Received: 10 February 2020

| Revised: 12 August 2020 | Accepted: 30 September 2020

DOI: 10.1111/idh.12475

ORIGINAL ARITCLE

Clinical comparison of an electric-powered ionic toothbrush
and a manual toothbrush in plaque reduction: A randomized
clinical trial
Takahiro Ikawa1,2| Koji Mizutani1| Takeaki Sudo1 | Chihiro Kano1 | Yuichi Ikeda1
Tatsuya Akizuki1 | Hiroaki Kobayashi1 | Yuichi Izumi1,3 | Takanori Iwata1
1
Department of Periodontology, Graduate
School of Medical and Dental Sciences,
Tokyo Medical and Dental University,
Tokyo, Japan2
Department of Periodontology, Facultyof Odontology, Malmö University, Malmö,
Sweden3

Oral Care Perio Center, Southern
TOHOKU General Hospital, Southern
TOHOKU Research Institute for
Neuroscience, Fukushima, Japan|

Abstract
Objectives: This study aimed to evaluate the plaque removal efficacy of a newly developed electric-powered ionic toothbrush vs. a manual toothbrush.
Materials and Methods: Manual or electric-powered ionic toothbrushes were randomly assigned to 30 healthy volunteers divided into two groups (Phase I). After
2 min of brushing, all tooth surfaces were stained with a plaque staining solution,and blinded examiners performed scoring using the Rustogi Modification of the Navy
Plaque Index. Plaque removal rate was calculated at the central incisors, first premo-

Correspondence
Koji Mizutani, Department of
Periodontology, Graduate School of
Medical and Dental Sciences, Tokyo
Medical and Dental University, 1-5-45
Yushima, Bunkyo-ku, Tokyo, 113-8549,
Japan.
Email: mizuperi@tmd.ac.jp

lar and first molar, as representative teeth, in the maxilla and mandibula. One week

Funding information
JSPS KAKENHI Grant-in-Aid for Young
Scientists, Grant/Award Number:
18K17061

observed.

following Phase I, the same examinations were repeated in all subjects using anothertoothbrush (Phase II), as a crossover design.
Results: Electric ionic toothbrushes demonstrated a significantly higher plaqueremoval rate than manual toothbrushes in the premolar and molar areas (p < .05).
However, in the central incisor area, no statistically significant difference wasConclusions: Compared with manual toothbrushes, electric-powered ionic ones weresignificantly efficient in removing plaque in the premolar and molar areas.
KEYWORDS

dental plaque, electric-powered toothbrush, manual toothbrush, randomized controlled trial,
toothbrushing, young adult1|

of factors (eg. age, knowledge, manual dexterity and motivation).

I NTRO D U C TI O N

Maintenance of periodontal health is an essential aspect of personaloral hygiene.4–6 Using toothbrushes is the most commonly accepted

Dental plaque triggers changes in gingival health, which results in
1,2

slight swelling and bleeding from the gingival margin.

method of removing dental plaque.

Residual

Toothbrushes have various forms and designs to suit differ-dental plaques cause such gingival changes, which suggest thatent functional and scientific requirements. Ionic toothbrushes aregood oral hygiene by effective toothbrushing plays an important

expected to work by changing the tooth surface's polarity, there-role in oral health.3 Effective toothbrushing depends on a number

fore facilitating plaque removal. The principle of polarity showed© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Int J Dent Hygiene. 2020;00:1–6.	﻿

wileyonlinelibrary.com/journal/idh

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IKAWA et al.

that every element in nature has a positive or negative charge.7

2.2 | Subjects

In brief, teeth and plaque are generally negatively charged. The
plaque is absorbed onto the tooth surface via positive ions in the

Dental Research Ethics Committee of Tokyo Medical and Dental

saliva. Ionic toothbrush adopted lithium battery as the built-in

University (D 2017-046) approved this study. Before enrolment inelectric power and formed circuit through the two electrodes

the study, all subjects provided informed consent.

portions (grip and head of toothbrush). Negative ions were gener-

Thirty systemically healthy dentist volunteers (ie 23 males, sevenated from this electric circuit and blocked the adsorption caused

females, between the ages of 25 and 32 years) with at least 20 nat-by the cross-linking. Previous studies suggest that an ionic tooth-ural teeth were recruited in this study. The inclusion criteria were asbrush is more effective in plaque removal than a negative ionicfollows: five evaluable teeth in each quadrant (excluding all canine

toothbrush.7–9 On the contrary, a few studies show that ionicand third molars); no professional oral care during the study period;

10

abstinence of any oral hygiene care and procedures for 24 h before

especially in terms of a reduction in Gingival Index.11–13 There isdata collection; and healthy periodontal oral condition (<3 mm ofa need to develop ionic toothbrushes capable of efficiently andprobing pocket depth, <10% bleeding on probing, and no attach-effectively removing dental plaque.

