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There are several considerations we could make.
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I believe that most laboratories buying a quality denture base material would be looking at the products marketed as being "High Impact" quality. But do we really know how much stronger this material is?
To address the subjects of strength and free monomer content of a denture base, we are totally dependent upon the manufacturer to provide all the relevant scientific data. This could be in the form of a simple bar graph showing the high impact strength, flexural strength and amount of free monomer present after curing when compared to other products.
Unfortunately it seems that often the manufacturers although making claims for their materials in sales literature are unable or unwilling to provide the suitable data.
When looking at the data that is available, it would appear that in general high impact denture base materials have in fact a lower flexural strength (see graphs) than normal (standard) co-polymer denture base materials.
I found this to be a very interesting fact, as I believe that what is needed in a denture base material is one that combines high impact strength with a high flexural strength.
Over the past 30 years that I have worked in dental laboratories, it has been my experience that most of the dentures that fracture in the mouth, do so because they are flexing and have in effect age hardened.
So although the high impact acrylics are able to withstand a higher force of impact, i.e.: if dropped whilst cleaning, are they any more capable of being able to withstand the rigors of being worn in the mouth, (than a standard acrylic).
As this is what the dentures are being made for. This has to be an important area to consider when purchasing the acrylic. We have to ask ourselves are high impact acrylics worth the extra cost particularly if it sacrifices the flexural strength.
The free monomer content is also an area of concern. This is becoming more important as we become more aware of the possible health hazards associated with monomers. But also the more monomer conversion that take place during the curing cycle should mean that the finished denture will be more stable and less liable to shrinkage and warping and so of a more accurate construction.
Another area to consider may be the colour of the denture base material, it has been my experience that most "high impact" denture base materials can tend to be some what orange in appearance, this can sometimes lead to problems with aesthetics. (The orange coloration coming I believe from the rubber molecules, which are used to add the high impact strength to the material).
So although the high impact acrylics are able to withstand a higher force of impact, i.e.: if dropped whilst cleaning, we have to ask are they any more capable of being able to withstand the rigors of being worn in the mouth, (than a standard denture acrylic). As the dentures you provide for your patients are hopefully worn in the mouth and not in the patients handbag. This has to be an important area to consider when asking for a quality acrylic denture base.
Most manufacturers of high impact acrylics will provide leaflets explaining some of the advantages of their products, these are designed to be given to the patients, via, for example the your waiting room, these may help the patients become more aware of the options, between the standard or high impact denture base materials.
The product, which I have now been using on all private cases since March 1996 is marketed by "Kemdent©" as "Longlast" this product, I have found to be outstanding. The scientific data provided by the manufacturers show that this material "Longlast" combines both high impact and high flexural strength when compared to other high impact acrylics, {see graph}, with a low free monomer content. The colour of the "aesthetic pink veined" material I have also found to be more than satisfactory as there is hardly a hint of orange coloration.
The manufacturer has so much confidence in this product that as a bonus they are marketing it with a warranty option.
The warranty works by means of the laboratory supplying a warranty certificate on completion of a suitably completed appliance. The dentist is then able to give to the patient, on fitting the denture a warranty against fracture.
Of course this does not mean that the denture will never break {we live in the real world}, don't we?
The material has now been used in well over 700 cases,(over 3000 cases as of November 2000) in my laboratory and I have had only a handful returned to be repaired, in several of these there were obvious reasons for the fractures,
i.e.; immediate denture with rapid shrinkage of the tissues, or perhaps an inappropriate partial denture design, these dentures since being modified and repaired are now totally satisfactory.
It has been my experience that most patients appreciate the fact that there is a warranty, this is I believe because of the greater peace of mind afforded them when investing in their new dentures.
The only down side to the warranty system that I have found is that sometimes, because of perhaps a break down in communication with either the dentist or the patient, the warranty is given as a cast iron guarantee that the dentures will not break, as mentioned before of course that would be totally unrealistic. (In fact even motor manufacturers will not provide that sort of guarantee when purchasing a new car).
In conclusion then I think I have found the best material currently on the market.
Ps Have a look at the Graph Page comparing Longlast to other products.
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1998 Cotswold Dental Laboratory