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Three-dimensional skeletal and dentoalveolar sagittal and vertical changes associated with cantilever Herbst appliance in prepubertal patients with Class II malocclusion

Three-dimensional skeletal and dentoalveolar sagittal and vertical changes associated with cantilever Herbst appliance in prepubertal patients with Class II malocclusion



American Journal of Orthodontics and Dentofacial Orthopedics, 2022-05-01, Volume 161, Issue 5, Pages 638-651.e1, Copyright © 2021 American Association of Orthodontists


Introduction

This study aimed to assess sagittal and vertical skeletal and dentoalveolar changes through the use of 3-dimensional imaging in prepubertal Class II malocclusion patients treated with a cantilever Herbst appliance (HA). Condyle-glenoid fossa positional changes were also quantified.

Methods

This retrospective cohort study assessed 22 children (11.2 years ± 1.2) consecutively treated with a cantilever HA for 12 months and 11 untreated children (aged 9.3 ± 0.30 years) that served as controls. Cone-beam computed tomography was performed at baseline (T1) and at the end of the observation period (T2). Movements in the regions of interest were measured as linear displacements from cone-beam computed tomography images through algebraic calculations. A Student t test for independent samples was used for group equivalence testing at T1, and the treatment differences between T2 and T1 were evaluated by 2 analyses of covariance, one considering the expected growth unit as a covariate and the other with an annualized factor.

Results

The largest dental movement was a mesial movement of mandibular molars (3.70 mm), whereas the largest skeletal changes consisted of a larger relative length of the mandible (difference of 1.2 mm) in the HA group than in the control group.

Conclusions

Within the study limitations (retrospective cohort, historical control group, and sample size), 3-dimensional imaging suggests that HA corrected Class II malocclusion in a predominantly prepubertal sample through more dental than skeletal changes. The changes were more significant in the sagittal than in the vertical direction. In addition, relative stability in the condyle-fossa relationship was noted.

Highlights

  • Changes were assessed using a 3D landmark-based superimposition model.

  • Largest dental movement was the mesial movement of mandibular molars (3.70 mm).

  • Largest skeletal changes were an increased mandibular length (1.2 mm).

  • Herbst appliance corrected Class II malocclusion through more dental than skeletal changes.

  • The changes were more significant in the sagittal than in the vertical dimension.

The Herbst appliance (HA) is a fixed functional orthopedic appliance used to correct Class II malocclusion associated with mandibular deficiency. It does not depend on patient compliance, and treatment length ranges from 6 to 18 months. In the dentoalveolar region, maxillary teeth tend to move distally, whereas mandibular teeth tend to move mesially. Skeletal changes have also been observed. These changes reflect a posterior force vector on the maxillary dentition and an anterior force vector on the mandibular dentition.

The majority of Herbst studies have been performed using 2-dimensional (2D) cephalometric imaging, an approach that cannot adequately assess the complex interactions of 3-dimensional (3D) changes that occur with craniofacial growth and orthopedic treatment. In a recently published systematic review, it was recommended that the portrayed skeletal and dental changes attributed to the HA be interpreted with caution because of the low quality of evidence and publication bias. The limitations of this analysis were the small number of high-quality studies and uncontrolled consideration of cephalometric magnifications.

Currently, 3D imaging is widely accessible and able to quantify skeletal and dental measurements more accurately because distortions and superimpositions are eliminated. Many studies have attempted to develop reliable methods for assessing data from different time points using 3D imaging. Current methods rely on the voxel-based superimposition of the skull base or landmark-based superimpositions. , ,

Previous 3D studies about the HA have had some limitations, including small sample sizes, control groups treated with fixed appliances, and failure to report the changes in the 3 different spatial planes. This retrospective study is the first to assess 3D skeletal and dentoalveolar changes distinctly in the sagittal and vertical planes produced by a cantilever HA in Class II malocclusion, mostly in prepubertal patients using a landmark-based superimposition 3D method. Changes were compared with an untreated Class II malocclusion group. Condyle-glenoid fossa positional changes were also quantified.

