This document summarizes research on different treatment approaches for patients with arch length deficiency in the mixed dentition. It discusses the outcomes of: 1) doing nothing, which typically leads to worsening crowding over time; 2) arch expansion, which often results in significant relapse without lifelong retention; 3) early premolar extraction followed by treatment, which shows similar long-term instability as extraction in the permanent dentition; and 4) using passive lingual arches to preserve arch length via the "leeway space", which has demonstrated good long-term stability in maintaining anterior alignment without extractions or arch expansion.

1. EARLY TREATMENT SYMPOSIUM
Stability and relapse: Early
treatment of arch length
deficiency
Robert M. Little, DDS, MSD, PhD
Seattle, Wash
N
early 5 decades
ago, the faculty
of the Depart-
ment of Orthodontics at
the University of Wash-
ington began collecting
postretention records for
patients treated in their
private practices and at
theUniversity’sorthodon-
tic clinic. This collection
has grown to over 850
sets of records, the study
of which has molded our diagnostic, treatment-plan-
ning, and retention strategies. Others have done parallel
research, efforts we applaud, and from which we
continue to learn. Our clinically based hypotheses have
been tested, sometimes altered or even abandoned
because of these data.
We have been encouraged and sometimes discour-
aged by our own findings for cases treated in the full
permanent dentition.1
Advocates of earlier intervention
have been as enthusiastic as its opponents. However, it
is incumbent on all to test their opinions with data—
long-term postretention data.
THE PROBLEM
What is the treatment of choice for a preadolescent
patient with arch length deficiency? What if nothing is
done? What if the arches are enlarged to accommodate
the permanent teeth? What if premolars are extracted
early (serial extraction) followed by full treatment plus
retention? What if arch length is preserved in the mixed
dentition to accommodate the future permanent succes-
sors?
WHAT IF NOTHING IS DONE?
Coenraad Moorrees,2
in his classic 1959 textbook,
reported serial changes in dental arch dimensions of
untreated subjects with malocclusion. He showed that
arch length typically decreases with time from the
mixed dentition through the transitional dentition and
into early adulthood. He shocked readers by demon-
strating that arch length at age 5 is greater than at age
18! With canine eruption, arch width typically reaches
a maximum in the preteen years, followed by a slow,
persistent reduction over at least the next decade.
Parents (and often dental practitioners) might have a
problem with these concepts because the child obvi-
ously grows throughout these years, and one would
logically assume that the arch would enlarge as well.
Unfortunately, the arches tend to constrict in antero-
posterior and transverse dimensions, leading to further
crowding of an already inadequate dental arch. In our
studies, we found that this same trend is evident in
untreated normal subjects as well as those with spacing
pretreatment.3,4
Conclusion: Without treatment, a short arch length
will only get worse.
WHAT IF THE DENTAL ARCHES ARE ENLARGED?
The father of dental arch enlargement had to be
Edward Angle. His adage that only a complete dental
arch can yield an acceptable occlusion influenced many
orthodontists of that day and later. But some were
skeptical then (Case and others) and later (Tweed and
others). Tweed grew up professionally under the Angle
cloak. Noting significant relapse after his own nonex-
traction enlargement therapy, he went so far as to
retreat his patients with premolar extraction after the
significant relapse of his Angle-style nonextraction
treatment. But what if the arches are enlarged earlier?
To test the value and the efficacy of mixed dentition
arch enlargement (arch development), we gathered a
From the Department of Orthodontics, School of Dentistry, University of
Washington, Seattle.
Presented at the International Symposium on Early Orthodontic Treatment,
February 8-10, 2002; Phoenix, Ariz.
Am J Orthod Dentofacial Orthop 2002;121:578-81
Copyright © 2002 by the American Association of Orthodontists.
0889-5406/2002/$35.00 ϩ 0 8/1/124683
doi:10.1067/mod.2002.124683
578

2. sample of long-term postretention records at the Uni-
versity of Washington.5
As noted in the preface of that
article, advocates of enlargement suggest various strat-
egies:
1. Actively move anterior teeth labially with fixed or
removable appliances.
