Kazumi Onaga Nagayama Oyama, D.D.S.
Evandro Luiz Siqueira, D.D.S.
Marcelo dos Santos, D.D.S.
The objective of this study was to check the efficiency of four differents solvents and classify them according to their dissolving action. Methodology- four solvents were tested: xylol, eukaliptol, orange oil and halothane. They were analyzed by weight loss. Twenty #40 master cones, each one placed in a Petri dish, were used for each solvent and they were divided into four groups, and tested at intervals of 1, 5, 10 and 15 minutes, resulting in five samples for each interval. The results showed that xylol was the most rapid for the 5 minute interval. All solvents, after 10 and 15 minutes of action, had dissolving power on the gutta-percha cones, but orange oil was the solvent that proved to be the most efficient at the end of the studied intervals, followed by xylol, eukaliptol and halothane in that order. In this way, we could conclude that orange oil was the solvent that showed the most efficient result on the guta-percha. The statistical analysis, however, showed that statistically there were no differences among the samples (p ³ 0.05).
After the cleaning and shaping phases, where the desinfection of the root canal is completed, the dentist filling the root canal system with the intention of obstructing the contact of the internal and external environment with the dental organ.
Many times, however, the bacteria permeate in filling material for many reasons, necessitating a new desinfection, and therefore an endodontic retreatment.
Several techniques have been studied (SANTOS1, 1991), seeking speed and practicality in the manoeuvre of gutta-percha removal from the root canal system and for many of them the use of a solvent seems to be extremely valid in assisting in instrument removal of this material.
The previously most widely used chemical agent was chloroform. In spite of it being considered an excellent solvent, it was shown to have a high toxicity and to be a potential carcinogen. Its clinical use has been prohibited in humans since 1976. Studies have confirmed that substances placed in the pulp chambers of teeth have acess to the periapical tissues and to the circulatory system(HUNTER et al2, 1991).
In this way, we found some others solvents that are able to help in the removal of obturating material from the root canal system.
DELLA NINA et al3 (1980), assessing the property of several solvents, through weight loss of gutta-percha cones after solvent action at several intervals, concluded that xylol was the most efficient dissolving gutta percha cones. This solvent, in spite of being of a good quality, has some undesirable side effects. WOURMS et al4 (1990), evaluating various solvents, previously identified to dissolve gutta-percha, found in accounts that xylol has a toxic action in tissues. In 1993, PÉCORA et al5 investigating the softenning of gutta-percha of five kinds of solvents, do mention that, according to the Merck Index, xylol causes irritation in the mucosa by contact and by inhalation, and could also cause convulsions, insomnia, excitement and depression of the CNS, and can lead to death by respiratory depression.
Trying to eliminate this divergency between effectiveness and toxicity, many authours cite in their studies eukaliptol as a solvent that does not display any harmful side effects and is already a widely used substance for flavoring and fragrance5. However, WENNBERG & ORSTAVIK6 (1989), testing the dissolving ability of some solvent alternatives to chloroform, using a device for measuring penetration of an indentor into softened gutta-percha at various intervals, concluded that, at room temperature, eukaliptol was less effectivite than other solvents. In 1990, ZAKARIASEN et al7describing a technique of retreatment, noticed that eukaliptol, when heated, had its solvency power increased.
In 1992, PÉCORA8 introduced orange oil as a desintegration agent of zinc oxide-eugenol cement. In the following year the same author studying softenning of gutta-percha cones in endodontic retreatment, with a penetrometer apparatus which reproduces the penetration force of an endodontic file used on the sectioned roots of previously filled teeth, concluded that orange oil had the same dissolving action as xylol. This solvent, beyond its present good dissolving characteristics, does not show harmful side effects, has an expectorant action, a pleasant smell and is used in pharmaceuticals for fragrance and flavor9.
Halothane is used as an inhalation anesthetic. It has been mentioned as a solvent because of its high effectiviness in dissolving gutta-percha, besides being twice as effective and quick as eukaliptol4. In 1995, WILCOX10 comparing the effectiveness of halothane and chloroform in endodontic retreatment, using 30 mandibular premolars analyzed in a sonic digitizer, concluded that halothane shows the same effectiveness as chloroform. In the same way, GORDUYSUS et al11 (1997), evaluating the dissolving efficiency of different gutta-percha solvents, through weight loss, mention that halothane is an acceptable alternative to and equal to chloroform and xylol. Beyond this dissolving characteristic on gutta-percha, the authors are unanimous in relation to its clinical use: it is biocompatible, presents low toxicity and is safer. However, one restriction is its high volatility that can produce systemic changes, such as: hepatotoxicity (BARBOSA et al12, 1994), respiratory depression, cardiac arrhythymias, increasing sensitivity of the myocardial conduction system to epinephrine, reduced blood pressure4.
Thus, the present study aims to evaluate the dissolving action on gutta-percha cones, by weight loss, post action of four solvents at diferrent intervals.
MATERIALS AND METHODS
Fig. 1 Solvents used in study
Each solvent was tested at four different intervals: 1, 5, 10 and 15 minutes.
