A comparative study of lateral condensation, heat-softened gutta-percha, and a modified master cone heat-softened backfilling technique

A critical analysis of research methods and experimental models to study root canal fillings

Canal filling materials and techniques have been one of the most studied topics in Endodontics. A simple search using the mesh term "root canal filling" in PubMed revealed more than 11,000 articles, an impressive number that is much higher than "root canal disinfection" (5,544 articles) or even the popular "root canal preparation" (8,527 articles). The overriding importance attributed to root filling procedures is not merely intuitive. It derived from the appealing relevance given by the appearance of the white lines in common radiographs grounded on retrospective clinical data that had identified the quality of a root filling as one of the major causes of treatment failure (lack of healing). Since the publication of the Washington study, impressive efforts have been made for the release of new materials and techniques, as well as, for the development of a plethora of laboratory methods to assess the quality of root filling procedures. This narrative review aims to address and discuss the most relevant laboratory methods to assess the root canal filling. Since filling quality improvements have not translated into higher success rates, as reported in longitudinal clinical studies, more than to deliver a simple methodology-based review, this paper aims to present an in-depth critical view on the assessment of laboratory methods used to study the filling materials and techniques. Recent data indicate that the long-term dimensional stability/degradation over time of endodontic sealers plays a central role in the treatment outcome. In this context, laboratory methods should be developed focusing on predicting, at least to some degree, the long-term clinical behaviour of root canal fillings, rather than simply ranking different materials or techniques.

What Are the Chances of Resilon to Dominate the Market Filling Materials for Endodontics?

This paper is a literature review with additional virtual analyses of the authors’ own experimental research results. Knowledge from various areas was synergistically combined, appropriately for concurrent engineering, presenting several possible methodological approaches used in research, optimizing the selection of engineering materials and the conditions of their application with particular application in endodontics. Particular attention was paid to the theoretical aspects of filling material strengths, weaknesses, opportunities, and threats SWOT analysis. Attention was paid to the original concepts of Sustainable Dentistry Development in conjunction with Dentistry 4.0, which includes endodontics as an important element. The dentists’ actions, among others, in conservative dentistry, along with endodontics, requires close cooperation with engineers and the enginering sciences. Methods of root canal preparation were described, together with selected tools, including those made of nitinol. Principles concerning the process of cleaning and shaping the pulp complex are presented. The importance of obturation methods, including the Thermo-Hydraulic-Condensation THC technique, and the selection of filling materials with the necessary sealants for the success of endodontic treatment are discussed. The experimental studies were carried out in vitro on human teeth removed for medical reasons, except for caries, for which two groups of 16 teeth were separated. After the root canal was prepared, it was filled with studs and pellets of a filling material based on polyester materials, which has gained the common trade name of resilon or, less frequently, RealSeal (SybronEndo) with an epiphany sealant. The teeth for the first group were obturated by cold lateral condensation. In the second case the obturation was performed using the Thermo-Hydraulic-Condensation technique using System B and Obtura III. The experimental leakage testing was done using a scanning electron microscope SEM and a light stereoscopic microscope LSM, as typical research tools used in materialography. The research results, in a confrontation with the data taken from the literature studies, do not indicate the domination of resilon in endodontics.

Is Gutta-Percha Still the “Gold Standard” among Filling Materials in Endodontic Treatment?

