Dentin permeability after toothbrushing with different toothpastes

Purpose: To evaluate the interaction of smear layer produced during brushin g and dentifrice particles. Materials and Methods: Dentin disks were obtain ed from extracted human third molars. Dentin permeability was evaluated usi ng a hydraulic pressure apparatus working at 1 psi of pressure. After prepa ration, each sample was connected to the hydraulic pressure apparatus to ev aluate the permeability of dentin with the smear layer produced during spec imen preparation. After 5 min of measurements dentin was etched with 37% ph osphoric acid gel for 2 min, washed and gently dried with cotton to measure the permeability after smear layer removal. This was done to measure the m aximum permeability of each specimen (expressed as 100%). Then a second sme ar layer was produced using a #400 carbide paper under water for 1 min. Den tin permeability of the smear layer covered dentin was then measured, and e xpressed as a percent of the maximum permeability of that specimen, permitt ing each specimen to serve as its own control. The three toothpastes used ( Merfluan powder, Merfluan paste and Fluorigard) were applied on dentin surf aces using a small sponge to completely cover the dentin surface. After 5 s , each sample was connected to a mechanical device and brushed under water for 3 min with constant pressure of 250 gr using a Colgate medium toothbrus h. After this treatment, each sample was gently washed with tap water, gent ly air dried for 3-5 s and connected with the pressure apparatus to remeasu re the permeability after brushing. For SEM examination of dentin before an d after treatment with toothpaste and brushing, each dentin and enamel samp le was fixed in 2% buffered glutaraldehyde. Results: Dentin permeability pr oved unaffected by dentifrice treatments. SEM observations demonstrated the presence of dentifrice particles on dentin surface and inside dentin tubul es. Smear plugs produced during dentin brushing were not removed by dentifr ices.