Clin Oral Invest DOI 10.1007/s00784-013-1172-3
ORIGINAL ARTICLE
Analysis of tooth brushing cycles Yuki Tosaka & Kuniko Nakakura-Ohshima & Nozomi Murakami & Rikako Ishii & Issei Saitoh & Yoko Iwase & Akihiro Yoshihara & Akitsugu Ohuchi & Haruaki Hayasaki
Received: 21 May 2013 / Accepted: 19 December 2013 # Springer-Verlag Berlin Heidelberg 2014
Abstract Objective The aim of this study was to demonstrate the effectiveness of an analysis of tooth brushing cycles using a system that measures tooth brushing motion and brushing force with an accelerometer and strain tension gage attached to a toothbrush. Background Mechanical plaque removal with a manual toothbrush remains the primary method of maintaining good oral hygiene for the majority of the population. Because toothbrush motion has not been fully understood, it should be clarified by analysis of tooth brushing cycles. Methods Twenty healthy female dental hygienists participated in this study. Their tooth brushing motions were measured and analyzed using an American Dental Association-approved manual toothbrush to which a three-dimensional (3-D) accelerometer and strain tension gage were attached. 3-D motion and brushing force on the labial surface of the mandibular right central incisor Y. Tosaka : A. Yoshihara : A. Ohuchi Department of Oral Health and Welfare, Graduate School of Medical and Dental Sciences, Niigata University, 2-5274, Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan Y. Tosaka e-mail: [email protected] A. Yoshihara e-mail: [email protected]
and the lingual surface of the mandibular left first molar were measured, analyzed, and compared. Multilevel linear model analysis was applied to estimate variables and compare motion and forces related to the two tooth surfaces. Results The analysis of tooth brushing cycles was feasible, and significant differences were detected for durations and 3-D ranges of toothbrush motion as well as brushing force between the two tooth surfaces. Conclusion The analysis used in this study demonstrated an ability to detect characteristics of tooth brushing motion, showing tooth brushing motion to change depending on the brushed location. These results also suggest that more detailed instructions might be required according to patient’s oral condition.
Keywords Toothbrush . Motion . Cycle . Duration . Acceleration . Force
N. Murakami e-mail: [email protected] I. Saitoh e-mail: [email protected] Y. Iwase e-mail: [email protected] H. Hayasaki e-mail: [email protected]
A. Ohuchi e-mail: [email protected] K. Nakakura-Ohshima (*) : N. Murakami : I. Saitoh : Y. Iwase : H. Hayasaki Department of Pediatric Dentistry, Graduate School of Medical and Dental Sciences, Niigata University, 2-5274, Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan e-mail: [email protected]
R. Ishii Tokyo Metropolitan Center for Oral Health of Persons with Disabilities, 1-1, Kagurakawagishi, Shinjyuku-ku, Tokyo 162-0823, Japan e-mail: [email protected]
Clin Oral Invest
Introduction
Materials and methods
Control of plaque and debris is essential for the prevention of inflammatory periodontal diseases and dental caries, because plaque is the primary etiological factor in the introduction and development of both of diseases [1]. Plaque removal with a manual toothbrush represents the most frequently used method of oral hygiene. The bristles of the toothbrush should be able to reach and clean efficiently most areas of the mouth. In addition, commonly recommended tooth brushing times vary between 120 s (USA) and 180 s (Europe) [2]. However, changing behavior in this regard seems to be very difficult [3]. Achieving an optimal result depends upon the individual motivation as well as the technique of toothbrush movements, i.e., manual skills. A systematic review [4] revealed that the effectiveness of self-performed mechanical plaque removal using a manual toothbrush was not sufficient and needed improvement. Tooth brushing technique is not effectively changed by either descriptions in a leaflet or by demonstrations, suggesting a need to improve instructional strategies [5]. These authors also suggested that findings from sports and cognitive brain research would be indispensable to these strategies. Physical skills (e.g., eating [6], speech [7, 8], and sports [9, 10]) have been improved by training. Accordingly, tooth brushing should be also trained as a physical skill; however, real toothbrush motions have not been studied sufficiently to make training feasible. To overcome this deficiency, several kinds of equipment have been developed recently [11, 12]. Kim et al. [11] developed a three-dimensional (3-D) visualization system to give feedback to a subject during the brushing motion, and Graetz et al. [12] described a smart digital toothbrush monitoring and training system for correcting brushing motion and grip axis orientation in the at-home environment. Despite the development of these sophisticated devices, their analysis focused on an entire sequence of tooth brushing motion, from the beginning to the ending of the motion. However, tooth brushing motion is a series of component cycles. Therefore, as a cyclic physical skill, this brushing motion should be analyzed by its components, and instructions to improve the technique should refer to the cycle of the motion. The hypotheses of this study were that analysis of tooth brushing cycles, using an accelerometer and a strain tension gage, can (1) evaluate characteristics of tooth brushing and (2) detect differences of motion and force depending on brushed locations.
