive softening
and staining of the adjacent dentine.
Once the pulp has died, infection may spread to the
When infection has spread beyond the apex, the effect depends
on the severity of the inflammation. An acute abscess i s the most
Chronic apical infection may be present without clinical signs. cause the formation of a radicular cyst.
The X-ray changes then are those of a discrete peripheral lucency.
the fetus or infant is irradiated, damage to the developing tooth
germ can cause either absence of the tooth or gross hypoplasia,
both of primary and secondary dentition. In addition, mandibular
growth is retarded and hypoplasia results . Irradiation of the oral tissues (e.g. for soft-tissue sarcoma) affects the salivary glands and the nature of their secretions, which diminish
and become more acid. Caries is potentiated in a dry mouth andRadionecrosis
Initially, osteoporosis is seen, but the end-stage is a pattern of
mixed sclerosis and lysis. Pathological fractures and bone resorption
as well as sequestra are seen. Periosteal new bone is not prominent
in the mandible.
3-post inflammatory sclerosing osteitis.
5-localized fibrous dysplasia.
generalized dissease effecting teeth&jaws;
Hypopituitarism Hypoplasia of the jaws and teeth and delayed
dental age arc found, as would be expected.
pathognomonic bony change in this disease.
they are difficult teeth to radiograph.
Cysts of the jaws may conveniently be classified into:
I. Cysts of denial origin, developmental or post inflammatory
2. Non-dental, developmental or fissural cysts
3. Non-epitheliated cysts .
Post inflammatory Radicular (apical) cysts Most cysts of the
jaws are radicular. They lie directly upon the apex of a tooth.
which is usually diseased. They follow inflammation of the
pulp and apical bone, when a local apical area of chronic
inflammation, the granuloma. may result. This is seen radiologically
as a poorly defined para-apical area of bone
loss rather like a Brodie's abscess. The well-defined radicular
cyst results. Its dense opaque margin is continuous with the
lamina dura at the periphery of the cyst, but within the cyst the
lamina dura is destroyed. These cysts are generally less than
1.5 cnm in diameter and in grossly carious mouths may he
Treatment is by removal of the tooth and curettage. This should
result in bony healing with gradual obliteration of the cavity.
Should the cyst persist after dental extraction, it is known as a
residual cyst and its origin cannot be interred from a radiograph
(i) Odontogenic keratocyst (primordial cyst) These may
follow cystic degeneration of the enamel organ before the tooth
is formed, so that the cyst replaces the tooth, but they may also
arise from cctopic odontogenic epithelium. Should a normal
complement of teeth be present, the cyst is assumed to have
replaced a supernumerary tooth. Primordial cysts are more
common in young men, but may be seen at all ages. They are
slow-growing but may reach a very large size and may occupy
the entire ascending ramus . The cortex becomes
thinned and an axial view also demonstrates expansion in the
buccal-lingual plane. They are most commonly seen in the posterior
mandible and arc usually monolocular. These cases present
either because a critical size is reached and the patient feels a
fluctuant swelling of the mandible, or because of secondary
i nfection and purulent discharge.
Because of their growth potential, they may abut against an initially
unrelated and uneruptcd tooth. A dentigerous cyst is then simulated,
although the size and location may help in differentiation.
The diagnosis is in any case confirmed by enucleation and histologi
These cysts are almost inevitably ke atinised and are very likely
to recur unless removed completely. Long-tern follow-up is therefore
(ii) Dentigerous cyst (follicular cyst) Cystic degeneration of
the enamel organ may occur after the tooth has been formed but
before it has erupted. This results in a cyst related to the crown of
an uneruptcd tooth. Cysts enlarge in part because of local hydrostatic
imbalance. if the pressure within the cyst exceeds the eruplive
pressure of the tooth, that tooth is prevented from erupting. It
becomes displaced, often for some distance. Part of the crown
always remains in contact with the cyst
2. Developmental (fissural) cysts
These presumably occur at sites of fusion of embryonic processes.
Such cysts are:
a. Medial mandibular .
b. Medial rnaxillarvr c. Nasopalatine.
The nasopalaline ducts connect the nasal cavity
with the palate behind the central incisors. Four ducts are present in
utero, two on either side of the midline. Failure of normal ductal
obliteration may result in local epithelial remnants undergoing
lie between the upper lateral incisor and canine, the roots of which
are diverged. There is some doubt as to whether these are fissural or
i nflammatory. The majority are odontogenic keratocysts.
Simple bone cyst. These may follow trauma and are thus also
known as traumatic cysts. They appear in young patients, usually
boys, in the posterior aspect of the body of the mandible. Like other
types of cyst, they are vaguely spherical, well-defined, and surrounded
by a thin dense zone of reactive sclerosis.
radiolucency, displacing teeth. Again, the lesion is not common