2020, Number 2
Class II skeletal correction in Forsus™ appliance therapy. Case report
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Language: English/Spanish [Versión en español]
References: 20
Page: 125-134
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ABSTRACT
Introduction: Class II malocclusion is usually the result of a lack of mandibular development. Functional appliances for mandibular propulsion are an effective alternative in early treatment. Objective: Improvement of mandibular profile and advancement for overjet correction; establishment of bilateral class I molar and class I canine, as well as adequate anterior guidance; release of crowding; maintenance of overbite and the intermolar and intercanine distance of both arches. Case report: A 12-year-old female patient, with a retention 10% to 25% of expected growth. Class II skeletal due to mandibular retrusion and posterior mandibular rotation, vertical growth and increased overjet. After alignment and levelling, she received four months of treatment with Forsus™. Results: Improvement of profile, correction of overjet with lower incisors proclination and slight mandibular growth. Class I molar and canine relationship, and posterior mandibular rotation. Conclusions: The Forsus™ is a functional appliance effective in the treatment of class II malocclusion in patients with retained growth, which has mostly dentoalveolar effects.INTRODUCTION
Class II malocclusion can result from multiple combinations of dental and skeletal components,1 with skeletal mandibular retrusion being the most common feature.1,2 According to these findings, treatments aimed at changing the amount and direction of mandibular growth are more appropriate than those aimed at restricting maxillary growth.1
The effects of functional appliances for the correction of class II malocclusion are mostly dentoalveolar,3-5 such as lower incisors proclination, which increases the length of the mandibular arch.6
The decision to treat with functional appliances should be made in consideration of both the benefits and adverse effects to the patient.7
Several studies have been conducted to compare the effects of Forsus™ with other mechanics, as well as with fixed and removable functional appliances during the correction of class II malocclusion.3,8-11 For example, less dentoalveolar response is generated with the Forsus™ functional appliance than with the PowerScope.8 The Andresen activator, despite demonstrating greater skeletal changes, produces the same stimulation of mandibular growth and inhibition of maxillary growth as the Forsus™,9 with similar changes in profile, both being effective in the treatment of this type of malocclusion. Compared to the Twin Block, both have an effectiveness rate of 80%, although the Twin Block effect is mostly skeletal, while the Forsus™ is mostly dentoalveolar.10 Greater success is achieved with the Forsus™ for the correction of unilateral class II relationship, overjet and midline deviation than with the use of intermaxillary elastics.11
The main goals of Forsus™ treatment are to provide stimulation of mandibular growth11,12 and inhibition of maxillary growth.12,13 Skeletal effects include increased posterior lower facial height, counterclockwise mandibular rotation,12 increased occlusal plane height,14 and improved ANB and SNA angles.15 Among the most reported dentoalveolar effects are protrusion,12-14 proclination9,10,12,14,15 and intrusion12,14 of lower incisors, upper incisors retroinclination, distalisation9,14 and intrusion of upper first molars, and reduction of overbite and overjet.12
Other benefits that can be achieved through Forsus™ therapy include improving the profile15,16 and achieving increased pharyngeal airway space in class II division 1 patients with retrognathic mandible.17
The cervical vertebral maturation stages described by Lamparski were modified by Hassel and Farman in 1995,18 who established six stages of maturation. The fourth stage was called deceleration because growth begins to slow dramatically, with 10% to 25% of expected adolescent growth. The inferior borders of C2, C3 and C4 present a well-defined concavity and the vertebral bodies of C3 and C4 begin to acquire a square shape.18 According to the literature, the Forsus™ allows a more effective correction of the class II molar relationship during the C3-C4 stage of vertebral maturation than in the C5-C6 stage, which is a period of faster mandibular growth.19
We present a case of a class II dental and skeletal correction in a 12-year-old female patient with retained growth, using the Forsus™ functional appliance.
CLINICAL CASE
Diagnosis: a 12-year-old female patient, whose consultation reason was "Because my jaw is too far back"; dolichofacial biotype, oval face, long nose, thin lips, enlarged lower third and middle fifth, inclined and coincident interpupillary and intercommissural lines, convex profile, lip incompetence, medium and parallel smile, only upper teeth are exposed when smiling (Figure 1A). The intraoral analysis shows permanent dentition, initial caries lesions in upper and lower first and second molars, slight anteroinferior crowding, Angle class II molar and canine relationship and increased overjet (Figure 1B).
Model analysis shows continuous and oval arches, lower midline deviated 2 mm to the right, overjet of 5 mm and overbite of 3.5 mm, the curve of Spee of 2 mm, upper arch length discrepancy of -0.5 mm and lower of -3 mm, Bolton analysis with maxillary excess of 1.7 mm from 6-6 and 0.5 mm from 3-3.
The panoramic radiography showed possible upper airway obstruction, presence of third molar cavities, a crown-root ratio of 1:1.5, and roots of dental organs 12 and 22 inclined mesially (Figure 2A). No alterations were found in the temporomandibular joint.
The Steiner analysis was performed with Dolphin Imaging version 9.0.00.19 software on the initial lateral cranial radiography (Figures2B and C). Class II skeletal features include slight maxillary protrusion, posterior mandibular rotation and mandibular retrusion, vertical growth pattern, proclined and protruded upper and lower incisors (Table 1). Likewise, the fourth stage of skeletal maturation, according to Hassel and Farman, can be seen indicating the expected retained adolescent growth of 10-25%.
