There are a variety of dental radiographs, or x-rays, that we take. Dental radiographs can broadly be divided in to two categories:
- Intra-oral – where the x-ray film is inside the mouth
- Extra-oral – where the x-ray film is outside the mouth
Intra-oral Dental Radiographs
These radiographs are typically routine screening radiographs taken on patients. One bitewing is taken for each side to assess the posterior teeth. These are usually done in a horizontal manner, however they can also be done vertically to gain some more information.
Bitewings are useful for 2 main reasons:
- Caries assessment – they can help identify caries which is not clinically detectable such as interproximal caries or recurrent caries
- Bone assessment – they can allow us to look at bone levels in patients – typically healthy levels or with early bone loss
Periapical (‘around the apex’) radiographs are usually used to assess specific teeth. They provide you with more detail of structures around particular teeth.
Periapical radiographs are used for numerous reasons:
- Assessment of periapical pathology – as in the image above, periapical radiographs can help assess for the presence of periapical infection associated with a tooth. This will typically present as a radiolucent area. Other periapical pathology may also be visible such as cementoblastomas etc.
- Endodontic treatment – periapicals can be used through endodontic treatment to assess progression of stages including working length radiographs and obturation radiographs.
- Periodontal disease – periapicals are the gold standard radiograph for these patients. They can be used to assess moderate to severe boneloss cases.
- Ectopic teeth – periapical radiographs can be used to identify and localise ectopic teeth using a parallax technique (where 2 periapicals are taken in different positions to assess the location).
- Assessment of root morphology – this may be important prior to dental extractions, particularly for wisdom teeth.
These can either be maxillary, or upper occlusals, or mandibular, lower occlusals.
For this type of radiograph, the x-ray film is placed horizontally between the teeth, as shown below.
These views are helpful for a variety of reasons:
- Localisation of ectopic or impacted teeth
- Identification of salivary calculi – this is useful if there is believed to obstruction of the submandibular gland
- Identification of pathology, including cysts with bucco-lingual expansion
- Identification of foreign bodies
Due to the fact the film is placed between the teeth, occlusal views are also helpful in patients with trismus.
Extra-oral Dental Radiographs
Panoramic Radiographs (OPT/DPT/OPG)
This view is taken with a machine that rotates around the patient’s head. They provide us with an overview of the dentition as well as surrounding anatomy. They do not provide the detail that a periapical or bitewing may provide us, but they give us an overall view.
Reasons for carrying out a panoramic film include:
- Patients who cannot tolerate intra-oral views – this may be due to a strong gag reflex, and an OPT will provide us with an overview of their dentition.
- Assessment of wisdom teeth – OPTs allow us to assess the morphology of wisdom teeth but, more importantly, allow is to assess the interaction of the wisdom tooth with the inferior alveolar nerve.
- Assessment of trauma – OPTs enable assessment of mandibular fractures and, in conjunction with other views, assessment of fracture displacement.
Many of the newer OPT machines allow for sectional views. For example, if you only want to assess the lower right wisdom tooth, then you can just take a right-sided OPT. This reduces the radiation dose to the patient.
You can learn more about interpreting the anatomy of OPTs here.
Oblique Lateral Radiographs
Oblique lateral radiographs are helpful when patients cannot tolerate intra-oral radiographs. They are particularly helpful in children who may have reduced co-operation.
For an oblique lateral radiograph, the patient sits with the film against the side of their face and the x-ray beam coming obliquely from the opposite side of the face. This will ideally capture both sides of the jaw.
As well as assessing caries, they can be used to assess general jaw pathology.
Posteroanterior (PA) Radiographs
These can either be of the skull or of the mandible. PA skull views are helpful in assessing for pathology of the skull, such as Paget’s disease, or fractures of the skull vault.
For this type of image, the patient sits facing the x-ray film with their forehead and the tip of their nose touching the film. The x-ray tube is then placed behind the patient, horizontal to the occiput/base of skull.
For a PA mandible, the patient sits in the same way but we lower the beam so that it is level with the mandibular rami.
PA mandibles are usually done when assessing fractures of the mandible – commonly along with a panoramic film.
Occipitomental (OM) Radiograph
OM views are usually taken to assess fractures of the midface or sinus pathology. As we are usually assessing fractures with this view, we typically take it from two angles.
In order to take an OM view, the patient sits facing the x-ray film but, rather than having their head tilted forwards like in an PA mandible/skull, they tip their head backwards so that their chin is touching the x-ray film. For an OM 0º view, the x-ray tube is lined up horizontally with the occiput. In the image below, an OM 30º view is taken by then moving the x-ray tube to 30 degrees from the horizontal. This will provide us with two different views and we can compare them to assess any fractures.
These are usually taken as part of orthodontic treatment planning and to assess progression of treatment. They are taken using a cephalostat.
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