Introduction
Materials and methods
Ethical aspects
Study samples
Clinical examination
Statistical analysis
Results
Variables | MZ (n = 68) n (%) | DZ (n = 244) n (%) | Triplets (n = 33) n (%) | Singletons (n = 345) n (%) | M.births (n = 345) n (%) |
---|---|---|---|---|---|
Range of age, years | 3.4–17.8 | 2.2–16.4 | 5.2–11.1 | 2.5-17.11 | 2.2–17.8 |
Age in years, Mean (SD) | 8.10(3.30) | 7.26(2.74) | 7.53(2.10) | 7.46(2.80) | 7.45(2.82) |
Age groups | |||||
2–5 | 14(20.6) | 96(39.3) | 12(36.4) | 122(35.4) | 122(35.4) |
6–11 | 44(64.7) | 128(52.5) | 21(63.6) | 193(55.9) | 193(55.9) |
12–17 | 10(14.7) | 20(8.2) | - | 30(8.7) | 30(8.7) |
Gender | |||||
Female | 38(55.9) | 126(51.6) | 14(42.4) | 178(51.6) | 178(51.6) |
Male | 30(44.1) | 118(48.4) | 19(57.6) | 167(48.4) | 167(48.4) |
Mother education | |||||
Primary | 28(41.2) | 48(19.7) | 9(27.3) | 85(24.6) | 85(24.6) |
Secondary | 6(8.8) | 38(15.6) | - | 44(12.8) | 44(12.8) |
High school | 18(26.5) | 86(35.2) | 12(36.4) | 116(33.6) | 116(33.6) |
University | 16(23.5) | 72(29.5) | 12(36.4) | 100(29.0) | 100(29.0) |
Father education | |||||
Primary | 20(29.4) | 33(13.5) | 9(27.3) | 62(18.0) | 62(18.0) |
Secondary | 12(17.7) | 36(14.8) | - | 48(13.9) | 48(13.9) |
High school | 22(32.3) | 85(34.8) | 6(18.2) | 113(32.7) | 113(32.7) |
University | 14(20.6) | 90(36.9) | 18(54.5) | 122(35.4) | 122(35.4) |
Oral health status
Age groups | 2–5 | 6–11 | 12–17 | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Parameters | MZ | DZ | M. births | Singletons | MZ | DZ | M.births | Singletons | MZ | DZ | M.births | Singletons | |
d | Med (min-max) | 5 (0–11) | 5 (0–17) | 5 (0–17) | 6.5 (0–20) | 3 (0–16) | 2 (0–14) | 2 (0–9) | 2 (0–20) | -- | 0 (0–1) | 0 (0–1) | 0 (0–3) |
p-value | 0.914 | *0.007 | 0.134 | 0.674 | 0.309 | 0.060 | |||||||
m | Med (min-max) | 0 (0–7) | 0 (0–8) | 0 (0–8) | 0 (0–9) | ||||||||
p-value | 0.600 | 0.310 | |||||||||||
f | Med (min-max) | 0 (0–8) | 0 (0–7) | 0 (0–8) | 0 (0–9) | 1 (0–7) | 0 (0–7) | 0 (0–7) | 0 (0–10) | -- | 0 (0–1) | 0 (0–1) | 0 (0–3) |
p-value | 0.448 | 0.567 | 0.299 | 0.615 | 0.309 | 0.584 | |||||||
df | Med (min-max) | 6 (4–11) | 6 (0–17) | 6 (0–17) | 7 (0–20) | 5 (0–16) | 4 (0–14) | 4 (0–16) | 4 (0–20) | -- | 0 (0–2) | 0 (0–2) | 0 (0–5) |
p-value | 0.408 | *0.008 | 0.094 | 0.906 | 0.205 | 0.145 | |||||||
dmf | Med (min- max) | 7 (4–16) | 6 (0–19) | 6 (0–19) | 8 (0–20) | ||||||||
p-value | 0.279 | 0.054 | |||||||||||
D | Med (min-max) | 0 (0–4) | 0 (0–10) | 0 (0–10) | 0 (0–10) | 0 (0–6) | 1 (0–9) | 0 (0–9) | 1 (0–8) | ||||
p-value | 0.968 | 0.998 | 0.172 | 0.164 | |||||||||
M | Med (min-max) | 0 (0–3) | -- | 0 (0–3) | 0 (0–1) | ||||||||
p-value | 0.157 | 0.981 | |||||||||||
F | Med (min-max) | 0 (0–3) | 0 (0–3) | 0 (0–4) | 0 (0–6) | 1 (0–11) | 1 (0–6) | 1(0–11) | 0 (0–2) | ||||
