REVIEW

Brushing without brushing?—a review of the efficacyof powered toothbrushes in noncontact biofilm removal

Julia C. Schmidt & Christian Zaugg & Roland Weiger &

Clemens Walter

Received: 24 August 2011 /Accepted: 28 August 2012 /Published online: 23 September 2012# Springer-Verlag 2012

AbstractObjectives The aim of the present review was to analyze theimpact of the hydrodynamic effects created by poweredtoothbrushes on biofilm removal in vitro.Materials and methods A MEDLINE search was performedfor publications published by 20 May 2012; this search wascomplemented by a manual search. The study selection, datapreparation, and validity assessment were conducted by tworeviewers.Results Sixteen studies were included. The studies differedwith respect to the methods of biofilm formation and brush-ing protocols. Eighteen different powered toothbrush mod-els were evaluated. Toothbrushes with side-to-side actiondemonstrated biofilm removal without direct bristle contactto biofilms ranging from 38 to 99 %. Most studies foundbiofilm removal exceeding 50 %. Biofilm reduction usingmultidimensional toothbrushes was significantly lower thanby those with the side-to-side mode. Detachment forces dueto hydrodynamic phenomena, passing air–liquid interfaces,and acoustic energy transfer were suggested to cause reduc-tion of the biofilm.

Conclusion Noncontact biofilm reduction was obtainedby the hydrodynamic effects of some powered toothbrushesin vitro.Clinical relevance Powered toothbrushes may have thepotential to simplify self-performed oral hygiene. Howev-er, additional beneficial effects of higher amounts ofnoncontact biofilm removal in vitro have not been shownclinically, yet.

Keywords Powered toothbrush . Biofilm . Hydrodynamiceffect . Oral hygiene . Preventive dentistry

Introduction

Periodontitis is a multifactorial disease caused by infectionwith pathogenic bacteria organized in a biofilm. A biofilm isa complex microbial structure on a solid wet surface protect-ing the microorganisms from the host’s immune system andtherapeutic measures, including mouth rinsing with antisep-tics or antibiotics. Mechanical means are likely to be morepredictable in biofilm removal but may still leave biofilmbehind [1].

Removal of the supra- and subgingival biofilm is, there-fore, a main concern of both preventive and therapeuticmeasures. Optimal oral hygiene performed by the patientis an important goal of periodontal therapy to establishperiodontal health in the long term [2].

A major problem related to self-performed oral hygiene isthe cleaning of the interdental areas [3]. While differentmethods exist, including sticks, dental floss, and interdentalbrushes, the use of interdental brushes seems currently to bethe most efficient method [4–9]. Noncompliance with inter-dental hygiene measures, however, is a key problem in self-performed oral hygiene [10]. Inadequate compliance in turnis associated with progression of periodontal diseases

J. C. Schmidt :R. Weiger :C. Walter (*)Department of Periodontology, Cariology and Endodontology,University of Basel,Hebelstrasse 3,4056 Basel, Switzerlande-mail: clemens.walter@unibas.ch

C. ZauggDepartment of Physics, Institute for Quantum Electronics,ETH Zürich,Wolfgang-Pauli-Strasse 16,8093 Zürich, Switzerland

C. WalterDepartment of Oral Surgery, School of Dentistry,University of Birmingham,Birmingham, UK

Clin Oral Invest (2013) 17:687–709DOI 10.1007/s00784-012-0836-8

[11–13]. Time spent on oral hygiene as well as the use ofinterdental brushes were negatively correlated with furthertooth loss in treated periodontitis patients [14].

Powered toothbrushes have been developed to improveand facilitate oral hygiene [15, 16]. Various toothbrushmodes of action, including multidimensional and side-to-side action, exist and were classified in two recent system-atic Cochrane reviews [17, 18].

Bristle motion at a high frequency may generateturbulent fluid flows in the oral cavity. The fluid flowcauses hydrodynamic forces in terms of wall shearforces acting parallel to a surface [19, 20]. The amountof entrained air bubbles correlates with increasing fluidmotions. The passage of air bubbles along a substratumcreates thermodynamic surface tension forces and turbu-lent flow depending on the gas fraction, the velocity,and the diameter of the bubbles entrained [21–24]. Thevibration of toothbrush bristles may further enable en-ergy transfer in terms of sound pressure waves [25]. Inaddition, the acoustic energy is thought to increaseshear forces due to an oscillation of entrapped air bub-bles [26]. The interaction of these effects created bypowered toothbrushes is suggested to remove biofilmswithout bristle contact [27].

The aim of the present review was to evaluate the currentevidence regarding the efficacy of powered toothbrushes innoncontact biofilm removal in in vitro studies.

Methods

Outcome variables

The primary outcome variable was the quantification ofbiofilm removal following application of a poweredtoothbrush without contact to the surface, i.e., to thebiofilm, in vitro. The secondary outcome variables con-sidered the viability of biofilm-associated bacteria andhydrodynamic phenomena occurring during noncontactapplication.

Literature search

A MEDLINE search (PubMed) of resources published priorto 20 May 2012 was conducted using the validated key-words “powered” and “toothbrush” or “powered” and“toothbrushes” or “electric” and “toothbrush” or “electric”and “toothbrushes” or “sonic” and “toothbrush” or “sonic”and “toothbrushes” or “ultrasonic” and “toothbrush” or “ul-trasonic” and “toothbrushes.” Further databases besideMEDLINE were not reviewed. Any relevant work pub-lished in the English language and presenting pertinentinformation about the described outcome variables was

considered for inclusion in the review. Moreover, the refer-ences of studies examined for inclusion were thoroughlyanalyzed searching for further studies. However, there maybe other evidence but for convenience the search was lim-ited to English publications and the grey literature was notactively searched.

Validity assessment

One reviewer (J. S.) screened the abstracts of the searchresults for compliance with the inclusion criteria. The fulltexts of studies with questionable potential for inclusionafter the abstracts were read were further analyzed. A sec-ond reviewer (C. W.) reconsidered included studies as wellas exclusions. Disagreements were clarified by discussionbetween the two reviewers.

Results

Study characteristics

The combinations of the search terms resulted in a list of403 titles. Abstracts were first screened to identify possiblerelevant publications. Of these 403 initial titles, 382 wereexcluded following evaluation of the abstracts. The causesof exclusion were as follows:

& Review articles (72 publications),& Clinical studies (254 publications),& Animal studies (five publications),& Comments (five puplications),& Case reports (three publications),& In vitro studies without data on noncontact biofilm

removal (43 publications).

Full-text analysis was performed on the remaining 21publications [15, 22, 25, 26, 28–44]. Twelve publicationswere further excluded for the following reasons:

& No noncontact brushing [32]& Use of nonmicrobial substitute for biofilm [29, 31, 33,

36, 38]& Use of planktonic bacteria [34, 35]& No quantification of biofilm removal [30]& No powered toothbrushes [22, 26]& Review article [15]

Finally, a total of nine articles from the electronic searchof the MEDLINE database were included [25, 28, 37,39–44]. Seven additional publications were identified byscreening the references of the studies evaluated for inclu-sion [27, 45–50] (Fig. 1). Finally, 16 studies were integratedin the present review.

688 Clin Oral Invest (2013) 17:687–709

Analysis of the included studies

Microbial aspects and biofilm formation

Substratum Synthetics and substrates derived from animalsor humans were utilized for bacterial adhesion and biofilmformation. Titan [45], glass and quartz [25, 27, 44, 46, 49],hydroxyapatite [28, 40–43, 47], bovine enamel sections[48], and human enamel sections from noncarious molars[37, 39] were used in the experiments (Table 1).

