Chapter 9

The World Health Organisation (WHO) created a classification system for the varying types of traumatic dental injuries (TDIs) in 1992 (WHO, 1992). Two years later, this classification was modified by Andreasen and Andreasen (1994) in order to define and categorise trauma entities not presented in the original WHO classification (Tables 9-1 to 9-4).

Reports on the prevalence of TDI vary considerably due to the lack of homogeneity between studies examining this epidemiological measure. A national survey carried out in the USA, with a cohort of 154 million people between the ages of 6 and 50, revealed that almost one in three 6 to 20-year-olds and one in four 20 to 50-year-olds had suffered TDI (Kaste et al, 1996).

The accurate diagnosis of TDI is reliant on the acquisition of a thorough history, coupled with a systematic examination of the patient. This examination includes special clinical diagnostic tests and an appropriate radiographic assessment of the injured area(s) of the dentition, supporting tissues and, when indicated, adjacent soft tissues. The radiographic assessment is, and can only be, an adjunct to, and a component part of, the diagnostic process.

TDIs are often associated with the development of post-injury complications, such as pulp canal obliteration (Andreasen et al, 1987), pulp necrosis (Andreasen and Pedersen, 1985), the development of apical periodontitis (AP), root resorption (Andreasen and Pedersen, 1985), and marginal periodontal breakdown (Andreasen and Pedersen, 1985; Oikarinen et al, 1987). Any of these undesirable sequelae may occur in isolation or in combination with one or more of the others, and may result in tooth loss. As such, it is important that traumatically injured teeth are followed up clinically and radiographically in a systematic manner and according to the International Association of Dental Traumatology (IADT) guidelines, to ensure the earliest possible detection and management of these complications (IADT, 2012a). In many cases, radiographic signs of pulpal and/or periapical pathosis may be the first indication of the development of these types of complications.

Radiographic assessment of TDI

Background

Contemporary guidelines for the radiographic assessment and follow-up of traumatically injured permanent teeth advise that two periapical radiographs and an anterior occlusal radiograph be taken to assess the injured tooth (Flores et al, 2007a, b; IADT, 2012a, b). Further radiographs are specifically indicated to identify debris or tooth segments that have become embedded in soft tissues. The periapical radiographs should be taken with a beam aiming device, with the central X-ray beam centred on the tooth in question. The X-ray beam in the second periapical (parallax) radiograph should be laterally orientated to the tooth being imaged (Flores et al, 2007a, b; IADT, 2012a). However, due to the limitations of conventional radiography, the true nature of certain TDIs are extremely difficult to visualise using conventional radiographic examinations, and this is reflected in the number of radiographs recommended by the guidelines to assess the affected teeth.

Injuries occurring in the plane of the radiographic exposure (e.g. palatal luxation injuries, and fractures and comminution injuries to the labial cortical plate) and those obscured by overlying and adjacent anatomy (e.g. horizontal root fractures in which the X-ray beam is not orientated along the fracture line) may be very difficult to diagnose using conventional radiography (Andreasen, 1970; Bender and Freedland, 1983; Andreasen and Andreasen, 1985; Andreasen and Andreasen, 1988; Andreasen, 2007).

Though not yet considered routine in the assessment of TDI, cone beam computed tomography (CBCT) has been shown to improve the visualisation and nature of dentoalveolar injuries (IADT, 2012a), and is indicated in situations where conventional radiographs yield limited information (Patel and Saunders, 2013; European Society of Endodontology CBCT position statement, 2014).

CBCT is indicated in current IADT guidelines as a tool that improves the monitoring of healing and assessment of complications following TDI (IADT, 2012a). Systematic conventional radiographic follow-up of traumatically injured teeth is advised and may be necessary for up to 5 years, depending on the nature of the injury (IADT, 2012a, b).

Radiographic assessment of specific TDI

a. Injuries to the hard tissues and dental pulp

Conventional radiography

Crown fracture. The extent and nature of crown fractures (enamel infraction, uncomplicated crown fracture, and complicated crown fracture; see Table 9-1) are generally diagnosed from the history provided and the clinical examination carried out. Radiographic assessment of crown fractures is nonetheless necessary in order to rule out more serious concomitant TDI not necessarily evident clinically. Furthermore, radiographs taken at the time of the injury provide information about the size of the pulp and the stage of root development of the affected tooth/teeth (Fig 9-1). These radiographs are a baseline record with which subsequent follow-up radiographs can be compared in order to assess the pulpal and periapical status of the tooth and the development of complications over time.

In the case of complicated crown fractures that have been treated using vital pulp therapy techniques, the baseline radiographs can also be used to evaluate the development of a hard tissue barrier over the pulpal exposure with time. Uncomplicated and complicated crown fractures should be assessed according to the IADT guidelines (IADT, 2012a).

