A new approach for improving the birefringence analysis of dental enamel mineral content using polarizing microscopy

Abstract

Summary The main problem in interpreting birefringence of dental enamel under polarizing microscopy is the lack of physical constants able to allow the Wiener equation to be applied directly to the composition of such tissue. The present study introduces a new approach to circumvent this constraint. Because the nonmineral phase of enamel is heterogeneous, its refractive index can be computed in terms of its components (namely, water, which is partially replaced by the immersion medium, and organic matter), thereby providing a more acceptable refractive index to be used in the Wiener equation. Furthermore, the enamel mineral volume is ordinarily calculated on the basis of the density 3.15 g cm−3. The density 2.99 g cm−3 has been, however, reported to be more accurate for enamel hydroxyapatite, so enamel mineral volumes from selected published data were converted using such a density. The birefringence of mature enamel computed by the Wiener equation, taking into account the above refinements, matched, for the first time, published experimental birefringence values. The theoretical water and organic contents were also consistent with published experimental data. Thus, a direct application of the Wiener equation to the enamel composition has now been achieved. It is speculated that quantitative data on the mineral, the water and the organic contents of mature dental enamel can be derived from interpretation of birefringence in two immersion media (obtained before and after extraction of the organic matter) with this new approach.

Natural Enamel Caries: A Comparative Histological Study on Biochemical Volumes

“…Organic and water volumes were not obtained at 16 histological sites (8 out of 90 sites from the NE transversals, and 8 out of 57 NE sites from carious enamel transversals) because mineral volume exceeded 95% [Sousa et al, 2006]. Statistics on biochemical volumes (including mineral volume) were calculated for the fitted points (n = 219) only ( table 1 ).…”

“…Theoretical BR obs and experimental BR obs were equalized by changing the values of ␣ and ␤ (precision of 10 -3 for ␣ and ␤ and 10 -5 for BR obs ) iteratively. 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].…”

“…V 1 is the mineral volume fraction measured by microradiography, V 2 is the nonmineral volume fraction ( V 1 + V 2 = 1), and n 1 (1.62) and n 2 are the refractive indexes of the mineral and nonmineral volumes, respectively. The latter was given by Sousa et al [2006]:…”

“…In order to measure water and organic volumes, a theoretical BR obs value equal to the experimental BR obs was computed by [Sousa et al, 2006] …”

Análise da morfologia de incisivos fluoróticos de ratos por meio de microscopia eletrônica de varredura e microscopia de polarização

“…É uma técnica usada para analisar o conteúdo mineral do esmalte dental. A birrefringência observada no esmalte é a soma da birrefringência intrínseca (relacionado à fase mineral e com sinal negativo) e da birrefringência de forma (relacionada com a fase não mineral e com sinal positivo) (Sousa et al, 2006). …”