Braz Dent J (1998) 9(2): 67-76 ISSN 0103-6440
| Introduction | Material and Methods | Results | Discussion | Conclusions | References |
The subject of this paper was to study the behavior of the periapical tissues of dogs' teeth after biopulpectomy and dressing with calcium hydroxide or a corticosteroid-antibiotic association, before root canal filling with zinc oxide eugenol (ZOE) or Sealapex sealers. The teeth were overinstrumented and dressed for 7 days before the root canal filling. The animals were sacrificed 180 days after treatment and the specimens were prepared for morphological analysis. Specimens treated with Sealapex presented a higher number of cases with biological closure than ZOE. When the root canals were filled with ZOE, better results were observed with the use of the Ca(OH)2 dressing.
Key Words: calcium hydroxide, corticosteroid, antibiotic, intracanal dressing.
Currently, the possibility of root canal treatment in one sitting in cases of biopulpectomy is not questioned. However, it must be understood that it is not always possible to conclude treatment in only one session. In these cases, the integrity of the pulp stump and periapical tissues should be maintained, providing a repair close to the ideal, which is with apical closure by the deposition of hard tissue (Coolidge and Kesel, 1956; Holland and Souza, 1985).
Holland et al. (1969) used corticosteroid associated with an antibiotic as a dressing in dogs' teeth. The histological results showed that these drugs were related to the preservation of pulp stump vitality and the integrity of the periapical tissues. Smith et al. (1976), in a histological study in dogs' teeth, reported that with the use of a corticosteroid there was better control of the inflammatory reaction after pulpectomy. Nery et al. (1974) reported that the action of even the most irritating materials was controlled when a corticosteroid-antibiotic dressing was used in the treatment of dog root canals. Moraes et al. (1977) compared the behavior of dog periapical tissues using camphorated p-monochlorophenol, Cresalil and a corticosteroid-antibiotic association. The most biocompatible medication was the corticosteroid-antibiotic association. Holland et al. (1980) studied in dog's teeth three corticosteroid-antibiotic associations: Otosporin, Otosylanar and Panotil. Forty-eight hours after treatment, Otosporin showed the best results, preserving the vitality of the pulp stump and controlling the intensity of the inflammatory reaction of the periapical tissues. In 1981, Holland et al. tested the same 3 products in cases of over-instrumentation. Seven days after treatment, they observed better results with Otosporin. Neoformed connective tissue growing into the root canal, reconstituting the pulp stump destroyed by the over-instrumentation was observed. In the control group, the periapical tissue was inflamed and disorganized.
Currently, calcium hydroxide (Ca(OH)2) is being used as a dressing more frequently. This drug has been used in cases of necropulpectomy, providing a high repair index in teeth with periapical lesion (Souza et al., 1989). Little emphasis has been given in cases of biopulpectomy. However, the action of Ca(OH)2 close to the pulp stump and periapical tissues has been reported to be similar to that described for pulp tissue (Holland, 1971). The presence of birefringent granulations (apatite crystals) is observed at 2 days by polarized light characterizing the reaction between the calcium ions from Ca(OH)2 and the carbonic gas of the tissue. These granulations appear in the bordering area between the necrosed and vital pulp stumps. In this phase, deposition of other calcium salts from the organism were also observed. At 7 days, the deposition of calcium salts from the organism is accentuated. The periodontal ligament exhibits a mild inflammatory reaction, which indicates a favorable reaction of that tissue to the tested drug (Holland et al., 1978b). These results, observed in dogs' teeth, were confirmed through morphological and histochemical studies conducted in human teeth (Leonardo and Holland, 1974; Holland et al., 1977a).
The purpose of this research was to study, in dogs' teeth, the behavior of the periapical tissues after biopulpectomy and dressing with calcium hydroxide or a corticosteroid-antibiotic association before root canal filling with two different sealers.
Material and Methods
Sixty roots of mongrel dogs' teeth were used in this study. The animals were anesthetized with 3% sodium Nembutal and treatment was always conducted in 2 sessions. In the first one, the coronary openings were made, the pulp was removed and the canals were negotiated by a crown-down technique.
All root canals were over-instrumented up to K file #20. The canals were then prepared up to the canal-dentin-cement limit up to K file #40, in such a way as to obtain a main canal foramen. Finally, a step-back preparation was made up to H file #80.
During instrumentation, the root canals were thoroughly irrigated with saline. After drying, half of the root canals were dressed with an association of hydrocortisone, neomycin and polymyxin B (Otosporin, Wellcome), and the other half with calcium hydroxide in distilled water.
Seven days later, the dressings were removed and the root canals were filled using the lateral condensation technique with gutta percha points and ZOE (S.S. White) or Sealapex (Sybron-Kerr) sealers.
One hundred and eighty days after treatment the animals were sacrificed, and the specimens were fixed in 10% neutral-buffered formalin.
After decalcification in formic acid-sodium citrate, the specimens were embedded in paraffin, cut serially at six-micrometer thickness, and these sections were stained with hematoxylin and eosin.
