Evaluation of soft-tissue changes in young adults treated with the Forsus fatigue-resistant device

Introduction

This study aimed to evaluate the effects of the Forsus fatigue-resistant device (FRD) EZ2 appliance (3M Unitek, Monrovia, Calif) on facial soft tissues by using images obtained from cephalometric radiographs and 3-dimensional (3D) facial scanning system.

Methods

A total of 20 patients treated with the Forsus FRD EZ2 appliance were included in this study. The cervical vertebral maturation index was used to determine growth and development stages, and the subjects were investigated at cervical vertebral maturation stages 5 and 6 (ie, postpeak period). Three-dimensional facial scanning images were obtained with 3dMD Face (3dMD Ltd, Atlanta, Ga). Cephalometric radiographic images were taken before placement of the appliance (T0), immediately after removal (T1), and at the 6-month (T2) follow-up after the removal of the appliance. For comparison of the data, one-way repeated-measures analysis of variance and paired t test were used at P < 0.05.

Results

Statistically significant changes were found in the Wits value, IMPA, L1P-NB (°), L1-NB (mm), L1P-APog, U1P-L1P, overjet, overbite, Ls-E, and labiomental angle in T0-T1. In T0-T2, statistically significant changes in the Wits, IMPA, L1P-NB (°), overjet, overbite and Ls-E values were observed.

Conclusions

The results revealed that the correction of malocclusion with Forsus FRD EZ2 appliance in patients at the postpeak period was mainly dentoalveolar. The soft tissues were affected to a limited extent. Three-dimensional facial scanning demonstrated similar accuracy and precision to traditional cephalometry, being a repeatable and accurate tool for linear and surface measurements.

Highlights

  • Forsus fatigue-resistant devices did not affect sagittal or vertical planes in postpeak patients.

  • Changes in maxilla and mandible were dentoalveolar only.

  • Significant differences in soft-tissue profiles in postpeak patients were not found.

Skeletal Class II malocclusion is one of the most common anomalies and constitutes 12%-49% of orthodontic malocclusions. , In Class II malocclusions, the disruption of harmony between the structures forming the craniofacial system manifests itself in unconformity in jaw relationships in the sagittal plane, and is caused by genetic and/or environmental factors. Upper jaw protrusion, lower jaw retrusion, or a combination of both can be seen with this malocclusion in which lower jaw retardation has generally been reported. Functional appliances are one of the treatment alternatives for these malocclusions and can correct the skeletal imbalance and profile disharmony in individuals with Class II malocclusion.

Functional appliances are divided into removable and fixed groups, with many different designs within each group. These two types of functional appliances have some advantages over each other. Because of their size and poor stability in the mouth, patient adaptation with removable functional appliances is difficult. Thus, fixed functional appliances have been developed to eliminate the disadvantages created by removable functional appliances.

Several systematic reviews have focused on the treatment effects of removable functional appliances, , fixed functional appliances, , or both. A debate as to whether fixed functional appliances can stimulate mandibular growth and result in long-term skeletal changes remains.

Perinetti et al assessed the skeletal and dentoalveolar effects of fixed functional appliances, alone or in combination with comprehensive treatment, on pubertal and postpubertal patients with a Class II malocclusion. The authors reported that dentoalveolar effects were generally seen regardless of the treatment timing. Mesial movement of the mandibular dentition, mesial movement or tipping of lower first molars, and proclination of lower incisors , were observed in the mandible, whereas distal movement of the maxillary dentition, distal tipping of upper first molars, and/or retroclination of upper incisors , were reported in the maxilla. These authors also pointed out the improvement of the profile, mainly due to soft-tissue pogonion and B-point advancement.

Ishaq et al concluded that fixed functional appliances appear to have no significant positional or dimensional skeletal effects on the mandible in growing subjects with Class II malocclusion. They also pointed out that a slightly greater skeletal dimensional effect was observed in the pubertal period than in the postpubertal period, although this difference was not statistically significant.

Forsus fatigue-resistant device (FRD; 3M Unitek, Monrovia, Calif), which requires minimum patient cooperation, is a fixed functional appliance developed in recent years and preferred by some orthodontists because of its ease of application.

Franchi et al assessed the dental, skeletal, and soft-tissue effects of Forsus FRD in growing patients with Class II malocclusion using lateral cephalograms. The authors concluded that the Forsus FRD was effective in correcting Class II malocclusion with a combination of skeletal (mainly maxillary) and dentoalveolar (mainly mandibular) modifications. In addition, the authors reported that soft-tissue measurements showed a significantly greater backward movement of the soft tissue A point in the Forsus FRD group.

