Abstract
The purpose of this study was to compare the shear bond strength and Adhesive Remnant Index of four different veneering ceramic materials to ceramic brackets. Additionallly, a further aim of this study was to overcome the etching using hydrofluoric acid which is noxious and could seriously damage the corneas of the eyes. Two surface conditioning methods of four ceramic materials before bonding brackets were examined: in group 1 an air particle abrasion with 25 μm aluminium trioxide (4 seconds at a pressure of 2.5 bars) and subsequently a silane coupling agent (Espe Sil, 3M Unitek, Monrovia, USA) was applicated on one side of each ceramic specimen (10 per group). In group 2 one side of each sample (20 per group) was etched with 37.0 per cent orthophosphoric acid for two minutes and was followed by a silane application (Espe Sil, 3M Unitek, Monrovia, USA). After this procedure the self-ligating ceramic brackets Clarity SL (3M Unitek, Monrovia, USA) brackets were bonded to the ceramic blocks and a thermocycling process started (5°C - 55°C, 6000 cycles). Then, shear bond strength and Adhesive Remnant Index (ARI) were measured. To determine statistical differences Oneway-ANOVA and Tukey Post-hoc test were performed. Hydrofluoric acid seems not to be justifiable anymore for preparing the surface of dental ceramic restorations before bracket bonding. Sandblasting with 25 μm aluminium trioxide and the use of orthophosphoric acid (37.0 per cent) seem to prepare the surface of ceramic restoration sufficiently before ceramic bracket bonding. The found level of shear bond strength values seems to be sufficient for bonding ceramic brackets to ceramic restorations.
Highlights
Dental ceramics are nowadays often used as restorative material as veneers, crowns and bridges because of their aesthetic appearance, their outstanding mechanical properties and their biocompatibility
In group 2 one side of each sample (20 per group) was etched with 37.0 per cent orthophosphoric acid for two minutes and was followed by a silane application (Espe Sil, 3M Unitek, Monrovia, USA). After this procedure the self-ligating ceramic brackets Clarity SL (3M Unitek, Monrovia, USA) brackets were bonded to the ceramic blocks and a thermocycling process started (5 ̊C 55 ̊C, 6000 cycles)
Adhesive Remnant Index (ARI) scores: “0”: no composite remained on the enamel; “1”: less than 50% of the composite remained on the enamel; “2”: more than 50% of the composite remained on the enamel; “3”: all composite remained on the enamel
Summary
Dental ceramics are nowadays often used as restorative material as veneers, crowns and bridges because of their aesthetic appearance, their outstanding mechanical properties and their biocompatibility. The increased demand by adults for orthodontic treatment results in the necessity for orthodontics to attach brackets and tubes on ceramic restorations. The difficulty of orthodontic bracket bonding is its semipermanent nature. Bond strength should be high enough to resist accidental debonding during treatment and low enough to remove the bracket from the ceramic without generating excessive force which might damage the peridentium of the tooth or the restoration [1,2]. As a result of the basic investigations of Buonocore (1955) the direct bonding te-. Chnique has revolutionized bonding brackets to teeth [3]. Over the years a lot of attention has been paid to improving the acid-etching technique, primers and adhesives
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