Jesus Djalma PÉCORA1
Antônio Luís CUSSIOLI1
Danilo M. Zanello GUERISOLI1
Melissa A. MARCHESAN1
Manoel D. SOUSA-NETO2
1Faculty of Dentistry of Ribeirão Preto, University
of São Paulo, Ribeirão Preto, SP, Brazil
2Faculty of Dentistry, University of Ribeirão Preto (UNAERP), Ribeirão Preto, SP, Brazil
3University Camilo Castelo Branco, Dental Association of the State of São Paulo, São Paulo, SP, Brazil
Correspondence: Prof. Dr. Jesus Djalma Pécora, Departamento de Odontologia Restauradora, Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, 14040-904 Ribeirão Preto, SP, Brasil. e-mail: email@example.com
Braz Dent J (2001) 12(1): 27-30 ISSN 0103-6440
INTRODUCTION | MATERIAL AND METHODS | RESULTS | DISCUSSION | RESUMO | REFERENCES
The effect of Er:YAG laser application and EDTAC on the adhesion of epoxy resin-based endodontic sealers to human dentin was evaluated in vitro. A total of 99 extracted human maxillary molars with their crowns worn flat were used. The teeth were divided into 3 groups: group 1, the dentin surface received no treatment; group 2, EDTAC was applied to the dentin surface for 5 min; group 3, the dentin surface received Er:YAG laser application (2.25 W potency; 11 mm focal distance; 4 Hz frequency; 200 mJ energy; 62 J total energy; 313 mean impulse). Three teeth from each group were analyzed by scanning electron microscopy for changes in dentin surface. The epoxy resin root canal sealers used were: AH Plus®, Topseal®, Sealer 26®, AH 26®, and Sealer Plus®. The zinc oxide eugenol-based sealer Fillcanal® was used as control. Adhesion was measured with a Universal testing machine. The results showed a statistically significant difference at the level of 1% among the dentin treatments. The dentin treated with Er:YAG laser showed greater adhesion with the sealers than dentin treated with EDTAC which was greater than dentin that received no treatment. The Tukey test showed the formation of 5 groups in decreasing order of adhesion: AH Plus, Topseal and Sealer 26, AH 26, Sealer Plus, and Fillcanal (Grossman cement).
Key words: Endodontics, Er:YAG laser, root canal sealer.
Because a hermetic seal of root canals is essential in Endodontics, sealing materials and their properties are of vital importance for the success of root canal treatment. The properties of the root canal sealers can be classified as physico-chemical, antimicrobial and biological. In 1984, a series of regulations and tests were made effective, created one year earlier by the American Dental Association (1) for the standardization of research of these properties. However, no model for adhesion and apical microleakage tests was adopted.
Adhesion of a root canal sealer means its capacity to attach to the dentinal walls of the root canal and provide bonding between it and gutta-percha points. Ørstavik (2) reported the use of the Universal testing machine to perform adhesion tests of the root canal sealers. This method was also used by Hyde (3), Wennberg and Ørstavik (4), and Sousa-Neto (5).
During the chemo-mechanical preparation of the root canal, a smear layer is produced, which is a negative factor in root canal obturation, because it is constituted by organic and inorganic material located on the interface between the root canal walls and the sealing material and weakly attached to them. Thus, it interferes in the adhesion of the sealing material to the root canal walls (6-8). Researchers have recommended a final flush of EDTA (ethylenediaminetetraacetic acid) after the biomechanical preparation of the root canal in order to remove this smear layer (9-11). Recently, Takeda et al. (12) showed the capacity of Er:YAG laser in removing smear layer. Sousa-Neto (13) reported that after Er:YAG application on dentin surface, the adhesion of Sealer 26 increased.
The objective of the present research is to evaluate the effect of EDTAC and Er:YAG laser on the adhesion of epoxy resin-based root canal sealers to human dentin.
MATERIAL AND METHODS
The enamel of the occlusal surface was removed from ninety-nine human molars from laboratory stock with a number 4138 diamond bur (KG Sorensen, Barueri, SP, Brazil) in a high speed handpiece cooled with water. After obtaining a flat occlusal surface, the teeth were fixed by their roots in an acrylic resin base to be adapted to the Instron Universal testing machine (model MEM 2000, Curitiba, PR, Brazil).