ment loss). Exclusion criteria were as follows: presence of any phys-

toothbrushes were different from conventional toothbrushes,

Manual and powered toothbrushes are equally effective in

ical limitation or restriction that might preclude normal oral hygiene

reducing signs of clinical gingival inflammation and plaque re-procedures, removable prosthesis or orthodontic appliance, signs ofmoval.14 However, recent clinical trials and systematic reviews

periodontitis (ie recession >2 mm and acute symptoms), treatment

have shown that powered toothbrushes are safer than manualwith antimicrobial agents in the preceding 3 months, use of mouth

ones. Additionally, powered toothbrushes removed 11% and 21%

rinse, pregnancy and breastfeeding.

more plaque than manual toothbrushes in short- and long-term
studies, respectively.15 These results demonstrate that powered
toothbrushes represent an alternative to manual toothbrushing.16

2.3 | Study design

Generally, powered toothbrushes require a high level of plaqueremoval with a less-than-ideal brushing technique. For example,

According to a previous study,18 the sample size was calculated

the focus has been placed on designing toothbrushes that allow

based on the percentage of plaque scores with differences of 0.11

for greater access and more effective plaque removal at more dif-

between the groups, with an standard deviations (SD) of 0.1, signifi-

ficult-to-reach areas of the mouth, including interproximal sites.

cance level of 5% and power of 80% (n = 14.0).

Thus, over time, there have been numerous variations, which have

Figure A1 in Appendix 1 illustrates the study design. This study

led to significant product improvements.17 However, it remains

was designed as a randomized, single-blinded, crossover clinicalunclear whether the combination of ionic and electric-powered

trial with two visits. Volunteers were instructed not to brush their

toothbrushes offers any additional benefit in plaque reduction.

teeth and perform any other oral hygiene procedures (ie chewing

The aim of this randomized, crossover clinical trial study was togum, mouthwash) for 24 h before each visit. Additionally, volun-

evaluate plaque reduction efficacy of a new electric-powered ionicteers had to refrain from eating, drinking or smoking in the past

toothbrush and compare it to that of a manual toothbrush in a sin-

4 h. During each visit, subjects underwent an oral examination,gle use.

including probing pocket depth and bleeding on probing. Staining
was performed with plaque staining solution (Red-Cote®; Sunstar).

2|

M ATE R I A L S A N D M E TH O DS

2.1 | Electric-powered ionic toothbrushFirst, a full-mouth oral photography (facial and lingual/palatal tooth
surfaces) was performed on all volunteers to evaluate prebrushing plaque scores. Then, they were randomly assigned to one of
the two toothbrush groups by a computerized balance and assignment programme (Appendix Figure A1): (a) electric-powered ionic

The toothbrushes used in the test group were new electric-powered®

toothbrush (test) and (b) manual toothbrush without anion activa-

ionic toothbrushes (Figure 1A; IONPA , Ionic Co., Ltd.). This pow-

tion (control). The volunteers brushed with the assigned toothbrush

ered toothbrush was slightly larger than the conventionally usedfor 2 min without using a mirror. Immediately after teeth brushing,

manual one. In this study, the powered and manual toothbrushes

oral photography was performed for post-brushing plaque scores.

had same-sized brush heads (approximate width 30 mm × length

All the volunteers performed manual toothbrushing using the Bass

240 mm × height 15 mm). It has replaceable brush heads, and thetechnique. Investigators (CK and TS) instructed the subjects in using

sonic waves move with a speed of up to approximately 22,000

the power toothbrush by same contents before the timed brushingstrokes per minute. An ion activation is expected to occur by hold-session. The investigators, who did not make the plaque assessment,

ing a metal part, being generated from the brush bristles (Figure 1B).

supervised brushing. After 1 week, the volunteers returned for the

The toothbrushes used in the control group had the same design asfinal visit and repeated the procedures using another toothbrush.

the electric-powered ionic toothbrushes, with no electricity or anion

Pre- and post-brushing plaque (Appendix Figure A2) was scoredactivation.

using the Rustogi Modification of the Navy Plaque Index (RMNPI),

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IKAWA et al.

F I G U R E 1 New electronic-powered ionic toothbrush. A, Device (IONPA®). B, Components of electronic-powered ionic toothbrush

Jichi Medical University, Saitama). Statistical analysis between

TA B L E 1 RMNPI scores
Test groups

ControlgroupsBaseline (Pretoothbrush)

0.61 ± 0.13

0.63 ± 0.11

Post-toothbrush

0.11 ± 0.08*,†

0.22 ± 0.09*

Note: Mean ± standard deviation was analysed for statisticalsignificance by Student's t test, p < .05; n = 30.
*Significantly different from the baseline.
†

Significantly different from the control group.

sites was performed using Student's t test for paired observations(p < .05) for normally distributed samples or Wilcoxon's rank-sum
tests (p < .05) for the rest of them.

