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The Effect of Different Interdental Cleaning Devices on Clinical Parameters

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Abstract and Figures

Objective: This study was designed to evaluate the effectiveness of a Waterpik dental water jet (DWJ) with a prototype jet tip and a regular jet tip as compared to floss as an adjunct to daily toothbrushing on plaque and gingival bleeding. Methods: 108 subjects participated in this 30-day, 3-group parallel, single blind study. 36 subjects were randomly assigned to each group. Group A used a DWJ with a regular jet tip, Group B used a DWJ with a prototype jet tip and Group C used waxed floss. Subjects brushed twice daily with a manual toothbrush and standard dentifrice for two minutes and used either the DWJ or floss once daily in the evening. Gingival bleeding (BOMP) and plaque (TMQ&H) were assessed at baseline, day 14 and day 30. All subjects were professionally instructed by a dental hygienist in the use of a DWJ or floss and received written instructions for all products to be used. Results: The addition of the DWJ to manual toothbrushing resulted in significantly better reductions in gingival bleeding as compared to floss. There were no significant differences between the tips, with the standard jet tip showing a 26% reduction and the prototype jet tip showing a 20% reduction at day 14, and 17% and 15% respectively at day 30. There was a 13% reduction for the floss group at day 14, and 0% at day 30, demonstrating no overall improvements in oral health for the floss group. No significant differences were reported in plaque reductions between the groups. Conclusion: The use of a DWJ with either a standard jet tip or prototype jet tip combined with manual toothbrushing is significantly more effective in reducing gingival bleeding scores as compared to the use of floss. This study was funded by a research grant from Water Pik, Inc.
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© International Academy of Periodontology
Journal of the International Academy of Periodontology 2011 13/1: 2–10
Correspondence to: N.A.M. Rosema. Department of Period-
ontology, Academic Centre for Dentistry Amsterdam (ACTA),
University of Amsterdam and VU University Amsterdam, Gus-
tav Mahlerlaan 3004 1081 LA Amsterdam, The Netherlands.
E-mail: M.Rosema@acta.nl
The Effect of Different Interdental Cleaning
Devices on Gingival Bleeding
Nanning A. M. Rosema1, Nienke L. Hennequin-Hoenderdos1,
Claire E. Berchier1, Dagmar E. Slot1, Deborah M. Lyle2 and
Godefridus A. van der Weijden1
1Department of Periodontology, Academic Centre for Dentistry
Amsterdam ACTA, University of Amsterdam and VU University
Amsterdam,The Netherlands, and 2Water Pik Inc, Fort Collins, CO, USA
Abstract
Objective: To compare the effectiveness of an oral irrigator (OI) with a prototype jet
tip or a standard jet tip to oss as adjunct to daily toothbrushing on gingival bleeding.
Methods: In this single masked, 3-group parallel, 4-week home use experiment, 108
subjects were randomly assigned to one of three groups: 1) OI with a prototype jet tip;
2) OI with a standard jet tip; 3) waxed dental oss. All groups used their assigned prod-
uct once a day as adjunct to twice daily toothbrushing for two minutes with a standard
ADA reference toothbrush. Professional instructions were given by a dental hygienist in
OI use or oss use according to written instructions. All subjects also received a tooth-
brush instruction leaet (Bass technique). Subjects were assessed for both bleeding and
plaque at baseline and after two weeks and four weeks and were instructed to brush
their teeth approximately 2 to 3 hours prior to their assessment. Results: With respect to
mean bleeding scores the ANCOVA analysis with baseline as covariate and week 4 as
dependent variable showed a signicant difference between groups in favor of both the
oral irrigator groups. For plaque, however, no signicant difference among groups was
observed. Conclusion: When combined with manual toothbrushing the daily use of an
oral irrigator, either with prototype or standard jet tip, is signicantly more effective in
reducing gingival bleeding scores than is the use of dental oss, as determined within
the limits of this 4-week study design.
