The most common problem presented to the orthodontist is correction of skeletal Class II malocclusions. In the past, most Class II malocclusions have been corrected with surgical procedures, headgear and/or elastic therapy.

In most cases, the improper bite is caused by a lower jaw that is too far back in relationship to the rest of the face. A good indicator of this type of malocclusion would be a case where the upper lip is balanced with the rest of the face by sliding the lower jaw forward, thus creating a more pleasing profile.

Photos: Patient Class II profile and Patient sliding sliding jaw forward.

When the patient is still growing, it is possible to accentuate the growth of the lower jaw to catch up with the upper part of the face by using the Bite Jumping appliance. The Bite Jumper is a functional appliance because it postures the patient's lower jaw in a forward direction. Over a period of months, this forward posture of the lower jaw promotes growth in the same direction. Recent research has shown that this appliance has the ability to inhibit maxillary anterior growth and produces an increase in mandibular length.

The Crown and/or banded Bite Jumping (Herbst) appliances, because they are permanently attached to the teeth for the duration of treatment, address the lack of success that functional appliances have experienced in the past due to patient compliance. Even though this appliance prevents the lower jaw from moving backward, opening and closing movements still occur easily and patients fully adjust to the appliance in about a week.

Photos: CBJ buccal and front.

Evolution and Overview of Current Crown Bite Jumping Designs

The Herbst or Bite Jumping appliance is by no means new to orthodontics. It was first developed by Dr. Emil Herbst in 1905 and reintroduced by Dr. Hans Pancherz in the mid to late seventies. These designs usually incorporated bands or acrylic type splints which were prone to breakage. However, the Herbst Bite Jumping appliance has finally found it's place in the last few years as technology has advanced allowing the orthodontic industry to design a more easily fabricated, sturdier and comfortable appliance. Thus, the Crown Bite Jumping Appliances.

There are several advantages to the Crown (Herbst) Appliance over other designs.

1. No removable parts, thus cooperation is therefore not an issue, treatment time is predictable.
2. Breakage is minimal and hygiene is not a problem.
3. Stainless steel crowns are easier to fit, stronger, less expensive and have more retention than bands.
4. Correction of Class II malocclusions are treated more efficiently making treatment much easier on the orthodontist, staff, patients and parents.
5. Orthodontic appliances can be worn in conjunction with CBJ's
6. The patient's profile immediately looks better after the appliance has been inserted.

There are many Crown / Cantilever Bite Jumping (CBJ) designs and components that aid the clinician in solving skeletal Class II correction.

To view the various current designs used by the following orthodontists, please click on their name:

Dr. Terry Dischinger

Dr. John "Bob" Smith

Dr. Joe Mayes

Crown Bite Jumper Design Variations

Diagnostic Records:

Diagnostic records requirements are as diversified and unique as the clinicians' diagnoses. Listed below is a compilation of recommended records.

1. Cephlometric x-ray
2. Sub mental vertex x-ray for tomogram
3. Transcranials
4. Slides, photos or imaging
5. Impressions for diagnostic study models
6. Diagnostic wax bite
7. Take second set of impressions for CBJ appliance fabrication. (May duplicate original diagnostic models if they are in perfect condition).

Note: If sending your appliance to a laboratory you will not have to separate the patient for space between the molars and second bicuspids before taking impressions for work models. The lab will disk the teeth during fabrication of the appliance. However, the patient should be separated one week before they return for insertion of the CBJ appliance.

Impressions for Work Models:

Maxillary and mandibular alginate impressions are required for the working models. Impressions must be free of distortions, bubbles and voids. Perforated or metal impression trays are recommended when taking impressions directly on the patient. Disposable trays may be used with care (when duplicating arches from diagnostic study models) as they have a tendency to distort. It is important to keep in mind that the laboratory technician can only make an appliance to fit the models it receives and it all starts with the impressions.

Bite Registrations:

Bite registrations are not necessary when fabricating crown or banded bite jumping appliances. Work models may be marked indicating desired initial advancement.

Placing Separators:

Exact placement of the separators will be determined by the design of the Bite Jumping Appliance being used. Cantilever designs only require separation of maxillary and mandibular first permanent molars. Check the exact Bite Jumping design being fabricated before placing separators. Most separators are placed one week before the appliance is inserted.

Design Exceptions that Effect Separator Placement:

1. When crowns are to be placed on the lower second primary molars, even though the first permanent molars are present. This usually occurs if the operculum covers the distal of the lower first permanent molar. Always check the panorex x-ray to make sure that the second primary molars are securely anchored.
2. The patient may present with a very small vestibule and not have enough room in the back cheek area to accommodate the Bite Jumping appliances axle if placed on the first permanent molar. In this case the appliance is sometimes fabricated more mesial in the posterior section of the mouth utilizing the second primary molar.

