Introduction
This study aimed to evaluate the effects of 3 different fixed or removable functional appliances on the soft tissue changes in patients with Class II Division 1 malocclusion using 3-dimensional images.
Methods
A total of 60 patients with Class II Division 1 malocclusion (38 girls and 22 boys; mean age, 12.35 ± 1.01 years) were treated with 3 different functional appliances, namely, Twin-block (TB) (group TB, n = 20), mono-block (MB) (group MB, n = 20), or Herbst (H) (group H, n = 20) for 9.55 ± 1.46 months. Three-dimensional photographs of each patient were taken at the baseline and the end of the therapy with a 3dMD Face system (3dMD, Atlanta, Ga). Statistical analyses were performed using the dependent samples t test, 1-way analysis of variance, Kruskal-Wallis, Mann-Whitney U, and Wilcoxon signed rank tests.
Results
No statistically significant differences were detected for soft tissue changes except for the lower facial width found, at least in group H ( P <0.05). Volumetric differences in the mandible were similar between the groups ( P >0.05). A statistically significant decrease in total facial height and an increase in convexity angle and facial depth were detected in all groups after treatment compared with the baseline ( P <0.05). The upper and lower facial height, lower lip height, and nasal width were statistically significantly increased in the TB and MB groups after treatment compared with the baseline ( P <0.05) and similar to those in group H ( P >0.05).
Conclusions
TB, MB, and H appliances may promote the facial soft tissue profile, including volumetric improvement, in the mandibular region.
Highlights
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Twin-block, mono-block, and Herbst appliance treatments can positively affect soft tissue profiles.
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The effects were similar in all 3 groups.
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Volumetric increases in the mandible were produced by all 3 appliances.
Class II malocclusion is reported to be 1 of the most extensive orthodontic problems and is present in approximately one third of the population. The most common clinical finding of Class II malocclusion is mandibular skeletal retrusion, which can be eliminated by increasing the mandibular growth and preventing the disharmony of the skeletal jaw base and the unesthetic facial appearance. Different types of functional appliances, both removable and fixed types, have been used to stimulate mandibular growth to correct skeletal and occlusal discrepancies. However, no consensus has been reached in the literature regarding which type of appliance (either fixed or removable) is more effective in the treatment of patients with this malocclusion. Clinicians may generally decide on the type of appliance according to patient compliance influencing the benefit from the treatment. Different types of appliances are used worldwide. For example, Twin-block (TB) was reported to be the most popular functional appliance in the United Kingdom and Herbst (H) appliance in the United States. In Turkey, Mono-block (MB) was reported to be the most preferred type.
Esthetic appearance is 1 of the major expectations of orthodontic patients. An imbalance in the soft tissue profile caused by mandibular skeletal retrusion may require patients with Class II Division 1 to have orthodontic treatment. The treatment of Class II Division 1 with removable appliances improved the negative social experience and self-concept scores. Although the soft tissue profile is important for orthodontic patients, research generally evaluates the skeletal and dental outcomes of functional appliances rather than the soft tissue changes. Moreover, only a few studies , evaluated the soft tissue changes after treatment with functional appliances using the 2-dimensional measurements of lateral cephalograms. In the development of 3-dimensional (3D) imaging systems, the results of the orthodontic treatment were reported to be evaluated more accurately and objectively. The commonly used 3D imaging systems are laser scanning, stereophotogrammetry and computed tomography, , which was previously used for the evaluation of the treatment outcomes of functional appliances in orthodontic patients. , Laser scanning was claimed to be time consuming, to cause distortion because of movement, and to harm the eyes because of the laser beam. Computed tomography, which causes radiation, may also negatively affect the human body. Conversely, the 3D stereophotogrammetry technique shortens the imaging time, thus eliminating the residual motion with no harmful effect on human health, and its reproducibility has gained popularity. ,
To date, no study has compared the commonly used functional appliances, namely, TB, MB, and H, for the clinical outcomes of soft tissue in patients with Class II malocclusion using the 3D stereophotogrammetry technique. Thus, this study aimed to evaluate the effects of 3 different fixed or removable functional appliances on the soft tissue changes in patients with Class II Division 1 malocclusion using 3D images.