Ca(OH)2-ZOE experimental group
Six cases exhibited complete biological filling by deposition of neoformed cementum. The neoformed cementum was deposited inside the canal, at the level of the main apical foramen (Figure 1), or invading the periodontal ligament (Figure 2). There was an absence of inflammatory reaction in the periodontal ligament, except in one case that contained small chronic infiltrate in a restricted area. One case (Figure 2) showed biological closure next to dentin chips condensed in the apical area during instrumentation.
Five specimens exhibited partial biological closure, with a gap in the neoformed bridge, where the filling material communicated with the periodontal ligament (Figure 3). There was always a mild chronic inflammatory reaction.
Four cases did not exhibit biological closure. In 2, neoformed cementum covering the root canal walls was observed. The connective tissue reached the filling material and exhibited a mild chronic inflammatory reaction. The other 2 specimens showed slight overfilling. The filling material was involved by a fibrous capsule, exhibiting a mild chronic inflammatory reaction in one case and a moderate reaction in the other.
The small accessory root canals exhibited connective tissue without an inflammatory reaction and with biological closure by neoformed cementum at its most coronal portion.
Ca(OH)2-Sealapex experimental group
Twelve specimens showed complete biological closure (Figure 4 and 5) by neoformed cementum deposited at the main apical foramen. Eight cases did not exhibit an inflammatory reaction in the periodontal ligament. Four cases showed a mild chronic inflammatory reaction close to the particles of the filling material present in the apical periodontal tissue (Figure 5).
In 3 specimens the biological closure was partial and there was overfilling. Black particles of the filling material were observed in the root canals and periapical tissues. Moderate or mild chronic inflammatory reaction was observed around the overfilled material.
The small accessory root canals exhibited connective tissue without inflammation and with biological closure in its most coronal portion (Figure 6).
Otosporin-ZOE experimental group
Three cases exhibited complete biological closure of the main apical foramen, with the neoformed cementum in contact with the gutta percha point or with hard tissue chips. These cases did not show any inflammatory reaction in the periodontal ligament.
Four specimens exhibited partial biological closure. One of them contained an overfilling of dentin chips with neoformed cementum deposited on those fragments. Close to a gap in the hard tissue bridge a moderate chronic inflammatory reaction was observed.
Biological closure was absent in 8 cases. In 2 specimens there was only slight neoformed cementum in the apical portion and a lack of connective tissue in the root canal. One case showed a mild chronic inflammatory reaction, while the inflammatory reaction was moderate in the other. The other 6 cases exhibited ingrown connective tissue and cementum deposition on the walls of the root canal, reaching the proximity of the filling material (Figure 7 and 9). The ingrown connective tissue showed a mild chronic inflammatory reaction (Figure 8). In 3 cases, the chronic inflammatory reaction in the periodontal ligament was of moderate intensity.
The pulp stump observed in the small accessory root canals exhibited vitality or not, and in some cases showed biological closure by cementum deposition in its most apical portion.
Otosporin-Sealapex experimental group
In this experimental group, there were 11 cases of complete biological closure of the main apical foramen. Five of these cases did not present an inflammatory reaction in the periodontal ligament (Figure 10). A mild chronic inflammatory reaction was observed in 4 cases (Figure 11), while in the other 2 the inflammatory reaction was moderate. In these 6 cases with biological closure and an inflammatory reaction, there was overfilling.
The biological closure was partial in 3 specimens. Of these, 2 exhibited overfilling and a chronic inflammatory reaction of mild to moderate intensity. In the third case, a mild inflammatory reaction was observed.
One case did not exhibit biological closure but only overfilling and a moderate chronic inflammatory reaction next to the filling material.
The pulp stumps contained in the small accessory root canals exhibited vitality and an absence of inflammatory reaction. In its most coronary portion, there was biological closure by neoformed cementum in most cases.
In all cases with overfilling with the Sealapex sealer, in both this and the other experimental group, the observed inflammatory reaction was restricted to the area of the sealer. Macrophages were the predominant cellular element observed.
A summary of the results is given in Table 1. The percent of biological closure is illustrated in Figure 12.
In cases of biopulpectomy, not using a biocompatible dressing, or another dressing can be injurious to the pulp stump and periapical tissues (Holland et al., 1969). Thus, we treated the teeth in two sessions, varying the dressing and the root canal sealer. When Ca(OH)2 is applied immediately after over-instrumentation, unlike that which occurs in the presence of organized tissue, it tends to be reabsorbed and substituted by periodontal connective tissue (Stromberg, 1969; Holland et al., 1979). The ingrown connective tissue totally changes the morphologic condition because there is a substitution of Ca(OH)2 by organized tissue.
A similar result can be observed with a corticosteroid-antibiotic association. Seven days after over-instrumentation and application of a dressing with Otosporin, there was an ingrowth of connective tissue into the cementum portion of the root canal (Holland et al., 1981). However, this does not occur with all corticosteroid-antibiotic associations, as reported by Holland et al. (1981), which is why we chose Otosporin in this investigation.
