| Dentin hypersensitivitity is most prevalent in the world. At present, there are many methods to treat dentin hypersensitivitity. However, most of these are not satisfactory. Pulsed Nd﹕YAG laser is a new method. But the studies in this field are few and there are some problems for further application, such as no uniform standard in laser output energy and in clinical evaluation. The aim of this study: 1)to examine the effects of Nd﹕YAG laser on curing dentin hypersensitivitity through three methods: experiment in vitro, animal experiment and clinical examination, 2) to offer reference for further study on curing dentin hypersensitivitity by Nd﹕YAG laser.Experiment in vitroThe parameters of Nd﹕YAG laser used in this study were selected by measuring the temperature changes in pulp chambers while the dentin surfaces were irradiated by laser under different output parameters.The ultrastructure changes of dentin lased by Nd﹕YAG laser were observed under scanning electron microscope(SEM). The dentinal tubule orifices were closed. The integrality and the toughness on tooth surfaces were evaluated and the relation between laser output energy and dentinal ultrastructure was studied. The results showed that dentinal tubule orifices were better closed under 56~111 J/cm2 energy output and no crater or fissure was found. When calcium fluoride varnish was applied before the dentin surface was irradiated by Nd﹕YAG laser, the dentin surfaces were more flat than that without calcium fluoride varnish applied. The results indicated Ca+2 and F- incalcium fluoride varnish entered the dentin and make the dentin surface flat, which can improve the dentin resistibility for attrition.Animal experimentFour healthy local mongrel dogs were selected and the teeth were prepared for dentin hypersensitivitity models under abdominal anesthesia. One week later, each tooth was irradiated by Nd﹕YAG laser with three parameters. And the one of the four dogs was killed immediately and the teeth were extracted, immediately transected in lased areas and fixed in 10% formaldehyde solution. The other three dogs were killed respectively at 3, 7 and 30 days after lased and the teeth were extracted and treated as above. Histopathologic examination showed there was no irreversible pulp injury when the dentin surfaces were irradiated by Nd﹕YAG laser with 33 J/cm2 and 56 J/cm2 output (output : 1 W). Vessel dilatation and exudation were found when lased under 111 J/cm2 output. Pulp reactions were obvious during 3 days after lased. Alkaline phosphatase examination: After fixed, decalcified and selected, all experimented teeth were stained with the Ca-Co method in order to examine the alkaline phosphatase activity in dental pulp cells. The grey values were measured through MiDeLeng image analysis system, and the data were analyzed statistically. The results showed the alkaline phosphatase activities in dental pulp cells were significantly different in different periods (p<0.01) and there is no relation between the the alkaline phosphatase activities and the laser energy (p>0.05).The parameters used in this experiment were safe to the dental pulp tissue. All the dental pulp reactions were reversible, though they became more obvious as the laser output energy increased.Clinical examinationSelected were The teeth, which were diagnosed as dentin hypersensitivitity, resulting from occlusal abrasion, exposing of tooth neck and wedge-shaped defect, but not from injury, caries and so on. The teeth were randomly divided into three groups: lased, lased with CaF2, Gluma. The patients were followed up at 30, 90 and 180 days after the treatment. The results showed that the effective ratios of the three groups immediately after the treatment were high and they were respectively 87.6%, 91.0% and 95.3%. But after 30 days or more long, the effective ratios of the three groups decreased at a different rate. Three months later, there was a significant difference between lased-with-CaF2 group and Gluma group on effective rati... |
PDF Full Text Request