read a review of A Discussion of New Orthodontic Concepts by Dr. Fred Schudy

Philippe Mollard, PhD, PU^a

The history of the discovery of the importance of the vertical dimension has been published in Article 2 of the Schudy Chronicles on the Internet. The term, "mechanism of jaw growth and function"Orthodontics. was given to the new concept.

The thing that prompted the intensive study was a complete failure of the treatment of a patient, a dear friend. The patient, a female age 13, was unaware that the "gummy smile" and muscle strain was due to poor treatment. I was completely devastated. After many sleepless nights I told myself that, "I will find out why the treatment failed if it is the last thing I ever do in my life."

I started studying every night until 2:00 to 3:00 in the morning. This went on for many months. Without going into detail, the concept was developed in a period of four years, starting from scratch (including learning cephalometrics), by a lot of "past midnight oil" and lots of "blood, sweat, and tears." In 1960 the study was completed and I was using the new concepts in my practice. The work was published in 1964 and 1965 and was declared a classic in 1991 by the American Association of Orthodontists.

Again, I would like to say that I feel very humble and grateful for the opportunity to contribute something of value to our beloved profession.

Since the question is not specific, I must presume that the term "violate" means increasing the vertical dimension. We must also presume that the question pertains to adults, after growth has been terminated.

For our purpose, we will presume that "violating the vertical dimension" means increasing the distance from the ANS to Menton—increasing the distance from chin to nose.

It is my studied opinion that this distance can be increased in adults, with impunity. This can be done by increasing the height of either the mandibular or maxillary teeth; but the restorative device, whether fixed or removable, must contact all teeth in the opposite arch when the teeth are in centric occlusion.

In speaking of the "control of the vertical dimension," I presume you mean both inhibition and stimulation of growth of the molar teeth. When the clinician has a thorough knowledge of anatomy and treatment principles, he or she is well equipped to avoid surprises as treatment progresses; however we never get smart enough to completely avoid "bad surprises."

Some of these surprises are as follows:

1. Slow growth of molar teeth, either upper or lower molars.

2. Sudden cessation of growth of the condyles, and the molars continue to grow.

3. Stubborn resistance of lower molars to forward movement.

4. Insensitivity to early recognition of trouble.

5. Insensitivity to early recognition of non-compliance.

6. Failure of early recognition that lower anterior teeth are moving lingually faster than molars are moving forward.

7. Failure to check arch width at each appointment.

8. Failure to avoid intrusion of lower incisors. When these teeth are intruded they have a strong tendency to erupt posttreatment and cause a return of the overbite.

These are some of the oversights which may creep into our treatment and cause bad surprises.

When confronted with too much vertical growth of molars, we usually rely on the high pull face bow. This device was first developed in our office for the purpose of inhibiting the growth of upper molars. When the upper 2nd molars are present we band the first molar and extend a wire to the occlusal surface of the 2nd molar, soldered to the first molar band. This inhibits both molars. Also we sometimes fail to completely level the lower arch.

I have no objection to palatal bars and posterior bite blocks, but I feel that they are usually not as effective as the high pull headgear.

I do not believe that the J-hook headgear is sufficient to control the extreme case. I compliment the Tweed Foundation on the routine use of this headgear. It holds the anterior end of the palatal plane and the upper incisors upward. This is very desirable from the standpoint of aesthetics and function.

Good tough question!!! I do not think it is possible to predict the type and amount of mandibular rotation in a growing patient. I have had some experience, after the fact, of sending head films to commercial laboratories; and the answers never offer any help.

In 1984, Skieller, Björk and Linde-Hansen wrote an article on the prediction of mandibular growth rotation in the AJODO. In the December 1998 issue of the AJODO Leslie, with eight other authors collaborating at Iowa University, reviewed the article by Skeiller et al. The results of their study was that mandibular rotation cannot be predicted.

Since we thoroughly understand what causes mandibular rotation, we can easily devise procedures which would tend to prevent some of this rotation, but rotation per se is not always objectionable. Please see Article 41 of the Schudy Chronicles on the Internet, published in January, 1999. http://vsbw.com/~schudyf/list.html

There are certain principles which need to be observed in daily clinical practice regarding the occlusal plane. In general, when treating the low angle case where the posterior end of the occlusal plane is too low and there is a deep bite, we move the molars occlusally to open the bite, and this causes the occluso-mandibular angle to become still lower. In the high angle case where the occluso-mandibular plane angle is too high, we try to cause the lower incisors to move upward to close a possible open bite, and this tends to make the occluso-mandibular plane still higher. When the angle is too high we make it higher, and when it is too low we make it lower???