Treatment objectives: improve the mandibular profile and advancement for overjet correction; establish bilateral class I molar and class canine, as well as adequate anterior guidance; release crowding; maintain the overbite, and the intermolar and intercanine distance of both arches.
Treatment plan: alexander 0.018" upper and lower brackets, upper bands with double tube and lower bands with single tube. Alignment and leveling with archwire sequence 0.014" Nitinol (NiTi), 0.014" stainless steel (SS), 0.016" SS, 0.016" × 0.022" SS and 0.017" × 0.025" SS. Forsus™ appliance placement (four to six months). Retention.
Treatment alternatives: conventional brackets. Extractions of upper first premolars, anterior retraction and settling. Retention.
Treatment progression: placement of upper and lower bands and brackets with 0.014" NiTi archwire (Figure 3A). Alignment and levelling archwire sequence until 0.017" × 0.025" SS archwires are reached and panoramic radiography is taken to evaluate root parallelism.
At nine months after the start of treatment, the 0.017" × 0.025" SS archwires are cinched, each arch is ligated in a 6 to 6 8-shape; a transpalatal arch and Forsus™ appliance are inserted (Figure 3B).
Continuous revision of the propulsion appliance is performed for four months, then the Forsus™ is removed and ¼ 4.5 oz class II vector elastics are indicated (Figure 4).
The upper archwire was replaced with a progressive torque archwire and elastics were suspended, and when a slight relapse was observed, class II vector elastics of ¼ 6.5 oz were indicated again. Brackets were removed after one year and five months of treatment. The retention was a bite plane in the upper arch and a fixed lower retainer is cemented from canine to canine.
RESULTS
The profile and aesthetics of the smile were improved (Figures 5A and 6A), the overjet was corrected by proclination of the lower incisors by 3o, which can be seen in the IMPA value in Table 1, and in the slight mandibular growth of the patient (Figures 6B and 7C). The maxilla descended as a consequence of the patient's growth, and posterior mandibular rotation and mandibular advancement was observed (Figure 7C). A 2o decrease in ANB was obtained (Table 1).
Class I molar and canine relationship was established (Figures 5B and 8), anterior guidance, crowding release, levelling and slight extrusion of upper molars improved the overbite.
The anteroposterior facial results were favourable, however, the increased dolichofacial pattern could not be avoided as a consequence of the mechanical elastics generating posterior mandibular rotation. This can be seen in the final lateral cranial radiography and superimpositions (Figures 7B and C), as well as the root parallelism in the panoramic radiography (Figure 7A). The patient and her family were very satisfied with the results.
DISCUSSION
The ideal time to treat class II malocclusions is adolescence, near the peak of growth.20 By means of mandibular propulsion, a better facial profile can be achieved from mostly dentoalveolar changes in the lower arch.16
Among the treatment options for this type of malocclusion is the Forsus™ appliance, which maintains the mandible in a constant anterior position and which has been reported in different publications to have an effect on class II patients with mandibular deficiency.2,5,13,16,20
The 12-year-old patient presented in this study had a class II skeletal condition, an initial ANB of 6o and a convex profile. The treatment consisted of mandibular propulsion with Forsus™ and the main changes obtained during correction were lower incisors proclination, which allowed reduction of the overjet, and a significantly more aesthetic facial profile. Goracci and Cacciatore20 also obtained an improvement in overjet and aesthetics in a patient aged six years and nine months, with early treatment with Forsus™, who still had retained growth like our patient.
In the case reported by Jain et al,2 of a 14-year-old patient, also with retained growth, 10 mm of overjet and an ANB of 7o, a correction of the dento-skeletal relationships was achieved, with a 3o decrease in the ANB and an improved facial profile. She experienced less incisor proclination, which may be attributed to the use of a sectional archwire with torque prior to Forsus™ placement.
For greater control of secondary dentoalveolar effects, such as marked proclination of the lower incisors, Turkkahram et al13 recommend the use of the Forsus™ with bone anchorage.
Finally, in our case, a CT scan before and after treatment would have been ideal to evaluate whether condylar remodelling was generated by the stimulus of the orthopaedic appliance. It is therefore recommended for future studies.
CONCLUSIONS
In patients with class II malocclusion due to mandibular retrognathism, who present slight retained growth, treatment with the mandibular propulsor provides favourable results in the correction of the overjet, as well as improving the aesthetics of the patient's profile.
The Forsus™ can be a method of correction for malocclusion II, with mainly dentoalveolar effects, which improves the profile of growing patients.
REFERENCES
AFFILIATIONS
1 Alumna de la Especialidad en Ortodoncia. Departamento de Clínicas Odontológicas Integrales. Centro Universitario de Ciencias de la Salud. Universidad de Guadalajara, México.
2 Egresada de la Especialidad en Ortodoncia. Departamento de Clínicas Odontológicas Integrales. Centro Universitario de Ciencias de la Salud. Universidad de Guadalajara, México.
3 Profesor de la Especialidad en Ortodoncia. Departamento de Clínicas Odontológicas Integrales. Centro Universitario de Ciencias de la Salud. Universidad de Guadalajara, México.
CORRESPONDENCE
José de Jesús García López. E-mail: pepegalop@yahoo.com.mxReceived: Marzo 2021. Accepted: Junio 2021.