Pediatric Dental Health

November 1, 2001

Should Children Have White Dental Fillings?see photo
The restoration of primary teeth is an important component of children’s oral health care. Many parents want to know if their children should have white dental restorations. The answer depends upon many factors.

Amalgam has been the material of choice for many years in the restoration of children’s teeth. Recently, however, tooth-colored dental restorative materials have become popular for use in children’s teeth. A major reason is the growing demand for esthetic dental restorations.

WHAT KINDS OF TOOTH-COLORED MATRIALS ARE AVAILABLE?

There are basically three types of tooth-colored materials which are used to restore posterior primary teeth: resin-modified glass ionomers, composites, and compomers.
Resin-modified glass ionomers (RMGI) are glass ionomer cements to which a resin has been added for strength.
Composites are a tooth colored material consisting of two main components: a matrix and a filler.
Compomers are polyacid-modified resin composites. They consist of a single, hydrophobic resin which is filled with acid-leachable glass particles similar to those found in glass ionomer cements.

HOW DO TOOTH COLORED RESTORATIONS WORK?
Conventional glass ionomers are derived from aqueous polyalkenoic acid and a glass component. When the powder and liquid are mixed together, an acid base reaction occurs. Resin-modified glass ionomers (RMGI) work by the fundamental acid-base reaction, which is supplemented by a second resin polymerization reaction.
In addition to its micro-mechanical adhesion to dentin, enamel, and cementum - RMGI chemically bonds to the calcium in dentin and enamel.
RMGI also releases fluoride. Fluoride is released from glass ionomer and RMGI not only when it is placed, but also after fluoride treatments and brushing with fluoride toothpaste. This is because glass ionomer acts as a fluoride reservoir.
Finally - although the shear bond strength of RMGI to tooth structure is only 4-5 mPa, this restorative material succeeds because its coefficient of thermal expansion is very close to that of a tooth. In other words, when the tooth expands, the RMGI expands in a like fashion.
Composites are composed of a resin matrix, an inorganic filler, and an interfacial phase. The matrix provides the framework, and the filler imparts its mechanical properties onto the composite.
Compomers are similar to composites. They have a wear rate about 3 times that of a composite, however. In addition, compomers require placement of a bonding agent to ensure adequate retention to dentin surfaces.

WHAT ARE THE ADVANTAGES OF A TOOTH-COLORED RESTORATION?
Resin-modified glass ionomer (RMGI) is a tooth-colored material that bonds chemically to the tooth, and releases fluoride for a relatively long period of time.
An amalgam restoration neither releases fluoride, nor adheres to the tooth.
Finally – less tooth enamel needs to be removed by the dentist when an adhesive, tooth-colored restoration is placed in a tooth, than when an amalgam restoration is placed.

WHAT ARE THE DISADVANTAGES OF A TOOTH-COLORED RESOTRATION?
The time required for a dentist to place a tooth-colored restoration is usually greater than that required for an amalgam restoration.
A tooth-colored restorative material is not as forgiving as dental amalgam insofar as the dentist’s clinical technique is concerned. Contamination of the cavity preparation may occur before the restorative material has been placed.
A tooth-colored restoration is not as durable as an amalgam restoration. This is because its compressive and tensile strengths are not as great as that of an amalgam restoration.
A composite restoration often “fails” because new caries can develop underneath the filling (recurrent caries).

CLINICAL TECHNIQUE FOR PLACING RESIN-MODIFIED GLASS IONOMER:
Provide adequate local anesthesia.
The operative field must be kept clean and dry during insertion of the resin-modified glass ionomer (RMGI). Therefore, placing a rubber dam is highly recommended.
Pre-wedging of the tooth during tooth preparation will protect the gingival tissue, as well as the interdental rubber dam. Pre-wedging also makes it easier to achieve contact with the adjacent tooth after the restoration has been inserted.
The matrix band should be burnished to the proper contour before placing the RMGI.
Powder and liquid components of RMGI may be hand-spatulated using the highest powder/liquid ratio, and ensuring that all of the powder is sufficiently wetted by the acid solution.
Incremental placement of the RMGI is recommended to prevent voids. RMGI is best placed into the cavity preparation using a syringe tip such as the Centrix. The mixed RMGI is syringed into place starting from the bottom of the preparation. Once the preparation is overfilled, the material can be compressed onto the tooth using a gloved finger.
The RMGI cement is light-cured for forty seconds.
All glass ionomer cements should be kept free of moisture and contamination during the initial setting period – which can last 3-4 minutes if self-cure material is used.
Finally, trim the restoration and establish final contours using finishing burs. Check the occlusion.

CONCLUSION:
Dental esthetic demands have increased during the last decade. As the strength and durability of tooth-colored restorative materials continue to improve, they will be used more frequently to restore the posterior teeth of children. Resin-modified glass ionomer (RMGI) may be useful for the restoration of children’s posterior teeth because: it does not require a lengthy etching and bonding procedure, it releases fluoride, it bonds directly to dentin and enamel, and its coefficient of thermal expansion is similar to that of natural tooth. Nevertheless, stainless steel crowns may be more appropriate to use when restoring the proximal carious lesions in a child who has a high risk for caries disease.

An article in the Journal of the American Dental Association discussed the success of resin-modified glass ionomer (RMGI) cement as a restorative material in primary teeth. This study provided data from one practitioner who was the owner of the practice. The 306 children who were studied had a total of 864 RMGI restorations place by the author of the study. The overall success rate for two-surface, Class II posterior restorations was 93.3 percent over an average of 4 years and one month’s time in the mouth.

Croll TP, Bar-Zion Y, Segura A, Donly KJ: Clinical performance of resin-modified glass ionomer cement restorations in primary teeth. JADA, August 2001; 132:1110-1115.

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