American Journal of ORTHODONTICS Volume 72, Number
ORIGINAL
6, December,
1977
ARTICLES
Secondmolar extraction in orthodontic treatment David
W. Liddle,
Warren,
D.D.S.
Ohio
W
hen I started a combined practice of orthodontics and general dentistry in 1924, orthodontists were located mostly in the large cities. Perfection with a full complement of teeth was the order of the day, usually achieved by expansion beyond the natural limits of the supporting bone and alveolar tissue. Appearance was often unnatural, and ultimate reversion to original positions of the teeth was inevitable. Anthropologists report that at one time human beings had thirty-six teeth. Over the years I have seen five patients with one fourth molar. Perhaps evolution is trying to tell us that, with easier living habits and refined foods, we can do with fewer teeth. At a time when appearance is so important and people are so tooth conscious, it seems appropriate that a thorough study be made of the causes of malocclusion, with preventive orthodontics and interception in mind whenever possible. Since second permanent molars are quite subject to decalcification and decay in an unclean area, they should come under close scrutiny in any evaluation of archlength problems. A broad, comprehensive basic education is necessary before we should even think of looking at the fine young people who come to us, hoping that we are professionally competent and morally dedicated to treat them as we would our own families. True orthodontics means criticizing the past and developing the best possible future for our children. The purpose of this article is to stimulate interest in the developing permanent molar areas, which have been greatly neglected in the past. Future research will surely reveal the potential force generated by the developing second and 599
600
Am. J. Orthod. December 1977
Liddle
Fig. 1. Case 1, A, removal of retention.
Pretreatment
photograph.
B,
Posttreatment
photograph
6 years
after
third molars that causes malocclusion in so many instances. My procedure, whenever reasonable, has been to intercept this forward force by the extraction of all four permanent second molars. Extraction of premolars in many cases is a means of treating the effect, not the cause, of malocclusion. We have all seen the Teen Age and Miss America beauty pageants showing the beautiful teeth and smiles of the young contestants. My patients and I would rather settle, if necessary, for the slight protrusion which many of the beauties show, rather than a concave, “dished-in appearance” with loose contact areas, an unnatural smile, and short second premolars where larger, more beautiful first premolars should be located. Forty years ago I was forced to make a decision about extraction. A certain family would not consent to any form of medical or surgical intervention for a 12-year-old boy with a developing Class I arch-length discrepancy. I dissected and reset the teeth on study models to show what the dentition would look like after all four permanent second molars had been extracted and with all third molars in the second molar positions. Not until then was permission granted to extract the second molars. Cases
illustrating
second-molar-extraction
treatment
Four cases of second molar extraction are included in this article to illustrate occlusal relations several years after completion of treatment. They show what can be accomplished with this method of treatment.
Volume Number
Fig. 2. Case 6 years
Case
Second molur extraction
72 6
1. following
A and
B, Pretreatment
removal
of
plaster
casts.
C and
b,
Posttreatment
plaster
601
casts
retention.
1
A X&year-old girl had a Class II, Division 1 malocclusion with a 9 mm. protrusion of the upper anterior teeth. Four permanent second molars were extracted. This was the area where the cause of the irregularity was most apparent. Every effort should be made to retain an attractive smile line that will show all of the premolars. In all seeond-molar-extraction cases in which extraoral force is to be applied, there is a definite understanding with the patient that complete cooperation is essential in order to achieve distal orthodontic and sometimes orthopedic movement of both teeth and arches. In this case, the patient’s cooperation was excellent throughout treatment with cervical traction and Class II elastics. From 4.5 to 5 ounces of pull was placed on each side with the cervical appliances and elastics. (It is gratifying to see the time record cards of the exceptional patients who wear extraoral traction and elastics as much as 24 hours per day. Patients often seem to want to outdo each other and even to eat with appliances in place.) In this patient, a series of bite plates was worn; this is true in all close-bite cases in which the lower incisors occlude into the palate. All of the upper teeth were banded. Twin 0.011 inch (0.279 mm.) arch wires were placed with canine hooks for Class II elastics. Coil springs, 0.036 by 0.010 inch (0.914 by 0.254 mm.), were used on the end sections from upper twin arch hooks distal to the bucoal tubes. Coil springs, 0.045 by 0.010 inch (1.143 by 0.254 mm.), were used on the end sections of the
602
Am. J. Ovthd. December lb77
Liddle
Fig. 3. Case
Fig.
1. Occlusal
4. Case
1. intraoral
views
of
views
pretreatment
6 years
and
after
posttreatment
retainers
had
plaster
been
removed.
casts.
