Investigation of the Effect of Sealer Use on External Root Surface Temperature During Root Canal Obturation Using Warm Vertical Compaction Technique-an in Vitro Study

INTRODUCTION

Endodontic treatment is carried out in order to preserve a tooth whose pulp has been damaged either by trauma or infection. The aim of successful endodontic therapy is thorough debridement of the infected pulp tissue, cleaning and shaping of the root canal system so that the canal space can be prepared to be filled with an inert root canal filling material thus preventing any future predilection of re-infection.¹ An ideal root canal filling should fill the entire root canal system and form a homogenous mass.² To achieve a three-dimensional root canal filling a core obturating material along with a root canal sealer is used.³

Root canal sealers fill the irregularities and penetrate into dentinal tubules, providing an hermetic seal of the root canal system. They reduce apical,coronal microleakage and help to obtain an impervious seal along the dentinal walls. Different types of sealers based on various formulas are available.⁴ Among the recent advances, calcium silicate based sealers such as iRoot SP have gained substantial attention. This sealer has good biocompatibility, antibacterial property, flowability and bioactivity. It is available as a premixed, ready-to-use injectable sealer. It is composed of calcium silicates, calcium phosphate monobasic, calcium hydroxide, zirconium oxide, filler, and thickening agents.⁵

Another group of sealers are epoxy resin-based sealer. AH Plus is the most frequently used epoxy resin-based sealer. It has good physical, chemical properties, lower rates of water solubility and good sealing ability with the possibility of dentin adhesion. AH Plus consists of two paste system, which is delivered in two tubes and in a new double barrel syringe. The resin paste contains epoxy resin, calcium tungstate, zirconium oxide and aerosol iron oxide. The amine paste contains adamenthas amine, N, N didenyl – 5 – oxanone diamine, zirconium oxide, aerosil and silicone oil.⁶

Among the root canal obturating materials gutta-percha is the most commonly used. Its chemical and physical properties such as inertness, biocompatibility, plasticity when warmed, ease of removal for post or retreatment makes it a popular material of choice. Many Gutta-Percha obturation techniques are used to fill root canals.⁷ Among the various obturation techniques, Schilder’s warm vertical compaction technique is commonly used. In this technique heat is used to soften the obturation material thereby providing dense obturation with lower risk of void formation and better adaptation to the root canal complexities.⁸The potential disadvantage of this technique is the heat used during condensation of gutta-percha can lead to temperature rise on the root surface.⁹ The rise in temperature above critical threshold of 45°C or 10°C above body temperature for a duration >1 min may be sufficient to cause potential thermal injury to the periodontium. It results in interrupted the blood flow in the periodontium, protein denaturation followed by increase in alkaline phosphatase causing surface resorption of the cementum, bone tissue injury, alveolar bone necrosis and bone ankylosis.¹⁰

Hence the aim of this study was to investigate the effect of two different sealers on the heat generated at the external root surface during obturation using warm vertical compaction technique.

METHODOLOGY

Firstly, ethical review was done and approval was attained by the institute research ethics committee (AJEC/REV/220/2019).This in vitro research study was conducted in the department of conservative dentistry and endodontics, for duration of three months after receiving ethical approval 20 single rooted human teeth with complete root formation were selected for this study. Soft tissues and the calculus were removed from the teeth. Subsequently, all the teeth were decoronated, and the root lengths were standardized at 15 mm. The working length was determined to be 1 mm shorter from the apical foramen. The shaping and cleaning of root canals was done using protaper system. Canals were enlarged upto F3 file. The irrigant used was 5% sodium hypochlorite of approximately 20 mL per root canal. Before the obturation, passive ultrasonic irrigation was applied with an Irrisonic tip (Helse Dental Technology, S~ao Paulo, SP, Brazil), which was activated by an ultrasonic EMS device (Hu-Friedy, Chicago, IL). Then, the root canals were dried with absorbent paper points, and the samples were divided into 2 experimental groups (group A and group B). Each group consisted of 10 teeth.

Group A:

In this group, a calcium silicate-based sealer i.e. iRoot SP ((Innovative BioCreamix Inc., Vancouver, Canada),) was used according to the manufacturer’s instructions. The canals were completely coated. A F 3 gutta percha cone that fitted and gave tug-back was chosen. The gutta percha cone was then slowly inserted into the root canal until the working length was reached and obturation was completed using warm vertical compaction method using system B device.

Group B:

An epoxy resin-based sealer, AH Plus (Dentsply, Konstanz, Germany) was dispensed and manipulated according to the manufacturer’s instructions,and the canal walls were thinly coated with a #30 lentulo spiral. An F 3 gutta percha cone that fitted and gave tug-back was chosen. The gutta percha cone was coated with sealer and then slowly inserted into the root canal until the working length was reached and obturation was completed.

OBTURATION USINGS WARM VERTICAL COMPACTION METHOD.

All the teeth in both groups were obturated using warm vertical compaction method using System B Heat Source (SybronEndo). The technique employed was as recommended by the manufacturer and followed the Buchanan technique. A medium-large insert tip, which bound in the canal 3 mm from the working length, was selected. The System B unit was preset to 200â—¦C as recommended by the manufacturer. following which the selected gutta-percha cone which was coated with the sealer and placed in the canal. It was thermo softened and apically condensed.

MEASUREMENT OF THE RISE IN TEMPERATURE ON THE EXTERNAL ROOT SURFACE

The temperature measurement was carried out using a thermocouple device which in turn is connected to a digital thermometer to produce an accurate reading. The root lengths of all teeth were standardized at 15 mm and the measurement of the rise in temperature was carried out at the apical 5mm of the root for all teeth. The rise in temperature on the external root surface of teeth during obturation in group A and group B was measured in Ëšc and recorded.

