The Effectiveness of Water Flossing Versus Regular Flossing for Oral Hygiene in Children Aged 10-15 Years: A Randomized Clinical Trial
Phase: NA
Conditions: Plaque Accumulation
Sponsor: King Abdulaziz University

Date: 31 / 12 / 2024 
The Effectiveness of Water Flossing Versus Regular 
Flossing for Oral Hygiene in Children Aged 10-15 
Years: A Randomized Clinical Trial 
 
2. Materials and Methods 
2.1. Ethical Approval 
The study protocol was reviewed and approved by the Research Ethics 
Committee of the Faculty of Dentistry, King Abdulaziz University, Jeddah, 
Saudi Arabia (Approval No. 169-11-24). Written informed consent was 
obtained from all parents or legal guardians prior to participation, in 
accordance with the Declaration of Helsinki. 
2.2. Study Design 
This study was designed as a randomized, controlled crossover clinical trial. 
Each participant used both interdental cleaning methods, water flossing and 
regular flossing, in two separate visits with a 14-day washout period 
between interventions to minimize carryover effects. 
2.3. Study Setting 
The study was conducted at the College of Dentistry and the University 
Dental Hospital, King Abdulaziz University, Jeddah, Saudi Arabia. 
Participant recruitment and data collection took place between November 
2024 and April 2025. 
2.4. Sample Selection 
Participants were recruited using a convenience sampling approach from 
patients attending the College of Dentistry and the University Dental 
Hospital at King Abdulaziz University. Eligible participants who met the 
inclusion criteria were enrolled after obtaining informed parental consent. 
2.5. Randomization 
2.5.1. Sequence Generation 

Random allocation sequences were generated using an online 
randomization tool (https://www.randomizer.org). Two sets of random 
numbers were created, corresponding to the two intervention orders. 
2.5.2. Allocation Concealment 
Each allocation code was printed, cut into identical slips, and sealed in 
opaque envelopes. The envelopes were placed in a single container. Upon 
recruitment, each participant selected one envelope to determine their 
assigned intervention sequence. 
2.6. Blinding 
Due to the nature of the interventions, blinding of the participants and 
operators was not feasible. However, the statistician responsible for data 
analysis was blinded to the group assignments to minimize analytical bias. 
2.7. Inclusion and Exclusion Criteria 
The inclusion criteria included children aged 10-15 years, medically fit and 
systemically healthy, with no  active orthodontic treatment or space 
maintainer with no use of any type of dental floss within the previous 24 
hours. Children with fewer than four posterior proximal contacts were 
excluded from the study. 
2.8. Sample Size Calculation 
The sample size was calculated using G*Power software (version 3.1.9.7), 
based on the findings of Abdellatif et al., who compared the efficacy of water 
flossers and regular floss in plaque removal [13]. Assuming a power of 80%, 
a two-tailed significance level (α) of 0.05, and an effect size derived from the 
cited study, a total of 44 participants (22 per group) were required to achieve 
sufficient statistical power. 
2.9. Study Procedures 
Participants were screened according to the inclusion and exclusion criteria. 
Parents were informed that participation was voluntary and that all collected 
data would remain confidential and accessible only to the research team. 
Each participant was randomly assigned to start with one of the following: 
● 
Group A: Unflavored, unwaxed regular dental floss (Oral-B, 
USA)(Figure 1a), or 
● 
Group B: Water flosser (Waterpik Cordless Plus Water Flosser, 
USA)(Figure 1b). 

After the first visit, a 14-day washout period was observed before the 
crossover intervention was applied. 
At the first visit, demographic data (participant initials, age, and sex) and 
group allocation were recorded. A clinical examination was performed to 
assess the Plaque Index (PI) using the criteria of Silness and Löe (1964). All 
participants received standardized oral hygiene instructions, including 
brushing twice daily with the Modified Bass Technique using a soft-bristled 
toothbrush and fluoridated toothpaste. Participants received instructions on 
the proper use of the assigned interdental cleaning method and performed 
the procedure independently. 
The Plaque Index (PI) was recorded for all teeth according to the following 
criteria: 
● 
0: No plaque in the gingival area. 
● 
1: A film of plaque adhering to the free gingival margin and adjacent 
tooth area, detectable only by a probe. 
● 
2: Moderate accumulation of soft deposits visible to the naked eye 
within the gingival margin. 
● 
3: Abundant soft matter within the gingival pocket and/or along the 
gingival margin. 
At the second visit, participants switched to the opposite cleaning method 
(water flosser or regular floss), and plaque scores were reassessed using the 
same PI criteria. 
2.10. Statistical Analysis 
Descriptive statistics, including means, medians, standard deviations, 
interquartile ranges (IQRs), minima, and maxima, were calculated to 
summarize the data. Normality was assessed using the Kolmogorov-Smirnov 
test, and Levene’s test was conducted to evaluate the assumption of equal 
variances. Due to the violation of the normality assumption, the Wilcoxon 
signed-rank test was used for the comparison of plaque scores between water 
floss and regular floss. This test was also used for additional paired 
comparisons, including before and after flossing, anterior versus posterior 
teeth, maxillary versus mandibular arches, and right versus left sides. 
Linear regression analysis was used to assess the association between gender 
and plaque scores after flossing for each flossing method, with adjusted 

models controlling for age and number of surfaces flossed. The significance 
level was set at p-value = 0.05. All analyses were performed using Stata 
version 16.1 (StataCorp, College Station, TX). (a) 
 
