OANA BOTOACA, EDWIN SEVER BECHIR, RALUCA MONICA COMANEANU, STEFANIA COMAN, MIHAIL TARCOLEA, LAURENTIU DRAGUS PRELIMINARY STUDY ON THE TENSILE STRENGTH OF SOME ADHESIVE MATERIALS USED TO LUTING BRACKETS 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 (tmax ~ 25 MPa), is clearly highlighted. Vertise Flow is follow by the Orthocem adhesive used for sample 1 with tmax ~ 14 MPa, then the Neobond adhesive used in sample 4 with tmax ~ 13 MPa, and the weakest of the adhesives is Grandio Flow used for sample 3 (tmax ~ 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.