The use of ¯owable composites as ®lled adhesives Roland Frankenberger a , * , Manuela Lopes b , Jorge Perdiga Äo c , Wallace W. Ambrose d , Bruno T. Rosa e a Policlinic for Operative Dentistry and Periodontology, University of Erlangen-Nuremberg, Glueckstrasse 11, D-91054 Erlangen, Germ b Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, 16-212 Moos Tower B 515 Delaware St SE, MN 55455, USA c Division of Operative Dentistry, Department of Restorative Sciences, University of Minnesota, 8-450Moos Tower B 515 Delaware St SE, Mi MN 55455, USA d School of Dentistry, Dental Research Center, University of North Carolina at Chapel Hill CB no. 7455, Chapel Hill, NC 27599-74550, US e Private practice, Londrina, PR, Brazil Received 17 October 2000; received in revised form 23 March 2001; accepted 9 April 2001 Abstract Objective: The effect of ®lled adhesives on bonding resin composites to dentin has not been fully understood. Due to th ®lled adhesives may act as stress breakers. The aim of this in vitro study was to evaluate the use of ¯owable composites on bonding to enamel and dentin without the use of an intermediate bonding resin. Materials and methods: Enamel and dentin bond strengths of OptiBond FL, Syntac Classic, and EBS Multi combined eithe proprietary bonding agent or a ¯owable resin composite (Ultraseal XT Plus or Revolution) were measured. The tests were c microtensile device at a crosshead speed of 1 mm/min after 24 h of storage at 378C in water. Mean bond strengths were a Wilcoxon test and multiple comparisons according to the Mann-Whitney U-test. The micro-morphology of corresponding resin±dentin interfaces of the same teeth were analyzed using SEM and TEM. Results: The control groups with adhesive systems used as per manufacturers' protocol showed bond strengths of 38.9±41.1 MPa to enamel and 28.8±33.4 MPa to dentin. With respect to bond strength to etched enamel, only Ultraseal XT Plus as bonding level of the control groups. When used as bonding agents on dentin, both ¯owable composites produced lower microtensil etched and primed dentin than did the control groups. Micro-morphological analysis using SEM and TEM resulted in hybrid for both control and experimental groups. However, many areas of the resin±dentin interface showed insuf®cient penetra composites at the top of the hybrid layer as well as numerous tubules obstructed by ®ller particles. Conclusions: The ¯owable composites tested in this study should not be used to replace bonding agents. Flowable comp viscosity, such as Ultraseal XT Plus, may bond to enamel adequately without the requirement of an intermediate bonding resin. q 2002 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved. Keywords: Enamel bonding; Dentin bonding; Hybrid layer; Resin composites; Flowable composites; Filled adhesives 1. Introduction The increasing attractiveness of tooth-colored restora- tions has promoted research in this particulararea of operativedentistryduringthe last few years [1±3]. For ClassII restorations, resin-based restorative materials are now being used instead of amalgam [4,5]. Due to the characteristic polymerization shrinkageof resin-based composites, clinicalsuccesswith composite restorative materials is fundamentally dependent on effectiveand durable adhesion to enamel and dentin [6±8]. Bonding to enamel is now accepted as clinically reliable, because acidic etchants, such as 30±40% phosphoric acid capable of creating microporosities on the enamel surface which enable the penetration of polymerizable monomers to providemicromechanical retention [9,10].However, dentin still remains an unpredictable substrate for adhesio The wettubularmicrostructure, combined with the high organic content, is responsible for bonding to dentin being far more dif®cult to perform [11±14]. Although different approaches of surfacepre-treatment are available, acid- etchingand subsequent penetration of reactiveprimer molecules into the decalci®ed dentin surface is the most Dental Materials 18 (2002) 227±238 dental materials 0109-5641/02/$22.00 + 0.00 q 2002 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved. P II: S 0 1 0 9 - 5 6 4 1 ( 0 1 ) 0 0 0 4 0 - 9 www.elsevier.com/locate/dental * Correspondingauthor.Tel.: 149-9131-853669; fax: 149-9131- 853603. E-mail address: frankbg@dent.uni-erlangen.de (R. Frankenberger).