CLINICAL INSERTION OF
THE CANTILEVERED (Next Issue: Treatment Sequence)
Step 1. Many clinician’s will take corrected tomograms or transcranial x-rays prior to seating the Herbst appliance. This is done to evaluate the initial position of the condyle.
- Tomogram Transcranial
Step 2. Remove all separators. Step 3. Fit crown Herbst components on teeth (one at a time and then removing them to prevent aspiration) checking size and length of crown.
The crown should slide in easily, with some resistance, and slide down on the occlusal surface without pinching the soft tissues.
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.
Crown Adjustments: Crown is loose crimp the mesial and distal of the stainless steel crowns, using Howe pliers or one similar to the type you use for straightening bands after they have been tied on the teeth. Adjusting a crown in this manner can tighten it up to one-half size.
Pearl: If the crown still seems a little large after crimping, you may try over filling the crown with glass ionomer at cementation to compensate for the extra crown space.
Crown is too tight it may have been over crimped and you will need to straighten or flatten out the edges of the crown with Howe pliers. You can also trim the crown gingivally. Care must be taken whenever trimming crowns because certain types of contoured crowns get considerably larger when trimmed.
Crown is too long if the patient complains that it is uncomfortable on the gingival tissue. Using a heatless stone or scissors you can slightly trim the edges to relieve impingement.
Note: Crown or Crowns Do Not Fit. Upper and lower impressions for a new set of working models should be taken. The original work models may have been distorted. When possible, direct fit a new crown on the tooth. If this is not possible give the laboratory a detailed explanation of the problem with the crown. When returning a Herbst appliance to a commercial laboratory it is very useful for them to have the original models because examination of the original and new models may help to identify the fabrication problem.
Step 4: Evaluate the placement of the Mandibular Cantilever Arms (if present). Check that the mandibular cantilever arms are aligned properly. If they are too far from the teeth they will cause cheek irritation. If they are tipped too far inward they will impinge on the gingival tissue.
Adjustments to the mandibular cantilever arms are usually made with three prong headgear pliers. Any up-down, in-out, or torque corrections must be made at this time. It is almost impossible to make these adjustments after the appliance has been cemented. (Adjust as described in section 7 of the Pre-Insertion Check List).
Cantilever out too far Adjustment w/pliers Cantilever corrected
Step 5: Evaluate Occlusal Rests. Occlusal Rests need to be checked for their approximation to the teeth.
Adjustments are easily made with Howe or Bird Beak Pliers. However, caution should be taken when adjusting rests as they can break if annealed too much.
Step 6. PREPARE APPLIANCE FOR CEMENTING:
1. Dry the Herbst appliance and all it’s components thoroughly.
Pearl: If you have made considerable adjustments to occlusal rests and /or crowns you may want to re-micro etch before cementing the Herbst component. 2. Use Ceka Bond to attach the upper tubes to the maxillary crowns. This procedure is very important for two reasons. First, the Ceka bond will keep the screws from coming loose during treatment and second, it is very difficult to place screws in the upper mechanism after cementation due to the anatomy. Lower rods are attached after the appliance is cemented.
Pearl: To help keep the upper tubes from falling down into the patient’s mouth during cementation, place an 1/8" diameter elastic around the screw and upper tubes on the maxillary crowns. The elastics are then removed during the cleaning procedure.
3. Place tooth paste or lotion in any and all open areas of the Herbst components. This includes upper tubes, upper and lower archwire slots, both axles and also in the expander screw if one has been incorporated into the Herbst design.
Step 7: CEMENT THE HERBST APPLIANCE
1. Mix cement and place in the crowns. Crowns should be full. A glass Ionomer type cement is usually preferred such as, Fuji I, Ormco Protech or OptiBand.
Pearl #1: Make sure the doctor is at the chair and ready to proceed as you are filling crowns with cement. If the cement hardens, you will loose about forty-five minutes cleaning out the crowns and re-etching.
Pearl #2: Using "Allrap" or a similar material over the mixing slab will cut cleanup. This material is found through dental supply houses and is the same material general dentists use to cover their equipment for sterilization considerations.
Pearl #3: Ormco’s ProTech (Gold) glass ionomer is very good to use because it’s gold color is easily seen when cutting through the crown during the removal procedure.
2. Isolate and dry tooth. With a cotton applicator place a thin film of Vaseline or a little Chap Stick on the occlusal surface of the tooth. This will keep the glass ionomer out of the grooves and keep your clean up time to a minimum when the crowns are removed.
3. Clean excess cement from crowns and surrounding teeth immediately using the air-water syringe suction. When using a glass ionomer there is no reason to wait for it to set up before rinsing.
Pearl: If there was a problem with one of the crowns fitting properly (too large or small) and considerable adjustments were made, you may want to let that crown’s cement cure before cleaning off the excess.
4. Bond occlusal rests (if applicable). Prepare the teeth for light cure bonding one arch at a time. Place enough adhesive to fill in the occlusal grooves of the tooth and cover the metal rests. Cure adhesive with light. Note: Second molar rests are never bonded.
Pearl: An adhesive booster is suggested to increase bond strength.
Step 8: INTERLOCKING THE HERBST MECHANISMS
Remove elastics from upper tubes. Slip lower rod into the upper tube, place rod eyelet over the axle and hold, guiding the patient’s lower jaw into the advanced forward position. At first, patient’s have a tendency to resist closing in this position. (Lower screws do not need to be placed during this phase. If they are, you may spend more time removing them if adjustments need to be made).
Interlocking Check List:
Midline Correct Buccal Midline Correct
Midline Off Buccal Midline Corrected w/ shim
If the lower rods are too long they can be corrected as described in section 5 of the Pre-Insertion Check List last issue of the OC-J.
Rod Too Long Rod Correct Length
If the patient has been advanced properly and disengages easily, you will need to replace the lower rod with a longer one, taking note that the upper tube may also have to be changed as described in sections 4 and 5 of the Pre-Insertion Check List.
Note: To keep from disengaging some patient’s may end up in a Class III over corrected position. This is a rare problem. However, because of the patient’s anatomy, advancing to a Class III position may be the only way to keep the Herbst interlocked. (Patients that are advanced like this usually relapse to an end to end relationship within a couple of weeks).
Should one side of the Herbst mechanism be hard to engage after the other side has been connected, have the patient slide their jaw away from the side to be adjusted. Slip the lower rod into the upper tube and then place the eyelet over the lower axle.
If there are no problems with the Herbst mechanisms and the appliance fits properly dip the lower screws in Ceka Bond and place in the lower axle..
Post Insertion Instructions to Patient and/or Parent:
The Orthodontic CYBERjournal wishes to thank both Paula Allen for her article and Allesee Orthodontic Appliances (AOA) for permission to publish this information.
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: p-allen-noble@mindspring.com or Paula S. Allen or more directly: Paula S. Allen 1-800-990-3485 |
