Comparative Evaluation of Shear Bond Strength of Resin Modified Glass Ionomer Cement and Biodentine as Dentin Substitutes to Bonded Silver Amalgam and Composite Resin
Riddhi Thakkar1, Sandya Kini2, Nagaraja P Upadhya3
1 Postgraduate Student, Conservative Dentistry and Endodontics, Manipal Academy of Higher Education, Manipal, Karnataka, India.
2 Professor and Head, Conservative Dentistry and Endodontics, Manipal Academy of Higher Education, Manipal, Karnataka, India.
3 Associate Professor, Department of Dental Materials, Manipal Academy of Higher Education, Manipal, Karnataka, India.
NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR: Dr. Sandya Kini, Manipal College of Dental Sciences, Department of Conservative Dentistry and Endodontics, Manipal- 576104, Karnataka, India.
E-mail: drsandyakini@gmail.com
Introduction
The bond strength between the restorative material and the tooth, as well as between the restorative material and the base, is an important factor and can determine the longevity of a dental treatment.
Aim
Comparative evaluation of shear bond strength of Resin modified glass ionomer cement and Biodentine as dentin substitutes to Bonded silver amalgam and Composite resin.
Materials and Methods
Acrylic resin blocks of dimension 3x1.5x1.5 cm were made. A total of 40 acrylic blocks containing a central hole (wells) with 4 mm diameter and a 2 mm height were prepared. The samples were randomly divided into two groups- Group 1 and Group 2 having 20 samples each. The wells of Group 1 and Group 2 were filled with Resin Modified Glass Ionomer Cement (RMGIC) and Biodentine, respectively according to manufacturer’s instructions. The samples of each group were further divided into four subgroups (n=10): Group 1A, 1B, 2A, 2B. The surface of Group1A and 2A were etched and then treated with adhesive (Adper single bond-2, 3M ESPE) and restored with nanohybrid composite resin and specimens of 1B and 2B were etched and treated with adhesive (Meta P & Bond- MetaBiomed) respectively and were restored with silver amalgam. All the samples were stored in artificial saliva for 24 hours at 37.5°C, 100% humidity and were subjected to shear bond strength testing.
Results
Group 1A (RMGIC + Composite) showed the highest shear bond strength values-29.58 MPa followed by Group 2A (Biodentine + Composite resin) - 5.59 MPa, Group 1B (RMGIC + Bonded silver amalgam) - 3.96 MPa and least was seen in Group 2B (Biodentine + Bonded silver amalgam) - 0.445 MPa.
Conclusion
This study concluded that combination of Composite resin and RMGIC or Composite resin and Biodentine showed higher shear bond strength values as compared to a combination of RMGIC and Bonded silver amalgam or Biodentine and Bonded silver amalgam.
Introduction
To maintain normal form and function of a tooth, enamel and dentin, need to be relained; if lost due to caries etc, they must be replaced. A dentin substitute or a base when used reduces postoperative sensitivity caused by materials used to restore the tooth and also protects the pulp [1]. Various materials like; zinc oxide eugenol, zinc polycarboxylate, glass ionomers and few newer ones like MTA, biodentine etc., have been used as dental substitutes [2].
Glass ionomers are currently very popular products that not only bond ionically to the tooth structure but also are capable of releasing fluoride [3]. However, the conventional auto-cure glass ionomer cements are susceptible to wear and have poor marginal integrity, due to which they cannot be placed over occlusal surfaces involving centric stops [4]. Also, to the changes in oral pH, glass ionomers will act like buffers, which will cause their surface degradation in areas where saliva cannot wash oral acids away [5]. To overcome these disadvantages, resin modified glass ionomers were introduced which not only capable of releasing fluoride and providing good adhesion but also have better resistance to microleakage and have less solubility than a conventional glass ionomer [6,7]. Also, superior bond strengths were observed with resin-modified cements bonded to composite resin (9.17 to 16.23 MPa) as compared to conventional glass ionomers probably due to the superior cohesive strength of these cements and due to the chemical bonding between the resin bonding agent and the non-reacted resinous phase of the glass ionomer cement [8].
