Dental imaging methods for the detection of early tooth decay

Tanya Walsh, Richard Macey, Philip Riley, Anne-Marie Glenny, Falk Schwendicke, Helen V Worthington, Janet E Clarkson, David Ricketts, Ting-Li Su, Anita Sengupta

Why is it important to improve the detection of dental caries (tooth decay)?

Dentists often aim to identify tooth decay that has already advanced to a level which needs a filling. If dentists were able to find tooth decay when it has only affected the outer layer of the tooth (enamel) then it is possible to stop the decay from spreading any further and prevent the need for fillings. It is also important to avoid a false-positive result, when treatment may be given when caries is absent.

What is the aim of this review?

This Cochrane Review aimed to find out how accurate X-ray images and other types of dental imaging are for detecting early tooth decay as part of the dental 'check-up' for children and adults who visit their general dentist. Researchers in Cochrane included 77 studies published between 1986 and 2018 to answer this question.

What was studied in the review?

Three main types of dental imaging were studied in this review: analogue or digital radiographs (X-rays) and three-dimensional (3D) imaging (cone beam computed tomography (CBCT)). We studied decay on the occlusal surfaces (biting surfaces of the back teeth), the proximal surfaces (tooth surfaces that are next to each other), and smooth surfaces.

What are the main results of the review?

Researchers in Cochrane included 77 studies with a total of 15,518 tooth sites or surfaces, where typically 63% of tooth sites or surfaces had enamel caries. Some of these studies reported on more than one type of imaging, on both the permanent and primary ('milk') teeth or different tooth surfaces, and this gave us 104 sets of data to use. If these methods were to be used by a dentist for a routine dental examination, out of 1000 tooth sites or surfaces seen:

  • the use of these methods will indicate that 336 tooth sites or surfaces will have early tooth decay, and of these, 43 (13%) will have no disease (incorrect diagnosis - false positive);
  • of the 664 tooth sites with a result indicating that early tooth decay is absent, 337 (51%) will have early tooth decay (incorrect diagnosis - false negative).

This high proportion of false-negative results means that early signs of decay will be missed. We found evidence that 3D imaging methods were better than analogue or digital radiographs at identifying early disease but that analogue radiographs were better at identifying disease-free tooth surfaces.

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How reliable are the results of the studies in this review?

We only included studies that assessed healthy teeth or those that were thought to have early tooth decay. This is because teeth with deep tooth decay would be easier to identify. However, there were some problems with how the studies were conducted. This may result in these methods appearing more accurate than they are, increasing the number of correct results. We judged the certainty of the evidence to be low due to how the studies selected their participants and the large number of studies that were carried out in a laboratory setting on extracted teeth, and the variation in the results.

Who do the results of this review apply to?

Studies included in the review were carried out in South America, Europe, Asia, and the US. A large number of studies examined extracted teeth, while clinical studies were completed in dental hospitals or general dental practices.

What are the implications of this review?

Low-certainty evidence suggests that imaging for the detection or diagnosis of early tooth decay may result in a relatively high proportion of false-negative results, with the potential for early disease to become more advanced. If left untreated, the opportunity to provide professional or self-care practices to arrest or reverse early tooth decay will be missed.

How up-to-date is this review?

The electronic searches retrieved used studies published up to 31 December 2018.

Read the full review.

Walsh T , Macey R , Riley P , Glenny A-M , Schwendicke F , Worthington HV , Clarkson JE , Ricketts D , Su T-L , Sengupta A . Imaging modalities to inform the detection and diagnosis of early caries. Cochrane Database of Systematic Reviews 2021, Issue 3. Art. No.: CD014545. DOI: 10.1002/14651858.CD014545.