There is a wide variation of the opinions of orthodontists regarding the management of the vertical position of the mandibular incisors in treatment.

For the last 35 years, one school of thought has been expressing admonitions against the intrusion of these teeth. In 1998 a clinician² carefully explained how to intrude the lower incisors.

When one so-called authority on the subject strongly advises against intrusion and another so-called authority advises intrusion, that is as far apart as you can get. One of them is wrong!

It is a sad commentary to have such a difference of opinion exist in a well established specialty of dentistry. In fact, it is a shameful indictment of our profession.

The reason this is so serious, is that it is at the heart and soul of successful orthodontic treatment. When the lower incisors are appreciably intruded, they are the most unstable of all anatomical structures in the craniofacial complex—the primary cause of overbite relapse and incisor crowding.

We read a great number of articles about producing stable treatment results; yet seldom if ever do we read anything concerning the intrusion of lower incisors.

If we really want to solve our retention problems, we must begin to realize that the lower incisors are an important key to successful treatment.

Some authors seem reluctant to discuss intrusion, so they speak of "relative" intrusion, but they never tell you what they mean by relative intrusion. Relative intrusion is the difference in the vertical height of the incisor teeth at the beginning of treatment, and the height to which the teeth are destined to grow without treatment.

So when the lower incisor is intruded into the bone, you have both relative intrusion and actual intrusion. Thus "relative" intrusion is a non-entity, not worth discussing.

The position of the apex of the lower incisor relative to the mandible is a very important study. Early in the evolution of our field of endeavor the position of the lower incisor relative to the mandible, began to attract attention. It was early observed that malalignment usually starts in the lower incisor teeth.

Tweed¹ felt that the apex of the lower incisor should not be moved with relation to the mandible; however there are situations where it is very desirable to move this tooth lingually. (Please see Fig. 8, page 262 in bibliography No. 3.)

In leveling the lower arch in non extraction treatment where all of the teeth are in contact, it is difficult to avoid moving the apices of the incisors lingually. To avoid this undesirable movement, a rectangular arch must be used and labial root torque must be applied. This is not for the purpose of moving the apices labially but to prevent them from moving lingually. This procedure was discussed in 1963 in No. 4 in the bibliography, as well as in the Chronicles on the Internet in 1997.

When there is such a wide difference of opinion on such a fundamental concept as the management of the lower incisor in treatment, both sides of the question have a moral obligation to their colleagues and to society to show many treated cases to prove their point. Please see Article No. 16

It would have been quite appropriate for the clinician who recommends intrusion to have shown the results of the treatment, to prove to the reader that the pretreatment plans were successfully accomplished. It is hoped that others will come forth with their opinions. This is an important concept worthy of our collective attention.

Bibliography

¹Tweed, C.H.: The Frankfort-Mandibular Plane (FMIA) in Orthodontic Diagnosis, Treatment Planning and Progmoses, Angle Ortho, 1954; 24:121-169.

²Braun, Stanley: Diagnosis Driven Versus Appliance Driven Treatment Outcomes, Orthodontics for the Next Millenium, Chapter 2, page 31.

³Schudy, Fred F.: Sound Biologic Concepts in Orthodontics, Schudy and Schudy, D. Armstrong Co. Inc., Houston, Texas, 1992, Fig.8, page 262.

⁴Schudy, Fred F.: The Cant of the Occlusal Plane and the Axial Inclinations of Teeth as Related to Diagnosis and Treatment, Angle Ortho., April 1963.

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