Objective: To investigate the mechanisms of lanthanides prevention of human root surface carious-like lesions and to compare the effectiveness of lanthanum (La) with that of cerium (Ce) and fluoride (F). Various treatment procedures were also compared.
Materials and methods: Acetic buffers containing lanthanum, cerium, and fluoride (500 ppm) were used individually or in combination to treat 48 cementum-dentin samples. The acid-resistant capacity of various treatment procedures was evaluated by means of scanning electron microscope, electron microprobe, and polarizing light microscope analyses.
Results: The acid-resistant effects of lanthanide element were comparable to those of fluoride, and their acid-resistant effects were even stronger when combined with fluoride and cerium. These effects are likely due to the formation of La(Ce)HAP, FLa(Ce)HAP, and lanthanum/cerium phosphate compounds.
Conclusion: Combined F/La(Ce) was more effective in the prevention of root surface caries than were lanthanides alone.