19.3 Pit & Fissure Sealant Armamentarium, Placement & Clinical Evaluation

19.3 Pit & Fissure Sealant Armamentarium, Placement & Clinical Evaluation

Pit and fissure sealants are one of the most effective non-invasive preventive interventions available in modern dentistry. In Canada, the placement of pit and fissure sealants is an authorized intra-oral clinical duty for Level II dental assistants who have completed certified training.

While systemic and topical fluorides are exceptionally effective at preventing smooth-surface enamel caries, they provide less protection for the deep, narrow pits and fissures of posterior teeth. Sealants close this vulnerability by providing a physical, impermeable micro-mechanical barrier.

Biological Rationale and Anatomical Vulnerability

Occlusal surfaces represent only about 12% to 15% of total tooth surfaces, yet they account for 80% to 90% of all dental caries in children and adolescents.

The Anatomical Dilemma of Pits and Fissures

During odontogenesis, enamel develops from separate developmental lobes. When these lobes coalesce over the occlusal table, incomplete fusion produces irregular narrow developmental grooves, pits, and fissures:

• Fissure Dimensions vs. Toothbrush Bristles: Occlusal fissures often measure less than 0.1 mm (100 $\mu\text{m}$) in width, with some narrowing to 0.01 mm at their base. Conversely, standard soft nylon toothbrush bristles average 0.2 mm (200 $\mu\text{m}$) in diameter. Toothbrush bristles are physically incapable of penetrating the deep recess of a fissure to mechanically remove bacteria.
• Biofilm Incubator: Food debris, fermentable carbohydrates, and microscopic bacteria (measuring ~1 $\mu\text{m}$) pack into deep fissures, creating an undisturbed anaerobic incubator protected from salivary flushing and bicarbonate buffering.

                    THE ANATOMICAL MISMATCH OF OCCLUSAL FISSURES
                                         │
                     TOOTHBRUSH BRISTLE DIAMETER (~0.2 mm)
                                        ▼
                         [     BRISTLE TIP     ]
                         =======================
                                    │
                                    │   (CANNOT ENTER)
                                    ▼
               \                                         /
                \     OCCLUSAL ENAMEL INCLINE           /
                 \                                     /
                  \             ─── 0.1 mm ───        /
                   \          ┌───────────────┐      /
                    \         │ FISSURE ENTRY │     /
                     ─────────┘               └─────
                              │  MICROBIAL    │
                              │   BIOFILM     │  <-- Trapped bacteria & food debris
                              │  INCUBATOR    │      (1 μm bacteria thrive undisturbed)
                              └───────────────┘

The Physical Barrier Mechanism

Sealants do not rely on chemical toxicity to kill bacteria. Instead, a low-viscosity resin flows into the cleaned pit-and-fissure network by capillary action. Once polymerized, the resin forms mechanical resin tags that lock into etched enamel microporosities, physically sealing pits from the oral cavity. This entombs any residual bacteria, cutting off their access to exogenous dietary carbohydrates and halting acid production.

Clinical Indications and Contraindications

Appropriate case selection is vital for maximizing clinical success and cost-effectiveness:

Clinical Indications

1. Deep, Narrow, Retentive Pits and Fissures: Pits and fissures that catch a sharp explorer tip, exhibit steep anatomical slopes, or demonstrate deep developmental morphology.
2. Newly Erupted Permanent Molars: Sealants should be placed as soon as the tooth has erupted sufficiently to allow complete moisture isolation:
   • First permanent molars: Usually erupt between ages 6 and 7.
   • Second permanent molars: Usually erupt between ages 12 and 13.
   • Deep pits on primary molars, premolars, and the lingual pits of maxillary incisors (e.g., dens invaginatus variations) are also indicated in high-risk patients.
3. Incipient Non-Cavitated Enamel Caries: Research confirms that placing sealants over early, non-cavitated enamel lesions (lesions confined strictly to enamel without dentinal involvement) successfully arrests caries progression by cutting off fermentable carbohydrates and starving Streptococcus mutans.
4. High Caries Risk Patients: Patients categorized under CAMBRA as Moderate or High risk (e.g., patients with a history of caries, xerostomia, orthodontic appliances, or poor motor skills).

