Radiographic Assessment of Lower Third Molar

Radiographic Assessment of Mandibular Third 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 The Lower Third Molar itself. The Lower Second Molar. The 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: 3.The roots: Note in particular: The size. The shape. The presence and extent of caries. 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). 4. The relationship of the apices with the inferior dental canal (IDC) . 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.

5. The depth of the tooth in the alveolar bone Winter`s Lines . Using the root of the 2nd Molar as a guide.

Winter`s Lines

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 the prognosis of the tooth to determine whether the second molar should be extracted instead of, or as well as, the third molar. The main features to examine 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: • 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.

Mesioangularly impacted /8". Note the unfavourable root curvatures (black arrow), the uninterrupted upper tramline of the inferior dental canal (open white arrow) and the conically shaped root of /7~(solid white arrows).

Slightly distoangularly impacted 8. Note the favourable conically shaped roots, the uninterrupted upper tramline of the inferior dental canal (open white arrows) and the radiolucent area distal to the crown (black arrows) caused by the residual follicle.

Transversely positioned /8. The crown is viewed end-on Transversely positioned /8. The crown is viewed end-on. Note that the bucco /lingual obliquity of the tooth cannot be determined from this radiograph. Horizontally impacted 8. Note the pincer-shaped roots and their indentation of the upper margin of the inferior dental canal (open white arrows), radiolucency beneath the crown (solid black arrows) caused by the follicle. In addition, note the carious lesions in 7 (open black arrows).

Vertically positioned /8with very unfavourable root 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).