The paper is an extensive monographic review of the literature, and also uses the results of the authors’ own experimental research illustrating the noticed developmental tendencies of the filling material based on gutta-percha. The whole body of literature proves the correctness of the research thesis that this material is the best currently that can be used in endodontics. Caries is one of the most common global infectious diseases. Since the dawn of humankind, the consequence of the disease has been the loss of dentition over time through dental extractions. Both tooth caries and tooth loss cause numerous complications and systemic diseases, which have a serious impact on insurance systems and on the well-being, quality, and length of human life. Endodontic treatment, which has been developing since 1836, is an alternative to tooth extraction. Based on an extensive literature review, the methodology of qualifying patients for endodontic treatment was analyzed. The importance of selecting filling material and techniques for the development and obturation of the root canal during endodontic treatment was described. Particular attention was paid to the materials science aspects and the sequence of phase transformations and precipitation processes, as well as the need to ensure the stoichiometric chemical composition of Ni–Ti alloys, and the vacuum metallurgical processes and material processing technologies for the effects of shape memory and superelasticity, which determine the suitability of tools made of this alloy for endodontic purposes. The phenomena accompanying the sterilization of such tools, limiting the relatively small number of times of their use, play an important role. The methods of root canal preparation and obturation methods through cold side condensation and thermoplastic methods, including the most modern of them, the thermo-hydraulic condensation (THC) technique, were analyzed. An important element of the research hypothesis was to prove the assumption that to optimize the technology of development and obturation of root canals, tests of filling effectiveness are identified by the density and size of the gaps between the root canal wall, and the filling methods used and devices appropriate for material research, using mainly microscopy such as light stereoscopic (LSM) and scanning electron (SEM). The most beneficial preparations were obtained by making a longitudinal breakthrough of 48 natural human teeth, extracted for medical reasons, different from caries, with compliance with all ethical principles in this field. The teeth were prepared using various methods and filled with multiple obturation techniques, using a virtual selection of experimental variants. The breakthroughs were made in liquid nitrogen after a one-sided incision with a narrow gap created by a diamond disc using a materialographic cutter. The best effectiveness of the root canal filling was ensured by the technology of preparing the root canals with K3 rotary nitinol tools and filling the teeth with the THC thermoplastic method using the System B and Obtura III devices with studs and pellets of filling material based on gutta-percha after covering the root canal walls with a thin layer of AH Plus sealant. In this way, the research thesis was confirmed.

Evaluation of different root canal filling techniques in severely curved canals by micro-computed tomography

AIM

To fill the severely curved root canals with different filling techniques and to compare these techniques using micro-computed tomography (micro-CT).

MATERIALS AND METHODS

Sixty extracted mandibular first molars (degree of root canal curvature >25°) were selected. All samples were divided into four groups and filled with one of the following techniques: lateral condensation, single-cone, continuous-wave obturation, and core carrier. After they were scanned by micro-CT, the total area, filled area and void area of the root canal were calculated. The Mann-Whitney U and Kruskal-Wallis tests were used for statistical analysis (p < 0.05).

RESULTS

It was shown that significantly more filling material was used in the lateral condensation and core carrier technique groups at 2 and 5 mm than in the single-cone and continuous-wave obturation technique groups (p < 0.05). It was observed no statistically significant difference at 8 mm (p > 0.05).

CONCLUSION

No technique could completely fill in root canal. Regarding the coronal part, all techniques can be used for more effective filling as long as a good condensation is achieved. The use of a plugger with an optimal size according to the localisation of root canal curvature and the choice of a heat-resistant root canal sealer affects the success of the treatment in the thermoplastic techniques.

Micro-computed tomography evaluation of the prevalence and morphological features of apical bifurcations

Background/purpose

Apical bifurcation, as a common variation in root canal morphology, has great clinical significance for root canal treatment. The aim of this study was to investigate the morphological characteristics of the apical bifurcated canal in Chinese teeth based on a large sample size using micro-CT.

Materials and methods

One thousand and four hundred Chinese permanent teeth were scanned by using micro-CT with the resolution of 15 μm. The number of apical bifurcations was calculated and the vertical distance of apical bifurcations was recorded. The diameter and angles of the apical bifurcated canals were further measured using the centerline algorithm method.

Results

Ninety-two apical bifurcations were detected in 15 anterior teeth, 27 premolars, and 46 M. The median vertical distance of apical bifurcations was 1.1 mm from the apex (ranging from 0.3 to 3.5 mm). Ninety-eight-point nine percent of the apical bifurcations were located less than 3 mm from the apex. The smaller angle of apical bifurcated canals with the main canal was 20.4°. The larger angle of the apical bifurcated canals with the main canal was 32.9°. The median diameter of apical bifurcated canals was 195.0 μm.

