Journal of Medical Systems, Vol. 23, No. 1, 1999 PC Controlled Toothbrush/Dentifrice Abrasion Machine Gungor Bal,1 Sadullah Uctasli,2 and Erdal Bekiroglu1 A toothbrush/dentifrice abrasion machine was developed to use in dental research laboratory. The mechanism was designed as a hexagonal block driven by two stepping motors which move the mechanism in four directions. In order to control the stepping motors speed, position and direction commands or signals were generated by a software written in C Programming Language and then these commands were applied the stepping motor drives through parallel port of a personal computer. The toothbrush/dentifrice abrasion machine was finally used to measure different longevity of tooth brush. It was experimentally shown that the mechanism can be used for highly accurate position and speed applications. KEY WORDS: toothbrush/dentifrice; C Programming language; stepping motor. INTRODUCTION Wear is a loss of material which is seen in the oral cavity by the loss of the original anatomical form of the material. Wear of tooth structure and restorative materials may result from physiological or pathological conditions. In order to maintain oral hygiene, dental tissues and dental materials are subjected to toothbrush/toothpaste abrasion. This may cause wear on dental tissues and dental materials during the removal of surface deposits. Up to now, a more reliable way of studying body abrasion is to use a toothbrush machine with dentifrices and prophylaxis materials. Traditionally, abrasion with transverse toothbrushing machines on flat specimens was the method of choice. Such tests are normally made to mimic brushing cycles used by patients and may be useful in predicting the abrasive wear of materials.(1-5) In vitro toothbrushing can be a valuable tool in the overall assessment of the stability of dental restorative materials. Hence, in the present study, it was decided to develop a toothbrush/toothpaste abrasion machine to assess the abrasion resistance of both dental materials and tooth brushes. Since they offer many advantages, stepping motors were chosen in the present 1University of Gazi, Electrical Education, Besevler, 06500 Ankara, Turkey. 2University of Ankara, Faculty of Dentistry, Besevler 06500 Ankara, Turkey. 27 0148-5598/99/0200-0027$16.00/0 1999 Plenum Publishing Corporation
28 Bal, Uctasli, and Bekiroglu study, to provide an example of mechanical movements. Stepping motors are highly accurate pulse driven motors that change their angular position in steps, in response to input signals from digitally controlled systems. Stepping motors are used for the precise positioning of mechanical systems. The step angle movement of a stepping motor can be known from its structure. It is also easy to change the rotational direction of step motors by changing phase sequences. (6,7) DESIGN AND IMPLEMENTATION OF A TOOTHBRUSH/DENTIFRICE ABRASION MACHINE In this study, speed, position, and direction information were generated by a personal computer and then the information was downloaded to the parallel port, which interfaces to stepping motor drive circuits. A block diagram of the system shown in Fig. 1 consists of three main parts: a mechanical system with two stepping motors, drive circuits with dc power supply, and a personal computer (PC). MECHANICAL SYSTEM The mechanical system was designed as a hexagonal block which offers six surfaces which are at different positions and three toothbrushes were mounted on each surface. Thus, a total of 18 brushes were used for the test. In order to provide more realistic conditions, teeth specimens were located under the brushes in the Fig. 1. A block diagram of toothbrush/dentifrice abrasion machine.
PC Controlled Toothbrush/Dentifrice Abrasion Machine 29 block. A block is fitted to the base of the bath on the center line. The bath contains sufficient slurry to cover the specimens during the test and the quantity of slurry to cover the specimens during the test and the quantity of slurry used were standardized at 100 ml for tests. Water pipes were fitted to the base of the bath to keep water temperature constant. The water temperature was 45 C which maintained a slurry temperature of 37 C.(8) When the three brushes of one surface finish the brushing process, the mechanism is rotated 60 mechanical degrees in vertical positions to start a new brushing process. The mechanism can be moved in four different directions: backward and forward movement in vertical(x) and horizontal(y) directions. While stepping motor-1 (SM1) controls the movement in the X direction, SM2 controls the movement in the Y direction. SM2 also rotates mechanic surfaces at 60 mechanical degrees. An overall view of the toothbrush/dentifrice abrasion machine is shown in Fig. 2. DRIVE CIRCUIT A drive circuit used for a stepping motor is shown in Fig. 3. Four-phase hybrid stepping motors were used to control the mechanical system. The drive circuits can operate in a full-step operation. Only two phases are energized during a one-step operation. To drive each phase winding, a Darlington connected power transistor Fig. 2. Toothbrush/dentifrice abrasion machine.