Material and methods

This retrospective study was approved by the local Research Ethics Committee of Positivo University (process no. 2.207.562). The sample consisted of cone-beam computed tomography (CBCT) images from girls aged 9-12 years and boys aged 10-13 years consecutively treated with cantilever HA at the outpatient dental clinic affiliated with a university ( Table I ). As of 2010, the University’s clinic started using CBCT imaging to diagnose patients with significant skeletal discrepancies. All available patients with HA (n = 22) up to 2016 that met the inclusion criteria were considered.

Table I
Sample characteristics
Characteristics Herbst Control
n 22 11
Boys 12 8
Girls 10 3
Initial age, y 11.2 ± 1.2 9.3 ± 0.30
Time between CBCT scans, y 1.5 ± 0.4 1.9 ± 0.5
CVM stage 1 4 1
CVM stage 2 9 8
CVM stage 3 3 2
CVM stage 4 4 0
CVM stage 5 2 0

The following inclusion criteria were used: Class II molar relationship with at least half cusp on both sides, pronounced overjet (>4 mm), convex facial profile suggestive of mandibular retrognathia, and an improved facial profile when the mandible was positioned forward. Patients subjected to previous orthodontic treatment, tooth agenesis, and history of abnormal bone growth were excluded from the study.

The HA group included 22 patients (12 boys and 10 girls) with a mean age of 11.2 ± 1.23 years at baseline, treated with a cantilever HA ( Fig 1 ). Seven patients required maxillary expansion with a Hyrax appliance for a mean period of 4 months. This appliance was removed before the placement of the HA. The PMA telescopic system (3M Unitek Abzil, São José do Rio Preto, São Paulo, Brazil) was used. All appliances contained Rollo bands (American Orthodontics, Sheboygan, Wis) on the 4 first molars and a cantilever on the mandibular molars. A transpalatal arch was used for the maxillary molars, and a lingual arch with occlusal rests on the deciduous second molars or the mandibular second premolars attached to the mandibular first molars. A construction bite registration was obtained for edge-to-edge incisor relationship, with a mean mandibular advancement of 7.2 mm (max: 10 mm, min: 4 mm) in a single step. The appliance was worn for at least 12 months.

HA treatment of a prepubertal patient. (A) pretreatment; (B) immediately after HA placement; (C) HA removed after 12 months of treatment. (D) T1 − T2 CBCT superimposition on skull base: brown, initial; green , final.
Fig 1
HA treatment of a prepubertal patient. (A) pretreatment; (B) immediately after HA placement; (C) HA removed after 12 months of treatment. (D) T1 − T2 CBCT superimposition on skull base: brown, initial; green , final.

The control group (CG) included 11 patients (8 boys and 3 girls) with a mean age of 9.3 ± 0.30 years at baseline, with the same characteristics as those described for the HA group. These patients underwent an examination at baseline and, for different reasons—especially lack of availability of their parents or legal guardians to bring them to the dental appointments, in addition to financial hardships associated with treatment costs—could not initiate orthodontic treatment. After approximately 18 months, new contact was made with the patients, and they underwent a new examination (including orthodontic records) and were referred to treatment.

CBCT imaging was considered appropriate by the teaching institution for patients with Class II malocclusion with significant skeletal discrepancies.

The patients were grouped on the basis of their skeletal maturation stage, determined by the cervical vertebral maturation (CVM) method proposed by McNamara and Franchi ( Table I ).

All patients underwent a CBCT scan examination at baseline (T1) and the end of the observation period or up to 7 days after Herbst treatment (T2). The time between CBCT scans in the HA group was, on average, 1.5 years with a standard deviation of 0.4 years. This long period is due to a delay of approximately 4 months in initiating treatment, including the time for maxillary expansion. The average time in the CG was 1.9 years, with a standard deviation of 0.5 years.

