Table of Contents:
The present study aimed to evaluate the retreatment efficiency of root canal fillings performed with AH Plus, Apexit Plus, Hybrid Root SEAL (HRS) and GuttaFlow in combination with an experimental GuttaFlow primer. In detail, this study should answer the question whether a retreatment size exceeding the initial instrumentation by two instrument sizes reveals differences in terms of retreatment efficiency regarding conventional sealers compared to adhesive sealers.
Materials und Methods
The root canals of 56 straight human incisors were instrumented with FlexMaster files to an apical size of .04/#35, separated longitudinally, re-assembled, molded within polyurethane (PUR) blocks and finally instrumented with a FlexMaster file .04/#40. Then root canals were obturated with a size .04/#40 gutta-percha cone and AH Plus, Apexit Plus, Hybrid Root SEAL or GuttaFlow/GuttaFlow primer respectively and stored for 14 days (37°C/100% humidity). Endodontic retreatment was performed stepwise using EndoSequence instruments of sizes .04/#40, .04/#45 and .04/#50. Additionally, the required retreatment time to achieve the working length was recorded. After each retreatment step the resin blocks were separated and microphotographs of the apical, middle, and coronal part of both halves of the root canal were taken (Zeiss Stemi SV6). Sealer residues were calculated with an image analysis software (Leica Qwin) and the amount of residues was expressed as percentage of residue-coated canal surface (PRCS). Statistical analysis was performed with SPSS 16.0 (SPSS Inc.) software.
Stepwise enlargement of instrumentation size from size .04/#40 to .04/#50 significantly reduced the amount of sealer residues within all 4 groups (p<0.05). In this respect, the amount of residual sealer depended on the sealer type (p<0,05): adhesive sealer Hybrid Root SEAL left significantly more residues than conventional sealers Apexit Plus (coronal: p=0.016, middle: p=0.000, apical no significant differences) and GuttaFlow in combination with GuttaFlow primer (coronal: p=0.000, middle: p=0.000, apical: p= 0.004). Microscopic evaluation revealed following results of PRCS:
retreatment step 1: AH Plus: 44,4%/50,4%/56,2%; Apexit Plus: 38,6%/ 39,3%/47,9%; GuttaFlow: 27,7%/35,9%/33,6%; HRS: 58,7%/70%/64,6%;
retreatment step 2: AH Plus: 35,5%/40,0%/34,7%; Apexit Plus: 27,2%/ 30,6%/33,5%; GuttaFlow: 15,2%/22%/25,2%; HRS: 45,6%/48,7%/46,4%;
retreatment step 3: AH Plus: 25,8%/26,5%/27,2%; Apexit Plus: 21,4%/ 20,6%/19,3%; GuttaFlow: 12,1%/16,6%/17,7%; HRS: 32,8%/37,6%/31,4%
Retreatment of the adhesive sealer Hybrid Root SEAL required a significantly longer overall instrumentation time than retreatment of root canal fillings with AH Plus (p=0.019), Apexit Plus (p=0.023) and GuttaFlow with GuttaFlow primer (p=0.002).
Within the limits of this study the adhesive sealer Hybrid Root SEAL was less efficient to retreat than the conventional sealers AH Plus, Apexit Plus and GuttaFlow sealer combined with an experimental GuttaFlow primer when using the same size of instruments. Enlargement of the root canal up to two sizes beyond the instrumentention size of the initial root canal treatment does not seem to be sufficient in terms of retreatment efficiency to significantly reduce adhesive sealers.