Pit and Fissure Sealants: Preventive Measures for Occlusal Caries

Tooth enamel contains natural indentations known as pits and fissures, which serve as common sites for cavity development. Due to their intricate morphology, these areas are highly susceptible to plaque accumulation and bacterial colonization, making them prime targets for early caries formation. In particular, the anatomical grooves and indentations on the occlusal surfaces of molars and premolars are highly susceptible to caries due to their complex structure, which makes them difficult to clean effectively. Addressing this issue requires targeted preventive measures, among which fissure sealing stands out as an effective strategy. Sealants serve as a protective barrier, preventing the accumulation of bacteria and food particles in these areas.

Fissures and pits present unique challenges for dental care due to their depth and difficulty in cleaning. Traditional caries prevention methods, such as fluoride application, help strengthen enamel but may not fully protect these intricate surfaces. The introduction of fissure sealants has provided a proactive approach, forming a physical barrier that prevents bacterial ingress and nutrient accumulation within these structures.

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Although fissure sealing is an investment, its economic efficiency is contingent on meticulous execution, the selection of appropriate materials, and patient cooperation. This technique not only serves as a preventive measure but also as a testing ground for advanced dental technologies, including adhesive systems, antimicrobial treatments, and surface preparation methods.

Caries Susceptibility and Enamel Maturation

The highest risk for caries development in first permanent molars occurs at 6–7 years of age, coinciding with their eruption. At this stage, enamel mineralization is incomplete, making these teeth particularly vulnerable to decay. Factors influencing enamel resistance to caries include:

• Intrinsic properties such as acid resistance, microhardness, and permeability.
• External conditions like saliva composition, plaque accumulation, carbohydrate intake, and immune response.

Because enamel lacks regenerative capacity, preventive measures must be prioritized. One key consideration is enamel permeability, which is significantly higher in newly erupted teeth. This permeability allows remineralization agents such as fluoride, calcium, and phosphorus ions to penetrate demineralized areas, aiding in caries prevention and early-stage reversal.

Diagnosing Fissure Caries

Early diagnosis of fissure caries is challenging due to the hidden nature of these lesions. The following diagnostic techniques are commonly used:

• Visual examination with proper lighting and a probe.
• Vital staining to detect demineralization.
• Radiographic imaging for deeper lesions.
• Electrometric analysis to assess enamel mineralization.

Fissures requiring sealing are classified into three types:

1. Open fissures – These allow free probe penetration and often exhibit demineralization.
2. Deep fissures – Although the color may be unchanged, the probe still enters freely.

Narrow fissures – The probe cannot penetrate, making diagnosis difficult, especially when pigmentation is present.

Sealant Material Selection

Fissure sealants provide an impermeable barrier, facilitating enamel maturation while protecting against cariogenic factors. Fluoride-containing sealants enhance caries prevention by releasing fluoride ions that contribute to enamel remineralization.

The selection of sealant materials depends on various factors, including retention strength, biocompatibility, and ease of application. The most commonly used materials include:

• Resin-Based Sealants (RBS) – Composed of Bis-GMA or similar monomers, available as chemically or light-cured sealants, they offer strong adhesion and durability.
• Glass ionomer cements (GICs) – These materials chemically bond to the tooth and release fluoride, promoting remineralization. They are particularly useful in cases where isolation is difficult or when sealing partially erupted molars and serve as temporary sealants with fluoride-releasing properties.
• Flowable Composites – Low-viscosity, light-cured resin materials with a higher percentage of resin and lower filler content than traditional composites, possess higher retention than GIS but similar to RBS when used with adhesive systems, and are generally more wear-resistant than traditional RBS due to their higher filler content.
• Hybrid materials – Resin-modified GICs and flowable compomers combine benefits of both resin and GIC materials, these materials provide moderate retention and fluoride release, offering a balance between strength and caries prevention.

Advances in Sealant Technology

Since the introduction of bis-GMA-based sealants in the 1970s, advancements in polymer chemistry have improved their clinical effectiveness. Modern sealants exhibit:

• Strong micromechanical retention to acid-etched enamel.
• Low solubility and resistance to oral conditions.
• Controlled working time for precise application.
• Improved aesthetic options, including transparent and color-changing formulations for easier monitoring.

