市售牙科陶瓷材料螢光反應之比較

Abstract

在紫外線照射下，自然牙會散發出淺藍色螢光，使自然牙在日光照明下顯得更潔白明亮。贗復物應該表現出近似於自然牙在陽光或紫外線燈管照明下產生的螢光反應。製作贗復物時沒有類似比色板的裝置做為修復材料與自然牙間的螢光反應比較，有著前牙贗復物的人們身處夜總會或舞廳等具有紫外線燈管照明的場所時，可能會表現與自然牙不同的螢光反應。由文獻回顧影響牙科陶瓷材料螢光反應的因素包括：不同發光中心成分，材料所含發光中心之百分比，層次厚度，燒製溫度以及燒製過程次數有關。市售陶瓷材料螢光反應的研究較少，全瓷系統之螢光反應報告更為稀少。肉眼對螢光強度的敏感度也少有討論。本實驗目的旨在觀察不同系統之已燒製牙科陶瓷樣本與未燒製粉末之螢光反應，研究肉眼對於各樣本螢光反應之辨識能力差異，進而了解可能發光中心組成及其對螢光光譜與肉眼觀察之影響，以利螢光比色板之製作以及牙科陶瓷螢光強度之調整。 共計29片圓錠樣本(厚度1 mm且直徑為1 cm；5系統 --- Procera AllCeram, Cercon Zirconia, IPS Empress II, Noritake Ex-3以及Shofu Vintage；兩色度 --- A1以及B4；3層 --- enamel、body以及opaque層或內核層)依各廠牌燒製指示製作。以各廠牌未燒製之A1粉末1 ~ 2 g檢驗熔融對螢光反應所造成的變化。以紫外線燈為光源，觀察受測樣本有無螢光反應。利用光譜儀進行激發光譜以及放射光譜的測量與記錄。未燒製粉末與相對應已燒製樣本皆以X光繞射儀檢視晶體結構，觀察是否燒製造成晶體結構變化而影響螢光反應。利用SEM觀察未燒製粉末之表面型態及粒徑大小。將各系統之enamel層樣本以固定365 nm激發波長下記錄各樣本之發射光譜。肉眼測試之受測者為20位具有經驗的牙醫師(平均年齡為29.6 歲)。利用紫外線燈光源讓受測者對樣本螢光亮度強弱進行順序排列。排列順序結果與光譜儀所得強度順序做比較。 實驗結果與結論：(一)Opaque層或內核材料大多無法表現適當之螢光反應。而enamel和body層之激發與放射光譜型態在多數系統中表現相近，僅螢光強度有差異，換算為CIE座標後皆位於藍光範圍內，與自然牙相近。推論製造商在製作瓷粉時運用相同發光中心成分於body與enamel層，但opaque層或內核材料則置入不同或是不添加發光團成分。(二)燒製過程造成光譜的變化主要在於螢光強度。(三)無晶體結構樣本發出與具晶體結構樣本相當的螢光強度，但發光機轉不明。(四)肉眼測試在將樣本分作兩組後能夠得到受測者較一致的排列結果，也能夠與光譜儀所得光譜強度配合，表示顏色不同的狀況下，會對光強度辨識造成影響。亮度最弱的兩個樣本間強度差異小，但受測者仍能辨別亮度強弱。亮度較強的樣本中，在強度差異有限狀況下仍然造成肉眼無法辨識，代表人眼對微光之辨識能力較對亮光之辨識力為強。

Under the exposure to ultraviolet, the natural teeth emit a light blue fluorescence, which may enhance the whiteness and brightness of teeth in daylight. Dental prostheses should present the fluorescence which can act as natural teeth in color and intensity under exposure of sunlight or artificial ultraviolet illumination. Since there is no guide for comparing restorative materials to natural teeth, people with anterior prostheses may present different fluorescence from their natural teeth when they go to nightclubs or discotheques with ultraviolet illuminations. According to the reviewed articles, the factors that would affect the fluorescence of dental porcelains are constituents of luminophores, shade difference, layer thicknesses, firing cycles and firing temperature. The fluorescent properties of commercial full ceramic systems for dental prosthesis were rarely reported and discussed in the previous researches. Human eye sensitivity to the intensity of fluorescence was also poorly investigated. The purposes of this experiment are to observe and analyze the fluorescence reaction of different systems of fired dental ceramic samples as well as the powders of dental ceramics, to study the sensitivity of human eyes to fluorescence of the different samples under ultraviolet illumination, then to discover the possible composition of luminophores and its influence to the fluorescence spectrum and to the visual observation, and to fabricate the guide of fluorescence comparison as well as to adjust the fluorescent intensity of dental ceramics. The total 29 pieces of sample disks (1 mm in thickness and 1 cm in diameter; 5 systems --- Procera AllCeram, Cercon Zirconia, IPS Empress II, Noritake Ex-3 and Shofu Vintage; 2 shades --- A1 and B4; 3 layers --- enamel, body and opaque layer or core layer) were fabricated according to the manufacturers’ instructions of firing procedures. 1 ~ 2 g enamel powders of A1 shade of each system were also examined for observation of the change after firing sequence. The fluorescence of samples was observed under ultraviolet illumination. Then the excitation and the emission spectrum of the samples were recorded by using the spectrofluorometer. The samples of powders and their corresponding enamel disks were examined by an X-ray diffraction instrument to observe the crystal structure, to see if the firing procedures affect the crystal structure and the influence to the fluorescence. By using the SEM, the surface conformation and particle diameter of the powders were observed and recorded. Then the emission spectra of sample enamel disks were recorded by using spectrofluorometer with excitation light of wavelength of 365 nm. The subjects of human eye test were 20 dentists with experience of anterior prostheses fabrication and shade selection (average age --- 29.6 years old). The samples were put on the black background with ultraviolet illumination, and let the subjects rank the intensity of fluorescence. The order of ranking result was then compared with the order of intensity of emission spectra. Experimental result and conclusion: (1) Most opaque and core layers were unable to present suitable fluorescence. In general, enamel and body layers presented similar pattern of emission spectra, but different intensity of fluorescence. CIE coordination of emission spectra were all located in the blue light scope. The manufacturers may utilized the same ingredient of activators to the body and the enamel layers, but different or no ingredient of activator was added into to opaque layer and core materials. (2) Firing procedures caused the change of emission spectrum mainly in the intensity of fluorescence. (3) Non-crystallization structure presented similar intensity of fluorescence to that of samples with the lattice structure. (4) After dividing the enamel samples into two groups, the subjects were able to make more consistent ranking, which result became more similar to the ranking of intensity of fluorescence obtained with the spectrofluorometer. This means that the brightness recognition and sensitivity of human eyes will be influenced under different color condition. The difference of fluorescence intensity is not large between the two samples of weakest brightness, but all subjects distinguished the difference. In contrast, human eyes hardly recognized the difference of intensity in brighter samples. It means human eye sensitivity to the dim light is higher than that to the brighter light.