FLUORIDE AND MINERAL-CONTENT IN HYPER-REMINERALIZED CORONAL BOVINE DENTIN INVITRO AFTER AN ACID CHALLENGE

In this paper the acid resistance of hyper-remineralized dentine was q uantified by means of fluoride and mineral measurements. Hyper-reminer alization was achieved by demineralization of dentine in an acidic gel system (pH 5) for 3 weeks, followed by remineralization in a solution containing 1.5 mM Ca, 0.9 mM phosphate and 10 ppm F at pH 7 and 37-de grees-C for 8 days. The samples were subsequently again demineralized in the gel system mentioned for 1, 2 and 3 weeks. Analysis for fluorid e was done by means of the microdrill biopsy technique and to obtain i nformation on the fluoride distribution by secondary ion mass spectrom etry (SIMS); mineral was assessed by microradiography. The results sho wed that in hyper-remineralized dentine the original fluoride content was approximately 30,000 ppm F. This value was still in the same order after the acid challenge of 3 weeks at pH 5. These values were substa ntially higher than the baseline values in sound or in demineralized d entine being about 900 ppm F. The main microradiographic result was th at there was no significant mineral change in the hyper-remineralized dentine due to the acid challenges. There was, however, a tendency for mineral redistribution deeper into the dentine lesion leading to lami nation phenomena. The SIMS experiments on some of the samples showed a fluoride distribution in agreement with the microdrill fluoride data. Furthermore a fluoride redistribution took place in deeper parts of t he lesion due to the acid challenges. The combined fluoride concentrat ion and microradiographical data indicate that fluoride-enriched and h ighly mineralized hyper-remineralized dentine is more acid resistant t han sound or demineralized dentine.