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Serial extraction: Precautions, limitations, and alternatives
EDITORIAL
Serial extraction: Precautions, limitations, and alternatives
T
he procedure known ;ts serial extractio?z has been around for a longer time than most orthodontists realize, yet it continues to be a matter of conflict and controversy. Its purpose is to reconcile a known amount of tooth material with a continuing deficiency in supporting bone, but its indications are elusive, its “deliberate speed” is an irritant to the impatient, its commonly accepted sequence is questioned, and there is no universal agreement on the term itself. Historically, the procedure goes back to the eighteenth century-principally to two Frenchmen, Bunon and Bourdet. They were among the first of several early writers to describe the removal of certain deciduous and permanent teeth in underdeveloped arches so that the remaining teeth could erupt into acceptable functional relations in the limited skeletal structures that are available for the developing dentition. Strangely, their early recommendations for the removal of teeth in deficient arches were ignored or forgotten for nearly two centuries. Perhaps it was because of a long series of appliances which were being devised that, hopefully, would create sufficient arch length to accommodate all of the teeth. But none of them was effective; too many “corrections” relapsed despite the best-designed devices. Unfortunately, this is still true today. It was not until the 1947-48 Transactions of the European Orthodontic Society had been published that the procedure was again presented. Working separately during the early 1930’s and 1940’s, Switzerland’s Rudolf Hotzl and Sweden’s Birger Kjellgren2 independently arrived at extraction sequences that were identical. Since there was little communication, even in the scientific community, during World War II, neither knew of the work of the other. Perhaps it is an example of “simultaneous discovery.” Kjellgren used the term seriaZ exfmcfio)l. Hotz suggested the equally acceptable and perhaps the more tlescriptive term of guida)lce of dezfal eruption by means of exfmctio~l. For as yet undetermined reasons, the specialty adopted the shorter term. In general, their extraction sequence was, first, the four deciduous canines; second, the four first deciduous molars; and, third, the four first premolars. Both men urged a cautious rather than precipitous approach to all extraction decisions. These same words of warning against indiscriminate extraction were also stressed by America’s Ijewel in his 1954 article based on his identical 95
96
Editorial
extraction sequence that also had its origin in the mid-1930’s. His early term wils deficient arch extraction sequence, but he accepted the shorter serinl tsfrnctio)l expression after it had been published by Kjellgren. It was the first time t)hat the term or the procedure had been described in detail by ikn American orthodontist. Still later, Tweed suggested the term preurthodo&ic guidance, and it also is preferred by Wagers in his article in this month’s issue of the eJ~~~~~i~. It is too early to forecast which term will ultimately be adopted. Actually, it makes little difference, for the three terms can be considered to be synonymous. Of much greater importance is (1) that the developing dentition recei-Jes competent supervision, (2) that no teeth of any kind be removed prior to a most precise and exacting case analysis, (3) that the case analysis be repeated preceding any subsequent extractions, and (4) that, when indicated, competent orthodontic treatment be provided. Whether called serial extraction or guidance, supervision of the developing dentition implies many things. A thorough knowledge of normal development is the first prerequisite. Equally important is the ability to determine when teeth should be retained rather than removed; this usually requires movement of teeth to create additional space, and this ability comes only with extensive experience in the actual treatment of malocclusion of all kinds. The orthodontic responsibility is one of discretion-extraction when undeniably indicated in the genuine arch-reduction malocclusion, but prudence and caution when future growth may still be adequate in the more moderate borderline irregularity. Supervision in serial extraction also means determining when first deciduous molars should be extracted before the deciduous canines. The purpose here is to retard canine eruption and encourage first premolar eruption before the canines erupt into the extraction spaces-a common occurrence in the lower arch. But there also is a much larger number of deceptively similar borderline malocclusions that should instead be treated either (I) with a full complement of teeth and not by serial extraction or (2) by postponing all extraction decisions until the permanent dentition. The competent diagnostician also knows when to trim mesial or distal surfaces of deciduous teeth to help permanent teeth to erupt in a favorable direction. In serial extraction, the act of removing the involved teeth is so simple that the casual observer tends to think that the entire concept is simple. The fact is that an extraction decision is much more difficult to make in the mixed den&on than in the permanent dentition. Potential growth is t,he reason. For all practical purposes, growth has ceased in the permanent dentition ; there either is or there is not enough skeletal structure to accommodate all the teeth. If not,, then extraction is often the only solution. The possibility of additional growth is what makes an extraction diagnosis in the mixed dentition so much more difficult than in the permanent dentition. This is especially true in the mild, borderline mixed-dentition malocclusion, for no one can forecast with precision that sufficient growth will not take place in any given patient. If, in such a case, normal growth occurs after the four premolars have been removed, then there are but two alternatives that can be
