Comparative evaluation of anesthetic delivery systems on pain, anxiety, and physiological responses in pediatric dental patients: A randomized clinical trial

Abstract

Injection-related pain and anxiety remain major challenges in pediatric dental care and may negatively influence cooperation and future dental attitudes. This randomized clinical trial compared four anesthetic delivery techniques; conventional manual syringe, computer-controlled local anesthetic delivery (CCLAD), vibration-assisted injection, and needle-free jet injection, in 112 children (6–10 years) undergoing pulpotomy. Pain was measured with the Wong–Baker Faces Pain Rating Scale and FLACC; anxiety with Venham’s Picture Test; physiological responses with heart rate and oxygen saturation; cooperation with Houpt’s scale; and parental satisfaction by questionnaire. Outcomes were assessed at prespecified procedural phases and analyzed separately for mandibular and maxillary arches. During anesthesia administration the Manual syringe group consistently demonstrated higher self-reported pain (Wong–Baker), greater behavioral distress (FLACC), and higher Venham anxiety scores compared with the three alternative techniques (P ≤ 0.05 for key comparisons). CCLAD was associated with more stable attenuation of both subjective and behavioral pain and relatively lower autonomic responses (heart rate), particularly during anesthesia. Jet injection and Vibration-assisted techniques generally reduced distress relative to the Manual syringe but with some site-dependent variability. Oxygen saturation remained stable across all groups, and Houpt cooperation scores were similar across techniques. Parental satisfaction was significantly higher in the alternative technique groups than in the Manual syringe group (P ≤ 0.05). In conclusion, alternative anesthetic delivery systems reduce injection-related pain and anxiety in children compared with conventional manual syringe administration without compromising physiologic safety or treatment feasibility; among the tested devices, CCLAD showed the most consistent benefit. These findings support selective adoption of alternative delivery techniques to improve the pediatric dental experience. Injection-related distress in pediatric dentistry is technique-dependent and concentrated during local anesthetic administration. The findings of this study support the clinical use of alternative anesthetic delivery systems as effective strategies for reducing pain and anxiety in children without adversely affecting treatment feasibility or safety. Selection of an appropriate anesthetic delivery technique may improve the overall dental experience for pediatric patients, enhance parental satisfaction, and contribute to more positive long-term attitudes toward dental care.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-50368-7.

Introduction

Dental fear is a common emotional response to real or perceived threat associated with dental care and is particularly prevalent in children and adolescents, where it may reduce cooperation, encourage avoidance of care, and lead to poorer oral health outcomes^1–3. Fear of injections is one of the most frequently cited causes of dental anxiety in young patients and contributes substantially to treatment-related distress^4,5. Local anesthetic injections pose a clinical paradox: they are required to enable pain-free treatment yet the act of needle insertion and pressure from solution deposition are themselves important sources of pain and anxiety for many children⁶. This injection-centered distress can undermine the benefits of anesthesia, negatively affect the child’s behavior during the visit, and influence parental perceptions and future dental attendance^7–9.

Clinicians have long used several strategies to reduce injection-related discomfort, including topical anesthetics, warming of anesthetic solution, and finer needles; however, these measures show inconsistent benefit in pediatric populations and often do not fully address behavioral distress related to the injection itself^9–11. In recent years, device-based approaches have been developed to modify the mechanics or sensory input of injection and thereby reduce perceived pain. Vibration-assisted devices apply high-frequency mechanical stimulation at the injection site and are hypothesized to reduce pain via gate-control mechanisms¹². Computer-controlled local anesthetic delivery (CCLAD) systems regulate flow rate and injection pressure to minimize rapid tissue distention, while needle-free jet injectors eliminate needle puncture by delivering anesthetic via a high-pressure fluid jet^7,13.

Although clinical studies have evaluated individual technologies, the existing literature is fragmented. Several randomized trials and systematic reviews support reduced pain and improved acceptance with CCLAD compared with conventional syringe techniques, and multiple studies have reported variable benefits with vibration-assisted or needle-free systems in select settings^14–17. However, most prior trials have compared only two techniques at a time, used differing outcome sets (for example self-report alone or behavioral observation alone), or were limited by small samples or split-mouth designs^13,18,19. Consequently, direct head-to-head evidence comparing CCLAD, vibration-assisted, needle-free jet injection, and conventional syringe administration across the full range of subjective, behavioral, and physiologic outcomes in pediatric patients remains limited. This gap complicates informed decision making by clinicians and policy-makers who must weigh effectiveness, safety, and practical considerations when selecting anesthesia delivery approaches for children.

The primary aim of this randomized parallel-arm trial was to compare the effect of four anesthetic delivery techniques (conventional manual syringe, computer-controlled local anesthetic delivery (CCLAD), vibration-assisted injection, and needle-free jet injection) on child-reported pain during local anesthetic administration, with child-reported pain during anesthesia measured by the Wong–Baker Faces Pain Rating Scale designated as the primary outcome. Secondary objectives were to compare the four techniques with respect to observed behavioral pain and distress (FLACC), self-reported anxiety (Venham’s Picture Test), physiologic stress responses (heart rate and oxygen saturation), overall cooperation (Houpt scale), and parental satisfaction. The null hypothesis (H0) for the primary outcome was that there would be no difference in child-reported pain during anesthesia among the four techniques, and the alternative hypothesis (H1) was that at least one technique would differ from the others with respect to child-reported pain during anesthesia.

Materials and methods

Study Design, ethics, and setting

This randomized parallel-arm controlled trial was conducted to evaluate alternative local anesthesia methods compared to conventional syringe-based injection. The study was registered at ClinicalTrials.gov (NCT07106138) on 05/08/2025 and received ethical approval from the research ethics committee at Latakia University (approval number: 2487). All procedures were conducted in adherence with the principles outlined in the Declaration of Helsinki (2000 revision). The parents of all included children were informed about the study procedures, objectives, and protocol, and gave their written informed consent before the start of the study. All procedures were done in the Department of Pediatric Dentistry, Faculty of Dental Medicine, Latakia University, Lattakia, Syria, between April 2024 and April 2025. The reporting of this trial followed the CONSORT guidelines closely. Figure 1 illustrates the CONSORT flow diagram of participant recruitment, allocation, and analysis.

