CHAPTER 17 Pit and Fissure Sealants and Preventive Resin Restorations
In 1955, Buonocore described the technique of acid etching as a simple method of increasing the adhesion of self-curing methyl methacrylate resin materials to dental enamel.1 He used 85% phosphoric acid to etch enamel for 30 seconds. This produces a roughened surface at a microscopic level, which allows mechanical bonding of low-viscosity resin materials.
The first materials used experimentally as sealants were based on cyanoacrylates but were not marketed. By 1965, Bowen had developed the bis-GMA resin, which is the chemical reaction product of bisphenol A and glycidyl methacrylate.2 This is the base resin to most of the current commercial sealants. Urethane dimethacrylate and other dimethacrylates are alternative resins used in sealant materials.
For the chemically cured sealants, a tertiary amine (activator) in one component is mixed with another component containing benzoyl peroxide, and their reaction produces free radicals, which initiates polymerization of the sealant material.
The other sealant materials are activated by an external energy source. The early light-activated sealants were polymerized by the action of ultraviolet rays (which are no longer used) on a benzoin methyl ether or higheralkyl benzoin ethers to activate the peroxide curing system. The visible light–curing sealants have diketones and aromatic ketones, which are sensitive to visible light in the wavelength region of 470 nm (blue region). Some sealants contain filler, usually silicon dioxide microfill or even quartz.
Sealant materials may be transparent or opaque. Opaque materials are available in tooth color or white. Transparent sealants are clear, pink, or amber. The clear and tooth-colored sealants are esthetic but are difficult to detect at recall examinations. Recent advances in sealant technology include light-activated coloring agents that allow for color change during and/or after polymerization. These compositional changes do not affect the sealant, but only offer some arguable benefit in the recognition of sealed surfaces.
The cariostatic properties of sealants are attributed to the physical obstruction of the pits and grooves. This prevents colonization of the pits and fissures with new bacteria and also prevents the penetration of fermentable carbohydrates to any bacteria remaining in the pits and fissures, so that the remaining bacteria cannot produce acid in cariogenic concentration.
Many clinical studies have reported on the success of pit and fissure sealants with respect to caries reduction. As the longevity of the sealant increases, the retention rate becomes a determinant of its effectiveness as a cariespreventive measure.
In 1983, a National Institutes of Health Consensus Panel considered the available information on pit and fissure sealants and concluded that “the placement of sealants is a highly effective means of preventing pit and fissure caries.… Expanding the use of sealants would substantially reduce the occurrence of dental caries in the population beyond that already achieved by fluorides and other preventive resources.”3
In 1991, Simonsen reported on a random sample of participants in a sealant study recalled after 15 years.4 He reported that, in the group with sealant, 69% of the surfaces were sound 15 years after a single sealant application, whereas 31% were carious or restored. In the group without sealant, matched by age, gender, and residence, 17% of the surfaces were sound, whereas 83% were carious or restored. He also estimated that a pit and fissure surface on a permanent first molar is 7.5 times more likely to be carious or restored after 15 years if it is not sealed with a single application of pit and fissure sealant.
The use of glass ionomer as a sealant material has the advantage of continuous fluoride release, and its preventive effect may continue with the visible loss of the material. Glass ionomer may be useful as a sealant material in deeply fissured primary molars that are difficult to isolate due to the child’s precooperative behavior and in partially erupted permanent molars that the clinician believes are at risk for developing decay. In such cases, glass ionomer materials must be considered a provisional sealant to be reevaluated and probably replaced with resin-based sealants when better isolation is possible. Because questions exist regarding the strength and retention of glass ionomer, further long-term research is necessary before it is recommended as a routine pit and fissure sealant material.
A 1996 survey of Indiana dentists5 found that 91% of them were placing sealants on permanent teeth, whereas in 1985 a similar study6 had found that only 73.5% were placing sealants on permanent teeth. This increased use of sealants may be related to increased practitioner comfort with the materials, because a direct correlation was found between sealant use and year of graduation from dental school. The increase may also be related to a decreased concern over the possibility of caries developing under the sealant.
Several studies have reported decreased viable bacterial counts in occlusal fissures that have been sealed. Handleman and colleagues placed an ultraviolet-radiation–polymerized sealant on pits and fissures of teeth with incipient caries.7 They reported a 2000-fold decrease in the number of cultivable microorganisms in the carious dentin samples of the sealed teeth compared with unsealed control teeth at the end of 2 years.
Going and colleagues obtained bacteriologic samples from teeth that had been sealed with an ultravioletradiation–polymerized sealant for 5 years.8 They found an apparent 89% reversal from a caries-active to a caries-free state in the sealed teeth.
Jeronimus and associates placed three different pit and fissure sealants on molars with incipient, moderate, and deep carious lesions.9 Samples of carious dentin were removed immediately after and 2, 3, and 4 weeks after placement of the sealants and bacteriologic cultures were made. They reported usually positive culture results in teeth where the sealant was lost. Although their short-term study indicated that incipient carious lesions may not be of prime concern when sealants are applied, they cautioned against the use of sealants over deeper lesions because of the potential for advancement of caries when sealants over these lesions are lost. One must keep in mind that their deep-lesion group consisted of teeth with caries that had advanced pulpally greater than half the distance from the dentinoenamel junction.
Studies have shown definitively that deficient sealants are not effective in caries prevention and that loss of sealants leads to immediate risk of caries attack from undercover surfaces. Sealants require regular maintenance and repair or replacement to assure success in caries prevention over the long term.
Going declared that, given the results of many well-documented studies, practitioners’ fear of sealing pits and fissures with incipient caries is not warranted.10 He pointed out that sufficient studies of scientific merit reported negative or low bacterial concentrations after sealant had been in place for several years.
Wendt and Koch annually followed 758 sealed occlusal surfaces in first permanent molars for 1 to 10 years.11 At the end of their study, evaluation of the surfaces that had been sealed 10 years previously revealed that only 6% showed caries or restorations. Romcke and associates annually monitored 8340 sealants placed on high-risk (for caries) first permanent molars during a 10-year period.12 Maintenance resealing was performed as indicated during the annual evaluations. One year after the sealants were placed, 6% required resealing; thereafter 2% to 4% required resealing annually. After 8 to 10 years, 85% of the sealed surfaces remained caries free.
Retrospective studies based on billing data from large third-party databases reveal that sealant use is still surprisingly low, even in populations for which sealants are a covered benefit.13,14 In addition, these studies show that the effectiveness of sealants in preventing the need for future restorative care on the sealed surfaces declines after the first 3 years following sealant treatment. These data argue again for the importance of vigilant recall and upkeep of sealants after placement.
Another concern is the placement of sealants immediately after topical fluoride application. Clinical and in vitro studies have shown that topical fluoride does not interfere with the bonding between sealant and enamel.15,16
The 2008, Evidence Based Clinical Recommendations for the Use of Pit and Fissure Sealants report by the American Dental Association on Scientific Affairs concluded that sealants are effective in caries prevention and can prevent the progression of early noncavitated carious lesions.17
The American Academy of Pediatric Dentistry’s Pediatric Restorative Dentistry Consensus Conference18 confirmed support for sealant use and published these recommendations:
To gain the greatest benefit, the clinician should determine the caries risk; thus, the term risk-based sealant treatment has come into use. In risk-based sealant treatment, the practitioner takes into account prior caries experience, fluoride history, oral hygiene, and fissure anatomy in d/>