A, Angle line projection

1. The patient sits upright and his head is stable.

Maxillary film: the head is slightly lower, and the auditory nasal line is parallel to the ground;

Mandibular film: the head is slightly inclined and the hearing line is parallel to the ground;

2. Place the photosensitive surface of the film on the lingual side and palatal side of the tooth to be examined, and place it vertically.

The edge of the front tooth is 7MM higher than the cutting edge.

The edge of the posterior tooth is higher than the cutting edge10 mm;

Make the photos form obvious contrast, and avoid the crown line or top image beyond the film.

3. The film is attached to the crown in the oral cavity, but it is not parallel to the long axis. The placement of the tube (the center line of the X-ray film) needs to be inclined at a certain angle so that it is perpendicular to the bisector of the included angle between the long axis of the tooth and the film.

Maxillary incisors: the bulbous canal is inclined 42; Fangs 45; Bicuspids and first molars 30; The second and third molars 28.

Mandibular incisors: head tilt-15; Fangs-18 to 20; Bicuspid and first molar-10; Second and third molars -5.

At the same time, it is necessary to change the angle according to the depth of the palate and the floor of the mouth and keep it vertical in order to obtain an accurate image.

Second, parallel projection

When parallel lines are used for projection, special film clips are needed, the film is parallel to the long axis of the tooth to be examined, the film needle is separated from the tooth to be examined, and it is not necessary to adjust the angle of the tube, and the center line of the X-ray is always perpendicular to the film. The image produced by parallel projection has the smallest tooth deformation.

Third, the advantages and disadvantages of corner projection technology

1, advantages: simple operation, no positioning device, and patients can fix themselves; The quality can be guaranteed, and the image is accurate and true.

2. Disadvantages: Time-consuming operation, easy to distort.

Advantages and disadvantages of parallel projection technology

1, advantages: accurate image with little distortion.

2. Disadvantages: Time-consuming and difficult to operate.

Taking dental films requires training from theory to operation.

Theoretically, we should master "three positions, two angles and one condition".

Three positions: head position, film position and X-ray center line position.

Two angles: vertical angle and parallel angle.

One condition: the conditions required for exposure (KV, mA, time).

In addition, the placement and fixation of X-rays are also very important.

Maxillary (anterior teeth +40. Premolar +30. Molar +20. )

Mandibular (anterior teeth-15. Premolar-10. Moore -5. )