INFLUENCE OF CONCENTRATION AND APPLICATION TIME OF MALEIC-ACID ON DENTIN PERMEABILITY

Objectives. Since dentin permeability ultimately affects bond strength , the purpose of this study was to compare the effects of different co ncentrations of maleic acid, and different exposure times on dentin pe rmeability. Methods. One hundred and thirty freshly extracted human no n-carious third molars were used. Hydraulic conductance was determined after various treatments. The teeth were divided into five groups. In the first group, the smear layer was untreated. In three other groups , 0.10, 0.25, or 0.5 M aqueous solution of maleic acid was applied on dentin slices for 15, 30, or 60 s. In the last group, the Scotchbond M ulti-Purpose dental adhesive system (3M Dental Products) conditioner w as applied for 15, 30 or 60 s. Results. After a 60 s exposure time, th e Scotchbond Multi-Purpose dentin conditioner or the 0.1 M solution of maleic acid was as effective at increasing dentin permeability as the 0.25 M and 0.5 M maleic acid solutions. The maximum dentin permeabili ty was reached after 15 s with 0.25 M and 0.5 M solutions of maleic ac id, after 30 s with Scotchbond Multi-Purpose and after 60 s with the 0 .1 M solution of maleic acid. During the first 30 s, the 0.1 M solutio n of maleic acid did not increase dentin permeability and did not comp letely remove the smear layer; a SEM examination of the dentin slices corroborated the functional results. Significance. The manufacturer's recommendation of 15 s of etching using Scotchbond Multi-Purpose condi tioning gel produced a moderate amount of etching which increases dent in permeability to about one-half its maximum value.