Fluoride penetration into dentine abutments in vitro

The diffusion of fluoride ions from various concentrations of sodium fluoride solution into the dentine of decoronated human canine teeth, prepared as for reception of overdentures, was studied in vitro. The decoronated preparations were immersed for 7 days in 2.0, 1.5, 1.0, 0.5 and 0.05% solutions of neutral-pH sodium fluoride and then fluoride penetration into the prepared transverse face of the dentine was assessed by electron microprobe. Only with high concentrations of fluoride (2.0%) was there significant penetration. In peritubular dentine, fluoride penetration could be measured to a depth of 400 microns, but in intertubular dentine penetration did not take place beyond 100 microns. These findings call into question the efficacy of patient-administered caries prophylaxis with low-concentration fluoride treatments in overdenture cases.