利用磷化銦量子點作為牙科複合樹脂之螢光來源

Abstract

於現代審美牙科發展下，牙科複合樹脂廣泛地作為復形充填之材料。臨床使用之樹脂復形材料主要組成為樹脂基質及無機填料粒子，故稱之為複合樹脂，其它添加物為引起聚合反應、加強材料之臨床操作特性與耐久性，且經色料調配可達到與牙齒顏色相配合及美觀要求。於紫外光照下，自然牙放出淡藍色之螢光，由文獻回顧中可知自然牙之激發光譜介於 300~450 nm之間，波峰約 390 nm，放射光譜約介於 410~600 nm，波峰約 470 nm。然而牙科複合樹脂基質與填料分子並未發出螢光，須加入螢光物質。與自然牙螢光相近之元素多屬於週期表中III、IV、V族之元素，市售複合樹脂使用之螢光物質，推論為銪、鈰、鐿等稀土元素氧化物或有機分子，隨著填料分子分散在樹脂中。此螢光物質等混合後之螢光表現複雜，且其螢光表現與所在之基質材料有關。於紫外線照射下，不同廠牌之複合樹脂均有其激發與放射光譜與螢光強度。自然牙之激發光譜範圍較市售複合樹脂為寬廣，市售複合樹脂可被激發之範圍較有限。牙科復形材料必須要有良好穩定性，才能適用於口腔內潮溼與溫差大之環境。市售複合樹脂之螢光強度於紫外燈照射與加速老化試驗後均減弱，代表樹脂中螢光物質其穩定性不佳。2009年硒化鎘（CdSe）量子點首先被提出摻入牙科複合樹脂作為螢光物質，然，硒化鎘量子點具高毒性，並不適用於生醫材料之發展。 本實驗目的為利用磷化銦（InP）量子點之螢光亮度強、光穩定性佳、可利用粒徑大小調控螢光且無生物毒性等特性，作為牙科複合樹脂之螢光來源。實驗中利用螢光光譜儀測試八種市售牙科複合樹脂之螢光激發與放射光譜，比較其與自然牙之相異，經CIE 13.3 Color Rendering Index 色度座標分析軟體計算螢光之色度座標，比較顏色之差異。使用以溶劑熱法合成之磷化銦量子點，測試摻入不同重量（0.5、1.0、1.5 mg）及不同粒徑（放光波長分別為553 nm與520 nm）之磷化銦量子點於牙科複合樹脂，以光譜儀測是混合後之螢光表現。亦摻入量子效率較高之磷化銦/硫化鋅量子點，測試是否可以較低之量子點重量比例即可達到所之螢光強度。經由氙弧燈試驗箱之老化試驗 120 小時，測試摻入磷化銦量子點於牙科複合樹脂其螢光穩定性是否優於市售複合樹脂，且利用數位比色儀記錄CIE L*a*b*值並計算試驗前後之色彩變化，探討其螢光強度變化之相關性。並進行細胞存活檢測與細胞內活性氧物質之測定，測試磷化銦量子點之生物相容性。 實驗結果與結論： （ㄧ）市售牙科複合樹脂之螢光表現與自然牙有所差異。市售複合樹脂激發光譜落於 340~410 nm ，最強激發波長落於 382∼395 nm，波形強度各相異，且波形較自然牙狹窄；而放射光譜落於 420~600 nm，最強放射波長落於 438∼451 nm，較自然牙偏藍位移，且每種品牌之間螢光強度及波形不同，但各品牌不同色度之間，差異在於螢光強度。（二）於 CIE 色度座標，市售複合樹脂落於淡藍色範圍，較自然牙更偏藍色區域。（三）磷化銦量子點具碳鏈呈疏水性之表面，可用於與牙科複合樹脂作混合。（四）可利用量子點之螢光亮度強、光穩定性佳及不同粒徑大小具不同放光波段等特性，作為牙科複合樹脂之螢光來源。摻入不同重量之磷化銦量子點可調控複合樹脂之螢光強度，且摻入不同粒徑之磷化銦量子點可調控複合樹脂之螢光放光波段。摻入磷化銦量子點至具螢光反應之牙科複合樹脂中，可使其放射光譜變得較為寬廣，以擬合自然牙之放光特性。（五）摻入磷化銦量子點至具螢光反應之牙科複合樹脂後，其 CIE 色度座標由淡藍色區域移至白色區域。（六）摻入量子效率較高之磷化銦/硫化鋅量子點，所需摻入之量子點重量較少即可達到接近自然牙螢光之強度。（七）經氙弧燈試驗箱老化測試 120 小時，市售複合樹脂之螢光強度下降50∼70%，摻入磷化銦量子點之牙科複合樹脂，其螢光強度下降5∼30%，表示磷化銦量子點為穩定之螢光來源。（八）經氙弧燈試驗箱老化測試 120 小時，市售複合樹脂Filtek™ Z350 XT、Estelite Sigma Quick、Primisa、Shofu Beautifil II 之色彩變化超過 3.3 ∆E_ab^* 單位。以線性迴歸分析各組螢光強度變化與顏色變化關係，得到Gradia Direct Anterior與Primisa兩者之螢光強度變化與顏色變化有於迴歸分析中具統計上顯著線性關係（p < 0.05）。（九）經細胞存活檢測，摻入磷化銦量子點及磷化銦/硫化鋅殼核量子點之複合樹脂、磷化銦量子點粉末及磷化銦/硫化鋅殼核量子點粉末對人類牙齦造纖維母細胞無細胞毒性（p > 0.05）。（十）經細胞內活性氧物質測定，摻入磷化銦量子點之複合樹脂較對照組產生較多之活性氧，但未達統計上顯著相關（p > 0.05）；而磷化銦量子點粉末及磷化銦/硫化鋅殼核量子點粉末較對照組產生較少之活性氧，同樣未達統計上顯著相關（p > 0.05）。（十一）磷化銦量子點具有良好之生物相容性。

