Clinical Guide to Principles of Fiber-Reinforced Composites in Dentistry

Pekka Vallittu, Mutlu Özcan

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN:
  9780081006078
• eBook ISBN:
  9780081006085
• Topic: Tecnología e ingeniería
• Subtopic: Biotecnología en medicina

Traditional dental materials such as metals and ceramics have a number of disadvantages such as cost and the significant damage caused in grinding to make space for such reconstructions. Fiber-reinforced composites (FRCs) are a novel group of dental materials characterized by fibrous fillers that are being increasingly used in place of traditional prosthodontic materials. They allow fabrication of minimally invasive, lightweight, durable and biocompatible restorations. This book will provide clinicians and students with theoretical and clinical guidelines to use the FRCs for dental applications. The book begins with an introduction to the fundamentals of FRCs in dentistry. Further chapters cover the treatment possibilities, fabrication and application procedures of FRCs, followed by information on care and maintenance. - Explores the mechanism of function of fibre-reinforced composites - Presents comprehensive information on the expanding field of fibre-reinforced composites and their increasing use in dentistry

Part I

Fundamentals of fiber-reinforced composites in dentistry

Outline

1 Key requirements for dental FRCs

2 Types of FRCs used in dentistry

3 Structural properties of dental FRC structures

1

Key requirements for dental FRCs

Pekka Vallittu, University of Turku and City of Turku, Welfare Division, Turku, Finland

Abstract

The oral environment, where dental constructs and devices are used, is host to various different hostile features of the masticatory system. The oral cavity is the first part of digestive canal, with the additional functions of communication both phonetically and through gesture. As part of the digestive canal, the oral cavity places demands on dental biomaterials and restorations, both mechanically and chemically. Dentition also plays a significant role in the articulation of sounds. In the context of humans, dentition as a part of the oral cavity is of importance for social wellbeing. The natural appearance of teeth in terms of color shade, surface texture, and basic shape of the teeth, has important culturally-related meaning for humans. In the modern world, patients are well aware of the possibilities of dental treatments and how they can fulfill the needs of function and appearance. Another critical aspect of dental biomaterials and restorations relates to temporal properties. The ageing of restorations of whatever material changes the physical and other materials’ properties. Adequate mechanical strength, high surface gloss, and good resistance against wear are examples of requirements for dental restorations. Additionally, biological aspects of biofilm adsorption of proteins and microbes contribute to longevity of restorations, adjacent tissues, and treatment outcome. Complexity of the oral environment, in combination with the complex multiphasic dental biomaterials and dental devices in restorative and prosthetic dentistry, challenges the dental profession in its aim for long-lasting treatment outcomes.

Keywords

Oral environment; key requirements; oral cavity; treatment outcome; dentistry; surface texture; FRC; fiber-reinforced composite; stress; load; oral microbes; microbial adhesion

Chapter Outline

1.1 Introduction: The Oral Environment 3

1.2 Mechanical Loads Faced by FRCs 5

1.3 Requirements for Minimally Invasive and Adhesive Restorations 9

1.4 Summary: Key Requirements for FRC Materials 9

References 9

1.1 Introduction: The Oral Environment

The oral environment, where dental constructs and devices are used, is host to various different hostile features of the masticatory system (Vallittu and Könönen, 2000). The oral cavity is the first part of digestive canal, with the additional functions of communication both phonetically and through gesture. As part of the digestive canal, the oral cavity places demands on dental biomaterials and restorations, both mechanically and chemically. Dentition also plays a significant role in the articulation of sounds. In the context of humans, dentition as a part of the oral cavity is of importance for social wellbeing. The natural appearance of teeth in terms of color shade, surface texture, and basic shape of the teeth, has important culturally-related meaning for humans. In the modern world, patients are well aware of the possibilities of dental treatments and how they can fulfill the needs of function and appearance (Vallittu et al., 1996). Another critical aspect of dental biomaterials and restorations relates to temporal properties. The ageing of restorations of whatever material changes the physical and other materials’ properties (Eliades et al., 2003). Adequate mechanical strength, high surface gloss, and good resistance against wear are examples of requirements for dental restorations. Additionally, biological aspects of biofilm adsorption of proteins and microbes contribute to longevity of restorations, adjacent tissues, and treatment outcome. Complexity of the oral environment, in combination with the complex multiphasic dental biomaterials and dental devices in restorative and prosthetic dentistry, challenges the dental profession in its aim for long-lasting treatment outcomes.