2. Passively move anterior teeth labially by removal of
lip forces.
3. Actively push molars distally by extraoral or in-
traoral means.
4. Widen the arch with fixed or removable devices.
5. Widen the mandibular arch by reciprocal response
to maxillary arch enlargement.
6. Enlarge the dental arch with a combination of
devices and means.
Twenty-six cases with records at least 6 years
postretention (range, 6-23 years) were evaluated. The
degree of relapse was significant and alarming. Al-
though the cases looked clinically acceptable at the end
of active treatment, the degree and severity of relapse
after retention was much worse than with other strate-
gies. In fact, these cases showed the poorest long-term
results of any strategies that we have studied.
Can the arches be enlarged? Absolutely! The prac-
titioner may even look upon this treatment as “conser-
vative” (no permanent teeth removed). Is anterior
alignment stable after removing the retainers? Unfor-
tunately, no.
Conclusion: Without lifetime retention, the strategy
of arch development will yield unacceptable results.
WHAT IF PREMOLARS ARE EXTRACTED EARLY
(SERIAL EXTRACTION) FOLLOWED BY FULL
TREATMENT PLUS RETENTION?
Our studies have shown that premolar extraction in
the full permanent dentition yields variable degrees of
quality, with only about 1 in 3 considered a success at
10 years postretention and even fewer at 20 years.6,7
No
pretreatment variable, such as initial crowding, gave
clues as to what to expect postretention.
Serial extraction, the sequential removal of certain
deciduous teeth followed by premolar extraction, logi-
cally should yield improved results. After all, the
commonly noted self-improvement of anterior crowd-
ing through physiologic drift should set the stage for
improved long-term stability.
A study of 30 first premolar serial extraction cases
that had subsequent orthodontic treatment and retention
showed results nearly identical to those treated with
first premolar extraction in the full permanent denti-
tion.8,9
The early extraction cases became simpler
during the observation stage before active treatment,
but to no avail. The same ratio of one-third acceptable
versus two-thirds unacceptable seemed to prevail. Sec-
ond premolar serial extraction fared no better.10
We cannot predict which premolar extraction cases
will succeed and which will fail. Whether extracted
early or late, the net result is the same.
Conclusion: Serial extraction of deciduous teeth to
temper a developing arch length problem followed by
premolar extraction and routine treatment yields no
long-term improvement over premolar extraction in the
full dentition and routine treatment. Long-term reten-
tion must be part of a premolar extraction strategy
whether the teeth are extracted in the mixed dentition or
in the full permanent dentition.
WHAT IF ARCH LENGTH IS PRESERVED IN THE
MIXED DENTITION TO ACCOMMODATE THE
FUTURE PERMANENT SUCCESSORS?
In 1947, Hays Nance11
taught us that there is a
difference between the space occupied by the decidu-
ous canines and molars in both arches and that needed
by the succedaneous permanent canines and premolars.
From G. V. Black’s material from 1902, Nance learned
that the mandibular arch average excess amount was
3.4 mm. He labeled this beneficial size differential
“leeway space.” The maximum leeway space that he
measured from cases in his practice was 8 mm and the
least was 0 mm. Enlarging the arch beyond this leeway
he considered futile.12
The issue is whether we can use
leeway space to offset crowded anterior teeth. Misin-
terpreting Nance, many thought that 3.4 mm of “leeway
space” had to be lost, but that was not what Nance was
recommending. He encouraged exact measuring of the
available and required arch lengths to determine the
leeway for each patient. He recommended a passive
lingual arch when the leeway space was equal to or
greater than the degree of anterior crowding. Review of
his own postretention records was promising with this
strategy, but are cases treated in this way stable in the
long term?
We had to wait 48 more years to learn the answer.