Conclusion

A high prevalence of apical bifurcation can be detected in the human permanent teeth, especially in posterior teeth. Most apical bifurcations locate within the apical 3 mm with a diameter more than 200 μm.

Microcomputed tomographic evaluation of techniques for warm gutta-percha obturation

Transparent epoxy resin root canal models were used to evaluate vertical condensation techniques for obturating lateral canals. The root canal model was configured with a straight main root canal and four right-angled lateral canals at 1.0 and 3.0 mm from the apex. Root canal obturation was performed with Thermafil, Obtura II, or NT condenser. Obturation volume in lateral canals was measured by three-dimensional microcomputed tomography, and one-way analysis of variance was used to analyze differences between groups. Lateral canals at 1.0 and 3.0 mm were uniformly filled by all obturation methods. Among the three obturation methods, Thermafil resulted in the highest obturation volumes for all lateral canals.

A Prospective Randomized Comparative Study of Cold Lateral Condensation Versus Core/Gutta-percha in Teeth with Periapical Lesions

INTRODUCTION

The aim of this study was to compare the outcome of root canal treatment using either Thermafil (TF; Dentsply Maillefer, Ballaigues, Switzerland) or the cold lateral condensation (CLC) obturation technique in teeth with periapical lesions and to investigate the influence on postoperative pain and treatment outcomes.

METHODS

After standardized root canal preparation technique, 112 teeth were obturated with either the TF or the CLC technique during 2 sessions by single operator. Postoperative pain, obturation length, and treatment outcomes were recorded. The teeth were reviewed clinically and radiographically for 2 years.

RESULTS

Although there were no significant differences between the techniques in the incidence of postoperative pain at 24 hours (P > .05), the incidence of pain was significantly higher in the TF group than in the CLC group at 48 hours (P < .05). During the 2-year follow-up period, there was no statistically significant difference in the success rate of the teeth treated with TF (96.4%) in comparison with those treated with CLC (98.2%) (P > .05).

CONCLUSIONS

In this study, the outcome of the root canal treatment of teeth using the TF and CLC techniques revealed that these techniques are useful for root canal obturation.

Endodontic and clinical considerations in the management of variable anatomy in mandibular premolars: a literature review

Mandibular premolars are known to have numerous anatomic variations of their roots and root canals, which are a challenge to treat endodontically. The paper reviews literature to detail the various clinically relevant anatomic considerations with detailed techniques and methods to successfully manage these anomalies. An emphasis and detailed description of every step of treatment including preoperative diagnosis, intraoperative identification and management, and surgical endodontic considerations for the successful management of these complex cases have been included.

Assessment of the sealing abilities of several root canal sealers and filling methods

OBJECTIVE

To evaluate the sealing abilities of two root canal sealers (epoxy resin-based AH Plus(®) and polydimethylsiloxane-based GuttaFlow(®)) and of five root filling techniques (lateral condensation, matched taper single gutta-percha point, laterally condensed-matched taper gutta-percha point, Thermafil(®) and continuous wave of condensation), using a bacterial leakage model.

MATERIALS AND METHODS

One hundred and seventy-four single-rooted human teeth were randomly divided into 10 test groups (n = 15) and two control groups (n = 12). The roots that were filled with the test material, using the different root filling techniques, were mounted in a two-chamber bacterial leakage model and Enterococcus faecalis was added to the upper chambers. The lower chambers of all of the specimens were checked every day during the test period (100 days). The day of turbidity was recorded for each sample. Statistical analysis was performed using the Kaplan-Meier and log-rank tests.

RESULTS

There was no significant difference between the epoxy resin-based and the polydimethylsiloxane-based sealers, irrespective of the filling techniques used (p > 0.05). The continuous wave of condensation technique was found to be superior to the other techniques (p < 0.05). The difference between the other groups was insignificant (p > 0.05).

CONCLUSIONS

AH Plus and GuttaFlow sealers showed similar levels of sealing ability. The continuous wave of condensation technique had the best sealing capability when compared to the other techniques.