Bacteria The biofilm formation was conducted in vitro [25,27, 28, 44, 46, 48, 49], in vivo [37, 39] and ex vivo [40–43,47]. Whereas the identity of bacteria and their applied con-centrations in in vitro biofilms were known, these parame-ters were not precisely defined in in vivo and ex vivobiofilms.

In vitro studies primarily formed monospecies biofilmsusing different Streptococcus mutans strains (Ingbritt, UA159, ATCC 700610, OSP 236, and NS) [27, 28, 44, 48, 50].The bacteria used in monospecies biofilms were Porphyr-omonas gingivalis (ATCC 33277), Actinomyces naeslundii(T14V), Streptococcus oralis (J22), Lactobacillus acidophi-lus (DSP 211), Streptococcus salivarius (DSP 248), andVeillonella alcalescens (DSP 203) [48].

In vitro dual-species biofilms were created by sequentialinoculation of A. naeslundii (T14V) and S. oralis (J22) or A.naeslundii (T14V) and Streptococcus sanguis (PK 1889)[25, 46, 49].

Additionally, multispecies biofilms were formed, usinghuman whole saliva as the inoculum [40–43, 47] in an ex

vivo model. Saliva samples were collected from 10 healthyvolunteers.

In contrast, Stanford et al. used biofilms formed in vivo[37, 39]. All biofilm samples were obtained from two pro-bands who continuously wore a palatal prosthesis with fixedenamel sections overnight.

Model biofilm system The (acquired) pellicle is impor-tant for in vitro and ex vivo biofilms. The use ofpooled human saliva is documented [25, 46, 49]. Hu-man saliva was collected from ten healthy volunteersand incubated with the substratum for 16 h. Addition-ally, saliva was supplementally added to the circulatingbacterial suspension.

The simultaneous flow of saliva and inoculum is de-scribed by Hope et al. [40–43]. Briefly, the flow of humansaliva containing oral bacteria started concurrently withartificial saliva and was continued for 8 days. Artificialsaliva consisted of hog gastric mucin without urea. Anothertype of artificial saliva used for pellicle formation comprisedsterile 2.5 % bovine mucin [28, 48] and 10 % fetal calfserum [45]. The incubation periods lasted 0.5, 12, and 1 h. Afew studies failed to include pellicle formation in theirbiofilm model [27, 44].

In vitro and ex vivo model biofilm systems may bedifferentiated into static and dynamic systems. Static bio-films were established in multiwell plates. Exclusively,monospecies biofilms were developed [45, 48]. Incubationperiods varied from 1 to 48 h. Dynamic biofilm systemsimitate the flow rate and shear forces caused by the dynamicflow of saliva in the oral cavity.

Potentially pertinent studies received from electronic search

(n=403)

Potentially pertinent full texts selected for detailed analysis

(n=21)

Studies included based on the MEDLINE database search

(n=9)

Studies included in the present review(n=16)

Studies excluded based onabstract evaluation (n=382)

Studies included based on themanual search (n=7)

Studies excluded based on full text analysis (n=12)

Fig. 1 Selection process of thestudies included

Clin Oral Invest (2013) 17:687–709 689

Tab

le1

Biofilm

mod

els

Firstauthor

(year

ofpu

blication)

Bacteria

Substratum

Biofilm

mod

elcharacteristics

Pellicle

form

ation(m

edium,

duratio

n)Incubatio

nof

bacteria

(medium,

duratio

n)Specifics

Wu-Yuanet

al.

(1994)

[45]

(a)Streptococcusmutan

sIngb

ritt

(a)Titanium

Invitrostatic

(a)–

(a)Brain–heartinfusion

broth+

2%

sucrose(48h)

(b)Porph

yrom

onas

ging

ivalisATCC33

27(b)Titanium

(b)10

%fetalcalfserum

(1h)

(b)PG

broth(1

h)

(c)Actinom

yces

naeslundiiT14

V(c)HA

(c)Saliva(overnight)

(c)Carbonate

buffer+0.23

mg/ml

fluoresceinisothiocyanate

isom

erI(1

h)

Stanfordetal.(19

97)

[37]

Individu

almix

ofintraoralbacteria

Hum

anenam

elsections

Invivo

Hum

ansaliv

a16

h2probands

wearpalatalprosthesis

with

fixedenam

elsections

Stanfordetal.(20

00)

[39]

Individu

almix

ofintraoralbacteria

Hum

anenam

elsections

Invivo

Hum

ansaliv

a16

h1probandwearpalatalprosthesis

with

fixedenam

elsections

Adamset

al.(2002)

[27]

S.mutan

sUA

159

Glass

Invitrostatic

and

dynamic

−Brain–heartinfusion

broth+2%

sucrose+

overnightcultu

reof

S.mutan

s(3

hattachmentperiod

(static)+

48hgrow

thperiod

(dynam

ic))

4-channeldrip-flow

reactorsystem

Hop

eet

al.(2002)

[40]

Bacteriaof

human

saliv

apo

olHA

Exvivo

dynamic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,20–40

years,go

odoral

health,no

nsmok

ersand

smokers)+artificialsaliv

a(hog

gastricmucin

with

outurea),

during

bacteria

incubatio

n(8

days)

Hum

ansaliv

a+artificialsaliv

a(8

days)

Constant-depthfilm

ferm

enters

Hop

eet

al.(2003)

[41]

Bacteriaof

human

saliv

apo

olHA

Exvivo

dynamic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,20–40

years,go

odoral

health,no

nsmok

ersand

smokers)+artificialsaliv

a(hog

gastricmucin

with

outurea)

during

bacteria

incubatio

n(8

days)

Hum

ansaliv

a+artificialsaliv

a(8

days)

Constant-depthfilm

ferm

enters

Hop

eet

al.(2003)

[42]

Bacteriaof

human

saliv

apo

olHA

Exvivo

dynamic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,20–40

years,go

odoral

health,no

nsmok

ersand

smokers)+artificialsaliv

a(hog

gastricmucin

with

outurea)

during

bacteria

incubatio

n(8

days)

Hum

ansaliv

a+artificialsaliv

a(8

days)

Constant-depthfilm

ferm

enters

Heersinket

al.

(2003)

[44]

S.mutan

sATCC70

0610

Glass

Invitrostatic

and

dynamic

–Brain–heartinfusion

broth+2%

sucrose+

overnightcultu

reof

S.mutan

s(24hattachmentperiod

(static)+

48hgrow

thperiod

(dynam

ic))

4-channeldrip-flow

reactorsystem

Busscheret

al.

(2003)

[46]

(a)A.na

eslund

iiT14

V-

J1andStreptococcus

oralisJ22

Quartz

Invitrody

namic

Hum

ansaliv

a(sam

ples

from

10vo

lunteers,go

odoral

health)

dissolvedat

1.5mg/mlin

adhesion

buffer

(16h)

Adhesionbuffer

(10min)

Parallel-plateflow

cham

ber

690 Clin Oral Invest (2013) 17:687–709

Tab

le1

(con

tinued)

Firstauthor

(year

ofpu

blication)

Bacteria

Substratum

Biofilm

mod

elcharacteristics

Pellicle

form

ation(m

edium,

duratio

n)Incubatio

nof

bacteria

(medium,

duratio

n)Specifics

(b)A.na

eslundiiT14V-

J1andStreptococcus

sang

uisPK1889

A.na

eslundii(inadhesion

buffer,

1×10

8bacteria/m

l)un

tilsurface

coverage

of1×10

6bacteria/cm

2

Adh

esionbu

ffer

(10min)

(a)S.

oralis(inadhesion

buffer+

1.5g/llyo

philizedhu

man

saliv

a,3×10

8bacteria/m

l;2h)

Yuenet

al.(2004)

[47]

Bacteriaof

human

saliv

apo

olHA

Exvivo

dynamic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,20–40

years,go

odoralhealth)

4–5days,aerobicconditions

Constant-depthfilm

ferm

enter

Hop

eet

al.(200

5)[43]

Bacteriaof

human

saliv

apo

olHA

Exvivo

dynamic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,20–40

years,go

odoralhealth,no

nsmokersand

smokers)

Hum

ansaliv

a+artificialsaliv

a(8

days)

Con

stant-depthfilm

ferm

enter

+Artificialsaliv

a(hog

gastric

mucin

with

outurea)

10%

sucrosesolutio

n24

hafter

inoculation(3×30

min/day)

Duringbacteria

incubatio

n(8

days)

Brambilla

etal.

