乳臼齒根管解剖形態之研究與鎳鈦旋轉器械應用於乳臼齒根管治療

Abstract

第一部分：應用高解析度斷層掃瞄分析乳臼齒根管解剖形態 對乳齒牙根的形態的認知大多數停留在牙根外形的描述：乳齒與恆齒不同，牙根細而彎曲。由於乳齒的牙根會吸收，牙根完整的乳齒取得不易，因而針對乳臼齒根管系統方面的研究很少。本研究的目的是藉由高解析度斷層掃描術及3D視覺化軟體來分析乳臼齒的立體根管形態，希望藉由更多的瞭解，能對日後乳齒根管治療品質的提升能有所裨益。材料與方法：收集罹患癌症病童 (年齡為3~7歲) 已拔除的乳齒，儲存於含0.1 % thymol的生理食鹽水中，選擇29顆牙根完整的乳臼齒來做為本研究的材料。將這些牙齒利用MCT-CB100MF (Hitachi Medical Corp., Tokyo, Japan) 進行高解析度斷層掃描分析，平均每顆牙齒得到180個縱切面，Voxel size為 0.1× 0.1× 0.1 mm。之後再將這些切面影像利用Amira® 2.2的 3D視覺化軟體進行切面的重組。描述根管的形態，並統計各種形態出現的比例。結果：以牙根數目來分類：上顎第一乳臼齒有50 % 為三牙根，50 % 為雙牙根 ( 遠心頰根與顎側根融合為一個板狀牙根 )；上顎第二乳臼齒有90 % 為三牙根，10 % 為雙牙根；而下顎方面，第一乳臼齒均為兩個寬扁的板狀牙根；第二乳臼齒則是有55.6 % 為三牙根，44.4 % 為雙牙根。若以個別牙根出現根管數目來統計：上顎第一乳臼齒的近心頰側根87.5 % 是單一根管，其餘則為雙根管；遠心頰根與顎側根均為單根管；當出現遠心頰側根與顎側根融合在一起時，75% 出現雙根管，其餘為三根管。上顎第二乳臼齒的近心頰側根出現單一根管與雙根管的機率各佔一半；遠心頰側根與顎側根均為單根管；當出現遠心頰側根與顎側根融合在一起時，則均為雙根管。下顎第一乳臼齒的近心根均為雙根管，遠心根出現單一根管與雙根管的機率各佔一半；下顎第二乳臼齒的近心根有11.9 % 為單根管，88.1 % 為雙根管；遠心根有75 % 為單根管，其餘為雙根管。遠心頰側根與遠心舌側根則全部為單一根管的情形。結論：利用高解析度斷層掃描的技術，配合Amira® 3D視覺化軟體可以在不破壞牙齒的前提下，正確的重現乳齒根管的解剖形態，並可同時呈現牙齒與根管位置的相對關係，有助於日後對乳齒根管治療的研究。 第二部分： 鎳鈦旋轉器械在乳臼齒根管治療上的應用 最近這數十年來，隨著牙科材料與臨床牙醫學的發展進步，針對牙髓壞死或出現不可逆牙髓炎的牙齒；根管治療的方式不再侷限於使用傳統的化學藥物毒死細胞或手動根管治療器械來做根管的清創；而是漸漸的以鎳鈦旋轉器械來取代傳統的治療方式。儘管各種不同設計的鎳鈦旋轉器械技術日趨成熟，並已廣泛的應用在恆齒列的根管治療上；然而在乳齒列方面的應用卻是少之又少，而且也缺乏完整的臨床追蹤與評估報告。本實驗的目的是希望尋找出一套適用於乳臼齒根管治療的器械與技術，從而提高根管治療的效率與效力。本實驗選擇了26個兒童的61顆需要做根管治療的乳臼齒，年齡從3.2歲到7.7歲。選擇來做臨床試驗的牙齒都是符合根管治療的適應症、牙根尖完整且病人無重大的全身性疾病。應用 ProTaper® 鎳鈦旋轉器械系統 ( SX and S2 ) 配合上我們修正過的操作程序來做樣本的根管擴大與清創，之後以Vitapex® 充填根管、利用乳臼齒不鏽鋼牙冠來做復形、並立即照術後根尖X光片以利日後追蹤評估。治療完成後，持續每三個月進行一次門診追蹤檢查，觀察記錄受試乳齒的臨床症狀、照根尖X光片；並以Coll & Sadrian ( 1996 ) 所提出的臨床與放射學上的標準，來評估根管治療的成功率。平均門診追蹤為12.2 個月，整體的治癒率為95.6 % ( 依不同的追蹤時間，治癒率從89.3 % ~100 % )。在治療的過程中，沒有任何的病例出現器械斷裂或側方牙根穿孔的情形。利用ProTaper® 鎳鈦旋轉器械，搭配我們根據乳齒根管解剖形態修正過後的操作程序，可以安全而有效的提高乳臼齒根管治療的效率與效力，根管治療的品質也可以同時提升。

