In vitro infrared thermographic assessment of root surface temperatures generated by the thermafil plus system

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.

Efficiency and Temperature Rise of File Ablation by Neodymium:Yttrium-Aluminum-Perovskite Laser In Vitro

INTRODUCTION

Retrieving a separated file in the root canal system requires a skilled clinician. A metal file can be removed by ablation via the neodymium:yttrium-aluminum-perovskite (Nd:YAP) laser; however, the efficiency and potential hazards of the ablation procedure are still unclear. The aim of this study was 2-fold: to investigate the efficiency of file ablation using the Nd:YAP laser and to evaluate the rise in temperature of the root surface in vitro.

METHODS

In part 1 of this study, #10 and #15 C-files (VDW GmbH, Munich, Germany) and ProTaper Next X1 and X2 files (Dentsply Maillefer, Ballaigues, Switzerland) were selected. Under 8.5×, the Nd:YAP laser was used to ablate the files starting at the tip of the file. The length of the file was recorded after each 5-pulse ablation. In part 2 of this study, 3 files each of the #15 C-file and the ProTaper Next X2 were separated in 6 distal roots of mandibular second molars with single canals. Two-pulse and 5-pulse modes were used to ablate the separated files, and the rise in root surface temperature was recorded with an infrared camera. Another 3 unaltered distal roots served as the negative control. For scanning electron microscopic evaluation, the teeth were split with bone scissors and observed under a scanning electron microscope to evaluate the surface change of the file and the root canal wall.

RESULTS

The average length of the ablated files after each 5-pulse interval was 0.113-0.158 mm with no statistical difference between the different files.The temperature rise of the negative control group (mean ± standard deviation = 1.86° ± 0.11°C and 5.81° ± 0.35°C for the 2- and 5-pulse group) was significantly lower than the roots with separated files (mean ± standard deviation = 3.74° ± 0.20°C and 4.02° ± 0.11°C for 2-pulse C-file and ProTaper Next X2; 8.47° ± 0.19°C and 9.04° ± 0.20°C for 5-pulse C-file and ProTaper Next X2). The temperature rise of all groups was lower than 10°C. The 2-pulse group showed a lower temperature rise than the 5-pulse group. The diameter or the type of alloy had no effect on the temperature rise.

CONCLUSIONS

Separated files (stainless steel or nickel-titanium alloy) can be ablated by the Nd:YAP laser. When the number of pulses is less than 5, the temperature rise of the root surface is considered safe to the surrounding periodontium.

Clinical studies on core-carrier obturation: a systematic review and meta-analysis

BACKGROUND

This systematic review aimed to evaluate the clinical performance of core-carrier obturation in endodontic treatment.

METHODS

Keywords of "(core carrier OR Thermafil) OR (cold lateral condensation OR lateral condensation) OR (warm vertical condensation OR vertical condensation) AND (obturation OR root canal filling) AND clinical study" were searched for all obtainable publications up to year 2017 in the databases of PubMed, ScienceDirect, EMBASE, Scopus and Web of Science. The success rate, short-term postoperative pain, overfilling and adaptation of core-carrier obturation from clinical studies were selected. Reviews, laboratory studies, animal studies and irrelevant reports were excluded.

RESULTS

1349 relevant articles were identified with 149 duplicated articles removed and 1173 irrelevant articles were excluded after screening. The titles and abstracts of the 19 identified articles were screened in the systematic review. The full texts of remaining articles were retrieved with data extracted for meta-analysis on the success rate, postoperative pain, overfilling and adaptation of obturation. The pooled success rate of core-carrier obturation was 83% (95% CI: 69%-91%). The pooled incidence of 1-day and 7-day short-term postoperative pain were 35% (95% CI: 15%-62%) and 6% (95% CI: 1-35%). The pooled proportion of teeth with overfilling and adequate adaptation of the obturation material were 31% (95% CI: 18%-50%) and 85% (95% CI: 75%-91%), respectively.

CONCLUSIONS

The success rate of endodontic treatment using core-carrier obturation was 83%. Short-term postoperative pain was not uncommon (24%). Most teeth (85%) had adequate adaptation using core-carrier obturation material, but a considerable amount of teeth (31%) had overfilling.

Thermal conductivity of different colored compomers

BACKGROUND

Compomers are mostly used in primary dentition. The thermal conductivity properties of traditional or colored compomers have not been investigated in detail so far. The aim of this in vitro study was to assess and compare the thermal conductivities of traditional and colored compomers.

METHOD

Two sets of compomers - namely, Twinky Star (available in berry, lemon, green, silver, blue, pink, gold and orange shades) and Dyract Extra (available in B1, A3 and A2 shades) - were included in this study. All of the traditional and colored compomers were applied to standard molds and polymerized according to the manufacturers' instructions. Three samples were prepared from each compomer. Measurements were conducted using a heat conduction test setup, and the coefficient of heat conductivity was calculated for each material. The heat conductivity coefficients were statistically analyzed using Kruskal-Wallis and Duncan tests. Uncertainty analysis was also performed on the calculated coefficients of heat conductivity.