Key words: Floss, dental water jet, oral irrigator, water osser, gingivitis, bleeding,
plaque, toothbrush
Introduction
Biolms are 3-dimensional arrangements of bacteria
that are loosely or more rmly adherent to teeth and
tissue (Costerton et al., 1994). Biolms consist of micro-
colonies of bacteria embedded in slimy matrices and are
self-sufcient, dynamic communities that can survive in
hostile environments (Marsh and Bradshaw, 1995) The
regular removal of dental plaque biolm, which contains
the bacteria responsible for caries formation and for
the etiology of gingivitis and periodontitis, is the well-
accepted conditio sine qua non of dental health (Gorur et al.,
2009). Mechanical removal is considered the most effec-
tive method to control the growth of the oral biolm. The
most common device used for mechanical plaque control
is either a manual or power toothbrush. As toothbrush
efcacy is limited to the surfaces of the teeth it can access
(facial, lingual, and occlusal), another device is needed to
clean the interdental area and the proximal surfaces of
the teeth and surrounding gingivae. Other factors that
affect the efcacy of mechanical plaque biolm removal
include brushing frequency, brushing time, toothbrush
design, and brushing technique (Jepsen et al., 1998; Van
der Weijden et al., 1993).
For most people, however, total plaque biolm
removal is not a realistic goal. It is difcult for patients
to effectively remove or disrupt the biolm from all
surfaces of the teeth on a daily basis (Douglass et al.,
1993; Brown et al., 1993). On average, people reduce
their plaque scores by approximately 50% by brushing
(Jepsen et al., 1998). Therefore, compliance with instruc-
tions is a major consideration when recommending any
self-care device. To be truly patient-centered, practitio-
ners must shift to recommending available tools that,
besides having demonstrated efcacy in reducing inam-
mation based on scientic evidence, are also preferred
by patients (Slot et al., 2008).
JIAP 10-005 Rosema.indd 2 04/01/2011 11:37:43
The Effect of Different Interdental Cleaning Devices on Gingival Bleeding 3
A dental water jet or water osser or oral irrigator
(OI) is an electric device that delivers a pulsating uid
via controlled pressure which is aimed at the removal
of interdental and subgingival plaque biolm on tooth
surfaces to reduce inammation as a supplement to
toothbrushing (Lobene, 1969; Drisko et al., 1987; Cobb et
al., 1988; Flemmig et al., 1990; Chaves et al., 1994; Flem-
mig et al.,1995; Barnes et al., 2005; Gorur et al., 2009).
The OI was introduced to the dental profession in 1962
and has been studied extensively for the past decades.
Clinical studies demonstrate that an OI is safe and can
signicantly reduce bleeding and gingivitis in a variety
of cohorts (Lobene et al., 1969; Flemmig et al., 1990;
Brownstein et al., 1990; Burch et al., 1994; Newman et
al., 1994; Flemmig et al., 1995; Felo et al., 1997; Barnes
et al., 2005; Sharma et al., 2008). However, erythrosine-
based plaque indices have yielded equivocal data. Some
studies have shown a reduction in plaque indices with
the use of the OI compared to toothbrushing alone
(Burch et al., 1994; Felo et al., 1997; Cutler et al., 2000;
Al Mubarak et al., 2002; Sharma et al., 2008), while other
studies showed no signicant differences (Ciancio et al,
1989; Brownstein et al., 1990; Walsh et al., 1992; Chaves
et al., 1994; Fine et al., 1994).
The OI is likely to provide a particular benet in
terms of gingival health to a large part of the general
public that does not clean the interproximal spaces
on a regular basis (Research, Science and Therapy
Committee, 2005). In 2001 the American Academy of
Periodontology stated, Among individuals who do not
perform excellent oral hygiene, supragingival irrigation
with or without medicaments is capable of reducing
gingival inammation beyond that normally achieved
by toothbrushing alone. This effect is likely due to the
ushing out of subgingival bacteria (Research, Science
and Therapy Committee, 2001).” In a 2005 position
paper, the American Academy of Periodontology stated
that “supragingival lavage can assist individuals with
gingivitis or poor oral hygiene. The greatest benet is
seen in patients who perform inadequate interproximal
cleansing. Patients report that the OI facilitates the
removal of food debris in posterior areas, especially
in cases of xed bridges or orthodontic appliances,
when the proper use of interdental cleaning devices is
difcult” (Research, Science and Therapy Committee,
2005). However, anecdotal discussions and commentary
continue concerning the appropriate use and efcacy
of this instrument. OI devices can be used with water
but also with antimicrobial agents (Flemmig et al., 1990,
Brownstein et al., 1990, Jolkovsky et al., 1990; Newman
et al., 1994, Fine et al., 1994; Chaves et al., 1994; Flemmig
et al., 1995; Felo et al., 1997).
