Simulation of Oral Challenges
Artificial Resynthesis Technology 1 (ART 1)
Dr. William H. Douglas, Dr. Ralph DeLong, Mr. Jon Dalrymple, and Mr. Neil Peterson (MTS) worked together to design a system that could simulate the mechanics of chewing and provide the environmental conditions that are found in the human mouth. Utilizing servo-hydraulics, this artificial mouth technology was to be used for materials assessment in the laboratory. The development of this Advanced Artificial Oral Environment (generally called A.R.T., for Artificial Resynthesis Technology) was supported by a grant from MTS and a later grant from the National Institute of Dental Research (RO1DE06762, The Development of an Advanced Artificial Mouth, 1984-1987).
As the name indicates, ART resynthesizes or replicates that part of the chewing cycle in which wear occurs between teeth. In the human chewing cycle, the teeth come together with the lower arch offset to one side from the upper arch. As the lower arch slides into central alignment with the upper arch, the force between the teeth rises from zero to about three pounds and back to zero again. This part of the chewing cycle usually takes about a quarter of a second. Researchers estimate the average person goes through this functional cycle about 300,000 times in a year. Running continuously, ART can complete these 300,000 cycles in less than a day.
Scientists are constantly searching for new restorative dental materials and they want to know the properties of these materials. Testing the new materials in human volunteers would require safety approval and force scientists to wait a year before knowing even the early wear properties of these materials. And because every person chews in a slightly different way, data from many volunteers would need to be averaged to get meaningful results. But ART chews every test material in the same way and gives valid results with only a few trials and in a few days.
Artificial Resynthesis Technology 2 (ART 2)
ART 2 is a two-station version of ART 1. ART 2 was purpose-built and included many added convenience factors. One further development of ART 2 was a modification to allow three-body wear (such as occurs when food is eaten) simultaneously with two-body wear. The combined use of ART 1 and ART 2 were key development tools in many common highly successful dental materials still in use today. Further developments of ART 1 and ART 2 will include extensions to the digitizing process, which will build on the established physiological foundations of the Artificial Mouth Technology.
Oral Hygiene Simulator
Tooth brushing has some of the features of the chewing cycle in that there is an application Force under Load control in one direction, with a Stroke control movement at approximately right angles. An independent four-station toothbrush simulator was developed and built on these principles. The brushes are held by four independent DC servo-motors under load control, and an effective movement at right angles is accomplished by a fifth motor. The tooth brushing simulator is very flexible and allows many different kinds of brush movement, including vertical, horizontal, and figure-eight configurations.
Tooth Brushing Forces
The tooth brushing forces were established by attaching strain gauges to toothbrushes and using human subjects to apply their usual tooth brushing techniques. Extensive clinical correlations have been carried out and published on the ranges of force, movement, and effective clinically equivalent brushing regimes in terms of time and frequency of brushing. As with ART 1 and ART 2, this simulator has played a crucial role in the development of polishable composites and the retention of materials and sealants on shallow cavities and dental fissures.
Artificial Caries and Remineralization
An in-vitro biophysical assay that simulates and measures the progress of caries formation has been developed. It forms an essential tool for the development and assessment of preventive and therapeutic agents. The extent of the de/remineralization is determined by the total amount of mineral loss, calculated from local mineral content of tooth structures. We use serial microhardness to calculate mineral content in enamel lesions. For dentin lesions, mineral content is converted from X-ray density (micro-radiography). The total amount of mineral loss is determined by comparing the mineral content in a lesion area with that of healthy tooth structures.