Part I:Three-dimensional Analysis of Root Canal Morphology of the Primary Molars by High-resolution Computed Tomography For better understanding of primary molar root canal morphology, a non-destructive high-resolution computed tomography was used to reconstruct the 3-dimensional anatomy of root canal systems of primary molars. Twenty nine extracted primary molars with intact root apex were selected from a collected sample stored in deionized water containing 0.1% thymol. The specimens were obtained from oncology child patients ( 3~7 year-old ) who required tooth extraction as part of their dental treatment. The chosen primary molars composed of 8 maxillary first primary molars, 10 maxillary second primary molars, 2 mandibular first primary molars, and 9 mandibular second primary molars. Study was carried by means of a commercially available high -resolution computed tomography device ( MCT-CB100MF, Hitachi, Medical Corp., Tokyo, Japan ) at 70 kv with voxel size of 0.1x 0.1x 0.1 mm and then reconstructed by Amira® 2.2. Grouping by the number of roots: 50 % of the maxillary first primary molars have three roots, and 50 % have two roots ( disto-buccal root fused to palatal root ); 90 % of the maxillary second primary molars have three roots, and the rest have two roots; all of the mandibular first primary molars have two roots with ribbon-shaped canals; 55.6 % of the mandibular second primary molars have three roots ( distal root divergent into two root in a bucco-lingual direction ), and the others have two roots. When grouping by the number of root canals in each root: 87.5 % of mesio-buccal root in maxillary first primary molars have one canal while the others have two canals, and all of the disto-buccal and the palatal roots have only one canal. However, in case of disto-buccal root fused to palatal root, 75 % of them have two canals, and the others have three canals. The prevalence of one canal and two canals in mesio-buccal root of maxillary second primary molars was the same. However, if the disto-buccal root fused to the palatal root, all of them have two canals. As regard to the mandibular primary molars, all of the mesial roots of the first primary molars have two canals, while the distal roots have the same prevalence between one and two canals. 88.1 % of the mesial roots in the primary second molars have two canals, and the rest have one canal; 75% of distal roots have one canal, and the others have two canals. There is only one canal in either disto-buccal or disto-lingual root. With high-resolution computed tomography, primary root canal system could be investigated in a non-destructive manner. Part II: Application of Ni-Ti rotary files for pulpectomy in primary molars Aim To explore the feasibility of nickel-titanium (Ni-Ti) rotary instruments for root canal preparation in primary molars. Methodology 61 primary molars with intact root apex in 26 children ( age range: 3.2 years to 7.7 years ) were treated. A modified protocol for Protaper® Ni-Ti rotary files using only two instruments ( SX and S2 ) was used for root canal preparation, and canals were filled with a calcium hydroxide-iodoform paste. All teeth were restored with stainless steel crowns. Post-operative radiographs were taken immediately following treatment and at 3-month intervals. Healing was assessed based on clinical and radiographic criteria. Results The overall healing rate was 95.6 % ( ranging from 89.3% to 100 %, depending on different follow-up time ) with mean follow-up of 12.2 months. Neither instrument separation nor lateral perforation occurred in any tooth. Conclusions With the modified protocol, ProTaper® Ni-Ti rotary files could be safely and efficiently applied for root canal instrumentation in primary molars, and the quality of treatment was good.