Gunay et al used lateral cephalograms to evaluate the short-term dentoalveolar and soft-tissue changes in late adolescent patients treated with the Forsus FRD. The authors reported that the Forsus FRD slightly improved the profile, and the soft tissue reflected the majority of the dentoalveolar changes (ie, the backward movement of the upper lip following the retrusion of maxillary incisors and no longer position of the lower lip behind the maxillary incisors).

Flores-Mir et al evaluated facial soft-tissue changes after the use of fixed functional appliances in patients with Class II Division 1 malocclusion through a systematic review of the literature. The authors reported that although fixed functional appliances produce some statistically significant changes in the soft-tissue profile, the magnitude of the changes may not be perceived as clinically significant. They also pointed out that 3-dimensional (3D) quantification of the soft-tissue changes was required to understand the soft-tissue changes obtained with the use of fixed functional appliances.

Several articles using Forsus FRD have been previously published. In these studies, 2-dimensional evaluations of dental, skeletal, and soft-tissue changes after the use of appliance were made. However, to our knowledge, no articles using 3D evaluations were found in the literature.

Traditional orthodontic records include patient photographs, lateral cephalometric and panoramic radiographs, and dental models. However, with the developing technology, the deficiencies of these methods are emerging. Thus, extraoral photographs can be limited to reflect real 3D images.

Currently, stereophotogrammetry, which is a 3D facial scanning system, has become commonly used with growing popularity among plastic surgeons, orthodontists, and maxillofacial surgeons. This system has become a valuable recording tool for diagnostic records because it allows the face to be assessed on all 3 planes of space.

The purpose of this retrospective clinical archive study was to evaluate the soft-tissue effects of Forsus FRD appliance by using cephalometric radiographs and images obtained from 3D facial scanning system in patients with skeletal and dental Class II anomalies characterized by mandibular retrognathia in postpeak period.

Material and methods

A power analysis using G*Power software (version 3.1.3; Franz Faul University, Kiel, Germany) determined that a sample size of 16 subjects per group would provide a power of 97% to detect significant differences with an 0.45 effect size and α value of 0.05 (critical χ 2 = 3.3403; noncentrality parameter λ = 19.44).

The records of T0 and T1 for 20 patients were completely available. The records of the T2 period were reviewed and evaluated for 16 patients because of 4 patients’ records not being available. Thus, for 2 periods, a total of 20 patients (10 boys, 10 girls) were included. As a routine protocol in our clinic, dental models, facial and intraoral photographs, and a set of 2D radiographs including cephalometric and panoramic radiographs are obtained from patients for orthodontic diagnosis and treatment planning.

The selection criteria were as follows: (1) no history of previous orthodontic treatment; (2) cervical vertebral maturation (CVM) stage 5 or 6 as determined by cephalometric radiographs ; (3) skeletal Class II relationship (ANB > 4°) ; (4) normal position of the maxilla to the cranial base; (5) mandibular retrognathy (SNB < 78°) ; (6) Class II molar and canine relationship; (7) normal or diminished vertical growth; (8) lower incisor position should be upright on basal bone or suitable for uprighting; (9) minimal crowding in dental arches (≤ 4 mm); and (10) body mass index is within normal limits.

All patients included in the study remained in similar body mass index values during the study period.

Maxillary and mandibular arches were bonded with 0.022 × 0.028-in MBT prescribed appliances. Leveling and aligning stages started with 0.016-inch nickel-titanium (Ni-Ti) and continued with 0.016 × 0.022-in Ni-Ti, 0.019 × 0.025-in Ni-Ti, and 0.019 × 0.025-in stainless steel (SS) archwires, respectively. Once leveling and aligning were achieved, the Forsus FRD EZ2 with suitable rod length were mounted on 0.019 × 0.025-in SS archwires bilaterally at both maxillary and mandibular arches ( Fig 1 ). A transpalatal arch was placed and the SS archwire was cinched back in the lower arch at the stage of appliance insertion. The lower parts of the Forsus FRD were placed distal to the mandibular canine teeth.

Fig 1
The Forsus FRD EZ2.

To evaluate the effects of Forsus appliance, the records were taken before the insertion of the appliance (T0), immediately after appliance removal (T1), and at 6 months follow-up (T2). The Forsus appliance was removed when the Class I or super Class I molar and canine relationship is achieved, and anterior teeth are mostly in a tête-à-tête position. In these 3 different time intervals, efficacy of the treatment on soft tissues was evaluated with lateral cephalometric radiography and 3D facial images, respectively.

