Root Surface Temperature Rises in Vitro During Root Canal Obturation With Thermoplasticized Gutta-Percha on a Carrier or by Injection

In vitro evaluation of temperature change on the root surface after the removal of root canal filling

This study aimed to compare the temperature changes occurring on the root surfaces after the removal of root canal filling with two different root canal sealers by two different reciprocating files. Sixty extracted teeth with a single root and canal were used in this study. After chemomechanical preparation, the root canals in the experimental groups were filled with gutta-percha and AH Plus or CeraSeal, while those of the control groups were filled with gutta-percha only. Resiproc or WaveOne Gold were used for the removal of the root canal filling. Temperature changes in the middle and apical third of the root surface were recorded by a thermal camera at different time intervals. Among the groups using the same sealer, the temperature rise observed on the root surface at the end of 90 s in the Resiproc groups was found to be significantly higher than that of the WaveOne Gold groups.

External Root Surface Temperature Control with 1,1,1,2-Tetrafluoroethane Intracanal Cryotherapy during Thermoplastic Obturation: An In Vitro Study

AIM

The aim of this in vitro study was to determine the effectiveness of 1,1,1,2-tetrafluoroethane (TFE) intracanal cryotherapy for external root surface temperature control during thermoplastic obturation.

MATERIALS AND METHODS

Thirty extracted adult single-rooted mandibular incisors were selected for this study. Endodontic shaping was performed until size X3 Protaper Next Rotary endodontic file. The teeth were divided into three groups: Group I-Control group wherein conventional irrigation was done using physiologic saline stored at room temperature, Group II-Irrigational Cryotherapy group using physiologic saline at 2.5°C, and Group III-Intracanal TFE cryotherapy group with intracanal refrigerant TFE application. Temperatures were recorded in the apical 3 mm before and after completion of each intervention and post thermoplastic obturation using a noncontact digital laser infrared thermometer.

RESULTS

Intracanal cryotherapy with TFE resulted in a mean decrease of 9.27°C compared with conventional irrigation that exhibited in a mean decrease of 2.13°C. Also, in intracanal cryotherapy group with TFE application, compared with the baseline (24.50°C), no significant differences were observed post obturation (24.61°C) with high-temperature-injectable gutta percha technique indicating good control of temperature rise on the external root surface.

CONCLUSION

Intracanal cryotherapy with refrigerant TFE was highly effective in controlling temperature rise on the external root surface during injectable thermoplastic obturation technique.

CLINICAL SIGNIFICANCE

Minimizing deleterious effects due to high temperatures generated during the thermoplastic obturation is critical. Clinically feasible measures to reduce the transmission of heat generated during thermoplastic obturation have been searched since long. In this regard, intracanal cryotherapy with TFE can be effectively used to control the rise of temperature on the external root surface when employing thermoplastic obturation technique.

Thermal and volumetric assessment of endodontic filling techniques using infrared thermography and micro-CT

PURPOSE

To assess root temperature during filling techniques and quantify the volume of endodontic filling materials using infrared thermography (IT) and micro-computed tomography (micro-CT).

METHODS

Ninety premolars were divided into three groups: lateral condensation (LC), single cone (SC) and thermomechanical compaction (TMC). For thermal analysis, 45 teeth were assessed using a FLIR T650sc IT camera during filling techniques and 45 teeth were scanned using a Nikon micro-CT to assess gutta-percha, cement, and void volumes. Descriptive and inferential statistical analyses were performed (non-parametric Mann-Whitney test, Kruskal-Wallis test, and Friedman test with Tukey's bidirectional analysis of variance).

RESULTS

TMC showed the highest temperature increase at 15 s after the procedure and a significant temperature decrease at 45 s after its completion. TMC showed the largest volume of gutta-percha and LC the highest void volume.

CONCLUSION

The temperature increase generated by gutta-percha endodontic filling techniques is within acceptable limits. A greater volume of endodontic cement was observed for the SL and LC filling techniques.

Emissivity evaluation of human enamel and dentin

Background: Human enamel and dentin temperatures have been assessed with non-contact infrared imaging devices for safety and diagnostic capacity and require an emissivity parameter to enable absolute temperature measurements. Emissivity is a ratio of thermal energy emitted from an object of interest, compared to a perfect emitter at a given temperature and wavelength, being dependent on tissue composition, structure, and surface texture. Evaluating the emissivity of human enamel and dentin is varied in the literature and warrants review. The primary aim of this study was to evaluate the emissivity of the external and internal surface of human enamel and dentin, free from acquired or developmental defects, against a known reference point. The secondary aim was to assess the emissivity value of natural caries in enamel and dentin.