(200

6)[48]

(a)S.

mutan

sOSP23

6Bovineenam

elsections

Invitrostatic

Hum

ansaliv

a(sam

ples

from

10volunteers);12

h)2.5mltrypticasesoybroth+

100μl

ofmicrobial

suspension

(36h)

(b)Lactoba

cillu

sacidop

hilusOSP211

(c)Streptococcus

salivariusOSP24

8

(d)Veillonella

alcalescensOSP40

3

vanderMei

etal.

(200

7)[49]

A.na

eslund

iiT14V-J1

andS.

oralisJ22

Quartz

Invitrody

namic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,go

odoralhealth)

dissolvedat

1.5mg/mlin

adhesion

buffer

(16h)

Adhesionbuffer

(10min)

Parallel-plateflow

cham

ber

(a)A.na

eslundii(inadhesion

buffer

orin

adhesion

buffer+

1.5g/llyo

philizedhu

man

saliv

a,1×10

8bacteria/m

l)un

tilsurface

coverage

of1×10

6bacteria/cm

2

Adh

esionbu

ffer

(10min)

S.oralis(inadhesion

buffer+

1.5g/llyo

philizedhu

man

saliv

a,3×10

8bacteria/m

l;2h)

(b)S.

oralis(inadhesion

buffer+

1.5g/llyo

philizedhu

man

saliv

a,3×10

8bacteria/m

l)un

tilsurface

coverage

of1×10

6bacteria/cm

2

Adh

esionbu

ffer

(10min)

Clin Oral Invest (2013) 17:687–709 691

(b)S.

sang

uis(inadhesion

buffer

+1.5g/llyop

hilized

human

saliv

a,3×10

8bacteria/m

l;2h)

Tab

le1

(con

tinued)

Firstauthor

(year

ofpu

blication)

Bacteria

Sub

stratum

Biofilm

mod

elcharacteristics

Pellicle

form

ation(m

edium,

duratio

n)Incubatio

nof

bacteria

(medium,

duratio

n)Specifics

A.na

eslundii(inadhesion

buffer

orin

adhesion

buffer+1.5g/

llyop

hilized

human

saliv

a,1×

108bacteria/m

l;2h)

Busscheret

al.

(2010)

[25]

A.na

eslundiiT14

V-J1

andS.

oralisJ22

Glass

Invitrody

namic

Hum

ansaliv

a(sam

ples

from

10vo

lunteers,go

odoral

health)

dissolvedat

1.5mg/mlin

adhesion

buffer

(16h)

2%

THB-sup

plem

entedadhesion

buffer

(15min)

Parallel-plateflow

cham

ber

A.na

eslundii(in2%

THB-

supplementedadhesion

buffer,

1×10

8bacteria/m

l)until

surface

coverage

of1×10

6bacteria/cm

2

Adh

esionbu

ffer

(15min)

S.oralis(in2%

THB-

supplementedadhesion

buffer+

1.5g/llyo

philizedhu

man

saliv

a,3×10

8bacteria/m

l;2h)

Adh

esionbu

ffer

(15min)

100%

THB(16h(growth

period

))

Verkaik

etal.(2010)

[50]

(a)S.

mutan

sNS

Glass

(a,b,

c,andd)

invitrody

namic

Hum

ansaliv

a(sam

ples

from

20vo

lunteers,go

odoral

health)

dissolvedat

1.5mg/mlin

adhesion

buffer

(16h)

Adh

esionbu

ffer

(30min)

Parallel-plateflow

cham

ber

(b)S.

oralisJ22

(e)Exvivo

dynamic

(a)S.

mutan

sNS(in2%

THB-

supplementedadhesion

buffer+

1.5mg/mllyop

hilized

human

saliv

a,3×10

8bacteria/m

l;2h)

(c)A.na

eslundiiT14

V-

J110

0%

THB(16h(growth

period

))

(d)A.na

eslundiiT14

V-

J1andS.

oralisJ22

(b)S.

oralisJ22(in2%

THB-

supplementedadhesion

buffer+

1.5mg/mllyop

hilized

human

saliv

a,3×10

8bacteria/m

l;2h)

(e)Bacteriaof

human

saliv

apo

ol10

0%

THB(16h(growth

period

))

(c)A.na

eslundii(in2%

SB-

supplementedadhesion

buffer,

1×10

8bacteria/m

l;2h

100%

SB(16h(growth

period

))

(d)A.na

eslundii(in2%

SB-

supplementedadhesion

buffer,

1×10

8bacteria/m

l)until

surface

coverage

of1×10

6bacteria/cm

2

Adh

esionbu

ffer

(30min)

S.oralis(in2%

THB-

supplementedadhesion

buffer+

692 Clin Oral Invest (2013) 17:687–709

The formation of multispecies biofilms was performed bymeans of dynamic systems; the apparatus selected variedfrom study to study. These included the parallel-plate flowchamber [25, 46, 49], the drip-flow system [27, 44], and theconstant-depth film fermenter [40–43, 47]. These devicesallow the continuous flow of a bacterial suspension and anutrient medium. The duration of biofilm formation variedfrom 3 h to 8 days.

Brushing protocols

Toothbrushes Wu-Yuan et al. were the first to analyze theinfluence of a toothbrush with side-to-side action on biofilmreduction by noncontact brushing [45]. Side-to-side tooth-brushes were either solely tested [39, 42, 44–46, 48] orcompared with powered toothbrushes presenting othermodes of action. Comparison with multidimensional tooth-brushes was predominant [25, 27, 28, 40, 41, 43, 47, 49,50]. Stanford et al. investigated a counter oscillation and aside-to-side toothbrush [37]. The most extensive study ofpowered toothbrushes in terms of different modes wasperformed by Buscher et al. [25]. The efficacy of atoothbrush with ultrasonic action in comparison to aside-to-side and a multidimensional toothbrush was alsostudied [28] (Table 2).

Toothbrush apparatus The angle of the toothbrush bristlestoward the biofilm was 90° in most studies. The bristleswere not in contact with any solid surface [25, 28, 37, 39,44, 46, 48, 49]. Apart from the orientation of the bristles,there was additional movement of the toothbrush in somestudies [27, 46, 49].

In addition, an interproximal model was developed tosimulate the exposure of interproximal biofilm to poweredbrushing from the buccal surface [27, 40–43, 47]. Thebristles were in direct contact with an artificial tooth surface.Hope et al. quantified the vertical and horizontal load of thebristles to be 62±5 g for the side-to-side toothbrushes inaccordance to the manufacturers’ recommendations. The hor-izontal load of the multidimensional toothbrushes amountedto 150±10 g, while the vertical load was minimal [40–43].The angle of the toothbrush head to teeth was 45° and 40° forside-to-side toothbrushes and 90° for multidimensional tooth-brushes, respectively.

Medium The analysis of biofilm removal by hydrodynamicphenomena requires a liquid in which to immerse the tooth-brush bristles and to imitate the mix of saliva, water, andtoothpaste in the oral cavity.