Retrieval of extensive gutta-percha extruded into the maxillary sinus: use of 3-dimensional cone-beam computed tomography

INTRODUCTION

Close proximity of the maxillary sinus to the roots of maxillary teeth can predispose to the inadvertent deposition of endodontic products into the maxillary sinus. One such material is thermoplasticized injectable gutta-percha, which has gained popularity of late. As a consequence of overfilling, some patients warrant surgical retrieval.

METHODS

A case report of extreme overextension of gutta-percha within the maxillary sinus after endodontic retreatment on tooth #14 was provided. The distobuccal and palatal canals had been obturated with gutta-percha master cones and backfilled with thermoplasticized injectable warm gutta-percha. The mesiobuccal canal had only been filled with thermoplasticized injectable warm gutta-percha, the origin of the extrusion. Imagery with 3-dimensional cone-beam computed tomography was performed for localization of the gutta-percha.

RESULTS

The patient underwent a Caldwell-Luc approach for removal of the extruded material. The gutta-percha was successfully removed intact, and the patient had an unremarkable postoperative course. However, the patient continues to have mild tenderness in the sinus region.

CONCLUSIONS

The featured case exemplified the consequence of overinstrumentation and ensuing inadequate apical stop. In these situations, the obturation of a maxillary tooth with thermoplasticized injectable gutta-percha, without master cones, can potentially result in overfilling and deposition into the antrum. Use of 3-dimensional cone-beam computed tomography could enhance endodontic diagnosis, serve as an aid for visualization of foreign materials within the sinus and contiguous soft tissue structures, and improve clinical outcome.

Postoperative pain after one-visit root-canal treatment on teeth with vital pulps: comparison of three different obturation techniques

OBJECTIVES

To investigate and compare postoperative pain after one-visit root canal treatment (RCT) on teeth with vital pulps using three different obturation techniques.

STUDY DESIGN

Two hundred and four patients (105 men and 99 women) aged 12 to 77 years were randomly assigned into three treatments groups: cold lateral compaction of gutta-percha (LC), Thermafil technique (TT), and Backfill - Thermafil obturation technique (BT). Postoperative pain was recorded on a visual analogue scale (VAS) of 0 - 10 after 2 and 6 hours, and 1, 2, 3, 4, 5, 6 and 7 days. Data were statistically analyzed using multivariate logistic regression analysis.

RESULTS

In the total sample, 87% of patients experienced discomfort or pain in some moment between RCT and the seventh day. The discomfort experienced was weak, light, moderate and intense in 6%, 44%, 20% and 6% of the cases, respectively. Mean pain levels were 0.4 ± 0.4, 0.4 ± 0.3, and 1.4 ± 0.7 in LC, BT, and TT groups, respectively. Patients of TT group experienced a significantly higher mean pain level compared to other two groups (p < 0.0001). In TT group, all patients felt some level of pain at six hours after RCT.

CONCLUSIONS

Postoperative pain was significantly associated with the obturation technique used during root canal treatment. Patients whose teeth were filled with Thermafil obturators (TT technique) showed significantly higher levels of discomfort than patients whose teeth were filled using any of the other two techniques.

Comparative analysis of carrier-based obturation and lateral compaction: a retrospective clinical outcomes study

The purpose of this retrospective study was to compare the outcome of primary endodontic treatment using a standardized cleaning and shaping technique and obturation with either lateral compaction or carrier-based obturation. Patients received primary endodontic treatment in the predoctoral dental clinic using a standardized cleaning and shaping protocol. All root canals were obturated using AH Plus(TM) sealer with lateral compaction of gutta-percha (LC) or carrier-based obturation (CBO). A total of 205 cases met the inclusion criteria. 71 teeth in 60 patients were recalled after 2 years and evaluated both clinically and radiographically by two independent examiners. Success was defined as a lack of clinical symptoms and a normal periodontal ligament space or reduction in size of a previously existing periapical radiolucency. Chi-square and logistic regression were used for statistical analysis with a significance level of P < 0.05. There was no difference in success rates between cases obturated with LC or CBO (P = 0.802); overall success rate was 83%. Molars had a significantly lower success rate (53%) than premolar and anterior teeth (89%) (P = 0.005), irrespective of the obturation technique used. When a standardized cleaning and shaping protocol was used by predoctoral dental students in a controlled university setting, there was no difference in success rates between cases obturated with LC or CBO.

