The Effect of Needle-free Injection System on Dental Injection Pain in Children: A Cross-over, Randomized Clinical Trial
Phase: NA
Conditions: Anesthesia, Local, Child Behavior, Pain
Sponsor: Marmara University

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial  
2. 
3. Materials and Methods 
 
3.1 Study design 
The present cross-over randomised clinical trial follows the Consolidated Standards of 
Reporting Trials (CONSORT) [Kaynak] guidelines and was performed at Marmara University, 
Shool of Dentistry, Department of Pediatric Dentistry clinics (Türkiye). The trial complies with 
the requirements set forth by the World Health Organization (WHO) and the International 
Committee of Medical Journal Editors (ICMJE). 
 
3.2 Study population 
The study population consisted of 28 children, aged 6 to 12 years of both genders who met the 
criteria were recruited for the study. The inclusion criteria were; children with good general 
health without any history of allergic reactions as determined by a written history; not currently 
taking any analgesics or sedative medication that would alter their pain perception; children 
demonstrated either ‘positive’ or ‘definitely positive’ behaviour according to the Frankl 
Behavior Scale (FBS); requiring treatment on their maxillary primary molars bilaterally with 
similar operative difficulties. The exclusion criteria were the existence of medical or 
developmental situations, history of chronic disease, ‘negative’ or ‘definitely negative’ 
behavior rating according to the Frankl Behavior Scale (FBS), and the presence of inflammation 
at the injection site. 
 
3.3 Procedure 
The study was conducted by two expert pediatric dentists. One of them gave all explanation, 
spoke with the children and carried out the anesthesia procedure and did the treatment procedure 
(FE) and the other (SP) was observing and assessing the children’s pain perception. 
In this study’s cross-over design, children received both types of injections before 
filling/pulpotomy treatment on their maxillary primary molars in two separate appointments 
with a minimum interval of at least 1 week between procedures, on a side of the dental arch 
with the use of a needle free injection and on the other side with the traditional syringe. Type 
and sequence of administration to each individual were randomly assigned (using a coin). All 
dental equipment were introduced using ‘tell-show-do technique. A total of 56 procedures were 
performed and divided into 2 groups according to the anesthesia technique. Non of the children 
have undergone any previous dental local anesthetic experience, in order to be not influenced 
by a positive or negative memory. 
3.3.1 Injection with the needle-free (NF) system 
The device used for needle free system was Comfort-in™ (Mika Medical Global Co, Busan, 
Korea) anesthesia device (Figure 1). The Comfort-in™ system, has a micro-hole injection 
needle (0.15 mm) that injects the anesthetic solution under the mucosa. The pressure can be 
controlled according to the dose of the drug to be used, thereby reduced the pain that may occur 
with the needle in the injection. Before the injection procedure, the children were demonstrated 
the popping sound produced by device to prevent reflex reactions, and they informed that they 
would feel as if their gum were punched. The NF injection device was prepared according to 
the manufacturer's instructions, placed in full contact with the buccal mucosa and a pre- 
withdrawn dose of 0.1 ml was applied to the buccal region for topical purposes by the pushing 
the top of the device. After 10-15 seconds, the same procedure was repeated with withdrawn 
dose of 0.3 ml. After 5 min the treatment commenced, and the children were instructed to raise 
their hand if they experienced pain during the procedure. Each time the child indicated pain, in 
accordance with the same protocol an additional 0.3 ml of anesthetic solution was administered, 
until the sufficient anesthetic effect was obtained and the final amount of anesthetic solution 

