title: Effects of ultrasonic instrumentation with different scaler-tip angulations on the shear bond strength and bond failure mode of metallic orthodontic brackets.
abstract: OBJECTIVE
  To evaluate the effects of ultrasonic instrumentation with different scaler-tip angulations on the shear bond strength (SBS) and bond failure mode of metallic orthodontic brackets.
  
  
  METHODS
  Adhesive pre-coated metallic brackets were bonded to 72 extracted human premolars embedded in autopolymerizing acrylic resin. The teeth were randomly divided into 3 groups (n = 24 each) to undergo no treatment (control group) or ultrasonic instrumentation with a scaler-tip angulation of 45° (45°-angulation group) or 0° (0°-angulation group). SBS was tested in a universal testing machine, and adhesive remnant index (ARI) scores were recorded. The Kruskal-Wallis test and Mann-Whitney U-test were used for statistical analysis.
  
  
  RESULTS
  The control group had a significantly higher mean SBS value than the treated groups, which showed no significant differences in their mean SBS values. The ARI scores were not significantly different among the groups.
  
  
  CONCLUSIONS
  Ultrasonic instrumentation around the bracket base reduces the SBS of metallic orthodontic brackets, emphasizing the need for caution during professional oral hygiene procedures in orthodontic patients. The scaler-tip angulation does not influence the SBS reduction and bond failure mode of such brackets.
authors: Department of Orthodontics, University of Bologna, Bologna, Italy.
authors: Giulio
authors: G
authors: Alessandri Bonetti
authors: Department of Orthodontics, University of Bologna, Bologna, Italy.
authors: Serena
authors: S
authors: Incerti Parenti
authors: Department of Orthodontics, University of Bologna, Bologna, Italy.
authors: Daniela Rit
authors: DR
authors: Ippolito
authors: Department of Orthodontics, University of Bologna, Bologna, Italy.
authors: Maria Rosari
authors: MR
authors: Gatto
authors: Department of Periodontology, University of Bologna, Bologna, Italy.
authors: Checchi
authors: C
authors: Luigi
keywords: Bonding; Bracket; Oral hygiene; Ultrasonics