Enamel infractions should be assessed with a single periapical radiograph only, unless signs or symptoms indicative of other problems are present. In the event of a crown fracture (of any type) occurring in isolation, the radiographic appearance of the affected tooth (apart from the loss of coronal tooth tissue) should appear normal. The tooth will have normal periapical architecture and the root form should be appropriate for the stage of development of the tooth.

Crown–root fracture. Crown–root fractures (Table 9-1) are most often clinically diagnosed based on the history provided, the symptoms the patient is experiencing, and visualisation of the fracture. Crown–root fractures in anterior teeth commonly have an oblique orientation and may be minimally displaced (Figs 9-2 and 9-3), as the fractured portion is retained in position by the fibres of the periodontal ligament (PDL). As such, they can be missed clinically, especially when occurring in posterior teeth, where the fracture orientation will be similar to that in anterior teeth but may involve the occlusal surface instead of extending onto the labial aspect of the tooth crown.

Crown–root fractures should be assessed according to the IADT guidelines (IADT, 2012a). However, the apical extent of crown–root fractures with the common oblique orientation is very often difficult to visualise using conventional radiographic examinations, regardless of the number of parallax exposures. This is because the oblique fracture will tend to run almost perpendicular to the X-ray beam in each of the examinations, and the fractured subgingival fragment is generally well adapted to the root of the tooth. The limitations of conventional radiographic examination (see Chapter 1) means it tends not to add to the information obtained from the clinical examination (Andreasen et al, 2007b).

Crown–root fractures with a buccolingual orientation will be more readily evident on conventional radiographs, as the X-ray beam will pass through the fracture line. Crown–root fractures with a mesiodistal orientation will be more difficult to detect with conventional radiographic views, as the fracture orientation will be perpendicular to the plane of the X-ray source. The periapical anatomy of the injured tooth will appear normal on conventional radiographs immediately after the injury, as long as there is not a concomitant luxation injury.

Horizontal root fracture. The diagnosis of horizontal root fractures (HRFs) is reliant on the radiographic demonstration of the injury (Andreasen et al, 2007a). However, HRFs are generally only visible on conventional intraoral radiographs when the central X-ray beam is orientated either directly through the fracture line, or within a maximum range of 15- to 20-degrees of the orientation of the fracture line (Bender and Freedland, 1983; Andreasen and Andreasen, 1988). When the X-ray beam passes directly through the fracture line, it will be represented radiographically as a single transverse radiolucency across the root. As the X-ray beam deviates from the plane of the fracture line (within the 15 to 20 degree range), the fracture will take on a more ellipsoid appearance on the radiograph (Figs 9-4 and 9-5). With greater deviations of the X-ray beam from the fracture plane, the fracture line becomes undetectable (Andreasen and Hjørting-Hansen, 1967). These are the findings in the presence of a single transverse fracture line. Multiple root fractures will have an irregular appearance radiographically (Andreasen and Hjørting-Hansen, 1967).

The course of HRFs can vary considerably, but is generally obliquely (more common in apical or mid-root fractures) or horizontally (more common in cervical third fractures) orientated. As such, periapical radiographs with a 90-degree horizontal angulation relative to the tooth under examination will be more useful at detecting horizontally orientated fractures, while occlusal views will be more useful at detecting oblique fractures. Multiple radiographic exposures are therefore necessary to assess teeth for HRFs (May et al, 2013; IADT, 2012a). However, even in situations where multiple exposures are utilised, HRFs may not always be detected in the immediate aftermath of the injury, especially if the fractured portions are still closely juxtaposed. Subsequent radiographs may then reveal a fracture. This may be due to separation of the fractured segments following subsequent haemorrhage, or granulation tissue build-up at the site of the fracture, or in the adjacent alveolar bone (Andreasen and Andreasen, 1988).

CBCT

Crown fracture. In cases of crown fracture, a CBCT examination might be prescribed to assess the affected tooth, or teeth, for more serious concomitant injuries. In the event that the injury is an isolated crown fracture, the CBCT data will provide a more diagnostically accurate and reliable assessment of the health of the periodontal tissues and the root of the affected tooth than that which can be provided by conventional intraoral radiography (Patel et al, 2009a; Durack et al, 2011) (Fig 9-1). In uncomplicated crown fractures, the thickness of the dentine wall at the base of the fracture and overlying the coronal pulp can be measured and compared with future scans to obtain a reliable qualitative and quantitative assessment of the degree of tertiary dentine formation following the injury. This provides some adjunctive information about the health of the pulp. In the same manner, in complicated crown fractures, review CBCT scans can be compared to the assessment scan taken at the time of the injury to objectively assess the presence and thickness (using measuring tools) of any dentine bridge formation over the exposed pulp. Conventional intraoral radiography can only offer a subjective assessment of dentinal bridge and tertiary dentine formation following crown fractures (Fig 9-1).

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