Periapical X-rays are frequently used because they provide valuable information about a patient’s teeth and other important structures that include the periodontium. Viewing the complete crown and the root structure of the tooth enables a dentist to make an accurate diagnosis concerning inflammation, caries, or bone loss. Periapical X-rays may be taken to examine a particular area or will form part of a series of full mouth X-rays.
Every clinician or dental assistant must be able to take good quality periapical X-rays. The paralleling technique is considered to be the best way to take periapical X-rays and when used correctly, it should produce reliable images with minimal distortion.
With this technique, the film is placed parallel to the long axis of a tooth, allowing the X-ray to be focused perpendicular to the long axis of the tooth. The patient is seated upright in the dental chair and should remove any removable dental appliances, glasses or jewelry that could interfere with the X-ray beam. Ensure they are seated high enough so it is easy to see the occlusal surfaces of the teeth and check for any aphthous ulcers or sores that could interfere with the images. If any are present, it may be necessary to consider a different technique as touching them with the film could exacerbate them. The patient is protected with a lead apron and thyroid collar.
It is often easier to prepare the X-ray equipment before the film is carefully situated in the patient’s mouth. Advance preparation reduces the time needed for the patient to hold the Rinn instrument in place which can be very useful if they find this particularly uncomfortable or have a strong gag reflex.
Once the patient is ready, the Rinn instrument can be assembled. When taking maxillary periapical, the film should be placed near to the palate midline and should not be placed against the palatal aspect of the teeth because this will result in the image being distorted, foreshortened, or will provide a view of the crown of the tooth but will not take images of the apices.
Mandibular periapical X-rays tend to be more difficult to take due to the position of the floor of the mouth and the tongue. The patient needs to be instructed to relax their mouth and tongue so the film can be placed between the mylohyoid ridge and the tongue. Guide the film into place with an index finger before asking the patient to slowly close their mouth. It is very important that the teeth are fully closed onto the bite surface as this will ensure the film is correctly positioned so the apical area is completely covered. Patients often find this type of X-ray quite uncomfortable but reminding them to relax their musculature can help improve comfort levels.
Common errors that can affect the quality of the image include failing to remove glasses or jewelry which may mean these objects obscure anatomical structures. Using the incorrect size of film or the incorrect orientation for the area being examined can result in incomplete coverage. Incorrectly focusing the X-ray on the film may result in important anatomical structures being obscured. Additionally, if the patient fails to bite down properly, the Rinn instrument may become incorrectly angled.
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