The objective of the present study was to test the
adjunctive effect to toothbrushing of an OI with either
a prototype jet tip or a standard tip in the potential to
improve gingival health over a 4-week period. This pro-
totype tip, which is congured with laments, may help
the user guide the tip along the gingival margin and the
interproximal area. Both OI tips were compared to the
use of dental oss. These treatments were combined
with the use of a regular at trimmed manual toothbrush
together with a standard dentifrice.
Materials and methods
Study population
One hundred seventy-two subjects (non-dental students)
from different universities and colleges in and around
Amsterdam responded to an e-mail advertisement and
reported for a screening appointment. The volunteers
were informed about the study, rst in a recruitment
letter and secondly at the screening. Participation was
not limited by race or gender. Subjects received a written
explanation of the background of the study, its objec-
tives and their involvement. Before screening for their
suitability they were all requested to give their written
informed consent. Subjects were required to fulll the
following criteria: ≥18 years of age, a minimum of
ve evaluable teeth in each quadrant (with no partial
dentures, orthodontic banding or wires); moderate
gingivitis (50% bleeding on marginal probing, Galgut et
al., 1998), an absence of oral lesions and/or periodontal
pockets > 5 mm and/or generalized recession, and the
absence of pregnancy and systemic diseases such as
AIDS, cirrhosis, diabetes, any adverse medical history
or long-term medication, or any physical condition that
limits manual dexterity. All subjects received oral and
written information about the products and purpose
of the study. One hundred eight subjects met the in-
clusion criteria and were enrolled into the study, which
was conducted in accordance to the ethical principles
that have their origin in the Declaration of Helsinki and
was consistent with Good Clinical Practice guidelines.
Medical Ethics Committee approval was obtained prior
to the start of the study (MEC 09/198 #09.17.1322).
All assessments took place at the Department of Peri-
odontology at ACTA, Amsterdam, The Netherlands in
September and October, 2009.
Study products
Three different interdental products were tested in this
study, one product per group, with 36 subjects enrolled
in each group. All subjects received a standard tooth-
brush (Oral-B Indicator 35, Procter & Gamble, Cincin-
nati, OH, USA, Figure 1) and standard uoride dentifrice
(Everclean, HEMA, Amsterdam, The Netherlands).
In addition, subjects were randomized (see below for
details) into one of three groups for assignment of an
interdental cleaning device:
JIAP 10-005 Rosema.indd 3 04/01/2011 11:37:43
4 Journal of the International Academy of Periodontology (2011) 13/1
Group 1 (OIP): OI (DWJ-Waterpik® Ultra Water
Flosser, Fort Collins, CO, USA) with a prototype jet tip
(Figure 2, test group).
Group 2 (OIS): OI (DWJ-Waterpik® Ultra Water
Flosser, Fort Collins, CO, USA) with a standard jet tip
(Figure 3, benchmark control group, Husseini et al., 2008).
Group 3 (DF): standard waxed oss (Johnson &
Johnson, New Brunswick, NJ, USA) (Figure 4, control
group).
Clinical assessment
Clinical parameters were assessed at baseline (S1), week
2 (S2), and week 4 (S3). First gingivitis and then plaque
was scored. All gingivitis assessments were carried out
by the same trained examiner (NLH). All plaque assess-
ments were carried out by a second trained examiner
(CEB). All examinations were carried out under the
same conditions. All teeth were examined for both
indices at six sites per tooth (disto-buccal, mid-buccal,
mesio-buccal, disto-lingual, mid-lingual, mesio-lingual)
except for 3rd molars.
Criteria
Gingivitis was assessed as the primary outcome using
the bleeding on marginal probing index (BOMP) as
described by Van der Weijden et al. (1994a, 1994b) and
Lie et al. (1998). In short, the gingival margin is probed
at an angle of approximately 60° to the longitudinal axis
of the tooth and the absence or presence of bleeding
is scored within 30 seconds of probing on a scale 0 - 2
(0 = no bleeding, 1 = pinprick bleeding, 2 = excessive
bleeding).
