Dental Sealants: Caries Prevention in Children and Adults

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Introduction

Dental caries remains the most prevalent chronic disease worldwide, with pit and fissure surfaces accounting for approximately 80–90% of all carious lesions in permanent teeth. The anatomical complexity of pits and fissures—narrow, deep, and often impossible to clean effectively with toothbrush bristles—creates an ideal environment for biofilm accumulation and acid production. Dental sealants, first introduced in the 1960s, provide a physical barrier that occludes these vulnerable surfaces, dramatically reducing caries risk. Despite decades of robust evidence supporting their efficacy, sealant utilization remains suboptimal in many populations.

Anatomical Rationale and Mechanism of Action

Pit and Fissure Vulnerability

Occlusal fissures present a unique caries challenge for several reasons:

• Morphology: Fissures measure approximately 0.1–0.2 mm in width at the orifice, far narrower than the 0.4–0.5 mm diameter of toothbrush bristles. This physical mismatch prevents mechanical plaque disruption in deep fissures.
• Enamel structure: The enamel at the base of fissures is typically thinner and less mineralized than smooth surface enamel, providing less resistance to acid demineralization.
• Stagnation: The deep, narrow architecture promotes substrate retention, prolonged acid exposure, and reduced buffering capacity from saliva.
• Rapid progression: Unlike smooth surface caries, fissure caries can progress from initial demineralization to cavitation relatively quickly due to the confined environment.

Sealant Mechanism

Sealants function through two primary mechanisms:

• Physical barrier: The sealant material flows into pits and fissures, polymerizes in situ, and creates a micromechanically bonded barrier that prevents nutrients from reaching cariogenic bacteria and blocks acid diffusion to the enamel surface.
• Active remineralization (some materials): Fluoride-releasing and bioactive sealants provide additional protection through fluoride ion release, promoting remineralization of adjacent enamel and inhibiting bacterial metabolism.

Sealant Materials

Resin-Based Sealants

Resin-based sealants are the most widely used type and the gold standard for pit and fissure sealing. They consist of a Bis-GMA or urethane dimethacrylate resin matrix with filler particles, applied using the acid-etch technique.

• Composition: Typically unfilled or lightly filled (0–40% by weight) to maintain low viscosity for optimal penetration into fissures. Higher filler content increases wear resistance but compromises flow.
• Polymerization: Available in both autopolymerizing (chemical cure) and photopolymerizing (light cure) formulations. Light-cured sealants offer controlled working time and are now standard.
• Bonding: Requires phosphoric acid etching (35–37%) for 15–20 seconds on enamel to create microporosities for resin tag penetration. The use of a bonding agent between etched enamel and sealant improves retention, especially in challenging moisture conditions.
• Retention rates: Complete retention at 1 year: 80–90%; at 5 years: 55–70%. Retention is the key determinant of caries prevention efficacy—sealants that remain fully intact reduce caries by approximately 80% compared to unsealed teeth.

Glass Ionomer Sealants

Glass ionomer cement (GIC) sealants offer distinct advantages for specific clinical scenarios:

• Moisture tolerance: Unlike resin sealants, GICs are hydrophilic and can bond in a moist field. This makes them ideal for partially erupted teeth where isolation is difficult.
• Fluoride release: Sustained fluoride release over months to years provides a caries-preventive reservoir effect. GICs can also recharge fluoride from topical applications (toothpaste, varnish, mouthwash).
• Chemical adhesion: Bonds to enamel and dentin through ionic and hydrogen bonding without acid etching, simplifying the technique.
• Disadvantages: Lower retention rates (5-year complete retention 10–20%) compared to resin sealants due to lower mechanical strength and wear resistance. However, even partially retained or fully lost GIC sealants show caries-preventive effects, likely due to residual glass ionomer material in fissures and the fluoride reservoir effect.

Polyacid-Modified Resin (Compomer) Sealants

Compomers combine resin chemistry with acid-base glass ionomer reactions. They offer intermediate properties—better wear resistance than GICs but with some fluoride release capability. Clinical studies show retention rates between GIC and conventional resin sealants.

Emerging Materials

• Bioactive sealants: Incorporate materials such as amorphous calcium phosphate (ACP), bioactive glass, or casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) to promote remineralization.
• Hydrophilic resin sealants: Modified resin formulations with enhanced moisture tolerance, bridging the gap between conventional hydrophobic resins and GICs.
• S-PRG (Surface Pre-Reacted Glass ionomer) fillers: Release six types of ions (fluoride, strontium, sodium, borate, aluminum, silicate) for multi-ion release with potential anti-cariogenic, antimicrobial, and remineralizing effects.

