Preventive dentistry includes a variety of patient and professional activities such as oral hygiene procedures to clean teeth and soft tissues, the uses of fluoride to control caries, chemo-pharmacologic agents to control periodontal disease, orthodontic space maintenance and interventions for the developing dentition, and treatment of susceptible surfaces of the teeth before they become carious. This article will focus on the use of pit and fissure sealants to prevent dental caries in children and adolescents.
During the last 30 years, there have been significant advances in the prevention of dental caries in children and adolescents. While caries has been decreasing on interproximal surfaces, the occurrence of occlusal pit and fissure caries is increasing.1,2
It has been reported that caries on occlusal and buccal/lingual surfaces of teeth account for almost 90% of caries experienced in children and adolescents.3 The reason for this high rate of caries relates specifically to the pit and fissure morphology of occlusal and buccal/lingual surfaces that are not affected by the caries-preventive effects of systemic and topical fluorides.
The connection between pits, fissures, and dental caries can be traced to 1778, when John Hunter stated in his Practical Treatise on the Disease of Teeth that fissures are “cracks on the hollow path of grinding surfaces of molars filled with black substances.”4 In 1889, Andrews described the pits and fissures of enamel as the occlusal surfaces of teeth that had small openings that often led to a larger cavity within the tooth.5 G.V. Black took a slightly different, more scientific approach when he described pits and fissures as access points for the caries process to occur.6
Typically, a clinician dries a tooth surface and uses a dental mirror and explorer during a clinical examination to make the observation that pits, fissures, and grooves are on the surfaces of teeth. The diagnosis of carious pits and fissures, however, can often be challenging, especially with recent changes in the approach to the diagnosis and treatment of caries.7,8 In recent years, the concept of sticking a sharp explorer into pits and fissures has been discarded in favor of the visual appearance of enamel, radiographic diagnosis, and new diagnostic devices.9 Even with newer technologies for caries diagnosis, it is still difficult to chart the progression of the disease,10-13 since considerable variation is noted when pit and fissure caries are examined histologically.14
Galil and Gwinnet14 demonstrated that some occlusal surfaces have only small, round openings while others have continuous grooves that separate the cusps. Occasionally, deep grooves exist that have small openings to the base of the dentinoenamel junction, and in most cases, these fissures and grooves are filled with debris and plaque. Nagano described 3 variations in pits and fissures according to their appearance in cross section: V-type, U-type, and I-type pit and fissures.15 In most cases, the shape of the pits and fissures makes them impossible to clean, which explains their high susceptibility to dental caries.
In the 1960s, Buonocore and co-workers investigated the use of resin adhesives to seal caries-susceptible pits and fissures.16,17 They described an acid-etch technique using phosphoric acid to etch the enamel surface, leaving a microscopically roughened surface that micromechanically retained the resin sealant. By the late 1970s and early 1980s, the clinical data on enamel etching, resin sealants, and caries prevention were supportive of this approach to prevention. A 4-year clinical evaluation of dental sealants demonstrated a caries reduction of 43% overall and significantly better sealant retention on premolars (84%) versus molars (30%).18 A subsequent 7-year study by Mertz-Fairhurst and co-workers reported that 66% of the sealants were fully retained and 14% were partially retained.19 Resin sealant loss was 20%. Further, caries reduction seen with sealants was 55%.
In a more comprehensive, 10-year observation of more than 8,000 sealants placed on permanent first molars, a complete resin sealant retention of 63% at 7 years, 58% at 9 years, and 41% at 10 years was observed.20 Simonsen has reported on the retention and effectiveness of a single application of resin sealant to permanent first molars.21,22 His results indicated that at 10 years, 56.7% of sealants were completely retained and 20.8% were partially retained. Sealant was missing from 6.9% of the surfaces, while 15.6% of the surfaces had been restored or were carious. In the sealed group, 84.4% of the pit and fissure surfaces of the first molars were caries-free. In the unsealed controls, only 31.7% of the first molars were caries-free. At 15 years, 27.6% of the teeth still had complete sealant retention, and 35.4% demonstrated partial retention. Of the sealed teeth, 68.7% were caries-free and only 17.2% of the controls were caries-free.