Fig. 1.

CONSORT 2010 flow diagram of participant recruitment, allocation, andanalysis. The flowchart shows participant flow, while arch-wise distribution of treated teeth is reported in Table 1.

Sample size estimation

The sample size was calculated using G*Power software (version 3.1.9.4; Heinrich Heine University Düsseldorf, Düsseldorf, Germany). The software is available at: https://www.psychologie.hhu.de/en/arbeitsgruppen/allgemeine-psychologie-und-arbeitspsychologie/gpower. G*Power software was used for a one-way ANOVA comparing four anesthetic delivery groups. The calculation was based on heart rate (HR) measured immediately after anesthesia in a previous randomized controlled trial comparing computer-controlled and traditional syringe techniques²⁰. In that study, the mean HR was 97.97 ± 1.87 bpm in the CCLAD group and 101.77 ± 8.09 bpm in the conventional syringe group (P = 0.009). Based on these values, the effect size (f) was estimated at 0.359. With a type I error (α) of 0.05 and a power (1–β) of 0.80, the minimum required sample size to detect significant differences among the four groups was 92 participants. To preserve statistical power under the possibility of dropouts or incomplete data, the sample size was conservatively increased by 20%, yielding a total target sample of 112 children (28 per group, 14 per arch). This inflation was used as an a priori planning assumption and did not reflect actual attrition in the final analysis. Heart rate was selected for sample size estimation as it represents an objective, continuously measurable physiological parameter with well-defined effect sizes in pediatric dental research, providing a conservative basis for detecting clinically relevant differences across anesthetic delivery techniques.

Participants

A total of 112 children were included in this study. All included participants met the following criteria:

• Aged 6 to 10 years old.

• Requiring a pulpotomy treatment in the lower or upper primary molars.

• Systematically healthy classified as ASA I or II.

• Demonstrating cooperative behavior during dental examination by being classified as positive or definitely positive on Frankl Behavior Rating Scale. On this scale, “Definitely Positive” indicates the child exhibits overtly positive behavior, such as smiling or laughing, while “Positive” indicates the child shows moderate acceptance of the procedure with verbal or physical signs of cooperation but without overt distress²¹.

• Patients with no prior experience with the study intervention.

Patients were excluded from the study according to the following criteria:

• Use of anxiolytics, analgesics, sedatives, or psychotropic drugs within 24 h prior to treatment.

• Patients with cognitive or developmental impairments affecting communication.

• Known allergy to local anesthetics or materials used in the study.

• Patients requiring emergency dental treatment.

• Presence of clinical or radiographic signs suggestive of irreversible pulpitis or necrosis in the study tooth, including spontaneous pain, swelling, sinus tract, abnormal mobility, furcation or periapical radiolucency, suppuration, or pathological internal or external root resorption.

• Advanced physiologic root resorption or an unrestorable tooth.

• Acute inflammation or abscesses at the site of injection.

Randomization, allocation, and blinding

Patient randomization was performed using a stratified block randomization method to ensure balanced allocation across intervention groups with respect to tooth location. Participants were first stratified according to the treated tooth (maxillary or mandibular primary molars). Within each stratum, block randomization with a fixed block size of four was applied to allocate participants equally to the four study groups. The randomization sequence was generated using a computer-based random number generator by an independent statistician not involved in patient recruitment, treatment, or outcome assessment.

Allocation concealment was achieved using sequentially numbered, opaque, sealed envelopes containing the group assignment for each participant. The envelopes were prepared by an independent researcher not involved in the conduct of the study and were opened immediately before treatment initiation, after confirmation of eligibility and acquisition of written informed consent.

Due to the distinct visual and operational characteristics of the anesthetic delivery systems, blinding of the operator and participants during real-time data collection was not feasible. To maintain separation between treatment delivery, outcome recording, and data analysis, the clinical procedures were performed by the treating pediatric dentist, real-time outcome measures were recorded by a trained postgraduate research assistant who was not involved in treatment delivery, and statistical analysis was performed by an independent statistician. Heart rate and oxygen saturation were captured electronically by the pulse oximeter and stored in the device log. Child self-report measures, including the Wong–Baker Faces Pain Rating Scale and Venham’s Picture Test, were administered at the prespecified time points and recorded immediately onto standardized case report forms. Behavioral measures, including FLACC and Houpt scores, were observed and documented live using predefined scoring sheets. After each treatment session, all paper forms and device logs were de-identified and assigned a study identification code that did not reveal group allocation or device type. Data entry, verification of recorded scores, and final statistical analyses were performed after de-identification by investigators blinded to group allocation. Any ambiguous behavioral entries or discrepancies identified during data verification were resolved by consensus between the blinded investigators. These procedures were used to preserve objectivity in outcome handling despite the unavoidable lack of blinding during treatment. The workflow is summarized in Supplementary Table S1.

Grouping

Eligible patients were randomly allocated into four equal groups (n = 28 per group). Each group included 14 maxillary primary molars and 14 mandibular primary molars:

1. Conventional manual syringe delivery group.

2. Vibration-assisted local anesthesia delivery group.

3. Needle-free jet injection group.

4. Computer-controlled local anesthetic delivery group.

Study intervention

Before the start of each treatment session, patients were seated comfortably in the dental chair and eligibility criteria were reconfirmed. All clinical procedures were performed by the same experienced pediatric dentist to ensure procedural standardization and to minimize operator-related variability. To standardize the dental procedure across the four study groups, only maxillary or mandibular primary molars indicated for pulpotomy were included. The indication for pulpotomy was confirmed after clinical and radiographic examination by the treating pediatric dentist. Teeth were considered eligible when they were vital and restorable, had deep carious lesions or carious pulp exposure consistent with normal pulp or reversible pulpitis, and showed no clinical or radiographic signs of irreversible pulpitis or necrosis. Specifically, teeth with spontaneous pain, swelling, sinus tract, abnormal mobility, furcation or periapical radiolucency, or pathological internal or external root resorption were excluded. Teeth with advanced physiologic root resorption or an unrestorable crown-root condition were also excluded. These selection criteria were based on current pediatric pulp therapy guidance, which recommends pulpotomy only for vital primary teeth with appropriate clinical and radiographic findings. Rubber dam isolation and placement of a full-coverage stainless steel crown were planned as part of the restorative protocol in accordance with guideline-based standards for vital pulp therapy in primary molars^22,23.

