Dentofacial changes following treatment with a fixed functional appliance and their three-dimensional effects on the upper airway
, and | Oct 07, 2021
About this article
Article Category: research-article
Published Online: Oct 07, 2021
Page range: 284 - 293
DOI: https://doi.org/10.21307/aoj-2021.031
© 2021 Yousef Abdalla et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.
Figure 1.
Figure 2.
Figure 3.
Stepwise backward linear regression model showing skeletal changes (structural method) with significant effects on changes in airway volume and MCA.
| Coefficient | SE |
|
(95% CI) |
|
|
|
|---|---|---|---|---|---|---|
| Volume change | ||||||
| Intercept | 7093.4 | 594.9 | <0.001 | (5,904.7–8,282.0) | ( |
0.51 |
| Hyoid sagittal change (mm) | 500.4 | 66.4 | <0.001 | (367.3–633.4) | ||
| Pogonion sagittal change (mm) | 615.3 | 146.1 | <0.001 | (323.0–907.6) | ||
| Mandibular forward rotation (o) | 584.4 | 256.9 | 0.027 | (68.2–1,100.5) | ||
| MCA change | ||||||
| Intercept | 102.5 | 16.2 | <0.001 | 70.1–134.8 | ( |
0.35 |
| Hyoid sagittal change | 5.9 | 1.2 | <0.001 | (3.5–8.3) | ||
| Pogonion sagittal change | 7.5 | 2.5 | 0.005 | (2.3–12.5) | ||
| Mandibular forward rotation (o) | 4.4 | 1.67 | 0.011 | (1.0–7.7) | ||
Inclusion and exclusion criteria.
| Inclusion criteria | Exclusion criteria |
|---|---|
| Orthodontic treatment requiring a fixed FA (Hanks Telescoping Herbst, American Orthodontics, Sheboygan, WI) | Previous orthodontic treatment |
| Biting in habitual intercuspal position | Movement artifacts |
| Full unit Angle class II molar relationship pre-treatment and a class I relationship post-treatment | Swallowing during scan acquisition |
| Class II skeletal base (ANB>5 degrees) | |
| A non-extraction orthodontic treatment plan | |
| Pre- and post-treatment CBCT scans with imaging of the cranial base, maxilla, mandible and first four cervical vertebrae and associated airways | |
| Children between 8 and 15 years of age |
Differences between the two groups before treatment.
| FA | Control | |
|---|---|---|
| ANB (degrees) | 6.2 (±1.8) | 3.2 (±2.1)*** |
| Airway volume (mm3) | 10,442.6 (±3,485.8) | 12,169.3 (±4815.3)** |
| Airway MCA (mm2) | 112.8 (±44.7) | 132.5 (±70.5)* |
| Age (years) | 12y, 0m (±1y, 6m) | 12y, 0m (±1y, 5m) |
| Skeletal age (CVMS12/number) | 1 = 9; 2 = 19; 3 = 33; 4 = 11; 5 = 1 | 1 = 9; 2 = 19; 3 = 33; 4 = 11; 5 = 1 |
| Gender | M = 36; F = 37 | M = 36; F = 37 |
| Time between scans | 1y, 11m (±11m) | 1y, 11m (±10m) |
| Mandibular inclination | 33.2 (±6.0) | 34.9 (±6.1) |
Linear mixed effect modeling analysis for the significant T0–T1 differences in pre- and post-treatment cephalometric measurements between FA and control groups (conventional method).
| Angle | Group | Change (o) |
|
(95% CI) |
|---|---|---|---|---|
| Mandible | ||||
| SNB | Control | 0.03 | 0.85 | (‒0.31–0.38) |
| FA effect | +0.95 | <0.001 | (0.46–1.43) | |
| SNPg | Control | 0.35 | 0.04 | (0.02–0.68) |
| FA effect | +0.59 | 0.01 | (0.12–1.05) | |
Cephalometric landmarks19 used to assess FA changes using both the structural and conventional methods (illustrated in Figure 1).