For this purpose, phosphate-buffered saline solution [37,40–43], phosphate-buffered saline solution supplementedwith artificial saliva (i.e., hog gastric mucin) [37, 40–43],adhesion buffer [25, 46, 49], sterile Ringer solution [27],T

able

1(con

tinued)

Firstauthor

(year

ofpu

blication)

Bacteria

Sub

stratum

Biofilm

mod

elcharacteristics

Pellicle

form

ation(m

edium,

duratio

n)Incubatio

nof

bacteria

(medium,

duratio

n)Specifics

1.5mg/mllyop

hilized

human

saliv

a,3×10

8bacteria/m

l;2h)

100%

THB(16h(growth

period

))

(e)Fresh

human

saliv

a(sam

ples

from

2vo

lunteers,go

odoral

health)in

adhesion

buffer

(1:1,

2×10

8bacteria/m

l;2h)

10%

freshhu

man

saliv

a(sam

evo

lunteers;16

h(growth

period

))

Rob

ertset

al.(2010)

[28]

S.mutan

s(clin

ical

isolatefrom

the

University

ofWashing

ton)

HA

Invitrostatic

Sterile

2.5%

bovine

mucin

(30min)

Trypticasesoybroth+yeast+20

%sucrose+

S.mutan

s(48h)

HAhy

drox

yapatite,THBTod

dHew

ittbroth,

SBSchaedlersbroth

Clin Oral Invest (2013) 17:687–709 693

Tab

le2

Brushingprotocols

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

Wu-Yuanet

al.

(199

4)[45]

Son

icarea

(a)0–2–4

(a)15

Untreated

substrate

(a)3

90°(bristlesto

substrate)

PBS

(a)SEM

(a)Rem

aining

bacteria/m

m2

(mean±SD

)→calculationof

%removal

Significant

morebiofilm

remov

alforall

cond

itionscompared

with

control(except

forPorphyrom

onas

gingivalisat4mm

and

15sandActinom

yces

naeslundiiat

4mm

and5s)*

Decreaseof

biofilm

removalwith

increasing

distance

Decreaseof

biofilm

removalwith

shorter

exposure

time(m

ajor

removalwith

in5s)

(b)1–2–3–4

(b)5–15–30

(b)8

Manualm

ovem

ent

(±3mm,

perpendicularto

bristle

movem

ent,

2×/5s)

Short

bristles2

mm

immersed

(b)Fluorescence

microscop

e(b)Reductio

nin

fluorescen-

ce→calcula-

tionof

%remov

al(m

ean

±SD)

Rem

oval

ofStreptococcusmutan

s—

61%

(4mm,15

s)to

100%

(0mm,1

5s)

Nocontact

Rem

ovalof

P.ging

ivalis

—24

%(4

mm,15

s)to

100%

(0mm,1

5s)

Rem

oval

ofA.

naeslundii:

24%

(4mm,15

s)to

87%

(1mm,15

s)

Biofilm

removalat

distances>2mm

appearsto

vary

with

characteristicsof

bacteria

Stanfordet

al.

(199

7)[37]

Son

icarea

0–2–3(side-to-

side

toothbrush)

5–10–15

(side-

to-side

toothbrush)

Untreated

substrate

12(side-to-side

toothbrush)

90°(bristlesto

substrate)

PBS

SEM

Rem

aining

log 1

0

ofCFU/m

m2

(mean±

SD)→

calcula-

tionof

%remov

al

Side-to-sidetoothbrush

Interplakb

3(cou

nter

oscillatio

ntoothb

rush)

10(cou

nter

oscillatio

ntoothbrush)

29(cou

nter

oscillatio

ntoothbrush)

Nomov

ement

15ml

Cultiv

ation

Impact

ofdistance—

decrease

ofbiofilm

remov

alwith

increasing

distance

(significant

at5s*

and

nonsignificant

at10

and15

s)

694 Clin Oral Invest (2013) 17:687–709

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

Nocontact

Rem

oval—

58(3

mm,5

s)to

95%

(0mm,5

s)and76

(3mm,1

5s)to

95%

(0mm,15

s)

Impact

oftim

e—no

differencesof

biofilm

remov

alwith

increasing

expo

sure

timeat

0and2mm

Decreaseof

biofilm

remov

alwith

shorter

exposure

timeat

3mm*

Counter

oscillatio

ntoothbrush—no

biofilm

remov

al

Stanfordet

al.

(200

0)[39]

Son

icarea

0–2–

35–15

Untreated

substrate

1090

°(bristlesto

substrate)

Saliva+

tap

water

Cultiv

ation

Rem

aining

CFU/

mm

2

→calculation

of%

remov

al(m

ean±SD)

Decreaseof

biofilm

remov

alwith

increasing

distance

by“on-mod

us”side-to-

side

toothbrush*

ManualOral-B

toothb

rush

cManualm

ovem

ent

(10or

30mesial–

distalstrokes)

Decreaseof

biofilm

remov

alwith

shorter

exposure

timeat3mm

by“on-mod

us”side-

to-sidetoothbrush

Differentiatio

nin

activ

ated,e.g.,

“on-mod

us”,and

inactiv

ated,e.g.,

“off-m

odus”

Morebiofilm

remov

alby

“on-mod

us”side-

to-sidetoothbrush

comparedwith

“off-

mod

us”side-to-side

toothbrush

Bristlesin

contact

(loadnotdefined)

Rem

oval—

65(3

mm,5

s)to

92%

(0mm,5

s)by

“on-mod

us”side-

to-sidetoothbrush

and

5(3

mm,5s)

to21

%(0

mm,5s)

by“off-

mod

us”side-to-side

toothbrush

Adamsetal.

(2002)

[27]

Son

icareElited

7.5(m

ean)

15Untreated

substrate

9Brush

head

totooth

—45°(side-to-

side

toothbrush)

Ringer

buffer

Live/dead

staining

Biofilm

thickness

(mean±SD

)→Significant

morebiofilm

remov

alat

0–15

mm

byside-to-side

Clin Oral Invest (2013) 17:687–709 695

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

and90°

(multid

imension-

altoothbrush)

calculation

of%

removal

toothbrush

compared

with

control*

Oral-B3D

Excele

Interproximal

mod

el30

ml

CLSM

Nosign

ificant

differencesbetween

biofilm

thicknessof

areasexpo

sedto

multid

imensional

toothbrush

andcontrol

Nomov

ement

Bristles

partially

CCD

camera

Cellviability

Significant

morebiofilm

remov

alby

side-to-

side

toothbrush

com-

paredwith

multid

i-mensionaltoothbrush*

Bristlesin

contact

(loadnot

defined)

Immersed

Flow

visualization

Decreaseof

biofilm

remov

alwith

increasing

distance

byside-to-side

tooth-

brush

Rem

oval—

57(0–5

mm),53

(5–10

mm),

and43

%(10–15

mm)

byside-to-side

tooth-

brushand16

(0–5

mm),13

(5–10

mm),

and19

%(10–15

mm)

bymultid

imensional

toothbrush

Noinfluenceon

bacterialviability

with

either

toothbrush

Airbubblesprojected

throughinterproximal

space

Velocity

ofairbubbles

andshearstress

byside-to-side

toothbrush

higher

than

bymultidi-

mensionaltoothbrush

Hop

eet

al.

(200

2)[40]

Son

icareElited

1.6(nearest)

5–

6Brush

head

totooth—

40°

(side-to-side

toothbrush)and

90°

PBS+0.8g/

lho

ggastric

mucin

Cultiv

ation

Rem

aining

CFU/

mm

2→

calcula-

tionof

%remov

al(m

ean

±95

%CI)

Significant

morebiofilm

remov

alby

“on-

mod

us”toothbrushes

comparedwith

“off-

mod

us”*

696 Clin Oral Invest (2013) 17:687–709

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

(multid

imen-

sion

altoothbrush)

Oral-B3D

eInterproximal

mod

el7ml

Significant

morebiofilm

remov

alby

“on-

mod

us”side-to-side

toothbrush

(32.23

%)

comparedwith

“on-

mod

us”multid

imen-

sion

altoothbrush

(9.48%)*

Differentiatio

nin

activ

ated,e.g.,

“on-mod

us”,and

inactiv

ated,e.g.,

“off-m

odus”

7ml

Movem

ent(0.62

Hz,9.5mm)

Bristlesin

contact

—62

±5g

horizontal

and

vertical

load

(side-to-side

toothbrush)and

150±10

gho

rizontal

and

minim

alvertical

load

(multid

imen-

sion

altoothbrush)

Hop

eet

al.

