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Comparative in vitro study of apically extruded material after different technique of root canal instrumentation

Root canal instrumentation - apically extruded material

Luis Pascoal VANSAN
Jesus Djalma PÉCORA
Wanderley Ferreira da COSTA
Ricardo Gariba SILVA
Ricardo Novak SAVIOLI

Este trabalho está publicado no Brazilian Dental Journal 8(2(:79-83, 1997

Disciplina de Endodontia da Faculdade de Odontologia de Ribeirão Preto - USP, Ribeirão Preto, SP, Brasil.


Forty extracted human upper central incisors were submitted to root canal instrumentation 1 mm from the apex by the standard, step-preparation, crown-down, and ultrasound techniques, using distilled and deionized water as irrigating solution.

The extrusion product was collected into a collecting device for extruded material especially fabricated for this purpose. Extrusion was calculated by the determination of the mass of extruded material.

The step-preparation technique promoted a larger amount of extrusion than the standard technique, which in turn promoted greater extrusion than the crown-down and ultrasound techniques. All techniques used promoted extrusion of material beyond the apical foramen.

Key Words: Root canal instrumentation, apically extruded material.


A successful intervention in the root canal consists of the cure and repair of the tissues involved and is based on the fulfillment of the following requirements: chemical-mechanical instrumentation, microbiological control and root canal sealing. It should be pointed out that the various phases of endodontic treatment are interdependent, with equivalent and additive importance and responsibility in terms of successful or unsuccessful total treatment. Among these phases, chemical-mechanical instrumentation of the root canal is the one requiring most time and best preparation on the part of the professional.

Several studies have shown that dentin filings, necrotic tissue, pulp remnants, microorganisms and irrigating solution may be forced towards the periapical tissues during root canal instrumentation. Thus, extrusion of the material is a problem that occurs with the use of various instrumentation techniques (Heuer, 1963; Chapman et al, 1968; Vandevisse & Brilliant, 1975; Martin & Cunningham, 1982; Fairbourn et al, 1987; Ruiz-Hubard et al, 1987; McKendry, 1990; Lee et al, 1991).

The objective of the present study was to compare the quantity of material extruded through the apical foramen during root canal instrumentation using four different instrumentation techniques, i.e., standard, step-preparation, crown-down and ultrasound.

Material and Method

Forty newly extracted human upper central incisors were used. The teeth had a fully formed foramen and were of approximately equal length, i.e., 21 to 22 mm, and their apical foramen had a diameter similar to that of a 20 file. For the three techniques of manual instrumentation we used 15 to 40 K Maillefer files, and for ultrasound we used an Enac apparatus coupled to a pressurized reservoir containing the irrigating solution. Mani K files were used with the ultrasound apparatus.

Distilled and deionized water was used as irrigating solution for all techniques studied, in the volumes routinely applied in each technique.

Four groups of 10 teeth each were used for each instrumentation technique. All instrumentation techniques were executed with the tooth fixed in a device for the collection of extruded material previously fabricated for this study (Figure 1D). The device consists of an acrylic body with a lateral orifice at an angle that permits placement of the teeth attached to a spring always at the same inclination (Figure 1E). The device contains an opening in the upper end that permits contact with the root of the tooth and another opening in the lower end for drainage of the irrigating solution utilized. This lower end is removable and is fitted with a screw-on adaptation measuring 20 mm in diameter (Figure 1A) used to hold the filter paper (Figure 1B).
This ensemble is connected to a metal rod with a clamp and fixed to a universal support fitted with two metal clamps, one of them used to fix the metal rod and the other used to hold a 25 mm burette containing distilled and deionized water (Figure 1 C). The objective was to wash the root portion at the end of each instrumentation, spilling onto the filter paper the remaining extrusion material, which adhered to the outer portion of the apical third.

A pilot study showed that filter paper disks moistened with 3 ml distilled and deionized water would dry and reacquire the initial mass after being placed in an oven at 37oC for 90 minutes.

Extrusion was calculated by weighing the materials that passed through the apical foramen of the tooth and were collected on the filter paper disk, as shown in figure 1 F1 for standard instrumentation, in figure 1 F2 for step-preparation, in figure 1 F3 for the crown-down technique, and in figure 1 F4 in the ultrasound technique. As a safety margin, we determined that the disks containing the extruded material needed to be left in the oven at 37oC for 3 hours. The weight was considered to be final only when it maintained the same value after three consecutive weight determinations made at 30-minute intervals.

The mass of the extruded material was calculated as the difference between the mass of the paper disk before and after collection of the material extruded through the foramen opening of the tooth during root canal instrumentation.

All weight determinations were performed with an MLW scale with a margin of error of 0.01 mg.


The experimental data of the present study consisted of 40 numerical values corresponding to the mass (mg) of the materials extruded through the apical foramen as a function of the techniques for root canal instrumentation utilized. The values were obtained from the factorial product of 4 instrumentation techniques x 10 teeth (replications) (table I).

TABLE I Mass (mg) of the material extruded through the apical foramen of the root canal.
  Techniques for root canal instrumentation
Replications Standard Step-Preparation Crown-Down Ultrasound
1 19.8 26.6 0.4 1.2
2 18.5 49.1 1.1 0.6
3 15.5 48.6 4.8 1.8
4 17.6 33.0 0.8 2.6
5 9.6 40.4 0.4 1.4
6 26.5 33.1 1.0 1.9
7 24.5 25.6 5.9 3.4
8 22.8 38.4 5.0 2.3
9 23.5 18.3 3.5 2.1
10 9.5 50.1 2.5 3.0

Preliminary statistical tests applied to the original data indicated that data distribution was not normal. The data were then transformed to square roots in order to improve the unfavorable characteristic of sample distribution. When preliminary tests were again applied to determine normality, it was concluded that when the square roots of the original data were used the sample distribution was normal and homogeneous, thus permitting the application of parametric statistical tests. Analysis of variance showed high significance at the 1% level of probability for the hypothesis of equality, indicating that there were differences between the techniques for root canal instrumentation studied in terms of their action in promoting extrusion of the material through the apical foramen. A complementary Tukey test was carried out to compare the mean values for the extrusions provoked by the four techniques (table II).

