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Abstract
Introduction
In the management of dentofacial deformities, variable movement of the maxilla can be made possible by a Le Fort I osteotomy. Posterior impaction of the maxilla necessary for rotation of the maxillomandibular complex enhances the functions and esthetic results. In cases of posterior impaction of the maxilla, an increase in the figure of the occlusal plane angle and incisor inclination can occur. This study reports the relationship between the amount of posterior impaction and the change in the occlusal plane angle and incisor inclination in a Le Fort I osteotomy by preoperative and postoperative lateral cephalograms.
Materials and Methods
Twenty patients who had undergone orthognathic surgery in Dong-A University Medical Center participated in this study. Lateral cephalometrics, within 3 weeks prior to surgery and 3 days after surgery, were used for analysis. Pre and postoperative measurements of the occlusal plane angle and incisal inclination based on the Frankfort horizontal (FH) plane were performed. X and Y were defined as the amount of vertical change in the upper incisor tip and the amount of vertical change in the upper first molar mesial cup tip through the operation. The amount of final posterior maxillary impaction was determined by subtracting Y from X, which is the difference in vertical height. According to the amount of posterior maxillary impaction, the change in the occlusal plane angle and incisal inclination was measured.
Results
The average posterior maxillary impaction was 2.91 mm and the average change in the occlusal plane angle and incisal inclination was 6.54�after surgery. As a result, each mm of posterior maxillary impaction changed the occlusal plane angle and incisal inclination by 2.25�. Statistically, there was high significance. Two cases were observed: one with the same amount of posterior maxillary impaction performed on both the right and left showing 2.20�, and the other with a different amount of posterior maxillary impaction performed showing 2.35�. In this case, there was no significance difference between the two cases.
Conclusion
Each mm of posterior maxillary impaction changes the occlusal plane angle and incisal inclination by an average of 2.25�. In posterior maxillary impaction, there was no significant difference in the amount of change in the occlusal plane angle and incisal inclination regardless of whether there was an equal amount of posterior maxillary impaction on both sides. This study is expected to help in the presurgical orthodontic preparation and presurgical treatment planning.
References
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Fig. 1.
Anatomic landmark used in this study. (S: sella, N: nasion, Po: porion, Or: orbitale, UM: upper fist molar mesial cusp tip, U1: upper incisor cusp tip)
Fig. 2.
Measuring parameters. (X: vertical change of upper incisor, Y: vertical change of upper first molar, Y-X: amount of posterior Mx. impaction)
Table 1.
Average occlusal plane angle and incisal inclination in presurgical state
| Mean | Range | |
|---|---|---|
| occlusal plane angle | 7.2 | −1.75–12.24 |
| incisal inclination | 122.46 | 114.31–132.7 |
Table 2.
Average amount of posterior impaction and average amount of change of occlusal plane angle, incisal inclination after surgery
| Amount | Mean | Range | SD |
|---|---|---|---|
| PI | 2.91 | 0.26–7.75 | 1.78 |
| OPA, II change | 6.54 | 0.5–16 | 3.77 |
| OPA, II change due to PI | 2.25* | 1.5–3.1 | 0.39 |
Table 3.
Average amount of change of occlusal plane angle, incisal inclination in same posterior impaction and differential posterior impaction
| Mean | SD | N | P value | |
|---|---|---|---|---|
| Same posterior impaction | 2.2 | 0.27 | 10 | 0.393∗ |
| Differential posterior impaction | 2.35 | 0.38 | 10 |
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