Prior to the initiation of treatment, all dental instruments and materials were introduced to the child using the tell-show-do behavior management technique. Rapport and trust were established during the initial phase of the appointment to minimize procedural anxiety.

Local anesthesia was administered according to the patient’s assigned intervention using one 1.8 mL cartridge of 2% lidocaine with epinephrine 1:100,000 (see supplementary table S1). After anesthesia administration, a standardized latency period was observed before rubber dam placement and initiation of treatment. No outcome measures were collected during the latency period; all assessments were recorded only at the predefined time points specified in the outcome section. Efforts were made to maintain an efficient treatment flow without compromising clinical quality, with a typical treatment duration of approximately 30 to 40 min. The treatment session was considered complete upon placement and finishing of the final restoration using stainless steel crowns.

Anesthesia delivery systems

Conventional manual syringe delivery group

Topical anesthetic gel (20% benzocaine) was applied to the injection site using a cotton roll for 60 s following gentle drying of the oral mucosa⁶. Local anesthesia was administered using a standard dental aspirating syringe. One 1.8 mL cartridge of local anesthetic solution (lidocaine HCl 2% with epinephrine 1:100,000) was delivered slowly and continuously over approximately 60 s, in accordance with established anatomical landmarks for maxillary buccal infiltration or mandibular inferior alveolar nerve block techniques. A 27-gauge needle was used for all injections, as previous evidence has demonstrated no significant differences in pain perception among 25-, 27-, and 30-gauge needles¹⁸. Aspiration was performed prior to anesthetic deposition to ensure patient safety. Care was taken not to show the injection needle to the patient during anesthesia administration.

Vibration-assisted local anesthesia delivery group

Local anesthesia was administered using the VibraJect device, a battery-powered vibration attachment mounted onto a conventional dental syringe. The device generates high-frequency micro-vibrations that are transmitted along the syringe and needle during anesthetic delivery, with the aim of reducing pain perception during needle insertion and anesthetic deposition^6,24. Prior to injection, topical anesthetic gel (20% benzocaine) was applied to the injection site for 60 s, as described for the conventional syringe group. Local anesthesia was then administered using the VibraJect-mounted syringe, employing the same anesthetic solution, needle gauge, injection technique, volume, and injection duration as in the conventional manual syringe group. Vibration was activated immediately before needle insertion and maintained throughout the entire anesthetic administration.

Needle-free jet injection group

Local anesthesia was administered using the Comfort-in system (MIKA Medical Co., Busan, Republic of Korea), a needle-free jet injector designed for transmucosal delivery of local anesthetic solutions. The device utilizes a spring-loaded mechanism to generate high-pressure energy, enabling rapid penetration of the anesthetic solution through the oral mucosa without the use of a needle. This mechanism is based on high-velocity jet injection, whereby a small volume of anesthetic is delivered under pressure, producing immediate localized anesthesia at the application site²⁵. Although this technique is primarily intended to provide superficial infiltration anesthesia, previous studies have utilized jet injection devices to provide anesthesia deep enough to perform pulpotomy on primary molars²⁶. Local anesthesia was delivered by positioning the Comfort-in device perpendicular to the mucosal surface at the intended injection site. A standardized volume of anesthetic solution was administered in accordance with the manufacturer’s recommendations (a total of 0.3 cc of 2% lidocaine with 1/100,000 epinephrine).

Computer-controlled local anesthetic delivery group

In the computer-controlled local anesthetic delivery group, local anesthesia was administered using the Star Pen system (Woodpecker Medical Instruments, China). This pen-style, computer-controlled device regulates anesthetic flow rate and injection pressure throughout administration. The mechanism of action is based on delivering the anesthetic solution at a slow, constant, and pre-programmed rate, thereby reducing tissue distension and discomfort associated with rapid or uncontrolled injection. By minimizing pressure fluctuations, computer-controlled systems aim to enhance patient comfort while maintaining adequate anesthetic depth¹⁷. Prior to injection, topical anesthetic gel (20% benzocaine) was applied to the injection site for 60 s. Local anesthesia was then administered using the Star Pen device with the same anesthetic solution, needle gauge, injection technique, total volume, and injection duration as used in the conventional manual syringe group.

Outcome measures and assessment time points

Due to the nature of the anesthetic delivery systems, blinding of the operator, patients, and the investigator performing real-time outcome assessments during anesthesia administration was not feasible. To minimize assessment bias, all outcome measures were collected using standardized protocols and predefined assessment time points. Outcome scoring after trea^tment completion, data entry, and statistical analysis were performed by investigators who were blinded to group allocation. For transparency, Supplementary Table S2 lists which measures were recorded in real time (HR, SpO₂, WBFPRS, VPT, and live FLACC/Houpt observations) and which steps (data entry, score verification, and statistical analysis) were performed by blinded investigators after de-identification. No outcome measures were recorded during the latency period; assessments were performed only at the predefined time points after anesthesia administration and during subsequent procedural stages. Primary and secondary outcome measures are described below.

Primary outcome measures

Child-reported pain during anesthesia was evaluated using:

1. Wong–Baker Faces Pain Rating Scale (WBFPRS): WBFPRS is a validated self-reported pain assessment tool commonly used in pediatric populations. The scale consists of six facial expressions representing increasing levels of pain, scored from 0 (no hurt) to 10 (hurts worst) in increments of two. Children were asked to select the face that best reflected their perceived pain intensity²⁷. The WBFPRS was administered at three time points: after local anesthesia administration, after rubber dam application, and after completion of the treatment session. The assessor used standardized, age-appropriate language and maintained a neutral demeanor to avoid influencing the child’s responses.

