Association between fluoridated toothpaste use and dental caries in Nigeria: A systematic review and meta-analysis

This systematic review and meta-analysis of 12,719 Nigerian children and adolescents found that while fluoridated toothpaste use is widespread, it is significantly associated with a 16% reduction in dental caries odds primarily in urban and rural settings, with the protective effect varying by residential location and baseline caries severity.

The Gist

Imagine your mouth is a bustling city, and the teeth are the buildings. Sometimes, tiny, mischievous "acid monsters" (bacteria) attack these buildings, causing holes. We call these holes cavities or dental caries.

For decades, scientists have known that fluoridated toothpaste is like a super-strong, magical shield paint. When you brush with it, it hardens the buildings, making them much harder for the acid monsters to break down.

This paper is a massive investigation by a team of researchers in Nigeria. They wanted to answer two big questions:

1. How many Nigerian kids are actually using this "magic shield" toothpaste?
2. Does using it actually stop the holes from forming in their teeth?

Here is the story of what they found, explained simply.

The Big Picture: A Nationwide Search

The researchers didn't just look at one school or one town. They acted like detectives, digging through thousands of old reports, studies, and data from all over Nigeria. They looked at 18 different studies involving nearly 13,000 children and teenagers.

The Good News:
They found that the "magic shield" is everywhere! Between 62% and 96% of the kids they studied were using fluoridated toothpaste. It's like almost everyone in the city has a shield.

The Twist: It's Not a Simple "Yes or No"

You might think, "If everyone has a shield, everyone should be safe." But the researchers found something surprising. The shield works differently depending on where you live.

Think of Nigeria as having three types of neighborhoods:

1. The Busy City (Urban): High stress, lots of sugar, maybe less access to dentists.
2. The Quiet Countryside (Rural): Different challenges, maybe less access to anything.
3. The Suburbs (The "University Town"): A middle-ground area with good schools, better access to doctors, and generally healthier habits.

Here is what the data showed:

• In the City and the Countryside: The shield worked wonders! Kids who used the fluoride toothpaste had significantly fewer cavities. In these tough neighborhoods, the toothpaste was the difference-maker.
• In the Suburbs: The shield didn't seem to make a statistical difference. Why? Because the kids in the suburbs were already doing so many other things right (eating better, visiting dentists, having better hygiene) that their teeth were already strong. The toothpaste was there, but it was like wearing a raincoat in a sunny park—it didn't change the outcome because the "rain" (cavities) wasn't as heavy to begin with.

The "Outlier" Problem

When the researchers first crunched the numbers, the results were a bit messy and confusing. It was like trying to hear a song when one person in the room was shouting off-key.

They realized one specific study from a rural area was shouting so loud it was messing up the whole song. When they gently asked that one study to step aside (a statistical move called removing an "outlier"), the music cleared up. Suddenly, the data showed clearly: Yes, the toothpaste reduces the risk of cavities by about 16%.

The "Why" Behind the Mystery

The authors used two clever ideas to explain why the toothpaste worked better in some places than others:

1. The "Saturation" Effect: In the suburbs, almost everyone already has the shield and eats less sugar. So, adding the shield doesn't change the score much because the score was already good.
2. The "Need" Factor: In the city and countryside, life is harder. Sugar is cheaper, and dentists are farther away. In these "high-risk" zones, the toothpaste is a lifeline. It's the one thing standing between a healthy tooth and a cavity.

The Takeaway for Everyone

This study teaches us a valuable lesson about health: One size does not fit all.

• For the "High-Risk" neighborhoods (Cities and Countryside): We need to make sure everyone has access to this magic shield toothpaste. It's a cheap, effective way to stop cavities where they are most likely to happen.
• For the "Low-Risk" neighborhoods (Suburbs): We shouldn't stop using the toothpaste, but we know it's not the only thing that matters. We need to focus on other things, like eating less sugar and visiting the dentist, because the toothpaste alone isn't the hero there; it's just part of a team.

In short: Fluoridated toothpaste is a great tool in Nigeria's toolbox. It works best when the "acid monsters" are strongest. The researchers are now calling for more long-term studies to keep watching how this shield protects Nigerian smiles as the country changes.

Technical Summary

1. Problem Statement

Dental caries remains a significant global public health issue, linked to systemic disorders and developmental delays. While fluoridated toothpaste is a proven preventive tool globally, its efficacy in low- and middle-income countries (LMICs) like Nigeria is complex.

• Context: Nigeria has regulations mandating fluoride in toothpaste, yet access is uneven due to economic downturns and the rise of cheaper, non-fluoridated alternatives.
• Knowledge Gap: There is a lack of context-specific evidence regarding the association between fluoridated toothpaste use and dental caries prevalence in Nigeria. Existing literature does not sufficiently address how this relationship varies across different geographic settings (urban, rural, suburban) and demographic groups.
• Objective: To systematically review the prevalence of fluoridated toothpaste use among Nigerian children/adolescents and quantify its association with dental caries, stratified by location and baseline risk.

