Introduction

Other than cost, one of the most commonly used excuses for not having a dental radiograph unit is the lack of information or training available on reading and diagnosing dental radiographs. Everybody can figure out what a tooth looks like, but how do you know something is wrong?

This lecture will first discuss the structures seen on the normal dental radiograph and then move into commonly seen pathology in the private practice. As with any procedure the more times you perform it or train on the topic, the better you will get at it and the more confident you will feel. Dental radiology is crucial to piecing together the diagnosis and subsequent dental treatment plan.

Since dental radiographs are small in size, there is no space to place a right/left marker. Dental film does come complete with a solution for that – the bubble or dimple. On digital systems, there can be square shape on the image. The bubble has two sides - convex and a concave. The convex side is the side that is facing the radiographic beam. There are two ways to use this bubble – 1) when the convex side of the beam is facing the examiner, you are essentially looking at the patient nose to nose, and 2) when you look at the film with the concave side of the bubble facing you, you are looking at the teeth from the inside of the patient's mouth looking out. Which ever way you choose, you must be consistent. Everyone at the clinic must agree on which side of the bubble to look at. The most commonly used method is the convex side up.

With the digital system, contact technical support to confirm film orientation.

Next, if you are looking at maxillary cheek teeth, the crowns should be pointing down and for mandibular cheek teeth the crowns should be pointing up. The cheek teeth should be positioned with the mesial teeth towards the center. Hence, knowing you dental anatomy is very important.

1→P4→P3→P2→P1→I3→I2→I1→Nose←I1←I2←I3←P1←P2←P3←P4←M1

Once your radiographs are dry, use film mounts – placing the films with the bubbles/dimples facing the same way (convex, concave) with the labial most teeth towards the center. Make sure they are labeled and dated so that you can monitor progress.

Normal anatomy

Dentin – The dentin is generally the radiopaque structures of the tooth

Pulp Chambe /Root Canal – The pulp chamber in the crown and the root canal in the root are the internal radiolucent structure that runs through the center of the tooth.

Periodontal Ligament – The periodontal ligament suspends the tooth to the alveolar bone. It appears as a radiolucent line between the tooth and the alveolar bone.

Alveolar Bone – The alveolar bone provides the socket where the tooth resides.

Lamina Dura – The lamina dura is cortical bone which lines the alveolus. The lamina dura appears as a radiopaque line between the periodontal ligament and the alveolar socket.

Mental foramina – The middle and posterior mental foramina are found on the buccal aspect of the mandible just apical to the second premolar and third premolar respectively. They are radiolucent and, depending on the angle of your x-ray beam, can be confused for an area of bone lysis. A solution for this problem is to reshoot the radiograph. The position of the foramina will shift with relation to the beam. The area of lysis will not move.

Symphysis – The symphysis is where the two sides the of the mandible meet. The joint is fibrous and presents as a thin, irregular radiolucent line between the two sides.

Mandibular Canal – The mandibular canal houses the nerves and vessels which supply the mandibular teeth. It is a radiolucent tube that runs along the ventral border of the mandible.

Palatine Fissures – The palatine fissures are located on the ventral rostral aspect of the maxilla. On radiograph they appear as two side-by-side radiolucent ovals with the radiopaque line of the nasal septum running between them.¹