Dentin remineralizing ability and enhanced antibacterial activity of strontium and hydroxyl ion co-releasing radiopaque hydroxyapatite cement.

Dental caries is an infection of the mineralized tooth structures that advances when acid secreted by bacterial action on dietary carbohydrates diffuses and dissolves the tooth mineral leading to demineralization. During treatment, clinicians often remove only the superficial infected tooth structures and retain a part of affected carious dentin to prevent excessive dentin loss and pulp exposure. Calcium hydroxide is used to treat the affected dentin because it is alkaline, induces pulp-dentin remineralization and decreases bacterial infection. Presence of strontium ions has also been reported to exhibit anticariogenic activity, and promote enamel and dentin remineralization. The objective of the present study was to develop novel hydroxyapatite cement from tetracalcium phosphate which gradually releases hydroxyl and strontium ions to exhibit antibacterial activity. Its potential to remineralize the dentin sections collected from extracted human molar tooth was studied in detail. The pH of all the experimental cements exhibited a gradual increase to ~10.5 in 10 days with 10% strontium substituted tetracalcium phosphate cement (10SC) showing the highest pH value which was sustained for 6 weeks. 10SC showed better antibacterial property against S. aureus and E. coli at the end of 1 week compared to other cements studied. It also exhibited the highest radiopacity equivalent to 4.8 mm of Al standard. 10SC treated dentin section showed better remineralization ability and highest elastic modulus. We can conclude that the hydroxyl and strontium ions releasing tetracalcium phosphate cement exhibits good antibacterial property, radiopacity and has the potential to encourage dentin remineralization.