Spring 2001 Presentation Summary:

Dr. Klontz is an experienced teacher of modern Tweed technique. Through the years he has taught 53 two-week Tweed courses at Oklahoma University.

At the Annual Session he presented the modern Tweed diagnostic and force delivery system for the Class II individual. Of course, he reminded the audience that this presentation could only provide an overview of the techniques he teaches and is not intended to be a thorough discussion of the topic.

Dr. Klontz began his talk with the consideration of balanced facial proportions.

Faces First with a Planned Objective

There is no shortage of interest in discussing facial beauty and what most experts agree on are the characteristics of the ideal face. First, the face looks best when the vertical facial proportions follow the familiar rule of facial thirds.

From the lateral perspective, according to Holdaway and others, the upper lip should have 1–3 mm of upper lip curl. A flat upper lip is not pleasing.

The lower lip should support the upper lip and have a slight curl to it as well, and then curve into a prominent chin.

A pleasing profile line should touch the chin, both lips, and then pass through the center of the nose. Asian, Black, and some Hispanic populations have the line further forward in the nose. Orthodontic treatment should have these vertical and lateral facial proportions as the esthetic goal.

Diagnostic Concerns

Knowing the importance of a balanced face, Dr. Klontz uses Tweed’s Facial Angle (FMIA= 62 - 70 – 08 degrees) with the Tweed triangle to diagnose his cases.

When a face falls within the norm for these values, the lower incisor is upright over the basal bone and there is a pleasing profile line. Another simple guideline, described by Lavern Merrifield, is the intersect of the profile line with the Frankfort Horizontal Line or "Z angle." This value should be 72 – 78 degrees.

Many give lip service to the vertical dimension, but often this area falls by the wayside with actual treatment. The occlusal plane must be carefully considered.

Depending upon the facial type, all growth of the mandible is both downward and forward in varying proportions. In Class II growing patients, it is critical to prevent eruption of the upper molars as hinging open the mandible tends to oppose any mandibular forwar\growth.

Dr. Klontz went on to describe six measures that determine a successful case. Additionally, he uses these measures to arrive at a value for the craniofacial difficulty of the case. Adhering to these measurements has changed the way Dr. Klontz practices. These six measures are FMA, ANB, Z Angle, IMPA, Occlusal Plane, and Posterior/Anterior Facial Height.

When Class II case cannot be treated successfully to these norms, he will require extractions of four first bicuspids or upper first and lower second bicuspids.

In some situations, even this will not bring the case to normal values, further requiring extractions of either lower third molars and upper second molars or upper first molars and lower thirds is also done. Of course, this is done only when the upper third molars are not undersized. [Reviewer’s Note: No comments were made regarding the problem of aligning the upper third molars when they do erupt, usually well after braces have been removed.]

Directional Force Systems

The key to individualized, quality orthodontic treatment is controlled precision archwire manipulation. In 1978, Dr. Lavern Merrifield and Dr. Klontz devised the "directional force system" to accomplish the Tweed objectives.

Five concepts were identified and include sequential banding of the teeth, sequential tooth movement, sequential mandibular anchorage preparation, directional forces with control of the vertical dimension, and timing of treatment.

Initially, in extraction cases of four first bicuspid teeth, all the teeth are banded or bonded except the first molars. This provides a long lever arm for control of the terminal molar.

The first archwires are smaller rectangular wires, which allows for early torque control (anchorage preparation). Early vertical control is very important and often overlooked. The laterals are not tied in until crowding is resolved. Headgear is worn to help with the Class II correction and Alastiks move the upper cuspids distally.

Initially space closure is done with a rectangular wire. The teeth may be moved one at a time, two at a time or in small groups. First, the upper cuspids are moved back into the extraction spaces, then the lower incisors are brought back to upright them over the basal bone. The anchorage for this movement is additional distal tip added to the second molars.

At the end of 12–15 months, another stabilizing rectangular wire is placed and work continues on the upper arch in what is called the Class II Correction Phase. In this next phase, the maxillary posterior molars are moved distal to achieve a Class I relationship. First, the second molars are moved distal to a Class I position with a .020" X .025" ss helical bulbous loop made flush to the tube. A spur is put on the archwire, distal to the second bicuspid brackets, which serve as the purchase point for the distal force. None of the upper anterior teeth move forward as headgear and Class II elastics are worn for anchorage.

After this, the first molar is moved distally using an open coil spring placed on the archwire, distal to the spur. Then the second premolar is moved posteriorly using Alastik ties on the buccal and palatal surfaces. Simultaneously, the cuspid teeth are moved distal by placing the open coil spring distal to the Class II hook. Now, the cuspids will move regardless of whether the patient wears the Class II elastics or not. To get distal tooth movement, you need a compliant patient! Finally, a closing loop archwire is placed to retract the upper incisor teeth.

Extraction of upper first and lower second bicuspid teeth is similar with notable changes in the lower arch. First, the lower second molars and the first molars are banded. A cherry loop is placed in the lower arch wire and tied into place. When activated, the distal portion of the archwire moves down putting downward and forward pressure on the first molar roots. This uprights the molar teeth without opening up more space. This wire is placed in one to two visits, then the shoehorn closing loop wire is placed.

For cases with a level curve of Spee and an upright first molar, this wire becomes the beginning wire. The lower first molar teeth are actively brought forward and the second molars drift passively with the first molars. The band is then removed from the first molar and placed on the second molar, again creating a long lever arm to the second molar. An x-ray film is taken to check the first molar roots before the lower third molars are extracted. Completion of the case follows as in the extraction of four bicuspids, described above.

Non-extraction Class II correction is done using the same treatment sequences with some minor variations.

High angle cases, defined as those with a FMA of >30 degrees, always provide an added level of difficulty.

Three of the six measurements noted above involve the vertical dimension; they are the Z angle, FMA, and Posterior/Anterior Facial Height. In these cases it is critical to control extrusion of the posterior teeth. This is achieved with high pull headgear and careful wire bending and bracket placement.

If you do not have room to set the posterior anchorage, you must make room with extractions of third molars or the vertical dimension will be out of control. Cases with missing third molar teeth tend to take longer as the posterior distal tip must occur into mature bone instead of extraction sites.

Final Considerations in the Class II Patient

Treatment is not yet complete after removal of the braces. The patient is in the transitional occlusion. Final occlusion is achieved after 6–12 months of settling.

Dr. Klontz has found measurable mandibular growth in the post treatment period in all Class II patients. He calls this the mandibular response, which he takes into consideration at all phases of his cases—particularly when considering the timing for beginning a case.

When surgery is a certainty, Dr. Klontz will wait as long as possible for completion of growth before beginning the case. Finally, no patient is dismissed until decisions regarding the third molar teeth have been made.

If you wish to learn more about Modern Tweed Mechanics you may contact Dr. Klontz at Oklahoma University.

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