Volume Number
73 6
Second molar extraction
Fig. 5. Case Panorex retainers.
film
1. Radiograms showing third
prior molars
to in
removal second
of four second molar positions
molars and posttreatment 6 years after removal
603
of
extraoral inner bows from canine hooks to the buecal double tubes. All of the lower teet,h were banded, and 0.022 inch (0.559 mm.) round wires were used to correct the close-bite. Lower canine hooks carried tandem Class III elastics to the distal aspect of the upper molars to counteract the Class II pull, and to gain some distal movement of the lower posterior teeth. During the use of Class III tandem elastics, the extraoral force was doubled to compensate for excessive elastic pressure. A flat arch wire, 0.010 by 0.022 inch (0.254 by 0.559 mm.), was used for the final leveling and uprighting of all the teeth. I have been amazed to see, in some of the ideal, cooperative Class II patients a synchronous mass movement of 0.25 inch (6.35 mm.) into fairly normal occlusion in 31LJ months, with no noticeable soreness of the teeth. With upper second molar extraction, there is surely greater opportunity for distal orthodontic and orthopedic movement. A positioner was worn for 6 months. Six years later this young lady is very happy, with normal occlusion and a beautiful “Hollywood” smile. Orthodontists should at least consider seriously the indications and advantages of second molar extraction. I am not the onI>
604
Am. J. OrtJm4 December 1977
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Fig. 6. Case 2. A, Pretreatment removal of retainers.
photographs.
B, Posttreatment
photographs
one who is treating certain cases of malocclusion with second molar have never heard of anyone else doing it for 40 years, If someone does this treatment method, it may be lost for many years to come. Case
3 years
extraction, not speak
after
but I out on
2 This case involved a Class I malocclusion with a deep overbite of 6 mm. in a 13-yearold girl. The arch-length discrepancy was due to an overabundance of tooth structure and insufficient bony base. It posed the usual problem of extraction. Should it be premolars or molars? Since it was apparent that the crowding was in the molar area, all four permanent second molars were extracted. The upper first permanent. molars were banded with double buccal tubes. An extraoral appliance with inner-bow coil springs and 4 ounces of pressure was worn for 8 months to reposition upper molars distally. The upper central and lateral incisors were banded, and 0.011 inch (0.279 mm.) twin arch wires were used for leveling and rotations. Light coil springs, 0.009 by 0.036 inch (0.229 by 0.914 mm.), were used on the upper arch to aid in repositioning the molars distally and to unlock the pressure that was overcrowding the anterior teeth. A series of bite plates with slight palatal inclines were used to help depress the lower anterior teeth and to help reposition the arches and jaws in their normal relations. The lower molars, incisors, and canines were banded and an 0.022 inch (0.559 mm.) round wire was used for leveling and realigning the teeth. Light coil springs, 0.009 by OW6 inch (0.229 by 0.914 mm.), were used to reposition the molars distally and to open spaces for the canines and premolars. Treatment of this ease took 29 months, primarily because of tardy canine eruption, which required rotation due to overcrowding. This case would have responded more rapidkf if the four second molars had been extracted at an earlier age, as I had originally sug-
Second molar extraction
Fig.
7. Case
3 years
2. A and
following
B, Pretreatment
removal
of
plaster
casts.
C and
D,
Posttreatment
plaster
605
casts
retainers.
gested. It often is difficult to influence the patient, parents, and family dentist until the malocclusion becomes apparent. With excellent cooperation and growth, the case progressed very well. A positioner was worn for 6 months. After 4 years the occlusion has remained stable, and the beautiful smile showing all premolars is very rewarding to patient and orthodontist alike. case
3 The patient a E-year-old boy, had a Class III skeletal malocclusion. The upper face was flat and retruded, with the lower lip protruding beyond the upper lip. The upper and lower anterior teeth were crowded, and the upper canines were nearly blocked out of the arch. The preoperative casts were dissected and articulated into normal occlusion to determine the treatment objectives. The four permanent second molars were extracted in order to relieve the arch-length discrepancy and to assure the best possible occlusal relations and appearance by keeping all of the premolars. Bands were placed on the upper first premolars and first molars, and a palatal expansion arch was placed. The expansion screw was turned one or two quarter-turns each day, depending on the patient’s comfort. With good cooperation, the upper premolars and molars were moved buceally into normal buccolingual relations with the lower teeth. A series of palatal radiograms was taken. The screw was sealed with acrylic, and the expansion arch acted as a retainer for 3 months while all teeth were beinng realigned. Upper and lower
606
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Liddle
Fig. 8. Case
Fig.
9. Case
2. Occlusal
2. Intraoral
views
views
of
pretreatment
4 years
after
and
treatment
posttreatment
had
plaster
been
completed.
casts.
Volume Number
Fig.
72 6
10.
Second
Case
Panorex film of retainers.
2.
