الفهرس 
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Abstract
Background: Retainer is a necessary procedure when orthodontic treatment complete to avoid relapse due to periodontal fiber elasticity and to allow for alveolar bone regeneration. Compare the influence of vertical force on the failure of three fixed retainers: CAD/CAM polyether ether ketone (PEEK), CAD/CAM fiber glass reinforced composites (FRCs), and lingual retainer wire ”Bond-A-Braid™”.
Materials and methods: One hundred and eight maxillary first premolars teeth were randomly allocated to three groups: group A (CAD/CAM PEEK), group B (CAD/CAM FRC), and group C (lingual retainer wire ” Bond-A-Braid™”). These retainers were bonded using Assure Plus Bonding Resin and GO TO Paste. For each specimen, a loading cycling and thermocycling machine was used. The failure debonding forces were measured on the interproximal segments using a universal testing machine with a cross-head speed of 1 mm/min. The adhesive remnant index (ARI) was calculated after identifying types of failure with a stereomicroscope at (X 20) magnification.
Results: group B and group C showed the highest failure bonding forces, with a mean of 209.67±16.15 and 86.81±4.59 Newton, respectively. However, group A had a statistically significant lower bond failure force, with a mean value of 45.73±4.48 Newton. At baseline, there was a statistically significant difference in connector retainer displacement between the three studied groups (p<.001). The ARI score was not statistically significant (p<.001) between the three study groups; for groups A and B, the ARI was predominantly score 3, and group C showed a mixed score of 2 and 3. The failure mode of retainers was investigated using an optical stereomicroscope. In group B, there was a cohesive breakdown in the retainer, and groups A and C exhibited failures primarily in the adhesive at the retainer interface.
Conclusion: All groups differed significantly, with group A having the lowest debonding force and group B having the highest. Furthermore, there was not a substantial variation in ARI, but there was a significant difference in connector retainer displacement and the types of failure amongst the three groups.
Key words: Fixed retainer, CAD\CAM, Digital orthodontics, FRC, PEEK