Material and methods

Thirty patients were included in this study, based on the study by Burkhardt et al. Findings from the multivariate analysis of variance indicated that at least 80% statistical power necessitated a minimum sample size of 15 in each group to detect a significant difference between the groups.

The 30 growing patients were divided into 2 groups. The Herbst group consisted of 6 males and 9 females, with a mean age of 11.60 ± 0.82 years, whereas the distalization group consisted of 4 males and 11 females, with a mean age of 11.46 ± 1.30 years. The treatment duration was 11.73 ± 1.39 months and 14.60 ± 0.51 months for the Herbst and distalization groups, respectively.

Ethical approval for this study was obtained from the Ethical Committee of Izmir Katip Çelebi University (no. 91). The parents of the subjects included in this study signed informed consent forms.

Late-mixed or early-permanent dentition, depended mandibular retrognathia (SNB <78°), skeletal Class II relationship (ANB >4°), angle Class II molar relationship, <4 mm crowding in dental arches (according to model analysis), and vertically normal growth (25°< SN-GoGn <39°) were the inclusion criteria for this study. In contrast, systemic disease, orthodontic treatment history, congenital tooth defect or permanent tooth extraction, severe facial asymmetry, and poor oral hygiene were the exclusion criteria.

Mandibular incisor proclination, gingival thickness, gingival height, palatal bone thickness, and palatal depth were also evaluated during treatment planning. Treatment assignment for patients was determined on the basis of diagnostic criteria provided by 1 orthodontist (A.B). Patients matching the criteria were included in the appropriate treatment group (without randomization), after evaluation of intraoral and extraoral photographs, plaster casts, and radiographs.

Furthermore, the efficacy of Herbst and distalization treatments on hard tissue was evaluated with cephalometric radiographs, whereas differences in soft tissue were evaluated using 3D facial scans.

Lateral cephalometric radiographs were obtained in a natural head position, with teeth in centric occlusion and lips in a rest position. To analyze cephalometric radiographs, we determined 35 landmarks and created 14 planes. A total of 39 measurements, including 20 skeletal, 16 dental, and 2 soft-tissue measurements were performed using Dolphin Imaging software (version 11.8; Dolphin Imaging and Management Solutions, Chatsworth, Calif).

In this study, the 3dMD face imaging system (3dMD Inc., Atlanta, Ga) was used to obtain 3D images, and 3dMD Vultus software (3dMD) was used to process and measure images. Face scans were captured in a digital recording studio designed as a separate section in the clinic to ensure minimal patient interaction with the outside. The records were taken in a natural head position, which was repeatable. Patients were told to release facial muscles, swallow, and look into their own eyes in a mirror placed between the cameras with eyes open.

The scanning time lasted approximately 1.5 ms. After the face scan, the records were examined using 3dMD viewer software (3dMD Inc.). The process was repeated if the face scan result was below the ideal image quality. Three-dimensional images were processed to remove confounding regions by clipping the extraneous surface data from the neck, ears, and scalp hair ( Fig 1 ).

Processed images by clipping the extraneous surface data from the neck, ears, and scalp hair.

The acrylic-splint Herbst design was used, with the Type IV Herbst (Dentaurum, Ispringen, Germany) telescope system. There was a limited amount of side movements during the opening and closing movements of the jaw and chewing. The base pieces were soldered to a 1-mm-diameter wire sculpture formed on the model in which they were located on the buccal side of the maxillary first molars and the mandibular first premolars. Hyrax screws were added to the upper splints to prevent upper jaw constriction. The maxillary splint was covered with acrylic from the mesial side of the canine to the distal side of the molars, whereas the mandibular splint was extended from the distal sides of the first molars ( Fig 2 ).

Acrylic-splint Herbst appliance design.

The maxillary splints were cemented with glass ionomer cement (3M ESPE, Ketac Cem Easymix, Dentsply DeTrey GmbH, Konstanz, Germany) in all patients, and the mandibular splints were removable to ensure good oral hygiene. The use of the appliance continued until the super Class I molar relationship was achieved and overjet eliminated. After the active Herbst appliance therapy, a monoblock-type retention device was delivered to the patient to obtain good interdigitation and stable mandibular position. The total treatment time for the Herbst group was 11.73 ± 1.39 months.

