Radiographic and rheological properties of a new endodontic sealer

Gianluca Gambarini, MD, DDS¹; Luca Testarelli, DDS¹; Giancarlo Pongione, DDS¹; Robero Gerosa, DDS²; and Massimo Gagliani, DDS³

1 Department of Endodontics, University of Rome, Rome, Italy 2 Department of Endodontics, University of Verona, Verona, Italy 3 Department of Endodontics, University of Milan, Milan, Italy

Keywords Abstract

Real Seal sealer, root canal filling materials, root

canal obturating materials. A new dual-cured resin sealer has recently been proposed as an innovative endodontic filling material. Being a new endodontic material, no in vitro research

Correspondence

has been published yet on Real Seal’s (RS) physical properties. Therefore, the

Professor Gianluca Gambarini, Cironvallazione

aim of the present study was to evaluate and compare radiopacity and rheol-

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ogical properties of the RS sealer with those of currently available endodontic

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sealers (Roeko Seal Automix and Bioseal). All tests strictly followed American

doi: 10.1111/j.1747-4477.2006.00005.x National Standards Institute/American Dental Association (ANSI/ADA) specification No. 57, which indicates test methods and establishes minimal requirements of flow, film thickness and radiopacity of endodontic sealers. Results showed that significant differences were found among sealers in the different test methods. However, RS showed values complying with ANSI/ADA specification No. 57 requirements in all tests. Hence, the new RS sealer exhibited radiographic and rheological properties suitable for clinical use.

innovative endodontic filling material. Real Seal sealer

Introduction

(RS) could be defined as a dental resin composite material Filling of root canals is currently achieved using a that bonds with both the RS obturating points (a soft resin combination of endodontic sealer and gutta-percha. core filling material that looks and handles like traditional Gutta-percha is widely used owing its good physical and gutta-percha) and root canal walls, in order to provide biological properties (1), but the lack of adhesiveness to excellent coronal and apical seal. According to the manu-canal walls and sealer is an important disadvantage. A facturer this bond prevents bacterial penetration and satisfactory seal cannot be obtained without the use of a creates a monoblock by joining the two materials. Some sealer, because gutta-percha does not spontaneously preliminary research has shown the new obturating bond to dentine walls (2). An ideal endodontic sealer system to seal the root canal significantly better than should flow along the entire canal wall surface, fill all traditional filling materials (7–9). voids and discrepancies between gutta-percha and canal Endodontic filling materials of all types should meet walls, and adhere firmly both to dentine and gutta-per-certain general requirements. In ascending order of imcha (3). However, some studies have showed how adhe-portance, they should be non-toxic (10), compatible with sion of endodontic sealers to gutta-percha can be poor (4) living tissues, and exhibit chemical and physical properties and that all canal fillings may allow bacterial penetration suitable for clinical use. Being a new endodontic material, over time (5,6). no in vitro research has been published yet on RS physical

Therefore, there have been renewed efforts to develop properties. Therefore, the aim of the present study was to better sealer and core obturation materials and tech-evaluate and compare radiographic and flow and film niques. Recently, a new dual-cured resin (Real Seal, thickness properties of the RS sealer with those of cur-SybronEndo, Orange, CA) sealer has been proposed as an rently available endodontic sealers.

© 2006 The Authors Journal compilation © 2006 Australian Society of Endodontology

Radiographic and Rheological Properties G. Gambarini et al.

Table 1 Endodontic sealers used in the study, manufacturer and main components

RSA, Roeko Seal Automix.

Materials and methods

Three endodontic sealers were selected for the study: Roeko Seal Automix (RSA) (Roeko, Langenau, Germany), Bioseal (BS) (Ogna, Milan, Italy) and Real Seal (RS). Table 1 shows materials, manufacturers and main components. All materials were mixed following manufacturers’ instructions. All tests strictly followed American National Standards Institute/American Dental Association (ANSI/ ADA) specification No. 57 (11), which indicates test methods and establishes minimal requirements of flow, film thickness and radiopacity of endodontic sealers.

Flow

Following ANSI/ADA Specification No. 57 guidelines, a volume of 0.5 mL of the sealer was mixed according to manufacturer’s directions and, 180 s after the commencement of mixing, was placed (using a graduated hypodermic syringe) at the centre of a glass plate and covered by an identical plate (40 mm × 40 mm and 5 mm thick). Then, a load of 100 g was placed carefully and centrally on the top of the glass plates. Ten minutes after the commencement of mixing, the load was removed and the maximum and minimum diameters of the compressed disc of sealer were measured. If the diameters agreed to within 1 mm, the mean of the two diameters was recorded. If the two diameters were not within 1 mm, the test was repeated. Six flow tests were performed for each sealer, and the mean value of each of the specimens was calculated to the nearest millimetre. Data were statistically analysed using Anova and Student-Newman–Keuls’ tests.

Film thickness

A small amount of the sealer was mixed according to manufacturer’s directions and was placed between two glass plates having a contact surface area of 200 mm² and with a uniform thickness exceeding 5 mm. At 180 s after the start of mixing, a load of 150 N was carefully applied vertically onto the top glass plate, ensuring that the material filled the entire area between the top and bottom glass plates. Ten minutes after the start of mixing, the thickness of the sealer film was measured using a micrometre assem-bled on a stereo-microscope (Lomo MBC-10). Four tests were performed for each sealer. Data were statistically analysed using Anova and Student-Newman–Keuls’ tests.

