Effects of animal-assisted therapy on dental anxiety, behavior, and perceptions in young pediatric patients: a blinded randomized controlled trial

Abstract

Background

Between 6 and 22% of children are affected by dental anxiety. Dental anxiety is a significant barrier to dental care and is associated with dental avoidance and negative oral health outcomes. Pharmacological methods of anxiety management are costly, carry risks of adverse outcomes, and may not be acceptable to some families. Alternative non-pharmacological methods are needed for the safe and effective delivery of dental care. Although there is an abundance of literature regarding animal-assisted therapy (AAT) in medicine, only preliminary studies on AAT exist in dentistry. To identify optimal outcome measures for evaluating AAT in pediatric dental contexts, a randomized controlled trial protocol was developed.

Methods

A prospective randomized controlled trial protocol was developed to examine the impact of AAT on objective (heart rate, salivary stress and pain markers, and observational coding) and subjective self-reported measures of anxiety, pain, and dental expectations in pediatric patients. The study is designed to enroll 180 pediatric patients (4–8 years old), randomized into three arms (n = 60 per arm) with stratification by age (< 6.5 vs ≥ 6.5) and gender (block size = 4). Two therapy protocols (+ Short AAT and + Long AAT exposures) will be compared relative to an active control (coloring a dog picture) during a diagnostic dental visit consisting of an oral exam, dental cleaning, and simulated bitewing intraoral radiographs.

Discussion

This study will provide information on optimal outcome measures to evaluate the impact of AAT on dental anxiety and behavior in pediatric dental patients. Determining the effects of AAT in pediatric dental care may provide a safe, non-pharmacological method of anxiety and behavior management, with broad translational impact.

Trial registration

This trial was registered on ClinicalTrials.gov with number NCT05464888, on 15 July 2022 (first submitted to ClinicalTrials.gov) and 19 July 2022 (first posted to ClinicalTrials.gov).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-025-08970-z.

Administrative information

Note: the numbers in curly brackets in this protocol refer to SPIRIT checklist item numbers. The order of the items has been modified to group similar items (see http://www.equator-network.org/reporting-guidelines/spirit-2013-statement-defining-standard-protocol-items-for-clinical-trials/).

Title {1}	Effects of animal-assisted therapy on dental anxiety, behavior, and perceptions in young pediatric patients: a randomized control trial Trial acronym: BARK: Study protocol for Behavioral management and Anxiety Reduction in Kids—animal assisted therapy in dentistry trial
Trial registration {2a and 2b}	ClinicalTrials.gov ID: NCT05464888 First submitted: 07/15/2022 First posted: 07/19/2022 Study start (actual): 02/02/2023 Other study ID: IRB #22-1454
Protocol version {3}	Version 1.1 22.05.2024
Funding {4}	This work is supported by the Southern Association of Orthodontists Research Award (to G.K.). The project described is supported by the National Center for Advancing Translational Sciences (NCATS), National Institutes of Health (NIH), through Grant Award Number UL1TR002489, and through the National Institute of Dental and Craniofacial Research (NIDCR) with a K08 grant (K08DE030235) (to L.J.) and with an R03 grant (R03DE032768) (to L.J.). The content is solely the responsibility of the authors and does not represent the official views of the NIH.
Author details {5a}	Grace Kapov, DMD, MS | Orthodontic Resident, Department of Orthodontics, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: gkapov@unc.edu Kasey Linton, BS | Research Technician, Department of Orthodontics, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: klinton@unc.edu Christopher Gatewood, DDS | Graduated Dental Student, Advanced Dental Associates, Inc., Chapel Hill, NC, USA | Email: cgatewo4@live.unc.edu Chuwen Liu | PhD Candidate, Department of Biomedical Sciences, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: chuwen@email.unc.edu Timothy Strauman, PhD | Professor of Psychology and Neuroscience, Duke University, Durham, NC, USA | Email: tjstraum@duke.edu Eric Hodges, PhD, FNP-BC, FAAN | Associate Professor, School of Nursing, University of North Carolina, Chapel Hill, NC, USA | Email: eric.a.hodges@unc.edu Christina Graves, PhD | Assistant Professor, Department of Biomedical Sciences, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: cxg@email.unc.edu Caroline Sawicki, DDS, PhD | Assistant Professor, Department of Pediatric Dentistry and Dental Public Health, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: caroline_sawicki@unc.edu Di Wu, PhD | Associate Professor, Department of Biomedical Sciences, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: did@email.unc.edu Kimon Divaris, DDS, PhD | Professor, Department of Pediatric Dentistry and Dental Public Health, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: kimon_divaris@unc.edu Laura Jacox, PhD, DMD, MS* | Assistant Professor, Departments of Orthodontics and Biomedical Sciences, Adams School of Dentistry, University of North Carolina, Chapel Hill, NC, USA | Email: ljacox@live.unc.edu *Corresponding author Laura Jacox, PhD, DMD, MS Departments of Biomedical Sciences and Orthodontics, Adams School of Dentistry, University of North Carolina, 270 Brauer Hall, CB #270 Chapel Hill, NC 27599, USA Tel: (847) 702-0988 Email: ljacox@live.unc.edu
Name and contact information for the trial sponsor {5b}	University of North Carolina at Chapel Hill, Office of Sponsored Programs 104 Airport Dr # 2200 Chapel Hill, NC 27599 (919) 966-3411
Role of sponsor {5c}	The content is solely the responsibility and under the authority of the authors and does not represent the official views of the NIH. The sponsor and funders did not play a role in study design, collection, management, analysis, data interpretation, report writing nor submission of the report for publication.

Introduction

Background and rationale {6a}

Dental anxiety (DA), or strong negative feelings associated with dental care, has been shown to affect 6–15% of adults and 6–22% of children, with a higher prevalence in younger preschool-aged children than adolescents [1–6]. Although there are a host of factors that can contribute to DA, evidence indicates that early childhood conditioning can play an important role in its development [2, 4]. Notably, DA has the potential to reinforce itself through a perpetuating cycle of care avoidance and negative oral health outcomes, including greater prevalence of decay, dental pain, infections, need for emergent care, extractions, and even hospitalizations [2, 7–16]. Delayed diagnosis and treatment can also negatively impact outcomes for elective care like orthodontics, where treatment timing relative to dental development and craniofacial growth is key for optimal outcomes [17, 18]. Successful management of DA in pediatric patients is essential to delivering safe and effective care and minimizing negative conditioning experiences in childhood.

The American Academy of Pediatric Dentistry (AAPD) publishes behavior guidance recommendations for pediatric patients including both non-pharmacological and pharmacological interventions to assist with DA. The AAPD details approaches like tell-show-do, positive reinforcement, and positive pre-visit imagery as basic non-pharmacological methods [19]. For patients with heightened DA, pharmacological interventions, such as nitrous oxide, oral conscious sedation, and general anesthesia (GA), can be used. Nitrous oxide is often effective for anxiolysis but has contraindications, including use in patients with congestion due to allergies or with very young, pre-cooperative stage children [19, 20]. Oral sedation with benzodiazepines carries risks of loss of airway control and/or respiratory depression [20]. GA is associated with low risk of serious adverse events, including cardiovascular instability, neurological injury, and even death [21, 22]. Additionally, GA is costly, at roughly $7300 per case (around $10,300 adjusted for inflation in 2025) [21]. In 2015 alone, GA-treatment costs for children under 8 resulted in an expenditure of $16.7 M ($23.4 M adjusted for inflation in 2025) in North Carolina [23]. GA costs are a major financial burden to both private-pay families and state Medicaid systems [21, 23]. Understandably, caretakers are interested in alternatives to costly and potentially risky pharmacological interventions.