2. Methodology

The study adhered to PRISMA guidelines and was registered with PROSPERO (CRD42022362116).

• Search Strategy: A comprehensive search was conducted across PubMed, Web of Science, Scopus, Embase, AJOL, and Google Scholar (Jan 2001–Jan 2026), supplemented by grey literature and reference list screening.
• Eligibility Criteria (PIO Framework):
  • Population: Children and adolescents (6 months–19 years) in Nigeria.
  • Intervention: Use of fluoridated toothpaste.
  • Outcomes: Dental caries prevalence and severity (measured by dmft/DMFT indices).
  • Study Design: Cross-sectional, cohort, and case-control studies.
• Data Extraction & Quality: Two independent reviewers extracted data. Risk of bias was assessed using an adapted Hoy et al. tool (9 domains). Inter-rater reliability was excellent (Kappa = 0.90).
• Statistical Analysis:
  • Model: Random-effects meta-analysis using the Mantel-Haenszel method.
  • Metrics: Pooled Odds Ratios (OR) with 95% Confidence Intervals (CI).
  • Heterogeneity: Assessed via Cochran's Q and $I^2$ statistics.
  • Sensitivity/Outlier Analysis: Studentized residuals and leave-one-out analysis were used to identify influential studies.
  • Moderator Analysis: Subgroup analyses were performed by geopolitical zone, study design, and dentition type. Meta-regression tested publication year and sample size.
  • Bias Assessment: Funnel plots, Egger's test, and rank correlation tests were used to detect publication bias.

3. Key Contributions

• First Comprehensive Meta-Analysis: This is the first systematic review to quantify the specific association between fluoridated toothpaste and caries specifically within the Nigerian context.
• Contextual Nuance: It moves beyond a binary "effective/ineffective" conclusion to demonstrate that the efficacy of fluoridated toothpaste is moderated by residential location (urban, rural, vs. suburban).
• Theoretical Framework Application: The discussion integrates the Socio-Ecological Model (SEM) and Diffusion of Innovations (DoI) theory to explain why protective effects vary by setting (e.g., saturation effects in suburban areas vs. high impact in resource-constrained rural/urban areas).
• Policy Relevance: Provides evidence-based guidance for resource allocation, suggesting that fluoride promotion strategies should be tailored to specific geographic risk profiles.

4. Results

• Study Selection: From 1,194 records, 18 studies (n=12,719 participants) met inclusion criteria. All studies were assessed as having a low risk of bias.
• Prevalence of Use: Fluoridated toothpaste use is widespread in Nigeria, ranging from 61.9% to 95.8%, with the highest usage in suburban and urban settings.
• Caries Prevalence: Varied significantly by setting:
  • Rural: 35.5%
  • Urban: 16.0% – 81.6%
  • Suburban: 3.4% – 13.5%
• Meta-Analysis Findings:
  • Initial Pooled Estimate: Including all 14 relevant studies, the initial OR was 0.69 (p=0.123), which was not statistically significant, with high heterogeneity ($I^2$ = 81.7%).
  • Outlier Removal: One influential outlier study (Okoye et al., 2011) was identified and removed.
  • Final Pooled Estimate: After removal, the odds of dental caries were 16% lower for users of fluoridated toothpaste (OR = 0.84; 95% CI: 0.71–0.99; p=0.04). Heterogeneity dropped to 0.0%.
• Subgroup Analysis:
  • Geographic Location: The protective association was significant in Urban and Rural settings but absent in Suburban settings.
  • Study Design: Hospital-based studies showed a significant 41% reduction in caries odds, whereas population-based studies showed only a 5% reduction (p=0.008).
  • Dentition Type: Significant reductions were seen in mixed (26%) and permanent (13%) dentitions, but not in primary dentition.
  • Regional: Consistent protective effects were found in both Southern and Northern regions.
• Publication Bias: No significant publication bias was detected (Egger's test p=0.32).

5. Significance and Implications

• Context-Dependent Efficacy: The study concludes that while fluoridated toothpaste is generally protective, its impact is most detectable in high-risk environments (rural and urban areas with higher baseline caries rates). In suburban areas, where caries rates are naturally lower due to better access to care and higher oral health literacy, the isolated effect of toothpaste is statistically masked (saturation effect).
• Strategic Resource Allocation: Public health interventions should not be "one-size-fits-all."
  • High-Risk Areas (Rural/Urban): Prioritize access to fluoridated toothpaste through subsidies and integration with maternal-child health programs.
  • Low-Risk Areas (Suburban): Focus on multifactorial prevention (sugar reduction, sealants) while maintaining fluoride use as a baseline.
• Future Research Directions: The authors call for longitudinal and quasi-experimental studies to establish causality, specifically investigating adult populations and the underrepresented Northern geopolitical zones of Nigeria.
• Policy Impact: The findings support the continued regulation of fluoride in toothpaste but highlight the need for complementary strategies to address socioeconomic and infrastructural determinants of oral health in Nigeria.