Sealant Selection

Dental sealants were developed in the 1960s by Michael Buonocore, DDS, and dental scientists at the Eastman Dental Center in Rochester, New York.^1–3 A thin plastic coating of an organic polymer (resin), a sealant is placed into the pits and fissures of newly erupted molar teeth that are susceptible to dental caries.^1–7 This placement acts as a physical barrier, sealing off the pit or fissure from caries-producing oral bacteria, thereby preventing decay.^1–7 Sealants can help shield grooved areas of the tooth where fluoride toothpaste is not as protective. They can reduce caries by approximately 80% in 2 years after initial placement and may remain effective for nearly 5 years.^1,3,6,7 Sealants cost one-third less than a restorative filling and can be placed after an initial assessment verifies no extensive decay is present.^6,7 Some research shows that sealant placement in areas of early decay can help to control and manage caries on occlusal and approximal surfaces.^1,3,6 There are two main types of sealants: resin and glass ionomer cements (GICs).

RESIN-BASED SEALANTS

Sealants are categorized by color, fluoride releasing or nonfluoride releasing, method of polymerization (hardening), and filler content (silica, glass, or quartz particles added to increase strength and resistance to occlusal wear).^1–4 The variety of colors ranges from clear to tinted and opaque, which aid in the sealant’s application into pit and fissures and margin identification during retention checks.^1–4 Sealants containing fluoride increase resistance to caries formation and remineralize incipient carious lesions.^1,2,4 Many sealants are composed of dimethyacrylate monomers that may include bisphenol A-glycidyl methacrylate (Bis-GMA); they are classified as self-cured (autopolymerized) or light-cured (photopolymerized).^1–4 Unfilled sealants are clear (making placement difficult to see), may not require occlusal adjustment, and are less resistant to wear over time.^1,2,4 Filled sealants can be tinted, and may require occlusal adjustment after placement and light curing.^1,2,4

INDICATIONS

Evidence shows that 80% to 90% of caries lesions originate from pits and fissures in the occlusal surfaces of posterior teeth.^3–8Patients should be assessed for caries and their risk for lesion progression determined. Then sealants can be placed on pit and fissure surfaces that are either at risk for caries or already exhibit incipient, noncavitated lesions in order to halt the progression.^1,2,4,7Caries risk assessment includes determining oral, behavioral, medical, and environmental factors that raise the risk for caries.^1,2,4,7Oral factors include frequency of brushing, prescribed orthodontic appliances, and a diet high in sugar and refined carbohydrates. Behavioral risk factors encompass illicit or recreational drug use that may cause xerostomia. Medical risk factors include conditions that increase risk of caries formation and medications that cause xerostomia. Environmental risk factors comprise nonfluoridated drinking water and low socioeconomic status.^1,2,4,7 Sealants are indicated for patients at any age who are at risk for caries. Sealants may be particularly helpful for patients age 3 and older who are at high caries risk with deep occlusal fissures.^1,2,4 

Safety glasses should be donned by all patients to provide a barrier to the acid etch solution and cure light.^1,2,4 The use of resin-based sealants that are photopolymerized shrink toward the source of the curing light, and therefore may be prone to marginal leakage.^4,9 The phosphoric acid (etch) solution used when placing resin sealants should not contact the patient’s oral tissues.^1,2,4Resin sealants may require self-etching bonding agents, which may not provide as good retention as acid-etch techniques.^1,2,4,7Some sealant material retention is dependent on moisture control achieved by maintaining a dry field during etching and placement.^1,2,4,5,7,9 However, some resin materials can be placed in a moist field. Overmanipulation of sealant material by the clinician may result in air bubbles and voids, decreasing the sealant’s effectiveness.^1,2,4 

CONTRAINDICATIONS 

Sealants should not be placed if the following is present: radiographic assessment determines active occlusal or proximal decay into the dentin; insufficient eruption; primary tooth is near exfoliation; shallow coalesced and self-cleansing pits and fissures; or allergies to sealant materials.^1–4 

There has been some concern regarding allergic reactions to sealants and adverse effects of exposure to bisphenol-A (BPA), which is present in some resin sealant products.^1,3,4,7,8,10 Pure BPA is rarely used in dental materials; however, some resin-based sealants can contain its derivatives.^1,3,7,8,10 A transient amount of BPA has been detected in the saliva or bloodstream of some patients up to 3 hours after sealant application, but any residual sealant material can be rinsed away with water or blotted with a cotton roll.^1,3,4,7,10Current evidence suggests patients are not at risk for estrogen-like effects when resin sealants are used; however, precautions should be taken (dental dam use) to minimize exposure to BPA.^1,3,4,7

