A comparison of the efficacy of conventional and new retreatment instruments to remove gutta-percha in curved root canals: an ex vivo study.

AIM: To compare the efficacy of conventional and new retreatment instruments when removing gutta-percha root fillings in curved root canals. METHODOLOGY: A total of 56 curved molar roots were instrumented with ProFile instruments and filled using system B and Obtura II. The root fillings were removed with manual K-files and Hedström files (Dentsply Maillefer), ProFile (Dentsply Maillefer), R-Endo (Micro-Mega) or ProTaper Universal retreatment files (Dentsply Maillefer). Eucalyptol was used as a solvent with all techniques. Bucco-lingual and proximal radiographs of the roots were exposed and the percentage area of the remaining material was calculated by dividing the area of remaining filling material by the area of canal wall. Data were statistically analysed with Kruskal-Wallis and Mann-Whitney U tests (P = 0.05). RESULTS: None of the techniques completely removed the root filling materials. No significant differences were found amongst the coronal, middle and apical thirds in both radiographic projections (P > 0.05). In the bucco-lingual direction, the remaining filling material was significantly less following manual instrumentation than R-Endo and ProTaper instrumentation (P < 0.05). In the proximal view, it was significantly less following manual and ProFile instrumentation than R-Endo (P < 0.05). Complete removal of filling material occurred only in three specimens (with manual instruments). Manual instruments were significantly faster than R-Endo and ProFile (P < 0.05). More procedural errors (five fractured instruments and two perforation) were noted when using ProTaper (P < 0.05). CONCLUSIONS: In this laboratory study in curved molar roots, ProTaper Retreatment and R-Endo instruments were less effective in removing filling material from canal walls than manual and ProFile instruments.

Comparison of cold lateral compaction and continuous wave of obturation techniques following manual or rotary instrumentation.

AIM: To compare different combinations of root canal preparation and obturation technique. METHODOLOGY: A total of 48 freshly extracted human maxillary central incisors were divided into two identical groups on the basis of root canal length and apical diameter. The root canals were prepared by manual crown-down pressureless technique or with a rotary system (ProFile; Dentsply Maillefer, Ballaigues, Switzerland) in a crown-down technique. The coronal diameter and apical size of the root canals were standardized in both preparation techniques. Each main group was then divided into two subgroups and obturated with either cold lateral compaction or continuous wave of obturation with System B (EIE-Analytic Technology, Orange, CA, USA). The distribution of filling material in each canal was assessed by stereomicroscopic examination of eight cross-sections on each tooth. Areas of sealer, gutta-percha and voids were measured on the digital images of a total of 384 samples. Manipulation time and apical extrusion for each group was also determined. Data were statistically analysed using Kruskal-Wallis, anova (Bonferroni/Dunn) or Student's t-test. RESULTS: The percentage of sealer, gutta-percha and voids area between the obturation techniques was not significantly different (P > 0.05). Continuous wave groups had significantly more apical extrusion of sealer (P < 0.05), while none of the obturation techniques had gutta-percha extrusion. Rotary instrumentation was significantly faster than the manual technique (P < 0.05); continuous wave obturation was significantly faster than lateral compaction (P < 0.05). Total manipulation time in the rotary/continuous wave group was significantly shorter than the other groups (P < 0.0001). CONCLUSION: The distribution of filling materials was similar in all combinations of instrumentation and obturation techniques. The continuous wave technique was faster than lateral compaction and it extruded more sealer.