Sealant loss of 5 to 10% per year is observed when reviewing the published data.23 These data further suggest the importance of periodic re-evaluation of teeth with sealants, with reapplication if necessary. If there is a negative aspect to the use of sealants, it would be the failure of clinicians to re-evaluate and reapply sealants when they are lost or failing. Failure to maintain sealants will lead to pits and fissures again becoming susceptible to bacterial colonization and caries formation, with the need for invasive tooth restorations.23
RISK ASSESSMENT: WHICH TEETH NEED TO RECEIVE SEALANTS?
Based on clinical studies, teeth can be classified as to their risk for development and progression of caries. Heller and colleagues compared teeth that were sound (intact) and at risk for caries progression (incipient lesion) by examining sealed and unsealed teeth in the same mouth.24 At 5 years, teeth that were initially sound had a caries rate of 13% if unsealed and 8% when sealed. Teeth that were classified as at-risk had a caries rate of 52% at 5 years when unsealed compared to only 11% when sealed. While the benefit of sealing sound teeth is small (a difference of 13% to 8%), there is no doubt that at-risk teeth realize a substantial benefit if they are sealed before they are affected by caries.
Currently, there are no generally accepted methods for identifying which teeth are considered to be at risk for development of caries and hence should be sealed. A possible criterion that may be used is the determination of whether the tooth has deep occlusal pits and fissures. Classically, the diagnosis of pit and fissure caries is made using a sharp explorer tip and tactile feedback as the explorer is probed into pits and fissures. Typically, the diagnosis of caries is made if the explorer tip, when forced into the pit and fissure, displays resistance to removal. The reliability of the use of an explorer in diagnosing pit and fissure caries when there was resistance, however, was only 24%, meaning that 76% of the time that resistance was present, there was no caries.25 In addition, concern has been expressed that a sharp explorer tip can damage a demineralized white spot lesion of the enamel by cavitating the surface or that bacteria on the tip of the explorer can cross-infect teeth.26,27
While the use of an explorer and radiographs forms the basis of the diagnosis of caries, a new device that uses laser fluorescence (DIAGNOdent, KaVo) has improved the reliability of caries diagnoses in pits and fissures.10,13,28 The device takes advantage of the light-reflecting and fluorescing properties of normal, healthy enamel when compared to caries-affected enamel. Using a laser with a wavelength of 655 nm, there is no fluorescence of sound tooth structure, while carious tooth structure displays fluorescence. A visual display and audio cues signal the clinician to these changes. The instrument gives a digital read-out for caries activity with recommendations for treatment interventions. These recommendations, which the manufacturer makes, are values of zero to 14, indicating no special measures; 15 to 20, indicating sealant placement and topical fluorides; 21 to 30, indicating further assessment of caries risk, caries activity testing, sealant placement, and more frequent recall intervals; and 30, indicating restoration of the pit and/or fissure and the recommendations for 21 to 30. Regarding the reliability of various techniques used for diagnosis of pit and fissure caries, one study compared visual techniques assessing the appearance of the pit and/or fissure for changes in color and opacity to the use of disclosing solution. The visual techniques were correct 53% of the time and the caries disclosing dye was correct 43% of the time.29 In a comparison of 4 different diagnostic techniques (radiographs, sharp explorer, caries disclosing dye, and DIAGNOdent), accuracy varied considerably.30 When using radiographs, the false-positive rate was 25%. A sharp explorer missed 25% of the carious lesions (false negatives), and when the use of the explorer indicated that caries was present, the diagnosis was wrong 12% of the time (false positives). Disclosing dye was the least accurate, missing 40% of the carious lesions that were present, and 20% were false positives. Laser fluorescence was the most accurate: 90% of the carious lesions were accurately diagnosed with no false positives. Other studies have confirmed the value of laser fluorescence.31-33
The cost effectiveness of sealants depends on sealant retention. While the rate of sealant retention on occlusal surfaces is relatively high at 5 years,18-21 sealant retention in buccal and lingual pits and fissures is considerably lower. Barrie and co-workers examined sealant loss at 2 years on buccal and lingual surfaces. They compared self-cure and light-cure sealants.34 Complete sealant retention of the self-cure sealant on occlusal surfaces was 88% compared to 35% on the buccal/lingual surfaces. The light-cure sealant had a retention rate of 81% for the occlusal surfaces compared to a 39% rate of retention on the buccal/lingual surfaces. From these reports, it is obvious that the occlusal surfaces are easier to protect from caries than buccal/lingual surfaces. While the loss of sealant on occlusal surfaces averages 5 to 10% annually, the percentage for buccal and lingual surfaces increases to 30% per year.