Radiograms
showing
third
prior molars
to
removal
in second
of molar
four
second positions
molar
extraction
molars
and
4 years
607
posttreatment
following
removal
0.010 by 0.022 inch (0.254 by 0.559 mm.) arches were placed and Class III elastics were worn for 12 months. Upper 0.010 by 0.036 inch (0.254 by 0.914 mm.) coil springs were placed from the molars to the canines to move the upper anterior teeth into normal OCclusal relations with the lower anterior teeth. Class III elastics were also worn with 8 ounces of pull on each side. A positioner was then worn for 6 months. The patient cooperated well throughout treatment. Orthopedics, orthodontics, and growth accomplished normal occlusal relations and a pleasing smile. The third molars are slowly but surely growing forward to take the place of the second molars as I have always found them to do in the 40 years I have been treating malocclusion with second molar extraction. Case
4 This case involved mm. upper protrusion patient did not want them.
a Class II, Division 1 malocclusion in a 12-year-old girl with a 12 and 6 mm. deep overbite. This case was a real challenge because the anterior bands, and I agreed to try to treat the malocclusion without
608
Fig.
Am. J. Orthod. December 1977
Liddle
11.
removal
Case of
3. A,
Pretreatment
photographs,
B, Posttreatment
photographs
1 year
after
retainers.
The occlusion was mutilated by early loss of the lower right first molar. The overcrowding was relieved in this sector, however, and in 3 years the lower second molar had migrated forward to nearly fill the first molar position. The teeth in the remaining three sectors were crowded; therefore, both upper second molars and the lower left second molar were extracted. The case was further complicated because the patient did.not return for treatment until 1 year after the extractions. The upper first molars were banded, and an extraoral appliance with labial elastiee from canine hooks were worn for 2 years. Bite plates were also worn during this period. This case shows what can be accomplished by average g-hour, 5-ounce headgear wear over a 2-year period. At the young age of 14 the third molars had erupted into the second molar positions. A tooth positioner was worn for about a year. The occlusion is good, and this young lady is very happy with her beautiful smile, which includes all of the premolars. Discussion
One of my most important early lessons in orthodontics was that one should never try to move a tooth until there is a place for it. Patients have told me many times that after all four second molars had been removed they felt relieved of the apparent pressure that had existed in the posterior areas of their dentitions. There is a possibility that mental tension may also have been relieved. Modern literature speaks only timidly about second molar extraction, and then only about upper second molars in a few Class II cases. Lower second molars are retained even when a third molar impaction is developing. The lower third molars are then extracted after all treatment has been completed. Finally, the upper third molars are permitted to occlude with the lower second molars. This
Volume Number
Second molar extraction
72 6
Fig. 12. Case 3. A and B, Pretreatment 6 months following removal of retainers.
plaster
casts.
C and
D, Posttreatment
plaster
609
casts
is not only an unnatural occlusion; it also is biologically wrong to attempt orthodontic treatment in an already overcrowded arch. The width of all the bands adds to the arch-length discrepancy, and extraction of impacted lower third molars often does irreparable damage to the distal surfaces of the lower second molars. During the years of waiting for eruption of upper third molars, it is almost impossible to retain the lower second molars in their proper positions after the upper second molars have beeen extracted. Elongation is natural, and with the force of impacted lower third molars pressing against them, the lower second molars can erupt as much as ys inch beyond their natural line of occlusion. This occurs long before the upper third molars erupt far enough to create whatever occlusal relations are then possible. There are many ways of reaching the same objective in treatment and, undoubtedly, the four-second-molar method is not easy to come by. Many orthodontists have told me they would be afraid to try it, and most of them look at me strangely upon the mere mention of it. The reason is that we all have been taught to think of premolars as the culprits causing many forms of malocclusion. It took
610
Am. J. Orthod.
Liddle
Fig.
13.
Fig.
December
Case
3. Occlusal
14. Case
views
3. Intraoral
of
views
pretreatment
1 year
and
after
retainers
posttreatment
had
plaster
been
removed.
casts.
1977
Second molar extraction
Fig. 15. Case 3. A, Pretreatment Panorex film prior Posttreatment Panorex film showing third molars following removal of retainers.
to removal in second
of four second molar positions
611
molars. B, 6 months
me many years of trial and a few of errors most of which were due to lack of cooperation on the part of the patients. It takes the complete courage of one’s convictions, and a thorough understanding and cooperation with the patient, the family, and the family dentist. Patients and parents should be fully informed, and I enjoy letting them talk. They are usually very understanding and helpful, especially when they see good results. Early recognition, careful diagnosis, and optimum treatment give the best results during the mixed-dentition and prepubertal growth periods. Borderline
612
Liddle
Fig. 16. Case removal
of
Am. J. Orthd December 1977
4. A, Pretreatment retainers.
Fig. 17. Case 4. before debanding.
A and
photographs.
B, Pretreatment
plaster
8, Posttreatment
casts.