Editorial
97
taken-artificial replacements or partial space closure and an associated concave, dished-in profile. Many orthodontists have been faced with this decision in cases referred to them after four first premolars had been extracted without consultation and without their knowledge. A far more appropriate procedure in these borderline malocclusions would be to delay all extraction until the permanent dentition. Orthodontists have long since been able to close extraction spaces effectively in the permanent dentition when the removal of first premolars has been determined to be essential in the treatment of underdeveloped dental arches. This, moreover, can be done in a single treatment period, whereas extraction in the mixed dentition often requires two separate treatment periods. Delayed treatment of these borderline malocclusions also has another advantage, for a competent diagnosis often calls for the extraction of second premolars, not first premolars. Borderline cases usually require that most of the space closure be accomplished by moving molars mesially, rather than by moving anterior teeth posteriorly. The reason is simple; eight anterior teeth, including the first premolars, provide effective anchorage in each arch-much more so than do six anterior teeth when the first premolars have been extracted. The purpose is to maintain the incisors in their original positions directly over the alveolar crest in order to prevent a posttreatment concave facial profile. In serial extraction supervision, “the goal is always normal occlusion with a full complement of teeth, but the purpose of the observation period may be defeated if the extraction program is undertaken too early and further growth is interrupted as a result.“3 Our 1954 article went on to say: “In the meantime, the procedure known as serial extraction has been essentially a program of patience, of continuous observation and study, of proper timing, and of delay and postponement until growth and development have accomplished their mission.”
B. F. D. REFERENCES
1. Hotz, Rudolf: Active supervision of the eruption of teeth Orthod. Sot., 1947-1948, pp. 34-47. 2. Kjellgren, Birger: Serial extraction as a corrective procedure Trans. Eur. Orthod. Sot., 1947-1948, pp. 134-160. 3. Dcwel, B. F.: Serial extraction in orthodontics : Indications, procedures, AM. J. ORTHOD. 40: 906-926, 1954.
by
extraction,
in dental objectives,
Trans.
orthopedic and
Eur. therapy,
treatment
Serial extraction: Precautions, limitations, and alternatives
T
he procedure known ;ts serial extractio?z has been around for a longer time than most orthodontists realize, yet it continues to be a matter of conflict and controversy. Its purpose is to reconcile a known amount of tooth material with a continuing deficiency in supporting bone, but its indications are elusive, its “deliberate speed” is an irritant to the impatient, its commonly accepted sequence is questioned, and there is no universal agreement on the term itself. Historically, the procedure goes back to the eighteenth century-principally to two Frenchmen, Bunon and Bourdet. They were among the first of several early writers to describe the removal of certain deciduous and permanent teeth in underdeveloped arches so that the remaining teeth could erupt into acceptable functional relations in the limited skeletal structures that are available for the developing dentition. Strangely, their early recommendations for the removal of teeth in deficient arches were ignored or forgotten for nearly two centuries. Perhaps it was because of a long series of appliances which were being devised that, hopefully, would create sufficient arch length to accommodate all of the teeth. But none of them was effective; too many “corrections” relapsed despite the best-designed devices. Unfortunately, this is still true today. It was not until the 1947-48 Transactions of the European Orthodontic Society had been published that the procedure was again presented. Working separately during the early 1930’s and 1940’s, Switzerland’s Rudolf Hotzl and Sweden’s Birger Kjellgren2 independently arrived at extraction sequences that were identical. Since there was little communication, even in the scientific community, during World War II, neither knew of the work of the other. Perhaps it is an example of “simultaneous discovery.” Kjellgren used the term seriaZ exfmcfio)l. Hotz suggested the equally acceptable and perhaps the more tlescriptive term of guida)lce of dezfal eruption by means of exfmctio~l. For as yet undetermined reasons, the specialty adopted the shorter term. In general, their extraction sequence was, first, the four deciduous canines; second, the four first deciduous molars; and, third, the four first premolars. Both men urged a cautious rather than precipitous approach to all extraction decisions. These same words of warning against indiscriminate extraction were also stressed by America’s Ijewel in his 1954 article based on his identical 95
96
Editorial
