牙齒變色原因可分：齒質改變的內因性及牙釉質表面染色的外因性。而牙齒漂白的方式有：牙科診所內的診間美白和日漸普遍的居家美白；當劑量超過安全範圍或長時間不正確的使用，則會造成許多不良反應。本實驗室先前邱政憲學長研究以牙齒美白試劑成分過氧化氫（Hydrogen peroxide，H2O2）對正常人類口腔角質細胞（Normal human oral keratinocytes，nHOK）的影響，在5mM H2O2 時1、8小時明顯造成細胞死亡，對DNA傷害有濃度依賴性；接著趙婉君學姊利用生物晶片尋找nHOK細胞之基因調控，觀察NFκB及c-fos表現有增加趨勢，可能誘發癌症變化。故本研究將牙齒美白試劑給藥時間延長至48小時，來比較時間因子相對關係，與1、8小時共同表現的基因，分別為ATF3、DDIT3、DHDH、DLX2，皆呈現Up regulated；其中ATF3和DDIT3屬同一個pathway：Apoptosis and survival_Role of PKR in stress-induced apoptosis，表示受到H2O2造成的氧化壓力會造成內質網壓力（ER stress），後續驗證也發現這些基因確實有表現，時間延長後所產生的ROS對nHOK傷害還存在，並使細胞走向細胞凋亡。 Tooth discoloration can be due to a multitude of reasons, which can be derived from intrinsic and extrinsic factors . Currently, at-home tooth whitening products have grown in popularity. Once the safe limits of hydrogen peroxide is exceeded, or the treatment duration is too long, it can have negative consequences on the tooth’s structures and result in adverse effects. Previous experiments conducted by Cheng-Hsien Chiu looked at the effects of hydrogen peroxide on normal human oral keratinocytes (nHOK).From his experiments, it was observed that cellular damage is correlated with treatment concentration in a dose dependent manner. Additionally, at 5 mM, cell death was observed regardless of whether the time interval was 1 hour or 8 hours. Furthermore,Wan-Chun Chao utilized microarray to look at whether nHOK under the treatment of hydrogen peroxide, results in alterations in the gene transcription pathway. It has been discovered that there is an increase in NFκB and c-fos protein expression when exposed to hydrogen peroxide treatment. The bleaching agent not only affects the cells internal ROS, but it can also result in cancer. This experiment focuses on the effects of tooth whitening agents over a prolonged treatment period of 48 hours and we looked at the effects of longer treatment time to oral cells. We noticed that the genes ATF3, DDIT3, DHDH, and DLX2 are upregulated. Additionally, we discovered that ATF3 and DDIT3 utilize the same pathway: Apoptosis and survival_Role of PKR in stress-induced apoptosis. These four genes are influced by various different factors and we have confirmed that these genes are expressed. It indicates that the oxidative stress caused by H2O2 can develop and result in endoplasmic reticulum stress (ER stress).The ROS generated by hydrogen perioxide continues to exist and impacts the cell by driving them towards apoptosis.