Biodentine, a tricalcium silicate cement was developed by Septodont’s Research Group as a novel material. Due to its good sealing ability with dentin, it is used as a dentin substitute [9]. Since Biodentine is recommended for use as a dental base under permanent restorations, studies were carried out to evaluate the bond strength of the material with different bonding agents, where on assessing the shear bond strength of an etch-and-rinse adhesive, a 2-step self-etch adhesive and a 1-step self-etch adhesive system to Biodentine at different intervals, it was seen that there was no significant difference between all of the adhesive groups at the same time intervals (12 minutes and 24 hours) [10].
In order to withstand occlusal forces and restore the occlusal anatomy, restorative materials are placed above dentin substitutes. In areas of the mouth that are difficult to isolate, like molars or sub-gingival cavities, silver amalgam can be considered one of the best filling materials. Concerns about, its inability to bond to the tooth, leading to microleakage led to the introduction of adhesive systems that reliably bond to both dentin and enamel [11]. Some of the adhesives used for bonding silver amalgam include All-Bond 2 (Bisco), Amalgambond Plus with HPA (high performance additive) powder (Parkell), Panavia EX, Panavia 21 (Kuraray), Optibond 2 (Kerr), Meta P & Bond (Meta Biomed) [12]. Silver amalgam has drawbacks like unaesthetic appearance, marginal deterioration, concerns about the mercury toxicity, making the coloured restorative materials popular. At least half of posterior direct restoration placements now rely on composite [13]. The introduction of inorganic fillers which are well dispersed in a resin matrix has been shown to be very effective in improving the performance of composite resins [14]. To test the adhesion of dental adhesives, shear bond strength test can be carried out [15]. In-vitro bond strength tests are useful and essential for predicting the performance of adhesive systems and possible correlation with clinical issues [16]. No studies to the best of our knowledge has been done to evaluate shear bond strength of Biodentine to Bonded silver amalgam. Thus, the purpose of our study was to evaluate and compare the shear bond strength of Resin modified glass ionomer cement and Biodentine as dentin substitutes to Bonded silver amalgam and Composite resin.
Materials and Methods
Institutional Ethical Committee approval was obtained before start of the study. (IEC no. -660/2015). The materials used in our study are shown in [Table/Fig-1]. A total of 40 acrylic blocks containing a central hole with 4 mm diameter and 2 mm height were prepared. The samples were randomly divided into various groups and subgroups as shown in [Table/Fig-2]. In Group 1 and Group 2, 20 samples were taken each and the holes were completely filled with RMGIC (Ionolux, Voco, Germany) and Biodentine (Septodont, Saint Maur des Fosses, France) respectively in accordance with the manufacturer’s instructions. [Table/Fig-1]. For RMGIC group, light curing was performed for 20 seconds. The tip of the light curing unit was held as close as possible to the surface of the filling. To achieve a smooth, glossy surface, a mylar strip was placed over the sample and gentle finger pressure applied for five minutes to compact the cement mass and minimise the porosity. After waiting 12 minutes, which is the initial setting time of Biodentine as per the manufacturer, the surfaces of all samples of both Group 1 and Group 2 were then etched with 37% Phosphoric Acid (Eco-Etch, Ivoclar, U.S.A) for 15 seconds, rinsed with water and blot dried. Then the samples were divided into four subgroups (n=10) as given in [Table/Fig-2]:
Materials used in the study.
