Received: 3 March 2017 Revised: 29 September 2017 Accepted: 1 October 2017

DOI: 10.1002/JPER.17-0149

ORIGINAL ARTICLE

The effect of toothbrushing and flossing sequence on interdental

plaque reduction and fluoride retention: A randomized controlled
clinical trial

Fatemeh Mazhari1 Marzie Boskabady1 Amir Moeintaghavi2 Atieh Habibi3

1 Dental Materials Research Center, Mashhad

Abstract
University of Medical Sciences, Mashhad,
Iran Background: Mechanical plaque control methods such as brushing and flossing are
2 Dental Research Center, Mashhad University highly recommended to remove dental plaque. The aim of this study is to evaluate the
of Medical Sciences, Mashhad, Iran efficacy of the sequence of brushing and flossing on reducing interdental plaque and
3 Dentist, Private Practice, Mashhad, Iran
increasing fluoride retention in that area.
Correspondence
Marzie Boskabady, Department of Pediatric Methods: This randomized controlled crossover trial was conducted on 25 dental
Dentistry, Faculty of Dentistry, Mashhad
students. After prophylaxis, they were asked to discontinue all forms of oral hygiene
University of Medical Sciences, Vakilabad
Blvd, P.O. Box 91735-984, Mashhad, Iran. for 48 hours. The study was performed in two phases with two-week washout inter-
Email: Boskabadymr@mums.ac.ir vals. In one phase, they first brushed, then flossed (sequence 1: brush-floss group). In
the other phase they initially used dental floss then brushed (sequence 2: floss-brush
group). At each phase, dental plaque (using the Rustogi Modified Navy Plaque Index)
and fluoride concentrations (using a fluoride ion specific electrode) were measured
before and after flossing and brushing, and the dental plaque reduction and fluoride
increase were compared between the two groups using the mixed model test. A sig-
nificance level of 5% was selected.

Results: In the floss-brush group interdental and whole plaque was reduced signif-
icantly more than the brush-floss group (p = 0.001, p = 0.009 respectively). How-
ever, marginal plaque did not show any statistically significant difference between the
two groups (p = 0.2). Fluoride concentrations in interdental plaque were significantly
higher in the floss-brush group than the other group (p = 0.027).

Conclusion: The results showed that flossing followed by brushing is preferred to

brushing then flossing in order to reduce interdental plaque and increase fluoride con-
centration in interdental plaque.

KEYWORDS
dental plaque, flossing, fluoride, randomized controlled trial, toothbrushing

Dental plaque biofilms play an important role in the range of methods available, mechanical removal of plaque
development and pathogenesis of caries, gingivitis, and remains the widely accepted method for maintaining good
periodontitis.1–3 Therefore, the control of dental plaque oral hygiene.4,5 The most common method of mechanical
biofilm is a major objective of dental professionals and crit- plaque control is toothbrushing.6 Nevertheless, this means of
ical to maintain and improve oral health. Several therapeutic plaque control cannot adequately remove the plaque from the
approaches to control dental plaque exist, but despite the wide interdental surfaces because access to these areas is difficult,

824 © 2018 American Academy of Periodontology wileyonlinelibrary.com/journal/jper J Periodontol. 2018;89:824–832.

