Index
It is a type of X-ray that shows the vertices of the teeth and the surrounding structures in a particular intraoral area.
Main indications for periapical adiography
The main clinical indications for periapical radiography include:
- Apical infection / inflammation detection.
- Evaluation of the periodontal state.
- Evaluation of the presence and position of non-erupted teeth.
- Evaluation of postoperative implants.
Ideal positioning requirements
Ideal requirements for the position of the image receptor (film package or digital sensor) and the x-ray beam, relative to a tooth include:
- The tooth under investigation and the image receptor should be in contact or, if not feasible, as close as possible.
- The image receptor should be positioned vertically with its long axis for incisors and canines, and horizontally for premolars and molars with sufficient receptor beyond the apices to register the apical tissues.
- The positioning must be reproducible.
radiographic techniques
The anatomy of the oral cavity cannot always meet all of these ideal positioning requirements. In an attempt to overcome the problems, two techniques have been developed for periapical radiography:
- The technique of parallelism.
- The bisected angle technique.
Parallel technique
- The image receptor is placed in a holder and placed in the mouth parallel to the longitudinal axis of the tooth under investigation.
- The X-ray head is directed at right angles (vertically and horizontally) of both the tooth and the image receptor.
- By using a film / sensor holder with still image receptor and X-ray tube head positions, the technique is reproducible.
This positioning has the potential to satisfy four of the five ideal requirements mentioned above.
However, the anatomy of the palate and the shape of the arches mean that the tooth and the image receptor cannot be parallel or in contact. The image receptor should be positioned at a distance from the tooth.
Package holder / film sensor
A variety of supports have been developed for this technique. The different holders vary in cost and design, but essentially consist of three basic components:
- A mechanism for keeping the image receptor parallel to the teeth that also prevents bending of the receptor.
- A bite block or platform.
- An X-ray beam device. This may or may not provide additional beam collimation.
Generally, the different components of the various brackets must be assembled before the bracket can be used clinically. The design of the bracket used depends on whether the tooth under investigation is:
- Anterior or posterior.
- In the mandible or maxilla.
- On the right or left side of the jaw.
These variables mean that assembling the bracket can be confusing, but it must be done correctly. To facilitate this assembly, some manufacturers now color-code the various components.
Once properly assembled, the full image receiver should be visible when viewed through the beam targeting device.
The choice of the holder is a matter of personal preference and depends on the type of image receptor: film package or digital sensor (solid state or phosphor plate) used.
Typically, the same anterior holder can be used for upper and lower right and left incisors and canines using a small image receptor (22 × 35 mm) with its long vertical axis.
In general, four images in the maxilla and three images in the mandible are required to cover the right and left incisors and canines.
Different brackets are generally required for the left and right premolar and mandibular maxillary and mandibular posterior teeth. The different designs allow the holders to hook on the cheek and corner of the mouth.
A large image receptor (31 × 41 mm) is ideally used with its horizontal longitudinal axis. Two images are generally required to cover the premolar and molar teeth in each quadrant.
Positioning techniques
- The patient is positioned with the head supported and the occlusal plane horizontal.
- The bracket is rotated so that the teeth under investigation touch the bite block.
- A roll of cotton wool is placed on the reverse side of the bite block.
- The subject is asked to bite gently, to balance the support in position.
- The locator ring moves down the indicator rod until it is just in contact with the patient’s face. This ensures the correct distance between the focal point and the film.
- The spacer cone is aligned with the locator ring.
- The exhibition is done.
The holder and image receptor are placed in the mouth as follows:
- Incisors and canines of the maxilla: The image receptor is positioned far enough back to allow its height to be accommodated in the roof of the mouth.
- Incisors and mandibular canines: The image receptor is positioned on the floor of the mouth, approximately in line with the lower canines or the first premolars.
- Maxillary premolars and molars: The image receptor is positioned in the midline of the palate, again to accommodate its height in the roof of the palate.
- Mandibular premolars and molars: The image receptor is positioned in the lingual groove next to the appropriate teeth.