Figure 1. Oral hygiene aids used in the study: (a) Regular dental floss (Oral-B, USA); 
(b) Water flosser (Waterpik Cordless Plus Water Flosser, USA). 
 
 
 
 
 
 
 
 
                  (a) 
                  (b) 

Consent Form  
Title of Research:  
 
The Effectiveness of Water Jet Floss and Interdental Flossing for Oral Hygiene in Children between 10 -15 
Years Old: A Randomised Clinical Trial 
 
Part I – Research Participant Information Sheet: 
A.  Purpose of the Research: 
This study aims to evaluate the effect of water floss 
and traditional dental floss on children's oral health. 
 
B.   Description of the Research:  
 
The process of cleaning teeth involves using a toothbrush with toothpaste. Some areas cannot be effectively 
cleaned using just a toothbrush, so it is necessary to use other tools like dental floss. There are devices that 
clean teeth in a manner similar to dental floss but use water, known as water flossers. These devices have 
proven effective in cleaning teeth for adults and orthodontic patients. The aim of this research is to present 
evidence-supported results regarding effective oral hygiene practices for children. By comparing the 
effectiveness of water flossing with traditional dental floss, this study helps identify the most effective 
method, which can influence recommendations for children's dental care. 
 
C.   Potential Risks and Discomforts:  
 
Bleeding gums, mild pain, and discomfort. 
 
D.   Potential Benefits:  
       
Cleaning teeth and teaching different 
methods for flossing, while choosing the most suitable one for the child. 
 
E.   Cost/s To participate in the research you will bear no additional costs or extra loss. 
 
 
F.  Compensation / Treatment: 
In the event of injury resulting from participation in this research study, Researcher will make a 
treatment to you, its facilities and professional attention. Financial compensation from KAUFD is 
not available. 

G.  Voluntary Participation: 
Participation in this study is voluntary.  You will suffer no penalty nor loss of any benefits to which you 
are otherwise entitled should you decide not to participate.  Withdrawal from this research study will not 
affect your ability to receive alternative methods of Dental care available at KAUFD. 
Significant new findings developed during the course of the research study which might be reasonably 
expected to affect your willingness to continue to participate in the research study will be provided to you. 
H.  Confidentiality: 
Your identity and medical record, as a participant in this research study, will remain confidential with 
respect to any publications that may result from this study.  Furthermore, your Dental/medical record may 
be reviewed by the Research Advisory Council or the agency sponsoring this research in accordance with 
applicable laws and regulations. 
 
I.  Contact Person(s): 
 
Dr. Abdalrahman M. Ainousa 
 
amainousa@kau.edu.sa
 
 
A signed copy of the consent form will be given to you. 
 
 
 
 
 
PART II - Authorization for performance of certain procedures: 
1.  I/surrogate authorize Dr. ____________________ and his/her associates to administer the following 
drugs, use the following devices or perform the following procedures during my treatment (or the 
treatment of the person named above for whom I am responsible) 
______________________________ 
 
2. I acknowledge that I have read, or had explained to me in a language I understand, the attached Research 
Participant Information sheet and that Dr. __________________________ has explained to me the nature 
of the procedures described in the Research Participant Information Sheet as well as any benefits to be 
expected, possible alternative methods of treatment, the attendant discomforts and risks reasonably to be 
expected and the possibility that complications from both known and unknown causes may arise as a 
result thereof.  I was given ample opportunity to comprehensively inquire about this study and procedures, 
and all my questions were answered to my satisfaction. 
 

3. I understand that I am not entitled for reimbursement for expenses incurred as a result of my 
participation in this study 
 
4.  I voluntarily accept the risks associated with the above-mentioned procedures with the knowledge and 
understanding that the extent to which they may be effective in my treatment (or the treatment of the 
patient named above, as the case may be) has not been established, that there may be side effects and 
complications from both known and unknown causes and that these procedures may not result in cure or 
improvement. 
5.  I understand that I am free to withdraw this consent and discontinue treatment with the above 
procedures at any time.  The consequences and risks, if any, which might be involved in the event I later 
decide to discontinue such treatment, have been explained to me adequately.  I understand that such 
withdrawal will not affect my ability to receive any dental/medical care made necessary by the 
performance of such studies or to which I might be otherwise entitled.