ORIGINAL RESEARCH


https://doi.org/10.5005/jp-journals-10015-2368
World Journal of Dentistry
Volume 15 | Issue 1 | Year 2024

An In Vitro Comparison of Seventh- and Eighth-generation Dentin Bonding Agents Microtensile Durability Employing Giomer


Vinayak Jyothi1, Pradeep Kumar2, Prathap MS Nair3, Vivian Flourish D’Costa4, Jayaprakash K Perla5

1–5Department of Conservative Dentistry and Endodontics, Yenepoya Dental College, Yenepoya University, Deralakatte, Mangaluru, Karnataka, India

Corresponding Author: Vinayak Jyothi, Department of Conservative Dentistry and Endodontics, Yenepoya Dental College, Yenepoya University, Deralakatte, Mangaluru, Karnataka, India, Phone: +91 9901876894, e-mail: vinayakjyothi1@gmail.com

Received: 02 December 2023; Accepted: 06 January 2024; Published on: 20 February 2024

ABSTRACT

Aim: The purpose of this study was to evaluate and compare the microtensile bond strength of Giomer resin (Shofu Beautifil II Refills) to dentin using eighth-generation dental adhesive (G-Premio Bond GC) and seventh-generation dental adhesive (BeautiBond bonding agent—Shofu).

Materials and methods: A total of 30 anonymized premolars were used. Two groups with 15 samples were allocated to each group. In group I, the seventh-generation bonding agent was used, and in group II, the eighth-generation bonding agent was used by keeping Giomer resin as the common restorative material in both groups. Samples were prepared by exposing the coronal dentin using a high-speed diamond disk. Etching of the exposed coronal dentin was done using 37% phosphoric acid, following which application of bonding agent was applied respectively by following the instruction manual of the bonding agent. Three equal increments of Giomer resin restorative material were made as blocks on the dentin surface of the tooth by light curing each increment for 30–40 seconds. A 21-gauge ortho wire was inserted through the resin block. The specimens were mounted in a universal testing machine. The microtensile force was applied parallel to the long axis of each specimen until the specimen was deboned. The tensile load at which the fracture occurs was recorded. The microtensile bond strength value was recorded in units of Mega Pascal (MPa). The results were analyzed using an independent t-test.

Results: There is a significant difference between the seventh- and eighth-generation bonding agents when bonded with Giomer resin (p < 0.05). The mean average force to debond Giomer from the eighth-generation bonding agent from the exposed dentin is 5.894 N. Whereas, to debond Giomer bonded with the seventh-generation bonding agent from the exposed dentin is 3.176 N. Hence, the result of the study shows that eighth-generation bonding agents have higher microtensile strength than the seventh-generation bonding agents when bonded with Giomer resin material.

Conclusion: In this in vitro study, eighth-generation, and seventh-generation bonding agents’ microtensile strength was determined individually by using Giomer as the restorative material. It was proved that the eighth-generation bonding agents have better microtensile strength than seventh-generation bonding agents.

Clinical significance: Choosing the parameter microtensile strength because the efficacy of dentin bonding agent is mainly evaluated by tensile or microtensile bond strength. In this study, it was proved that the eighth-generation bonding agent shows superior microtensile bond strength when compared to the seventh-generation bonding agent while employing Giomer as the restorative material. This study can help clinicians choose the best restorative material like Giomer, which is widely used for its good color matching, reduced microleakage, increased fluoride release, and bonding agent, which has higher strength.

How to cite this article: Jyothi V, Kumar P, Nair PMS, et al. An In Vitro Comparison of Seventh- and Eighth-generation Dentin Bonding Agents Microtensile Durability Employing Giomer. World J Dent 2024;15(1):1–5.

