|Year : 2014 | Volume
| Issue : 1 | Page : 1-8
Sealing ability of a new calcium silicate based material as a dentin substitute in class II sandwich restorations: An in vitro study
Raji Viola Solomon, Parupalli Karunakar, Deepthi Sarvani Grandhala, Chaitanya Byragoni
Department of Conservative Dentistry and Endodontics, Panineeya Mahavidyalaya Institute of Dental Sciences, Hyderabad, Telangana, India
|Date of Web Publication||5-Sep-2014|
Deepthi Sarvani Grandhala
Department of Conservative Dentistry and Endodontics, Panineeya Mahavidyalaya Institute of Dental Sciences, Kamalanagar, Dilsuknagar, Hyderabad, Telangana
Source of Support: None, Conflict of Interest: None
Background: Class ll sandwich restorations are routinely performed where conventional Glass ionomer cement (GIC) or Resin-modified GIC (RMGIC) is used as a base or dentin substitute and a light curing composite resin restorative material is used as an enamel substitute. Various authors have evaluated the microleakage of composite resin restorations where glass ionomer cement has been used as a base in class II sandwich restorations, but a literature survey reveals limited studies on the microleakage analysis of similar restorations with biodentine as a dentin substitute, as an alternative to glass ionomer cement. The aim of this study is:
- To evaluate the marginal sealing efficacy of a new calcium-silicate-based material (Biodentine) as a dentin substitute, at the cervical margins, in posterior class II sandwich restorations.
- To compare and evaluate the microleakage at the biodentine/composite interface with the microleakage at the resin-modified GIC/composite interface, in posterior class II open sandwich restorations.
- To compare the efficacy between a water-based etch and rinse adhesive (Scotch bond multipurpose) and an acetone-based etch and rinse adhesive (Prime and bond NT), when bonding biodentine to the composite.
- To evaluate the enamel, dentin, and interfacial microleakage at the composite and biodentine/RMGIC interfaces.
Materials and Methods: Fifty class II cavities were prepared on the mesial and distal surfaces of 25 extracted human maxillary third molars, which were randomly divided into five groups of ten cavities each: (G1) Biodentine group, (G2) Fuji II LC GIC group, (G3) Biodentine as a base + prime and bond NT + Tetric N-Ceram composite, (G4) Biodentine + scotchbond multi-purpose + Tetric N-Ceram composite, (G5) Fuji II LC as a base + prime and bond NT+ Tetric-N Ceram composite. The samples were then subjected to thermocycling, 2500× (5°C to 55°C), followed by the dye penetration test. Scores are given from 0 to 3 based on the depth of penetration of the dye at the cervical, dentin, and interfacial surfaces. The data was analyzed with the nonparametric Kruskal-Wallis and Mann Whitney U test.
Results: No statistically significant differences were found between the five groups in the enamel, dentin, and interfacial regions.
Conclusion: Within the limits of this in vitro study, biodentine is a new calcium-silicate-based material, which can be used as a dentin substitute in class II open-sandwich restorations, where its scores better than resin-modified GIC.
Keywords: Biodentine, dentin substitute, resin-modified glass ionomer cement, sandwich restoration
|How to cite this article:|
Solomon RV, Karunakar P, Grandhala DS, Byragoni C. Sealing ability of a new calcium silicate based material as a dentin substitute in class II sandwich restorations: An in vitro study. J Oral Res Rev 2014;6:1-8
|How to cite this URL:|
Solomon RV, Karunakar P, Grandhala DS, Byragoni C. Sealing ability of a new calcium silicate based material as a dentin substitute in class II sandwich restorations: An in vitro study. J Oral Res Rev [serial online] 2014 [cited 2018 Sep 20];6:1-8. Available from: http://www.jorr.org/text.asp?2014/6/1/1/140193
| Introduction|| |
Silver amalgam has been ruling the restorative dentistry for more than 150 years due to various advantages like durability, ease of use, and affordability.  On account of the growing demands for esthetics in the modern society, as also the increasing concerns about mercury toxicity, great importance is given to composite restorations. They provide various advantages like esthetic superiority, excellent surface finish, relatively simple application technique, sufficient durability, enhanced mechanical strength, and unlike amalgam restorations, they reinforce the remaining tooth structure. However, they often pose problems with marginal integrity, either due to high polymerization shrinkage, which in turn creates contraction forces that disrupt the bond to the cavity wall. The problems also arise due to the dimensional changes in the material, because of its high coefficient of thermal expansion. ,,,],[
In addition, the problems associated with adhesion like wetting capabilities, smear layer, surface energy, surface roughness, absence of enamel or poor enamel quality, inadequate condensation, method of polymerization, failure of isolation, and surface contamination also play a role in the marginal integrity of composite resins. 