CBCT scans were performed with standard head positioning (Frankfurt horizontal plane) at these settings: 120 kVp; 8 mA; 0.3-mm voxel size; scan time, 17.8 seconds; field of view of 170 mm × 170 mm; and patient in maximum intercuspation. An i-CAT (model 9140; Imaging Sciences International, Hatfield, Pa) was used. The CBCT images were exported as digital imaging and communication in medicine files.

CBCT images were analyzed using Avizo software (version 8.1; Mercury Computer Systems, Inc, Berlin, Germany). Landmarks were located on the sagittal plane and positioned on the axial and coronal planes 3 times by a single calibrated examiner (K.L.S.). Spherical digital markers (0.5 mm) were placed to determine the center of each point. Supplementary Figure and Table II show the 3D images and the definitions of the reference points and landmarks.

Table II
Definitions of distances between anatomic structures
Dentoalveolar measurements Skeletal measurements Temporomandibular joint measurements
ANTEROPOSTERIOR MEASUREMENTS
ELSA/PC16 Maxillary right first molar at the center of the largest cross-sectional PC area ELSA/A Distance between ELSA and A point ELSA/SRC Superior right condyle
ELSA/PC26 Maxillary left first molar at the center of the largest cross-sectional PC area ELSA/B Distance between ELSA and B-point ELSA/SLC Superior left condyle
ELSA/PC36 Mandibular left first molar at the center of the largest cross-sectional PC area ELSA/RMF Distance between ELSA and right mental foramen ELSA/PRC PRC
ELSA/PC46 Mandibular right first molar at the center of the largest cross-sectional PC area ELSA/LMF Distance between ELSA and left mental foramen ELSA/PLC PLC
ELSA/IS11 Incisal edge of maxillary right central incisor ELSA/ANS Distance between ELSA and ANS ELSA/SRGF Superior right glenoid fossa
ELSA/IS21 Incisal edge of maxillary left central incisor ELSA/PNS Distance between ELSA and posterior nasal spine ELSA/SLGF Superior left glenoid fossa
ELSA / II 31 Incisal edge of mandibular left central incisor ELSA/Pog Distance between ELSA and pogonion ELSA/PRGF Posterior right glenoid fossa
ELSA/II 41 Incisal edge of mandibular right central incisor ELSA/GoR Distance between ELSA and right gonion ELSA/PLGF Posterior left glenoid fossa
ELSA/MBA16 Mesial buccal root apex of maxillary right first molar ELSA/GoL Distance between ELSA and left gonion ELSA/ARGF Anterior right glenoid fossa
ELSA/MBA26 Mesial buccal root apex of maxillary left first molar PRC/A Distance between posterior right condyle and A point ELSA/ALGF Anterior left glenoid fossa
ELSA / MA36 Mesial root apex of mandibular left first molar PLC/A Distance between posterior left condyle and A point
ELSA / MA46 Mesial root apex of mandibular right first molar PRC/Pog Distance between PRC and Pog
ELSA/A11 Root apex of maxillary right central incisor PLC/Pog Distance between PLC and Pog
ELSA/A21 Root apex of maxillary left central incisor
ELSA/A31 Root apex of mandibular left central incisor
ELSA/A41 Root apex of mandibular right central incisor
VERTICAL MEASUREMENTS
IOF/PC16 Distance between superior most aspect of the right IOF outer border and maxillary right first molar at the center of PC ANS/RMF Distance between ANS and right mental foramen
IOF/PC26 Distance between the most superior aspect of the left IOF outer border and maxillary left first molar at the center of PC ANS/LMF Distance between ANS and left mental foramen
MF/PC46 Distance between right mental foramen and mandibular right first molar at the center of PC
MF/PC36 Distance between left mental foramen and mandibular left first molar at the center of PC

The methodology employed in this study consisted of 4 steps: identification of landmarks, coordinate system transformation, a superimposition using optimization calculations, and measurement of displacement of the assessed structures.

