In this study, computed tomography (CT) was used to assess three techniques for root canal filling removal. Seventy-five roots of extracted human lower incisors were filled with zinc oxide-eugenol sealer and gutta-percha and separated into three groups before gutta-percha removal (group 1, Gates Glidden burs + K-type hand instrumentation; group 2, K-type reciprocating instrumentation + NSK TEP E16R; group 3, ProTaper rotary instrumentation + NSK NAC E16R). Specimens were CT-scanned before and after filling removal. The mean rate of filling removal was 94.88%. Reciprocating instrumentation was the most effective and manual instrumentation associated with Gates Glidden burs was the least effective technique. Removal rate was significantly different for the three groups according to one-way anova (P = 0.049). The Tukey test showed a significant difference between groups 1 and 2 (P = 0.039) only. CT proved to be a reliable method for assessing root filling removal techniques.
"In the endodontic field, micro-CT has been used to evaluate root canal anatomy (Dowker et al. 1997, Rhodes et al. 1999, Verna & Love 2011), root canal geometry and shapes (Bjorndal et al. 1999, Peters et al. 2001, Hubscher et al. 2003) or to estimate root canal morphology and the spatial details after root canal instrumentation (Peters et al. 2003, Metzger et al. 2010, Markvart et al. 2012). It has also been used to analyse the porosities within root fillings (Jung et al. 2005, Zakizadeh et al. 2008, Hammad et al. 2009, Zogheib et al. 2011), in endodontic sealers (Saleh et al. 2009) or in filling techniques (Epley et al. 2006) and in re-treatment (Huumonen et al. 2006, Barletta et al. 2008) studies. However, no micro-CT studies have been performed to study the voids along the dentine/material interface after root filling procedures. "
[Show abstract][Hide abstract] ABSTRACT: Aim:
To investigate nondestructively the percentage of 3D voids and marginal gaps in a pre-defined interface volume of interest (VOI) within root fillings produced by Thermafil Obturators with either a hydrophobic epoxy-resin-based sealer (AH Plus) or a hydrophilic flowable calcium-silicate sealer [mineral trioxide aggregate (MTA) Flow].
Sixteen single root canals from extracted premolar teeth were prepared with ProTaper rotary instruments, randomly allocated into two groups (n = 8) and filled with size 30 Thermafil Obturators in association with AH Plus or MTA Flow sealers. The filled roots were stored at 37 °C in 5 mL of Hank's balanced salt solution (HBSS) used to represent body fluids and scanned after 7 days and 6 months using a high-resolution micro-CT. From each root, images of 3000 sections were analysed in 3D and binarized using a high-resolution micro-CT (4-μ resolution). The 3D distribution of voids (porosity and marginal gaps) at the gutta-percha-sealer-dentine interface was detected through a threshold grey level and expressed as percentage of the 40-μ-thick pre-defined interface VOI (20 μ of interface dentine and 20 μ of gutta-percha/sealer). A method of analysis based on the root canal segmentation was used, and coronal, middle and apical thirds considered separately. The percentage of 3D void volume was compared statistically using one-way anova (significance for P < 0.05). Environmental Scanning Electron Microscope with Energy Dispersive X-ray (ESEM-EDX) analysis was performed on the surface of both sealers after soaking in HBSS.
Micro-CT detected gaps at the dentine-sealer interface in both groups. Void volumes wider than 10.21 μm(3) with 1.35 μm diameter were detected. Cul-de-sac-type voids (blind pores) and through-and-through voids (continuous pores) were discriminated. The apical thirds had a significantly lower 3D void volume (P < 0.05) than the middle and coronal thirds. The 3D void volume reduced significantly (P < 0.05) over time. ESEM-EDX analysis revealed that MTA Flow sealer created a dense apatite layer after 7 days of immersion in HBSS, whilst only sparse calcium phosphate deposits were detected on AH Plus even after 28 days.
