The purpose of this study was to investigate the horizontal skeletal pattern and dental arch differences between Class III malocclusion patients and normal occlusion patients.
Twenty skeletal Class III malocclusion patients and ten normal occlusion patients were selected and 3D facial CT were taken to analyze the horizontal skeletal differences between the two groups.
In the horizontal comparison of the maxilla, skeletal width and perimeter were significantly smaller in skeletal Class III patients on ANS and A point reference planes. The difference between maxillary width of ANS and A point reference planes showed that there was greater constriction of the first and second premolar in skeletal Class III patients. In the horizontal comparison of the mandible, the widths of the canine and premolar area were significantly larger in skeletal Class III patients on B point reference plane. The differences between width of the upper and lower jaws (comparison of A and B reference planes) were significantly large in the canine and premolar area.
From this study, the characteristics of Class III malocclusion patients were shown through horizontal constriction of the maxilla. But to make clear further detailed characteristics of Class III malocclusion patients, additional studies are necessary.
Reference plane. 1, Maxillary midsagittal plane (Na-ANS-Ba); 2, ANS horizontal plane (A plane passing ANS perpedicular to Maxillary midsagittal plane); 3, A point horizontal plane (A plane passing A point parallel to ANS horizontal plane); 4, B point horizontal plane (B point-Gonion Lt.-Gonion Rt.); 5, antegonion horizontal plane (A plane passing center of gonion parallel to B point horizontal plane).
Maxillary reference plane. 5 reference planes (
Mandibular reference plane. 5 reference planes (
ANS (
B point (
The coordinates in A point reference plane (
The coordinates in B point reference plane (
Maxillary measurements
Measurement | Definition |
---|---|
① #13-#23 | The distance between #13-#23 (ANS, A point) |
② #14-#24 | The distance between #14-#24 (ANS, A point) |
③ #15-#25 | The distance between #15-#25 (ANS, A point) |
④ #16-#26 | The distance between #16-#26 (ANS, A point) |
⑤ #17-#27 | The distance between #17-#27 (ANS, A point) |
⑥ Canine arch length | The distance between (ANS, A point) and #13-#23 plane |
⑦ Premolar arch length | The distance between (ANS, A point) and #14-#24 plane |
⑧ Molar arch length | The distance between (ANS, A point) and #16-#26 plane |
⑨ Oblique canine height Lt. | The distance between (ANS, A point) -#23 |
⑩ Oblique canine height Rt. | The distance between (ANS, A point) -#13 |
⑪ Oblique molar height Lt. | The distance between (ANS, A point) -#26 |
⑫ Oblique molar height Rt. | The distance between (ANS, A point) -#16 |
Mandibular measurements
Measurement | Definition |
---|---|
① #33-#43 | The distance between #33-#43 (B point, Antegonion) |
② #34-#44 | The distance between #34-#44 (B point, Antegonion) |
③ #35-#45 | The distance between #35-#45 (B point, Antegonion) |
④ #36-#46 | The distance between #36-#46 (B point, Antegonion) |
⑤ #37-#47 | The distance between #37-#47 (B point, Antegonion) |
⑥ Canine arch length | The distance between B point and #13-#23 plane |
⑦ Premolar arch length | The distance between B point and #14-#24 plane |
⑧ Molar arch length | The distance between B point and #16-#26 plane |
⑨ #36 Width | The distance between #36 (B point) -#36 lingual point |
⑩ #46 Width | The distance between #46 (B point) -#46 lingual point |
⑪ #37 Width | The distance between #37 (B point) -#37 lingual point |
⑫ #47 Width | The distance between #47 (B point) -#47 lingual point |
⑬ Oblique canine height Lt. | The distance between B point - #33 |
⑭ Oblique canine height Rt. | The distance between B point - #43 |
⑮ Oblique molar height Lt. | The distance between B point - #36 |
⑯ Oblique molar height Rt. | The distance between B point - #46 |
⑰ Body length Lt. | The distance between B point - Go Lt. |
⑱ Body length Rt. | The distance between B point - Go Rt. |
Transverse comparison of basal bone in ANS horizontal plane
Measurement | Group 1 | Group 2 | Significance | ||
