J. Dent. 1992;
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which maintains adequate tissue oxygenation. However, the general trend of a decline in pulse rate and Sao, may be of more importance in patients with cardiopulmonary disease where these changes may add to an already preexisting lowSao, and hence render the patient at risk from respiratory depression.
Acknowledgements We are grateful for the financial assistance for these investigations provided by Kabivitrium, and for help given in the statistical analysis by Dr D. G. Wastell, Department of Computer Science, University of Manchester.
References Association of Anaesthetists (1989) Recommendations Standards
for and Recovery.
London, Association of Anaesthetists of Great Britain and Ireland. Evans C. S. and Dawson A. D. G. (1990) Oxygen saturation during general anaesthesia in the dental chair. A comparison of the effect of position on saturation. Br. Dent. J 168, 157-159. Ganong W. F. (1989) Review of Medical Physiology, 14th edn. Hemel Hempstead. Her& Appleton and Lange. Hook P. C. G. and Lavery K. M. (1988) New intravenous sedative combinations in oral surgery. A comparative study of nalbuphine or pentazocine with midazolam. Br. J. Oral Maxillofac. Surg. 26, 95-106. Read-Ward C. (1990) Intravenous sedation in general dental practice-why oximetry? Br. Dent. J. 168, 368-369. Report of an Expert Working Party (1991) General Anaesthesia, Sedation and Resuscitation in Dentistry. Prepared for the Standing Dental Advisory Committee.
Book Review Facial Growth, 3rd edition. D. H. Enlow. Pp. 562. 1990. Hardback, f 56.50.
This third edition of Enlow’s textbook on facial growth has been expanded by short chapters introducing the subjects of TMJ (Dibbets), facial heredity (Stuart Hunter), birth defects (Cohen), adult facial growth (Behrents), growth control (Enlow), masticatory function (Oven) and general body growth (Cederquist). The 562 pages now include 18 chapters, a list of over 1500 references and a detailed index. The book starts with an excellent chapter motivating the student to look at faces and facial details and is followed by another, also excellent, on the introductory concepts of the growth process, emphasizing the distinction between growth displacement of bones and remodelling. Chapter 3, ‘The facial growth process’, presents Enlow’s detailed account of the growth of the facial bones divided into 17 regions. It is profusely illustrated, but apart from a handful of histological figures, the over 100 illustrations are hypothetical line drawings and artist’s renderings, illustrating the author’s ideas and concepts. Enlow’s basic concept of facial growth is that of the counterpart principle: that the growth of one facial part relates specifically to that of other parts. Although the general concept seems reasonable enough, it is in fact hypothetical. Thus, there is no evidence presented to support the tenet used throughout this basic chapter: that dimension x develops in such and such a direction because of the development of dimension y. One of the criteria of a textbook is that it should provide an unbiased overview of key contributions and established knowledge within its field. In this respect, the book is less than up to standard because Enlow in his enthusiasm for ‘the
counterpart principle’ often gets carried away by his imagination. Some examples: in the frequently quoted figure 3-93, which illustrates ‘growth and remodelling of the human maxilla’ seen in a frontal section, the maxillary complex does not have a mid-palatal suture, and the illustration ignores Bjork’s implant documentation that the major part of the maxillary growth in width occurs in this suture. In the famous three-dimensional renderings of the surface remodelling of the maxillary complex, arrows indicate resorption of the anterior surface of the zygomatic arch (figures 3-l 1 1, 3-l 12, 3-l 30). although it is well established that there is no resorption here because implants inserted at this location remain in place from the age of 4 to adulthood. The conceptual tracings (figures 3-l 1, 3-l 2 and 3-l 3) show how the entire sella turcica is relocated about 4 mm forwards through the sphenoid bone. This does not agree with the detailed histological work of Melsen which documents that the anterior wall of sella is stable from the age of 6. Close scrutiny of this chapter reveals many such departures from established facts. Despite its sympathetic attempts to present an holistic view of the development of the craniofacial complex, it therefore often appears rather speculative in the text as well as the illustrations, and the unprepared student has no way of distinguishing between facts and imagination. Enlow’s Facial Growth thus is not a textbook in the usual sense of this work, i.e. an educational presentation of available documented knowledge in a field. Rather, it is a text with a message, namely that of the counterpart principle, which the author uses all his efforts to convey. In contrast, as mentioned above, several chapters of the book are written by invited authors. These are selfcontained and provide fine, brief, textbook-style overviews of their respective fields. B. Solow