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

366 Bernstein, Preston, and Lampasso
Table II. Changes in cephalometric measurements from T1 to T3
Measurement
T1 T2 T3
Mean SD Mean SD Mean SD
L4-COS line (mm) 2.47 0.69 0.19 0.31 0.69 0.64
L1-MP perp (mm) 38.89 3.02 39.42 2.94 41.08 3.27
L4-MP perp (mm) 32.50 2.76 35.31 3.01 36.31 3.18
L6-MP perp (mm) 29.16 2.14 31.47 2.81 32.70 3.20
L1-MP (°) 94.85 5.43 95.68 6.93 94.50 5.80
L1 to A-Po (mm) 1.18 1.98 0.34 1.51 0.24 2.04
L1-NB (°) 22.81 5.16 24.18 4.82 23.15 4.94
SNA angle (°) 82.03 3.33 79.39 4.08 79.76 4.14
SNB angle (°) 76.87 3.34 77.21 3.75 77.76 3.91
ANB angle (°) 5.16 1.60 2.18 1.76 2.00 2.25
Y-axis (°) 66.21 2.91 67.26 3.36 66.92 3.77
SN-MP (°) 31.23 4.35 32.21 5.54 31.65 6.30
SN-OP (°) 17.76 3.31 14.77 2.94 14.58 3.63
OP-MP (°) 13.47 3.18 17.44 4.58 17.06 4.23
SN-PP (°) 8.00 2.89 8.95 3.35 8.23 3.04
U6-PP perp (mm) 20.00 4.15 22.73 2.52 23.97 2.84
U6-PP (°) 78.89 6.29 81.00 6.24 83.11 6.27
U1-PP perp 26.29 2.46 26.87 2.84 28.29 3.10
U1-PP (°) 109.24 9.31 111.23 5.30 111.97 7.87
U1-NA (°) 19.18 8.27 22.68 4.25 23.68 5.74
U1-L1 (°) 134.27 13.56 130.53 7.02 131.35 7.98
L6-MP (°) 84.95 4.10 78.53 5.60 80.40 6.05
Perp, Perpendicular.
American Journal of Orthodontics and Dentofacial Orthopedics
March 2007
OP-MP angle was 3.90° (SD, 3.83). Both changes molar (L6), the most infra-occluded premolar (L4), and
were statistically significant (P .0001).
the most extruded incisor (L1) were measured with
According to the literature, angular changes of less reference to the mandibular plane. Since appositional
than 10° in the long axes of the teeth do not have a bony growth at the inferior border of the mandible can
significant effect on the perpendicular linear measure-
38
ments made from L1, L4, or L6 to the MP. In this
radiographic study, no patients had angular changes
greater than 10° for any teeth in question (Table III).
The mean COS at T1 for the 31 patients treated with
the continuous archwire technique was 2.47 mm (SD,
0.69 mm; range, 2.00-4.00 mm). The mean COS at T2
for this sample was 0.19 mm (SD, 0.31 mm; range,
0.00-1.00 mm) (P .0001). During treatment, the mean
reduction in the COS was 2.27 mm (SD, 0.77 mm),
which corresponds to a 92.16% average reduction in
this measurement. Twenty-one of the 31 subjects
(about 67.80%) were completely level at T2, but 10 had
slight residual COS at the end of this phase. The mean
COS at T3 was 0.69 mm (SD, 0.64 mm; range,
0.00-2.00 mm). The mean increase in the COS from T2
to T3 was 0.49 mm (SD, 0.69 mm) (P .001). The
overall mean time from T1 to T3 was 14 years 4
add significant amounts to these measurements, growth
prediction charts for normal white American youths
were used to calculate net treatment (T2-T1) and
posttreatment (T3-T2) changes.
months, with a range of 7 years to 28 years 8 months.
Over this period, the overall effect on the COS was an
average reduction of 1.78 mm, which represents a
72.97% reduction.
The perpendicular heights of the mandibular first
36 No growth data were
found for mandibular premolar heights (L4-MP); therefore,
figures midway between those of the molars and
36
the incisors were used for comparison. Growth adjustments
were made by adding the relevant mean
growth increments from the growth charts to the
respective measurements made at T2 and T3. Paired
t tests (with set at 0.01) were calculated for both
the growth-adjusted and the unadjusted measurements
(Table IV).
Analysis of the data, unadjusted for growth, showed
that there were statistically significant changes associated
with treatment for premolar (L4-MP) and first
molar (L6-MP) vertical heights (P .0001). The mean
treatment changes for the dental heights were 0.53 mm
(SD, 1.60 mm) for L1-MP, 2.81 mm (SD, 1.69
mm) for L4-MP, and 2.31 mm (SD, 2.28 mm) for
L6-MP (Table III). All unadjusted posttreatment (T3-
T2) t test results for the L1, L4, and L6 perpendiculars