[An X-ray crystallographic study on effect of acid etching method to enamel and enhancement of crystallinity of the etched enamel with gel method].

: With the purpose of studying the influence of enamel acid etching technique, and the effectiveness of a strengthening of tooth enamel by silicahydro gel method, the following groups were compared, analyzed and observed by the measurements of diffracted X-ray from thin layer specimens and by microarea X-ray diffraction from an X-ray crystallographic point of view. Group I: non-treated tooth enamel Group II: acid-etched tooth enamel Group III: tooth enamel by application of silicahydro gel method after being acid etched. The results obtained were as follows: 1. Qualitative analyses by the measurements of diffracted X-ray from thin layer specimens 1) Ca5(PO4)3F, Ca5F (PO4)3 and Ca3(PO4)2.xH2O were detected in every group, and Ca3(PO4)2.xH2O demonstrated a high reliable value in group III. 2) In comparison with groups I and II, group III clearly revealed a peak shift toward high angle side, however, a halo peak was not recognized in every group. 3) As a result of evaluating crystallinity, crystallinity became favorable in order of group II, group I and group III. 4) A-axis lattice constant shortened in order of group II greater than group I greater than group III, and c-axis lattice constant shortened in order of group II greater than group I = group III. 2. Qualitative analyses by microarea X-ray diffraction 1) Solid solution of Ca5(PO4)3F and Ca5(PO4)3(OH) proved to exist in every group and in each microarea. 2) A halo peak appeared in group II and showed the trend of disappearance in group III, however, no peak shift was observed in all groups. From the foregoing results, the loss of the utmost enamel surface layer exhibiting high crystallinity and the lowering of crystallinity by acid etching technique were revealed from an X-ray crystallographic point of view and furthermore if silicahydro gel method was applied, it was suggested that enamel would be restored or that crystallinity would be enhanced.