Longitudinal evaluation of minimally invasive protocols for the prevention and control of dental caries in Brazilian schoolchildren: a multicentre study protocol

Abstract

Introduction

Dental caries remains one of the most prevalent chronic diseases in childhood worldwide. In Brazil, untreated carious lesions continue to affect oral health and quality of life in school-aged children. Minimally invasive approaches for caries management have demonstrated feasibility in community settings and may expand access to preventive and restorative care in socially vulnerable populations.

Methods

This multicentre longitudinal intervention study will recruit 50 000 children aged 6–12 years from public schools in five Brazilian cities (Santos, Ponta Grossa, Brasília, Fortaleza and Belém). All participants will undergo clinical examination using the International Caries Detection and Assessment System (ICDAS) and will receive preventive and educational measures, including oral health counselling, supervised toothbrushing with fluoridated toothpaste (1100 ppm F), toothbrushes, toothpaste and application of Duraphat fluoride varnish to permanent molars and incisors. Among children with active carious lesions, 2500 will enter the longitudinal minimally invasive treatment phase according to lesion severity: fluoride varnish for ICDAS 1–2 lesions; fluoride varnish or atraumatic restorative treatment (ART) sealants for ICDAS 3 lesions; and ART with high-viscosity glass ionomer cement for ICDAS 4–6 lesions. Participants will be re-evaluated every 3 months for up to 24 months.

Expected outcomes

The primary outcome will be control of caries activity assessed longitudinally using ICDAS criteria. Secondary outcomes include inactivation of white spot lesions, survival of restorations and sealants and adherence to preventive measures. The study is expected to generate evidence to support public oral health policies and minimally invasive strategies for school-based caries management in Brazil.

Ethics and dissemination

This protocol has been approved by the human research ethics committee of Universidade Metropolitana de Santos—UNIMES (protocol number: 7.630.345. Approved on 10 June 2025). Results will be submitted to international peer-reviewed journals and presented at international conferences.

Trial registration number

NCT06999005 (registered on 14 May 2025).

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This multicentre protocol will evaluate minimally invasive caries management strategies in a large real-world school setting across five Brazilian cities from different geographic regions.

• Standardised caries assessment using International Caries Detection and Assessment System and a Standard Protocol Items: Recommendations for Interventional Trials-based follow-up schedule will strengthen methodological consistency and reproducibility across centres.

• The integration of universal preventive measures with targeted minimally invasive care reflects a scalable and clinically applicable model for public oral health programmes.

• A major limitation is the potential loss to follow-up over the 24-month evaluation period, which may affect estimates of lesion control and restoration/sealant survival.

• Given the pragmatic design and non-random allocation based on lesion severity and clinical indication, causal inference between treatment protocols may be limited.

Introduction

Dental caries is the most prevalent chronic disease of childhood, with a disproportionate burden in low- and middle-income countries, including Brazil.¹ Despite decades of research and advances in preventive technologies, global estimates show that hundreds of millions of children are affected by untreated lesions in their primary dentition, and more than two billion individuals suffer from caries in permanent teeth.^{1 2} This persistent challenge reflects profound inequities in the social determinants of health, with children from socioeconomically disadvantaged backgrounds and underserved communities being disproportionately affected.^{2 3}

The consequences of untreated caries extend far beyond the oral cavity. Pain, infection and difficulty in eating compromise nutrition and growth, while psychosocial impacts include reduced self-esteem, social withdrawal, school absenteeism and poor academic performance.^2–4 Oral health-related quality-of-life studies confirm that caries leads to functional limitations and emotional distress in children, highlighting the urgency of strategies that prevent and control the disease early.^{2 5 6}

Traditional restorative approaches, while effective in repairing cavitated lesions, often rely on invasive procedures involving rotary instruments and anaesthesia, which may generate fear and anxiety in children and require specialised infrastructure.^{7 8} In contrast, minimally invasive strategies have gained prominence as effective, affordable and patient-friendly alternatives that prioritise tissue preservation and patient comfort.^{4 9 10} Among the most widely studied approaches are fluoride varnish, atraumatic restorative treatment (ART) with high-viscosity glass ionomer cement, fissure sealants and chemomechanical caries removal with Papacárie.^{4 6 10–15}

