Comparison of Obturation Techniques for Oval Canals

Objectives: To evaluate the effectiveness of three obturation techniques following root canal preparation of oval canals using Ni-Ti rotary files. Methods: 42 oval canals of extracted teeth (maxillary and mandibular premolars, palatal roots of maxillary molars, distal roots of mandibular molars) were used. They were randomly divided into three groups; 1) ProTaper canal preparation (Dentsply Maillefer, Ballaigues, Switzerland) plus single cone obturation using matching gutta percha point, 2) ProTaper plus thermoplastic obturation technique (Thermafil), 3) Profile 0.06 taper and matching gutta percha point with lateral condensation technique. AH Plus colored by Sudan Black dye was used as sealer cement. Roots were sectioned at the apical, middle and coronal thirds. The surfaces of specimens were polished and photographed under x6, x12 and x25 magnification. The cross-sectional area of the canal space occupied by sealer cement and gutta percha was measured on each section with image analysis software and calculated as the sealer/canal ratio (%). Data were analysed statistically using ANOVA for effect of obturation technique and level of section. Results: The sealer ratio in oval canals indicated a wide variation with all obturation techniques, (12-34% of total cross-sectional area). Overall the sealer ratio was lowest in the Thermafil group followed by lateral condensation and Protaper single cone technique (p<0.01). In the apical third, most canal preparations were round, with no differences among techniques. In the middle and coronal thirds where canal cross sections were oval, a higher proportion of the canal space (>25% in the lateral condensation and single cone groups) was occupied by sealer. Conclusion: A thermoplastic technique resulted in the best obturation of oval canals. A single cone technique relied heavily on sealer cement for filling canals.