Source of support: Nil

Conflict of interest: None

Keywords: Eight-generation bonding agent, Giomer, Microtensile strength, Seventh-generation bonding agent

INTRODUCTION

In 1949, the history of dental adhesive started when Dr Hagger worked on dental adhesives and patented the first dental adhesive which was only dentin and not on enamel.1 Tentatively, the bonding agent was introduced in the early 1970s.2

In the past, the use of bonding agents in restorative dentistry is extensive. Bonding agents are applied to withstand the mechanical forces and stress, which can create a strong bond between the composite and the tooth. The success of adhesives depends on their adherence to the natural tooth on one side and to the resin restoration on the other side.3 The mechanism of dental adhesive bonding is based on the replacement of lost minerals with resin monomers, which eventually results in the micromechanical interlocking of polymer in the dental substrate.4 There are two ways where the adhesive system bonds with the dentin, either by eliminating the smear layer, that is, the etch and rinse technique, or by maintaining it as the substrate for bonding, that is the self-etch technique.5

Due to the increase in demand for esthetic restorations, the evolution of dental adhesives has brought changes in the chemistry, mechanism of operation, the number of steps involved in the procedure, the technique of application, and their clinical effectiveness.6,7 They are available in many systems like three-step, two-step, or single-step systems, which entirely depend on how the steps of etching, priming, and bonding to the tooth surface are accomplished.7 The most commonly used adhesives are the one-step self-etching adhesives due to their easy and fast application procedure. The commonly used bonding agents in the present clinical scenarios belong to the sixth-, seventh-, or most recent eighth-generation bonding agent.8

The seventh-generation bonding agent is an all-in-one bottle system that was introduced in the year 2002. They combine the etchant, primer, and adhesive in a single solution bottle. Clinicians consider using one-step, self-etch adhesives because they require a reduced and less complex number of clinical steps compared with multistep etch-and-rinse adhesives.3,9

Voco America introduced Voco Futurabond DC as an eighth-generation bonding agent, in the year 2010. There is an incorporation of nanofillers of an approximate particle size of 12 nm in the eighth-generation bonding agent. The newly introduced eighth-generation bonding agents are dual-cured, self-etching, nanoreinforced agents and produce comparable bond strengths to both dentin and enamel.10

Recently, a new group of composite resin-based tooth-colored restorative materials has been introduced, referred to as Giomers, which are methacrylate-based. They are a true combination of glass ionomers and composite resins. Giomers have filler content different from that of conventional composite resins.11 Giomers are fluoride-releasing resin material which contains “prereacted glass,” or PRG. They claim good color matching reduced microleakage and increased fluoride release compared with other resin materials. Studies have shown that micromechanical properties, biocompatibility, and bonding of Giomer are better in comparison to conventional composite.12

The efficacy of dentin bonding agents is mainly evaluated by tensile or microtensile bond strength, and this bond test is a very useful tool for bonding research.13 However, the microtensile bond strength test has been accepted as a versatile and reliable in vitro test to quantify the bonding effectiveness and stability of adhesive biomaterials bonded to tooth structures.

The main reason to compare these bonding agents is because seventh and eighth-generation bonding agents are considered to be widely and commonly used universal bonding agents. The ultimate aim of restorative dentistry is to provide optimum esthetics, long durability, and high strength, and should act like a smart material. This study is to analyze the durability and microtensile strength while bonding with Giomer and; hence, prove which bonding agent is superior so that it can be employed more in day-to-day clinical practice while opting for Giomer as the restorative material.

MATERIALS AND METHODS

This study was conducted within the duration of 2 weeks. Human permanent premolars, extracted for orthodontic purposes, were used in this study. The specimen tooth was preserved in saline. Ethical approval for this study (Protocol No: YEC2/590) was provided by the Yenepoya Ethics Committee 2 [Yenepoya (Deemed to be University)].

The sample size was calculated using G*Power software, version 3.1.9.4. At a 1% level of significance and 80% power by considering the mean of one group is 31.67 with a standard deviation of 2.12 and the mean of another group is 34.74 with a standard deviation of 2.45 (from the related article), the total sample size in each group is 15 (total sample size is 30).

Two groups consisting of 30 anonymized stored permanent human premolar teeth assigned into two groups, 15 in each group, were used in this study. The materials used in this study are the BeautiBond bonding agent, seventh-generation bonding agent (Shofu), GC G-Premio Bond, eighth-generation bonding agent (GC), Beautifil II Refills, and Giomer (Shofu).