Animal-assisted therapy (AAT) is a promising alternative method for patients involving a trained therapy animal and handler to calm anxiety [19, 24]. The literature regarding AAT in medicine is plentiful and indicates benefits in both inpatient and outpatient settings for anxiety, pain, and fear [25–28]. Though only a few studies exist in dentistry, data are promising and have shown AAT to be both safe and effective in reducing anxious behaviors, improving visit perceptions, and calming patients by evaluating cardiovascular measures, endocrinological biomarkers, and self-reported anxiety and fear [29–35]. However, further research is still needed in dental settings. Via this trial, we aim to examine self-reported subjective and quantifiable behavioral and physiologic outcome measures to assess the effectiveness of AAT in pediatric dentistry.

Objectives {7}

To objectively evaluate the use of AAT in pediatric dental patients, a randomized controlled trial (RCT) was designed where pediatric patients are randomized into one of two therapy protocols (+ Short AAT exposure, + Long AAT exposure) relative to an active control (coloring a dog picture) as part of a routine dental visit. This study aims to evaluate the effect of AAT on both objective and subjective measures of anxiety and fear in pediatric dental patients. To achieve this, the primary objectives are to measure mean heart rate (HR) and salivary hormone concentrations (cortisol, α-amylase, substance P, β-endorphin, and oxytocin) prior to, during, and after the study’s dental appointment. Secondary objectives include observational coding of behavior using the Frankl scale [36] and the Paediatric Dental Pain, Anxiety, and Fear Coding Approach (PAFCA) [37] throughout the visit, along with validated, self-reported pain, fear, and anxiety scales at specific times before, during, and after the dental visit (specified in Fig. 1). Next visit expectations (NVE) questions are asked at the end of the visit. Our hypothesis is that AAT significantly alleviates objective (physiologic and behavioral) and subjective (self-reported measures of anxiety, fear, and pain) parameters in pediatric dental patients. Specifically, we hypothesize that AAT will significantly improve behavioral outcomes, NVE, and biometric and self-reported measures of DA, fear, and pain in pediatric dental patients during a routine dental examination, with the + Short AAT exposure being the most efficacious.

Fig. 1.

Study visit timeline. Study participation begins in the waiting room with consent, assent, and randomization to intervention (+ Short AAT, + Long AAT, or − AAT active control). Subjects are fitted with a continuous HR monitor and the baseline saliva sample (S₁) is collected using a buccal oral swab. Pre-visit fear, anxiety, and pain surveys are administered. Upon survey completion, patients are moved to the clinical treatment room where a continuous video feed is started. In the treatment room, experimental subjects are introduced to the therapy animal and control subjects are presented with a picture of a dog to color for 3 min. For + Short AAT groups, the therapy animal leaves the room at the end of a 3-min standardized interaction. Comparatively, the therapy dog remains chairside for the entire dental visit in + Long AAT groups. A second saliva sample (S₂) and pain scale are collected after the 3 min elapse. The dental provider then enters the room to conduct a basic cleaning with a toothbrush and floss, followed by simulated bitewing radiographs. The third and fourth saliva samples (S₃ and S₄) and pain scales are collected respectively after each event. Subjects then receive a dental exam with a subsequent fifth saliva sample (S₅) and pain scale collection, in addition to post-visit fear, anxiety, and NVE surveys. At the conclusion of the visit, patients are compensated and provided with an exam report and a referral if needed. Mean HR is measured at 5-s intervals for 1 min following specific events including (T0) first salivette placement, concurrent with being present in the waiting room for 10 min; (T1) start of video; (T2) start of intervention; (T3) end of intervention (or second salivette placement if + Long AAT group); (T4) provider entering room; (T5) start of flossing; (T6) end of flossing; (T7) toothbrush insertion; (T8) toothbrush removal; (T9) first bitewing insertion (30 s); (T10) second bitewing insertion (30 s); (T11) end of simulated radiographs; (T12) start of dental exam; (T13) end of dental exam; and (T14) provider leaving room. Created in BioRender. Jacox, L. (2025) https://BioRender.com/p61d307

Trial design {8}

We are carrying out a prospective RCT assessing whether AAT (with a short or long therapy dog intervention relative to an active control) impacts physiological parameters, behavior and perceptions of anxiety, pain, and future expectations during a diagnostic dental visit (stressor) in pediatric dental patients (4–8 years old). The dental visit includes an exam, prophylaxis, and simulated bitewing radiographs, which are ubiquitously used and stressful interventions for young children (Fig. 1). Participants are identified by chart review of patients from University of North Carolina (UNC) Hospital Children’s Primary and Specialty Clinics and UNC Adams School of Dentistry (ASOD) Pediatric Dentistry Clinics, in addition to community recruitment (e.g., flyers, mass email announcements, ResearchForMe and ClinicalTrials.gov posting, and targeted social media ads). Children meeting all enrollment criteria are consented/assented and enrolled (Tables 1 and 2). Participants are randomly assigned to intervention or control groups using a stack of blinded, sealed envelopes containing a computer-generated random sequence with an even 1/3 probability allocation (N = 180 pediatric patients [n = 60 + Long AAT protocol; n = 60 + Short AAT protocol; n = 60 − AAT active control]) (Figs. 2 and 3). To minimize imbalances between subgroups, randomization is stratified by age (< 6.5 vs ≥ 6.5 years) and gender (block size = 4). The study framework aims to test superiority of an AAT protocol (short or long intervention) over the active control and to identify a panel of validated outcome measures to be used in future research.

Table 1.

Screening questions

Questions below must be answered no to qualify
Has your child received an oral exam or dental treatment in the past month?
Has your child required or is scheduled to receive sedation, restraint, or general anesthesia for dental care?
Does your child suffer from current dental pain?
Does your child suffer from dry mouth?
Does your child have autism or developmental delays?
Does your child have a chronic pain condition?
Does your child have a history of traumatic experiences with dogs or a significant fear of dogs?
Does your child have an allergy to dogs?
Does your child have a severe allergy to toothpastes?
Does your child have a dental syndrome?
Does your child have any medical or psychiatric conditions that would make study participation difficult?

Table 2.