3D facial images were obtained by using the 3dMD Face system (3dMD Ltd, Atlanta, Ga). All records were obtained at the same posture and position. Patients were positioned on an adjustable chair and instructed to look into his or her eyes in a mirror placed between the cameras with eyes open and facial musculature relaxed. All images were saved as TSB files and manipulated using 3dMD Vultus software (3dMD, Atlanta, Ga).

Skeletal and dental changes were evaluated using lateral cephalometric radiographs. All radiographs were taken with the same device (Orthopantomograph OP300; Instrumentarium Dental, Tuusula, Finland) in 10 seconds with an exposure time of 2.3 seconds and optimized patient dose. The landmarks are shown in Figures 2-4 ; definitions are available in Supplementary Tables I and II .

Fig 2
The landmarks on the frontal view of the 3dMD image.

Fig 3
The landmarks on the lateral view of the 3dMD image.

Fig 4
The landmarks on lateral cephalometric radiograph.

The positions and rotations on the 3D face image were controlled and regulated in the coordinate system as suggested by Plooji et al for analysis. In order to superimpose the 3D facial images, the registration protocol was performed on the forehead, upper nasal dorsum, and zygoma, which was reported by Maal et al as the most stable regions over time.

The root mean square (RMS) value, which is specified in the software manually and determines how consistent the registration process is, was recorded for each individual, and the superimpositions with the RMS value below 1 were re-evaluated. The RMS value has been applied so that it reaches the smallest possible value as in the study of Taylor et al. Positive values in the measurements indicate that the anatomical point moves anteriorly after treatment on the anteroposterior plane, and negative values indicate that the anatomical point moves backward (posteriorly) in the anteroposterior plane.

Both the changes in the color histogram and the millimetric changes between the 2 images were examined. The color histogram provides a visual assessment of the difference between the 2 superimposed images. When the result is positive, the second image topography is more apparent and when the result is negative, it is the opposite. The differences are represented along a color spectrum with values associated with each color. When comparing 2 images, the overpositive change is represented by the red code and the overnegative change is represented by the blue code ( Fig 5 ).

Fig 5
Superposition of 3dMD images in 2 different periods.

Statistical analysis

Data were analyzed using the SAS 9.3 Software (SAS Institute, Cary, NC). The Shapiro-Wilks test was used to determine whether the data containing the cephalometric and 3D facial image recordings in 3 different periods comply with the normal distribution. Parametric tests were used to compare the data after normal distribution of the data was determined ( P > 0.05), and descriptive statistics were shown as mean ± standard deviation. These values were tested using a one-way analysis of variance. Comparisons of the obtained records at different time intervals and binary comparisons were made with Bonferroni correction with a paired t test in SAS proc mixed procedure. For P < 0.05, the results were considered statistically significant.

Results

The same author repeated the measurements 1 week after the first measurements on 20 3D images and 20 cephalograms randomly selected from 10 patients. Intraclass correlation coefficients ranged from 0.9 to 1.00. No significant errors were found when repeated measurements were evaluated with paired t tests.

The cephalometric changes obtained with the Forsus FRD were shown in Table I . The changes in the Wits value were statistically significant between T0-T1 and T0-T2. Although there was no statistically significant change in the upper incisors, changes observed between T0-T1 and T0-T2 periods in IMPA, L1-NB (°), L1-NB (mm), and L1P-APog values, which express the anteroposterior position and inclination of the lower incisors, were statistically significant. Also, the increase in L6P-MD value, which indicates the vertical position of the lower incisors, was statistically significant ( P < 0.05). Although the OB and OJ values decreased significantly between T0-T1, they increased between T1 and T2 ( P < 0.001).

