鈣磷生醫材料於牙本質小管內的離子滲透及再結晶機制之研究

Abstract

目前市面上有許多號稱能有效緩解牙齒敏感症狀的商品,但卻沒有任何產品能立即而持久的療效。本團隊之前的研究顯示以明膠為模板的含碳酸鈣中孔洞二氧化矽複合材料 (簡稱中孔洞鈣矽材料,GCMS) 與 30%磷酸調拌,可以在 10 分鐘內,有效地阻塞牙本質小管達 30 μm,並且不會對牙齒造成酸蝕破壞, 而在細胞毒性實驗證實,中孔洞鈣矽材料的材料萃取液及中孔洞鈣矽材料/磷酸製劑經過牙本質屏障有好的細胞活性。因此，推測此材料具有應用於治療牙本質敏感症極大的潛力。 然而，對於此類鈣磷生醫材料於牙本質小管內的沉澱機制仍然是未知的。本團隊之前藉由Transwell dentin disc model 的結果發現，離子於酸性環境下較易通過0.2mm 的牙本質屏障且當離子整個帶電價數較高或是分子量較小時,其通過0.2 mm牙本質屏障的速度也較快，不過，針對離子於牙本質小管的通透性，再結晶物內鈣離子的來源以及如何控制材料於牙本質小管內的再結晶長度則仍然未知。做為一個理想的牙科臨床治療材料,本團隊希望進一步了解其在牙本質小管內沉澱結晶的機制,並了解牙本質小管對於離子的通透性以及其在活體內的效用性,以使未來能更容易將治療藥物帶入牙本質小管及牙髓神經。 因此,本研究的目的是: 1.了解含碳酸鈣中孔洞二氧化矽複合材料牙本質小管內的離子的通透性及 2.找出時間因子對於材料於牙本質小管內再結晶的影響 3.找出再結晶物內鈣離子的來源 4.利用動物實驗證實本團隊的GCMS 材料於活體內的效用 第一部分以Transwell dentin disc model 及離子層析儀確認GCMS/30%磷酸，中孔洞鍶氧化矽/30%磷酸，30%磷酸以及氫氧化鈣/去離子水製劑經由 0.25 mm 牙齒滲透所釋放的陰陽離子濃度。接著,再用 SEM 觀察這些牙本質試片。 第二部分以GCMS/30%磷酸製劑塗抹於牙本質試片上，並於四個不同的時間點將牙齒劈開並於SEM下觀察其再結晶的情況。另外，再以EDS分析再結晶物的成份以及其鈣磷比值。 第三部份以中孔洞鍶氧化矽/30%磷酸製劑塗抹於牙本質試片上，並以EDS分析再結晶物的成份，以確定再結晶物內是否有鈣離子的存在。 第四部分則進行動物實驗以評估GCMS/30%磷酸，中孔洞鍶氧化矽/30%磷酸製劑在活體的效用性。 結論：（1）鈣離子本身不易穿透牙本質屏障,酸性環境的磷酸根離子可能扮演前導的角色,磷酸根離子濃度提高而影響電位,對於鈣離子產生引力,使鈣離子進入牙本質小管,而後由於鈣離子以及磷酸根離子濃度超過Ksp而形成沉澱結晶。 （2）材料放置的時間愈長，則產生之結晶愈長，因此推測可以藉由時間因子來控制再結晶的長度。 （3）再結晶中的鈣離子有部份來自於牙齒。 （4）GCMS/30%磷酸，中孔洞鍶氧化矽/30%磷酸製劑在活體內有牙髓腔靜水壓存在下,仍可在牙本質小管內產生超過 60 μm 的結晶，並在不破壞牙本質的情形下有效封閉牙本質小管。

There are various kinds of commercial products claimed to be able to relieve the symptoms of dentin hypersensitivity, but none of the products have immediate and long-lasting effects. Our previous study showed that gelatin-templated calcium mesoporous silicate (GCMS) with 30% H3PO4 could efficiently occlude dentinal tubules by precipitation thus have great potential in treating dentin hypersensitivity. Also, GCMS with 30% H3PO4 could show great biocompatibility through dentin disc barrier. To be an idea dental material, it is important to find out the mechanism of ion permeability and recrrstaliiizaton of calcium phosphate biomaterial in dentinal tubule. Therefore, research goals of the present study is: 1. To find out the mechanism of ion permeability and recrystallization of CaCO3@ Mesoporous Silica-Phosphate in dentinal tubule 2. To find out the effect of time factor to the recrystallization of CaCO3@ Mesoporous Silica-Phosphate in dentinal tubule 3. To find out the source of calcium in the recrystallization in dentinal tubule 4. To evaluate the efficacy in vitro by animal study This research comprised of four parts. First, we used transwell dentin disc model and ion chromatography to measure the ion permeability of GCMS / 30% H3PO4 , SrCO3 mesoporous silicates / 30% H3PO4 , 30 % H3PO4 and calcium hydroxide. The second part we applied GCMS mixed with 30% H3PO4 in the dentin disc and observed the recrystallization in the dentinal tubule by SEM at four different time points. Furthermore, EDS was used to analyze the component of recrystallization. At third part, we applied strontium mesoporous silicates mixed with 30% H3PO4 in the dentinal tubule to find out the source of calcium in the recrystallization by using EDS. Fourth, we used animal study to evaluate the efficacy of GCMS / 30% H3PO4 , SrCO3 mesoporous silicates / 30% H3PO4 in vivo. In conclusion: （1）Calcium ion was not easily penetrate through the dentin barrier .PO43- could be a pilot to usher Ca2+ into dentinal tubules induce recrystallization.（2）The length of the recrystallization and the placement period of material are in direct proportion. (3) Partial calcium ion in the recrystallization was from the tooth. (4) GCMS/ 30% H3PO4 , SrCO3 mesoporous silicates / 30% H3PO4 had great efficacy in vivo.