Evaluation of the shear bond strength of metal bracket bonded to porcelain restorations : in vitro study

Abstract EN

Background : Direct bonding of orthodontic attachments to porcelain is a great challenge.

The purpose of this in vitro study to evaluate the effect of different methods of porcelain surface treatments on the bond strength of metal bracket bonded directly using ONE-STEP orthodontic adhesive and study the mode of bond failure.

Materials and methods : Sixty maxillary right central incisor porcelain denture teeth were randomly divided into six groups(Gp),ten specimens for each; Gp.I(P) : phosphoric acid 37 % (control), Gp.II(PS) : phosphoric acid 37% & silane coupling agent, Gp.III(HS) : hydrofluoric acid 9 % & silane coupling agent, Gp.IV(SP): sandblasting with 50 μm Al2O3 particles & phosphoric acid 37 %, Gp.V(SPS): sandblasting with 50 μm Al2O3 particles, phosphoric acid 37 % & silane coupling agent, Gp.VI(SHS): sandblasting with 50 μm Al2O3 particles, hydrofluoric acid 9 % & silane coupling agent.

Metal brackets were bonded to treated porcelain surfaces (Pc.) using One -Step alpha-dent® orthodontic adhesive.

After thermocycling the shear bond strength (SBS) & mode of bond failure were determined.

Results : One Way ANOVA-test showed a statistically highly significant difference (p = 0.000) in SBS of the nonsandblasting groups and also showed a statistically highly significant difference (p = 0.000) of the sandblasting groups.

SHS Gp.

had the highest values in mean shear bond strength (6.459 ± 13 Mpa) of all groups followed by HS Gp.( 3.961 ± 0.9 Mpa) then SPS Gp.(2.096 ± 0.5 Mpa) then SP Gp.(1.16 ± 0.8 Mpa).On the other hand both P & PS groups had zero Mpa values of SBS.

Conclusions : The most reliable procedure for bonding orthodontic brackets to porcelain surfaces is through the surface treatment combinations of three methods: sandblasting, 9 % hydrofluoric acid treatment and silane coupling agent application.

On the other hand all other methods produced insufficient SBS for orthodontic treatment.

Adhesive-porcelain interface failure was the predominant mode of bond failure in all groups except the last group, cohesive failure was the predominant & none of the samples displayed fractures within the porcelain itself during debonding.