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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
A Prospective Clinical Study to Evaluate the
Effect of Manual and Power Toothbrushes
on Pre-existing Gingival Recessions
Aim: To evaluate gingival recession changes after six months of brushing with an oscillating-rotating power
toothbrush (PT) or an ADA reference manual toothbrush (MT).
Methods and Materials: Healthy subjects with pre-existing recession were assigned to brush with either a PT
(n=55) or an ADA reference MT (n=54) according to a prospective randomized, controlled, single-blind, parallel
group design. Participants were asked to brush their teeth twice daily for two minutes each with the same fluoride
toothpaste. Clinical attachment loss and probing pocket depths (PPDs) were measured at six sites per tooth to
the nearest mm by one calibrated examiner at baseline and after six months. Gingival recession was calculated
as the differences between clinical attachment loss and PPDs overall and separately at individual sites.
Results: As compared with baseline, overall recession at six months was reduced from 2.35 ± 0.35 mm to 1.98
± 0.55 mm (p<0.001) in the PT group and from 2.26 ± 0.31 mm to 1.90 ± 0.45 mm (p<0.001) in the MT group.
The data showed 40% (power) and 38% (manual) of all recession sites improved by at least 0.5 mm while 51%
and 54% remained unchanged. Eight percent and 7% recessions increased over time. Differences between
groups were not statistically significant at either timepoint.
Conclusion: Both the PT and the MT significantly reduced pre-existing gingival recession after six months of
brushing. This may have been due to improved brushing technique (i.e., Hawthorne effect).
FREE full text provided by P&G Professional Oral Health.
Christof E. Dörfer, DDS, PhD; Daniela Joerss, DDS;
Diana Wolff, DDS
Abstract
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
Introduction
Gingival recession is marked by the apical
displacement of the gingival margin away from
the cemento-enamel junction (CEJ). This leads to
root exposure, which is esthetically unattractive
and may result in hypersensitivity and root
caries. While the cause of gingival recession
is not fully established, it is clear the etiology
is multifactorial.1 Research indicates recession
is associated with aging2 and is more common
in women than men.3 In addition, a variety of
anatomical, pathological, and physiological
factors have been implicated in the etiology.1
The most controversial issue is the possible role
of tooth brushing in promoting gingival recession.4
Tooth brushing has been shown to result in
gingival abrasions, but it is not known how such
abrasions may relate to gingival recession.5 There
is some circumstantial evidence tooth brushing
could be a causative factor in the development
of gingival recession.6,7 However, one influential
review of the evidence concludes “it is only with
‘under, over or abusive use [of tooth brushing]
when combined with erosion that significant harm
may be thus caused.”5 A very recent systematic
review states “data to support or refute the
association between tooth brushing and gingival
recession are inconclusive.”4
As researchers attempt to clarify this relationship,
it is important to consider any differential effects
of power and manual tooth brushing on gingival
recession. Power toothbrushes (PTs) with a
rotating-oscillating and pulsating action have been
shown to provide significant advantages for oral
health (specifically plaque removal and reduction
of gingivitis) over manual toothbrushes (MTs) in
long- and short-term studies.8,9 These systematic
reviews found no evidence PTs with oscillating-
rotating action cause any more abrasion of soft
tissue (gingivae, lips, tongue, inner surface of
cheeks, etc.) than manual brushing. A number of
other studies support this general conclusion,10,11
and one reports power brushing results in fewer
abrasions than manual brushing.12
While there is no established connection between
gingival abrasions and gingival recession, it is
nevertheless possible the use of devices with
a higher plaque removing capacity could be
associated with a higher risk of gingival recession.
Three long-term controlled clinical trials have
compared powered with manual tooth brushing
for changes in gingival health. Neither a rotary
electric brush,13 nor a counter-rotational electric
brush,14 nor an oscillating-rotating PT15 resulted in
differences in gingival recession compared with
manual tooth brushing. However, both the Boyd
et al.13 and the Wilson et al.14 studies used small
numbers of subjects (40 and 32, respectively),
and no studies examined pre-existing recessions.