Plaque was assessed as a secondary outcome using
the Turesky (1970) modication of the Quigley & Hein
(1962) plaque index (TQHPI) as described in detail by
Figure 1. Toothbrush - Oral-B indicator 35
Figure 2. OIP - oral irrigator with prototype tip
Figure 3. OIS - oral irrigator with standard tip
Figure 4. DF - standard waxed dental oss
JIAP 10-005 Rosema.indd 4 04/01/2011 11:37:47
The Effect of Different Interdental Cleaning Devices on Gingival Bleeding 5
Figure 5. Flowchart
Flowchart
Screening
Baseline (S1)
2 Weeks (S2)
4 Weeks (S3)
Statistical
Analyses
(ITT)
Screening
172 subjects
Excluded
64 subjects
Total: 108 subjects
Group 1: 36 subjects
Group 2: 36 subjects
Group 3: 36 subjects
BOMP & TQHPI
Professional instruction
Total: 106 subjects
Group 1: 35 subjects
Group 2: 35 subjects
Group 3: 36 subjects
BOMP & TQHPI
Drop-out
2 subjects
Drop-out
2 subjects
Total: 104 subjects
Group 1: 34 subjects
Group 2: 34 subjects
Group 3: 36 subjects
BOMP & TQHPI
Total: 104 subjects
Group 1: 34 subjects
Group 2: 34 subjects
Group 3: 36 subjects
Paraskevas et al. (2007). Briey, the teeth were dyed us-
ing a new cotton swab with fresh disclosing solution
(Mira-2-Ton®; Hager & Werken GmbH & Co. KG.
Duisburg, Germany) for each quadrant in order to dis-
close the plaque. Subsequently, the absence or presence
of plaque was recorded on a 6-point scale (0-5, 0 = no
plaque, 5 = plaque covering more than two-thirds of
the tooth surface).
Study design
This study was designed as single masked, 3-group paral-
lel, 4-week home use experiment. After meeting the inclu-
sion criteria, completion of a medical questionnaire and
informed consent, subjects returned to the clinic for their
rst (baseline) assessment (S1) for both clinical param-
eters (bleeding on marginal probing and plaque). At the
start of the experiment all subjects received a unique trial
number. Subjects were randomly assigned to one of three
groups according to a randomization list (www.random.
org). The allocation of products was carried out by the
study coordinator, who was responsible for allocation
concealment. All products were distributed in such a way
that blindness of the examiners was assured. At the last
visit (S3) the study coordinator assured blindness of the
JIAP 10-005 Rosema.indd 5 04/01/2011 11:37:48
6 Journal of the International Academy of Periodontology (2011) 13/1
examiners by collecting the study products in a separate
room from where the clinical examinations took place.
Subjects were also instructed not to mention anything
to the examiners that could lead to allocation disclosure.
During the 4-week experimental phase OIS and
OIP subjects used the OI once a day in the evening
with lukewarm tap water and were instructed to nish
one container of 500 ml at each occasion. Subjects in
the control group (DF) used standard waxed dental
oss once a day in the evening. At the baseline visit
(S1), immediately following the baseline assessment,
subjects used their allocated product for the rst time.
The study coordinator (NAMR) was present to provide
detailed verbal instruction, a demonstration to ensure
correct use, and aid with further personal instruction
when necessary. Subjects in both OI groups were
instructed to use the OI according to the instruction
leaet provided by the manufacturer. Subjects in the DF
group were instructed to use their product according
to the description of Van der Weijden et al. (2008). All
subjects in each group were instructed to brush twice a
day in their normal manner, once in the morning after
breakfast and once in the evening. In the evening they
subsequently used their assigned product (OI or DF).
All participants were instructed to refrain from using
any other oral hygiene product or device such as tooth-
picks, interdental brushes, mouthrinses, etc., during the
study period. To check for compliance, subjects were
asked to register the time of use of the products onto
a calendar record chart.
After two weeks (S2), subjects returned to the clinic
for the second clinical assessment for both gingivitis
and plaque. After four weeks (S3), subjects visited the
clinic for their nal assessment for both parameters.
Subjects were asked to return all products provided for
this study as well as the calendar record chart. On each
occasion subjects were instructed to brush between 2
and 3 hours prior to their appointments to avoid the
risk of increased bleeding on probing as a result of
toothbrushing (Abbas et al., 1990). The day prior to each
appointment all subjects received an SMS-message as a
reminder with the following text: “Remember that you have
an appointment at ACTA! Note that you need to brush your
teeth 2-3 hours prior to your visit. See you tomorrow! ACTA.”