RESULTS

Statistically significant differences were found (p<0.05) between the thermal conductivity properties of the traditional and colored compomers examined. Among all of the tested compomers, the silver shade compomer exhibited the highest coefficient of heat conductivity (p<0.05), while the berry shade exhibited the lowest coefficient (p<0.05). Uncertainty analyses revealed that 6 out of 11 samples showed significant differences.

CONCLUSIONS

The silver shade compomer should be avoided in deep cavities. The material properties could be improved for colored compomers.

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.

Polymerization behavior and thermal characteristics of two new composites at five temperatures: refrigeration to preheating

PURPOSE

Heat of composite polymerization (HP) indicates setting efficacy and temperature increase of composite in clinical procedures. The purpose of this in vitro experimental study was to evaluate the effects of 5 temperatures on HP of two new composites.

MATERIALS AND METHODS

From each material (Core Max II [CM] and King Dental [KD]), 5 groups of 5 specimens each were prepared and their total HPs (J/gr) were measured and recorded, at one of the constant temperatures 0℃, 15℃, 23℃, 37℃ and 60℃ (2 × 5 × 5 specimens) using a differential scanning calorimetry (DSC) analyzer. The data were analyzed using a two-way ANOVA, a Tukey's test, an independent-samples t-test, and a linear regression analysis (α=0.05).

RESULTS

No polymerization reactions occurred at 0℃; then this temperature was excluded from statistical analyses. The mean HP of the remaining 20 KD specimens was 20.5 ± 14.9 J/gr, while it was 40.7 ± 12.9 J/gr for CM. The independent-samples t-test showed that there were significant differences between the HP of the two materials at the temperatures 15℃ (P=.0001), 23℃ (P=.0163), 37℃ (P=.0039), and 60℃ (P=.0106). Linear regression analysis showed statistically significant correlations between environment temperatures and HP of CM (R(2)=0.777).

CONCLUSION

Using CM is advantageous over conventional composite because of its better polymerization capacity. However due to its high HP, further studies should assess its temperature increase in vivo. Preheating KD is recommended. Refrigerating composites can negatively affect their polymerization potential.

Evaluation of effectiveness of Er,Cr:YSGG laser for root canal disinfection: theoretical simulation of temperature elevations in root dentin

Erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers are currently being investigated for disinfecting the root canal system. Prior to using laser therapy, it is important to understand the temperature distribution and to assess thermal damage to the surrounding tissue. In this study, a theoretical simulation using the Pennes bioheat equation is conducted to evaluate how heat spreads from the canal surface using an Er,Cr:YSGG laser. Results of the investigation show that some of the proposed treatment protocols for killing bacteria in the deep dentin are ineffective, even for long heating durations. Based on the simulation, an alternative treatment protocol is identified that has improved effectiveness and is less likely to introduce collateral damage to the surrounding tissue. The alternative protocol uses 350 mW laser power with repeating laser tip movement to achieve bacterial disinfection in the deep dentin (800 microm lateral from the canal surface), while avoiding thermal damage to the surrounding tissue (T<47 degrees C). The alternative treatment protocol has the potential to not only achieve bacterial disinfection of deep dentin but also shorten the treatment time, thereby minimizing potential patient discomfort during laser procedures.

Denaturation temperatures of dentin matrices. I. Effect of demineralization and dehydration

The denaturation temperature (T(d)) of dentin collagen in mineralized versus demineralized teeth was examined as a function of dentin age and the extent of dehydration. Using differential scanning calorimetry, T(d) of mineralized dentin was shown to be between 160 degrees C to 186 degrees C, depending on whether it was from young or old dentin that was hydrated or dehydrated, respectively. Demineralized dentin exhibited a T(d) of 65.6 degrees C that increased with dehydration to 176 degrees C. The presence of apatite crystallites or interpeptide bonding increased the T(d) of demineralized matrices. Interpeptide hydrogen bonding seems to stabilize collagen to thermal challenge. Water breaks interpeptide hydrogen bonds making collagen more susceptible to thermal denaturation. Rises in intracanal temperature are unlikely to cause extensive denaturation of mineralized root dentin walls. However, hydrated or partially dehydrated root canal walls that have been partially demineralized with chelating agents or mild acids may be susceptible to thermal denaturation.

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

The aim of this in vitro study was to measure the temperature rise on the outer root surfaces of teeth during four different root canal obturation techniques. Sixty extracted human maxillary and mandibular premolars with a single canal were used. After root canal cleaning and shaping, the teeth were randomly divided into four groups of 15 teeth each and obturated with Thermafil obturators or Soft-Core obturators using Ultrafil or Trifecta low-temperature thermoplasticized gutta-percha techniques. Temperature changes on the external mesial root surfaces were measured using a thermal imaging camera. Lower temperature rises were found for Ultrafil and Trifecta techniques (2.14 degrees C and 2.03 degrees C, respectively) than for Thermafil and Soft-Core techniques (3.87 degrees C and 3.67 degrees C, respectively). These findings suggest that solid core gutta-percha combined with low-temperature injectable gutta-percha obturation techniques may impose less risk for thermal damage to the surrounding periradicular tissues.