Intraoral versus extraoral bitewing radiography in detection of enamel proximal caries: an ex vivo study

Objective: To compare the diagnostic accuracy of digital intraoral and extraoral bitewing (EO BW) radiography in the detection of enamel proximal caries regardless of their ability to separate contacts. Methods: Artificial caries with different degrees of decalcification was induced in 80 human sound premolars and molars using formic acid. Intraoral radiographs were taken with photostimulable phosphor plate (PSP) and complementary metal oxide semiconductor (CMOS), using the paralleling bitewing technique. Extraoral bitewing radiographs were obtained using Sirona digital panoramic X-ray unit (Sirona Siemens, Bensheim, Germany). In total, 160 proximal surfaces were assessed by 2 observers twice. Area under the receiver operating characteristic curve (Az) values for each image type, observer and reading were compared using z-tests, with a significance level of p <= 0.05. Sensitivity, specificity, positive predictive value and negative-predictive value for each observer and reading were calculated. Results: Spearman's test showed a strong positive correlation between the duration of demineralization and histological grading of carious teeth surfaces. For the three radiographic techniques, intraobserver reliability was strong to excellent. Moreover, interobserver agreement was strong. The differences between all detection methods were not statistically significant (p > 0.05). Intraoral bitewing using CMOS sensor had the highest sensitivity while EO BW had the highest specificity in the detection of incipient proximal caries. Conclusions: Within the limits of the ex vivo design, the difference in diagnostic accuracy between the three radiographic techniques was not significant. EO BW could be used in the detection of enamel proximal caries with results comparable with intraoral bitewing with PSP plate and CMOS sensor.