Evidence supporting these interventions is consistent. Fluoride varnish has been shown to effectively prevent caries initiation and arrest lesion progression, particularly among high-risk children.^{6 15} ART, using hand instruments and glass ionomer cement, offers survival rates comparable to conventional restorations even in occlusoproximal lesions, while preserving sound tissue and reducing the need for anaesthesia.^11–14 Sealants, especially when applied in school-based programmes, demonstrate strong effectiveness in reducing new lesions in permanent molars.^{6 15} Papacárie, as a chemomechanical agent, has proven effective for selective caries removal, producing less discomfort and higher acceptance among children compared with conventional drilling, which enhances treatment adherence.^{10 16}

From a public health perspective, the advantages of these minimally invasive strategies extend beyond clinical outcomes. They can be implemented in schools and community settings, broadening access for populations with limited availability of dental services.^{3 7 17} Cost-effectiveness studies consistently indicate that ART, sealants and fluoride varnish are highly cost-effective when compared with conventional restorative treatment or no intervention, offering substantial long-term savings for health systems.^{11 17 18} By combining prevention, treatment and education, minimally invasive approaches provide a sustainable pathway to reduce the disease burden and promote equity in oral health.^{2 18 19}

Within this scenario, Brazil faces persistent social and geographic inequalities in access to dental services. Large-scale evaluation of minimally invasive strategies across diverse regions is essential to generate robust evidence for their incorporation into public health policies. The ABOPED/COLGATE Towards the 100-Year Molar Project was designed with this purpose: to evaluate minimally invasive protocols, including fluoride varnish, ART sealants, ART with high-viscosity glass ionomer cement and the optional use of PapacarieDUO as an adjunctive chemomechanical agent during selective caries removal for the prevention and control of dental caries in children and adolescents from different Brazilian cities.

The present protocol was developed to evaluate the longitudinal clinical behaviour of carious lesions and the implementation of minimally invasive oral health strategies under routine school-based public health conditions in different Brazilian regions.

Methods

Study design

This is a pragmatic, multicentre, non-randomised, longitudinal interventional study designed to evaluate minimally invasive protocols for the prevention and control of dental caries in children and adolescents under real-world public health conditions. The study will be conducted in public schools located in five Brazilian cities (Santos, Ponta Grossa, Brasília, Fortaleza and Belém) under the coordination of the Brazilian Association of Pediatric Dentistry (ABOPED). Participant allocation will be based on clinical characteristics and caries lesion severity according to the International Caries Detection and Assessment System (ICDAS), ensuring that each participant receives the minimally invasive intervention considered clinically appropriate for their treatment needs.

According to the trial registry, the planned study start date is February 2026. Primary completion is anticipated for February 2028, and overall study completion is anticipated for December 2028. The protocol was developed in accordance with the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) statement. A SPIRIT figure summarising enrolment, interventions and follow-up assessments is presented in table 1.

Table 1. Schedule of enrolment, interventions and assessments of the study.

	Period of study
	Enrolment	Allocation	Post allocation							Closure
Timepoint*	−T1	T0	T1	T2	T3	T4	T5	T6	T7	T8
Enrolment
Screening for eligibility	X
Informed consent	X
Allocation		X
Interventions
Protocols 1 and 2: Fluoride varnish		X	X	X	X	X	X	X	X	X
Protocol 3: Sealant with glass ionomer cement (ART)+fluoride varnish		X	X	X	X	X	X	X	X	X
Protocol 4: Occlusal/proximal restoration with glass ionomer cement+fluoride varnish		X	X	X	X	X	X	X	X	X

^*Timepoint: −T1=pre-enrolment (screening and consent); T0=baseline (initial exam and allocation); T1=3 months; T2=6 months; T3=9 months; T4=12 months; T5=15 months; T6=18 months; T7=21 months; T8=24 months (final follow-up).

ART, atraumatic restorative treatment.