While it is desirable to seal all at-risk teeth, consideration also should be given to sealing difficult-to-access teeth such as those that are partially erupted. In these situations, isolation and soft-tissue considerations may make the placement of sealants less reliable. Dennison and co-workers investigated retention of sealants on at-risk teeth that were fully erupted compared to those that were partially erupted.35 Three years after resin sealant placement, it was found that none of the fully erupted, sealed teeth required replacement, while teeth that demonstrated gingival tissue at the level of the distal marginal ridge had a 26% replacement rate. When the gingival tissue was over the distal marginal ridge at the time of placement, the replacement rate was 54%. Clearly, access contributes to resin sealant retention.
Table. Considerations for premature sealant failure.
There are other factors that contribute to sealant success (Table). In many cases, the inability to isolate the field may create difficulty in placing a sealant. Resin adhesion to etched enamel requires a clear, dry enamel surface. Resins used as sealants are not moisture tolerant. If using a resin sealant, teeth ideally should be approaching full eruption or be fully erupted into the oral cavity before attempting the placement. Recent research has investigated the use of glass ionomer cements for sealant placement.36,37 Taifour and co-workers examined the use of glass ionomer sealants on newly erupted first molars.37 They reported glass ionomer sealant retention of 31% after 3 years. Pardi and co-workers reported similar low sealant retention rates after 3 years.38 Both groups did report that even with these rates of loss of glass ionomer sealants, there was a significant preventive effect with the use of glass ionomer sealants when compared to the control group. Based on these studies, one can deduct that glass ionomer sealants, which are moisture tolerant, have a definite place in preventing caries in occlusal pits and fissures for partially erupted and newly erupted teeth. Once the tooth is fully erupted, the glass ionomer sealant can be replaced with a resin sealant. This is consistent with the concept that all seal-ants need to be periodically re-evaluated. If there is partial or complete loss of sealant, then the clinician needs to reapply the sealant. In both studies cited above, there was no reapplication, only evaluation for sealant retention and the presence of caries.
Some concern has been raised over the sealing of undiagnosed, incipient carious lesions on the occlusal surface. In 1972, Handelman reported on sealing active caries in pits and fissures to determine if this procedure was harmful.39 He placed sealants over diagnosed occlusal carious lesions to evaluate the outcome. His 2-year analysis noted that clinical and radiographic findings suggest there was no progression of the carious lesions.40 Others confirmed Handelman’s findings.41,42 Therefore, based upon the evidence to date, placing sealants on at-risk teeth is a cost-effective technique.
TYPES OF SEALANTS
Sealant materials can be classified by their composition. Currently there are 2 basic sealant types: resin and glass ionomer. When a tooth is fully erupted and can be isolated, the clinical data support the use of resin-based sealants. When teeth are first erupting into the oral cavity, the use of glass ionomer sealants has some significant advantages.35-37 Glass ionomers as sealants have demonstrated a moisture tolerance combined with predictable fluoride release.36,37 At the current time, the published literature indicates that clinical retention of resin-based sealants for routine use is superior to that of glass ionomer-based sealants.43
Resin-based sealants can be classified by method of polymerization and characteristic properties. Sealants can be polymerized either chemically (autocure or self-cure) or by initiating the setting reaction with a visible light-curing device. Both self-cure and light-cure sealants provide equivalent clinical effectiveness.18-22 Sealants can be filled or unfilled. Clinical trials have demonstrated that unfilled sealants perform better than filled sealants.34 Sealants also can be either clear or colored. Colored sealants offer the advantage of visually being able to detect the presence or absence of the applied sealant on the tooth surface. Sealants that change color during polymerization have recently been introduced (Clinpro Sealant, 3M ESPE; Helioseal Clear Chroma, Ivoclar Vivadent). The Helioseal Clear Chroma changes from a clear to a green sealant after photopolymerization. This contrasting color may be beneficial when evaluating sealant retention. The Clinpro Sealant changes from a pink fluid when applied to an opaque white color after light-curing. At the current time, the best recommendation for a resin-based sealant would be one that is light-cured, unfilled, with a colorant.
