Natural enamel caries in polarized light microscopy: differences in histopathological features derived from a qualitative versus a quantitative approach to interpret enamel birefringence

Abstract

Summary Lesion area measurement of enamel caries using polarized light microscopy (PLM) is currently performed in a large number of studies, but measurements are based mainly on a mislead qualitative interpretation of enamel birefringence in a single immersion medium. Here, five natural enamel caries lesions are analysed by microradiography and in PLM, and the differences in their histopathological features derived from a qualitative versus a quantitative interpretation of enamel birefringence are described. Enamel birefringence in different immersion media (air, water and quinoline) is interpreted by both qualitative and quantitative approaches, the former leading to an underestimation of the depth of enamel caries mainly when the criterion of validating sound enamel as a negatively birefringent area in immersion in water is used (a current common practice in dental research). Procedures to avoid the shortcomings of a qualitative interpretation of enamel birefringence are presented and discussed.

Natural Enamel Caries: A Comparative Histological Study on Biochemical Volumes

“…Water and organic volumes are also predicted to exert an important effect on light scattering [Seinfeld and Pandis, 2006], polarization [Oldenbourg and Ruiz, 1989], and interference [Slayter and Slayter, 2000], affecting detection and monitoring of enamel caries by optical methods. Such volumes have been reported at histological layers of NEC [Medeiros et al, 2012] but have not been rigorously related to the differences among such layers. Thus, the aim of this study was to characterize the relationship between enamel histological points at certain zones (SL; body of the lesion, BL; normal enamel, NE) and the spatial distribution of biochemical volumes (including those related to pore volume) along prisms' paths.…”

“…A limitation of such an interpretation is that the required mathematical fitting of experimental and theoretical BR obs can only be achieved to mineral volumes ^ 95% [Sousa et al, 2006]. Detailed description and examples have been recently reported [Medeiros et al, 2012]. In addition, we introduced a new parameter, the water volume more easily available for diffusion ( ␣ d ):…”

“…Uncavitated approximal enamel carious lesions (opaque enamel with surface brightness after removal of dental plaque with water spray and dehydration with compressed air for 5 s; carious enamel group, n = 10; one lesion per tooth) and approximal surfaces with NE at the mid-coronal region (NE group, n = 10) were selected under stereomicroscopy by a calibrated examiner (kappa = 0.98) with regard to the diagnosis of noncavitated white-spot enamel caries lesions according to the criteria of Nyvad et al [1999]. Ground sections (final thickness of ϳ 100 m) were prepared as described recently elsewhere [Medeiros et al, 2012].…”

“…Thickness was obtained (mean of ten measurements) at the histological points using ImageJ (NIH, USA) assuming that the thickness at the cut edge was the same as that at the closest histological point (located ϳ 100-150 m away from the cut edge) along the transversal. Quantification of mineral volume using Angmar's equation was performed as described previously [Medeiros et al, 2012] Elliott [1997], and aluminum (density of 2.7 g/cm 3 ), available in the literature for the X-ray parameters used [NIST, 2004].…”

A comparative study of new and current methods for dental micro-CT image denoising

“…Transverse micro radiography (TMR) images of thin sections of the teeth 15 were considered as the generic smoothness model. Considering the TMR images and assuming the homogeneous structure of the enamel and dentin which is mainly composed of uniform hydroxyapatite crystals, 16 the noise-free images were expected to have a smooth and non-textural appearance (Figure 1).…”