The Fissure Seal Time Bomb Geoff Knight, BDSc, MSc, MBA, FICD
Melbourne, Australia

After a tooth erupts, it’s pH falls below 5.5 and oral environment dissolves away the outer layers of the more soluble carbonated apatite crystals. If the saliva is rich in calcium and phosphate ions, an outer shell of hydroxy apatite will form on the partially dissolved carbonated apatite surface replacing the metallic and carbonate ions.

If fluoride ions are also present in saliva, the fluoride ions will further replace the hydroxide ions in the hydroxy apatite to form fluor apatite. Enamel crystals formed of fluor apatite are best able to resist demineralization of the enamel surface from falls in pH due to any acidogenic bacterial activity in the surrounding environment.

The Resin Fissure Seal Time Bomb
When a freshly erupted tooth is fissure sealed with composite resin the carbonated enamel is isolated from the oral environment and the process of maturation from a carbonated apatite to a fluor apatite is prevented.

The outer layers of enamel in a fissure sealed tooth remain vulnerable to carious attack as soon as the fissure seal is removed or fails. A leaking fissure seal creates a difficult diagnostic problem as well as masking the advancing caries underneath (Fig. 1).

Fig. 1

An Alternative Solution
Research at the University of Adelaide suggests that glass ionomer cement is a semi-permeable membrane that in thin layers, of half a millimeter or less, enables the transport of calcium and phosphate ions.

Applying thin layers of GIC over the surfaces of newly erupted teeth protects not only the fissures but also the entire surface from caries attack and at the same time enables calcium and phosphate ions to pass through it to help mature the enamel below (Fig. 2). Fluoride ions in the glass ionomer cement are also available to form fluor apatite in the outer layers of enamel to enhance surface protection from future fluctuations in pH that may predispose to the development of dental caries (Figs. 3 & 4).

Fig. 2

Fig. 3

Fig. 4

Practical Application
GC Corporation has developed a glass ionomer cement specifically designed as a surface protection material. Called Fuji TRIAGE, it is a capsulated low viscosity GIC with the same adhesive properties as Fuji IX and releases 6 times the amount of fluoride.

Fuji TRIAGE has a neutral salmon color that is almost invisible in a thin layer on a tooth, but flags to a clinician that surface protection has been applied. Although the material is a purely chemical set GIC without any inclusion of resin, the application of a curing light just above the surface will precipitate setting of this material from between 20 and 40 seconds, making it particularly useful for pedodontic applications.

As the tooth erupts into occlusion, Fuji TRIAGE on the occlusal surface will wear away so as not to interfere with development of the occlusal table. During the time it had been on the tooth, fluor apatite would have formed in the outer layers of enamel.

For the first time dentists no longer have to rely upon parental compliance to apply topical fluoride to their children’s teeth. Now dentists are able to give children treatment that will protect their teeth from occlusal fissure caries throughout their lives. DT

Geoff Knight, BDSc, MSc, MBA, FICD, is a general dentist from Melbourne, Australia. A noted lecturer, Geoff will be presenting seminars in California on minimal intervention techniques during August (7 hours of CE is available for CA dentists through Fifth Quarter Seminars). He’ll be in Sacramento Aug. 2; San Francisco, Aug. 3 and in Los Angeles on Aug. 4th. For additional information on the seminars, phone 1-800-554-6394 or fax your request to 800-552-0222. You can also contact him by email at geoffbds@dentalk.com.au. Or visit his website at: www.dentalk.com.au.