Table I
Comparison of cephalometric changes
Parameter T0 (n = 20) T1 (n = 20) T2 (n = 16) P T0-T1 T1-T2 T0-T2
Mean SD Mean SD Mean SD
Skeletal
SNA 79.265 3.440 78.645 3.554 78.218 3.316 0.524 NS NS NS
SNB 75.255 3.542 75.005 3.325 74.793 3.241 0.746 NS NS NS
ANB 4.010 1.865 3.640 1.877 3.425 1.445 0.545 NS NS NS
Wits 2.245 2.573 0.19 1.763 0.318 1.531 <0.0001 *** NS ***
A-Na perp –1.760 3.530 −2.465 3.379 −2.431 3.587 0.277 NS NS NS
Pog-Na perp –7.945 5.839 −8.655 5.469 −8.243 6.915 0.613 NS NS NS
FH-NA 88.260 3.467 87.685 3.155 87.743 3.585 0.418 NS NS NS
N-CF-A 59.935 3.104 60.085 3.475 60.112 2.840 0.577 NS NS NS
Sgn-FH 60.415 3.669 60.760 3.205 60.343 4.221 0.614 NS NS NS
SN/Go-Gn 32.790 5.140 32.960 5.660 33.275 5.649 0.835 NS NS NS
PFH/AFH 63.280 4.525 62.960 5.528 62.731 4.371 0.726 NS NS NS
FMA 23.760 5.361 23.905 5.414 23.775 5.699 0.912 NS NS NS
SN-PP 10.285 3.194 10.405 3.616 10.425 3.161 0.403 NS NS NS
PP-MP 25.350 4.904 25.430 6.116 25.743 4.991 0.361 NS NS NS
NA-APog 5.215 5.164 4.855 4.798 4.375 4.252 0.537 NS NS NS
Sum total 395.645 5.083 396.015 5.580 396.125 5.409 0.759 NS NS NS
S-Go 72.115 7.134 72.575 7.028 72.668 6.320 0.788 NS NS NS
ANS-Me 62.570 5.847 63.685 6.081 63.587 5.335 0.139 NS NS NS
CoA 83.155 4.444 83.870 4.598 83.681 4.501 0.485 NS NS NS
Co-gn 107.505 7.009 108.835 7.633 108.631 6.610 0.236 NS NS NS
Mx-Md 24.350 4.105 25.385 4.208 24.956 4.111 0.102 NS NS NS
Dental
U1-SN 103.505 4.845 101.705 5.589 102.668 5.942 0.087 NS NS NS
U1-PP 113.810 5.414 112.185 5.823 112.768 6.497 0.23 NS NS NS
U1-NA 24.240 4.564 23.075 5.335 24.450 5.348 0.297 NS NS NS
U1-NA 4.870 1.769 4.010 1.937 4.087 1.796 0.063 NS NS NS
U1-MxOP 55.825 3.420 55.575 3.026 54.731 3.801 0.332 NS NS NS
L1-MdOP 66.025 4.286 64.645 4.054 64.568 3.731 0.065 NS NS NS
IMPA 92.430 5.318 97.965 4.811 96.800 5.343 <0.0001 *** NS **
L1-NB 23.335 5.156 28.475 4.438 27.937 4.340 <0.0001 *** NS ***
L1-NB 4.685 1.918 6.260 1.556 5.712 1.641 <0.0001 *** NS **
L1-APog 1.165 2.165 3.045 1.681 2.531 1.499 <0.0001 *** NS ***
U1-L1 128.430 6.221 124.665 5.441 124.375 5.949 0.002 ** NS *
U1-PP 26.790 3.095 27.455 3.247 27.487 3.241 0.319 NS NS NS
U6-PP 20.615 2.443 20.130 2.324 20.062 2.713 0.539 NS NS NS
L1-MP 34.510 3.252 33.790 2.877 34.006 3.149 0.306 NS NS NS
L6-MP 25.245 3.216 26.395 2.818 26.062 2.795 0.02 * NS NS
OB 2.570 0.91 0.99 0.869 1.468 0.755 <0.0001 *** NS ***
OJ 5.830 1.588 2.905 0.843 3.112 0.755 <0.0001 *** NS ***
Soft tissue
Nasal projection 13.955 2.072 14.635 2.266 14.668 2.251 0.071 NS NS NS
A′ –2.655 1.504 –2.595 2.002 –2.825 1.682 0.896 NS NS NS
B′ –13.735 3.364 –12.600 3.703 –12.737 3.227 0.063 NS NS NS
Pog׳ –12.115 3.968 –11.265 4.060 –10.987 3.413 0.065 NS NS NS
ULA 0.3 2.178 –0.02 2.340 –0.206 2.220 0.512 NS NS NS
LLA –4.245 2.808 –3.245 3.171 –3.793 2.998 0.072 NS NS NS
Soft-tissue convexity 125.715 3.427 125.895 3.661 125.893 3.051 0.508 NS NS NS
Nasofrontal angle 137.255 9.374 135.490 8.424 134.393 8.392 0.317 NS NS NS
Nasolabial angle 113.710 10.303 114.025 11.038 110.681 12.914 0.101 NS NS NS
LCTA 106.060 7.737 106.520 7.447 109.943 5.812 0.149 NS NS NS
Nasomental angle 123.945 4.525 123.365 3.661 121.806 4.371 0.153 NS NS NS
Labiomental angle 111.795 12.005 121.900 14.110 116.737 10.401 0.0008 *** NS NS
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May 12, 2020 | Posted by in Orthodontics | Comments Off on Evaluation of soft-tissue changes in young adults treated with the Forsus fatigue-resistant device
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