| DIAGNOdent is a recent instrument which detects caries by laser. Itsprinciple is that laser is absorbed by the mineral and organics of teeth.Then it produces fluorescence. We can judge the depth of cariesaccording to value and alarm. At present, its study is centered thesensitivity and specificity.Many factors could interfere DD such as the nature luster of teeth, bacteria plaque, stain or food residue, and so on. In clinic, it is usual thata lot of patients' teeth surfaces are colored by tobacco, tea, etc. It isdifficult to remove it. It could affect the value of DD when detectingcaries. Therefore, we should try to reduce theirs influences beforedetecting. Nowadays, the study about stain of tooth surface is lack.The cut-off points of DD is important to diagnose caries. However, its study is lack, too. The clinical trial of DD is difficult to operate becauseof the uncertainty gold standard.The objective of my study is to investigate the influence of stain to DDdetecting caries. At the same time, studying the cut-off points of DD fordetecting permanent and deciduous teeth.Part One The influence of stain to DD detecting cariesMethod: 29 patients who would like to do scaling were collected, andwere examined the buccal or lingual surface of their posterior teeth withDD before and after scaling. The deviance means of fluorescence valuesaccording to stain's scores ranking were analyzed. Results: There wasno obvious correlation between the means of fluorescence values'deviances and the stain's rankings. It had no difference between meansof DD before scaling and the means after scaling in various kindsranking. Conclusion: Generally, stain in facing has no obviousinfluence to DD's examining caries.Part Two The deviance of d value detecting before and afterextracted with DDMethod: 30 molars and 19 deciduous molars, which would be extractedwere collected. There were no obvious caries in their occlusal surface.The surfaces were detected by DD three times。They were stored in physiological saline after being extracted. 7days later, the same pointswere detected by DD again. Analyze the variance of d value before andafter extracted. Results: The d value after extracted was increasingaccompany with the increment of d value before extracted. Moreover, nosignificant difference of the two values for the same tooth. Conclusion: There is no significant difference between the d value in vivo and in vitroif teeth are stored only one week.Part Three Vitro study of the cut-off pointsMethods: Extracted molars and deciduous molars were collected. Theirocclusal fissures were detected by DD after cleaning. Then the teeth werecut following the detecting point, and exammed with stereoscope.Analyze the cut-off points of DD in the standard of examing results.Results: when DD detected molar fissures, it meaned no caries if thefluorescence value (d value) was o. The depth of caries was within halfenamel depth when the d value was among 1 and 33. It meaned normal, too. If the d value was more than 45, the depth surpassed half enameldepth. When DD detected deciduous molar fissure, it meaned no caries ifthe d value was o. The depth of caries surpassed half enamel depth if thed value was more than 25. Conclusion: A suitable cut-off points of DD ishelpful for detecting caries. Part Four Vivo study of the cut-off points for deciduous molarsMethods: 84 teeth were collected, including molars and deciduousmolars, whose surfaces had no obvious caries. Their fissures weredetected by DD. Then the depth of caries were judged according to thestandard of cut-off points in vitro study. They were drilled. At this time,the actual depth of caries were assessed on the basis of clinic examining.Analyze the accordance of the two diagnosing results. Result: Thediagnosing result in vitro study is accordance to the result in vivo fordeciduous molar. Conclusion: DD is suitable for the diagnosis ofdeciduous molar caries.
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