Monitoring and Evaluation of Biomaterials and their Performance In Vivo

Roger Narayan

• Publisher: Woodhead Publishing
• Year: 2016
• ISBN:
  9780081006047
• Topic: Medicine
• Subtopic: Medical Technology & Supplies

Monitoring and Evaluation of Biomaterials and Their Performance In Vivo provides essential information for scientists and researchers who need to assess and evaluate performance, monitor biological responses, gauge efficacy, and observe changes over time. Crucially, it also enables the optimization of design for future biomaterials and implants.

This book presents readers with comprehensive coverage of the topic of in vivo monitoring of medical implants and biomaterials.

• Contains a specific focus on monitoring and evaluation of biomaterials in vivo
• Multi-faceted coverage of materials function and performance
• Focuses on a range of implants and subsequent bodily reactions

Part One

Monitoring and evaluation of the mechanical performance of biomaterials in vivo

Outline

1. Nanostructured ceramics

2. Monitoring degradation products and metal ions in vivo

1

Nanostructured ceramics

L. Hermansson Doxa AB and Applied Research Sweden AB, Uppsala, Sweden

Abstract

This chapter deals with nanostructured bioceramics with a focus on the chemically bonded bioceramics, especially the CaO-Al₂O₃-H₂O (CAH), CaO-SiO₂-H₂O (CSH), and the CaO-P₂O₅-H₂O (CPH) systems and combinations thereof. The nanocrystal size is in the range 10–50 nm with an open porosity in the form of nanochannels with a width in the range 1–3 nm. These biomaterials are close in chemistry to apatite, the main chemical constituent in hard tissue, and these materials can favorably be produced at body temperatures, i.e., in situ in vivo. These biomaterials tolerate moist conditions. The hardening can be controlled to avoid shrinkage, and the thermal and electrical properties are close to those of hard tissue. A specific interesting combination of properties is the simultaneous appearing of bioactivity and bacteriostatic and antibacterial properties. More than 10 different dental applications are possible to produce. These deal with dental filling materials, dental luting cements, endodontic materials, stabilizing materials, and as coating materials on other implant materials. The materials can also be used within the orthopedic application field, as well as within drug delivery carrier systems for the controlled release of medicaments.

Keywords

Bioceramics; Chemically bonded ceramics; Dental; Nanoporosity; Nanostructures; Orthopedic and drug delivery carrier applications

1.1. Introduction

Ceramics are defined as inorganic nonmetallic materials and are often classified according to Table 1.1. Biomaterials based on ceramics are found within all the classical ceramic families: traditional ceramics, special ceramics, glasses, glass ceramics, coatings, and chemically bonded ceramics (CBC) [1,2]. Examples of bioceramics are given in Table 1.1.

This chapter deals specifically with bioceramics with nanostructures. The nanosize is defined as less than 100 nm. Nanostructured ceramics are found most frequently among the CBC [1] shown in Table 1.2.

The nanostructured chemically bonded ceramics have structures with the same general structure as hard tissue, i.e., small crystals, all surrounded by a softer interlayer, in the case of hard-tissue collagen layers, and in the case of the chemically bonded silicate, aluminate, and phosphate ceramics, nanothin water layers. The structures of all the apatite-based body ceramics (enamel, dentine, and hard tissue) include individual plates just above the nanosized level, approximately 0.2 μm, but composed of nanocrystals of approximately 20 nm in diameter [1,3].

Nanostructured bioceramics are also, to some extent, found within the special ceramics field based on zirconia, titania, silica, or other oxides produced by low-temperature sintering using laser techniques, hot pressing, or hot isostatic pressing [4,31].

This chapter will treat nanostructured ceramics with emphasis on nanostructured materials, not nanostructured particles, needles, wires et cetera.

1.2. Test methods for nanostructured ceramics

As early as 1946, Professor Powers [5] proposed that chemically bonded ceramics, specifically Ca silicate hydrates, ought to have an average crystal size of approximately 14 nm, based on BET measurements, i.e., based on the surface area measurement of dried cements. However, at that time the microscopes did not have efficient resolution to detect this. Approximately 50 years later the first actual micro/nanopictures of chemically bonded ceramics were presented [6], all of which demonstrated that the proposal of Professor Powers was right.

Table 1.1

Classification of ceramics and examples of bioceramics

Ceramics – classification	Examples of bioceramics
Traditional ceramics	Dental porcelain, (K2O-Al2O3-SiO2)
Special ceramics	Al-, Zr, and Ti-oxides
Glass	Bioactive glasses (Na2O-CaO-P2O5-SiO2)
Glass ceramics	Apatite (CaO-P2O5-H2O), Wollastonite (CaO-SiO2), Li-silicate based (Li2O-SiO2) and Leucite-based (K2O-Al2O3-SiO2)
Chemically bonded ceramics	Phosphates, aluminates, silicates, and sulfates

Table 1.2

Chemically bonded bioceramic systems

Group/name	Basic system
Calcium silicates	CaO-SiO2-H2O
Calcium aluminates	CaO-Al2O3-H2O
Calcium phosphates	CaO-P2O5-H2O
Calcium sulfates	CaO-SO3-H2O
Calcium carbonates	CaO-CO2

1.2.1. Micro/nanostructural evaluation

Methods used in the evaluation of the microstructures, including nanostructures, and phase and elemental analyses are traditional SEM, TEM, HRTEM, XRD, XPS, and STEM with EDX.

To analyze interfaces and calcified tissue at the highest level, transmission electron microscopy (TEM), in combination with focused ion beam microscopy (FIB), for intact site-specific preparation of the TEM samples at very high site-specific accuracy is recommended. This procedure is treated in detail in Ref. [7]. Cross-sectional TEM samples from the interface between, e.g., enamel and a dental filling material are produced by FIB. The system scans over a beam of positively charged gallium ions over the samples, similar to an electron beam in SEM. The ions generate sputtered neutral atoms, secondary electrons, and secondary ion...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Part One. Monitoring and evaluation of the mechanical performance of biomaterials in vivo
• Part Two. Monitoring and evaluation of the biological response to biomaterials in vivo
• Part Three. Monitoring and evaluation of functional biomaterial performance in vivo
• Index