Light-cured sealants are now preferred over chemically cured alternatives due to their convenience and reliable polymerization. Additionally, modified sealing techniques, such as "super-sealing," enhance retention by combining sealants with composite layering.

Modern research has confirmed that when applied correctly under dry conditions, composite-based sealants provide durable protection against caries. Delayed sealant placement in partially erupted teeth, using glass ionomer cement as a temporary measure, remains an acceptable approach. However, data shows that composite sealants significantly outperform glass ionomers in retention and caries prevention over time.

Interestingly, even when existing caries noncavitated lesions are sealed, the number of cariogenic bacteria decreases, and the percentage of noncavitated carious lesions that progress reduces.

Despite past debates, one principle remains unchanged: early intervention is key. First permanent molars, if left unsealed, are most vulnerable to caries between ages 6 and 9. But what if a complete eruption hasn't occurred and rubber dam isolation is impossible? The biggest challenge to successful sealing remains moisture control.

Preparation for Sealant Application

Before applying a sealant, proper preparation of the tooth surface is essential to ensure optimal adhesion and longevity of the material. This process includes:

1. Assessment of Occlusal Contacts: Since sealants have relatively low mechanical strength, they should not interfere with normal occlusal function. Checking occlusal contacts using articulating paper helps identify areas that should remain sealant-free.
2. Plaque and Debris Removal: The effectiveness of sealants depends on their ability to bond with clean enamel. Various methods for cleaning include:
   • Toothbrush cleaning with fluoride-free paste;
   • Professional polishing with pumice. A low-abrasive pumice slurry is applied to the occlusal surface using a rubber cup or a bristle brush. However, it may be less effective in cleaning deep, narrow fissures where the brush or rubber cup cannot reach;
   • Air abrasion using aluminum oxide or sodium bicarbonate. This technique removes pellicle, biofilm, and organic debris within deep pits and fissures, it can also create micro-retentive roughness, improving sealant bond strength. Some studies suggest that air abrasion can replace or reduce the need for acid etching, although this remains debated;
   • Ultrasonic cleaning for thorough plaque removal.
3. Isolation of the Tooth: Effective isolation prevents contamination by saliva, ensuring a strong bond between the sealant and enamel. Common methods include:
   • Rubber dam isolation (preferred for complete moisture control)
   • Cotton rolls and saliva ejectors (alternative, not preferable)

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Application Steps for Resin-Based Sealants

1. Etching: A 37% phosphoric acid gel is applied to the enamel surface for 15–20 seconds to create micropores that enhance sealant retention. Primary teeth require longer etching due to prismless enamel, but studies show 30-60 seconds is sufficient. The etched surface should appear chalky white for optimal bonding.
2. Rinsing and Drying: The etched enamel is thoroughly rinsed for 30 seconds and dried for 15 seconds.
3. Bonding Agent (Optional but Recommended): Bonding increases sealant retention by improving adhesion to enamel, etch-and-rinse bonding agents (4th & 5th generation) are best compared to self-etch adhesives, universal bonding systems may also be effective.

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       4. Sealant Placement: The material is carefully applied using a brush or applicator, ensuring it flows into the pits and fissures without forming air bubbles.

• Flowable resin-based sealants penetrate pits and fissures better.
• Unfilled resins flow better and don't require occlusal adjustment.
• Filled resins are more resistant to wear but may need occlusal adjustment.

       5. Polymerization: A curing light is used to harden the material, ensuring complete set and longevity, most sealants require 20-40 seconds of curing with an LED or halogen light.

       6. Final Inspection and Adjustments: The occlusion is checked, and any excess material is removed to prevent bite interference.

Summary of Clinical Recommendations

The prevention of pit and fissure caries remains a cornerstone of modern pediatric and preventive dentistry. Given the high susceptibility of newly erupted molars to caries, sealing these surfaces with appropriate materials significantly reduces the risk of decay. Advances in sealant technology continue to refine the efficacy, durability, and application of these materials, ensuring long-term protection against occlusal caries. By incorporating fissure sealing into routine preventive care, dental professionals can significantly contribute to improved oral health outcomes in children and adolescents.