Dental Biomaterials

Imaging, Testing and Modelling

R V Curtis, T F Watson

• Publisher: Woodhead Publishing
• Year: 2014
• Print ISBN: 9781845692964
• eBook ISBN: 9781845694241
• Topic: Technology & Engineering
• Subtopic: Biomedical Science
• Index: Technology & Engineering

Dental Biomaterials: Imaging, Testing and Modelling reviews the materials used in this important area, their performance and how such performance can be measured and optimised. Chapters review optical and electron microscopy imaging techniques for dental biomaterial interfaces. Specific materials such as dental cements, fibre-reinforced composites, metals and alloys are discussed. There is an analysis of stresses, fracture, wear and ageing in dental biomaterials as well as an evaluation of the performance of dental adhesives and resin-dentin bonds. Chapters also review ways of assessing the performance of dental handpieces, crowns, implants and prosthesies. The book also reviews the use of computer models in such areas as bond strength and shape optimisation of dental restorations.With its distinguished editors and team of experienced contributors DDental Biomaterials: Imaging, Testing and Modelling researchers, materials scientists, engineers and dental practitioners with an essential guide to the use and performance of dental biomaterials. - An essential guide to the use and performance of dental biomaterials - Reviews optical and electron microscopy imaging techniques for dental biomaterial interfaces - Analyses stresses, fracture, wear and ageing in dental biomaterials and evaluates the performance of dental adhesives and resin-dentin bonds

1

Characterizing the performance of dental air-turbine handpieces

B.W. DARVELL

J.E. DYSON, The University of Hong Kong, Hong Kong

Publisher Summary

The dental air-turbine handpiece rapidly gained widespread acceptance by the dental profession after its introduction in the late 1950s and it continues to be used as the main means of carrying out cutting work in clinical dental practice, whether of tooth tissue or restorative materials. In order to understand the performance of dental air-turbine handpieces in general, it is necessary to recognise the large number of factors involved and their complex interaction. However, it is not yet possible to characterise the cutting performance of these devices, dependent as they are on the behaviour of cutter and substrate, among other things. Cutting performance is understood to relate to the rate of reduction of the workpiece. This is affected by many factors; for example, operator characteristics, the handpiece itself, rotary cutting instrument design, coolant applied at the interface and the workpiece material. However, it is not possible to define a representative set of conditions for normal clinical service. Only benchmarking in certain respects, item by item, is currently feasible. The aspects of the performance of air-turbine handpieces of principal concern with respect to turbine performance are free-running speed, that is, with no external load applied, and torque as functions of speed, rate of air flow and supply pressure. However, since the bearings are the primary source of internal friction in most designs, a standardised lubrication protocol is an essential first step in any testing, at least for steel bearings. A self-contained test system has been designed to perform the most important tests.

1.1 Outline

After briefly outlining the general importance of air-turbine handpieces in dentistry (Section 1.2), a historical account of their development puts their present status into context (Section 1.3). However, in order to understand performance in general, it is necessary to recognize the large number of factors involved, and their complex interactions (Section 1.4). In essence, it is not yet possible to characterize the cutting performance of these devices, dependent as they are on the behaviour of cutter and substrate, amongst other things. Accordingly, it is as yet only feasible to document the physical aspects of the behaviour of the turbine itself (Section 1.5), but this leads to a number of figures of merit that may be used for product comparisons in an objective fashion that are tied to the physics of these machines. Even so, because of their internal complexity, primarily in terms of gas flow, it is necessary to resort to the ‘black-box’ approach and document input–output relationships, subsuming much unresolvable detail in some fitted parameters. Selection and application by the end-user nevertheless depends on a number of further issues of great importance, and these are discussed under the general heading of hazards (Section 1.6). The chapter closes with some general remarks on selection, usage, and areas where further study is essential.

1.2 General importance: applications, benefit

The dental air-turbine handpiece rapidly gained widespread acceptance by the dental profession after its introduction in the late 1950s, and it continues to be used as the main means of carrying out cutting work in clinical dental practice, whether of tooth tissue or restorative materials. In comparison with alternatives at the time, the reasons given for its usefulness included the following.

• Power: power-to-weight ratio very favourable, negligible transmission loss;

• Size: size and weight allow better control for long periods without tiring as well as good intraoral access;

• Speed: reduction of unpleasant vibration, finer control of cutting process;

• Effort: lower forces could be used yet with higher removal rates.

These considerations still appear to be pertinent.

1.3 Historical outline: development, features

A turbine is a motor in which a shaft is steadily rotated by the action of a current of fluid upon the blades of a wheel. Turbines powered by various fluids have evolved along several paths, and it is not possible to identify a single source for the development of dental systems.

The first air-powered dental engine design was patented in 1868¹ although in fact this was not a turbine but effectively a lobe pump operated in reverse. It was intended to be operated by mouth, foot bellows, or a compressed air vessel. The first true turbine dental handpiece, with a 13-bladed rotor, was patented in 1874,² with similar suggestions for operation as the lobe pump. It received little attention from the profession. A water-powered device in 1877³ also made provision for a fine stream of water to be directed as coolant onto the cutting instrument. A more elaborate device with a transmission clutch, a rotatable handpiece sheath, and revised mechanism for the attachment of cutting instruments followed in 1879,⁴ although details of the turbine rotor were not given and the drive fluid was not specified.

These machines were all somewhat bulky with their weight borne by the dentist’s hand. However, a water-powered engine, produced by S. S. White in 1881⁵ avoided this problem by the motor being mounted on a floor stand. A flexible shaft transmitted the drive in a fashion similar to that ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• Contributor contact details
• Preface
• Chapter 1: Characterizing the performance of dental air-turbine handpieces
• Chapter 2: Optical imaging techniques for dental biomaterials interfaces
• Chapter 3: Electron microscopy for imaging interfaces in dental restorations
• Chapter 4: Dental adhesives and adhesive performance
• Chapter 5: Mechanical stability of resin–dentine bonds
• Chapter 6: Dental cements: formulations and handling techniques
• Chapter 7: Mixed-methods approach to wear evaluation in posterior composite dental restorations
• Chapter 8: Shape optimization of dental restorations
• Chapter 9: Fibre-reinforced composites for dental applications
• Chapter 10: Fracture mechanics characterization of dental biomaterials
• Chapter 11: Modelling bond strength in dental biomaterials
• Chapter 12: Fracture and aging of dentine
• Chapter 13: Finite element analysis of stresses in dental crowns
• Chapter 14: Testing the performance of dental implants
• Chapter 15: Superplastic forming of dental and maxillofacial prostheses
• Chapter 16: Dental investment materials for casting metals and alloys
• Index