As sites with existing recessions are known to be
more susceptible to further recessions,6 the aim of
the present long-term, prospective, randomized,
controlled clinical study was to examine the influence
of tooth brushing with an oscillating-rotating PT and
a manual reference toothbrush on subjects with pre-
Clinical Significance: Based on these six-month data, concern that power tooth brushing results in a higher
risk for gingival recession is not warranted.
Keywords: Oscillating-rotating power toothbrush, gingival recession, Hawthorne effect
Citation: Dörfer CE, Joerss D, Wolff D. A Prospective Clinical Study to Evaluate the Effect of Manual and
Power Toothbrushes on Pre-existing Gingival Recessions. J Contemp Dent Pract 2009 July; (10)4:001-008.
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
had their first study visit (Visit 1; baseline) during
which subjects received oral assessments of
the soft and hard tissues, followed by clinical
measurements by the same examiner (DW)
who was blinded to the assigned treatment.
The examiner had been calibrated for intra-
examiner reproducibility. The clinical recession
measurements were carried out at six sites per
tooth and comprised periodontal measurements
of pocket depth, attachment levels, and gingival
recession. The sites were mesiobuccal,
centrobuccal, distobuccal, mesiolingual,
centrolingual, and distolingual. Plaque and gingival
health were assessed next but the data were not
analyzed in this study.
Periodontal pocket depth (PPD) at every site was
measured to the nearest mm using a periodontal
probe marked at each mm (PCPUNC15,
Hu-Friedy, Chicago, IL, USA), averaging upward
if the margin of the gingiva was between
markings. For proximal surfaces, the probe
was held at 45° to the long axis of the tooth to
prevent overestimations of pocket depth at the
interproximal spaces. The clinical attachment level
(CAL) at every site was measured as the sum of (i)
the distance between the CEJ to the margin of the
gingiva and (ii) the PPD. The CAL was scored as
negative if the margin of the gingiva was above the
CEJ and positive if the margin of the gingiva was
below the CEJ. If the CEJ was covered by a crown
or cervical restoration, the measurement was taken
from the most apical margin of the restoration.
Gingival recession at every site was calculated as
the difference between CAL and PPD.
Subjects were stratified based on mean gingival
recession, gender, smoking status, and age to
one of the two treatment groups: power brush
existing recessions. Within-group comparisons
of gingival recession facilitate the evaluation
of the progress of recession, while between-
group comparisons test the null hypothesis that
oscillating-rotating PT users and MT users show
no differences in the progress of recession.
Methods and Materials
Subjects and Study Design
This was a single center, randomized, examiner-
blind, parallel group study to compare the
effects of power brushing, using an Oral-B
ProfessionalCare® 7000 Model D17U power brush
(The Procter & Gamble Company, Cincinnati, OH,
USA), with manual brushing, using an American
Dental Association reference flat trim brush, on
oral tissues (Figure 1). This study assessed the
results after six months of twice daily brushing.
All subjects used a standard sodium fluoride
dentifrice (Blend-a-Med®; The Procter & Gamble
Company, Cincinnati, OH, USA).
The study protocol was approved by the
Independent International Freiburg Ethics
Committee before the start of the study, and
subjects gave written informed consent before
participating in any study procedures.
Subjects from the general population were
considered for the study according to the study
inclusion and exclusion criteria (Table 1). All
dental professionals and dental students were
excluded from participation to avoid bias.
Participants had to exhibit at least two sites with
gingival recession of at least 2 mm at baseline
to qualify for participation in the study. Qualifying
subjects were consecutively included.
Subjects who qualified to participate in the study
according to the inclusion and exclusion criteria
Figure 1. Oral-B ProfessionalCare 7000 toothbrush and
ADA reference MT.
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
Table 1. Inclusion and exclusion criteria for study participation.
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
baseline for all subjects from the maxilla and
the mandible. The stone replica recessions
were measured using a digital measuring
gauge by an examiner (SW) who was different
from the examiner who carried out the clinical
measurements and who was blinded with respect
to the results of the clinical measurements.
