Mannan G, Smallwood E R, Gulabivala K
Eastman Dental Institute for Oral Healthcare Sciences, University College London, UK.
Int Endod J. 2001 Apr;34(3):176-83. doi: 10.1046/j.1365-2591.2001.00359.x.
The null hypothesis tested in this study was that in single-rooted anterior teeth with simple root canal anatomy, different access cavity designs ('lingual cingulum', 'lingual conventional', 'incisal straight-line') do not influence the ability of endodontic files to plane the walls of the root canals.
Thirty extracted human maxillary anterior teeth were divided randomly into three groups for each access cavity. The access cavities were prepared according to predefined criteria and the roots embedded in individual polyvinyl-siloxane putty matrices. The matrices allowed these teeth to be split into buccal and palatal halves and to be reassembled. The split teeth enabled removal of pulpal remnants from the root canal system and the walls to be stained with an even layer of permanent black ink. Once dried, the split roots were reassembled in the putty matrices and a step-back filing technique was used to prepare the canals with water irrigation. The canal walls were examined for residual ink staining and scored by three independent assessors using an index devised for the purpose.
There was good agreement between the assessors. None of the access cavities allowed file contact with the entire root canal wall. The overall (palatal and buccal sections) scores showed significant differences (P < 0.01) between the access cavity groups in the extent to which the canal walls could be filed. The straight-line incisal access cavity had the greatest proportion of instrumented root canal surface. The lingual cingulum access cavity was the worst in this respect. The differences in residual ink scores between the access cavity types were significant for the buccal halves (P < 0.01) but not for the palatal halves (P > 0.05).
The null hypothesis was proven. Regardless of access cavity design, mechanical preparation did not allow instrumentation of the entire root canal wall. Straight-line access allowed the greatest proportion of the root canal wall to be instrumented and the lingual cingulum access the least.
本研究检验的无效假设是，在根管解剖结构简单的单根前牙中，不同的开髓腔设计（“舌隆突”、“舌侧传统型”、“切端直线型”）不会影响根管锉平整根管壁的能力。
30颗拔除的人上颌前牙随机分为三组，每组对应一种开髓腔设计。根据预先设定的标准制备开髓腔，并将牙根嵌入单独的聚乙烯硅氧烷油灰基质中。这些基质可使牙齿分成颊侧和腭侧两半，然后重新组装。劈开的牙齿便于清除根管系统中的牙髓残余物，并用均匀的一层永久性黑色墨水对根管壁进行染色。干燥后，将劈开的牙根重新组装在油灰基质中，并采用逐步后退法进行根管预备，同时用水冲洗。由三名独立评估者使用为此目的设计的指数对根管壁的残余墨水染色情况进行检查和评分。
评估者之间的意见高度一致。没有一种开髓腔能使锉与整个根管壁接触。总体（腭侧和颊侧部分）评分显示，不同开髓腔组在根管壁可锉削程度上存在显著差异（P < 0.01）。切端直线型开髓腔的器械操作根管表面比例最大。在这方面，舌隆突开髓腔最差。不同开髓腔类型之间的残余墨水评分差异在颊侧部分具有统计学意义（P < 0.01），但在腭侧部分无统计学意义（P > 0.05）。
无效假设得到证实。无论开髓腔设计如何，机械预备都无法对整个根管壁进行器械操作。直线型开髓能使最大比例的根管壁得到器械操作，而舌隆突开髓得到器械操作的比例最小。
