What are dentures made of?
Kinds of Denture Bases Available and their Suitability
All three can be made badly or wrongly designed, so it’s what’s done with them that’s most important!
- Hard Acrylic
- Chrome Cobalt Cast Alloy
- Flexible Thermoplastic
1. Hard Based plastic/acrylic/polymer (the “usually pink” part)
We firstly have to separate between full and partial dentures as they are completely different.
“Acrylic” is the most commonly used general term to describe this type of denture base for full and partial dentures. It is the hard plastic that’s moulded to shape, fitting against the gums and around the denture teeth. It is also by far the most common and widely used for dentures. Made well, they can be a complete solution – made badly; They are a total failure. Full dentures for patients with no real teeth left are generally all made of acrylic. All NHS dentures are made of acrylic as chrome dentures are too expensive and timely.
Acrylic dentures are usually promoted as two kinds which are Standard or Hi-Impact. We have always used Hi-Impact acrylic to make all our new dentures. However, it is not unbreakable when limited in thickness for partial and full dentures. Human bite force averages at about 160psi, which is proportionally the rough equivalent of a persons body weight. Without a doubt, the main food that breaks plastic dentures is bread in all its forms. This is because we exert full bite force when eating it. Some patients also have difficulty tolerating the thickness and way they feel in their mouth.
Partial Acrylic Dentures or Chrome Dentures? What do they feel like?
There are three main reasons why we make many more chrome partial dentures than acrylic.
- Strength: Tried and tested, we have had patients returning with chromes we made 30 years ago.
- Speech and overall feel in the mouth: They are much thinner and easier to get used to and speak with. The thickness of a business card moulded to fit, meaning the surface shape is the same as your mouth underneath, not several millimetres thick and glazed smooth like acrylic.
- Clasping options: Acrylic partials have preformed wire clasps bent to fit around your teeth and embedded in the plastic. Metal clasps on chromes are cast to fit around teeth which offer an improved fit with the option of flexible tooth shade-matched clasps. This often enables us to design them to clip in place, be smaller and cover less area in the mouth.
We have repaired several acrylic dentures a week for over 30 years which we often replace with chrome cobalt metal dentures as they are much stronger and thinner, making them far superior and nicer to wear.
2. Chrome Cobalt Cast Alloy Dentures
Chrome cobalt is a lost wax processed lightweight alloy casting that’s individually designed and made to fit around your teeth, with several design choices possible for each case. The alloy melts at more than 2000 degrees Celsius, and the technician’s skill doing the casting has a great effect on the overall fit. They are generally referred to as “chrome cobalt dentures” as chrome and cobalt are the alloy’s two main ingredients. When finished, they house the pink acrylic gum and the denture teeth where your tooth spaces are. Made well, they are a fantastic solution. Made poorly, they are a total failure. We see many patients with new chromes that they cannot wear and just don’t fit. Usual reasons are that the alloy castings have warped, impressions are often not accurate, or the design is wrong or a combination.
Several makes and variations of alloy are available to use with differing castability properties, flexibility, and strength. Chrome Cobalt is generally the strongest and easiest to wear Partial Denture. The thickness of a business card but only when well designed, well made and fitted. We use one of the best Vitallium 2000+ alloy for all our castings.
3. Flexible Thermoplastic
Flexible Thermoplastic – In our view, they are only suited for a small percentage of cases where the base’s flexible nature is an advantage and can be extended to wrap around real teeth to hold a small denture in where the others would fail. This, however, is not very common. They are less hygienic and also cannot have additional teeth added to them successfully. I frequently make chrome cobalt partial dentures to replace flexible dentures for patients that have issues with them.
Depending on which denture base option is the best one for you, finishing new dentures can take anywhere from two appointments on the same day to over ten appointments over three weeks to make, depending on the complexity of your specific case and the kind of denture base you need so generalising is not really possible. As outlined above, there are many types of new dentures available. I will show you these, together with various kinds of teeth and each set of new denture combinations’ associated costs. This way, you will be able to make an informed decision as to which set of dentures you prefer. Together, we can then decide upon the right course of action and denture treatment for you. After discussing the cause of your denture issues, I will help you make the right decisions to solve them.
Partial Acrylic Dentures
Acrylic Partial Dentures
When you have natural teeth left, a denture that fills the gaps is called a partial denture. Acrylic (hard pink plastic) dentures can be made very quickly and cheaper for all denture base options. They are several millimetres thick, and it can take several days to get used to wearing acrylic partials as lisping can be an issue. However, many people find them a complete solution that they are pleased with when well-made.
Acrylic Partial Dentures – The main factors behind their success or failure
Your adaptive capability
- One of the main reasons that an acrylic partial can fail (when well made) is due to the patient’s adaptive capability. This is basically how bothered you are by the denture being there. Some patients forget about their new acrylic denture after a couple of days and adapt their speech so nobody would know. Still, other patients cannot get used to them, meaning they have a poor subconscious adaptive capability. Usually, having a thin chrome alloy denture solves the problem, but chrome dentures are not available on the NHS.
How well made your partial acrylic denture is
We see lots of patients who have new acrylic partial dentures (both NHS and Private) which they cannot wear for several reasons – too thick – too far back in the palate – bite measurements are wrong (cannot chew – noisy-painful) over extended edges, causing lifting and pain – loose – poor appearance or incorrect design. Also, constant breakages due to the quality of materials used.
Acrylic is not strong enough because of your bite.
