Abstract
Introduction:Failure of orthodontic bonded retainers may affect the orthodontic results and cause relapse.
Objectives:To compare in vitro the effect of vertical load on failure of three different bonded lingual retainers:Flat braided wire “Bond A. Braid", Dead soft wire “RESPOND", Fiber reinforced composite “Infibra Ribbon". Bonded with Tetric-N Flowadhesive system.
Materials and Methods:Ninetymandibular incisors were used in the study, thirty specimens (N=30) in triads divided into 3 groups (n=10 for each group). Roots of the incisors were covered with elastomeric impression material to mimic periodontal ligaments elasticity and embedded in triads in acrylic resin blocks. They were randomly divided into 3 groups to receive the following retainer wire materials:Group A (Flat braided wire “Bond A. Braid"), Group B (Dead soft wire “RESPOND"), and Group C (Fiber reinforced composite “Infibra Ribbon"). And these retainer wires were bonded to the lingual surfaces using Tetric-N Flowadhesive system.The three groups were subjected to 10,000 thermal cycles between 55▫C & 5▫C using a thermo-cycling machine. Each specimen was subjected to loading forces at the incisal edge of the middle incisor for 125,000 cycles. Then failure forces were measured using a Universal Testing Machine at a cross head speed (1mm/min) applied on the wire of the interproximal segments.Failure sites were determined and the adhesive remnant index (ARI) was observed using a stereomicroscope at (×20) magnification.
Results:Mean debonding forces were 46.27 ±
12.28, 36.03 ± 6.09, 30.09 ± 15.73 N for Groups A,B and C respectively, presenting significant difference between the groups (p < 0.05). The highest value for the mean force was found for the Bond-A-Braid (group A) and the lowest value for the mean force was found for the FRC (group C). There was no statistically significant difference in displacement among test groups. There was no fracture occurred of any wire. There was no significant difference between the distribution of the ARI score between the three groups (p=0.322).The ARI scores were observed under the optical stereomicroscope showing multiple failures at the composite-wire interface and the tooth-composite interface.
Conclusions: There was a significant difference between “Bond A. Braid" wire and “FRC" where “Bond A. Braid" had the highest debonding forces and the “FRC" had the lowest debonding forces. There was no significant difference in displacement of the retainers between the three groups. There was no significant difference between the ARI of the lingual retainer systems and types of failure as well.