Elsevier

Dental Materials

Volume 26, Issue 5, May 2010, Pages e171-e180
Dental Materials

Review
Biodegradation of acrylic based resins: A review

https://doi.org/10.1016/j.dental.2010.01.006Get rights and content

Abstract

Objectives

The development of different types of materials with application in dentistry is an area of intense growth and research, due to its importance in oral health. Among the different materials there are the acrylic based resins that have been extensively used either in restorations or in dentures. The objective of this manuscript was to review the acrylic based resins biodegradation phenomena. Specific attention was given to the causes and consequences of materials degradation under the oral environment.

Data and sources

Information from scientific full papers, reviews or abstracts published from 1963 to date were included in the review. Published material was searched in dental literature using general and specialist databases, like the PubMED database.

Study selection

Published studies regarding the description of biodegradation mechanisms, in vitro and in vivo release experiments and cell based studies conducted on acrylic based resins or their components were evaluated. Studies related to the effect of biodegradation on the physical and mechanical properties of the materials were also analyzed.

Conclusions

Different factors such as saliva characteristics, chewing or thermal and chemical dietary changes may be responsible for the biodegradation of acrylic based resins. Release of potential toxic compounds from the material and change on their physical and mechanical properties are the major consequences of biodegradation. Increasing concern arises from potential toxic effects of biodegradation products under clinical application thus justifying an intensive research in this area.

Introduction

Acrylic based resins consist of polymeric materials based on polymethylmethacrylate. These dental materials are the result of a free radical polymerization reaction. They can be classified as chemical, heat or light activated depending on the factor that initiates the reaction. Chemical or autopolymerized materials involve a chemical activator like N,N-dimethyl p-toluidine [1]. For heat-polymerizing materials, heat can be generated by hot water bath or microwave energy, while the light polymerizing uses visible light as energy source [2], [3], [4].

Acrylic based resins are frequently used in daily dental practice, as they are able to provide the essential properties and necessary characteristics to be used in diverse functions. Most common use of the materials includes denture bases and denture liners, orthodontic appliances and temporary crowns [4], [5], [6].

Denture bases are composed of pre-polymerized polymethylmethacrylate (PMMA) or polyethylmethacrylate (PEMA) powder particles along with a peroxide initiator and a pigment, which are mixed with methacrylate monomers (methylmethacrylate, hexamethyleneglycoldimethacrylate, hydroxylethylmethacrylate, n-butylmethacrylate, tetrahydrofurfurylmethacrylate) and cross-linking agents such as ethyleneglycoldimethacrylate, trimethylolpropane trimethacrylate or 1,6-hexanediol dimethacrylate [1], [7], [8], [9].

Denture liners are used to improve the fit of denture bases, thus re-establishing the retention, support and stability of removable prostheses [10]. Several types of these materials are available, they can be hard reline resins or soft lining materials. Soft lining materials can be divided into two groups [4]. The first comprises materials in which the liquid is made of monomer components, such as methyl, ethyl or butylmethacrylate and phthalates, citrates or sebacates as plasticizers. The second group is similar to tissue conditioners, in which the liquid contains a mixture of plasticizers and ethyl alcohol [4], [11], [12], [13], [14].

Orthodontic appliances are used for space maintenance, thumb deterrent, tipping teeth, overbite reduction, block movements and retention. PMMA is the material most commonly used for manufacturing the polymeric part of these orthodontic appliances [15].

Temporary crowns are used during the interval between tooth preparation and placement of the definitive crown. There are several types of acrylic resin materials available for provisional restorations as PMMA or PEMA resins [16].

An important issue regarding the clinical application of the acrylic based resins is their biodegradation. It can be defined as the changes on their chemical, physical and mechanical properties due to the oral environment conditions.

In the oral cavity the materials are exposed to a rather complex milieu that comprises different endogenous (proteins, enzymes, polysaccharides, bacteria) and exogenous substances (all different sorts of compounds coming from the diary intake diet). These components establish a complex and intricate interplay of interactions, which result along with an important mechanical action, in a general biodegradation phenomena towards the biomaterials present in the oral cavity. These processes may permanently alter the properties of the material and compromise its function.

