EDX-depth-profiling Test Method For Mineral Content Study In De/remineralization Processes

Objectives:  

Chemical treatments and dental materials in conventional clinical practice either in endo or conservative dentistry can modify the mineral content of near dental hard tissues.

A new method to study the mineral content of human enamel and dentin in de-/remineralization processes has been defined.

Methods:  

Dentin slices (0.8 mm thick) were demineralized in EDTA 17% for 2h.

Enamel samples (0.4 mm thick) were demineralized in acetate buffered solution (1.5 mM CaCl₂; 0.9 mM KH₂PO₄; 0.1 ppm F (NaF); 50 mM acetic acid, vestiges of thymol (0.1%), adjusted to pH 4.5 with KOH).

Dentin and enamel samples were treated with a calcium-silicate MTA cement and soaked in HBSS following Gandolfi remineralizing technique.

All the samples were embedded in a self-curing resin and cut perpendicularly to the treated surface to obtain cross sections.

Cross surfaces were polished (to 2000-grit paper) and EDX-depth-profiling was carried out starting from the treated surface, and calcium and phosphorous were detected throughout all the cross section. Enamel and dentin samples were analyzed as natural/mineralized, after

demineralization and after remineralization.

Results:  

EDX-depth-profiling after demineralization: Two areas with different mineral content are identifiable in demineralized dentin: demineralized area (D) till approx. 50 microns depth from and mineralized (M) starting from 50 microns depth.  Four areas are classifiable in enamel samples (expressed in microns depth from the surface): demineralized (D, 0-30 microns), partially mineralized (PM, 30-80 microns), sub-surface lesion (SL, 80-140 microns), mineralized (M >140 microns).

EDX-depth-profiling after remineralization:  In dentin, disappearance/reduction of the D area and appearance of a remineralized area (R).  In enamel, disappearance of D, PM and SL areas and appearance of remineralized area (R) adjacent to the M area.

Conclusions:

A new standard test method to monitor the changes in mineral content of chemically treated dentin and enamel has been defined and proposed.