Enrollment criteria summary

Inclusion	Exclusion
4–8 year old healthy dental patients	Significant dog allergies and/or fear of dogs
English or Spanish speaking	Existence of a significant language barrier
Scheduled to receive a dental visit with a dental exam, cleaning and simulated radiographs, and has not received a dental cleaning or oral exam in the past month	Patients scheduled to receive or previously requiring sedation, restraint, or GA during dental visits
Parental consent and patient assent to participate indicating the participant (or legally acceptable representative) has been informed of all pertinent aspects of the trial and all their questions have been answered	Developmental/cognitive disability such that the patient cannot self-assent, comprehend, and follow the requirements of the study based on research site personnel’s assessment
Children who have no established psychiatric disorders nor severe DA	Patients with current dental pain, developmental delays, or severe acute or chronic medical or psychiatric conditions that would increase the risk associated with participation or make the subject inappropriate for entry in trial
Children with a history of well-managed anxiety, depression, and/or attention-deficit/hyperactivity disorder (ADHD)	Psychiatric conditions that are excluded include autism spectrum disorder, conduct disorder, obsessive-compulsive disorder, oppositional defiant disorder, post-traumatic stress disorder, Tourette syndrome, and severe, unmanaged anxiety, depression and/or ADHD or other significant psychiatric disorder that would prevent participation, as judged by the investigator
Stable physical health (ASA I–II), decided at the discretion of the study coordinator and principal investigator (PI)	Known allergies or significant adverse reactions following exposure to dogs or the use of oral hygiene products (toothpastes, mouth rinses, and prophy paste)
Able to comprehend and follow the requirements of the study (including availability on scheduled visit dates) based on research site personnel’s assessment	Children who are afraid of dogs or had a prior negative experience with dogs as reported by the parent or child

Fig. 2.

Enrollment flow chart. Potentially eligible participants are screened through community recruitment and chart review of UNC Hospital Children’s Primary and Specialty Clinics’ and UNC ASOD Pediatric Dentistry Clinic patients, and contacted via phone. All interested participants meeting all inclusion criteria (Table 2) are consented/assented, randomized, and enrolled. Pediatric participants (N = 180) are enrolled and equally randomized to one of three arms (+ Short AAT, n = 60; + Long AAT, n = 60; − AAT Control, n = 60). Patients randomized to both the + Short AAT (n = 60) and + Long AAT (n = 60) are introduced to the therapy dog in a standardized intervention for 3 min prior to the start of the dental visit. This standardized, brief interaction includes introduction to the animal, petting, feeding treats, and paw-shaking. For the + Short AAT intervention, this interaction concludes with the child saying goodbye as the therapy dog and handler leaves the room before the dental visit begins, as is routinely and feasibly done in UNC pediatric dental clinics. For the + Long AAT intervention, the dog and handler remains chairside throughout the dental visit, similar to other studies with long AAT interactions; the dog can sit on the chair with the child if desired by the patient [30–32]. Controls (− AAT, n = 60) engage in an active control (coloring a picture of a dog) for 3 min prior to the start of the dental visit. Created in BioRender. Jacox, L. (2025) https://BioRender.com/u57p054

Fig. 3.

Schedule of enrollment, interventions, and assessments. Potential study participants are first screened for eligibility via phone (− t₁), and eligible participants are then scheduled for an in-person study visit. After arrival, participants and guardians are consented/assented (t₀). Baseline assessments are then collected (t₁) prior to allocation to intervention (t_a), including HR, saliva samples, and pain, fear, and anxiety surveys. Patients then move to the clinic room for the remainder of the visit, including intervention (t₂), prophylaxis (t₃), simulated radiographs (t₄), and a dental exam (t₅)

Methods: participants, interventions, and outcomes

Study setting {9}

All study visits are conducted in the private Jacox Laboratory clinical research rooms at UNC ASOD in Chapel Hill, NC. Consent and assent are obtained in a private waiting room outside of the clinical research rooms. After obtaining consent, continuous HR data (using a wrist-worn device), baseline fear, anxiety, and pain surveys, and the first saliva sample (using a buccal oral salivette) are collected. Participants are then escorted to the private clinical research room for the remainder of the study visit.

Eligibility criteria {10}

Participants are children aged 4–8 years old who have not received a diagnostic dental exam and cleaning in the previous month (Tables 1 and 2). Prior to enrollment, potential participants’ legal guardians are asked a series of screening questions during a phone call (Table 1). Individuals meeting all enrollment criteria are scheduled for a study visit, sent consent documents by email, and then are consented, assented, and enrolled in person at the study visit (Table 2). To be enrolled, children must have no significant allergies to or fear of dogs. They must have no significant developmental delays, have no medical or psychiatric comorbidities, and be in stable physical health (ASA I–II) as judged by the study team. The full list of enrollment criteria is included in Table 2.

Participation does not change already planned dental restorative care for the children, but exam findings and a dental provider referral (when needed) are provided to the child’s legal guardian at the visit’s end.

Who will take informed consent? {26a}

Informed parental consent and child participant assent are obtained by a trained, HIPAA-compliant study coordinator. Consent and assent documentation is sent to legal guardians by email at least 1 day in advance of their study visit to allow them time to review documentation. When the guardian and participant arrive for the study visit, the study coordinator reviews these documents and answers any questions. Since all participants are minors aged 4–8 years old, signed informed consent (guardian) and assent (youth) are obtained prior to enrollment and allocation into one of the study arms.

Additional consent provisions for collection and use of participant data and biological specimens {26b}

In addition to participant consent documentation, legal guardians are provided with a consent form for storage of biological specimens, without identifying information, in a biorepository. This informed consent form permits the researchers to store the biological specimens and biometric data (i.e., including saliva samples, HR data, and videographic data) collected during the study visit for future, unspecified use. By signing this consent form, participants and caregivers give their permission for researchers to use these de-identified biological specimens and biometric data in future studies. Saliva samples are collected at multiple time points during the study visit and stored at − 80 °C prior to downstream processing and analyte analysis. HR and videographic data are collected simultaneously throughout the study visit and are stored on secure UNC ASOD servers.

Interventions

Explanation for the choice of comparators {6b}

As there is a lack of guidelines on AAT use in dentistry, this protocol incorporates two AAT interventions: the + Short and + Long AAT protocols. The + Short AAT protocol is a brief, feasible, and easily disseminated approach that is routinely used in UNC’s pediatric dental clinics; the patient is introduced to the dog by the handler for 3 min at the appointment start and then the handler and dog leave the room when the dental care begins. The 3-min period was empirically determined and is a standardized intervention developed by our pediatric dentist dog handlers, who have introduced the therapy dog to hundreds of pediatric patients. It allows for the dog to circulate through the clinic and interact with many patients. The + Long AAT protocol incorporates a therapy animal and handler who are introduced to the patient before the dental visit with the same 3-min initial interaction and then are seated chairside throughout the appointment, similar to some other AAT dental studies [30–32]. An active control of coloring of a dog picture was selected based upon recommendations from our behavioral science collaborators; an active control helps to engage young participants and is consistent with other behavioral studies [38, 39]. Control patients did not have any interaction with the therapy animal during the study visit and were not told about AAT.

Intervention description {11a}

For participants randomized to the + Short AAT intervention, the handler brings the therapy dog to the patient, introduces them, and allows the child to pet the dog, shake its paw, feed it treats, and say goodbye for 3 min prior to the dental visit. The + Long AAT protocol includes the same 3-min introduction designed for the + Short AAT intervention. However, the therapy dog and handler remain chairside throughout the remainder of the dental visit. Rather than participate in the 3-min therapy animal interaction used by the + Short and + Long AAT protocols, active controls engage in a coloring activity where they are provided with crayons and an image of a dog for 3 min prior to the dental visit.

