LYSANDA PASTE: A NEW OPTION FOR ROOT-END FILLING

T ABSTRACT 1PhD, Professor, Department of Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil. 2PhD, Associate Professor, Department of Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil. 3PhD, Assistant Professor, Department of Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.


INTRODUCTION
Endodontic surgery is an acceptable procedure in cases of failure of endodontic treatment 5,12 .
Lysanda is a zinc oxide-eugenol material presented in two pastes; it is widely used in Prosthodontics. Dutra and Horta 11 (1994), Custodio and Costa 7 (1994) and Bernardineli 3 (1995) used this materials for root-end filling with good results and excellent adaptation to the cavity walls. Morais 18 (2003) studied the reaction of rat subcutaneous connective tissue to Lysanda paste, MTA and Portland cement containing iodoform and observed that Lysanda paste caused significantly lower inflammatory reaction than MTA and Portland cement, including formation of a more organized fibrous capsule compared to the other two groups.
Root-end filling materials require radiopacity to allow better radiographic visualization. Bismuth oxide, barium sulfate, zinc oxide and iodoform are radiopacifiers used in Endodontics and root-end filling materials 4,6,10,21 . Since Lysanda paste does not show this characteristic, it is important to determine whether the presence of these substances (zinc oxide or iodoform) would alter the properties of this paste and influence the apical marginal sealing of root-end fillings.

MATERIAL AND METHODS
The root canals of 50 single-rooted teeth from the tooth bank of the Department of Restorative Dentistry, Endodontics and Dental Materials, Dental School of Bauru were instrumented by the stepback technique, irrigated with saline, dried with absorbent paper points and filled with gutta-percha, zinc oxide and eugenol by the lateral condensation technique.
The apices were cut into approximately 2 mm at 45 o with a #699 tapered bur in a buccal direction. The teeth were rendered impermeable by application of fast-setting Araldite and nail varnish. Apical cavities were prepared to a depth of 2 mm with #2 round bur, complemented by irrigation with saline. The teeth were randomly divided into five groups of 10 teeth each and submitted to root-end filling with the following test materials: Group I -Lysanda paste with iodoform; Group II -Lysanda paste with iodoform and calcium hydroxide; Group III -Lysanda paste with iodoform and zinc oxide; Group IV -Lysanda paste with zinc oxide; and Group V -MTA.
In Group I, 0.62 g of red Lysanda paste and 0.46 g of white Lysanda paste were placed on a plate, with addition of 0.22 g of iodoform, and were mixed for 30 s. The material was then inserted in the root-end cavity with a blunt-tip probe until complete filling. Excess material was immediately removed. Procedures for Group II were the same as performed for Group I, with addition of 0.22 g of iodoform and 0.11g of calcium hydroxide. In Group III, the procedures were the same as those for Group I, with addition of 0.11 g of iodoform and 0.11 g of zinc oxide. In Group IV, the procedures were the same as for Group I, with addition of 0.22 g of zinc oxide. In Group V, MTA was prepared by mixing the power with distilled water until the ideal consistency for root-end filling was obtained.
After root-end filling, the teeth were immediately immersed in 2% aqueous methylene blue solution and incubated for 24 hours in an oven at 37 o C in humid environment, with a small container with water.
Then, the teeth were removed from the dye and sectioned buccolingually with a diamond disc, until half of root canal filling and consequently the root-end filling were exposed. This area was analyzed by reflected light microscopy for determination of leakage at buccolingual interfaces, in millimeters.
Data were statistically analyzed by one-way analysis of variance to investigate the possible significant differences between groups. Table 1 shows the means and standard deviations of apical leakage observed for the experimental groups, namely 0.44 mm for Group I (Lysanda + iodoform), 0.46 mm for Group II (Lysanda + iodoform + calcium hydroxide), 0.48 mm for Group V (MTA), 0.68 mm for Group IV (Lysanda + zinc oxide), and 0.77 mm for Group III (Lysanda + iodoform + zinc oxide).

