In vivo evaluation of electrophoresis-aided re-mineralization on surface topography and chemical composition of de-mineralized enamel: an in vivo animal model study

Introduction
The most mineralized and rigid tissue in the human body is tooth enamel. Enamel, the outermost covering of teeth, is made of hydroxyapatite, which is arranged in a well-organized prism structure to absorb loads. De-mineralization occurs when the most widely available and soluble material is removed from the enamel rods’ periphery and it is exposed to acids, increasing the enamel’s surface porosity, and allowing more acids to diffuse into the tissue and lose mineral ions.

Objectives
To evaluate whether an electrophoresis-aided system improved re-mineralization of de-mineralized enamel more than a traditional technique in rabbits with initial enamel lesions using different re-mineralizing agents.

Material and methods
Initial enamel lesion was produced through acid etching, and three re-mineralizing agents, such as nano-hydroxyapatite, casein phospho-peptide amorphous calcium phosphate, and bioactive glass, were applied to labial surface using traditional or electrophoresis-aided techniques. Surface topography and chemical composition were evaluated using environmental scanning electron microscope/energy dispersive X-ray spectrometer at baseline, after de-mineralization, and after re-mineralization, at different time periods, such as 2 weeks and 5 weeks for a traditional technique, and 3 hours and 5 hours for an electrophoresis-aided technique.

Results
Environmental scanning electron microscope showed that re-mineralizing agents enhanced re-mine­ralization of surface topography following different application periods. Energy dispersive X-ray spectrometer results revealed that for the traditional technique, there was no statistically significant difference between mean Ca : P ratio values of the three materials at 2 and 5 weeks. For the electrophoresis-aided technique, nano-hydroxyapatite showed the highest effect, with the most insignificant effect demonstrated in bioactive glass at both 3 and 5 hours.

Conclusions
Applying different re-mineralizing agents significantly influences enamel topography and chemi­cal composition, and accelerate the effect of re-mineralizing agents. Moreover, the dynamics of re-mineralizing agents might be accelerated by electrophoresis.