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial 
 
were recorded. Precautions were taken to prevent tissue ballooning. After the treatment,   
duration of the analgesia effect (min) were also recorded. The presence of post-operative pain  
in patients was assessed via a phone call 1 day after the procedure. 
3.3.2 Injection with the traditional method (TM) 
The TM was used with traditional syringe on the opposite side of the dental arch. The injection 
site was dried with a cotton-tip applicator, and topical anesthetic spray (Lidocaine 10%, 
Vemcain, Turkey) was applied to the injection area with cotton-tip for 1-2 min. The traditional 
injection was performed with a 26-gauge, 40-mm, disposable syringe with a needle (Genject, 
Turkey). The depth of penetration was only a few millimeters and 0.3ml of anesthetic solution 
was deposited. After 5 min the treatment commenced, and the children were instructed to raise 
their hand if they experienced pain during the procedure. Each time the child indicated pain, in 
accordance with the same protocol an additional 0.3 ml of anesthetic solution was administered, 
until the sufficient anesthetic effect was obtained and the final amount of anesthetic solution 
were recorded. Precautions were taken to prevent tissue ballooning. After the treatment, 
duration of the analgesia effect (min) were also recorded. The presence of post-operative pain 
in patients was assessed via a phone call 1 day after the procedure. 
Both NF and TM anesthesia techniques were performed with 4% articaine hydrochloride with 
1/100,00 epinephrine (Ultracaine D-S forte, Hoechst Canada Inc., Montreal Queebec, Canada) 
as an anesthetic agent. 
 
3.3.3 Subjective assessment 
Pain levels were subjectively evaluated using the Wong-Baker Faces Pain Rating Scale (WB 
PRS) (Wong DL, 1988), which measures the unpleasantness or affective dimension of a child’s 
pain experience. The PRS consists of a set of cartoon faces with varying facial expressions 
ranging from a smile/laughter to tears, and each child is asked to select the facial expression 
that best represents his/her experience of discomfort. Each face has a numerical value ranging 
from 0 (smiling face, ‘no hurt’) to 5 (crying/screaming face, ‘hurts worst’). This scale was 
explained to the children carefully in advance. Immediately after the each injection, the children 
were asked to rate the level of pain perceived during the administration, using the PRS. 
 
3.3.4 Objective assessment 
Pain level also objectively evaluated by the operator using the Face, Legs, Activity, Cry, 
Consolability (FLACC) Scale. (Merkel SI, 1997) This scale includes the following points: face, 
leg, activity, cry and consolability. Each one of these five categories records either 0, 1, or 2 
which result in either a minimum degree of 0 or a maximum degree of 10. According to this 
scale: 0 = quiet and relaxed (no pain), 1–3 = mild discomfort or pain, 4–6 = moderate pain, and 
7–10 = severe pain. 
 
3.4 Data collection 
A structured form was designed to collect information regarding 
(1) patient’s age; 
(2) gender; 
(3) type of teeth injected 
(4) type of dental treatment (filling or pulpotomy); 
(5) total amount of local anesthetics (LAs) used (ml) 
(6) duration of the analgesia effect (min) 
(7) post-op pain (after one day) 
(8) score on WB PRS after injection 
(9) score on FLACC during injection. 

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial 
Statistical Analysis 
Post hoc power analysis was conducted for the study and the results of the comparison between 
the injection systems and Wong Baker scores were evaluated. According to this, with a total 
data set of 28 individuals, consisting of two independent groups and two dependent 
measurements, the power of the study was found to be 0.94 according to the G*Power 3.9.1.4 
program, based on the partial eta squared (η²) value of 0.108 obtained with a 0.05 error margin 
from the repeated measures ANOVA. The data were statistically analyzed using SPSS software 
(version 15.0, SPSS). Paired t-tests or Wilcoxon nonparametric tests were used to compare data 
within groups over two time periods, according to check the distribution whether normally 
distributed or not. The Chi-square test (X²-test) was also used to compare discrete random 
variables. Spearman’s Rho correlation coefficient was used to find any relationship between 
two continuous variables. A p-value ≤ 0.05 was considered statistically significant. 
 
4. Results 
Total of 28 children, consisting of 18 girls (64.3%) and 10 boys (35.7%) aged 6–12 years were 
involved in this study. Mean age was 8.07 years with a standard deviation of 1.41 years. At the 
end of this study, a total of 56 injections were obtained for 28 children as NF injection (n = 28) 
and TM injection (n = 28). 
 