A total of 50 000 children between 6 and 12 years of age will be recruited from public schools in the participating cities. All children will be clinically examined to determine caries activity, with lesion assessment performed according to the ICDAS, a validated system widely used in clinical and epidemiological studies to allow sensitive detection of caries lesions and to guide minimally invasive management.^{20 21}

Examiner training and calibration

All examiners will receive standardised theoretical and clinical training on ICDAS criteria before study initiation. Calibration sessions will include the evaluation of clinical photographs and in vivo examinations of children not included in the main sample. Inter-examiner and intra-examiner reliability will be assessed using Cohen’s kappa statistics, and a minimum kappa value of 0.75 will be considered acceptable for participation in data collection activities. To maintain consistency throughout the multicentre follow-up period, recalibration sessions will be performed at predefined intervals, and standardised diagnostic criteria and examination procedures will be reinforced across all participating centres to minimise diagnostic variability over time.

Inclusion criteria

Children will be eligible if they are aged 6–12 years, are enrolled in participating public schools in the selected cities, have at least one erupted permanent first molar, present clinical conditions compatible with the study objectives and have written informed consent signed by a legal guardian and assent provided by the child. For inclusion in the intervention phase, children must present active caries lesions classified according to ICDAS scores 1–6 and be able to attend quarterly follow-up visits over the 24-month study period.

Exclusion criteria

Children will be excluded if they require endodontic treatment or present extensive pulpal involvement, have systemic diseases or medical conditions that contraindicate dental care, have known allergy to any material used in the study, including fluoride varnish or high-viscosity glass ionomer cement, participate in another clinical dental study that may interfere with the outcomes or do not provide informed consent/assent. Participants may also be withdrawn at any time at the request of the child or legal guardian.

Participant recruitment and selection

All children aged 6–12 years enrolled in participating public schools will be invited to undergo oral clinical screening performed by trained and calibrated examiners using ICDAS criteria. Children identified with active carious lesions compatible with the minimally invasive intervention protocols and meeting the eligibility criteria will be consecutively invited to participate in the longitudinal phase of the study after informed consent and assent procedures. The target sample of 2500 participants represents a convenience population-based sample derived from the screened school population across the participating centres. This recruitment strategy was adopted to reflect real-world public health conditions and implementation feasibility within socially vulnerable school populations.

Ethics and dissemination

The study will be conducted in accordance with the ethical principles of the Declaration of Helsinki (World Medical Association, 2013) and current Brazilian regulations for research involving human participants, including Resolution CNS No. 580/2018, Resolution CNS No. 510/2016 and Federal Law No. 14.874/2024. The protocol was approved by the Human Research Ethics Committee of Universidade Metropolitana de Santos—UNIMES (certificate number: 89429825.1.0000.5509/7.630.345; approval date: 10 June 2025).

Written informed consent will be obtained from parents or legal guardians, and assent will be obtained from participating children prior to enrolment. Two signed copies of the informed consent form will be obtained, with one copy retained by the legal guardian and the other by the research team (online supplemental file 1). Participation will be voluntary, and participants may withdraw from the study at any time without any prejudice to dental care or school activities. Researchers may also discontinue a participant’s involvement if considered clinically necessary. All participant information will be treated confidentially. Data will be coded and securely stored, with access restricted to authorised members of the research team. No identifiable personal information will be disclosed in publications or presentations arising from this study.

The findings of this study will be disseminated through publication in peer-reviewed scientific journals, presentations at national and international conferences and communication with participating institutions and stakeholders. The results are expected to contribute to evidence-based public oral health strategies for schoolchildren.

Sample calculation

The study sample was defined based on feasibility and implementation considerations, reflecting the operational capacity of a large-scale multicentre public health intervention conducted in Brazilian public schools. Approximately 50 000 children aged 6–12 years are expected to undergo oral clinical screening for caries activity across the participating centres. From this screened population, 2500 children presenting active carious lesions and meeting the eligibility criteria will be enrolled in the longitudinal intervention phase and allocated to minimally invasive treatment protocols according to lesion severity as defined by ICDAS criteria.