| Landmark | Abbreviation | Definition |
|---|---|---|
| Reference points | ||
| Sella | S | Centre of the sella turcica |
| Nasion | N | Most anterior point of the frontonasal suture |
| A point | A | Most posterior point on the anterior contour of the maxillary alveolar arch |
| B point | B | Most posterior point on the anterior contour of the mandibular alveolar arch |
| Pogonion | pg | Most anterior point on the mid-sagittal mandibular symphysis |
| Gnathion | gn | Most inferior point on the mandibular symphysis |
| Spinal point | sp | Apex of the anterior nasal spine |
| Pterygomaxillary | pm | Intersection between the nasal floor and the posterior contour of the maxilla |
| Basion | ba | Most postero-inferior point on the clivus |
| Articulare | ar | Intersection of external contour of the cranial base and posterior contour of the condyle |
| Infradentale | id | Most anterio-superior point on the lower alveolar margin, |
| Hyoid | hy | Hyoid bone |
| Reference lines | ||
| Chin line | CL | Tangent to the chin through id |
| Upper incisor line | ILs | Axis of the upper central incisor |
| Lower incisor line | ILi | Axis of the lower incisor |
| Mandibular line | ML | Tangent to the lower border of the mandible through gn |
| Nasal line | NL | Line through sp and pm |
| Nasion-sella line | NSL | Line through N and S |
| Ramus line | RL | Tangent to the posterior border of the mandible |
| Conventional method | ||
| Relation of maxilla to cranial base | SNA | The angle of sella-nasion to A point |
| Relation of mandible to cranial base | SNPg | The angle of sella-nasion to Pg |
| Relation of basal part of mandible to the cranial base | SNB | The angle of sella-nasion to B point |
| Sagittal relationship of the jaws | ANB | The angle of A point to nasion to B point |
| Inclination of the Maxilla | NSL/NL | Then angle between the nasion-sella line and the nasal line |
| Mandibular inclination | NSL/ML | Angle between the nasion-sella line and the mandibular line |
| Vertical jaw relationship | NL/ML | Angle between the nasal line and the mandibular line |
Linear mixed effect modeling analysis for the significant differences in skeletal changes over time between FA and control groups determined by the superimposition on stable structures according to Bjork (structural method).11
| Group | Horizontal change (mm) |
|
(95% CI) | Vertical change (mm) |
|
(95% CI) | Total change (mm) |
|
(95% CI) | |
|---|---|---|---|---|---|---|---|---|---|---|
| Maxilla | ||||||||||
| A point | Control | 0.8 | 0.001 | (0.32–1.25) | 1.52 | 0.001 | (0.85–2.19) | 1.67 | 0.001 | (1.16–2.18) |
| FA effect | ‒0.65 | 0.04 | (‒0.02–‒1.30) | +1.04 | 0.03 | (0.11–1.98) | +0.27 | 0.45 | (‒0.43–0.98) | |
| Mandible | ||||||||||
| B point | Control | 0.78 | 0.01 | (0.19–1.36) | 2.94 | <0.001 | (2.25–3.62) | 3.00 | <0.001 | (2.38–3.63) |
| FA effect | +0.95 | 0.02 | (0.14–1.76) | +3.42 | <0.001 | (2.47–4.38) | +3.52 | <0.001 | (2.66–4.39) | |
| Pogonion | Control | 1.45 | <0.001 | (0.82–2.08) | 2.64 | <0.001 | (1.82–3.46) | 3.02 | <0.001 | (2.26–3.78) |
| FA effect | +0.90 | 0.04 | (0.03–1.78) | +2.42 | <0.001 | (1.28–3.56) | +2.62 | <0.001 | (1.57–3.67) | |
| Hyoid | Control | 1.19 | 0.27 | (‒0.94–3.33) | 4.18 | 0.02 | (0.69–7.68) | 4.34 | 0.02 | (3.86–5.39) |
| FA effect | +1.99 | 0.01 | (0.46–3.52) | ‒2.27 | 0.36 | (‒2.61–7.17) | ‒0.63 | 0.39 | (‒2.7–1.74) | |