| Sl. No. | Material | Manufacturer | Method of application |
|---|
| 1. | Resin Modified Glass Ionomer Cement (RMGIC) | Ionolux, Voco, Germany | Powder/liquid ratio 3.2 : 1 g/g), Light cured for 20 seconds |
| 2. | Biodentine | Septodont, Saint Maur des Fosses, France | Mixing premeasured unit dose capsules in a high-speed amalgamator for 30 seconds. |
| 3. | Adhesive system for composite | Adper single bond 2 ESPE, U.S.A. | Applied over the surface and light cured for 20 seconds. |
| 4. | Adhesive system for Bonded amalgam | META P&Bond adhesive, METABIOMED, U.S.A. | Applied over the surface and light cured for 10 seconds. |
| 5. | Silver amalgam | High copper admixed, Disperse Alloy, Dentsply dental corp., U.S.A | Preproportioned amalgam capsules were used to standardise the amalgam and they were triturated in an amalgamator. In all the samples, the amalgam was condensed by a serrated round condenser with a diameter of 1 mm by a single operator |
| 6. | Composite resin | Filtek Z350 XT 3M ESPE, U.S.A. | Light curing for 40 seconds |
Illustration of samples randomly divided into various groups and subgroups
Group1A- specimens of RMGIC + Composite
Group 1B- specimens of RMGIC + Bonded silver amalgam
Group 2A- specimens of Biodentine + Composite
Group 2B- specimens of Biodentine + Bonded silver amalgam
The samples were pretreated with adhesive Adper Single Bond 2 (3M, ESPE, USA) for the samples to be restored with Composite resin and with Meta P & bond adhesive (MetaBiomed, USA), for samples to be restored with silver amalgam. Thereafter, light-curing (Elipar Highlight; 3M ESPE, Seefeld, Germany) was performed and the samples were restored with Bonded silver amalgam (High copper admixed disperse alloy, dentsply dental corp., USA) and Composite resin (Filtek Z350 XT, 3M ESPE, USA) respectively according to manufacturer’s instructions [Table/Fig-1]. into a cylindrical shaped plastic tube with an internal diameter of 3 mm and a height of 2 mm with a plastic cement carrying instrument. All the samples were stored in artificial saliva for 24 hours at 37.5°C and 100% humidity.
Shear Bond Strength Test
For shear bond strength testing, the specimens were held in a holder placed on a Universal Testing Machine (Instron 3366, USA) and the measurement carried out at a crosshead speed of 1.0 mm/minute. Shear bond strength in MPa was calculated by dividing the peak load at failure with the specimen surface area (F/r2). Specimens that underwent pre-test failures were excluded from the statistical analysis.
Statistical Analysis
All the analysis was done using SPSS version 20. A p-value of <0.05 was considered statistically significant. Intra and intergroup comparisons were done using Kruskal-Wallis, One-way ANOVA and Mann-Whitney U tests.
Results
Upon considering the mean shear bond strength values amongst all sub-groups on intergroup comparison [Table/Fig-3], statistically significant difference was observed (p<0.001). It was seen that values of bond strengths obtained followed the order: 1A>2A>1B>2B. Hence, RMGIC bonded to Composite resin showed the highest shear bond strengths amongst all the subgroups and Biodentine bonded to Bonded silver amalgam showed the least shear bond strength. On intra group comparison also [Table/Fig-4], the differences obtained between all the groups statistically significant (p<0.001). Groups 1A, 2A attained higher bond strength values were obtained than group 2A and 2B. On comparing the shear bond strength values of Group 1B and 2B, Group 1B demonstrated higher shear bond strength values than 2B.
