Osseous defects

Osseous defects are the bone changes that are associated with periodontal disease other than the horizontal bone loss.

1.Interproximal crater:

Interproximal crater is a trough like or saucer shaped defect occuring in the alveolar crest of the interproximal bone.The bony defect has four walls – the buccal and lingual cortical plates and the roots of two adjacent teeth.The marginal bone of the interproximal crater appears thin.

2.Proximal intrabony defect:

Proximal intrabony defect is a vertical defect of the bone extending from the crest of the alveolus and in an apical direction.It is a defect  surrounded by four walls,the buccal and the lingual cortical plate,the hemiseptum and the root of the involved teeth.Radiographically the proximal intrabony defect appears “v” shaped adjacent to the affected root surface.

3.Interproximal hemisepta:

A hemiseptum is defined as the bone of the interdental septum that remains on the root of the uninvolved adjacent tooth after destruction of either the mesial or the distal portion of the interproximal bone septum.The hemiseptum results due to the loss of bone on the mesial or the distal aspect of a root surface.Radiographically the hemiseptum is a “V” or “U” shaped.

4.Inconsistent bony margins:

Inconsistent bony margins refer to irregular resorption of the cortical bone of the buccal or lingual alveolar cortical plate.Radiographically this bony change appears as irregular loss of the height of the alveolar crest.

5.Bony pockets:

Bony pockets usually occur together with proximal bony defects.Bony pockets are seen on the buccal aspect of the roots.Radiographs may not be very useful in the diagnosis of bony defects on the buccal or the lingual cortex.

Luxation

Luxation of the teeth refers to dislocation or loosening of the teeth due to loss of the periodontal attachment.The loosening can be

a.Intrusive luxation:

Intrusive luxation results when the tooth is displaced in to the alveolar bone.

b.Extrusive luxation:

Extrusive luxation refers to displacement of the tooth out of the socket.

c.Lateral luxation:

In lateral luxation the tooth is displaced to the side.

Luxation involves the anterior teeth.The clinical features that are seen are :

1.The affected tooth may be mobile.

2.Bleeding is seen through gingival crevice.

3.There is tenderness on percussion.

In intrusive luxation the tooth will be pushed in to the socket and the crown length appears shortened.In extrusive luxation the tooth will be pushed out of the socket and the crown lenth appears elongated.

The radiographic changes seen are as follows.In intrusive luxation there is disruption of the continuity of the lamina dura in the apical region.In extrusive luxation there is widening of the periodontal ligament space in the periapical region which is radiographically apparent as periapical radiolucency.In case of lateral luxation there is widening of the periodontal ligament space on one side and obliteration of the periodontal ligament space on the other side with evidence of damage to the lamina dura of the involved side.Either pulpal necrosis or calcification of the pulp chamber and the root canal can occur eventually which will be radiographically eveident as periapical lesion or obliteration of the pulp chamber and the root canal.

Juvenile periodontitis

Juvenile periodontitis or periodontosis is characterised by severe and rapid loss of the alveolar bone.Familial pattern of  distribution of this disease is also known as a result of genetic transmission of susceptibility.

There are two forms of Juvenile periodontitis – Localised and generalised.

The localised form is characterised by angular bone loss involving the first molars and the incisors.There can be no irritants seen also in some cases.The maxillary teeth are involved more than the mandibular teeth  and the teeth are involved bilaterally.The onset of Juvenile periodontitis is usually after adolescence.The affected individuals have an inherited defetc of neutrophil chemotactic function.

In the generalised form of Juvenile periodontitis there is involvement of many teeth.It usually has a late onset occuring between ages 20 and 30.Apart from the premolars and the incisors,the generalised form involves the canines,the premolars and the second molars.It is also considered as an extension of the local form.

Concussion

Concussion is a traumatic injury that involves the tooth.There is crushing injury to the apical vasculature and the periodontal ligament of the apical region leading to inflammatory edema.Thus it involves the supporting tissues of the teeth.As there is accumulation of inflammatory edema in the apical region,the affected person will suffer from pain.The involved tooth may be slightly elevated from the socket.This results in pain while biting.The radiographic change that is noticeable in concussion in widening of the periodontal ligament space at the apex.Evidence of pulpal necrosis and periapical lesion may be noted after a variable period of time.