Statistical Analysis
No power calculation was conducted before
the start of the study, but subject recruitment
was aimed at having 50 subjects per group
completing the study. Gingival recession was of
primary interest in this study, and changes from
baseline at six months were assessed using
the Wilcoxon non-parametric test for paired
samples and group differences in changes from
baseline were assessed using the non parametric
Mann-Whitney-U Test. Proportions of improving,
unchanged, and increasing recession sites were
calculated as well. The Pearson’s product-moment
correlation coefficient was used to assess the
relationship between clinical and stone replica
assessments of gingival recession. All statistical
tests were two-sided and used a significance level
of α=0.05.
Results
A total of 109 subjects were enrolled in the study
and 106 subjects (53 in the PT group; 53 in the
MT group) completed the study. The remaining
subjects were withdrawn from the study because
of the use of antibiotics during the last three
weeks prior to the six months examination. The
demographic details of subjects who completed
the study are summarized in Table 2.
The mean baseline and Month 6 periodontal
pocket depth, clinical attachment level, as well as
plaque and gingivitis index values are summarized
in Table 3.
The results of recession measurements at
preexisting recessions are given for all sites and
separate for tooth type in Table 4.
Analysis of the clinical data for all pre-existing
recession sites showed recession was highly
significantly reduced from baseline to month
six (p <0.001). Analysis of the data for different
tooth types showed recession was significantly
reduced for both the manual and power brush at
or manual brush. All subjects were instructed
to brush their teeth twice daily for two minutes
each time using the sodium fluoride dentifrice
supplied. Subjects assigned to the PT group
received brushing instructions according to the
manufacturer’s package insert and were required
to demonstrate their brushing technique prior to
leaving their facility. Subjects assigned to the MT
group received instructions on an individual basis
as recommended by the investigator, and any
errors in brushing were corrected.
Subjects returned to the center after three months
(Visit 2) and were supplied with a new manual
brush or brush head, as appropriate. The standard
toothpaste, which was available throughout
the study on request, was also supplied at
this visit. Any questions raised by the subjects
were answered and brushing instructions were
reviewed. Subjects were instructed to return to the
center after another three months for a second
oral examination.
At six months (Visit 3), subjects received
oral assessments of all soft and hard tissues
followed by the same clinical measurements as
those conducted at Visit 1. Clinical recession
measurements were validated by comparing
the clinical evaluation of gingival recession with
recession measurement using stone replicas from
high precision full mouth impressions. Dental
impressions with a high precision polyethergum
impression material (i.e., casts) were taken at
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
Table 2. Baseline demographic characteristics of subjects who completed the study.
Table 3. Probing Pocket Depths (PPD [mm]), Clinical Attachment Levels
(CAL [mm], Plaque (TMQHI) and Gingivitis-Index (GI) at all sites. Mean
values ± standard deviations are given for baseline and six-month results.
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
Table 4. Recessions at sites with initial recession (mm) in total and separate for different toothtypes.
Mean values ± standard deviations are given for baseline and six-month results.
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
groups were obtained for any measures of
gingival recession. This is in general agreement
with previous findings, none of which recorded
greater gingival abrasion or gingival recession
with powered than with manual brushes.11-15
Thus, despite the fact that PTs with a rotating-
oscillating and pulsating action have been shown
to be more effective than MTs in plaque removal
and control of gingivitis,8,9 these gains are not
at the cost of increased gingival abrasion or
recession. A failure to find a difference between
groups can sometimes be the result of a lack of
statistical power rather than the genuine absence
of an effect; however, in the present study the
substantial number of subjects in each group
provides sufficient power to give confidence in
the conclusion there is no difference in gingival
recession following power or manual brushing.
It is known further recession is most likely to
occur at sites where there has already been
some degree of recession,5 in the present study
consideration of these sites provides a very
sensitive measure of the effects of tooth brushing
on gingival recession. Not only was there no
increase in recession in these sites, there was
a highly significant decrease. In light of these
findings, it can be concluded with confidence that
neither power nor appropriate manual brushing
increases gingival recession.
the central incisor, the canine, the first and second
premolar, the first and second molar, and for the
manual brush at the lateral incisor. No statistically
significant group differences in recession were
seen at any site.