Method: Fourteen whole human molar teeth were paired within a thermally stable chamber at 30°C. Two additional teeth (one sound and one with natural occlusal caries–ICDAS caries score 4 and radiographic score RB4) were sliced and prepared as 1-mm-thick slices and placed on a hot plate at 30°C within the chamber. A 3M Scotch Super 33 + Black Vinyl Electrical Tape was used for the known emissivity reference-point of 0.96. All samples were allowed to reach thermal equilibrium, and a FLIR SC305 infrared camera recorded the warming sequence. Emissivity values were calculated using the Tape reference point and thermal camera software.

Results: The external enamel surface mean emissivity value was 0.96 (SD 0.01, 95% CI 0.96–0.97), whereas the internal enamel surface value was 0.97 (SD 0.01, 95% CI 0.96–0.98). The internal crown-dentin mean emissivity value was 0.94 (SD 0.02, 95% CI 0.92–0.95), whereas the internal root-dentin value was 0.93 (SD 0.02, 95% CI 0.91–0.94) and the surface root-dentin had a value of 0.84 (SD 0.04, 95% CI 0.77–0.91). The mean emissivity value of the internal enamel surface with caries was 0.82 (SD 0.05, 95% CI 0.38–1.25), and the value of the internal crown-dentin with caries was 0.73 (SD 0.08, 95% CI 0.54–0.92).

Conclusion: The emissivity values of sound enamel, both internal and external, were similar and higher than those of all sound dentin types in this study. Sound dentin emissivity values diminished from the crown to the root and root surface. The lowest emissivity values were recorded in caries lesions of both tissues. This methodology can improve emissivity acquisition for comparison of absolute temperatures between studies which evaluate thermal safety concerns during dental procedures and may offer a caries diagnostic aid.

Effect of sintering temperature on the physiochemical properties, microstructure, and compressive strength of a bioceramic root canal sealer reinforced with multi-walled carbon nanotubes and titanium carbide

AIM

Bioceramic root canal sealers like BioRoot RCS have received significant attention for use in endodontics. The addition of a nanophase material like multi-walled carbon nanotubes (MWCNTs) and titanium carbide (TC) to its matrix combined with pressureless sintering might have the potential for improved physiochemical, microstructure, and compressive strength properties.

METHOD

ology: MWCNTs and TC nanomaterials were added at a percentage of 1 wt% to a definite weight of pristine BioRoot RCS. Two composites were prepared by ball milling followed by pressureless sintering in static nitrogen at temperatures 600 °C and 800 °C. The setting time, solubility, pH, compressive strength, and density were determined and compared to pristine BioRoot RCS. The microstructural properties of the composites were investigated by XRD, FTIR, Raman spectroscopy, and SEM.

RESULTS

The final setting time before and after sintering at 600 °C of the composites was accelerated compared to Bioroot RCS (p = 0.016). The solubility of Bioroot/TC sintered at 600 °C was the lowest (p = 0.07) and its compressive strength was the highest among the sintered samples (p = 0.01). The incorporation of MWCNTs and TC had a significant increase in the compressive strength of Bioroot RCS (p < 0.05).

CONCLUSION

The obtained results support the addition of nanomaterials to Bioroot RCS and the use of pressureless sintering.

In Vitro Infrared Thermographic Assessment of Temperature Change in the Pulp Chamber during Provisionalization: Effect of Remaining Dentin Thickness

Interim crowns and partial fixed dental prosthesis materials generate exothermic heat during polymerization. The amount of heat transmitted to the pulp chamber can be a function of several factors, including the thickness and quality of the remaining dentin after crown preparation. The aim of this in vitro study was to measure with infrared thermography the temperature changes on the adjacent surface of the chamber roof of premolar teeth extracted from young and old patients (having different thicknesses of remaining dentin after crown preparation) during fabrication of provisional resinous restorations. Twenty extracted human first and second maxillary premolar teeth (10 from young patients, with a relatively large pulp chamber, and 10 from older patients, with a relatively small pulp chamber) were used. The roots were sectioned to expose the inner side of the chamber roof, and the crowns were provisionalized after preparation for a metal-ceramic crown. Two provisional materials, Turbo Temp 2 and Luxatemp Fluorescence, were used. Temperature changes on the inner side of the chamber roof were measured at 2-second intervals using an infrared thermal imaging camera. After completion of the temperature recordings, the teeth were sectioned and the remaining dentin thickness was determined. The older group (mean thickness: 2.82 mm) and younger group (mean thickness: 1.9 mm) differed significantly in dentin thickness (P < 0.014). The mean greatest temperature increases recorded on the chamber roof of teeth with less remaining dentin were 4.07°C for Turbo Temp 2 and 3.94°C for Luxatemp Fluorescence, while increases in the premolars with greater dentin thickness were 1.69°C for Turbo Temp 2 and 1.64°C for Luxatemp Fluorescence. Significant interactions were found between tooth groups (P < 0.000001for Turbo Temp 2 and for Luxatemp Fluorescence). No significant differences were found between assessed materials regardless of the thickness of the remaining dentin (P > 0.38for the older group and P > 0.29 for the younger group). Dentin had a significant effect in limiting the temperature increase generated during polymerization of provisional materials, indicating good thermal insulating properties of this tissue. A remaining dentin thickness of 1.9 mm or more is sufficient to protect the pulp from any temperature increase during provisionalization using tested materials.

