Safa B. M. Alawy, Eman M. El Shourbagy And Safaa A. Ghobashy,

ABSTRACT
Aim Of The Work: The Aim Of This In Vitro Study Was To Evaluate The Effects Of Recycling And Repeated Recycling With Erbium: Yttrium Aluminum Garnet (Er:YAG) Laser On Shear Bond Strength And Surface Characteristics Of Stainless Steel Orthodontic Brackets.

Materials and Methods: Ninety Extracted Upper First Premolars And Ninety Stainless Steel Brackets Were Used For This Study. The Brackets Were Bonded To The Premolars And Were Randomly Divided Into Three Groups Of 30 Teeth/each: Group I (control), Group II (brackets Debonded And Recycled One Time Using Er:YAG Laser), And Group III (brackets Debonded And Recycled Two Times Using Er:YAG Laser). Twenty Samples From Group II And III Were Rebonded Again To The Same Re-prepared Enamel. Sixty Bonded Samples (20/each Group) Were Subjected To Shear Bond Strength Testing Using Universal Testing Machine. The Shear Bond Strength Data Were Analyzed With One-way ANOVA Test, Followed By Tukey�s Test. The Bracket/adhesive Failure Modes Were Scored As Adhesive Remnant Index. The Chi-square Test Was Used To Evaluate Statistical Differences In The Adhesive Remnant Index Scores Among Groups. Ten Debonded Brackets From Each Group Were Examined Under A Scanning Electron Microscope To Identify The Surface Characteristics Of The Brackets� Mesh.

Results: The Results Of This Study Demonstrated That The Mean Shear Bond Strength Of All Groups Were More Than That Recommended For Successful Orthodontic Bonding, There Was No Significant Difference Between Group I And Group II (P>0.05). Repeated Recycled Brackets (group III) Had Significantly Lower Shear Bond Strength (P?0.001) Than Other Groups. Scanning Electron Microscopic Analysis Showed Maximal Removal Of Adhesive From The Brackets Recycled One Time With Er:YAG Laser With Well-defined Lattice Structure, And No Damage To The Bracket Base. There Was Incomplete Removal Of The Adhesive From Repeated Recycled Brackets, Flattening And Distortion Were Observed In Two Samples. Conclusion: Er:YAG Laser Recycled Brackets Can Be Used As An Alternative To New Brackets In Case Of Bond Failure Which Might Provide Cost Reduction. However, In Case Of Second Bond Failure To The Same Bracket, It May Be Preferred To Use A New One Instead Of Reusing It For Second Time.