In the study, when the distributions of the parameters (gender, type of dental treatment, type of 
teeth, and post-operative pain) were evaluated according to the type of injection technique, it 
was found that there was no statistically significant difference between the groups. (Table 1) 
 
 
Table 1. Distribution of injection techniques based on evaluation parameters 
Variables 
Needle Free (NF) 
n 
Traditional 
Method (TM) 
n 
Total 
p 
Gender 
Girl 
18 
18 
36 
1,000 
Boy 
10 
10 
20 
Type of dental 
Filling 
22 
14 
36 
0,051 
treatment 
Pulpotomy 
6 
14 
20 
Type of teeth injected 
1st primary molar 
2nd primary 
molar 
12 
16 
7 
21 
19 
37 
0,259 
Post-op pain (after 
one day) 
Pain 
5 
7 
12 
0,746 
No pain 
23 
21 
44 
*The Chi-square test (X²-test) was also used to compare discrete random variables. 
Accordingly Table 2, in the group that received Needle-Free anesthesia in the first session and 
Traditional Method in the second session, the Wong-Baker scores were 4.44±3.28 and 
1.55±0.88, respectively. On the other hand, in the group that received Traditional Method 
anesthesia in the first session, the WB score was 1.68±1.91, while in the Needle-Free anesthesia 
group, the WB score was 2.52±2.56. In both cases, regardless of the method of anesthesia 
applied first, no statistically significant difference was found in the two groups. In the FLACC 
scores, for the Traditional Method - Needle Free group significant change was observed (p = 
0.025) while for the Needle Free- Traditional Method group no statistically significant 
difference was observed (p=0.141). There were significant differences in the Amount of  
Anesthetic Solution (ml) and Duration of the Analgesia Effect (min) between the first and 
second visits for both injection methods, respectively as p=0.003 for NF-TM and p<0.0001 for 

10.04.2017 
 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial  
 
TM-NF groups. The amount of anesthetic solution used for the 1st visit NF injection was 
0,91±0,48 ml and 0,65±0,30 ml was for the 2 nd visit NF injection. These amounts were 
statistically lower than TM injection in both visits. In the first visit, the mean duration of the 
analgesia effect in the NF group was 85.00±39.05 min, whereas in the second visit, the mean 
duration for NF injection was found to be 90.26±43.25 min. In the TM group, the mean 
anesthesia duration for the first and second visits was 140.00±59.97 min and 130.00±50.74 min, 
respectively. Regardless of the visit in which it was first applied, the duration of the analgesia 
effect in the NF group was found to be statistically significantly shorter than in the TM group 
(p<0,001). 
 
Table 2: Comparison of the 1st visit and 2nd visit measurements for continuous random 
variables in Needle Free-Traditional Method and Traditional Method - Needle Free 
 
1st visit 
2nd visit 
p 
Wong Baker (WB) Scores 
Needle Free-Traditional Method 
Traditional Method - Needle Free 
4,44±3,28 
1,68±1,91 
1,55±0,88 
2,52±2,56 
0,056 
0,119 
FLAAC 
Needle Free-Traditional Method 
Traditional Method - Needle Free 
0,78±1,09 
0,21±0,41 
0,11±0,33 
0,68±0,67 
0,141 
0,025 
Amount of Anesthetic Solution (ml) 
Needle Free-Traditional Method 
Traditional Method - Needle Free 
0,91±0,48 
1,37±0,42 
1.62±0,38 
0,65±0,30 
0,003 
<0,0001 
Duration of the Analgesia Effect (min) 
Needle Free-Traditional Method 
Traditional Method - Needle Free 
85,00±39.05 
140,00±59,97 
130,00±50,74 
90,26±43,25 
0,001 
<0,001 
*paired t-test was used 
*Needle Free-Traditional Method group: 1st visit Needle Free and 2nd visit Traditional Method was used of injection. 
*Traditional Method - Needle Free group: 1st visit Traditional Method and 2nd visit Needle Free was used of injection 
Table 3: Wong-Baker and FLACC Scores in Needle Free-Traditional Method and 
Traditional Method - Needle Free groups based on gender 
 