Clinical Contraindications

1. Well-Coalesced, Shallow Grooves: Teeth with broad, flat, self-cleansing occlusal anatomy that are easily maintained with normal toothbrushing.
2. Frank Cavitation into Dentin: Teeth with cavitated carious lesions extending into dentin require operative cavity preparation and surgical restoration, not sealants.
3. Interproximal Caries: If bite-wing radiographs reveal active proximal carious lesions requiring Class II restoration, an isolated occlusal sealant is contraindicated because the marginal ridge will be removed during cavity preparation.
4. Partially Erupted Teeth with Inadequate Isolation: If the distal marginal ridge is covered by an operculum of gingival tissue or if moisture control cannot be maintained, resin placement must be delayed or a temporary glass ionomer sealant used.
5. Caries-Free Adult Teeth: Teeth that have remained caries-free for many years in low-caries-risk adults typically possess natural resistance and do not routinely require sealants.

Sealant Material Science: Resin-Based vs. Glass Ionomer

Sealant materials possess distinct chemical formulations, setting reactions, and physical properties:

1. Resin-Based Sealants

Resin-based sealants are dimethacrylate formulations derived from Bis-GMA (bisphenol A-glycidyl methacrylate) or UDMA (urethane dimethacrylate) oligomers, diluted with low-viscosity monomer diluents (such as TEGDMA) to maximize capillary flow.

• Polymerization Mechanisms:

  • Light-Cured (Photopolymerized): Formulated with a photoinitiator (commonly camphorquinone). When exposed to visible blue light at a wavelength of 450 to 490 nanometers (nm), free radicals are released to trigger rapid polymerization within 20 to 30 seconds. Light curing provides unlimited working time, allowing the operator to carefully tease the resin into grooves before initiating the set.
  • Self-Cured (Chemical / Autopolymerized): A two-component system consisting of a liquid base and catalyst (benzoyl peroxide and tertiary amine accelerator). Once mixed, free radicals form chemically, providing approximately 60 to 90 seconds of working time and setting fully within 2 to 3 minutes. Disadvantages include unavoidable incorporation of air bubbles during manual mixing and lack of operator-controlled setting time.

• Filler Content (Filled vs. Unfilled Resins):

  • Filled Sealants: Contain microscopic glass, quartz, or silanated silica filler particles (ranging from 20% to 50% filler by weight). Fillers dramatically enhance wear resistance and compressive strength. However, filled sealants have higher viscosity and require mandatory occlusal evaluation with articulating paper and mechanical adjustment using rotary burs if high spots exist; they will not naturally abrade away.
  • Unfilled Sealants: Contain no filler particles; composed entirely of clear, tinted, or opaque unfilled resin. Because unfilled sealants possess very low viscosity, they flow effortlessly into deep, narrow microscopic fissures. A significant clinical advantage of unfilled sealants is that minor occlusal high spots naturally self-abrade through normal mastication within 24 to 48 hours, eliminating the need for rotary handpiece adjustment.

2. Glass Ionomer (GI) Sealants

Formulated from fluoroaluminosilicate glass powder and polyacrylic acid liquid, glass ionomer sealants adhere to tooth structure through chemical ionic chelation with calcium in enamel and dentin.

• Moisture Tolerance: Highly hydrophilic and can be placed in moist environments where absolute rubber dam isolation is impossible (e.g., partially erupted first molars covered by distal gingiva or uncooperative young children).
• Continuous Fluoride Release: Releases high levels of protective fluoride into adjacent fissure walls over extended periods.
• Retention Considerations: Glass ionomers have significantly lower physical retention rates than resin sealants due to lower tensile strength and brittle wear. However, even if the bulk material is lost, microscopic glass ionomer plugs often remain embedded in the fissure base, continuing to confer caries resistance.

Material Comparison: Resin-Based vs. Glass Ionomer Sealants

Step-by-Step Clinical Placement Protocol

Proper technique during each phase of sealant placement is required to achieve high retention and avoid premature microleakage.

Step 1: Surface Preparation and Cleaning

• Clean all occlusal pits and fissures thoroughly using a prophy bristle brush or prophy cup with a slurry of flour of pumice and water, or utilize an air-polishing unit.
• Rinse the tooth surface thoroughly with water spray for 20 to 30 seconds to evacuate all pumice particles, then dry with clean compressed air.

