Making the Most of Sealant Usage

Placing pit and fissure sealants—the mechanical obstruction of deep fissures by acid etch-dependent bonding of composite resins—is now considered a standard of care to prevent fissure caries.

Myths concerning dental sealants have risen and faded over the past 40 years. Dedicated investigators, through bench and clinical studies, have provided improved understanding and clinical advancements. Today’s understanding of sealant effectiveness and best practices will also undergo careful scientific scrutiny. Undoubtedly, some truths of today will become faded myths of tomorrow.

Which Teeth Should Receive Sealants?

Effectively sealing teeth with true caries risk and maintaining the sealants over time create the best cost-benefit ratio. The question is which teeth benefit from sealant treatment? A review of family and personal history and tooth level factors that correlate most with future decay are the best risk indicators.

The ultimate benefit of sealants is the teeth saved from decay. To properly assess benefit, the caries rates on sealed teeth are compared to the caries rates on nonsealed teeth. Therefore, the national decline in occlusal caries affects benefit analyses. As the actual caries rate on nonsealed surfaces decreases, the number of sealants placed to protect each fissure from decay increases and thus the percent effectiveness of the sealants decreases. The greatest benefits from sealant treatment are gained from determining the caries risk of teeth and then sealing those with the highest risk of caries. This understanding of risk-based sealant treatment is not new but its adoption has been slow.^1,2

The concept of risk-based sealant application is supported by published data. One example comes from a 5-year study of caries rates after sealant application.³ Molar teeth in school children were screened prior to a sealant program. The initial diagnoses scored the fissures into two groups—healthy and incipient occlusal lesions.³ In this study, which was done in a fluoridated community, the molars that scored initially as healthy became carious at a rate of 13% if not sealed and at a rate of 8% if sealed, representing a modest protective effect (13% versus 8%). Molars scored initially as questionable became carious at a rate of 52% if not sealed and at a rate of 11% if sealed. This latter difference represents a striking protective effect (52% versus 11%).

Caries rates have fallen dramatically for populations in industrialized nations. Latest data analyses of caries^4-7 show the following:

1. Small subgroups of the general population continue to experience the bulk of dental caries.
2. Lower educational levels and lower socioeconomic status correlate with increased caries experience.
3. Primary tooth caries rates and distributions differ from rates and distributions in permanent teeth.
4. Permanent molar occlusal surface caries rates are lower than expected.

Caries rates on all permanent tooth surfaces have dropped for each age level for four subsequent national caries surveys covering years between 1971 and 1994.⁵ Specific to this discussion, the prevalence of decayed or filled occlusal surfaces on first permanent molars in children age 10 years dropped from about 55% to about 15% between national surveys in 1971-1974 and 1988-1994. In the same time period, the prevalence of decayed or filled occlusal surfaces on permanent second molars in children age 16 years has dropped from about 68% to about 25%. None of this decrease in occlusal decay is attributable to sealant use but rather a reflection of the population-wide decrease in decay due to fluoride and better dental habits. In spite of this dramatic shift in occlusal decay, the occlusal surfaces of molar teeth still represent the most common site of new decay in young patients.

These changes in understanding the caries process in pits and fissures mean that we need to rethink sealant usage. The majority of fissures and pits are no longer destined to become carious in the first 3 years after tooth eruption and some fissures and pits will not become carious at all. The rate of caries initiation is slower and over a much longer span of time. Therefore, it is faulty to emphasize sealant placement only within a few years of eruption. Sealant use must be based on patient, tooth, and surface risk factors, and this risk analysis may change at any time during the life of the patient.

The unsealed and unrestored fissures may reach an at-risk stage at a later time due to changes in patient habits, oral microflora, or physical condition. Therefore, these fissures must continually be evaluated into adulthood and sealant placement may be appropriate later in life if risk is increased by lifestyle or health-related changes. The best risk assessment for occlusal decay is done by looking at past caries experience, family habits, fluoride history, plaque load, fissure anatomy, and presence of incipient enamel caries.

What Techniques are Best for My Patients?

1. Patient/family education. Before sealants are placed, the patient and, if appropriate, the parent/caretaker must understand the limits of protection offered by sealants. Often lay people assume that placing sealants protects all surfaces of the teeth forever. People must understand that only certain tooth surfaces will be protected and that this protection is limited. Understanding that periodic review of sealant status is important, along with repairs and replacements when necessary.
2. Clean the surface. The tooth surfaces to be sealed need to be cleaned prior to acid etching to remove the biofilm and allow access to the enamel by the acid. A dry bristle brush on a prophy angle is sufficient for cleaning. Avoid enameloplasty except in cases where caries diagnosis is extremely difficult or questionable. There is no proven advantage to sealant success by using enameloplasty routinely and indiscriminate enameloplasty can open the bottom of fissures into dentin resulting in potentially greater caries risk later.
3. Isolate the tooth. In spite of great improvements in sealant materials, maintaining a dry field for effective bonding to enamel, with saliva control as a basic rule, is still essential. Four-handed dental methods along with good cotton roll isolation have been shown to be as effective for saliva control and eventual sealant success as rubber dam isolation.¹²
4. Acid etching. Place the acid (gel or liquid) widely over the enamel surface. The most common error is to limit acid to the depth of the grooves. It is essential to etch broadly over the surface so there is no chance that the sealant margin is placed on unetched enamel.
5. Rinse and dry. After etching, rinse completely and then air dry carefully. Better to err on the side of over-dryness than over-wetness, even with materials that suggest “wet bonding.” Look for the visual frostiness of the etched enamel surface.
6. Bonding agent. Sealant success is better if a bonding agent layer is placed and air thinned prior to placing the sealant material. This step helps sealant material flow into deep fissures, helps bonding in areas of inadvertent moisture contamination, and improves clinical retention of sealants.^13-15 It involves placing bonding agent directly on the etched, rinsed, and dried enamel surface, air thinning the bonding agent to avoid pooling of the agent, then immediately placing sealant on the bonding agent covered surface.
7. Sealant application. Place sealant carefully onto the fissured surface, flowing from one end of the fissure carefully through the fissure complex to avoid air bubbles. Cover only the fissures and a small area of the fissure walls. Do not over-bulk the surface with material. Keep the sealant out of occlusion if at all possible.
8. Polymerization. Polymerize completely! Check your light source for correct intensity. Use sufficient polymerization time so that the depth of polymerization reaches the tooth surface under the sealant.
9. Occlusal check. Make sure you have not changed the occlusion by your sealant placement. With filled sealants or flowable composites, occlusal checking is even more essential, since these materials do not quickly wear with occlusal function.
10. Follow-up. Show the patient and family what has been sealed and explain again the need for follow-up and repair in order to make sealants a true decay prevention agent. Check sealed teeth carefully at every examination. Look for stained margins, discolored enamel near the sealant margin, defects or bubbles, and frank loss of sealant in caries-susceptible fissures. Look carefully at bite-wing radiographs for any evidence of advancing occlusal decay. Repair faulty sealants and replace lost ones.