Methods
A total of 60 patients (25 boys and 35 girls; mean age, 12.80 ± 1.35 years) with Class II mandibular retrusion who applied to the Department of Orthodontics, Faculty of Dentistry, İnönü University were involved in this study ( Table I ). Ethical approval was obtained from the human ethics committee of the İnönü University (#2015-110). A written informed consent form was obtained from the parents or guardians of all the participants. The inclusion criteria were skeletal Class II malocclusion (ANB >4°), mandibular retrusion (SNB <78°), overjet ≥5 mm, Class II incisor, canine, and molar relationship, and patients who were at the maximum pubertal growth excretion at the beginning of treatment. The exclusion criteria were a history of orthodontic or orthopedic treatment, presence of any craniofacial anomaly, systemic disease that could affect the dentition, poor cooperation, and inadequate oral hygiene. Hand-wrist radiographs were taken to determine the growth stage of each patient, and the patients selected were all at the maximum pubertal growth excretion at the beginning of treatment previously used in the literature.
At the beginning of the study, randomization was performed with pre-prepared random number tables with block stratification on the child’s sex previously used in the literature. Sixty patients were randomly divided into 3 groups equally, namely, TB group (n = 20; 12 girls and 8 boys), MB group (n = 20; 11 girls and 9 boys), and H group (n = 20; 12 girls and 8 boys), according to the type of functional appliance that they were treated with.
The modified design of the TB appliance of Clark was used in this study. The working bite was adjusted with the incisors in an edge-to-edge relationship and at 2-4 mm beyond the freeway space for MB and TB, but the working bite was recorded with the incisors in an edge-to-edge relationship for H. The patients were checked every 4 weeks. When a normal or corrected overjet in the retruded position was detected, the active treatment was ended. The patients used the functional appliances for 9.35 ± 1.10 months.
The 3D photographs of all the patients were obtained using the 3dMD Face system (3dMd, Atlanta, Ga) at the beginning and at the end of the functional appliance therapy. The acquisition of the 3D images and the analysis of the obtained images were performed by the same examiner (O.C.G.). The 3dMD system includes high-speed, precision stereoscopic cameras to produce 3D polygonal models and texture images that capture the human face and head surface accurately. It features 180° face capture speeds (ear to ear) at 1.5 ms, 2 modular units consisting of 6 machine vision cameras, an industrial-grade flash system and <0.2 mm root mean square or better geometric accuracy. The 3D images can be created in 7 seconds. The 3dMD system automatically creates a continuous 3D polygon surface network from all synchronized stereo pairs with a single x, y, z coordinate system. All images were taken with the head in the natural head position, the teeth in centric occlusion and the lips in repose. The 3dMD software automatically matched all color information in the mesh, and no stretching of images was required. The images were obtained in the .tsb format, and software (3dMDvultus; 3dMD) was used to evaluate 3D facial images. The program has the ability to move images in 3 directions of space and to mark soft tissue landmarks.
The analytical template used in the study was created, and the desired angular and linear measurements and ratios were defined. The linear measurements were the nasal width (alr-all), mouth width (chr-chl), upper lip height (sn-stos), lower lip height (stoi-gn), upper face height (n-stos), lower face height (sn-gn), total face height (n-gn), middle facial width (bizygomatic width), and lower facial width (bigonial width) ( Table II ; Fig 1 ). The angular measurements were the nasolabial angle (c-sn-ls), labiomental angle (li-sl-pog), convexity angle (n-sn-pog), total convexity angle (n-prn-pog), upper lip angle (chr-ls-chl), lower lip angle (chr-li-chl), right side gonial angle (trr-gor-me), left side gonial angle (trl-gol-me), mandibular body convexity (gor-pog-gol), lower facial convexity in the horizontal plane (trr-pog-trl), mandibular angle (gor-me-gol), and Holdaway’s angle (n-pog-ls) ( Table II ; Fig 1 ). The ratios were the posterior lower facial height or anterior lower facial height, facial depth, and lower facial height ratio ( Table II ; Fig 1 ).