Secondary outcome measures

Secondary outcomes included the assessment of physiological stress and safety, anxiety and observed behavioral distress, cooperation and treatment feasibility and acceptability, as follows:

1. Heart rate monitoring (HR): HR was recorded at four time points throughout the treatment session using a pulse oximeter (I-Medical Pulse Oximeter IM-X1805, I-Medical GmbH, Berlin, Germany)¹: before the administration of local anesthesia², immediately after administration³, during rubber dam application⁴, and during treatment at the cavity preparation step, as this represents the most invasive and potentially anxiety-provoking operative step. This sequence of measurement time points is designed to capture anticipatory stress, procedural stress, and peak stress throughout the treatment session.

2. Oxygen saturation (SpO₂) monitoring: SpO₂ was monitored using the same pulse oximeter device used for HR monitoring to ensure physiological safety, as oxygen saturation reflects adequacy of ventilation and absence of respiratory compromise. SpO₂ was recorded at the same time points as HR measurements.

3. Venham’s Picture Test (VPT): VPT is an eight-item self-reported anxiety assessment tool specifically designed for young children aged 3–8 years. The test consists of paired cartoon figures depicting neutral and anxious emotional states²⁸. Children are asked to select the figure that best represents how they feel at the moment. Each anxious response scores one point, yielding a total score ranging from 0 to 8, with higher scores indicating greater anxiety. The scale was administered at the same three time points as the WBFPRS: after local anesthesia administration, after rubber dam application, and after completion of the treatment session. The same standardized instructions and neutral administration approach were applied. Although originally designed for younger children, the Venham Picture Test has been previously applied in children up to 10 years in dental anxiety research²⁹.

4. FLACC Behavioral Pain Assessment Scale: The FLACC scale is an observational behavioral pain assessment tool which evaluates five behavioral categories (face, legs, activity, cry, consolability), each scored from 0 to 2, yielding a total score from 0 (no pain) to 10 (severe pain)³⁰. Children were observed for 1–3 min at each assessment time point, and FLACC scores were recorded during local anesthesia administration, during rubber dam application and during the treatment procedure.

5. Houpt Behavior Rating Scale (HBRS): HBRS is a behavioral assessment tool used to evaluate children’s behavior and cooperation during dental treatment. This tool was developed to assess the child’s tolerance of dental procedures and the overall success of treatment. This scale evaluates movement^1–4, crying^1–4, and overall behavior^1–6,21. The scale rating was recorded after the completion of the treatment session.

6. Parental satisfaction: Parent satisfaction was measured using a 5-point Likert scale (1 = very dissatisfied to 5 = very satisfied) regarding their child’s comfort and overall treatment experience. Higher scores indicate greater satisfaction.

Statistical analysis

Statistical analysis was performed using IBM SPSS Statistics (version 29.0.2.0; IBM Corp., Armonk, NY, USA). The version-specific IBM support page is: https://www.ibm.com/products/spss-statistics. The normality of data distribution was assessed using the Kolmogorov–Smirnov test. Quantitative variables, including age, heart rate (HR) and oxygen saturation (SpO₂), were expressed as mean ± standard deviation. Within-group comparisons across different time points were conducted using the paired-sample t-test, while intergroup comparisons were performed using one-way analysis of variance (ANOVA) to allow for clinically interpretable comparisons between anesthetic techniques. Additionally, heart rate (HR) was further analyzed using a two-way repeated measures ANOVA to assess the effects of group and time, as well as their interaction. When the assumption of sphericity was violated, the Greenhouse–Geisser correction was applied. When statistically significant differences were detected, post-hoc pairwise comparisons were carried out using the Bonferroni correction. Categorical nominal variables (e.g., gender and tooth distribution) were compared using the Chi-square test. Categorical (ordinal) variables, including Wong–Baker pain scores, FLACC pain scores, Venham anxiety scores, Houpt behavior ratings, and parental satisfaction, were analyzed using non-parametric statistical tests and are presented as mean ranks. For within-group comparisons across multiple time points, the Friedman test was applied. When a statistically significant Friedman result was obtained, post-hoc pairwise comparisons between time points were performed using the Wilcoxon signed-rank test to identify the specific periods showing significant differences. For variables assessed at only two time points, within-group comparisons were directly analyzed using the Wilcoxon signed-rank test. Intergroup comparisons were conducted using the Kruskal–Wallis test, followed by Mann–Whitney U tests for pairwise comparisons when appropriate. All statistical tests were two-tailed, and the level of statistical significance was set at P ≤ 0.05.

Results

All statistical analyses were sufficiently powered to detect intergroup differences where present.

Demographic data

A total of 112 children were enrolled and equally distributed among the four study groups. For each anesthetic delivery technique, an equal number of maxillary and mandibular primary molars were treated. Accordingly, for each arch, 56 children were included, with 14 participants allocated to each anesthetic delivery group. Each child received a single local anesthetic injection using one technique in one arch only. The mean age of the study population was 8.13 ± 1.3 years (range: 6–10 years). The mean ages in the Manual syringe, CCLAD, Vibration-assisted, and Jet injection groups were 7.60 ± 1.2, 8.28 ± 1.6, 8.28 ± 1.3, and 8.35 ± 1.2 years, respectively. Although the mean age of the participants was above 6 years, this is consistent with the selected age range (6–10 years), and no significant differences in age distribution were observed among the study groups (P = 0.132). Overall, 61.6% of the participants were boys (n = 69) and 38.4% were girls (n = 43). The distribution of boys and girls was comparable across the four anesthetic delivery groups, regardless of the treated arch. The proportion of girls was 39.3% in the Manual syringe group, 25% in the CCLAD group, 50% in the Vibration-assisted group, and 39.3% in the Jet injection group. No statistically significant differences in gender distribution were detected among the groups (P = 0.201). All treated teeth were primary first or second molars located in either the maxillary or mandibular arch. The distribution of tooth type and location varied among the study groups, as detailed in Table 1. All children underwent the same dental procedure (pulpotomy) following local anesthesia. According to Frankl’s Behavior Rating Scale, 42.86% of the children (n = 48) were classified as definitely positive, while 57.14% (n = 64) were classified as positive. No statistically significant differences in Frankl behavior ratings were observed among the study groups (P = 0.173). The study flow, including recruitment, allocation, and analysis, is summarized in the CONSORT flow diagram (Fig. 1). The demographic and baseline characteristics of the study participants are summarized in Table 1.