Criteria for discontinuing or modifying allocated interventions {11b}

Participants who are randomized to AAT interventions have the dog interaction discontinued in the event that the therapy dog is deemed visibly uncomfortable, afraid, or aggressive by either the therapy animal handler or the study team at any point during the study visit. If this occurs, the therapy animal is promptly removed from the clinical treatment room, ending the interaction between the participant and animal. AAT interventions are also discontinued upon participant or legal guardian request or if the patient develops a noticeable, previously unreported, allergic reaction to the dog. In all cases, participants are excluded from analysis if they discontinue early in the visit (before or during the intervention or before any dental interventions), and their randomized allocation is reentered into the pool. If any participants must discontinue participation mid-visit (after intervention and some dental interventions), their data will be included in the intention-to-treat analysis, and their allocation will not be reentered into the pool. Data collected after discontinuation will be logged as missing data.

Strategies to improve adherence to interventions {11c}

To improve adherence to the study protocol, dental providers and study coordinators implement routine, non-pharmacological basic behavior guidance techniques as recommended by the AAPD, including tell-show-do, voice control, distraction, and positive reinforcement [19, 40]. Providers explain, demonstrate, and complete all procedures, and reinforce desired behavior throughout the visit. Patients are provided with a mirror during prophylaxis to demonstrate brushing techniques, and if distracted, they are redirected using changes in voice cadence or volume. Since this is a single visit study, there are no systems in place to enhance follow-up and adherence after the visit.

Relevant concomitant care permitted or prohibited during the trial {11d}

Patients are encouraged to continue seeing their family or pediatric dentist for routine care after the study visit, such that there is no prohibited concurrent care. Patients are not seen for a study visit within 1 month of their prior, routine dental prophylaxis and exam.

Provisions for post-trial care {30}

Legal guardians of the minor participants are provided with a summary of intraoral exam findings by the dentist. The summary includes an assessment of oral hygiene and any findings of oral pathology, dental caries, malocclusion, and urgency of seeing a dental provider for any additional treatment. Recommended additional treatment options include instructions to continue routine care as scheduled, seek additional care in the next month, or seek additional care urgently. All guardians are informed that the study exam does not replace routine dental care with their child’s dentist. A referral for a nearby pediatric dentist or specialty provider is provided if the participant has no established dental home or requests provider recommendations.

Outcomes {12}

The primary outcome of this RCT is to measure the impact of AAT on objective measures of stress using HR and salivary stress and pain hormone concentrations (cortisol, α-amylase, oxytocin, substance P, and β-endorphin) prior to, during, and after the dental visit. Participants are fitted with a Polar Verity Sense (Polar Electro, USA) HR monitor around their wrist at the start of the visit. HR (beats per minute) is plotted over time to evaluate potential elevations or depressions; mean HR is calculated at key events during the visit in 5-s intervals over 1 min; key events are summarized in the legend of Fig. 1.

Salivary samples are collected using salivettes (SalivaBio Oral Swab, Salimetrics, LLC., Carlsbad, CA, USA) placed bilaterally in the lower buccal vestibule. Samples are collected at five key time points: baseline, after AAT intervention or active control coloring, after prophylaxis, after simulated bitewing radiographs, and after the intraoral exam. Salivettes are left in the buccal vestibules for 2 min to accumulate sufficient saliva and then stored in Swab Storage Tubes (Salimetrics, LLC., Carlsbad, CA, USA). At the end of the visit, the salivettes inside Swab Storage Tubes are spun at 1500 × g per manufacturer instructions to isolate the saliva and stored at − 80 °C prior to downstream analysis. Enzyme-linked immunosorbent assay (ELISA) analyses of salivary cortisol and α-amylase are performed by the UNC Biobehavioral Lab. Salivary pain biomarkers, including substance P, β-endorphin, and oxytocin, will be quantified using a custom-built Milliplex® Luminex panel. Stress and pain hormone levels will be evaluated at specific time points and relative to baseline, following visit events.

Secondary objectives include observational coding of behavior throughout the visit using PAFCA and scoring behavior with the Frankl scale by the licensed dental provider [36, 37]. Two video cameras for behavioral coding are set up in the exam room and turned on upon entry. One camera, positioned above the chair, is directed towards the patient’s upper body. A second camera is located along the wall at the base of the chair to capture a more holistic view of the room. Video recordings are monitored throughout the visit and are later coded using Noldus Observer XT software by calibrated examiners. Coding begins with watching a video from start-to-finish, followed by re-watching the video with detailed coding. To avoid examiner fatigue, coding sessions are limited to 2 h. Details for our coding protocol are included in Bocklage et al. [37].

Secondary objectives also include subjective, self-reported pain, fear, and anxiety scales at specific times before, during, and after the dental visit to gain information about the patient experience and to provide a patient-reported outcome (specified in Figs. 1 and 3). NVE questions are asked at the end of the visit so patients can report on how the visit influenced their view of future dental care. Validated questionnaires include the Modified Child Dental Anxiety Scale (MCDAS), the Child Fear Survey Schedule-Dental Subscale (CFSS-DS), and the Wong-Baker FACES Pain Rating Scale (FACES), which are used widely in similar studies with children [41–50]. The CFSS-DS, MCDAS, and FACES surveys are given in the waiting room at the beginning of the visit. After these initial surveys, the FACES scale is administered at three more specific time points during the study visit concurrent with saliva collections: post-intervention, post-dental cleaning, and post-simulated radiographs (Fig. 1). Following the completion of the visit, the CFSS-DS, MCDAS, and FACES surveys are completed once more in addition to NVE questions (NVE questions are included in Table 3). Peer-reviewed publications evaluating NVE questions were not available at the time of study design, so we developed our own under the guidance of a survey expert at the UNC Odum Institute for Research in Social Science. A series of questions were pre-tested by 15 lay people (aged 4–35), with iterative revisions to ensure comprehension and clarity. The NVE questionnaire consists of three questions to evaluate participants’ happiness, sadness, excitement, and fear regarding future dental visits. Answer choices regarding specific emotions use facial emojis (see Fig. 4 and Additional file 1) and are assigned scores of − 2 to + 2, where each question is scored with its own scoring criteria. The combination of these objective and subjective outcome measures will allow us to identify optimal outcome measures for future studies and will help to evaluate the efficacy of AAT.

Table 3.

Next visit expectations survey

Question		Answer choices and assigned scores
1. In general, how do you feel about going to the dentist next time?	a. Happiness	Very happy (+2), a little happy (+1), in the middle (0), a little not happy (−1), not happy (−2)
	b. Sadness	Not sad (+2), a little not sad (+1), in the middle (0), a little sad (−1), very sad (−2)
	c. Excitement	Very excited (+2), a little excited (+1), in the middle (0), a little not excited (−1), not excited (−2)
	d. Fear	Not scared (+2), a little not scared (+1), in the middle (0), a little scared (−1), very scared (−2)
2. Did today’s visit change how you feel about going to the dentist next time?		Yes, don’t know, no
3. After today’s visit, how do you feel about going to the dentist next time?	a. Happiness	More happy (+2), a little more happy (+1), the same (0), a little less happy (−1), less happy (−2)
	b. Sadness	Less sad (+2), a little less sad (+1), the same (0), a little more sad (−1), more sad (−2)
	c. Excitement	More excited (+2), a little more excited (+1), the same (0), a little less excited (−1), less excited (−2)
	d. Fear	Less scared (+2), a little less scared (+1), the same (0), a little more scared (−1), more scared (−2)

Fig. 4.

