GSK - TOOTH DEMONSTRATOR

GSK - Tooth Demonstrator

Project:	GSK - Tooth Demonstrator
Client:	GSK
Date:	12 July 2010
Duration:
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Ogle Models and Prototypes were approached by GSK to discuss the manufacture of a large-scale tooth model. The aim of the model was to show one of the two established mechanisms for treating dentin hypersensitivity. Dentin hypersensitivity is a common but painful condition affecting 18-42% of the adult population. It has been defined as “short, sharp pain arising from exposed dentin in response to stimuli, typically thermal, cold, evaporative, tactile, osmotic or chemical which cannot be ascribed to any other form of dental defect or pathology” (Int. Dent. J. 2002; 52: 367-375). The cause of dentin hypersensitivity is generally agreed to result from the exposure of dentin following either loss of the protective enamel layer or via gum recession. GlaxoSmithKline (GSK) Consumer Healthcare wanted a large-scale tooth suspended in a tank filled with water, the tooth to have a section of exposed dentin to be covered with a fine filter, water to be sucked from inside the tooth through the dentin filter and then exhausted back into the tank. As the water circulated, particles suspended in the water would become attached to the dentin filter, demonstrating how a GSK toothpaste blocked the exposed pores of the dentin, thereby reducing the sensitivity of the exposed area. With just three weeks to complete the model Ogle commenced work: The first stage was to take an existing 3D model of a tooth which was then modified to reflect the required shape, section and size. The CAD model was then further remodelled to include the exposed dentin area; the design was then approved by GSK. Following several discussions it was decided that the best method would be to make a hollow rapid prototyped model using Ogle’s in-house laser sintered nylon (SLS) machine. The tooth model would incorporate a removable dentin filter grill and include the internal waterways which would terminate with inlet and outlet tubes protruding from the bottom of the model. This meant a clear tank could be constructed with just two holes through the bottom face and the tooth model could be lowered in and the inlet and outlet tubes located through the holes and sealed in place. The clear tank was to be fixed on top of a base which would carry the pump, associated plumbing and electrics, keeping this easily accessible. Further modelling was carried out to include the waterways, filter and filter recess into the tooth CAD model. When completed, the CAD model was converted to an STL file – the language for all rapid prototyping systems. The STL files of the tooth and filter were then prepared and downloaded onto the latest EOS P730 SLS machine and construction commenced. Once built and cool enough, the tooth was removed from the build chamber, finished and then sent to the paint department to be fully paint-finished in two colours. At the same time, a clear acrylic tank was constructed along with a fabricated ABS base housing. The pump and associated copper plumbing were then constructed and fitted securely under the base, ready to receive the tooth model. Once painted, the tooth model was assembled and ready for testing – this was the crunch point and time was running out! With two GSK Consumer Healthcare scientists from the Weybridge Innovation Centre on site, the tank was filled with water and the model switched on. Initially, with the water appearing to be circulating fine, the coloured particles were then introduced into the water. Straight away, this showed that the water flow was not keeping the particles suspended evenly. The GSK Consumer Healthcare scientists had foreseen this problem and with their help, after many adjustments to the water outlet using baffles and tubes, a make-shift solution was found, however, this was not visually acceptable. We quickly needed a clear alternative to be modelled up and made using the stereolithography (SLA) process with the latest water clear resin. The rapid prototyping department quickly produced a CAD model and downloaded it to the SLA machine to be built overnight. The other problem that had arisen was that the particles were being sucked through the surround of the filter and were gradually being liquidised by the pump. What was left of the particles were then blocking the filter and making a mess. While the clear SLA baffle was being built overnight, the tank was emptied of water and everything dried and cleaned down. The filter was then removed and more perforations were made in the fine mesh to improve flow-through and the filter and mesh were then fitted and sealed back into the tooth much more securely. By mid-day we had the new clear SLA baffle which was then fitted and bonded into position, all finished if it worked! But we could not test until the sealant had fully cured by the next morning, so we were sweating overnight! Early Saturday morning the tank was refilled with water and then fired up. Relief! The model was working perfectly! Good water flow, even suspension of particles in the water which were slowly sticking to the improved filter demonstrating as required and the clear baffle looked good. The model was then packed and couriered over to GSK Consumer Healthcare where it was used as a demonstration tool that week for a major presentation. Mission accomplished!