Infiltration of demineralised bovine dentine with nano-particulate solutions

Methods: Dentine oblong specimens (5mm x 1mm x 1mm) were obtained from bovine incisor teeth. One block was assigned as the sound dentine control. The remaining dentine blocks were demineralised by immersion in 4N formic acid for 48h. One of these blocks was assigned as the demineralised dentine control. The remaining demineralised specimens were subsequently immersed in 2 different nano-HA solutions and 1 colloidal silica solution. The solutions used were: 15% nano-HA in distilled water (HAdw), 15% nano-HA in a 50:50 solution of distilled water and acetone (HAdw-a) and colloidal nano-particulate silica (Si). The infiltration period was 24h followed by a dehydration process. Transmission electron microscopy (TEM) was used to visually determine the presence of nanoparticles within the demineralised dentine collagen matrix. Energy dispersive x-ray (EDX) was used to confirm the presence and quantify the amount of the calcium (Ca), phosphorus (P) and silicon (Si) ionic elements. The absorbance rate of these nano-particulate solutions on sound and demineralised dentine was determined with contact angle measurements.

Results: TEM images confirmed the presence of nanoparticles in the demineralised dentine matrix for all the solutions tested. EDX confirmed an increase in the levels of Ca, P and Si elements. Si nanoparticles infiltrated the collagen matrix in the greatest concentration. The (HAdw-a) solution was the most effective in raising the levels of calcium within the demineralised collagen matrix (14% of the sound dentine control). Contact angle measurements confirmed that for all the solutions tested, the demineralised dentine specimens were more absorbent than the sound dentine.

Conclusion: Silica and hydroxyapatite (HA) nanoparticle solutions are capable of infiltrating demineralised bovine dentine collagen.