Australasian Dental Practice 2000; Vol 11 (2): 42, 44
Julian Hodges BA. DMS. says Australians wear more custom-made mouthguards than any other nation, but questions if they are as safe as their makers claim?
In Germany, 5% of mouthguards are custom-made, in the USA and the UK the estimate is 10%. In Australia, because of continuous work by the dental community for at least 15 years, the estimate is 12% or more.
The Australian recreational sports person is more aware of the potential risks. So whilst there is worldwide evidence of a rise in the number of tooth injuries, Australian injuries may not be escalating the same rate.
The continuing emphasis and growth in the demand for mouthguards has led to a rapid increase in the range of mouthguard materials and equipment for sale. In turn, unsupported claims have been made about the protective capability of mouthguards.
Even published research differs widely. For instance, Professor Jurgen Hoffman and his team at Tubingen University (Germany) proved that a mouthguard with hard bonded layers would proved more protection (Endod Dent Traumatol 1999; 15:157-163).
Yet, within a few weeks from now, the ADA (Australia) Dental Journal will publish a paper based on research by Dr Bill Westerman that comments, according to the draft, that there has been no adequate study regarding power distribution and the use of hard inserts. It concludes, ‘the inclusion of hard layers would lead to a greater risk of dentoalveolar injury.’
Unfortunately, the studies are not directly comparable. Dr Westerman worked with mouthguard materials. Professor Hoffman researched the total cushioning effect of a mouthguard. There is a significant difference and for Dr Westerman the publication will help reinforce his claim that Airgards are superior.
Conflicting claims are being made about the origin of pressure laminated mouthguards, sometimes called Type IV. When were these mouthguards invented? In March 1983 Peter Natt of London described the construction of pressure laminated mouthguards in the ‘Dental Technician’. In 1985 and then 1989 the Dental Health Foundation (University of Sydney – Australia) published illustrated manufacturing instructions in ‘Dental Outlook’ (Vol 11 No1 and Vol 15 No3). In addition, Dr Keith Hunter and others realising the potential of pressure laminated mouthguards have been making them for more than 15 years.
Surprises in new research
Irrespective of the validity of various claims, the fundamental question is, how protective are mouthguards and are they as safe as their makers claim? Hoffman and his team provided some surprises. Using unique test equipment and protocols (Figure 1), they evaluated the cushioning effect and the distribution, or dissipation of forces with the different mouthguard designs.
In the study, the deflection values of teeth with a mouthguard were correlated with the values of unprotected teeth. The transmission forces to the cuspid and molar region were also studied.
The comparative results (it is not possible to realistically replicate playing conditions) confirmed earlier research. For instance, that the cushioning effect is directly related to the thickness of the formed material and that there are considerable differences in the protection due to differences in the manufacturing process and variations in the composition of materials.
These concepts are not difficult to grasp but, the devil, as they say, is in the detail.
By measuring the deflection of teeth caused by impact forces, the Germans were able to investigate the conduction of forces transmitted through the entire dental arch. The result was that mouthguards with a heavy bonded layer (Playsafe Heavy Pro – Figure 2) showed, ‘The smallest amount of force conduction onto the adjacent teeth’.
With a single exception, all mouthguards showed the ‘greatest drop in cushioning values at an impact force of 500N’. However, The Heavy Pro design showed the smallest changes and ‘achieved the best results with regard to a stable cushioning capability independent of the intensity of the force applied’. (Author’s use of italics).
Dr Westerman’s research shows that his Airgard material achieved a 32% ‘reduction in transmitted forces when impacted by forces less than 10kN’. (Aust Dent J 1997; 42:(3): 189-91).
Dr Westerman’s latest study reaches the obvious conclusion that hard materials are less absorbent that soft. Interestingly he shows that absorption increases the closer the hard material is to a tooth. Our tests have shown that soft materials critically deform at high impact and therefore it is illusory to hope that pure absorption will provide adequate protection. For instance, pure absorption is unlikely to protect a hockey player or high collision sports person from the concentrated high impact.
In a most significant statement Dr Westerman advises, ‘Absorption by any mouthguard material will be inadequate and the transmitted forces will cause damage to the dento-alveolar complex although not as much as would occur if a mouthguard was not being worn.’
The Germans in testing a mouthguard as opposed to a piece of material, showed that as impact increases there is a decrease in the impact absorption, again a logical conclusion.
For laminated mouthguards when impact is increased from 250N to 500N, impact absorbency decreases by about 5%. When the air cell mouthguards were subjected to the Tubingen tests, total cushioning decreased by a startling 72% – the combination of a soft material and an air volume that was too small to provide adequate cushioning. At that point, the mouthguards with a hard bonded layer (Playsafe Heavy Pro) had 650% more impact absorption. (Figure 3).
Julian Hodges is an international thermoforming and mouthguard consultant. He introduced pressure laminated mouthguards to Australia in 1984 and he lectures on the concepts and trains dental specialists in mouthguard fabrication. Julian Hodges represents the ADIA on the Standards Australia Technical Committee for Sports Mouthguards.