- If the way your teeth meet when you bite means the acrylic is limited in thickness, this often can lead to breaking your partial acrylic denture even when made of the most robust Hi-Impact acrylic. Believe it or not, the average human-biting force is roughly 160 psi. I always equate it to your approximate body weight. This is the equivalent of standing on your denture. I repair several dentures each week, and the vast majority are broken from eating bread in all its forms. I have been asking “what were you eating when it broke” for years to thousands of people, and their answer almost always is bread. Because you know it’s soft, you bite with a maximum force, so as it compresses, it spreads the pressure against the denture and breaks it. We put no conscious effort into biting hard!
- A partial acrylic denture is not clinically strong enough in many cases because of the natural teeth’ positions.
Chrome Cobalt Alloy Dentures
Chrome cobalt partial dentures
Chrome cobalt dentures are thin, lightweight alloy castings. They fit around your real teeth housing the pink gum part and denture teeth as a combination of materials joined together. They have several big advantages over acrylic partial dentures but again, only when well made, designed and fitted. We get patients with new private chrome cobalt dentures they cannot wear due to being poorly made, the wrong design, or just don’t fit.
- Chrome alloy dentures are not available on the NHS due to the higher cost of manufacturing them and being more timely and difficult to make.
- Chrome cobalt dentures have the best strength of all partial dentures yet are a business card’s thickness.
- They help prevent neighbouring teeth from moving out of position and drifting.
- Chromes help makes eating easier and more comfortable.
- They are better for your overall oral hygiene.
- They are thinner and far less intrusive for patients with sensitive gag reflexes.
- They are far easier to get used to and speak with
- They can often be designed to be smaller, covering far less surface area and uncover your palate.
- Chromes can have superior flexible tooth shade or clear Flexi clasps, which improves your smile.
- They do not taste metallic.
- They do not set off the scanner in Airports.
- They are not visible as they are housed behind your teeth.
- They do not go rusty – I have returning patients with chrome dentures I made over 30 years ago.
- But they do understandably cost more and take much longer to make with more appointments to do them properly.
The three main reasons I make my patient’s chrome cobalt dentures is
- Their acrylic denture kept cracking, breaking, or teeth came off.
- They could not tolerate the acrylic dentures smooth, thick, plastic feel, often with lisping issues.
- Their acrylic denture was loose. We can make Chrome Dentures tighter with special flexible clasps.
First Impressions of Metal Dentures
When shown chrome dentures outside the mouth, patients first reactions are not very positive as all you can see visually is shiny metal. I have to say that its looks are completely irrelevant as in the mouth; it is not visible. All you notice in the mouth is how thick a denture is. If I think a chrome denture is the best option for you and you are not sure, I often state that I will refund you if you cannot wear it.
Partial Flexible Dentures (Valplast)
I have to say I am not a great fan of flexible dentures. On occasion, they are the best option to solve a problem by having a more Flexi grip (where the pink base is extended to wrap around the real teeth to hold them in place) for a few cases I get. The base (the pink part) is made of thermoplastic (like nylon) and a completely different material to the denture teeth made of a hard acrylic/composite, which causes a problem as they are not very well chemically bonded together. The teeth are held in place with holes drilled through them that the flexible pink is moulded through, thus creating problems with staining between the two non bonded materials. Also, having seen many patients coming in with flexible dentures they have had for some time, they seem to go very kind of furry and rough. I have been to lectures lead by top specialist hospital prosthodontists that refuse to make them stating that they are far less hygienic than all other kinds of dentures. Patients ask me to polish and clean them, but I can never achieve the “almost new” look like chrome or acrylic dentures.
The other thing is that they are the same in “bulk” thickness as well made acrylic dentures without the thin advantages of chrome dentures. So ok, flexible sounds great and is marketed to great effect with the “unbreakable” slogan, but I make more patients chrome dentures that had problems with flexible dentures than I have made new Flexible dentures to date.
There are, however, continual developments in this area trying to improve the bonding to denture teeth and the capability to add new teeth to flexible dentures. Still, in my experience so far, it is not satisfactory.
Complete Full Dentures
Complete Full Dentures
Complete full dentures have to fill in all the space that has gone where your gums and teeth once were. The pink bases are usually made of hard based acrylic/polymer, which is moulded around and chemically joined to the teeth. Depending on varying clinical mouth shapes, the variations in the shape, size and bulk of the pink parts of the dentures and teeth are limitless. They should not be made with flexible bases but often can have silicone soft linings under the hard bases to make them more comfortable for some patients with sensitive gums.
For full denture considerations, the scenarios and problems are completely different from partials.
- Is it a straight forward replacement of worn dentures you have been happy with?
- Do we use the copy denture technique to copy your existing complete dentures’ appearance by doing the mould in your denture?
- Do you have problems with fit and function, pain, ability to speak properly, chew your food, or loose dentures?
- Does the appearance and position of your denture teeth need changing- more lip support, tooth shape, tooth shade and position?
- Do you have a photo of how your real teeth used to look so we can copy how you used to look with photo mapping?
- Do you have a new private or NHS denture that has an unsatisfactory fit, function or appearance?
- Can we make thinner and stronger complete upper alloy dentures? Yes.
- Can we make full upper and lower dentures with soft silicone linings? Yes – suitable for sensitive or bony ridges.
I know thousands of patients that I have helped wear complete full dentures with no problems. Still, there is a small minority that can have more difficulty because of either their personal adaptive tolerances or unsuitable mouth and gum shapes. Again it is far too complicated to generalise. Still, I usually change some of the tooth positions and shape settings on most of the complete new sets of dentures I make for my patients to improve them compared to their current dentures.
Complete full dentures when made properly.
- Restore your facial vertical dimensions, avoiding the collapsed look
- Allow patients to speak properly.
- Provide facial lip support restoring your appearance
- Allow patients to chew
- Restore your self-confidence and self-esteem