MAZHARI ET AL. 825

particularly in posterior areas.7 Periodontal and gingival laboratory procedures (fluoride measurement) were processed
lesions are predominantly observed at these sites,8 which are in the School of Pharmacy, Mashhad University of Medi-
also frequently affected by caries.9,10 Therefore, interdental cal Sciences. This randomized, controlled, crossover, clinical
cleaning accompanied by toothbrushing are cornerstones in trial study was conducted on 25 healthy dental students in the
achieving plaque control in daily oral care. Various products age range of 20 to 25 years (mean age: 23.2±1.22 years) in
have been designed to remove interdental plaque, and among May 2014. Twenty-three of the participants were female and
these, the widely recommended tool is dental floss.11 two were male. All the participants signed informed, written
It is not possible for mechanical approaches to remove consent forms before participating in the study.
plaque completely; hence, using fluoride products can play The following criteria were applied to select the samples
an important role in caries prevention.12 Research has shown for the study:
that fluoride is effective in the prevention of dental caries Inclusion criteria:
in several ways: inhibiting demineralization, enhancing rem-
ineralization, and inhibiting bacterial metabolism.13–15 Särner 1. Healthy individuals having all their permanent teeth
found that using a fluoridated dental floss could elevate flu- (except third molars),
oride concentrations in the interdental area up to 10 times 2. Individuals with a normal unstimulated salivary flow rate,
higher than the non-treated sites.16 Also, fluoridated tooth- 3. Individuals free from cavitated carious lesions,
pastes can increase the concentration of fluoride in dental 4. Individuals with no antibiotic use during the last four
biofilm.17,18 weeks,
Whether it is better to floss before or after brushing is
5. Individuals who did not take any medication that may
not clear. Some dentists argue that flossing should come first
interfere with salivary flow rate,
because you stir up the particles and plaque that the toothbrush
can brush away subsequently. The fluoride from your tooth- 6. Individuals with no fluoride mouth rinse use during the
paste is also more likely to reach the interdental areas if food previous two weeks.
wedged in between the teeth is removed before brushing. The
one study that has evaluated this issue has found that floss- Exclusion criteria:
ing followed by brushing provides effective plaque control.5
1. Individuals with any type of systemic illness or periodon-
Others recommend brushing be done first and their rationale
titis,
is that brushing teeth first removes the bulk of the particles on
the teeth and flossing afterward can remove interdental plaque 2. Individuals with crowns or severe crowding.
better. It could also force the remaining bit of fluoride that is
Inclusion and exclusion criteria were checked by the prin-
left on the teeth from toothpaste into the interdental spaces.
ciple investigator (F.M.)
Determining the best flossing and brushing order has still
to be established because of the very few studies done on
this topic and in fact only one study has addressed this issue 1.1 Sample size
specifically.5 Therefore, the aim of this study was to evalu- The pilot study was done on four participants. The mean and
ate and compare the effects of brushing and flossing order in standard deviation of interdental plaque reduction for brush-
removing interdental plaque and increasing interdental fluo- floss and floss-brush groups were calculated (0.542 ± 0.14 and
ride retention. The hypothesis was that no difference in effi- 0.634 ± 0.07 respectively). A confidence level of 95% and a
cacy would be found between the two sequences. power of statistical test of 80% were considered for the study.
Twenty-three samples were calculated, which was increased
to 25 to improve the validity of the study.

1 M AT E R I A L S A N D M E T H O D S 1.2 Experimental protocol

This study was approved by the Research and Ethics In the initial appointment, each participant was given a soft
Committee, Faculty of Dentistry, Mashhad University of toothbrush (Trisa AG, Triengen, Switzerland), a toothpaste
Medical Science, Mashhad, Iran. It was registered at Clinical- containing 1450 ppm fluoride (Pooneh with 1450 ppm flu-
Trials.gov with a registration number of NCT02971514 and oride, Paxan co,Tehran, Iran), and a thin waxed, fluoridated
date of November 2016, and it was conducted and reported dental floss (Mina, Mina co, Tehran, Iran) (Figure 1) to use
in accordance with the declaration of Helsinki for Biomedical during the study and they were instructed not to use any
Research Involving Human Subjects. mouthwash or other fluoridated products during the study.
The clinical procedures were conducted in the Pediatric Also, the modified bass technique and the appropriate method
Dentistry Department, Mashhad Dental School; and the of flossing were taught to them with model demonstrations.19
826 MAZHARI ET AL.

principle examiner (M.B.), who also did the baseline assess-

ment, performed the post-flossing plaque examination and
interdental plaque sampling to analysis its fluoride content.
Sequence 2 (floss-brush sequence): All the procedures
were the same as in sequence 1 except that the participants
were asked to brush and rinse after flossing.

