| Background:Tooth trauma of permanent frontteeth is common in oral disease, and its incidence rate have increased in recent years. The root tip of young permanent teeth wound would developed completely after 3~5 years since dental eruption .Because of this, vital pulpotomy was patented by Witzel in 1872,it means nullinfestation or infestation light tooth pulp was removed and normal root pulp was concerned. There are two pulp-cap is frequently used to vital pulpotomy in clinically: indoform calcium hydroxide and glutaral. But they are not so satisfactory. Fortunately, the pulsed Nd:YAG laser was introduced in 1960. Studies have revealed that the laser had the abilitities of solidify and vaporize both the endepidermis and the inflammatory infiltration soft tissue. Pulsed Nd:YAG laser as a new method to pulpotomy. The laser profit a lot to the patients who suffer from pulpitis due the good quality of it's electromagnetic field and biostimulation effect there is only lightly reaction after the threatment .But there are some still 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 vital pulpotomy through two methods: animal experiment and clinical examination, 2) to offer reference for further study on vital pulpotomy by Nd:YAG laser.ObjectiveThis study is to obtain an effective energy by comparing the generation effect of 3 different laser energy levels with pulpotomy and thus to provide theoretical support for the chronic pulpotomy therapy by the pulsed Nd:YAG laser. Establish experimental pulpotomy animal model similar to pulpotomy of mankind in dogs to approach the 3energy levels of the pulsed Nd:YAG laser was used to establish the relationship between energy parameters irradiation on dental pulp, the safety to pulp tissue, then the proper parameters may obtain and apply for chronic pulpotomy therapy .Materials,methods and results Animal experiment1.Three healthy local mongrel dogs were selected and the teeth were prepared for vital pulpotomy, each tooth was irradiated by Nd:YAG laser with three different parameters. And the one of the three dogs was killed after 3 days and the teeth were extracted, immediately fixed in 10% formaldehyde solution. The other two dogs were killed respectively at 7 and 30days after lased and the teeth were extracted and treated as above.Histopathologic examination showed there was no significant difference between experimental group and control group when the vital pulpotomy surfaces were irradiated by Nd:YAG laser with 1 W output.But, there was an obviously surpassing in pulp tissue of experimental group when the vital pulpotomy surfaces were irradiated by Nd:YAG laser with 2W output. There was vacuolar degeneration and pulp necrosis in pulp tissue when the vital pulpotomy surfaces were irradiated by Nd:YAG laser with 3W output. Pulp reactions were obvious during 3 days after lased.2.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) .The parameters of 40Hz 2w 50mJ used in this experiment were beneficial to the dental pulp tissue of vital pulpotomy. Clinical examination3. Selecting the extracted integrantly constant premolar teeth of the adolescents of 12~15 years whose teeth should be treated for orthodontic purposes. The teeth were pulp cut off and exposed to the laser with 2W output whose dose was confirmed by the previous experiment and were extracted according to the different observing timetable: 3 days, 15 days and 30 days. In histological level,there was an obviously surpassing in pulp tissue of experimental group when the vital pulpotomy surfaces were irradiated by Nd:YAG laser with 2W output in each timetable. Pulp reactions were obvious during 3 days after lased. 4. 167 cases of primary motar teethes were selected and randomly divided into the experimental group and control group. Each tooth of experimental group was irradiated by Nd:YAG laser with 40Hz 2w 50mJ output after vital pulpotomy .The curative effects of half,one, three and six months after operation were comparatively analyzed with following up the patients.ConclusionThere was no significant damage when the vital pulpotomy surfaces were irradiated by Nd:YAG laser with 40Hz 2w 50mJ output. there was an effective hemostasis and bacteriocidal effect , moreover , the parameters of 40Hz 2w 50mJ used in this experiment were beneficial to the dental pulp tissue of vital pulpotomy, par example, enhancing reaction activity of pulp tissue, promoting the ALP activities of dental pulp cells and encouraging formation of dentine bridge. So Nd:YAG laser is a prospective method to operate vital pulpotomy. |
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