First, reference points at the skull base were used to establish the coordinate system and plane orientation. The right and left external auditory canals, right and left foramina ovalia, foramen magnum, and a point equidistant from the points at the center of each foramen spinosum (ELSA ), were identified.

Later, a coordinate system transformation was performed, subtracting the vector that describes the distance between ELSA and the original position (0, 0, 0) and repositioning all the other anatomic structures.

After that, an optimization problem had to be solved for the CBCT images taken at baseline and at the end of treatment to be superimposed on the Cartesian system. The relative distance and the relationship of angles between the landmarks were calculated on each image, and then an algorithm was developed by using linear algebraic equations for the necessary corrections.

Finally, the face was marked to indicate the skeletal and dental changes and the position of the condyle and mandibular fossa. The total variation observed in the treatment period was calculated by the difference between the distances measured in different periods (T2 − T1). Distance (d) in millimeters was determined by the following equation:






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x


1





x


2



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y


1





y


2



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(



z


1





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The anatomic distances used in the present study are described in Table II .

Statistical analysis

The normality of the data was assessed by the Kolmogorov-Smirnov test. P <0.05 was considered statistically significant. Data were analyzed by SPSS software (version 20.0; IBM, Armonk, NY).

A Student t test for independent samples was used to compare the HA and CG with baseline (T1) values. Because of the difference in time between CBCTs in both groups, the sample had to be adjusted for the final assessment considering differences in expected growth (T2 − T1). Therefore, 2 statistical approaches were used: (1) analysis of covariance with the expected growth unit (EGU) factor. EGU corresponds to an individualized estimate of growth intensity expected to occur in orthodontically untreated patients of the same sex and age at a specific time interval. (2) Analysis of covariance with changes in annualized measurements to control the time difference between radiographs.

Based on the repeated measurements in 3 different periods by the same evaluator, the intraclass correlation coefficient (ICC) was then estimated. The images were remeasured 15 days after the first measurements. The third evaluation was carried out 30 days after the second one. All data from both groups (HA and CG) and baseline measurements for the 3 coordinates of each point (x, y, and z) were used. Dahlberg formula was used to calculate the random error.

Results

For the precision of landmarks, with few exceptions, ICC values were very close to 100%, indicating good reliability. Overall, the ICCs of the landmarks were greater than 0.962, 0.959, and 0.987 on the x-, y-, and z-axes, respectively. The poorest ICC on the x- and y-axes was for B-point, measuring 0.962 and 0.959, respectively. The poorest ICC on the z-axis was for the right infraorbital foramen, measuring 0.987. The random error of most landmarks was <1 mm. The greatest error on the x-axis was for posterior right condyle, measuring 1.03 mm. The greatest error on the y-axis was for root apex of right lower central incisor, measuring 1.24 mm. The greatest error on the z-axis was for B-point, measuring 1.11 mm.

The descriptive statistics of dentoalveolar changes summarized in Table III suggest that, at baseline, the maxillary and mandibular molars were more anteriorly positioned in the HA group than in the CG, with a statistically significant difference for the crowns and roots. The maxillary incisors were more labially positioned, with a statistically significant difference for the crowns of maxillary and mandibular central incisors. The mandibular incisors were in relatively similar positions. Therefore, one can observe that, at baseline, the Class II malocclusion characteristics were more pronounced in the HA group than in the CG because the mean distance between the maxillary and mandibular molars was 5 mm vs 4 mm, whereas overjet had a difference of 7 mm vs 4 mm, respectively, indicating a more severe Class II malocclusion in HA than in the CG.