| Treatment | n | Male | Female | Age, y M ± SD |
Duration of treatment, mo M ± SD |
|---|---|---|---|---|---|
| Twin-block | 20 | 8 | 12 | 12.35 ± 1.01 | 9.55 ± 1.46 |
| Mono-block | 20 | 9 | 11 | 12.95 ± 0.82 | 9.35 ± 0.93 |
| Herbst | 20 | 8 | 12 | 13.11 ± 2.22 | 9.15 ± 0.93 |
| Variable | Definition |
|---|---|
| Linear (mm) | |
| Nasal width (alr-all) | The distance from alare right to alare left |
| Mouth width (chr-chl) | The distance from cheilion right to cheilion left |
| Upper lip height (sn-stos) | The distance from subnasale to stomion superioris |
| Lower lip height (stoi-gn) | The distance from stomion inferioris to gnathion |
| Upper face height (n-stos) | The distance from nasion to stomion superioris |
| Lower face height (sn-gn) | The distance from subnasale to gnathion |
| Total face height (n-gn) | The distance from nasion to gnathion |
| Middle facial width (bizygomatic width) | The distance from zygion right to zygion left |
| Lower facial width (bigonial width) | The distance from gonion right to gonion left |
| Angular measurements (u) | |
| Nasolabial angle (c-sn-ls) | The angle subtended by nasal tip, subnasale, and labrale superioris |
| Labiomental angle (li-sl-pog) | The angle subtended by labrale inferioris, sulcus inferioris, and soft tissue pogonion |
| Convexity angle (n-sn-pog) | The angle subtended by nasion, subnasale, and soft tissue pogonion |
| Total convexity angle (n-prn-pog) | The angle subtended by nasion, pronasale, and soft tissue pogonion |
| Upper lip angle (chr-ls-chl) | The angle subtended by chelion right, labrale superioris, and chelion left |
| Lower lip angle (chr-li-chl) | The angle subtended by chelion right, labrale inferioris, and chelion left |
| Right side gonial angle (trr-gor-me) | The angle subtended by tragion right, gonion right, and menton |
| Left side gonial angle (trl-gol-me) | The angle subtended by tragion left, gonion left, and menton |
| Mandibular body convexity (gor-pog-gol) | The angle subtended by gonion right, pogonion, and gonion left |
| Lower facial convexity in the horizontal plane (trr-pog-trl) | The angle subtended by tragion right, pogonion, and tragion left |
| Mandibular angle (gor-me-gol) | The angle subtended by gonion right, menton, and gonion left |
| Holdaway’s angle (n-pog-ls) | The angle subtended by nasion, pogonion, and labrale superioris |
| Ratio | |
| Posterior lower facial height/anterior lower facial height | Tragion right-gonion right/subnasale-pogonion |
| Facial depth | Tragion-subnasale/tragion-gnathion |
| Lower facial height ratio | Subnasale-stomion/stomion-gnathion |
Pre- and postsurface operation images were recorded to calculate the mandibular volume change. When the recording was completed, the reference surface was created using a brush tool on the nasal bridge and forehead. The software calculated a root mean square value that should be ≤0.5. Whether it was lower or not, the procedure was repeated. Soft tissue changes in the mandibular region were assessed by 3D soft tissue analysis, which was performed using the points described by Farkas et al. The region of interest monitored on the superimposition model was selected with the paintbrush tool ( Fig 2 ). Volume changes in the selected region were calculated using the volume calculation tool of the software.
The landmark identification and measurement procedures of the 20 patients (randomly selected from the study groups) were repeated after 4 weeks by the same investigator (O.C.G.). The intraclass correlation coefficient between the first and the second measurements was calculated. For all measurements, the intraclass correlation coefficient was 0.839-0.998, which means that the acceptable reliability and reproducibility of all measurements were specified.
Statistical analysis
The normal distribution of the data, expressed as the mean ± standard deviation, was determined through the Kolmogorov-Smirnov test. The statistical evaluation of the pre- and posttreatment values between the test groups was performed using parametric and nonparametric tests. Intragroup comparisons were conducted using the dependent sample t test and the Wilcoxon signed rank test. One-way analysis of variance was used when the volume difference values were evaluated, and multiple comparisons were determined with Tukey honest significant difference test. Intergroup comparisons were conducted using the Kruskal-Wallis test (Bonferroni adjustment) and 1-way analysis of variance, and multiple comparisons were determined with Tukey honest significant difference test. The data were analyzed using the SPSS software (version 22.0; IBM, Armonk, NY). A P value <0.05 was accepted as the significant level in all evaluations.
