次氯酸鈉於現代根管治療學當中是最重要的沖洗溶液，除了極佳的殺菌消毒功用之外，亦有不錯的溶解組織之功效；然而次氯酸鈉是一個強氧化劑，本身性質極度不穩定，其效能主要取決於溶液當中「有效氯」的濃度。所謂的有效氯（Available chlorine）乃是指次氯酸鈉水溶液中所有具有氧化的次氯酸與次氯酸根離子之總和。有效氯的濃度會隨著時間、光線照射、加熱、接觸空氣、有機物消耗、金屬或金屬離子的影響，而產生降解。因此在診間盛放的次氯酸鈉溶液有可能因周遭環境的影響導致濃度發生改變，進而影響根管治療時沖洗的效能。
本研究旨在模擬現有牙科臨床環境與一般盛放次氯酸鈉的方式，依不同變因的改變，使用硫代硫酸鈉與碘化鉀來進行碘滴定法，以觀察分裝後次氯酸鈉沖洗液之濃度變化。
實驗結果顯示，四週過後，接受光線照射並且與空氣接觸的次氯酸鈉有效氯濃度衰退最多（-62.63％），其次是與空氣接觸但無光線影響的組別（-53.46%），再者為受光線影響但限制與空氣接觸的組別（-23.26%），不受光線空氣干擾的次氯酸鈉其有效氯僅衰退-4.65%，經檢驗確實有顯著差異。
是以，次氯酸鈉的有效氯濃度會因為時間而產生衰減，並且光線照射與空氣接觸都將會加快次氯酸鈉濃度衰減的速率。因此，建議於診間使用時應盛放於褐色瓶中防止光線照射，並且應蓋上避免長時間與空氣接觸。
Sodium hypochlorite is the most important irrigant in modern endodontology because of its well-known antimicrobial effect and tissue-dissolving activity. However, sodium hypochlorite is an unstable chemicals for being a strong oxidizers . The activity of sodium hypochlorite depends on the concentration of available chlorine. The available chlorine is the sum of the concentrations of HOCl and OCl- in sodium hypochlorite solution. Its concentration would be changed by time, light, heat, air, organic, metals and metallic ions. Therefore, the sodium hypochlorite stored in the clinic could be interfered by the surroundings. Its change in concentration may affect the efficacy of irrigation during root canal treatment.
This study is to simulate the ways of storing the sodium hypochlorite on the table in dental clinics, to observe the change in concentration in different situations by using iodometric titration.
The result revealed : 4 weeks later, G1 group ( exposed to light without coverage ) showed greatest regression in concentration of available chlorine (-62.63%), followed by G3 group ( stored in darkness without coverage ) -53.46%, G2 group (exposed to light with coverage ) -23.26%, and G4 group ( stored in darkness with coverage ) -4.55%. The analysis showed significant difference( p<0.05 ) between G1 v.s. G4, G3 v.s. G4 and G2 v.s. G4.
Thus, the concentration of sodium hypochlorite would be regressed as time goes by. Exposing to light and contacting with air would speed the rate of degradation of available chlorine in sodium hypochlorite. For this reason, we recommend the sodium hypochlorite should be kept in brown bottle to prevent the effect of light. Besides, proper coverage would enhance the stability of sodium hypochlorite.