After the nal assessment habitual oral hygiene proce-
dures were resumed.
Data analyses
The unit of analysis was the subject and collected data
were analyzed as intention to treat. The bleeding scores
were used as the main response variable (Galgut et al.,
1998) and plaque scores as secondary response variable.
A priori calculations with an alpha of 0.05, a difference
of 0.0883 (between groups) of the bleeding index with
80% power, based on a pooled SD of 0.13 as derived
from previous studies supported a sample size of 105.
An analysis of covariance (ANCOVA) with S1 as cov-
ariate and S3 as dependent variable was performed to
compare groups over time (Heynderickx et al., 2005).
Analyses comparing differences between the test and
control groups at each time point were performed
using non-parametric tests. Explorative analyses were
performed to investigate the origin of the overall differ-
ences. P values of < 0.05 were accepted as statistically
signicant.
Results
Of 108 subjects who started the trial, four subjects did
not complete the protocol. One chose not to continue
the trial for personal reasons. Another left the country
and moved abroad. Two did not attend the second visit
because of scheduling conicts. This resulted in a study
population of 104 subjects providing evaluable data
(Figure 5). The study population data on demographics
and pre-study oss habits are presented in Table 1. No
adverse events were reported by any of the subjects who
participated in this study.
Results for bleeding on probing are presented in Table
2. The overall ANCOVA analysis showed a statistically
signicant difference between the three groups (p =
0.007). Mean overall reductions after four weeks of use
(S1 to S3) were 0.15 for the OIP group, 0.17 for the OIS
group, and 0.02 for the DF group. The mean bleeding
scores of the three groups did not differ signicantly at
baseline. At session 2 the scores decreased for all three
groups. Post testing showed that both the OI groups
provided signicantly lower bleeding scores as compared
to the DF group. At session 3 a statistically signicant
difference could be detected among the three groups.
Post testing showed that again both the OI groups had
signicantly lower bleeding scores as compared to the
DF group. The 95% condence interval of the differ-
ence compared to the DF group at S3 was -0.27 ± -0.04
for the OIP group and -0.28 ± -0.05 for the OIS group.
Results for plaque index are presented in Table 3.
With regard to the plaque scores the overall ANCOVA
analysis showed no statistically signicant differences
among the three groups (p = 0.126). Mean overall re-
ductions after four weeks of use (S1 to S3) were -0.09
for the OIP group, 0.06 for the OIS group, and 0.01
for the DF group.
Discussion
Effective brushing remains the most obvious way of
maintaining low levels of plaque and good gingival
health. Gingivitis is known to be associated with the
onset of periodontitis, and although the relationship be-
tween these two conditions may not be fully understood,
the importance of maintaining good gingival health and
JIAP 10-005 Rosema.indd 6 04/01/2011 11:37:48
The Effect of Different Interdental Cleaning Devices on Gingival Bleeding 7
this with traditional dental oss (Asadoorian, 2006).
Thus, compliance with oss is low (Warren and Chater,
1996), and various adjuncts for interdental cleaning have
been studied. Dental oss, toothpicks, woodsticks and
interdental brushes have all been recommended for
this purpose.
The present study focussed on the ability to reduce
gingival inammation in a population of young individu-
als with moderate gingivitis using an OI. The OI works
through the direct application of a pulsed stream of
water or other solution. A study duration of four weeks
was chosen to monitor the changes in the bleeding index,
which meets the ADA guidelines on OI’s for studies as-
sessing the effects of adjunctive therapies on reduction
of gingivitis (ADA, 2008). Studies of longer duration
will more clearly demonstrate the clinical benet that
subjects will obtain from this product.
The efcacy of use of oss on the bleeding index
was considered inconclusive in a systematic review by
Berchier et al. (2008). The results of the present study are
Table 1. Demographic data and pre-study ossing habits of the study population.
OIP, oral irrigation device with prototype jet tip; OIS, oral irrigation device with standard jet
tip; DF, dental oss
Total OIP OIS DF
N 104 34 34 36
Female 74 24 27 23
Male 30 10 7 13
Age [range] (SD) 21.8 [18-36] 21.9 (3.2) 21.1 (2.3) 22.4 (3.1)
Daily oss users 6 2 1 3
Weekly oss users 16 7 4 5
Monthly oss users 20 9 7 4
Seldom/never oss users 62 16 22 24
Table 2. Mean bleeding index (BOMP) and mean % bleeding scores for all groups at all sessions.
