The Later Calcification of the Bacterial Molds in the Human Dental Calculus Formed by the Extracellular Calcification

ln the bacterial molds of human dental calculus formed by the extracellular calcification, whitlockite and octacalcium phosphate crystals as well as apatite crystals were occasionally precipitated in the later stages of calculus formation . Thus, the deposits would be similar to the calculus formed by both the intraand extracellular calcifications . Key werds: human dental calculus, extracellular calcification , bacterial molds, later calcification, scanning electron microscopy As is well known, there exist the intraand extracellular calcifications of oral microorganisms in human dental calculus'-5) . The crystals are biological apatites including hydroxyapatite , Cadeficient and carbonate apatites'-8), although oral microorganisms were occasionally replaced by Mg-containing whitlockite crystals9-11) . The formation processes will be roughly divided into 3 cases : I to III1-541,12); case I: the intraand the extracellular calcifications occur at almost the same time, case II: the intracellular calcification first occurs followed by the extracellular calcification, and case III: the extracellular calcification first occurs. In case III, the bacterial molds will be retained during the time of the calculus formation , although the deposits of case III would become like a calculus of case I in the later formation stage. In this study, crystals deposited within the bacterial molds were investigated with scanning electron microscopy (SEM). Materials and Methods Supraand subgingival dental calculi attached to human teeth, which had been used in our previous studies, 9-11,13,14) were also used in these observations. The fractured calculus were treated with 10% sodium hypochlorite (Na0C1) for 1 hour in order to remove organic debris9-'2, 14,15). This was followed by rinsing in running water for 1 hour and drying in the air. The samples were observed with a Hitachi S-430 SEM at 20 kV accelerating voltage after coating with a 10 to 15-nm platinum-palladium layer .