in
Surgical and
Orthodontic Treatment
of Impacted Teeth
Associate Professor
Faculty of Dentistry
University Paris V, France
Director
The International Center for the Study of Clinical Orthodontics
Verona, Italy
English Translation by
Former Adjunct Associate Professor
Department of Human Behavior
Columbia Dental School
New York, New York
Paris, Chicago, Berlin, Tokyo, London, Milan, Barcelona, Istanbul, São Paulo, Mumbai, Moscow, Prague, and Warsaw |
First published in French in 2005 by Quintessence International, Paris
Le Traitement orthodontique et chirurgical des dents incluses
© 2006 Quintessence International
Quintessence International
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All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher.
Design: STDI, Lassay-les-Châteaux, France
Printing and Binding: EMD, Lassay-les-Châteaux, France
Printed in France
The authors extend their thanks to:
Jean-François Andréani
Guy Chaumanet
Robert Chatagnon
Thierry Chatagnon
Jean-Louis Giovannoli
Laurent Glas
François Guyomard
Gérard Motto
Franck Renouard
Jean-Claude Talmant
Pierre Vion
This book addresses the problems associated with impacted teeth in children and adolescents from both orthodontic and surgical perspectives. Emphasis is placed on a prophylactic approach to reduce or, when possible, eliminate the need for surgery. However, there are cases for which surgery is unavoidable; therefore, this text describes strategies for designing intervention in specific anatomic situations. Above all, its goal is to help orthodontists plan treatment to meet the needs of their patients.
Many individuals have contributed to the successful completion of this volume. My collaboration with Professor of orthodontics François Guyomard, on Chirurgie parodontale orthodontique (Edition CdP, 1999), allowed me to adapt the principles of mucogingival surgery for use in orthodontic surgery. Professor Frans P. G. M. van der Linden kindly gave his permission to use images from his atlas, Development of the Human Dentition (Harper & Row, 1976), to illustrate specific problems that children may endure during tooth eruption. The knowledge I gained in preparing to publish a number of articles with Danielle Pajoni, an authority in computerized tomography, proved invaluable in helping me to visualize the exact anatomic locations of ectopic teeth. Finally, I have worked closely over the last few years with Xavier Korbendau, who has contributed his clinical skills to the surgical treatment of a number of patients with complex problems.
Jean-Marie Korbendau, DDS, MS
Cover | |
Table of Contents | |
Acknowledgments | |
Preface | |
1 | Stages of Eruption of Permanent Teeth |
Components of Eruption Bony crypts Dental follicle | |
Localization of the Bony Crypts of the Maxillary Permanent Teeth Incisors Canines | |
Intraosseous Eruptive Pathways Eruption of the incisors Eruption of the canines Relationship of canines and lateral incisors | |
Relationship of Malpositioned Tooth Buds to Anatomic Structures Incisors Canines | |
2 | Orthodontic and Radiographic Assessment of Impacted Teeth |
Orthodontic Assessment Eruption and dental age Impaction of teeth Impacted central incisor Impacted maxillary canine | |
Radiographic Assessment Conventional radiography Periapical radiographs Occlusal radiographs Computerized tomography Prescriptions for supplementary examinations | |
Extraction of Impacted Teeth Orientation of the tooth bud and the eruptive trajectory Malformation of roots Ankylosis Dentigerous cysts | |
3 | Preventive Treatment of Impactions |
Supernumerary Teeth and Odontomas | |
Impacted Maxillary Primary Canines Overretention of primary canines Palatally positioned permanent canines Labially positioned permanent canines | |
Providing Eruptive Guidance Expansion of the anterior maxilla Advancement of the anterior segment Distalization of the buccal segments Extraction of permanent teeth | |
4 | Criteria for Choosing Orthodontic and Surgical Protocols |
Stages of Orthodontic Treatment Impacted canines Impacted central incisors Impacted premolars Impacted molars | |
Surgical Approaches to Impacted Teeth Replaced and displaced flaps Palatal approach Buccal approach | |
5 | Impacted Maxillary Canines: Palatal Approach |
Classification of Palatally Impacted Canines | |
Class 1 Impaction Impacted tooth near palatal mucosa Deep bony impaction | |
Class 2 Impaction Superficial impaction | |
Class 3 Impaction Deep bony impaction | |
6 | Impacted Maxillary Canines: Buccal Approach |
Superficial Impactions Direct access flap Apically displaced flap Apically and laterally retracted flaps | |
Palatal Impactions Apically retracted buccal flaps | |
Deep Bony Impactions Replaced mucoperiosteal flap | |
7 | Impacted Mandibular Teeth |
Eruption of Mandibular Incisors | |
Eruption of Mandibular Canines Ectopic trajectories of emerging canines Transmigration of mandibular canines | |
Eruption of Mandibular Premolars | |
Bibliography | |
Stages of Eruption of Permanent Teeth |
Components of Eruption
At the embryonic bell stage, the dental bud is made up of three parts: the dental organ, the dental papilla, and the dental follicle (Fig 1-1). Embryonic tissue derived from the dental lamina organizes itself around this group, adapting to growth of the tooth bud; lamellar bone then gradually begins to replace it, forming an encasement of bone known as the bony crypt. Inside this casement, calcification of the crown and formation of the root both begin.