In terms of proportions, 40% of recession sites in
the power tooth brushing group and 38% in the
manual toothbrushing group were improved by at
least 0.5 mm. These values corresponded with
52% and 54% of unchanged sites and 8% and 7%
of increasing recession sites, respectively.
Analysis of the stone replica validation data
showed full agreement (a difference of <0.5 mm) in
72.3% of comparisons with clinical measurements;
96.8% of measurements differed by ≤1 mm. The
mean difference (± standard deviation) was 0.4 ±
0.7 mm and the correlation was highly significant
(Pearson’s r = 0.761; p <0.001).
No adverse effects on oral hard and soft tissues
were observed in either treatment group during
examination of the oral cavity (Figure 2).
Discussion
The primary aim of this controlled, parallel group
study was to compare the effect on gingival
recession of use of the Oral-B ProfessionalCare®
7000 PT with manual brushing over a period of
six months. No significant differences between
Figure 2. Stone replica validation of clinical recession measurement. Absolute recession
values [mm] measured clinically (blue) and on stone replica (green) as well as their absolute
difference [mm] (yellow) and the standard deviation of the differences (purple) are given.
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
of oral hygiene there was a positive correlation
between age and gingival recession. This was
interpreted as indicating that prolonged tooth
brushing induced gingival recession. However,
in an observational study of 100 dental students
the presence of gingival recessions in patients
with a high standard of oral hygiene was related
to wrong toothbrushing technique, too much
strength exerted in brushing, overbrushing, and
usage of hard toothbrush bristles.16 These findings
were supported by Tezel et al., who concluded
recession is particularly associated with
toothbrushing technique, in particular horizontal
scrubbing.7 Another observational study, which
focused on the use of hard or soft MTs, reported
recession was far more pronounced in subjects
who had used a hard toothbrush and for users
of hard toothbrushes a correlation between the
percent of surfaces with recession and increasing
brushing frequency.17
In observational studies such as these it is
unsafe to draw conclusions about causation from
correlational evidence alone. Thus, Serino et
al.’s finding of a positive correlation between age
and gingival recession6 has been interpreted as
evidence of the amount of toothbrushing, which
necessarily increases with age, results in greater
gingival recession. However, these findings could
have been an effect of aging alone, regardless
of toothbrushing, or the correlation might, as
suggested above, have been mediated by the
hardness of the toothbrushes or by brushing
technique. Experimental studies, such as the
present one, provide much more reliable evidence
of causation and where, as in this case, there is
As discussed in the introduction, while it appears
both manual or power tooth brushing may result
in some gingival abrasion, there is no convincing
evidence this leads to gingival recession.4,5 There
are a number of experimental studies which
demonstrate a causal association between tooth
brushing and gingival abrasion but there are
few such studies of gingival recession. In one
large scale, six-month study comparisons in
gingival recession were made between a group
of subjects using an oscillating-rotating powered
brush (n=76) and a group using a manual brush
(n=81); at the end of the study, no significant
changes from baseline were found in either
group.15 A smaller scale one-year study found
no change in gingival recession over the period
of the study in either the manual or the power
brushing group, although the power brush was
more effective in plaque removal.14 Another one-
year study of periodontal maintenance patients
using either manual or power brushes found no
changes in PPD or loss of attachment.13 The
conclusion from these rather limited studies,
therefore, is that tooth brushing does not lead
to gingival recession. Given differences in
procedure, sample size, and subject populations
these studies are not necessarily inconsistent
with the improvement found in the present study.
However, as noted in the introduction, there are
a range of studies which suggest there is an
association between amount of tooth brushing
and the development of gingival recession.6,7
The highly significant reversal in recession
in our study is in complete conflict with these
findings and is entirely unexpected. It should
be noted the present experiment was a well
controlled prospective study: subjects were
enrolled according to pre-defined inclusion and
exclusion criteria; assignment to groups was
randomized and single-blinded; outcomes were
assessed by a trained and calibrated examiner
whose assessments were verified by impression
based casts. There is no reason, therefore, to
doubt the reliability of these results. By contrast,
the findings which suggest toothbrushing results
in gingival recession used a different and less
convincing methodology. In general, they
report a range of observations carried out at
a particular time and derive conclusions from
correlational findings. Thus, Serino et al.6 found
in a population of subjects with a high standard
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
non-compliant adolescents by the deliberate
induction of this effect and this improvement
can extend over six months.20 This provides
support for the notion the reduction in gingival
recession achieved in this study was due to the
same mechanism. It should be noted Hawthorne
effects, unlike placebo effects, are the result
of real changes in behavior; these behavioral
changes are an unintended consequence of
exposing subjects to a study protocol. In this
study it is suggested this resulted in improved
tooth brushing and this, in turn, reduced
gingival recession. Whatever the reason for the
improvement it clearly merits further investigation
particularly if it offers the possibility of reversing
gingival recession.
