펄스형 Nd-YAG 레이저 조사에 의한 법랑질 내산성 증가 기전에 관한 연구
A STUDY OF THE MECHANISM OF IMPROVING ACID RESISTANCE OF BOVINE TOOTH ENAMEL AFTER PULSED Nd-YAG LASER IRRADIATION
이영순, 손흥규,
소속 상세정보
이영순 ( ) - 연세대학교 치과대학 소아치과학교실
손흥규 ( ) - 연세대학교 치과대학 소아치과학교실
KMID : 0358919960230030640
Abstract
결론
레이저 조사에 의한 법랑질 내산성변화를 측정하기 위해 펄스발진형 Nd-YAG 레이저를
조사한 후 칼슘의 용출량을 측정하고 방사선 회절분석, 적외선 분광분석 및 주사전자현미경
으로 관찰하여 다음과 같은 결론을 얻었다.
1. 칼슘의 용출량은 조사한 레이저의 에너지 밀도가 증가할수록 감소하다가 70
J/cm2 에서 증가하였다. 각군의 평균치간의 개별비교 결과 50
J/cm2과 나머지 군간의 통계학적 유의차가 있었다. (P<0.05)
2. X-선 회절분석결과 레이저를 조사한 후 용해도를 증가시키는 P-TCP가 약간 생성되었
지만 에너지 밀도가 높을수록 (002), (004) 피크가 가늘고 크게 나타나 결정이 c축방향으로
성장했음을 나타내어 결정의 산에 대한 용해도는 감소할 것으로 사료된다.
3. 내산성이 크게 증가한 50J/cm 에서 격자상수 (lattice parameter)는 a축은 신장되었으
며, c축은 약간 감소하였으나 큰 변화는 없었다.
4. 적외선 분광분석 결과 레이저 조사 에너지 밀도가 증가할수록 phosphate band (600∼
550 cm-1)와 B-carbonate band (=870, 1415-1455 cm-1)는 감
소하고 A-carbonate band (1590 cm-1)는 증가하였다.
5. 레이저 조사후 주사전자현미경상 관찰시 50J/cm2 조사군까지는 치면의
융합이 일어나 평활한 면을 보이므로 투과도가 감소할 것으로 생각되며
70J/cm2 레이저 조사군에서는 치질의 파괴를 보여 법랑질 투과도가 증가할
것으로 생각된다.
이상의 결과로 보아 법랑질에 Nd-YAG 레이저 조사시 50 J/cm2 에서 내산
성이 가장 크게 증가하였으며 법랑질 내산성증가는 법랑질 융합에 의한 투과도의 감소와 탄
산염 소실 및 결정 크기 증가 등에 의한 용해도의 감소가 함께 작용하여 나타나는 것으로
사료된다.
#초록#
The purpose of this study was to examine the mechanism of improving acid
resistance of Nd-YAG laser irradiated tooth enamel and determine the most effective
energy density for improvine acid resistance. The bovine tooth enamel were lased with
a pulsed Nd-YAG laser. The energy densities of exposed laser beam were varied from
10 to 70J/cm2.
To investigate the degree of improving acid resistance by irradiation, all the samples
were submerged to demineralize in 0.5 N HClO4 solution for 1 minute.
After 1 minute, 0.05% LaCl3 was added to the solution for interrupting the
emineralization reaction. The amounts of dissolved calcium and phosphate in the solution
were measured by using an atomic absorption spectrophotometer and the UV/VIS
spectrophotometer, respectively.
To examine the mechanism of improving acid resistance, X-ray diffraction analysis,
infrared spectroscopy, and scanning electron microscopy were taken. The X-ray
diffraction pattern of the samples were obtained in the 10°∼80°2θ range with Cu-K
α radiation using M18HF(Mac Science Co.) with X-ray diffractometer operating at 40
KV and 300mA. The infra-red spectra of the ground samples in 300 mg KBr pellets
10mm diameter were obtained in the 4000 cm-1 to 400 cm-1
range using JASCO 300E spectrophotometer. The scanning electron microscopy was
carried out using JSM6400(JEOL Co.) with 500∼2000 times magnification.
The results were as follow
1. The concentration of calcium dissolved from lase irradiated enemel with
50J/cm2 was significantly lesser than that of unlased control group
(p<0.05)
2. From the result of the X-ray diffraction analysis, β-TCP, which increases acid
solubility, was identified in lased enamel but the diffraction peaks of (002) and (004)
became sharp with increasing energy density of laser irradiation. This means that the
crystals in lased samples were grown through the c-axis and subsequently, the acid
solubility of enamel decreased.
3. The a-axis parameter was slightly increased by laser irradiation, whereas the
c-axis parameter was almost constant except for a little decrease at
50J/cm2.
4. In the infra-red spectra of lased enamels, phosphate bands (600∼500
cm-1, B-carbonate bands (870, 1415∼1455 cm-1), and
A-carbonate band (1545 cm-1) were observed. The amounts of phosphate
bands and the B-carbonate bands were reduced, on the other hand, the amount of the
A-carbonate band was increased by increase the energy density.
5. The SEM experiments reveal that the surface melting and recrystallization were
appeared at 30J/cm2 and the cracks were observed at
70J/cm2.
From above results, It may be suggested that the most effective energy density for
improving acid resistance of tooth enamel with the irradiation of Nd-YAG laser was
50J/cm2. The mechanism of improving acid resistance were reduction of
permeability due to surface melting and recrystallization of lased enemel and reduction
of acid solubility of enamel due to decrease of carbonate content and growth of crystal.
acid resistance; tooth enamel; β-TCP; Nd-TAG lase; X-ray diffraction; infrared spectroscopy; scanning electron microscopy;
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