拔下之人類牙齒其螢光與色度關係

Abstract

紫外光照射下，自然牙會呈現淡藍色之螢光，此性質使牙齒看起來更亮白，故製做補綴物時亦需考慮此特性，始可於不同光線環境下看起來擬真自然，故了解自然牙之螢光性質對於製作美觀之復形體非常重要。牙科復形材料如樹脂與瓷粉，亦常添加螢光劑以模擬自然牙螢光效果，文獻上大多數學者支持有機物質造成螢光，亦有作者對於螢光、年齡、性別與齒位之相關性進行比較，但對於明確之螢光物質與發光機制卻不清楚，亦無螢光反應對於牙齒呈色影響之研究。為能對於自然牙螢光性質進一步了解，以幫助牙科臨床上進行良好之比色，於製作補綴物時達到更擬真之效果，我們利用螢光光譜儀測量人類拔下之自然牙樣本之螢光，並使用數位比色儀記錄其CIE (Commision International De L’eclairage)色度，將所獲得資料進行分析比較。研究目的專注於確認自然牙螢光機制，辨別自然牙不同部位之螢光差異，測量自然牙螢光光譜並比較其與性別、年齡、齒位之關係，並將光譜與臨床比色結果互為對照。 從43位拔牙病人中收集65顆牙齒樣本，並記錄病人之年齡、性別、齒位等資料。其中5顆牙經切片後分別測量以400℃加熱除去有機質、以EDTA(ethylenediaminetetraacetic acid)溶液脫鈣後測取螢光並與原始螢光進行比較。另外60顆牙齒以高速磨牙手機各取下4×4×2 mm大小之樣本，將樣本置入校正過之光激發光譜儀內，分別從牙釉質面與牙本質面進行激發光譜與放射光譜之測量與記錄，計算每一樣本螢光之CIE光度座標。另使用牙科臨床適用之數位比色儀測 IV 量每一樣本CIE L*a*b*色度座標，將螢光光譜儀與數位比色儀所測得之資料互相比較。 實驗結果與結論：(一)自然牙樣本螢光因為高溫破壞而消失，然而隨脫鈣時間增加，螢光表現加強，因此推論有機螢光物質應為自然牙螢光之成因。(二)於同一顆牙齒之切塊，牙本質面之螢光強度遠大於牙釉質面之螢光強度。(三)自然牙樣本其激發光譜大約介於波長300 nm至450 nm之間，激發波峰約為390 nm；放射光譜大約介於波長410 nm至600 nm之間，放射波峰約為470 nm，不同個體之間其光譜會有個別差異。(四)自然牙螢光之CIE座標值於藍光至藍綠光範圍。(五)源自同一個體之自然牙樣本其光譜結構與光譜顏色之CIE座標相似但其螢光強度不同。(六)將螢光強度與CIE Lab以複迴歸比較，自然牙波峰螢光強度與色度座標中之b值呈現負相關並達統計上顯著，即螢光強度越強，色度座標越偏向藍光。(七)色胺酸之螢光其激發光譜介於紫外光至370 nm之間，激發波峰約為300 nm；放射光譜大約介於波長370 nm至550 nm之間，放射波峰約為380 nm，CIE色度座標為藍紫光。因與自然牙螢光光譜不相似，推測色胺酸不是自然牙中之螢光物質。

The natural teeth emit blue fluorescence under the exposure to ultraviolet. It is essential that dental prostheses present such fluorescent character to be as vivid as natural teeth even thought under special light source. Therefore, some chemical activators were added to commercial dental restorative material or porcelains to mimic the fluorescence of natural teeth. Several researchers concluded that organic luminophore may be the possible candidates of dental fluorescence. Furthermore, a few studies demonstrated fluoresce intensity was age-dependent and the sex and the type of tooth have no significant influence on tooth fluorescence. The mechanism of fluorescence of natural teeth, however, was not yet clear. Very few attempts have been made in exploring the relationship between fluorescence and tooth color. Since understanding the fluorescence may improve the esthetics of dental prostheses, we measured the fluorescent spectra of extracted human teeth and recorded the CIE coordinates of tooth color. The purposes of this study were to explore the mechanics of fluorescence of natural teeth, to correlate the fluorescent spectra of a natural tooth with the donor’s sex and age and the type of tooth, and to analyze if there is any correlation between fluorescence VI and tooth shade. Sixty-five extracted human teeth from 43 patients were collected and the sex, age of the patient and type of tooth were also recorded. Five of the samples were sectioned and then separately processed with 400℃ heat to denature the organic compound of teeth or soaked in EDTA solution to demineralize the teeth. The fluorescent spectra of the original and treated samples were measured. Otherwise, a specimen with a size of 4×4×2 mm was cut from each of the other 60 natural teeth by means of high speed dental hand piece. The excitation and emission spectra were obtained from the enamel side and the dentin side using corrected PL spectrophotometer. The CIE coordinates (X, Y) of each sample were also computed. In addition, the CIE L*a*b* color scales were measured with a colorimeter and compared with fluorescence intensity. Experimental results and conclusion：(1) The fluorescene of a tooth was diminished with heat and increased with demineralization, which suggested that organic luminophore could be the candidates of fluorescence. (2) The fluorescence of dentin is much stronger than enamel in a tooth. (3) The wavelength of the excitation spectra of extracted human teeth was around 300 nm to 450 nm with peak at 390 nm, as well as the wavelength of the emission spectra of extracted human teeth was VII around 410 nm to 600 nm with peak at 470 nm. There was inter-individual difference in fluorescence spectra and intensity. (4) The X and Y values of tristimulus calculated from the spectra located in blue to greenish-blue region in the CIE color space. (5) Different teeth from the same individual showed spectra with similar peak wavelength and CIE coordinates but different fluorescent intensity. (6) Regarding to the correlation between fluorescence and L*a*b* color scale, the peak intensity of fluorescence was statistically negatively correlated to the b value. It meant that a higher fluorescence intensity was accompanied with a higher blue tone in a tooth. (7) The wavelength of the excitation spectra of tryptophan, a suggested candidate of fluorescence, was around short wavele UV light to 370 nm with peak at 300 nm, and the wavelength of the emission spectra was around 370 nm to 550 nm with peak at 380 nm. The fluorescence of tryptophan located in purple-blue area. As a result, the tryptophan may not a possible candidate of the fluorescence.