Zain 2018.

Study characteristics
Patient Sampling	Method of sampling: selected; "ninety preliminary investigation sites with ICDAS code 0, 1, 2 (n = 30 each) were identified" Included conditions: sound and early caries teeth Teeth: permanent premolars Sealants: not reported Restorations: not reported Surface: occlusal
Patient characteristics and setting	Age: not reported Sex: not reported Ethnicity: not reported Country: Malaysia Setting: extracted teeth Number of participants/teeth/sites: 54 teeth, 71 sites Prevalence: enamel 0.7, dentine 0
Index tests	Category of test: SS‐OCT Imaging System (OCS1300SS, Thorlabs Ltd, UK) Sequence of test(s): OCT prior to reference standard Examiner training and calibration: "two trained and calibrated examiners" Threshold applied: "non‐cavitated fissure caries is considered to be present when bands of elevated back scattered intensity, in the range of ‐15 dB to ‐5 dB, which are sub‐surface and diffused in nature were observed. Intensity in the same range which is limited to one to two pixels thick on the surface was NOT considered as carious" Device specifics: "intensity range is presented as yellow and red by the Large DR3 colour map of the Thorlabs OCT capturing software"
Target condition and reference standard(s)	Category: histology ‐ polarized light microscopy Sequence of index test and reference standard: index test then reference standard Training of examiner: 2 trained and calibrated examiners Blinding to index test: not clearly reported Multiple tests: no Site selection: sectioned teeth Target condition: sound, enamel caries; "absence of dark brown and black areas at the investigation sites were considered as sound whereas, the presence of these dark brown and black areas were regarded as carious"
Flow and timing	Participants with index test but no reference standard: unclear "a final cohort of seventy one investigation sites were selected based on the Ekstrand histology criteria" Participants with reference standard but no index test: 0 Time interval between tests: minimal Participants receiving both tests but excluded from results: 71/104 included in final analysis
Comparative
Notes
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	No
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Unclear
Could the selection of patients have introduced bias?		High risk
Are there concerns that the included patients and setting do not match the review question?			High
DOMAIN 2: Index Test (All tests)
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
If multiple tests were applied were different examiners used for each (in vivo)?
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 3: Reference Standard
Is the reference standards likely to correctly classify the target condition?	Yes
Were the reference standard results interpreted without knowledge of the results of the index tests?	Unclear
Could the reference standard, its conduct, or its interpretation have introduced bias?		Low risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and Timing
Was there an appropriate interval between index test and reference standard?	Yes
Did all patients receive the same reference standard?	Yes
Were all patients included in the analysis?	No
Could the patient flow have introduced bias?		High risk

CP‐OCT = cross‐polarization optical coherence tomography; DIFOTI = digital fibre‐optic transillumination; ECM = electronic caries monitor; FOTI = fibre‐optic transillumination; ICDAS = International Caries Detection and Assessment System; microCT = microcomputed tomography; NIR = near‐infrared; OCT = optical coherence tomography; QLF = quantitative light‐induced fluorescence; SS‐OCT = swept source optical coherence tomography.