Forsus Class II Correctors as an Effective and Efficient Form of Anchorage in Extraction Cases

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1 Forsus Class II Correctors as an Effective and Efficient Form of Anchorage in Extraction Cases by Lisa Alvetro, DDS, MSD After receiving her DDS summa cum laude from Ohio State University, Dr. Alvetro completed her residency at Case Western Reserve University and now lectures there as an Associate Clinical Professor teaching Practice Management. After more than 16 years of private practice in Sidney, Ohio, Dr. Alvetro continues to focus on team development, innovative products and efficient processes to sustain a quality practice. Forsus Class II Correctors: A Reliable Anchor The Forsus Class II Corrector has been shown to be an effective appliance in the correction of Class II malocclusions. Its success lies with its ease of use, durability and independence from patient compliance. Often practitioners consider its use instead of headgear and Class II elastics. However, as we continue to gain clinical experience with the appliance we have found it also to be very useful in treating extraction cases. When a Forsus corrector is incorporated into our treatment protocol for patients that require extractions we find an increase in efficiency and predictability of treatment outcome. In extraction cases a headgear can be useful as maxillary anchorage in maintaining molar position during anterior retraction. Maintaining maxillary molar position and avoiding anchorage loss is often required to achieve an ideal occlusion and optimal facial esthetics. However, the use of headgear is completely dependent on patient compliance, leaving the success of our treatment in the control of our patients. Our alternative is to use the Forsus appliance as a headgear. We use it to maintain maxillary anchorage or distalize the maxillary molars to obtain a Class I molar relationship during the closure of extraction spaces. This approach is independent of patient compliance and ensures a successful treatment outcome. In extraction cases, another clinical challenge can be to maintain mandibular incisor position and torque during mandibular space closure. Often when attempting to slide the mandibular posterior buccal segments forward the mandibular incisors respond by retracting or losing torque resulting in an increase in overjet. We have found the Forsus corrector to be the solution to this clinical situation by using the mesial force of the pushrod to maintain the incisor position. Therefore, the Forsus corrector is serving two roles during extraction space closure. In the maxillary arch it acts as a headgear for anchorage during maxillary retraction and in the mandibular arch it maintains mandibular incisor position during posterior protraction (Figure 1). Our standard Forsus corrector set up for space closure is seen in Figure 2. Our bracket selection is SmartClip SL3 Self-Ligating Appliance System utilizing the MBT Versatile+ Appliance System prescription with -6 of torque in the mandibular incisors. Our standard installation uses a ligature with bite guard on the 1st bicuspid under the mandibular beta titanium archwire. The maxillary archwire is a posted NiTi for the Forsus Fatigue Resistant Device. The rod size is selected for ideal activation of 200 grams. NiTi coil springs are attached to the maxillary 1st molars and posts on the maxillary archwire. In the mandibular arch the NiTi coil springs are attached to the mandibular 1st molar and onto the cupid brackets with a wire ligature. 1 Figure 1: Force vectors associated with Forsus Class II Correctors. 2 Figure 2: Typodont photo to demonstrate space closure set up.