The teeth were divided randomly into 3 groups of 33 samples each. The first group received no treatment at all. In the second group, 50 µl of EDTAC was placed on the dentin surface for 5 min. This EDTAC solution was fabricated at the Endodontics Research Laboratory (FORP-USP, Ribeirão Preto, SP, Brazil) and consists of an aqueous solution of 15% EDTA (Merck, Rio de Janeiro, RJ, Brazil) at pH 7.3 and 0.1% Cetavlon® (cetyltrimethylammonium) (Sigma, St. Louis, MO, USA). The third group received irradiation with Er:YAG laser (KaVo Key laser II, Warthausen, Germany) on the dentin surface, with the following parameters: 11 millimeters focal distance perpendicular to the dentin surface, 4 Hz frequency, 200 mJ energy, 1 min application time and 2.25 W power, totaling 62 J of energy.
Six root canal sealers were used in this experiment: Sealer 26 (Dentsply,
Petrópolis, RJ, Brazil), AH 26 (Dentsply, Konstanz, Germany), AH
Plus (De Trey-Dentsply, Konstanz, Germany), Sealer Plus (Dentsply, Petrópolis,
RJ, Brazil), Topseal (Dentsply-Maillefer,
Ballaigues, Switzerland) and Fillcanal (D.G. Ligas Odontológicas, Rio de Janeiro, RJ, Brazil). Five repetitions for each experimental group were performed for each root canal sealer.
Aluminum cylinders (10 mm high x 6 mm internal diameter) with stainless steel handles were placed on the dentin surface and fixed laterally to the teeth with wax. After preparation according to manufacturers' directions, the sealers were carefully placed inside the cylinders with the aid of a vibrator. The material was then placed at 37oC, 95% humidity for a period 3 times greater than the normal setting time of the sealer.
The samples were placed in an Instron Universal testing machine (model MEM 2000), with a grip that held the aluminum cylinder handle and exerted vertical traction. The machine was calibrated to run at a constant speed of 1 mm/min until the aluminum cylinder containing the sealer was detached. The traction force necessary to detach the device from the tooth, given in kilograms-force (KgF) and later transformed to MegaPascal (MPa), was recorded. The Tukey test was used for statistical analysis (p<0.01). Three teeth from each group were evaluated by scanning electron microscopy for changes in the dentin surface.
Figure 1 shows the mean values of the adhesion test for the 6 sealers. Statistical analysis showed significant differences (p<0.01) between the tested sealers, except for Topseal and Sealer 26, that were statistically similar. The sealers can be ranked in decreasing values of adhesion to dentin: AH Plus, Sealer 26 and Topseal, AH 26, Sealer Plus, and Fillcanal.
The treatments for dentin showed significant differences (p<0.01) between treatments, with higher adhesion values for dentin irradiated with Er:YAG laser. Dentin with no treatment revealed the lowest adhesion values, and dentin treated with EDTAC was in an intermediate position.
Adhesion is among the properties that an ideal root canal sealer must have, according to Grossman (14) and Branstetter and Fraunhofer (15).
The American Dental Association, in 1983, established a series of regulations and tests for the studyof the physical properties of root canal sealers. However, due to the lack of consensus among researchers, adhesion tests were not standardized. Ørstavik (2) proposed the use of the Universal testing machine to test root canal sealer adhesion. This method was also used by Hyde (3), Wennberg and Ørstavik (4) and Sousa-Neto (5,16). The Universal testing machine promotes better uniformity and greater reproducibility, providing more accurate results, and tension values in MegaPascal (MPa) favor comparison of results, because it is an internationally accepted unit.
The adhesion of Grossman type root canal sealers to dentin is established by electrostatic bonding and not by its penetration into the dentinal tubules. For this reason, the action of EDTAC and Er:YAG laser did not significantly increase adhesion values of Fillcanal to dentin. Ionic bonding between rosin and dentin is weak by its own nature (5).
Epoxy-based sealers show higher adhesion to dentin and among these, AH Plus had the highest values for the traction test. Topseal and Sealer 26 presented inferior adhesion values compared to AH Plus, but superior to the other tested sealers. According to the manufacturers (Dentsply), Topseal and AH Plus have the same formulation. The difference between them lays in the fact that AH Plus is produced by De Trey, a Dentsply subsidiary in Germany, and Topseal is produced by Dentsply-Maillefer in Switzerland. Manufacturers in different countries use chemical compounds acquired and produced in different places with different manufacturers and packing. In terms of adhesion to dentin, they have distinct behaviors. Sealer 26, produced by Dentsply from Brazil, showed adhesion to dentin similar to Topseal. It is an epoxy-based sealer with a formula similar to AH Silver Free, except that Sealer 26 has calcium hydroxide in its formulation while AH Silver Free does not. This addition of calcium hydroxide to the formula implies a reduction of the bismuth trioxide percentage.