In addition, biodegradation of a biomaterial can produce leachable products, which in turn may induce a series of biological responses on cells and tissues. Biodegradation impact on the biocompatibility of acrylic materials is controversial [17] but concern about its clinical significance is a fact as subjective and objective complaints about these materials are increasing [18].

Section snippets

Causes for biodegradation

The polymeric materials were classically recognized as large stable structures with a high degree of resistance to biodegradation. However, several studies conducted especially with composites materials, showed that polymers may be subject to a myriad of degradation processes in the oral cavity [19], [20].

Polymer degradation does not occur as a result of isolated processes, multiple factors as saliva, chewing, thermal and chemical dietary changes may be responsible for the biodegradation

Consequences of biodegradation

A major clinically significant consequence of acrylic based resins biodegradation is the release of potential toxic unbound/uncured monomers or/and additives from the polymer network. The released compounds may have a toxic effect on the oral cavity. With respect to materials stability, biodegradation may induce significant changes in materials physical and mechanical properties that may ultimately lead to the catastrophic failure of the material.

Unexplored topics and areas for future research

Biodegradation of acrylic based resins under the oral environment has been so far uncompleted studied. Some questions that need to be investigated include: which enzymes are involved in the in vivo process of acrylic resins degradation? What are their co-factors? Is the saliva of one individual more likely to degrade certain materials than that from another person? What is the level of the different products in vivo?

A gap in the published literature exists regarding in vitro studies that allow

Conclusions

The following conclusions are draw from this review:

  • 1.

    Acrylic based resins are intensively used in dentistry practice as restorative, liners or as denture base materials. These substances are made by polymerization of methacrylate related monomers. Materials can be classified as chemical, heat or light polymerizing depending on the factor that initiates the polymerization reaction.

  • 2.

    Increasing concern arises regarding the safe clinical application of these materials due to their biodegradation

References (126)

  • B.A. Lin et al.

    Identifying enzyme activities within human saliva which are relevant to dental resin composite biodegradation

    Biomaterials

    (2005)
  • B. Willershausen et al.

    The influence of oral bacteria on the surfaces of resin-based dental restorative materials: an in vitro study

    Int Dent J

    (1999)
  • D.W. Jones et al.

    Dental soft polymers: plasticizer composition and leachability

    Dent Mater

    (1988)
  • H. Minami et al.

    In vitro evaluation of the influence of repairing condition of denture base resin on the bonding of autopolymerizing resins

    J Prosthet Dent

    (2004)
  • N.J.A. Jepson et al.

    Influence of dietary simulating solvents on the viscoelasticity of temporary soft lining materials

    J Prosthet Dent

    (2000)
  • T. Koda et al.

    Leachability of denture-base acrylic resins in artificial saliva

    Dent Mater

    (1990)
  • H. Tsuchiya et al.

    Leaching and cytotoxicity of formaldehyde and methylmethacrylate from acrylic resin denture base materials

    J Prosthet Dent

    (1994)
  • P.K. Vallittu et al.

    Residual monomer content and its release into water denture materials

    Dent Mater

    (1995)
  • E.K. Viljanen et al.

    Analysis of residual monomers in dendritic methacrylate copolymers and composites by HPLC and headspace-GC/MS

    Dent Mater

    (2006)
  • M. Kawaguchi et al.

    Effect of light-exposure duration on the amount of leachable monomers from light-activated reline material

    J Prosthet Dent

    (1996)
  • G.D. Stafford et al.

    The loss of residual monomer from acrylic orthodontic resins

    Dent Mater

    (1985)
  • Y. Hashimoto et al.

    Estrogenic activity of tissue conditioners in vitro

    Dent Mater

    (2003)
  • H. Tsuchiya et al.

    Flow injection analysis of formaldehyde leached from denture-base acrylic resins

    J Dent

    (1993)
  • S. Sadamori et al.

    The usage period of dentures and their residual monomer contents

    J Prosthet Dent

    (1992)
  • R.E. Weaver et al.

    Reactions to acrylic resin dental prostheses

    J Prosthet Dent

    (1980)
  • D.M. Bohnenkamp

    Traumatic stomatitis following an intraoral denture reline: a clinical report

    J Prosthet Dent

    (1996)
  • J. Giunta et al.