Intergroup comparison of shear bond strength using kruskal-wallis one-way anova.
| GROUP | Minimum-maximum valueMegapascals(Mpa) | Median(q1,q3)(MPa) | p value |
|---|
| 1A- RMGIC + COMPOSITERESIN | 26.61-33.44 | 29.58(28.24, 31.04) | p<0.0001 |
| 1B- RMGIC+BONDED SILVERAMALGAM | 2.91-5.85 | 3.96(3.60, 4.30) |
| 2A- BIODENTINE+COMPOSITE | 6.31-3.84 | 5.59(4.38, 5.79) |
| 2B- BIODENTINE +BONDED SILVER AMALGAM | 0.05-1.7 | 0.445(0.11, 0.93) |
Intra-group variations in shear bond strength using Mann-Whitney U test.
| GROUP | GROUP | P value |
|---|
| RMGIC + COMPOSITERESIN(1A) | BIODENTINE+COMPOSITERESIN(2A) | p<0.001 |
| RMGIC+BONDEDSILVER AMALGAM(1B) | BIODENTINE+BONDEDSILVER AMALGAM (2B) | p<0.001 |
| RMGIC + COMPOSITERESIN(1A) | BIODENTINE+BONDEDSILVER AMALGAM(2B) | p<0.001 |
| BIODENTINE+COMPOSITERESIN(2A) | RMGIC+BONDEDAMALGAM(1B) | p<0.001 |
| RMGIC + COMPOSITERESIN (1A) | RMGIC+BONDEDAMALGAM(1B) | p<0.001 |
| BIODENTINE+COMPOSITERESIN(2A) | BIODENTINE+BONDEDSILVER AMALGAM (2B) | p<0.001 |
Discussion
Wide range of different classes of materials has been introduced for the replacement of lost dentin as dentin substitutes. RMGIC is the modification of conventional glass Ionomers in which resin monomers were added which not only improved the handling characteristics of the material, but also led to improved bonding with Composite resins as proven by numerous studies [17]. Where as Biodentine, has both therapeutic pulp capping capabilities as well as the ability to be used as a bulk filling material, thus simplifying the restorative process [18]. Thus RMGIC and Biodentine have been used as dentin substitutes in this study.
During sample preparation, manufacturer’s instructions were followed for every material. No changes were made regarding the manipulation and mode of application. Adper single bond, fifth generation adhesive (3M ESPE, USA), was used to bond Composite resin to both resin modified glass ionomer cement and to Biodentine. Adper Single Bond Adhesive is a total etch, visible-light activated dental bonding agent incorporating 10 percent by weight of 5nm diameter silica filler along with Bis Phenol A Glycidyl Methacrylate (Bis GMA), Hydroxyethyl Methacrylate (HEMA), dimethacrylates, ethanol, water, a novel photoinitiator system and a methacrylate functional copolymer of polyacrylic and polyitaconic acids. A few materials have been developed for amalgam bonding specifically and have shown excellent adhesive properties to both tooth structures and enhancing bonding to amalgam alloys [12]. One such novel adhesive, Meta P & Bond (MetaBiomed, USA) was used in the present study for Bonding silver amalgam to both RMGIC and to Biodentine. It is an unfilled adhesive, composed of Bis Phenol A-Glycidyl methacrylate, Pyromellitic glycerol methacrylate, 2-hydroxyethylmethacrylate and ethyl alcohol.
It is recommended that these materials, when used as base or dentin substitute, should be restored with a permanent restoration, thus, in the present study, the two most frequently used restorative materials silver amalgam and a nanohybrid composite resin which has good resistance to wearing and offer good polishability have been used [19].
The bond strength between the restorative material and the tooth, as well as between the restorative material and the cavity liner or a base, is an important factor and can determine the quality and longevity of a dental treatment and hence, the shear bond testing was carried out between the dentin substitute and the restorative material in our study. Our findings demonstrated that RMGIC bonded to Composite resin (Group 1A) showed the highest shear bond strength median value of 29.58 MPa as compared to other groups. This could be attributed to the presence of monomer groups that ensure a stable and comprehensive chemical bonding between the substrates [20]. Unpolymerised HEMA on the surface of RMGIC intensifies the surface wetting capability of the bonding agent, leading to increased bond strength when polymerised [21].
