[Demonstration of crystal orientation in rat incisor dentin by a PSPC-MDG system]

A PSPC (Position Sensitive Proportional Counter)-MDG (Micro Diffract Goniometer) system was applied to show the crystal orientation in the rat linugal dentin. The X-ray diffraction from a specimen was recorded by usual chart recorder instead of the classical film method. Specimens were about 150 microns wide and 100 microns thick of pillar form with the long axis of specimen parallel to the dentinal tubules. When the X-ray was irradiated in the labiolingual dicection, the peak intensity of (002) was stronger than that of the combined peak of (211) and (112). The more it rotated from the first position along the long axis of specimen, the more the peak intensity of (002) weakened, and after it rotated at 90 degrees the peak of (002) completely disappeared. The results indicated that the crystals were well-oriented in the lingual dentin. The axis of crystal orientation was almost parallel to the tooth axis, but swayed within the range of about 30 degrees.