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Correcting Class II Malocclusions with the Forsus Appliance Dr. Lisa Alvetro

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by Dr. Lisa Alvetro

As clinical orthodontists we are continually faced with the need to correct Class II malocclusions. Transforming them into functional, stable and aesthetically pleasing Class I occlusions can be challenging. To ensure that we achieve this successful outcome, a treatment approach that is independent of patient cooperation becomes essential. This treatment approach must be reliable, predictable and convenient for our patients. It must also be a technique that is easily incorporated into our existing clinical protocol.

In our clinic we have found that the Forsus™ Fatigue Resistant Device fulfills all of these criteria. We find it to be effective in correcting Class II malocclusions that are of varying origins. Due to the force vectors generated by the appliance and the ability to manipulate them during treatment, the appliance can be used in Class II malocclusions that originate from maxillary protrusion, mandibular retrognathia or the combination of both. By adjusting the Forsus appliance and the vector of force it delivers we are also able to use it in both our deepbite and openbite Class II patients.

Often clinicians rely on the use of Class II elastics to correct Class II relationships. Not only is this technique completely dependent on patient cooperation but might also involve vectors of force that are counterproductive. The attachment location of Class II elastics creates an extrusive and distal force on the maxillary incisors. The resulting side effects can be loss of maxillary labial crown torque, extrusion of the maxillary incisors, deepening of the bite and an increase in maxillary anterior gingival display. The Class II elastic force on the mandibular molars creates a vertical force vector that can extrude posterior molars, increasing posterior vertical dimension and create a downward and backward rotation of the mandible, thus increasing the severity of the Class II relationship.

We find Forsus creates a force system that is better suited to correct Class II relationships than the forces delivered through Class II elastics. Torque loss and extrusion of the Maxillary incisors is no longer a challenge and the intrusive force on the maxillary molars aids in our Class II correction. The side effect of mandibular incisor proclination often associated with fixed Class II correction appliances can be controlled. We accomplish this through the use of negative torque in the mandibular incisor brackets and placing the mandibular push rod distal to the first bicuspid. Figure 1 shows force vectors associated with Class II elastics and the Forsus appliance.

A Forsus appliance consists of three major components: a mandibular archwire, telescoping spring module that attaches to the maxillary first molar and a mandibular push rod that is used for activation. Several design options exist for the Forsus spring module and its installation. The spring module can be attached using the L pin module (Fig. 2) or the EZ2 (Fig. 3).

Options exist for the attachment location of the spring module. If using the L pin module, the location of attachment can be either through the occlusal or through the gingival headgear tube on the maxillary first molar. If using the EZ2 module, attachment is through the occlusal headgear tube on the maxillary first molar. We choose the spring module design, L Pin or EZ2 module, and location of attachment based on treatment objectives and force requirements needed to correct the existing malocclusion.



Forsus spring options that we utilize are:
  1. EZ2 module in an occlusal headgear tube (Fig. 4) producing the most horizontal component of force.
  2. L Pin module in an occlusal headgear tube (Fig. 5) the most adjustable variation for attachment.
  3. L Pin module in a gingival headgear tube (Fig. 6) producing the most vertical component of force.
EZ2 modules inserted into an occlusal headgear tube exert the most horizontal force vector. We consider it our substitution for Class II elastics and headgear in patients with flat to average mandibular planes. This attachment method was used in the patient seen in (Fig. 7) pre treatment cephalometric film and (Fig. 8) pre treatment photos. A stable treatment result is shown in the one-year retention cephalometric film (Fig. 9) and photos (Fig. 10).

The L Pin module inserted into an occlusal headgear tube is the option that is most adjustable. It allows for customization of spring placement in both a horizontal and vertical direction. By adjusting the L Pin from behind the headgear tube the spring module can be positioned in a buccal or horizontal direction. This might be helpful in a clinical situation where a maxillary transverse deficiency exists at the time of Forsus placement. The transverse deficiency will correct as the appliance is activated due to the horizontal component of force exerted on the posterior maxillary teeth.

L Pin modules inserted into occlusal headgear tubes can also be useful when a molar is mesially rotated. The mesial rotation of the molar places the spring in an undesirable location that might interfere with the occlusion. By adjusting the L Pin distal to the molar headgear tube the spring can be relocated to avoid occlusal interference. As the appliance is activated the mesial rotation of the molar will be corrected.

The L Pin module inserted in a gingival tube creates the most vertical force system. This attachment is selected for Class II patients with steep mandibular planes, increased lower face heights and anterior openbites. Maximizing the vertical component of force allows us to optimize maxillary molar intrusion while leveling the posterior occlusal plane. Intrusion of the maxillary molars can lead to auto rotation of the mandible that combines with the horizontal component of force of the appliance to aid in correction of the Class II relationship.

An example is shown where Forsus is placed in a gingival tube using the L Pin attachment to maximize molar intrusion during Class II correction. An open-bite malocclusion, increased lower face height and steep mandibular plane can be seen on the pretreatment cephalometric film (Fig. 11). Pre-treatment photos show a Class II dental relationship with an anterior open bite (Fig. 12).

The post treatment cephalometric film (Fig. 13) demonstrates through the use of Forsus in a gingival headgear tube the maxilla to mandible relationship can be corrected. Post treatment photos (Fig. 14) show open bite closure, improved facial aesthetics and occlusal relationship.

