背景、目的 探討根管治療藻膠包埋模型其含水量對電子式根管長度測定器準確度之影響。 方法 組A(15顆牙)爲100%飽和溼度,組B(14顆牙)爲自然濕度組保存於27℃恆溫箱,每隔24小時記錄藻膠重量及Root ZX測量之牙齒長度至120小時:得出兩組實際牙齒長度(AL)減去測量長度(EDL)之差值(SD),評估藻膠失水量與SD值之變化以學生的t-test統計分析。 結果 組A在24小時含水量異常增高後與組B同樣按時間增長呈線性失水,在24小時組A的SD值有顯著差異。本實驗得出兩組SD差值維持在0.3mm。 結論 根管治療實習藻膠模型以Root ZX量測,建議維持在含水量73%到62.5%環境才可提供準確的工作長度測量。
Background/Purpose. To evaluate whether the water content in alginate endodontic models affects the accuracy of the Root ZX apex locator in determining the working length of root canals. Methods. Twenty-nine extracted single-rooted teeth were embedded in alginate models and divided into two groups. Group A (15 teeth) was stored in a completely sealed box and placed in an incubator so that the humidity level would reach 100%. Group B (14 teeth) was stored in a box without a cover to simulate natural humidity. Models in both groups were stored in a 27℃ incubator for up to 120 hours. The percentage of water content in alginate was measured by weighing the invested models at different measuring time points. The distance from the incisor edge or cusp tip to the major foramen of the root apex indicated the actual tooth length (AL).The electronically determined length (EDL) was measured by a K file advanced into the root canal to just beyond the major foramen, and then withdrawn counter-clockwise until a flashing bar appeared at the ”APEX” of the Root ZX. The measurements were performed at different time intervals. The subtraction difference (SD) between AL and EDL was recorded for each tooth in each group. The SD values at five different measuring time points in each group were then compared by a Student's t-test. Results. No significant difference in SD was observed in either group when the water content of alginate remained within the range of 73% to 62.5%. An average constant subtraction difference of 0.30 mm was found in group B. Conclusion. The Root ZX apex locator provided accurate and stable working length measurements when the water content in the alginate invested models remained within the range of 73% to 62.5%.