Biodegradation of Dentin-Resin Adhesion and the Prevention: A Systematic Review

Review Article

J Dent & Oral Disord. 2020; 6(3): 1131.

Biodegradation of Dentin-Resin Adhesion and the Prevention: A Systematic Review

Dennis* and Abidin T

Department of Conservative Dentistry Faculty of Dentistry, Universitas Sumatera Utara, Medan, Indonesia

*Corresponding author: Dennis, Department of Conservative Dentistry Faculty of Dentistry, Universitas Sumatera Utara, Medan, Indonesia

Received: April 17, 2020; Accepted: May 11, 2020; Published: May 18, 2020


Composite resin is a tooth-colored restorative material with aesthetic and highly desirable. However, this restorative material may change slowly due to degradation. Degradation of composite resins structures is caused by mechanical processes such as sliding, abrasive, and fatigue and chemical processes such as beverages, food, microorganism and hydrolytic enzyme or catalyst containing saliva. Degradation may involve particle fillers, coupling agents and matrix. Various strategies have been implemented to extend the life of the composite resin adhesion to the tooth structure, including the use of ethanol wet bonding and applications of chlorhexidine as an inhibitor of matrix metalloproteinases (MMP’s). Thus, remineralization appears to be the cognitive approach for extending the longevity of resin-dentin bonds. Guided tissue remineralization recaptures the hierarchical order and dimension of apatite crystals of normal mineralized collagen. It represents a revolutionary approach to improve the durability of resin-dentin bonds using a particle-mediated, non-classical crystallization strategy. This paper presents an overview of contemporary strategies for preventing degradation of resin-dentin bonds and provides an evaluation of their applicable foreground on the durability of resindentin bonds.

Keywords: Biodegradation; Composite resin; Dentin-resin adhesion; Prevention


Composite resin restorative material is the most widely used materials for the dentist and patient today. This is because the value of the esthetic result produced by the restorative material is very satisfying. In addition, composite resin restorations produce a good bond to the surface of the enamel or dentin [1]. Composite resin material was first discovered in 1951 by Knock and Glenn. Since then, the composite resin restorative materials continue to grow until now. In 1962, Bowen expanded the material by adding material bisphenol glycidyl dimethacrylate (bis-GMA) that play a role in strengthening the chemical bonds between composite resin filler particles. Until now, all kinds of resin composites contain bis-GMA [2,3].

Although composite resin material produce good aesthetic, shape but surface of composite resin restorations can change over time. This will affect the mechanical properties of the composite resin. The process of this change is known as composite resin degradation. Degradation of composite resins is the missing or releasing chemical structure of composite resin such as Bis-GMA due to some processes [1]. This degradation causes the damage of the restoration and eventually resulting in the non-durable restoration. The mechanical properties of composite resins are not only influenced by its containing chemical structure but also influenced by environmental conditions such as pH changes and oral cavity humidity [4].

Failure of dental restorations is a major concern in dental practice. Up to half of all composite resin restorations failed within 10 years. A randomized clinical trial for the past 7 years has shown that the risk of secondary caries was 3.5 times greater in the composite resin compared to amalgam restorations. This explains the reason of taking an effort to extend the life of the resin composite restoration [5].

According Ferracane, et al. (2006) and Goperfich, et al. (1996), composite resin degradation mechanisms associated with the two processes of mechanical and chemical processes. Causes of mechanical processes such as sliding, abrasive, and fatigue meanwhile composite resin degradation due to chemical processes caused by hydrolysis enzymes or saliva containing catalysts [1,2]. Various strategies have been implemented to extend the life of the composite resin adhesion to the tooth structure, including the use of ethanol wet bonding and applications of chlorhexidine as an inhibitor of matrix metalloproteinase [6].

The purpose of this paper is to investigate the degradation of resin composite restorative materials used in dentistry includes definition, etiology and mechanisms, as well as the prevention of degradation of resin composite. In this paper, it is also described about the adhesion of composite resin and factors that affect adhesion of composite resin to the tooth structure.

Composite resin

By definition, composite is a material consisting of two or more components. Resin composites are complex materials, which generally consist of organic components (resin) that form the matrix, inorganic filler material, interfacial materials to unify the resin and filler, initiator systems to enable hardening or polymerization mechanism, stabilizers (inhibitor) and pigments. Organic components (resin) and inorganic components (filler) are incorporated into a system that will affect the polymerization. Usually the filler particles are coated with a binding agent to link the organic components (resin). Most of the resin matrix containing aromatic monomers with high viscosity which is bis-GMA (bisphenol-A diglycidyl dimethacrylate) that synthesized by Bowen in the USA in 1960. Low viscosity monomer is also incorporated in them, such as TEGDMA (Triethylene Glycol dimethacrylate), EGMA (Ethylene Glycol Dimethacrylate) and HEMA (Hydroxyl-Ethyl Methacrylate) [1-3].

