Ultimate tensile strength of tooth structures Marcelo Giannini a, * , CarlosJose´Soares b , Ricardo Marins de Carvalho c a Department of Restorative Dentistry, Piracicaba School of Dentistry, University of Campinas, Av. Limeira, 901, Piracicaba, SP, Brazil b Department of Operative Dentistry, School of Dentistry, University of Uberlaˆndia, Uberlaˆndia, MG, Brazil c Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of Sa˜o Paulo, Bauru, SP, Brazil Received 23 October 2002; received in revised form 20 March 2003; accepted 28 April 2003 KEYWORDS Tensile strength; Enamel; Dentin; Dentin – enamel junction Summary Objective. This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) and dentin – enamel junction (DEJ) using the microtensile technique. It was hypothesized that the UTS of dental structures varies according to location and nature. Methods. Intact occlusal enamel surfaces from extracted human third molars were etched with 37% phosphoric acid and bonded with a one-bottle adhesive system. The bonded occlusal surfaces received a resin composite build-up and teeth were serially, vertically sectioned into several 0.7 mm thick slabs. Each slab was then trimmed to a dumbbell-shaped specimen with irrigated diamond burs to reduce the cross-sectional area to approximately 0.5 mm 2 at E, D or DEJ. E was tested according to its prismatic orientation (parallel, EP; and transversally, ET) and D as function of depth (superficial, DS; middle, DM and deep, DD). Specimens were tested in tension in an Instron testing machine at 0.5 mm/min. Results were analyzed by one-way ANOVA and Duncan’s Multiple Range test. Results. UTS mean values ðN ¼ 20Þ were, MPa (SD): DEJ, 46.9 (13.7) b ; EP, 42.1 (11.9) b ; ET, 11.5 (4.7) d ; DS, 61.6 (16.2) a ; DM, 48.7 (16.6) b and DD, 33.9 (7.9) c . Enamel stressed transversally to its prismatic orientation was significantly weaker ðp , 0:05Þ: Dentin depth significantly affected its UTS ðp , 0:05Þ: DEJ presented UTS that was similar to EP and DM ðp . 0:05Þ: Significance. The UTS of dental structures varies according to its nature and location. Q 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. Introduction The tooth is the only mineralized organ that is located partially internal and partially external to the body. To minimize wear during function, the tooth includes highly mineralized tissues that present physical properties based on their compo- sition and micro morphology. 1 The anatomical crowns of teeth are covered by dental enamel, which is the hardest tissue in the body, and is composed of 92–96% of inorganic matter, 1–2% of organic material and 3–4% of water by weight. 1 Most of the inorganic matter is hydroxyapatite that is contained in the basic structural unit of enamel, Dental Materials (2004) 20, 322–329 http://intl.elsevierhealth.com/journals/dema 0109-5641/$ 30.00 Q 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/S0109-5641(03)00110-6 *Corresponding author. Tel.: þ 55-194305340; fax: þ 55- 194305218. E-mail address: giannini@fop.unicamp.br