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Toothbrushes after use are contaminated by many microorganisms including bacteria, fungi and viruses. We are thinking of making an anti-bacterial toothbrush by including ceramics in the bristle. But if the ceramic-containing bristles are too hard for the tooth and gingiva, it cannot be used as a toothbrush. So, before examining the antibacterial properties, we evaluated the feeling by asking students of dental hygiene. In our preliminary experiment, we determined the most appropriate width and length of ceramic-containing bristles. The students used this toothbrush and answered the questions. Almost all the students were satisfied with the new toothbrush with ceramic-containing bristles. Moreover, the new toothbrush was found to be comparable with the world-wide sold toothbrush. We obtained data that the ceramic-containing bristles were acceptable. Further study to investigate the anti-bacterial properties and effective cleanliness are in progress.

Methods: Approximately 70% of the patients were female and most were in their 40s. We analyzed the possible causes of halitosis. Results: More than half of the patients exhibited a thick tongue coating. Low salivary flow was present in 23.6% of males and in 39.4% of females. Pocket depth ≥6 mm was found in 44.2% of males and in 16.7% of females. We also analyzed treatment provided after breath odor measurement. Most of the patients with physiological halitosis and pseudohalitosis did not receive further treatment, but some were treated at the COD with scaling and professional tooth cleaning. Many of the patients with genuine halitosis received dental treatment at the COD. We referred patients from other clinics and from distant locations to their local doctors for treatment. Conclusion: Halitosis had various causes, and the role of dental hygienists, including scaling, root planing, and tooth brushing instruction, are important in decreasing breath odor. Dental hygienists play an important role in communication with halitosis patients.

Many people worry about their breath odor, and the importance of halitosis treatment is increasing. Consequently, it is necessary for dental hygienists to obtain a basic knowledge of halitosis. To achieve this, we must improve the motivation of dental hygienist students to acquire such knowledge. To this end, we conducted a questionnaire survey to assess the awareness and knowledge of the problem among dental hygienist students and compared the results of the survey for students in the first and third grades. The percentage of students who perceived the oral malodor of patients was higher in the third grade group. The third graders also placed a greater importance on the participation of dental hygienists in halitosis treatment. Most students in both grades believed that demand for halitosis treatment would increase, although there were students in the first grade that did not hold this view. A similar percentage of students in the two grades were willing to study halitosis, although some first grade students were not at all interested. Many more students in the third grade wanted to take part in halitosis treatment. Student knowledge of halitosis was approximately the same in both grades, but, surprisingly, the third graders gave some incorrect answers in this area. From the results of this study, the third grade students appeared to have higher motivation to study halitosis treatment than the first graders. However, the upper grade students seemed to lack some knowledge, which may be due to the extended time since they had studied the topic at school. It is necessary for us to improve student motivation for studying halitosis and for maintaining their knowledge in order to better perform the treatment of halitosis after the students become dental hygienists.

To compare twin-motor sonic toothbrushes (TST) with conventional sonic (CST) and electric (CET) toothbrushes in terms of plaque removal efficacy.A single-blind, triple-treatment cross-over study was conducted involving 36 participants. Each subject refrained from brushing for 24 hours; subsequently, subjects were screened for dental plaque in premolars and molars with the Rustogi Modified Navy Plaque Index. Plaque removal efficacy was determined according to percentage of plaque score reduction in a single toothbrushing under supervision for 2 minutes at the base of whole tooth surfaces and approximal areas.35 subjects completed this study. No meaningful difference in pre-brushing plaque score was observed among the three toothbrushes. In molars, TST (48.3+/-3.3%) was higher in plaque removal efficacy relative to CST (40.4+/-2.4%, P= 0.0064) and CET (36.7+/-2.8%, P= 0.0001). This trend was obvious in approximal areas of the lingual aspect of the mandible; 24.8% for TST versus 13.4% for CST (P= 0.0048) and 15.0% for CET (P= 0.0168). In premolars, TST displayed the greatest plaque removal efficacy, although the difference was significant exclusively for comparison with CET. These findings indicate that TST is more efficacious than CST and CET in terms of removal of plaque from molars, in particular, at approximal areas in the lingual aspect of the mandible, possibly due to new functions such as floating bristles and twin magnetic motors, which produce sonic vibration.

