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The Sealant Story

A look at the evolution of the dental sealant.

The use of dental sealants to prevent caries in the first and second permanent molars of children and adolescents continues to grow. Research shows that sealant placement on the permanent molars significantly decreases the incidence of caries formation.1,2 Permanent molars have narrow pits and fissures in which bacteria and substrate collect. These surfaces are difficult to access with a toothbrush—making them prime targets for caries formation. Fluoride therapy is also less effective at preventing caries in these teeth because of the tooth’s occlusal morphology.

Community socioeconomic status (SES) is a contributing factor to the incidence of dental caries. The prevalence and intensity of dental caries has declined sharply among children of higher SES due to their increased access to dental care as well as increased sealant usage.3,4 Among children of lower SES, caries remains a public health problem.3 According to the United States National Library of Medicine (NLM), tooth decay is one of the most common disorders affecting American children today, second only to the common cold.5 NLM also states that tooth decay is a primary concern for children living in families who are at or below the poverty level.6

ORIGIN OF THE DENTAL SEALANT

Pit and fissure sealants were introduced in the 1960s but were not widely used until the 1980s. The idea for the dental sealant was born in 1955 when Michael G. Buonocore, DMD, MS, chairman of the Department of Dental Materials at the Eastman Dental Center in Rochester, NY, developed a technique for acid-etching enamel. He discovered that acrylic resin could be bonded to the tooth structure by applying 30% to 50% phosphoric acid to a carefully dried tooth.7 The inorganic fraction of the surface enamel was dissolved to a depth of 3 microns to 10 microns and the porous surface allowed the resin to flow and lock into the enamel pores—literally forming a mechanical bond. The mechanical bond formed a physical barrier that prevented substrate, such as fermentable carbohydrates, from reaching the acid-producing bacteria that initiate decay.7

CHANGES IN DENTAL SEALANT MATERIALS

Dental sealant materials have undergone significant changes since their introduction. The material initially used had a high resistance to flow, and its viscosity was so high that it often ran over the occlusal surfaces, spilling over the margins of the tooth onto other surfaces such as the mesial, distal, lingual, and buccal surfaces. The materials today are easier to handle and more viscous so the sealant remains on the tooth surface until it is light cured.

In the 1960s, the dental sealant had to be mixed in a dappen dish before it could be applied to the tooth. It had to be mixed and applied quickly so that the material would not set before it could be light cured. Manufacturers addressed this problem by making premeasured ready-mixed capsules that could be applied without mixing. These ready-mixed capsules have a low viscosity that helps prevent the overflow of the material onto other surfaces. Normally these materials are applied in a dry field to prevent moisture contamination when the sealant is applied to the tooth’s surface. However, new sealant products* are available that can be cured in a moist environment. These sealants do not necessitate the complete drying of the tooth surface after etching, but rather, they can be applied after a light drying, which leaves the tooth surface slightly moist.

A new sealant adhesive** is also available that contains an acidetch ingredient, which eliminates the need for acid-etch liquid or gel. The adhesive is dried after application instead of being rinsed off. Acid-etch materials have also improved over time. Etching the tooth by dipping a brush or cotton swab into the etch liquid, then applying to the tooth surface is no longer the only option. Acid-etch gels now come in syringes with disposable tips that make it easier to apply the etch exactly where the pits and fissures appear on the tooth surface.

SAFETY CONCERNS

The safety of sealants was re-examined in the late 1990s when concerns arose regarding bisphenol-A (BPA), a chemical that was thought to leak from the dental sealant after application. BPA is a chemical that mimics the estrogen hormone. Research conducted by Olea et al indicated that after applying a commercial dental sealant, detectable levels of BPA ranging from 3.3 ppm to 30 ppm were present in saliva samples.8 This created concern regarding the use of sealants in children because exposure to such pseudo- hormones may alter normal development and may increase the risk of cancer. However, this research was conducted initially on rodents. Within this study population, the BPA triggered an estrogen- like activity in the rodents as well as an acute oral toxicity to the sealant material. When the same test was performed on humans, the amount of BPA found in the saliva of study participants was 50 times lower than the amount seen in the rodent specimens based on the weight of the subjects.8

