March, 2003

Interview with Dr. Robert Ricketts (Part 2)

Interviews with Icons: Part 2 of the Interview with Dr. Robert Ricketts; Interviewed by Dr. Larry White

En Español

Dr. Larry White

You have used the Kloehn headgear exclusively for your entire professional life as opposed to directional pull retractors. What justification can you make for this selection even with high mandibular plane patients?

Dr. Ricketts: Again, the answer is not simple. For me to justify is to vindicate or to free myself from criticism or suspicion. By the nature of the question it implies that I must defend my views against opposition. I certainly would prefer to absolve my differences with approximately one half of our colleagues. I have made heroic efforts to support my claims through the production of scientific evidence.

To be just is to be right and fair. It further means that a person should be impartial, remain unbiased, be correct and above all be precise and exact. In 1959 I worked so hard and performed 35,000 measurements on six samples of fifty patients each, which was reported in 1960. Data revealed differences twelve times greater than required for significance statistically. After the presentation, I vomited blood and had to take almost a year off due to a breakdown. Most traumatic was the rejection of the findings so desperately complied. Again the story needs to be told.

In March of 1950 while a research fellow, I was welcomed to study with Dr. Kloehn for three days in his office. Because no head films were available, I could only measure on models and in the mouths of his patients in addition to photographic appraisals. This led to speculations because of no head plates for measurements.

It should be understood that Dr. Silas Kloehn claimed only to originate a joining of the dental arch bar with the face bow (in one unit). Prior to that, it was connected with a prong and a swivel. Oppenheim had soldered beads of metal for stops on the old E-arch in 1934. Kloehn also prepared straps to go over the head to replace the "head cap" net. He employed intermaxillary elastics extraorally. He treated the younger mixed dentitions in order to be more efficient in serving a large area as the only orthodontist in Appleton, Wisconsin and about 100 mile radius.

Of interest was whether or not changes beyond the alveolar process were being produced. Other interests were the effects of expansion with no other apparatus used and the effect and improvements in the lower or concomitant arch. In addition, a question was raised regarding the production of diastemas between the upper central incisors.

We measured about a five to two ratio and sometimes more of widening between the upper molars and increases transversely between the lower molars. The questions arose regarding how it was produced and how much could be expected? In my visit I did not see open bites produced, but I saw deep bites corrected. Because the head strap received no tension we cut it off and maintained only the neck strap. It was then termed "head gear" and/or cervical traction.

On returning to Chicago, I was given permission to treat some very extreme Class II eight year old open bite children in order to monitor them with head plates and joint laminagraphy. I reported typical patients as case reports in 1955, 1957 and 1960. More than alveolar bone was affected robustly.

With the excitement of a new modality to correct Class II, many colleagues followed a "band wagon" effect. They began to use elastic tension as tight as the patient could tolerate. Carrying over the policy of full-time intermaxillary wear, they used the same practice with extra-oral traction. They did not expand and hence produced cross bites. Within five years many clinicians became alarmed with the extrusion of the upper molars. The "wedge effect" was proclaimed and by the mid 1960’s the Kloehn headgear with cervical traction was damned and condemned as guilty of injury. In the 1970’s table clinics and presentations were widespread toward "high pull" off molars with the notion that open bites could be closed in that manner.

Because the high mandibular plane was grossly interpreted to be a predictor of vertical facial growth, and because the open bite would be worsened with further molar extrusion, there came to be a general consensus that cervical pull was a risky treatment in the open bite, Class II with the high mandibular plane angle. I dare say this is still standard belief and adamant teaching.

I also fell for this idea of further mandibular rotation for a time in the 1950’s. In certain patients the high-pull looked encouraging. I used high-pull before I had heard of anyone else using it. But then I gathered some patients and compared them to the cervical method. Dr. Hilgers joined our staff with all of the conviction of high-pull fresh out of Northwestern University. He left before he could witness the final outcome. The high pull patients were taking longer to correct and the behavior of mandibular growth was not reaching the predictions! The condyles in some patients were flattening in the area of contact with the eminencies. All was not well with the high-pull craze. I came to reject high-pull off molars for about eight reasons which grew into twenty-four. These are listed in my book, Stretching the Orthodontic Mind to New Dimensions.