Table III
Dentoalveolar measurements at T1 and the difference in displacements (T2 − T1)
Measurements Period CG HA P
Mean SD Mean SD
Anteroposterior measurements
ELSA/PC16 T1 54.40 2.11 57.14 3.98 0.015
T2 − T1 3.12 0.80 0.29 2.40 0.001
T2 − T1 1.66 0.36 0.10 1.68 0.008
ELSA/MBA16 T1 54.97 2.10 57.43 3.54 0.042
T2 − T1 2.24 1.28 1.17 2.39 0.278
T2 − T1 1.15 0.59 0.73 1.58 0.633
ELSA/PC26 T1 54.3 1.7 57.0 4.2 0.015
T2 − T1 2.7 1.0 0.41 3.08 0.035
T2 − T1 1.44 0.46 0.14 2.02 0.073
ELSA/MBA26 T1 55.17 1.98 57.24 3.78 0.048
T2 − T1 2.74 1.75 1.35 2.42 0.165
T2 − T1 1.48 1.12 0.89 1.53 0.352
ELSA/PC36 T1 58.5 1.6 62.6 4.4 0.001
T2 − T1 3.72 1.35 5.10 2.52 0.060
T2 − T1 2.01 0.75 3.59 1.61 0.001
ELSA/MA36 T1 67.15 2.27 71.57 4.55 0.001
T2 − T1 4.12 1.24 4.77 3.15 0.292
T2 − T1 2.29 0.89 3.29 1.86 0.033
ELSA/PC46 T1 58.4 2.26 62.9 4.23 0.001
T2 − T1 4.03 0.90 5.26 2.14 0.060
T2 − T1 2.20 0.58 3.82 1.79 0.002
ELSA/MA46 T1 67.48 2.63 71.79 4.42 0.006
T2 − T1 4.41 1.31 4.69 2.46 0.614
T2 − T1 2.40 0.75 3.39 1.93 0.040
ELSA/IS11 T1 82.61 3.49 86.68 4.71 0.017
T2 − T1 3.64 1.91 1.13 2.12 0.031
T2 − T1 2.03 1.30 0.75 1.46 0.191
ELSA/A11 T1 67.43 2.40 70.10 4.19 0.060
T2 − T1 3.29 1.29 1.14 1.92 0.008
T2 − T1 1.76 0.71 0.80 1.36 0.089
ELSA/IS21 T1 82.94 2.64 86.60 5.03 0.010
T2 − T1 3.26 0.89 1.30 2.17 0.062
T2 − T1 1.79 0.65 0.86 1.50 0.350
ELSA/A21 T1 67.56 2.32 69.87 4.42 0.058
T2 − T1 2.89 0.98 1.30 1.81 0.027
T2 − T1 1.54 0.53 0.93 1.29 0.256
ELSA/II31 T1 78.15 3.04 79.1 4.44 0.531
T2 − T1 3.25 0.93 5.22 2.28 0.010
T2 − T1 1.78 0.60 3.68 1.54 0.001
ELSA/A31 T1 79.81 2.34 81.72 4.41 0.115
T2 − T1 3.57 1.28 4.06 1.93 0.364
T2 − T1 1.95 0.83 2.91 1.46 0.031
ELSA/II 41 T1 78.03 3.06 79.09 4.47 0.485
T2 − T1 3.30 0.86 5.42 2.37 0.007
T2 − T1 1.81 0.59 3.80 1.57 0.001
ELSA/A41 T1 79.87 2.06 81.60 4.41 0.136
T2 − T1 3.53 1.12 4.08 2.25 0.358
T2 − T1 1.92 0.71 2.93 1.64 0.034
Vertical measurements
IOF/PC16 T1 29.47 1.46 30.73 2.67 0.156
T2 − T1 1.54 0.91 1.57 1.20 0.947
T2 − T1 0.81 0.46 1.05 0.81 0.355
IOF/PC26 T1 29.82 1.39 30.98 2.78 0.120
T2 − T1 2.22 2.04 1.63 1.20 0.235
T2 − T1 1.28 1.34 1.11 0.77 0.666
MF/PC36 T1 21.37 1.71 20.20 1.95 0.104
T2 − T1 −0.01 0.95 −1.56 1.90 0.001
T2 − T1 0.01 0.54 −1.08 1.04 0.001
MF/PC46 T1 21.34 1.39 19.66 2.21 0.029
T2 − T1 −0.43 0.65 −1.15 0.93 0.019
T2 − T1 −0.24 0.38 −0.88 0.78 0.018

Student t test for independent samples, P <0.05.

