2. Index tests for caries.

Test	Characteristics	Intended use in clinical pathway	Other information
Visual or visual‐tactile examination	Identifying caries according to their visual appearance, aided by a dental mirror and probe, on clean and dry teeth	The fundamental step in the detection of caries, but limited in the diagnosis of early lesions. All patients presenting to a dental clinician will receive a visual examination	Advantages: completed and interpreted quickly with minimal invasion and little cost except clinician training and time Disadvantages: early caries are difficult to observe visually, depth and severity of lesions cannot be assessed, approximal lesions cannot be seen
Radiography	Bitewing radiology is the most commonly used method. Others include: subtraction radiographs which provides a semi‐automated method for monitoring progression of lesions (Ellwood 1997; Wenzel 2000) and cone beam computed technology (CBCT) which provides a 3‐dimensional image which appears to offer great potential for diagnosis with increased levels of radiation (Horner 2009)	Widely used as an adjunct to aid detection and in particular to inform the clinician of the depth and severity of lesion (Wenzel 1995; Whaites 2013) Relevant on occlusal surfaces but also in approximal location which are otherwise difficult to assess visually	Advantages: radiographs aid the detection of caries and are shown to be more sensitive than visual examination on approximal and occlusal lesions (Wenzel 2004) Disadvantages: limitations exist when detecting early caries in enamel surfaces. There is a small but real risk over patient exposure to ionising radiation, which has to be balanced with the patient's age, caries risk, and time since previous radiograph (Pitts 2017). Digital radiographic methods have shown benefits for patients with the speed in which they can be viewed and for the ability to manipulate images for increased clarity (Wenzel 2006)
Fluorescence	The breakdown of enamel alters the characteristics of its structure, when exposed to light‐inducing fluorescence diseased teeth respond differently to sound teeth. There is potential for mineral loss to be quantified and used to aid the diagnostic decision and treatment pathway (Angmar‐Månsson 2001; Matos 2011). Fluorescence is typically divided into laser fluorescence and light fluorescence (i.e. DIAGNOdent type devices and quantitative light‐induced fluorescence (QLF) type devices)	Potential to aid the clinician in identifying early caries which may not be possible with a visual examination alone. QLF emits either green or red light and may ascertain whether the lesion is active or arrested	Advantages: the potential to identify changes in tooth characteristics that are otherwise unobservable in a visual‐tactile examination Disadvantages: uncertainty of the reliability of devices and the ability to detect disease and health
Fibre‐optic transillumination	Fibre‐optic transillumination (FOTI) uses a light emitted from a handheld device which when placed directly onto the tooth illuminates the tooth (Pretty 2006). Any demineralisation should appear as shadows in the tooth due to the disruption of the tooth's structure due to caries	An adjunct to the visual examination, particularly useful for detecting approximal caries, with its strength being in identifying early caries in enamel and dentine (Davies 2001). A further advancement with fibre‐optic techniques combines this with a camera to capture an image which may or may not be linked to software for analysis, digital imaging FOTI (DIFOTI)	Advantages: the potential to identify changes in tooth characteristics that are otherwise unobservable in a visual‐tactile examination Disadvantages: uncertainty of the reliability of devices and the ability to detect disease and health
Electrical conductance	The demineralisation of the tooth is reported to have an effect on the tooth's electrical conductance. This is measured by placing a probe on the tooth which measures any potentially higher conductivity which occurs due to carious lesions being filled with saliva (Tam 2001)	An adjunct to the visual examination	Advantages: the potential to identify changes in tooth characteristics that are otherwise unobservable in a visual‐tactile examination Disadvantages: uncertainty of the reliability of devices and the ability to detect disease and health. Particularly due to the necessity to place the probe in an identical location for a reproducible result