A dental paste of synthetic tooth enamel that rapidly and seamlessly repaired an early carious lesion by nanocrystalline growth is described in the Brief Communications section of the Feb. 24 issue of the journal Nature.
Current methods for restoration of caries are less than ideal for early lesions, because a lot of healthy tooth must be removed to restore the tooth. With this in mind, Japanese researchers Dr. Kazue Yamagishi and colleagues developed a crystalline white paste of modified hydroxyapatite containing fluoride that is chemically and structurally similar to natural enamel. They used the paste to repair an early carious lesion in a mandibular premolar.
Researchers brushed a tiny amount of an acidic solution on the affected tooth part and then quickly applied the paste before the solution dried. Within 15 minutes of treatment, an approximately 20-micrometer-thick layer formed on the treated area. Time-lapse microscopy revealed that the hydroxyapatite crystals of the enamel initially dissolved slightly during the acid treatment, but then new crystals regrew when researchers applied the paste—a source of the crystals. This provided a continuous crystal structure that extended from the original enamel into the regrown layer.
Using transmission electron microscopy (TEM), researchers found no evidence of an obvious structural gap at the interface between the regrown layer and the enamel region. They did find that the regrown area contained elongated crystals that grew across the interface and were oriented regularly to the tooth surface, both evidence that the paste had integrated properly with the tooth enamel.
For comparison, researchers repaired a similar lesion using acidic phosphate fluoride (APF) solution, a treatment for early carious lesions that does not necessitate removal of healthy tooth enamel. They examined the results of the APF treatment using TEM and found the presence of a calcium fluoride layer less than 1-µm-thick covering the enamel and a gap at the interface.
Researchers concluded that the new dental paste can reconstruct enamel without excavating healthy tooth structure, in a process that not only repairs small lesions but also helps prevent more carious lesions by strengthening the natural enamel.
