EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

treatment goal at the end of treatment. The expectation is that the case will settle
into a stable Class I occlusion.
The occlusal surfaces of the casts were photocopied at 200% of natural
size. From this photocopy, 41 anatomical landmarks were digitized (Figure 3-3).
The procedure was performed on three sets of dental casts. Landmarks were
identified on the dental casts for (T1), (T2), and (T3). Photocopies of the casts
were then digitized using DentoFacial Planner ® software. Measurement
reliability of the sample lies in the fact that a single technician, Ms. Donna
Niemczyk, digitized all the records.
Five lines were drawn on the mandibular arch photocopy (Figure 3-4).
Lines were drawn along the left and right buccal segments centered over the
alveolar ridge. The point of intersection of these lines, anterior to the incisors,
forms the Buccal Segment Angle. A line bisecting this angle was drawn, as well
as a line connecting the left and right canine cusp tips, and left and right first
molar buccal grooves. On the maxillary casts, three lines were drawn, namely a
line from the incisive papilla to the midline mark between the molars, a line
between maxillary first molar mesial buccal cusp tips crossing the gum lines, and
a line connecting the maxillary canine cusp tips.
Using the lines drawn on the casts, six mandibular arch landmarks were
identified (Figure 3-5):
1. Midline point: The intersection of the buccal segment angle bisector line with
a perpendicular line crossing the incisal edge of the more protrusive central
incisor.
2. Anterior-midarch dividing points (left and right): This coincides with the
contact points of the mandibular canines first or second premolars in a wellaligned
and stable mandibular dental arch. They are centered over basal
bone and are slightly buccal to the buccal segment line.
3. Occlusal depth points (left and right): This is the line drawn across the buccal
segment line corresponding to the occlusal depth value (times the photocopy
magnification factor) distal to the first molar. The procedure is repeated on
the other side.
4. H point: A point on the midline of the mandibular occlusal plane at the
intersection of the buccal segment bisector with a line drawn tangent to the
distal of the more distal first molar and perpendicular to the buccal segment
bisector.
41