Table 1.

Demographic and baseline characteristics of the study participants. Abbreviations: none. Gender, tooth location, and Frankl’s behavior rating scale were analyzed using the chi-square test. Age was analyzed using one-way ANOVA.

Variables		Manual Syring (n = 28, 14 in each arch)	CCLAD (n = 28, 14 in each arch)	Vibration-assisted (n = 28, 14 in each arch)	Jet Injection (n = 28, 14 in each arch)	Total (n = 112, 56 in each arch)	P-value
Gender	Boys	60.7% (n = 17)	75% (n = 21)	50% (n = 14)	60.7% (n = 17)	61.6% (n = 69)	0.201
	Girls	39.3% (n = 11)	25% (n = 7)	50% (n = 14)	39.3% (n = 11)	38.4% (n = 43)
Age		7.60 ± 1.2 years	8.28 ± 1.6 years	8.28 ± 1.3 years	8.35 ± 1.2 years	8.13 ± 1.3 years	0.132
Tooth Location	Primary Upper first molar	28.6% (n = 8)	28.6% (n = 8)	39.3% (n = 11)	28.6% (n = 8)	31.3% (n = 35)	1.000
	Primary Upper Second molar	21.4% (n = 6)	21.4% (n = 6)	10.7% (n = 3)	21.4% (n = 6)	18.8% (n = 21)
	Primary Lower first molar	21.4% (n = 6)	17.9% (n = 5)	32.1% (n = 9)	21.4% (n = 6)	23.2% (n = 26)
	Primary Lower Second molar	28.6% (n = 8)	32.1% (n = 9)	17.9% (n = 5)	28.6% (n = 8)	26.8% (n = 30)
Frankl’s Behavior Rating Scale	Definitely Positive	39.3% (n = 11)	46.4% (n = 13)	42.9% (n = 12)	42.9% (n = 12)	42.9% (n = 48)	0.173
	Positive	60.7% (n = 17)	53.6% (n = 15)	57.1% (n = 16)	57.1% (n = 16)	57.1% (n = 64)

Heart rate and oxygen saturation assessment

Heart rate (HR) was analyzed using a two-way repeated measures ANOVA to evaluate the effects of group and time. In the mandibular arch, Mauchly’s test indicated a violation of sphericity (P = 0.002); therefore, Greenhouse–Geisser correction was applied. The analysis revealed a significant main effect of time (P < 0.001), as well as a significant interaction effect between group and time (P = 0.018), indicating that changes in HR over time differed among the study groups. In the maxillary arch, sphericity was also violated (P < 0.001), and Greenhouse–Geisser correction was used. A significant main effect of time was observed (P = 0.001), whereas no significant interaction between group and time was detected (P = 0.264), suggesting a similar pattern of HR changes across all groups. Consistent with these findings, a transient increase in HR was observed during anesthesia in the mandibular arch, where the Manual syringe group showed higher values compared with the CCLAD and Jet injection groups (P = 0.006 and P = 0.022, respectively), while no significant differences were detected at other time points. No statistically significant differences in oxygen saturation (SpO₂) were observed between groups or across time points in either arch (P > 0.05). Overall, HR variations were primarily time-dependent, with technique-related differences evident only in the mandibular arch, whereas oxygen saturation remained stable across all conditions. Table. 2..

Table 2.

Descriptive statistics (mean ± SD) of heart rate (HR) and oxygen saturation (SpO₂) across study groups and time points, with summary results of two-way repeated measures ANOVA. Abbreviations: DA, during anesthesia; DR, during rubber dam; DT, during treatment; Pre, pre-anesthesia.*Statistical analysis differences (P < 0.05). HR was analyzed using two-way repeated measures ANOVA

Jaw	Variable	Time Point	Manual Syringe	CCLAD	Vibration-Assisted	Jet Injection	P-value
			Mean ± SD
Lower Jaw	HR	Pre	97.93 ± 14.32	91.43 ± 16.41	91.29 ± 10.61	93.57 ± 8.20	Time effect (P < 0.001*), Group × Time effect (P = 0.018*)
		DA	116.93 ± 15.50	95.07 ± 18.72	102.93 ± 18.22	98.00 ± 12.69
		DR	107.36 ± 16.20	91.36 ± 19.17	98.14 ± 8.98	96.57 ± 12.89
		DT	99.36 ± 16.75	89.86 ± 16.19	93.00 ± 12.64	99.79 ± 15.65
	SpO2	All time points	~ 98–99	~ 98–99	~ 98–99	~ 98–99	> 0.05
Upper Jaw	HR	Pre	93.64 ± 15.68	95.07 ± 11.52	97.93 ± 8.53	93.57 ± 10.23	Time effect (P = 0.001*), Group × Time effect (P = 0.264)
		DA	108.71 ± 15.02	96.00 ± 11.43	110.00 ± 31.90	103.14 ± 14.87
		DR	94.00 ± 15.97	96.86 ± 10.48	103.00 ± 13.40	95.71 ± 12.34
		DT	97.29 ± 13.16	94.21 ± 9.47	101.71 ± 20.12	98.14 ± 9.90
	SpO2	All time points	~ 98–99	~ 98–99	~ 98–99	~ 98–99	> 0.05

Pain and anxiety assessment

Wong-Baker faces pain rating scale

In the mandibular arch, the Manual syringe group reported higher Wong–Baker pain scores than the CCLAD group (P = 0.005), Vibration-assisted group (P = 0.041), and Jet injection group (P = 0.001) after anesthesia, and remained higher than the CCLAD group (P = 0.009) and Vibration-assisted group (P = 0.001) after treatment. In the maxillary arch, the Manual syringe group also reported higher scores than all other groups after anesthesia.