In distalization group, the appliances used in the study are supported only by miniscrews. Under local anesthesia, 3-mm predrilling was performed before the mini-implant application. The screws have a total length of 11.6 mm and a diameter of 2 mm and consist entirely of titanium (The Aarhus System Miniscrews; American Orthodontics, Tuttlingen, Germany). The screws were placed 3-6 mm to the right and left of the sutura palatina media bilaterally in the transversal plane and posterior to the third palatinal ruga in the sagittal plane.

After selecting appropriate bands for the maxillary first molar teeth, the impression was made with alginate. A stainless steel sliding tube with a diameter of 0.9 mm was bent and placed in the palatal sides of molar bands. The distalization arch with a 1-mm-diameter stainless steel wire was twisted around the screws and passed through the sliding tubes. In the mesial side of the first premolars, solder was used on the arch to act as a stopper. An open coil spring was placed between the sliding tube and the stopper to apply 240 g of distalization force. Miniscrews and distalization arch were fixed to each other with composite material (3M Unitek, Monrovia Calif) ( Fig 3 ). If an occlusal interference was detected between maxillary and mandibular teeth, a mandibular removable appliance was delivered to the patient to enable molar distalization.

Miniscrew-supported intraoral distalization appliance.

Patients were given appointments at 4-week intervals. The activation was achieved with crimpable stoppers placed to the distal side of solders. Thus, the desired force was maintained. After Class I molar relationship was obtained, anterior teeth were bracketed, and a 17 × 25-inch beta-titanium utility arch was applied for retraction. Premolar teeth were not bracketed to allow distal movement through transseptal fibers. After obtaining the ideal overjet, the anterior brackets were removed, and all records taken initially from the patients were repeated. The mean duration of treatment was calculated as 14.6 ± 0.51 months.

The 3dMD Vultus analysis program was used to analyze the 3D data (3dMD). In the program, 3D images were placed in appropriate and standard positions in 3 dimensions of the space before the points were determined. The reference points are marked after the reference planes have been created on the 3D facial image ( Fig 4 , A and B ).

A, The reference points created on the 3D facial image (front). B, The reference points. created on the 3D facial image (profile).

Linear, angular, and proportional analyses were performed after the points were marked in the 3D face scan.

Profile images of the patients were taken before and after treatment from standardized images in the 3dMD Vultus program. All images were standardized in size, and each numbered between 1 and 60. The presentation and evaluation of the profiles were done similar to the study by Mergen et al. The study included 2 groups of 10 persons, who were at least in the fourth year of being an orthodontic assistant or Os and LP. In terms of being familiar with the profiles, 5 descriptive images were recorded in our clinic but not included in the study and presented to the evaluators. The 60 profile images included in the study were presented to the evaluators in the same order, with intervals of 10 seconds. The attractiveness of photographs was then scored using a Likert scale between 1 and 7 (1 = lowest, 7 = highest).

Results

Interclass correlation coefficients were calculated to evaluate the method error. A correlation of ≥85% was found between repeated measurements. The minimum and maximum coefficients were between 0.893 and 0.996 for cephalometric measurements and 0.861 and 0.994 for soft-tissue measurements.

When the initial (T0) cephalometric values of the study groups were compared, the only statistically significant differences were found for Wits appraisal ( P = 0.05) and overbite ( P = 0.028) ( Table I ).

Initial (T0) and final (T1) changes with Herbst treatment are presented in Table II .