The chelating agent EDTAC increased adhesion values when compared to the dentin without any treatment. EDTAC removes smear layer, which can permit the penetration of epoxy-based sealers into the dentinal tubules. This favors a greater bonding between dentin and sealer, increasing the adhesion values compared to dentin without treatment (Figure 2).
Application of Er:YAG laser to dentin surface caused higher adhesion
of epoxy-based sealers. This
can be explained by two factors: a) the removal of smear layer, exposing dentinal tubules that are partially filled with sealer, creates a "tag" (17), and b) the conditioning of the dentin surface, causing a higher mechanical bonding between sealer and intertubular dentin by increasing the area termed micro-retentive pattern (18) (Figure 3). This pattern did not increase the adhesion values of Fillcanal, a zinc oxide eugenol-based sealer.
Sousa-Neto (13) reported that application of Er:YAG laser to dentin promoted an increase in adhesion values of Sealer 26. This was confirmed by this experiment which showed that application of Er:YAG laser and EDTAC to the surface of human dentin increased the adhesion of endodontic sealers. It is important to remember that the laser beam was applied perpendicularly to the dentin surface and that the results obtained may be due to this direction. Within root canals, the laser beam is applied with an optic fiber and the beam direction may be different. This factor needs to be evaluated further.
Thus, this study opens perspectives for more research to investigate the effect of direction of the laser beam when applied within the root canal using various diameters of optic fiber and also if greater adhesion leads to less marginal infiltration.
Research was supported by a grant from CNPq to Dr. Jesus D. Pécora.
Pécora JD, Cussioli AL, Guerisoli DMZ, Marchesan MA, Sousa-Neto MD, Brugnera-Junior A. Estudo in vitro do efeito da aplicação do laser Er:YAG e da solução de EDTAC na superfície dentinária sobre a adesividade de seis cimentos endodônticos. Braz Dent J 12(1):27-30.
Estudou-se in vitro o efeito da aplicação do laser Er:YAG e da solução de EDTAC na superfície dentinária sobre a adesividade de diferentes cimentos endodônticos à base de resina epóxica. Foram utilizados 99 molares superiores humanos de estoque que tiveram suas coroas desgastadas até se obter uma superfície plana transversal ao longo eixo do dente e foram divididos em três grupos com 33 dentes cada. No primeiro grupo, a superfície de dentina não recebeu nenhum tratamento. No segundo, aplicou-se sobre a dentina uma solução de EDTAC por cinco minutos e, no terceiro, a dentina recebeu a aplicação do laser Er:YAG com os seguintes parâmetros: potência 2,25 W; distância focal 11 mm; freqüência de 4 Hz; período de aplicação de 1 minuto e energia de 200 mJ, totalizando 62 J de energia aplicados ao dente. Três dentes de cada grupo foram enviados para a análise de microscopia eletrônica de varredura. Os cimentos endodônticos à base de resina epóxica testados foram os seguintes: AH Plus, Topseal, Sealer 26, AH 26 e o Sealer Plus. O cimento Fillcanal, cimento tipo Grossman à base de óxido de zinco e eugenol, foi utilizado como controle. A força de adesão foi detectada por meio de uma Máquina Universal de Ensaios. Os resultados evidenciaram haver diferença estatística significante ao nível de 1% de probabilidade entre as condições de tratamento da dentina e os diferentes cimentos endodônticos. Assim, a dentina tratada com laser Er:YAG propiciou a maior adesividade, a dentina tratada com a solução de EDTAC proporcionou adesividade intermediária e a dentina que não recebeu tratamento algum mostrou a menor adesividade. No que diz respeito aos cimentos endodônticos testados, o teste de Tukey mostrou a formação de 5 grupos em ordem decrescente de adesividade à dentina: AH Plus, com a maior adesividade; Topseal e Sealer 26, com valores estatisticamente semelhantes; AH 26; Sealer Plus; e Fillcanal, com o menor valor de adesividade.
Unitermos: endodontia, laser Er:YAG, cimentos obturadores dos canais radiculares.
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Accepted August 14, 2000
Braz Dent J 12(1) 2001