Conclusion
• Bothgroupsshowedareductioninthe
amount of recession over the period of the
study.
• Overaperiodofsixmonthstherewasno
difference in the amount of gingival recession
in groups using the Oral-B ProfessionalCare®
7000 PT and a MT.
• Itispossiblethatthisisduetoimproved
brushing technique engendered by the
‘Hawthorne effect’.
Clinical Significance
Based on these six-month data, clinicians should
not be concerned that power tooth brushing
results in a higher risk for gingival recession.
apparent conflict greater weight should be placed
on experimental findings. It may, therefore, be
accepted that in this study brushing with either
a MT or a PT reduced gingival regression
over a six-month period. It seems possible the
correlations obtained in observational studies are
due to the use of inappropriate toothbrushes and
brushing techniques rather than the mere amount
of toothbrushing; this is also the conclusion
reached in the most recent systematic review of
the literature.4
It appears, as compared to the small number of
other experimental studies,13-15 the experimental
manipulation in this study was particularly
effective in inducing better oral hygiene. A
possible causal mechanism is provided by the
‘Hawthorne effect’. The term ‘Hawthorne effect’
refers to any ‘unexplained result in an experiment
on human subjects, on the assumption the result
occurred simply because the subjects were in an
experiment and, thereby, experienced something
that otherwise would not have affected them.18,19
The effect is also recognized as a reaction of
subjects to the realization they are in a study
and are being observed.17 In the present study
the subjects were alerted to the fact they were
participating in a clinical trial and this may have
changed their behavior. In particular, it may
have led to more careful and systematic tooth
brushing which, in turn, may have served to
reduce gingival recession. It has been shown
oral hygiene can be significantly improved in
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The Journal of Contemporary Dental Practice, Volume 10, No. 4, July 1, 2009
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About the Authors
Christof E. Dörfer, DDS, PhD
Dr. Dörfer is a Professor and Chair of the Department for Conservative Dentistry,
School of Oral Medicine, Christian-Albrechts-University at Kiel and the Director of the
Clinic for Conservative Dentistry and Periodontology, Center for Oral Diseases at the
University Hospital of Schleswig-Holstein in Kiel, Germany. His research interests
include the prevention of oral diseases and their consequences on systemic health.
He is member of the International Association for Dental Research and its Continental
European Division and of the German and European Federation of Periodontology.
e-mail: doerfer@konspar.uni-kiel.de
Daniela Joerss, DDS
Dr. Joerss is an Instructor in the Department for Conservative Dentistry of the School
of Oral Medicine at Ruprecht-Karls University in Heidelberg, Germany. Her research
interests are preventive dentistry and adhesive dentistry.
e-mail: joerss.daniela@med.uni-Heidelberg.de
Diana Wolff, DDS
Dr. Wolff is an Assistant Professor in the Department for Conservative Dentistry of the
School of Oral Medicine at Ruprecht-Karls-University in Heidelberg, Germany. She is
a specialist in esthetic dentistry and operative dentistry. Her research interests are in
preventive dentistry and cariology.
e-mail: wolff.diana@med.uni-Heidelberg.de
Acknowledgements
The authors thank Maryann Cugini for her support in developing the draft protocol, Dr. Nina Tremmel
for her assistance during the course of the study, and Dr. Jane Mitchell (MWS Ltd, Staffordshire, UK)
for assistance with manuscript preparation. The study was funded by the Procter & Gamble Company,
Cincinnati, OH, USA.