Glass ionomer sealants adhere to tooth structure based upon an ionic bond between the glass ionomer and the calcium within the enamel.44,45 For this reason, glass ionomers have been referred to as self-adhesive to tooth structure. A microleakage study comparing a resin sealant to a glass ionomer sealant concluded that while the resin-based sealant performed better, a glass ionomer could be a viable alternative as a pit and fissure sealant.46
Recently, a glass ionomer sealant (Triage, GC America) was introduced that is termed a “smart” sealant in that it offers additional benefits other than physically sealing the pits and fissures. Triage’s unique chemistry makes it a “smart” restorative material that allows for fluoride release to the surrounding tooth structure. Additionally, it has a semipermeable surface, which allows the calcium and phosphate ions that are present in saliva to pass through the sealant and combine with the fluoride to produce remineralization of the enamel as a fluorapatite. Another unique characteristic of a glass ionomer is that it provides a burst of fluoride for remineralization combined with a prolonged fluoride release over time. If the patient is following the recommendation to use a fluoride toothpaste, then the patient is renewing the glass ionomer with new fluoride ions every day. Triage, as with all glass ionomers, is self-adhesive, moisture tolerant, and fluoride-releasing. This glass ionomer sealant can be used in clinical situations where there is limited access and difficulty in isolation of the occlusal surfaces from saliva contamination.
CLINICAL TECHNIQUE—RESIN SEALANT: A CASE REPORT
|Figure 1. Susceptible pit and fissures on occlusal surfaces of mandibular second premolar and second molar.|
An examination of a 15-year-old patient revealed that the mandibular first and second molars were sealed (Figure 1). The history revealed that the first molar had been sealed 5 years previously, and the second molar was sealed 2.5 years previously. The examination revealed that the first molar was still sealed, and there was no need for reapplication of sealant. The second molar had stained fissures on the occlusal surface and no sealant present.
The DIAGNOdent device was used to examine and evaluate the occlusal surfaces of the second molar. The readings were consistent with an early carious lesion that could be sealed. The first and second premolars in the same quadrant were evaluated as well. It was determined visually that the second premolar had a fissure that could be susceptible to caries. The treatment plan was to reseal the mandibular second molar and seal the second premolar. Once the diagnosis was made, the decision regarding isolation for placement of sealant was based upon the patient’s expressed concern regarding use of the dental dam. Using a tongue shield-based saliva ejector, cotton rolls, and driangles, adequate isolation to place sealants was achieved. Ideally, especially for children, the best isolation of the field is accomplished with a dental dam. In many circumstances, sealants can be successfully placed using absorbents that are changed between steps. Regardless of the method of isolation, it is important to note in the patient’s record how the teeth were isolated to provide additional information on the future success or failure of sealants for each patient.
|Figure 2. Occlusal surfaces being cleaned with pumice paste and a prophylaxis cup.|
After isolation, the teeth were cleaned with a water/pumice paste using a prophylaxis cup on a slow-speed handpiece (Figure 2). The adhesion of sealant to enamel surfaces can be enhanced by cleaning the occlusal surfaces with a nonfluoride, pumice prophylaxis paste47 or by using an air-abrasion device.48 The surfaces of the teeth were thoroughly rinsed with an air/water spray and then dried. The wet absorbents (cotton rolls and driangles) were frequently replaced during the sealant procedure.
|Figure 3. Etching the occlusal surfaces.|
|Figure 4. Etchant rinsed from teeth for 10 seconds with air/water spray.|
|Figure 5. Etched occlusal surfaces.|
Next, the teeth were etched for 15 seconds with a 32% phosphoric acid etchant (Figure 3). The etchant was thoroughly rinsed from the teeth with an air/water spray for 10 seconds (Figure 4), then the surfaces of the teeth were completely dried with air spray. The enamel surface had a dull, frosted appearance (Figure 5). It can also be seen in Figure 5 that the existing sealant on the occlusal surface of the mandibular second molar was still sealing the pits and fissures and did not need to be removed prior to resealing the tooth. Although the most common practice is to directly apply the sealant to the etched enamel, the use of an intermediate adhesive resin before sealant placement has been studied. The use of an intermediate adhesive resin has the potential to increase sealant retention.49,50 One disadvantage of this procedure is that it increases the number of steps and time required for sealant application. This is associated with an increase in cost and the potential for contamination when treating a pediatric patient. Contamination can result in premature loss of the sealant.43
|Figure 6. Application of sealants with an application tip.||Figure 7. Application of sealant with a microapplicator brush.|
|Figure 8. Light-curing the sealants.||Figure 9. Sealants after light-curing.|
Sealant was then applied to the occlusal surfaces. Some sealants have unit-dose dispensing with a separate canula tip (Figure 6). For this case, the sealant was applied with a microapplicator brush (BendaBrush Micro, Centrix, Figure 7). The sealant should be placed so as to cover all pits and fissures and extend onto the cusp ridges. The thickness of sealant should be at least 0.3 mm.21,22 A light-cured sealant was used, and curing was for 10 seconds with an LED light (Allegro, Den-Mat, Figure 8). It is important that the light tip be at right angles to the curing surface. If the diameter of the light tip is less than the area of the occlusal surface being sealed, it is necessary to cure the sealant multiple times depending on the area covered by the light tip. When curing, the tip is placed as close to the surface of the sealant as possible. The sealants were then evaluated for retention and seal of the occlusal surfaces (Figure 9).
