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

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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
American Journal of Orthodontics and Dentofacial Orthopedics Volume 131, Number 3 Table III. Cephalometric measurements from T1 to T3 Measurement Treatment changes (T1-T2) to the mandibular plane (Tables III and IV) were statistically significant (P .01). After the relevant age- and sex-related mean growth increments were added to the data, the following results Posttreatment changes (T2-T3) Total change (T1-T3) Mean SD Mean SD Mean SD L4-COS line (mm) 2.50 0.77 0.49 0.69 1.78 0.74 L1-MP perp (mm) 0.53 1.60 1.66 2.30 2.19 2.37 L4-MP perp (mm) 2.81 1.69 1.00 2.00 3.81 2.15 L6-MP perp (mm) 2.31 2.28 1.23 2.38 3.53 2.24 L1-MP perp: growth (mm) 0.87 0.66 0.21 L4-MP perp: growth (mm) 1.26 0.00 1.26 L6-MP perp: growth (mm) 0.61 0.23 0.84 L1-MP (°) 0.82 6.08 1.18 5.21 0.35 3.91 L1 to A-Po (mm) 1.51 1.57 0.10 1.31 1.41 1.57 L1-NB (°) 1.37 4.81 1.03 4.21 0.34 4.35 SNA angle (°) 2.65 2.17 0.37 2.23 2.27 2.51 SNB angle (°) 0.34 1.29 0.55 1.34 0.89 1.58 ANB angle (°) 2.98 1.55 0.18 2.06 3.16 2.34 Wits (mm) 0.52 1.86 0.06 1.45 0.59 1.95 Y-axis (°) 1.05 1.34 0.34 1.33 0.71 1.73 SN-MP (°) 0.98 2.43 0.56 2.44 0.42 2.75 SN-OP (°) 2.98 3.09 0.19 2.56 3.18 3.22 OP-MP (°) 3.90 3.83 0.32 3.14 3.58 3.18 SN-PP (°) 0.95 1.91 0.73 1.64 0.23 1.78 U6-MP perp (mm) 2.73 2.85 1.24 1.59 3.97 2.56 U6-MP (°) 2.11 5.32 2.11 5.40 4.23 5.67 U1-PP perp (mm) 0.58 1.99 1.42 1.79 2.00 2.20 U1-PP (°) 1.98 9.29 0.74 5.22 2.73 9.00 U1-NA (°) 3.50 8.09 1.00 3.92 4.50 7.24 U1-L1 (°) 3.70 11.37 0.82 6.55 2.92 10.28 L6-MP (°) 6.42 3.04 1.87 4.63 4.55 5.37 Perp, Perpendicular. Table IV. Paired t tests for cephalometric measurements Measurements T1 vs T2 T2 vs T3 COS P .0001 P .0004 L1 perp to MP P .0742 P .0004 L4 perp to MP P .0001 P .0093 L6 perp to MP P .0001 P .007 L1 perp to MP, growth P .0052 P .0001 L4 perp to MP, growth P .0001 P .0627 L6 perp to MP, growth P .1482 P .0001 L1 to MP P .4569 P .2181 L1 to A-Po line P .0001 P .6829 L1 to NB P .1227 P .1822 SN-MP P .0316 P .2072 Y-axis P .0001 P .1651 OP-MP P .0001 P .5151 SN-OP P .0001 P .6769 SN-PP P .0095 P .0198 ANB angle P .0001 P .6357 Perp, Perpendicular. Bernstein, Preston, and Lampasso 367 were recorded. The mean adjusted (T2-T1) changes for L1-MP and L4-MP (Tables III and IV) were statistically significant (P .0052). The mean treatment changes allowing for growth were –0.87 mm for L1-MP, 1.26 mm for L4-MP, and 0.61 mm for L6-MP. The negative value calculated for the incisor represents relative intrusive movement over this time period. The posttreatment (T3-T2) changes for L1-MP and L6-MP adjusted for growth were statistically significant (P .0001). The mean net posttreatment dental movements, taking growth into account, were 0.66 mm for L1-MP, 0.00 mm for L4-MP, and 0.23 mm for L6-MP. At T2, the mean increase in mandibular incisor inclination to the mandibular plane was 0.82° (SD, 6.08°) (Table III). The mean amount of relapse (T3-T2) was –1.18° (SD, 5.21°). A negative number represents lingual movement (uprighting) of the mandibular incisors relative to the MP. The overall effect (T3-T1) on the mandibular incisor inclination to the MP was –0.35° (SD, 3.91°). Associated with orthodontic treatment, the mandibular incisors advanced a mean distance of 1.51 mm (SD, 1.57 mm) relative to the A-Po line (Table III).
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