Based on the advancement of Pog, 45 subjects whose △Pog-VRP was above the median (> 2.3 mm), were categorized into GRG, while the rest half were PRG (≤ 2.3 mm). The demographic information is indicated in Table. 1. In general, there is no significant difference between PGR and GRG in age (PRG, 11.2 ± 1.1 years; GRG, 10.8 ± 1.0 years, P = 0.11), gender (PGR, 23/45 males; GRG, 20/45 males, P = 0.53) and CS (PRG, 42/45 with CS3; GRG, 44/45 with CS3, P = 0.31). When △Pog-VRP was adjusted by the individual growth (△N-Ba), those with △Pog-VRP/△N-Ba > 0.3 were deemed as having good response (adjGRG), while the rest (≤ 0.3) half were categorized into adjPRG. The two groups were comparable in age (adjPRG, 10.9 ± 1.1 years; adjGRG, 11.0 ± 1.0 years, P = 0.17) and gender (adjPGR, 22/45 males; adjGRG, 21/45 males, P = 0.83) and CS (PRG, 42/45 with CS3; GRG, 44/45 with CS3, P = 0.31).
The cephalometric measurements for PRG and GRG are displayed in Table 2. Subjects from GRG had a significantly lower value of ∠Na-Go-Me (71.8° ± 4.4° v.s 73.8° ± 3.9°, P = 0.03), ∠MP-OP (17.0° ± 3.9° v.s. 18.7° ± 3.7°, P = 0.04), sum of angels (395.7° ± 5.1° v.s. 393.4° ± 5.4°, P = 0.04). All of these baseline values corresponds to the vertical dimensions. In addition, numerical but non-significant difference were observed in ∠SN-MP (32.8° ± 6.1° v.s. 35.0° ± 5.6°, P = 0.07) and ∠L1-MP (38.8° ± 2.7° v.s. 39.7° ± 2.7°, P = 0.10).
Table 1
Baseline demographic characteristics on individuals with different treatment response
| PRG (N = 45) | GRG (N = 45) | P | Adj_PRG (N = 45) | Adj_GRG (N = 45) | P |
Age | 11.2 (1.1) | 10.8 (1.0) | 0.11 | 10.9 (1.1) | 11.1 (1.0) | 0.17 |
Male | 23 (51.1) | 20 (44.4) | 0.53 | 22 (48.9) | 21 (46.7) | 0.83 |
CS | | 0.31 | | | 0.31 |
CS3 | 42(93.3) | 44 (97.8) | | 42 (93.3) | 44 (97.8) | |
CS4 | 3 (7.7) | 1 (2.2) | | 3 (7.7) | 1( 2.2) | |
Table 2
Baseline cephalometric characteristics on the subjects from poor response group (PRG) and good response group (GRG)
Baseline cephalometric variables | PRG (N = 45) Mean (SD) | GRG (N = 45) Mean (SD) | P |
AP | | | |
SN-NPo (°) | 76.3 (3.8) | 76.6 (3.2) | 0.69 |
Ar-Go-N (°) | 47.5 (4.0) | 47.4 (3.3) | 0.90 |
SNA (°) | 81.9 (4.0) | 82.2 (3.6) | 0.79 |
SNB (°) | 75.8 (3.6) | 76.0 (3.2) | 0.77 |
ANB (°) | 6.2 (2.4) | 6.2 (1.9) | 0.99 |
Po-NB (°) | 1.1 (0.9) | 1.1 (0.9) | 0.90 |
OJ (mm) | 7.9 (2.2) | 7.6 (2.1) | 0.63 |
Inter-incisor (°) | 112.0 (9.1) | 111.5 (8.4) | 0.80 |
UL-EP (mm) | 3.8 (2.4) | 3.7 (2.3) | 0.75 |
LL-EP (mm) | 2.6 (3.1) | 3.1 (2.5) | 0.41 |
Pog-VRP (mm) | 58.7 (5.5) | 57.6 (4.7) | 0.35 |
Vertical | | | |
SN-MP (°) | 35.0 (5.6) | 32.8 (6.1) | 0.07 |
Na-S-Ar (°) | 125.1 (4.6) | 124.4 (4.7) | 0.49 |
Ar-Go-Me (°) | 121.3 (5.5) | 119.7(6.2) | 0.18 |