A total of 30 anonymized stored human permanent premolar teeth were collected and cleaned thoroughly, and samples were stored in a saline solution for the duration of 1 week. The teeth were then divided into two groups and allocated to each of the dentin bonding agents used. With a high-speed diamond disk, coronal dentin was exposed, and the occlusal enamel was polished with wet 600-grit silicon carbide paper. The teeth were bonded with the adhesive system as follows. Adhesive systems used in the study are1 BeautiBond bonding agent, the seventh-generation bonding agent (Shofu) and2 GC G-Premio Bond, and the eighth-generation bonding agent (GC). The Giomer resin used in this study was Shofu Beautifil II Refills. Samples were then divided into two groups of 15 each. In the first group, a seventh-generation bonding agent was used, and in the second group, an eighth-generation bonding agent was used.

Dentin surfaces were acid-etched with 37% phosphoric acid for 15 seconds and then rinsed with water for 10 seconds. Excess amounts of water were removed using a paper point. Immediately after blotting, one coat of dentin bonding agent was applied and left undisturbed for 10 seconds, then dried thoroughly for 5 seconds under minimum air pressure and then light-cured for 20 seconds (as per manufacturer). After bonding, three increments of approximately 2.5 mm thickness Giomer resin were placed on the bonded surface of dentin. Each increment was light-cured for 30–40 seconds. At the end of this procedure Giomer block of approximately 7–8 mm height was obtained.

All the specimens of both groups were stored in distilled water at 37°C for 24 hours. A twisted 21-gauge stainless steel ortho wire with a loop was placed and pierced through the Giomer resin specimen for the test. Then, the specimens from both groups were taken for microtensile bond strength (Fig. 1).

Fig. 1: Sample preparation

Microtensile Bond Strength Test

The specimens were mounted in a universal testing machine. Microtensile force was applied parallel to the long axis of each specimen until the specimen was debonded. The tensile load at which the fracture occurs was recorded. The microtensile bond strength value was recorded in units of Mega Pascal (MPa) (Fig. 2). The results were analyzed using an independent t-test.

RESULTS

The aim of this study was to evaluate and compare the microtensile bond strength of Giomer resin (Shofu Beautifil II Refills) to dentin using eighth-generation dental adhesive (G-Premio Bond GC) and seventh-generation dental adhesive (BeautiBond bonding agent-Shofu). For intercomparison, we have used the independent t-test.

The mean average force to debond Giomer from an eight-generation bonding agent is 5.894 N. Whereas, to debond Giomer bonded with a seventh-generation bonding agent is 3.176 N. (Table 1). Hence, the result of the study shows that the eight-generation bonding agents have better microtensile strength than seventh-generation bonding agents when bonded on Giomer resin material.

Table 1: Comparison of seventh- and eighth-generation bonding agents
Group Mean Standard deviation p-value* 95% confidence interval
Lower Upper
Seventh-generation 3.176 0.3728 0.0001 −3.06595 −2.37005
Eight-generation 5.894 0.54206

*, p < 0.05 is considered significant

Clinically opting for the eight-generation bonding agents over the seventh-generation bonding agent while employing Giomer as the restorative material provides better success in terms of strength.

DISCUSSION

The major objective of restorative dentistry is to restore teeth in a way that allows the conservation of healthy dental tissues, esthetics, function, and durability. Due increase in demand for esthetic restorations lead to the evolution of dental adhesives, which have brought changes in the chemistry, physical properties, mechanism of operation, the number of steps involved in the procedure, the technique of application, optical properties, and their clinical effectiveness.6,7 Adhesive restorations bond directly to the tooth structure and reinforce weakened tooth structure.14 Development of newer dentin bonding agents aims to improve the bonding quality and reduce the time consumption in application.15 Most common bonding agents used today belong to the sixth-, seventh-, or the most recent eighth-generation.8

The seventh-generation bonding agents were introduced in the year 2002.9 According to Freedman et al. seventh-generation adhesive is the most compatible formulation of dentinal adhesives in the market.9 The seventh-generation adhesives are insensitive to the amount of residual moisture on the surface of the preparation. The bond strength of both dentin and enamel are essentially the same, regardless of the moisture or lack of moisture on the prepared surfaces. Thus, moist bonding is not required.9 This is a one-bottle dentin bonding agent that contains 2-hydroxyethyl methacrylate (HEMA) monomers in order to improve the wettability of the dentin surface. HEMA helps in improving the binding of the hydrophilic collagen of the dentin to the hydrophobic composite resin material.8

