Analysis of operator variability in standardized root canal preparation with Ni—Ti instruments Analisi della variabile operatore nella preparazione canalare standardizzata con strumenti AL Ni—Ti

Summary Objectives: The aim of this study is to assess the influence of the operator variability during the preparation of standard resin blocks and the learning process with Ni—Ti instruments, the null hypothesis being that there are no significant differences regarding dentin removal, variation of the angle and radius of curvature, centering of the preparation, and time required by operator with different clinical experience. Materials and methods: 100 standard resin blocks were used for this study. The blocks were dividedinto4groupsof25,andeach groupwasassigned to adifferent operator.Operators 1and 2 were 4th year DDS undergraduate students that had never performed endodontic treatments and as such could be considered as inexperienced operators. Operators 3 and 4 were 2 clinicians with 10 years experience and that were familiar with endodontic treatments and instrumentation (experienced operators). Many parameters were measured and compared. Result: Differences could be detected between the 2 different level of clinical experience. Conclusions: Under the experimental conditions ofthis study, experience ofthe operators can be considered as a crucial factor when all the other parameters are kept standard. In conclusion the null-hypothesis has to be rejected. Statistically significant differences exist in dentin removal, in the variation of the degree of curvature, in the centering of the preparation and in the time needed for the preparation when operators with different clinical experience where tested.