Radiographic Assessment of Lower Third Molar

Radiographic Assessment of MandibularThird Molars

Clinical symptoms associated with lower third molar usually treated by extraction, many factors that influence & determine the difficulty of extraction, are revealed by pre-operative radiograph.

Radiographic Assessment of Lower Third Molar

•Periapical Radiograph : a. Film Holding Devise.b. Beam Direction.

•Panoramic Tomography.

•Oblique Lateral Radiograph ( Bi-molar ).

Periapical Radiographs :

It must be with good quality & accurate geometric relationship with surrounding structures.

The main difficulties include the placement of the film sufficiently posterior to record the entire tissues & the inferior dental canal.Solutions:

*Using the needle holder to hold the film in its position & ask the patient to close his mouth this will lead to relax the tissue of the floor of the mouth , and allow the film easy to placed more posterior until the frontal edge of the film is placed opposite to the mesial side of 1st. molar.

*Beam direction centering about 1cm. from the lower border of the mandible at the point on the line drop from the outer canthus of the eye.

Radiographic Interpretation

üThe Lower Third Molar itself.

ü The Lower Second Molar.

üThe Surrounding Bone.

A. Lower third molar assessment

The main features to examine include:1.Angulation.2. The crown.3.The roots.4. The relationship of the apices with the inferior dental (ID) canal.5. The depth of the tooth in the alveolar bone.6. The buccal or lingual obliquity.

1.Angulation

2. The crown:Note in particular:

a. The size.

b. The shape.

c. The presence and extent of caries.

d. The presence and severity of resorption.

3.The roots: A. The number.

B. The shape.

C. Curvatures, whethere they are favorable or unfavorable.

D. The stage of development.

The IDC appears as two thin, parallel radiopaque lines (TRAM line).*Loss of TRAM line: The root & IDC are in contact.*Narrowing of the TRAM line:. The lingual aspect of the root is grooved by

the IDC. *Sudden change of the direction of TRAM line:. The apex of the root grooved by IDC.Radiolucent band across the root: The root is grooved or tunneled through by the IDC.

4. The relationship of the apices with the inferior dental canal (IDC) .

5. The depth of the tooth in the alveolar bone

ØWinter`s Lines .

ØUsing the root of the 2nd Molar as a guide.

Ø Winter`s Lines

Ø Root of the 2nd. Molar as a guide

6. The buccal or lingual obliquity

Buccal obliquity: The crown is inclined toward the cheek.Lingual obliquity: The crown is inclined toward the tongue.

Determination of the tooth position in horizontal plane is done by :

1.Lower oblique occlusal view .2.Lower cross sectional occlusal view .

B . The Lower Second Molar.

The second molar is assessed to determine theprognosis of the tooth to determine whether thesecond molar should be extracted instead of, or as well as, the third molar. The main features toexamine include:• The crown• The roots.

The crown:Note in particular:• The condition and extent of existing restorations.• The presence of caries.• The presence and severity of resorption.The roots:Note in particular:• The number.• The shape, and if it is conical.• The periodontal status.• The condition of the apical tissues.

C:Assessment of the surrounding bone:

The main features to examine include:• The anteroposterior position of the ascending ramus, to determine access to the tooth and the amount of overlying bone.• The texture and density of the bone.• Evidence of previous pericoronal infection.

Vertically positioned /8with very unfavourableroot curvatures.

Two radiographs showing some of the radiographic features suggestive of an intimate relationship with the inferior dental canal. A. A radiolucent band is evident across the root (arrowed) and there is a change in direction of the ID canal.B.A radiolucent band evident across the root and the ID canal is narrowed (arrowed).