Influence of drying and HEMA treatment on dentin wettability.
OBJECTIVE
The aim of this study was to evaluate the effect of drying time and primer pre-application (35% HEMA in water) on water spreading/infiltration on dentin.


METHODS
Freshly extracted molars were embedded in resin and sectioned on their coronal side. Flat occlusal dentin surfaces were prepared using wet SiC paper from nos. 80-4000. A computerized contact angle device complementing a special software (Wingoutt) was used to measure the contact angle (theta) kinetics of a reference liquid (pure H(2)O) in the ten groups each of ten dentin surfaces during 120 s: Gp1: etched (37% phosphoric acid for 15 s) and blot-dried; Gp2: 3 s dried; Gp3: 5 s air-dried; Gp4: 10 s air-dried; Gp5: 20 s air-dried; Gp6: 30 s air-dried; Gp7: 1 min dried with hair dryer; Gp8: 5 s air-dried and HEMA treated; Gp9: 30 s air-dried followed by HEMA treatment; Gp10: HEMA treated prior to 30 s air-drying. three drops were applied on each sample. 40 contact angles were recorded for each drop with a frequency of one measure every 3 s. A one-way ANOVA test was used for data analysis. A PLSD test was conducted to identify statistical differences between pairs of groups at a reliability level of 95%.


RESULTS
At each measurement time, air-drying, whatever its duration, significantly decreased the wetting ability of the pure water on the etched dentin in comparison with the blot-dried group. The contact angle increases with drying time. No significant differences in water contact angle were obtained between 3, 5 and 10 s in spite of a slight decrease in the spreading/infiltration ability of water the longer the drying time. HEMA increases the spreading/infiltration ability of water on 5 or 30 s air-dried etched dentin surfaces; 30 s air-drying did not alter the spreading/infiltration ability of the water on etched and HEMA treated dentin.


CONCLUSIONS
Dentin hydrophobicity increases depending on air-drying time. HEMA-based primer allows to prevent collagen collapse, which may be created by air-drying and partly rewet the collapsed collagen network.
Department of Biomaterials, Faculty of Dental Surgery, University of Paris V, 1 Rue Maurice Arnoux, F-92120, Montrouge, France.
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D000704:Analysis of Variance; D003094:Collagen / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000737:chemistry*; D003806:Dentin Permeability; D003890:Desiccation; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008689:Methacrylates / Q000737:chemistry*; D008963:Molar; D017155:Wettability
D008689:Methacrylates; C005044:hydroxyethyl methacrylate; D003094:Collagen