الفهرس 
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Abstract
Objective: the present study was conducted to evaluate and compare the effect of using three different deproteinizing agents on the shear bond strength (SBS) of metal orthodontic brackets. Materials and Methods: One hundred forty premolars were randomly divided into seven groups (n=20) according to the type and the application protocol of the deproteinizing agents. Metal orthodontic brackets were bonded on the buccal surfaces of all premolars after acid etching with 37% phosphoric acid for 15 seconds using Transbond XT adhesive and primer. In group I no deporoteinizing agent was applied. In groups II, IV and VI the 5.25% NaOCl, Papacarie DuoTM and Bromelain® were applied respectively before acid etching. In groups III, V and VII the deproteinizing agents were applied after acid etching. The SBS, the penetration depth of adhesive resin tags and the adhesive remnant index (ARI) were assessed. Data analysis were performed using ANOVA, LSD post-hoc, t and chi-square tests. Results: Application of the deproteinizing agents before or after acid etching significantly increased the SBS (P<0.05). However, no significant difference was found in the SBS between the groups with the same deproteinizing agent (P>0.05). Application of deproteinizing agents before or after acid etching significantly increased the penetration depth of resin tags (P<0.05). The ARI results revealed no significant difference between the studied groups (P>0.05). However, after the deproteinizing agents were applied, the bond failure was mostly at the adhesive bracket interface. Conclusion: 5.25% NaOCl, Papacarie DuoTM and Bromelain® could be used successfully to enhance the bond strength of metal orthodontic brackets.