(P ≤ 0.05), whereas no between-group difference was seen after treatment. Overall, the manual syringe technique was associated with the highest pain scores, particularly immediately after anesthesia.

FLACC behavioral pain assessment scale

In the mandibular arch, the Manual syringe group showed higher FLACC scores than the CCLAD group (P = 0.004) and Jet injection group (P = 0.001) during anesthesia. In the maxillary arch, the Manual syringe group had higher FLACC scores than all other groups during anesthesia and rubber dam placement (P ≤ 0.05); during treatment, the Jet injection group remained higher than the CCLAD group (P = 0.002) and Vibration-assisted group (P = 0.018). Overall, behavioral distress peaked during anesthesia and was most pronounced with the manual syringe, whereas CCLAD generally showed the most favorable pattern.

Venham’s picture test

During anesthesia, the Manual syringe group exhibited higher Venham anxiety scores than the CCLAD group (P = 0.004) and Jet injection group (P = 0.001) in the mandibular arch and all other groups in the maxillary arch (P = 0.001). Overall, the manual syringe technique produced the greatest anxiety response. Table.3.

Table 3.

Intergroup comparison of non-parametric outcomes, including Wong-Baker, FLACC, Venham, Houpt, and satisfaction scores. Abbreviations: AA, after anesthesia; AT, after treatment; DA, during anesthesia; DR, during rubber dam; DT, during treatment. *Statistical analysis differences (P < 0.05).

Jaw	Variable	Time Point	Manual Syring	CCLAD	Vibration−Assisted	Jet Injection	P−value	Post−hoc (Mann−Whitney U)
			Mean Rank
Lower Jaw	Wong Baker	AA	2.54	2.36	2.43	2.00	0.001*	Manual > CCLAD (P ≤ 0.005), Manual > Vibration (P ≤ 0.041), Manual > Jet (P ≤ 0.001)
		AT	1.86	1.93	1.68	2.21	0.006*	Manual > CCLAD (P ≤ 0.005), Manual > Vibration (P ≤ 0.041), Manual > Jet (P ≤ 0.001)
	Venham	DR	2.36	2.21	2.39	1.96	0.001*	Manual > CCLAD (P ≤ 0.004), Manual > Jet (P ≤ 0.001)
	FLACC	DA	2.82	2.39	2.54	2.54	0.008*	Manual > CCLAD (P ≤ 0.001), Manual > Jet (P ≤ 0.009)
		DR	1.61	1.75	1.75	1.61	0.165	−
		DT	1.57	1.86	1.71	1.86	0.306	−
	Houpt	AT	2.18	2.07	2.21	2.07	0.130	−
	Satisfaction	AT	9.43	36.36	32.71	35.50	0.001*	Manual < CCLAD, Vibration, Jet (P ≤ 0.001)
Upper Jaw	Wong Baker	AA	2.21	1.96	2.04	2.11	0.001*	Manual > CCLAD, Vibration, Jet (P ≤ 0.001)
		AT	1.93	2.18	2.14	2.11	0.051	−
	Venham	DR	2.57	1.96	2.00	2.07	0.001*	Manual > CCLAD, Vibration, Jet (P ≤ 0.001)
	FLACC	DA	2.68	1.96	2.29	2.29	0.001*	Manual > all groups (P ≤ 0.05)
		DR	1.61	1.86	1.71	1.29	0.001*	Manual > others (P ≤ 0.05)
		DT	1.71	2.18	2.00	2.43	0.009*	Manual > CCLAD (P = 0.044); Jet > CCLAD (P ≤ 0.002), Jet > Vibration (P ≤ 0.018)
	Houpt	AT	2.00	2.07	1.96	1.75	0.079	−
	Satisfaction	AT	10.00	36.16	32.18	35.21	0.001*	Manual < CCLAD, Vibration, Jet (P ≤ 0.001)

Overall Cooperation and satisfaction assessment

Houpt scores

Houpt scores were comparable among groups in both arches, indicating similar overall cooperation.

Parent satisfaction

Parental satisfaction was lower in the Manual syringe group than in the other groups in both arches (P ≤ 0.05). Overall, cooperation was similar, but satisfaction favored the alternative delivery techniques.

Discussion

This randomized controlled trial showed that the null hypothesis was rejected, because conventional manual syringe administration produced higher pain, anxiety, and autonomic stress during anesthesia than CCLAD, vibration-assisted injection, and needle-free jet injection, while oxygen saturation and overall cooperation remained comparable. CCLAD demonstrated the most consistent benefit, especially during the injection phase.

Baseline demographic assessment demonstrated a high degree of comparability among the study groups, thereby strengthening the internal validity of the trial and minimizing the influence of potential confounding factors. Heart rate findings indicated a significant time effect in both arches, confirming that HR changed across the procedural stages of treatment. However, the pattern of HR change differed by group only in the mandibular arch, where the significant group × time interaction suggests that the response to injection was technique dependent. Conventional syringe injections were associated with more pronounced heart rate elevations during anesthesia, whereas children receiving anesthesia via CCLAD showed a more stable HR pattern across time points. The vibration-assisted and jet injection techniques demonstrated more variable physiologic responses, with effects that appeared less consistent across arches. In contrast, no significant group × time interaction was observed in the maxillary arch, indicating a more uniform physiologic pattern across techniques in that setting. Oxygen saturation remained unchanged across all groups and measurement intervals, indicating the absence of systemic physiological compromise. Overall, these findings suggest that heart rate elevations predominantly reflect acute injection-related stress and pain anticipation rather than anesthetic inadequacy, and that the magnitude of this response may depend on both the delivery technique and the arch being treated. Similar findings have been reported in pediatric populations, where CCLAD use was associated with attenuated autonomic responses compared with conventional injections^16,31.

