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

Jaana Ohtonen,Pekka K Vallittu,Lippo Lassila,Eija Säilynoja

doi:10.3390/ma14092319

Jaana Ohtonen, Pekka K Vallittu + Show 2 more

Open Access

https://doi.org/10.3390/ma14092319

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Abstract

The purpose of this study was to investigate the effect of retainer material and retainer position on a tooth to resist movement of the tooth in a simulation model. Bidirectional continuous glass fiber-reinforced composite (FRC) retainers and control retainers of steel wires were tested. The FRC retainers had a polymer matrix of bisphenol-A-glycidyldimethacrylate (bis-GMA) and poly(methylmethacrylate) (PMMA), and it was cured with a photoinitiator system. The retainers were adhered to a lower jaw Frasaco model in two different positions. Resistance against the movement of one tooth was measured from two directions. The average load values within the FRC retainer groups were higher than within the metal retainer groups. The load values for the groups loaded from the axial direction were higher than those loaded from the buccal direction. FRC retainers, which were located 1–2 mm from the incisal edge, showed higher load values than those located 4–5 mm from the incisal edge. There was a significant difference in load values between FRC retainers and metal retainers (p < 0.01). The wire position and the direction of force also had significant effects (p < 0.01). There were no significant differences between metal retainer groups. The results of this study suggest that metal retainers are more flexible, allowing for tooth movements of larger magnitude than with FRC retainers.

Highlights

Orthodontic retention has an important role in orthodontic treatment for maintaining an achieved outcome
The fiber-reinforced composite (FRC) retainers (HS glass, Universal Star Group Limited, Ningbo, China) and two brands of metal retainers—five strands of stainless steel wire (Penta One, 0.55 mm corresponding to 0.0215 inches, Masel, Ortho Organizers, Carlsbad, CA, USA, Lot F1408572) and flattered 8-braided stainless steel wire (Straight 8 Lingual Retainer Wire, 0.71 mm × 0.20 mm corresponding to 0.028 inches × 0.008 inches, Db Orthodontics, Silsden, United Kingdom, Lot no 134378)—were tested using a loading test to determine flexural stiffness of the retainers, which were bonded to the lingual surface of the Frasaco models
When the force was axial, load values were higher in the FRC retainer groups if the retainer was placed closer to the incisal edges (1–2 mm) than in the cervical area (4–5 mm)

Summary

Introduction

Orthodontic retention has an important role in orthodontic treatment for maintaining an achieved outcome. Proper retention is needed to prevent unwanted, possible relapse from occurring [1,2,3,4]. Retention devices, such as retainers, can be fixed or removable [5]. Fixed retainers in the lower jaw are typically bonded to all six front teeth or only to the canines [5,6]. Fixed retainers are made from monofilament stainless steel wire (0.030 or 0.032 inches, corresponding to 0.752 or 0.0813 mm), multistranded round stainless steel [7,8], or flattened eight-braided stainless steel wires [9,10]

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