Root Surface Temperature Increases during Root Canal Filling In Vitro with Nd:YAG Laser-Softened Gutta-Percha

The aim of this in vitro study was to measure the temperature increases produced on the mesial and vestibular root surfaces of premolar teeth during a laser-softened gutta-percha obturation technique. We studied 12 extracted human premolar teeth with a single canal. After root canal cleaning and shaping, the teeth were obturated with gutta-percha that had been softened with a neodymium-doped yttrium aluminium garnet (Nd:YAG) laser (CTL 1503) at a wavelength of 1.064 nm. The laser setup parameters included a 30 Hz frequency and a 200 mJ/pulse with optical fiber tips of 0.320 mm diameter. A sectional warm gutta-percha condensation was used. Temperature changes on the whole mesial and vestibular outer surfaces of the roots were measured at approximately 2 s intervals with an infrared thermal imaging camera. A significantly higher increase in temperature was observed for the mesial root surface (7.5°C) compared to the vestibular surface (3.7°C) (p ≈ 0). The findings suggested that root canal filling with Nd:YAG laser-softened gutta-percha in premolar teeth is not likely to damage the surrounding periradicular tissues. To obtain valid temperature results, the measurement should be performed on the surface with the thinnest root wall.

Microscopic assessment of the sealing ability of three endodontic filling techniques

Background

Several techniques have been proposed for root canal filling. New rotary files, with non-standardized taper, are appearing, so, points adapted to the taper of the last instrument used to prepare the canal can help in the obturation process. The aim of this study is to assess the sealing ability of different root canal filling techniques.

Material and Methods

Root canals from 30 teeth were shaped with Mtwo and divided in three groups; A, standard lateral condensation with size 35 and 20 gutta-percha points; B, standard lateral condensation and injected gutta-percha; C, single gutta-percha point (standardized 35 Mtwo), continuous wave technique and injected gutta-percha. Root surfaces were covered with nail varnish, except for the apical 2 mm, and submerged in a NO3Ag2 solution; apical stain penetration was measured in mm. Data were compared using the Kruskal-Wallis test with a 90% confidence interval.

Results

A and B groups showed stain leakage in the 90% of the cases, whereas it was of 80% for group C. Stain leakage intervals were 1-5 mm for groups A and B and 1-3 mm for group C. There were no statistically significant differences between the three studied groups (p>.05).

Conclusions

All the analyzed root canal filling techniques showed some apical stain leakage, without significant differences among them.

Key words:Gutta-percha filling, microleakage, single cone, injected gutta-percha, warm gutta-percha.

Heat conductive properties of set root canal sealers

OBJECTIVE

The aim of this study was to examine the thermal conductivity of five different root canal sealers in vitro.

MATERIALS AND METHODS

Sealapex, AH Plus, AH 26, Endomethasone and RoekoSeal root canal sealers were examined. These materials were prepared in accordance with the manufacturer's instructions and applied to standard molds. Three samples of each material were prepared. The samples were kept for 5 days under 37°C conditions. Measurements were taken using a heat conduction unit (P.A. Hilton Ltd. Stockbridge, Hants, UK). The thermal conductivity coefficient was calculated for each sample using the Fourier equation. Coefficients were analyzed statistically by the Kruskal-Wallis test.

RESULTS

Significant differences were found for thermal conductivity between some materials (p < 0.05). The conductivity coefficient of AH Plus was found to be higher than those of the other materials (p < 0.05). No statistically significant differences were found between AH 26 and RoekoSeal (p > 0.05) and the conductivity coefficients of these sealers were found to be lower than those of the other materials (p < 0.05). No statistically significant differences were found between Sealapex and Endomethasone (p > 0.05) and the conductivity coefficients of these sealers were found to be lower than that of AH Plus but higher than those of RoekoSeal and AH26 (p < 0.05).

CONCLUSIONS

The results showed that root canal sealers functioned as thermal insulators and had different heat-conductive properties that depended on their composition.

