Hexagonal disk-shaped crystals were found in caries-arrested enamel as well as in early and old dental calculi with scanning electron microscopy. The crystals which were constructed with wafer-like laminations linked together, formed rosette-like structures, or aggregated with each other. The main components were calcium phosphate with a small amount of Mg under energy-dispersive X-ray microanalysis. The crystals were frequently coexistent with Mg-containing whitlockite (WH) while no WH crystals were observed in the early calculus; thereby, the pH range of the formation sites might be lower than that of WH crystals.
The antibacterial effect restorative materials is important for obtaining good prognosis. The purpose of this study was to evaluate the antibacterial effect of trial composite resins which were made with Clearfil SC II and antibacterial powder as a filler. Four kinds of antibacterial powder were used : two kinds of Cellewall; far infrared radiating ceramic materials YYT 1 and YYT 1A, Bactekiller; antibacterial zeolite and Zeomic; zeolite with antibacterial ion were mixed with Clearfil SC II at the content of 5, 10, 15, 20, 30, 40, 50 wt %. Cariogenic bacteria Streptococcus mutans Ingbritt, was used in this experiment. Disks were placed in petri dishes and the width of inhibitory zone was evaluated after 24 hours. In order to evaluate the effect of saline solution, the disks were stored in saline solution for 24 and 48 hours and the inhibitory zone were also evaluated same condition. The conclusion is that the new composite resins containing Zeomic had a strong antibacterial effect against S. mutans and this effect of Zeomic was not reduced after storage in saline solution.