C and
photographs
D, Posttreatment
1 year
after
plaster
casts
Yolulne Number
72 6
Fig. 18. Case
Second molar extraction
4. Occlusal
views
of pretreatment
and
posttreatment
plaster
613
casts.
cases offer a great opportunity. Group or individual meetings with general dentists to study normal occlusion and developing malocclusion are good for mutual cooperation and public relations. Prognosis for life should be our objective-not intermittent, unstable relief. With the premolar-extraction method, relapse often occurs upon eruption of the third molar. This cannot be easily overcome by extraction of third molars and retreatment at an important social and college period for the patient. Extraction of second permanent molars, with 10 to 12 mm. of spa.ce relief, usually satisfks most arch-length problems and, needless to say, it is not apparent when the patient smiles. I have never seen third molars fail to erupt into good, useful occlusion in second molar spaces, without appliances, when uninhibited by prolonged impaction. Nor do we see drifting or loose contact areas in carefully selected cases. Of my present active-treatment patients, 91 per cent have undergone second molar extractions. Many of the remaining 9 per cent would also have had second molar extractions if I could have seen them sooner. If we could be clairvoyant enough to foresee developing arch-length discrepancies from an overabundance of tooth material and insufficient supporting structures, then enucleation of the permanent second molars would be ideal. One of my greatest thrills in orthodontics comes from second-molar-extraction treatment, especially for younger patients in families whose older children have had premolar extraction and active treatment. Many of these second-molar-extraction cases do not need further help. Thirty-five years ago I thought I could go one step farther and enucleate only third molars at an early age. After some success, I suddenly stopped it when one patient developed a long-standing facial paralysis due to deep interference with the posterior facial nerve. It is also possible to injure the developing second molar
614
Liddle
Fig.
19. Case
4. Intraoral
fig. 20. Case 4. Pretreatment both upper second molars. earlier date.
views
after
radiograms Lower right
patient
had
worn
prior to removal first permanent
a retainer
of lower molar had
for
3 months.
left second molar and been extracted at an
Volume Number
Fig. 21. positioner
Second
12 6
Case 4. Posttreatment that was worn for
radiograms. 1 year.
Normal
contact
molar
relations
extraction
later
restored
615
by
a
enamel organs. Second molar extraction is closer to the site of the malocclusion, and it gives more rapid response in treatment than does third molar extraction. I have shown comparatively difficult cases in order to stimulate interest in the extraction of the four second permanent molars, at least in the early developing cases. After extraction, the first molars begin to move distally toward their original positions in response to pressure from the forward areas of the dentition. The overcompressed interstitial connective tissue fibers help to move the premolars and canines to a more normal occlusion, Light extraoral force and light elastics are usually used in treatment. Tandem Class III elastics can be used in bimaxillary protrusion cases if the extraoral traction to the upper arch is increased. I use 0.046 inch (1.168 mm.) (inner diameter) buccal tubes with 0.045 (1.143 mm.) inner bows on the extraoral appliance to ensure less friction, less discomfort, and better cooperation. Before- and after-treatment models and photographs in the accompanying cases show the possibilities of second-molar-extraction treatment. Postretention radiograms also show the slow but definite eruption of the upper and lower third molars into good contacting relations with the first molars. Since prevention is the watchword of all health professions, all branches of dentistry have a boundless opportunity and an obligation to be ever watchful for early signs of malocclusion, just as they are for cavities and for threats to the periodontal health of the supporting tissues.
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Am. J. Orthod. December 1977
Liddle
A lifetime of work seems to hang in the balance, since each new patient presents varying degrees of classification and malocclusion. Hasty judgment should not rush us into premolar extraction and possible later third molar extraction. In all arch-length problems, serious consideration should be given to extraetion of all four permanent second molars. Eruption time is usually earlier in girls than in boys. Optimum extraction time is when the overcrowding begins, and this is usually when the second molars are trying to erupt. Third molars often will then erupt at the age of 13, and they usually are in good occlusion at age 14. Lower third molars usually take 1 or 2 years longer to erupt than upper third molars because there is more dense cortical bone in the lower arch. If the second molar concept has a place in prevention or interception, children in the growth years from 8 to 12 years, before second molar eruption, should be examined for developmental irregularities. If crowding is occurring, lateral films of the molar areas may reveal the source of the malocclusion. If we, a~ orthodontists, are convinced at this developmental stage that arch length is insufficient and overcrowding is developing (and it does not take a computerized analysis to tell us that), then a serious consideration of second molar extraction is essential. I understand the difficulty of making any change in diagnostic methods, and I do not wish to unduly influence any orthodontist in his treatment proeedurerr. Yet I will consider it worth while if I have added just a little toward orthodontic concepts and treatment in reaching the ultimate goal of all orthodontists-a beautiful smile with the best possible occlusion. I want to thank Morris M. Stoner and James V. Yartuccio encouragement in the preparation of this article. 6014 Untin
Savings Bldg.
for
their
interest
and