Braz Dent J (1990) 1(1): 37-44 ISSN 0103-6440
| Introduction | Material and Methods | Results | Discussion | Conclusion | References |
The authors studied, in vitro, by light microscopy and by morphometric analysis, the cleaning capacity of Dakin's solution, water and Tergentol, when used as auxiliary solutions to ultrasonic instrumentation of root canals. After irrigation and instrumentation, 15 extracted human mandibular incisors, with a single root and with only one canal, were submitted to routine histological processing with serial 6-µm sections stained with hematoxylin and eosin. The results showed that Dakin's solution energized by ultrasound leaves root canals with less debris than Tergentol; water falls into an intermediate position. The apical third showed more debris than the middle third, and none of the irrigating solutions left the root canals free of debris.
Key words: root canal, instrumentation, ultrasound, irrigating solutions.
Recently, different devices from those already used in the treatment of root canals, not only in characteristics but also in functioning such as sonic and ultrasonic equipment for instrumentation, have been added to the endodontic arsenal.
Numerous studies have shown the efficiency of ultrasonic instrumentation in the cleaning of root canals, Richman (1957) being the first to recommend its use for this purpose.
Cunningham et al. (1982) studied comparatively, in vitro, the effectiveness of root canal cleaning by ultrasonic instrumentation and by manual instrumentation. They concluded that root canals instrumented by ultrasound were significantly cleaner, at all levels, than canals instrumented manually.
Costa et al. (1986) compared, with scanning electron microscopy, manual and ultrasound instrumentation of root canals observing that ultrasonic instrumentation was more effective than manual instrumentation in the removal of dentinal debris.
Also, that same year, Costa et al. (1986) observed, by histological sections and morphometric analysis, that ultrasonic instrumentation provided better cleaning of the root canals than manual instrumentation.
The objective of the present study was to analyze, in vitro, the cleaning ability of Dakin's solution, water and Tergentol, when associated with ultrasonic instrumentation of root canals.
The irrigating solutions used during ultrasonic instrumentation were Dakin's, Tergentol (lauryl diethyleneglycol ether sodium sulfate, Searle) and deionized distilled water.
The teeth were placed in individual containers, numbered from 1 to 15, containing a 0.1% aqueous solution of thymol, with the objective of maintaining them hydrated and free from microbial proliferation. They were then stored in the refrigerator at 9°C until use.
The 15 teeth were randomly separated into 3 groups of 5 teeth each, identified by the irrigating solution used.
The ultrasonic unit Profiendo (Dabi-Atlante, Ribeirão Preto, SP, Brazil), with a potency of 25 kHz, was used for root canal instrumentation (Figure 1).
The files used for ultrasound were of the K-Flex type (21 mm; Sybron-Kerr, São Paulo, Brazil). Kerr files (#15; Sybron-Kerr, São Paulo, Brazil) were used for the initial manual preparation of the root canals.
Techniques of instrumentation and irrigation
At the time of use, the teeth were removed from the thymol solution and washed in running water for 1 h. .
The surgery of access to the pulp chamber was performed by the method recommended by Ingle et al. (1979), and the entrance into the root canal prepared with a Batt burr, with the pulp chamber always filled with the irrigating solution to avoid blocking the lumen of the root canal with particles of dentin.
The full extension of the root canal was then explored by manual instrumentation (Kerr file #15) establishing as the real working length the distance measured up to 0.5 mm below the root apex.
Manual instrumentation was performed with a #15 file to dilate the root canal and allow the introduction of the file energized by ultrasound, so that it could function freely in the interior of the canal. During this phase, the canal was irrigated with 2 ml of the irrigating solution. The ultrasonic unit Profiendo was regulated to allow an irrigating flow of 30 ml/min. The K-Flex file was selected for the ultrasonic system so that it could freely reach the entire working length.
Each file was used in the interior of the root canal for I minute in slow, short, back-and-forth movements. In all cases, 3 instruments of increasing consecutive sizes from the first, which was started by ultrasound, (files #15, #20, #25, and #30) were used; each canal required 5 min of instrumentation.
After instrumentation, the reservoir of the unit was washed and filled with distilled water for the final irrigation of the canal with a flow of 30 ml/min. For this final irrigation, a #15 file was placed in the ultrasonic unit and introduced into the interior of the already prepared canal for I min, with care taken not to touch the canal walls.
The same method was used with all of the teeth, only changing the irrigating solutions tested.
