I.INTRODUCTION
Oral hygiene education involves knowledge transfer, but must also consider current habits and personal skills. The American Dental Association (ADA) recommends brushing the teeth twice a day with gentle force and with circling or sweeping movements1). Improper brushing techniques can damage the gingiva and promote dental caries.
Many different techniques of toothbrushing have been proposed and developed, which include scrubbing, bass, modified bass, fones, and roll2). Toothbrushing normally consist of vigorous horizontal, vertical, rolling and/or circular movements3). According to the ADA, young adults should adopt the modified bass technique to remove more plaque than the scrub and the fones techniques, especially in dental sulci and interdental spaces4). However, the modified technique is hard to learn and requires a certain degree of skill. More than 75% of adults still employ the method of toothbrushing they first learned in their childhood5). This method requires time to learn and is not very effective6).
The main problem hindering development of toothbrushing techniques that are both effective and readily learned is the lack of an objective or concrete evaluation method.
The present study details an integrated hardware system to assess the intuitive education and evaluation for toothbrushing.
Assessments to improve oral hygiene involve measuring the levels of dental plaque and the specific contribution of everyday oral hygiene habits of brushing force and individual brushing technique. However, most reports have studied only one aspect of tooth brushing habits and the effectiveness for plaque removal7).
In this study, the newly invented toothbrush based on 32-bit RISC core micro-controller is described. To trace the position and orientation of toothbrushing in the mouth, absolute coordinate information of toothbrushing must be known. The novel system allows a user to monitor their brushing pattern using a 3-axis gyroscope, 3-axis accelerometer, 3-axis magnetic sensor, one load-cell and Bluetooth devices. A personal computer provides an on-line, real-time display of activity and orientation measurements during toothbrushing. By applying a tilt-compensated azimuth and position calculation algorithm, which is generally used in small 9-axis and load-cell devices, the spatial inclination and orientation of toothbrushing traits can be determined. The signal trace is analyzed to extract clinically relevant information.
The present study investigated whether the novel toothbrush is a useful alternative toothbrushing educational tool and to assess the patients brushing. To confirm the effectiveness of this system, eight periodontist brushed the teeth in a dental model using five toothbrushing techniques, and compared the results.
II.MATERIALS AND METHODS
1.System configuration
Back and forth movements of bristles were measured using a LSM303DLM 3-axis accelerometer (STMicroelectronics, USA). The sensitivity of the accelerometer was set to 2~8 g (g: gravitational acceleration, 1 g = 9.8 m/s2). Various movements comprising rotation of toothbrush through the bristle axis were measured by a model L3G4200D gyroscope (STMicroelectronics). The sensitivity of the gyroscope was set to 250~2,000 degree/second, dps). For identifying the brushing location regarding upper and lower parts, a model LSM303DLH 3-axis magnetic sensor (STMicroelectronics) was used (Fig. 1).
The sensitivity of the magnetic sensor was set to 1.3~8.1 gauss. A common type of magnetic sensor for this system was the fluxgate sensor (Table 1).
The toothbrush coordinating systems were Pitch (Y axis), Roll (X axis), and Yaw (Z axis) value. Brushing force was measured using a CZL616C one load cell (phidgets, Canada). The sensitivity of the load cell was set to 0.8 ± 0.1 mV/V (0~780 g). A simple formula converted the measured mV/V output from the load cell to the measured force; Measured Force = A x Measured mV/V + B (A: Sample value, B: offset (0.8)). To find A, capacity was used; Capacity = A x Rated Output (A = Capacity / Rated Output; A = 780 / 0.8; A = 975). Since the offset was quite variable between individual load cells, it was necessary to calculate the offset for each sensor. Output of the load cell with no force on it and the mV/V output were measured (Offset = 0 - 975 x Measured Output).
2.Subjects
Eight right-handed periodontologists in Chonnam National Dental Hospital participated. The dental model was set to the 12 o’clock direction during brushing. Upper and lower occlusal lines were located in a parallel direction with the flat-topped desk. Brushing was conducted every 10 seconds in 16 areas with every brushing technique (Fig. 3(a)).
3.Pitch, Roll, and Yaw
The Pitch, Roll, and Yaw motions on the aforementioned axes were calculated using the 3-axis accelerometer, 3-axis gyroscope, and 3-axis magnetic sensor (Fig. 2).
4Statistics
Data analysis was completed using SPSS 20.0 (SPSS, Chicago, IL, USA) statistical data analysis software. The mean and standard deviation of five techniques were compared using t-test. The paired t-test was used to compare five techniques at different interval within the 8 periodontologists of the toothbrushing method. A significance level of P = 0.05 was used in all statistical tests.
III.RESULTS
1.Sensor setting position and brushing procedure
Motion values were adjusted according to their baseline because experimental brushing was conducted in 16 different areas (upper/lower and right/left regions). Roll, Pitch, and Yaw value at the upper right posterior buccal aspect (2.5, 120, and 165, respectively) indicated the starting point of sensor value (Fig. 3(a)). Experimental brushing procedures were performed in numerical order start from upper right posterior buccal aspect (Table 2).
2.Software design
The novel toothbrush comprised hardware (toothbrush itself) and Bluetooth software that received data from toothbrush and communicated information. User friendliness was a key goal. The left panel in Fig. 4 shows the 3-dimensional movement of the toothbrush; this presentation helped motivate subjects and retain their interest during toothbrushing instruction. The middle panel of the figure depicts statistically extracted components of Pitch, Roll and Yaw motion in the upper lane, and accelerometer velocity and load cell pressure data in the lower panel. Finally, the right-most portion of the figure depicts the location of toothbrushing in real time including database icons (Fig. 4).
