A cheap technique for producing germanium - based photoinitiators was developed

Patients who have had fillings may be familiar with the process: the dentist drills a small hole in the tooth and squeezes in a filling made of liquid plastic; the doctor then irradiates the filler with an ultraviolet lamp to break down the photoinitiator into free radicals, which in turn solidifies the filler.

Germanium - based photoinitiators have been widely used in dentistry for many years. It has the advantage of being able to absorb longer wavelengths of light, so there is no need to use harmful ultraviolet light as a curing source. This nontoxic photoinitiator has become a great help to dentists. However, its production costs are extremely high. A kilo or so of manufacturing costs can almost buy a car.

A team led by Michael Haas, a chemist at the Technical University of Graz, Austria, describes a novel method for synthesizing germany-based photoinitiators in the journal of Applied Chemistry. Not only does the new method require no sulfur (which produces an unpleasant smell), but it is simpler, more efficient and less expensive than traditional methods. According to the researchers, the new synthesis method is a one-step strategy, and the product separation process is very simple. In the new process, the researchers removed multiple silicon-based protective groups at once and separated the target product using a simple crystallization process. The improvement of the manufacturing process has laid the foundation for further application of germanium based photoinitiators in the biomedical field, which is expected to promote the production of contact lenses, artificial limbs and new implants.

Haas' team has turned over the new process to partner Ivoclar Vivadent AG. While the dental products company already had a safe germanium based photoinitiator (Ivocerin®) in its catalog, its manufacturing process had serious flaws. "For Ivocerin®, the synthesis process is complex, multi-step and requires a costly process to remove reaction by-products, resulting in a significant yield loss," Haas said. The new initiator will significantly reduce the price of dental fillings in the future, with clear economic advantages."