Results
Eight patients with compliance problems were excluded, and thus 60 participants, with 20 in each group, were included in the study. No statistically significant differences were found for age, sex, and treatment period between the groups ( P >0.05).
Evaluation of the linear measurements showed that the nasal width, lower lip height, and lower facial height increased and that the lower facial width decreased in the TB and MB groups ( P <0.05). The upper facial height increased in the MB group ( P <0.05). The mouth width increased in the H group ( P <0.05) ( Table III ).
| Measurement | Twin-block | Mono-block | Herbst | ||||||
|---|---|---|---|---|---|---|---|---|---|
| T 1 | T 2 | P | T 1 | T 2 | P | T 1 | T 2 | P | |
| M ± SD | M ± SD | M ± SD | M ± SD | M ± SD | M ± SD | ||||
| Linear measurements (mm) | |||||||||
| Nasal width (alr-all) | 29.85 ± 2.48 | 30.81 ± 3.17 | 0.025 † | 31.42 ± 3.04 | 32.32 ± 3.20 | 0.044 † , ‡ | 32.23 ± 3.30 | 32.41 ± 3.04 | 0.611 |
| Mouth width (chr-chl) | 44.03 ± 2.25 | 45.10 ± 3.02 | 0.169 | 46.92 ± 2.4 | 47.48 ± 3.13 | 0.357 | 46.52 ± 3.49 | 48.32 ± 2.97 | 0.003 † |
| Upper lip height (sn-stos) | 22.69 ± 2.92 | 21.93 ± 3.52 | 0.143 | 22.39 ± 3.41 | 22.58 ± 2.94 | 0.732 | 24.28 ± 3.69 | 23.58 ± 3.12 | 0.296 |
| Lower lip height (stoi-gn) | 35.54 ± 3.45 | 37.68 ± 3.43 | 0.002 † | 37.62 ± 3.04 | 38.88 ± 2.53 | 0.026 † | 39.29 ± 3.97 | 39.86 ± 4.48 | 0.482 |
| Upper face height (n-stos) | 22.69 ± 2.92 | 21.93 ± 3.52 | 0.218 | 69.49 ± 3.67 | 71.31 ± 3.87 | 0.002 † | 71.89 ± 5.78 | 72.82 ± 5.37 | 0.351 ‡ |
| Lower face height (sn-gn) | 57.96 ± 4.58 | 59.35 ± 5.03 | 0.045 † | 59.72 ± 4.81 | 61.29 ± 4.21 | 0.017 † | 63.33 ± 6.00 | 63.15 ± 6.71 | 0.845 |
| Total face height (n-gn) | 101.89 ± 6.37 | 105.11 ± 6.50 | 0.001 † | 105.29 ± 4.95 | 108.96 ± 4.74 | 0.000 † | 109.83 ± 7.61 | 111.36 ± 7.79 | 0.048 † |
| Middle facial width (bizygomatic width) | 133.99 ± 4.96 | 136.15 ± 4.96 | 0.001 † | 140.58 ± 13.48 | 140.07 ± 6.28 | 0.002 † , ‡ | 137.21 ± 6.36 | 137.86 ± 6.47 | 0.230 |
| Lower facial width (bigonial width) | 122.42 ± 5.70 | 125.02 ± 5.03 | 0.000 † | 127.67 ± 14.93 | 126.80 ± 5.03 | 0.037 † , ‡ | 125.13 ± 5.74 | 124.68 ± 4.99 | 0.523 |
| Angular measurements (u) | |||||||||
| Nasolabial angle (c-sn-ls) | 117.54 ± 7.55 | 115.53 ± 6.69 | 0.030 | 113.28 ± 9.36 | 112.97 ± 9.41 | 0.720 | 116.33 ± 7.82 | 115.47 ± 10.61 | 0.546 |