1.3 Randomization and blindness

The principle investigator (F.M.) performed the randomiza-
tion process before starting the study as follows: Initially 13
opaque, sealed envelopes each containing number 1 represent-
ing sequence 1 (brush-floss), and 12 similar envelopes each
containing number 2 representing sequence 2 (floss-brush)
were prepared. Next, a random number from 1 to 25 was
assigned to the envelopes using a research randomizer pro-
FIGURE 1 Toothbrush, toothpaste, dental floss, disclosing tablet,
gram. Based on order of their entry into the study, the partici-
prophylactic paste and Eppendorf container used in the study
pants were given a numbered envelope with the same random
number assigned by the research randomizer program.
The study was conducted in the single blind method, as
Participants were asked to brush their teeth twice and floss
the principle examiner (M.B.) was blind to the sequence of
once a day during the washout intervals. It is important to
plaque control, although the patient and operator could not be
note that, the compliance of participants was evaluated at each
blinded.
phase (before starting brushing and flossing) by the principle
operator (A.H.) and if the participants were not properly fol-
lowing the instructions, they were taught again. 1.4 Plaque assessment
The study was performed in two phases (each phase lasted In each phase after chewing a disclosing tablet, plaque
48 hours) with two-week washout intervals between the was scored using the Rustogi Modified Navy Plaque Index
phases (Figure 2). Each 48-hour period included two sessions. (RMNPI) before (baseline) and after plaque removal.20 The
At session one, the participants underwent a professional pro- index divides buccal and lingual surfaces into nine areas
phylaxis by the principle operator (A.H.), in which a rubber (A to I) that are scored for the presence (score = 1) or
cup prophylaxis and a non-fluoride paste (Kemdent, Swin- absence (score = 0) of plaque (Figure 3). It assesses the
don, Wiltshire, UK) (Figure 1) was applied. At this point amount of plaque on a whole mouth basis (areas A-I), inter-
in the study, the participants were instructed to discontinue dental basis (areas D and F), and the gingival margin basis
all oral hygiene practices. After 48 hours (session two), the (areas A, B, C). To calculate the mean RMNPI score for
participants were summoned for the next steps. They were each participant, the total number of tooth areas with plaque
placed randomly into the sequence 1 (brush-floss sequence) present was divided by the total number of tooth areas scored
or 2 (floss-brush sequence): (for 28 teeth there was a total of 504 sites for the whole
Sequence 1 (brush-floss sequence): The participants who mouth, 112 sites for the interdental and 168 sites for the
had not eaten anything for about one hour, chewed one dis- marginal). Finally, the amounts of plaque reduction (base-
closing tablet (Svenska Dentorama AB, Stockholm, Sweden) line minus post-plaque removal amounts) were calculated
(Figure 1) and rinsed their mouth with water, according to the and mean reduction in the whole mouth plaque, interdental
manufacturer's instructions. Next, they underwent a baseline and marginal plaque scores were compared between the two
plaque examination using the Rustogi Modified Navy Plaque sequences.
Index. This index enables the examiner to evaluate and record
the amount of dental plaque at both marginal areas and inter-
1.5 Fluoride assessment in interdental plaque
proximal areas of the tooth.20 Also, samples of interdental
plaque were collected for fluoride analysis, using a dental For measurement of fluoride content of dental plaque, sam-
floss. Afterward, they brushed for three minutes with their pling was done as follows: 1) Lips and buccal mucosa was
assigned toothbrush with 1.5 g of toothpaste, which was pre- retracted using a sterile lip retractor. 2) The participant was
weighted, and then rinsed with 30 mL of tap water for 10 sec- asked to swallow saliva just before plaque sampling to min-
onds. Flossing followed for two minutes and then they just imize saliva contamination of the dental plaque. 3) Dental
spat out. Thereafter, the participants again chewed one dis- plaque was collected from the interdental surfaces between
closing tablet in order to disclose any remaining plaque. The premolars and molars using a 30-centimeter fluoride-free
MAZHARI ET AL. 827

FIGURE 2 Flowchart of the study design

Japan). The weight of collected dental plaque (WP ) was cal-

culated as follows:

WP =W2 − W1

Then, the amount of fluoride in plaque was determined

using an ion selective fluoride electrode (Metrohm Co.,
Herisau, Switzerland) after extraction with 0.5 M HClO4 ,
which was buffered with TISAB II (Total Ionic Strength
Adjusting Buffer solution [JENEWAY, England]). The mass
of fluoride of each sample was divided by plaque weight and
the result was presented as ppm. The difference of the amount
of fluoride before and after plaque removal was compared
between the two sequences.
FIGURE 3 Schematic illustration of the RMNPI plaque record-
ing index. The RMNPI scores plaque as either present (score = 1) or 1.6 Statistical methods
absent (score = 0). Whole mouth = Areas A, B, C, D, E, F, G, H, and I;
Marginal = Areas A, B, and C; Interdental = Areas D and F Statistical analysis was performed using the Statistical Pack-
age for the Social Sciences (SPSS) software, version 16. Data
were presented as mean ± SD. The normal distribution of the
dental floss and placed inside Eppendorf containers (Figure 1) data was tested using the Kolmogorov-Smirnov test. Mixed
containing 1 ml distilled water. Each Eppendorf containing Model was used to compare the reduction of dental plaque
piece of dental floss and distilled water were weighted before and the increase of fluoride concentration in plaque between
(W1 ) and after plaque sampling (W2 ) using an electronic the two sequences. Level of significance was considered at
balance (Libror AEU-210, Shimadzu Corporation, Kyoto, P < 0.05.
828 MAZHARI ET AL.

