Kenji Koba

Effect of calcium hydroxide paste dressing on uninstrumented root canal wall

Dissolution of soft tissues on the uninstrumented root canal wall by an intracanal dressing of calcium hydroxide paste was examined by scanning electron microscopy (SEM). The roots of human extracted teeth were split longitudinally into halves, and the pulp tissue was removed by forceps. Then, the halves were divided randomly into three groups. Specimens in the control group were given no treatment. Specimens of the 1-wk group were stored for 7 days in calcium hydroxide-saline paste under the condition of 100% humidity and 37 degrees C. Specimens of the 4-wk group were stored for 28 days in the same manner, but washed and replaced into new paste every week. Root canal walls of these specimens were compared under a scanning electron microscope. A layer of odontoblasts was observed in the control group, whereas it had disappeared completely in the 1- and 4-wk groups. However, the predentin remained almost intact in the 1-wk group, and although the surface was eroded, in the 4-wk group. It was found that calcium hydroxide paste dressing could dissolve the odontoblastic cell layer, but had little effect on predentin.

A histopathological study of the effects of pulsed Nd:YAG laser irradiation on infected root canals in dogs.

The effects of pulsed Nd:YAG laser irradiation during root canal treatment of infected teeth were investigated histopathologically in dogs. One hundred and eight teeth with a single root in 15 healthy adult beagle strain dogs were used in this study. After inducing infected teeth, each root canal was shaped with up to at least a #40 K-file; then, after coating with black ink, the canal was irradiated using the following parameters: 1 W, 30 pps, for 1 and 2 s, and 2 W, 30 pps, for 2 s. The degree of inflammation of the periapical regions at 2, 4, and 8 wk was examined histopathologically by light microscopy. Inflammation of the periapical regions in the laser-treated groups was significantly less than that in the control group at 4 and 8 wk (p < 0.05). These results suggest that pulsed Nd:YAG laser is useful for root canal treatment of infected teeth, if appropriate parameters are selected.