The Intraoral Examination
Seat the patient upright in the dental chair, making sure they are comfortable. Always support the patient’s head against the headrest; this is easier for the patient and the operator. Place protective shielding on the patient, making sure that the thyroid collar is secure, as it is the most important part of the apron. Older aprons contain lead; newer aprons contain a lead-equivalent material. The latest recommendation from the National Council of Radiation Protection and Measurements (NCRP) states, “Thyroid shielding shall be provided for patients when it will not interfere with the examination. Technological and procedural improvements have eliminated the requirement for the radiation protective apron, provided all other recommendations of the Report are rigorously followed, unless required by state regulation.”3 These recommendations include among others: sensor holders, proper technique, selection criteria, and rectangular collimation when able. Be sure to comply with your state mandated requirements.
The operator should assess the mouth by performing a brief intraoral examination. Feel the anterior lingual mandible and assess its morphology; is the bone upright or is it sloped? If the bone is sloped, the operator will need to position the sensor posteriorly to avoid the bone and the sensitive soft tissues covering the bone. Feel for palatal and mandibular tori. If large mandibular tori are present, place the sensor posterior to avoid the thin, sensitive tissues covering the tori. If the tori are small, try to position the sensor between them and as far forward as possible to successfully image the premolars. Note the position of the teeth, especially the canines. If the canines are extremely forward in the jaw, there may not be a way to image the distal canine crown. If there is extreme malposition and crowding, there may not be a path to open the compromised contacts. Marginal ridges that parallel and create a clean separation between crowns allow the radiation path to parallel and ‘open’ the contact. When a tooth is out of alignment, i.e., one is buccal and one is lingual, the marginal ridges often overlap, thereby eliminating the separation of crowns and the possibility of open contacts. Knowing what is achievable before beginning the radiographic examination will lessen the operators stress.
Start with the easiest images first to gain rapport with the patient. The patient is more likely to tolerate an uncomfortable position of a sensor when they know you care about their comfort and are being as efficient as possible. Ask the patient to smile as you position the sensor, do not allow the lips to close around the holder at any point during the setup process. Seeing the teeth and the interproximal contacts as you position the sensor and ultimately the PID is critical. When the sensor is uncomfortable, the patient wants to open and relieve the pressure. Keep the patient smiling, and reposition the sensor away from the sensitive tissues. Make sure the patient is biting down fully. The sensor holder’s bitepiece must be in contact with the teeth at all times during setup and exposure. If the patient does not bite down all the way and hold the sensor in place, the apices may not appear on periapical images, and bitewings may not capture bone levels. Rod and ring aiming instruments move together, but the ends move in opposite directions from each other. The tooth is the pivot point, and the sensor holder and the aiming ring move about that point. An easy analogy is the teeter-totter…when one person is in the air, the other is on the ground. Whether the PID is up or down, following the ring will cover the sensor with radiation. The complexities become apparent when we actually get in the mouth and find that the maxillary palate is shallow, or that large mandibular tori are present that compromise the sensor’s position.
Bitewings are the preferred image type when diagnosing caries and periodontal bone loss. The addition of vertical angulation to the periapical technique, whether paralleling or bisecting, tends to superimpose anatomical structures over the teeth. The margins of restorations and crowns superimpose with the crestal bone on the image and the ability to diagnose caries at those margins on periapical views is impossible. Paralleled periapical views tend to superimpose fewer structures than bisected periapical views. Vertical angulation is necessary to image apices and surrounding bone. Excessive vertical angulation should be avoided, except in the case of exceptionally long roots where the apex needs to be recorded.
Whether using the Paralleling Technique with rod and ring aiming instruments, or the Bisected Angle Technique with appropriate sensor holders, the operator will assess horizontal and vertical angulations throughout the procedure. Knowing how the teeth are positioned in the jaw is critical. In Figure 4, the black lines represent the long axis of the posterior and anterior teeth of this particular teaching mannequin. Assess the position of the teeth in your patient’s mouth during the initial examination. The patient should always be positioned upright, with the skeletal midline perpendicular to the floor (head should not be tipped to one side or rotated), and the occlusal plane parallel with the floor of the room. This increases the odds of acquiring images where the radiographic tooth length is as close as possible to the actual tooth length.
(A) Long axis of posterior teeth as viewed from the front. (B) Long axis of anterior teeth as viewed from the side.