TABLE II Tukey test comparing the mean values for the four techniques (square roots of the data)
Technique Means Critical value (a = 0.1)
Step-preparation 5.96#  
Standard 4.27+ 1.05
Crown-down 1.45*  
Ultrasound 1.39*  

Means followed by equal symbols did not differ significantly


Root canal instrumentation requires technical knowledge to be applied to the biological area, so as to obtain a well instrumented and disinfected canal without damage to its biological structure. Since the root canal includes the space that contains the pulpar organ, one of its ends is in the pulp chamber and the other(s) correspond to the apical foramina. Thus, the act of instrumentation of the root canals, of itself, causes the possible extrusion of material through the foramen by virtue of the anatomy of the canal itself.

Researchers have long been trying to develop instrumentation techniques that will minimize this problem. In the present study we made an attempt to develop a specific experimental model using natural teeth in which all possible variables could be controlled, with only the extrusion in the presence of the different techniques of root canal instrumentation being left for concrete analysis.

Root canal instrumentation using filing movements may force the material to the periapex since, as pointed out by Grossman (1956), files act as pistons. The present findings confirm these observations, as shown by the high index of material extrusion observed with the conventional and step-preparation techniques compared to the ultrasound and crown-down techniques, in which the canal is instrumented with vibratory and rotary movements, respectively. The step-preparation technique promoted more extrusion probably because, in addition to the use of the standard technique for the apical third, the memory instrument that runs along the entire length of the canal is employed after each instrument of larger caliber is used when backing up during root canal instrumentation, a fact that can cause extrusion.

The present results also agree with those reported by Ruiz-Hubard (1987) who demonstrated a better performance of the crown-down technique compared to the step-preparation technique. The present results concerning the amount of material extruded with the use of the ultrasound technique agree with those reported by Martin & Cunningham (1982).

The present observations showing that all instrumentation techniques used in the study promoted extrusion of the material beyond the apical foramen confirm and support the data reported by other investigators, who stated that extrusion is unavoidable with the use of any instrumentation technique (Chapman et al, 1968; Weine, 1976; Martin & Cunningham; 1982, Fairbourn Et Al, 1987; Ruiz-Hubard et al, 1987; Mckendry, 1990; Lee et al, 1991; Myers & Montgomery, 1991).

A general overview of the present results shows that they almost fully agree with those reported in the literature.


On the basis of the methodology employed and of the results obtained, we conclude that:

1. there was extrusion of material through the apical foramen of the teeth with the use of all techniques of root canal instrumentation studied.

2. The step-preparation technique promoted greater extrusion of material through the apical foramen than the other techniques studied.

3. The ultrasound and crown-down techniques form a pair, with statistically similar results and promoted less extrusion of material through the apical foramen.

4. The standard technique promoted less extrusion of material through the apical foramen than the step-preparation technique and greater extrusion than the crown-down and ultrasound techniques.


Chapman CE, Colle JG, Beagrie GS: A preliminary report on the correlation between apical infection and instrumentation in endodontics. J Br Endod Soc 2: 7-11, 1968

Fairbourn DR, McWalter GM, Montgomery S: The effect of four preparation techniques on the amount of apically extruded debris. J Endod 13: 102-8, 1987

Heuer MA: The biomechanics of endodontic therapy. Dent Clin North Am 13: 341-59, 1963

Grossman LI: Tratamento dos canais radiculares. 2nd ed. Rio de Janeiro, Atheneu 1956.

Lee SJ, Strittmatter EJ, Lee CS: A compararison of root canal content extrusion using ultrasonic and hand instrumentation. Endod Dent Traumatol 7: 65-8, 1991

Martin H, Cunningham WT: The effect of endosonic and hand manipulation on the amount of root canal material extruded. Oral Surg 53: 611-3, 1982

McKendry DJ: Comparison of balanced forcs endosonic, and step-back filling instrumentation technics: quantification of extruded apical debris. J Endod 16: 24-7, 1990

Myers GL & Montgomery S: A comparison of weights of debris extruded apically by conventional filing hand canal master thecniques. Endod 17: 275-9, 1991

Ruiz-Hubard EE, Gutman JL, Wagner MJ: A quantative assessiment of canal debris forced periapically during root canal instrumentation using two different techniques. J Endod 13: 554-8, 1987

Weine F S, Kelly R F, Bray K E: Effect of preparation with endodontic hand piece on original canal shape. J Endod 2: 298, 1976

Vande-Visse JE, Brilliant JD: Effect of irrigation on the production of extruded material at the root apex during instrumentation. J Endod 1: 243-6, 1975
  COPYRIGHT 1999 Webmaster J.D. Pécora, Reginaldo Santana Silva Update 21/sept, 1999
Esta página foi elaborada com apoio do Programa Incentivo à Produção de Material Didático do SIAE - Pró - Reitorias de Graduação e Pós-Graduação da Universidade de São Paulo


Figure 1
Figure 1 Device constructed to collect extruded material.

Figure 2 Figure 3
Figure 2. device of acrylic with a lateral orifice. Figure 3.

Figure 4 Figure 5
Figure 4. Figure 5. Paper discs showing collected material after instrumentation. © 1999 - 2002, Todos os direitos reservados.
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