33

IntroductionThe number of adult patients who seek orthodontic treatment is increasing. These patients often have lithium disilicate ceramic restorations. The orthodontist has to find a procedure to ensure that the brackets bond effectively to these restorations. In 2011, a new family of adhesives, universal adhesives, was introduced. They are capable of bonding to ceramic and are considered “multimode” because they are suitable for both an etch-and-rinse or a self-etch approach. The objective of this in vitro study was to evaluate the shear bond strength of metal brackets to lithium disilicate ceramic restorations using a universal adhesive.Materials and MethodsForty machinable lithium disilicate ceramic blocks (IPS e.max CAD, Ivoclar) were prepared according to the manufacturer’s instructions. Each specimen was randomly assigned to one of four groups (n = 9 or 10) defined by the pretreatment protocol. Protocol 1: hydrofluoric acid 9% (HF) + silane + orthodontic adhesive (Transbond™ XT Light Cure Adhesive Primer, 3M ESPE); protocol 2: HF + universal adhesive (Scotchbond Universal®, 3M ESPE); protocol 3: universal adhesive only; protocol 4: Monobond Etch & Prime® (Ivoclar) + universal adhesive. Next, an upper cuspid bracket (3M ESPE) was bonded to each specimen with a composite resin (Transbond™ XT, 3M ESPE). The shear bond strength between the ceramic and the bracket was measured using a universal testing machine. A one-way ANOVA (ANalysis Of Variance) followed by Tukey’s post hoc test was performed to investigate the difference in shear bond strength between the groups.ResultsProtocol 2 (43 MPa) and protocol 4 (36 MPa) showed the highest shear bond strength values and were statistically different from protocol 1 (25 MPa) and protocol 3 (21 MPa).ConclusionDespite the lower bond values obtained in the study, which were nonetheless higher than the minimum expected, the application of a universal adhesive alone appears to be a safe procedure that seems to provide sufficiently strong and resistant bonding between the ceramic and the bracket. However, clinical studies should be conducted before a recommendation can be made.