In order to study the effect of pulse Nd:YAG laser on hypersensitive dentin and inner wall of root canal.The morphologi- cal changes were observed with a SEM.The results showed that the low power with high energy density.Laser irradiation did not do harm to normal teeth tissue.The melted layer of dentin matrix extended to dentinal tubles,and the dentinal tubles were sealed to a depth of 15 um.The conventional preparation of root canal with laser irradiation provided much advantage in clearing the stained layer of inner wall in comparison with conwentional preparation of root canal alone.

ObjectiveTo investigate the protective effect of cytochrome P4502D6 （CYP2D6） and cytochrome P4503A4 （CYP3A4）， key enzymes of drug metabolism in liver， on acute liver injury in water extract of Glycyrrhizae Radix et Rhizoma （WEOGRR）. MethodHealthy male Kunming mice were divided into normal group， model group， WEOGRR low-， medium- and high-dose groups （5， 10， 15 g·kg^-1·d^-1） and positive drug group （diammonium glycyrrhizinate， 75 mg·kg^-1·d^-1）， with 10 in each group. One week after preventive administration， acute liver injury model was induced by single intragastric administration of 270 mg·kg^-1 Tripterygium Glycosides tablets， and samples were collected after 18 h. The pathological changes of liver were observed by hematoxylin-eosin （HE） staining. Serum liver function indexes including alanine aminotransferase （ALT）， aspartate aminotransferase （AST）， γ-glutamyl transpeptadase （γ-GT）， alkaline phosphatase （ALP）， and total bilirubin （TBIL） as well as the levels of oxidative stress indexes including malondialdehyde （MDA） and superoxide dismutase （SOD） in hepatocytes were determined by biochemical method. Real-time polymerase chain reaction （Real-time PCR） and Western blot were performed to detect the mRNA and protein expression levels of CYP2D6 and CYP3A4， respectively. ResultCompared with normal group， model group had significant hepatocyte swelling and inflammatory cell infiltration （P<0.01）， increased AST， ALT， γ-GT， ALP and TBIL （P<0.05）， elevated MDA and decreased SOD （P<0.01） as well as down-regulated mRNA and protein expression levels of CYP2D6 and CYP3A4 （P<0.05）. Compared with the model group， the normal group had intact liver structure without obvious abnormality， and the WEOGRR groups and positive drug group presented alleviated hepatocyte swelling and inflammatory cell infiltration （P<0.01）， reduced AST， ALT， γ-GT， ALP and TBIL （P<0.01）， lowered MDA and increased SOD （P<0.01） as well as up-regulated expression levels of CYP2D6 and CYP3A4 （P<0.01）. ConclusionThe protective effect of WEOGRR on acute liver injury induced by Tripterygium glycosides tablets may be related to reducing the contents of AST， ALT， γ-GT， ALP and TBIL in serum， inhibiting MDA and increasing the activity of SOD in liver cells， and enhancing the activities of CYP2D6 and CYP3A4， thus accelerating the metabolism of toxic substances.