FP core carrier technique: thermoplasticized gutta-percha root canal obturation technique using polypropylene core

Core carrier techniques are unique among the various root canal filling techniques for delivering and compacting gutta-percha in the prepared root canal system. Thermafil (TF), considered the major core carrier device, is provided as an obturator consisting of a master core coated with thermoplasticized gutta-percha. We have devised a thermoplasticized gutta-percha filling technique using a polypropylene core, FlexPoint® NEO (FP), which was developed as a canal filling material that can be sterilized in an autoclave. Therefore, FP can be coated onto thermoplasticized gutta-percha and inserted into the prepared canal as a core carrier. The FP core carrier technique offers many advantages over the TF system: the core can be tested in the root canal and verified radiographically; the core can be adjusted to fit and surplus material easily removed; furthermore the core can be easily removed for retreatment. The clinical procedure of the FP core carrier technique is simple, and similar that with the TF system. Thermoplasticized gutta-percha in a syringe is heated in an oven and extruded onto the FP core carrier after a trial insertion. The FP core carrier is inserted into the root canal to the working length. Excess FP is then removed with a red-hot plastic instrument at the orifice of the root canal. The FP core carrier technique incorporates the clinical advantages of the existing TF system while minimizing the disadvantages. Hence the FP core carrier technique is very useful in clinical practice. This paper describes the FP core carrier technique as a new core based method.

In Vitro Infrared Thermographic Assessment of Root Surface Temperatures Generated by High-Temperature Thermoplasticized Injectable Gutta-Percha Obturation Technique

The aim of this in vitro study was to measure the temperature rises on the outer surface of roots produced by high-temperature thermoplasticized injectable gutta-percha technique. Thirty extracted human teeth with a single canal (15 maxillary central incisors and 15 mandibular central incisors) were used in this study. After root canal cleaning and shaping, the teeth were obturated with the injected gutta-percha heated to 160 degrees C (Obtura II). Temperature changes on the whole mesial outer surface of the roots was measured using an infrared thermal imaging camera. It showed that the use of gutta-percha heated to 160 degrees C to fill the maxillary central incisors and mandibular central incisors resulted in the rises of the root surface temperature by 8.5 degrees C and 22.1 degrees C, respectively. In conclusion, the injection of the gutta-percha heated to 160 degrees C into the root canal of maxillary central incisors produces temperature on the outer root surfaces below the theoretical critical level and, therefore, should not cause damage to supporting periradicular tissues. The injection of gutta-percha into the root canal space of the mandibular central incisors in vitro, resulted in an elevation of the root surface temperature by more than 10 degrees C.

Root Surface Temperature Rises In Vitro During Root Canal Obturation Using Hybrid and Microseal Techniques

The aim of this in vitro study was to measure the temperature rise on the outer surface of roots during filling with hybrid technique and Microseal. Twenty extracted human maxillary and mandibular premolars with a single canal were randomly divided into two groups of 10 teeth each. In the first group, the teeth were filled with hybrid technique (thermomechanical compaction with Engine Plugger used following lateral condensation of the apical part of the canal), the second group was filled using Microseal. After root canal obturation the filling material was removed and the obturation procedure was repeated. A total of 20 obturations in each group were performed. Temperature changes were measured using a thermal imaging camera. The temperature of certain regions of the mesial surface was analyzed and the highest temperature values were recorded. Statistical analysis was performed using the Mann-Whitney U test. The mean increase of temperature during the hybrid technique with Engine Plugger was 23.8 degrees C, while during Microseal it was significantly lower (p = 0.000001) at 5.5 degrees C. The temperature rise generated by Microseal was below the critical level and should not damage supporting structures, however, the hybrid technique generated a relatively high temperature rise that may cause periodontal tissue damage.

Root surface temperature rises during root canal obturation, in vitro, by the continuous wave of condensation technique using System B HeatSource

OBJECTIVES

This in vitro study evaluated increases in root surface temperature during the continuous wave of condensation technique using a System B HeatSource.

STUDY DESIGN

Forty-five extracted human teeth (15 maxillary central incisors, 15 mandibular central incisors, and 15 maxillary canines) were used. After root canal cleaning and shaping, the teeth were filled with the continuous wave of condensation technique using a System B HeatSource. Temperature changes on the whole mesial and vestibular outer surfaces of the roots were measured using an infrared thermal imaging camera.

RESULTS

The results of this in vitro study showed that the use of the continuous wave of condensation technique to fill the maxillary central incisors and maxillary canines produced temperature rises below the critical level. In the mandibular central incisors the use of a System B HeatSource resulted in elevation of the root surface temperature by more than 10 degrees C.

CONCLUSION

The continuous wave of condensation technique using the System B HeatSource produces temperature changes on the outer root surfaces, which, in the case of teeth with relatively thin dentinal walls, can reach relatively high values.