Dental caries is still the principal challenge that occupies the efforts of clinical and public health dentists alike. Whether in the field of caries research, dental education and dental epidemiology or in the clinical decision making in dental practices, the appropriate means of caries detection and measurement is required. This has led to proliferation of literature about how best to detect and diagnose dental caries in various settings [1
]. The most common and traditional method is by a visual inspection of the tooth surfaces. Great progress has been made in the development of novel techniques and technologies that aid the detection of dental caries. These caries detection aids aspire to increase the sensitivity of visual caries detection as well as maintaining a good level of specificity [2
]. The majority of these systems were validated using visual caries determination methods [3
]. The need for clinically reliable caries detection methods has however led to the development and refinement of visual systems such as the ICDAS (International Caries Detection and Assessment System) and the Universal Visual Scoring System (UniViSS) [6
Dental surveillance surveys and large epidemiological studies have traditionally depended on the use of visual dental examination techniques as the caries detection method. This is because for dental public health purposes, visual determination is simple, requires low technology and is easy to administer. This method of caries detection is however not appropriate in comparative studies where examiners collecting caries information need to be “blind” to various attributes of the different populations; for example the residential status of participants in the evaluation of water fluoridation schemes or to the allocation of participants in randomized control trials. Other caries detection methods such as radiographs, or more innovative techniques/technologies such as Quantitative Light-induced Fluorescence (QLF), fibre-optic trans-illumination (FOTI) and electronic caries monitoring (ECM) [8
] will not be suitable to use in such studies for a variety of reasons.
The use of radiographs to ensure examiner “blinding” is an unviable proposition as it is fraught with ethical dilemmas in terms of justifiable risks from exposure to ionizing radiation and problems with validity in detecting occlusal caries [9
]. Although dental caries and enamel fluorosis present as different lesions, it may be difficult to use the QLF techniques that are commercially available to make a distinction [10
]. QLF is more suited to laboratory based research and clinical work involving precise measurement of changes in mineralization of tooth-tissue. ECM is a very sensitive caries detection method which can be affected by factors such as the presence of water, ambient light, and tooth temperature [11
As digital imaging fibre-optic trans-illumination (DiFOTI) produces images that can be stored, it could be considered for ensuring examiner “blinding”. It is however very cumbersome to handle and time consuming to use. It also requires considerable amount of training to achieve the level of competence needed for it to be used as a caries detection method [8
]. As such, none of the so called “novel” methods for caries detection appear appropriate for use in epidemiological studies where blinding is required.
However, a simple and economical method of “blinding” may be for examiners to inspect photographs of participants’ teeth rather than examine the subjects visually.
Photographic images have been used in dentistry in a variety of ways [12
] and intra- and extra- oral cameras have evolved rapidly over recent years with a commensurate decrease in cost and complexity of use. With the advancement in technology, there are various intra-oral cameras now in use in clinical dental practice. There are however very few studies in the literature that have investigated the use of intra-oral images and caries diagnosis. In a study by Elfrink et al [15
], intra-oral photographs were used to score caries and hypo-mineralization on primary molars in a clinical setting and the results suggest that intra-oral photographs may be used in clinical practice and large epidemiological studies with some degree of confidence. The main method of caries determination in the UK National Health Service epidemiological surveys is via a visual examination method developed and described by the British Association for the study of Community Dentistry (BASCD) [16
]. Before intra-oral photographs can be recommended for use in epidemiological studies their performance must be assessed against the established BASCD visual examination method and the reference standard for caries diagnosis of histological section.
The purpose of this study was to compare diagnostic performance for the detection of caries into dentine of photographs with an established visual examination method and histological section as the reference standard. The following hypotheses will be tested to determine if:
1. There is significant difference in visual examination scores for the extracted teeth recorded by a group of examiners (to test inter-examiner reliability for the visual examination)
2. There is significant difference in visual examination scores for the extracted teeth recorded by the same examiner on two different occasions (to test intra-examiner reliability for the visual examination method)
3. There is a significant difference in photographic assessments of the extracted teeth viewed by a group of assessors (to test inter-examiner reliability for the photographic assessments)
4. There is a significant difference in assessments scores of photographs of the extracted teeth viewed by the same assessor on two different occasions (to test intra-examiner reliability for the photographic assessments)
5. There is a significant difference in recorded dental caries between the visual, photographic and histological methods of detecting caries at “the caries into dentine” level.