Abstract
Secondary root canal treatment requires the complete removal of filling materials with different chemical-physical properties. A newly developed single-use NiTi instrument (Reciproc Blue, RB) may be more effective in root canal retreatment. The aim of the present study was to evaluate morphology and composition of remnants after retreatment with RB compared to traditional K-File technique, in canals obturated with Thermafil/AH Plus. Twenty-four single-rooted human teeth were shaped with NiTi obturated with AH-Plus/Thermafil and retreated using RB NiTi instruments or manual K-Files. Radiographs were taken to evaluate endodontic space and radiopacity of residual filling-material before/after procedures. After retreatment, samples were longitudinally split and observed by environmental scanning electron microscopy connected to energy dispersive X-Ray spectroscopy (ESEM-EDX) to analyze the debris/remnant position, microchemistry, and dentinal surface morphology. Time for retreatments was recorded and compared using one-way ANOVA (p-value = 0.05). Radiopaque filling residuals were found in both groups. RB system resulted statistically faster than manual K-File in retreatment procedure (p < 0.001). Root canal space radiographic appearance obtained after retreatment with RB was wider than K-File (p < 0.05). ESEM-EDX revealed 4 different morphological dentin area. Area-1: debris-free with typical Ca, P, and N composition of dentin and detected in 70% of the surface. Area-2: presence of deproteinized smear layer free from N and debris in 15% of the surface. Area-3: a thick packed smear layer N-free and with fine debris consisting of trace elements from sealer in 10% of the surface. Area-4: packed with debris and trace elements. No difference was observed between both instruments regarding root canal space appearance and ESEM-EDX analysis. Both systems were able to remove filling material but created a dentine morphology composed of packed debris and filling materials embedded into the smear layer. Dentin surface composition resulted in collagen depleted by irrigation procedures. The reciprocating system required less time to complete retreatment.
Highlights
The main concept behind secondary root canal treatment procedures is the removal of all root canal filling materials infected debris and dentin smear layer that are responsible for periapical disease [1,2,3]
This study aimed to explore the composition and the morphology of debris inside root canals after secondary root treatment of teeth filled with AH Plus and Thermafil system
Limited information is present in literature regarding the morphology of the debris, the root canal wall morphology, and microchemical modifications after secondary root canal treatment, most of the studies focused on root canal filling materials removal efficiency through 3D radiographic analyses [11,16,17,18,19]
Summary
The main concept behind secondary root canal treatment procedures is the removal of all root canal filling materials infected debris and dentin smear layer that are responsible for periapical disease [1,2,3]. Root canal space is filled with materials with different physical and chemical properties that must be removed. Traditional instrumentation techniques require the use of a series of manual files or rotary NiTi instruments which may undergo fractures, leading to inadequate root canal treatment. For these issues, several new approaches and techniques are being developed
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