3.Working diagram of the novel toothbrush
Five brushing techniques were tried. Results are summarized in Fig. 3(b) – Yaw motion is indicated in blue and Roll motion in green. Considering the pattern by the Modified bass method in the upper right posterior buccal aspect, vibration pattern in three separate lines were noted, followed by a downward rectangular shape (Roll). The patterns were repetitive and transient. For the Bass technique, three separate vibrating lines were apparent, similar to the first part of the Modified bass technique. When the patterns of the Bass and Roll techniques overlapped, the patterns of the Modified bass technique were revealed. For pressure by load cells, by same method in same area, pressure was increased as the vibration was ongoing, but its pressure was decreased when Roll motion begins. For the Scrubbing method, three lines (Pitch, Yaw, and Roll) overlapped in three upper right posterior buccal aspects, indicating that brushing was conducted in a small area compared to the three separate lines in the Modified bass method. In addition, pressure level was always high during brushing (Fig. 3(b))).
4.Pitch motion
Sixteen areas were brushed by every technique, followed by comparison with their Pitch motions. In the occlusion area (upper and lower, right and left), there were no significant differences. In the Bass and Fones techniques, motions were significantly similar to each other, except the upper left posterior lingual and upper anterior lingual areas. Contrary to the Bass and Fones techniques, a Pitch motion of the Fones and Rolling techniques were statistically different (Table 3).
5.Roll motion
Comparing statistically to each technique in every area, only the Bass and Fones techniques were statistically similar in the lower anterior buccal aspect, while the Roll motion was significantly similar to all techniques in upper left posterior buccal area, except the Bass and Scrubbing, and the Fones and Rolling techniques (Table 4).
6.Yaw motion
The yaw motion could be always detected in every area. Considering the yaw motion, it is not well permitted in limited oral cavity. In 16 areas, significantly differences were observed in only 9 areas. Considering the Bass and Fones techniques, their yaw motion was significantly similar in lower right posterior buccal area (Table 5.).
7.Pressure
The pressure during brushing was sensed by load cells. In all occlusal area, pressure values were absolutely different from each other, which indicates the different pressure is applied to occlusal area by each technique. Considering the applied pressure during brushing, many techniques were significantly similar in upper right posterior buccal, upper left posterior lingual and lower left posterior lingual area. Examining carefully the pressure values, the Modified bass and Rolling techniques showed the significantly similarity to pressure value, except the lower right posterior lingual and occlusal area (Table 6).
IV.DISCUSSION
Toothbrushing is a mechanical cleaning procedure that can be considered one of the most reliable means of controlling plaque, provided cleaning is sufficiently thorough and performed at regular intervals8). It is a simple, low-tech, user-friendly approach that is widely accepted and affordable to most people.
Several toothbrushing methods have been proposed9), with the Bass technique10) and the Roll method being two of the most commonly recommended techniques in dental practice11). Katz et al12) opined that the Bass technique is superior to the Roll method in cleaning the tooth tissue adjacent to the gingival tissue, the gingival margins, and the sulcus. They recommended the modification of the Bass method combining this technique with the Roll method (Modified Bass technique) to ensure the complete plaque removal of both coronal surfaces and gingival margins.
Most studies have evaluated which brushing method was superior to others to introduce a specific toothbrushing method or to better hone the performance of thre subject’s normal toothbrushing practice. This present study evaluated the brushing motion when a dentist persuades the patients to change their method of oral hygiene. To delineate the brushing motion in the small and dark oral cavity, a new toothbrush containing several sensors was invented to evaluate the delicate brushing motion before and after brushing instruction.
The outputs from the embedded sensors were converted to pitch, roll, and yaw motion data. The pressure values were calculated by load cells during brushing. The orientations of the toothbrush in the oral cavity were described using an x, y, and z coordinate system in combination with pitch, roll, and yaw. Pitch can be defined as an upward or downward rotation. The roll motion is the rotational movement of the line of occlusion while the yaw is called the toothbrush can move in vertical direction.
Considering the upper right posterior buccal aspect, the Bass and Roll techniques were very similarity in every motion and pressure, despite their inherently dissimilar motions. However, their motions are similar in upper right posterior buccal area encasing the three walls. It is hard to shape the proper trait of toothbrushing in this small and conical narrow area. Only the pitch motion was different when the Roll and Scrubbing techniques were compared. Considering the pitch motion (up and down, or in front and back) provides a better understanding in both the Roll and Scrubbing techniques.
Contrary to our expectations, the pressure values were completely different when comparing every toothbrushing technique in the occlusal area. When a patient was asked to specific brushing technique, the pressure varied with each technique, although all techniques had a similar brushing motion.
Yaw motion, which has a descriptive definition as a movement of vertical direction, is of limited value. The movement direction to the gingiva from the cheek is not typically encountered in brushing. The motions of the Bass and Scrubbing, Fones and Scrubbing, Modified Bass and Scrubbing, and the Rolling and Scrubbing in the upper and lower anterolingual area were significantly similar to each other. To brush the upper anterolingual area, the toothbrush is assumed to be directed at first to the teeth from the tongue.
Although the present study compared every brushing technique and revealed a similar motion in 16 oral cavity areas, every technique can be differentiate their motion and generate a unique pattern during brushing, in which the information received in three motions were collected and analyzed.
V.CONCLUSION
The novel toothbrush can work in every motion (Pitch, Roll and Yaw) and can differentiate every brushing technique. Furthermore, it can be useful to educate a patient on toothbrushing and to evaluate their achievement. The proposed monitoring system may aid dental care personnel in patient education and instruction in oral hygiene regarding brushing style.
