Korean J Orthod.  2015 Sep;45(5):268-272. 10.4041/kjod.2015.45.5.268.

A new type of clear orthodontic retainer incorporating multi-layer hybrid materials

• Ahn HW
• Kim KA
• Kim SH

• KMID: 2068522
• DOI: http://doi.org/10.4041/kjod.2015.45.5.268

Abstract

Clear thermoplastic retainers have been widely used in daily orthodontics; however, they have inherent limitations associated with thermoplastic polymer materials such as dimensional instability, low strength, and poor wear resistance. To solve these problems, we developed a new type of clear orthodontic retainer that incorporates multi-layer hybrid materials. It consists of three layers; an outer polyethylenterephthalate glycol modified (PETG) hard-type polymer, a middle thermoplastic polyurethane (TPU) soft-type polymer, and an inner reinforced resin core. The resin core improves wear resistance and mechanical strength, which prevent unwanted distortion of the bucco-palatal wall of the retainer. The TPU layer absorbs impact and the PETG layer has good formability, optical qualities, fatigue resistance, and dimensional stability, which contributes to increased support from the mandibular dentition, and helps maintain the archform. This new type of vacuum-formed retainer showed improved mechanical strength and rate of water absorption.

Keyword

Polyethylenterephthalate glycol modified; Retention; Thermoplastic; Thermoplastic polyurethane

MeSH Terms

Absorption
Dentition
Fatigue
Orthodontic Retainers*
Orthodontics
Polymers
Polyurethanes
Water
Polymers
Polyurethanes
Water

Figure

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  Figure 1 The fabrication process of multi-layer vacuum-formed retainers (VFRs). A, Inner reinforced resin core. B, Connection with thermoplastic dual layers. Threepoint occlusal contact is achieved during the vacuum forming procedure. C, Final product. D, Schematic diagram of multi-layer VFRs.

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  Figure 2 The change in water absorption rates for up to 2 weeks according to the number of layers in the vacuum-formed retainers.

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  Figure 3 Clinical application of the multi-layer vacuum-formed retainer (VFR) in a patient with bruxism. A, Debonding (delivery of the multilayer VFR). B, One-year after retention. The form and function of the VFR was well maintained.

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