 
Gender 
Needle Free-Traditional 
Method Group 
p 
Gender 
Traditional Method-Needle 
Free Group 
p 
1st visit 
Needle Free 
2nd visit 
Traditional 
Method 
1st visit 
Traditional 
Method 
2nd visit 
Needle 
Free 
Wong Baker 
Girl 
N=6 
4.1, (1.5-8.5) 
2, (0-2) 
0,141 
Girl 
N=12 
2, (0.5-2) 
1, (0-3.5) 
0,558 
Boy 
N=3 
4.1, (2-4) 
2, (2-2) 
0,18 
Boy 
N=7 
0, (0-4) 
2, (2-4) 
0,059 
FLACC 
Girl 
N=6 
0, (0-1.5) 
0, (0-0.25) 
0,414 
Girl 
N=12 
0, (0-0) 
0.5, (0-1) 
0,053 
Boy 
N=3 
1, (0-1) 
0, (0-0) 
0,180 
Boy 
N=7 
0, (0-1) 
1, (0-1) 
0,317 
*Wilcoxon nonparametric test was used 
*Needle Free-Traditional Method group: 1st visit Needle Free and 2nd visit Traditional Method was used for injection. 
*Traditional Method - Needle Free group: 1st visit Traditional Method and 2nd visit Needle Free was used for injection 
* The values are presented as Median, (Inter Quartile Range) 
 
In our study, which used a crossover design, we evaluated the effect of gender differences on 
Wong-Baker and FLACC scores for needle-free and traditional method injections administered 

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial 
in different sequences over two sessions. The analysis showed no statistically significant 
differences between the groups (Table 3). Similarly, present study evaluated the impact of the 
type and sequence of restorations (filling-filling, filling-pulpotomy, pulpotomy -filling) on 
Wong-Baker and FLACC scores for needle-free and traditional method injections administered 
in different sequences over two sessions. Results demonstrated that there were no statistically 
significant differences between the groups (Table 4). 
Table 4: Wong-Baker and FLACC Scores in Needle Free-Traditional Method and 
Traditional Method - Needle Free groups based on type of dental treatment 
 
Type of Dental 
Treatment 
Needle Free-Traditional 
Method Group 
p 
Type of Dental 
Treatment 
Traditional Method-Needle 
Free Group 
p 
1st visit 
Needle Free 
2nd visit 
Traditional 
Method 
1st visit 
Traditional 
Method 
2nd visit 
Needle Free 
Wong 
Baker 
Filling-Filling 
N=4 
7, (3-9.5) 
2, (0.5-2) 
0,109 
Filling-Filling 
N=8 
2, (0.5-2) 
2, (0.5-5.5) 
0,167 
Filling- 
Pulpotomy 
N=3 
4, (2-4) 
2, (0-2) 
0,180 
Filling- 
Pulpotomy 
N=2 
0, (0-0) 
1, (0-1) 
0,317 
Pulpotomy- 
Filling 
N=2 
1, (0-1) 
2, (2-2) 
0,317 
Pulpotomy- 
Filling 
N=9 
2, (0-3) 
2, (0-4) 
0,655 
FLACC 
Filling-Filling 
N=4 
0.5, (0-2.5) 
0, (0-0) 
0,180 
Filling-Filling 
N=8 
0, (0-0) 
1, (0-1) 
0,096 
Filling- 
Pulpotomy- 
N=3 
1, (0-1) 
0, (0-0) 
0,180 
Filling- 
Pulpotomy- 
N=2 
0, (0-0) 
0.5, (0-0.5) 
0,317 
Pulpotomy- 
Filling 
N=2 
0, (0-0) 
0.5, (0-0.5) 
0,317 
Pulpotomy- 
Filling 
N=9 
0, (0-1) 
1, (0-1) 
0,257 
*Wilcoxon nonparametric test was used 
*Needle Free-Traditional Method group: 1st visit Needle Free and 2nd visit Traditional Method was used for injection. 
*Traditional Method - Needle Free group: 1st visit Traditional Method and 2nd visit Needle Free was used for injection 
* The values are presented as Median, (Inter Quartile Range) 
*filling-filling group: 1st visit filling and 2nd visit filling restoration have been done 
*filling-pulpotomy group: 1st visit filling and 2nd visit pulpotomy restoration have been done 
*pulpotomy-filling group: 1st visit pulpotomy and 2nd visit filling restoration have been done 
Table 5. Amount of Anesthetic Solution (ml) in Needle Free-Traditional Method and 
Traditional Method - Needle Free groups based on type of dental treatment 
 
