9. Remedy
_____While not all the released ingredients deter the properties of the device, these can be harmful, the most significant in this regard being the plasticizers and the derivatives of bis-phenol A. Better the cure, the lesser the leaching and the safer the product (a higher molecular weight of the polymer and a denser cross-linking).
_____To remove leachable ingredients, hemispheres made as described above were treated in different ways before their exposure for 24 h in a permanganate gel. Fig. 9.1 shows the influence of post-treatment on the leaching of a cold cure acrylate (Jet, Lang Dental, Wheeling, IL). The treated samples were arranged in columns: A was used for controls, i.e. for untreated samples, B for these left for 24 hours in water added with a detergent followed by intense rinsing, C for boiled for ten minutes in water and D for these left for 24 hours in rubbing alcohol (70% isopropanol).
_____As it can be seen, just leaving in water or extracting with a harmless solvent doesn’t work, while boiling for ten minutes in water leads to a significant reduction in leaching.
_____The potential health risks of many plastics and polymers used in orthodontics have been under scrutiny for over 40 years, and its workhorse, Bowen’s resin, or bis-GMA, for almost half a century. An adult treated with orthodontic polymers containing bis-GMA degradation products, such as formaldehyde and methacrylic acid, is actually exposed to 1/10,000 times for formaldehyde and 1/1,600,000 times for methacrylic acid, less than the admissible level.90
_____Summing up the situation, Dr. Gordon J. Christensen, founder and director of Clinical Research Associates and a respected clinician who specializes in dental biomaterials, took at the 1998 Chicago Dental Society meeting the same position as the FDA: “We must weigh the known benefits against the alleged risk.”
_____This is no excuse, however, for paying less attention to the possible nociceptive effects of the polymers: un homme averti en vaut deux (a warned man is worth two). New products should be launched only after undergoing thorough investigation, and manufacturers should provide as much information about their products as is feasible. When one considers the large number and variety of products that are launched, the limitations of the various governmental agencies treating those used in orthodontics is obvious. While polymers in general present a relatively low risk, the clinician should feel responsible for the iatrogenic effects they may induce and should be willing to go an extra mile by using do-it-yourself methods to test them, if necessary.
_____Continuous awareness of the risk incurred should lead manufacturers to strive to replace the older, more harmful products with new ones that are less harmful, even if this requires them to incur additional expenses. The public should appreciate such efforts while not succumbing to hysterias such as those caused by the use of amalgam.
_____The method used to detect polymer leaching presented above is so sensitive that it is currently applied to tap water. Associated to boiling the polymeric devices, this do-it-yourself method allows the manufacturer to optimize his polymer-containing products and the clinician to select the least harmful ones.
_____References
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