Whole-arch distalization using extraradicular miniscrews
to correct lip incompetence and bidental protrusion
by Dr. Adith Venugopal
Temporary anchorage devices play a
crucial part in anchorage management,
which is critical for orthodontic success.
Mini-implants, often known as miniscrews,
are a valuable absolute anchorage solution
in orthodontics. Although they are most
commonly placed in areas of the alveolar
process between the roots of adjacent teeth,
other locations, known as extraradicular
sites, have been suggested.
Miniscrews in the infrazygomatic
crest (IZC) and mandibular buccal shelf
(BS) areas offer unique benefits, including
reduced risk of root damage, larger quantities
of cortical bone at insertion points, no interference with mesiodistal movement
of teeth or groups of teeth, and low failure
rates when compared with interradicular
miniscrews. This allows the use of miniscrews
with larger diameter and length, and
allows simultaneous movement of the entire
dentition. This makes them suitable for a
wide range of orthodontic movements that
require an effective and safe anchorage
system, thereby expanding the horizons
of treatment options.1
Case selection for placement
of extraradicular screws
Extraradicular screws may be employed
in patients requiring maximum anchorage
for tooth movement such as protraction,
retraction, intrusion, extrusion, uprighting,
segmental or full-arch therapy, and
asymmetric tooth movement. Though it
can be used in the treatment of various
malocclusions, in my practice I limit the
use to distalization of entire maxillary or
mandibular dentition cases, especially for
subjects who have relapsed and have already
had their premolars previously extracted. It
may also be a good method to use in patients
who refuse to have therapeutic premolar
Diagnosis and treatment plan
A 24-year-old patient came to the office
complaining about incompetent lips and
protruding teeth and jaws. A missing lower
right first molar was noticed during clinical
examination, as well as a Class III molar
and canine relationship on the left and a
Class I canine relationship on the right. The
lower midline was moved to the right by
2 mm. The patient had a steep mandibular
plane on a Class III skeletal base, as seen
on radiographs. Root canal therapy was
performed on tooth #21. On #36, there
was a significant decay. The existence of a
mesially inclined #38 with proclined upper
incisors was noted (Fig. 1).
Fig. 1: Pretreatment extraoral and intraoral pictures and radiographs.
Extraction of #14, #24 and #34 was
proposed. The upper and lower canine-to-canine
segments would then be retracted
into the available extraction spaces using
interradicular implants placed between
the upper and lower second bicuspids and
This strategy was offered to the patient,
but he declined because of aesthetic concerns;
he worried about the bicuspid extraction
spaces being visible for several months.
Because of this, it was decided to extract the
third molars and insert four extraradicular
miniscrews (two IZC and two BS) in an
attempt to distalize the entire maxillary
and mandibular dentition at the same time.
Upper and lower arches were bonded
with 0.022-inch MBT prescription brackets.
A sequence of NiTi wires, varying in size
from 0.014 inch to 0.016 inch to 0.018-by-0.025 inch, was used to level and align the
arches. After the upper and lower arches were perfectly aligned, teeth #18, #28 and
#38 were extracted and two IZC and two
BS implants were placed to begin whole-arch
distalization. A powerchain was extended
from the implant head to hooks inserted
distal to the lateral incisor brackets on a
0.019-by-0.025-inch stainless steel archwire
for whole-arch distalization (Fig. 2).
Fig. 2: Whole-arch distalization of the maxillary and mandibular arches using
infrazygomatic crest and mandibular buccal shelf miniscrews, respectively.
A force of 350 g per side was applied.
Because the miniscrews are clear off the
roots of the dentition, it is possible to achieve
an uninhibited mesiodistal movement
of the whole arch (Fig. 3). The rate of
distalization was approximately 0.5 mm
per month for both the arches, which is
slower because of the increased resistance
offered by many teeth.
Fig. 3: Midtreatment radiographs illustrate the placement of
extraradicular screws clear off the roots of the dentition.