Type of 
Dental 
Treatment 
Needle Free-Traditional Method 
Group 
p 
Type 
of 
Dental 
Treatment 
Traditional Method-Needle Free 
Group 
p 
1st visit Needle 
Free 
2nd visit 
Traditional 
Method 
1st visit 
Traditional 
Method 
2nd visit 
Needle Free 
Amount of 
Filling- 
0,65, (0.325- 
1.3, (1.05- 
0,068 
Filling- 
1.1, (1-1.85) 
0.55, (0.325-0.9) 
0,012 
Anesthetic 
Filling 
1.125) 
1.85) 
Filling 
Solution 
N=4 
N=8 
(ml) 
Filling- 
0.9, (0.3-0.9) 
2, (1.5-2) 
0,180 
Filling- 
1.4, (1.3-1.4) 
1, (1-1) 
0,180 
Pulpotomy- 
Pulpotomy- 
N=3 
N=2 
Pulpotomy- 
1.35, (1.2-1.35) 
1.75, (1.5- 
0,180 
Pulpotomy- 
1.5, (1.1-1.85) 
0.6, (0.3-0.9) 
0,008 
Filling 
1.75) 
Filling 
N=2 
N=9 
*Wilcoxon nonparametric test was used 
*Needle Free-Traditional Method group: 1st visit Needle Free and 2nd visit Traditional Method was used for injection. 
*Traditional Method - Needle Free group: 1st visit Traditional Method and 2nd visit Needle Free was used for injection 
* The values are presented as Median, (Inter Quartile Range) 
*filling-filling group: 1st visit filling and 2nd visit filling restoration have been done 
*filling-pulpotomy group: 1st visit filling and 2nd visit pulpotomy restoration have been done 
*pulpotomy-filling group: 1st visit pulpotomy and 2nd visit filling restoration have been done 
Table 5 showed the evaluation whether the type and sequence of different restorations administered in 
different sequences over two sessions with needle-free and traditional method 

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial  
 
injections resulted in any differences in the amount of anesthetic solution used. The results 
indicated a significant difference in the amount of anesthetic solution used in the group that 
received TM injection in the first session and NF injection in the second session, the group that 
received filling in both the first and second sessions, and the group that received pulpotomy in 
the first session and filling in the second session. A significantly lower amount of anesthetic 
solution was used in the NF injection in both groups (Table 5). 
 
According to Spearman’s Rho correlation coefficient test, no correlation was found between 
age and Wong Baker, FLACC scores, and the amount of anesthetic solution administered 
respectively (p=0,830, p=0,436, p=0,976). Similarly, no correlation was found between Wong 
Baker scores and the amount of anesthetic solution administered (p=0,537) and Wong Baker 
scores and the duration of the analgesia effect (p=0,468). However, a negative correlation was 
found between the FLACC score and the amount of anesthetic solution (p=0,033). Moreover a 
positive correlation was found between the FLACC score and Wong Baker scores as well as 
between the amount of dose administered and duration of analgesia effect respectively 
(p=0,000, p=0,009). 
 
Informed Consent Form (English) 
 
VOLUNTARY CONSENT FORM 
I have read the text above, which shows the information that should be given to the volunteer before 
the study. I have been given written and verbal explanations about these. Under these conditions, I 
agree to participate in this clinical trial voluntarily and without any pressure or coercion. 
 
Volunteer 
Name-surname 
Address (telephone no., fax no., if available, ...): 
 
Signature: 
 
 
For those under custody or guardianship, the name and surname of the parent or guardian: 
address (telephone no., fax no., if any,...): 
 
Signature: 
 
 
Name-surname and signature of the researcher who made the explanations: 
 
 
Organization official who witnessed the consent process from the beginning to the end 
 
name-surname: position: 
 
Signature: 
 