Numerous comparative studies have been done in accordance with seventh-generation bonding agents. Somani et al. proved in their study that the microleakage value was higher in the seventh-generation than the sixth-generation bonding agents.8 Varma et al. evaluated the sealing capacity of fifth- and seventh-generation bonding agents and proved that single bond universal had a better sealing capacity at both coronal and apical portion of the teeth.8,16

The blending of nanotechnology with adhesive dentistry led to the development of eighth-generation bonding agents.6 They are dual-cured, self-etching, nanoreinforced agents and produce comparable bond strengths to both dentin and enamel.10 The eight-generation bonding agents contain nanofiller particles, which include microfilters and submicron glass. These nanofiller particles bond with the resin matrix after light curing and thereby act as a strengthening element for dentin, which is demineralized by replacing the solubilized apatite filler crystallites.8 The mechanism of action of the eight-generation bonding agent slightly varies; they use a smear layer as the bonding substrate, leaving residual smear plugs that cause less dentinal fluid flow than etch and rinse adhesive. This mild etching property of the nanobonding agent leaves the hydroxyapatite crystals available for the chemical bonding of functional monomers to calcium, which aids in interface stability.10 As a result, this structural condition improves the mechanical properties of the hybrid layer of eighth-generation adhesive. Thus, they tend to produce higher in vitro bonds.8

Kamath and Arun proved that the eight-generation bonding agents have the least microleakage when compared to sixth- and seventh-generation bonding agents.17Ababakr et al. evaluated the shear bond strength efficacy of seventh and eighth-generation bonding agents and found that the highest strength was seen in the eighth-generation bonding agent.18

These are the following reasons why the eighth-generation bonding agent is superior to the seventh-generation bonding agent.

The eight-generation dentin bonding agents have a lower pH value of 1.4 in comparison to the higher pH value of 1.8 seventh dentin bonding agents. Because of the lower pH, a complete removal of the smear layer is achieved; hence, better bond strength is obtained.8

The 4-methacryloyloxyethyl trimellitic acid monomer is used in G-Premio Bond for promoting adhesion. The solvent used here is acetone. Acetone, being a good water chaser, also prevents the etherification of carboxyl acid groups, which in turn improves demineralization and enhances wetting.

According to a study by Joseph et al., increased bond strength in eight-generation bonding agents is due to the incorporation of nanosized cross-linking silica fillers. The highest bond strength values among all the tested groups can be attributed to the presence of similar silica fillers in the G-Premio Bond.18,19

The HEMA, which is a hydrophilic monomer added to the seventh-generation bonding agents, facilitates BisGMA solubility, which in turn produces a tough, highly cross-linked polymer network. However, following polymerization, HEMA attracts water, leading to water resorption, hydrolytic degradation, nano leakage, and the resultant decline in the bond strength of the seventh-generation bonding agent. The eight-generation bonding agent does not contain HEMA.10

Esthetic dentistry has been widely advocated since there was an increasing demand for materials that resemble the natural tooth. A new group of restorative materials, referred to as Giomers, has been introduced.20 Giomers are a true combination of glass ionomers and composite resins.12 Giomers are similar to conventional methacrylate-based composite resins. They contain inorganic fillers, measuring 0.01–0.5 µm, of PRG ionomer instead of pure glass or quartz fillers. Both Giomer and conventional composites are used in a similar manner with the application of an adhesive system.20 The acid-base reaction of Giomer has taken place before mixing the fillers with resin, contrary to acid-modified composite resins, and then the material is lathed and mixed with the methacrylate resin as filler.12 Giomer exhibits a favorable esthetic appearance, easy polishing, strength, and release and recharging of fluoride.20 The clinical success, micromechanical properties, and biocompatibility of Giomer restorations are better in comparison to conventional composite resin, and it has been shown in various in vivo as well as in vitro studies.12