Floating action toothbrush bristles have been incorporated into a V-shaped sonic toothbrush. The base of the bristles moves down or up according to the pressure of the toothbrush being applied to a tooth surface. It was thought that this floating action with sonic vibration may generate new motion for increased plaque removal efficacy through increased contact between bristles and tooth surfaces. The objective of this investigation was to compare the plaque removal efficacy of a sonic toothbrush with floating bristle action (Float-Brush) to either a conventional V-shaped sonic toothbrush (Techno-Brush) or a manual toothbrush.A single-blind, three-treatment cross-over study was performed on 42 subjects. Each subject refrained from brushing for 24 hours, followed by assessment for dental plaque on the Ramfjord teeth employing the Rustogi Modified Navy Plaque Index. Plaque removal efficacy was determined by the percentage of plaque score reduction in a single-use toothbrushing under supervision for two minutes.Forty participants completed this study. No significant difference in pre-brushing plaque scores was detected among the three toothbrushes. In the comparison of whole mouth mean scores, plaque removal efficacy of the Float-Brush (65.0%) was significantly higher than that of the Techno-Brush (59.1%, p = 0.0487) and the manual toothbrush (50.9%, p0.0001). Superiority of the Float-Brush was similar to whole mouth scores, when comparing the gumline and interproximal tooth area scores.These findings indicate the superiority of the Float-Brush for plaque removal compared to the Techno-Brush and the manual toothbrush.

The improvement of the base line stability of a silicon diaphragm piezoresistive pressure sensor is described. When a miniature pressure sensor mounted on a catheter tube is used for biomedical instrumentation, its surface is subject to ionic contamination, which causes electrical instabilities in the form of base line drift. The resistance modulation, which is attributed to the field effect of outer impurity ions, is proved experimentally to be the dominant mechanism of the drift. To eliminate the electrical drift, it is necessary to keep the resistance of piezoresistors constant, even if undesirable impurity ions exist. For this reason, a novel buried piezoresistor structure is proposed and studied experimentally. p + piezoresistors were formed on a thin n − diaphragm 10 μm thich and were then buried under an n + diffusion layer. This buried piezoresistor sensor gives an excellent stability (1.5 mmHg/day) in every atmosphere, including wet air.

The fabrication of a miniature blood pH monitoring system formed on a silicon wafer using a pH ISFET and a new type of micro-valve actuator is described. The system samples the blood from the vein, measures its pH and calibrates zero drift of the sensor automatically and periodically. The main body of the system, the micro-cell, is made of a silicon wafer and a Pyrex glass plate processed by IC technology (micro-machining). This cell is significantly smaller, lighter and more portable than presently available blood gas analysers, in particular, the sample volume reduction is a very distinctive feature of it. The total necessary sample volume of the system is about 10 μl.

In neuro-physiology, it is important to record neural impulses from the central neural system simultaneously. For this purpose, a silicon substrate which forms a multimicroelectrode was fabricated and a precise fabrication of a 10 μm thick microelectrode with a 30 μm wide tip was achieved by using Si dry etching. The high-quality insulation of the electrode in a physiological solution was obtained by using Ta and high-temperature CVD Si3N4. However, Ta itself is not adequate for the recording site because it is oxidized easily in an electrolyte causing the increase of the electrode impedance. Platinum-black was electroplated on the titanium surface in order to stabilize and reduce the electrode impedance. The interelectrode crosstalk between electrodes and signal attenuation due to the parasitic capacitances were 0.4% and 4.4%, respectively.