CLINICAL TECHNIQUE— GLASS IONOMER SEALANT: A CASE REPORT
|Figure 10. Partially erupted mandibular second molar with a highly invaginated occlusal surface.|
An 11-year-old child presented with an erupting mandibular second molar that demonstrated highly invaginated occlusal pits and fissures (Figure 10). The second molar teeth had been erupting for the past 12 months and remained incompletely erupted. The height of the gingival tissues surrounding the erupting crown precluded isolation with a dental dam. Isolation would have been necessary if an acid-etch, resin-based adhesive sealant were used. Since the isolation would have been difficult, a moisture-tolerant glass ionomer sealant (Fuji Triage) was selected. An explanation was made to the parent that this sealant would not be as durable as a resin sealant, but would be useful in sealing the tooth during this susceptible time. At a subsequent visit, the glass ionomer sealant could be replaced with a resin sealant.
|Figure 11. Tooth cleaned with pumice/water paste and a prophylaxis brush.||Figure 12. Application of tooth conditioner to occlusal surface for 10 seconds.|
|Figure 13. Thin layer of Fuji Triage applied to the occlusal surface.||Figure 14. Fuji Triage sealing the occlusal surface of the second molar.|
The occlusal surface of the tooth was cleaned with a prophylaxis cup and a paste of water and flour of pumice (Figure 11). An air-abrasion system could have been used to clean the occlusal surface. The area was rinsed and dried. Cotton roll and blotter isolation combined with high- and low-volume evacuation was used to control the moisture in the area. The tooth was cleaned for 10 seconds with a cavity cleaning agent (GC Cavity Conditioner, GC America, Figure 12). This agent is not an etchant but a surface cleaner that allows the glass ionomer to form strong ionic bonds with the tooth structure. While the tooth was being conditioned, the dental assistant was activating the Fuji Triage capsule. A pink-colored Fuji Triage was used. Recently, a white Fuji Triage color has been introduced. That choice is based on clinician preference. The capsule was shaken and tapped to loosen the powder. Placing the capsule at right angles to a tabletop surface and pressing in the activation plunger activated the capsule. The working time for the glass ionomer is 1.5 minutes after mixing, with a setting time of 2.5 minutes. Once mixed, the capsule was placed into the syringe for application onto the occlusal surface of the tooth. A thin layer of Fuji Triage was applied to the occlusal surface of the tooth (Figure 13). Fuji Triage has a viscosity that facilitates flow of the material onto the occlusal surfaces. Using a microapplicator, the glass ionomer sealant was spread in a thin coating over the exposed pits and fissures. Fuji Triage has a unique setting reaction. Once mixed, it will harden with a self-setting reaction; by using a curing light for 10 seconds, the heat will accelerate the setting reaction. Once the material was set, the occlusion was checked. Occlusal adjustment was not needed since the tooth was not fully erupted. The final restoration provides a preventive seal of the oc-clusal surface (Figure 14). The occlusal surface of the first molar was resealed at a later appointment.
Sealants are a highly effective preventive measure for reducing pit and fissure caries. Simonsen’s comprehensive review of the literature43 on sealants included 1,465 references from 1971 to 2001. The following subheadings were included: laboratory studies; clinical technique and tooth preparation; etching time; auxiliary application of pit and fissure sealant; retention and caries prevention; fluoride used with sealants and fluoride-containing sealants; glass ionomer materials as sealants; options in sealants: filled versus unfilled, colored versus clear, autocure versus light-initiated; sealant placed over caries in a therapeutic manner; cost effectiveness of sealant application; underuse of pit and fissure sealant; estrogenicity issue; use of an intermediate bonding layer to improve retention; new developments and projections; and summary and conclusions. He concluded from this examination of peer-revi