Correcting “Prescriptions for Failure”

There is nothing worse than receiving an appliance back from the lab only to find out that it just won’t do what you intended it to do. Unfortunately, this usually occurs because of a breakdown in laboratory/doctor communication. In this series of articles in Continuum, we will explore some of the more common facets of orthodontic appliance design (as presented in Space Maintainers’ Principles of Appliance Therapy for Adults and Children textbook) and how they can be applied to help give your patients the beautiful smile they want.

In the past, “appliance therapy” only referred to the use of simple orthodontic appliances like a space maintainer or a Hawley retainer. Today, this term encompasses a wide variety of appliances that are used through every phase of a patient’s treatment. Whether you are placing implants, performing periodontal surgery, or simply doing interceptive orthodontics, you will need to use appliances to help control and direct your patients’ treatment.

Space Maintainers’ Principles of Appliance Therapy for Adults and Children textbook was introduced to help you integrate the use of appliances into your practice. Although there are over 500 appliances illustrated, it is rare to find an appliance that is exactly what you need for a patient. In fact, the book’s main purpose is just to give you ideas. It is up to you to design a specific appliance to fit your patient’s needs.

Let’s start off by looking at four typical prescriptions that lead to failure.

1. “Fabricate a lower removable appliance to align the anteriors.”

Many cases are sent to the lab with only a lower model like this. The dentist has prescribed an appliance to correct the lower anterior crowding. However, as you can see from these views, when coupled with the patient’s upper model, it becomes clear that the prescription should not just be for a lower appliance. To correct the lower anterior crowding, space must first be regained by either moving the upper anteriors out labially, correcting the deep bite, or both, prior to attempting to correct the lower anterior crowding.

Lower anterior crowding can be the result of a wide variety of situations and is one of the most common orthodontic maladies. Before sending working models to the lab, carefully examine them. With the models occluded in maximum intercuspation, carefully assess the overbite and overjet. Are the lower anteriors in contact with the lingual of the upper incisors? Is the bite excessively deep? Is there adequate overjet and sufficient intercanine width to round out and align the incisors? The answer to these questions will help determine the most successful approach. Often, you will find it necessary to first open the vertical. When sufficient intercanine width is lacking, you may find that anterior interproximal reductions will not be adequate to gain the room required. In these situations, pre-treatment with Functional Appliances, or full arch bracketing, may be required.

2. “Please make an upper Hawley retainer.”

Appliance #1161

A simple Hawley retainer like the one seen above (Appliance #1161 from the Principles of Appliance Therapy textbook) was fabricated with full acrylic palatal coverage, Adams clasps on the first molars, and a standard labial bow running from the distal of both cuspids. Unfortunately, the patient would not wear the appliance because her lower teeth kept making contact with the Adams clasps during function. To avoided this problem, the doctor should have checked the patient’s occlusion, sent an opposing cast and requested a design with no occlusal interferences.

Appliance #1165- The San Antonio Retainer. Note the lack of occlusal interferences.

3. “Design and fabricate an upper bruxism splint.”

Although over 80% of the splints made today are maxillary splints, this is not enough information to properly fabricate one that will work. Always send thorough instructions describing the splint’s occlusal scheme. For example, a proper prescription might say: “An upper horseshoe splint (Appliance #6193 in the Principles of Appliance Therapy textbook) with point contact on all posterior teeth, slight cuspid rise and brush contact in the anteriors during protrusive.” Also send a proper construction bite that represents the splint’s ideal vertical and AP position.

Appliance #6193 - The upper horseshoe splint.

4. “I would like to correct the crowding in the upper anterior region. Please design an expansion appliance to make room for the blocked-out cuspids.”

Three Screw Sagittal expansion appliance (#1106) made to tackle movement in the anterior, posterior, and lateral direction.

“Expansion appliance” usually refers to a group of appliances that are used for arch development. Depending on the type of appliance, you can develop an arch in an anterior/posterior direction, a lateral direction, or limit its lateral development to the anterior or posterior region. As you can see, it is essential to diagnose the cause of the crowding before selecting an appliance to treat it.

Then, and only then, will you be able to give the lab the specific instructions it needs to make you an appliance that will work. A basic diagnosis should include an arch width and arch length analysis helping determine the amount of crowding and better selecting the appropriate appliance design..

Appliance #1105 - Class II Division 2 Sagittal Appliance showing anterior development.		Appliance #1251 - Upper Sagittal showing distilization of molars.