Comparison of groups in relation to the difference between T1 and T2, including EGU and T1 evaluation as covariates.

Comparison of groups regarding the difference between T1 and T2 considering annualization and including T1 assessment as a covariate.

After treatment, the anterior movement of the crown of maxillary right and left first molars was more limited, with a mean difference of 1.56 mm and 1.30 mm, respectively, compared with the annualized average movement. The mean anterior displacement of the maxillary molars in the HA group was 0.12 mm vs 1.57 mm in the CG.

The mandibular molars in the CG showed a mean anterior movement of 2.01 mm for the left first molar and 2.20 mm for the right first molar. In contrast, the HA group showed a larger anterior movement (3.59 mm and 3.82 mm, respectively). The mean anterior displacement of the mandibular molars, assessed by the ELSA/pulp chamber [PC]36 and ELSA/PC46 measurements in the HA group, was 3.70 mm vs 2.10 mm in the CG.

At T2 − T1, the anterior movement of maxillary incisors was restricted in patients wearing HA. The mandibular right and left central incisors in the HA group revealed the anterior crown movement of approximately 2.0 mm when compared with the CG, with statistically significant differences. The apices of teeth moved 1.93 mm in the CG and 2.92 mm in the HA group, also with statistically significant differences ( Fig 2 ).

Results for anteroposterior and vertical dentoalveolar measurements. Image representative of the mean (right and left) dentoalveolar displacements, using the annualized mean, in CG (A) and HA group (B) .
Fig 2
Results for anteroposterior and vertical dentoalveolar measurements. Image representative of the mean (right and left) dentoalveolar displacements, using the annualized mean, in CG (A) and HA group (B) .

In the vertical measurements (infraorbital foramina [IOF]/PC16 and IOF/PC26), the maxillary molars intruded an average of 1.0 mm in both groups with a difference of 0.04 mm in the annualized statistics and 0.28 mm in the EGU statistics, without significant difference.

Regarding vertical measurements, the CG had a mean extrusion of mandibular molars of approximately 0.12 mm (FM/PC36 of 0.01 mm and FM/PC46 of −0.24 mm), compared with extrusion of 0.98 mm (FM/PC36 of −1.08 mm and FM/PC46 of −0.88 mm) in the HA group. There were statistically significant differences in both measurements ( Fig 2 ).

The statistical analysis of the maxillary and mandibular measurements ( Table IV ) suggests that the maxilla was in a similar position at baseline in both groups, whereas the mandible was anteriorly positioned in the HA group, with a difference of approximately 2.75 mm (85.98 mm for the HA group and 83.23 for the CG) at point B and 3.34 mm at the pogonion (Pog). In addition to these 2 points, the distance of ELSA from the right and left mental foramina (RMF/LMF) and the right and left gonion revealed significant differences at T1. At T2 − T1, these parameters showed no statistical difference, but there was some constraint on the maxilla in the HA group because the anterior movement from point A was significantly smaller than the CG (0.51 mm and 1.23 mm, respectively).