p-value | 0.050 | 0.554 | 0.870 | 0.536 | |||||||||
DMF | Med (min-max) | 0 (0–4) | 0 (0–10) | 0 (0–10) | 0 (0–10) | 1 (0–20) | 3 (0–9) | 2 (0–20) | 2 (0–14) | ||||
p-value | 0.512 | 0.854 | 0.179 | 0.758 |
Age groups | Parameters | rDZ (95% Cl) | rMZ (95% Cl) | h2 (95% Cl) | c2 (95% Cl) | rDZ/rMZ p value |
---|---|---|---|---|---|---|
2–5 | d | 0.612 (0.38, 0.77) | 0.845 (0.10, 0.98) | 0.466 (-0.56, 0.51) | 0.379 (0.16, 0.43) | 0.102 |
m | 0.601 (0.36, 0.77) | 0.764 (-0.11, 0.97) | 0.326 (-0.94, 0.40) | 0.438 (0.23, 0.48) | 0.331 | |
f | 0.127 (-0.16, 0.40) | -- | -- | -- | ||
df | 0.597 (0.36, 0.76) | 0.514 (-0.44, 0.92) | -0.166 (-1.60, 0,32) | 0.680 (0.16, 0.73) | 0.707 | |
dmf | 0.618 (0.38, 0.78) | 0.745 (-0.14, 0.97) | 0.254 (-1.04, 0.38) | 0.491 (0.39, 0.52) | 0.454 | |
6–11 | d | 0.380 (0.14, 0.58) | 0.719 (0.38, 0.89) | 0.678 (0.48, 0.71) | 0.041 (-0.1, 0.27) | *0.006 |
f | 0.638 (0.45, 0.77) | 0.581 (0.18, 0.82) | -0.114 (-0.54, 0.10) | 0.695 (0.12, 0.72) | 0.615 | |
df | 0.404 (0.17, 0.60) | 0.703 (0.36, 0.88) | 0.598 (0.38, 0.61) | 0.105 (-0.02, 0.32) | *0.015 | |
D | 0.507 (0.29, 0.68) | 0.582 (0.18, 0.82) | 0.150 (-0.22, 0.28) | 0.432 (0.4, 0.54) | 0.526 | |
F | 0.306 (0.06, 0.52) | 0.593 (0.19, 0.82) | 0.574 (0.26, 0.60) | 0.019 (-0.07, 0.22) | *0.044 | |
DMF | 0.519 (0.30, 0.69) | 0.664 (0.30, 0.86) | 0.290 (0, 0.34) | 0.374 (0.3, 0.52) | 0.213 | |
12–17 | d | -0.111 (-0.69, 0.56) | ||||
f | -0.111 (-0.69, 0.56) | |||||
df | -0.167 (-0.72, 0.52) | |||||
D | 0.525 (-0.20, 0.88) | -- | -- | -- | ||
M | -- | -- | -- | -- | ||
F | 0.031 (-0.61, 0.65) | 0.761 (-0.52, 0.99) | 1.460 (0.18, 1.48) | -0.699 (-0.73, 0.31) | *0.041 | |
DMF | 0.678 (0.00, 0.93) | 0.825 (-0.41, 0.99) | 0.294 (-0.82, 0.32) | 0.531 (0.41, 0.87) | 0.447 |
Oral habits
Age groups | Oral Habits | MZ n (%) | DZ n (%) | M.births n (%) | Singletons n (%) | Pairwise Concordance (95% Cl) | Tetrachoric correlation (95% Cl) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
MZ pairs | DZ pairs | MZ pairs | DZ pairs | ||||||||||||
r | p value | r | p value | r | p value | r | p value | ||||||||
2–5 | Mouth breathing | 1(7.1) | 16(16.7) | 18(14.8) | 27(22.1) | - | 0.271 | 0.062 | - | 0.495 | 0.095 | ||||
p value | 0.692 F | 0.137 | (0.07, 0.47) | (0.32, 0.67) | |||||||||||
Nail biting | 3(21.4) | 13(13.5) | 21(17.2) | 20(16.4) | 0.645 | 0.117 | 0.379 | *0.008 | 0.999 | 0.286 | 0.644 | *0.033 | |||
p value | 0.426 F | 0.864 | (0.16, 1.12) | (0.19, 0.57) | (0.90–1.08) | (0.49, 0.80) | |||||||||
Bruxism | 1(7.1) | 13(13.5) | 16(13.1) | 31(25.4) | - | 0.030 | 0.837 | - | 0.074 | 1.000 | |||||
p value | 0.691 F | *0.015 | (-0.18, 0.24) | (0.6, 0.88) | |||||||||||
Lip biting | 1(7.1) | 0(0) | 1(0.8) | 13(10.7) | - | - | - | - | |||||||