Because the study was designed as a pragmatic implementation-oriented protocol conducted under real-world public health conditions, a convenience population-based sampling strategy was adopted rather than a formal probabilistic sampling approach based on hypothesis-testing assumptions and statistical power estimation. This design prioritises feasibility, external validity and applicability in socially vulnerable school populations from different Brazilian regions. Methodological literature supports feasibility-driven and convenience-based approaches in implementation and public health research, provided that the rationale and limitations are clearly acknowledged and transparently reported.^{22 23}

Interventions

All participating children (n=50 000) will receive preventive and educational measures, including oral health counselling, supervised toothbrushing with fluoridated toothpaste (1100 ppm F) and the provision of toothbrushes and toothpaste. Supervised toothbrushing with fluoride toothpaste is recommended as an effective and cost-efficient strategy for school-based oral health programmes, particularly in disadvantaged populations.²⁴ In addition, Duraphat (Colgate) 5% sodium fluoride varnish will be applied to the first permanent molars and incisors of all children. The clinical efficacy of Duraphat in both preventing caries and promoting the inactivation of active white spot lesions has been demonstrated in randomised clinical trials and systematic reviews.^25–27 Fluoride varnish applications will be performed by trained professionals according to standardised clinical procedures and manufacturer recommendations. Participants will be monitored throughout follow-up visits, and any unexpected event, intolerance or adverse reaction associated with the interventions will be documented and managed appropriately by the clinical team. If clinically necessary, subsequent fluoride applications may be suspended according to clinical judgement and participant safety considerations.

Among children diagnosed with active carious lesions, 2500 will be enrolled in the longitudinal minimally invasive treatment phase and managed according to ICDAS-based treatment protocols

Non-invasive care group (NICG)

Protocol 1—Preventive fluoride varnish: Application to erupting or erupted first permanent molars and incisors, in a single session, followed by quarterly applications for maintenance.

Protocol 2—Fluoride varnish for active white spot lesions: Four consecutive weekly applications aimed at lesion inactivation, followed by quarterly maintenance applications.

Protocol 3—ART sealant: For ICDAS 3 lesions on first permanent molars. The protocol involves surface cleaning with a toothbrush or cotton pellet, relative isolation, application of high-viscosity glass ionomer cement, digital pressure with a gloved finger and petroleum jelly, followed by fluoride varnish application. Quarterly follow-up will be conducted.

Minimally invasive care group

Protocol 4—ART: For lesions classified as ICDAS 4–6, provided pulp vitality is preserved. Selective caries removal will be performed with hand instruments, with optional use of PapacarieDUO to facilitate removal, followed by restoration with high-viscosity glass ionomer cement. Digital pressure with petroleum jelly will be applied for adaptation and sealing. Fluoride varnish will also be applied. Quarterly follow-up visits will be performed.

Outcome variables

Primary outcome

Control of caries activity: Assessed using the ICDAS, a validated method for sensitive detection and monitoring of lesions.^{20 21} Clinical examinations will be performed at baseline and every 3 months up to 24 months. Control of caries activity will be defined according to the absence of lesion progression, reduction in lesion activity or maintenance/arrest of carious lesions over follow-up, as assessed by ICDAS criteria.

Secondary outcomes

Inactivation of active white spot lesions: Evaluated after the initial four-week cycle of fluoride varnish applications and at subsequent follow-up visits (3, 6, 12, 18 and 24 months).

Survival of restorations and sealants: Survival and integrity of ART restorations and sealants. Assessed at 3, 6, 12, 18 and 24 months according to the criteria proposed by Gomes et al.¹⁹

Oral health promotion indicators: Adherence to supervised toothbrushing, use of fluoridated toothpaste and attendance at quarterly recall visits will be monitored throughout the study.

Statistical analysis

Data will be analysed using descriptive and inferential statistics with a significance level of 5% (p<0.05). Baseline characteristics will be described according to intervention protocol and participating centre. Categorical variables will be presented as absolute and relative frequencies, while continuous or ordinal variables will be summarised using means and SD or medians and IQRs, depending on data distribution. Normality of continuous variables will be assessed using the Shapiro-Wilk test.

Because participant allocation is based on clinical indication and lesion severity rather than random assignment, adjusted analyses will be performed to reduce the influence of potential confounding variables. Clinically relevant covariates will include age, sex, participating city/centre, baseline ICDAS score, lesion severity, type of intervention received, adherence to follow-up visits, supervised toothbrushing and use of fluoridated toothpaste.