(200

3)[41]

Son

icarePlusd

2.65

(mean)

(side-

to-sidetooth-

brush)

5–

6Brush

head

totooth—

40°

(side-to-side

toothbrush),90°

(multid

imen-

sion

altoothbrush)

PBS+0.8g/

lho

ggastric

mucin

Cultiv

ation

Rem

oved

CFU/

mm

2→

calcula-

tionof

%remov

al(m

ean

±IR)

Significant

morebiofilm

remov

alby

“on-

mod

us”toothbrushes

comparedwith

“off-

mod

us”toothbrushes*

Oral-BD15

e1.62

mm

(mean)

(multid

imen-

sion

altooth-

brush)

Interproximal

mod

el7ml

Significant

morebiofilm

remov

alby

“on-

mod

us”side-to-side

toothbrush

(48.45

%)

comparedwith

“on-

mod

us”multid

imen-

sion

altoothbrush

(15.86

%)*

Differentiatio

nin

activ

ated,e.g.,

“on-mod

us”,and

inactiv

ated,e.g.,

“off-m

odus”

Movem

ent(0.62

Hz,9.5mm)

Bristlesin

contact:

62±5g

horizontal

and

vertical

load

Clin Oral Invest (2013) 17:687–709 697

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

(side-to-side

toothbrush),150

±10

gho

rizontal

andminim

alvertical

load

(multid

imen-

sion

altoothbrush)

Hop

eet

al.

(200

3)[42]

Son

icarePlusd

2.65

(mean)

15Untreated

substrate

1040

°(brush

head

totooth)

PBS+0.8g/

lho

ggastric

mucin

Cultiv

ation

Rem

oved

CFU/

mm

2(m

ean±

95%

CI)→calcula-

tionof

%remov

al(m

ean

±95

%CI)

Significant

morebiofilm

remov

alby

“on-

mod

us”toothbrushes

(73.70

%)compared

with

“off-m

odus”

toothbrushes

(3.66

%)*

Interproximal

mod

el7ml

Differentiatio

nin

activ

ated,e.g.,

“on-mod

us”,and

inactiv

ated,e.g.,

“off-m

odus”

Movem

ent(0.62

Hz,9.5mm)

Bristlesin

contact

(loadof

62±5g)

Heersinket

al.

(200

3)[44]

Son

icared

0–0.5–1–1.5

15Untreated

substrate

490

°(bristlesto

substrate)

Nanopure

water

Live/dead

staining

Biofilm

thickness

(mean±

SD)→

calcula-

tionof

%remov

al

Significant

morebiofilm

remov

alforall

distancescompared

with

control*

Nomov

ement

CLSM

Decreaseof

biofilm

remov

alwith

increasing

distance

Nocontact

Digitaltim

e-lapse

microscop

eCellviability

Rem

oval—

20(1.5

mm)

to>99

%(0

mm)

Flow

visualization

Noinfluenceon

bacterialviability

after

brushing

compared

with

control

Localized

turbulence

with

airbu

bblesand

fluid,

opaque

layerof

remaining

biofilm

afterexposure

Busscheret

al.

(200

3)[46]

Son

icared

0–2–

4–6

20Handlingof

flow

390

°(bristlesto

substrate)

Adh

esion

buffer

7CCD

camera

Rem

aining

bacteria/

Decreaseof

biofilm

remov

alwith

698 Clin Oral Invest (2013) 17:687–709

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

cham

ber

with

out

brushing

mm

abov

ebiofilm

orwetted

brush

(im-

mersedin

water

once)+

film

-wetted

biofilm

cm2→calcula-

tionof

%remov

al(m

ean

±SD)

increasing

distance

of>2mm

Movem

ent(20

sing

lestrokes

back

andforth)

Phase

contrast

microscop

eMorebiofilm

remov

alforallconditions

comparedwith

control

Nocontact(at0

mm

load

of<40

g)

CFU/m

m2in

adhering

aggregates

Noinfluenceof

wetted

andim

mersedstates

onbiofilm

remov

al

Rem

oval

ofA.

naeslundiiand

Streptococcusoralis—

33(6

mm)to

94%

(0mm),wettedand14

(6mm)to

99%

(0mm),

immersed

Rem

oval

ofA.

naeslundiiandS.

sanguis—

22(6

mm)

to92

%(0

mm),wet-

tedand45

(6mm)to

99%

(0mm),im

-mersed

Yuenet

al.

(200

4)[47]

IntelliClean

System

(Sonicare)

d

1–2mm

15Untreated

substrate

36Ang

le(brush

head

totooth)

not

defined

7mld

iluted

saliv

asubstitute

(33%

(v/

v) Ringer’s)

Cultiv

ation

Rem

oved

CFU/

ml(m

ean±SD)

andlog(CFU/

ml;mean±SD)

Significant

morebiofilm

remov

alby

side-to-

side

toothbrush

(3.7

times)comparedwith

multid

imensional

toothbrush*

Oral-B

Professional

Care70

00

Interproximal

mod

el

Movem

ent

Bristlesin

contact

(loadno

tdefined)

Hop

eet

al.

(200

5)[43]

Son

icarePlus

2mm

(nearest)

5–

7(side-to-side

toothbrush)

Brush

head

totooth—

40°

(side-to-side

toothbrush),90°

(multid

imen-

sion

altoothbrush)

PBS+0.8g/

lho

ggastric

mucin

Cultiv

ation

Rem

oved

and

remaining

CFU/m

m2

(mean±95

%CI)→calcula-

tionof

%remov

al(m

ean

±IR)

Significant

morebiofilm

remov

alby

side-to-

side

toothbrush

(32.00

%)comparedwith

multid

imensional

toothbrush

(15.31

%)*

Oral-B3D

D17

e5(m

ultid

imen-

sion

altoothbrush)

Interproximal

mod

el7ml

Com

parisonto

Hop

eet

al.[42]—sign

ificant

morebiofilm

remov

alwith

outsupplemented

Movem

ent(0.62

Hz,9.5mm)and

Clin Oral Invest (2013) 17:687–709 699

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

sucrose(48.45

%)

comparedwith

supplementedsucrose

(32.00

%)by

side-to-

side

toothbrush

minim

alvertical

load

(multid

imen-

sion

altoothbrush)

Noinfluenceof

sucrose

supplementatio

non

biofilm

remov

alby

multid

imensional

toothbrush

Brambilla

etal.