| Labiomental angle (li-sl-pog) | 113.31 ± 15.35 | 117.29 ± 11.05 | 0.093 ‡ | 109.67 ± 12.57 | 116.49 ± 14.43 | 0.020 † | 124.51 ± 12.62 | 123.82 ± 10.97 | 0.740 |
| Convexity angle (n-sn-pog) | 156.10 ± 5.40 | 160.50 ± 5.08 | 0.000 † | 156.59 ± 6.41 | 159.50 ± 5.81 | 0.000 † | 154.99 ± 4.67 | 157.09 ± 5.08 | 0.001 † |
| Total convexity angle (n-prn-pog) | 127.34 ± 4.61 | 129.07 ± 4.57 | 0.004 † | 126.96 ± 5.10 | 127.68 ± 5.17 | 0.198 | 126.54 ± 4.07 | 127.52 ± 3.81 | 0.018 † |
| Upper lip angle (chr-ls-chl) | 100.47 ± 5.57 | 102.64 ± 5.61 | 0.100 ‡ | 102.37 ± 6.78 | 103.99 ± 6.30 | 0.065 | 96.71 ± 5.08 | 101.72 ± 5.97 | 0.000 † |
| Lower lip angle (chr-li-chl) | 127.75 ± 5.00 | 125.69 ± 4.25 | 0.048 | 125.32 ± 4.38 | 124.02 ± 4.96 | 0.100 | 124.13 ± 4.09 | 123.67 ± 5.21 | 0.667 |
| Right side gonial angle (trr-gor-me) | 141.59 ± 4.34 | 142.85 ± 4.88 | 0.345 | 141.87 ± 6.37 | 141.86 ± 5.56 | 0.546 ‡ | 140.15 ± 6.65 | 140.21 ± 9.04 | 0.979 |
| Left side gonial angle (trl-gol-me) | 136.82 ± 4.96 | 139.48 ± 6.54 | 0.031 † | 137.42 ± 7.84 | 138.75 ± 4.28 | 0.417 | 138.83 ± 7.20 | 137.82 ± 6.34 | 0.496 |
| Mandibular body convexity (gor-pog-gol) | 74.99 ± 2.79 | 74.61 ± 3.18 | 0.400 | 77.36 ± 7.90 | 74.33 ± 2.34 | 0.003 † , ‡ | 75.14 ± 3.23 | 73.67 ± 3.37 | 0.004 † |
| Lower facial convexity in the horizontal plane (trr-pog-trl) | 63.26 ± 1.73 | 64.80 ± 3.26 | 0.031 † | 63.32 ± 3.46 | 64.69 ± 1.49 | 0.095 ‡ | 64.68 ± 2.62 | 65.47 ± 2.63 | 0.025 † |
| Mandibular angle (gor-me-gol) | 74.12 ± 3.11 | 73.68 ± 3.15 | 0.230 | 77.13 ± 7.75 | 74.21 ± 2.55 | 0.003 † , ‡ | 74.73 ± 3.23 | 73.46 ± 3.40 | 0.005 † |
| Holdaway’s angle (n-pog-ls) | 17.51 ± 2.92 | 14.41 ± 3.05 | 0.000 † | 17.61 ± 4.63 | 14.90 ± 4.34 | 0.000 † | 17.50 ± 4.43 | 15.71 ± 4.32 | 0.002 † |
| Ratio | |||||||||
| Posterior lower facial height/anterior lower facial height | 0.49 ± 0.08 | 0.50 ± 0.09 | 0.504 | 0.53 ± 0.07 | 0.50 ± 0.08 | 0.150 | 0.47 ± 0.07 | 0.49 ± 0.07 | 0.142 |
| Facial depth | 0.92 ± 0.02 | 0.91 ± 0.02 | 0.000 † | 0.93 ± 0.02 | 0.92 ± 0.02 | 0.001 † , ‡ | 0.93 ± 0.02 | 0.92 ± 0.02 | 0.025 † |
| Lower facial height ratio | 0.64 ± 0.10 | 0.58 ± 0.11 | 0.008 † | 0.59 ± 0.09 | 0.58 ± 0.07 | 0.416 | 0.62 ± 0.10 | 0.59 ± 0.07 | 0.255 |
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