On intra group comparison, our study demonstrated higher bond strength values for the groups in which the dentin substitute was bonded to composite resin where Adper Single Bond 2, fifth generation total etch adhesive (3M ESPE) was used which has silica filler as one of its components. Meta P & Bond adhesive, a fifth generation bonding agent is an unfilled adhesive. It has been proven that filled adhesives like Adper single bond act as an intermediate shock-absorbing elastic layer between resin composite and dentin, thereby increasing the bond strength to dentin [22]. Thus, it can be said that in Groups 1A, 2A, higher bond strength values were obtained than group 2A and 2B.
On comparing the shear bond strength values of Group 1B and 2B, Group 1B demonstrated higher shear bond strength values than 2B and the difference was statistically significant (p<0.001). It was seen that the shear bond strength of Group 2B attained very low values (0.445 MPa). It could be attributed to the fact that Biodentine’s initial setting reaction takes approximately 12 minutes after mixing the powder and the liquid where a hydrated calcium silicate gel structure is formed which has weak physico-mechanical properties. For upto two weeks, the crystallisation of the calcium silicate hydrate gel structure continues, leading to maturation of Biodentine [23]. Hence, it’s recommended that placement of permanent restoration over the Biodentine should be delayed for a period of two weeks. Also, the presence of monomer groups in both RMGIC as well as in adhesive Meta P & bond could ensure better chemical bonding of both the groups leading to higher bond strength values of group 1B as compared to group 2B [20].
Limitation
In the present study, bonding was performed to Biodentine immediately after 12 minutes to depict a single visit clinical procedure. However, being a porous material, it needs at least two weeks time for crystallisation of hydrated calcium silicate gel to attain bulk strength adequate enough to withstand the polymerisation stresses [23]. This could be the reason for low bond strength in the Biodentine group. Also, in future studies SEM evaluation can be carried out in order to further elucidate the reasons for the differences in the bond strength and observing the modes of failure.
Conclusion
The study concluded that: The shear bond strength of RMGIC to Composite resin is best followed by Biodentine to Composite resin with statistically significant difference (p<0.001) when bonded using Adper single bond 2 adhesive system. The shear bond strength of RMGIC and Biodentine to Bonded silver amalgam showed lesser values with statistically significant difference (p<0.001) when bonded using unfilled Meta P & Bond adhesive system.
[1]. Weiner R, Liners and bases in general dentistry Aust Dent J 2011 56:11-22. [Google Scholar]
[2]. Craig RG, Powers JM, Restorative dental materials 2002 11th edSt LouisMosby [Google Scholar]
[3]. Donly KJ, Segura A, Kanellis M, Erickson RL, Clinical performance and caries inhibition of resin-modified glass ionomer cement and amalgam restorations Am J Dent 1999 130(10):1459-66.10.14219/jada.archive.1999.005610570589 [Google Scholar] [CrossRef] [PubMed]
[4]. Knight GM, McIntyre JM, Bond strengths between composite resin and auto cure glass ionomer cement using the co-cure technique Aust Dent J 2006 51(2):175-79.10.1111/j.1834-7819.2006.tb00423.x16848267 [Google Scholar] [CrossRef] [PubMed]
[5]. Nicholson JW, Czarnecka B, The biocompatibility of resin-modified glass-ionomer cements for dentistry Dent Mater 2008 24(12):1702-08.10.1016/j.dental.2008.04.00518539324 [Google Scholar] [CrossRef] [PubMed]
