Damage of the Interface Between an Orthodontic Bracket and Enamel – the Effect of Some Elastic Properties of the Adhesive Material

The aim of this study was to investigate the magnitude of debonding stress of an orthodontic bracket bonded to the enamel with resin systems having different elastic properties. For the same purpose, sixty human premolars were randomly divided into four groups according to the adhesive system used for bonding brackets: G Fix flowable resin (GFI) with Everstick NET (ESN), GFI, G Aenial Universal Flow (GAU) with ESN, and GAU. The brackets were stressed in the occlusogingival direction on a universal testing machine. The values of debonding load and displacement were determined at the point of debonding. The elastic modulus of the tested materials was determined using nanoindentation. An analysis of variance showed a significant difference in the loads required to debond the bracket among the groups tested. The GAU group had the highest elastic modulus, followed by the GFI and ESN groups. ARI (Adhesive Remnant Index) scores demonstrated more remnants of the adhesive material on the bracket surface with adhesives having a higher elastic modulus. Taking into consideration results of the present in-vitro study, it can be concluded that the incorporation of a glass-fiber-reinforced composite resin (FRC) with a low elastic modulus between the orthodontic bracket and enamel increases the debonding force and strain more than with adhesive systems having a higher elastic modulus.</p

Evaluation of an experimental silane primer system in promoting adhesion between orthodontic bracket and ceramic

The aim of the study was to evaluate in vitro the effect of an experimental silane primer system on the adhesion strength of metallic orthodontic brackets bonded to a ceramic surface. For this purpose, a total of 180 glazed ceramic porcelain fused to metal (PFM) veneer were randomly assigned into 2 groups of 90 specimens, according to the primer used. Each group was further divided into 3 subgroups according to the surface treatment to be received, thus there were 6 study groups; three with 3-acryloxypropyltrimethoxysilane (ACPS) silane primer, namely 1a (pretreatment with hydrofluoric acid, HF), 1b (pretreatment with grit-blasting) and 1c (pretreatment with tribochemical silica-coating) and 3 with a novel silane system (ACPS+bis-1,2(triethoxysilyl) ethane (BTSE)) assigned as 2a (HF), 2b (grit-blast), and 2c (tribochemical silica coating). The samples were evaluated for surface roughness (Ra) before and after surface conditioning. Next, 15 samples from each subgroups were subjected to thermo-cycling and remaining 15 samples served as the baseline (n = 15). Adhesion strength (the shear bond strength, SBS) was recorded using a universal testing machine. Debonding failure types were classified according to the adhesive remnant index (ARI). Contact angles of the primers were measured. Data were analyzed by ANOVA and Tukey’s multiple comparison post hoc analysis. The highest SBS at baseline (26 8+1 7 MPa) and after thermocycling (24 6+1 7 MPa) was observed in group 2c, and the lowest (9 6+1 5 MPa and 4 5+1 1 MPa) was found in group 1a. Specimens pretreated with tribochemical silica-coating exhibited the highest Ra and the lowest Ra was observed in HF treated specimens. The application of experimental silane primer system on specimens pretreated with tribochemical silica-coating demonstrated increased adhesion of orthodontic brackets making it an excellent choice in orthodontic bonding for a relatively long term use