Giomer had the highest value for compressive strength (271 MPa), which was in accordance with the study conducted by Quader et al., which showed the resin-based PRG fillers and cross-linked polymer matrices that resulted in higher compressive strength than the acid-base reaction in glass ionomers. Giomer is a better restorative material than any fluoride-releasing material.21 Walia et al. conducted a study and proved the compressive strength of Giomer was highest in comparison to ceram-x, zirconomer, and ketac molar.22 Beautifil is one of the products of Giomer category having S-PRG technology, and it is the restorative material that we have used in our study, according to Manuja et al. Giomer bond is a glass ionomer base, tricurable, all-in-one, filled adhesive based on PRG technology and consists of 4-AET, 4-AETA, UDMA, HEMA, PRG filler, fluoroaluminosilicate glass, acetone, water, and initiator. Due to the inclusion of these fillers, Giomer possibly showed higher shear bond strength compared to glass ionomer cement.23

The primary objective while assessing the bond strength of a dentin bonding agent is to analyze and assess its retention capability to the dental hard structure. Advancements in bonding systems have focused on enhancing the bonding efficacy, quality, and shortening the consumption in application. Tooth, dentin surface, type of bond strength to be tested (shear or tensile), type of bonding agent used, storage media, composite restorative material, and testing procedures are the various factors affecting the bond strength.7 Application of microtensile load results in better stress distribution at the adhesive interface compared to conventional tensile or shear loads and yields more accurate results with less diversity.4 This test enables better stress distribution due to the smaller interface area.5 According to Sano et al., the microtensile strength is more accurate than the traditional test.13

The main intention behind this study is to create awareness in choosing the dentin bonding agent, which is still a debatable topic, and in this study, it is proved that the eight-generation bonding agent shows superior microtensile bond strength when compared to the seventh-generation bonding agent. The material of choice for this study is Giomer. Giomers claims good color matching reduced microleakage and increased fluoride release compared with other resin materials. Giomers have been used widely across the world for their specific properties. It is a unique study that has been done regarding nano adhesives and Giomers. Choosing the parameter microtensile strength because the efficacy of dentin bonding agents is mainly evaluated by tensile or microtensile bond strength, and this bond test is a very useful tool for bonding research. Henceforth, this study will help clinicians to choose the best restorative material and best bonding agent for successful and long-term results.

CONCLUSION

This study comparatively evaluated the microtensile bond strength of the newly introduced eight-generation dentin bonding adhesive G-Premio Bond (Gc) with seventh-generation dentin bonding adhesive BeautiBond bond agent (Shofu) with Beautifil Ii Refills, Giomer (Shofu). There was a statistically significant difference in the microtensile bond strength between the eight-generation (mean value strength 5.89 MPa) and seventh-generation (mean value strength 3.17 MPa) bonding agent, which clearly proves that the eight-generation bonding agent has superior microtensile bond strength when compared to seventh-generation bonding agent when applied on Giomer resin restoration.

Figs 2A to C: (A) Mounting of sample in the universal testing machine; (B and C) Deboned sample after checking the microtensile strength

REFERENCES

1. Sofan E, Sofan A, Palaia G, et al. Classification review of dental adhesive systems: from the IV generation to the universal type. Ann Stomatol (Roma) 2017;8(1):1–17. DOI: 10.11138/ads/2017.8.1.001

2. Freedman G. Adhesion: past, present, and future. Oral Health 2019;109(7):8–14.

3. Navyasri K, Alla RK, Vineeth G, et al. An overview of dentin bonding agents. Int J Dent Mater 2019;1(2):60–67. DOI: 10.37983/IJDM.2019.1204

4. Pouyanfar H, Seyed Tabaii E, Aghazadeh S, et al. Microtensile bond strength of composite to enamel using universal adhesive with/without acid etching compared to etch and rinse and self-etch bonding agents. Open Access Maced J Med Sci 2018;6(11):2186–2192. DOI: 10.3889/oamjms.2018.427

5. Mallick R, Sarangi P, Mohanty S, et al. Micro-tensile bond strength of different adhesive systems on sound dentin and resin-based composite: an in-vitro study. J Conserv Dent 2015;18(5):379–383. DOI: 10.4103/0972-0707.164036

6. Taneja S, Kumari M, Bansal S. Effect of saliva and blood contamination on the shear bond strength of fifth-, seventh-, and eighth-generation bonding agents: an in vitro study. J Conserv Dent 2017;20(3):157–160. DOI: 10.4103/0972-0707.218310

