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Practice Solutions: American Orthodontics by Graham Jones, DDS, MDS

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Header: A Preferred Corrector
by Graham Jones, DDS, MDS

Orthodontists are faced with selecting methods of Class II correction that are predictably effective, efficient and comfortable for the patient. Since there are so many philosophies on timing and technique for Class II correction and many methods have been proven to be effective when employed appropriately, the individual orthodontist's choice often boils down to a practice management decision.

When treating mild to moderate Class II cases, I typically prefer to wait until the permanent dentition is erupted so I can use full arches of upper and lower brackets and either Class II elastics or fixed, spring-based Class II correctors. Available evidence indicates that most Class II correction occurs due to dentoalveolar effects, regardless of the appliance that is used. Elastics are convenient and inexpensive, and can be very predictable if patient compliance is good. But elastics can have shortcomings—the most obvious being that they rely on patient compliance completely to be effective. In some cases, elastics may also be contraindicated because of their typical side effects of mandibular molar and maxillary incisor extrusion.

In cases where patient compliance may be poor or Class II elastic mechanics may be contraindicated, fixed Class II correction springs can be a useful option to have on hand. I prefer correction springs to more conventional laboratory-fabricated appliances because they can be incorporated into my typical bracket setup at any time I choose, without the need for significant appliance modification or additional appointments for laboratory construction. Additionally, most fixed Class II correction springs allow for the patient's bite to be evaluated in centric relation to assure the correction is not a result of mandibular posturing; thus, greater stability can be achieved.

Not all Class II correctors are created equal
I've found that American Orthodontics' PowerScope 2 Class II corrector has some advantages over other Class II correction springs. The three most notable:
  • a more ideal line of action
  • uncomplicated, quick installation
  • improved patient comfort
PowerScope 2 appliances' more horizontal line of action means that dental side effects are minimal compared to other Class II correctors, which can have a more vertical line of action. The expected result is less bite opening effects and less clockwise rotation of the occlusal plane. Because of this, little additional modification to my existing setup is needed.

When treating asymmetric or unilateral Class II cases, the horizontal line of action helps avoid potential occlusal canting while correcting the malocclusion. Additionally, vertical effects on the maxillary molars are minimal, which means the appliance can be used without concern for vertical discrepancies developing between maxillary first and second molars—even if maxillary second molars have not yet erupted or been bonded. This means that PowerScope 2 can even be installed early in treatment, or toward the end of final stages of treatment to achieve the final bit of Class II correction that a burned-out or noncompliant patient may not be capable of providing.

Molars do not necessarily need to be banded, nor do second molars need to be incorporated to place the appliance, although incorporating second molars is part of my routine. The main requirements when placing the PowerScope 2 are having stainless- steel wires with a 0.025-inch horizontal dimension in place and providing a tied-back or cinched mandibular wire to prevent space opening distal to the mandibular canine. Because preinstallation requirements are minimal and the appliances are easy to place, installation can be done during a normal adjustment appointment in my office whenever I choose.

As for patient comfort, the ball-and-socket-joint design allows for good range of patient motion and little to no tissue irritation noted. I've switched a few patients from other Class II correctors to PowerScope 2, and they've said the new appliance was more comfortable. Other patients have remarked that they prefer it to elastics, which is not a common finding for me with fixed Class II springs. With early versions of the PowerScope I encountered attachment nut breakage, but more recent improvements have eliminated this breakage in my experience.

Patient 1

Adjusting the appliance
The typical effects seen when using the PowerScope 2 are dentoalveolar—most notably, mesial movement of the mandibular dentition and some distal movement of the maxillary molars. When initially placing the appliance, I recommend not tying back the maxillary molar. It will often be observed that a space will open between the maxillary first molar and maxillary second premolar because of the distal force of the appliance on the maxillary molar. When the maxillary molar has moved into a Class I relationship with the mandibular molar, the PowerScope can be used as anchorage for retraction of the maxillary premolars and canines, sequentially, into Class I relations.

Unlike some other Class II correction springs, PowerScope 2 is a one-size-fits-all appliance, so careful attention must be paid to the activation. There are activation lines provided on the lower portion of the telescoping mechanism to provide a guideline for activating the appliance. When the patient bites down into centric relation, the upper rod should obscure the upper activation line to assure the appliance is active. If you can see all three lines, the 260gm internal spring will not be sufficiently active to provide Class II correction.

Shims can be added to the lower rod of the appliance until the appliance is sufficiently active. I like to use 1mm or 2mm shims until the appliance is active, then add additional 1mm shims when needed at future appointments to ensure the appliance stays appropriately active. It is very important to not overactivate the appliance. Class II correction springs are not designed to be posturing appliances like Herbst, MARA or other functional appliances. With the appliance in place, the patient should be able to easily occlude in centric relation. If not, the appliance may be overactive, and appliance breakage is likely to occur.

Patient 2

Patient 2 cont.

Case studies
I've found PowerScope 2 appliances to be useful in asymmetric Class II cases and cases requiring space closure with Class II anchorage. I've included two such cases here to demonstrate the mechanics and results. Patient 1 was an asymmetric Class II patient who was unreliable with his headgear and elastics wear. Patient 2 needed anchorage during space closing to avoid exacerbating the overjet, which can occur if the lower incisors are retracted during space closing. This can be challenging in patients with underlying Class II patterns. Both patients were leveled and aligned into .019x.025 stainless-steel wires using .022 slot self-ligating brackets. For space closure, I used a lower posted steel wire and elastic modules attached from the lower first molars to the soldered posts. In the maxilla, no tie-backs or elastics were used initially, but eventually elastomeric chains were used to consolidate maxillary spacing. When spaces were closed and Class I occlusion was achieved, the PowerScope 2 devices were removed and finishing procedures commenced. I often use torquing springs at the end of the treatment to fine-tune anterior coupling.

It should be noted again that I expect only dentoalveolar effects from fixed Class II springs, not significant growth modification. As with any Class II correction, favorable growth is a great asset and usually results in more ideal and faster overall treatment. But when growth modification is not an option or patient compliance is poor and dentoalveolar compensation is deemed to be an appropriate course of treatment, I've found the PowerScope 2 to be an excellent tool to use for Class II correction.

Dr. Graham Jones is the owner of Jones Family Orthodontics in Monroe, Washington. Jones attended dental school at the University of California at San Francisco, where he received his dental degree. While in dental school, Dr. Jones served as class president and received several awards for outstanding leadership, ethics and research. He was accepted into the orthodontic residency program at St. Louis University in Missouri, where he received his orthodontic certificate and a master's degree in Dental Science.



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