Na-Go-Me (°) | 73.8 (3.9) | 71.8(4.4) | 0.03 |
S-Ar-Go (°) | 149.3 (4.9) | 149.8(5.1) | 0.64 |
Y-axis (°) | 59.3 (3.0) | 59.6(3.1) | 0.63 |
ANS-Me (°) | 61.1 (4.0) | 60.4(4.0) | 0.49 |
N-ANS (°) | 49.8 (2.5) | 49.3(2.9) | 0.41 |
N-Me (°) | 108.5 (5.2) | 107.4(5.4) | 0.31 |
PFH/AFH (%) | 64.7 (4.6) | 66.1(4.5) | 0.16 |
AUFH/ALFH (%) | 81.8 (5.9) | 81.7(5.5) | 0.96 |
OB (mm) | 3.9 (1.2) | 3.9(1.1) | 0.93 |
FMIA (°) | 56.1 (6.7) | 54.9(6.1) | 0.38 |
IMPA (°) | 101.2 (6.6) | 103.3(6.8) | 0.13 |
MP-OP (°) | 18.7 (3.7) | 17.0(3.9) | 0.04 |
OP-FH (°) | 5.2 (3.3) | 5.5(3.1) | 0.62 |
SN-OP (°) | 16.3 (5.1) | 15.7(4.8) | 0.56 |
Sum-of-angle (°) | 395.7(5.1) | 393.4(5.4) | 0.04 |
Dento-Alveolar | | | |
U1-FP (°) | 13.8(2.9) | 13.5(2.9) | 0.63 |
L1-FP (°) | 6.4(2.8) | 5.9 (2.5) | 0.43 |
U1-PP (°) | 26.4(2.2) | 26.5(2.4) | 0.75 |
U6-PP (°) | 19.9(1.8) | 20.1(1.9) | 0.51 |
L1-MP (°) | 39.7(2.7) | 38.8(2.7) | 0.10 |
L6-MP (°) | 29.6(2.2) | 29.2(2.5) | 0.40 |
Mandibular dimensions |
Co-Gn (°) | 101.5 (5.6) | 100.8(5.0) | 0.50 |
Go-Me (°) | 62.6 (4.5) | 62.4 (3.7) | 0.84 |
Go-Po (°) | 68.4(4.5) | 68.4(3.9) | 0.96 |
Go-Co (°) | 50.7(4.8) | 50.8 (4.5) | 0.90 |
Cranial Based dimensions |
N-Ba (mm) | 97.9(4.4) | 99.1(4.1) | 0.20 |
S-Ar (mm) | 33.5 (3.5) | 33.9(3.2) | 0.53 |
Bold indicates P < 0.05 |
Similar results in the vertical dimensions were observed between adjPRG and adjGRG (Table 3). A significantly smaller value of ∠SN-MP (32.4° ± 5.5° v.s. 35.4° ± 6.0°, P = 0.02), ∠Na-Go-Me (71.6° ± 4.1° v.s. 74.0° ± 4.0°, P < 0.01), and sum of angles (393.1° ± 4.6° v.s. 396.1° ± 5.7°, P < 0.01) were found in the subject from adjGRG, with reference to that of adjPRG. Moreover, subjects in adjGRG showed a higher ratio of PFH/AFH (66.4 ± 3.8% v.s. 64.4 ± 5.0%). A marginal significant difference was observed in ∠Ar-Go-Me (119.4° ± 5.6° v.s. 121.6° ± 6.0°, P = 0.08) and ∠MP-OP (17.1° ± 3.8° v.s. 18.6° ± 2.9°, P = 0.05).
Table 3
Baseline cephalometric characteristics on the subjects from adjusted poor response group (adjPRG) and adjusted good response group (adjGRG)
Baseline cephalometric variables | adjPRG (N = 45) | adjGRG (N = 45) | P |
AP | | | |
SN-NPo (°) | 76.1 (3.9) | 76.8 (3.0) | 0.33 |
Ar-Go-N (°) | 47.5 (3.9) | 47.4 (3.5) | 0.88 |
SNA (°) | 81.8 (4.1) | 82.3 (3.5) | 0.56 |
SNB (°) | 75.6 (3.8) | 76.1 (3.0) | 0.53 |
ANB (°) | 6.2 (2.1) | 6.2 (2.2) | 0.97 |
Po-NB (°) | 1.0 (0.8) | 1.2 (0.9) | 0.21 |
OJ (mm) | 7.8 (1.9) | 7.7 (2.3) | 0.77 |
Inter-incisor (°) | 111.4 (8.4) | 112.0 (9.1) | 0.73 |
UL-EP (mm) | 3.9 (2.3) | 3.6 (2.4) | 0.56 |
LL-EP (mm) | 3.0 (2.9) | 2.7 (2.7) | 0.56 |
Pog-VRP (mm) | 58.4 (5.0) | 57.9 (5.3) | 0.68 |
Vertical | | | |
SN-MP (°) | 35.4 (6.0) | 32.4 (5.5) | 0.02 |
Na-S-Ar (°) | 124.9 (4.7) | 125.7 (4.6) | 0.84 |