Thanks to Steve Dugoni et al,13
looking at Art Dugoni’s
records, we learned that leeway space could be success-
fully held to offset anterior crowding with excellent
long-term results. They reviewed the records of 25
patients treated with a mandibular lingual arch designed
to maintain but not advance all 4 mandibular incisors a
minimum of 5 years postretention. All had maxillary
arch 2 ϫ 4 appliances, some combined with headgear,
as needed. The mandibular deciduous molars were
extracted, as needed, to facilitate eruption of the pre-
molars. About half had circumferential supracrestal
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 121, Number 6
Little 579

3. fibrotomies, and a similar number had interproximal
enamel reduction.
These cases fared much better in the long term than
did our premolar extraction and arch development
cases. Steve Dugoni prodded us to search for records
from our collection, and we found a few, all with
equally great results (Fig). Apparently, Nance had been
correct; we can use the full leeway space to our
advantage.
Conclusion: For mixed dentition cases in which
leeway space is favorable compared with anterior
crowding, use a passive lingual arch. The results appear
to be quite stable.
AFTERTHOUGHT
Dick Riedel, former orthodontic chairman at the
University of Washington, enjoyed describing a chance
meeting at an orthodontic conference many years ago.
An elderly gentleman leaned over and whispered a
question to Riedel as the speaker was going on and on
about Nance and his many insights. “What do you think
of this Nance material?” Riedel leaned over and re-
plied, “Nance is my hero. He had it dead right!” The old
gentleman quietly said, “That’s a relief. Let me intro-
duce myself. I’m Hays Nance.”
I think I’ll go back and read Hays Nance once more.
REFERENCES
1. Little R. Stability and relapse of mandibular anterior alignment.
University of Washington studies. Sem Orthod 1999;5:191-204.
2. Moorrees C. The dentition of the growing child. A longitudinal
study of dental development between 3 and 18 years of age.
Cambridge: Harvard University Press; 1959.
3. Sinclair P, Little R. Maturation of untreated normal occlusions.
Am J Orthod 1983;83:114-23.
4. Little R, Riedel R. Postretention evaluation of stability and
relapse: mandibular arches with generalized spacing. Am J
Orthod Dentofacial Orthop 1989;95:37-41.
5. Little R, Riedel R, Stein A. Mandibular arch length increase
during the mixed dentition: postretention evaluation of stabil-
ity and relapse. Am J Orthod Dentofacial Orthop 1990;97:
393-404.
6. Little R, Wallen T, Riedel R. Stability and relapse of mandibular
anterior alignment: first premolar extraction cases treated by
traditional edgewise orthodontics. Am J Orthod 1981;80:349-65.
7. Little R, Riedel R, Artun J. An evaluation of changes in
mandibular anterior alignment from 10 to 20 years postretention.
Am J Orthod Dentofacial Orthop 1988;93:423-8.
8. Little R, Riedel R, Engst E. Serial extraction of first premolars—
Fig. Nonextraction treatment without arch development. A, Pretreatment (age 8 years 2 months); B,
end of phase 1 nonextraction treatment (age 12 years 0 months); C, end of phase 2 comprehensive
treatment (age 13 years 6 months); D, 16 years postretention (age 33 years 8 months).
American Journal of Orthodontics and Dentofacial Orthopedics
June 2002
580 Little

4. postretention evaluation of stability and relapse. Angle Orthod
1990;60:255-62.
9. Little R. The effects of eruption guidance and serial extraction on
the developing dentition. Ped Dent 1987;9:65-70.
10. McReynolds D, Little R. Mandibular second premolar extrac-
tion—postretention evaluation of stability and relapse. Angle
Orthod 1991;61:133-44.
11. Nance H. The limitations of orthodontic treatment. I. Mixed
dentition diagnosis and treatment. Am J Orthod Oral Surg
1947;33:177-223.
12. Nance H. The limitations of orthodontic treatment. II. Diagnosis
and treatment in the permanent dentition. Am J Orthod Oral Surg
1947;33:253-301.
13. Dugoni S, Lee J, Varela J, Dugoni A. Early mixed dentition
treatment: postretention evaluation of stability and relapse. An-
gle Orthod 1995;65:311-20.
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