A practitioner's guide to gutta-percha removal during endodontic retreatment

Comparing the softening effect of three gutta-percha solvents on different types of gutta-percha with different application durations

Introduction

During non-surgical endodontic retreatment, gutta-percha (GP) solvents are indispensable in difficult cases when used with mechanical removal, however studies comparing their efficacy against different types of GP are limited. The purpose of this study was to investigate the softening effect of three solvents on the conventional (CGP), cross-linked carrier-based (CLGP), and thermoplasticized (TGP) and compare the effect of time on the softening effect of the solvents.

Methods

Tested GP were embedded in cuboidal blocks of stone with their upper surfaces exposed (1 mm diameter). Three commercial GP solvents based on D-Limonene (DL), Eucalyptol oil (EO), and orange oil (OO) were added to the exposed GP before an indenter (weight = 1Kg) was applied. Using a digital camera, the indentation depth was measured (mm) directly after applying the solvent and indenter (T = 0), and after 1, 2, and 3 min of application (T = 1,2,3). The means of indentation depth were calculated and compared using a two-way analysis of variance and Tukey's post-hoc test to assess the effect of the types of solvent, GP for each application duration, and Friedman's test to evaluate the effect of application duration on the softening effect of solvents.

Results

The type of GP (F = 261.43, p < 0.001), type of solvent (F = 3.57, p = 0.015), and application duration (F = 53.088, p < 0.001) were all found to significantly affect GP softening. DL exhibited the highest and only significant effect on CGP after 1 min (p < 0.05), while OO had the only significant effect against CLGP when applied for at least 2 min (p < 0.05). Both OO and EO had significant softening effects on TGP instantly or after 1 min of application, respectively.

Conclusions

The results of this study revealed that the softening effect of GP solvents varies depending on their type, their application duration, and the type of GP.

Influence of Filling Material Remnants on the Diffusion of Hydroxyl Ions in Endodontically Retreated Teeth: An Ex Vivo Study

AIM

To assess the influence of remnants of filling material on hydroxyl ion diffusion from calcium hydroxide (CH) paste, measured by the pH value, in retreated teeth.

MATERIALS AND METHODS

A total of 120 single-rooted extracted teeth were prepared up to a size 35 hand file and filled. For retreatment, the specimens were divided into four groups (n = 20): ProTaper Universal Retreatment (PUR), PUR with additional instrumentation (PURA), Mtwo Retreatment (MTWR), and MTWR with additional instrumentation (MTWRA). Negative (NEG) and positive (POS) control groups were composed by 20 specimens each one. The specimens, except NEG, were filled with CH paste. The retreated groups were scanned using cone-beam computed tomography (CBCT) for analysis of filling remnants. The pH assessment was performed at the baseline, after seven, 21, 45, and 60 days of immersion in saline. Data were analyzed using Shapiro-Wilk and Levene's test, followed by a two-way analysis of variance (ANOVA) and Tukey's test.

RESULTS

Additional instrumentation (PURA and MTWRA) were superior regarding removal of the filling material (p <0.05); however, without significant difference (p >0.05). The mean pH value in all groups increased (p <0.05). After 60 days, no statistical difference was observed among POS and PURA; and MTWR and MTWRA. There was less diffusion of hydroxyl ions when the amount of remnants was greater than 59%.

CONCLUSION

Additional instrumentation improved the ability to remove filling material in both systems. All groups presented increasing pH; however, the higher the amount of remnants, the lower the diffusion of hydroxyl ions.

CLINICAL SIGNIFICANCE

The amount of remnants allows less diffusion of calcium hydroxyl ions. Thus, additional instrumentation improves the ability to remove these materials.

The Efficacy of Two Novel Retreatment Systems in the Removal of Root Canal Obturating Materials (An In vitro Study)

BACKGROUND: The complete removal of root filling material is one of the main goals of non-surgical endodontic retreatment. Thus, the development of new techniques and instruments aiming to promote this task presents clinical significance. AIM: The purpose of the study was to assess the amount of residual root canal filling materials (gutta-percha/sealer) after using two different endodontic retreatment systems and ultrasonic tip. METHODS: Forty-five mandibular premolar teeth were mechanically instrumented and obturated. Retreatment was performed using two different Endostar RE (Group 2), Rogin retreatment system (Group 3), and ultrasonic tip (Group 1). Roots were separated buccolingually into two halves. A digital camera connected to the stereomicroscope captured images to each half. Image-J software was used to evaluate and measure the areas with remaining filling material in each third (cervical, middle, and apical). RESULTS: Data analysis revealed significant differences between the groups in the coronal, middle, and apical thirds (p < 0.05). The ultrasonic retreatment tips (G1) were significantly more efficient in removing the gutta-percha and sealers compared to the Rogin (G3) and Endostar (G2) retreatment endodontic kits. CONCLUSIONS: All the file systems left some filling material in the canals. Ultrasonic retreatment tip had maximum efficacy for the removal of filling materials in comparison with the retreatment file systems under investigation.

Efficacy of reciprocating instruments and final irrigant activation protocols on retreatment of mesiobuccal roots of maxillary molars: a micro-CT analysis

Objectives

This study evaluated the efficacy of 3 reciprocating systems and the effects of 2 instruments for irrigant activation on filling material removal.

