Ferreira J M, Palamara J, Phakey P P, Rachinger W A, Orams H J
Department of Physics, Monash University, Clayton, Victoria, Australia.
Arch Oral Biol. 1989;34(7):551-62. doi: 10.1016/0003-9969(89)90094-0.
Laser-induced changes in plano-parallel sections were examined by light microscopy (LM) and scanning electron microscopy (SEM), and correlated with ultrastructural changes as observed by transmission electron microscopy (TEM). LM and SEM revealed two different changes--extensive crazing, and crazing and cratering. Rough exposed enamel was commonly found, resulting from lifting off and removal of the top layer of crazed, or crazed and cratered, enamel. The type of induced change was mainly dependent on the energy density used (range approximately 0.8 to approximately 200 J cm-2) and on enamel prism orientation. Lased enamel was also softer than unlased enamel. TEM of both crazed enamel and rough exposed enamel revealed that most crystals generally resembled those of unlased enamel in size and shape, but that inter- and intra-crystalline voids were present in some areas. The crazed and cratered enamel had significant ultrastructural changes: new homogeneous and inhomogeneous crystals of apatite with a different shape and larger size than those of the original, and a loss of prismatic structure. The lack of uniformity of the laser effect on crazed and cratered enamel was shown by variation in crystal packing (from good to poor), variations in crystal size from area to area, and the presence of pockets of poorly packed homogeneous crystals alongside pockets of well-packed inhomogeneous crystals. The crazing, crazing and cratering, rough exposed enamel and the greater number of voids, as well as the relative softness of lased enamel do not indicate an overall ultrastructural improvement. However, the larger apatite crystal size and loss of prismatic structure in crazed and cratered areas may partly explain previous observations of reduced rates of subsurface demineralization in lased enamel.
通过光学显微镜（LM）和扫描电子显微镜（SEM）检查了平行平面切片中激光诱导的变化，并与透射电子显微镜（TEM）观察到的超微结构变化相关联。LM和SEM揭示了两种不同的变化——广泛的裂纹以及裂纹和凹坑。通常会发现粗糙的暴露釉质，这是由于掀起并去除了有裂纹或有裂纹和凹坑的釉质顶层所致。诱导变化的类型主要取决于所使用的能量密度（范围约为0.8至约200 J/cm²）以及釉柱方向。激光处理过的釉质也比未处理的釉质更软。对有裂纹的釉质和粗糙暴露的釉质进行TEM分析表明，大多数晶体在大小和形状上通常与未处理的釉质晶体相似，但在某些区域存在晶间和晶内空隙。有裂纹和凹坑的釉质有明显的超微结构变化：出现了形状和尺寸与原始晶体不同的新的均匀和不均匀的磷灰石晶体，并且棱柱结构消失。激光对有裂纹和凹坑的釉质影响缺乏均匀性表现为晶体堆积的变化（从好到差）、不同区域晶体尺寸的变化以及排列紧密的不均匀晶体区域旁边存在排列疏松的均匀晶体区域。裂纹、裂纹和凹坑、粗糙暴露的釉质以及更多的空隙，以及激光处理过的釉质相对较软，并不表明整体超微结构有所改善。然而，有裂纹和凹坑区域中较大的磷灰石晶体尺寸和棱柱结构的消失可能部分解释了先前观察到的激光处理过的釉质中表面下脱矿速率降低的现象。
