The bulk of a tooth is formed of



Download 16.89 Kb.
Date28.11.2016
Size16.89 Kb.
Anatomy

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



enamel i n the form of a thimble or cap . Enamel is insensitive

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 .

Infection;

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

periapical region.

When infection has spread beyond the apex, the effect depends

on the severity of the inflammation. An acute abscess i s the most

marked reaction,

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.



Radiation changes in the jaw
Radiation and chemotherapy cause damage to developing teeth.

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.



DDX OF sclerosing lesion of the jaw s;

1-hypercementosis

2-cementoma.

3-post inflammatory sclerosing osteitis.

4-odontomes(complex &compouind).

5-localized fibrous dysplasia.

6-pagets dissease.
generalized dissease effecting teeth&jaws;

Hypopituitarism Hypoplasia of the jaws and teeth and delayed

dental age arc found, as would be expected.



Hyperparathyroidism Subperiosteal bone resorption is the

pathognomonic bony change in this disease.



Gigantism Dental separation again results from jaw enlargement,

they are difficult teeth to radiograph.



Cyst of jaws;

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

multiple .

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

cal examination.

These cysts are almost inevitably ke atinised and are very likely

to recur unless removed completely. Long-tern follow-up is therefore

advisahle.

(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

cystic degeneration.



d. Globulomaxillar_y. These cysts look like an inverted pear and

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.



Non epithelialised bone cyst;

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.



Aneurysrnal bone cyst. These present as a well-defined expansile

radiolucency, displacing teeth. Again, the lesion is not common



i n the jaws. and histology is usually needed to confirm its identity.

They may be secondary to other tumours

Share with your friends:


The database is protected by copyright ©dentisty.org 2019
send message

    Main page