Effect of desensitizing agents on the hydraulic conductance of human dentin subjected to different surface pre-treatments--an in vitro study.
OBJECTIVE
The aim of this study was to evaluate the variation of fluid filtration across dentin treated with different formulations of potassium oxalate gels and one gel of acidified sodium fluorophosphate, under five different pre-conditioned dentin surfaces.


METHODS
The methodology used for the measurement of hydraulic conductance of dentin in the present study was based on the model suggested by Pashley, Stewart and Galloway [Arch Oral Biol 29 (1984)379]. Two hundred dentin discs 1 mm in thickness, obtained from human extracted third molars, were divided into 20 groups of ten specimens each. The groups corresponded to the following experimental materials: 3% potassium oxalate gel-pH 4; 6% potassium oxalate gel-pH 4; 3% potassium oxalate gel-pH 2.5 and 1.23% fluoride gel (APF gel)-pH 3.6-3.9, applied to dentin under the following surface conditions: air-dried, blot-dried, wet, EDTA air-dried; EDTA blot-dried. General MANOVA and post-hoc Duncan tests were performed on the data.


RESULTS
Regardless of surface pre-treatment the 3% potassium oxalate gel-pH 2.5 produced the greatest reduction in dentinal filtration (p<0.05) even after citric acid challenge. In general, air-drying the dentin was the best surface pre-treatment (p<0.05). The interaction between the material and surface pre-treatment showed values of hydraulic conductance similar for most of the combinations, but the 3% potassium oxalate gel-pH 2.5 under wet conditions produced the largest reduction in hydraulic conductance. The APF gel produced the smallest reduction in hydraulic conductance when compared with the other materials, regardless of surface pre-treatment.


CONCLUSIONS
the potassium oxalate gels studied in this investigation have a great potential for tubule occlusion and, consequently, should be effective treatments of dentinal hypersensitivity, regardless of dentin wetness.
Pereira
José C
JC
Department of Restorative Dentistry, Bauru School of Dentistry, University of São Paulo, São Paulo, Brazil. jcper@fob.usp.br
Segala
Angela D
AD
Gillam
David G
DG
D000149:Acidulated Phosphate Fluoride / Q000494:pharmacology; D000388:Air; D002614:Chelating Agents / Q000494:pharmacology; D019343:Citric Acid / Q000494:pharmacology; D003764:Dental Materials / Q000494:pharmacology*; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D003806:Dentin Permeability / Q000187:drug effects*; D003807:Dentin Sensitivity / Q000188:drug therapy*; D019234:Dentinal Fluid / Q000187:drug effects; D004492:Edetic Acid / Q000494:pharmacology; D005782:Gels; D006801:Humans; D010070:Oxalates / Q000494:pharmacology; D016369:Smear Layer; D014867:Water
D002614:Chelating Agents; D003764:Dental Materials; D005782:Gels; D010070:Oxalates; D014867:Water; D019343:Citric Acid; D000149:Acidulated Phosphate Fluoride; D004492:Edetic Acid