How To Use This Book

This book functions in several ways. Firstly, it is a reflection of the huge scope of materials in dentistry today, the challenge to the dentist of tomorrow. There can be no reduction in this challenge as time goes on, rather will it increase. In that light, this book is a tool kit of ideas that can be applied in principle and in fact to any conceivable product in the future. This may seem like a grandiose claim, but if the identification of the fundamentals has been successful it must be true. That is the nature of materials science. Specific new polymers or composite combinations will almost certainly appear that have not been anticipated, but this should not matter. This is not an encyclopaedic treatise, but a foundation text that nevertheless serves that long-term purpose. It should permit answers to questions not specifically addressed here to be worked out. It should be clear that whilst much work in a dental practice may be routine, it is the ability to recognize and deal with the non-routine events or conditions that is the mark of the professional. One must be prepared to think.

Secondly, it contains an undergraduate-level course in the subject. The level has been set appropriately, and has been shown to be well within such a student’s ability. The target in mind in writing it has been the explanation in chemical and physical terms of the choices of material and procedure that are in use in everyday, clinical dentistry in a manner that empowers the student to be in charge and control of what is done, rather than blindly following instructions with no capacity to recognize what is happening and intervene, adjust, or make independent, rational, scientific decisions, or indeed explain and justify treatment. This will be required more and more in respect of health insurance claims. In addition, in an increasingly litigious and regulated world, where accountability is paramount, a professional is no longer protected by a qualification and afforded unquestioning trust. As a professional, one may be called upon to defend a decision where something has gone wrong. It would seem essential that an appropriate knowledge and demonstrable understanding of the materials be part of the duty of care.[1]

Thirdly, this is a source book, a reference for pursuing, as a first step, the ideas and equations needed for laboratory work, whether as part of undergraduate curriculum practical classes or further study. At the undergraduate level, and in the vast majority of cases, it is not necessary to learn the equations or their derivation deliberately and explicitly. The practising dentist does not need them. It is therefore not appropriate that they be examinable as such. Nevertheless, it is important that the essence of these equations is understood: what variables are involved (e.g. stress, time), and in what sense (such as proportionally, inversely). The simpler equations, for example for Young’s modulus, viscosity or surface tension, will in any case be absorbed almost automatically. The algebraic manipulations have deliberately been kept simple, but even if one’s mathematical abilities are not up to reading and following these step by step, the text is intended to provide a parallel description of the process. Likewise, many diagrams are included to illustrate behaviour, structure and so on. These, too, should not be memorized. Rather, the nature of the trend or pattern of behaviour in broad terms should be identified. If the controlling factors are understood, the goal will have been achieved.

Fourthly, it is intended to demonstrate that instructions for use or clinical procedures are (or, at the very least, should be) justifiable, founded in reason and logically traceable. Nothing should be taken on faith – including what is in this book![2] Be prepared to challenge dogmatic teaching or unsubstantiated claims. There must exist an explanation for every decision, every observation, every effect. Even so, in some cases, our understanding is incomplete (abrasion springs to mind), but the principle still stands. Therefore, identifying the path of the explanation, the chain of reasoning, should give confidence that dentistry has emerged from the mire of mediaeval magic, from the mystical arts of mere technical craftsmen, from the not-to-be questioned received wisdom of dogmatic practitioners, and from the era of the data handbook that lists simply what is rather than why. In that sense, nothing in this book is here just because it is interesting: it all has a purpose, a place in that chain intended to illuminate one idea or another. Thus, commonplace examples – or other non-dental topics – may be mentioned in order to underline the reality and broad applicability of the ideas. Because, in places, the path is long, the student may not be able to see the ultimate goal or the part being played by a given idea. A little patience is required for things to fall into place – not everything can be said at once. Then again, the experience, background and knowledge of students do vary. It has been necessary in places to overlap what may have been taught prior to entry into university in order better to ensure that the path is complete for everyone. In that case, the material will serve for revision. There are also many paths, which touch and cross each other in an elaborate network, so that cross-references are included liberally to assist in recognizing when other ideas are relevant.

This book does not deal with the operative techniques, laboratory procedures, or other matters of a direct treatment kind. These issues are dealt with in many other texts, and cross-reference should be made to those for the clinical background, handling instructions and so on. It is emphasized that dental materials science is a foundation on which clinical dentistry relies, whether or not it is recognized, and the implications and value of its contribution can only be found in the proper context. Study of dental materials science in isolation is not a meaningful proposition because the clinical decisions should be in terms of and based on what it teaches. This may be understood better by reference to Fig. 1.3. The factors include not just the properties of the material but also the manner and conditions of use. These are seen to be acting on or through some kind of process, which then has an identifiable outcome. But the crucial point is then how this affects dentistry: what is the clinical implication of that outcome? How is treatment constrained? What limitations to performance in actual service might there be? Again, the ultimate purpose is patient well-being, and the present goal is to enable, facilitate and enhance just that.

As indicated above, this is not an encyclopaedia. There is no attempt to cover all the many varieties of monomer, adhesives, and filler, for example. Such catalogues are available elsewhere. Examples are used to illustrate principles, with such alternatives as are necessary to make a specific point, but always in a manner that may be applied elsewhere, even for products and systems yet to be invented.

So, to study. The terminology is of evident importance: knowing what the words mean and the context of their use allows comprehension of what is said, and the means of communication for reports and examinations (see the companion “Glossary”[3]). Much of this can be achieved by simply reading the appropriate portion of text once through, as for example in preparation for a lecture. At this stage one should not worry whether the chain of reasoning has been understood or a mechanism is clear, it is unimportant. If a lecture then follows, it will be easier to understand. The relevant text can then be read through again, but now more carefully, this time identifying passages which cause some difficulty, but not dwelling unduly on them. There are many approaches to understanding concepts, and it may be that after reading other material, whether in other chapters of this book or in other dental materials texts, the ideas will be clearer. Still, if not, do not waste time struggling – ask for help. In any case, if there is any doubt about the relevance or comprehension of a cross-reference, follow it up until a secure foundation is found. Then retrace your steps. Reinforcement will give you confidence.

Try also to develop mental models, images in your mind of what is going on. Do not let the ideas remain just words on the page. Much of what is of interest here is dynamic: active processes of flow, diffusion, reaction and deformation. Ultimately, what is being described is observable behaviour, the macroscopic dependent on the microscopic. Verbal memory is not comprehension; it is not a viable route to understanding.

It will also be of value in consolidating the ideas, and in integrating them with clinical teaching, to begin to think about what is being done in the laboratory and on the clinic in terms of this subject. Try to relate your observations to the theory, and to answer clinical questions in these terms. This will give practice in using the tool kit, practice in thinking, and confidence in the meaning and utility of the subject.

Overall, a systematic, steady, integrated approach to your study will yield a comprehension of the basis of much of modern dentistry in a manner that will become a second-nature, background, almost invisible part of your dentistry. It will be an investment for a long career, no matter what changes occur in the products and techniques.