We must keep in mind that the occlusal plane is not an entity but a junction between two entities. The occlusal plane changes its inclination only when a segment of teeth moves vertically. Rather than noting that this plane has changed, we should note just which segment of teeth has moved vertically to produce this change. Then,is this tooth movement what we would desire?

For instance, if we are treating a high angle case with open bite tendencies and any segment of molars moves occlusally, we are getting into trouble. If we are treating a low angle case where condylar growth is excessive and molar height is deficient, we would desire that lower molars move occlusally and the occlusal plane tip up posteriorly with relation to the mandibular plane. This would facilitate overbite correction without intruding lower incisors. Lower incisors should never be intruded in growing patients, if it can be avoided. Please see Article 16 in the Schudy Chronicles.

The inclinations of the occlusal plane and the mandibular plane do not change unless there has been a change in the relationship of vertical effective condylar growth and vertical molar growth. This is as dependable as the sun coming up every morning.

I feel that there have been a number of important new concepts emerge in recent years. These concepts are listed below:

1. New stable landmarks have been identified for accurately measuring the dentofacial complex, both vertically and horizontally. "Sella horizontal," a line through sella turcica parallel to the Frankfort line is a stable landmark from which all points can be vertically measured.

2. "The great divide," a line drawn downward from sella perpendicular to Frankfort, divides structures which grow forward from those which grow posteriorly. It is a landmark from which all structures in the complex can be accurately horizontally measured. Please see Article 1 and Article 24 of the Schudy Chronicles.

3. The importance of the reduction of the gonion angle was reported in 1974, but has been emphasized in recent years. Please see Article 1, Figures 5 and 6, and Article 8 in the Schudy Chronicles.

4. The condylion/gnathion distance is significantly influenced by the reduction of the gonion angle.

5. In recent years it has been established that sella horizontal, the great divide and sella nasion are far superior to all other methods of superimposition. Please see Article 11 in the Schudy Chronicles.

The one most important characteristic of the treated case, is the proper vertical and horizontal position of the maxillary incisors. This position of these teeth in the maxilla is critical to function and aesthetics. The angulation of these teeth, both labiolingually and anteroposteriorly, is also critical.

The execution of the proper torque is of overriding importance. The crowns of the maxillary incisors must have a forward inclination regardless of the size of the root/crown angle. Generally the maxillary incisors should have an angulation of about 24° to line NA.

The upper incisors should be placed anteroposteriorly to give optimal aesthetics, vertically to give optimal aesthetic effect, and the torque should be adequate to produce optimal aesthetics and function.

Since the "how to do" changes from decade to decade, I must only speak of principles. In general, the entire profession seems to have given up on trying to use extra oral anchorage. If we decide in advance that our patients will not wear headgears, then of course they will not. I still say that we have an obligation to our patients, their parents, and our profession to convince our patients and parents of the importance of extra oral anchorage.

In some cases there is no substitute for an upward force on the maxillary incisors. If this force can be provided, with impunity, by intra oral forces, all well and good. If not, then only extra oral forces will produce an ideal result.

Many cases need from 2 to 5 Mmm. of intrusion and this can best be produced with extra oral force. Many orthodontists allow the anterior end of the palatal plane and the incisors to move downward. This is wrong, and extra oral force will prevent this undesirable tooth movement.

For many years we have been urgently advising colleagues to avoid the intrusion of lower incisors, for the reason that they have a strong tendency, in growing patients, to erupt posttreatment—resulting in bite closure and crowding of lower incisors.

We read numerous articles pertaining to stable treatment results, but the intrusion of lower incisors is never mentioned. If we ever hope to consistently produce stable treatment results we must realize that the lower incisor plays an important role. We have shown many treated cases where 10 and 11 Mmm. of overbite has been reduced to about 1 Mmm. without intruding lower incisors. Please see Article 16 in the Schudy Chronicles. In the treatment of adults we cannot avoid intrusion of lower incisors, but fortunately lower incisor intrusion for adults does not have the strong tendency to relapse posttreatment.

