Proton probe and acid etching for determining fluoride profiles in porous porcine enamel

An acid-etch technique and a proton probe were used to obtain profiles of changes in fluoride concentrations across enamel of 24 normal and 24 fluorotic porcine teeth. Polished and unpolished sections were used for probe measurements, and blocks of enamel cut from tissue adjacent to the sections were used for acid etching. Additional blocks were etched with acid containing dye to study penetration of acid beyond the sampling sites. Probe-derived values were characterized by wide fluctuations. They were also higher than acid-etch values, and this difference was reduced but not eliminated by polishing the sections prior to scanning. Profiles obtained with the two methods followed a parallel course in fluorotic and normal enamel. Thus, errors due to chemical estimations of enamel depth with the etch technique were not demonstrated, although penetration of acid deep to the surface of the porous fluorotic enamel was observed. Further development of the precision of the probe method is required to optimize the unique advantage provided by the potential accuracy, speed of data collection, and spatial resolution of this method.