Root Canal Treatment Using Thermoplasticized Carrier Condensation Technique

BACKGROUND

The management of pulpally and apically infected teeth has evolved into a modality of conservation with predictable degree of success. Root canal treatment often requires protracted chairside time. A new technique involving placement of thermoplasticized core carrier obturators was compared with conventional lateral condensation technique.

METHODS

A prospective, comparative, in-vivo cohort study was carried out on randomly selected 100 patients visiting a tertiary care centre from July 2005 to July 2007, for primary, non-surgical conservative management of teeth requiring root canal treatment. Two groups of fifty cases each were managed with lateral condensation and thermoplasticized core carrier obturation techniques. Outcome variables were rate of obturation and failure rates as assessed by clinical and radiological evaluation.

RESULT

The time taken in case of lateral condensation of maxillary central incisor was 17.30 ± 3.373 minutes and 28.07 ± 2.586 minutes in case of mandibular molar. In the thermoplasticized carrier condensation technique, for the central incisors it took 13.00 ± 1.376 minutes and 21.07 ± 2.463 minutes for mandibular molars. The mean rank value for time taken for obturation as per Mann Whitney U test (p < 0.01) were 27.88 for maxillary incisor and 44.73 for mandibular molar in the lateral condensation technique and 13.13 and 16.27 respectively for thermoplasticized gutta percha carrier condensation. The values were statistically significant. With 16% and 14% cases having unsatisfactory filling as evaluated by post filling radiograph, Chi square test two tailed p value was 0.6836 and there was no statistically significant difference between the two groups. An absolute failure rate of 10% was seen in lateral condensation group and 6% in thermo-plasticized carrier condensation group. Fisher exact 2-tailed p value was 0.71 and the difference in failure rate was not statistically significant.

CONCLUSION

Root canal obturation by thermoplasticized core carrier condensation technique is an effective alternative to conventional lateral condensation technique in terms of quick and successful outcome.

Technique acquisition in the use of two thermoplasticized root filling methods by inexperienced dental students: a microcomputed tomography analysis

INTRODUCTION

Limited endodontic experiences in dental schools suggest the need for easy-to-learn techniques. Therefore, two simplified root filling methods were assessed for adequacy and expediency when performed by inexperienced students.

METHODS

Eight students were trained (45-minute lecture and 90-minute practice) in use of ProTaper Obturators (PTO) and System-B/Calamus (SBC). They subsequently filled the root canals in two extracted, single-rooted teeth per method (n = 32). Canals were preshaped and prefitted with obturators and master cones. The volume of root-filling voids determined by microcomputed tomography imaging in 1-mm increments, time to complete fillings, and students' responses in questionnaires were analyzed (independent-sample t test and Mann-Whitney U test).

RESULTS

PTO had a significantly smaller void volume in the apical 6 mm of canals (P < 0.001), required significantly shorter time (P < 0.001), and was perceived as easier to learn and use but less likely to be favored after graduation than SBC.

CONCLUSION

These results suggested that the PTO root filling method was particularly suitable for teaching when endodontic experiences available for students are limited.

Evaluation of the apical infiltration after root canal disruption and obturation

The aim of this study was to evaluate two root canal filling techniques used in teeth that had their apical foramen disrupted and compare the apical infiltration with an ideal clinical situation. Twenty-seven freshly extracted single-rooted teeth were selected and radiographed to confirm the existence of a single and straight root canal. The crowns were removed at a mean distance of 11 mm from the apex. The teeth had the root canals instrumented and were randomly assigned to 3 groups (n=9): ND group - root canals were filled using the lateral compaction technique and no disruption was performed; DRF group - the apical constriction was disrupted by advancing a #40 K-file 1 mm beyond the original working length, the canals were reinstrumented to create an apical ledge at 1 mm from the apical foramen and were obturated with a master gutta-percha cone with same size as the last file used for reinstrumentation; DF group - the teeth had the apical constriction disrupted and the canals were obturated with a master gutta-percha cone that fit at 1 mm from the apex. The teeth were submitted to dye leakage test with Rhodamine B for 7 days, using vaccum on the initial 5 min. The teeth were sectioned longitudinally and the leakage was measured in a linear fashion from apex to crown. There was no statistically significant difference (p>0.05) between the groups that had the apical foramen disrupted (DF, DRF), but significant difference was found between the disrupted groups and the non-disrupted one (p<0.01). In conclusion, none of the evaluated techniques was able to prevent apical infiltration, so working length so the working length determination has to be established and maintained carefully.

