目前牙齒美白主要可分為診間美白（In-office）與居家美白（Night guard vital tooth bleaching；At-home）兩種方式。“居家美白” 它是使用10~15 ％ carbamide peroxide塗抹在病人的牙托上，睡前使用配戴八小時，連續使用八星期以達美白效果。其原理為carbamide peroxide與唾液接觸時，可以分解成H2O2 及 尿素。H2O2滲透到牙齒琺瑯質與象牙質可進行氧化還原作用，將色素分子打碎成較細的分子，除去牙齒上的色素，但H2O2分子也會很容易接觸牙齒周圍的組織，穿過細胞膜造成細胞毒性產生牙齦傷害。
在本實驗室之前的研究以 H2O2 對人類正常口腔角質細胞內的體染色體、粒線體染色體及反應的蛋白質的傷害，發現隨時間因素細胞傷害會越來越大而濃度因素不管在5mM H2O2在一小時或八小時造成細胞死亡及傷害非常明顯；而粒線體染色體部份在一小時 5mM 細胞膜電位就會有明顯下降的改變。反應的蛋白質部份針對受到濃度影響產生變化的蛋白質包括cyclophilin、TPC-1 subunit delta、annexin A2、calmodulin like protein 3；粒線體蛋白部份包括 ND5、 COII 、ND4、ND6受到濃度和時間影響皆有不一樣的變化，但是否還有其他反應的蛋白質未檢查出，所以再探討RNA在轉譯成蛋白質過程中是否產生變化，利用生物晶片方法試圖確定正常人類口腔角質細胞在使用H2O2後之基因調控途徑。因此確定了三個基因（ZNF350，RNF185和ABL2）在人類正常口腔角質細胞使用 H2O2 在8小時後Q-PCR的RNA表現量有增加之現象。這三個基因與金屬結合的途徑及修復機制有密切的關係，證明人類正常口腔角質細胞受氧化壓力影響會誘導體內保護機制產生。 Recently, tooth bleaching has become a popular treatment due to patient demands for healthy teeth and beautiful smile. “Home bleaching” or the “night guard vital bleaching” technique was first described and published in 1989 by Haywood and Heyman. It used 10-15 % carbamide peroxide in patient’s night guard for several weeks. H2O2 is active bleaching components which not only act as strong oxidant agent but also one of the reactive oxygen species. It can be broken down into water and oxygen molecules and convert into free radicals. In our previous lab research, Dr. C.H Chung observed the normal human oral keratinocyte (NHOK) under exposure of H2O2 can cause cell death, nuclear DNA (nDNA) oxidative damage, mitochondrial DNA4977 deletion (mtDNA4977) and mitochondrial membrane potential change.
The purpose of this study is to characteristic gene expression profiles that distinguish the responses to oxidative stress in human normal oral keratinocyte cell lines using microarray. Next, we sought to identify pathways and gene networks significantly regulated in normal and treatment cells in response to H2O2. We identified three genes (ZNF350, RNF185 and ABL2) have altered in response to H2O2 in human normal oral keratinocyte. These three genes are closely related with metal binding pathway and play a great role in repair mechanism. Our findings present strong evidence that persistent oxidative stress induce a crucial protective mechanism in normal oral keratinocyte.