3|

R E S U LT S

During the study, any product-related adverse events were notobserved.
Table 1 outlines the RMNPI scores. The RMNPI scores of theas previously reported.19,20 Briefly, the buccal and lingual surfaces

two groups were significantly smaller in the post-toothbrush groupsof each tooth were divided into nine areas and disclosed plaque was

vs. the pretoothbrush groups (p < .05). Furthermore, the test groups

scored as present (scored as 1) or absent (scored as 0). It assesses thewere more effective than control groups in terms of post-toothbrushamount of plaque on marginal (3 areas), interproximal (2 areas), andRMNPI scores (p < .05).

buccal and lingual (nine areas). Plaque removal rates were calculated

Plaque reduction percentages are shown in Table 2. Plaque re-at the following locations: central incisors, first premolars and firstduction was significantly higher in the electric-powered ionic tooth-molars. The following calculation was used:brush group (85.4% ± 9.2% and 85.1% ± 10.33%, respectively) thanPlaque removal rate = RMNPI (Pre) − RMNPI (Post)/RMNPI(Pre) × 100 (%).

in the manual toothbrush group (58.9% ± 14.6% and 58.4% ± 13.7%,
respectively) at the premolar and molar areas. Particularly, reduction

A single, experienced dental examiner (TI) who was blinded toof interdental plaque in the electric-powered toothbrush increased

the randomized toothbrush assignment made all the plaque scoresby 85.6% and 96.5% compared with manual ones. However, thewith an interval of >72 h. Intra-examiner agreement produced aplaque reduction in central incisor did not significantly differ be-

Cohen's kappa (κ) of 0.729.

tween the test and control groups at all sites (p = .31, 0.11, 0.82 and
0.09, respectively).

2.4 | Statistical analysis

4|

DISCUSSION

Data were compared between test and control sites and expressed
as means and SDs. Sample distribution was investigated using the

Despite the limitations of this randomized, single-blinded, and cross-Shapiro-Wilk test, with Analysis Soft (EZR, Saitama Medical Center,over clinical trial study, compared with the manual toothbrushes,

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IKAWA et al.

TA B L E 2 Mean ± standard deviation of plaque removal rate (%)
Tooth type

Brush type

FacialLingual/Palatal

Marginal

Interproximal

Whole

IncisorManual77.38 ± 15.77

68.39 ± 15.19

79.04 ± 14.40

54.56 ± 26.23

73.50 ± 12.60

Electric-powered81.40 ± 17.36

74.39 ± 18.00

76.69 ± 24.43

67.43 ± 23.61

78.36 ± 13.98

Manual63.16 ± 19.15

54.79 ± 14.65

60.26 ± 16.77

44.86 ± 21.47

58.84 ± 14.64

Electric-powered

87.21 ± 10.11*

83.93 ± 10.84*

84.54 ± 11.91*

83.26 ± 14.55*

85.39 ± 9.20*

Manual60.72 ± 18.34

56.52 ± 15.56

58.25 ± 14.22

43.13 ± 21.46

58.39 ± 13.70

*

*

*

*

85.09 ± 10.33*

PremolarFirst molar

Electric-powered

88.35 ± 9.32

81.09 ± 13.55

82.96 ± 11.70

84.72 ± 16.79

Note: The removal plaque rate for facial, lingual/palatal, marginal, Interproximal and whole mouth at incisor, first premolar and first molar.
*p < .05, significant difference between manual and electric-powered toothbrush by Student's t test; n = 30.

plaque reduction in the electric-powered ionic toothbrushes wasthen, the sonic toothbrushes were superior to the manual ionic ones

more effective at the premolar and molar areas, and similar at thealthough no significant difference could be observed between two

central incisor area. Additionally, there was no report of adverse orgroups. In this randomized clinical study, a newly developed pow-

mechanical problems. Thus, the newly developed electric-powered

ered ionic device was used to improve the power and frequency.

ionic toothbrush was as effective and safe as the manual one.

