Treatment of complex malocclusion requires meticulous treatment planning aiming at finding the etiology to modify the growth potential thereby giving a result which is in harmonious relationship with underlying skeletal, dental and overlying soft tissue. Here we are presenting a case of skeletal and dental class II malocclusion with hyperactive facial muscles treated using a hybrid myo-functional appliance. A 13-year-old male patient presented with skeletal class ii malocclusion with retrognathic mandible and a prognathic maxilla with dentoalveolar angle’s class II division I malocclusion, hyperactivity of mentalis muscle and other facial musculature. The plan was to treat the malocclusion with a hybrid functional appliance consisting of an oral screen and bionator buccinator loops to eliminate the abnormal muscle forces and a lower guide lane to advance the mandible forward. The patient wore this appliance for 9 months to achieve a class I skeletal and dental pattern.
KEY WORDS: CLASS II MALOCCLUSION, HYBRID APPLIANCE, FUNCTIONAL APPLIANCE , ORAL SCREEN
Authors of this article acknowledges the valuable contribution of Dr. Mimansa Kaushik (Ex. P.G. Student), and Dr. Nibedita Biswas (P.G . Student), Department of Orthodontics, K.D. Dental College Mathura, in making of this article.
In orthodontic practice, treatment of complex malocclusion requires meticulous treatment planning aiming at finding the etiology to modify the growth potential thereby giving a result which is in harmonious relationship with underlying skeletal, dental and overlying soft tissue The etiology of class II malocclusion can be skeletal, soft tissue, dental and habitual factors. Skeletal ClassII could be because of maxillary protrusion,mandibular retrusion or a combination of both1. According to Mc Namara1, 75 % of class II skeletal discrepancies are attributed due to mandibular retrognathism.
The various treatment modalities for skeletal discrepancies include growth modification, dental correction , camouflage and orthognathic surgery depend on significant factors like the age of the patient and the severity of the defect. Growth modification is the treatment of choice in a growing individual, that requires treatment planning in terms of identifying the forces which have restrictive effect on the physiological growth of individual . Therefore, a proper treatment plan should encompass a component approach towards treating a malocclusion as a net of all the factors causing the malocclusion as outlined by Vig and vig2. Hybrid appliance generate a cumulative effect resulting from growth modification and adaptation in response to therapeutic biomechanical interference which may be manipulated to result in clinically significant morphologic alterations in the growing child's dentition and craniofacial skeleton. Hybrid functional appliances are specifically and individually designed to exploit the natural processes of growth and development of that individual. It determines the selection of the component and their assemblies, resulting in appliance design that matches the needs of individual patient2.
A 13 year old boy in the pubertal growing phase, presented with skeletal Class II jaw base relationship and a dental Angles class II malocclusion as shown in figure 1 & 2 . He had a prognathic maxilla and retrognathic mandible with convex profile, posterior facial divergence, an obtuse nasolabial angle , potentially competent lips, hyperactive mentalis and with deep mentolabial sulcus.
Intraorally, the molars were in a Class II relationship and the Incisors were in Class II relationship with overjet of 10 mm and overbite of 6mm.
The cephalometric analysis showed a Class II skeletal pattern with ANB angle of 90 and maxillary incisors UI to SN was100º.and mandibular plane angle of 420 which signifies a hyperdigent growth pattern (figure -4). Evaluation of patient’s cervical vertebrae (CVMI) suggested that the patient was in a pubertal growth spurt with CVMI stage 3 (acceleration stage) which indicated optimal timing for orthopaedic functional therapy for a Class II discrepancy. No symptoms of temperomandibular joint disorder was detected.
Fig. 1: Pre Treatment Extra Oral Photographs
Fig. 2: Visual Treatment Objective
Fig. 3: Pretreatment Intra Oral Photographs
Fig. 4: Pre Treatment Radiographs
Sagittal correction during the pubertal growth phase was indicated for this patient along with the reduction in the hyperactivity of the peri-oral musculature. It was planned for a bi-phase therapy with the first phase of treatment intended for the sagittal correction with functional orthopedic approach followed by a second phase of fixed orthodontic mechano therapy. A removable modified Bionator with an oral screen incorporated (Hybrid Appliance)as shown in figure 5, was fabricated to stimulate the forward mandibular growth along with shielding of the buccal segments from the abberant muscles. This was followed by second phase of treatment with fixed appliance mechanotherapy for space closure and finishing and detailing of the occlusion..
Fig. 5: Hybrid Applaince In Position
A hybrid appliance was fabricated with horizontal advancement of 5 mm and vertical correction of 5mm.The patient was instructed to wear the appliance full time except during contact sports and during meals.
After 9 months of wear, a Class I molar and canine relationship was achieved on both the sides with improvement of facial profile and overbite reduced from 6mm to1mm and overjet reduced from 10mm to 3mm (figure 6&7) . Nasiolabial angle increased from 107 to 1300 (figure -8).
Fig. 6: Post Functional Extra Oral Photographs
Fig. 7: Post Functional Intra Oral Photographs
Fig. 8: Post Functional Radiograph
Phase II treatment
Immediately following the phase I therapy, multibanded fixed appliance therapy with MBT 0.22 appliance was initiated for final tooth alignment and to achieve harmonious intercuspation.
Various treatment modalities for treating Class II Div I malocclusion have been reported. Functional appliances are very effective in treating growing individuals and favorable results have been reported from various studies in achieving a harmonious relationship between maxilla and mandible when treated during growth phase4,5.
In this case, the functional appliance of choice was a Twin block with high pull headgear, but the patient denied to wear . After considerable deliberation, a hybrid appliance was fabricated as a modified bionator with an oral screen.
The principle of the bionator is to modulate muscle activity, enhance the normal development of the inherent growth pattern and eliminate abnormal and deforming environmental factors7,8 . Oral screen helps in guiding the lower lip into a more forward position and eliminating the lip trap, thereby enabling the dentoalveolar development to follow normal pattern9. It also helps in shielding the dentoalveolar structures from the deleterious effects of the abnormal buccal musculature.
In this case, the cephalometric analysis indicated a mandibular retrusive position, hyperdivergent growth pattern, increased overbite and overjet. With the modified bionator and oral screen (hybrid appliance), a favorable skeletal, dental and soft tissue relationships was achieved. Cephalometric analysis indicated a significant skeletal anterior repositioning. The ANB angle decreased by 6º, maxillary incisors inclination decreased from 100º to 93º, and the mandibular incisors were proclined (LIMPA-91-94º. The overjet correction was from 10mm to 3mm and the nasolabial angle increased from 107 to 130ºwhich signifies improvement in the nasolabial angle
Subjects treated at the peak of pubertal growth phase by advancement of mandible with the help of functional appliance regulation achieved a favorable skeletal and dental occlusion. In this case, a single step advancement using the Hybrid appliance not only facilitated the correction of the malocclusion but also corrected the peri oral musculature. This is a desirable consequence for long term stability of the treatment results achieved.
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