I often get the question about the retainer and aligner plastics we use at ODL. Our techs have tried almost every thermal-formed material available, and I recommend two companies. For our conventional plastic, the material from Leone is excellent. It has a high resistance to breakage compared to similar products and a high level of clarity. It also has an affordable price tag. For a premium material, we use Zendura by Bay Materials, a Silicon Valley R&D startup. They make quite a few claims about their product, and I must admit, they shine in almost all of them. I offer customers when they start with our Vivid retention product a free retainer with Zendura. 9 out of 10 times they pay the premium. In this post, I want to focus mainly on the Zendura material.
One of the reasons Zendura performs well is because of its proprietary and very expensive polyurethane (TPU) resin using high-end manufacturing processes. By comparison, all the other orthodontic plastics available today from companies like Dentsply/Essix and Scheu Dental for making aligners and retainers are all made from relatively inexpensive “commodity” resins, primarily polyester (PETG). It is the same basic resin used to make plastic pop bottles, and this mostly accounts for why those materials do not perform nearly as well as Zendura.
The only other materials in use today for making clear aligners and retainers made from a polyurethane resin are the materials used by Align Technology for making its Invisalign products. Bay Materials developed and used to supply plastic to Align Technology for its aligners, which pioneered today’s clear aligner industry and played a role in Align’s early success.
Zendura has an excellent balance of all the properties for making a high performing aligner and retainer, including excellent stress retention, crack resistance, clarity and stain resistance.
Stress retention is a fundamental property of Zendura to resist changes in the plastic throughout each treatment phase. What this means is the plastic maintains its memory and provides a constant pressure resulting in successful tracking with our Vivid Aligners. It is also why you will notice better long-term retention with our Vivid Retainers. “Zendura’s unique rigid polyurethane formulation combines high strength and ductility with low-stress relaxation and practical toughness.” – Bay Materials
Eliminating breakage means improved patient wear compliance and reduces remakes. Because of Zendura’s strong polymer backbone, it has a high resistance to cracking. In impact strength tests conducted alongside other preferred orthodontic materials, Zendura is found to be 2X more crack resistant than its closest competitors. Zendura appliances have been used in retention and also night guard applications for periods as long as three years.
Clarity and Stain Resistance
The oral cavity is a particularly harsh environment. Highly caustic and staining agents like mustard, tea or coffee are often present. Zendura maintains exceptional clarity and color stability throughout the treatment phase. Bay materials conducted stain testing. Retainers were submerged in yellow mustard and placed in a 37C (98.6F) oven for 24 hours. Zendura showed little color change, while its closest competitor had over 3X the amount of yellowing.
ODL makes its clear retainers (Zendura) using 0.76mm (.030″) thick material. This gauge is thinner than nearly all the other products which recommend .040 (1mm) due to their lower resistance to cracking. Zendura is a high-end plastic, so at 0.76mm, it is more than thick enough to handle all the rigors patients can throw at them. Also, the thinner the material used to make an appliance, the more comfortable it will be in the patient’s mouth.
Zendura is also BPA, phthalate, and gluten-free, making it one of the safest materials available.