Twenty gutta percha cones were tested for each solvent. They were placed in the center of Petri dishes (figure 2). These dishes containing gutta-percha cones were 5 cm in diameter, were divided into four groups, and resulted in five samples for each interval.
Fig. 2 -Gutta percha cone immersed in solvent
All gutta-percha cones samples in this study came from the same manufacturer (Tanari), were the same number (#40), the same lot and had the same inspection dates. They were weighed on a high precision analytic scale prior to being tested (Mettler-Toledo AB204) and after were then stored in Petri dishes.
Five ml of solvent was used on each sample of gutta-percha cones which were completely immersed in the solvent. Timing began immediately after with a stopwatch.
At the end of the interval, the remaining solvent was removed using a disposable plastic syringe. After 5 ml of ethilic alcohol 92.8º INPM (Copersucar) was introduced for 5 minutes to wash the gutta percha cone. The remaining alcohol was removed with a plastic syringe and 5 ml of distilled water was introduced for 5 minutes. After this time, the remaining water was removed with a disposable syringe and the samples were kept at room temperature so that they could dry for one hour. A dish containing the cones was weighed to determine the new values of the cone weights.
The results of the dissolving tests on gutta percha are showed in table 1.
Averages of percentage weight differences of dissolved gutta-percha
Based on the above table shown, we can note that after 1 minute, all the solvents studied have aweight increase, and orange oil was the solvent that accumulated more weight (0.37%), followed by xilol and eukaliptol with 0.07% and halothane with 0.06%, respectively.
At the 5 minute interval, the only substance that showed dissolving action was xilol.
At the 10 and 15 minute intervals, the solvent that had the greatest dissolving power was orange oil, with 5.07% of weight loss, followed by xilol with 3.64%, eukaliptol with 1.85% and lastly halothane with 0.19% of weight loss.
The statistical analysis, however, showed that statistically there were no differences among the samples (p ³ 0.05), by Kruskal-Wallis' test.
According to our study, all the solvents, when they are analised between the intervals of 10 and 15 minutes, showed dissolving power on the gutta percha cones. The xilol and the orange oil showed more effectiveness. These data are according to previous studies of Della Nina et al3, where they analised the solvency ability of several solvents through the weight loss and they described that xilol was more efficient. Our results confirm the observation made by other authors where they describe that orange oil presents the same action as xylol. In addition, Spanó et al13, mentioned the solvency ability of essentials oils, and they concluded that they can substitute the toxic solvents.
Analysing 32 kinds of solvents, Wourms et al4 presented halothane as a successful alternative and described a material with high viscosity, which the authors call "halopercha". Hunter et al2 compared the effectiveness of halothane and eukaliptol with chloroform, in terms of the penetration power over the gutta percha and they relate the acceptable alternatives. The high volatility of halothane, however, shows that there is no advantage if the solvent evaporates before the gutta percha become soft. In addition, we noticed that between the 10 and 15 minute intervals, the formation of a substance with dense viscosity was present and we believe that probably because of this characteristic of halothane, the percentual loss of gutta percha cone weight was discreet if compared to the others solvents tested.This was our efforts to try to minimize its volatility, a mixing of halothane with hard viscosity vehicle, the propilenoglicol, in one to one proportion. Even so we noticed a fast evaporation of this solvent.
Though these authors mention that the effectiveness of eukaliptol is increased, when it is heated7, in our work, we notice that it was one of the solvents that showed the least power of action and we wish to emphasize that there are many more efficient alternatives.
We noticed after 1 minute, an increase in the weight of the cones, and probably this fact is associated with the incorporation of the solvent liquid into the gutta percha cones, probably there was no time to promote solvency, but we believe that more detailed study is needed.
In 5 minutes of action the only substance that showed solvency on gutta-percha cones was xylol and is in concordance with prior studies3,5. Despite this prover action, its clinical use is limited due to its harmful effects.
Many solvents are available in the market, but we must consider the solvency potential and the grade of toxicity of each before using them clinicaly.
Based on our results, we can note that all the solvents that were studied, possessed solvency ability over the gutta percha cone, however orange oil was the substance that promoted the best results, followed by xilol, eukaliptol and halothane, in that order.
In relation to orange oils toxicity a deeper study is necessary, because up to the present study there have not been studies of the harmful effects of this substance.
After analising the results, we can conclude:
1. Xylol was the solvent that presented the fastest solvency action among the tested substances.
2. Eukaliptol and halothane were the solvents that showed the least power of solvency.
3. Orange oil was the solvent that showed the greatest power of solvency between the time 10 and 15 minutes of action on the gutta percha cones.
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The etilic alcohol and the destilated water do not have sufficient properties by themselves to dissolve the guta percha cones11. All the substances that were studied can be mixed in etilic alcohol13.
*Fórmula & Ação Farmácia de Manipulação
Research Laboratory of FOUSP Dentistry Departament
Author: Kazumi Onaga Nagayama Oyama
Endodontics - Clinical Practice, Education and Research
Av. Prof. Lineu Prestes, 2227 - Cidade Universitária - Butantã - CEP 05508-900 - São Paulo - SP