19 June 2019

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What are the best cleaning methods for thermoform retainers?

Davide Elsido

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In the May 2019 issue of the Journal The Angle Orthodontist an article was published concerning long-term effects of various cleaning methods on polypropylene/ethylene copolymer retainer material. Following the completion of orthodontic treatment, one of the most important goals is maintaining the finished result. It was reported that approximately 70% of orthodontic cases result in some degree of relapse. The causes of relapse are due to a number of different factors, including the periodontium, occlusion, soft tissue, and growth. Clear thermoplastic retainers have increased in popularity due to their desired esthetics and ease of fabrication. The two most common materials used for vacuum-formed retainers (VFRs) are polyethylene polymers and polypropylene/ethylene copolymers. Polyethylene polymers are considered more esthetic because the material is virtually transparent; however, polypropylene/ethylene copolymers are considered to be more durable and flexible.

MATERIALS AND METHODS  
In the study, eight different cleaning methods evaluated were:

• Invisalign Cleaning Crystals (Align Technology, Inc.; San Jose, Calif);
• Retainer Brite Cleaning Tablets (Dentsply International; York, Pa);
• Polident Antibacterial Denture Cleaner (GlaxoSmithKline; Philadelphia, Pa);
• Listerine Cool Mint (Johnson & Johnson Consumer, Inc.; New Brunswick, NJ);
• 2.5% vinegar; 0.5% sodium hypochlorite; 3% hydrogen peroxide;
• tooth brushing with distilled water.

For all eight cleaning methods, five of the 10 specimens were subjected to tests for flexural modulus, and the other five specimens were subjected to tests for light transmittance and surface roughness.

RESULTS
The results indicate that different cleaning methods affect the long-term light transmittance of the studied polypropylene/ethylene copolymer retainer material. H2O2 is not recommended as a cleaning solution for polypropylene/ethylene copolymer retainer material due to its powerful oxidizing abilities.
 At the present time, there is no ideal cleaning method for polypropylene/ethylene copolymer retainer material.

CONCLUSIONS
Different retainer materials required different cleaning solutions to maintain their original translucency and flexibility. Even if the conclusions of this article don’t have a strong clinical relevance, it gives ground for reflection on these devices, which are usually delivered to patients with limited information about their maintenance.

For additional informations: 
Long-term effects of various cleaning methods on polypropylene/ethylene copolymer retainer material