Choosing Sealant Material

Most resin sealant materials on the market share similar bonding characteristics. The variations in filler content, color, and consistency among materials may not affect clinical success, but these factors influence professional choice based on each the desired feel and visualization of the material.

Glass ionomer-based sealant materials release fluoride that may be an aid in delaying the caries attack, but to date, this glass ionomer family of materials has not shown sufficient retention in clinical studies.¹⁶ These materials may be useful as preventive agents over short periods when resin-based sealants cannot successfully be placed.

Two recent advances in resin sealant chemistry are important and deserve further clinical study.

1. Sealants have been formulated from relatively hydrophilic (water loving) resins in order to allow some “moist bonding.” This advance is largely in response to previous findings that a hydrophilic bonding agent layer under sealants adds to the clinical success.¹⁵ Anecdotal reports seem favorable. Long-term clinical studies have not been done.
2. Novel resin-based calcium phosphate materials tested in vitro have been shown to release calcium and phosphate ions sufficient to remineralize adjacent tooth structure.¹⁷ Sealants using this chemistry are now available and may offer clinically significant remineralizing potential although the clinical studies have not yet been done.

REFERENCES

1. Rozier RG. The impact of recent changes in the epidemiology of dental caries on guidelines for the use of dental sealants: epidemiologic perspectives. J Public Health Dent. 1995;55:292-301.
2. Rethman J. Trends in preventive care: caries risk assessment and indications for sealants. J Am Dent Assoc. 2000; 131(suppl):8S-12S.
3. Heller KE, Reed SG, Bruner FW, Eklund SA, Burt BA. Longitudinal evaluation of sealing molars with and without incipient dental caries in a public health program. J Public Health Dent. 1995;55:148-153.
4. Brown LJ, Wall TP, Lazar V. Trends in total caries experience: permanent and primary teeth. J Am Dent Assoc. 2000;131:223-231.
5. Brown LJ, Wall TP, Lazar V. Trends in untreated caries in permanent teeth of children 6 to 18 years old. J Am Dent Assoc. 1999;130:1637-1644.
6. Brown LJ, Wall TP and Lazar V. Trends in untreated caries in primary teeth of children 2 to 10 years old. J Am Dent Assoc. 2000; 13:93-100.
7. Kaste LM, Selwitz RH, Oldakowski RJ, Brunelle JA, Winn DM, Brown LJ. Coronal caries in the primary and permanent dentition of children and adolescents 1-17 years of age: United States, 1988-1991. J Dent Res. 1996;75:631-641.
8. Handelman SL, Buonocore MG, Heseck DJ. A preliminary report on the effect of fissure sealant on bacteria in dental caries. J Prosthet Dent. 1972;27:390-392.
9. Mertz-Fairhurst EJ, Curtis JW Jr, Ergle JW, Rueggebert FA, Adair SM. Ultraconservative and cariostatic sealed restorations: results at year 10. J Am Dent Assoc. 1998;129:55-66.
10. Ekstrand KR, Ricketts DN, Kidd EA, Qvist V, Schou S. Detection, diagnosing, monitoring and logical treatment of occlusal caries in relation to lesion activity and severity: an in vivo examination with histological validation. Caries Res. 1998;32:247-254.
11. Swift EJ Jr. Fluoride release from two composite resins. Quintessence Int. 1989:20:895-897.
12. Straffon LH, Dennison JB, More, FG. Three-year evaluation of sealant: effect of isolation on efficacy. J Am Dent Assoc. 1985;110:714-717.
13. Hitt JC, Feigal RJ. Use of a bonding agent to reduce sealant sensitivity to moisture contamination: an in vitro study. Pediatr Dent. 1992; 14:41-46.
14. Hebling J, Feigal RJ. Use of one-bottle adhesive as an intermediate bonding layer to reduce sealant microleakage on saliva-contaminated enamel. Am J Dent. 2000;13:187-191.
15. Feigal RJ, Musherure P, Gillespie, B, Levy-Polack M, Quelhas I, Hebling J. Improved sealant retention with bonding agents: a clinical study of two-bottle and single-bottle systems. J Dent Res. 2000;79:1850-1856.
16. Simonsen J. Pit and fissure sealant: review of the literature. Pediatr Dent. 2002;24:393-414.
17. Dickens SH, Flaim GM, Takagi S. Mechanical properties and biochemical activity of remineralizing resin-based Ca-PO4 cements. Dent Mater. 2003;19:558-566.

From Dimensions of Dental Hygiene. July 2004;2(7):18-20.