NVE questionnaire facial emoji scales. Subjects are surveyed on their happiness, sadness, excitement, and fear regarding future dental visits, both in general and specifically after the study visit (NVE questions are included in Table 3). Subjects respond using emoji scales for each emotion, which are scored -2 to +2 (right to left on scale)

Participant timeline {13}

Prospective participants and their guardians are contacted via a phone call, where they are evaluated for eligibility through screening questions (Tables 1 and 2). Participants meeting all criteria are enrolled and scheduled to attend an in-person study visit at UNC ASOD (Figs. 1 and 3). Upon arrival at the dental school, participants and their guardians are escorted to a private waiting room where informed consent and assent are obtained. Participants are then outfitted with a wrist-borne, wireless continuous HR monitor (Polar Verity Sense, Polar Electro, USA); baseline HR is gathered after a few minutes of rest and the device remains on the patient throughout the visit. While in the waiting room, a baseline unstimulated saliva sample (S₁) is collected using salivette swabs and pre-visit surveys on fear (CFSS-DS), anxiety (MCDAS), and pain (FACES) are administered. Patients are then escorted to a private clinical treatment room, where GoPro video cameras are positioned unobtrusively to collect continuous full-body videographic data for later observational coding in Noldus Observer XT software using the PAFCA coding approach. Once in the clinic room, participants are either presented with an active control activity (coloring a picture of a dog) or are introduced to a canine therapy animal by their handler (+ Short AAT and + Long AAT). After 3 min, a second saliva sample (S₂) is collected, and the pain survey is administered. Participants receive a basic dental cleaning, simulated bitewing radiographs using a non-operational Nomad X-Ray device, and an oral exam by a licensed dentist (Fig. 1). Additional saliva samples and the pain survey are collected at key timepoints throughout the visit (S₃–S₅, Fig. 1). At the conclusion of the visit, patients complete self-reported post-visit fear, anxiety, pain, and NVE surveys, and the legal guardian is provided with a clinical report with any findings and recommendations.

Sample size {14}

To guide sample size, power calculations are completed for our primary outcome analysis of salivary cortisol and α-amylase levels. We estimate the study’s sample size (n = 50 per group, 150 total) to have 80% power to detect effect sizes of 0.81, where 0.81 corresponds to 117.8 (U/mL) α-amylase and 11.8 (nmol/L) cortisol [51]. α will equal 0.05, and thus we will use a conventional p < 0.05 statistical significance criterion. In anticipation of a 15% attrition rate, n = 60 children/group will be enrolled (Fig. 2).

Recruitment {15}

Potential participants are identified through chart review of pediatric patients at UNC Hospital Children’s Primary and Specialty Clinics and UNC ASOD Pediatric Dentistry Clinics. Community recruitment, including flyers, mass email, and targeted advertisements on Facebook and Instagram, is also implemented in addition to a ResearchForMe and ClinicalTrials.gov study posting.

Assignment of interventions: allocation

Sequence generation {16a}

Participants are assigned to one of two interventions or an active control group with an even allocation (1/3) probability using a computer-generated random sequence generated by a statistician, who is not part of the study team. Randomization is stratified by age (< 6.5 vs ≥ 6.5) and gender (block size = 4) to reduce imbalances between subgroups.

Concealment mechanism {16b}

Results of the computer-generated random sequence are placed in opaque, blinded, sealed envelopes. One sealed envelope is opened by a study coordinator at the start of each visit to determine participants’ allocation arm, after informed consent (legal guardian), assent (patient), and enrollment. If a participant is excluded from analysis due to early discontinuation, his or her randomized allocation is placed back into an opaque, sealed envelope that is reentered into the pool.

Implementation {16c}

Study coordinators ask a series of screening questions to determine if the participant meets enrollment criteria prior to scheduling, enrollment, and allocation (Tables 1 and 2). All participants (and their legal guardian) are enrolled, consented, and assented by a trained, HIPAA-compliant study coordinator. Once consented and enrolled, a blinded, sealed envelope is opened to determine allocation of the participant. The allocation sequence is generated using a computer-generated random sequence by a statistician, who is not on the patient-facing study team.

Assignment of interventions: blinding

Who will be blinded {17a}

Due to the study’s use of a dog and handler for the short and long AAT arms and coloring for the active control, child participants and dental providers cannot be blinded during the study visit. However, participants and their legal guardians are not informed of possible interventions before the study visit during screening; the therapy dog is not mentioned and guardians who are aware of the possibility of animal therapy are asked to not mention this to their children. Therefore, patients randomized to one arm are not aware of the other possible interventions. Participants and providers are unaware of a patient’s allocation, until the start of the dental visit. During the dental visit, participants and providers can see the intervention (coloring or dog) and therefore are unblinded. Staff members in charge of allocation and assignment are not on the dog study team and are not involved in data analysis. Staff and students involved in data analysis are blinded to the allocation of participants and their exposure, except for behavioral coding of video where the dog is sometimes visible.

Procedure for unblinding if needed {17b}

There is no unblinding procedure, as the participants and dental providers are unblinded during the dental study visit itself. As a result, if a safety or allergy concern arises, they are already aware of their intervention and can report it to any necessary medical personnel. For analysis, there is no need to unblind data as it has no health-related implications for the patients and no follow-up information is provided.

Data collection and management

Plans for assessment and collection of outcomes {18a}

All data are collected by trained, HIPAA-compliant study coordinators. To fulfill the primary objectives, HR and saliva samples are collected throughout the visit for downstream analyses. Continuous HR data are collected by the Polar Verity Sense (Polar Electro, USA) wearable wrist device, which has been validated and previously used to measure HR as a reflection of stress [52, 53]. Mean HR is plotted over time and measured relative to specific visit events. Passive, unstimulated saliva samples are collected using SalivaBio Oral Swabs (Salimetrics, LLC., Carlsbad, CA, USA) at five specified time points (S₁–S₅, Fig. 1) and stored at − 80 °C. Salivary cortisol will be measured by an Expanded Range High Sensitivity Salivary Cortisol Immunoassay Kit (Salimetrics®, State College, PA) in duplicate and according to the manufacturer’s instructions. Salivary α-amylase will be quantified using a Salivary α-amylase Kinetic Enzyme Assay Kit (Salimetrics®, State College, PA) according to manufacturer recommendations in singles. ELISA analyses of salivary data are completed by the UNC Biobehavioral Lab, whose technicians have extensive experience with these techniques. Salivary pain biomarkers, including β-endorphin, oxytocin, and substance P, will be quantified using a custom-built Milliplex® Luminex panel, which is a validated platform used for salivary analyses to detect and quantify expressed proteins [54–57]. Salivary hormone and mean HR data are compared across time points and events (Fig. 1).