Study population The participants in this study were 20 right-handed female dental hygienists. All participants belonged to the Tokyo Metropolitan Center for Oral Health of Persons with Disabilities, and all dental hygienists participated in this research. Dental hygienists were selected because they represent the most-trained professional for tooth brushing. All participants were given oral and written information about the purpose and detailed procedures of the study. The inclusion criteria were (1) dentition with a minimum of 24 teeth, (2) good general health, and (3) dental hygienists. Exclusion criteria were (1) serious disease, (2) active periodontitis, or (3) previous history of periodontitis; (4) oral removable or fixed prostheses or orthodontic appliances; (5) allergies to dental materials; (6) smokers; and (7) any physical disability with a potential influence on oral hygiene performance. Subjects’ average age was 33 years and 6 months (standard deviation (SD) 8.9, range 21 years and 4 months to 46 years and 7 months). The study protocol received approval from the Ethical Committee of the Faculty of Dentistry, Niigata University (23-R511-05), and each subject was given informed consent before participating in the study. Study design and procedures The Butler GUM 211 manual toothbrush (Sunstar Butler®, Chicago, IL, USA), approved by the American Dental Association, was used in this study. A wireless accelerometer (MPM606/400B, MicroStone® Inc., Saku City, Nagano Prefecture, Japan) was attached to the tail of the toothbrush, and a strain tension gage (KFG-C15, KYOWA® Inc., Tokyo, Japan) was taped to the neck of the toothbrush (Fig. 1). The strain gage attached to each toothbrush was calibrated at 300-g weight individually. Measuring errors of both devices were at most ±2 % of the measuring range in bench tests. The weight of each sensor was 8 and 0.5 g, respectively. An instructed task for each participant was to brush two dental surfaces: (1) the labial surface of the mandibular right central incisor (RCI) and (2) the lingual surface of the mandibular left first molar (LFM) (Fig. 2). Because the coordinate system was defined by the direction of the accelerometer attached to the toothbrush, (1) the X-axis was along the tooth brushing axis (i.e., the left-right direction at RIC), (2) the Y-axis was perpendicular to the X-axis (i.e., in a superior–inferior direction), and (3) the Z-axis was perpendicular to the X–Y plane (i.e., in a labial–lingual direction) (Fig. 2). Each surface was brushed twice for 10 s, (i.e., two 10-s trials). No other instructions were given to each subject.
Clin Oral Invest
Right
Accelerometer
Strain Tension Gage
MP-M606/400B Microstone Inc.
KFG-C15 KYOWA Inc.
Left
X axis Y axis Brushing area
Inter-face DBU-120 KYOWA Inc.
Z axis
Fig. 2 Brushing area and coordinate system at each surface. Arrows indicate motion along the X- and Z-axes. The Y-axis is not shown because it is perpendicular to the plane of the figure
Division into cycles
Windows PC Fig. 1 Diagram of the system. An accelerometer and a strain tension gage were attached to the tail of the handle and to the neck of the toothbrushes, respectively
In addition, subjects received the same toothbrush 1 week before the experiment, so they would be able to use it in their own usual manner.