Another important area of concern in the marginal integrity of composite restoration is the shape of the cavity. The C factor, which is the ratio of the bonded surfaces to the unbounded surfaces is directly related to the microleakage of the composite. One of the weakest areas in a class II cavity preparation is at the gingival margin. It is related to the insufficient enamel for bonding in that region, as composite materials bond better to enamel than dentin. ,,
All these problems ultimately lead to microleakage, which is clinically the undetectable passage of bacteria, fluids, molecules or ions between a cavity wall and the restorative material. It results in postoperative sensitivity, secondary or recurrent caries, pulpal pathology, marginal discoloration, and a breakdown of certain cements. ,,,
One of the methods developed to overcome the drawbacks associated with composite restorations is the sandwich technique. It was first developed by McLean et al., in 1985. Both the materials provide advantages to the final restoration, where glass ionomer cement replaces (GIC) the dentin and composite resin replaces the enamel. Such restorations enjoys the advantages of composite cement as well as GIC restorations, like caries resistance, due to its fluoride-releasing ability, remineralization capability, it reduces the amount of composite that is needed there by reducing the shrinkage, it provides chemical adhesion to the tooth, it has a lower moduli of elasticity, hence, can act as an elastic buffer or a stress-breaking barrier, it eliminates the need for acid etching, and reduces postoperative sensitivity. ,,,,
However, this restoration is associated with certain drawbacks like the limited bond strength between composites and conventional GIC, due to the absence of chemical bonding. Sandwich restoration with conventional GIC as a liner showed failure rates of 35% after two years and 75% after six years. Resin-modified GIC (RMGIC) have proven to exhibit a true adhesive bond in various literature reports. However, an inherent drawback of RMGIC is bond degradation with noticeable hydrolysis over a period of six years, as evidenced by investigators. ,
On the basis of the ideal characteristics of mineral trioxide aggregate (MTA), a new calcium silicate-based material, biodentine, has been introduced. A lot of research is being carried out on calcium silicate-based materials, on their ability to be used in vital pulp therapy and perforations, but there are very few studies conducted where biodentine is used as a dentin replacement material in deep class II restorations.
The aim of the study is to compare and evaluate the marginal sealing ability of biodentine with resin-modified glass-ionomer cement (Fuji II LC), when used as a base in sandwich restoration, using resin-based adhesives (Prime and Bond NT and Scotch Bond Multipurpose) and composite material (Tetric N-Ceram).
| Materials and Methods|| |
The experimental design consists of a collection of extracted teeth, where 25 extracted human maxillary molars [Figure 1], free of caries, restorations, and cracks were selected for the study and stored in chloramine solution (1%), until use, for not more than one month.
Prior to cavity preparation, the teeth were scaled and cleaned with pumice slurry. Fifty, class II, box-only cavities were prepared on the mesial and distal sides of the molar using cylindrical diamond burs under a water-cooled, high-speed, airotor handpiece. The depth of the occlusal cavity was around 2 mm [Figure 2], width of the cavity was 2 mm [Figure 3], and the length of the axial wall was 6 mm [Figure 4]. Half of the restorations were made on the mesial side and the other half were made on the distal side and they were randomly divided into five groups (n = 10), depending on the method of restoration. When Biodentine or Fuji II LC was used as a dentin substitute, the Tetric N-Ceram composite (shade A2), was used for all restorations. Every restoration was alternated with every other restoration of the remaining groups.
The groups can be described as follows:
Experimental group I
One gram of powder in a Biodentine (Septodont; St Maur Des Fosses, Val-de-Marne, France) capsule was mixed with 180 μl of liquid for 25 seconds, with an amalgamator, at room temperature. The cavities were filled with an amalgam plugger, without any prior surface treatment of enamel or dentin. The finishing and polishing procedures were carried out using the diamond bur, under a water spray, after storing it in an incubator at 90% relative humidity and room temperature, for 60 minutes [Figure 5] and [Figure 10].
Experimental group II
The cavities were conditioned with 10% polyacrylic for 20 seconds, followed by rinsing the cavities thoroughly with water for 20 seconds, and then the cavities were filled with Fuji II LC (GC; Tokyo, Japan). The teeth were then stored in an incubator, followed by the finishing and polishing procedures using a diamond bur under a water spray [Figure 6] and [Figure 10].