Table IV
Skeletal measurements at T1 and the difference in displacements (T2 − T1)
Measurements Period CG HA P
Mean SD Mean SD
Anteroposterior measurements
ELSA/A T1 74.12 1.82 75.49 3.55 0.154
T2-T1 2.31 0.82 0.82 1.91 0.047
T2-T1 1.23 0.39 0.51 1.30 0.183
ELSA/B T1 83.23 2.29 85.98 4.76 0.032
T2-T1 4.10 1.54 4.73 2.71 0.387
T2-T1 2.25 1.03 3.34 1.94 0.063
ELSA/RMF T1 78.12 2.26 80.99 4.37 0.018
T2-T1 3.63 0.69 4.05 2.40 0.497
T2-T1 1.98 0.49 2.89 1.75 0.057
ELSA/LMF T1 78.22 1.81 81.29 4.31 0.008
T2-T1 3.82 0.73 3.74 1.93 0.940
T2-T1 2.08 0.53 2.63 1.36 0.128
ELSA/POG T1 91.30 2.57 94.67 5.07 0.016
T2-T1 3.87 1.05 4.29 2.62 0.471
T2-T1 2.08 0.57 3.06 1.90 0.056
ELSA/GoR T1 60.58 3.43 63.64 4.31 0.049
T2-T1 3.08 1.61 3.29 1.84 0.642
T2-T1 1.75 0.96 2.40 1.52 0.124
ELSA/GoL T1 60.93 20.86 64.28 4.31 0.026
T2-T1 2.59 1.50 2.61 2.56 0.825
T2-T1 1.50 0.88 1.95 2.07 0.243
ELSA/ANS T1 75.01 1.71 76.38 3.66 0.155
T2-T1 1.63 0.81 1.20 2.73 0.863
T2-T1 0.85 0.36 0.79 1.86 0.500
ELSA/PNS T1 32.60 1.63 33.27 2.45 0.419
T2-T1 0.55 0.67 0.29 1.64 0.862
T2-T1 0.32 0.41 0.14 1.16 0.887
PRC/A T1 88.53 3.13 90.91 3.89 0.089
T2-T1 2.31 1.59 1.42 1.89 0.544
T2-T1 1.23 0.82 0.88 1.47 0.977
PLC/A T1 89.31 3.60 91.14 4.07 0.217
T2-T1 2.12 1.50 1.31 1.81 0.399
T2-T1 1.11 0.72 0.89 1.23 0.939
PRC/POG T1 104.03 3.45 107.56 4.94 0.042
T2-T1 3.72 1.11 4.65 2.23 0.112
T2-T1 1.97 0.51 3.25 1.44 0.003
PLC/POG T1 104.20 3.95 107.13 4.66 0.084
T2-T1 3.60 0.80 4.32 2.28 0.159
T2-T1 1.93 0.42 3.03 1.49 0.007
Vertical measurements
ANS/RMF T1 50.25 2.10 51.69 4.40 0.213
T2-T1 1.29 1.07 1.49 1.92 0.869
T2-T1 0.69 0.58 1.11 1.60 0.436
ANS/LMF T1 49.92 2.53 51.43 4.03 0.266
T2-T1 1.55 1.47 1.95 1.76 0.621
T2-T1 0.83 0.80 1.48 1.77 0.248

Student t test for independent samples, P <0.05.

Comparison of groups in relation to the difference between T1 and T2, including EGU and T1 evaluation as covariates.

Comparison of groups regarding the difference between T1 and T2 considering annualization and including T1 assessment as a covariate.

Mandibular length, measured by posterior right condyle (PRC)/Pog and posterior left condyle (PLC)/Pog, had a larger significant increase, with a mean difference of approximately 1.20 mm (PRC/Pog: 1.97 mm and 3.25 mm; PLC/Pog: 1.93 mm and 3.03 mm in the CG and HA group, respectively, for annualized changes), with larger, albeit nonsignificant, anterior movement from point B in the HA group ( Fig 3 ).

Results for anteroposterior and vertical skeletal measurements. Image representative of the mean (right and left) skeletal displacements, using the annualized mean, in CG (A) and HA group (B) .
Fig 3
Results for anteroposterior and vertical skeletal measurements. Image representative of the mean (right and left) skeletal displacements, using the annualized mean, in CG (A) and HA group (B) .

