Remaining dentine thickness in mandibular premolars instrumented with two methods

Abstract

Background: Remaining dentine thickness after root canal instrumentation may be the main iatrogenic factor thatcorrelates the future root resistance against fracture. This study was conducted to measure the remaining dentinethickness (RDT) at the junction of coronal and middle third of human mandibular premolars’ root canals before andafter instrumentation with step-back technique using Gates-Glidden in serial sequence and balanced forcetechnique with crown-down preparation using the Teflon muffle mould systemMaterials and Methods: Twenty extracted, untreated human mandibular premolar roots were embedded in an autopolymerizing acrylic resin. The acrylic-root blocks were cut vertically and scanned using flatbed scanner. Thescanned images were processed with Adobe Photoshop CS8 and saved in TIFF format. RDT was measured usingAdobe Photoshop CS8 ruler at the junction of coronal and middle third of root canal both mesially and distally; thenthe 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 downpreparation. Finally, the sections were separated again, and RDT were measured.Results: Very highly significant difference was recorded between RDT before and after instrumentation regardingmesial side for both techniques (p = 0.000); while the distal side scored highly significant difference for bothtechniques (p = 0.01). No significant difference was found between the used techniques for the amount of removeddentine thickness P=0.168.Conclusion: Root canal instrumentation with both techniques removed similar amount of dentine thickness anddidn’t compromise RDT at junction of coronal and middle third of mandibular premolars root canal. However bothtechniques removed significant thickness of dentine mesially and distally. Dentine thickness before instrumentationwas found to be the most significant factor determining RDT after instrumentation.