Orthodontic Treatment of Impacted Teeth. Adrian Becker

describing individual conditions or just a customized approach to the treatment of a specific case, are published with the aim of complementing the book. The site also features a “troubleshooting impacted teeth” page for individual clinical consultations – open to anyone, whether orthodontist, patient or concerned parent. Details of the patient and his/her condition will need to be filled in and existing radiographs, CBCT and other relevant information uploaded. A report is returned to the sender within a few days with suggestions and recommendations for treatment.

      The clinical research on which this text is largely based has been the product of long‐term cooperation with Professor Stella Chaushu, PhD, DMD, MSc, Chairperson of the Orthodontic Department in Jerusalem, to whom are due my special thanks. I am grateful to my co‐authors who have advised me in my writing of several of the chapters herein and to a number of my colleagues who have sent me illustrative material which I have included, with their permission. I would also like to recognize Mr. Israel Vider, director of the Dent‐Or Imaging Center in Jerusalem, for his CT imaging expertise, his assistance in granting me access to his technical laboratory and for his work on several of the illustrations that are published in this edition.

      Adrian Becker

      Jerusalem, October 2011

      Preface to the Fourth Edition

      As the fourth edition of this book goes to print, I am happy to present a much‐enhanced text, both in terms of the verbal discussion and the illustrated figures, which is offered in a similar pattern to its predecessors. The third edition of Orthodontic Treatment of Impacted Teeth, published in 2012, had 15 chapters. This new edition comprises 21 chapters, of which several are completely new and, together with the significant additions and improvements, the overall content is now approximately 60% larger.

      Video clips and other 3D illustrations cannot be published in book form, thus preventing the printed literature from matching the advances in the recording of radiographic imaging that is now commonplace in dental schools, in radiographic imaging centres and in private dental offices. This is particularly so in relation to orthodontics, in general and to accurate positional and pathological diagnosis, that are so essential in the resolution of tooth impaction, in particular. In order to overcome these serious illustrative limitations, I have included a Companion website adjacent to the text, to enhance the orthodontist’s ability to use the existing presentation modes (secondary reconstructions), to extract the maximum information that is available in a cone beam CT scan. A number of 3D video clips are presented, to illustrate how to refine the diagnostic know‐how, which can only be to the benefit of the patient. These are embedded in PowerPoint presentations, with concise accompanying comment to highlight the salient points at issue. This should assist those who still have 3D comprehension difficulty in accurately locating the impacted tooth.

      There are many new areas in the present text that feature aspects that have not been fully described in the literature to date. There are also a number of supposed truths that are shown to be spurious and contrary to our understanding of the biological process.

      Just to mention a few of the many examples that the reader will find in this edition:

       Did you know that hooked roots are not a reason that teeth do not erupt (see Chapter 13)?

       Unerupted incisor teeth that have been severely damaged by trauma inflicted in infancy remain high in the maxilla adjacent to the nasal floor, neither growing their roots nor showing any signs of ever erupting into the mouth. Can these teeth be mechanically erupted? Will they develop roots of a sufficient length that will contribute to the tooth surviving into adulthood? Will the eruption of these teeth generate new bone that could naturally rehabilitate the formerly deficient alveolar ridge (see Chapter 6)?

       Instead of developing a long straight root, the severely traumatized central incisor in a 2‐year‐old child may develop a root that continues to grow at an acute angle to the calcified portion of the tooth, to form a tightly curved or angled dilaceration. The root continues to grow in the wrong direction, necessitating root canal treatment and root amputation to enable the orthodontist to re‐align the majority portion of the tooth. Perhaps there is a way to correct the direction of the further root growth and thereby achieve a normally apexified vital tooth with a perfect crown, indistinguishable from and aligned with its beautiful adjacent counterpart (see Chapter 6).

       There appears to be a cut‐off age of 9 years for the maxillary lateral incisor to develop at least half its normal root length. If there is less than a half root at this age, as seen in a small or peg‐shaped tooth, the chances that the unerupted canine will become the victim of eruption disturbance become notably exaggerated (see Chapter 6).

       Conventional wisdom has it that mandibular second and third molars are sometimes impacted because their roots are being ‘held down’ by entanglement with the inferior alveolar canal (mandibular branch of the trigeminal nerve). We maintain that this view is unfounded (see Chapter 13). It is more likely that another factor, such as invasive cervical root resorption (ICRR), enlarged dental follicle, crowding of adjacent teeth and even possibly pre‐eruption intra‐coronal resorption, represents the primary aetiology that prevents eruption (the ‘cause’). With the root apices then growing in cramped circumstances, in close proximity to pathological entities or anatomical limits, the further erratic development of the root ends inevitably results in entanglement with the nerve and vascular bundle (the ‘effect’).

       You have just finished the phase 1 treatment of a child, for the treatment of a cross‐bite or an impacted incisor or for maxillary anterior crowding, and he is now 8 years old. As the final flourish, you have aligned the incisors and paralleled their roots into their final adult orientation. The four incisors look beautiful and the parents are happy. In order to hold on to this delightful result, a fixed or removable retainer will need to be placed, until the child is ready for phase 2 treatment in 3–4 years’ time. The question that needs to be asked is: Will the ‘attention to detail’ at this early stage and the apparently laudable ‘intention to fully exploit the capabilities of an existing orthodontic appliance’ be to the patient’s overall benefit, or will they raise the spectre of iatrogenic damage in the long term, by potentially disturbing the eruption of the canine (see Chapters 6, 7 and 18)?

      A word about the tooth‐numbering convention used in this book. For the most part, the narrative in this volume refers to the individual teeth by their full descriptive title. Thus, we may refer to an impacted maxillary left permanent canine tooth or an infra‐occluded deciduous mandibular second molar tooth – a six‐word definition for a very small entity. However, for the sake of brevity and particularly for the annotation of teeth in an illustration, an author will prefer to use a shortened code for each tooth. The numbering system we have used here is the Fédération Dentaire Internationale (FDI) numbering system. This system has been widely accepted in many parts of the world, being easy to understand, logical and adaptable to the various tooth groups. It is compatible with computerized representation and uses the same description of the teeth on either side and in either jaw in a symmetrical and rapidly recognizable manner.

      The method assigns a two‐number code to each tooth. The first number defines the quadrant in which the tooth is found. Thus, the right maxillary quadrant, from midline to last molar, is given the number 1. The left maxillary quadrant is number 2; the left mandibular quadrant number 3; and the right mandibular quadrant number 4. The individual teeth are then numbered from 1 to 8, beginning from the midline and proceeding to the last molar. In this