Clinical Application Technique

Step-by-Step Protocol for Resin Sealants

1. Cleaning: Prophylaxis with pumice and water slurry or air abrasion. Avoid prophy paste with fluoride or oil, which can interfere with etching. Ultrasonic or air polishing with sodium bicarbonate may improve debris removal from deep fissures.
2. Isolation: Rubber dam isolation provides the best moisture control and is strongly recommended when feasible. Cotton roll isolation with high-volume evacuation and saliva ejector is an acceptable alternative when rubber dam is impractical (e.g., partially erupted teeth).
3. Etching: Apply 35–37% phosphoric acid gel to pits and fissures, extending 1–2 mm onto adjacent cusp inclines. Etch for 15–20 seconds on permanent teeth, 30 seconds on primary teeth. Avoid over-etching, which can reduce bond strength.
4. Rinse and dry: Rinse thoroughly for 20–30 seconds to remove all etchant. Dry with oil-free compressed air until enamel appears frosty white. Any contamination with saliva requires re-etching for 5–10 seconds.
5. Bonding agent (optional but recommended): Apply a thin layer of unfilled bonding resin to etched enamel, gently air-thin, and light-cure. This improves sealant penetration into deep fissures and enhances retention.
6. Sealant application: Apply sealant material using a dispensing tip or brush. Allow flow into fissures without trapping air bubbles. Use an explorer or microbrush to guide material into deep fissures. Avoid overfilling, which creates high occlusal contacts.
7. Polymerization: Light-cure according to manufacturer instructions (typically 20–40 seconds per tooth). Ensure the light tip is positioned as close as possible to the sealant surface.
8. Evaluation: Check sealant with an explorer for complete coverage, absence of voids, and absence of high occlusal contacts. Adjust occlusion with a finishing bur or polishing disc if necessary. Confirm complete polymerization by probing for any tacky or uncured surface.

Special Considerations

• Partially erupted teeth: Operculum coverage prevents adequate isolation. Glass ionomer sealants are preferred. Alternatively, defer resin sealing until full eruption.
• Incipient caries: Non-cavitated carious lesions (ICDAS 1–2) can be sealed. Sealing arrests lesion progression by cutting off the nutrient supply. Enameloplasty (minimal mechanical opening) is not routinely indicated; evidence shows no difference in outcomes between invasive and non-invasive sealing of incipient lesions.
• Questionable lesions: If cavitation is suspected but cannot be confirmed visually, a small exploratory opening with a 1/4 round bur may be used. Frankly cavitated lesions (ICDAS 3+) should receive a preventive resin restoration rather than a sealant alone.

Indications and Patient Selection

Pediatric Patients

Children and adolescents are the primary target population for sealants, as newly erupted permanent molars are at highest caries risk. The ADA and AAPD recommend sealing permanent first molars (erupt at approximately 6 years) and second molars (erupt at approximately 12 years) as soon as eruption is complete and isolation is feasible. Primary molars with deep pits and fissures in high-caries-risk children may also benefit from sealing, though evidence for primary tooth sealants is less robust.

Adult Patients

Adults with deep pit and fissure anatomy, incipient fissure caries, or elevated caries risk benefit from sealants. While historically considered a pediatric procedure, evidence supports sealing caries-susceptible fissures at any age. Adults with xerostomia (medication-induced, radiation-induced, Sjögren's syndrome) are particularly appropriate candidates.

Caries Risk Assessment

Sealants are most cost-effective when targeted to high-caries-risk individuals. Risk factors guiding sealant placement include: visible plaque on teeth, frequent sugar consumption, low socioeconomic status, previous caries experience, presence of white spot lesions, inadequate fluoride exposure, and special healthcare needs.

Effectiveness and Evidence

• Caries reduction: Cochrane systematic review (2017): resin sealants reduce occlusal caries by 73–79% at 2–4 years compared to no sealant in children and adolescents. Long-term studies show sustained protection with regular maintenance.
• Retention vs. effectiveness: Fully retained sealants provide the greatest protection, but even partially retained sealants show significant caries reduction compared to unsealed teeth. This is partly because residual sealant material often remains in the deepest, most vulnerable parts of fissures even when clinical examination shows partial loss.
• Cost-effectiveness: School-based sealant programs demonstrate significant cost savings by preventing the need for more expensive restorative treatment. Sealing is more cost-effective than waiting for caries to develop and restoring with restorations that have a finite lifespan.
• GIC vs. Resin: Resin sealants have higher retention, but GIC sealants show comparable caries prevention, particularly in settings where isolation is compromised. The choice should be individualized.

Maintenance and Repair

Sealants should be evaluated at every recall visit for retention, marginal integrity, and the presence of caries. Partially lost sealants can be repaired by cleaning, etching the exposed enamel and existing sealant, and applying additional sealant material. Complete replacement is indicated only when loss is extensive or caries is detected beneath the sealant. Annual sealant retention checks are recommended, with repair as needed.

Conclusion

Dental sealants are a safe, effective, and cost-efficient caries prevention strategy with decades of high-quality evidence supporting their use. Resin-based sealants remain the gold standard for optimal conditions, while glass ionomer sealants provide a valuable alternative for moisture-compromised situations. The key to clinical success lies in proper isolation, meticulous technique, and regular maintenance. Expanding sealant utilization in both pediatric and adult populations represents one of the most impactful opportunities for caries prevention in contemporary dentistry.

References

1. Ahovuo-Saloranta A, Forss H, Walsh T, et al. Pit and fissure sealants for preventing dental decay in permanent teeth. Cochrane Database Syst Rev. 2017;7:CD001830.
2. Beauchamp J, Caufield PW, Crall JJ, et al. Evidence-based clinical recommendations for the use of pit-and-fissure sealants. J Am Dent Assoc. 2008;139(3):257–268.
3. Wright JT, Crall JJ, Fontana M, et al. Evidence-based clinical practice guideline for the use of pit-and-fissure sealants. J Am Dent Assoc. 2016;147(8):672–682.e12.
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