FIGURE 4 Comparison of the total, interdental and marginal plaque scores before and after plaque removal in the two groups

2 RESULTS In general, some dentists recommend flossing before brush-

ing and others suggest brushing first to clean the mouth from
Twenty-five participants with a mean age of 23.2±1.22 years large food particles and then flossing with the objective to
participated in this study. The minimum age was 21 and the focus more on eliminating interdental plaque. The current
maximum was 25. Twenty-three (92%) of the participants study was designed to discover which sequence is better and
were female and two of them (8%) were male. its results have shown that the usage of dental floss before
Total, interdental, and marginal plaque amounts before and brushing reduces the amount of interdental plaque signifi-
after mechanical plaque removal for the two sequences of the cantly more than after brushing.
study are shown in Figure 4. Figure 5 shows the mean fluoride It is probable that by using dental floss before brushing, the
concentration in dental plaque. The average of reduction of existing soft particles in the interdental area are pushed out
total, interdental, and marginal plaque and the increase in the by the floss and brushing immediately afterward can elimi-
fluoride concentration in sequences 1 and 2 are presented in nate those particles much easier. However, when we use den-
Table 1. tal floss after brushing, much of the particles that are being
Reduction of total and interdental plaque in the floss-brush removed by dental floss would stay in place. Moreover, in
group was significantly higher than the brush-floss group the floss-brush sequence, after brushing, the mouth is rinsed
(p = 0.001, p = 0.009 respectively). Although the amount and the washing procedure further helps to better eliminate
of marginal plaque in both groups was reduced after plaque plaque. However, in the brush-floss sequence, usually the
removal, the difference between the two groups was not signif- washing procedure is not done after flossing, which justifies
icant (p = 0.2). Increase fluoride concentration of interdental the existence of more amounts of interdental plaque residue.
plaque was also significantly higher in the floss-brush group In a similar study done by Turkzaban et al., they studied the
than the brush-floss group (p = 0.027). effect of the sequence of brushing and dental floss on plaque
control and gingival inflammation.5 Their study results also
showed that using dental floss before brushing provides more
3 DISCUSSI O N statistically significant reduction in plaque amount on teeth,
although it did not significantly affect the amount of gingival
In the present study, we aim to clarify whether the sequence of inflammation. In their study, the difference of plaque reduc-
toothbrushing and flossing would influence interdental plaque tion was significant only among men. They explained this sit-
amount and fluoride retention. uation by stating that females have better oral health habits
and they would thus performed oral health behaviors more
rigorously regardless of the brushing and flossing sequence.
a) The effect of the sequence of toothbrushing and flossing In our study, almost all of the participants were female, thus
on reducing interdental plaque. it was not possible to compare between the two genders.
MAZHARI ET AL. 829

FIGURE 5 Comparison of the fluoride concentration of interdental plaque before and after plaque removal in the two groups

TABLE 1 Mean ± SD of reduction of the total, interdental, and marginal plaque scores and increased fluoride concentration before and after
plaque removal in the two groups
Measured parameters Floss-Brush (Mean ±SD) Brush-Floss (Mean ±SD) P valuea
Total plaque reduction 0.42 ± 0.13 0.35 ± 0.11 0.001
Interdental plaque reduction 0.61 ± 0.16 0.39 ± 0.19 0.009
Marginal plaque reduction 0.61 ± 0.17 0.59 ± 0.13 0.2
Increased fluoride concentration (ppm) 254.91 ± 265.98 130.71 ± 152.02 0.027
a
Comparison between the two groups was done using the mixed model.