Table II

Comparison of cephalometric measurements within and between groups

Measurements	Herbst			Distalization			Group effect	Time effect	Group × time effect	Intergroup treatment effect
	T0	T1	T1 – T0	T0	T1	T1 – T0	P	P	P	P
Maxillary measurements
SNA	81.82 ± 3.45	82.01 ± 3.15	0.19 ± 1.36	81.92 ± 3.03	82.60 ± 3.08	0.68 ± 1.82	0.760	0.147	0.410	0.410
Co-A	81.44 ± 4.46	84.75 ± 4.60	3.31 ± 2.86 ∗∗∗	79.42 ± 3.50	82.04 ± 4.72	2.61 ± 3.33 ∗∗	0.123	<0.001	0.542	0.542
A-N⊥FH	−2.30 ± 3.11	−3.46 ± 3.69	−1.16 ± 1.80	−2.46 ± 3.23	−4.31 ± 3.32	−1.85 ± 3.11 ∗∗	0.658	0.003	0.462	0.462
N-CF-A	58.13 ± 3.20	59.90 ± 3.72	1.77 ± 2.51 ∗∗	57.78 ± 2.41	56.96 ± 3.11	−0.82 ± 2.37	0.131	0.295	0.007	0.007
FH-NA	92.45 ± 3.31	93.52 ± 3.73	1.07 ± 1.86	92.65 ± 3.45	94.60 ± 3.55	1.95 ± 3.34 ∗∗	0.594	0.005	0.381	0.381
Mandibular measurements
SNB	75.42 ± 2.72	77.29 ± 3.30	1.87 ± 1.45 ∗∗∗	75.73 ± 2.46	76.02 ± 2.36	0.24 ± 1.32	0.632	<0.001	0.003	0.003
Co-Gn	101.01 ± 7.06	107.82 ± 6.08	6.80 ± 3.15 ∗	99.25 ± 3.30	100.92 ± 3.73	1.54 ± 3.06	0.070	0.622	0.158	0.008
Go-Gn	69.04 ± 5.79	71.35 ± 6.22	2.31 ± 0.54 ∗∗∗	66.08 ± 5.85	68.72 ± 5.92	2.64 ± 0.54 ∗∗∗	0.202	<0.001	0.67	0.670
Pog-N⊥FH	−4.46 ± 4.51	−0.20 ± 6.76	−3.30 ± 5.16 ∗∗	−4.38 ± 4.52	−2.02 ± 4.52	−2.53 ± 3.01	0.581	0.004	0.382	0.621
Maxillomandibular measurements
ANB	6.41 ± 1.84	4.72 ± 1.41	1.69 ± 1.34 ∗∗∗	6.14 ± 2.18	6.59 ± 2.43	−0.45 ± 1.61	0.250	0.030	<0.001	<0.001
CoGn-CoA	19.56 ± 3.85	23.06 ± 3.13	3.50 ± 3.06 ∗∗∗	19.83 ± 2.64	20.56 ± 3.72	0.72 ± 2.33	0.346	<0.001	0.001	0.001
Wits appraisal	5.56 ± 1.88	1.22 ± 2.61	−4.34 ± 2.42 ∗∗∗	3.56 ± 1.73	3.74 ± 2.25	0.17 ± 2.10	0.703	<0.001	<0.001	<0.001
Vertical measurements
SN-GoGn	31.49 ± 3.33	31.51 ± 4.49	0.02 ± 2.78	33.50 ± 3.81	34.56 ± 4.20	1.06 ± 2.31	0.077	0.258	0.276	0.276
GoGn-FH	20.86 ± 2.87	19.99 ± 4.60	−0.86 ± 3.13	22.77 ± 3.95	22.58 ± 3.93	−0.19 ± 4.25	0.082	0.444	0.626	0.626
SN-PP	8.29 ± 2.60	8.54 ± 2.51	0.25 ± 1.48	8.83 ± 2.61	8.16 ± 2.83	−0.67 ± 1.91	0.934	0.507	0.150	0.150
PP-Mp	26.50 ± 2.91	25.44 ± 4.37	−1.05 ± 3.49	28.02 ± 3.33	28.92 ± 3.24	0.90 ± 3.39	0.033	0.904	0.132	0.132
Inner angle sum	394.81 ± 3.45	394.00 ± 4.33	−0.81 ± 2.62	396.84 ± 3.54	377.08 ± 3.06	0.24 ± 2.91	0.464	0.310	0.349	0.304
y-axis	58.12 ± 2.36	57.06 ± 3.54	−1.06 ± 2.36	58.43 ± 2.95	57.86 ± 2.31	−0.56 ± 3.97	0.519	0.184	0.683	0.683
S-Go	67.06 ± 5.01	72.81 ± 4.50	5.75 ± 3.59 ∗∗∗	64.82 ± 2.58	67.24 ± 4.29	2.42 ± 3.02 ∗∗	0.010	<0.001	0.011	0.011
