THE EDITOR'S CORNER

As I was preparing the case report that appears on page 597 of this issue, I could not escape the feeling that serial extraction is one area of orthodontics where most of us fly by the seat of our pants, where some of us fly a predetermined pattern over cloud formations and expect to see the same clouds all the time, and where many of us are afraid to fly.

Lack of specific information about preorthodontic guidance or serial extraction procedures is responsible for all three of these phenomena. With no clear guidelines to cover every situation, it is small wonder that some won't fly. However, if successfully managed preorthodontic guidance could routinely intercept a developing malocclusion and result in shortening active treatment by many months, then here is a subject whose potential has yet to be realized on a scale that you could call significant.

In recent time, there have been two sources of material on this subject that have presented a substantial amount of clinical material and discussion. They are Dr. Charles Tweed's book, Clinical Orthodontics (The C.V. Mosby Co., St. Louis, 1966) and Dr. Warren Mayne's chapter on Serial Extraction in Dr. T. M. Graber's book, Current Orthodontic Concepts and Techniques (W.B. Saunders Co., Philadelphia. 1969).

It is my impression that Dr. Tweed, in applying serial extraction to his arch length discrepancy cases, generally extracted the Ds first at approximately age 7-8. He followed this with the extraction of the Cs and 4s approximately one year later at age 8-9. and he seemed to prefer to let the Es exfoliate on their own if they were not delayed in this process. His results in following this procedure most often showed a straightening and uprighting of the anterior teeth, an increase in overbite, and an alignment of the teeth that permitted their correction in approximately one year to a year and a half or less of active orthodontic treatment.

Critique of Tweed Serial Extraction Procedure

Dr. Tweed's procedure in serial extraction has been criticized by those who contend that it too often results in too much uprighting of the anterior teeth and too much flattening or dishing-in of the profile; by those who claim it causes excessive bite closure; by those who say it delays improvement in anterior irregularities and by those who say that if you are waiting for the eruption of the Ss anyway, there is no need for haste except in those cases in which you need a maximum natural uprighting of anterior teeth.

Dr. Mayne favors an extraction sequence that starts with Cs to permit improvement in the alignment of the incisors quickly, followed by an individualized approach to successive steps in serial extraction.

If we define serial extraction as the successive extraction of teeth to improve the pattern and position of teeth as the deciduous teeth are lost and the permanent successors erupt, we are then going to be guided by the timetable of the individual's teeth, and treatment is now geared to this one individual and how his complex of teeth are behaving. There may be cases in which it will be obvious that early removal of the four first bicuspids will be of great advantage. For the most part, however, there is no need for haste. There is time to make that judgment as the dentition develops with serial extraction guidance. There is a wide range of time in growth and development among people, between arches in the same person, and among teeth in the same arch.

Need for Caution

Forcing oneself to make a decision about the teeth too early and at a time when all the facts are not yet known has made serial extraction perform an occasional disservice to the dentition. You will try hard to remember a case in which orthodontic treatment could not be accomplished successfully because serial extraction had not been done. On the other hand, each of us can probably remember a case or cases in which orthodontic treatment was less than satisfactory because serial extraction had been done improperly--bicuspids extracted too early and the full space miraculously remains, or anteriors dished in either because of excessive lingual axial inclination or because of unexpected growth at chin point.

It is strange that we are so hazy on one of the most fundamental aspects of orthodontic understanding--the timing of eruption and the changes that occur in a developing dentition. What is needed is more clinical information--clinical demonstrations with models, photographs and x-rays to give all of us an accumulation of visual experience on this subject. In order to create the clinical information, each practicing orthodontist must pay more attention to the completeness of his records than most of us generally do. Dr. Tweed pointed this out when he mentioned that he was one of the few orthodontists with complete records to document his cases. It seemed more of a lament than his own personal pride.

Need for Records

Each of us should have some simple way of taking photographs of our patients' teeth at every visit and x-rays at all the significant intervals. Someone might develop a system which would permit the patient to take his own photographs of his teeth every time he came to the office. We can't get too much from the opinion of others or the formulas of others on serial extraction. We would get something from case records, the actual experience that they can show and document, and that, of course, was one reason for presenting the case that I selected from the Editor's Casebook this month.

Serial Extraction Without Treatment?

There are two aspects to serial extraction that must be discussed. One is the idea that serial extraction is a treatment in itself, that the occlusion resulting from a program of serial extraction will be a satisfactory occlusion. It would be nice if that were true, but it rarely happens. This does not mean, however, that orthodontics must be so rigid that we will refuse to advise and guide a program of serial extraction for patients for whom orthodontic treatment with appliances is out of the question for reasons of finances or geography. With a clear understanding that the result will represent an improvement and not an optimum orthodontic result, great service can be rendered to people with teeth that would otherwise erupt in an unsightly crowded condition, if serial extraction guidance is used for a local or general condition. For a general condition it might be well to limit these cases to Class I occlusions with a good ANB relationship, no deep overbite, an FMA over 30º and a favorable growth trend as Dr. Tweed has stated. One should be circumspect in carrying serial extraction through extraction of permanent teeth in low FMA angle cases, especially with lingually inclined lower anterior teeth.

Without Extraction of Permanent Teeth?

A second point for discussion about serial extraction is the assumption that it includes the inevitable extraction of permanent teeth. Except for cases that are so obviously deficient in arch length that there can be no question about the need for extraction of permanent teeth, it is advisable to reevaluate the case following the eruption of the first bicuspids. Cases do change in ways that are most significant. Arch width increases, chin point grows, anterior inclinations change; growth patterns emerge; caries, other pathology, and accidents occur; FMA angles change. Treatment plans may also change. For one thing you might decide that it would be advantageous to remove second bicuspids instead of first.

Serial extraction should be used in cases of extreme crowding or ectopic eruption, including tendencies to crossbite, to encourage or permit the eruption of permanent teeth to positions that are better than they would be without serial extraction. Serial extraction is accompanied by observation and by space maintainer or regainer appliances wherever such assistance is needed for a favorable result.

Favorable results

Favorable results from serial extraction can include:

1. Uncrowding of anterior teeth by self-correction.

2. Spontaneous midline correction.

3. Distal migration of mesially placed cuspids.

4. Uprighting of anterior teeth.

5. Maximizing self-correction and reducing treatment time with active orthodontic appliances.

Unfavorable results

Unfavorable results from serial extraction can include:

1. Only partial relief of crowding.

2. Failure of eruption of tooth or teeth.

3. Failure of cuspids to migrate into the arch.

4. Deep overbite.

5. No reduction of active treatment time.

6. Excessive flattening or dishing in of the teeth, related to excessive lingual axial inclination of incisors plus growth of chin point.