In this article we describe the clinical evaluation in of Active Vertical Corrector (AVC), which is a removable or fixed orthodontic appliance that intrudes the posterior teeth by reciprocal forces. By the use of magnets for posterior intrusion of teeth, the mandible is allowed to rotate in upward and forward directions. The uniqueness of this appliance is that it corrects anterior open bite problems by reducing anterior facial height. This appliance treats the cause (over eruption of posterior teeth) and provides better facial balance and esthetics than most conventional orthodontic treatment procedures.
Correct force application is the prescription of orthodontic tooth movement.1,2 Skeletal open bites are caused mainly by over eruption of the upper posterior teeth and, or vertical over growth of the posterior dentoalveolar complex. These could be due to posterior rotation of the mandible, superior repostioning of the glenoid fossa due to under development of the anterior portion of the maxilla, or a combination of these effects.2,3
Surgical intervention such as Lefort I procedure is the treatment of choice for a severe skeletal open bite. Orthodontically, early correction can be achieved through high pull headgears, activators, combined headgear and upper plate, open bite bionator, activator headgear combinations active and passive bite blocks and vertical chin cups.3-5
Treatment of the malocclusion is either by extrusion of anterior teeth or intrusion of posterior teeth. Extrusion of anterior teeth posed aesthetic problems like a gummy smile.5 Other than the conventional force systems a new force system has been introduced in orthodontics. This is the magnetic force system.
The Active Vertical Corrector is an adaptation of the bite block therapy, introduced in 1986 by Dr. Eugene. L. Dellinger.4 The Active Vertical Corrector (AVC) works as an energized bite block. The Active Vertical Corrector is a simple removable appliance which consists of posterior occlusal bite blocks containing repelling magnets (Figure 1). It intrudes the posterior teeth causing the mandible to rotate upward and forward in much the same way that it would if the maxilla were surgically impacted. Hence Active Vertical Correctors are now used as an alternative to orthognathic surgery in anterior open bite cases in patients of all ages.6
A clinical evaluation of three cases treated with Active Vertical Correctors is presented. This treatment approaches the problem at its cause (over eruption of posterior teeth) and provides better facial balance and esthetics than most conventional orthodontic treatment procedures.
The aim and objectives of our study was to clinically evaluate the skeletal and dental changes that occur during treatment with the Active Vertical Corrector (AVC) and its effectiveness in treating anterior open bite malocclusions.
Materials and Methods
The Active Vertical Corrector is a patented appliance of Allessee Orthodontic Appliances (AOA). It consists of two posterior occlusal splints, one for the upper and one for the lower jaw. Samarium cobalt magnets are incorporated into the acrylic splints over the occlusal region of the teeth to be intruded (Figure 1). One magnet per distal quadrant is used. The magnets in the upper splints are incorporated in a mode to repel the magnets in the lower splints therefore the appliance is a combination of acrylic posterior bite blocks and repelling magnetic forces.
To prevent unwanted crossbite development due to the shearing forces of repelling magnets, angled buccal flanges are added to the lower occlusal splint to stabilize the appliance during lateral jaw movements.
A heavy gauge stainless steel wire connects the occlusal splint of each arch. The magnets generate a force of 700 grams per unit at zero air gap in repulsion.
Criteria for case selection
Three cases were selected for our study. Presence of anterior open bite was the main criteria. If the anterior open bite was of skeletal origin rather than dental origin it was preferred. Patient with dental open bites were also considered. Patients in the growing age and in the mixed dentition period were preferred, so as to elicit maximal skeletal response. The patient should be encouraged to wear the AVC throughout the day.
The AVC appliance is cemented or bonded in place. At the end of 12 weeks the appliance can be removed and the AVC can be worn as a removable appliance. At the end of 12 weeks the patient will have had enough change to be encouraged to continue wearing the appliance on a removable basis.
Results and observations
A girl aged 11 years and 2 months had a mild skeletal anterior open bite of 1.5 mm with a lower gonial angle of 75°. After the treatment as a fixed appliance for three months an overbite correction of 3 mm was achieved. This closure was excessive causing the anteriors to occlude creating a posterior open bite of 2.5 mm. Proper functioning of the anterior teeth and acceptable aesthetics were achieved (Figures 2,3,4 &,5).