7. Chauhan U, Dewan R, Goyal NG. Comparative evaluation of bond strength of fifth, sixth, seventh, and eighth generations of dentin bonding agents: an in vitro study. J Oper Dent Endod 2020;5(2):69–73. DOI: 10.5005/jp-journals-10047-0103

8. Somani R, Jaidka S, Arora S. Comparative evaluation of microleakage of newer generation dentin bonding agents: an in vitro study. Indian J Dent Res 2016;27(1):86–90. DOI: 10.4103/0970-9290.179837

9. Freedman G, Leinfelder K. Seventh-generation adhesive systems. Dent Today. 2002;21(11):106–111.

10. Ganesh AS. Comparative evaluation of shear bond strength between fifth, sixth, seventh and eighth generation bonding agents: an in vitro study. Indian J Dent Res 2020;31(5):752–757. DOI: 10.4103/ijdr.IJDR_635_19

11. Savadi-Oskoee S, Kimyai S, Savadi-Oskoee A, et al. Effects of different etching strategies on the microtensile repair bond strength of beautifil II giomer material. J Clin Exp Dent 2018;10(8):732–738. DOI: 10.4317/jced.54436

12. Matis BA, Cochran MJ, Carlson TJ, et al. A three-year clinical evaluation of two dentin bonding agents. J Am Dent Assoc 2004;135(4):451–457. DOI: 10.14219/jada.archive.2004.0209

13. Sano H, Chowdhury AFMA, Saikaew P, et al. The microtensile bond strength test: Its historical background and application to bond testing. Jpn Dent Sci Rev 2020;56(1):24–31. DOI: 10.1016/j.jdsr.2019.10.001

14. Deepa VL, Damaraju B, Priyadharsini BI, et al. Comparative evaluation of microshear bond strength of 5(th), 6(th) and 7(th) generation bonding agents to coronal dentin versus dentin at floor of pulp chamber: an in vitro Study. J Int Oral Health 2014;6(5):72–76.

15. Kamble SS, Kandasamy B, Thillaigovindan R. In vitro comparative evaluation of tensile bond strength of 6th, 7th and 8th generation dentin bonding agents. J Int Oral Health 2015;7(5):41–43.

16. Varma M, Sedani S, Nikhade P. Comparative evaluation of 5th- and 7th-generation bonding agents: an in vitro study. J Datta Meghe Inst Med Sci Univ 2019;14(9):166–170. DOI: 10.4103/jdmimsu.jdmimsu_46_19

17. Kamath D, Arun CR. Comparative evaluation of microleakage of class ii composite restoration by using 6th 7th and 8th generation dentin bonding agents. An in vitro study. Int J Appl Dent Sci 2019;5(1):147–150.

18. Ababakr H, Bakr D Kh, Saleem SS, et al. Evaluating shear bond strength efficacy of seventh and eighth generation bonding agents. An in vitro study. EDJ 2022;4(2):135–143. DOI: 10.15218/edj.2021.18

19. Joseph P, Yadav C, Satheesh K, et al. Comparative evaluation of the bonding efficacy of sixth, seventh and eight generation bonding agents: an in vitro study. Int Res J Pharm 2013;4(9):143–147.

20. Ajami AA, Bahari M, Hassanpour-Kashani A, et al. Shear bond strengths of composite resin and giomer to mineral trioxide aggregate at different time intervals. J Clin Exp Dent 2017;9(7):906–911. DOI: 10.4317/jced.53791

21. Quader SA, Alam MS, Bashar A, et al. Compressive strength, fluoride release and recharge of giomer. Update Dent Coll J 2013;2(2):28–37. DOI: 10.3329/updcj.v2i2.15533

22. Walia R, Jasuja P, Verma KG, et al. A comparative evaluation of microleakage and compressive strength of ketac molar, giomer, zirconomer, and ceram-x: an in vitro study. J Indian Soc Pedod Prev Dent 2016;34(3):280–284. DOI: 10.4103/0970-4388.186746

23. Manuja N, Pandit IK, Srivastava N, et al. Comparative evaluation of shear bond strength of various esthetic restorative materials to dentin: an in vitro study. J Indian Soc Pedod Prev Dent 2011;29(1):7–13. DOI: 10.4103/0970-4388.79913

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