In the development of modern esthetic dentistry, dental ceramics and composite resins are widely used as filling material of artificial crowns and restorations. The clinical resin-restorative materials are mainly composed of resin matrix and inorganic filler particles, and so called composite resins. Other additives in the composite resins are used to cause polymerization, ease the clinical operation and strengthen the durability of the materials. By adding pigments and stains, the restorative material can match the shade with natural teeth and achieve the esthetic requirements. Under the exposure to ultraviolet, the natural teeth emit blue fluorescence. Literature review shows the excitation spectra of the natural teeth are between 300~450 nm with peak at 390, and the emission spectra are between 410~600 nm with peak at 470 nm. However, the resin matrix and filler of dental composite resin do not fluoresce. Fluorescent substances must be added to mimic the blue fluorescence on natural teeth. The luminophores with similar fluorescence are elements of the periodic table III, IV and V group, and generally supposed to be europium, cerium, ytterbium and other rare earth oxide or organic molecules. Theses luminophores may be blended with filler and dispersed in the resin matrix. The fluorescent performances of these luminophores are more complex when they are mixed, and are affected the matrix. Under the exposure to ultraviolet, different brands of commercial dental composite resins have different excitation and emission spectra and fluorescent intensity. The excitation spectra of natural teeth are wider than those of composite resins’, which means that the composite resin can only be excited at a narrower range. Restorative materials must have good stability to endure the damp environment and fluctuate temperature of oral cavity. The fluorescence properties of commercial composite dental resins decay after ultraviolet-accelerated aging, which means the stability of the luminophores, may not be good enough. In 2009, semiconducting material, cadmium selenide quantum dots (CdSe QDs) are first used as luminophores in dental composite resin. However, CdSe QDs are not suitable for biomaterial due to its toxicity. The purpose of this study is to use the biocompatible indium phosphide quantum dots (InP QDs), which have bright, highly tunable fluorescence emission that depends sensitively on their size, as the luminophore for dental composite resins. By photoluminescence, eight different brands of dental composite resins were tested. The optical properties of composite resins were compared with natural teeth’s from the excitation, emission spectra, and CIE coordinates. The InP quantum dots were synthesized by solvothermal method. Different weight (0.5, 1.0 and 1.5 mg) and different size ( λem 520 nm and λem 553 nm) of InP QDs were blended into dental composite resins and tested by photoluminescence. InP/ZnS QDs, which had higher quantum yield, were bleded into composite resins in order to test if fewer amounts of QDs were needed to achieve the fluorescent intensity of natural teeth. The blended samples were tested by accelerated-aging in xenon test chamber for 120 hours to see if the fluorescence of InP QDs were more stable than the commercial resins. CIE L*a*b* coordinates were recorded before and after by colorimeter, in order to correlate the differences in color and fluorescent intensity. MTT assay and ROS assay were performed to confirm the biocompatibility of InP QDs. Experimental results and conclusion: (1) The fluorescent property of commercial composite resins differ from natural teeth. The excitation spectra of composite resins are between 340~410 nm with peak at 382~395 nm. The shape and intensity of the spectra variate between groups and the excitation range are narrower than natural teeth’s. The emission spectra of composite resins are between 420~600 nm with peaks at 438~451 nm which are more blue-shifted than natural teeth’s. The shape and intensity variate between groups, and intensity differ between shade in the same brand. (2) The X and Y values of tristimulus calculated from the spectra located in blue region in the CIE color space, which are blue-shifted compared with natural teeth. (3) The carbon chains on the surface InP QDs made them hydrophobic, which make them suitable to blend with composite resins. (4) InP QDs, with bright, highly tunable fluorescence emission that depends sensitively on their size, can be used as the luminophores for dental composite resins. The intensity of fluorescence can be controlled by blending different amount of InP QDs and the emission range by different size of InP QDs. The emission spectra can be broadened by blending InP QDs into composite resins with fluorescence in order to simulate the spectra of natural teeth. (5) The coordinates of CIE color space of the composite resin blended with InP QDs shift to white region. (6) The composite resin blended with InP/ZnS QDs, which have better quantum yield than InP QDs, can achieve the fluorescent intensity with fewer amounts. (7) After accelerated-aging in xenon test chamber for 120 hours, the fluorescent intensity lowered 50~70% in commercial composite resins, but lowered 5~30% in composite resin blended with InP QDs, which means that the fluorescent property of InP QDs are stable. (7) The commercial composite resins, such as Filtek™ Z350 XT、Estelite Sigma Quick、Primisa、Shofu Beautifil II , show difference in color more than 3.3∆E_ab^* units after accelerated-aging in xenon test chamber for 120 hours. The difference in color and fluorescent intensity of Gradia Direct Anterior and Primisa show a significant relationship (p < 0.05). (8) The composite resin blended with InP QDs and InP/ZnS QDs, the powder of InP QDs and InP/ZnS QDs are biocompatible with Human gingival fibroblasts in MTT assays (p > 0.05). (9) The composite resins blended with InP QDs has more ROS production than the control group, but are not significantly different (p > ve.05). However, the powder of InP QDs and InP/ZnS have less ROS production, also are not significantly different (p > 0.05). (10) InP QDs are biocompatible.