Effect of moisture and drying time on the bond strength of the one-step self-etching adhesive system

OBJECTIVES: To investigate the effect of dentin moisture degree and air-drying time on dentin-bond strength of two different one-step self-etching adhesive systems. MATERIALS AND METHODS: Twenty-four human third molars were used for microtensile bond strength testing of G-Bond and Clearfil S3 Bond. The dentin surface was either blot-dried or air-dried before applying these adhesive agents. After application of the adhesive agent, three different air drying times were evaluated: 1, 5, and 10 sec. Composite resin was build up to 4 mm thickness and light cured for 40 sec with 2 separate layers. Then the tooth was sectioned and trimmed to measure the microtensile bond strength using a universal testing machine. The measured bond strengths were analyzed with three-way ANOVA and regression analysis was done (p = 0.05). RESULTS: All three factors, materials, dentin wetness and air drying time, showed significant effect on the microtensile bond strength. Clearfil S3 Bond, dry dentin surface and 10 sec air drying time showed higher bond strength. CONCLUSIONS: Within the limitation of this experiment, air drying time after the application of the one-step self-etching adhesive agent was the most significant factor affecting the bond strength, followed by the material difference and dentin moisture before applying the adhesive agent.

Dimensional accuracy and detail reproduction of two hydrophilic vinyl polysiloxane impression materials tested under different conditions.

Background and Objectives: A limitation of vinyl polysiloxane (VPS) impression materials is hydrophobicity, and manufacturers have added surfactants and labeled these new products as "hydrophilic." The purpose of this investigation was to evaluate and compare the dimensional accuracy and surface detail reproduction of two hydrophilic VPS impression materials under dry, moist, and wet conditions. Materials and Methods: Ten impressions were made under dry, moist, and wet conditions respectively, with monophase, and regular body VPS impression material using a stainless steel metal die similar to that described in American Dental Association (ADA) specification 19, with lines scribed on it. Dimensional accuracy was measured by comparing the average length of the middle horizontal line in each impression to the same line on the metal die, by using a measuring microscope. The surface detail was evaluated. A one-way analysis of variance and Student t-test were used to compare mean dimensional changes (α = 0.05). Results: Conditions (dry, moist, and wet) did not cause significant adverse effects on the dimensional accuracy of either material. The mean dimensional changes were 0.00084% (+0.00041%) for monophase and 0.00119% (+0.00033%) for regular body. Monophase material was satisfactory in detail reproduction 100% of the time in dry conditions, 90% in moist, and only 20% in wet conditions. The regular body showed 100% satisfactory impressions in dry, 80% in moist, and 10% in wet conditions. With the additional smooth surface evaluation, only under dry conditions impressions with clinically acceptable surface quality were produced. Conclusions: Dimensional changes for both materials were well within ADA standards of minimal shrinkage value of 0.5%.