Remineralization vs Restoration

Q. The concept of minimally invasive dentistry is gaining attention. Can you explain the theory?

A. Minimally invasive dentistry is the exact opposite of the “extension for prevention” concept that began in the 1950s and was popular until about 10 years ago. Within the “extension for prevention” model of care, when a small lesion appears in a pit or fissure, the restoration margins are extended so they include the entire fissure as a preventive measure. On the other hand, the goal of minimally invasive dentistry is to intervene with a process prior to restoration. If restoration becomes necessary, then the most minimal restoration that is required should be done. In minimally invasive dentistry, the focus is on removing debris to ensure that the tissue has not been damaged and then repairing the lesion with topical fluorides or another medicament to remineralize rather than restore.

Q. What led dentistry to the concept of minimally invasive?

A. I think the concept originated with the knowledge that a lesion can be reversed. When a lesion is reversed, it becomes more resistant to future attacks when fluoride is included in the remineralization, whether it’s remineralized with a toothpaste, a mouthrinse, a topical fluoride, or a fluoride varnish. The idea is that if the caries process can be intercepted at an early stage and reversed chemically with professional treatments, then restorative procedures are not necessary.

Q. How does this correlate to the wellness model of care versus the disease model of care?

A. Minimally invasive dentistry is in fact promoting a wellness model, where surgical procedures are avoided and interventions, preventions, and repair mechanisms are used instead. The disease model is simply a surgical model of care.

Q. What is the role of remineralization in minimally invasive dentistry?

A. Remineralization is vital. Every time we eat a meal, have a snack, or drink a cup of coffee with sugar, the bacteria attack by producing acids. After a period of time following the attack, our normal defense mechanisms try to repair the damage. This defense mechanism is basically saliva, plus any help it can get from fluoride, which comes from drinking fluoridated water, using a fluoride toothpaste, etc. With this in mind, the repair process is remineralization. If the attack occurs so often during the course of a day that there isn’t enough time to repair the damage, then the net effect over a period of time is an early lesion or a white spot. The white spot will continue to grow if no treatment is provided. This is where minimally invasive dentistry comes in. It supports applying a fluoride varnish, modifying patients’ eating habits, and improving patients’ oral hygiene habits so the lesion is reversed.

Q. Is this possible for those with xerostomia?

A. Patients with xerostomia may not have enough repair forces, ie, saliva. For instance, patients who are undergoing radiation in the head and neck region often have their salivary glands damaged by the treatment so they may need to have their teeth totally restored or even extracted and replaced with dentures before they begin radiation therapy. In a clinical study my colleagues and I completed years ago, we looked at a group of patients with head and neck cancer who were instructed to rinse once per day with both chlorhexidine and fluoride. The rinsing ended up being very effective.¹ It helped the patients maintain their dentition. A regimen that controls the bacteria as well as provides fluoride to promote remineralization is imperative in this patient population. Maintaining dentition without saliva is difficult.

Q. What techniques and materials are used to enhance remineralization?

A. Data exist to suggest that amorphous calcium phosphate, eg, Novamin^®, Recaldent^®, and glass ionomer cements and restorative materials enhance remineralization but the research is preliminary. Saliva is saturated with enough calcium and phosphate for the repair process. Fluoride acts as a catalyst to enhance the rate of remineralization or repair. Some evidence shows that adding calcium phosphate enhances the remineralization process but more research is needed. Glass ionomer products also work because they contain fluoride.

Q. If the concentration of calcium and phosphate ions in saliva was analyzed in a variety of different people, would everyone have the same concentration?

A. Yes, it doesn’t vary much because saliva reflects the serum calcium and phosphate levels. Even if the intake of calcium is so low that the levels go into a negative state, the body will actually draw calcium from bone to maintain the serum levels, which is reflected in the saliva levels.

Q. With fluoride therapy, will white spot decalcification go away entirely?

A. Yes, but it’s slow. A study done in the Netherlands was the first clinical trial to demonstrate remineralization.² In the study, patients with white spots and lesions had all of their frank lesions restored and the white spots were followed for 7 years. In the 7 years, half of the white spots disappeared. This is because of saliva. So the next logical question is how to speed up the remineralization process.

Q. Are specific tooth surfaces more easily remineralized than others?

A. The odds are always better if the white spot is on a smooth surface, because it can be cleaned with a toothbrush and the plaque can be removed. The toughest ones are in the fissures and pits because they’re the most difficult surfaces to keep clean. The caries process is exactly the same whether it’s on a smooth surface or a fissure, it’s still the white spot formation process.

Q. How would a dental professional determine if an early lesion on the occlusal surface should be remineralized or receive a restorative procedure?

A. If no breaks in the enamel exist, then I would apply fluoride and encourage diet changes and improved oral hygiene. I would then want to see that patient again within 30 days. If the patient seemed particularly high risk, I would emulate the protocols used in European clinics and have the patient back for a series of fluoride varnish applications in 1 or 2 week intervals for three or four treatments. This would arrest the caries and render the surface stronger than regular enamel.

Q. What are the current concepts of remineralization for primary teeth?

A. The caries process is exactly the same, whether it occurs in adults or children or in primary teeth or permanent teeth. Demineralization and a loss of mineral in the acid occurs. Saliva attempts to repair the damage. The rates may differ because of oral hygiene and diet differences. Therefore, whatever works in permanent teeth will also work in primary teeth.

Q. Is it indicated to give children fluoride varnish on the occlusal surfaces as they’re erupting?

A. The prime time for a tooth to decay is the first 2 years after eruption because the enamel is not yet fully calcified at the time the tooth erupts. It’s soft and only partially calcified, as a result, it’s more susceptible to demineralization, but fluoride induces calcification. Thus, a fluoride varnish application is indicated.

REFERENCES

1. Katz S. The use of fluoride and chlorhexidine for the prevention of radiation caries. J Am Dent Assoc. 1982;104:164-170.
2. Backer Dirks O. Posteruptive changes in dental enamel. J Dent Res. 1966;45:503-511.

From Dimensions of Dental Hygiene. February 2007;5(2): 26-27.