In vitro assessment of bonding of the total-etch adhesive to carious dentin in molars treated with and without 38% silver diamine fluoride: a study protocol

Introduction

The conventional treatment of a carious tooth is the complete removal of carious dentin followed by its restoration. However, authors like Yoshiyama et al. and Ceballos et al. advocated the preservation of this carious dentin while restoring the lost tooth structure using adhesive resin restoration. This would help to preserve the remaining tooth structure and prevent its further loss.^1,2

With total-etch adhesives, there may be a possibility of bonding and sealing of vital carious dentin. This isolates the remaining bacteria from any refined carbohydrates that exist in the saliva.

But there is a possibility that the residual active bacteria may provide antigens to the pulpal chamber and cause induction of cytokine reactions, which may lead to chronic pulp inflammation. So, there is a need to search for a material that can be used underneath the final restorative material which would make these viable bacteria dormant for arresting the caries progression.

38% Silver Diamine Fluoride (SDF) is one such material that has an antibacterial effect on carious dentin. It inhibits the bacterial enzyme collagenase and trypsin, thus making the remaining bacteria ineffective in carious dentin, which in turn inhibits caries progression.³ It causes the hardening of dental caries, promotes calcification, and, restores the lattice imperfections.⁴ It improves the crystallinity of hydroxyapatite crystals in the tooth. The silver particles obturate the dentinal tubules and prevent collagen denaturation in demineralized dentin. Incidence of secondary caries decreases when the tooth is conditioned with 38% SDF before restoring it with GIC and resin composite.⁵

However, to date, no research is available which has evaluated the effect of 38% SDF on carious dentin when used beneath total-etch adhesive followed by restoration with resin composite. In order to validate its use, it is most important to first establish the effect it may have on the bonding of the total-etch adhesive to carious dentin.

To understand this effect, we must first evaluate the microtensile bond strength (μTBS) of the total-etch adhesive to carious dentin when treated with 38% SDF. So, the research question here is that does total etch adhesive show similar microtensile bond strength to carious dentin in molars when treated with and without 38% silver diamine fluoride.

The null hypothesis is that total etch adhesive does not show similar microtensile bond strength to carious dentin in molars when treated with and without 38% silver diamine fluoride.

The alternate hypothesis is that the Total etch adhesive shows similar μTBS to carious dentin in molars when treated with and without 38% silver diamine fluoride.

Aims and objectives

Methods

Extracted permanent molars will be collected and stored in 0.9% Saline (Abaris, India). Scaling of the teeth will be undertaken before the intervention using ultrasonic scaler tips (Woodpecker Scaler Tips, China). All the samples will be mounted in self-curing acrylic resin (DPI, India) by embedding their radicular portion in it whereas the coronal portion will remain exposed. The entire procedure will be carried out under the Dental Operating Microscope (DOM) (ZEISS OPMI pico, Germany). Superficial dentin will be removed using air-rotor (NSK, Japan) and round bur-BR-41 (Mani Inc, Japan). The samples will be examined under the DOM at 8.5× magnification to remove any defective, hypoplastic or cracked specimen. 1-2 drops of 38% silver diamine fluoride (SDF) solution will be dispensed in a mixing well. In Group 1, at 5.1× magnification the carious tooth surface will be coated with a single layer of 38% SDF using an applicator tip for 10 seconds. SDF will be allowed to get absorbed for the next 1 minute after which the excess will be wiped off using a cotton Q-tip. The specimen will be washed with water for 15 s and air-dried for 5 s.⁶ This will be followed by restoration with final restorative material (total etch adhesive and resin composite). In Group 2, the surface will be left as it is without any application of 38% SDF. It will be only be restored with total etch adhesive and resin composite.

The final restoration in both the groups will be carried out at 5.1X magnification. Here, the surface etching is done with 37% phosphoric acid (Prime Dental Etching Gel Etchant, India) for 15 s and then will be washed with distilled water for the next 10 s. A total-etch adhesive bonding agent (3M ESPE Adper Single Bond 2 Refill Bonding Agent, United States) will be applied for 20 s and be lightly blown with compressed air for 5 s to create a thin uniform layer of material. This will then be cured for the next 20 s.⁷ The lost tooth structure will then be built using resin composite material (Spectrum Micro hybrid composite, Dentsply, USA) by oblique layering technique,⁸ with each increment having thickness of 1-2 mm, cured for 30 s using LED Light Curing Unit (Woodpecker, China) with light intensity of 1000 mW/cm².⁹ The restoration will be built to a bulk of at least 6 mm-7 mm. Teeth will then be stored in physiological saline at 37°C for 24hrs at 100% humidity in an incubator (Labbyscopes, India) for complete setting.¹⁰

Conclusion

The study may provide us with a new restorative technique that will not only be less invasive by preserving the remaining tooth structure but will also prevent the risk of caries progression beneath the restoration. Thus, this will contribute to the longevity of the tooth life by the maintenance of its pulpal health which will contribute to the durability and long-term successful outcome of the direct restoration procedure.