Clear aligners are now ubiquitous in orthodontics and likely a key part of your practice. You understand your role in producing an aligner that will ensure treatment success. But have you ever stopped and thought about a more basic factor in the effectiveness of that aligner—the material used to form it?
You know the names Invisalign and ClearCorrect, but do you know Zendura® and the key role it plays in the manufacture of clear aligners? Orthodontic Products interviewed Ray Stewart, PhD, principal and founder of Bay Materials LLC, which developed Zendura, a polymer resin that was key to the early development of clear aligners. Stewart talks to us about Zendura’s continued role in the manufacturing of clear aligners and about how orthodontists can incorporate this same material into their own practices to create in-office post-treatment retainers.
Orthodontic Products: What is Zendura, and why was it first developed?
Ray Stewart: Zendura is a thermoformable material with two primary applications. Orthodontists as well as small to large-size labs use it to form post-treatment retainers, and companies like ClearCorrect use it to form clear aligners. The first generation of Zendura was developed in 1999 by a group of material scientists at Bay specifically for orthodontic applications to provide the optimum balance of the key properties essential to orthodontic treatment. That later led to our developing and manufacturing the first generation of material used by Align Technologies Inc to manufacture its Invisalign product, known internally as EX30. When we first started working with them, they were experimenting with PC and later polyester materials, and breakage was prevalent with those materials. We developed an entirely new formula using polyurethane resins and are very proud of the role we played in the early days helping Align build and grow their business.
OP: What sets Zendura apart from other materials on the market?
Stewart: Zendura is considered a “premium” thermoformable material because it is made of relatively expensive medical-grade polyurethane resins and manufactured using very advanced proprietary processes and equipment. That’s why Zendura offers such superior stress retention, crack resistance, and stain resistance properties. By comparison, the other types of materials used for aligners or thermoformed retainers use relatively inexpensive polyester resins. Polyester resins are cheaper and a little easier to handle than polyurethane resins, but the trade-off is its performance and durability properties, which are inferior to those of polyurethane.
OP: What companies are using (or have used) Zendura for clear aligners?
Stewart: Zendura today is used broadly in North America and many international markets by dental labs, orthodontists, and major providers like ClearCorrect. Bay Materials is the sole provider of both aligner and retainer material to ClearCorrect. They like it so much they even make it available to their customers to make retainers in-house. Millions of appliances have been produced with Zendura for orthodontic applications.
OP: Why should orthodontists use Zendura to form their own post-treatment retainers?
Stewart: There are three components to forming truly durable, commercial-quality post-treatment retainers in-office. The first two are material and equipment selection, and the third is technical know-how. If you want to form long-lasting, commercial-quality retainers for post-treatment applications, you always want to use the very best material available. Zendura is the most expensive material, but in the materials market you get what you pay for. The cost of one broken retainer to your practice and to the patient will easily add up to hundreds of dollars. So, material selection is one area you don’t want to scrimp on. Also, if you break down the cost of producing a retainer in-office, material cost is far and away the smallest cost. Plus, if your patient is happy with their long-lasting retainer, they will be a repeat customer.
OP: What equipment do you recommend orthodontists use to fabricate appliances using Zendura?
Stewart: We strongly recommend to all our customers that they use pressure thermoformers, rather than vacuum thermoformers, to form both retainers and aligners. It’s all about psi. Even though the Zendura sheets we sell are only 0.30 inches in thickness, or 0.76 mm, it is still a much tougher material than the other thermoplastic materials available. So, to get excellent adaption, or detail, you should definitely use a pressure former. Vacuum formers offer only 11 to 14 psi, while pressure formers offer from 40 to 60 psi. The higher the psi, the better the adaption of the thermoplastic material.
You can still form Zendura with a vacuum former, though, and we have a lot of customers who do. Buying a good pressure former will be one of the best investments you’ll make for your practice.
OP: How long does it typically take to form a Zendura-based appliance in-office—for example, a retainer—and what is the life expectancy of the appliance?
Stewart: An experienced orthodontist or tech can use Zendura to form a retainer or aligner in just 3 to 5 minutes, depending on the type of thermoformer used. With a pressure former, it will take less time, and with a vacuum former, a little longer. The more time-consuming aspect of making retainers and aligners in-office is trimming the formed pieces. We can teach a novice tech how to form commercial-quality appliances with Zendura in as little as 15 to 20 minutes. A highly experienced tech can knock them out pretty quickly.
We have several how-to videos on YouTube on how to make and trim appliances made with Zendura. Retainers sourced from a lab or an aligner company are going to cost an orthodontist from $75 to $450 per set, while a set made in-office will cost about $28, of which about $20 is labor. So, retainers are high-margin items.
On the durability of Zendura, we have received feedback back from many orthodontists that their patients’ appliances made with it are able to last for 3 years or more and still “fit like a glove.”
OP: Do you have any tips for orthodontists using Zendura?
Stewart: If you aren’t forming your own post-treatment retainers in-office, I strongly recommend you make it a priority. Post-treatment retainers are a high-margin item, and they will prove a very profitable new revenue stream. And when you take that step, don’t scrimp on thermoplastic material and equipment selection. Using the best material available will pay big dividends immediately. If you haven’t tested Zendura yet, contact our Team Zendura Dental sales department and they’ll send you some free sheets. The material really sells itself.
And you’ll recoup your investment in a good pressure former in a few months. You’ll also find that having one will enable you to form many more products than you previously did because it extends your capabilities so significantly. If you can’t afford a new one, look for a good used one on Craigslist or eBay. We’ve tested most of the pressure formers available, and they are all very good. Some are easier to operate, which can also be an important feature.
OP: What’s next for Zendura?
Stewart: We’re developing an entirely new generation of Zendura, called Zendura XL, to ensure that it stays on the leading edge of the orthodontic materials market. It will set a new standard of excellence for both performance and durability in all the key properties. For retainer applications, it will offer still better crack resistance, stress retention, and stain resistance—the three properties of most interest to orthodontists. For aligner applications, it will offer a highly calculated progressive rate designed to provide faster and more precise movement of teeth and improved patient comfort. I can’t really say anything else about Zendura XL until it is commercially available in late 2015 or early 2016. OP