The major cause of failure of root canal treatment is the persistence of microbial infection in the root canal system and/or in the periradicular region (1). When the primary treatment fails, a non-surgical endodontic retreatment is indicated (2). The key to successful endodontic retreatment is to thoroughly debride the canal system of infected or necrotic pulp tissue and microorganisms and to efficiently remove the filling materials from the root canal system (3). Organic solvents are chemical compounds which have been shown to aid in removal of the root canal filling materials (4-6).
Xylol has been shown to dissolve the root filling materials most effectively but it was reported to have carcinogenic potential and toxicity to tissues (7). Essential oils, such as orange oil and eucalyptus oil, have been reported to be safe and useful for this purpose (5, 8, 9).
Currently, there are no studies which show the effectiveness of these solvents on F3 ProTaper Universal Gutta-percha points. Hence, the purpose of this study was to compare and asses the dissolving efficacy of various endodontic solvents such as formulated orange oil, orange oil and formulated eucalyptol on F3 ProTaper Universal Gutta-percha points.
Materials and Methods
This was a comparative and laboratory study employing one commercial brand of F3 ProTaper Universal™ gutta-percha points (Dentsply Maillefer, Ballaigues, Switzerland), within expiration date. Two-hundred samples were randomly divided into four experimental groups and further subdivided in fifty samples for each solvent (Table 1). Formulated orange oil (Oleo de Laranja, Phormula Ativa, Recife, Brazil), orange oil (Citrol, Biodinamica, Ibiporă, Brazil) and formulated eucalyptol (Eucaliptol, Nectar Plus, Campina Grande, Brazil) were tested as solvents and compared with xylol (Xileno PA, ISOFAR, Duque de Caxias, Brazil) – (control group). After that, the points were weighed on an analytical balance (AUY120, Shimadzu, Japan) and the values were recorded considering four decimal places after the decimal point to identify the baseline weights of each specimen prior to solvent action. Subsequently, each gutta-percha point was put onto watch glass, 7X45mm in length, which was immersed into experimental solution at room temperature for the following immersion times: 5, 10, 20, 25 and 30 minutes.
|Group 1||Orange Oil||50||F3|
|Group 2||Formulated Eucalyptol||50||F3|
|Group 3||Formulated Orange Oil||50||F3|
|Group 4 (control)||Xylol||50||F3|
The samples were removed from a glass vial after the specified immersion period, washed in 100 mL of double-distilled water, and allowed to dry for 72 h at room temperature.
A new weighing was performed in order to compare and calculate the weight loss. The mass loss was recorded by weighing which was performed after every minute of action of the solvent on the points. The dissolving rate of gutta-percha was calculated from the difference between the original weight of gutta-percha and its final weight using the following formula: M= Mf-Mi
where:Mf = post-immersion weight;Mi = pre-immersion weight.
Means and standard deviations of weight loss were calculated at each time interval for each group of specimens. The data were tabulated and statistically analyzed by Kruskal-Wallis test using the SPSS (Statistical Package for the Social Sciences) 21 data analysis software for Windows (SPSS Inco., Chicago, USA) with the value of statistical significance set at 0.05.
The solvent action of xylol, formulated orange oil, orange oil and formulated eucalyptol are summarized in Table 2. Also, the standard deviation and mean weight loss of F3 ProTaper Universal gutta-percha point is presented.
(*):Statistically significant differences at level .05. (1): Kruskal Wallis test If all the letters in parentheses are different it is demonstrated a significant difference between the solvents in each evaluation time.
Based on the methodology employed, it was possible to identify the solvents with higher power of dissolving F3 ProTaper Universal gutta-percha points within the periods of evaluation. With regards to the means weight loss provoked by each solvent at 30 minutes of immersion time, xylol (control) showed the greatest weight loss, followed by formulated orange oil, orange oil and formulated eucalyptol. The results of the loss at each minute are presented in Table 2.
Taking into consideration these results, xylol (control) exhibited greater capacity of dissolution than formulated orange oil, orange oil and formulated eucalyptol at all experimental periods of time, with a statistically significant difference.