Adhesion mechanism of composite resin

An effort to improve the adhesion of composite resin to dental tissue is the use of acid etching and adhesive bonding material. Buonocore, et al. (1955), introduced the concept of bonding with the acid etching that modifies the enamel demineralization using acidic agent.2 The process of acid etching on enamel surface will produce microscopic roughness on the surface called the enamel tags or micropore in order to obtain a physical bond between resin composite and enamel that creates micromechanical retention . The success of these efforts has led researchers to apply etching on dentin, but though the dentin is etched but composite resin adhesion to dentin surfaces is harder than the adhesion of the enamel surface. The difficulty is because dentine constitutes more complex tissue than enamel [2].

Enamel is an almost complete mineralized tissue, while dentin is a living tissue that consists of inorganic component (45%), organic components (33%) and water. Organic composition of dentin substrate has structure of ultra tubules and heterogeneous. Thus, it can be said that the factors influencing adhesion difficulties of composite resin on the dentin is the variation of mineralization rate and the presence of fluid in the dentinal tubules that hinders the adhesion. [2,3].

The mechanism of composite resin adhesion on dentin depends on the number of smear layer. Smear layer is a layer of inorganic debris on the surface of dentin because of preparation. Smear layer is expected to produce a barrier that protects the pulp from the damaging pulp stimulation, but its function is only temporary. To overcome this, dentin etching is done remove the smear layer. Fusayama, et al. (1980) reported that dentin etching will form a micromechanical adhesion between dentin and resin composite as well as to dissolve the smear layer [2].

Smear layer removed by etching with phosphoric acid 35 -37% for 15 seconds which leads to the opening of dentinal tubules. Etching of the intertubular and peritubular dentin resulted in penetration and adhesion for bonding material to form the hybrid layer. Hybrid layer is the enamel, dentin and cementum which are infiltrated by the resin [1,2].

Basically dentin bonding system consists of three components, namely:

a. Etchant: Acid etching leads the tooth surface etched with an acidic substance into roughness. Etchant can increase microscopic roughness through decalcification of enamel surface by removing the prismatic and interprismatic mineral crystals. In addition, etchant can also improve the enamel surface free energy to produce enough resin monomer infiltration as the retention of composite resin restorations, dentin surface decalcification by dissolving the hydroxyapatite crystals of the peritubular and intertubular dentin in order to open dentin tubules so that fibers and collagen in the intertubular dentin will be exposed to monomer infiltration (in a total-etch adhesive system) or modify the smear layer (the self-etch adhesive systems) [1,2].

b. Primer: Primer is a hydrophilic low viscosity monomer. This causes the material is easy to adapt to the dentine surface which is also hydrophilic. Priming process produces a chemical bond, the intermolecular interaction between carboxyl or phosphate groups of primer with collagen (in a total-etch adhesive system) or hydroxyapatite crystals which covers the collagen (in self-etch adhesive system). Adhesive is usually available in the form of a solution with 60-80% solvent such as: BPDM / HEMA, HPDM / NTG-GMA, 4 META / MMA, glutaraldehyde [1,2].

c. Bonding agent (adhesive resin): Adhesive resin is generally hydrophobic and is compatible with primer and resin composites. Polymerized resin adhesive attached to collagen fibrils (total-etch system) and the remaining of hydroxyapatite crystals (the self-etch systems) produces interfacial structures called “hybrid layer”[1,2].

Factors affecting the adhesion between resin and tooth structure

Adhesion to the tooth surface is affected by several factors, namely:

a. Operator: The successful adhesion of restorative material to the tooth surface depends on the operator technique, such as restoration techniques that require proper isolation of the work area, good manipulation, procedure of etching and bonding, layering technique of insertion, the shaping and polishing of restoration [2,6].

b. Material: There are different types of restorative materials that utilize different application procedures. With total etch adhesive system, composite resin material relies on phosphoric acid etching procedure to the tooth surface. Phosphoric acid etching is used to remove the rest of the cement, smear layer, dentin which contains eugenol and demineralized dentin [2,6].

c. Tooth structure: Dentin has high water content. This causes the failure of resin adhesion to peritubular hydroxyapatite and dentin organic material produces lesser hydroxyapatite so making it less resistant to acid. Demineralized hydroxyapatite has poor quality because it can not form resin tags [2,6].

d. Effect of solvent: Solvent has a role to elevate water from the dentin surface that provides a reaction between dentin and the hydrophilic adhesive. According Perdiago, et al (2001), the strength of the dentin bonding done with repeated humidification depends on the type of solvent in a humidification system and re-humidification time. Here are the advantages and disadvantages of the material on the system solvent adhesive (Table 1) [2,6].