p value | -- | *0.001 | |||||||||||||
Cheek biting | 0(0) | 1(1) | 1(0.8) | 1(0.8) | - | - | - | - | |||||||
p value | -- | 1.000 F | |||||||||||||
Pencil biting | 0(0) | 0(0) | 1(0.8) | 2(1.6) | - | - | - | - | |||||||
p value | -- | 1.000 F | |||||||||||||
Tongue thrust | 0(0) | 0(0) | 0(0) | 1(0.8) | - | - | - | - | |||||||
p value | -- | -- | |||||||||||||
Digit sucking | 1(7.1) | 6(6.3) | 7(5.7) | 0(0) | - | 0.999 | *<0.001 | - | 0.999 | *<0.001 | |||||
p value | 1.000 F | *0.014 F | (0.96, 1.02) | (0.96, 1.02) | |||||||||||
6–11 | Mouth breathing | 9(20.5) | 23(18) | 32(16.6) | 48(24.9) | 0.869 | *<0.001 | 0.125 | 0.323 | 0.999 | *0.001 | 0.252 | 0.377 | ||
p value | 0.715 | *0.045 | (0.72, 1.02) | (-0.05, 0.30) | (0.95, 1.03) | (0.08, 0.42) | |||||||||
Nail biting | 4(9.1) | 29(22.7) | 35(18.1) | 37(19.2) | -0.087 | 0.701 | 0.064 | 0.615 | -0.999 | 1.000 | 0.120 | 0.723 | |||
p value | *0.049 | 0.794 | (-0.40, 0.22) | (-0.11, 0.24) | (-1.03,-0.95) | (-0.05, 0.29) | |||||||||
Bruxism | 3(6.8) | 28(21.9) | 31(16.1) | 51(26.4) | - | 0.114 | 0.371 | - | 0.216 | 0.448 | |||||
p value | *0.025 | *0.013 | (-0.06, 0.29) | (0.05, 0.39) | |||||||||||
Lip biting | 3(6.8) | 8(6.3) | 12(6.2) | 36(18.7) | 0.690 | *<0.001 | -0.058 | 0.650 | 0.999 | 0.091 | 0.298 | 1.000 | |||
p value | 1.000 F | *<0.001 | (0.46, 0.92) | (-0.23, 0.12) | (0.95, 1.03) | (0.13, 0.47) | |||||||||
Cheek biting | 0(0) | 1(0.8) | 1(0.5) | 5(2.6) | - | - | - | - | |||||||
p value | -- | 0.215 F | |||||||||||||
Pencil biting | 6(13.6) | 8(6.3) | 16(8.3) | 31(16.1) | 0.261 | 0.241 | 0.211 | 0.094 | 0.506 | 0.338 | 0.496 | 0.220 | |||
p value | 0.196 F | *0.020 | (-0.04, 0.56) | (0.04, 0.38) | (0.24, 0.78) | (0.34, 0.65) | |||||||||
Tongue thrust | 1(2.3) | 1(0.8) | 2(1) | 7(3.6) | - | - | - | - | |||||||
p value | 0.447 F | 0.092 | |||||||||||||
Digit sucking | 1(2.3) | 2(1.6) | 3(1.6) | 1(0.5) | - | - | - | - | |||||||
p value | 1.000 F | 0.623 F | |||||||||||||
12–17 | Mouth breathing | 1(10) | 4(20) | 5(16.7) | 1(3.3) | - | 0.509 | 0.133 | - | 0.299 | 0.647 | ||||
p value | 0.640 F | 0.195 F | (0.08, 0.94) | (-0.17, 0.77) | |||||||||||
Nail biting | 3(30) | 1(5) | 4(13.3) | 8(26.7) | 0.612 | 0.272 | - | 0.999 | 0.400 | - | |||||
p value | 0.095 F | 0.197 | (-0.01, 1,23) | (0.92, 1.06) | |||||||||||
Bruxism | 1(10) | 3(15) | 4(13.3) | 5(16.7) | - | - | - | - | |||||||
p value | 1.000 F | 1.000 F | |||||||||||||
Lip biting | 1(10) | 1(5) | 2(6.7) | 9(30) | - | - | - | - | |||||||
p value | 1.000 F | *0.020 | |||||||||||||
Cheek biting | 0(0) | 0(0) | 0(0) | 0(0) | - | - | - | - | |||||||
p value | -- | -- | |||||||||||||
Pencil biting | 0(0) | 3(15) | 3(10) | 3(10) | - | 0.667 | *0.035 | - | 0.481 | 0.200 | |||||
p value | 0.532 F | 1.000 F | (0.30, 1.04) | (0.05, 0.92) | |||||||||||