---|---|---|---|---|---|
Mean | SD | Mean | SD | ||
#13-#23 | 14.94 | 7.43 | 25.07 | 7.94 | † |
#14-#24 | 33.69 | 6.80 | 42.32 | 7.52 | † |
#15-#25 | 51.30 | 7.03 | 66.23 | 9.37 | ‡ |
#16-#26 | 70.12 | 7.36 | 74.96 | 3.29 | NS |
#17-#27 | 54.31 | 4.36 | 58.15 | 5.24 | ∗ |
Canine arch length | 7.69 | 2.61 | 9.27 | 2.57 | NS |
Premolar arch length | 12.01 | 3.24 | 13.75 | 2.62 | NS |
Molar arch length | 25.80 | 2.73 | 28.51 | 3.09 | ∗ |
OCH Lt | 10.84 | 4.57 | 15.52 | 4.35 | ∗ |
OCH Rt | 10.85 | 4.26 | 15.92 | 4.38 | † |
OMH Lt | 39.09 | 3.09 | 47.25 | 2.03 | ‡ |
OMH Rt | 44.41 | 3.81 | 47.11 | 2.47 | NS |
Mann-Whitney U test, NS means non-significance;
Transverse comparison of basal bone in A point horizontal plane
Measurement | Group 1 | Group 2 | Significance | ||
---|---|---|---|---|---|
Mean | SD | Mean | SD | ||
#13-#23 | 22.98 | 9.08 | 30.13 | 7.85 | NS |
#14-#24 | 38.56 | 3.96 | 42.65 | 5.39 | ∗ |
#15-#25 | 49.33 | 4.32 | 56.88 | 5.29 | ‡ |
#16-#26 | 62.62 | 4.80 | 67.27 | 2.09 | ∗ |
#17-#27 | 64.56 | 5.47 | 68.00 | 2.19 | NS |
Canine arch length | 5.36 | 1.94 | 7.15 | 1.22 | ∗ |
Premolar arch length | 9.84 | 2.18 | 11.75 | 1.57 | ∗ |
Molar arch length | 23.43 | 3.31 | 26.11 | 2.20 | ∗ |
OCH Lt | 14.29 | 9.24 | 16.58 | 3.85 | NS |
OCH Rt | 13.40 | 4.60 | 17.45 | 4.65 | ∗ |
OMH Lt | 38.96 | 2.83 | 42.61 | 1.59 | † |
OMH Rt | 39.73 | 3.38 | 42.68 | 1.59 | ∗ |
Mann-Whitney U test, NS means non-significance;
Basal bone width difference between ANS, A point horizontal plane (bone width on ANS plane-bone width on A point plane)
Difference of basal bone width | Group 1 | Group 2 | Significance | ||
---|---|---|---|---|---|
Mean | SD | Mean | SD | ||
Canine area | -8.04 | 8.36 | -5.06 | 3.48 | NS |
1st premolar | -4.87 | 5.11 | -0.33 | 4.37 | ∗ |
2nd premolar | 1.96 | 4.78 | 9.35 | 5.40 | † |
1st molar | 7.50 | 3.56 | 7.69 | 2.82 | NS |
2nd molar | -10.3 | 5.92 | -9.85 | 4.67 | NS |
Significance determined by Mann-Whitney U test, NS means non-significance;
Transverse comparison in B point horizontal plane
Measurement | Group 1 | Group 2 | Significance | ||
---|---|---|---|---|---|
Mean | SD | Mean | SD | ||
#33-#43 | 32.13 | 7.11 | 24.96 | 7.36 | ∗ |
#34-#44 | 41.62 | 3.92 | 38.28 | 4.56 | NS |
#35-#45 | 52.52 | 3.32 | 50.97 | 4.30 | NS |
#36-#46 | 66.33 | 4.35 | 66.56 | 7.03 | NS |
#37-#47 | 81.91 | 4.83 | 83.61 | 5.92 | NS |
Canine arch length | 6.31 | 2.92 | 3.27 | 2.18 | † |
Premolar arch length | 10.70 | 2.93 | 7.49 | 2.03 | † |
Molar arch length | 25.88 | 2.68 | 26.03 | 10.60 | ∗ |
#36 width | 15.63 | 2.84 | 18.50 | 4.25 | ∗ |
#46 width | 19.46 | 4.70 | 21.40 | 3.21 | NS |
#37 width | 15.41 | 2.49 | 17.49 | 4.69 | NS |
#47 width | 17.96 | 2.57 | 21.04 | 4.10 | ∗ |
Oblique canine height Lt. | 17.04 | 4.22 | 12.65 | 4.01 | † |
Oblique canine height Rt. | 17.53 | 4.28 | 13.29 | 4.24 | ∗ |
Oblique molar height Lt. | 42.13 | 3.43 | 40.57 | 3.53 | NS |
Oblique molar height Rt. | 42.23 | 2.98 | 40.12 | 3.83 | NS |
Body length Lt. | 87.79 | 7.04 | 86.99 | 4.35 | NS |
Body length Rt. | 87.68 | 8.69 | 86.59 | 2.61 | NS |
Significance determined by Mann-Whitney U test, NS means non-significance;
Transverse comparison in antegonion horizontal plane
Measurement | Group 1 | Group 2 | Significance | ||
---|---|---|---|---|---|
Mean | SD | Mean | SD | ||
#33-#43 | 35.92 | 7.30 | 26.49 | 9.28 | ∗ |
#34-#44 | 45.77 | 4.98 | 40.91 | 5.96 | NS |
#35-#45 | 57.81 | 4.68 | 54.72 | 5.80 | NS |
#36-#46 | 71.69 | 4.16 | 71.09 | 6.16 | NS |
#37-#47 | 83.48 | 3.81 | 85.92 | 4.82 | NS |
Significance determined by Mann-Whitney U test, NS means non-significance;
Basal bone width difference between A point, B point horizontal plane (Bone width on A point plane-bone width on B point plane)
Difference of basal bone width | Group 1 | Group 2 | Significance | ||
---|---|---|---|---|---|
Mean | SD | Mean | SD | ||
Canine | -9.14 | 9.24 | 5.17 | 12.88 | ∗ |
1st premolar | -3.06 | 3.59 | 4.38 | 6.47 | † |
2nd premolar | -3.18 | 4.31 | 5.91 | 3.78 | † |
1st molar | -3.71 | 5.60 | 0.72 | 5.61 | NS |
2nd molar | -17.35 | 4.84 | -15.61 | 5.26 | NS |
Significance determined by Mann-Whitney U test, NS means non-significance;