Beyond physiologic responses, pain perception varied according to the anesthetic delivery technique. Both subjective self-reported pain, assessed using the Wong–Baker Faces Pain Rating Scale, and objective behavioral pain, evaluated using the FLACC scale, consistently demonstrated higher scores in children receiving anesthesia via the conventional manual syringe. Differences were most pronounced during the anesthesia phase and were particularly evident in mandibular injections, whereas pain scores tended to overall converge during rubber dam placement and operative treatment with some technique- and site-specific exceptions. Alternative delivery techniques demonstrated variable effects on pain perception. CCLAD was associated with the most consistent attenuation of both subjective and behavioral pain responses, while vibration-assisted and jet injection techniques showed more modest and site-dependent effects. Reductions in pain scores that involved shifts across adjacent Wong–Baker categories or marked decreases in FLACC scores may be considered clinically meaningful, particularly during mandibular anesthesia. These findings parallel the anxiety outcomes, where children in the manual syringe group exhibited higher anxiety levels during anesthesia, and support the well-established interaction between anxiety and pain perception. Although anxiety was not the primary outcome, its parallel reduction during anesthesia with certain delivery systems supports its role as a contextual modulator of pain perception rather than an isolated behavioral endpoint.

The convergence of pain scores during rubber dam placement and treatment across all groups likely reflects the establishment of effective local anesthesia and the resolution of anticipatory fear associated with injection. This supports the notion that pain perception in pediatric dental care is dominated by a brief, injection-centered event rather than the operative procedure itself. The more pronounced differences observed during mandibular anesthesia may be explained by the greater depth, duration, and perceived invasiveness of inferior alveolar nerve blocks, which heighten both emotional and sensory responses and render technique-related differences more detectable. The greater sensitivity of the FLACC scale during anesthesia further underscores its ability to capture immediate procedural distress, whereas Wong–Baker scores may reflect a more global and cognitively mediated pain appraisal.

The arch-related differences observed for the jet injection and vibration-assisted techniques likely reflect differences in anesthetic demand, tissue resistance, and baseline procedural distress between the maxillary and mandibular arches rather than the device alone. In pediatric dentistry, infiltration is the standard approach for maxillary teeth, whereas mandibular pulpal procedures more often rely on IANB; moreover, increasing mandibular cortical thickness may reduce the effectiveness of infiltration anesthesia³². Pediatric studies also indicate that IANB is generally associated with greater pain than infiltration, which may amplify any benefit of adjunctive devices in the mandibular arch^33,34. Needle-free jet systems have mainly been investigated as infiltration techniques, and the best recent pediatric trial in primary maxillary molars showed reduced injection pain but only 75% complete anesthetic success, suggesting that these systems may be less predictable when deeper or more reliable anesthesia is required^7,35. By contrast, vibration-assisted devices primarily target needle-insertion discomfort, and the pediatric evidence remains mixed, with one VibraJect trial showing lower VAS and FLACC scores and a more recent IANB trial showing no significant reduction in pain or anxiety^36,37. Therefore, the mandibular arch may provide more room to detect a benefit from these adjuncts because baseline distress is typically higher, whereas the maxillary arch may show a floor effect^32,33.

Age may have influenced the magnitude and expression of injection-related distress, even though the four study groups were age-balanced and no statistically significant intergroup difference in mean age was detected. In children aged 6 to 10 years, pain perception, coping ability, and the accuracy of self-report can vary according to developmental maturity, cognitive level, and emotional regulation. Pediatric pain literature indicates that self-report is feasible in school-aged children when age-appropriate tools are used, although the reliability and interpretability of pain ratings become more robust with increasing age^38,39. In addition, younger children tend to exhibit higher dental fear and anxiety than older children, which may partly explain the greater variability in behavioral and subjective responses observed in some participants near the lower end of the age range^5,40. Therefore, age is unlikely to have confounded the between-group comparisons in the present trial, but it may have contributed to within-group variability in pain and anxiety responses. Future studies with larger samples should consider age-stratified analyses to determine whether younger and older children respond differently to alternative anesthetic delivery systems^41,42.

The present findings are consistent with previous reports demonstrating reduced pain and anxiety associated with CCLAD compared with conventional syringe-based anesthesia¹⁴. Evidence supporting vibration-assisted techniques has also been reported, although with greater variability across clinical settings and assessment tools¹⁵. Additional clinical studies have described reductions in injection-related pain and anxiety with alternative delivery methods; however, the magnitude and consistency of these effects appear to depend on technique, injection site, and outcome measure^13,26,43.

Despite the observed differences in pain perception and anxiety during anesthesia administration, overall cooperation during the dental procedure was comparable across all anesthetic delivery techniques, as reflected by similar Houpt scores in both arches. This finding indicates that all evaluated methods were clinically effective in facilitating successful completion of pulpotomy without behavioral interruption. Importantly, the absence of differences in cooperation does not diminish the relevance of the pain and anxiety findings; rather, it suggests that alternative delivery systems improve the quality of the treatment experience without being a prerequisite for procedural feasibility. Previous studies have reported improved child behavior and cooperation associated with alternative anesthetic delivery systems, even when formal cooperation scores do not differ significantly¹³. Moreover, improvements in patient comfort and reduced anxiety have been shown to positively influence cooperation and future dental attitudes, effects that may not always be fully captured by standardized behavior rating scales⁴⁴.

In contrast, parental satisfaction differed significantly among groups, with caregivers of children treated using the manual syringe reporting lower satisfaction levels compared with those in the alternative delivery groups. Parental perception is strongly influenced by visible signs of child distress and emotional comfort, particularly during anesthesia administration, and therefore serves as a meaningful indicator of the overall acceptability of the dental visit⁴⁵. The higher satisfaction associated with computer-controlled, vibration-assisted, and jet injection techniques underscores their potential value in enhancing caregiver confidence and acceptance of dental care, which may have important implications for long-term treatment adherence and attitudes toward dental treatment in pediatric populations. Earlier clinical evaluations of needle-free anesthetic systems reported favorable levels of patient acceptance and preference, findings that align with the enhanced parental satisfaction observed in the present study⁴⁶. Systematic reviews further support the association between alternative delivery systems, improved patient comfort, and behavioral outcomes that are intrinsically linked with satisfaction in pediatric dentistry¹³.