2 NiTi coil springs are selected to provide the force for space closure due to their ability to provide a constant force on the dentition that does not degrade over time. The strength of the NiTi coil springs is selected based on molar and incisor position. Sliding mechanics in the posterior buccal segments are enhanced due to the reduced friction environment provided by the SmartClip Self-Ligating Bracket. Therefore, the combination of the constant force of the NiTi coil spring and the SmartClip brackets creates an efficient system for space closure. 75 grams Forsus Class II Correctors 100 grams 75 grams If the Forsus Appliance is ideally activated at 200 grams it can be assumed that it exerts a distal force of 100 grams on the maxillary molar and a mesial force delivered by the pushrod of 100 grams in the mandibular arch. If a NiTi coil spring is selected that delivers 200 grams of force, it can also be assumed that the force will be exerted equally in a mesial and distal direction. In the maxillary arch 100 grams of mesial force is exerted on the molars by the NiTi coil spring and 100 grams of distal force is exerted on the anterior teeth through the post on the archwire. The distal force of the Forsus corrector on the maxillary molar counteracts the mesial force exerted by the NiTi coil springs. The result is that the maxillary molars maintain their position while the anterior teeth retract. In the mandibular arch the NiTi coil springs exert a mesial force of 100 grams on the molar and a distal force of 100 grams on the anterior teeth through its attachment on the cuspid. The 100 grams of force exerted by the Forsus corrector pushrod is used to counteract the 100 grams of distal force of the NiTi coil springs that is placed on the mandibular anterior teeth. The result is that the mandibular anterior teeth remain in position and the mandibular posterior segment protracts (Figure 3). 4 Forsus correctors 100 grams Figure 4: Reduce the strength of the maxillary to prevent mesial molar advancement. In Class II cases, this force imbalance can be used to distalize molars. Forsus correctors 100 grams Forsus Class II Correctors 100 grams 5 75 grams 75 grams Forsus Class II Correctors 100 grams Figure 5: Reduce the strength of the mandibular to prevent anterior torque loss and potentially uprighting the mandibular incisors. If at any time during maxillary space closure it appears that anchorage is being lost and the maxillary molars are slipping mesially, the strength of the NiTi coil spring is reduced. This reduces the mesial force placed on the maxillary molar by the NiTi coil spring. In a Class II molar relationship, this imbalance of force where the distal force is greater on the maxillary molar than the mesial force of the NiTi coil springs can be used to distalize the maxillary molars during maxillary anterior retraction to obtain a Class I relationship (Figure 4). Forsus correctors 100 grams 3 Figure 3: With equal counteracting force at the maxillary molar and the mandibular anterior segment, s retract maxillary anterior teeth and protract the mandibular posterior segment. During mandibular space closure, if the mandibular incisors appear to be losing torque or retracting, the strength of the NiTi coil springs in the mandibular arch is reduced. This reduces the distal force from the NiTi coil spring on the mandibular anterior teeth. This imbalance of force results in a greater mesial force from the Forsus corrector springs, and the mandibular incisors procline (Figure 5).

3 In the clinical situation where both the maxillary molars need to be distalized and the mandibular incisors to be advanced, the force produced by the Forsus Appliance springs can be increased by the addition of a split crimp. This additional activation will increase the distal force placed on the maxillary molars by the spring module and increase the mesial force placed on the mandibular incisors by the pushrod. The forces produced by the NiTi coil springs in the maxillary and mandibular arches will remain the same. The net result is a greater distal force on the maxillary molar producing distalization while still retracting the maxillary anterior teeth. In the mandibular arch, the posterior teeth protract while the mandibular incisors upright. Case 1 The initial photos and cephalometric film of a 13 year old patient are seen in Figures 6-7. Due to the amount of crowding it was determined that extractions were needed. When considering the anterior posterior relationship of the maxilla to mandible, it was determined that to achieve optimal alignment and occlusion a Forsus appliance would be used in combination with our SmartClip Self-Ligating Appliance System. As part of our treatment plan, the maxillary 1st bicuspids and mandibular 2nd bicuspids were extracted. The maxillary and mandibular arches were leveled and aligned without any attempt to close extraction spaces. Instead the extraction spaces were only used to align the dentition and position the incisors within the maxillary and mandibular arches. The cephalometric film taken at 12 months treatment progress is immediately prior to Forsus corrector placement (Figure 8). The mandibular archwire is the Beta wire and the maxillary arch is a posted Nitinol wire. Note that a Class II molar relationship, overjet and extraction space still exist in the malocclusion. When the Forsus corrector is placed, the NiTi coil springs are attached in the maxillary and mandibular arches as shown in Figure 2. The NiTi coil springs will close the extraction spaces while the Forsus corrector will act as maxillary anchorage and support mandibular incisor position and correct the anterior posterior relationship. Figure 9 demonstrates the extraction space closure, molar relationship and overjet after Forsus corrector and NiTi coil springs have been in place for 3 months. 6A 6B 9A 9B 6C 9C 9D 6D 6E 9E 9F 6F Figure 6: Case 1 maxillary 1st bicuspids and mandibular 2nd bicuspids were extracted. 6G 9G Figure 9: At 15 months into treatment, 3 months wearing Forsus Appliances. 9H 7 8 Figure 7: Initial cephalometric x-ray. Figure 8: 12 month cephalometric x-ray, before Forsus Appliance installation.

