The combined occluding effects of fluoride-containing dentin desensitizer and Nd-Yag laser irradiation on human dentinal tubules: an in vitro study

The purpose of the present study was to evaluate the combined occluding effects of fluoride-containing dentin desensitizer and neodymium:yttrium aluminum garnet (Nd-YAG) laser irradiation on human dentinal tubules. All six of the groups of dentin samples (A-F) included in this study received applications of fluoride-containing dentin desensitizer. Groups B, D, and F also received Nd-YAG laser irradiation. Groups A and B served as controls, to allow observations of the occluding effects on the dentinal tubules before and after Nd-YAG laser irradiation. Groups C and D were treated with 0.5 M vitamin C solution, whereas groups E and F underwent brushing with an electric toothbrush. Scanning electron microscopy (SEM) revealed that the fluoridated dentinal tubule-occluding agent (FDTOA) formed a fine crystalline deposit on the dentin surface. After soaking in 0.5 M vitamin C solution for 3 hours, the crystalline deposit of the FDTOA was completely dissolved. Furthermore, brushing of the teeth 3,600 times removed most of the occluding agent. When the application of FDTOA was combined with Nd-YAG laser irradiation, the dentin melted and then recrystallized. The occluding agent was thus 'burned into' the dentinal tubules, and could neither be dissolved by vitamin C solution nor removed by brushing. Therefore, we concluded that the FDTOA combined with Nd-YAG laser irradiation burns the occluding agent into the dentinal tubules, thereby resisting the effects of an acidic diet and brushing, and increasing the duration of the desensitizing effect.