EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

This inference raises an important question: There are roughly three times
as many women as men in the sample (123 versus 43), and it can only be hoped
that those men that agreed to be recalled are representative of the sex at large. It
is speculated that men are less concerned about their occlusions and, thus,
relatively indifferent to undergoing a recall examination. There is, however, no
practical way of testing this. This problem is common to all orthodontic-recall
studies because there is no way to coerce former patients to participate.
Table D-4 lists the 17 variables that exhibit statistically significant sex
differences in the amounts of in-treatment change. Most of these variables are
dependent on tooth relationships. Except for incisor segment ratio and incisor
segment depth, all of these variables (15 of 17) changed more in the boys than the
girls. The theme seems to be that those variables that were more deviant in boys
at the start of treatment (e.g., overjet, overbite, ANB, AOBO, Curve of Spee)
warranted more correction during treatment. These changes are illustrated using
the data for the AOBO discrepancy (Figure 4-4). The typical male orthodontic
patient has a greater AOBO discrepancy at the start of treatment (perhaps
because of differential selection of who actually receives treatment). Boys also
experience a significantly greater in-treatment change, which leads to the sex
differences noted here.
The 14 significant sex differences that occurred after treatment (Table D-5)
are of particular interest since they constitute difference in the aging process (in
combination with any relapse tendencies). Inter-canine width and inter-molar
width, both in the maxilla and mandible, differed between men and women
because women experienced greater relapse—where ‘relapse’ is constriction of
these widths with age. Average changes were small—less than a millimeter.
FMIA increased in both sexes, but significantly more in men.
FMA flattened about 2 on the average in men, but the mean change was
trivial in women (Figure 4-5). We speculate that this flattening is due to growth
at the gonial process due to greater muscle force of the elevator muscles in males,
and it may well reflect the continued decrease in FMA seen in childhood and
adolescence (Ricketts 1972).
SNB—in combination with ANB and AOBO—changed a bit both in men
and women, but in opposite directions. The change in SNB was positive in men
(~ 0.6), but negative in women (~ 0.3). Since the change in SNA was
statistically inconsequential in both sexes (~ 0.0), the increase in SNB (and in
ANB) in men discloses that mandibular growth slightly exceeded that of the
maxilla, making the skeletal profile a bit less retrognathic by the recall
examination. In women, mandibular growth lagged slightly behind, creating a
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