4 Case 2 Although the patient in Figure 10 has a Class I molar relationship, evaluation of the initial cephalometric film (Figure 11) reveals a discrepancy between the maxilla and the mandible. Therefore our treatment plan included the use of the SmartClip Self-Ligating Appliance System combined with Forsus Class II Correctors. To alleviate the crowding within the arches an extraction pattern of maxillary and mandibular 1st bicuspids was selected. Figure 12 is the post leveling aligning progress cephalometric film. This film is pre extraction space closure and pre Forsus corrector placement. Since the mandibular 1st bicuspids were extracted a variation of our Forsus corrector placement exists. In this case the Forsus corrector pushrod is located distal to the mandibular cuspids. The NiTi coil springs are attached in the standard location. 10A 10B 10C 10D 10E 10F Figure 10: Case 2. 10G 10H Figure 11: Case 2 initial cephalometric x-ray. Maxilla and mandible discrepancy. Figure 12: Case 2 progress cephalometric x-ray after levelling and aligning.

5 Case 2 progress photos are shown (Figure 13) at 15 months total treatment time. The Forsus Class II Corrector and NiTi coil spring combination have been in place 4 months to close the maxillary and mandibular extraction spaces and establish a Class I molar and cuspid relationship. Our clinical protocol is that once the maxillary and mandibular extraction spaces are closed and an ideal overjet and molar relationship achieved, the Forsus correctors and the NiTi coil springs remain in place passively for one 6-8 week appointment interval. At the next appointment the Forsus corrector and NiTi coil springs are removed. To ensure that extraction spaces remain closed the maxillary and mandibular arches are be chained with power chain from first molar to first molar. The case now proceeds into the finishing stage of treatment. Progress photos taken at 19th month of treatment (Figure 14) are 2 months post Forsus corrector removal with the case requiring a slight amount of midline correction following settling of the occlusion. 13A 13B 13C 13D 13E 13F Figure 13: At 15 months into treatment, 4 months wearing Forsus Appliances. 13G 13H 14A 14B 14C 14D 14E 14F Figure 14: At 19 months into treatment, 8 weeks after Forsus Appliance installation. 14G 14H

6 Total treatment time for this patient was 20 months. Treatment results are seen in Figure 15 and Figure 16. Positive changes were observed in the facial profile and aesthetics (Figure 17-18). A comparison of the initial malocclusion and final occlusion demonstrates a pleasing result (Figure 19). 15 Figure 15: Final cephalometric x-ray. 16A 16B 16C 16D 16E 16F Figure 16: Final Case 2 photos. 20 months of treatment time. 16G 16H 17A Figure 17: Case 2 pre- and post-treatment. 17B

7 Figure 18: Case 2 pre- and post-treatment. 18A 18B 18C 18D 18E 18F Figure 19: Case 2 pre- and post-treatment. 19A 19B 19C 19D Conclusion: The combination of Forsus Class II Correctors with the SmartClip Self-Ligating Appliance System can create an efficient treatment protocol in extraction cases. The loss of maxillary anchorage and control of mandibular incisor position is no longer a challenge during space closure. Clinically its ease of use and acceptability by patients makes it an excellent treatment choice for many cases. We appreciate the predictability and independence from patient compliance that ensures successful treatment outcomes. Case photos provided by Dr. Lisa Alvetro. Reprinted from Orthodontic Perspectives Vol. XVII No M. All rights reserved.