Self-reported DA is assessed using the MCDAS at the beginning and conclusion of the study visit. The MCDAS is a modified version of the widely used Corah’s Dental Anxiety Scale [58] and contains questions about specific dental procedures [59]. It has been commonly used with children aged 4–15 and is a reliable and validated test [41–44]. The CFSS-DS is used to measure self-reported dental fear at the start and end of the appointment. This reliable and validated tool [42, 45, 46] has been used in children aged 4–14 for similar studies to ask about specific dental fear items [47, 48]. The participant’s perceived pain is measured at five specified time points throughout the visit (Fig. 1) using the FACES survey, a tool which reports high validity and responsiveness in children as young as 3 [49, 50]. Future expectations are evaluated at the appointment end by our NVE questionnaire, which was developed and extensively pre-tested by the investigators in association with a research survey expert at the UNC Odum Institute for Research in Social Science (described above in Outcomes {12}); 15 respondents aged 4–35 pre-tested the survey to confirm reliability, comprehensiveness, and clarity.

All participant response data are collected using the Carolina Data Acquisition and Reporting Tool (CDART) dental toolkit program, which stores de-identified data on a secure, encrypted UNC server. The CDART data collection forms are included in Supplementary information (see Additional file 1).

Continuous videographic recordings are collected by two GoPro Hero9 cameras in the clinic room, located both above the patient’s chair and across the room facing the foot of the chair. Two cameras are used in case one fails to function and provide two views for full-body data. All data are directly uploaded to and stored on secure UNC servers. Behavioral coding of videographic data is completed by two experienced, calibrated coders with Noldus Observer XT software using PAFCA [37]. Training and calibration for coders are described in a recent publication reporting the PAFCA coding methodology [37], with inter-rater reliability checks every five coded videos.

Multiple licensed dental providers will be employed in this study. To limit variability, all providers are trained and calibrated on the study protocol, have in-room directions to ensure consistent study flow, and are provided with a script for interacting with the patient (Additional files 2 and 3). Prior to seeing patients, providers are calibrated by practicing the study visit script and procedure with trained study coordinators to ensure familiarity, consistency, and protocol adherence. All providers are trained at UNC ASOD and have similar approaches to treatment recommendations.

Plans to promote participant retention and complete follow-up {18b}

All participant data are collected during a single study visit. While participants’ guardians are provided with a referral for any outstanding treatment needs, there is no need for follow-up or retention for the sake of the study. If a participant must discontinue participation mid-visit, their data collected during the visit will be included in the intention-to-treat analysis, as described below. Data collected after discontinuation following intervention will be logged as missing, and participants who discontinue prior to intervention will be excluded from the study and analysis.

Data management {19}

All data collected during the study are stored on secure, encrypted, password-protected UNC servers. Data are only accessible to study personnel who have all received HIPAA, Human Subjects and Good Clinical Practice training through the CITI program. All personnel are certified to work with patient data on clinical trials. Additionally, study coordinators and healthcare providers have been trained in and approved for the use of protected health information, the CDART electronic research database and EPIC medical record system. Research coordinators monitor all study staff to ensure protocol compliance and quality assurance. Any protocol deviations are recorded by study personnel during the study visit. Investigators and study coordinators meet weekly to review any unanticipated problems, adverse events, and protocol deviations to ensure proper recording, reporting, and response plans. Information on data de-identification and use of linkage files is included below under Confidentiality.

Confidentiality {27}

All participant information and linkage files are stored in Excel spreadsheets on password-protected, secure UNC servers. Information on screened, potential participants (i.e., screen failures) who are deemed ineligible or declined participation is destroyed quarterly. For all enrolled and consented patients, an Excel linkage file that relates patient names and contact information with random alphanumeric codes is created and stored securely and separately from the patients’ study data; only key study personnel have access to this separate linkage file. All participant data collected at the study visit are de-identified, through labeling with the alphanumeric codes. Data are analyzed and used by the study team with these random alphanumeric identifiers. The linkage file connecting the alphanumeric codes and identifiable information will be destroyed upon conclusion of the study. The encrypted, password-protected UNC CDART database is used to store all data coded with alphanumeric codes. Any paper records, including consent forms, are stored in locked file cabinets only accessible by members of the study team. Data transfers are only done using UNC servers between research team personnel with secure user accounts.

Plans for collection, laboratory evaluation, and storage of biological specimens for genetic or molecular analysis in this trial/future use {33}

Throughout the study visit, unstimulated saliva samples are collected using salivettes placed in the participant’s buccal vestibules. These samples are later centrifuged at 1500 × g for 10 min and aliquoted into pre-labeled, 1-mL Eppendorf collection tubes for storage at − 80 °C until analysis. ELISA analyses are conducted on saliva samples to measure salivary cortisol and α-amylase by the UNC Biobehavioral Lab. Salivary pain biomarkers will be quantified using a custom-built Milliplex® Luminex panel. Any unused samples are returned to storage in a specimen repository at UNC ASOD for future unspecified use in ancillary studies. Legal guardians sign a consent form for storage of biological specimens in a biorepository, such that our team can use the de-identified specimens and physiologic data for future, unspecified use, including genetic or molecular analyses.

Statistical methods

Statistical methods for primary and secondary outcomes {20a}

For all primary and secondary outcome measures, initial analyses will entail calculation of descriptive statistics and visualization of distribution and range both overall and at previously indicated key visit events in an intention-to-treat analysis. Primary biometric outcome data measures (HR and salivary hormones) will be tested to determine if the data are normally distributed before measuring differences between intervention groups (− AAT Control, + Short AAT, and + Long AAT) both overall, and at specific timepoints. Salivary cortisol, α-amylase, and pain biomarker data will be log₁₀-transformed prior to analysis and testing. Biometric response data, after logarithmic transformation, if necessary, that are determined to follow normal distribution will be evaluated using one-way ANOVA or linear regression models if covariates need to be considered. Post hoc analyses after ANOVA testing for significance of pairwise comparisons between intervention groups will be performed using Tukey’s test. If specific pair-wise comparisons between an intervention group against the control is to be investigated, Dunnett's test shall be used instead of Tukey’s after ANOVA. Both Dunnett's test and Tukey’s test output adjusted p-values to control the overall error rate (family-wise error rate). Non-normally distributed primary outcome data will be analyzed in one of the three strategies. One is to use nonparametric tests (e.g., Kruskal–Wallis) to evaluate differences between intervention groups, with Dunn's test as the post-hoc method for p-value adjustment. Second, outcome data after transformation, e.g., log transformation, may be fit in a linear regression model. Third, depending on the distribution of the data, generalized linear models (GLM) may be considered, for example, Poisson distribution for count data or Zero-inflated negative binomial distribution (ZINB) for zero-inflated count data [https://pubmed.ncbi.nlm.nih.gov/37167422/]. False discovery rate (FDR) to control false positive rates for multiple testing adjustment will be considered after fitting linear regression models. Secondary outcome measures, including observational coding and self-reported anxiety, fear, pain, and NVE, will also be assessed for normality prior to analysis. Observational coding data will be evaluated using one-way ANOVA and Tukey’s post hoc analyses if normal, or Kruskal–Wallis tests with Dunn’s post hoc if non-normal. Subjective survey data (anxiety, fear, NVE, and pain) will be analyzed via Kruskal–Wallis and post hoc Dunn’s tests.

