Thermoplastic materials have been available in prosthetic dentistry for more than 30 years and the market place continues to grow with new and existing companies manufacturing their own products.
What makes these dentures different from traditional partial dentures is the material from which they are made and how they are made.
Unlike acrylic dentures, they are made from a thermoplastic nylon resin that is ultra thin, very flexible (think more comfortable for chewing and speaking) and is so durable that one company – Valplast – offers a lifetime warranty for fractures or breaks.
The material doesn’t absorb odors or stains, and if patients suffer from allergies to acrylic or certain metals, it’s a great choice. It contains no BPAs and is considered the most biocompatible material.
Some patients feel that the appliance “disappears” or is “invisible” in their mouth, thus the esthetics of it is far superior to conventional acrylic/metal partial dentures.
The cost may be slightly higher than conventional acrylic partial denture because the fitting and finishing time at the lab is increased, but the result makes it well worth it.
Thermoplastics like Flexite, TCS (IFLEX) and Valplast all differ from regular thermosets like acrylic powder and liquid because they are already polymerized (cured) when manufactured and shipped to your lab. They can be manufactured in many forms, from sheet to pellets to powder. Once heat is introduced, the plastic is softened to the desired state and then injected into a mold. The only thing that changes is its physical shape; there are no actual chemical changes. Thermoplastics will differ depending on their molecular composition – some require higher temps to become moldable and some require greater injection pressures.
One advantage of this material is that there is also flexibility in the design of the types of clasps. We can often use the circumferential ring clasp on any freestanding tooth and it works well on medially tipped mandibular molars. It can make an excellent transitional restoration during the healing period on implant cases.
Your dental lab will have its preference for which thermoplastic material it prefers to work with. Some are more difficult to finish, fit and adjust than others. Some may require more repairs to the teeth than others. Some may prefer a specific material because of the color blending. A conversation with your technician will help you decide the best material for your patient.
The biggest challenge for the dentist is the adjusting and polishing of the material. Do not think acrylic when polishing by using a quick and pressure-applied motion. Think of dividing the appliance in sections and spending one minute per section. That will seem like a long time when your experience is only conventional acrylic resin.
Whether or not you are using Valplast, Flexite, TCS or Iflex, each company has a system for polishing. If you are going to provide these partial dentures, be sure you have the armamentarium to polish them well.
The partial needs a smooth and satin finish before polishing so use the appropriate rubber wheels. I typically round the edges of the wheel when I receive them so that I don’t accidentally cut into the nylon with a sharp edge. If there are any spots that the wheel cannot access, I recommend using a Robinson wheel in a horizontal motion with a light dusting technique.
Patients are very happy with these prostheses because they are fabricated readily and don’t require multiple try-in appointments. I suspect in the future we will make very few traditional metal acrylic removable partial dentures as this material excels for all our patients. The challenge for us is in adjusting it.
Mary Anne Salcetti, DDS, PC, Spear Visiting Faculty