Analysis of mode of fracture and adhesive remnant index of self-adhesive composite resin on sound and bleached enamel surface
Introduction: Orthodontic bracket bonding with enamel surface of teeth is the fundamental procedure for orthodontic treatment and is directly related with an effective and successful teeth alignment. The objective of study was to analyze adhesive remnant index (ARI) of self-adhesive resin used for orthodontic brackets, to assess bond strength, and to determine the type of bond failure and its location.
Materials and Methods: This was an experimental study conducted at School of mechanical and chemical engineering SCME (NUST) with a duration of 6 months. Sixty premolar teeth between the age of 13-25 were randomly selected. The inclusion criteria were non dried, non-fractured teeth with intact buccal surface. All teeth were stored in normal saline. They were then divided into three equal groups. (n=20). Group one was a non-bleached (control group). Group two was bleached and bracket bonded on the same day. While group three was bleached two weeks prior to bracket bonding. Orthodontic brackets were bonded with RelyXU 200 self-adhesive on all respective groups. Mechanical de bonding was performed at Universal Testing Machine at the cross-head speed of 1 m m/sec. The (ARI) adhesive remnant index and fracture mode was determined with the stereo microscope having six-fold magnification and grading was carried out for given groups.
Results: For ARI, Pearson Chi Square test showed significance level of 0.01 which indicated significant difference among groups. The failure mode of self-adhesive was mainly adhesive at the enamo – adhesive interface.
Conclusions: The RelyX U200 showed the trend of adhesive failure for all groups with no adhesive on enamel surface or very minimal amount of adhesive on enamel. This enables the orthodontist to spend much less time on the post bonding cleanup. Iatrogenic damage to enamel due to rotary instrument is also reduced.
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