In the early studies I noted maxillary orthopedics, to an extent, which was unquestionable. Anecdotal, patients showed excellent vertical condyles and ramus growth. At first this was described as a lucky chance growth experience. Then in the 1960s, data of mandibular behavior in the cervically treated samples showed greater growth than the controls. Even yet this finding was glossed over and was thought to be due to a chance difference in selection – even in samples of 100 treated and 100 non-treated averaged out.

In 1969 evidence from an extensive study revealed that the "core" of the mandible bent upward and forward. By 1971 we determined that the typical growth of the mandible followed a curve and that little if any resorption occurred at the external oblique ridge. Careful studies confirmed that an "arc" could be constructed in order to forecast long-range growth behavior. Prior to that, we had shown in a 1966 paper (June, AJO) that vertical ramal behavior was affected in six-year-old children treated by cervical traction on the second deciduous molars. This was, of course, branded ludicrous.

We also showed that loss of the first permanent molars at age ten years could cause degerative joint disease from chronic compression. This was consistent with Firstsman’s findings on the growing rat.

For the next fifteen years the profession began to splinter. Some went back to cervical traction alone. Many built whole theories on high-pull and developed strong resentment of any questioning. Others moved away from extraoral traction and into mandibular posturing. Still, others elected to attempt to treat teeth to the high convexity with no concern for maxilla-mandibular incongruities.

But a hallmark study by Baumrind et al in 1981 was shocking. It showed that a statistically significant mandibular growth increase was present in patients treated with cervical gear. To the contrary, a statistically significant decrease of mandibular growth occurred in the high-pull group.

Our interpretation, in light of the growth curve, is that the human growing condyle needs freedom from compression on the upper and forward areas in order to develop the preferred goal of a more square mandible. Therefore the mild extruding action of the cervical pull shows intrusion of the lower molars and a favorable height increase in the ramus. Thus, cervical traction lowers the high mandibular plane angle if employed with care!

This finding was deemed by the Baumrind group to be unexplainable. They did not refer to my work in 1960, 1966 and 1971 much before their publication in 1981.

Ironically, cervical traction turns out to be the most favorable treatment for the Class II openbite, high convexity growing child having the high mandibular plane angle (meaning short ramal height). This is because it rotates the palate together with the midface complex to include the key ridge also taking the muscle attachments and soft tissues of the nose with it.

It has been difficult to teach that the palate is tipped downward anteriorly while the occlusal plane tips downward posteriorly! Cervical traction closes the bite without upper incisor extrusion. This is accomplished while at the same time it assists with vertical growth of the condyle, which closes the growth curve of the mandible! The key for application is to understand the complete biological-physical process. For all the appearance of simplicity, cervical traction is maybe the most powerful ally available for the sophisticated clinician.

I have just completed a book with five chapters for the details. It is entitled "Extra Oral Traction – A Phoenix". Readers can see it at the web page, rickettsbiopro.com. It also covers the face mask for Class III.

The greatest resistance for acceptance of cervical traction comes from the belief and the fear provoked by the old discipline. Perhaps there is a failure to recognize the biology of a growing patient in contrast to the static idea of treating a model on an articulator. My approach takes patience and explanations to the child and family. If the response clinically is not as would be expected, look at the functional problems of the patient rather than throwing out a beautiful modality.

Would it be useful for us all to measure and communicate in millimeters rather than inches and grams rather than ounces?

Dr. Ricketts: Yes. It is amazing how strong habits and customs can become entrenched. In science a division of ten in the metric scale is easier to manage than a division of twelve.

