How to measure and analyse the texture of food, cosmetics, pharmaceuticals and adhesives.

Tuesday, 23 January 2018

Measuring the Physical Properties of Denture Adhesives

With an ageing population, it is no surprise that there are more people wearing dentures.

Around half of all denture wearers use an adhesive to help with both comfort and confidence. In this market, it is important to uphold standards of both texture and adhesive properties. Otherwise, customers will be uncomfortable at best, or if they rely on adhesive for denture retention, face the embarrassment of dentures becoming unattached during the day should the adhesive fail. 

There are three main types of denture adhesive – powders, paste and lining strips. The choice of adhesive depends on the consumer’s preference, although the most popular are paste adhesives, supplied in squeezable tubes. As well as brand, flavour and colour variation, adhesives are available in various strengths.

Stable Micro Systems offer a wide range of testing techniques to assess the performance of denture glues. The best way of testing any adhesive product is to replicate its conditions of use as closely as possible. In all cases, if the adhesive is too strong the consumer will find removal very uncomfortable. Conversely, a weak adhesive is redundant and will not see repeat use.

Powder based adhesives are used by shaking a thin layer of powder onto the interior of the denture and pressing it onto the gum by biting down for a few seconds. Powder adhesive is well-suited to a standard adhesive test using a flat probe onto a flat surface, pulling the probe away from the surface. In this case, the environment must be moist and a range of pressures must be tested to represent the range of biting pressures of the target consumer group, while keeping the hold time constant. 

If suitable materials are available, a substrate made of a softer gum-like material may be used. The maximum force while withdrawing the probe corresponds to the force necessary to pull the denture directly away from the palate. This is particularly important for consumers who eat sticky foods and find the denture is pulled away during mealtimes. 

Sachet / Tube Extrusion Rig
Paste adhesives only work well if applied in a thin layer. Consequently, the expulsion of the product from the tube is of high importance. The product must extrude in a controlled way with a force high enough to prevent the paste running out freely, but low enough that an elderly customer can use the product without any help. 

Stable Micro Systems offer a Tube Extrusion Rig, originally designed for toothpaste tubes, to mimic this expulsion force. As well as packaging considerations, an altered version of the adhesive test suggested for powder is an excellent way of measuring the holding force of a paste fixative.

Multiple Indexing Plate
Finally, adhesive lining strips also face the difficulty of providing an optimum holding force. These are moistened and laid down on the denture surface, again fixed in place by applying pressure in the mouth. The Multiple Indexing Plate by Stable Micro Systems offers an excellent testing solution for strip adhesives. This plate allows ten individual adhesive tape tests to be performed on a single sample (or ten smaller samples) using a domical probe. 

As with the powder test, the moisture level must be kept constant during this test as the adhesive relies on a small amount of water to adhere to the roof of the mouth.

Contact Stable Micro Systems for more information on all areas of texture testing and physical property analysis.

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