Cone-beam computed tomography in pediatric dentistry

 

Introduction

Cone-beam computed tomography (CBCT) is used for a wide variety of dental diagnostic uses, including in children and young people. CBCT typically has a radiation dose of one or more orders of magnitude greater than that for conventional radiography. This is important in pediatric use because of the higher levels of risk associated with X-ray exposure in young age groups. This has stimulated efforts on justification and dose optimization of CBCT in the pediatric context. In addition, the financial costs of using CBCT instead of, or in addition to, conventional imaging is likely to raise the overall costs of healthcare unless its use leads to cost-savings elsewhere along the patient care pathway.

Radiation dose and risk are not primary determinants of whether or not to use a diagnostic X-ray technique. An importat principle of radiation protection, justification, requires that the potential benefits of its use outweigh the risk. Criteria for using an imaging modality should be based on evidence rather than opinion, ideally on a body of evidence at the higher levels of diagnostic efficacy with a low risk of bias.

 

Can CBCT be used safely in pediatrics?

 

Caries detection

The research relating to CBCT and caries diagnosis relied predominantly on ex vivo research and most studies indicated a minor difference in diagnostic accuracy when CBCT imaging was used compared with intraoral radiography. Ex vivo/in vitro imaging might result in better quality images than those obtained clinically, while artifact from adjacent high attenuation restorations is usually absent. An ex vivo study reported that the cavitation of proximal lesions can be identified more accurately when using CBCT than when using bitewing radiographs. The same group followed this up by a clinical diagnostic accuracy study, included in our review, which confirmed the ex vivo findings and concluded that cavitated caries should be reported on scans taken for other purposes. There was no research evidence at higher levels of diagnostic efficacy. Existing guidelines provided a unanimous view against using CBCT as a standard tool for caries diagnosis.

 

Acute dental infections

There was no diagnostic efficacy evidence to suggest that acute dental infection is an indication for CBCT and no relevant guidelines were found. There was evidence, from systematic reviews of ex vivo studies, that using CBCT can give a higher diagnostic accuracy efficacy than conventional radiography for mechanically or chemically prepared periapical bone cavities. Research from observational studies of patients shows that using CBCT results in greater numbers of periapical inflammatory lesions being identified than when periapical radiography is used. Although there is a risk that false-positive diagnoses are partly responsible for this, it seems likely that true diagnostic yield from CBCT is higher than from radiographs. Several guideline publications suggest that CBCT might be used as an aid to the diagnosis of periapical pathosis when conventional radiography reveals nothing but there are contradictory clinical signs and/or symptoms.

 

Dental trauma

The evidence from systematic reviews of diagnostic accuracy studies predominantly performed ex vivo is that, for non-endodontically treated teeth, CBCT can lead to very high diagnostic accuracies for root fracture. Furthermore, these levels of accuracy are higher than when using periapical radiographs. The fact that ex vivo studies lack the impact of patient movement and that the systematic reviews identified risks of bias in a large proportion of these must be recognized. For endodontically treated teeth, most of the evidence suggested that diagnostic accuracy using CBCT for detecting root fracture is lower and that false-positive diagnoses may occur. No solely pediatric studies were available and none on trauma to teeth from the primary dentition. The diagnostic thinking efficacy study by Bornstein et al. (2009), found that fracture location on the palatal surface of the root was more coronally placed on CBCT than on radiographs. In particular, a cervical fracture was more commonly seen on CBCT, potentially influencing management. This paper was cited in a review publication by May et al. (2013) who devised a pathway for selection of CBCT that is potentially useful, but which needs further research on its impact.

 

Dental anomalies

The evidence in this context dealt with localization of unerupted and impacted teeth, mainly permanent maxillary canines. Although one diagnostic accuracy study was identified, which reported high accuracy for tooth localization, it was of low quality. The diagnostic thinking studies have each reported that using CBCT led to a change in diagnosis of tooth position in a substantial minority of cases, although none of the studies was of the highest quality. Studies that looked at changes in treatment planning using CBCT found these in a proportion of cases, with increased confidence of clinicians. It seems likely that these findings would be true for any unerupted tooth requiring treatment. There was no evidence that patient outcomes are changed, but there was an increase in financial costs when using CBCT. There was little diagnostic efficacy evidence for other dental anomalies apart from case studies. These included reports that CBCT was useful to image morphological anomalies of teeth, particularly in the context of planning endodontic treatment, notably for dens invaginatus anomaly, fusion, and gemination.

 

Developmental disorders

With regard to developmental disorders, the publications identified by the current review were dominated by CBCT imaging of cleft lip and palate (CLP) patients. The evidence suggested that CBCT scanning prior to the procedure of bone grafting is appropriate because it permits a volumetric assessment of the defect. It has advantages over CT in terms of radiation dose. It might be useful in imaging the teeth around a cleft, but the evidence that this changed treatment plans or prognosis was lacking in the literature. Management of clefts is not a specific role of pediatric dentists, although they may be part of an interdisciplinary team caring for a patient. Apart from CLP patients, the review found a role for CBCT in the production of three-dimensional datasets of the facial skeleton. There was very little evidence about the value of CBCT in specific craniofacial syndromes apart from some case studies.

 

Pathological conditions

The evidence regarding the diagnostic value of CBCT for resorption of teeth was weighted towards that associated with unerupted maxillary canine teeth. It is probably the most common pediatric use of CBCT and may be relevant to pediatric dentists working with their orthodontic colleagues. There is a reliance on ex vivo/in vitro studies of diagnostic accuracy. A review of such studies found higher sensitivity but equivalent specificity for resorption detection using CBCT compared with intraoral radiography. Artificial lesions, made with a bur or application of acid, are not the same as in vivo resorption. Nonetheless, on balance, it seems reasonable to suggest that a cross-sectional imaging technique, with sufficient image quality, will out-perform a two-dimensional technique for detecting resorptions of teeth, particularly on buccal and lingual surfaces. Studies on diagnostic thinking efficacy reported changes in diagnosis in a proportion of cases when using CBCT. Some of the clinical studies cited above did not use intraoral radiographs as comparator imaging, only panoramic radiography, which might underestimate the value of radiographs compared with CBCT. External cervical resorption is a different entity radiologically to resorption associated with tooth impactions and is impossible to model accurately in ex vivo studies. Several studies reported that using CBCT changed treatment plans in over half of cases.

 

Conclusions

No strong recommendations on CBCT are possible, except that it should not be used as a primary diagnostic tool for caries. Guidelines on the use of CBCT in the pediatric age group should be developed cautiously, taking into account the greater radiation risk and the higher economic costs compared with radiography. CBCT should only be used when the adequate conventional radiographic examination has not answered the question for which imaging was required. Clinical research in pediatric patients is required at the higher levels of diagnostic efficacy of CBCT.