A new type of ISFET with a Parylene gate as a site-free and ion-blocked membrane has been proposed for a reference electrode. The reference ISFET should be insensitive to the variation of ion concentrations of all ions or a specific ion in the electrolyte and should have a constant gate surface potential. In this paper, the operation of this reference ISFET is analysed by the site binding model and the conditions required to make the gate surface potential constant are examined. In general, the surface potential of an electrolyte-insulator-semiconductor (EIS) system is determined by two factors, i.e., the available surface site density of the insulator and the total charge density of the semiconductor, and it can be made constant by controlling the total charge density of the semiconductor. The preliminary experimental results on the electrolyte-Parylene-Si diode and ISFET are in good agreement with the theoretical calculations and suggest that a reference ISFET could be realized by using the Parylene gate.

Pd-gate MIS hydrogen sensors have serious drift problems and decreased sensitivity after long term operation. We have shown that the serious drift can be eliminated with Pd/Pt hydrogen sensing gate and Ag/Cu/Pd/Pt reference gate differential-type sensors. The decrease of sensitivity can be miniized by high temperature annealing in air. The decrease of sensitivity after 1000 hours of operation is less than 10%. It is considered that this decrease is due to a decrease of hydrogen adsorption sites on the Pd gates surface, which becomes oxidized during high temperature operation in air. This oxidation is observed with XPS and AES. The sensitivity abruptly decreases for operation at 100°C and below. This decrease is due to water adsorption on the Pd surface. H 2 O and OH peaks are observed in FTIR spectra for Pd powder in 1% hydrogen gas in synthetic air, and the solubility of Pd metal for hydrogen abruptly decreases because of water adsorption on the surface at 100 °C and below.

Ionic channels in biological membranes are one of the elementary transport elements passing specific ions across the membranes. The objective of this investigation is to design a two-microelectrode-voltage clamp system which is able to detect ionic channel noise of the membrane current in the mammalian exocrine gland acinus, an electrical unit, consisting of about 100 acinar cells. Since two high-resistance intracellular microelectrodes are used, the coupling capacitance between two electrodes makes the operation of the measurement system unstable and places a severe restriction on the experiment. In our measurement system a simple low-pass filter is inserted in the feedback system of the membrane voltage. As a result, the system operation is stabilized via the compensation of the frequency characteristic of the feedback system. If the noise inherent to the measurement system is large enough to mask the ionic channel noise of the membrane current, the channel noise below the noise level of the system cannot be detected. Since the noise of the measurement system is found to be due mainly to microelectrodes, properties of the electrode noise are analyzed in the present work. From the results, the system noise is evaluated quantitatively and the detection limit of the ionic channel noise is determined. Furthermore, the voltage is clamped for the electrically equivalent circuit to the acinar surface membrane and the operation of the voltage clamp system and the system noise level are investigated experimentally.

A multi-microelectrode for simultaneous recording of single-unit action potentials is a useful device for studying the organization and function of neural systems. We have fabricated a silicon probe which integrates a multi-microelectrode and interface circuits (preamplifier and analog switches) on a silicon chip by silicon planar and three-dimensional fabrication technology. This electrode has the following advantages: (1) it is easy to arrange the location of recording sites simply by changing photomasks; (2) crosstalk between the multi-electrodes can be reduced by the shielding effect of the silicon substrate; (3) integration of microelectrodes and preamplifiers on the same silicon chip eliminates the undesirable effects of stray lead capacitance; (4) analog swithces serve as selectors or multiplexers for a parallel to series conversion of multichannel signals of neural activities. In this paper, the design and fabrication processes of multi-microelectrode and interface circuits are described. In particular, the characteristics of polysilicon electrodes, design of a low-noise MOSFET for the preamplifier and silicon three-dimensional processes for the electrode probe are considered.

The gate surface of an ion-sensitive field effect transistor (ISFET) was covered with a penicillinase-adsorbed Langmuir-Blodgett (LB) membrane in order to examine the potentiometric response to H+ ion and penicillin G. The LB membrane-modified ISFET exhibited pH response of -30--40mV/pH, whereas near-Nernstian response was obserbed for the ISFET without LB membrane. The ISFET penicillin sensor showed the potentiometric response to penicillin G at milimolar level in 5mM phosphate buffer. The penicillin sensor could be used to determine penicillin G for more than 12 days without any deterioration.