The motion of the toothbrush while brushing both surfaces is shown in Fig. 3. Because the motion of the toothbrush was a series of repeated cyclic movements, the changes of each 3-D displacement and the brushing force measured by the strain tension gage can be plotted simultaneously (Figs. 4 and 5). Each individual’s motion was divided into its component cycles, which were evaluated using a specially written computer program.
Data analysis 15
Conversion to displacement from acceleration Displacements (i.e., changing position of the accelerometer) and brushing force were sampled at 100 Hz (1/0.01 s), and the resulting data was stored in a text file on a Windows® PC. According to the definitions of acceleration a(t), velocity v(t), and displacement u(t), these two equations hold: Z vt ¼ aðt Þdt þ C 1 Z uð t Þ ¼ vðt Þdt þ C 1 t þ C 2
where C1 and C2 are the constants of integration. These calculations were performed with use of the software (MVP-VD-S, MicroStone® Inc., Saku City, Nagano Prefecture, Japan) that was provided by the same company that developed the accelerometers used in this study.
[mm]
Y axis
10
5
X axis
0 -15
-10
-5
0
5
10
15
[mm] -5
-10
Red: Labial Surface of Right Central Incisor (RCI) Black: Lingual Surface of Left First Molar (LFM) -15
Fig. 3 An example of the surface view of 10 s of brushing motion at both the RCI and the LFM. This serial motion can be divided into its component cycles as shown in Figs. 4 and 5
Clin Oral Invest
The starting frame of each cycle was identified as the frame at the minimum position, which was a frame with more than seven consecutive frames with increases along the X-axis followed by more than seven consecutive frames with decreases along the X-axis. The program continued along the trace until it identified the next starting frame, which marked the end of the cycle. The frame that showed the maximum position between two starting frames was the frame dividing the cycle into the first and second halves, and indicated the turning point of the direction motion (Figs. 4 and 5). To be included as a valid cycle, each cycle had to be less than 500 ms in duration. SS X range ðiÞ SS Y range ðiÞ SS Z range ðiÞ SS BF range ðiÞ
Selection of representative cycles For each participant, trial, and surface, the program identified no more than 10 cycles that showed the least deviations from the set of four standard scores for each cycle as described below. First, the means and SDs were computed for four measurements (displacement range along the X-, Y-, and Z-axes and the brushing force (BF) range) calculated for each individual from all of their cycles. Each range was defined as the difference between the maximum and the minimum values of each displacement and BF within a cycle. Each standard score (SS) was computed by subtracting the individual’s observed cycle value from the mean and dividing the difference by the SD as below:
¼ Absolute value ðMean X range−X range ðiÞ=SD X rangeÞ ¼ Absolute value ðMean Y range−Y range ðiÞ=SD Y rangeÞ ¼ Absolute value ðMean Z range−Z range ðiÞ=SD Z rangeÞ ¼ Absolute value ðMean BF range−BF range ðiÞ=SD BF rangeÞ
This calculated SS indicated a cycle’s amount of deviation from the mean of all cycles for each variable. Overall cycle deviations (OCD) were estimated based on the cycles’ range of displacements and brushing force range using
OCD ðiÞ ¼ SS X range ðiÞ þ SS Y range ðiÞ þ SS Z range ðiÞ þ SS BF range ðiÞ
Fig. 4 An example of displacements along the X-, Y-, and Z-axes and brushing force (x10) during a tooth brushing sequence. Each curve on the X-, Y-, and Z-axes and brushing force represents a component cycle of the brushing motion
where SS refers to the standard scores calculated for each individual’s series of tooth brushing cycles. Cycles with the lowest OCD were considered the most representative for each individual surface, for each trial of each participant. It should be emphasized that using only the ten most representative cycles reduces overall variability, and especially betweencycle random variability. This method has been previously applied to analysis of chewing cycle kinematics [13] and has been proven to reduce variation [14].