After the chemical-mechanical preparation of the root canals, the teeth were immersed in a solution of 10% formalin for 48 h, after which they were submitted to routine histological processing using 6-mm thick transverse sections stained with hematoxylin and eosin.
For the morphometric study, 10 semi-serial sections of the middle and apical thirds of each tooth were selected, separating the first section of every 50 serial sections in each one of the two regions and discarding the rest.
One of the lenses (6X) of the photomicroscope (Photomax, Olympus) was fitted with a 400-point grid, with the real space between 2 neighboring points being 500 mm. The objective used (10X) provided a final magnification of 60X which permitted an integral panoramic view of the section of dental tissue.
The points which occurred in two regions of the section - the clean area and the area with residues - were counted considering the sum of the points of the two areas as the total area of the root canal, without calculating the real value in terms of another measuring unit which was not the actual number of points counted.
After counting the points in the clean area and the area with debris in the canal, the percentage of the area of debris in the apical arid middle thirds was counted for each element of the 3 experimental groups, using the proportional relation between the number of points occurring in this area and the total number of points included in the area of the canal.
Preliminary tests showed that the sample distribution was normal (with a probability of 25% for the hypothesis of equality with a normal mathematical curve) besides being homoscedastic and with an independent variation which authorized the use of parametric tests (analysis of variance).
The analysis of variance (Table 2) showed statistical significance at the level of 1% of probability for the 2 factors of variation studied (irrigation solutions and root thirds), and non-significance for the interaction between them.
To define which of the irrigation solutions was significantly different from the others, the complementary Tukey test was used for this factor of variation (Table 3).
The Tukey test showed a statistical difference between the means of Tergentol and Dakin's solution with water being in an intermediate position, without definition if it was statistically equal to Tergentol or to Dakin's solution.
The statistical non-significance of the interaction of thirds X solutions indicated by the analysis of variance showed that the increase in the percent of debris always occurs in the same direction, i.e., from the middle region to the apical, no matter which solution is utilized.
There appears to be a general consensus that the chemical-mechanical preparation always leaves debris, organic as well as inorganic, in the interior of the root canal (Tucker et al., 1976; Moodnik et al., 1976; Cunningham et al., 1982; Costa et al., 1986). The studies performed have shown that not all walls of the canal receive the action of the instruments, commonly leaving areas completely untouched.
The new methods of preparation of the root canal which use energization by ultrasound allow continuous irrigation with a large volume of irrigating solution. These methods have been studied extensively to verify their efficiency in the dentin section as well as their real ability to remove resulting debris (Martin et al., 1980; Cunningham et al., 1982; Costa et al., 1986).
The results obtained in the present work show that Dakin's solution (mean = 1.08%) was -the solution which left the smallest amount of residue in the interior of the canals, followed by water (mean = 2.16%), and finally, Tergentol (mean = 3.09%), which left the greatest amount of debris (Figure 2).
The fact that Dakin's solution was the best cleaner of the root canal confirms the findings of Cunningham et al. (1982). This may be due to the potentiation of the solvent action of the sodium hypochlorite solutions when energized by ultrasound.
Tergentol, however, when energized by ultrasound allowed the greatest amount of debris to be left in the interior of the root canals, probably because of the large quantity of foam formed during the ultrasound energization, making an efficient contact of the irrigating liquid with the canal walls more difficult. In fact, it is known that the foam from a detergent can be eliminated by the addition of an anti-foam agent, and this could explain the results presented by Tergentol.
In this study, water occupied a position equidistant and statistically undefined between Dakin's solution and Tergentol. This position is due only to the mean values compared. In fact, this signifies only that the test used can consider a difference between the means 3.09 (Tergentol) and 1.08 (Dakin's solution) as statistically relevant, but cannot confirm the same in relation to the differences between these 2 and the intermediate value of 2.16 (water).
None of the irrigating solutions energized with ultrasound studied in the present work was capable of eliminating all of the debris in the root canals, since none of them left the root canals completely free of debris.
2. The apical third showed a greater amount of debris than the middle third, regardless of the solution used.
3. Dakin's solution, as an irrigating solution energized by ultrasound, left the root canals with less debris than Tergentol.
4. Water, as an irrigating solution energized by ultrasound, occupies a middle position, undefined between the effective action of Dakin's solution and the less efficient action of Tergentol.
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Correspondence: Professor Luiz Pascoal Vansan, Faculdade de Odontologia de Ribeirão Preto, Universidade de Sfio Paulo, 14050 Ribeirão Preto, SP, Brasil.
Accepted September 24, 1990
Eletronic publication: august 1997