Class II malocclusions are observed at a high frequency in the daily practice of orthodontists; however, within Class II, there is large variability. Dentoalveolar relationships and skeletal patterns must be distinguished within Class II. Correctly diagnosing and establishing the etiology of the malocclusion is essential for determining the proper treatment plan.
When it is necessary to stimulate mandibular growth by repositioning the mandible forward, different removable and fixed functional appliances are frequently used for Class II correction.1 One of these fixed functional appliances is the 3M™ Forsus™ Fatigue Resistant Device. This system is used in conjunction with fixed multibracket appliances and consists of a push rod that acts on the cuspid or first bicuspid, which is inserted into a nickel-titanium cylinder and exerts an approximate force of 200 grams when activated.²
If we consider that the majority of Class II malocclusions are due to mandibular retrusion, treatment with the Forsus Corrector could be a reasonable option for managing this type of malocclusion.3 Compensatory extractions in the upper arch should therefore be limited to cases in which there is a marked protrusion of the upper lip to avoid adversely impacting the patient’s profile.⁴
Materials and methods
The patients included in the present study came from the Asturian Institute of Dentistry, University of Oviedo (Oviedo, Spain).
The sample consisted of the studies and records of 15 patients (8 men and 7 women) diagnosed with Class II mandibular malocclusion, aged between 12 and 19 years.The study inclusion criteria were as follows:
In all cases, a lateral cephalometric X-ray was available before the start of the study, with another immediately before placing the Forsus and a final X-ray at the end of treatment (Figure 1).
The distribution by gender was 8 men (53.33%) and 7 women (46.66%), with an average age of 13.93 years at the start of treatment and 16 years at the end of treatment.
Fixed appliances with a 0.018” bracket slot height with MBT prescription were used with the Forsus Device in working phase of orthodontics treatment. The mean total treatment length was 27.13 months, and the mean time of Forsus Device use was 6.13 months.
The cephalometric X-rays (taken immediately prior to Forsus Device application and at the end of treatment) of all patients included in the study were traced using Dolphin Imaging 11.7 Premium software. Figure 2 shows the detailed tracing of the skeletal planes before placement of the Forsus Device (pretreatment) and after completing the treatment (post-treatment).
Figure 2. Initial tracing before placement of the Forsus device and final tracing after treatment completion
The cephalometric analysis generated 22 variables: 9 angular, 12 linear, and one index for each plot.The variables analyzed were as follows:
To study the changes after using the Forsus Device, Student’s t-test or the Wilcoxon test for paired samples was used depending on whether data normality could be verified. The level of significance was defined as 0.05. The statistical analysis was performed using the R (R Development Core Team) program, version 3.4.4.
Results and clinical cases
Table 1 summarizes the initial (pretreatment) mean and standard deviations before placing the Forsus Device and final values after treatment (post-treatment), showing the significance of Student’s t-tests for related data. For the nonparametric Wilcoxon signed-rank test, the medians and the interquartile range (P25 and P75) are shown.
Means, std dev, and significance of data before installing the Forsus device and after treatment.
The means (DT) are shown in the case of parametric test and medians (P25-P75) in the case of nonparametric. T-Student test or Wilcoxon test were applied for the paired samples.
We found statistically significant changes for the variable’s Mandibular length (Co-Gn), SNB, Wits appraisal, Mx/Md diff, ANB, Overjet, Molar relation, Upper lip to E-Plane and Lower lip to E-Plane. Figure 3 shows those variables with statistically significant changes.
Changes in the different variables after using the Forsus Device.
Occlusal improvement occurred both in the molar relation and in the protrusion. Sagittal improvement was also observed in the Wits variable. Skeletal improvement was seen both in mandibular size and in its relationship with the maxilla. Anterorotation of the mandible was also observed in SNB and ANB. This was due to one of the benefits that treatment with the Forsus Device has over other techniques such as intermaxillary elastics—while the former causes an intrusive effect, the intermaxillary elastics cause extrusion of the lower molar, increasing the vertical dimension of the patient.
The aesthetic effect on the patient’s profile is related to the changes in the projection. In our study, there was a significant retrusion of both the upper and lower lip, which maintains a relationship with the correction of the projection and the position of the upper incisor. The retrusion of the lower lip may seem contradictory with the mandibular change; however, this situation arises because the lower lip rested on the upper incisor in most of the sample patients. This labial protrusion represents the position of the lips with respect to the chin and nose. Regarding the upper lip, despite having retruded significantly, both the upper and lower values remained within the norm. Regarding the lower lip, overall the patients started with a lower retruded lip, and although within the norm, the retrusion caused by the Forsus Device can be considered aesthetically displeasing. In contrast, it can be advantageous in those patients with a labial protrusion. Figure 4 shows the facial changes in one of the sample patients treated with the Forsus Device.
One of the problems commonly described with the use of the Forsus Device is the increase in the proclination of the lower incisors, especially in those cases where the clinical characteristics hinder complete Class II correction. However, in our study, no significant increase in this angle was produced. This was due to the use of full-length steel arches that are cinched, the use of continuous metal, and the incorporation of second molars in the system. Part of the performed treatment sequence is shown in Figure 5; the total duration of treatment was 24 months, and the use of Forsus was 6 months. Although the Class II correction of the midline and teeth on the left side was not complete in this case, it was based on a very unfavorable dental and skeletal sagittal relationship.
In relation to the patient biotype of the 12 patients, the skeletal vertical relationship was maintained. In three cases, patients acquired a more hypodivergent biotype, while no case presented a change towards a more hyperdivergent biotype. This is because the Forsus Device did not cause molar extrusion.
The Forsus Device demonstrated an occlusal Class II correction improvement, as evidenced by the molar relationship and the projection. There was no significant increase in the vertical dimension of patients. With proper management of the device, unwanted effects like an increase in the inclination of the lower incisor can be avoided.
The Forsus Device is an effective option for the treatment of those cases with a Class II molar relationship with little potential for mandibular growth.
1. Vijayalakshmi PS, Veereshi AS, Management of severe class II malocclusion with fixed functional appliance: forsus, The Journal of Contemporary Dental Practice 2011;12:216-220
2. Vogt W, The forsus fatigue resistant device, Journal of Clinical Orthodontics 2006;40:368-377
3. Jain AK, Patil AK, Ganeshkar SV, Sangamesh B, Chugh T, Non-extraction treatment of skeletal class II malocclusion, Contemporary Clinical Dentistry 2012 ; 3 : 334-337
4. Janson G, Mendes LM, Junqueira CH, Garib DG, Soft-tissue changes in class II malocclusion patients treated with extractions: a systematic review, European Journal of Orthodontics 2016;38:631-637
Iván Menéndez Díaz, DDS, MSc, P.hD, earned his dentistry license, Master in Orthodontics and Dentofacial Orthopedics and Ph.D. in Dentistry from the University of Oviedo. Eager to share his passion for dentistry and orthodontics as an educator, Dr. Díaz is a professor in orthodontics and assistant professor in surgery and medical-surgical specialties at Oviedo. He runs an exclusive private practice in orthodontics.
Teresa Cobo Díaz earned her degree in Dentistry at the European University of Madrid and Master in Orthodontics and Dentofacial Orthopedics at the University of Oviedo. She earned her Ph.D at the University of Oviedo. She is currently a Professor in Postgraduate Training in Orthodontics of the University of Oviedo and Assistant Professor in Surgery and Medical-surgical Specialties at the University of Oviedo. Dr. Díaz is a specialist in Lingual Orthodontics using the 3M™ Incognito™ Appliance System and an expert on Orthognathic Surgery. She owns a private practice exclusively in orthodontics.
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