Exatidão e precisão das réguas milimetradas utilizadas durante procedimentos endodônticos Accuracy and precision of the millimeter rules used for endodontic procedures

Introduction : The use of millimeter rules is of fundamental importance for the proper conduct in the various stages of endodontic treatment. The professional should be concerned by the accuracy and precision of these instruments in order to avoid possible measurement errors and interpretation able to frustrate the endodontic therapy. Objective: This study was aimed to evaluate the accuracy and precision of millimeter rulers sold in Brazil used during endodontic procedures and evaluate the use and preference of this instrument by professionals working in this area. Methodology: Preliminarily, experts and graduate students in endodontics were consulted regarding the use and the brand preference for millimeter rules. In parallel, a hundred rulers have been selected divided into ten groups of ten units each, according to the manufacturer and the type of material used. Each ruler was measured in 30 mm by means of an electronic digital caliper, and the accuracy assessed by comparing the rulers with a gold-standard ruler credited by the Laboratory of Metrology – MEC-Q/BA. As for the accuracy the results were compared between the units of each group. Results: The questionnaire applied revealed that 19.23% of respondents did not know how to refer to the rulers’ brands used and 23.07% reported using more than one millimeter ruler to perform endodontic procedures. A millimeter ruler produced by Maillefer was the most cited by respondents, followed by Intermedium and Microdont. Evaluation of rulers produced by Maillefer revealed greater accuracy, while the greatest accuracy was accredited to rulers produced by JON. The ruler made of polymer by Maquira was considered the least accurate and precise. Conclusion: As the millimeter endodontic rulers analyzed were neither precise nor accurate, the Professional should use the same ruler throughout treatment.