However, if we would assume that females performed oral as in the interdental areas. Because both groups used similar
health habits more rigorously than males, significantly greater brushing methods and brush types, we could predict that there
reductions in interdental plaque in our study could place an would not be any significant differences in either method. Per-
even more emphasis on the importance of the floss-brush haps because of this issue, in Turkzaban et al.’s study the order
sequence. Of course, methods for dental plaque assessment in of brushing and flossing had no effect on gingival inflamma-
these two studies were different. In Turkzaban et al.’s study,5 tion, because the plaque adjacent to the gingival that causes
PCR and PI indices based on Silness and Loe's method21 were gingivitis was removed similarly in the sequences.
used, whereas in the current study the RMNPI was used.
b) The effect of the sequence of toothbrushing and flossing
In this study, aside from evaluating interdental plaque,
on increasing interdental plaque fluoride retention.
the amount of whole mouth plaque and marginal plaque
was examined. The whole mouth plaque, similar to interden- Fluoride application in decay prevention has been approved
tal plaque was significantly reduced more in the floss-brush in many studies.18,22,23 Fluoride can increase the resistance
group than the brush-floss group. However, no significant of teeth to acid because of incorporation into the enamel
difference was observed regarding the amount of marginal minerals.24 Fluoride increases the protein absorption in cells
plaque. Considering the fact that interdental plaque is counted and results in a reduction in the ability of oral bacteria to
as part of the total plaque, its reduction will affect the total growth and metabolism in an acidic environment.24 Fluoride
plaque amount. also plays a direct role in reducing the activity of cariogenic
Regarding marginal plaque (A to C) because it is adjacent bacteria by preventing the phenomenon of glycolysis in sac-
to interdental areas (D and F), we supposed that it could have charolytic bacteria.25 It prohibits polysaccharide absorption
been affected by the sequence of brushing and flossing; how- and degradation by the bacterial cell.24
ever, it was not the case. It is probable that areas are mostly It has long been proven that a therapeutic agent, in order
cleaned by brushing, so using dental floss is not as effective to be effective, needs to reach the targeted sites and remain
830 MAZHARI ET AL.

there.26 Accordingly, in order to benefit from fluoride, it needs The time of exposure of plaque to fluoride is also another
to be present in the targeted area, that is, plaque-enamel inter- influencing factor. The studies have shown that the gen-
face. Literature has shown that the application of topical flu- eral concentration of plaque fluoride and penetration of flu-
orides, such as daily use of fluoridated toothpastes and den- oride inside the plaque depends on the contact duration with
tal floss can prevent dental caries.27–29 In fact, they combine fluoride.36,37 For example, while using NaF solution for 30
the removal of dental plaque with the cariostatic effect of minutes, fluoride reaches deep into the plaque and this means
fluoride.30 It has been well established that plaque, after flu- that even in thick biofilm plaque (more than 1 mm), if given
oride exposure, serves as a reservoir for fluoride that releases sufficient time, fluoride penetration into the deeper layers of
its contents into oral fluids and maintains a prolonged pro- plaque is possible.35 However, in the routine process of oral
tective effect against dental caries.28,31,32 Fluoride concen- hygiene, this amount of time is not practical; but some studies
tration has been shown to be much higher in plaque than have shown that contact with fluoride for 120 seconds causes
in saliva and this is of utmost importance because of the higher concentrations of fluoride in plaque compared with 30
close relationship and proximity of plaque with the enamel seconds of contact.35,38 In the present study, all the partici-
surface.33 pants brushed for 3 minutes.
Many studies have shown that there is a direct relationship The water rinsing time and duration after brushing also
between the fluoride concentration of toothpaste and reduc- have an effect on residual fluoride in plaque. Studies have
tion of dental caries.22,27,34 For example, in one study, a flu- shown that immediate water rinsing of the mouth after brush-
oride level above 0.04 ppm in the fluids around the teeth ing with fluoridated toothpaste greatly reduces the amount
has been related to risk reduction of tooth decay in some of fluoride in the mouth.39–43 Because the mouth is usually
clinical studies.34 Also, in another study the required fluo- rinsed after brushing,44 and almost all the participants in our
ride concentration to prohibit activities of acidogenic bac- study stated that they routinely washed their mouth with about
teria ranged from less or equal to 10 ppm to less or equal two handfuls of water (excessive for this purpose), to stan-
to 190.35 In Watson et al.’s study it was obvious that if the dardize and decrease the amount of water, we decided that the
exposure time of plaque to fluoride was more than 30 sec- participants should rinse with 30 ml of water, which is almost
onds, such a concentration of fluoride in plaque would be less than twice commonly used.
manifested.35 In the present study, the fluoride concentra- Finally, the results of this study revealed that the floss-brush
tion that existed in the interdental plaque in the floss-brush sequence leads to a higher level of fluoride residue in inter-
group was 551.8 ppm and in the brush-floss group it was dental plaque compared with the brush-floss sequence. It is
455.95 ppm, which are higher than those in the mentioned highly probable that dental floss application before brushing
study35 in which the exposure time to fluoride was 2 minutes. caused food particles to be eliminated and plaque thickness to
In the current study the brushing time with fluoride tooth- be reduced and increased toothpaste fluoride accessibility to
paste was 3 minutes, this was why we had a higher con- plaque residue. However, in the brush-floss method, in addi-
centration of fluoride in the plaque. The important point is tion to reduction of toothpaste fluoride accessibility and sub-
that these amounts are much more than the required minimal sequently less penetration in the interdental areas, the plaque
concentration of fluoride to prohibit activities of acidogenic surface layers were being eliminated because of the usage of
bacteria. dental floss after using toothpaste. Studies have shown that
There are many factors that affect the amount of fluoride when we have a short exposure time of plaque to fluoride, flu-
penetration into dental plaque and in this study the two groups oride is only able to penetrate into the surface layers and after
were matched according to them. One of the factors is tooth- that it is able to penetrate deeper.35,36 Therefore, less fluoride
paste fluoride concentration and because individuals in the level in the brush-floss sequence is justifiable. Considering the
study did not have a high risk for caries, we used toothpaste fact that this study has been conducted for the first time, there
with 1450 ppm fluoride for all participants, which is counted is no similar study to compare it with.
as a standard concentration of fluoride in toothpaste. In addi-
tion, fluoride compounds used in toothpaste (sodium fluo-
ride vs. sodium monofluorophosphate) may be effective on 3.1 Limitations
the amount of fluoride residue on plaque. Duckworth et al.’s This study was done on dental students who have sufficient
study has shown that toothpaste containing NaF is more effec- skills in using a toothbrush and dental floss; the findings
tive than toothpaste containing Na2 PO3 F in increasing plaque would be more generalizable if the sample included people
fluoride concentration by 31 to 39%.26 However, in Naumova from the general population. Further, there was a chance that
et al.’s study they did not observe any difference between these the efficacy of using dental floss before brushing would be
two types of fluoride combinations.36 In the current study, more evident if this study was done on people with improper
all the subjects used toothpaste containing Na2 PO3 F and the contacts between their teeth, which cause food impaction.
results have shown its effectiveness. Also, because most male dental students did not consent to
MAZHARI ET AL. 831

