60 www.medfak.ni.ac.rs/amm Original article UDC: 616.314.14:615.46 doi:10.5633/amm.2020.0208 BONDING EFFICIENCY OF UNIVERSAL ADHESIVE TO DENTINE IN DIFFERENT ETCHING AND CURING MODES Milan Miljković 1 , Stefan Dačić 2 , Goran Radenković 3 , Milica Jovanović 4 Adhesive bond strength and polymerization shrinkage are influenced by many different factors, including etching mode and light properties of a curing source. Different etching and curing techniques have been developed in an attempt to reduce polymerization shrinkage and stress development, thereby increasing the bond strength at the composite/dentine interface. The purpose of this study was to evaluate the influence of total-etch and self-etch mode as well as continuous and soft-start light curing mode on micro-tensile bond strength of bulkfill composite to dentine using universal adhesive. According to the etching and lightcuring mode applied, teeth were randomly divided into four different groups (n = 15): TC (total-etch, continuous mode), TS (total-etch, soft-start), SC (soft-start, continuous mode) and SS (self- etch, soft-start). Cylindric composite build-ups were made with 3M FiltekBulkfill Posterior. Specimens were subjected to micro tensile bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The failure force was recorded in Newton (N) and calculated in MPa as a ratio of Newton to the surface of the bonded area. Data were analyzed using two- way ANOVA and Students t-test.Micro tensile bond strength was not affected by the lightcuring mode since no significant statistical difference was determined between the continuous and soft-start groups, irrespective of the etching mode used. On the other hand, micro tensile bond strength was highly influenced by the etching mode since significant statistical difference was determined between the total-etch and self-etch groups, irrespective of the lightcuring mode. Acta Medica Medianae 2020;59(2):60-65. Key words: bond strength, universal adhesive, total-etch, self-etch, soft-start 1 University of Niš, Faculty of Medicine, Research Center for Biomedicine, Niš, Serbia 2 Clinic of Dentistry, Department for Restorative Dentistry and Endodontics, Niš, Serbia 3 University of Niš, Faculty of Mechanical Engeneering, Laboratory for testing materials and machinery, Niš, Serbia 4 University of Kragujevac, Faculty of Medical Sciences, Department of Dental Prosthetics, Kragujevac, Serbia Contact: Milan Miljković 5/2 Maksim Gorki St., 18000 Niš, Serbia E-mail: milandent89@yahoo.com Introduction Strong adhesive bond between the filling and cavity walls is mandatory for long-lasting composite restorations. To achieve a strong adhesive bond, proper clinical technique and tooth surface prepara- tion is required (1). The quality of adhesive bond is usually determined by measuring micro tensile or shear bond strength to enamel or dentine. Achieving optimal adhesive bond to dentine is more compli- cated when compared to enamel, due to the presence of smear layer and histological differences between the two substrates (2). In order to improve their clinical efficacy, the composition of dental adhesive systems is under constant development and new products are con- tinuously introduced to the market. As a result, several generations of bonding agents are now available in the dental market with different number of bottles and their application technique (3). Multi- step total-etch adhesives are still considered to be the gold standard in achieving a strong bond despite of their time-consuming and technique-sensitive ap- plication. On the other hand, self-etch adhesives have greatly simplified the adhesive application pro- cess since they do not require a separate acid etching step, rinsing and drying. These systems have gained a lot of popularity in the last few years because they are extremely easy to use and time- saving (4). The most recently introduced adhesive sys- tem to the dental market is "universal" or "multi- mode" adhesive which can be applied in total-etch, self-etch, or selective-etch mode, as well as on dif- ferent materials. The goal of this new adhesive system is to further simplify the bonding procedure and clinicians’ decision making when considering bonding agents and adhesive techniques (5).