Apparently we historically adopted the inch scale from the body. The flattened thumb was an inch, the foot was 12 inches and the yard was a good span for a step. I do not know where it all started but a cubit (for the pyramids) was the fist to the elbow in length and horses were measured in "hands". In fact, the width of a railroad started with the spaces from the center of the horses’ rear ends as they were teamed for pulling a sled, a plow or a wagon.

In orthodontics, the early workers were dominated by Americans. Hence the scale of a screw thread and the size of wires and thickness of bands were measured in thousands of an inch.

However, orthodontics is now a world profession. We measure tooth movements in millimeters. Cephalometrics data is in millimeters. It is rather ridiculous that we continue to measure appliances on the inch scale. A millimeter is 1000th of a meter. Maybe we can be a force for change!

First, let us create a scale for standard sizes commonly used. There are 25.4 mm in one inch. The size in inches such as .022" multiplied by 25.4 yields in mm .022" x 25.4 = 0.558 mm. (rounded to .56).

To make it easier for the mind to handle:

• an anterior band is .004" = 0.10 mm.
• a ligature wire is .010" = 0.25 mm (1/4)
• a round wire .020" = 0.51 mm (1/2)
• a round wire .030" = 0.76 mm (3/4)
• a round wire .040 = 1.02 mm (or 1)

This forms a simple frame of reference.

As taught in edgewise technique historically, a tooth was to be activated the width of the rectangular wire. Thus, in height that is about .56 mm, but in the horizontal plane the distances would be 0.74 mm or half again greater. We try to be scientific on measuring the force in grams per mm of deflection.

The same principle, applied to the .016" x .016" Elgiloy, which I commonly use would mean a distance of 0.41 mm in both directions. The following scale may be useful for a quick reference:

The same semantic situation applies in the measurement of force times lever arm length in moment of force or torque. We communicate in gram – mm of moment in calculations of force.

Calculations have indicated that 2000 grams – mm of moment will move a molar. The .016" x .016" (or .41 x .41 mm) blue Elgiloy wire has precisely that capacity. Consequently, is any larger wire required for clinical use? We found it was not.

The traditional slot size in the edgewise bracket was .022" x .028". However, as manufacturers discovered, the clinician could not place a wire of the exact same dimension in the bracket. For that reason, they quietly enlarged the slot to .0225" or even .023". By revising the chart the .023 would be 0.58 mm and the .0225 would be 0.57 mm. The edgewise dimension was the width of a Joe Dandy disc cut or about 1/2mm. This is the so-called science involved historically in bracket sizes.

Even further, we refer to elastics in terms of "pull". Thirty years ago I suggested to manufacturers to produce a 1.0 mm square wall thickness as a standard, but not everyone listened. I counted twenty-seven different sizes commercially and the labels varied immensely.

On a package will be listed the size and the oz. The pull rating is calculated at three times the stretch of the resting elastic

One pound is 453.6 grams and one ounce is 28.35 grams. Therefore a five-ounce pull would be about 142 grams. For simplicity, we usually say one ounce is 30 grams. Thus, five ounces is about 150 grams. So if we measure forces in grams for activation, why do we continue to use ounces for elastics?

A typical condition for elastic pull clinically is the Class II. At the start the severity differs but the range is around 30 to 35 mm of distance from the molar tube to the hook anterior to the canine bracket. Objectives differ, but we usually try to produce a pull of about 150 grams because of the oblique nature of the pull.

The most common latex elastic is 5/16 or about 8mm. Stretched to 20 mm it yielded around 100 grams. At 25 mm the pull was around 125 grams. Stretched to a length of 30 mm it yielded 150 grams. This sort of fits but it would be better if we had uniformity and demanded standards for improved clinical science. It would be much simpler to change the length of the elastic rather than to be confused by wall thickness differences.

Watch for Part 3 of this thoughtful and thought provoking interview with Dr. Ricketts!

Interview by:

Dr. Larry White

Interview with Dr. Robert Ricketts: 1, 2, 3, 4, 5, 6