Ar-Go-Me (°) | 121.6 (6.0) | 119.0 (5.8) | 0.04 |
Na_Go_Me (°) | 74.0 (4.0) | 71.6 (4.1) | < 0.01 |
S_Ar_Go (°) | 149.6 (4.9) | 149.5 (5.2) | 0.92 |
Y-axis (°) | 59.5 (2.9) | 59.5 (3.2) | 0.99 |
ANS_Me (°) | 61.3 (3.9) | 60.2 (4.0) | 0.20 |
N_ANS (°) | 49.9 (2.9) | 49.2 (2.5) | 0.25 |
N_Me (°) | 108.8 (5.7) | 107.1 (4.8) | 0.11 |
PFH/AFH (%) | 64.4 (5.0) | 66.4 (3.8) | 0.04 |
AUFH/ALFH (%) | 81.6 (5.5) | 82.0 (5.9) | 0.74 |
OB (mm) | 3.8 (1.2) | 4.1 (1.1) | 0.24 |
FMIA (°) | 55.6 (5.3) | 55.4 (7.4) | 0.87 |
IMPA (°) | 101.2 (5.9) | 103.2 (7.4) | 0.16 |
MP_OP (°) | 18.6 (2.9) | 17.1 (3.8) | 0.05 |
OP_FH (°) | 5.3 (3.6) | 5.4 (2.8) | 0.81 |
SN_OP (°) | 16.7 (5.1) | 15.3 (4.5) | 0.17 |
Sum-of-angle (°) | 396.1 (5.7) | 393.1 (4.6) | < 0.01 |
Dento-Alveolar | | | |
U1-FP (°) | 13.9 (2.4) | 13.4 (3.3) | 0.45 |
L1-FP (°) | 6.4 (2.6) | 5.9 (2.8) | 0.46 |
U1-PP (°) | 26.7 (2.2) | 26.2 (2.4) | 0.37 |
U6-PP (°) | 19.9 (2.0) | 20.1 (1.7) | 0.56 |
L1-MP (°) | 39.6 (2.9) | 38.9 (2.5) | 0.27 |
L6-MP (°) | 29.4 (2.4) | 29.3 (2.3) | 0.85 |
Mandibular dimensions |
Co_Gn (°) | 101.5 (6.0) | 100.8 (4.5) | 0.71 |
Go_Me (°) | 62.6 (3.9) | 62.5 (4.3) | 0.95 |
Go_Po (°) | 68.3 (4.2) | 68.5 (4.2) | 0.84 |
Go_Co (°) | 50.7 (5.2) | 50.7 (4.1) | 0.98 |
Cranial Based dimensions |
N_Ba (mm) | 98.1 (4.5) | 98.9 (3.9) | 0.42 |
S_Ar (mm) | 33.2 (3.9) | 34.1 (2.5) | 0.19 |
Bold indicates P < 0.05 |
Next, those variables with P < 0.10 in Tables 2 & 3, together with age, gender and CS were included in the regression analysis to determine the association with the treatment outcome. As shown in Table 4, age (β = -0.21,95%CI, -0.19 to -0.003, P = 0.04), and Na-Go-Me (β = -0.26, 95%CI, -0.06 to -0.01, P = 0.01) were found to be the independent predictors of Pog advancement (Model 1). In addition, when the Pog advancement was adjusted by △N-Ba, we found that only Na-Go-Me (β = -0.29༌95%CI -0.06, -0.01, P < 0.01) was included in the final model (Model 2). Additionally, the significant linear correlation of Na-Go-Me with △Pog-VRP (R2 = 0.09, P < 0.01) and △adjPog-VRP (R2 = 0.09, P < 0.01) was depicted in the scatter plot (Fig. 2)
Table 4
Multivariate regression analysis of treatment outcome against explanatory variables
| β | 95%CI | P |
Model 1 | | | |
Age | -0.10 | -0.194 to -0.003 | 0.04 |
Na-Go-Me | -0.03 | -0.055 to -0.006 | 0.01 |
Model 2 | | | |
Na-Go-Me | -0.03 | -0.058 to -0.010 | < 0.01 |
Model 1: The dependent variable is GRG with PRG as reference. The independent variables include age, gender, CS, ∠SN-MP, ∠Na-Go-Me, ∠MP-OP, and Sum of angle. |
Model 2: The dependent variable is adjGRG with adjPRG as reference. The independent variables include age, gender, CS, ∠SN-MP, ∠Na-Go-Me, ∠MP-OP, Sum of angle, ∠Ar-Go-Me, PFH/AFH. |