Buccal and lingual caries

Buccal caries involves the buccal tooth surface and lingual caries involves the lingual tooth surface.Clinical examination is more useful and important in the diagnosis  of buccal and lingual caries as radiographically it may not always be possible to detect caries due to superimposition of the dense normal tooth structure.It is also not definitely possible to differentiate between buccal and lingual caries based on a radiograph.If buccal and lingual caries is radigraphically detectable,it appears as a small circular radiolucent area surrounded by dense area of normal tooth structure.

Recurrent caries

Secondary or recurrent caries occurs adjacent to a restoration.

The predisposing factors are:

1.Marginal leakage.

2.Defective margins of restoration.

3.Fracture of restoration in the marginal region.

4.Incomplete removal of caries.

5.In adequate cavity preparation.

Radigraphically recurrent caries appears as a radiolucent areabelow or adjacent to a radiopaque restoration.

Radiation caries

Radiation caries

Radiotherapy involving the head and neck region with resultant irradiation of the salivary glands causes:

1.Decreased saliva secretion.

2.Increased viscosity of the saliva.

3.Acidic pH of the saliva.

4.Loss of buffering capacity of the saliva.

These factors contribute to the development of caries.Three types of radiation caries have been seen.

They are:

A.First type of radiation caries that involves the cementum and dentin in the cervical region of the teeth.It progresses around the teeth.

B.The second type is the superficial lesion involving the buccal,occlusal,incisal and palatal surfaces.

C.The third type appears as dark pigmentation of the entire crown.

Root surface caries

Root surface caries usually begins in the cervical region of the teeth and involves the cementum and the dentin below the cervical region.There is no involvement of the enamel.

Some of the predisposing factors are:

1.Bone loss due to periodontal disease.

2.Gingival recession.

Clinical examination alone may not be useful in the diagnosis of root surface caries especially in the proximal region.Radiographic examination reveals the extent of involvement of the tooth structure.It appears as a cupped out or crater shaped radiolucency below the cemento-enamel junction(CEJ).This caries must be differentiated from a cervical burnout.

Thermography

Thermography is ageneric title for various methods of quantifying the temperature distribution from body surfaces.There are three forms of thermography.The are:

1.Liquid crystal thermography (LCT)

2.Infrared thermography (IRT)

3.Microwave thermography (MCT)

LCT uses cholesterol compounds showing colour changes with changes in temperature.MCT and IRT allow the detection of thermal emission froma surface in the microwave and infrared regions of the electromagnetic spectrum.Though still under trial,thermography may find its application in oral inflammatory conditions,screening of oral cancer,management of burns or wound healing and in the charaterisation of craniomandibular disorders particularly temperomandibular joint dysfunction.

Nuclear medicine

In nuclear medicine ,radioactive compounds  are used to study certain tissues to which these compounds have affinities.Nuclear medicine is a diagnostic radiation science.The various radioactive compounds used in nuclear medicine are also called as radionyclides or radioactive nuclides.A nuclide refers to a species of atom having in its nucleus a particular number of protons and neutrons.Hydrogen has three nuclides,ordinary hydrogen or protium,heavy hydrogen or deuterium  and tritium.

The radioactive substances may be radioactive elements or compounds such as 18F-,113mIn+++,99mTcO4 or they may be nonradioactive carrier compounds labelled with a radioisotope  such as 67Ga-labelled citrate,99mTc labelled polyphosphate or 125I labelled human serum albumin.

The radioactive compounds are injected in to the body and their concentration in the target tissues is detected by external detectors and imaging systems.Using the radionuclides,the study of various organs or tissues depends on:

1.Uptake by an organ.

2.Excretion.

3.Dilution.

99mTc is used in the study of the thyroid and the salivary glands.99Tc is used for bone scan.Labelling sulphur-colloid with 99mTc can be used to study the reticuloendothelial cells in the liver and the spleen.Cyanocobalamin labelled with 57Co or 60Co is used in Schiling’s test.Apart from the diagnostic aspects the radionuclides can also be used in therapy like treatment of hyperthyroidism,thyroid cancer,etc.