Correctly exposing intraoral receptors includes four basic steps: receptor placement, vertical PID (cone) angulation alignment, horizontal PID (cone) angulation alignment, and central ray centring. Technique errors can occur if any of these steps are completed improperly.
Patient Preparation Errors
Dental professionals should always explain the radiographic procedure to the patient and give clear instructions as to what the patient can do to help ensure a quality image, avoid retakes and reduce radiation exposure. The most common error in this category is movement. Factors causing a patient to move include:
Discomfort can be addressed by gentle, proper receptor placement, instructing the patient to close slowly, and the use of cushioned edges which can be attached to the receptor. Receptors placed more toward the midline of the palate and toward the tongue on the mandible will make placement more comfortable for the patient. Bending, folding or creasing film or a digital phosphor plate receptor will produce artefacts that may compromise the diagnostic quality of the radiographic image.
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The headrest on the dental chair should be placed against the occipital lobe at the base of the back of the head. This will support the head during radiographic procedures and reduce the chance of movement. Proper headrest placement positions the occlusal plane parallel to the floor and the midsagittal plane perpendicular to the floor for maxillary periapicals and bitewings. It is helpful to readjust the head to raise the patient’s chin up slightly for mandibular periapicals. This improves visibility into the floor of the mouth for receptor placement and keeps the floor of the mouth more relaxed.
Gagging / Swallowing
The gag reflex is a protective mechanism of the body that serves to clear the airway of obstruction. All patients have gag reflexes, some more sensitive than others. The gag reflex can be stimulated when the receptor contacts the soft palate, base of the tongue, or the posterior wall of the pharynx. For some patients, gagging may be associated with a past negative dental experience. Patience and reassurance is necessary to help the patient overcome their anxiety. When exposing a full mouth survey of radiographic images, it is recommended to begin in the anterior region of the mouth. An anterior placement is less likely to stimulate the gag reflex and will also help the patient become more accustomed and comfortable with the procedure.
To ensure a quick and smooth patient experience, prepare all equipment before the receptor is placed inside the mouth. The exposure settings should be set in advance, and the tubehead should be placed in the approximate area of exposure. It may help to encourage the patient to swallow once before the placement of the receptor. It is best not to mention gagging or give tongue instructions. Start placements in the anterior region of the mouth particularly when a complete full mouth survey is indicated. In addition, the patient can be instructed to release the biting pressure or remove the receptor as soon as the exposure is complete. Other recommended procedures to control gagging include deep breathing through the nose or mouth, anesthetizing the mouth with lozenges, mouthwash, topical anaesthetic agents, or refocusing the patient's attention.14 The use of a sprinkle of salt on the tongue; patient press application of pressure on a point in the palm of the hand, or on the inner forearm or on the chin15,16 or tapping the temporal bone near the ear17 can help in the reduction of the gag reflex. Distraction techniques such as instructing the patient to raise one leg, bend the toes toward the body, humming, etc. will focus attention on the task rather than on gagging. When a patient begins to gag, remove the receptor, be confident and reassuring, and try again. A panoramic radiographic image may be a useful adjunct to intraoral radiographic images when the molar projections are extremely difficult for the patient to tolerate or for the clinician to obtain.
Some patients may need assistance during the radiographic procedure due to physical or cognitive disability, injury or medical condition. In such circumstances, it may be necessary to ask a family member or guardian to assist in holding the patient in position. Shielding should be provided for both the patient and person providing the assistance. The clinician must consider what technique would work best in the situation. For instance, a patient with Parkinsons disease can better tolerate intraoral radiographs which have short exposure times rather than a panoramic image which requires a sustained still position and longer exposure cycle. Familiarity with the bisecting angle and occlusal techniques may be useful in situations that are less than ideal and require alternative approaches to imaging.