[6]. Simon JF, Darnell LA, CE 2-Considerations for proper selection of dental cements Compend Contin Educ Dent 2012 33(1):28-36. [Google Scholar]
[7]. Estafan D, Pines MS, Erakin C, Fuerst PF, Microleakage of Class V restorations using two different compomer systems: an in vitro study J Clin Dent 1999 10(4):124-26. [Google Scholar]
[8]. Zanata RL, Navarro MF, Ishikiriama A, da Silva e Souza Júnior MH, Delazari RC, Bond strength between resin composite and etched and non-etched glass ionomer Braz Dent J 1997 8(2):73-78. [Google Scholar]
[9]. Kaup M, Dammann CH, Schäfer E, Dammaschke T, Shear bond strength of Biodentine, ProRoot MTA, glass ionomer cement and composite resin on human dentine ex vivo Head Face Med 2015 11(14):1-8.10.1186/s13005-015-0071-z25908430 [Google Scholar] [CrossRef] [PubMed]
[10]. Odabas ME, Bani M, Tirali RE, Shear bond strengths of different adhesive systems to biodentine Scientific World Journal 2013 2013:62610310.1155/2013/62610324222742 [Google Scholar] [CrossRef] [PubMed]
[11]. Bharti R, Wadhwani KK, Tikku AP, Chandra A, Dental amalgam: An update J Conserv Dent 2010 13(4):204-08.10.4103/0972-0707.7338021217947 [Google Scholar] [CrossRef] [PubMed]
[12]. Setcos JC, Staninec M, Wilson NH, The development of resin-bonding for amalgam restorations Br Dent J 1999 186:328-32.10.1038/sj.bdj.480010210333638 [Google Scholar] [CrossRef] [PubMed]
[13]. Yeli M, Kidiyoor KH, Nain B, Kumar P, Recent advances in composite resins - A review J Oral Res Rev 2010 2(3):134-36.10.5368/aedj.2010.2.3.134-136.pdf [Google Scholar] [CrossRef]
[14]. Förster S, Plantenberg T, From self-organizing polymers to nanohybrid and biomaterials Angew Chem Int Ed Engl 2002 41(5):688-714.10.1002/1521-3773(20020301)41:5<688::AID-ANIE688>3.0.CO;2-3 [Google Scholar] [CrossRef]
[15]. Barkmeier WW, Cooley RL, Laboratory evaluation of adhesive systems Oper Dent 1992 (Suppl 5):50-61. [Google Scholar]
[16]. Hiraishi N, Breschi L, Prati C, Ferrari M, Tagami J, King NM, Technique sensitivity associated with air-drying of HEMA-free, single-bottle, one-step self-etch adhesives Dent Mater 2007 23(4):498-505.10.1016/j.dental.2006.03.00716690113 [Google Scholar] [CrossRef] [PubMed]
[17]. Wilson AD, Resin-modified glass ionomer cements Int J Prosthodont 1990 3(5):425-29. [Google Scholar]
[18]. Septodont BiodentineTM scientific file, 2010 [Google Scholar]
[19]. Ernst CP, Martin M, Stuff S, Willershausen B, Clinical performance of a packable resin composite for posterior teeth after 3 years Clin Oral Investig 2006 10(2):119-25.10.1007/s00784-006-0041-816555069 [Google Scholar] [CrossRef] [PubMed]
[20]. Costa SB, de Oliveira RV, Montenegro RV, Fonseca RB, de Carvalho FG, de Barros S, Bond strength evaluation of composite resin bonded to glass ionomer cements after different periods of setting Int J Adhes Adhes 2013 47:146-50.10.1016/j.ijadhadh.2013.08.010 [Google Scholar] [CrossRef]
[21]. Farah CS, Orton VG, Collard SM, Shear bond strength of chemical and light-cured glass ionomer cements bonded to resin composites Aust Dent J 1998 43(2):81-86.10.1111/j.1834-7819.1998.tb06095.x9612981 [Google Scholar] [CrossRef] [PubMed]
[22]. Nunes MF, Swift EJ, Perdigão J, Effects of adhesive composition on microtensile bond strength to human dentin Am J Dent 2001 14(6):340-43. [Google Scholar]
[23]. Bachoo IK, Seymour D, Brunton P, Clinical case reports using a novel calcium-based cement Br Dent J 2013 214(2):61-64.10.1038/sj.bdj.2013.5323348450 [Google Scholar] [CrossRef] [PubMed]