Remaining dentine thickness in mandibular premolars instrumented with two methods

الملخص EN

Background : Remaining dentine thickness after root canal instrumentation may be the main iatrogenic factor that correlates the future root resistance against fracture.

This study was conducted to measure the remaining dentine thickness (RDT) at the junction of coronal and middle third of human mandibular premolars’ root canals before and after instrumentation with step-back technique using Gates-Glidden in serial sequence and balanced force technique with crown-down preparation using the Teflon muffle mould system Materials and Methods : Twenty extracted, untreated human mandibular premolar roots were embedded in an auto polymerizing acrylic resin.

The acrylic-root blocks were cut vertically and scanned using flatbed scanner.

The scanned images were processed with Adobe Photoshop CS8 and saved in TIFF format.

RDT was measured using Adobe Photoshop CS8 ruler at the junction of coronal and middle third of root canal both mesially and distally ; then the sections were reassembled with a muffle .Ten roots were instrumented using step-back technique using Gates-Glidden in a serial sequence.

Ten roots were instrumented using balanced force technique with crown down preparation.

Finally, the sections were separated again, and RDT were measured. Results : Very highly significant difference was recorded between RDT before and after instrumentation regarding mesial side for both techniques (p = 0.000) ; while the distal side scored highly significant difference for both techniques (p = 0.01).

No significant difference was found between the used techniques for the amount of removed dentine thickness P = 0.168. Conclusion : Root canal instrumentation with both techniques removed similar amount of dentine thickness and didn’t compromise RDT at junction of coronal and middle third of mandibular premolars root canal.

However both techniques removed significant thickness of dentine mesially and distally.

Dentine thickness before instrumentation was found to be the most significant factor determining RDT after instrumentation.