牙体牙髓病的正确临床操作需要对不同器械、工具和设备在治疗过程中的使用有仔细详尽的认知。即使是对于最简单的病例，违背了器械的使用限制或是错误使用器械也可能会导致严重的医源性事故，妨碍正常根管治疗的继续进行。

本文将介绍一例既往治疗的上颌中切牙根管内存在阻射影异物，并伴有症状的根尖周炎。

Proper clinical practice in Endodontics requires careful and detailed knowledge on the know how of using different instruments, tools and devices used in the treatment course. Even in the simplest cases, violating the limitation of some instruments or misusing/misplacing those instruments may lead to severe iatrogenic errors which may act as a barrier against providing the proper standard of endodontic care.

The aim of this article is to present a case of previously treated maxillary central incisor with a radiopaque foreign body and symptomatic apical periodontitis.

图1. 术前评估。

患者男，29岁。主诉上颌中切牙烤瓷全冠脱落，并在全冠脱落前数周出现咬合不适。临床检查见一上颌中切牙预备状，并有先前治疗史，叩诊轻微疼痛。根尖片显示在根管的中段存在一不透射折断片，异物至根尖段的根管似乎没有预备。最终诊断为干髓术后的根尖周炎。

Pre-operative evaluation

29 years old male presented complaining of dislodged PFM crown from a maxillary central incisor which has been sensitive to biting for couple of weeks before crown loss. Clinical examination revealed a previously treated and prepared maxillary central incisor that is tender to mild percussion. Radiographic examination revealed a radiopaque fragment in the middle portion of the root canal. Apical to the fragment, the canal didn’t seem to be prepared.

A diagnosis of a pulpless, previously treated tooth with apical periodontitis was finally recorded

图2. 根管治疗前的冠方重建与隔离。

由于牙冠残缺并有需多次治疗的可能性，于是决定在治疗期间进行适当的根管治疗前冠方重建，以保持可接受的美观，并有助于对患牙进行复杂的隔离。使用厚橡皮障布和212 SA橡皮障夹进行初步隔离。光固化牙龈屏障树脂进行二次隔离。

Pre-endodontic build up and isolation

Due to the crown mutilation and the possibility of mutli-visit treatment, a decision was taken to execute a proper pre-endodontic build up to maintain acceptable esthetics during the treatment period and to aid in the otherwise complicated isolation of the tooth

Primary isolation was done using 212 SA clamp and heavy rubber sheet. Secondary isolation was done using a light curable gingival barrier. 

图3. 建立至折断片的直线通路。

在高倍显微镜下，去除腭侧所有的牙本质悬凸，实现对折断片的直线视野。此过程通过使用金刚砂涂层的超声工作尖修整先前的髓腔入路来完成。

Straight line access to the fragment

Under high microscopic magnification, straight line visual access to the fragment was achieved by removing all overhanging dentin palatally. This was done by refining the previously attempted access using diamond coated ultrasonic tip.

图4. 计划取出异物折断片。

分析上颌中切牙根管冠方的横截面形态，可以假设折断片紧贴腭侧（窄部）牙本质而在唇侧（宽部）留有空间。通过插入20#手用K锉从唇侧绕过了折断片证实了这一假设。计划在折断片的舌侧进行一个180°的预备，深度1~2mm，直到可以确切观察到折断片的松动。

Planning retrieval of the foreign fragment

Due to the cross-section of the coronal part of the root canal in a maxillary central Incisor, it was assumed that fragment is engaging dentin palatally [in the narrow part] while being free in the labial direction [wide part]. This was confirmed by inserting a hand #20 k-file bypassing labial to the fragment.

The plan was to prepare a 180 degrees preparation to a depth of 1-2 mm lingual to the fragment until visual confirmation of looseness is evident

图5. 折断片取出的条件。

必须强调的是处理的不同阶段决定了不同条件和方法的使用。在预备阶段，干燥条件可以保证视野的清晰，也要注意吹风冷却的使用。最重要的是采用10秒法则，以免损伤牙周组织。在松动阶段，潮湿的条件可以产生空穴效应和声流效应有助于进一步松解。

Conditions for fragment management

It has to be highlighted that different stages of management dictate the use of different conditions and media.

During preparation phase, a dry condition was used to provide good visibility, where cooling during preparation is done using a stropko tip blow. It is important to adopt the mother in law rule [10 second rule] during the preparation phase to avoid periodontal damage

During the loosening phase, wet condition is used to provide a cavitation effect and acoustic streaming that will aid in loosening

图6. 取出各阶段使用的介质。

在松动阶段，由于矿物油的低表面张力和低粘度可以渗透到折断片的下方而被使用。在取出尝试中，橄榄油因为其高润滑潜能和高粘度而被使用。

Type of media used in each step of management:

During the loosening phase, Mineral oil [Johnson’s baby oil] was used as it permeates beneath the fragment well owing to low surface tension and viscosity

During the retrieval attempt, based on the recommendation of Dr. Yoshi Terauchi, olive oil has been used owing to its high lubrication potential as well as its high viscosity.

超声激活尝试取出折断片

一旦折断片在根管内跳动，橄榄油就可以注入髓腔至窝洞洞缘。超声工作尖在唇侧或腭侧激活直至折断片弹出根管。本病例的折断片似乎是折断的Endo-Z车针。

Retrieval attempts using Ultrasonic activation

Once the fragment become dancing in the root canal space, Olive oil was used to fill the pulp chamber to the cavo-surface margin. An ultrasonic tip was activated in the preparation site and labially [alternatively] until the fragment popped out from the root canal. It appeared that the fragment was a broken Endo-Z bur.

图7. 观察确认。

取出后，高倍显微镜下确认根管内没有任何障碍物。根管预备使用的往复运动机用锉（45#05锥度）。

Visual Confirmation 

After retrieval, high magnification was used to confirm that the root canal space is free from any impediment.

Canal preparation was done using reciprocating files [45/.05]

图8. 充填。

确定合适主尖后，根管使用热牙胶垂直加压充填。

Obturation:

Following cone fitting procedures, the root canal was obdurated using GP and resin sealer using warm vertical compaction technique.

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