An increase in the height of molar teeth causes an increase in nasion/menton distance. At a 1963 lecture by a very prominent clinician, I placed this written question in an appropriate repository. When the speaker got around to my question he gave many evasive answers, but never mentioned molar growth. While I knew the answer to the question, I did not announce it to the audience—I was there to listen and learn.

Lower incisors should not be intruded in growing patients for the reason that they have a strong tendency to erupt posttreatment. This causes a return of the overbite and a crowding of lower incisors. Upper incisors, in many cases, need to be intruded to improve aesthetics and function. Why do I say this? Thousands of patients have been studied and this is what was observed to be true.

Intrusion of maxillary incisors helps to correct and maintain the overbite correction because these teeth do not have a strong tendency to erupt posttreatment, when there has been ample torque and when the overbite has been reduced to one Mmm. The good occlusion helps to prevent posttreatment eruption of both upper and lower incisors. These concepts have a powerful effect on treatment.

Again, we have studied thousands of cases and have observed that well torqued upper incisors contribute to stable results, while poorly torqued incisors lead to a collapse of the overbite and crowding of the lower incisors. In the poorly treated case there is much vertical functional force on the incisors, while in the correctly treated case the functional forces are primarily on the posterior teeth.

The upper first bicuspid is usually a multi-rooted tooth, has a longer root which resists lateral functional forces better than the second bicuspid, is larger, which helps produce better first molar occlusion, has a longer buccal cusp which aids the cuspid disocclude the posterior teeth in lateral excursions, has a better aesthetic effect than the shorter crown on the second bicuspid, and produces a better alignment of cusp tips to enhance the smile.

Contrary to conventional opinion, treatment is much easier when second bicuspids are extracted. When second bicuspids are extracted the lower incisor can be prevented from moving too far lingually if the right principles are applied and the correct diagnosis has been made. There are other advantages to removing second bicuspids as opposed to removing first bicuspids which we will not discuss here.

Through the years we have observed a prevailing opinion among many orthodontists that when excessive vertical development is produced during treatment, that it is not stable posttreatment; that the teeth will be intruded, producing some loss of the vertical development. We have never observed that to occur. It is our studied opinion that teeth will always remain at the attained vertical level to which they have been moved. They will not be intruded from normal muscle function.

Yes, there is a dependable way that we can know that the overbite correction will be stable. If we have a way of determining whether or not overbite correction will be stable it will help us greatly with our retention problems. We know that overbite correction is closely associated with vertical development of the lower face. We have personally studied the relationship between the increase in lower face height and the depth of the overbite before treatment. We have found that when lower face height (Ans to menton) increases as much or more than the depth of overbite and growth has ceased, then the overbite correction is permanent. Of course it goes without saying that the torque of the incisors must be adequate and the interincisal angle must be correct.

BIBLIOGRAPHIE

1. Schudy FF. The Schudy Chronicles. http://vsbw.com/~schudyf/index.html

2. Schudy FF. Discussion de certains nouveaux concepts orthodontiques. 20 articles des Schudy Chronicles. 1997. Nelson & Meyer ed. Paris.

3. Skieller V., Björk A. et Linde-Hansen T. Prediction of mandibular growth rotation evaluated from a longitudinal implant sample Am J Orthod Dentofac Orthop- 1984 Nov 359-370.

4. Leslie LR, Southard TE, Southard KA, Casko JS, Jakobsen JR, Tolley EA, Hillis SL, Carola C et Logue M. Prediction of mandibular growth rotation : assessment of the Skieller, Björk and Linde-Hansen method. Am J Orthod Dentofac Orthop 1998;114:659-67.

5. Leslie LR, Southard TE, Southard KA, Casko JS, Jakobsen JR, Tolley EA, Hillis SL, Carola C et Logue M. Prévison de la rotation de croissance mandibulaire : évaluation de la méthode de Skieller, Björk et Linde-Hansen. Am J Orthod Dentofac Orthop Ed franç 1999;5:76-84.

Dr. Schudy’s book : "A Discussion of some new orthodontic concepts" is available at : Nelson & Meyer, Inc. 103, rue Villiers de l’Isle Adam 75020 Paris - France - tél & fax : 33 (0)1 43 61 06 36. - ajodo1ef@aol.com

To get information on obtaining Dr. Schudy's book contact Dr. Philippe Mollard at : AJODO1EF@ aol.com