BACKGROUND
Many traumatic dental injuries present to medical general practitioners or hospital emergency departments as either isolated injuries or as an under recognised part of multi-trauma events [1]. Without appropriately trained dental staff present to perform a thorough assessment, it is often left to the hospital radiologist to detect traumatic injuries to the teeth and surrounding structures in these circumstances [2]. Early and accurate diagnosis has been found to have a significant effect on the prognosis of traumatised teeth, especially when early referral is required to facilitate effective tooth saving management [3] When other injuries are present, injuries to the teeth and supporting structures are often overlooked, and although they are rarely life threatening their misdiagnosis can ultimately lead to the loss of injured teeth, which has functional, aesthetic and social consequences that can seriously impact upon quality of life [4]. This educational exhibit aims to enhance the diagnostic confidence of traumatic dental injuries by providing a brief revision of the relevant dental anatomy, a review of the classification of dental injuries (with corresponding clinical correlation) and a pictorial display of key radiographic findings to look for while screening for dental injury.
NORMAL RADIOGRAPHIC ANATOMY
The image is that of a lower molar, aquired via Cone-beam CT (CBCT) and displayed in a sagittal section. The tooth is divided into 2 main regions, the crown (the visable part of a normal healthy tooth) and the root (usually not visable clinically unless the gingiva has receded or the tooth is over erupted).
The crown has an outer casing of enamel 1-2mm thick, surrounding an inner core of dentine that houses the pulp chamber at its center. Radiographically, the enamel is easily deliniated from dentine due to it being much more radiopaque.
The root has no enamel on its surface, but instead a softer substance known as cementum which embeds the fibres of the periodontal ligament and holds the tooth within its socket (alveolar bone). The cementum surrounds the radicular dentine, which houses a variable number of root canals (2 in this image) that transmit nerves and vessels from the root apex to the pulp chamber, thus allowing the tooth to remain vital.
Surrounding the root of the tooth is the alveolar bone of the corresponding jaw (mandible in this case). The cortex of this bone (Lamina Dura) makes up the walls to each tooth socket. The radiolucent space bewteen the lamina dura and the cementum of the tooth root is known as the periodontal space, which contains the periodontal ligament and normally measures between 0.15-0.21mm. Widening or loss of this space can indicate periodontal pathology in cases of trauma (luxation injuries).
CLASSIFICATION OF TRAUMATIC DENTAL INJURIES
Below is a schematic representation of the sites of injury to the dentition, with more in depth descriptions within the tables that follow. A key deliniation to make within the diagnostic process is the risk to the vital structures of the teeth, that being the pulp chamber and root canals. Any exposure of the dental pulp results in a significant worsening of the prognosis of the tooth without treatment, thus why these injuries are referred to as "complicated" fractures.
CLINICAL PEARL: Crown fractures are most commonly reported in permanent (adult) teeth, with the maxillary incisors being the teeth most affected due to their position in the mouth and relationship to other teeth.
CLINICAL PEARL: Luxation injuries are the most common traumatic injury in the primary (baby) teeth. Primary teeth are not discussed within the scope of this exhibit.