The present study aims to assess the ability of saliva, both in vitro and in situ, to prevent surface mineral loss from enamel and dentine when exposed to an erosive challenge. Fifteen groups of four varnished thin tooth sections were stored in saliva collected from individuals taking part in the in situ study and a further eight groups, each containing four sections, were stored in deionised water. In vitro, sections were stored in saliva or water for 14 days, In addition, fifteen subjects each wore an appliance with four varnished sections. Appliances with sections were worn for 14 days. All sections were exposed to 25 mi of erosion solution for 5 min twice daily. Microradiography and image analysis of the recovered sections demonstrated significant protection of surface mineral loss from enamel and dentine by saliva in vitro and in situ compared with deionised water (p < 0.05), Significantly less mineral loss (p < 0.05) was observed for enamel and dentine stored in situ compared with storage in saliva in vitro. Generalised linear modelling demonstrated both the subject and protocol had significant effect on mineral loss. A weak positive correlation (r = 0.64) was noted when in situ and in vitro mineral loss from enamel were compared, demonstrating greater reactivity of the in vitro enamel specimens to the erosion challenge. The dentine data did not show any linear correlation, Saliva protected against mineral loss by erosion and, for enamel, in vitro results demonstrated a weak positive correlation with in situ results. (C) 1999 Elsevier Science Ltd. All rights reserved.