[mm] / [N]
To Figure 5
20.0
15.0
10.0
5.0
0.0 1500
1600
1700
1800
1900
-5.0
-10.0 Series2 X Series3 Y -15.0
Series4 Z Series1 Brushing
-20.0
Force ( ×10 )
[ms]
Clin Oral Invest [mm] / [N]
1st half duration
20.0
2nd half duration
Total Duration 15.0
10.0
5.0
0.0 1706
1716
1726
1736
-5.0
Range of Displacement
Fig. 5 An example of a single tooth brushing cycle from Fig. 4. Curves are provided for motion along the three orthogonal axes and the brushing force (x10). Also measurement variables are explained in this figure. An entire movement sequence was divided into component cycles and half cycles based on the X-axis motion because the movement along this axis was twice as long or more than the movement along the Yand Z-axes
[ms]
-10.0 Series2 X Series3 Y -15.0
Series4 Z Series1 Brushing
Force (×10 )
-20.0
Statistical analysis Using the ten most representative cycles from each of two trials from each participant (i.e., 20 cycles), another computer program calculated durations of the total cycle, as well as durations of the first and second halves of each cycle (Fig. 5), the range of displacement for each axis (X-, Y-, and Z-axes), the 3-D range, and the brushing force range. These Table 1 Comparison of mean cycle durations (milliseconds), 3-D ranges (millimeters), and brushing force range (newtons) between the RCI and LFM Measures
Labial surface of the right central incisor (RCI) Mean
Lingual Difference surface of the left first molar (LFM)
S.E. Mean
S.E.
Mean S.E.
Results
Cycle duration [ms] Total 220.80 1st half 112.00 2nd half 108.80 3-Dimensional ranges [mm] X-axis 10.56 Y-axis 3.09 Z-axis 4.96
1.08 16.55 0.49 5.56 0.61 6.90
11.30 5.99 0.64 2.47 0.73 1.95
1.53** 0.69** 0.86*
3-Dimensional 12.47 Brushing force range [N] 0.62
1.23 19.20 0.07 0.95
1.57 0.07
1.74** 0.10**
S.E. standard error of the mean *p
ORIGINAL ARTICLE
Analysis of tooth brushing cycles Yuki Tosaka & Kuniko Nakakura-Ohshima & Nozomi Murakami & Rikako Ishii & Issei Saitoh & Yoko Iwase & Akihiro Yoshihara & Akitsugu Ohuchi & Haruaki Hayasaki
Received: 21 May 2013 / Accepted: 19 December 2013 # Springer-Verlag Berlin Heidelberg 2014
Abstract Objective The aim of this study was to demonstrate the effectiveness of an analysis of tooth brushing cycles using a system that measures tooth brushing motion and brushing force with an accelerometer and strain tension gage attached to a toothbrush. Background Mechanical plaque removal with a manual toothbrush remains the primary method of maintaining good oral hygiene for the majority of the population. Because toothbrush motion has not been fully understood, it should be clarified by analysis of tooth brushing cycles. Methods Twenty healthy female dental hygienists participated in this study. Their tooth brushing motions were measured and analyzed using an American Dental Association-approved manual toothbrush to which a three-dimensional (3-D) accelerometer and strain tension gage were attached. 3-D motion and brushing force on the labial surface of the mandibular right central incisor Y. Tosaka : A. Yoshihara : A. Ohuchi Department of Oral Health and Welfare, Graduate School of Medical and Dental Sciences, Niigata University, 2-5274, Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan Y. Tosaka e-mail: [email protected] A. Yoshihara e-mail: [email protected]
and the lingual surface of the mandibular left first molar were measured, analyzed, and compared. Multilevel linear model analysis was applied to estimate variables and compare motion and forces related to the two tooth surfaces. Results The analysis of tooth brushing cycles was feasible, and significant differences were detected for durations and 3-D ranges of toothbrush motion as well as brushing force between the two tooth surfaces. Conclusion The analysis used in this study demonstrated an ability to detect characteristics of tooth brushing motion, showing tooth brushing motion to change depending on the brushed location. These results also suggest that more detailed instructions might be required according to patient’s oral condition.