30 Bal, Uctasli, and Bekiroglu Fig. 3. Drive circuit for a stepping motor. was used. A 4-bit signal is necessary to control drive circuits for changing directions. A logic sequencer was used to control phase sequences. (9) COMPUTER AND SOFTWARE Although a 75MHz Pentium Personal computer was used to control fully the toothbrush/dentifrice mechanism, any PC configuration can also be used. The operation of the system, the setting of some parameters for different test conditions are performed by a software written in C Programming Language. A total of four control signals sent to the parallel port (0 x 378) are clock and direction signals for each separate motor. The step angle of the motor is 1.8.
PC Controlled Toothbrush/Dentifrice Abrasion Machine 31 For one revolution, 5 = 360/Ts = 360/1.8 = 200 pulses are required. The speed of the motor is n = 60 X f/s so the speed of the motor can be changed by changing the clock frequency generated by a computer.(10) In the present study, the timer function of C programming language was used for time calculation. While stepping motor SM2 makes up and down movement in 18 positions, the stepping motor SM1 makes a one-step movement in horizontal axes (X). SM1 also moves the mechanism in forward and backward directions. The signals, produced by computer, to provide these movements were photographed on an oscilloscope (Fig. 4). These actions can be adjusted and repeated as desired number of cycles through the software. When the desired cycles for one surface are achieved, SM2 rotates the mechanism in a 60 position to bring the next surface to the toothbrushing process. The flowchart of the software program is shown in Fig. 5. CONCLUSION Brushing machines are capable of evaluating the abrasion resistance of dental materials. Tooth brushing equipment designers have attempted to impose controls on motion, load, temperature, etc., reporting closer correlation with clinical experience. In most studies, different kinds of brushing machines have been used to measure Fig. 4. Oscillograms of SM1 and SM2 clock signals.
32 Bal, Uctasli, and Bekiroglu Fig. 5. Flowchart of software program.
PC Controlled Toothbrush/Dentifrice Abrasion Machine 33 the wear procedure occurring in the mouth. The behavior of these different machines on dental restorative materials has been evaluated by various methods, e.g., (a) volume loss, (1) (b) weight loss, (2,8) (c) thickness loss, (11) (d) surface roughness profilometer, (5,8) (e) scanning electron micrographs. (5,12) In the present study, the designed toothbrush/abrasion machine is capable to evaluate volume loss, weight loss, and thickness loss. Additionally, abraded surfaces of the dental materials can be evaluated by a surface roughness profilometer and a scanning electron microscope. REFERENCES 1. Aker, J.R., New composite resins: comparison of their resistance to toothbrush abrasion and characteristics of abraded surfaces. J. Am. Dent. Assoc. 105:633-635, 1982. 2. Kanter, J., Koski, R.E., & Martin, D., The relationship of weight loss to surface roughness of composite resins from simulated toothbrushing. J. Proshet. Dent. 47:505-513, 1982. 3. De Gee, A.J., Ten Harkel-Hagenaar, E., & Davidson, C.L., Structural and physical factors affecting brushwear of dental composites. J. Dent. 13:60-70, 1985. 4. Johannsen, G., Redmalm, G., & Ryden, H., Surface changes on dental materials. The influence of two different dentifrices on surface roughness measured by laser reflexion and profilometer techniques. Swed. Dent. J. 13:267-276, 1989. 5. Chung, K.H., The relationship between composition and properties of posterior resin composites, J. Dent. Res. 69:852-856, 1990. 6. Kenjo, T., Stepping Motors and Their Microprocessor Controls, Calerendon Press, Oxford, 1984. 7. Acarnley, P.P., Stepping Motors: A Guide to Modern Theory and Practice, England, 1992. 8. Harrington, E., Toothbrush-dentifrice abrasion, Brit. Dent. J., August 1982. 9. Kenjo, T., Power electronics for the microprocessor or age. Oxford Science Publications, New York, 1990. 10. Bal, G., & Bekiroglu, E., Design and implementation of digitally controlled stepping motor drives for toothbrush/dentifrice mechanism. Int. Conf. Electrical Mach., 803-808, 1998. 11. Uctasli, S., Some mechanical properties of resin based dental material, PhD Thesis. The Dental School University of Birmingham, December 1991. 12. Ehrnford, L., Surface microstructure of composite resins after toothbrush-dentifrice abrasion. Acta Odontal. Scand. 41:241-245, 1983.