One important aspect of longevity of treatment outcome relates to the accumulation of oral microbes on the surface of dental constructs and dental tissues. Accumulation and colonization of microbes involves adherence of microbes to the substrate (Douglas, 1985). When a dental material or device is exposed to the oral cavity, a noncellular acquired biofilm covers the material surface by adsorption of extracellular molecules of glycoproteins and proteoglycans, which influences the attachment of cells to the surface. In some cases there can be continuous process of biofilm adsorption-desorption, but in the oral cavity adsorption dominates and causes accumulation of plaque on the material surface. Material properties like surface free energy, hydrophilicity, and surface texture influence adhesion of microorganisms. Rough surfaces and those having high surface energy are both known to adsorb more microbial biofilm on the surface than smooth and low energy surfaces (Glantz, 1971; Quirynen and Bollen, 1995). Surface roughness and surface texture is considered both macroscopically and ultrastructurally. Macroscopic textures are responsible for the aggregation of particulates of the biofilm, whereas ultrastructural features have more importance for the microstructural attachment of the biological components of biofilm, including parts of microbes. Any surface which is exposed in the oral cavity is covered instantly with a salivary biofilm called acquired pellicle, which has several functions, but may also promote the adhesion of certain microbes.

One of the key pathogenic microorganisms in relation dental diseases and reconstructive treatments outcome is Streptococcus mutans. There is existing information on how S. mutans behave on the surface of different kinds of dental materials, including fiber-reinforced composites (FRCs) with various kinds of reinforcing fibers (Tanner et al., 2000, Tanner et al., 2001). Adherence of S. mutans is related also to the presence of proteins and some other microorganisms, such as Candida albicans. Out of FRC materials, glass FRC binds the least amount of S. mutans to the surface, and ultra high molecular weight polyethylene (UHMWP) fibers bind the highest amounts of microbes to the surface (Fig. 1.1). This was confirmed also by a clinical study of plaque accumulation on the surface of various dental materials (Tanner et al., 2003). Studies where denture base polymers have been reinforced with glass fibers showed that the glass fibers running along the surface of the palatal plate of the denture do not enhance the growth of C. albicans on the denture base material (Waltimo et al., 1999). This has been confirmed both with the heat-cured and autopolymerized denture base polymer of polymethylmethacrylate. Thus, if the glass fibers are exposed during polishing of the denture, the reinforcing material of glass fibers appears not to increase the adherence of this common microbe. Despite the relatively low microbial adherence to the glass FRC, it is recommended to cover the FRC with particulate filler resin composite, and in the removable denture, with a layer of acrylic resin, which allows better surface gloss and natural-looking appearance for the restoration (Tanner et al., 2001). However, the surface coverage of the FRC with particulate filler resin composite does not influence to the water absorption of the material over time, which affects some physical properties of the resin composite over time. Water diffuses into the polymer matrix with simultaneous leaching of curing reaction residuals (residual monomers, oxidation products of initiators and activators) of the polymer matrix regardless of the surface coverage.

Figure 1.1 Relative adsorption of S. mutans on the surfaces of different dental materials (Tanner et al. 2002).

In a wider perspective of the goals of dentistry, the oral environment should also be understood as a field where host defense mechanisms and threats by pathogens are competing and can provoke leaching of dental hard tissues but also human-made materials. Pathogenic oral microbes of, e.g., S. mutans and Lactobacillus are well known to produce acids which locally can lower the pH of the tooth surface to the level of 5.4–4.4, which is a critical value, where significant amounts of enamel are dissolving. Thus, although the polymer matrix of the FRC protects the fibers from the direct influence of decreasing pH, the FRC, and more precisely reinforcing fillers and their adhesive interfaces, could be prone to the leaching and degradation. This means that individual treatment entity of existing teeth or parts of teeth in combination with restorations made by dental professionals is in the best-case scenario long-lasting results; but they may be damaged earlier than expected for several reasons. The oral environment needs restorations to be ea...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Preface
• Rationale
• Introduction
• Part I: Fundamentals of fiber-reinforced composites in dentistry
• Part II: Applications of fibre-reinforced composites in dentistry
• Index