Keywords Toothbrush . Motion . Cycle . Duration . Acceleration . Force
N. Murakami e-mail: [email protected] I. Saitoh e-mail: [email protected] Y. Iwase e-mail: [email protected] H. Hayasaki e-mail: [email protected]
A. Ohuchi e-mail: [email protected] K. Nakakura-Ohshima (*) : N. Murakami : I. Saitoh : Y. Iwase : H. Hayasaki Department of Pediatric Dentistry, Graduate School of Medical and Dental Sciences, Niigata University, 2-5274, Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan e-mail: [email protected]
R. Ishii Tokyo Metropolitan Center for Oral Health of Persons with Disabilities, 1-1, Kagurakawagishi, Shinjyuku-ku, Tokyo 162-0823, Japan e-mail: [email protected]
Clin Oral Invest
Introduction
Materials and methods
Control of plaque and debris is essential for the prevention of inflammatory periodontal diseases and dental caries, because plaque is the primary etiological factor in the introduction and development of both of diseases [1]. Plaque removal with a manual toothbrush represents the most frequently used method of oral hygiene. The bristles of the toothbrush should be able to reach and clean efficiently most areas of the mouth. In addition, commonly recommended tooth brushing times vary between 120 s (USA) and 180 s (Europe) [2]. However, changing behavior in this regard seems to be very difficult [3]. Achieving an optimal result depends upon the individual motivation as well as the technique of toothbrush movements, i.e., manual skills. A systematic review [4] revealed that the effectiveness of self-performed mechanical plaque removal using a manual toothbrush was not sufficient and needed improvement. Tooth brushing technique is not effectively changed by either descriptions in a leaflet or by demonstrations, suggesting a need to improve instructional strategies [5]. These authors also suggested that findings from sports and cognitive brain research would be indispensable to these strategies. Physical skills (e.g., eating [6], speech [7, 8], and sports [9, 10]) have been improved by training. Accordingly, tooth brushing should be also trained as a physical skill; however, real toothbrush motions have not been studied sufficiently to make training feasible. To overcome this deficiency, several kinds of equipment have been developed recently [11, 12]. Kim et al. [11] developed a three-dimensional (3-D) visualization system to give feedback to a subject during the brushing motion, and Graetz et al. [12] described a smart digital toothbrush monitoring and training system for correcting brushing motion and grip axis orientation in the at-home environment. Despite the development of these sophisticated devices, their analysis focused on an entire sequence of tooth brushing motion, from the beginning to the ending of the motion. However, tooth brushing motion is a series of component cycles. Therefore, as a cyclic physical skill, this brushing motion should be analyzed by its components, and instructions to improve the technique should refer to the cycle of the motion. The hypotheses of this study were that analysis of tooth brushing cycles, using an accelerometer and a strain tension gage, can (1) evaluate characteristics of tooth brushing and (2) detect differences of motion and force depending on brushed locations.