Micro-CT proved to be a powerful nondestructive 3D analysis tool for visualizing the porous internal microstructure of dental/endodontic materials at the interface with dentine. The proportion of voids was least in the apical third of root canals. Voids reduced over time in the presence of simulated body fluid.
International Endodontic Journal 10/2012; 46(3). DOI:10.1111/j.1365-2591.2012.02124.x · 2.97 Impact Factor
"Residual necrotic tissue or bacteria beneath either gutta-percha or sealer can be responsible for periapical inflammation or pain.1 Thus, the main objective of nonsurgical retreatment is to remove all material filling from the root canal and to regain access to the apical foramen.2 The techniques used to remove gutta-percha are varied and included the use of hand or rotary instruments, with or without heat, and solvents and/or ultrasound.3,4 "
[Show abstract][Hide abstract] ABSTRACT: This study was designed to evaluate the fracture resistance of retreated roots using different rotary retreatment systems.
Forty eight freshly extracted human canine teeth with single straight root canals were instrumented sequentially increasing from size 30 to a size 55 using K-files whit a stepback technique. The teeth were randomly divided into three experimental and one control groups of 12 specimens each. The root canals were filled using cold lateral compaction of gutta-percha and AH Plus (Dentsply Detrey, Konstanz, Germany) sealer in experimental groups. Removal of gutta-percha was performed with the following devices and techniques: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), R-Endo (Micro-Mega, Besançon, France), and Mtwo (Sweden & Martina, Padova, Italy) rotary retreatment systems. Control group specimens were only instrumented, not filled or retreated. The specimens were then mounted in copper rings, were filled with a self-curing polymethylmethacrylate resin, and the force required to cause vertical root fracture was measured using a universal testing device. The force of fracture of the roots was recorded and the results in the various groups were compared. Statistical analysis was accomplished by one-way ANOVA and a post hoc Tukey tests.
There were statistically significant differences between the control and experimental groups (P<.05). However, there were no significant differences among the experimental groups.
Based on the results, all rotary retreatment techniques used in this in vitro study produced similar root weakness.
[Show abstract][Hide abstract] ABSTRACT: Despite improvements and advances in materials and methods, root canal treatment is not always suc-cessful. As a result, practitioners are faced with the challenges of managing endodontic failure in every-day clinical practice. Non-surgical retreatment is a widely practised option and offers another chance of salvaging a failing, previously root-treated tooth. Understanding the causes of failure is critical to correcting the inadequacies related to a previously root canal-treated tooth. Persistent intraradicular in-fection is the commonest cause of failure 1,2 . During initial root canal treatment, the detectable presence of residual intraradicular bacteria has a significant effect on outcome 3 ; it was reported that after five years the success rate dropped from 94% to 68% 4 . Other causes of failure include extraradicular infec-tion, cystic lesions, extruded root canal filling or other exogenous materials causing a foreign body reaction, cholesterol crystals and scar tissue formation 5,6 . From a microbiological perspective, a distinc-tion has to be made between teeth that are tech-nically well root canal-treated and those that are not, as this will have a bearing on the retreatment approach. Teeth with inadequately instrumented and poorly obturated root canals may be associated with larger periapical radiolucencies. Those that have not been properly chemomechanically debrided tend to have a similar microbiota to untreated root ca-nals 3,7 . On the other hand, well-treated cases as-sociated with continuing periapical pathosis have a different microbiological balance, both qualitatively and quantitatively. In these cases, there are fewer microbial species and the microbiota is dominated by facultative rather than strict anaerobes 3,7,8 . A fundamental step in non-surgical retreatment is the removal of the existing root filling material to permit radicular access. Different root filling materials require different techniques of removal. The endodontic literature is littered with studies exploring the relative merits of one technique of removal over another. In this review, the focus is on the experimental models and techniques employed to investigate the removal of root filling materials during non-surgical retreatment. The correlation and clinical relevance to everyday endodontic practice is also discussed.
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