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Fraunhofer using smart materials to make clear aligner therapy cheaper, more sustainable

Researchers in Germany have synthesised a thermoplastic polyurethane that reacts to heat and water of body temperature for use in aligner treatment. (Image: Fraunhofer)

Wed. 3 May 2023


POTSDAM, Germany: Researchers at the Fraunhofer Institute for Applied Polymer Research (IAP) and the University Hospital of Düsseldorf have developed a new smart material for clear aligner treatment. The team has developed aligner trays that incorporate shape memory polymers and can be used to complete a number of steps in the treatment of malocclusion, thereby enabling new treatment concepts and cutting costs.

Shape memory polymers are smart materials made from plastics that can predictably and precisely change their shape when prompted to do so by external stimuli such as temperature, light, or electrical or magnetic fields. The technology has already led to a number of developments in biomedical applications, and the researchers at Fraunhofer IAP say that their use in clear aligner therapy combines effective tooth movement with a greater efficiency in the use of resources.

“Aligners made of shape memory polymers allow to control the force acting on the teeth and thus make therapy more patient-friendly,” Dr Thorsten Pretsch, head of the synthesis and polymer technology research division at Fraunhofer IAP, commented in a press release. “Our aligner allows several steps of tooth correction to be implemented at once,” Dr Pretsch stated.

The institute explained that a thermoplastic polyurethane that reacts to heat and water of body temperature was synthesised for use in aligner treatment. “Depending on how high the temperature is or how much water the material absorbs, the change in shape of the aligner can be divided up into any number of individual steps,” Fraunhofer IAP said. The advantages of the technology include reducing the number of clear aligner trays used during treatment, reducing material waste and lowering treatment costs.

In a series of tests, the research team used aligner trays made with the material to successfully move teeth and was able to confirm gradual changes in the shape of the aligner over a period of time using water and body temperature as stimuli. The results were published in the study “Dual stimuli-responsive orthodontic aligners: An in vitro study” in a special issue of Materials, titled Materials and Techniques in Dentistry, Oral Surgery and Orthodontics, on 14 April 2023.

“In the future, the shape memory effect could be triggered by saliva within the oral cavity,” Fraunhofer IAP pointed out, adding that material thickness and the gradual heating of the aligner trays additionally controls the force applied to the teeth. “For orthodontic applications, these special features harbour a number of unique advantages in aligner therapy—from smaller shape adjustments through controlled heating to a reduction in the number of treatment steps,” Dr Pretsch emphasised.

To date, the new smart material has been tested on model dental crowns, and further material development is needed in order to prepare it for clinical application.

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