Considering the total weight loss provoked by each solvent, all solutions caused the highest dissolution of gutta-percha at immersion time of 30 minutes.
Numerous methodologies have been proposed to evaluate retreatment techniques. It has been suggested that hand file (2, 10) including stainless steel hand file (2, 10), rotary instruments (11), reciprocating systems (12), ultrasound (3) and immersion of gutta-percha point in the solvent solution (13) can be used to effectively clean the root canal system. Although gutta-percha points have been widely used in endodontics for root canal filling, there are few reports in the literature that evaluated solvent capacity on the great taper gutta-percha points. The goal of the present study was to evaluate the dissolving effect of solvents on F3 ProTaper Universal gutta-percha points. The methods used in this study are similar to those used in numerous basic studies conducted on gutta-percha solvents in which the dissolving efficacy of solvents was assessed by the difference between the original pre-immersion weight and the post-immersion weight (8, 14, 15).
According to the classification of residual solvents, xylol is a solvent with major capacity of dissolution of gutta-percha (8, 14, 16). The results of the present study are in agreement with those obtained by previous authors, because xylol (control) showed a significantly higher dissolution rate of gutta-percha in all tested periods of time. Also, the result obtained for xylol is statistically more significant than the results obtained for eucalyptol and orange oil (ranging from 1 - 5 minutes).
The data of the present research reveal that the F3 ProTaper Universal™ gutta-percha points were soluble to various degrees in the aforementioned solvents. Our results show that xylol was the most effective solvent followed by essential oils (eucalyptol and orange oil). Several recent studies have also reported that xylol is the most effective solvent (6, 17). However, some researchers stated that orange oil and eucalyptol are safe and more biocompatible alternatives to Xylol (18). Unlike these results, a study (19) showed that both chloroform and eucalyptol are strong cytotoxic solvents. However, the authors do not consider them to be a factor that increases the level of DNA lesions in mammalian cells.
In accordance with the present research, Gomes et al. (14) showed that xylol has a high dissolving rate of gutta-percha in all tested times. The rate obtained for xylol was statistically more significant than that obtained for eucalyptol and orange oil (ranging from 1 - 5 minutes).
In the present study, all solvents exhibited the greatest percentage of dissolution at five minute interval. It is noteworthy that although gutta-percha points are composed of gutta-percha itself, zinc oxide, waxes, resins and other compounds, the solvents acted only on gutta-percha. Accordingly, it seems that the greatest percentage of dissolution occurred in a time interval of five minutes because in the remaining time there would have been a smaller amount of gutta-percha within the point, hence a smaller area of action for the solvent. The results of some studies have shown that after five minutes, the solvents exhibited a higher dissolution rate than after 10 minutes, suggesting that the solution must be used for at least 5 minutes.
There are few studies confirming the solvent capacity of the tested solvents. Tanomaru-Filho et al. (16) concluded that solvents such as xylol, eucalyptol, and orange oil showed a good solvent capacity. Xylol was more efficient for conventional gutta-percha removal, whereas other solvents were more efficient for thermoplastic gutta-percha removal. In agreement with Tanomaru-Filho et al. (20), Magalhăes et al. (8) evaluated the solvent capacity of xylol, eucalyptol, chloroform and orange oil and reported that xylol was the most efficient solvent, while other solvents acted in a similar fashion. Aguiar et al. (20) also observed that both eucalyptol and orange oil were effective in the removal of filling material from root canals, which does not comply with the results of the study obtained by Karlović et al. (21) who reported that the greatest amount of remaining root canal filling was found after retreatment with orange oil, followed by halothane. The results of their study also showed that eucalyptus oil exhibited the best dissolving capacity. The results obtained in the present study demonstrated that xylol was the most effective solvent in dissolving gutta-percha points, followed by formulated orange oil, orange oil and formulated eucalyptol oil.
Considering the results obtained and the methodology employed, it can be concluded that xylol was the most effective in dissolving F3 gutta-percha points, followed by formulated orange oil, orange oil, and eucalyptol. There were no statistically significant differences between the solvent capacity of formulated orange oil and formulated eucalyptol and orange oil, thus confirming the fact that they can be used in endodontic retreatment as alternative solutions to replace xylol.