ANS-Me	59.60 ± 6.49	62.85 ± 7.62	3.25 ± 3.26 ∗∗∗	59.40 ± 2.74	61.28 ± 3.07	1.88 ± 2.66 ∗	0.645	<0.001	0.217	0.217
Interdental measurements
U1-L1	118.38 ± 6.29	121.90 ± 6.79	3.52 ± 5.54	118.82 ± 7.70	123.78 ± 6.70	12.29 ± 9.20	0.775	0.323	0.866	0.004
Overjet	6.56 ± 1.42	2.78 ± 0.42	−3.77 ± 1.48 ∗∗∗	5.98 ± 1.16	3.10 ± 0.59	−2.88 ± 1.22 ∗∗∗	0.633	<0.001	0.082	0.082
Overbite	5.34 ± 0.96	3.26 ± 1.08	−2.08 ± 1.44 ∗∗∗	4.28 ± 1.48	3.50 ± 1.37	−0.78 ± 1.36 ∗	0.284	<0.001	0.017	0.017
Maxillary dentoalveolar measurements
SN-U1	110.89 ± 7.78	103.87 ± 4.89	−7.02 ± 6.15	108.70 ± 6.45	90.32 ± 3.25	−12.38 ± 8.07 ∗∗∗	0.033	<0.001	0.081	0.050
PP-U1 (°)	119.18 ± 5.44	112.42 ± 4.39	−6.75 ± 5.95	117.53 ± 4.08	100.48 ± 3.59	−12.78 ± 8.86 ∗∗∗	0.040	<0.001	0.056	0.037
U1-NA (°)	29.07 ± 5.98	21.86 ± 3.01	−7.21 ± 6.11 ∗∗∗	26.79 ± 5.99	16.36 ± 6.42	−12.43 ± 8.78 ∗∗∗	0.031	<0.001	0.069	0.069
U1-NA (mm)	5.97 ± 2.75	3.59 ± 1.43	−2.38 ± 2.12 ∗∗∗	4.77 ± 2.38	1.50 ± 2.70	−3.26 ± 2.78 ∗∗∗	0.035	<0.001	0.335	0.335
U1⊥PP	25.97 ± 2.88	27.56 ± 3.29	1.59 ± 1.67 ∗∗	25.68 ± 1.81	26.46 ± 1.89	0.78 ± 1.96	0.430	0.001	0.236	0.236
U6⊥PP	18.96 ± 2.71	19.23 ± 2.59	0.26 ± 1.44	17.99 ± 1.36	18.45 ± 1.39	0.46 ± 1.07	0.244	0.131	0.682	0.682
U1-MxOP	49.86 ± 5.03	54.37 ± 3.30	4.51 ± 3.89 ∗∗	50.40 ± 5.32	62.18 ± 6.45	11.78 ± 6.83 ∗∗∗	0.014	<0.001	0.001	0.001
Mandibular dentoalveolar measurements
L1-MdOP	59.80 ± 3.32	59.17 ± 5.27	−0.62 ± 4.11	61.16 ± 3.57	61.27 ± 2.23	0.10 ± 2.72	0.166	0.686	0.570	0.570
IMPA	95.93 ± 5.88	100.22 ± 6.55	4.29 ± 4.43 ∗∗∗	95.63 ± 4.70	95.46 ± 4.67	−0.16 ± 4.57	0.179	0.018	0.011	0.011
L1-NB (°)	26.14 ± 4.59	31.52 ± 4.91	5.38 ± 3.36 ∗∗∗	28.24 ± 5.85	28.58 ± 4.23	0.34 ± 4.15	0.801	<0.001	0.001	0.001
L1-NB (mm)	5.34 ± 1.76	7.09 ± 1.91	1.75 ± 0.93 ∗∗∗	5.87 ± 2.15	6.05 ± 1.88	0.18 ± 1.07	0.713	<0.001	<0.001	<0.001
L1-APog	0.68 ± 1.63	3.38 ± 1.45	2.70 ± 1.17 ∗∗∗	1.75 ± 1.87	1.71 ± 2.02	−0.04 ± 1.64	0.618	<0.001	<0.001	<0.001
L1⊥Mp	33.52 ± 3.68	34.82 ± 3.80	1.30 ± 2.10 ∗	33.46 ± 1.84	34.85 ± 2.57	1.39 ± 2.33 ∗	0.985	0.003	0.909	0.909
L6⊥Mp	22.92 ± 3.13	25.72 ± 2.79	2.80 ± 1.57 ∗∗∗	23.02 ± 2.27	24.44 ± 2.16	1.42 ± 1.79 ∗∗	0.521	<0.001	0.033	0.033
Soft-tissue measurements
Lower lip to E-line (mm)	−0.32 ± 1.78	−0.14 ± 1.64	0.18 ± 1.68	0.96 ± 2.93	0.59 ± 2.37	−0.36 ± 1.53	0.198	0.762	0.354	0.354
Upper lip to E-line (mm)	−1.64 ± 1.55	−3.80 ± 1.34	−2.15 ± 1.78 ∗∗∗	−1.32 ± 2.34	−1.88 ± 2.20	−0.56 ± 1.57	0.084	<0.001	0.015	0.015

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