The Ion Sensltlve Field-Effect Transistor (ISFET) 1s a new, integrated device composed of a conventional ion selective electrode and an InsulatedGate FET(IGFET) The device 1s slmllar to the conventional IGFET except that the metal gate electrode 1s removed m order to expose the underlying msulator layer to solution The gate msulator plays the role of an ion selective electrode Figure 1 shows the prmclple of the ISFET The first ISFET was reported by Bergveld [ 11, and V~IXOUS devices of this type have been described m recent papers [ 2 61 ISFETs have potential advantages over conventronal zon selective electrodes m theurapid response, small size, and low output impedance Addltlonally , the use of IC technology allows the fabrlcatlon of ISFETs for the detection of several ion species sunultaneously These advantages of ISFETs are extremely attractive for P1omedlca.l apphcations The nature of ISFETs requires that they are used m solutions of electrolytes which, from the electronic point of mew, are hostile enwonments The electrical mtegnty of the whole ISFET assembly 1s cntlcal and a prerequlslte for the stable operation of those devices, and, especially, the protection of the gate msulator from ion migration and hydration 1s crltlcally unportant For these reasons, the charactenstlcs of ISFETs are greatly dependent on the structure and the method of fabrication of the device

The fabrication of an integrated microprobing head for fault analysis of MOS ICs is described. The micrpoprobe is etched out from a silicon wafer to a tip size of about 10 μm and it has an NMOS impedance transformer intergrated very close to the tip. The input capacitance of this device is smaller than 0.1 pF and the delay time (at 50% of the final value) is lower than 100 ns at a 100 kΩ signal source resitance. This is a significant improvement n the response time of a conventional microprobe.

We developed a new technique to eliminate low-frequency ECG noise by the use of a specially designed high-pass phaseless filter. The phaseless filter was tested by computer-simulated ECG signals and it proved to be highly effective in eliminating ECG noise without any significant deformation of the ST segment level. The maximum distortion of ST segment level at 0.8 Hz cut off frequency of this filter is equivalent to the distortion of the usual ECG Amp having 0.1 Hz cut off frequency (JIS). Furthermore, studies of the stabilized ECG recordings during exercise, which became possible by using the phaseless filter, enabled us to develop a method of automatic analysis of the heart rate-ST segment level relationship during and after exercise. The submaximal exercise ECG test was done on 78 ostensibly healthy men. The heart rate (X axis) and three points on the ST segment levels (Y axis) were plotted automatically on an X-Y recorder. Although a great variety of patterns were drawn, we could discern clearly different patterns for normal subject and those with typical ischemic heart disease. Further analysis of this relationship will undoubtedly contribute to the detection of ischemic heart disease.

The effects of ionic strength of the sample solution and enzyme load on the potentiometric response of a urea sensor based on an ion-sensitive field effect transistor (ISFET) were examined. The output voltage of the sensor for urea solutions shifted slightly when NaCl was added to the solutions. The enzyme load on the ISFET gate affected the potentiometric response significantly. The sensor showed a higher response when the ISFET gate was coated with an enzyme membrane with a higher content of urease.

Design and fabrication methods, along with the results of a preliminary evaluation, are described for microprobe ISFET sensors intended for extracellular ion-activity measurements. The devices are 5 mm long with a gradual taper to the tip where the cross-sectional area is 30 × 30 μm2. Since the ion-sensing area is located at the end of the tip, a very small sensing region is achieved. Photo-induced noise generated in the depletion zone of the long drain diffusion layer was found to be particularly troublesome. This effect was greatly reduced by the use of an opaque tantalum thin film deposited on the probe surface. Preliminary tests of micro pH, pNa and pK ISFETs have shown that it is possible to measure extracellular ion activities using ISFETs.

The gate of ion sensitive field effect transistor (ISFET) was coated with urease-albumin membrane to fabricate a micro urea sensor. Potentiometric response of the sensor is markedly dependent on the nature of the membranes. Using the sensor with a thiner membrane (ca. 2μm), linear response with a slope of -44 mV/decade has been obtained over the range of 1×10-4-5×10-3mole/dm3 (M) urea concentration, response time being 2 min. In contrast, for the thicker membrane (ca. 10 μm), Nernstian response with 30 min of the response time has been obtained. The diffusion rate of H+ or OH- in the membranes has been estimated to be a main factor governing the response time of the sensor. Some operating variables such as the buffer concentration and the life time of the sensor have been also examined.

