http://www.revistadechimie.ro REV.CHIM.(Bucharest)♦70♦ No. 1 ♦2019 84 Preliminary Study on the Tensile Strength of Some Adhesive Materials Used to Luting Brackets OANA BOTOACA 1 , EDWIN SEVER BECHIR 2 , RALUCA MONICA COMANEANU 1 *, STEFANIA COMAN 3 , MIHAIL TARCOLEA 4 , LAURENTIU DRAGUS 5 1 Titu Maiorescu University of Bucharest, Faculty of Dental Medicine, 67A Gh. Petrascu, 031593, Bucharest, Romania 2 University of Medicine, Pharmacy, Sciences and Technology of Targu Mures, Faculty of Dental Medicine, 38 Gheorghe Marinescu Str., 540142, Targu Mures, Romania 3 CMI Dr. Coman Stefania, 9 Grivitei, 120039, Buzau, Romania 4 Politehnica University of Bucharest, Faculty of Material Science and Engineering, 313 Splaiul Independentei, 060042, Bucharest, Romania 5 Dunarea de Jos University of Galati, Faculty of Medicine and Farmacy, 35 Al. I. Cuza Str., 800010, Galati, Romania In our study we compared in vitro the tensile strength of 4 types of adhesive systems used for brackets, two using bonding and two self-etching. The detachment test were made by the Instron® 8801 universal mechanical testing machine, from the Mechanical Testing Laboratory of the Materials Resistance Department, the Faculty of Engineering and Management of Technological Systems, the Polytechnic University of Bucharest. From the experimental results we find that the used adhesives offer good shear resistance. Vertise Flow adhesive used for sample 2, which has the highest shear stress at break ( τ max ~ 25 MPa), is clearly highlighted. Vertise Flow is follow by the Orthocem adhesive used for sample 1 with τ max ~ 14 MPa, then the Neobond adhesive used in sample 4 with τ max ~ 13 MPa, and the weakest of the adhesives is Grandio Flow used for sample 3 ( τ max ~ 12 MPa). We believe it is necessary to carry out further studies on larger batches of samples to obtain results that can be validated by statistical analysis. Keywords: bracket, tensile strength, adhesion, dental materials Among the requirements for acceptable dental material is the biocompatibility. Multiple studies present the benefits of biomaterial properties, as well as the need to reduce their use failures and the need to optimize their biomechanical performance [1]. For this reason, used dental materials must ensure the resistance [2]. The adhesive system of brackets has to present high enough bond strength to resist the forces that are applied during daily activities, but low enough in order to allow for a debonding at the end of the treatment in a way that leaves the surface of the enamel intact. [3] At present time, there are adhesive systems with and without bonding for fixing brackets. Studies [4,5] have shown that self-etching adhesive systems exhibit traction resistance similar to conventional bonding systems. During mastication, the developed forces vary widely, requiring different dento-periodontal units asymmetric [6], which can lead to the detachment of the brackets. The retention of the bracket on the tooth is influenced by bracket morphology [7-9], as well as the particularities of the adhesive system used [10]. Experimental part In our study we compared in vitro the tensile strength of 4 types of adhesive systems used for brackets, two using bonding and two self-etching. The four dental materials tested were: Orthocem, produced by FGM, applied on sample 1; Vertise Flow, manufactured by Kerr, applied on sample 2; Grandio Flow, produced by VOCO, applied on sample 3; Neobond, manufactured by Densply, applied on sample 4. We selected four teeth extracted in orthodontic purpose, two lower incisors and two lower premolars, and on each we fixed a metal bracket with the adhesive materials above. * email: monica_tarcolea@yahoo.co.uk; Phone: 0723860069 All authors have equal contributions to the study and the publications. From the time of extraction to the application of the brackets, the teeth were kept in the physiological serum to avoid desiccation of the dental hard tissues. In order to apply composite materials, the teeth were initially demineralized with 37% Orthophosphoric Blue Etch, for a period of 15 s , after which they were flushed and air-jetted from the dental unit. After demineralization, washing and drying, for Neobond and Grandio Flow we applied universal bonding from 3M, with light-curing for 20 s. We applied on each bracket one of the adhesive material, we placed the brackets on the teeth, and started light- curing of adhesives. The light-curing was performed for each tooth in 3 directions, for the time period recommended by the manufacturers for each dental adhesive. After applying the brackets to the detachment test, the samples were kept in a humid atmosphere, so that there was no excess of liquid but no completely anhydrous medium that could compromise the adhesion of the composites to the dental tissues (fig. 1). For the experiments, the samples were embedded in a resin (fig. 2). The detachment test were made by the Instron® 8801 universal mechanical testing machine, from the Mechanical Testing Laboratory of the Materials Resistance Fig. 1. Keep samples in a wet environment