RESULTS
One-way analysis of variance showed no significant differences in apical leakage between the different experimental groups (Table 2).

DISCUSSION
In the present study, there were no differences in apical leakage between groups. Lysanda paste yielded similar results as the other groups, regardless of the substances added (Table 1). Dutra and Horta 11 (1994) analyzing root-end fillings in dog's teeth, confirmed the high effectiveness of Lysanda paste compared to amalgam. Custódio and Costa 7 (1994) investigated the marginal leakage of root-end fillings with Lysanda, amalgam, ionomer and resin, and observed significantly better results for Lysanda. This is in agreement with the present results, including the observation of excellent adaptation of Lysanda paste with its components and of MTA.
The addition of other materials to Lysanda paste also provided satisfactory results, as shown by the numerical differences that yet were not statistically significant. The highest leakage rates, without statistical difference, were observed for Groups III and IV, which contained zinc oxide, probably due to lack of affinity between its components.
Analysis of Table 1 shows that the lowest leakage occurred in Group I (Lysanda with iodoform), without statistically significant difference compared to MTA.
According to Bramante and Berbert 5 (2000), four aspects are important for the success of root-end filling: the employed material, including its adequate physical, chemical and biological characteristics, is probably the most important factor. As mentioned earlier, numerous materials have been tested for root-end filling, all of which have advantages and disadvantages, yet certainly without meeting all or most requirements for good sealing.
With respect to Lysanda paste, one of the first studies using this material for root-end filling was conducted by Bernardineli 3 (1995), who demonstrated its high sealing  ability and excellent adaptation to the cavity walls, especially when compared to other materials. These data indicate the possible application of Lysanda paste as a new root-end filling material. However, the addition of radiopaque substances was needed to better test this material. In this respect, zinc oxide, calcium hydroxide and iodoform, either alone or in combination, seemed to be the ideal substances for this purpose, due to their good biocompatibility and broad clinical applicability. The advantages of iodoform as an intracanal medication include the formation of granulation tissue, new bone formation and lesion repair, leading to indication of its use. Zinc oxide and calcium hydroxide also show broad clinical applicability and their biological effects are widely known.
Another important aspect is the biocompatibility of Lysanda paste; its good acceptance is mainly related to the clinical indications of the material itself.
Morais 18 (2003), evaluating the reaction of rat subcutaneous connective tissue to MTA, Portland cement with iodoform and Lysanda paste, observed no difference between materials at 7 and 30 days, while at 60 days Lysanda paste showed significantly less inflammatory reaction than the other two cements. Portland cement with iodoform induced an even more organized fibrous capsule than MTA. An interesting aspect reported by Morais 18 (2003) is that the use of iodoform with Portland cement, whose combination with other cements is poorly known, yielded satisfactory results when compared to Lysanda and even to MTA, somehow agreeing with the present results observed for addition of iodoform to Lysanda paste.
Conversely, in our opinion, the use of Lysanda paste is encouraging, even though its indication in dentistry has always been limited. In this context, a very important aspect is its low cost, in contrast to MTA, which has a relatively high cost. The combination of Lysanda with other substances was necessary to complement some of its properties, as required for clinical application.
All these observations suggest that MTA may still be indicated for root-end filling. Lysanda paste with iodoform yielded the best result and thus can also be considered a good option as root-end filling material, as demonstrated by its positive aspects observed in the present experiment and in previous studies.
Studies using Lysanda paste are limited, but the definitely promising results encourage further investigations, especially on its biological properties, to confirm its qualities as a root-end filling material and as a possible paste or cement for root canal filling in the future.

CONCLUSIONS
Overall, the analysis of the results allowed the following conclusions: 1. Apical marginal leakage occurred in all groups; 2. Lysanda paste with iodoform showed the lowest leakage, without statistically significant difference compared to other groups; 3. All materials can also be considered good options as root-end filling materials.