Experimental group III
G3 (Biodentine, Prime and bond NT, Composite):
The cavities were filled as in group I and biodentine was removed to just below the maximum convexity of the tooth. Acid etching of enamel and dentin was carried out using 37% phosphoric acid for 30 seconds and 15 seconds, respectively, before being thoroughly rinsed (10 seconds) and dried. Prime and bond NT (DENTSPLY De Trey, Konstanz, Germany) was applied on all surfaces (dentin, enamel, and Biodentine) and light cured for 20 seconds [Figure 7] and [Figure 10].
Experimental group IV
A procedure similar to the one in group III was carried out except that Scotchbond Multi-Purpose (3M ESPE, St Paul, MN, USA) was used as a bonding agent.
The resin composite (Tetric N-Ceram DENSPLY) was applied in groups III and IV, in increments of a maximum of 2 mm each, and were light cured for 40 seconds, followed by finishing the restorations using a diamond bur with a water spray [Figure 8] and [Figure 10].
Experimental group V
Fuji II LC was applied, similar to group 2, and the restorative procedure was carried out as described for group III using prime and bond NT as a bonding agent [Figure 9] and [Figure 10].
|Figure 10: Description of shades used in the diagrammatic representation of groups|
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The samples were stored in artificial saliva, cola, and citrus juice for three days, at 37°C, and then subjected to thermocycling in water baths for 2500 cycles, alternatively at 5°C and 55°C, with a dwell time of 15 seconds. All tooth root apices were sealed with sticky wax, to prevent the dye penetrating through the apex and all the tooth surfaces were coated with two layers of nail varnish 1 mm beyond the restoration margins. All specimens were placed in a 2% methylene blue solution for 24 hours and then they were rinsed with water and subjected to sectioning using a diamond disk. Each section was subjected to binocular stereomicroscopic evaluation at 100×. The values were recorded as depth of penetration of the dye along the cavity walls [Figure 11], [Figure 12], [Figure 13].
|Figure 11: Stereomicroscopic photograph with score 0 for cervical microleakage in case of the resin-modified GIC group|
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|Figure 12: Stereomicroscopic picture showing score 3 at the cervical margins of resin-modified GIC|
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|Figure 13: Stereomicroscopic picture showing score 1 for biodentine at cervical margins|
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Scores for the cervical margins were:
0 = No penetration.
1 = Leakage extending within the first half of the cavity wall.
2 = Leakage extending beyond half, but not as far as the cervical cavity floor.
3 = Leakage extending beyond the cervical cavity wall and reaching the cavity floor.
Scores for Biodentine/RMGIC to resin composite interfaces were:
0 = No penetration.
1 = Leakage extending within the first half of the interface wall.
2 = Leakage extending beyond half, but not as far as the interface wall.
3 = Leakage extending beyond the interface wall and reaching the cavity floor.
The scores for the enamel margins were:
0 = No penetration.
1 = Leakage extending within the first half of the enamel wall.
2 = Leakage extending beyond half, but not as far as the dentin-enamel junction.
3 = Leakage extending beyond the enamel-dentin junction.
Enamel microleakage was compared using the Mann Whitney U test. Dentin and interfacial microleakage was compared using the Kruskal Wallis analysis of variance (ANOVA).
| Results|| |
No significant difference was seen among the groups with respect to enamel microleakage [Table 1] and Chart 1].
No significant difference was seen in the groups with respect to dentin and interfacial microleakage [Table 2] and Charts 2 and 3].
No significant difference was seen with respect to the different solvents in the bonding agents.
| Discussion|| |
Biodentine™ is a new, biologically active cement, which has dentin-like mechanical properties and can be used as a dentin replacement material in the crown and root. Biodentine is a calcium silicate-based cement indicated in various treatment modalities like pulpotomy, apexification in immature teeth, managing perforation of the pulp floor, managing perforation of root canals, in internal and external resorption, retrograde root canal filling, as a provisional seal, and finally as a base in sandwich restorations. ,,
Prime and Bond ® NT is a universal self-priming dental adhesive, designed to bond light cured composite materials and compomer materials to enamel, dentin, metals, and ceramic. The reduction in the component steps simplifies the use, helps in maintaining a superior bond strength, and provides protection against microleakage. Various studies have shown the superior sealing ability of this bonding agent. 