    Allergic stomatitis caused by self-polymerizing resin

    Oral Surg Oral Med Oral Pathol

    (1976)
  • P.A. Leggat et al.

    Toxicity of methylmethacrylate in dentistry

    Int Dent J

    (2003)
  • T.S. Gonçalves et al.

    Allergy to auto-polymerized acrylic resin in an orthodontic patient

    Am J Orthod Dentofacial Orthop

    (2006)
  • J.H. Jorge et al.

    Cytotoxicity of denture base acrylic resins: a literature review

    J Prosthet Dent

    (2003)
  • F.M. Vale et al.

    Acrylic bone cement induces the production of free radicals by cultured human fibroblasts

    Biomaterials

    (1997)
  • G. Ciapetti et al.

    In vitro testing of the potential for orthopedic bone cements to cause apoptosis of osteoblast-like cells

    Biomaterials

    (2002)
  • H.W. Yang et al.

    Assessment of genetic damage by methyl methacrylate employing in vitro mammalian test system

    Biomaterials

    (2003)
  • T. Atsumi et al.

    (Meth)acrylate monomer-induced cytotoxicity and intracellular Ca2+ mobilization in human salivary gland carcinoma cells and human gingival fibroblast cells related to monomer hydrophobicity

    Biomaterials

    (2006)
  • W. Att et al.

    N-Acetyl cysteine prevents suppression of oral fibroblast function on poly(methylmethacrylate) resin

    Acta Biomater

    (2009)
  • S.H. Kim et al.

    Effects of dibutyl phthalate and monobutyl phthalate on cytotoxicity and differentiation in cultured rat embryonic limb bud cells; protection by antioxidants

    J Toxicol Environ Health A

    (2002)
  • N. Kojima et al.

    Restored viability and function of dental pulp cells on poly-methylmethacrylate (PMMA)-based dental resin supplemented with N-acetyl cysteine (NAC)

    Dent Mater

    (2008)
  • S. Sadamori et al.

    Dimensional changes of relined denture bases with heat cured, microwave-activated, autopolymerizing, and visible light cured resins. A laboratory study

    Aust Dent J

    (1995)
  • B.L.T. León et al.

    Loss of residual monomer from resilient lining materials processed by different methods

    Rev. Odonto Ciênc

    (2008)
  • G. Bayraktar et al.

    Influence of polymerization method, curing process, and length of time of storage in water on the residual methyl methacrylate content in dental acrylic resins

    J Biomed Mater Res B: Appl Biomater

    (2006)
  • N. Celebi et al.

    Effect of polymerization methods on the residual monomer level of acrylic resin denture base polymers

    Polym Adv Technol

    (2008)
  • M. Braden

    Some aspects of the chemistry and physics of dental resins

    Adv Dent Res

    (1988)
  • R.M. Sawtell et al.

    Heterocyclic methacrylates for clinical applications-further studies of water sorption

    J Mater Sci Mater Med

    (1997)
  • M.J. Mendonça et al.

    Weight loss and surface roughness of hard chairside reline resins after toothbrushing: influence of postpolymerization treatments

    Int J Prosthodont

    (2006)
  • E.C. Munksgaard

    Plasticizers in denture soft-lining materials: leaching and biodegradation

    Eur J Oral Sci

    (2005)
  • M.H. Gutierrez-Villarreal et al.

    The effect of citrate esters as plasticizers on the thermal and mechanical properties of poly(methyl methacrylate)

    J Appl Polym Sci

    (2007)
  • G. Hong et al.

    Relationship between plasticizer content and tensile bond strength of soft denture liners to a denture base resin

    Dent Mater J

    (2004)
  • B. Ebadian et al.

    Evaluation of tissue reaction to some denture-base materials: an animal study

    J Contemp Dent Pract

    (2008)
  • J.P. Santerre et al.

    Relation of dental composite formulations to their degradation and the release of hydrolyzed polymeric-resin-derived products

    Crit Rev Oral Biol Med

    (2001)
  • M. Braden et al.

    Diffusion in water in composite filling materials

    J Dent Res

    (1976)
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