GLASS IONOMER CEMENTS AND SEALANTS

GICs are composed of aluminosilicate glass (powder) and polymeric water-soluble acid (liquid) set through an acid-base reaction that is mixed to form a viscous paste.^9,11–13 GICs are less acidic compared to zinc phosphate, more compatible with dental pulp, set within 2 minutes to 3 minutes, and can be hand-mixed using a spatula.^12,13 The material can also be presented in a capsule separated by a membrane, which is broken prior to the capsule being vibrated in an amalgamator for a set time.¹² GICs have been used in dentistry to repair cervical lesions (both carious and non-carious), cavity liners/bases, fissure sealants, orthodontic band and bracket materials, and as a luting cement since the early 1970s.^3,7,11,12

Type I cements are luting and bonding materials used for cementing crowns, bridges, inlays, onlays, and orthodontic appliances. They are fast-setting and water resistant.^8,11,12 Type II cements are restorative materials used for posterior restorations or repairs, fast setting, and have early resistance to water uptake.^8,11,12 Type III cements are lining cements applied beneath crowns, placed in fissures of molars, are fast-setting, and have low solubility in oral fluids.^8,11,12 In 1991, resin-modified glass ionomers (RMGIs) were introduced to improve the physical properties and decrease the water sensitivity of conventional materials.^11,12 RMGIs contain a polymerisable resin known as hydroxyethyl-methacrylate (HEMA) that may have the additional setting reaction of a resin, which may be self-curing and/or light curing.^11,12

RMGIs can be used as interim therapeutic restorations (ITRs) and for application in the atraumatic restorative technique (ART).^6,7,11–13 ITRs are fillings placed without the use of anesthesia or drilling.^6,7 ART uses hand instruments to remove caries-affected dentin and enamel after which high-viscosity glass ionomer cement is placed to repair the tooth.^10–12 All glass ionomer dental materials release fluoride ions.^{2–7,9,11,14} The difference between traditional glass ionomer and RMGI is that RMGIs offer enhanced esthetics, less solubility, and greater strength than regular glass ionomers, yet retain some of their fluoride-releasing characteristics.^11–13 Under oral acidic conditions, greater amounts of calcium are released from RMGIs, causing a buffering effect of the oral flora.¹² 

Due to their fluoride-releasing properties that may last several years, GICs and RMGIs are indicated for restoration of root caries; Class V abrasion and erosion lesions; and Class I, Class II, and Class III caries on primary teeth.^7,9,11–13 RMGIs have increased strength, easy flow ability into pits and fissures, and improved wear and resistance compared with GIs.^4,7,9 All glass ionomers can be placed in less than ideal clinical situations and enable chemical bonding to both enamel and dentin; thermal expansion similar to that of tooth structure; and reduction in hypersensitivity.^4,7,9,12 Glass ionomers are also hydrophilic, meaning they have a tendency to absorb water and may be placed in the presence of moisture.^4,7,12,15,16 Lastly, glass ionomers can act as a fluoride reservoir, with absorption occurring from the use of mouthrinses, dentifrices, and topic fluoride applications. This may provide protection from secondary decay formation.^{3,4,7,9,11,12,16} 

CONTRAINDICATIONS

If high-quality resin sealant placement is desired and a modern clinic is accessible, then GICs are probably not the first choice.^7,8,10,12 Several studies demonstrate that glass ionomers have shorter retention rates than resin-based sealants, may be brittle, and show high rates of occlusal wear.^{3,4,5,9,12,17–19,20} Due to their low retention rates, GICs may not be recommended for routine clinical use; however, they can protect pit and fissures against caries over 2 years due to their fluoride-releasing properties.^7,16–19,20 Because RMGIs contain properties similar to resin sealants, the HEMA emitted from the RMGIs may be a contact allergen for patients and dental personnel. However, no reports of allergies have been identified in the literature reviewed.¹² 

CONCLUSIONS 

Deciding on which type of sealant material to use depends on myriad factors. The benefits of both materials are based on retention and integrity in pit and fissures and fluoride release over time.^16–19,20 Resin sealants typically provide greater longevity than GICs. For instance, research shows that light-cured resin sealants were retained in pits and fissure of molar teeth longer than glass ionomers.^16–18,20 Other studies, however, suggest that neither material was superior to the other in caries prevention.^16,19,20,21Glass ionomer sealants are recommended in ITR and ART.^6–8,10 In the final determination of material selection, oral health professionals should assess the clinical situation, as well as individual patient factors/needs to obtain the ultimate goal—caries prevention.

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