(200

6)[48]

Son

icare

Adv

ance

d7

5–15–30

Untreated

substrate

3090

°(bristlesto

substrate)

PBS

Viablebiom

ass

assay(M

TT

assay)

Optical

density

(mean±

SD)→

calcula-

tionof

%remov

al

Significant

morebiofilm

remov

alof

S.mutan

sandS.

sanguis

biofilm

scompared

with

control*

and

morebiofilm

remov

alwith

increasing

exposure

time

Nomov

ement

1ml

Spectroph

otom

eter

Reduced

remov

alof

L.

acidop

hilusandV.

alcalescensbiofilm

sNocontact

vanderMei

etal.(2007)

[49]

Son

icare

Adv

ance

d

Oral-B3D

Professional

Care70

00e

0–2–

420

Handlingof

flow

cham

ber

with

out

brushing

390

°(bristlesto

substrate)

Adh

esion

buffer

CCD

camera

Rem

aining

bacteria/

cm2→calcula-

tionof

%remov

al(m

ean

±SD)

Noinfluenceof

wetted

andim

mersedstates

onbiofilm

remov

al

Movem

ent(20

sing

lestrokes

back

andforth)

7mm

abov

ebiofilm

orwetted

brush

(im-

mersedin

water

once)+

film

-wetted

biofilm

Phase

contrast

microscop

eSignificantly

more

biofilm

remov

alof

A.

naeslundiiandS.

oralissequence

comparedwith

S.oralisandA.

naeslundiisequ

ence*

Nocontact(at0

mm

load

of<40

g)

%of

remaining

bacteria

inaggregates

of≥1

0

Significantly

more

biofilm

remov

alby

contact-brushing

com-

paredwith

noncon

tact

brushing

*

Significant

morebiofilm

remov

alby

side-to-

side

toothbrush

com-

paredwith

multid

i-mension

altoothbrush

underallcond

itions*

700 Clin Oral Invest (2013) 17:687–709

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

Decreaseof

biofilm

remov

alwith

increasing

distances

byboth

toothbrushes

Sequence“streptococci

insaliv

afollo

wed

byactin

omyces

insaliv

a”appeared

more

difficulttoremov

eand

leftmorelarge

coaggregates

than

sequence

“actinom

yces

insaliv

afollo

wed

bystreptococci

insaliv

a”regardless

oftoothbrush

mod

e*

Multid

imensional

toothbrush

tend

edto

leavemorelarge

aggregates

than

side-

to-sidetoothbrush

Busscheret

al.

(201

0)[25]

Oral-BS18

Sonic

Com

plete

1–2–

4–6

20Handlingof

flow

cham

ber

with

out

brushing

390

°(bristlesto

substrate)

Adh

esion

buffer

Live/dead

staining

Biofilm

volumes

perun

itarea→calcula-

tionof

%remov

al(m

ean

±SD)

Decreaseof

biofilm

remov

alwith

increasing

distance

Son

icareElite

(Standard

Elitebrush

head)

Movem

ent

(20sing

lestrokes

back

and

forth)

CLSM

Rem

oval—

60to

78%

(1mm)by

alltooth-

brushes

Son

icare

Flexcare

(Standard

Flexcare

brushhead)

Nocontact

Percentageof

live/dead

bacteria

inthe

volume→

cal-

culatio

nof

%viability

ofbiofilm

s(m

ean)

31to

40%

(6mm)by

severalside-to-side

andmultid

imensional

toothbrushes

Panason

icEW

1045

(SR18)

Exp

ansion

,−29

to−86

%(4–6mm)by

severalside-to-side

andmultid

imensional

toothbrushes

D18 Professional

Noinfluenceon

bacterialviability

after

Clin Oral Invest (2013) 17:687–709 701

Tab

le2

(con

tinued)

Firstauthor

(yearof

publication)

Toothbrush

Distance(m

m)

Tim

e(s)

Control

n/cond

ition

Toothbrush

apparatus

Medium

Analysismetho

dOutcome

variables

Results

Care(EB17

brushhead)

brushing

compared

with

control

D18 Professional

Care(EB18

Pro

White

brushhead)

Verkaik

etal.

(201

0)[50]

Oral-BSonic

Com

pletee

0–2

20Handlingof

flow

cham

ber

with

out

brushing

390

°(bristlesto

substrate)

No inform

a-tio

n

Phase

contrast

microscop

ewith

aultra-long

working

distance

objective

Fractional

surface

coverage

byadhering

bacteria→

calculationof

%remov

al(m

ean±SD)

Nodifferencesof

biofilm

remov

albetweentoothbrushes

at0mm

Oral-B

Professional

Care78

50e

Movem

ent(20

sing

lestrokes

back

andforth)

Immersed

state

MatLab-based

coun

ting

prog

ram

Morebiofilm

remov

alat

2mm

byside-to-side

than

bymultid

imen-

sion

altoothbrush,

lowestbiofilm

remov

-al

bymanualtooth-

brushat

2mm

ManualOral-B

softindicator

Regular

40c

Nocontact,at

0mm—90

gload

(side-to-side

toothbrush),150

gload

(multid

imen-

sion

altoothbrush),and

220gload

(manual

toothbrush)

Reduced

biofilm

remov

alof

A.

naeslundiiandof

dual

speciesbiofilm

scomparedwith

S.oralisand

multispecies

biofilm

sat

0mm

Reduced

biofilm

remov

alof

A.

naeslundiibiofilm

s(0–1%)compared

with

remaining

biofilm

sat

2mm

Rob

ertset

al.

(201

0)[28]

Ultreo

f3

5Untreated

substrate

1090

°(bristlesto

substrate)

Dentifrice

slurry

(17

% toothpaste

in distilled

water)

Pho

tographs

with

digitaldental

camera

Normalized

pixel

value(m

ean±

SD)→

calcula-

tionof

%remov

al(m

ean)

Biofilm

remov

alwith

out

bristle

contactby

all

toothbrushes

Modified

Ultreo

Nomov

ement

Bristles

immersed

Stand

ard(4.8

mm)

circular

region

ofinterest

Significant

morebiofilm

removal

byultrasonic

toothbrush

(64%)

comparedwith

702 Clin Oral Invest (2013) 17:687–709

Tab

le2

(con

tinued)

Firstauthor

(yearof

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Clin Oral Invest (2013) 17:687–709 703

nanopure water [44], diluted saliva substitute [47], and adentifrice slurry consisting of 17 % toothpaste in distilledwater [28] were employed.

Despite the different liquid volumes, the toothbrush bris-tles were always partially immersed. In addition, biofilmremoval was studied using a wetted substratum and a wettedtoothbrush [46, 49].

Exposure time and distance To evaluate the influence ofvarying times and distances on biofilm removal bynoncontact brushing, exposure time and distance wereanalyzed. Alteration of the distance along with a con-stant exposure time elucidated the influence of differentdistances on biofilm removal. The distances varied from0 to 6 mm with an exposure time of 15 or 20 s [25, 44,46, 49].

A few studies analyzed the alteration of both param-eters to assess the impact of exposure time as well as ofdistance [37, 39]. Some studies, however, did not ana-lyze either exposure time or distance [27, 28, 40–43,47]. The distance between bristles and biofilm was notuniform because of the interproximal model [27, 40–43,47]. The mean separation between bristles and biofilmwas 2.65 mm. The exposure time of 5 s was arrived atby considering the average time of brushing in relationto the number of teeth [27, 28, 40–43]. Furthermore, anexposure time of 15 s was used [27, 42, 47].

Results

Toothbrush efficacy: biofilm removal Biofilm removal wasquantified by microscopic analyses, including the use of aconfocal laser scanning microscope combined with live/dead staining [25, 27, 44], a scanning electron microscope[45], a phase-contrast microscope connected to a charge-coupled device (CCD) camera [46, 49], and a fluorescencemicroscope [45]. The quantification of biofilm removal wasfurther determined by viable count procedures [37, 40–43,47], by means of a viable biomass assay combined with themeasurement of optical densities [48], and by normalizedpixel values on photographs [28] (Table 2).

The included studies consistently reported biofilm reduc-tion by noncontact brushing of tested side-to-side, multidi-mensional and ultrasonic toothbrushes [25, 27, 28, 37,39–50]. Side-to-side toothbrushes yielded significantlymore biofilm removal than multidimensional brushes[27, 40, 41, 43, 47, 49, 50]. Biofilms were not reduced bycounter oscillation toothbrushing [37].

