Both operator and heat treatment determine the centring ability of Reciproc® files in vitro

To determine the shaping ability of reciprocating files without/with post-manufacturing heat treatment (Reciproc®/Reciproc blue®, VDW) when used by six operators of similar level of experience.

Plastic training blocs with curved root canals (5 mm radius, 55° angle) were mounted in a dental manikin. Each operator prepared six specimens with each instrument system using the file sizes R25, R40 and R50 consecutively. Specimens were photographed, and deviations from the centre of the canal were measured at intervals of 0.5 mm and averaged for the apical, middle and coronal part of the canal. Data were tested for significance using the Mann-Whitney U test and two-way ANOVA with instrument systems and operators serving as factors.

Deviations were observed towards the outer curvature in the apical and coronal and to the inner curvature in the middle segment of the canal. They were larger after using larger size instruments and were smaller when using Reciproc blue® compared to Reciproc®. Significant differences among operators were observed in the middle (all sizes) and coronal part of the canals (only sizes R25 und R40). Coronally, interaction between the main factors was significant as well.

Post-manufacturing heat treatment significantly improved shaping ability of the reciprocating file system Reciproc®. The observed differences among operators suggest the possibility of further improvement by providing specific training for prospective users.

Maintenance of root canal curvature may be improved by using post-manufacturing heat-treated instruments, but specific training should be recommended as well.