Work Models for Appliance Fabrication:

Crowns to be Furnished and Placed Indirect by Laboratory Technician:

Impressions are poured in hard orthodontic stone. The models must be free of any voids or distortions. The work models are hand articulated into the advanced position, (usually a Class I, edge to edge). Mark advancement guidelines on the models in pencil (upper and lower). The laboratory will use these lines to mount the models to the clinicians prescription.

Note: If the patient's models present with a cross bite when articulated into the advanced position, this is an indication that the maxillary arch is too narrow. The patient will need to have the upper arch expanded before placing the CBJ appliance, or an expander can be incorporated into the appliance during fabrication. If the patient's maxillary arch is too narrow, the rods and tubes on the Bite Jumping appliance will bind impinging on the lower crowns or lower posterior teeth. The upper tube will not close over the cantilever, and the patient will not be able to close their mouth.

Before sending the work models to a commercial lab they should be referenced to the prescription sheet for design specifications and inspected by the clinician or clinical coordinator to ensure that they have been marked properly.

Pearl: #1

A common cause of incorrect crown adaptation is the presence of the operculum tissue over the distal of the lower molars. In this situation it is recommended that the lower molars be sized with bands allowing the lab technician to use them as an aid in identifying the molars' distal cusps being hidden under the tissue. Thus crown adaptation accuracy is greatly enhanced.

Crowns To Be Furnished And Fit Directly By Clinician Or Clinical Staff:

Fitting your own crowns will require keeping an inventory of crowns. There are seven sizes of molar crowns of which four are used regularly. Most staff are accustomed to fitting bands, which are available in many sizes, however because of the sizing limitations, crowns will not fit precisely. There will be a little play in them when seated. Currently there are three types of crowns on the market suitable for Crown Bite Jumper fabrication: Ormco Crowns, 3M Unitek Stainless Steel Crowns and 3M Unitek Ni-Chro Crowns;

Note: Since crowns are expensive and tend to distort when fitting, you may find it convenient to purchase a crown sizing kit to facilitate the trial sizing procedure. Ormco Corporation has a precontoured, pretrimmed trial crown kit. When using this trial kit you must then use Ormco crowns. Should you be short on inventory you can notify your laboratory of the patient's Ormco Crown trial size ensuring an accurate indirect fit.

Direct Fitting Crowns:

1. Fit crowns on teeth (one at a time and then removing them to prevent aspiration) checking size and length of crown. Starting with a size five crown and going up or down will help the novice in sizing.
2. The crown should slide in easily, with some resistance, and slide down on the occlusal surface without pinching the soft tissues.
3. Once the crown has reached about three-quarters of its seating position with thumb pressure, it is beneficial to use a bite stick to complete seating. Place handle portion of the bite stick in the central groove of the crown at an angle matching the cuspal incline and have the patient bite it down from there.
4. The crown can be removed with your fingers, or a crown remover pliers.

Impressions:

1. Crowns to be incorporated into the work model will require that the impressions be taken with the crowns seated on the teeth. Remove crowns, place in impressions securing with wax, glue, or preferably a pinning technique to ensure that the crowns to not move while pouring the stone. *Alert: Due to the smooth form of crowns they can easily be placed in the impressions backwards.

Your pre-fit crowns to be placed indirect on the work models by the lab will require that the impressions be taken with the crowns removed from the teeth. Crowns to be re-fit on the work models by the laboratory should be identified, bagged and the bags stapled to the prescription sheet. Work models should be poured in hard orthodontic stone.

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The Orthodontic CYBERjournal wishes to thank both Paula Allen for her article and Allesee Orthodontic Appliances (AOA) for permission to publish this information.

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About the Author:
Paula is the clincal liason for Allesee Orthodontic Appliances (AOA). Many of you know Paula from her 30 years in the industry. She worked in an orthodontic practice for fourteen years and has attended and lectured at continuing education seminars, presented staff and doctor's clinics at the Great Lakes, Midwest, Southern, and Mid-Atlantic constituent meetings, as well as, for the American Association of Orthodontists. Paula has visited and interacted with hundreds of orthodontic offices. Her experience in orthodontics covers a wide range of areas.

Clinical management of the bite jumping appliances, especially the crown versions is one of the areas in which she has been extremely active over the last ten years. Her involvement in "hands on" clinical systems and techniques has given her valuable insights into what must be done in the orthodontic practice from a clinical perspective to facilitate predictable, profitable and excellent treatment results.

She can be reached at:

Paula S. Allen
Clincal Liason
Allesee Orthodontic Appliances (AOA)
13931 Spring Street
Sturtevant, WI 53177
USA

or more directly:

Paula S. Allen
Clincal Liason (AOA)
463 Club View Drive
Lawrenceville, GA 30043
USA

1-800-990-3485