Considering that a distance of 2 mm and an exposuretime of 15 to 20 s were the most commonly parameters forexamining side-to-side toothbrushes, there was a widerange, i.e., from 38 to 99 %, in the percentage of biofilm

removed. Most studies, however, found >50 % biofilmremoval by side-to-side toothbrushes [25, 46, 49, 50]. Incontrast, biofilm reduction by multidimensional tooth-brushes was frequently <50 % [49, 50]. The percentage ofbiofilm removal at a 2-mm distance and after 5 s of exposurewas reported as 74 [45] and 65 % [37] by side-to-sideaction. Regarding the efficacy of side-to-side brushes ininterproximal models with a mean distance of approximate-ly 2 mm and an exposure time of 5 s, there was biofilmremoval of 32 [40, 43], 48 [41], and 74 % [42]. In contrast,multidimensional toothbrushes achieved a biofilm reductionof 9 [40], 15 [43], and 16 % [41] using the same interprox-imal model.

Some studies analyzed the influence of different expo-sure times on biofilm reduction by side-to-side toothbrushes[37, 39, 48]. At distances of 0, 1, and 2 mm, there was nosignificant influence of exposure time (ranging from 5 to30 s). The majority of bacteria were removed within the first5 s of exposure. At a distance of ≥3 mm, however, expo-sures longer than 5 s had significantly greater effects [37,39]. Brambilla et al. confirmed reduced biofilm removal at7 mm after 5 s compared with exposures of 15 and 30 s [48].

Concerning the distance between toothbrush bristles andthe biofilm, increasing distances almost invariably resultedin decreased biofilm removal by side-to-side and multidi-mensional toothbrushes [25, 27, 37, 44, 46, 49]. Neverthe-less, biofilm removal at a 4-mm distance and after 15 to 20 sfluctuated around 60 % by side-to-side action in most stud-ies [27, 46, 49]. Biofilm removal was also found at adistance of 6 mm [27, 46]. In contrast, Busscher et al.observed expansion of the biofilm after noncontact brushingfor the first time [25]. At 4 mm, biofilm expansionamounted to approximately 86 % using a side-to-side tooth-brush and to 29 % by a multidimensional toothbrush. At6 mm, biofilms were expanded by 43 % using another side-to-side toothbrush. Other tested powered toothbrushesyielded biofilm removal between 30 and 40 % at a 6-mmdistance [25].

The reduction of biofilm by noncontact brushing seemsto be dependent on the types of bacteria constituting thebiofilm [48, 49]. Removal of S. mutans and S. salivariusmonospecies biofilms amounted to 41 and 30 %, respective-ly. In contrast, monospecies biofilms of L. acidophilus andV. alcalescens were not significantly reduced [48]. More-over, biofilm removal differed among the sequences ofinoculated bacteria [49]. Verkaik et al. compared the effectof noncontact brushing on monospecies, dual-species, andmultispecies biofilms [50]. At a distance of 2 mm and after20 s of exposure, monospecies biofilms of A. naeslundii(T14V) showed the least removal investigating both side-to-side and multidimensional toothbrushes. In contrast, mono-species biofilms of S. mutans were completely removed byhandling of the flow chamber. The greatest differences

704 Clin Oral Invest (2013) 17:687–709

between side-to-side and multidimensional toothbrusheswere observed for multispecies biofilms with side-to-sideaction showing more biofilm removal [50].

The state of immersion of the substratum and the bristlesdid not affect the percentage of biofilm removal [46, 49].Biofilms with a thin liquid film were removed by a wettedtoothbrush comparable with an immersed toothbrush. Acompletely dry powered toothbrush, however, removed sig-nificantly less bacteria.

Toothbrush efficacy: viability of biofilm-associated bacter-ia Studies using live/dead staining of biofilms reported nodifferences in the distribution of live and dead cells in testsand controls [27, 44]. The percentage viability of biofilmswas 84 % before and 82 % after brushing [25].

Hydrodynamic phenomena A few studies examined the pres-ence of hydrodynamic phenomena to explain biofilm removalby noncontact brushing. Adams et al. visualized the move-ment of fluid and air bubbles by means of a CCD camera [27].They observed multiple air bubbles traveling through theinterproximal area and calculated the velocity of air bubblesand the corresponding shear forces. The velocity of bubblesand the extent of shear forces did not differ significantlybetween side-to-side and multidimensional toothbrushes de-spite different biofilm removal efficacies. Using a digital time-lapse microscope, Heersink et al. also described fluid turbu-lences in which air bubbles were seen [44].

The importance of fluid, either in terms of fluid or evenjust as droplets, was emphasized by Busscher et al. whencomparing the efficacy of completely dry, wetted and im-mersed toothbrushes [46]. Busscher et al. further analyzedthe energy transfer by acoustic pressure waves and correlat-ed it to powered toothbrushes [25].

Discussion

The aim of the present review was to analyze the efficacy ofpowered toothbrushes in noncontact brushing. A total of 16publications were included from the electronic search of theMEDLINE database and from a further manual search. Datawere exclusively collected from in vitro studies.

Included studies were analyzed with regard to the tech-nical and microbial aspects of the applied methods as well asin terms of quantitative biofilm removal, the viability ofbiofilm-associated bacteria and hydrodynamic phenomena.

The mode of action of powered toothbrushes was definedin two recent systematic reviews [17, 18]. A consensusexists that toothbrushes with side-to-side, multidimensional,and ultrasonic action enable biofilm removal by noncontactbrushing although biofilms were not completely eliminatedfrom surfaces [25, 27, 28, 37, 39–50]. Biofilm reduction

was more pronounced by side-to-side toothbrushes than bymultidimensional action [27, 40, 41, 43, 47, 49, 50]. How-ever, an extrapolation of these findings to powered tooth-brushes not analyzed in this review should be undertakenwith care. A shift in the distribution of live and dead bacteriaafter noncontact brushing was not observed. The interplayof hydrodynamic action, passing air bubbles and acousticenergy transfer was associated with biofilm removal.

Therapy of periodontal diseases and the establishment ofperiodontal health in the long term require well-performeddental plaque removal by the patient on a daily basis.Noncompliance with oral hygiene measures, in particularwith difficult to access areas, such as the interdental area,however, is observed frequently [10, 14]. If powered tooth-brushes are able to remove biofilms efficiently withoutbristle contact, they would probably simplify and conse-quently improve self-performed oral hygiene. However, upto now there is no proof that this will work in a clinicalsituation, as well.

When comparing the in vitro data from the includedstudies, differences in brushing protocols and biofilm for-mation need to be considered:

1. An important parameter is the strength of the in vitrobiofilm. The adhesiveness of biofilms depends on thephysical properties of the surface, such as roughness[51]. Irregularities of the tooth structure in terms offissures and pits increase bacterial colonization andoffer protection from shear forces. When using artificialsubstrates, such as glass and quartz [27, 46], the exper-imental results may be biased. The adhesion of salivarypellicle constituents and subsequently of adherent bac-teria is presumably less than on tooth structures. Irre-spective of physical and chemical differences withrespect to enamel, titanium sections imitate implantsurfaces [45]. The adhesiveness and thus the strengthof biofilms is further dependent on the acquired salivarypellicle providing receptors for bacterial binding [52]. Itis suggested that the strength of biofilms is less severe inmethods evaluated without saliva for pellicle formation.

2. Bacteria have been identified adhering as early colonizersto tooth surfaces and preceding the attachment of latecolonizers [53]. Both Actinomyces and Streptococcus spe-cies are considered to be early colonizers [54]. Usingthese bacteria in in vitro biofilms, adhesion to the salivarypellicle can be expected [25, 50]. Gram-negative bacteria,such as P. gingivalis, become more prominent in thebiofilm at a later stage. They prefer receptors on otheroral bacteria forming coaggregates to those of the salivarypellicle. This finding needs to be considered when usingthese bacteria in in vitro monospecies biofilms [48].