STATISTICAL ANALYSIS

The mean rise in temperature in both the groups was measured. Subsequently Students t test was used to test the significant difference in the rise in temperature between group A: teeth that were obturated with iRoot SP sealer and group B: where AH plus sealer was used.

RESULT

The mean temperature rise, and standard deviation (SD) recorded on the apical third of the outer root surfaces during obturation in both groups was analyzed. The mean ±SD of rise in temperature in group A and group B are 3.22 ± 0.42 and 4.28 ±0.73 respectively. Analysis using Student t test indicates that there is statistically very high significant difference in the mean temperature rise between the two groups (p < 0.01).The mean rise in temperature in group B (4.28 ±0.73) was significantly higher than group A (3.22 ± 0.42) as represented in table I.

Table I: Statistical significance in the rise in temperature in group A and group B using Student t test analysis

DISCUSSION

The present study evaluated the effect of iRoot SP and AH Plus sealers on the heat generated at the external root surface during obturation with system B. This study reveals that there is significant rise in temperature on the external root surface between both groups. However, at no given point of time, did the temperature change on the external root surface exceed the critical temperature on using warm vertical compaction method.

In order to improve the quality of obturation various obturation systems have been developed. Techniques such as warm vertical compaction method using system B helps to attain a more homogenous mass. The heat used in this technique helps to increase the flow of the gutta percha into the relatively in accessible areas, thus enhancing the adaptability of the obturating material along the canal walls.¹¹ System B technique helps to produce a denser and more dimensionally stable root canal filing.¹²

Root canal sealers along with the solid core obturating material such as gutta percha play a major role in achieving a fluid tight seal of the root canal system. Gutta-percha has no adhesive qualities to dentin regardless of the obturation techniques used. Therefore, root canal sealers play a major role in achieving the fluid tight seal.¹³ Recent advances in root canal sealers have led to the development of calcium silicate-based sealer such as iRoot SP sealers. These sealers have crystalline structure similar to the tooth and bone apatite materials. It has superior properties such as bonding to the root dentin and antibacterial property. It also has good apical seal and clinical characteristics.¹⁴ On the other hand epoxy resin sealers such as A H Plus has high dimensional stability, low shrinkage, reduced solubility and enhanced micro-retention to the root canal dentin.¹⁵

Despite the excellent physiochemical properties of both the sealers, in this study there is a rise in root surface temperature. The mean temperature rise at the apical third for group A was 3.22 ± 0.42 and group B was 4.28 ±0.73 respectively. At p value < 0.01, the mean temperature rise was statistically significant and group B was greater than group A. The analysis was done using student t test and it indicates that there is statistically very high significant difference in the mean temperature rise between the two groups.

Subsequently, when correlated with the clinical situation, although both the groups showed statistically significant rise in temperature in the apical third at their respective P values, the temperature change on the external root surface did not exceed the critical temperature. The critical temperature for injury to the attachment apparatus has been reported to be 10°C above the human body temperature. A study conducted by Eriksson and Albrektsson using a sophisticated vital microscopic method concluded that the temperature for bone injury may be as low as 47°C or 10°C above human body temperature (37°C).¹⁶

In the present study, the heat generated within the root dentine is transmitted to the attachment apparatus but since at no given point of time did it go beyond the critical temperature. It can be concluded that both the sealers did not have a drastic influence on the rise in root surface temperature. A rise in root surface temperature above the critical temperature is associated with denaturation of alkaline phosphatise, thereby bone alkaline phosphatase is rapidly inactivated causing deleterious effects on the alveolar bone, cementum and periodontal ligament.¹⁷ In this study since the rise in temperature is significantly less than the critical temperature, it can be concluded that the use of both iRoot SP and AH Plus sealers along with warm vertical compaction method using system B heat source does not damage the surrounding tissues.

The results of this study supported the hypothesis that there was a statistically significant difference in temperature measurements among both the groups. However, when correlated with the clinical situation, the temperature rise is significantly less than the critical temperature of 10°C. This result may be attributed to poor thermal conductivity of dentine (1.36 ×10−3 cal / s/cm 2 /C/cm) which helps to dissipate the heat and prevent its transfer to the attachment apparatus.¹⁸ In addition, gutta-percha is poor thermal conductor of heat, and does not allow heat transmission. In vivo the presence of blood circulation in the periodontal membrane and the wetness of dentine due to the presence of dentinal fluids in the tubules also contribute to limit heat transmission resulting in lower temperature on the root surface.¹⁹ All of this indicating that the use of both sealers with warm vertical obturation techniques does not cause damage the periodontium.

CONCLUSION

Within the limitations of this study, it was found that there was a rise in temperature during endodontic obturation in both groups. The teeth that were coated with A H Plus sealer and further obturated with warm vertical compaction method using system B heat source caused greater rise in root surface temperature. However, when correlated with a clinical situation, the temperature rise is significantly less than the critical temperature. This indicates that the use of A H Plus or iRoot SP sealer along with warm vertical compaction method may not have any damaging effect on the tooth and periodontium. However, there are certain limitations to the present study and hence caution must be exercised.

Disclosure and conflict of interest: Not applicable.

Acknowledgement: I wish to express my appreciation to Manipal University and staff of A J Institute of Dental Sciences, especially Dr Manjula for the statistical analysis.

REFERENCES