Authors’ response

Thank you for your letter. We appreciate your interest in our article. We will attempt to respond to your questions and comments in the order in which you presented them.

First, Tweed’s premise for his studies might be interpreted as you stated if only his 1936 lecture, “The treatment of Class II, division 1 malocclusions with the Angle edgewise arch mechanism,” was considered. In this April 1936 lecture to the E. H. Angle Society in Del Monte, Calif, he discussed the edgewise appliance and the most efficient ways he had found to use it. He stated,

A few remarks pertaining to treatment of double protrusions, which sometimes complicate the treatment of Cl. II Div. 1 malocclusions, cannot be evaded. Experience in my practice has demonstrated that the most unstable and therefore the most difficult cases to retain successfully are those in which the teeth are too far forward or are in double protrusion. In fact, the usual result after years of retention is relapse, particularly in the lower incisal segment of the arch.

He further stated,

If this is also true in your practices, it behooves us to be more cautious in our treatment so as not to produce this condition.

This lecture dealt primarily with the appliance and how, in Tweed’s opinion, it could be most effectively used.

His later papers and lectures that deal with his philosophy of treatment and his reasons for it, however, point directly to facial esthetic concerns. Perhaps his statement in the “Analysis of clinical results” section on page 33 of volume I of his 2-volume text best summarizes his statements in published articles and in lectures. Many of his articles and lectures use the same description of his “dilemma” and how it was solved. His textbook narrative is the most concise. He stated the following.

For more than 6 years I practiced and advocated the philosophy of orthodontic treatment that demanded the full complement of teeth. Late in 1934, as a result of my inability to create balance and harmony of face form in more than a few of my patients, I began an analysis of my practice results. This project called for dental casts, photographs and x-ray films of all patients treated by me up to that time. Records were secured for more than 80 percent of my patients. The photographs were classified into two groups: (1) those with balance and harmony of facial proportions (Fig 17) and (2) those that lacked these qualities (Figs 18 and 19).

In virtually every instance, those patients possessing balance and harmony of facial proportions had mandibular incisors that were upright over the basal bone, such as shown in (Fig 20). The patients that lacked these attributes of harmonious facial proportion had teeth that were too prominent and mandibular incisors that were not upright over basal bone. It was noted that the lack of harmony in facial contour was in direct proportion to the extent to which the denture had been displaced mesially into protrusion (Figs 18 and 19).

It was observed that the attainment of all four of my orthodontic objectives had been successful in only 20 percent of these patients. These harsh facts all but made me give up the practice of orthodontics.

In a 1948 seminar lecture, he described his first clinical study that led him to his life’s work. Facial esthetics was the first thing he mentioned when he discussed his clinical experiment with 2 patients.

Two similar subjects, both males, both similar as to age and health, and both with similar malocclusions were selected. Both were thought to present a discrepancy between tooth anatomy and basal bone. One was used as a control and treated conventionally, without removal of teeth. The other had all four first premolars extracted and was so treated that the mandibular incisors were placed on basal bone and the inclination of these teeth within the ±5° range. When the work was completed the control presented poor facial esthetics, an unstable mouth that required indefinite retention, and the investing tissues lacked a lot of that which is most desirable. The subject that submitted to the extraction of all four first premolars was rewarded with good facial esthetics, the retention period was less than six months, the mouth was stable and the investing tissues were healthy.

We appreciate your comments about the unstable dentitions. Yes, Tweed was concerned with instability, but our study of his writings and lectures led us to the conclusion that facial esthetics was his overriding concern.

The facial profile drawings used in the article were not the actual sizes. These drawings were added for clarification. They were constructed from plotted points that were based on the x and y coordinates for visual understanding. They were done as they were to enhance the visual understanding of how the profiles actually appeared. The profiles in the article were what could be described as “facial wigglegrams.”

The mean ages of the sample were the following: extraction sample, 13 years 1 month before treatment at T1; 15 years11 months after treatment at T2; and 39 years 4 months at T3 (4 male and 43 female subjects); and control, untreated sample, average age, 15 years 11 months at T2; and 52 years 11 months at T3 (36 male and 21 female subjects). The age difference between the treated and the control samples at T3 was discussed in the article.

Perhaps we could have done a better job with the explanation of our use of Ricketts’ E-plane. In his article entitled “Perspectives in the clinical application of cephalometrics. The first fifty years,” Ricketts’ opinion is succinctly explained. He stated the following.

The last factor in the lateral film is soft tissue, especially the relationship of the lower lip to the esthetic plane. The problems in evaluating esthetics are compounded by differences in racial types and in constitutional types within races. However, a start must be made somewhere to evaluate esthetics, and the lower lip to the E line (nose to chin) has proven to be highly satisfactory in the author’s experience. The labial surface of the lower lip is influenced by both lower and upper incisors, while the upper lip is influenced only by the upper incisor.

The upper lip is located ideally approximately 2 mm farther behind the line than the lower lip. This tends to hold true for most patients. As the nose grows and the chin develops, the lips gradually appear to contract into the face (Table 7). Starting with the lips slightly ahead of the esthetic line in the juvenile stages, the lower lip has dropped behind this line by adolescence and continues to retract in adults. This can occur especially rapidly with maturation of males in the late teens or early twenties.

Table 7. Relative protrusion of lower lip. Mouth flattens 0.25 mm each year with natural development Age 3 0 mm Age 8 −1.35 mm Age 13 −2.50 mm Age 18 Males −3.75 mm Age 23 Males −5.00 mm

The T3 profiles of both the treated and the control samples are within the E-plane values that Dr Ricketts considered to be normal.

Ours was not a study designed to define excellent facial esthetics. We did not state that the extraction sample had great faces at age 39 years 11 months. Rather, we wanted to know whether adolescent extraction treatment has a deleterious impact on the face during adulthood. We found that an extraction sample of patients had faces that were not significantly different from those in an untreated control sample from the general population. Hence, it is not correct to say that extraction orthodontics during adolescence has a deleterious effect on the patient’s face when he or she is a middle-aged adult.

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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Authors’ response
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