I n 1990, both dentists and dental materials companies no- ticed that metallic posts were too stiff when compared to dentin, leading to a critical transmission of loads to teeth previously weakened by instrumentation, dental caries, and extensive restorations. 11 This led to the development of fiber posts, which have been replacing the older methods for restoring endodontically treated teeth – that required large coronal destruction (metallic posts, crowns, and nonadhe- sive cements) – by techniques that preserve the dental tis- sue by utilizing adhesives and resin cements. 11,28 Currently, several types of dentinal adhesives are avail- able:9 total dentin etching, with previous acid etching fol- lowed by primer and adhesive applied separately (three- step) or combined (two-step), and self-etching systems, which contain a self-etching primer and an adhesive, sepa- rately (two-step) or in one solution (all-in-one). The total-etch systems require rinsing the acid etchant, which may overetch the dentin or obstruct the spaces around the collagen fibers if the echant is not well removed. Those with the primer and adhesive in a single bottle, and which contain acetone as a solvent, are very susceptible to moisture conditions of the dentin. When the dentin is ex- cessively dried, the interfibrillar space is reduced and the dif- fusion of resin monomers is incomplete.9 On the other hand, excess moisture leads to dissolution of acetone in wa- ter, with the accumulation of resin, resulting in bubbles and incomplete dentin sealing. 1 Within this context, self-etching primers seem to be more advantageous, since they contain a high concentration of acidic monomers that demineralize the substrate, do not need to be removed with water, and si- multaneously bond to the dentin. 31,34 The dentin structure is another important factor that should be taken into account in terms of bonding. Dentinal Effect of Adhesive System Type and Tooth Region on the Bond Strength to Dentin Renata Marques de Melo a /Graziela Ávila Prado Galhano a /Sílvia Helena Barbosa a / Luís Felipe Valandro b /Carlos Augusto Pavanelli c /Marco Antônio Bottino c Purpose: This study evaluated the bond strength of two total-etch adhesive systems (two- and three-step) and a self- etching system to coronal and root canal dentin. Materials and Methods: The root canals of 30 human incisors and canines were instrumented and prepared with burs. The posts used for luting were duplicated with dual resin cement (Duo-link) inside Aestheti Plus #2 molds. Thus, three groups were formed (n = 10) according to the adhesive system employed: All-Bond 2 (TE3) + resin cement post (rcp) + Duo-link (Dl); One-Step Plus (TE2) + rcp + Dl; Tyrian/One-Step Plus (SE) + rcp + Dl. Afterwards, 8 transverse sections (1.5 mm) were cut from 4 mm above the CEJ up to 4 mm short of the root canal apex, comprising coronal and root canal dentin. The sections were submitted to push-out testing in a universal testing machine EMIC (1 mm/min). Bond strength data were analyzed with two-way repeated measures ANOVA and Tukey’s test (p < 0.05). Results: The relationship between the adhesives was not the same in the different regions (p < 0.05). Comparison of the means achieved with the adhesives in each region (Tukey; p < 0.05) revealed that TE3 (mean ± standard deviation: 5.22 ± 1.70) was higher than TE2 (2.60 ± 1.74) and SE (1.68 ± 1.85). Conclusion: Under the experimental conditions, better bonding to dentin was achieved using the three-step total-etch- system, especially in the coronal region. Therefore, the traditional total-etch three-step adhesive system seems to be the best choice for teeth needing adhesive endodontic restorations. J Adhes Dent 2008; 10: xxxx-xxx. Submitted for publication: xxxxxxxx; accepted for publication: xxxxxxxx. Vol 10, No 1, 2008 1 ª PhD Student, Dent Mater and Prosthodontics Department, Dental School, São Paulo State University at São José dos Campos, São José dos Campos, SP, Brazil. b Professor, Prosthodontics Department, Dental School, Federal University at Santa Maria, RS, Brazil. c Professor, Dent Mater and Prosthodontics Department, Dental School, São Paulo State University at São José dos Campos, São José dos Campos, SP, Brazil. Reprint requests: Renata Marques de Melo, Rua Euclides Miragaia, 620, ap. 82, São José dos Campos, SP, Brazil 12245-820. Tel: +55-12-3947-9060, Fax: +55-12-3947-9010. e-mail: marquesdemelo@gmail.com