Generally, when one quarter of the root has developed, the tooth will start to erupt (van der Linden 1983). This is a complex process of many stages, none of which has been completely elucidated. However, it is clear that this mechanism ensures that root formation will be coordinated with development of the tooth’s periodontal environment, the dental bud’s osseous journey, the emergence of the crown into the oral cavity, and its eventual arrival at the occlusal plane.
Bony crypts
As this pre-eruptive tooth bud choreography proceeds, the bony crypts enact parallel movements; their ceilings, or cell walls, oriented toward the occlusal plane, form an opening that provides access to the gubernacular canal. This tunnel through bone, which contains a fibrous cord where epithelial remnants of the dental lamina persist, connects the crypt to the cortical plate and sometimes to the alveolar wall of the primary tooth. This collective voyage makes a profound impression on the tooth as it erupts (Fig 1-2).
Dental follicle
When the crown is completely calcified, cells of the follicular envelope exert primary control on the two active poles of the dental bud (Cahill and Marks 1980) (see Figs 1-1 and 1-3).
The apical pole serves as the site for the formation of the supporting dental tissues, cementum, periodontal ligament, and surrounding alveolus. Bone formed by apposition organizes around the roof of the crypt in relation to the walls of the developing root, which partially invests the space that the crown had occupied (Figs 1-4a and 1-4b). As a result, the architecture of the crypt changes as it keeps pace with the progress of tooth eruption. The coronary pole of the follicle continues to adhere to the crown until it fuses with the buccal epithelium before the tooth emerges into the arch.
It is this portion of the follicle that provides the osseous cleft through which the tooth passes along the gubernacular canal. Mononuclear cells that are the precursors of osteoclasts and osteoblasts are stored within the follicle before eruption begins (Craddock and Youngson 2004). The osteoclasts are then liberated to assist in preparing a path for migration of the permanent tooth’s crown by creating an opening in the vault of the crypt and by initiating resorption of the primary tooth’s root (Kawakami et al 2000).
At the same time, a cleft in the bone, several millimeters deep at the alveolar border of the single-rooted primary teeth, will ease the eruption of their successors (Fig 1-5). But the extent of this resorption varies according to the type of tooth. Premolars migrate into substantial alveolar craters, but canines, whose coronal dimensions are substantially larger than those of their primary predecessors, require even larger openings through which to move successfully. These two resorption processes, of bone and primary tooth roots, join to create space for passage of the permanent teeth.
The location of the opening of the gubernacular canal indicates the site in the lingual cortical plate where the permanent successor will emerge behind the primary tooth, although sometimes it will emerge directly into the primary tooth’s pulp cavity. In the first instance the gubernacular fibers bind into the gingival lamina propria; in the second they intersperse with the primary tooth’s periodontal membrane (Figs 1-6 and 1-7).
Not all of the mechanisms that govern the initiation of the eruption of permanent teeth are as yet understood, but many experiments have shown the important role that the dental follicle plays in this process. Accordingly, dental practitioners should adhere to well-established anatomic and physiologic operative protocols for freeing, or extricating, permanent teeth whose eruption has been delayed.
In surgical interventions, practitioners should be careful not to remove all of the follicular tissue that still envelops the crown of a tooth before its emergence, because in early stages of eruption, it is imperative that the portion of the root adjacent to the cementoenamel junction be protected by its follicle. Supracrestal fibers can only develop after the tooth emerges into the mouth, either by the normal physiologic means or with surgical assistance.
Furthermore, the coronal portion of the follicle is responsible for the bone resorption that enables the tooth to migrate. Therefore, the surgeon, after removing enough soft tissue to bond an attachment, should then remove bone lying in the tooth’s eruption pathway.
Localization of the Bony Crypts of the Maxillary Permanent Teeth
Incisors
While the bony crypts that surround most of the buds of the permanent teeth are interconnected, the intermaxillary suture separates the two maxillary permanent central incisors (as it did their primary predecessors), usually generating a characteristic posteruptive diastema (see Figs 1-5 and 1-11).
The crowns of the central incisors calcify under the floor of the nasal cavity and stimulate resorption, with a lingual bevel, of their primary predecessors, behind which they are forming. The crypts of the maxillary lateral incisors are located more lingually behind those of the central incisors so that, viewed frontally in 4-year-olds, half of their crowns would be masked by the central incisors. This backward positioning of the lateral incisor places it in the same plane as the canine, for whose eruption it will later serve as a guide. At this stage of calcification, which occurs in a constricted space, the developing permanent teeth are normally quite crowded.
