Leveling the curve of Spee with a continuous archwire technique: A ...

364 Bernstein, Preston, and Lampasso
Table I. Sample (n 31; 9 male, 22 female) and time
characteristics
Characteristic Time
Mean age at T1 12 y6mo
Mean age at T2 14 y 11 mo
Mean age at T3 26 y4mo
Mean treatment time (T2-T1) 2y5mo
Mean fixed retention time 3y4mo
Mean postretention time (T3-T2) 11 y5mo
type of occlusal relapse after orthodontic treatment.
3,12,17,21-30 In general, these studies noted - in
creases in overjet, overbite, and mandibular incisor
crowding along with decreases in arch length and arch
width. Although postorthodontic relapse was studied in
some detail, relatively little is known about the longterm
stability of leveling the COS and how the different
methods of arch leveling relate to its subsequent relapse.
The primary purpose of this investigation was to
determine radiographically the long-term effectiveness
of the Alexander discipline (continuous archwire technique)
in leveling the COS in Class II Division 1
deep-bite nonextraction patients. We also report on
some relevant cephalometric changes that take place
during arch leveling with the continuous archwire
technique. The cephalometric data obtained were used
to determine whether a COS that was leveled remains
stable in the long term.
MATERIAL AND METHODS
The sample for this retrospective study consisted of
the randomly selected orthodontic records of 31 white
patients treated without extractions in the private practice
of Dr R.G. “Wick” Alexander in Arlington, Texas
(Table I). These patients all met the following criteria
for selection: they had Class II (ANB angle 4°)
skeletal patterns, at least half-step Class II molar dental
relationships, incisor overbites of 50% or greater as
measured on the initial (T1) study models, and angles
between the mandibular plane (MP) (Go-Gn) and the
sella-nasion (S-N) line less than 32°. A COS equal to or
deeper than 2 mm was present on all T1 models.
Only patients with complete clinical records were
included in this study. These records consisted of
radiographs and dental casts taken at T1, posttreatment
(T2), and postretention (T3). All patients were retained
with lower fixed canine-to-canine lingual retainers for a
mean period of 3 years 4 months. The patients were all
treated with fully preadjusted fixed orthodontic appliances
according to the continuous archwire technique.
We selected this technique for this study because of its
American Journal of Orthodontics and Dentofacial Orthopedics
March 2007
Fig 1. Cephalometric landmarks and lines.
biomechanical principles that aim to provide a level
occlusal plane (OP) during and at the end of active
treatment. 31
Three radiographs (T1, T2, T3) were collected for
each subject. The 93 radiographs were assigned random
numbers to enable 1 investigator (R.L.B.) to measure
each in a random, blind fashion.
All radiographs were taken on a Quint Sectograph
machine (Los Angeles, Calif) and were hand traced by
1 operator (R.L.B.) from the original radiographs.
Standard cephalometric landmarks (S, N, ANS, PNS,
A, B, Go, Gn) were used to construct the reference lines
required to obtain the craniofacial measurements re-
32
corded in this study (Fig 1). The functional OP was
defined by a line intersecting the intercuspation of the
posterior occlusion (Fig 2).
33 The following additional
reference points and planes were used to measure the
COS; these form the focus of this study (Figs 1 and 2):
I1, the incisal tip of the most extruded mandibular
incisor; L6, the highest cusp tip of the mandibular
permanent first molar; L1-MP, tip of the L1 perpendicular
to Go-Gn; L6-MP, mesial cusp tip of the L6
perpendicular to Go-Gn; L4-MP, the cusp tip of the L4
perpendicular to Go-Gn; COS line, the line joining the