Tongue thrust | 0(0) | 0(0) | 0(0) | 1(3.3) | - | - | - | - | |||||||
p value | -- | -- | |||||||||||||
Digit sucking | 0(0) | 0(0) | 0(0) | 0(0) | - | - | - | - | |||||||
p value | -- | -- |
Occlusal measures
Age groups | Molar Classification | MZ n (%) | DZ n (%) | p value | M.Births n (%) | Singletons n (%) | p value | Pairwise Concordance (95% Cl) | Tetrachoric correlation (95% Cl) | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
MZ pairs | DZ pairs | MZ pairs | DZ pairs | ||||||||||||
r | p value | r | p value | r | p value | r | p value | ||||||||
2–5 | Flush terminal | 6(42.9) | 56(58.3) | *<0.001 | 74(60.7) | 84(68.9) | *0.044 | 0.558 | 0.203 | 0.829 | *<0.001 | 0.999 | 0.429 | 0.964 | *<0.001 |
(0.04, 1.07) | (0.71, 0.94) | (0.96, 1.02) | (0.91, 1.02) | ||||||||||||
Mesial step | 5(35.7) | 4(4.2) | 9(7.4) | 15(12.3) | 0.730 | 0.062 | -0.043 | 0.769 | 0.999 | 0.143 | 0.538 | 1.000 | |||
(0.31, 1.15) | (-0.25, 0.16) | (0.96, 1.02) | (0.37, 0.71) | ||||||||||||
Distal step | 3(21.4) | 36(37.5) | 39(32) | 23(18.9) | 0.645 | 0.117 | 0.644 | *<0.001 | 0.999 | 0.286 | 0.852 | *<0.001 | |||
(0.16, 1.13) | (0.49, 0.80) | (0.96, 1.02) | (0.74, 0.96) | ||||||||||||
6–11 | Class I | 17(38.6) | 37(28.9) | *<0.001 | 55(28.5) | 80(41.5) | *0.005 | 0.908 | *<0.001 | 0.506 | *<0.001 | 0.999 | *<0.001 | 0.732 | *<0.001 |
(0.78, 1.04) | (0,36, 0.66) | (0.97, 1.02) | (0.61, 0.85) | ||||||||||||
Class II | 15(34.1) | 66(51.6) | 94(48.7) | 66(34.2) | 0.904 | *<0.001 | 0.505 | *<0.001 | 0.999 | *<0.001 | 0.717 | *<0.001 | |||
(0.78, 1.04) | (0.35, 0.66) | (0.97, 1.02) | (0.60, 0.84) | ||||||||||||
Class II Div 1 | 0(0) | 18(14.1) | 21(10.9) | 21(10.9) | - | 0.371 | *0.002 | - | 0.642 | *0.013 | |||||
(0.21, 0.53) | (0.51, 0.78) | ||||||||||||||
Class II Div 2 | 4(9.1) | 1(0.8) | 5(2.6) | 14(7.3) | 0.999 | *<0.001 | - | - | - | ||||||
(0.95, 1.03) | |||||||||||||||
Class III | 8(18.2) | 6(4.7) | 18(9.3) | 12(6.2) | 0.999 | *<0.001 | 0.325 | *0.009 | - | 0.684 | 0.122 | ||||
(0.95, 1.03) | (0.16, 0.49) | (0.56, 0.81) | |||||||||||||
12–17 | Class I | 2(20) | 4(20) | 0.874 | 6(20) | 10(33.3) | 0.228 | 0.999 | *<0.001 | 0.509 | 0.133 | - | 0.299 | 0.300 | |
(0.88, 1.10) | (0.08, 0.94) | (-0.17, 0.77) | |||||||||||||
Class II | 6(60) | 10(50) | 16(53.3) | 15(50) | 0.408 | 0.495 | 0.200 | 0.580 | - | 0.309 | 1.000 | ||||
(-0.34, 1.15) | (-0.29, 0.69) | (-0.16, 0.78) | |||||||||||||
Class II Div 1 | 2(20) | 5(25) | 7(23.3) | 3(10) | - | 0.218 | 0.545 | - | 0.375 | 1.000 | |||||
(-0.27, 0.70) | (-0.08, 0.83) | ||||||||||||||
Class II Div 2 | 0(0) | 1(5) | 1(3.3) | 0(0) | - | - | - | - | |||||||
Class III | 0(0) | 0(0) | 0(0) | 2(6.7) | - | - | - | - |
