| 摘要: | 由於現代人對牙齒的功能及美觀愈來愈重視，牙齒的矯正治療也日趨普遍，然而矯正治療時間常常需要1年半到2年，再加上治療時必須在牙齒表面黏著矯正裝置，種種原因都容易造成口腔衛生不易維持，長期下來罹患齲齒、牙周病的機會大大增加，如果能夠有效縮短矯正治療的時間，不只可以減少患者治療時的不舒服，也能改善上述牙齒疾病的產生。根據觀察，矯正治療最耗費時間的動作就是空間關閉 (space closure)，當使用彈性鏈來進行空間關閉時，常常會遇到因為彈性鏈力量的衰減導致到後期雖然只剩一點點空間卻花很多時間去關閉，如果能夠對彈性鏈力量衰減模式有更進一步了解，就能夠在彈性鏈尚未失去拉動牙齒的力量前便加以更換，藉此可以縮短整個治療時間。
選用TOMY公司生產之Super chain (heavy force, short span) ，剪取120條8個環之super chain固定在自製壓克力支架上分成4組每組30條彈性鏈進行實驗，這4組分別為在恆溫37℃水中 (標示為M組)，在恆溫37℃水中但每日給予3次15-45℃溫度循環 (標示為T組)，在恆溫37℃水中但每日給予3次pH 4.9-7.3酸鹼溶液循環 (標示為P組)，另外一組則放置在室溫空氣中 (A組control)，共定6個時間點 (4天、7天、11天、14天、18天、21天)，每個時間點取5條彈性鏈使用拉力計 (Algol HF-10,日本)進行力量之量測，並用one-way ANOVA比較各組之差異及評估哪個時間點有較大力量之衰減。
結果顯示A組比起其他3組 (M、T、P組)，力量的衰減明顯較少，至於其他3組彼此之間則沒有太大的差異，彈性鏈一旦延伸，即使放置在空氣中，在第一個時間點內也會有大幅力量的衰減，當然另外3組力量的衰減又更嚴重，溫度循環的組別在所有時間點的力量衰減頗為一致，顯示溫度變化所造成的影響似乎比其他因素大，而酸鹼循環所造成的影響主要是在前1星期，會有比其他組別更快速的力量衰減，所有組別在3星期後力量至少都還有228.4克 (T組)，這個力量對一般前牙的移動來說力量應該是足夠，因此從實驗結果來看，彈性鏈在3星期內應該不需要更換。
More and more people are showing great concerns about the functions and aesthetics of their teeth and therefore asking for orthodontic treatment. Regular orthodontic treatment ideally takes about one or two years to finish. During the treatment we have to utilize many orthodontic appliances in order to realign the teeth. It’s quite difficult for patients to maintain good oral hygiene during the procedure. If we can find a way to decrease total orthodontic treatment time, it would help patients not only decrease the incidence of dental diseases like caries or periodontitis but also reduce discomfort during the treatment. In our clinical practice of orthodontic treatment, closing space performed by elastic chains is the most time-consuming procedure because elastic chains always degrade with time and we only replace them on a regular one-month recall. If we learn more about the force decay pattern of the elastic chains and replace them before they completely lose their elasticity, the total treatment time can be shortened.
One hundred and twenty (120) pieces of Tomy super chains (heavy force, short span) containing 8 rings on each piece were extended on 24 customized acrylic plates. All the samples were divided into four groups and each group had 30 pieces of elastic chains. Group 1 (group M) was immerged into 37℃ water bath. Group 2 (group T) was immerged into the same water bath but suffered from thermocyling (15-45℃) three times a day. Group 3 (group P) was also immerged into the same water bath but suffered from pH variations (pH 4.9-7.3) three times a day. The last group was placed in dry air under room temperature (group A, control). The force was examined by force gauge (Algol HF-10, Japan) at six intervals (4d, 7d, 11d, 14d, 18d, 21d). Statistic analysis (one-way ANOVA) was performed to compare the differences among these groups.
The results revealed A group always preserved more force level than the other three groups during 21days, while there was no obvious difference among the other three groups (M, T, and P groups). Elastic chains lost their force rapidly at the first time point when they were stretched, no matter under what kind of environment they were in. T group showed a consistent force decay pattern. This may represent that thermocycling has greater influence upon force decay than the other factors. P group had very rapid force decay in the first week (the first two time points) than the others. This means pH variations may influence the force level mainly in the initial stage. All the groups preserved a force level of more than 228.4 gm (the lowest one was T group), which is enough to realign a tooth. So it is not necessary to change the elastic chains within 3 weeks according to our research results. |