The measurement from the mental foramen to the anterior nasal spine (ANS/RMF and ANS/LMF) analyzed the anteroinferior facial height. The mean difference was 1.29 mm in the HA group and 0.76 mm in the CG, with an average difference of 0.5 mm in the annualized statistics, with no significant difference ( Fig 3 ).

The condyle-mandibular fossa relationship is shown in Table V . Descriptive statistics showed no statistically significant difference between the groups at T1 and T2 − T1, considering EGU or annualized changes.

Table V
Temporomandibular joint measurements at T1 and the difference in displacements (T2 − T1)
Measurements Period CG HA P
Mean SD Mean SD
Anteroposterior measurements
ELSA/SRC T1 44.57 2.23 45.04 2.98 0.644
T2 − T1 0.54 1.51 1.16 2.13 0.373
T2 − T1 0.28 0.79 0.76 1.38 0.279
ELSA/SLC T1 45.81 2.05 45.66 2.66 0.870
T2 − T1 0.85 1.20 0.42 1.79 0.309
T2 − T1 0.41 0.58 0.34 1.32 0.858
ELSA/PRC T1 44.76 2.32 45.77 2.90 0.321
T2 − T1 1.03 1.28 1.11 1.84 0.801
T2 − T1 0.54 0.62 0.72 1.21 0.562
ELSA/PLC T1 46.37 2.20 46.55 2.72 0.851
T2 − T1 0.78 0.99 0.44 1.89 0.512
T2 − T1 0.38 0.45 0.38 1.35 0.977
ELSA/SRGF T1 44.68 2.12 45.20 3.00 0.614
T2 − T1 0.57 1.32 1.13 2.10 0.404
T2 − T1 0.30 0.69 0.74 1.36 0.308
ELSA/SLGF T1 45.82 2.05 45.78 2.64 0.964
T2 − T1 1.12 1.39 0.41 1.76 0.136
T2 − T1 0.55 0.68 0.34 1.35 0.627
ELSA/PRGF T1 45.18 2.29 46.50 2.84 0.216
T2 − T1 1.33 1.34 0.89 1.91 0.568
T2 − T1 0.71 0.65 0.57 1.29 0.936
ELSA/PLGF T1 47.04 2.31 47.39 2.75 0.723
T2 − T1 0.87 1.17 0.49 1.83 0.522
T2 − T1 0.44 0.57 0.43 1.33 0.936
ELSA/ARGF T1 44.90 2.42 45.07 3.01 0.871
T2 − T1 0.42 1.29 1.15 2.32 0.326
T2 − T1 0.23 0.68 0.77 1.48 0.264
ELSA/ALGF T1 45.34 1.98 45.47 2.56 0.890
T2 − T1 1.33 1.13 0.37 1.82 0.069
T2 − T1 0.68 0.54 0.29 1.30 0.362

Student t test for independent samples, P <0.05.

Comparison of groups in relation to the difference between T1 and T2, including EGU and T1 evaluation as covariates.

Comparison of groups regarding the difference between T1 and T2 considering annualization and including T1 assessment as a covariate.

Both points marked on the mandibular condyle (ELSA/superior right condyle and ELSA/PRC) shifted more anteriorly in the HA group. The upper condyle position was previously displaced by 0.55 mm in the HA group and 0.34 mm in the CG, with no statistical difference. The posterior point shifted by an average of 0.58 mm vs 0.46 mm, respectively, without statistical difference.

In the mandibular fossa, 3 points were marked: superior, posterior, and anterior (ELSA/superior right glenoid fossa, ELSA/posterior right glenoid fossa, and ELSA/anterior right glenoid fossa). The upper position of the mandibular fossa displaced anteriorly with a higher average in the HA group (0.54 mm) than in the CG (0.42 mm). The posterior point of the mandibular fossa was displaced anteriorly with a lower average in the HA group (0.50 mm) than in the CG (0.57 mm). The anterior region of the mandibular fossa displaced anteriorly with a higher average in the HA group (0.53 mm) than in the CG (0.45 mm).

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