Study population The participants in this study were 20 right-handed female dental hygienists. All participants belonged to the Tokyo Metropolitan Center for Oral Health of Persons with Disabilities, and all dental hygienists participated in this research. Dental hygienists were selected because they represent the most-trained professional for tooth brushing. All participants were given oral and written information about the purpose and detailed procedures of the study. The inclusion criteria were (1) dentition with a minimum of 24 teeth, (2) good general health, and (3) dental hygienists. Exclusion criteria were (1) serious disease, (2) active periodontitis, or (3) previous history of periodontitis; (4) oral removable or fixed prostheses or orthodontic appliances; (5) allergies to dental materials; (6) smokers; and (7) any physical disability with a potential influence on oral hygiene performance. Subjects’ average age was 33 years and 6 months (standard deviation (SD) 8.9, range 21 years and 4 months to 46 years and 7 months). The study protocol received approval from the Ethical Committee of the Faculty of Dentistry, Niigata University (23-R511-05), and each subject was given informed consent before participating in the study. Study design and procedures The Butler GUM 211 manual toothbrush (Sunstar Butler®, Chicago, IL, USA), approved by the American Dental Association, was used in this study. A wireless accelerometer (MPM606/400B, MicroStone® Inc., Saku City, Nagano Prefecture, Japan) was attached to the tail of the toothbrush, and a strain tension gage (KFG-C15, KYOWA® Inc., Tokyo, Japan) was taped to the neck of the toothbrush (Fig. 1). The strain gage attached to each toothbrush was calibrated at 300-g weight individually. Measuring errors of both devices were at most ±2 % of the measuring range in bench tests. The weight of each sensor was 8 and 0.5 g, respectively. An instructed task for each participant was to brush two dental surfaces: (1) the labial surface of the mandibular right central incisor (RCI) and (2) the lingual surface of the mandibular left first molar (LFM) (Fig. 2). Because the coordinate system was defined by the direction of the accelerometer attached to the toothbrush, (1) the X-axis was along the tooth brushing axis (i.e., the left-right direction at RIC), (2) the Y-axis was perpendicular to the X-axis (i.e., in a superior–inferior direction), and (3) the Z-axis was perpendicular to the X–Y plane (i.e., in a labial–lingual direction) (Fig. 2). Each surface was brushed twice for 10 s, (i.e., two 10-s trials). No other instructions were given to each subject.
Clin Oral Invest
Right
Accelerometer
Strain Tension Gage
MP-M606/400B Microstone Inc.
KFG-C15 KYOWA Inc.
Left
X axis Y axis Brushing area
Inter-face DBU-120 KYOWA Inc.
Z axis
Fig. 2 Brushing area and coordinate system at each surface. Arrows indicate motion along the X- and Z-axes. The Y-axis is not shown because it is perpendicular to the plane of the figure
Division into cycles
Windows PC Fig. 1 Diagram of the system. An accelerometer and a strain tension gage were attached to the tail of the handle and to the neck of the toothbrushes, respectively
In addition, subjects received the same toothbrush 1 week before the experiment, so they would be able to use it in their own usual manner.
The motion of the toothbrush while brushing both surfaces is shown in Fig. 3. Because the motion of the toothbrush was a series of repeated cyclic movements, the changes of each 3-D displacement and the brushing force measured by the strain tension gage can be plotted simultaneously (Figs. 4 and 5). Each individual’s motion was divided into its component cycles, which were evaluated using a specially written computer program.
Data analysis 15
Conversion to displacement from acceleration Displacements (i.e., changing position of the accelerometer) and brushing force were sampled at 100 Hz (1/0.01 s), and the resulting data was stored in a text file on a Windows® PC. According to the definitions of acceleration a(t), velocity v(t), and displacement u(t), these two equations hold: Z vt ¼ aðt Þdt þ C 1 Z uð t Þ ¼ vðt Þdt þ C 1 t þ C 2
where C1 and C2 are the constants of integration. These calculations were performed with use of the software (MVP-VD-S, MicroStone® Inc., Saku City, Nagano Prefecture, Japan) that was provided by the same company that developed the accelerometers used in this study.
