Characterization of enamel in primary teeth by optical coherence tomography for assessment of dental caries.

BACKGROUND: Caries is a disease that affects both primary and permanent dentitions, therefore new methods of caries diagnosis need to be tested on primary teeth as well as on permanent teeth. AIM: This study reports the application of optical coherence tomography (OCT) to characterize sound dental structure and detect natural caries of human primary teeth. DESIGN: Six primary teeth were sectioned into thin slices ( approximately 1.5 mm), and analysed perpendicular to the enamel surface by two home-made OCT systems operating around 1280 and 840 nm. The generated images were compared with histology as the gold standard. RESULTS: We demonstrated the efficacy of the OCT technique to measure the depth of the enamel layer, whose result was statistically compared with histology (P = 0.823; P > 0.05) with good agreement. We also determined, through measurement of contrast values, an increase in backscattered intensity of the order of two to three times between sound and caries regions. CONCLUSIONS: We employed OCT generated images to characterize the enamel layer. The technique showed great potential to be used on paediatric dentistry clinical on early caries detection with no pain, as it is a noninvasive method.

In vitro imaging of remaining dentin and pulp chamber by optical coherence tomography: comparison between 850 and 1280 nm.

We report the application of optical coherence tomography (OCT) to generate images of the remaining dentin and pulp chamber of in vitro human teeth. Bidimensional images of remaining dentin and of the pulp chamber were obtained parallel to the long axis of the teeth, by two OCT systems operating around 1280 and 850 nm, and compared to tomography images using the i-CAT(R) Cone Beam Volumetric Tomography system as the gold standard. The results demonstrated the efficacy of the OCT technique; furthermore, the wavelength close to 1280 nm presented greater penetration depth in the dentine than 850 nm, as expected from scattering and absorption coefficients. The OCT technique has great potential to be used on clinical practice, preventing accidental exposure of the pulp and promoting preventive restoration treatment.

Near-infrared transillumination of teeth: measurement of a system performance.

Transillumination (TI) of dental enamel with near-infrared light is a promising nonionizing imaging method for detection of early caries lesion. Increased mineral loss (caries lesion) leads to increased scattering and absorption. Caries thus appear as dark regions because less light reaches the detector. The aim of this work was to characterize the performance of a TI system from the resolution of acquired images using the modulation transfer function at two wavelengths, 1.28 and 1.4 mum. Test charts with various values of spatial periods, mimicking a perfect caries lesion, were attached to tooth sections, followed by capture of the transmitted image, using both wavelengths. The sections were then consecutively reduced in thickness, and a sequence of all sizes of the test charts were used for repeatedly imaging procedures. The results show that the TI system can detect feature size of 250 mum with 30% modulation. From the information about how the image degrades as it propagates through enamel, we also examined the possibility of estimating the position of a simulated approximal caries lesion by comparing images obtained from the two sides of a tooth section.