Secondary analyses controlling for potential covariates and nuisance variables (i.e., age and gender) will be conducted for biometric data using ANCOVAs (if normally distribution) or ordinal logistic regression models (if non-normally distributed) with appropriate post hoc analyses. Continuous HR data will be further evaluated using a linear mixed effects model if normally distributed or a generalized linear mixed effects model if not, in which dental providers effects are treated as random effects. Since multiple dental providers will participate in study visits, we will also run a comparative analysis to evaluate for possible discrepancies in data between clinical examiners at both the interim and final analyses. All analyses will use a statistical significance threshold of p < 0.05 and will be performed using the GraphPad Prism software (Boston, MA) and R4.2.2.

Interim analyses {21b}

An interim analysis will be performed at the halfway point of the study when 30 participants have been enrolled in and completed each of the study groups (N = 90). The study will be stopped if no significant or borderline significant (p < 0.15) differences are found between the active control group and the two + AAT groups for any primary or secondary outcome. Interim results will only be made available to the study team and PI, and will not be published, as long as the study continues to full completion because they are based on underpowered analyses. At interim analysis, data collected with each dental provider will be compared across providers to identify any major differences in approach, to guide any necessary retraining for consistency. Due to the study’s minimal risks, we do not anticipate stopping the study for safety reasons. The study team and PI will review the results and determine whether there is a need to terminate the trial due to poor study performance.

Methods for additional analyses (e.g., subgroup analyses) {20b}

The study team will evaluate outcome measures for their feasibility and usability with consensus meetings at interim and final analyses. Outcomes will be evaluated for their clinical feasibility and our ability to gather complete datasets through qualitative comments and a review of datasets. Associations across outcome measures (subjective survey responses, coded behaviors, and objective measures) will be evaluated for correlations using Spearman’s ρ to construct a correlation matrix between measures. Outcome data may also provide for improved power calculations for future studies aimed at evaluating AAT intervention superiority.

Methods in analysis to handle protocol non-adherence and any statistical methods to handle missing data {20c}

All collected participant data will be considered in the main analysis as a randomized, intention-to-treat analysis. Participants with missing data (i.e., incomplete HR, insufficient saliva samples, or study discontinuation mid-visit) will still be included in analyses. Non-adherence is considered repeated refusal to follow the study protocol or requesting to be removed from the study by the guardian or patient. Participants who follow the study protocol through some of the dental care (prophylaxis, radiographs, or exam) and then discontinue participation (due to non-compliance or a request to end the visit) will have their data included through discontinuation; data collected after discontinuation will be logged as missing. Participants are excluded from the study and analysis only if they discontinue participation early in the visit (before or during the intervention or before any dental care); these participants will be removed from the dataset. Strategies are employed to reduce missing data, including behavior management approaches, back-ups of equipment, replacement of batteries and older devices, and careful reporting of incomplete data causes. Missing data will be addressed through a complete case analysis for each outcome measure. Subjects with missing saliva or HR timepoints, survey response items, or noncontinuous, incomplete video recordings will be excluded from analysis for that specific outcome measure.

Plans to give access to the full protocol, participant-level data, and statistical code {31c}

After completion of the study and publication, the public will be granted access to the protocol and de-identified participant data on ClinicalTrials.gov and in a publicly accessible database, the Carolina Digital Repository, which is a public repository funded by the National Institutes of Health (NIH). Identifying participant level data will never be released as linkage files will be destroyed by trained study personnel upon conclusion of the study. Without the linkage file, it is impossible to identify individual participants. Additional details can be found in the Data management, Data dissemination, and in the Availability of data and materials sections.

Oversight and monitoring

Composition of the coordinating center and trial steering committee {5d}

This study is a human subject investigation and is therefore governed by the UNC Institutional Review Board (IRB) and the Office of Human Research Ethics. This is a single site investigation, such that there is no coordinating center and no trial steering committee. In addition to conducting study visits, trained study coordinators are responsible for screening, enrolling, consenting, and scheduling all participants daily. The PI manages the lab personnel and study. The study coordinators and PI meet weekly to review the study and discuss any concerns. Monthly audits of study documentation are conducted by a clinical research unit (CRU), third-party staff.

Composition of the data monitoring committee, its role and reporting structure {21a}

This study has no data monitoring committee (DMC), as it evaluates a low-risk intervention and participants are healthy (ASA I–II). A DMC is not recommended or required for this protocol by the UNC IRB, NIH, and National Institute of Dental and Craniofacial Research (NIDCR).

Adverse event reporting and harms {22}

All unanticipated effects and adverse events will be documented and reported to the IRB committee supervising the study as soon as possible and always within 7 days of the event occurring, pursuant with their policy. The PI and study team will meet weekly to discuss any safety concerns, adverse events, or unanticipated problems. The investigator and third-party auditor from our CRU will monitor the study and subject data.

The use of AAT and data collection methods for saliva, continuous HR, video data, and survey responses carry no more than minimal risk for participants. In the case of an adverse event or other unintended effects, the participant will be referred to UNC Hospital along with their legal guardian. The UNC Hospital system will be responsible for all follow-up visits and procedures related to the adverse events. During business hours, when we plan to undertake study visits with research participants, there is an in-house emergency response team (i.e., onsite oral surgery team) that responds to medical emergencies. The UNC Hospitals are physically connected to the dental school allowing efficient transport to the emergency room if ever needed. A trained study coordinator will contact the participant 1 week following the adverse event for a follow-up check-in.

Frequency and plans for auditing trial conduct {23}

Monthly audits of data are completed by a third-party auditor, who is an experienced study coordinator and research hygienist in our UNC ASOD CRU.

Plans for communicating important protocol amendments to relevant parties (e.g., trial participants, ethical committees) {25}

For protocol changes, the PI and faculty collaborators will confer with each other and with the study team. In the event of a desired protocol amendment, the protocol change will be submitted to the IRB for approval. Once approved by the IRB, the protocol and version number will be updated for the team and on ClinicalTrials.gov. Changes in enrollment criteria would be updated on ClinicalTrials.gov, UNC ResearchForMe postings, and in any recruitment materials.

Dissemination plans {31a}

The protocol is included in detail in this publication. Results of the study itself will be published in separate manuscripts and made accessible to the scientific community, healthcare professionals, and the public. Findings will also be shared through national and international conference presentations; conferences will be for the dental healthcare community. De-identified data will be reported on the ClinicalTrials.gov database per government policy and in resulting publications. De-identified datasets will be made available to the Carolina Digital Repository, a NIH-funded public repository with data access policies and procedures consistent with NIH Data sharing policies and applicable laws and regulations. There are no contractual agreements affecting access to data and there are no publication restrictions.

Discussion

The goal of this RCT is to identify optimal outcome measures for studying AAT use in dental settings, to add to existing data on the impact of AAT on pediatric DA, and to determine potential superiority of an AAT protocol. The study’s results may also contribute to the development of guidelines for further research and implementation of AAT in dental offices.