Scotchbond multi-purpose is a three-step etch and rinse adhesive with water as a solvent in the primer. Various studies have evaluated the shear bond strength of this adhesive to moist enamel and dentin and showed superior results. 
Thermocycling was done to evaluate the thermal stability of the material in the present study and the samples were placed in different solutions to simulate the oral environment. Microleakage can be evaluated using various methods. In the present study, the dye penetration method is used to evaluate the adaptation of biodentine to the tooth and the composite. Dye penetration method is reliable, easy and commonly used method to detect the microleakage. The dye used in the present study is 2% methylene blue. Because of its low molecular weight it can easily penetrate microspaces between the various interfaces.
In the present study the efficiency of two etch and rinse adhesives with one containing water as a solvent and other containing acetone as a solvent in the primer have been evaluated. Water based etch and rinse adhesive help in re-expanding the collapsed collagen fibers by its ability to break hydrogen bond between the collagen fibers due to its high dielectric constant. ,,,,
Acetone unlike water has low hydrogen bonding capacity and is unable to reexpand the shrunken collagen fibers. Because of its ability to enhance the water evaporation it is used in the wet bonding technique where it is applied to wet dentin. ,
According to various studies, the solvent nature of the bonding agent has to be considered, with a net preference for an adhesive system that uses water or ethanol as a solvent. 
The results of the present study showed no significant difference in the sealing ability of both the adhesives in conjunction with biodentine and composite restoration. However, the Scotchbond multi-purpose group, with water as a solvent in the primer, showed a slightly more superior sealing ability than the prime and bond NT groups with acetone as a solvent in the primer.
Although there was no statistically significant difference in the sealing ability of biodentine and resin-modified GIC, the comparison of the microleakage scores of biodentine and composite resin showed lesser microleakage than RMGIC, with composite resin justifying the use of biodentine as an alternative to RMGIC, in deep cervical lining class II restorations. However, none of the materials had completely eliminated dye penetration through the interfaces.
The use of biodentine in sandwich restorations and its superior sealing ability in such restorations can be justified due to various reasons. Biodentine has an ability to form hydroxyapatite crystals on the surface of the cement on hydration. This process continues as the cement ages and helps to close the gap between the biodentine-composite interface and the biodentine-tooth interface. It micromechanically bonds to the tooth without any prior surface treatment of the tooth surface. On account of its high alkaline nature it causes caustic erosion of the dentin and penetrates into the dentinal tubules and adheres to the dentin. Although there will be initial contraction of cement during hydration there will be secondary expansion of the cement, explaining the sealing ability. Apart from the above-mentioned properties, the advantage of biodentine over resin-modified GIC is that it has no dissolution in the presence of saliva or any acidic solution. Its good physicochemical properties, like a short setting time, and high mechanical properties make it clinically easy to handle and compatible, not only in classical endodontic procedures, but also in restorative treatments as a dentin replacement material. As a result of the better handling properties of biodentine and its behavior in the stress-bearing areas of the posterior teeth, biodentine can be used as a posterior interim restorative material for up to six months, subsequent to which the thickness of the biodentine can be reduced and retained as a dentin replacement material beneath the final restorative material of choice. The advantage of using a calcium silicate-based material for dentin replacement is leaching of calcium hydroxide from the set cement.  Its biocompatibility adds to the other properties of the cement and makes it a reliable material to be used in deep cavities, in close proximity to the underlying pulp tissue.
| Conclusion|| |
Sandwich restorations were introduced in order to overcome the drawback of polymerization shrinkage of composite resin restorations, by lining the cavities with glass ionomer cement as a base. With the evolution of calcium silicate-based materials, research is been carried out to determine their effectiveness and biocompatibility in clinical situations. Biodentine is a novel, recently introduced material, which can fulfill the requirements needed for a dentin replacement material, especially in sandwich restorations, where the extent of the defect precludes proper isolation.
Within the limits of the present study it was found that biodentine could be a viable alternative to resin-modified glass ionomer cement, especially when placed in deep class II proximal lesions. Biodentine overcame the drawback of moisture sensitivity, as seen with GIC cement, and set even in the presence of moisture which was an added advantage.
As biodentine sets in the presence of moisture from the surrounding environment, the role of water used as a solvent in the bonding agent has also been evaluated in the current study, to understand the effect of moisture from the bonding agent, if any, in the sealing ability of biodentine. However, the results obtained indicate no or little effect of moisture on the bonding process, but further long-term clinical research trials are required to acquire a better understanding in this area.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13]
[Table 1], [Table 2]