Standard deviation in parentheses. Univariate analyses of covariance with session 1 as covariate and session 3 as depen-
dent variable. (p = 0.007). *Statistically signicant difference compared to DF group, p < 0.05 (Mann-Whitney). Statisti-
cally signicant difference compared to DF group, p = 0.020 (Mann-Whitney). OIP, oral irrigation device with prototype
jet tip; OIS, oral irrigation device with standard jet tip; DF, dental oss
N Session 1 Session 2 Session 3 Relative Reduction Relative Reduction
S1 – S2 S1 – S3
OIP - index 34 0.82 (0.25) 0.65 (0.24) 0.67 (0.26)
% 46 % 37 % 39 % 20 % 15 %
OIS index 34 0.83 (0.23) 0.61 (0.27)* 0.66 (0.26)*
% 46 % 34 % 38 % 26 % 17 %
DF - index 36 0.86 (0.26) 0.74 (0.26) 0.84 (0.30)
% 47 % 41 % 47 % 13 % 0 %
p - value
(Kruskal Wallis)
0.579 0.084 0.016
Univariate analyses of covariance with session 1 as covariate
and session 3 as dependent variable. (p = 0.126). OIP, oral
irrigation device with prototype jet tip; OIS, oral irrigation
device with standard jet tip; DF, dental oss
Table 3. Mean Quigley & Hein plaque scores ± standard
deviation for all groups at all sessions.
N Session 1 Session 2 Session 3
OIP 34 1.64 ± 0.43 1.61 ± 0.34 1.73 ± 0.37
OIS 34 1.79 ± 0.34 1.74 ± 0.29 1.73 ± 0.28
DF 36 1.60 ± 0.26 1.51 ± 0.27 1.59 ± 0.27
preventing periodontitis is well recognised (Van Dyke et
al., 1999). As the interproximal area is known as where
the onset of gingival inammation is likely to occur,
the reason for interproximal plaque control seems clear.
Although it is universally recognized that interproximal
cleansing is essential for controlling periodontal disease
(Löe, 1979), many people have difculty accomplishing
JIAP 10-005 Rosema.indd 7 04/01/2011 11:37:48
8 Journal of the International Academy of Periodontology (2011) 13/1
in support of this statement. In contrast, in the present
study both OI groups did show statistically signicant
improvements after four weeks. At the end of the study
both OI groups show a signicant 15 - 17% reduction
of the bleeding index as compared to baseline. For the
DF group this difference was not observed. Compari-
sons among groups showed a signicant difference at
four weeks between the DF group and both OI groups.
The absolute difference of 8% and 9% at four weeks
for both OI groups as compared to the oss group re-
veals a relative effect of 17% (OIP) and 19% (OIS). In
consideration of the ADA guidelines for oral irrigators,
the results of the present study do not reach the lower
limit of superiority of 20% as estimated proportionate
reduction related to clinical relevance as compared to
standard oral hygiene procedures (ADA, 2008). How-
ever, the ADA also has guidelines on adjunctive dental
therapies (ADA, 1997). In those guidelines a lower limit
of 15% is applied. The study outcomes of the present
study do comply with this guideline, indicating a poten-
tial benecial effect for the OI.
With respect to plaque, the DF group started with a
markedly lower score as compared to both OI groups.
All subjects were instructed to brush 2-3 hours prior
to examination, to reduce the risk of greater bleeding
tendency (Abbas et al., 1990). As the difference in PI
scores was consistent throughout the study and was not
reected in bleeding index scores, it seems that subjects
who were randomly allocated to the oss group coin-
cidently performed better instant plaque removal by
brushing at visit days. In a study carried out by Galgut
et al. (2000) the effect of unevenly distributed baseline
data is discussed and it was concluded that this might
not inuence the results and the conclusions drawn.
Historically, plaque reductions are considered a pre-
requisite for an oral hygiene device to be considered
effective (Löe et al., 1965). A recent systematic review
(Husseini et al., 2008) reported no statistically signicant
reduction in plaque when the OI was used as an adjunct
to toothbrushing when compared to toothbrushing only.