A potentiometric method for the determination of urea in human blood with an ion-sensitive field effect transistor coated with a urease-albumin membrane is described. The urea sensor exhibits a potentiometric response to urea concentrations in the range of 0.1-10 mM with a response time of ca. 3 min. Urea concentrations of diluted serum and plasma can be determined accurately with the sensor. Comparison with an official method (i.e. the urease-indophenol method) gave satisfactory results.

A hydrophobic polymer such as parylene has ion dissociation sites of extremely low density. An electrolyte-parylene interface manifests a constant potential independent of solution composition. The parylene-gate ISFET can be used as a solid state reference electrode. These films can also be used for the substrate of a CHEMFET, where the recent chemical modification technology is introduced. In this paper, the concept of a parylene-gate ISFET based on the site-binding model is investigated. As applications, a probe-type all solid state pH sensor integrating an Si3N4 gate, a parylene gate and an Au pseudo-reference electrode is discussed. A pK ISFET chemically modified with crown ether compounds is also reported.

To improve the capability of the ISFETs for measuring pNa and pK in living bodies, the ion selectivity of its sensor M2O-Al2O3-SiO2 (MAS, where M is an alkali metal) glass membrane was studied. The MAS membrane has been used as an ion-sensitive membrane of pNa and pK glass electrode and it has been known that its selectivity depends on the composition of the MAS membrane. To obtain the maximum ion selectivity of the pNa and pK ISFET, the relationship between the ion selectivity and the composition of the MAS membrane was investigated by measuring the ion selectivity over various compositions. It was confirmed that the selectivity of the MAS gate ISFET between Na+ ions and K+ ions depends on both the kind of alkaline cation and the ratio of the alkali metal to aluminum in the MAS membrane. As a result, the best composition of ion-sensitive membranes for pNa and pK ISFET was determined. A pNa ISFET was obtained which uses the LAS membrane containing Li as the alkali metal and has a selectivity of about 200 times for Na+ ions against K+ ions with a low output-voltage drift and a long life. A pK ISFET also was obtained which uses a KAS membrane containing K and has a selectivity of about 40 times for K+ ions against Na+ ions.

An integrated liquid-oxide-semiconductor FET structure is described. The structure is similar to a conventional n-channel depletion mode MOSFET except the gate metal is omitted. Immersing the device in a saline solution, the drain current is controlled by the potential between the source and the solution. Operated as an active recording electrode, the structure has several properties useful in neurological research.

Two kinds of enzyme sensors were fabricated by chemically immobilizing an enzyme on the gate surface of an ion-sensitive field effect transistor (ISFET). One is a trypsin-membrane/ISFET sensor, which can measure concentrations of N-benzoyl-L-arginine ethyl ester in the range from 5×10-4 to 5×10-2M. The other is an α-chymotrypsin-membrane/ISFET sensor, which can measure concentrations of N-acetyl-L-tyrosine ethyl ester solution in the range of 5×10-4-5×10-3M. The response of the sensors was affected markedly by pH and the concentration of the working buffer.

Recent research activities on solid state micro sensors in Japan are reviewed. Many kinds of micro sensors for chemical and physical quantitative analysis have been developed for biomedical instrumentation. Many of these sensors are fabricated with the advanced art of semiconductor technology, which is called micromachining. This technology enables fabrication of sensors so small that they can be used in catheter tubes etc. Moreover, it has brought out integrated sensing systems or multi sensors. In the field of chemical sensors, the development of ISFETs, i.e. ion sensitive field effect transistors, has been much advanced. These have been applied not only as ion sensors but also as biosensors or dissolved gas sensors. On the other hand, the major research activities on micro sensors for physical quantities have been on pressure sensors for measurements in blood vessels etc.

The fabrication of a microprobe for simultaneous, independent and in-vivo measurements of H+ and Na+ ion activities is described.