Collecting multiple objective and subjective measures is a valuable feature of the present protocol. Other existing studies of AAT utilize a single or limited number of outcome measures, with great variability in which measures are used across studies [31, 33, 34, 60]. Additionally, many of our measures (e.g., HR, salivary hormones, and self-report scales) are reliable, validated methods used in similar study designs and are feasible in children [41–50, 61, 62]. Relative to published literature, another strength of this study is its larger sample size (N = 180) with adequate power. Published sample sizes range from 12 to 102 participants [31, 33–35]. Participants’ age also varies greatly between studies, ranging from 4 to 14 years old [31, 33]. We selected a limited age range of 4 to 8 years old to minimize developmental differences between growing children, while still including those who are young enough to find routine, prophylactic dental visits anxiety-inducing and old enough to independently answer questionnaires [63–66]. Furthermore, other studies have used convenience sampling and/or chance randomization via coin flips to divide participants into study groups without stratification [31, 33]. For randomization, this study uses a robust computer-generated random sequence with an even 1/3 allocation and stratification based on gender and age to help create comparable groups.

Another unique aspect of this study is the evaluation of two AAT interventions. Some studies have had a therapy animal present for extended periods during dental visits, while others include only an initial interaction with the therapy dog [31, 33–35, 67]. By having both a long and a short dog protocol in this RCT, we hope to demonstrate which intervention is most effective at managing DA and influencing pediatric patients’ dental experiences. Standardizing AAT implementation protocols will be valuable for future studies while providing recommendations for implementation in practice.

The study population is not limited to children with DA because we do not know which patient populations will benefit most from AAT. It is possible that children who do not have DA or exhibit mild DA, but are likely to develop DA from adverse experiences, may benefit from AAT, whereas children with moderate to severe DA may be less responsive. Alternatively, AAT may benefit all groups to equal or varying degrees. The baseline DA assessment through self-report measures will allow future data stratification by level of DA (none, low, high) and offer insight into which pediatric DA groups may be most responsive to AAT.

It is important to note that potential issues can arise when administering self-reported questionnaires. Children may have never experienced certain situations in the questionnaires, such as a dentist drilling or receiving a filling, which can influence their reported dental fear and anxiety. Younger children could also experience survey fatigue, which can lead them to not fully consider their responses despite prompting. Due to these considerations and to achieve a holistic evaluation of AAT’s effects, this protocol implements both subjective and objective measures of fear and anxiety. Objective physiologic measures also provide a more mechanistic insight into effects of AAT. The inclusion of multiple subjective and objective measures of DA and fear will help provide a more complete understanding of the child’s experience and guide best practices for research on behavioral interventions in pediatric dentistry moving forward.

One potential limitation is the use of multiple licensed dental providers, despite our best efforts to calibrate these providers through training, scripting, and this protocol (Additional file 2). Prior to encountering study participants, providers practice the scripted visit with study coordinators to ensure protocol adherence and proper calibration between providers. Data collected with each dental provider will be compared to identify any major differences in approach at interim and final analyses, though we do not anticipate issues due to our training approach. Additionally, some children will require more non-pharmacological behavioral modification approaches (i.e., tell-show-do, volume modulation) than others based on their ability to comply with the protocol. This variation is representative of naturalistic dental treatment settings, and randomization to arms should help to account for this variability across children and providers. A future crossover study design with two study visits may provide some advantages, so that a participant can serve as their own control, thereby limiting the impact of sources of variation between participants.

Additional methods of behavior and anxiety management are needed within dentistry to limit use of more costly and risky pharmacological techniques. Providing positive dental experiences during childhood may also help mitigate the development of dental anxiety and improve lifelong oral health outcomes. Identifying optimal outcome measures for studies of behavioral interventions in pediatric dentistry and studying effects of AAT in children may provide additional non-pharmacological approaches for behavior and anxiety management for enhanced oral health.

Trial status

This trial was registered on ClinicalTrials.gov (ID: NCT05464888) on 19 July 2022. Status: Recruiting. Recruitment began on February 2, 2023. Estimated primary completion is Feb 2027. The current protocol version is 1.1 dated August 8, 2022.

Abbreviations

DA

Dental anxiety

AAPD

American Academy of Pediatric Dentistry

GA

General anesthesia

AAT

Animal-assisted therapy

RCT

Randomized controlled trial

HR

Heart rate

PAFCA

Paediatric Dental Pain, Anxiety, and Fear Coding Approach

NVE

Next visit expectations

UNC

University of North Carolina

ASOD

Adams School of Dentistry

ASA

American Society of Anesthesiologists

ADHD

Attention-deficit/hyperactivity disorder

ELISA

Enzyme-linked immunosorbent assay

CFSS-DS

Child Fear Survey Schedule-Dental Subscale

MCDAS

Modified Child Dental Anxiety Scale

FACES

Wong-Baker FACES Pain Rating Scale

CDART

Carolina Data Acquisition and Reporting Tool

PI

Principal investigator

NIH

National Institutes of Health

IRB

Institutional Review Board

CRU

Clinical research unit

DMC

Data monitoring committee

NIDCR

National Institute of Dental and Craniofacial Research

NCATS

National Center for Advancing Translational Sciences

Authors’ contributions {31b}

Project administration and supervision, L.J.; funding acquisition, L.J., G.K.; conceptualization, E.H., T.S., K.D., L.J.; visualization, K.L.; writing—original draft, G.K., K.L., C.G., L.J.; writing—review and editing, G.K., K.L., C.G., C.L., E.H., T.S., C.G., C.S., D.W., K.D., L.J. All authors read and approved the final manuscript.

Funding {4}

This work was supported by the Southern Association of Orthodontists Research Award (to G.K.). The project described was supported by the National Center for Advancing Translational Sciences (NCATS), NIH, through Grant Award Number UL1TR002489, and through the NIDCR with a K08 grant (K08DE030235) (to L.J.) and with an R03 grant (R03DE032768) (to L.J.). The content is solely the responsibility of the authors and does not represent the official views of the NIH.

Data availability {29}

Data will be reported to ClinicalTrials.gov per policy and will be included in resulting publications. The complete trial dataset will be accessible upon request, after publication, and will be housed at UNC ASOD. De-identified biometric datasets will be made available to the Carolina Digital Repository, a NIH-funded public repository with data access policies and procedures consistent with NIH Data sharing policies and applicable laws and regulations. There are no contractual agreements affecting access to data.

Declarations

Ethics approval and consent to participate {24}

This study is carried out in accordance with the Code of Federal Regulations on the Protection of Human Subjects (45 CFR Part 46), the NIH requirements for human subjects’ research and institutional policies of the UNC IRB and Office of Human Research Ethics (approved IRB #22-1454 enrollment and data collection, #24-0341 for analysis of biological specimens). Clinical Trial registration information: Data are collected as part of a registered clinical trial (Animal Assisted Therapy in Pediatric Dentistry (AAT): NCT05464888, registered July 2022, Status: Recruiting). Verbal assent (pediatric participant) and written informed consent (guardian) will be obtained from each participant in the study.

Consent for publication {32}

All authors gave their final approval for this publication and agreed to be accountable for all aspects of the work.

Competing interests {28}

The authors declare no competing interests. The funders had no role in the study design, collection and interpretation of the data, writing of the manuscript, or the decision to publish the results.