Morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province using three techniques, including periapical radiographs, the radiographs with files inserted the canals and the clearing technique.</p><p><b>METHODS</b>A total of 363 extracted mandibular first premolars were collected and numbered. Two preoperative radiographs were taken in buccolingual and mesiodistal directions respectively. After access opening, the files were placed in the canals and two other radiographs were taken. The mandibular first premolars with multi-canal system were selected and observed under dental operating microscope (DOM). The mandibular first premolars were made transparent and were categorized using the Vertucci's classification.</p><p><b>RESULTS</b>There were different results among the three approaches. Periapical radiographs could be used to distinguish only between one and multiple canals systems. The incidence of multiple canals was 33.33% from the radiographs with file. The mandibular first premolars had a high frequency (34.44%) of multi-canal system by clearing method. The root canal morphology of the mandibular first premolars showed great variance. The canal orifices of the mandibular first premolars with one or two canal distributed in a buccolingual line. The floor of pulp chamber of the mandibular first premolars with three or four canals was a plat form.</p><p><b>CONCLUSION</b>The mandibular first premolars have a high frequency multi-canal system and could be classified in many categories. Using DOM and radiographs with file is a useful way in judging the canal numbers and categories.</p>

Clinical evaluation of Nickel-Titanium rotary instruments in preparation of root canals / 中国基层医药

Objective To study and assess clinical application of two Nickel-Titanium(NiTi)rotary instru- ments,namely ProTaper and Hero 642,in preparation of root canals.Methods 125 teeth were divided into three groups and respectively instrumented by stainless K-files,ProTaper or Hero 642 rotary instruments.All teeth were obturated with lateral condensation method.The efficiency of preparation and obturation was analyzed with radio- graphs.Results NiTi rotary instruments were better in keeping the curvature and flow of curved canals than stain- less K files.There was no transportation,apical blockage and ledge in NiTi groups.The operative time was shorter and endodontic flare-up seldom occurred in NiTi groups.Conclusion The NiTi rotary instrumentation technique could be used to prepare curved root canals effectively and quickly.The future use of NiTi engine-driven rotary in- strument appeared to be promising.