Micro-hardness of dentine after silver diamine fluoride application

Abstract

OBJECTIVE: The study is to describe the variations in micro-hardness of silver diamine fluoride-treated dentine caries. METHODS: Children who participated in a 30-month clinical trial of silver diamine fluoride treatment with very mobile primary teeth were invited to have them extracted. Each tooth was sectioned longitudinally along the midline of the carious lesion and the surface of one half was polished using a metallurgical technique. The specimens were mounted and the hardness of the carious lesions was measured by the Knoop indenter of a micro-hardness tester using 5 gf for 10 seconds. The hardness of dentine was determined with the micro-hardness tester at sites below the surface of the tooth at the center of the carious lesion every 25 lm to the pulp. Three sets of measurements were made on each specimen on parallel tracks approximately 150–200 lm apart. RESULTS: The median Knoop Hardness (KH) in clinically diagnosed arrested caries was found to be more than 40 in the outer 50 lm of the surface lesion. It then lay mostly in the range of 20 to 30 at points deeper than 50–500 lm from the surface lesion. The KH of soft dentine caries was below 10 in the outer 50 lm of the surface lesion and was less than 15 in the outer 100 lm. It then gradually increased to 20 at 200 lm from the surface lesion. At a distance of 200 lm or more from the surface of the lesion, the micro-hardness of dentine was found to be in the range of 20-30. CONCLUSIONS: The Knoop Hardness in clinically diagnosed arrested dentine caries was more than 40 where as soft caries was below 10 in the outer 50 lm of the surface lesion.