Development of Dental Adhesive

• Dr. Muhammad Zakir, PhD Student Faculty of Dentistry

Introduction

Dental adhesive are considered as an important products in dentistry not only to provide a good adhesion between dental materials and the tooth structure but also for a good bonding between dental prosthesis and resin cements. The presence of a good dental adhesive between the two dissimilar surface not only increases the longevity of the material but also enhances the mechanical property of the prosthesis.

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Dental adhesives have been used widely in clinical restorative dentistry resulting in the bonding between the prosthesis and resin materials. Dental materials like zirconia, titanium, Cobalt-chromium alloys, other metal alloys and glass fibres are used as prosthesis and bonded to the tooth structure via resin composites.

Many researchers have studied the effect of coupling agents or the adhesive agents used in industries in the dental field, giving good results of bonding between the substrate and resin cement. But, still the main problem remains i.e., that these adhesives are considered hydrolitically unstable when they are subjected to the conditions mimicing the oral cavity. The reason behind the development of novel coupling agents are to somehow increase the longevity of adhesion between the dental materials for the patient. There has been an evolution of the coupling agnets in dentistry as different types of coupling agents are now being used like for e.g., silane coupling agents, zirconia coupling agents, phosphate based coupling agents.

Researchers and scientists have been thoroughly working on the enhancement of bonding by modifications of these dental adhesives.

Literature Reivew

Silanes in dentistry are used as primers for increasing the adhesion between various dental materials and prosthetic substrates. Silanes are also very biocompatible and cost-effective. Different studies have been conducted which have used different silanes for the adhesion of zirconia to resin cements, titanium, to resin cements and glass fibers to resin cements. But still not a single perfect material has been obtained. Some have hydrophilicity problems, some have the problem of reduced bond strength with aging and some have inferior adhesion properties when subjected to the oral conditions.

A study done by Matinlinna et al. showed that the bond strength of four experimental silane systems between zirconia and resin cement the 3-acryloxypropyltrimethoxysilane(ACPS), 3-styrylethyltrimethoxysilane(STYRX), 3-isocyanatopropyltriethoxysilane(ICS), 3-glycidoxypropyltrimethoxysilane (GPS) with a cross linking silane monomer bis-1-2-(triethoxysilyl)ethane (BTSE) was higher than the pre-activated dental silane product RelyX ceramic primer [1]. Similarly, another study by Matinlinna et al. stated that the by using some less usual functional monomers as experimental primers can enhance the bonding of resin to zirconia as the study proves by stating that 3-Acryloxypropyltrimehoxysilane, 3-glycidoxyproplytrimethoxysilane and styrylethyltrimethoxysilane increase the bonding of resin to zirconia when compared to the pre-activated dental silane product RelyX ceramic primer [2].

Zirconia is a very biocompatible material which has a high wear resistance due to it being dense. The zirconia which is used in dentistry has good mechanical and chemical properties making it a material of choice for many dental applications as it fulfills the functional requirements [3].

In dentistry Zirconia is used mainly as endodontic posts, implant abutments, crowns, bridges and implants. But the bonding of zirconia to resin is weak due to zirconia being an inert material. Thus, to promote the adhesion of zirconia to resins surface conditioning of zirconia is done mainly sandblasting with silica coated alumina particles followed by silanization with a silane coupling agent [4].

Titanium and its alloys are vastly used in the field of dentistry not only due to their biocompatibility but also due to their corrosion resistance and good mechanical properties. In dentistry titanium and its alloys are used to make prothesis appliances like metal frameworks for fixed and romovable partial dentures, full crowns, bridges, endodontic posts and dental implants [5,6]. Titanium is cemented after surface treatment by tribochemical silica a type of sandblasting treatment and and then silanized to give good bonding as it is a non-silica based material [7]. One main problem related to this titanium is it’s weak bond to the resin cements. Thus, to cover these problems many methods have been proposed and tested mechanical retention, chemical retention or a combination of both [8].

Problem Statement

Although there are quite a few adhesives which promote the bonding of different dental materials to the resin cements but most of them do not have a long term durability and with the passage of time the bond strength decreases leading to the failure of the prostheses due to the harsh oral environment. Therefore, there is a need for such an adhesive/bonding agent which not only has good bond strength but also is hydrolytically stable for a long time and being a long term solution for the patient.

Aims and Objectives

The aims of these studies will be to enhance the bonding/adhesion between zirconia-resin composite and Titanium – resin composite hydrolytically stable bonding systems:

• Studying the adhesive properties of a novel silane systems between Ti alloys – resin composites.
• Studying the adhesive properties of a novel silane systems between Zr alloys – resin composites.

References

1. Matinlinna JP, Choi AH, Tsoi JK-H. Bonding promotion of resin composite to silica-coated zirconia implant surface using a novel silane system. Clin. Oral Impl. Res. 24, 2013, 290-296.
2. Matinlinna JP and Lassila LV. Enhanced resin-composite bonding to zirconia framework after pretreatment with selected silane monomers. Dental Materials 27 (2011) 273-280.
3. Matinlinna JP and Mittal KL. Adhesion aspects in dentistry, VSP/Brill, Leiden; 2009.
4. Kaminski HD and Easton AD. Dental Materials Research, Nova Science, New York; 2009; 1-21.
5. Matinlinna JP, Tsoi JK-H, de Vries J. Busscher HJ. Characterization of novel silane coating on titanium implant surfaces. Clin. Oral Impl. Res. 24, 2013, 688-697.
6. Lin J, Shinya A, Gomi H, Matinlinna JP, Shinya A. In vitro evaluation of bonding durability of self-adhesive resin cement to titanium using highly accelerated life test. Dental materials journal 2011, 30 (6): 837-844.
7. Lung CYK and Matinlinna JP. Silanes for adhesion promotion and surface modification. Silane: Chemistry, application and performance, ISBN 978-1-62257-432-2; chapter 3; pages 87-109.
8. Almilhatti HJ, Neppelenbroek KH, Vergani CE, Machado AL, Pavarina AC, Giampolo AC. Adhesive bonding of resin composite to various titanium surfaces using different metal conditioners and surface modification systems. J Appl Oral Sci. 2013;21 (6): 590-596.