Materials and Methods

Forty mesiobuccal roots of maxillary molars were prepared up to size 25.06 and obturated. Micro-computed tomography (micro-CT) examination #1 was performed. Teeth were then divided into 4 groups (n = 10), according to the retreatment protocol: (1) manual, (2) Reciproc Blue, (3) WaveOne Gold, and (4) X1 Blue. Micro-CT examinations #2 and #3 were performed after filling removal and repreparation, respectively. Next, all teeth were divided into 2 new groups (n = 20) according to the irrigant activation protocol: XP Clean (XP Clean size 25.02) and Flatsonic (Flatsonic ultrasonic tip). Micro-CT examination #4 was performed after irrigant activation. Statistical analysis was performed with a significance level set at 5%.

Results

WaveOne Gold removed a significantly greater amount of filling material than the manual group (p < 0.05). The time to reach the WL was similar for all reciprocating systems (p > 0.05). X1 Blue was faster than the manual group (p < 0.05). Only manual group improved the filling material removal after the repreparation stage (p < 0.05). Both activation protocols significantly improved the filling material removal (p < 0.05), without differences between them (p > 0.05).

Conclusions

None of the tested instruments completely removed the filling material. X1 Blue size 25.06 reached the working length in the shortest time. XP Clean and Flatsonic improved the filling material removal.

A comparative study of the effects of gutta-percha solvents on human osteoblasts and murine fibroblasts

We aimed to investigate the in vitro physiologic effects of xylene, chloroform, orange oil and eucalyptus oil solvents for dissolving gutta-percha on L929 and HOB cell lines; 2.5 and 10 μL mL^-1 of these solvents were tested for 24, 48 and 72 h. Gutta-percha solvents inhibited the proliferation rate of fibroblasts in a dose- and time-dependent manner; however, no inhibition was detected in HOB (evaluated using MTT assay). None of the solvents induced apoptosis/necrosis in HOB cells at ≤2.5 μL mL^-1 concentration in contrast to L929 (determined using acridine orange/ethidium bromide dual staining). Each solvent tested reduced the migration rate of both L929 and HOB cell lines in a dose-dependent manner (evaluated using a scratch assay). Gutta-percha solvents can damage fibroblast-rich tissues. Osteoblasts seemed to be more resistant to the tested solvents, and excessive extrusion of solvents from the root canal may also damage the periradicular tissues and reduce the ability to repair.

The use of solvents for gutta-percha dissolution/removal during endodontic retreatments: A scoping review

This scoping review study aimed to map the evidence about solvents' use for gutta-percha dissolution and removal during endodontic retreatments. The study protocol followed the Joanna Briggs Institute guidelines, available online (https://osf.io/5vy8n/). Reporting was based on PRISMA Extension for Scoping Reviews. We selected dentistry studies that considered the effectiveness of solvents in gutta-percha dissolution in endodontic retreatments and compared their performance to the use of instrumentation techniques without solvents. The search and study screening were performed in PubMed and Scopus databases by two independent researchers. A descriptive analysis considered the study design, method/technique used for obturation, method/technique used for instrumentation during retreatment, solvent solutions tested, exposure time, and main findings. A total of 41 studies were included. Despite that, most studies suggested that solvents' use may complicate root canal cleanliness, regardless of the type of instrumentation used, and facilitate the presence of gutta-percha remnants in the root surface. Thus, the use of solvents should be avoided and its use should only be considered if the previous working length was not possible to access without it. Despite that, high heterogeneity was observed, further studies are still encouraged comparing the performance and effects of different solvents in different clinical scenarios.

Endodontic Retreatment Using a Single Instrument from four Nickel-Titanium Systems - A Micro-CT Study

Abstract This study evaluated the efficiency of using a single instrument from three different rotary multi-file systems and compared them with that of a reciprocating single-file for endodontic retreatment by means of micro-CT. Sixty extracted canines were prepared using a size F2 ProTaper Universal file and obturated. After 30 days of storage at 37ºC and 100% humidity, the teeth were randomly divided into four groups (n=15) based on the type of instrument used to retreatment: ProTaper Next (PTN), ProTaper Gold (PTG), TRUShape 3D (TS), and WaveOne (WO). The canals were retreated using only the size 40 instrument from each system according to the manufacturer’s recommendations for torque and speed. The time required to remove the filling material was recorded in seconds. The amount of initial and residual filling material and the quantity of dentin removed were assessed by means of micro-CT. Data were statistically analyzed (ANOVA and Kruskal-Wallis) at a 5% significance level. TS instruments required the highest (p<0.05) amount of time (mean, 384.80 ±144.92) compared with the WO (229.67±68.16) and PTG (248.67±64.22) and not so different from PTN instruments (327.67±133.3). No differences in the amount of dentin removed, initial and residual filling volume, and percentages of filling material were observed among the groups. The use of a single rotary instrument from the PTG, TS, and PTN systems was as effective as that of the single-file reciprocating WO system. However, none of the instruments was able to remove the filling materials completely.

Terpenoids as Potential Geroprotectors

Terpenes and terpenoids are the largest groups of plant secondary metabolites. However, unlike polyphenols, they are rarely associated with geroprotective properties. Here we evaluated the conformity of the biological effects of terpenoids with the criteria of geroprotectors, including primary criteria (lifespan-extending effects in model organisms, improvement of aging biomarkers, low toxicity, minimal adverse effects, improvement of the quality of life) and secondary criteria (evolutionarily conserved mechanisms of action, reproducibility of the effects on different models, prevention of age-associated diseases, increasing of stress-resistance). The number of substances that demonstrate the greatest compliance with both primary and secondary criteria of geroprotectors were found among different classes of terpenoids. Thus, terpenoids are an underestimated source of potential geroprotectors that can effectively influence the mechanisms of aging and age-related diseases.