Age groups | Occlusal traits | MZ n (%) | DZ n (%) | M.births n (%) | Singletons n (%) | Pairwise Concordance (95% Cl) | Tetrachoric correlation (95% Cl) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
MZ pairs | DZ pairs | MZ pairs | DZ pairs | |||||||||||||
r | p value | r | p value | r | p value | r | p value | |||||||||
2–5 | Anterior crossbite | 4(28.6) | 1(1) | 5(4.1) | 5(4.1) | 0.999 | *<0.001 | - | 0.999 | 0.048 | - | |||||
p value | *0.001 F | 1.000 | (0.90, 1.08) | (0.90, 1.08) | ||||||||||||
Posterior crossbite | 1(7.1) | 5(5.2) | 6(4.9) | 1(0.8) | - | -0.044 | 0.767 | -0.044 | 0.767 | 0.576 | 1.000 | |||||
p value | 0.567 F | 0.120 F | (-0.25, 0.16) | (-0.66, 0.58) | (0.41, 0.74) | |||||||||||
Anterior openbite | 0(0) | 3(3.1) | 3(2.5) | 1(0.8) | - | 0.377 | *0.008 | 0.377 | *0.008 | 0.721 | 0.122 | |||||
p value | 1.000 F | 0.622 F | (0.19, 0.57) | (-0.20, 0.95) | (0.58, 0.86) | |||||||||||
Deep bite | 0(0) | 1(0) | 0(0) | 1(0.8) | - | - | - | - | ||||||||
p value | -- | -- | ||||||||||||||
Increased overjet | 1(7.1) | 13(13.5) | 15(12.3) | 6(4.9) | -0.258 | 0.576 | 0.700 | *<0.001 | - | 0.913 | *<0.001 | |||||
p value | 0.691 F | *0.040 | (-0.86, 0.34) | (0.55, 0.85) | (0.83, 0.99) | |||||||||||
6–11 | Anterior crossbite | 5(11.4) | 2(1.6) | 10(5.2) | 19(9.8) | 0.796 | *<0.001 | - | 0.999 | *0.013 | - | |||||
p value | *0.013 F | 0.082 | (0.61, 0.99) | (0.97, 1.01) | ||||||||||||
Posterior crossbite | 4(9.1) | 4(3.1) | 12(6.2) | 1(0.5) | 0.549 | *0.008 | - | 0.999 | 0.136 | - | ||||||
p value | 0.206 F | *0.002 | (0.29, 0.81) | (0.97, 1.01) | ||||||||||||
Anterior openbite | 0(0) | 3(2.3) | 3(1.6) | 3(1.6) | 0.999 | *<0.001 | -0.028 | 0.826 | 0.999 | *0.045 | 0.669 | 1.000 | ||||
p value | 0.571 F | 1.000 F | (0.95, 1.03) | (-0.20, 0.15) | (0.97, 1.01) | (0.54, 0.80) | ||||||||||
Deep bite | 6(13.6) | 8(6.2) | 14(7.2) | 15(7.2) | 0.999 | *<0.001 | 0.488 | *<0.001 | - | 0.813 | *0.005 | |||||
p value | 0.196 F | 0.847 | (0.95, 1.03) | (0.34, 0.64) | (0.71, 0.92) | |||||||||||
Increased overjet | 3(6.8) | 18(14.1) | 24(12.4) | 27(14.0) | 0.796 | *<0.001 | 0.417 | *<0.001 | - | 0.640 | *0.002 | |||||
p value | 0.205 | 0.652 | (0.61, 0.99) | (0,26, 0.58) | (0.51, 0.77) | |||||||||||
12–17 | Anterior crossbite | 0(0) | 0(0) | 0(0) | 5(16.7) | - | - | |||||||||
p value | -- | 0.052 F | ||||||||||||||
Posterior crossbite | 0(0) | 0(0) | 0(0) | 1(3,3) | - | - | ||||||||||
p value | -- | -- | ||||||||||||||
Anterior openbite | 0(0) | 0(0) | 0(0) | 0(0) | - | - | ||||||||||
p value | -- | -- | ||||||||||||||
Deep bite | 0(0) | 1(2) | 1(3.3) | 1(3.3) | - | - | - | - | ||||||||
p value | -- | -- | ||||||||||||||
Increased overjet | 2(20) | 5(25) | 7(23.3) | 7(23.3) | 0.612 | 0.272 | 0.102 | 0.779 | - | 0.181 | 1.000 | |||||
p value | 1.000 F | 1.000 F | (-0.03, 1.26) | (-0.39, 0.60) | (-0.31, 0.67) |