Glass Fiber Reinforced Composite Orthodontic Retainer: In Vitro Effect of Tooth Brushing on the Surface Wear and Mechanical Properties

Abstract

Fiber reinforced composites (FRCs) are metal free materials that have many applications in dentistry. In clinical orthodontics, they are used as retainers after active treatment in order to avoid relapse. However, although the modulus of the elasticity of FRCs is low, the rigidity of the material in the form of a relatively thick retainer with a surface cover of a flowable resin composite is known to have higher structural rigidity than stainless steel splints. The aim of the present study is to measure load and bending stress of stainless steel wires, as well as flowable resin composite covered and spot-bonded FRC retainer materials after tooth brushing. These materials were tested with a three point bending test for three different conditions: no brushing, 26 min of brushing, and 60 min of brushing. SEM images were taken before and after different times of tooth brushing. Results showed that stainless steel was not significantly affected by tooth brushing. On the other hand, a significant reduction of values at maximum load at fracture was reported for both FRC groups, and uncovered FRCs were most affected. Concerning maximum bending stress, no significant reduction by pretreatment conditions was reported for the materials tested. SEM images showed no evident wear for stainless steel. Flowable resin composite covered FRCs showed some signs of composite wear, whereas spot-bonded FRCs, i.e., without the surface cover of a flowable resin composite, showed signs of wear on the FRC and exposed glass fibers from the FRC’s polymer matrix. Because of the significant changes of the reduction of maximum load values and the wear for spot-bonded FRCs, this technique needs further in vitro and in vivo tests before it can be performed routinely in clinical practice.

Fear of the Relapse: Effect of Composite Type on Adhesion Efficacy of Upper and Lower Orthodontic Fixed Retainers: In Vitro Investigation and Randomized Clinical Trial

“…The most recently proposed in dental practice are made of fiber-reinforced resin composite (FRC) [34,35] which guarantees high mechanical properties and good aesthetic effects [36]. However, further studies should be conducted in the future analyzing FRC wires' mechanical behavior [37].…”

The effect of composite bonding spot size and location on the performance of poly-ether-ether-ketone (PEEK) retainer wires

“…Multi-stranded wires had been the most common type of fixed retainers for decades [11] . The PEEK is a member of the family poly-aryl-ether-ketone, which is known for good strength, high mechanical fatigue strength, and having a very good chemical resistance [29] .…”

“…Each retainer has its downsides, like wire failure, unraveling, bond breakage, allergy, etc. [10,11] . Retainers should have qualities like being esthetic, biocompatible, adaptable with ease to the lingual surface [1] , capable of resisting deformation, passive at the time of placement [12] , having adequate flexibility to allow physiologic movement of the teeth, which helps to reduce stress concentration within the composite.…”

The Effect of Material Type and Location of an Orthodontic Retainer in Resisting Axial or Buccal Forces

“…Multistranded stainless steel wires are thin (0.0215 or 0.175 inches, corresponding to 0.55 or 0.45 mm) and flattered eight-braided wires are even thinner (0.016 × 0.026 or 0.028 inches × 0.008 inches, corresponding to 0.41 × 0.66 or 0.71 mm × 0.20 mm), whereas an FRC retainer with an overlaying flowable resin composite may become thicker, being, e.g., 0.75 mm (everStick Ortho ® 0.75 mm, Angelus Interlig ® 0.2 mm, Ribbond THM-Ortho ® 0.18 mm × 1.0 mm). A layer of flowable resin composite, which is used to cover the FRC core, is required to prevent wear of the FRC layer [ 18 ].…”