Several studies about BPA and dental sealant materials have been conducted since the Olea findings were published in 1996. Arenholt-Bindslev et al conducted a study about BPA leakage using two commercial dental sealants and reached an entirely different conclusion than Olea et al.9 Arenholt- Bindslev et al collected saliva samples immediately following, 1 hour following, and 24 hours following the application of dental sealants in human study participants. They found that BPA was present only in the saliva sample collected immediately after the application of the dental sealant in amounts ranging from 0.3 ppm to 2.8 ppm—levels approximately 10 times lower than those reported by Olea et al. No BPA was found in saliva samples collected at 1-hour intervals and 24-hour intervals.9

Fung et al conducted another study that looked at blood samples in addition to saliva samples. Saliva and blood samples were collected in human participants before sealant application and at intervals of 1 hour, 3, hours, and 24 hours, and 3 days and 5 days after application. Some but not all of the saliva samples collected 1 hour and 3 hours after application showed small amounts of BPA. However, no BPA was found in samples collected after 24 hours and none was ever found in the blood samples.10

Due to the information provided by these follow-up studies, it is widely accepted that dental sealants do not pose any health risk to patients. Studies continue to be conducted on BPA in dentistry and in other areas. Currently the BPA contained in consumer packaging, such as plastic containers and bottles, is being assessed for potential health risks.

CONCLUSION

As dental researchers continue to validate the safety and reliability of dental sealant materials, and as their continued use perpetuates a decline in the overall rates of dental caries, the placement of pit and fissure sealants will remain an important part of preventive dentistry. The challenge now is to increase access to dental sealants for all children, regardless of socioeconomic status.

As dental researchers continue to validate the safety and reliability of dental sealant materials, and as their continued use perpetuates a decline in the overall rates of dental caries, the placement of pit and fissure sealants will remain an important part of preventive dentistry. The challenge now is to increase access to dental sealants for all children, regardless of socioeconomic status.

ACKNOWLEDGMENTS

The author would like to thank Linda J. Weems, RDH, the dental school base manager at Children’s Aid Society of New York, and Nancy Duclonat, a student in the Dental Hygiene program at New York University’s College of Dentistry.

*ClearCheck™ SLP Sealant/Liquid Polisher, Shofu Dental Corp
Embrace™ WetBond™ Pit and Fissure Sealant, Pulpdent Corp
GC Fuji TRIAGE™, GC America Inc
**Adper Prompt L-Pop Self-Etch Adhesive, 3M ESPE Co

REFERENCES

  1. Francis R, Mascarenhas AK, Soparkar P, Al-Mutawaa S. Retention and effectiveness of fissure sealants in Kuwaiti school children. Community Dent Health. 2008;25:211-215.
  2. Ahovuo-Saloranta A, Hiiri A, Nordblad A, Mäkelä M, Worthington HV. Pit and fissure sealants for preventing dental decay in the permanent teeth of children and adolescents. Cochrane Database Syst Rev. 2008;8:CD001830.
  3. Gillcrist JA, Brumley DE, Blackford JU. Com mu nity socioeconomic status and children’s dental health. J Am Dent Assoc. 2001;132:216- 222.
  4. Weintraub JA, Burt BA. Prevention of dental caries by the use of pit-and-fissure sealants. J Public Health Policy. 1987;8:542-546.
  5. Dental cavities. Medline Plus. Available at: www.nlm.nih.gov/medlineplus/ency/article/001055.htm#causes/incidence/andriskfactors. Accessed June 5, 2009.
  6. National Institutes of Health. Diagnosis and management of dental caries throughout life. NIH Consens Statement. 2001;18:1-23.
  7. Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res. 1955;34:849.
  8. Olea N, Pulgar R, Pérez P, et al. Estrogenicity of resin-based composites and sealants used in dentistry. Environ Health Perspect. 1996;104:298-305.
  9. Arenholt-Bindslev D, Breinholt V, Preiss A, Schmalz G. Timerelated bisphenol-A content and estrogenic activity in saliva samples collected in relation to placement of fissure sealants. Clin Oral Investig. 1999;3:120-125.
  10. Fung EY, Ewoldsen NO, St Germain HA Jr, et al. Pharmacokinetics of bisphenol A released from a dental sealant. J Am Dent Assoc. 2000;131:51-58.

From Dimensions of Dental Hygiene. July 2009; 7(7): 28, 30-31.

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