The lateral incisor crypts are closer to the occlusal plane than those of the other teeth in the arch; calcification proceeds at varying rates in the maxilla as a function of the length of the tooth roots (van der Linden 1976).
Canines
The bony crypts of the canines are located near the external border of the nasal fossae anterior to the sinuses, from which they are separated only by a thin lamina of bone (Figs 1-8 and 1-9).
Taken together, the maxillary teeth have a conical appearance. As a result, the bony crypts of the canines, which are placed higher than the others, are the most internal. Their buds develop behind the roots of the primary teeth and behind the buds of the other permanent teeth.
In a view of a skeletal specimen of a 4-year-old child, the primary first molar, the bud of the first premolar, and the bud of the permanent canine have the appearance of three steps of an ascending stairway tipped toward the anteroexternal angle of the opening of the nasal cavity (see Fig 1-8).
Intraosseous Eruptive Pathways
Eruption of the incisors
The central incisors migrate labially to emerge in the arch in a position somewhat labial to that occupied by the primary teeth. After the central incisors have assumed their places, the lateral incisors begin their voyage labially through a narrow passageway alongside the roots of the central incisors. As the lateral incisors take their places in the arch, they reduce the size of the initial midline diastema.
During the labial migration of the lateral incisors, their roots begin developing with a mesiopalatal tilt in the crypts in which the crowns formed. The positioning of the bony crypts determines the orientation of the emerging lateral incisors. At this stage, the roots of the incisal teeth tend to converge, and the extent to which they occupy space in the maxilla will sculpt the eruptive pathways of the canines. If crowding develops in the mixed dentition, there will not be enough room for the lateral incisors to migrate labially between the roots of the central incisors and the primary canines, and the corridors for the canines will not be defined.
Eruption of the canines
By the time children are 6 to 7 years old, calcification of canine crowns has been completed and, as root formation proceeds along the nasal border in the crypt that the crowns had occupied, the teeth are ready to begin erupting. They maintain their spatial relationships with the nasal and antral cavities as well as with the other teeth in the arch during calcification (Figs 1-10 and 1-11). As they move along the lower third of the lateral incisor roots, the canines erupt almost vertically within the dental arch, usually with a mesial inclination of several degrees (Fig 1-12).
Still moving at the side of the lateral incisors, the canines continue their journey until they reach the occlusal plane. After passing the centers of resistance of the lateral incisors, the emerging canines begin to exert a mesial pressure on the lateral incisor roots and then on their crowns, which straightens the anterior dentition. The long axes of these teeth progressively lose their apical convergence as the midline diastema completes its closure (Figs 1-13a and 1-13b).
During the 3 or 4 years that precede the eruption of the maxillary canines, their proper position can be confirmed by palpating the labial region distal to the lateral incisors.
Age | Position of maxillary canines |
8 to 9 years: | Canine bulge at the apex of the primary tooth |
10 to 11 years: | Lower and more pronounced bulge |
11 to 12 years: | Primary canine becomes mobile |
Relationship of canines and lateral incisors
When children are 8 to 9 years old, the roots of the lateral incisors are, in theory, sufficiently well formed to sustain the contact of the mesial angles of the canine crowns and to guide canine eruption. Moving thus along the walls of the lateral incisor roots, the canines upright the incisors and establish good proximal contacts (Becker 1998). If the crowns of the canines and the roots of the lateral incisors do not meet in the same plane, the canines will pass across the roots either inside or outside the dental arch, and their eruptive paths will be secondarily modified.
When the nasal cavity is narrow, the intercanine distance will be too small for the canine to establish contact with the distal wall of the lateral incisor root, and the canine will slide along the root’s labial surface (Fig 1-14).
The canine cannot be described at this stage as being malpositioned because its eruptive trajectory has not yet changed and the greater part of its root still lies palatally (Figs 1-15a and 1-15b). If the lateral incisor is congenitally absent, the canine will descend directly into the palatal aspect of the arch and will frequently erupt into the position of the missing lateral incisor (Fig 1-15c).
Even if the distance between the canines is wide enough to allow them to erupt into good alignment, they may still go astray if:
• The lateral incisors cannot provide the needed guidance because they are congenitally absent; their root development is delayed; or their configuration, size, or positioning makes them inadequate for the task.
• The tooth bud’s orientation is disturbed, which can lead to the tooth’s eventual eruption going off course, most often in a medial oblique way. If this happens, the tooth will be impacted if the crown breeches the vertical line extending alongside the external wall of the nasal cavity (see chapter 2; Williams 1981).
Relationship of Malpositioned Tooth Buds to Anatomic Structures
Contact with certain anatomic structures can alter the morphology of erupting maxillary anterior teeth. Malposition of a tooth bud can be primary (genetic) or secondary (as a result of trauma). In cases of primary dystopia, the bud will be normal in formation but malpositioned, a situation that occurs most often with central incisors and canines.
Incisors
dilacerations