A l2-month longitudinal in vitro leakage study on a new silicon-based root canal filling material (Gutta-Flow)

OBJECTIVE

This study was performed to determine in vitro the short- and long-term sealing ability of a recently developed silicon-based root canal filling material (Gutta-Flow).

STUDY DESIGN

Sixty human upper central incisors were divided into 3 groups (n = 20). The root canals were instrumented and obturated with laterally compacted gutta-percha and AH26 sealer (group 1), continuous-wave thermal compaction (System B technique) and AH26 sealer (group 2), and Gutta-Flow technique (group 3). Leakage along entire root canal fillings was measured by the movement of an air bubble in a micropipette connected to the experimental root using a fluid-transport model. Short-term leakage measurements were carried out for 3 hours after 24 hours of equilibrium establishment. Leakage was measured again and at 3, 6, and 12 months after the initial measurement.

RESULTS

At the 3-hour measurement, no significant differences were found among the 3 experimental groups. Long-term leakage measurements showed that at 3 and 6 months no significant differences were existed between Gutta-Flow and the other 2 techniques. However, at 12 months, root canal fillings with Gutta-Flow leaked significantly less than fillings of lateral compaction and System B technique.

CONCLUSIONS

Gutta-Flow technique showed a similar sealing ability to either lateral compaction or System B technique. This comparison improved significantly over time. These findings may be related to the possible expanding capacity of the material and the partial dissolution of the sealer over time in the other 2 groups.

Ex vivo comparison of digital images with conventional radiographs for detection of simulated voids in root canal filling material

AIM

To compare the diagnostic potential of direct digital images with conventional radiographs for the detection of simulated root canal voids.

METHODOLOGY

The root canals of 80 extracted maxillary incisors with straight root canals were prepared and filled and the specimens divided into two groups: (i) a group of 40 teeth without voids; and, (ii) a group of 40 teeth with voids created in the root filling. Each root was imaged using the paralleling technique with a CCD-based digital system and F-speed film. Totally, there were 240 images: conventional radiographs (n = 80), digital images (n = 80) and digital zoomed images at 2x magnification (n = 80). These were interpreted for voids by a radiologist (without prior knowledge of the distribution of the voids). The reliability of the radiologist was confirmed using Cohen's Kappa Statistic, with the kappa value found to be >0.08. The sensitivity, specificity and predictive values were calculated. The differences in sensitivity and specificity between the imaging systems were then assessed using the Exact McNemar significance probability at the 95% significance level.

RESULTS

The sensitivities (95% CI) of conventional radiographs, digital images and zoomed images were 0.68 (0.57-0.78), 0.83 (0.74-0.91) and 0.80 (0.71-0.89), respectively. The specificities of the conventional radiographs, digital and zoomed images were 0.80 (0.71-0.89), 0.83 (0.74-0.91) and 0.83 (0.74-0.91), respectively. The positive predictive values (95% CI) were 0.77 (0.68-0.86), 0.83 (0.74-0.91) and 0.82 (0.74-0.90), respectively. The negative predictive values (95% CI) were 0.71 (0.61-0.81), 0.83 (0.74-0.91) and 0.80 (0.72-0.89), respectively. There were no significant differences between the sensitivity and specificity of digital images and conventional radiographs, and of digital images and zoomed images during the detection of voids in root fillings (P > 0.05).

CONCLUSIONS

Under the conditions of this laboratory study, the diagnostic performance of digital images and conventional radiographs, and between the digital images and digital zoomed images for simulated void detection in root fillings were not significantly different.