Radiopacity

The sealers were prepared according to manufacturer’s specifications and placed in 20 stainless steel ring moulds (Diameter 10 ± 0.01 mm, height 1 ± 0.01 mm). Five specimens were performed for each sealer tested. An X-ray machine capable of producing radiation at 70 kV and 10 mA was used in conjunction with five radiographic films (31 mm × 41 mm) of speed group D (Ultra Speed, Kodak, Rochester, USA), to obtain a radiograph of the test specimens and the aluminium step wedge. The aluminium used for beam filtration and step wedge was an 1100 alloy (a 98% aluminium alloy) in accordance with American Society of Testing and Materials (ASTM) Specification B209. For each radiograph the aluminium step wedge was placed on the centre of each film and four specimens of the sealer were placed around the aluminium step wedge. Three radiographs were taken, one for each tested product. The focal length chosen was 300 mm. According to Specification No. 57 the radiopacity of endodontic sealers must to be not less than the equivalent of 3 mm of aluminium. The radiographs were then digitized and analysed using analytical imaging software (Image Pro Plus 4.1, Media Cybernetics, Silver Spring, USA). Data were statistically analysed using Anova and StudentNewman–Keuls’ tests.

Results

Flow

The results for the flow test are given in Figure 1. Mean values (and SD) of flow are expressed in millimetres: RSA = 32.7 (±1.4), BS = 38.5 (±2.8), RS = 37.9 (±1.2). Significant differences were found between RSA and the other materials tested as analysed by ANOVA (P > 0.001) and Student-Newman–Keuls’ test. BS and RS showed the

G. Gambarini et al. Radiographic and Rheological Properties

best results. Data were also compared with minimal requirements specified in ANSI/ADA Specification No. 57, which requires a minimum value greater than 20 mm. All the materials showed a mean diameter of the disc greater than the minimum required values (20 mm).

Film thickness

The results for the film thickness test are given in Figure 2. Data (expressed in microns) were recorded as follows: RSA = 9.3 (±1.01); BS = 41.2 (±3.1); RS = 24.9 (±0.87). Significant differences were found among the materials tested as analysed by ANOVA (P < 0.001) and StudentNewman–Keuls’ test. RSA showed the best results.

Data were compared with requirements specified in ANSI/ADA Specification No. 57, which requires a value lower than 50 microns. All sealers showed values complying with the above-mentioned requirements.

Radiopacity

The results for the radiopacity test are given in Figure 3. Mean values for radiopacity (mm aluminium) of the sealers were the following: RSA = 4, BS = 2.8, RS = 4.6. ANOVA (P < 0.001) and Student-Newman–Keuls’ test showed statistically significant differences between BS and the other sealers. RS showed the best results. Data were also compared with minimal requirements specified in ANSI/ADA Specification No. 57. Only RSA and RS showed values complying with the above-mentioned requirements (minimum equivalent to 3-mm aluminium).

Discussion

Flow is an essential property of endodontic filling materials (3). Ideally, materials with good flowability and low surface tension can be easily placed along the entire root canal and be capable of wetting the canal walls, thus providing well-adapted fillings. This is very important for the new dual-cured resin-based RS sealer, which is intended to obtain a very strong bond with both canal walls and the core filling material, thus creating a monoblock by joining the two materials (8). As a consequence, the entire root canal system is filled with a system that resembles a typical composite resin coronal restoration. It is also important for endodontic sealers to set slowly and to flow for as long as possible. RS setting time is adequate, but it can be easily shortened if needed (mainly to achieve an immediate coronal seal) by light-curing the filling material.

RS material showed excellent flow properties in vitro. No statistically significant difference was found between RS and BS, the latter showing the best results in the present study. However, all tested endodontic sealers exhibited values complying with ANSI/ADA Specification No. 57 minimal requirements. Moreover, the tendency to flow is also dependent on manipulation. Improper mixing ratios (12) may result in too liquid a sealer (and consequently a greater amount of released components), increasing the risk of extrusion of sealers into periapical tissue and a more severe tissue reaction. It has been shown that the release of eugenol from zinc oxide-eugenol-based sealers can induce irritation in soft tissues because of its cytotoxic properties (10). RSA and RS sealers have special automix syringes, which allow consistent mixing of the material, making the procedure easier and more predictable. Moreover, the RS Thinning Resin may be used to modify the viscosity of the sealer if needed.

Film thickness is an important characteristic of endodontic sealers: the smaller the film thickness, the greater the ability of the material to fill even the smallest voids or discrepancies and perhaps enter the dentinal tubules. Results of the present study showed that RS provided better values than the zinc oxide-eugenol-based sealer. However, all sealers complied with ANSI/ADA requirements for film thickness.

Radiopacity is an essential property of endodontic filling materials. It is important to be able to see the root canal filling on a radiograph to detect its presence and extent. International standards require a minimal radiopacity equivalent to 3 mm of aluminium, yet some commercially

© 2006 The Authors Journal compilation © 2006 Australian Society of Endodontology

Radiographic and Rheological Properties

available products do not meet this requirement, as shown by Tagger and Katz (13). The results obtained with the sealers in this study are consistent with these statements. RSA and RS proved to be sufficiently radiopaque, while BS did not meet ANSI/ADA specification No. 57 minimum requirements.

Some authors have suggested a higher limit of radiopacity, equivalent to at least 4 mm of aluminium, seems more desirable (9). As far as resin-based sealers are concerned, radiopacity can easily be modified by incorporation of mineral radiopaquers, but worry has been expressed that a sealer that is too opaque may mask imperfections in the filling, especially when it is used in conjunction with gutta-percha. Radiopacity of RS sealer

(4.6 mm) was found to be an excellent compromise, as values higher than four are considered to satisfactorily display the radio-contrast between the root canal filling and other structures, even in difficult areas such as maxillary molars, without masking the core-filling material.

Conclusions

The new endodontic RS sealer showed values complying with ANSI/ADA Specification No. 57 requirements in all tests (flow, film thickness and radiopacity).

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