EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

The present sample consisted of the remaining 166 cases (Table 3-1). All
patients were American whites, with pretreatment ages between 8.26 and 43.36
years. Patients at T3 were a minimum of 10.0 years out of treatment. All fixed
retainers were removed approximately 2-3 years after posttreatment. Following
removal, no mandibular retention was used, and maxillary retainer wear was left
up to the discretion of the patient.
Sample Description
One part of the sample consisted of 69 subjects (23 males; 46 females) who
had been placed in a fixed mandibular canine-to-canine retainer and a maxillary
removable retainer (traditional Hawley-type) at the end of active treatment. The
other part of the sample consists of 97 subjects (20 males; 77 females) who were
placed in maxillary and mandibular removable retainers (traditional Hawleytype).
Both groups exhibit a low proportion of males because of men’s lower
uptake of orthodontic services plus their reluctance to return for a recall
examination.
Pretreatment (T1), posttreatment (T2), and recall (T3) records were
available for all of these 166 cases (Figure 3-1). Mean initial examination age for
the sample was 13.94 years (Table 3-1). Posttreatment records were taken at a
mean age of 16.89 years, with the total treatment time for the sample averaging
2.94 years. The interval from the posttreatment to recall examination was on
average 16.03 years for the sample, with an average recall age of 32.92 years.
Description of Data Entry
Steps in the cast analysis (conducted by the Tweed Foundation research
group) were this: Landmarks on each cast were marked with a soft lead pencil.
Vertical lines were drawn on the maxillary cast on the buccal surfaces of the right
and left first molar from the mesial buccal cusp tip to the gum line. On the
mandibular cast, a vertical line was drawn one millimeter distal to the
mesiobuccal groove on the buccal surface of the first molars (Figure 3-2).
Holding the casts in occlusion (maximum interdigitation), the Left Molar
Correction and Right Molar Correction values were measured, from the marks
made as just described. This method produces a value 1.0 mm greater than
commonly obtained (Baume et al. 1973; Harris and Corruccini 2008). The
difference occurs because the Tweed Foundation teaches over correction of Class
II cases to about 1 mm past traditional Angle Class I occlusion. That is the
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