Vol 6, No 1, 2004 7 The Influence of Storage Time and Cutting Speed on Microtensile Bond Strength Alessandra Reis a /Marcela Rocha de Oliveira Carrilho b /Marcos Schroeder c / Luciane Lima Franco Tancredo d /Alessandro Dourado Loguercio a a Assistant Professor, Department of Dental Materials and Operative Dentistry, University of Oeste de Santa Catarina, SC, Brazil. b Postdoctorate trainee, Department of Restorative Dentistry, Dental Materi- als, Piracicaba School of Dentistry, University of Campinas, Piracicaba, SP, Brazil. c Assistant Professor, Department of Dental Materials and Operative Dentistry, University of Gama Filho, Rio de Janeiro, RJ, Brazil. d Graduate Student, Department of Dental Materials, University of São Paulo, São Paulo, SP, Brazil. Purpose: The aim of this study was to verify the influence of the storage time and the cutting speed during speci- men preparation on the bond strength of a single-bottle adhesive to dentin. Materials and Methods: A flat dentin surface was exposed in 36 human third molars. The adhesive system (Single Bond) was applied according to the manufacturer’s instructions, and composite resin crowns (Z250) were con- structed incrementally. Specimens were stored for 10 min, 24 h, or 1 week in distilled water at 37°C before being longitudinally sectioned in both the “x” and “y” directions at different cutting speeds (0.5, 1.6, and 2.6 m/s) to obtain sticks with a cross-sectional area of approximately 0.8 mm 2 . The specimens were tested in a tensile load machine (0.5 mm/min) and the fracture mode analyzed. A two-way ANOVA with storage time (3 levels) and cutting speed (3 levels) as factors was used to compare the mean microtensile bond strengths. Results: Highly significant main effects and interaction (p < 0.0001) were detected. The highest mean bond strength was obtained with a storage time of 1 week and cutting speed of 2.6 m/s. The lowest mean was found when the specimens were prepared immediately after composite resin placement and sliced at 0.5 m/s. Conclusion: Both the storage time and the cutting speed may affect the bond strength results. Therefore, these variables must be controlled in microtensile bond strength tests. Key words: microtensile test, cutting speed, resin-dentin bond strength. J Adhes Dent 2004; 6: 7–11. Submitted for publication: 20.02.03; accepted for publication: 12.05.03. Reprint requests: Dr. Alessandra Reis, Universidade do Oeste de Santa Catari- na, Campus Joaçaba, R. Getúlio Vargas, 2125, Bairro Flor da Serra, CEP: 89600-000, Joaçaba/SC, Brazil. Tel/Fax: +55-49-551-2000. e-mail: reis_ale@ hotmail.com n order to determine the properties of bonding systems, many researchers have carried out a variety of bond strength evaluations. Recently, Al-Salehi and Burke 1 re- viewed test methods and variables used in 50 published investigations of bond strength, finding that shear and tensile tests are the most commonly used. However, sev- eral drawbacks have been reported about these meth- I ods, mainly those related to nonuniform stress distribu- tion. 21,22 The microtensile test was primarily proposed to evalu- ate the bond strength between adhesives and very small regions of dental tissue; the conclusion was reached that the bonded interface of small specimens had a better stress distribution during test loading. 21,22 This test in- volves bonding the adhesive resin to dentin, which is then covered with a composite resin. After curing and storage, the specimen is vertically sectioned into multi- ple serial slabs and trimmed to reduce the cross-section- al area to about 0.8 mm 2 before testing. 29 Although the original version is still being used, many other approach- es have been introduced. One of them was the so-called nontrimming microtensile test, in which the composite resin build-up is sectioned vertically and perpendicular to the adhesive interface into 5 or 6 slabs; however, the blade does not pass entirely through the dentin. Then, af- ter rotating the specimen 90 degrees, another 5 to 6 sec- tions are made, resulting in 25 to 30 sticks in molar teeth. 31