According to studies, the average amount
of distalization on the lower arch is less
than 3 mm.2 That is because once the
second molar’s distolingual root contacts
the mylohyoid ridge, further distalization is
impossible. Further distal force would simply
tip the second molar distally, increasing
the likelihood of relapse. Before deciding
on entire-arch distalization as a treatment
option, it is best to measure the distance
between the distolingual root of the second
molar and the mylohyoid ridge on an apical
section—not coronal—of a CBCT image
(Figs. 4a and 4b).
Fig. 4a: CBCT slice shows the coronal section of
the dentition. Note the sufficient space available
for distal movement of the second molars.
Fig. 4b: CBCT slice shows the apical section
of the dentition. Note the proximity of the
distolingual root to the mylohyoid ridge,
making distal movement of the second
The application of force dictates the line
of force and, ultimately, the movement of
the occlusal plane while retracting the upper
anterior segment. Typically, the force system
involves anterior retraction induced by the
force generated by a NiTi spring or chain
elastics, which connects the mini-implant
to a hook affixed to the archwire. Similar to
our case, when retraction force is provided
by a force that passes below the CR, anterior
teeth tend to rotate clockwise, resulting in
torque loss and a vertical extrusion force on
the incisors.1 To counteract this, more positive
crown torque on the wire in the anterior region
was incorporated. The resultant force vector
caused an upward and backward movement
of the incisors, resulting in incisor intrusion
and retraction (Figs. 5a–c).3
Fig. 5: Schematic comparison among Burstone’s incisor root spring (5a), continuous arch
with lever arm (5b), and combined use of miniscrews and continuous arch with additional
torque on the archwire (5c).3
All resultant spaces were substantially
closed by retraction after 30 months of active
treatment. Distalization was achieved in all
quadrants, with retraction and intrusion
of the upper incisors and uprighting of the
lower incisors. The patient demonstrated
improved aesthetics, a satisfactory occlusion
and lip competence after orthodontic therapy
Fig. 6: Posttreatment extraoral and intraoral pictures and radiographs.
Fig. 7: Before and after profile comparison.
Fig. 8: Superimpositions of pre- (black) and
posttreatment (red) cephalometric tracings.
With clinical experience, it is possible
to suggest that:
- It is hard to achieve further lip
retraction once lip competence
- Premolar extractions cannot
be substituted for whole-arch
distalization, because of anatomical
limitations as mentioned earlier.
- Line of force control is crucial to get
desired vertical changes.
- Incorporation of torque (labial crown)
helps maintain positive inclination
while retracting, and also aids in
intrusion of incisors.
1. Almeida MR. Biomechanics of extra-alveolar mini-implants.
Dental Press J Orthod. 2019 Sep 5;24(4):93-109. doi:
10.1590/2177-6709.24.4.093-109.sar. PMID: 31508712;
2. Kim SH, Cha KS, Lee JW, Lee SM. Mandibular skeletal
posterior anatomic limit for molar distalization in patients
with Class III malocclusion with different vertical facial
patterns. Korean J Orthod. 2021 Jul 25;51(4):250-259. doi:
10.4041/kjod.2021.51.4.250. PMID: 34275881; PMCID:
3. Kim SJ, Kim JW, Choi TH, Lee KJ. Combined use of
miniscrews and continuous arch for intrusive root movement
of incisors in Class II division 2 with gummy smile. Angle Orthod.
2014 Sep;84(5):910-8. doi: 10.2319/080713-587.1.
Epub 2014 Feb 7. PMID: 24512532.
Dr. Adith Venugopal is a clinical instructor and
associate professor of orthodontics and dentofacial
orthopedics at the University of Puthisastra,
Phnom Penh, Cambodia, and an adjunct professor
of orthodontics at Saveetha Dental College and
Hospitals in Chennai, India. He also has a private
practice at Pachem Dental Clinic in Phnom Penh.
Venugopal has published several scientific studies and clinical reports in
international peer-reviewed scientific journals, and has been an invited
keynote speaker at many international orthodontic congresses. He has held
courses and workshops on TAD-based biomechanics worldwide. His current
research and clinical interests are on TAD-assisted biomechanics for tooth
movement, adult Class III correction and gummy smile corrections.