Objective: To test the null hypothesis that enamel deproteinization with 10% papain gel does not increase the shear bond strength of orthodontic brackets bonded with resin-modified glass ionomer cement (RMGIC). Materials and Methods: One hundred and twenty bovine incisors were used and divided into eight groups: 1) Transbond XT according to the manufacturer's recommendations, 2) Transbond XT deproteinized with 10% papain gel, 3) RMGIC without enamel deproteinization and without etching, 4) RMGIC without enamel etching and with deproteinization with 10% papain gel, 5) RMGIC deproteinized with 10% papain gel and etched with polyacrylic acid, 6) RMGIC deproteinized with 10% papain gel and etched with phosphoric acid, 7) RMGIC deproteinized with 2.5% sodium hypochlorite, and 8) RMGIC etched with polyacrylic acid. After bonding, the mechanical tests were performed in a Universal mechanical test machine. The values obtained were submitted to an analysis of variance and afterward to the Tukey test (P , .05). Results: It was demonstrated that group 2 presented the highest shear bond strength value, and this differed statistically from the others; group 3 presented the lowest value and showed no differences from groups 4, 5, 7, and 8. Regarding the Adhesive Remnant Index, groups 2 and 6 presented the best results and groups 3 and 8 the worst. It could be concluded that enamel deproteinization with 10% papain gel increases the shear bond strength, irrespective of the etching agent. Conclusions: The hypothesis is rejected. Papain gel was shown to be a new ally in the orthodontic clinic. (Angle Orthod. 2012;82:541-545.)

BackgroundThe objective of this study was to verify the hypothesis that enamel deproteinization with papain gel at concentrations of 2%, 4%, 6%, 8%, and 10% increases shear bond strength as concentration increases.MethodsA total of 180 bovine mandibular permanent incisors were used, divided into six groups (n = 30), and denominated as follows: group 1 is the control group (CG) in which brackets are bonded with resin-modified glass ionomer cement (RMGIC) according to the manufacturer's recommendations and groups 2, 3, 4, 5, and 6 have brackets bonded with RMGIC after enamel deproteinization with papain gel at concentrations of 2%, 4%, 6%, 8%, and 10%, respectively. After bonding, teeth were immersed in artificial saliva and kept at a temperature of 37°C for 24 h. Mechanical tests were then performed in a universal mechanical test machine EMIC DL 5000 (Sao Jose dos Pinhais, Brazil). Values obtained were submitted to analysis of variance and then to Tukey's test (p < 0.05).ResultsThe results demonstrated that groups 5 and 6 showed the highest shear bond strength, differing statistically from the other groups (p < 0.05). CG with no papain gel used showed the lowest value and in turn showed no differences for groups 2, 3, and 4. As regards adhesive remnant index, CG showed statistical differences from the others. Groups 2, 3, 4, 5, and 6, in which papain gel was used, presented no statistical differences among them (p > 0.05).ConclusionsIt was concluded that enamel deproteinization with 8% and 10% papain gel increases shear bond strength of orthodontic brackets bonded with RMGIC.