extraction sequence that also had its origin in the mid-1930’s. His early term wils deficient arch extraction sequence, but he accepted the shorter serinl tsfrnctio)l expression after it had been published by Kjellgren. It was the first time t)hat the term or the procedure had been described in detail by ikn American orthodontist. Still later, Tweed suggested the term preurthodo&ic guidance, and it also is preferred by Wagers in his article in this month’s issue of the eJ~~~~~i~. It is too early to forecast which term will ultimately be adopted. Actually, it makes little difference, for the three terms can be considered to be synonymous. Of much greater importance is (1) that the developing dentition recei-Jes competent supervision, (2) that no teeth of any kind be removed prior to a most precise and exacting case analysis, (3) that the case analysis be repeated preceding any subsequent extractions, and (4) that, when indicated, competent orthodontic treatment be provided. Whether called serial extraction or guidance, supervision of the developing dentition implies many things. A thorough knowledge of normal development is the first prerequisite. Equally important is the ability to determine when teeth should be retained rather than removed; this usually requires movement of teeth to create additional space, and this ability comes only with extensive experience in the actual treatment of malocclusion of all kinds. The orthodontic responsibility is one of discretion-extraction when undeniably indicated in the genuine arch-reduction malocclusion, but prudence and caution when future growth may still be adequate in the more moderate borderline irregularity. Supervision in serial extraction also means determining when first deciduous molars should be extracted before the deciduous canines. The purpose here is to retard canine eruption and encourage first premolar eruption before the canines erupt into the extraction spaces-a common occurrence in the lower arch. But there also is a much larger number of deceptively similar borderline malocclusions that should instead be treated either (I) with a full complement of teeth and not by serial extraction or (2) by postponing all extraction decisions until the permanent dentition. The competent diagnostician also knows when to trim mesial or distal surfaces of deciduous teeth to help permanent teeth to erupt in a favorable direction. In serial extraction, the act of removing the involved teeth is so simple that the casual observer tends to think that the entire concept is simple. The fact is that an extraction decision is much more difficult to make in the mixed den&on than in the permanent dentition. Potential growth is t,he reason. For all practical purposes, growth has ceased in the permanent dentition ; there either is or there is not enough skeletal structure to accommodate all the teeth. If not,, then extraction is often the only solution. The possibility of additional growth is what makes an extraction diagnosis in the mixed dentition so much more difficult than in the permanent dentition. This is especially true in the mild, borderline mixed-dentition malocclusion, for no one can forecast with precision that sufficient growth will not take place in any given patient. If, in such a case, normal growth occurs after the four premolars have been removed, then there are but two alternatives that can be
Editorial
97
taken-artificial replacements or partial space closure and an associated concave, dished-in profile. Many orthodontists have been faced with this decision in cases referred to them after four first premolars had been extracted without consultation and without their knowledge. A far more appropriate procedure in these borderline malocclusions would be to delay all extraction until the permanent dentition. Orthodontists have long since been able to close extraction spaces effectively in the permanent dentition when the removal of first premolars has been determined to be essential in the treatment of underdeveloped dental arches. This, moreover, can be done in a single treatment period, whereas extraction in the mixed dentition often requires two separate treatment periods. Delayed treatment of these borderline malocclusions also has another advantage, for a competent diagnosis often calls for the extraction of second premolars, not first premolars. Borderline cases usually require that most of the space closure be accomplished by moving molars mesially, rather than by moving anterior teeth posteriorly. The reason is simple; eight anterior teeth, including the first premolars, provide effective anchorage in each arch-much more so than do six anterior teeth when the first premolars have been extracted. The purpose is to maintain the incisors in their original positions directly over the alveolar crest in order to prevent a posttreatment concave facial profile. In serial extraction supervision, “the goal is always normal occlusion with a full complement of teeth, but the purpose of the observation period may be defeated if the extraction program is undertaken too early and further growth is interrupted as a result.“3 Our 1954 article went on to say: “In the meantime, the procedure known as serial extraction has been essentially a program of patience, of continuous observation and study, of proper timing, and of delay and postponement until growth and development have accomplished their mission.”
B. F. D. REFERENCES
1. Hotz, Rudolf: Active supervision of the eruption of teeth Orthod. Sot., 1947-1948, pp. 34-47. 2. Kjellgren, Birger: Serial extraction as a corrective procedure Trans. Eur. Orthod. Sot., 1947-1948, pp. 134-160. 3. Dcwel, B. F.: Serial extraction in orthodontics : Indications, procedures, AM. J. ORTHOD. 40: 906-926, 1954.
by
extraction,
in dental objectives,
Trans.
orthopedic and
Eur. therapy,
treatment