In the present experiment, after the application of the dressing, a group of teeth were filled with a sealer containing ZOE, a substance considered to be a tissue irritant (Erausquin and Devoto, 1970; Holland et al., 1977b). However, in this study, the results presented interesting data, with the presence of a generally mild chronic inflammatory reaction. We believe that this has some relationship with the studied dressings, as well as with the relatively long post-operative period. Souza et al. (1995) observed that when using a corticosteroid-antibiotic dressing before root canal filling with ZOE, 7 days later there was a minor tissue reaction compared to the one observed when no dressing was used. However, at 180 days there was no difference between the groups. On the other hand, Holland et al. (1977b) reported a severe inflammatory reaction with ZOE, shortly after treatment in only one session; however, this reaction decreased with time.
Comparing the results obtained with ZOE after the Ca(OH)2 dressing with the Otosporin dressing, we observed some interesting results. The occurrence of total and partial biological closure was more frequent with Ca(OH)2. Similarly, the occurrence of an inflammatory reaction was less expressive in this group. Another notable result was the biological behavior of the pulp stumps contained in the small accessory root canals. While biological closure could also be observed in some cases of the corticosteroid-antibiotic group, in the Ca(OH)2 group it was almost the rule. Ca(OH)2 was applied in contact with a blood clot close to the main apical foramen, but in the small accessory root canals it was in contact with organized tissue. Holland et al. (1978b) and Souza et al. (1995) demonstrated that there is calcification of the most coronary portion of the pulp stump at 7 days. In the present experiment that process was not disturbed by the root canal filling with ZOE.
In the Ca(OH)2-ZOE group, 6 cases of complete biological closure were observed in the main foramen, of which 1 had a close relationship with the presence of dentin chips. In the Otosporin-ZOE group there were 3 cases of biological closure of which 2 had a close relationship with dentin chips. There are several reports of dentin chips stimulating the deposition of hard tissue in dental pulp (Holland et al., 1978a), and periapical tissues (Holland et al., 1989), which would justify our observation. On the other hand, the cases of biological closure seen in the Ca(OH)2-ZOE group seem to be related to the performance of Ca(OH)2. The property of Ca(OH)2 in stimulating this occurrence was reported in several studies (Holland, 1971; Leonardo and Holland, 1974; Holland et al., 1978a,b, 1982). Holland et al. (1978b) and Souza et al. (1995) observed calcification of the coronary portion of the pulp stump contained in the small accessory root canals in dogs' teeth, 7 days after treatment. This was also observed in the pulp stump of human teeth by Holland et al. (1977a) at 2 and 15 days after treatment.
The results obtained in the Ca(OH)2-ZOE group, together with those reported by Souza et al. (1995), suggest that, in cases of the use of Ca(OH)2 as a dressing for one week after biopulpectomy, a series of well-known events is started. These events would not be altered by root canal filling with ZOE, mainly when the Ca(OH)2 dressing was placed in contact with organized tissue.
When root canals were filled with Sealapex, 12 cases (80%) of biological closure were observed after the use of a Ca(OH)2 dressing, and 11 cases (73.3%) when Otosporin was used. This incidence of biological closure was greater that that reported by Holland and Souza, (1985) and Bonetti Filho (1990), who observed 35 and 50% biological closure, respectively. These authors performed over-instrumentation and root canal filling in a single session. These data and ours point out the importance of the use of a dressing for the organization of a new pulp stump, in cases of overinstrumentation and, consequently, for better performance of the Ca(OH)2 contained in the root canal sealer.
The presence of a mild chronic inflammatory reaction in the periodontal ligament was observed in some cases of root canals filled with Sealapex due to a minor over-filling which was more frequent in the group where Otosporin was used for dressing. This occurred less frequently when using Ca(OH)2. Macrophages with black particles from the filling material have already been described in other reports. However, biological closure was described in these cases (Holland and Souza, 1985; Holland et al., 1990).
A larger number of cases with biological closure (60%) were obtained with the use of Ca(OH)2 as a dressing than with Otosporin (46.6%). A significant difference was obtained with the two root canal sealers: Sealapex exhibited 76.7% biological closure, while ZOE only 30%.
When Ca(OH)2 was used as a dressing the biological closure of the pulp stumps of the small accessory root canals was similar for the two studied sealers; however, the best results were obtained with Sealapex, when the dressing was Otosporin.
1) Using Otosporin as the dressing, biological closure of the main foramen was observed in 73.35% of the cases when the filling material was Sealapex and 20% with the sealer ZOE.
2) Using Ca(OH)2 as the dressing, biological closure of the main apical foramen was observed in 80% of root canals filled with Sealapex and 40% with the sealer ZOE.
3) Using Ca(OH)2 as the dressing, no difference was observed in relation to the small accessory root canals, with the two sealers.
4) When the dressing was Otosporin, the small accessory root canals showed a larger incidence of biological closure when the sealer was Sealapex.
5) When particles of Sealapex reach the periodontal ligament, they generally cause a mild inflammatory reaction, characterized mainly by macrophagic activity. In the absence of biological closure, and even without overfilling, ZOE frequently produced a mild chronic inflammatory reaction.
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Correspondence: Prof. Titular Roberto Holland, Rua José Bonifácio, 1193, Vila Mendonça 16015-050 Araçatuba, SP, Brasil.
Accepted september 11, 1998
Electronic publication: April, 1999