  Caution

  Prophy Paste Prohibition: Never use commercial prophy pastes to clean fissures prior to sealant placement! Commercial pastes contain flavoring oils, lubricating glycerin, and fluoride that leave a microscopic film on enamel, preventing phosphoric acid from etching the enamel prisms and causing immediate bond failure.

Step 2: Moisture Isolation (The Critical Determinant)

• Isolate the operative site using rubber dam isolation (the clinical gold standard) or cotton roll isolation paired with dry angles (Dri-Angles covering Stensen's parotid duct) and continuous high-volume evacuation (HVE).
• The 0.5-Second Saliva Disaster: Moisture contamination is the single most common cause of sealant failure. If saliva contacts etched enamel for even 0.5 seconds, salivary proteins instantly coat the micropores, remineralizing the surface and blocking resin penetration. If salivary contamination occurs at any stage after etching, the tooth must be thoroughly rinsed, dried, and re-etched for 10 to 15 seconds.

Step 3: Acid Etching (Conditioning)

• Apply 35% to 37% phosphoric acid gel to the entire pit and fissure network, extending the gel approximately 2 to 3 millimeters up the cuspal inclines.
• Leave the acid etchant undisturbed for 15 to 30 seconds (20 seconds is standard for permanent molars; primary teeth require 30 seconds due to their aprismatic enamel structure).
• Avoid rubbing or scrubbing the acid onto the enamel with an applicator, as this fractures the fragile etched enamel prisms.

Step 4: Rinsing and Drying

• Rinse the etched enamel thoroughly with an air/water syringe for 15 to 20 seconds to remove all acid residue, while holding the HVE tip close to the tooth.
• Dry the enamel thoroughly with clean, oil-free, moisture-free compressed air for 15 seconds. (Always test the air syringe on the patient's bib or a mirror first to confirm no water or oil droplets leak from the dental unit lines).
• Visual Inspection of the Etched Surface: Successfully etched enamel must display a uniform dull, frosty, chalky-white appearance. If the enamel appears shiny or normal, reapply etchant for an additional 15 seconds.

Step 5: Sealant Placement

• Dispense sealant material carefully into the deepest central pit, allowing the material to flow into adjoining fissures by capillary action.
• Use the sharp tip of a dental explorer or microbrush to gently tease the resin through all grooves and buccal/lingual extensions, dislodging any entrapped air bubbles.
• Do not overfill the occlusal table. Sealant should cover the fissures smoothly without pooling excessively over marginal ridges or cusp tips.

Step 6: Light Polymerization (Curing)

• Position the tip of the LED curing light perpendicular (90 degrees) to the occlusal surface, holding the light guide approximately 1 to 2 millimeters above the sealant without touching the uncured resin.
• Wear protective orange eye filters and cure for 20 to 30 seconds (or per manufacturer's instructions), ensuring the light beam covers all margins.

Step 7: Clinical Evaluation and Finishing

• Tactile Exploration: Immediately check the sealant with a sharp dental explorer. Attempt to dislodge the material using gentle upward tipping forces. The sealant should be rock-hard, firmly bonded, and completely free of marginal crevices, air voids, or tacky spots.
• Interproximal Flossing: Pass dental floss through the mesial and distal contact spaces to ensure no excess resin has flowed interproximally to bridge the contact area.
• Oxygen-Inhibited Layer Management: When resin polymerizes in room air, ambient oxygen inhibits the surface layer of monomer from curing, leaving a microscopic sticky film. Wipe the cured sealant surface with a moist cotton roll or wet gauze sponge to remove this sticky unpolymerized monomer, eliminating an unpleasant taste and reducing the risk of mucosal sensitization.
• Occlusal Check: Place articulating paper in forceps and have the patient tap lightly in centric occlusion and grind in lateral excursions. If using an unfilled sealant, high spots do not require adjustment. If using a filled sealant, any contact marks on the resin must be carefully adjusted down using a slow-speed handpiece with a small round bur (#2 or #4) or a white composite finishing stone until all opposing centric stops land entirely on natural enamel.

Step 8: Patient Instructions and Recall Maintenance

• Patients may eat and drink immediately following light-cured sealant placement.
• Re-evaluate sealant retention and marginal seal at every 6-month preventive recall appointment. If a sealant becomes partially lost or chipped, clean the exposed area, re-etch, and apply fresh sealant.