The need
The human body comprises a variety of free-form, complex surfaces that change over time and vary between individuals. Capturing the composition of these structures to a high level of accuracy requires precision dimensional measurement. Various measurement techniques are used to collect different types of information about free-form surfaces. For instance, some provide data on surface form or shape while others capture the surface roughness. To obtain a full picture of the surface morphology and how the morphology changes with time the data produced from all the techniques must be combined. Merging such datasets has proven a longstanding problem for researchers and manufacturers of equipment.
One area where this is a particular challenge is in dental research, as teeth are highly complex surfaces. Quantification of dental wear is crucial to the understanding of tooth decay and requires measurements to be performed both before and after wear occurs. The aim is to deliver high precision of measurement and high density of data collected over a large area.
The solution
Through NPL's medical imaging accelerator for industry programme, funded through the Industrial Strategy Challenge Fund, NPL and TaiCaan Technologies Ltd worked together to devise a technique allowing precise quantification of dental wear. The project combined TaiCaan's optical metrology techniques with NPL's X-ray computed tomography (XCT) techniques. It is the first example of dental metrology studies conducted using XCT combined with optical measurements to this level. The datasets generated by the two techniques before and after dental wear were aligned using mathematical algorithms.
To test the robustness of the data, a group of researchers at King's College London, one of the leading dental research institute in the UK, conducted a feasibility study. When weak citric acid solution is applied to the tooth surface, it causes minor, but detectable, wear which simulates the corrosive effect of soft drinks. The NPL and TaiCaan methods were then used to examine small changes in tooth surface composition caused by the application of citric acid. The dental surfaces were analysed before and after applying citric acid and the optical and XCT technologies were able to detect differences in tooth wear.
The impact
The success of the work conducted by NPL and TaiCaan will enable researchers to gain a better understanding of the causes, the consequences and the process of tooth decay. With enhanced knowledge on the topic, TaiCaan is looking to publish academic papers, and to work with the University of Southampton and King's College London to secure grant funding for future research into the area. The work will form the basis for the design of new dental wear measurement machines for research institutions, helping to accelerate the development of products for tooth wear prevention and treatment, including the next-generation of toothpastes and toothbrushes.
The success of the NPL and TaiCaan collaboration may be applied to other areas of medical research that involve complex surfaces. Similar metrology and data techniques have the potential to be used to measure other free-form surfaces, such as knee or hip joints.
The work has also opened up new commercial opportunities for TaiCaan, paving the way to larger customer base through the development of new software methods and new instruments for use in dental schools.