Despite a lack of effect on plaque index, the studies that
were included in this review did nd a signicant effect
on bleeding and gingival indices. The mechanisms of
actions underlying these clinical changes for the bleeding
index in the absence of a clear effect on plaque are not
understood, although different hypotheses have been
put forward (Husseini et al., 2008). One of the hypoth-
eses is that supragingival irrigation alters the popula-
tion of key pathogens, reducing gingival inammation
(Flemming et al., 1995). Another hypothesis is that the
water-pulsation may alter the specic host-microbial
interaction in the subgingival environment (Chaves et
al., 1994). There is also the possibility that the benecial
action of an OI is at least partly because of the removal
of loosely adherent soft deposits interfering with plaque
maturation and stimulation of the immune response
(Frascella et al., 2000). Other explanations could be a
mechanical stimulation of the gingiva or a combina-
tion of the above-mentioned factors (Frascella et al.,
2000; Flemmig et al., 1990). Furthermore, irrigation may
reduce the thickness of the plaque, which may not be
easily detectable using 2-dimensional scoring systems
(Jolkovsky et al., 1990).
The absence of an effect for DF at four weeks may
also seem surprising. A transient effect of 6% BI re-
duction was observed at two weeks. However, a recent
systematic review supports this nding that dental oss
has no signicant effect on plaque or bleeding indices
(Berchier et al., 2008). The small effect observed at two
weeks is most likely the result of a novelty or Hawthorne
effect. The Hawthorne effect is a reaction of subjects to
the realization they are in a study and are being observed
(Adair et al., 1984). The novelty effect and Hawthorne
effect can be considered as certain placebo effects. The
impact of a placebo effect should not be underestimated
(Finniss et al., 2010). In a study by Feil et al. (2002), the
Hawthorne effect was intentionally used and shown to
improve oral health. The novelty effect is something
that could have inuenced all groups within this model.
Subjects were pre-selected on having “no experience”
with an OI, whereas only six out of the 104 were regular
ossers (Table 1). The rebound that is observed from
the 2-week to the 4-week follow-up is, however, most
evident in the oss users. With respect to the Hawthorne
effect, this is probably not only present in the DF group
but also in both OI groups, as subjects were selected on
having a bleeding index of > 50%. However at session
1 the bleeding index was already reduced to 46-47%
for all three groups. This indicates that subjects already
acted as if they were entered into the protocol before
the rst assessment of the primary response variable.
The results of the present study add to the existing
data and clearly show a reduction in inammation from
using an OI. Interestingly, the reduction in bleeding
could not be linked to plaque removal. This is similar
to data presented by Flemmig et al. (1990) showing no
change in plaque scores for either the brushing group
or the brushing and irrigation group from baseline to 6
months, but a signicant difference in bleeding on prob-
ing and gingival index scores in favor of the irrigation
group. Likewise, Flemmig et al. (1995) reported that the
water irrigation group was signicantly better at reducing
bleeding on probing and gingival index scores compared
to the regular oral hygiene group at six months. Also
in this study there were no statistically signicant dif-
ferences detected in plaque scores among the groups.
Chaves et al. (1994) found similar reductions in plaque
scores for water irrigation compared to toothbrush-
ing alone, and a signicant difference for bleeding on
probing in favor of the irrigation group at six months.
JIAP 10-005 Rosema.indd 8 04/01/2011 11:37:48
The Effect of Different Interdental Cleaning Devices on Gingival Bleeding 9
These studies support the present data in nding no
correlation between reduction of plaque biolm and
inammation in 3-6 months.
Conclusion
There is a long-standing, well-documented body of
evidence supporting the use of an oral irrigator. An oral
irrigator is at least as effective as dental oss for reducing
gingival bleeding and gingivitis. When combined with
manual toothbrushing the use of an oral irrigator, either
with a prototype or standard jet tip, is signicantly more
effective in reducing gingival bleeding scores as com-
pared to the use of dental oss, as determined within
the limits of this 4-week study design.
Acknowledgment
The study was performed in commission of ACTA
Research BV.
Waterpik Inc, Fort Collins, CO, USA initiated the
study project and provided study products. ACTA
Research BV received nancial support for their com-
mitment to appoint this project to the Department of
Periodontology of ACTA.
D.M. Lyle is the director of professional and clini-
cal affairs for Water Pik, Inc. The authors employed by
ACTA declare that they have no conict of interest.
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