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial  
 
Declaration of the Participant/Patient 
I was informed by Dr. Figen Eren Giray that medical research would be conducted at Marmara 
University Faculty of Dentistry, Department of Pedodontics and I was given the above information 
about this research. After this information, I was invited as a "participant" (subject) in such research. 
If I participate in this research, I believe that the confidentiality of my personal information, which 
should remain between me and the physician, will be treated with great care and respect during this 
research. I have been given sufficient confidence that my personal information will be carefully 
protected during the use of the research results for educational and scientific purposes. 
I can withdraw from the research without giving any reason during the conduct of the project. 
However, I am aware that it would be appropriate to inform the researchers in advance that I will 
withdraw from the research in order not to leave them in a difficult situation. I am also aware that I 
can be removed from the research by the researcher in order to avoid any damage to my medical 
condition. I do not assume any financial responsibility for the expenses to be incurred for the 
research. I will not be paid. I have been given the necessary assurance that any medical intervention 
will be provided in the event of any health problem that may arise, whether directly or indirectly, as 
a result of the research. I know that I will not be under any financial burden regarding these medical 
interventions. If I encounter a health problem during the research; I know that I can call Dr. Figen 
Eren Giray at the Department of Pedodontics, Faculty of Dentistry, MÜ. Faculty of Dentistry and at 
02164211621/1542 I do not have to participate in the research and I cannot participate. I have not 
encountered any coercive behavior about my participation in the research. I also know that it will not 
bring any harm. 
I have understood all the explanations given to me in detail. After a period of reflection on my own, 
I have made the decision to take part in this research project as a "participant". I accept the invitation 
to do so with great satisfaction and voluntarily. I will be given a copy of this signed form. If I refuse 
to take part, I understand that this will not affect my medical care and my relationship with the 
physician.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial 
 
GÖNÜLLÜ BİLGİLENDİRME FORMU 
 
 
Objective: To evaluate the anesthetic effect of a needle-free injection system in children using 
different methods in clinical to be evaluated as 
 
The method to be used in the study: 
The success of treatment in pediatric dentistry depends on the child's lack of pain and cooperation. 
Fear of pain is an important barrier to dental treatment and this may negatively affect general health. 
The first method used for this purpose is to numb the tooth with local anesthesia (LA) before 
treatment. 
 
In this procedure, your child's teeth will be numbed so that the necessary dental treatment can be 
carried out painlessly. For this purpose, the teeth will be numbed before the treatment of two baby 
teeth using two different methods. In one of the sessions, a routine injection will be used. 
In the other, the tooth to be treated will be numbed using a needle-free injection system. Whether the 
teeth are numb before the treatment will be checked by lightly pricking the probe into the gum, if the 
numbness is not complete, additional numbing will be done with injection application and dental 
treatment will continue after the numbness is completely achieved. There may be a slight bleeding in 
the gum during the pricking of the probe. If pain is felt again despite additional numbing during 
dental treatment, your child will be asked to raise his/her hand and numbing will be done again with 
injection. 
To assess the fear and anxiety your child feels during both LA methods, a picture with facial 
expressions will be shown and he/she will be asked to show how he/she feels by choosing one of the 
facial expressions. Before and during the procedure, a pulse oximeter device that can measure pulse 
and oxygen saturation (SpO2) values will be attached to the finger and the values will be recorded. 

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial  
 
Side effects and negative effects that may occur as a result of participating in the study: 
 
Your child may experience anxiety, pain and bleeding gums during numbing of the tooth before the 
treatment, the gums may bleed when the probe is gently inserted into the gums during numbness 
control, and sores on the cheek, lips or tongue may occur as a result of your child scratching, biting 
or chewing the numb area after numbing. 
 
Depending on the medication used during anesthesia, systemic reactions such as syncope, allergic 
reaction 
complications may occur. 
 
With needle injection, complications such as needle breakage, infection or emphysema (swelling) 
can occur. 
 
In the needle-free injection system, there may be a bitter taste if the solution is sprayed into the 
mouth, and slight bleeding of the mucosa may occur if it is administered in a different angle.

10.04.2017 
The Effect of Needle-free Injection System on Dental Injection Pain in 
Children: A Cross-over, Randomized Clinical Trial  
 
Privacy: 
The names of the individuals participating in the research will be kept confidential and will not be 
disclosed without their consent.