Leveling the curve of Spee with a continuous archwire technique: A ...

370 Bernstein, Preston, and Lampasso
second-order movement relapsed an average of 1.87°
(SD, 4.63°), resulting in a mean long-term uprighting
of –4.55°.
A straight-wire approach to Class II orthodontic
treatment requiring leveling of the COS has been
associated with increases in the vertical dimensions of
the face. 3,5-7 An analysis of the data from this study
shows that in our patients the treatment did not have a
major effect on 2 measurements of lower facial height.
Although the Y-axis changed statistically significantly
from T1 to T2 (P .001), the mean change was only
1.05°. During treatment, the MP angle (SN-MP)
changed by less than a mean of 1.0° (SD, 2.43°),
which was not statistically significant (P .0316).
There were changes in the mean angular relationships
of the OP during treatment. During treatment,
there were a mean reduction of –2.98° in the SN-OP
angle and a mean increase of 3.90° in the OP-MP angle.
These changes occurred during the leveling of the COS,
and they represent counterclockwise rotation in the OP.
The posttreatment changes in these 2 angles were not
statistically significant (P .01).
We studied only patients with Class II Division 1
malocclusions with specifically defined parameters.
Our results cannot be arbitrarily extrapolated to the
success that can be achieved with other categories of
malocclusions such as those characterized by vertical
growth patterns.
CONCLUSIONS
1. It is feasible to determine the depth of the COS
from cephalometric radiographs taken with the
Quint Sectograph cephalometer.
2. The continuous archwire technique effectively leveled
the COS in this sample of Class II Division 1
deep-bite patients treated without extractions.
3. In this study, the leveling of the COS with the
continuous archwire technique occurred by a combination
of mainly premolar extrusion and, to a
lesser extent, incisor intrusion.
4. In the subjects studied here, the continuous archwire
technique effectively controlled the mandibular
incisor position during the leveling process.
These results appear to be stable in the long term.
6. The –6° of tip back in the molar band tipped the
mandibular first molar back at least that amount
during treatment.
7. In this study, the continuous archwire technique did
not cause excessive opening rotation of the Y-axis
or the MP angle.
American Journal of Orthodontics and Dentofacial Orthopedics
March 2007
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