Since our discovery of the material Polyoxymethylene (POM) just before the first lockdown in March 2020, we have been working with this new material every day for three years. We have gained a lot of experience with it and know which prosthetic solutions we want and can create and which ones we don’t.

It is perhaps time now to share our experiences from the past years, especially since a scientific article has recently been published in the Journal of Clinical Medicine MDPI about this special material.

The POM partial prosthesis; what is it and what do you call it?

In the beginning, we encountered some challenges, such as the naming of the removable appliance we started with. Is it a “frame” made of POM, or is it a partial prosthesis like a partial plate prosthesis made of pink PMMA plastic?

One thing is certain; a partial prosthesis made of POM is definitely not the same as a metal frame prosthesis. Many principles that apply to a metal frame, such as the design, the periodontally friendly nature of a frame, and the preparation of occlusal supports and clasp outputs, do not apply to a partial prosthesis made of POM.

However, the POM partial prosthesis is also not the same as a plastic partial plate prosthesis made of PMMA. In our opinion, this simple and relatively affordable appliance is really intended for use in a transitional dentition. To easily add elements to such a plate prosthesis when they are ready for extraction.

So what is the POM partial prosthesis then?

Our experience shows that the POM partial prosthesis is actually a hybrid form that also lies in terms of design between the partial plate prosthesis and the metal frame prosthesis.

Like a metal frame, the POM partial prosthesis is intended to be used in a stable dentition. POM is tooth-colored, biocompatible, hypoallergenic, fits beautifully, is extremely strong, resilient, 0.7 mm thick (as light as a feather), provides comfort, has minimal palate coverage, and tooth-colored anchors.

POM practically does not absorb moisture, only minimally changes color, but … is difficult to polish and bring to a real high gloss. As a result, staining can develop on the lingual/palatal side of the POM surface, which also depends on the user’s oral hygiene and diet.

The color is not as unaesthetic as metal but is acceptable. So it’s important to show it to a patient in advance so that the aesthetic result does not disappoint. Some anchors, even if they are tooth-colored, can be visible if they are in the aesthetic zone.

The POM partial prosthesis turns out to be an ideal product for people who (sometimes extremely) struggle with gagging (hyper-thin palatal plate that also fits nicely due to CAD-CAM manufacturing). But also for people who suffer from allergic reactions to PMMA or, for example, Nickel (because POM is hypoallergenic) or people who grind their teeth excessively – due to its strength – because we also make bite splints and splints from it. The POM splints are much more durable than all the other splints we make.

What preparations does the dentist make when starting with a POM appliance?

Not much, actually. First of all, it is not necessary to make preparations in the teeth for occlusal supports and the like. Perhaps it is sometimes convenient (and also better for the end result) to reshape adjacent teeth that have migrated and sometimes tilted due to diastemata that have arisen from extractions by removing strong undercuts. Pre-making a frame design and individually imprinting it with a plastic spoon is not necessary.

The dentist can suffice by making two accurate, bubble-free alginate impressions in the first appointment (pre-smearing the dentition for the best result is highly appreciated), taking a maximum occlusion registration, and determining the tooth color. If a mouth scanner is available in the practice, making a scan of the dentition and capturing the maximum occlusion is, of course, sufficient.

What types of provisions have we made

with POM in the past 3 years? Actually, all the provisions mentioned below started as experiments in consultation with the practitioner and the patient. After all, the material and way of working were completely new to everyone.

• First, we started with the POM partial prosthesis in the upper and lower jaw,
• and the POM mini (a unilateral removable appliance of 1 to 3 elements that is also suitable for use immediately after implantation instead of an Essix retainer),
• an individual solitary POM anchor for one element, combined in a partial plate prosthesis made of PMMA or as part of a metal frame prosthesis,
• various types of bite plates and splints for (severe) bruxists or people suffering from epilepsy or spasms,
• the partial prosthesis with a Dahl plateau or with POM uplays to increase the bite, the classic uplay frame as you know it but now without anchors and made of POM,
• a telescope bridge in POM as a multi-year semi-permanent provision,
• a palatal POM plate in a 100% complete dentition to close a defect that has occurred in the palate (due to cocaine use),
• for the edentate maxilla a palatal plate made of POM instead of a full metal plate to create a strong and hyper-thin prosthesis (plate 0.7 mm thick!),
• POM reinforcements embedded in implant-supported prostheses,
• a POM partial prosthesis in a (sometimes severely mutilated) dentition with Locators incorporated implants, the ‘snap-on teeth’ in POM. Various removable provisions in POM, especially for Special Dentistry, such as ‘snap-on teeth’ as we call them; a ‘snap-on teeth’ looks like an Essix retainer or a bleaching tray but is made of tooth-colored POM.
• The ‘snap-on teeth’ can also be made in a CR position (i.e., in a new bite) and ‘clicks’ right into the undercuts of the teeth and thus attaches to the dentition. You can imagine that this provision could be a solution for Oligodontics and their practitioners and that people with severe tooth wear and therefore a lot of hard tissue loss could also benefit from it.
• We have made several unique products, such as a VP in pink combined with dentin-colored POM for an edentulous patient allergic to PMMA.
• For an edentulous patient with 6 implants in the maxilla and mandible that were clamping and grinding everything that dental technicians had previously made for him, we made two fully screw-retained bridges in dentin-colored POM.

What should you not want to make in POM?

Actually, we have come to the conclusion that we no longer want to make immediate provisions with POM. It doesn’t work in the long term because the tissue shrinks and the POM partial prosthesis no longer fits nicely over time, despite relining the saddles. Sometimes it is possible to add an element to a POM partial prosthesis, but sometimes it is not. POM partial prostheses should only be made in a stable dentition, as mentioned before.

Cleaning

is still a bit of an issue; the lingual and palatal areas facing the tongue can accumulate some staining. We advise the patient to brush the POM appliance thoroughly with a rotating toothbrush while the POM partial prosthesis is still in situ. This can apply some pressure to the POM surfaces. Afterward, remove the POM partial prosthesis and continue brushing it, as well as the natural dentition, of course.

We recommend occasionally soaking the POM partial prosthesis in a vinegar solution or in a glass of fresh cola, for example (due to the citric acid in it) to dissolve any existing plaque and tartar.

Another option is to have the POM appliance polished and brought to a high gloss by the dental technician once a year if desired. It will look like new again.

The technical costs of a POM partial prosthesis are significantly lower than those of a metal frame prosthesis. For information on technical costs and for all special provisions and requests involving POM, you can call or email us.

Durability

Polyoxymethylene is a thermoplastic material (melting point 235 degrees), so it is recyclable. The residue left after milling a provision is delivered to a company that processes it into new POM products for us. This is how we ensure sustainability with this material.

Colors

POM is available in the following colors:

• A1
• A2
• A3
• A3.5
• B1
• C1
• C3
• Prosthetic Pink

What is POM?

The plastic is a polymer. The official name is Polyoxymethylene (abbreviated as POM), also known as polyacetal, is a polymer that is primarily used in industry due to its hardness. The substance is also known under the trademark Delrin, developed by DuPont. Polyoxymethylene was discovered by Hermann Staudinger, a German chemist who received the Nobel Prize in Chemistry in 1953. *The material is often used for parts in machinery (such as gears) as a replacement for metal. The advantage is that it does not oxidize and does not require oil or ball bearings for smooth mechanical movement. The brand name of this material is Zirlux Acetal, originating from California.