[mm]
Y axis
10
5
X axis
0 -15
-10
-5
0
5
10
15
[mm] -5
-10
Red: Labial Surface of Right Central Incisor (RCI) Black: Lingual Surface of Left First Molar (LFM) -15
Fig. 3 An example of the surface view of 10 s of brushing motion at both the RCI and the LFM. This serial motion can be divided into its component cycles as shown in Figs. 4 and 5
Clin Oral Invest
The starting frame of each cycle was identified as the frame at the minimum position, which was a frame with more than seven consecutive frames with increases along the X-axis followed by more than seven consecutive frames with decreases along the X-axis. The program continued along the trace until it identified the next starting frame, which marked the end of the cycle. The frame that showed the maximum position between two starting frames was the frame dividing the cycle into the first and second halves, and indicated the turning point of the direction motion (Figs. 4 and 5). To be included as a valid cycle, each cycle had to be less than 500 ms in duration. SS X range ðiÞ SS Y range ðiÞ SS Z range ðiÞ SS BF range ðiÞ
Selection of representative cycles For each participant, trial, and surface, the program identified no more than 10 cycles that showed the least deviations from the set of four standard scores for each cycle as described below. First, the means and SDs were computed for four measurements (displacement range along the X-, Y-, and Z-axes and the brushing force (BF) range) calculated for each individual from all of their cycles. Each range was defined as the difference between the maximum and the minimum values of each displacement and BF within a cycle. Each standard score (SS) was computed by subtracting the individual’s observed cycle value from the mean and dividing the difference by the SD as below:
¼ Absolute value ðMean X range−X range ðiÞ=SD X rangeÞ ¼ Absolute value ðMean Y range−Y range ðiÞ=SD Y rangeÞ ¼ Absolute value ðMean Z range−Z range ðiÞ=SD Z rangeÞ ¼ Absolute value ðMean BF range−BF range ðiÞ=SD BF rangeÞ
This calculated SS indicated a cycle’s amount of deviation from the mean of all cycles for each variable. Overall cycle deviations (OCD) were estimated based on the cycles’ range of displacements and brushing force range using
OCD ðiÞ ¼ SS X range ðiÞ þ SS Y range ðiÞ þ SS Z range ðiÞ þ SS BF range ðiÞ
Fig. 4 An example of displacements along the X-, Y-, and Z-axes and brushing force (x10) during a tooth brushing sequence. Each curve on the X-, Y-, and Z-axes and brushing force represents a component cycle of the brushing motion
where SS refers to the standard scores calculated for each individual’s series of tooth brushing cycles. Cycles with the lowest OCD were considered the most representative for each individual surface, for each trial of each participant. It should be emphasized that using only the ten most representative cycles reduces overall variability, and especially betweencycle random variability. This method has been previously applied to analysis of chewing cycle kinematics [13] and has been proven to reduce variation [14].
[mm] / [N]
To Figure 5
20.0
15.0
10.0
5.0
0.0 1500
1600
1700
1800
1900
-5.0
-10.0 Series2 X Series3 Y -15.0
Series4 Z Series1 Brushing
-20.0
Force ( ×10 )
[ms]
Clin Oral Invest [mm] / [N]
1st half duration
20.0
2nd half duration
Total Duration 15.0
10.0
5.0
0.0 1706
1716
1726
1736
-5.0
Range of Displacement
Fig. 5 An example of a single tooth brushing cycle from Fig. 4. Curves are provided for motion along the three orthogonal axes and the brushing force (x10). Also measurement variables are explained in this figure. An entire movement sequence was divided into component cycles and half cycles based on the X-axis motion because the movement along this axis was twice as long or more than the movement along the Yand Z-axes
[ms]
-10.0 Series2 X Series3 Y -15.0
Series4 Z Series1 Brushing
Force (×10 )
-20.0
Statistical analysis Using the ten most representative cycles from each of two trials from each participant (i.e., 20 cycles), another computer program calculated durations of the total cycle, as well as durations of the first and second halves of each cycle (Fig. 5), the range of displacement for each axis (X-, Y-, and Z-axes), the 3-D range, and the brushing force range. These Table 1 Comparison of mean cycle durations (milliseconds), 3-D ranges (millimeters), and brushing force range (newtons) between the RCI and LFM Measures
Labial surface of the right central incisor (RCI) Mean
Lingual Difference surface of the left first molar (LFM)
S.E. Mean
S.E.
Mean S.E.
Results
Cycle duration [ms] Total 220.80 1st half 112.00 2nd half 108.80 3-Dimensional ranges [mm] X-axis 10.56 Y-axis 3.09 Z-axis 4.96
1.08 16.55 0.49 5.56 0.61 6.90
11.30 5.99 0.64 2.47 0.73 1.95
1.53** 0.69** 0.86*
3-Dimensional 12.47 Brushing force range [N] 0.62
1.23 19.20 0.07 0.95
1.57 0.07
1.74** 0.10**
S.E. standard error of the mean *p