Not only can the spring design and location be selected by the clinician but the mandibular push rod location can be selected as well. Our clinical protocol routinely places the push rod distal to the mandibular first bicuspid in most cases (Fig. 15). Using the first bicuspid attachment location, the push rod lies flush with the dentition while creating a favorable vector of force in the supporting mandibular dentition. Figure 16 shows the mandibular push rod placed distal to the cuspid. This location was the originally manufactured design and is still an option used clinically by many orthodontists. However we have found by placing the rod distal to the first bicuspid it allows the rod to be used in its manufactured form requiring no additional modification for patient comfort. Patients appreciate the bicuspid rod location due to increased comfort and that the appliance remains out of sight even when the patient smiles or during functions such as talking and chewing (Fig. 17).

Clinically, the bicuspid location (Fig. 15) appears to provide better control of our lower incisor position by reducing incisor proclination. In our clinical study of the first 25 sequentially treated Class II cases in which the mandibular rod was placed distal to the first bicuspid the incisor proclination was reduced by 50 percent with an average value of 2.8 degrees of increased proclination during treatment as measured by IMPA. We have also been able to determine from our in-office studies that the amount of Class II correction in the anterior posterior direction is not affected and remains the same with either the bicuspid or cuspid push rod location.

Our first choice for push rod location is the first bicuspid. However, the mandibular cuspid position might be indicated in cases of severe mandibular retrusion to create the correct activation of the appliance. In this situation the first bicuspid might be in such a retruded position that it places the Forsus appliance in to vertical of a position. This position might generate too much vertical force and not enough horizontal or anterior posterior force for effective Class II correction. In this clinical situation we start with the mandibular push rod distal to the cuspid. Once the maxillary to mandibular relationship begins to improve, the rod will be relocated distal to the first bicuspid to activate the appliance.

As we continue to use the Forsus appliance we have determined that they are effective in many clinical situations. One such situation is in extraction cases that require conservation of maxillary anchorage to maximize dental and facial treatment results. An example is seen in (Fig. 18) where severe crowding exists in both arches with a Class ll dental relationship and moderate overjet. A mandibular deficiency is seen in the pre-treatment cephalometric film (Fig. 19). Either type of spring module can be used in this case with its purpose to maintain maxillary anchorage and correct the Class II relationship while improving the mandibular position.

In this case the pre-forsus cephalometric film (Fig. 20) shows that the arches are leveled and aligned and the maxillary and mandibular incisor position and torque are established prior to Forsus placement. Extraction spaces are closed after the Forsus appliance has been placed (Fig. 21).

Treatment time, 15 months and Forsus in place three months. Extraction space closure is accomplished using NiTi open coil springs that will deliver a light and continuous force. The Forsus appliance is activated to correct the Class II dental relationship. The force on the maxillary molar from the spring will act as a headgear in the maxillary arch maintaining molar position preserving anchorage during maxillary space closure and maxillary incisor retraction. The mandibular rod of the Forsus appliance will support the mandibular incisor position as the posterior buccal segments are protracted mesial. The result is an efficient system that corrects the dental relationship while closing extraction spaces and is independent of patient cooperation for successful results.

Another clinical challenge is a Class II case requiring significant maxillary retraction in combination with maxillary incisor intrusion. The Forsus appliance creates a favorable force system that will allow us to accomplish our treatment objectives in an easy and effective way. Either spring module design or location of attachment in either the occlusal or gingival headgear tubes can be used. Selection is dependent on the vertical factors in the case analysis. From the pre-treatment photos (Fig. 22) a significant maxillary incisor procumbancy and anterior vertical maxillary excess exists. A unilateral Class II dental relationship also exists. From the pre-treatment cephalometric film (Fig. 23) it is determined that incisor intrusion along with retraction is indicated. Since the patient is 15 years of age correction will need to be dental in nature. Forsus was used to correct the Class II dental relationship through distalization and then maintain the correction during maxillary incisor retraction and intrusion. Photos at six months retention (Fig. 24) and the cephalometric film is at debond (Fig. 25). Both demonstrate an improved dental relationship with reduced incisor protrusion and decreased maxillary anterior gingival display. The improvement in facial aesthetics can be seen when comparing Figure 26 and Figure 27.

The versatility of the Forsus appliance system combined with its ease of use has created an environment where we can confidently approach challenging clinical situations. We use it as part of our initial treatment plan and present it at the consultation appointment. We utilize Forsus in any case that requires Class II correction, maxillary distalization or anchorage. The ability to manipulate the force vector based on case analysis and treatment objectives makes the Forsus appliance adaptable to many clinical situations. Combining these advantages with the independence from patient cooperation has made our daily clinical experiences more enjoyable for me, my team and our patients.
Author’s Bio
Dr. Lisa Alvetro graduated Summa Cum Laude from the Ohio State University Dental School in 1991. She then completed her orthodontic residency through Case Western Reserve University, where she currently serves as an Associate Clinical Professor. Dr. Alvetro has more than 16 years experience operating her custom designed, state-of-the-art practice in Sidney, Ohio. Dr. Alvetro continues to focus on efficient processes, innovative products and team development to sustain a quality practice. As a 3M advocate for four years, she has lectured extensively in the United States as well as Canada, Europe, India, Japan, Australia and Russia. Dr. Alvetro and Alvetro Orthodontics support and organize dental mission trips to Tanzania, Africa. In addition to the annual trips with other dental professionals in the area, the office continues to be involved in the African village. Dr. Alvetro and her team spearheaded the construction of the Angel House Orphanage, which was completed in November 2009.
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