participate in the study, almost all participants were female 10. Bruzda-Zwiech A, Filipińska R, Borowska-Strugińska B,
and we could not compare the effect of order of brushing and Żądzińska E, Wochna-Sobańska M. Caries experience and
flossing between two genders. distribution by tooth surfaces in primary molars in the pre-
school child population of lodz, poland. Oral Health Prev Dent.
2015;13:557–566.

4 CONC LU SI ON 11. Van der Weijden F, Slot DE. Oral hygiene in the prevention of
periodontal diseases: the evidence. Periodontol 2000. 2011;55:104–
123.
The results of the study revealed that flossing followed by
12. Sälzer S, Slot DE, Van der Weijden FA, Dörfer CE. Efficacy of inter-
brushing provided statistically significantly greater reductions
dental mechanical plaque control in managing gingivitis–a meta-
in interdental plaque and higher fluoride retention compared review. J Clin Periodontol. 2015;42:Suppl 16:s92–105.
to the group that used dental floss after brushing.
13. Van Loveren C. Antimicrobial activity of fluoride and its in
vivo importance: identification of research questions. Caries Res.
ACKNOW LEDGMENTS 2001;35(Suppl 1):65–70.
This study was based on a thesis (No. = 2663) written by 14. White DJ, Nelson DG, Faller RV. Mode of action of fluoride: appli-
Atieh Habibi submitted to the dental school in partial fulfil- cation of new techniques and test methods to the examination of the
ment of the requirements for the DDS degree. The authors mechanism of action of topical fluoride. Adv Dent Res. 1994;8:166–
would like to extend their appreciation to the vice chancel- 174.
lor for research of the Mashhad University of Medical Sci- 15. Stoodley P, Wefel J, Gieseke A, Debeer D, von Ohle C.
ences (MUMS) for the financial support of this work. Also, Biofilm plaque and hydrodynamic effects on mass transfer, flu-
oride delivery and caries. J Am Dent Assoc. 2008;139:1182–
we extend our appreciation to the Kerman University of Med-
1190.
ical Sciences, Kerman, Iran, for providing the laboratory
16. Sarner B, Lingstrom P, Birkhed D. Fluoride release from naf- and
solutions. The authors declare that they have no conflicts of
amf-impregnated toothpicks and dental flosses in vitro and in vivo.
interest in connection with this paper. Acta Odontol Scand. 2003;61:289–296.
17. Duckworth RM, Morgan SN, Burchell CK. Fluoride in plaque fol-
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