Taken together, the present findings indicate that injection-related distress in pediatric dental care is a brief, technique-sensitive event that exerts a disproportionate influence on physiological, behavioral, and subjective outcomes. Differences among anesthetic delivery systems were most evident during anesthesia administration and diminished once effective local anesthesia was established, underscoring the injection phase as the critical determinant of the child’s experience. Variability across techniques and injection sites highlights the importance of aligning delivery systems with procedural demands rather than assuming uniform effectiveness across clinical contexts. Importantly, none of the evaluated techniques compromised anesthetic adequacy or physiological safety, supporting their clinical applicability within appropriate indications.

The present findings should not be interpreted as advocating universal replacement of the conventional manual syringe. Rather, they suggest that CCLAD and other alternative delivery systems may offer a patient-centered advantage in selected children by reducing injection-related pain and anxiety, an effect that has also been reported in pediatric systematic reviews and clinical trials^16,47. However, implementation must be considered in light of practical limitations. Recent reviews note that CCLAD systems may involve higher initial cost, longer administration time, and greater space requirements than conventional syringes, which can limit routine adoption in many settings^48,49. Therefore, in resource-constrained public clinics, selective use for highly anxious children or special-care patients may be more realistic than universal deployment, whereas in private practice the decision may depend on case mix, patient expectations, and procurement capacity. This interpretation is consistent with the view that improved comfort does not automatically imply broad feasibility in all clinical environments^49,50.

Real-world implementation requires consideration of cost, device availability, and operator training. Representative retail prices and product specifications were obtained from manufacturer and vendor listings and are provided here for illustrative purposes only. For example, the Woodpecker Medical Instruments Star Pen and similar pen-style devices are listed at relatively low retail entry prices in some markets, whereas higher-end CCLAD systems and complete units may be marketed at substantially higher price points. Similarly, needle-free jet injector kits and their single-use adaptors are commonly advertised at modest retail prices but may incur recurring consumable and maintenance costs. These illustrative price and specification data were retrieved from manufacturer and vendor web pages^51,52.We therefore recommend interpreting price estimates as approximate market figures subject to regional variation and institutional procurement processes.

Adoption of these devices also requires operator familiarization and, for many systems, brief device-specific instruction or continuing education. Vendor and professional continuing-education resources⁵³ commonly provide introductory training modules and device-specific safety guidance. The learning curve for controlled-rate devices is generally modest, focusing on setup, injection site adaptation, and appropriate indications, but competency training and adherence to manufacturer recommendations are important to minimize complications. In public or resource-constrained clinics, higher upfront cost and competing procurement priorities may limit routine adoption; in private practices, selective adoption (for example, use for highly anxious children or those with special needs) or shared device models may be more feasible. Practical implementation strategies include pooled device procurement across clinics, selective application for high-need cases, including device costs in selected case fees when appropriate, and pursuing institutional funding or grants for pilot implementation. Future studies should evaluate cost-effectiveness, maintenance and consumable costs, and workflow impacts of alternative delivery systems in both public and private practice settings.

Several limitations of the present study should be acknowledged. First, although outcome scoring after treatment completion, data entry, and statistical analysis were performed by investigators blinded to group allocation, several assessments (physiologic measures and live behavioral observations) were necessarily recorded in real time by an unblinded research assistant due to the visible differences among devices. To reduce the risk of observer bias we used standardized CRFs and predefined scoring criteria, ensured that the research assistant received calibration training before study start, and de-identified all records prior to entry and analysis. Nevertheless, the potential for residual observer bias in live behavioral ratings remains a limitation and should be considered when interpreting behavioral outcomes. Second, although the four groups were age-balanced, the study included children aged 6 to 10 years, and pain self-report in children remains developmentally dependent. Children in this age range can generally use age-appropriate pain scales, but interpretability and behavioral expression may still vary with maturity, cognitive development, and emotional regulation. Therefore, age may have contributed to within-group variability, even if it was unlikely to confound the between-group comparisons. Third, the trial was conducted at a single center and included only cooperative ASA I-II children requiring pulpotomy in primary molars. Accordingly, the findings may not be fully generalizable to younger children, less cooperative patients, medically complex children, other treatment types, or different clinical settings. CONSORT 2025 also highlights the importance of discussing external validity and whether results can be generalized to participants who differ by age, severity, or care setting⁵⁴. Fourth, the study did not include a formal cost-effectiveness analysis, nor did it measure workflow impact, maintenance burden, or full implementation costs. This is particularly relevant for CCLAD, because recent reviews note that although CCLAD may reduce pain, its disadvantages include higher cost, longer administration time, and greater space requirements. Future studies should therefore evaluate not only clinical efficacy but also economic feasibility and real-world adoptability in public and private practice settings. Finally, the sample size was powered for overall group comparisons and not for detailed interaction analyses by age or arch. Future multicenter trials with larger samples should examine whether the magnitude of benefit differs by age group, arch, anxiety level, and treatment complexity, and should also include longer follow-up to determine whether improved injection experiences translate into better future dental attitudes and attendance.

Conclusions

Within the limits of this randomized clinical trial, the mode of local anesthetic delivery influenced children’s pain and anxiety responses during injection. Compared with the conventional manual syringe, CCLAD, vibration-assisted injection, and needle-free jet injection were associated with lower injection-related distress, while overall cooperation and physiological safety remained comparable across techniques.

Electronic Supplementary Material

Below is the link to the electronic supplementary material.

Abbreviations

ANOVA

Analysis of Variance

CCLAD

Computer–Controlled Local Anesthetic Delivery

FLACC

Face, Legs, Activity, Cry, Consolability Pain Scale

HR

Heart Rate

IBM

International Business Machines

SpO₂

Oxygen Saturation

SPSS

Statistical Package for the Social Sciences

VPT

Venham’s Picture Test

WBFPRS

Wong–Baker Faces Pain Rating Scale

Author contributions

Sara Badr led the study’s conceptualization, designed the methodology, managed the project, curated the data, conducted the investigations, and drafted the initial manuscript. Abdul Wahab Nourallah contributed to the conceptual framework, assisted in methodological planning and project management, provided essential resources, supervised the work, and participated in drafting and revising the manuscript.

Funding

This study was self-funded by the authors of this paper.

Data availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.