To the best of our knowledge, this is the first study to demonstrate

In this study, we used toothbrushes with the same design andthe effects of electric-powered ionic toothbrush on plaque reduc-evaluated them as an effective device for powered and ionic, whichtion in healthy volunteers. This study also evaluated whether an

can provide additional benefits to toothbrush in terms of plaque re-ionic powered toothbrush can serve as a suitable device for ionic,

duction. In plaque reduction, this new electric-powered ionic tooth-therefore providing additional benefits to the tooth surface in terms

brush was effective in sites that are difficult to reach for effectiveof plaque reduction. As shown in previous studies18,22 and system-brushing, such as the interproximal region at the premolar and molar

atic reviews,15,23 powered toothbrushes were recognized as usefulsites. However, the fact that we did not explore the complete po-

devices in plaque removal compared with manual ones. Since thetential of ionic toothbrush for plaque reduction is a study limitation.

additional effect of ionic for plaque removal has not shown so far,Further research is warranted to compare this electric-powered

further studies are warranted to compare other powered and man-ionic toothbrush with other powered toothbrushes. Another study

ual toothbrushes without ionic in short- and long-term studies. Also,

limitation was the inclusion of volunteers who were young dentists

it will be necessary to test the efficacy of the electric-powered ionicwith oral health who had motivation and dental skills. Furthermore,

toothbrushes in patients with periodontal disease, as well as in el-

considerably more male subjects than the female ones were enrolled

derly subjects with hand motility difficulties.

in our study. However, there was no significant sex-based difference

In conclusion, the ionic powered toothbrush was significantly(the data were not shown). Therefore, our results suggested no

more effective than a manual one in reducing plaque. Such findings

benefit in terms of the effectiveness of toothbrushing among themay provide an additional option for daily oral hygiene practices ofsubjects.

patients aiming for the improvement in plaque control.

Previous studies,9,12–14 comparing an ionic toothbrush with amanual one, suggested that ionic toothbrushes are predictably
effective in plaque scores at short-term evaluation (4 weeks,1112

6 weeks

5|

C LI N I C A L R E LE VA N C E

7and 3 months ) and also gingivitis scores at long-term

trial (6 months7). Nevertheless, another study3 has suggested that

5.1 | Scientific rationale for the study

electric toothbrushes' effect on established plaque and gingivitis
did not show a significant difference in a five-month clinical trial period. Furthermore, our previous study

21

concluded that periodontal

Plaque reduction efficacy of a new electric-powered ionic toothbrush is unknown.

parameters and total bacteria, including Porphyromonas gingivalis,
were not statistically different between the ionic electric vs. manual
toothbrush group. Therefore, to date, it remains unclear whether the

5.2 | Principal findings

ionic electric toothbrush offers any additional benefit in plaque andgingivitis scores.

Assessment of plaque removal rate between electric-powered ionic

Results of this revealed that ionic powered toothbrushes had

toothbrush and a manual toothbrush was performed. Owing to bothsignificantly better outcomes compared with the manual ones in re-electric-powered and anion activation, the plaque removal effi-

ducing plaque, especially at molar sites, in a single use. A previous

ciency was improved in the molar area that showed low accessibility

study13 compared the efficacy of sonic and ionic toothbrushes, andof brush.

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IKAWA et al.

5.3 | Practical implications
Electric-powered ionic toothbrush is a useful device for removing
plaque and helps prevent dental problems caused by plaque.
AC K N OW L E D G E M E N T S
The authors had full control of the data and analyses and received
no commercial input in the preparation of the study. This study was
supported by JSPS KAKENHI Grant-in-Aid for Young Scientists
Number 18K17061. Dr Takahiro Ikawa has been an ITI Scholar at
the Department of Periodontology, Faculty of Dentistry, Malmö
University, Malmö, Sweden (Chair Prof. Andreas Stavropoulos) during the year 2019/2020. The Ionic Corporation, Chiba, Japan, supported this study to provide test and control brushes.
C O N FL I C T S O F I N T E R E S T
The authors report no conflicts of interest related to this study.
AU T H O R C O N T R I B U T I O N S
K.M., T.I., T.S. and C.K. performed most of the experiments; T.A.
and K.H. assisted in some studies; Y.Ik., T.S. and K.M. analysed thedata; and Y.Iz., and T.I. critically reviewed the data and drafted themanuscript.
ORCID
https://orcid.org/0000-0001-9862-4281

Takahiro Ikawa
Koji Mizutani

https://orcid.org/0000-0002-1610-7430

Yuichi Ikeda

https://orcid.org/0000-0001-7557-658X

Takanori Iwata

https://orcid.org/0000-0002-5461-7298

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How to cite this article: Ikawa T, Mizutani K, Sudo T, et al.
Clinical comparison of an electric-powered ionic toothbrush
and a manual toothbrush in plaque reduction: A randomized
clinical trial. Int J Dent Hygiene. 2020;00:1–6. https://doi.
org/10.1111/idh.12475

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IKAWA et al.

APPENDIX A

Figure A1 Study design. This study was designed as a randomized, single-blinded, crossover clinical trial with single use

Figure A2 Oral Photographs. Teeth surfaces were stained with plaque staining solution. Oral photographs were taken before (a)/after (b)brushing the teeth