Associations between categorical variables will be evaluated using Pearson’s χ² test or Fisher’s exact test when appropriate. Multivariable logistic regression models will be used to investigate factors associated with caries lesion control and lesion inactivation. For longitudinal analyses of ICDAS scores and lesion activity over follow-up, repeated-measures approaches will be considered according to the structure of the data, taking into account within-participant correlation over time and potential centre effects related to the multicentre design.

The survival and integrity of ART sealants and restorations will be assessed using Kaplan-Meier survival analysis, and comparisons between groups will be performed using the log-rank test. When appropriate, Cox proportional hazards regression models will be used to evaluate factors associated with time to failure, with adjustment for clinically relevant covariates.

Missing data and loss to follow-up will be documented and described throughout the study period. Whenever available, reasons for missed evaluations or participant withdrawal will be recorded. Analyses will be performed using the available data obtained at each follow-up assessment, and sensitivity analyses may be considered depending on the extent and pattern of missing data observed during follow-up. Patterns of attrition will be examined descriptively to assess whether losses differ according to baseline characteristics, intervention protocol or participating centre.

Discussion

This study protocol presents a multicentre initiative designed to address one of the most pressing challenges in paediatric oral health in Brazil: the prevention and control of dental caries in school-aged children. All participating children will benefit from preventive interventions, including oral health counselling, supervised toothbrushing, provision of hygiene kits and the professional application of Duraphat fluoride varnish to permanent molars and incisors. This universal approach underscores the preventive and public health focus of the project, aiming to promote oral health and reduce the onset and progression of caries in a broad population.

All participating children included in the programme will receive preventive care and clinically appropriate minimally invasive management whenever active lesions are identified. Participant allocation is based on lesion severity and clinical indication in order to preserve ethical and appropriate care within school-based public health settings.

In addition to these preventive measures, children with active carious lesions will receive targeted minimally invasive treatments. Depending on lesion severity, these may include additional fluoride varnish applications, sealants or ART. These interventions, supported by robust scientific evidence, will be delivered in school-based settings across different Brazilian regions, allowing the project to test their feasibility and sustainability under real-world public health conditions.^{9 13 24}

The main limitation anticipated is the challenge of maintaining participant follow-up over the 24-month study period, which is common to large-scale community interventions. This limitation has also been highlighted in economic and implementation analyses of minimally invasive approaches, where long-term adherence is a key factor influencing outcomes.¹⁸ Nevertheless, this is outweighed by the strength of conducting a nationwide multicentre study that combines universal prevention with targeted care for active disease, a model supported by recent systematic reviews of preventive strategies for childhood caries.²⁴

Another limitation of the protocol is the absence of patient-reported outcomes, such as pain perception and oral health-related quality of life measures. The study was primarily designed to prioritise longitudinal clinical monitoring and implementation feasibility within large-scale school-based public health settings. In addition, the inclusion of validated subjective assessment instruments across multiple centres and prolonged follow-up periods would substantially increase operational complexity and the risk of incomplete data collection. Nevertheless, patient-reported measures may provide important complementary information regarding treatment experience and should be considered in future studies evaluating minimally invasive oral health strategies in children.

The present study includes a large multicentre sample recruited through school-based feasibility and convenience sampling rather than probabilistic national sampling procedures. Consequently, the findings may not be fully generalisable to the entire population of Brazilian children with active caries. In addition, the pragmatic and non-randomised nature of the protocol limits strict causal inference between interventions and outcomes, since participant allocation is based on clinical characteristics and lesion severity in order to preserve ethical and clinically appropriate management within school-based public health settings. Nevertheless, the inclusion of socially and geographically diverse public-school populations across multiple Brazilian regions, combined with prospective longitudinal follow-up, may strengthen external validity and provide relevant evidence regarding minimally invasive oral health strategies under routine public health conditions.

Overall, this protocol is expected to contribute significantly to paediatric dentistry and public health in Brazil. By integrating universal preventive care with minimally invasive treatments for children with active lesions, the study aims to establish a replicable model for reducing the burden of dental caries in school-aged populations. Beyond its clinical impact, the project is designed to generate evidence capable of guiding sustainable oral health policies in Brazil, addressing regional inequalities and supporting the incorporation of cost-effective strategies into the public health system.