3. In addition to adhesiveness, which depends on the substra-tum, the acquired pellicle and early microbial colonizers,

Clin Oral Invest (2013) 17:687–709 705

the strength of oral biofilms depends also on cohesiveness[55]. Several factors may affect cohesiveness: bacteriainvolved in biofilm formation, the presence of exopolysac-charides and environmental factors such as hydrodynamicsand nutrient concentration. Bacteria increase the strength ofa biofilm by coaggregation to a defined set of partners.Using A. naeslundii and S. oralis in dual-species biofilms,coaggregation of these bacteria is expected [56]. Coaggre-gation of bacteria is also assumed in ex vivo biofilmsderived from human whole saliva [40–43, 47] as well asin in vivo biofilms [37, 39].

4. The presence of exopolysaccharides strengthens thebiofilm [55, 57]. The amount of exopolysaccharidesrises with increasing time and nutrient concentration.Accordingly, the adhesion and growth curves of bacteriain biofilm model systems need to be considered.

5. Hydrodynamic conditions during growth influence bio-film strength. Increased hydrodynamic shear decreasedthe biofilm strength and changed the architecture fromuniform carpet like to more fluffy with increased thick-ness [57]. Some model biofilm systems considered theimpact of hydrodynamics. The parallel-plate flow cham-ber allows for the circulation of bacteria and nutrientsby means of hydrodynamic pressure at a wall shear ratecorresponding to physiological conditions [25, 46, 49].Whereas adhesion of bacteria in a drip-flow reactorsystem occurs statically, nutrients subsequently flowduring a 48-h growth period [27, 44]. In contrast, thestrength of biofilms grown in static systems withoutshear differ significantly from that observed in naturalintraoral biofilms [50, 58].

6. Brushing protocols as well as toothbrush apparatusesdiffered among the in vitro studies included. Basically,toothbrushes can be mounted either without any bristlecontact to a solid surface or in an interproximal modelwith bristle contact with artificial teeth. Evidence existsthat bristle load influences the deformation of bristles aswell as the efficacy of brushing [32, 59]. Moreover, ininterproximal models, the fluid is impelled into theinterproximal space, generating high shear forces [25].Without this narrow set-up, fluid and energy transferwould spread across a larger area and in several direc-tions. It is suggested that these arrangements affectbiofilm removal in interdental spaces [25].

7. Most liquids used to transfer hydrodynamic phenome-na, such as phosphate-buffered saline, show lower vis-cosities and lower colloid content than the mix of saliva,toothpaste and water in vivo. The addition of artificial orhuman saliva, however, reflects the salivary component[28, 40–43, 47], whereas supplementation with tooth-paste imitates the dentifrice slurry [28, 40–43]. It issuggested that different liquid viscosities and volumesinfluence the bristle velocity, the fluid flow, the

formation of air bubbles and the shear forces [59].Otherwise, the use of toothpaste in brushing protocolswould probably distort toothbrush efficacy by affectingthe chemical antibacterial efficacy [60]

8. The time spent for an oral hygiene session is on average2 to 3 min [61, 62]. This means that the time availablefor cleaning a tooth surface interproximal spaceamounts to 4 to 6 s (2 min0120 s, 120 s/28 teeth04.28 s; 3 min0180 s, 180 s/28 teeth06.43 s). Therefore,exposure times of 5 s seem to be realistic and compara-ble to in vivo brushing times [40–43]. Exposure of thebiofilm during a period of 20 s, however, would implyan overall brushing time far from clinical reality thatmay be of less clinical relevance.

To what extent the mechanisms of hydrodynamic action,passing air–liquid interfaces, and acoustic energy transfercontribute to the noncontact biofilm removal by poweredtoothbrushes was not separately investigated.

Hydrodynamic fluid shear forces were estimated byAdams and coworkers to amount approximately 0.9 Pa forthe side-to-side toothbrush and 0.5 Pa for the multidimen-sional toothbrush [27]. In an aqueous solution, these valueswould correspond to fluid shear rates of about 0.9 and0.5 s−1. For bacterial detachment from surfaces, however,shear rates of at least more than 10,000 s−1 due to increasedfluid flow were suggested to be essential. The efficacy of thehydrodynamic forces in bacterial reduction depends on thecell surface hydrophobicity of bacteria [19]. The transitionof a laminar in a turbulent fluid flow generally results in anincrease of shear forces [20]. Bristle motion may causeturbulences as described by Heersink and coworkers andthus shear rates are possibly high enough to stimulate mi-crobial detachment [44].

The amount of entrapped air bubbles increases propor-tional to the fluid flow [19]. To remove bacteria from asurface the formation of a three-phase boundary betweenair bubbles, fluid and bacteria is required. Thus, surfacetension forces become effective exceeding hydrodynamicshear forces by several orders of magnitude. The efficacyof bacterial detachment is influenced by the amount of gasin the fluid, the velocity and the diameter of the bubbles[22–24]. The visualization of air bubbles in the includedstudies supports the concept that powered toothbrushes in-volve passing air–liquid interfaces in biofilm removal al-though the proportion in detachment forces was notevaluated [27, 44].

In addition, the vibration of toothbrush bristles may en-able acoustic energy transfer. The energy transfer to thebiofilm is thought to depend on the frequency and amplitudeapplied [25]. The formation of oscillatory fluid motions andpressure waves may generate additional shear forces on thebacteria. Furthermore, the oscillation of entrapped air

706 Clin Oral Invest (2013) 17:687–709

bubbles is suggested to enhance shear forces by micro-streaming and cavitation effects [26]. The extent to whichthe acoustic energy created by powered toothbrushes con-tributes to biofilm reduction, however, is unclear.

There may be a more complex interaction if there isintermittent tooth contact resulting in contact and noncon-tact biofilm removal. For clarity, the present review referredexclusively to noncontact biofilm removal.

Directions for further research

The data from this review are promising and suggest thepossibility of noncontact biofilm removal by the tooth-brushes analyzed. However, for future research the follow-ing parameter may be considered.

The use of

1. Multispecies biofilm models2. A flow chamber model3. Saliva for pellicle formation on a suitable substratum4. An adjustable toothbrush apparatus, in terms of bristle

angulation, distance, and load5. Clinically relevant brushing protocols, in terms of

brushing time, brushing distance, and liquid brushingenvironment.

Noncontact brushing may have the potential to improveoral hygiene in difficult to access areas, as up to now theclinical effectiveness of different types of powered tooth-brushes does not correlate with the results of their respectivenoncontact biofilm removal capacities in vitro [18]. Thisconflict needs to be addressed in an appropriate clinicalsetting. Recently, a review provided a methodological guid-ance for randomized clinical trials comparing differenttoothbrushing modes [63]. The authors concluded that fu-ture clinical studies may require a longer follow-up, a stan-dardization of indices and clinical relevant thresholds fordifferences in plaque and gingival health.

Conclusions

In conclusion, a great heterogeneity in microbial parameter,biofilm formation, and/or brushing protocols exist amongthe studies included in the review. However, noncontactbiofilm removal by powered toothbrushes was a frequentfinding. The results of this review can only be applied to thetoothbrushes actually tested. Detachment forces, includingshear forces, air bubbles interactions, and acoustic energytransfer are suggested to cause noncontact biofilm removalin vitro. Moreover, the clinical gain of noncontact biofilmremoval is still unknown. There is no clinical study avail-able, evaluating the extent of noncontact brushing to theobserved superiority of powered over manual toothbrushing

in terms of plaque reduction. In vitro data should not betranslated to the clinical situation.

Conflict of interest The authors declare that there is no conflict ofinterest. An in vitro analysis of the efficacy of powered toothbrushes iscurrently under preparation. The latter project is supported in part by anunrestricted grant by the Swiss Society of Dentistry (SSO) with theproject number 264-12 (18.06.2012).

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