Artículos de Corticotomia

1. ORIGINAL ARTICLE
Comparison of corticotomy-facilitated vs
standard tooth-movement techniques in dogs
with miniscrews as anchor units
Yehya Ahmed Mostafa,a
Mona Mohamed Salah Fayed,b
Samah Mehanni,c
Nader Nabil ElBokle,d
and Ahmed Mostafa Heidere
Cairo, Egypt
Introduction: One method used to accelerate orthodontic tooth movement is the corticotomy-facilitated (CF)
technique. The purposes of this study were to (1) identify the effect of the CF technique on orthodontic tooth
movement compared with the standard technique, and (2) explore the histologic basis of the difference be-
tween the 2 techniques. Methods: Six dogs, aged 6 to 9 months, were used in this study. Extraction of the
maxillary second premolar and miniscrew placement were done bilaterally in the maxilla. On the right side,
the corticotomy was performed. The first premolars were distalized against the miniscrews with nickel-tita-
nium coil springs on both sides. One dog was killed each week after orthodontic force application.
Results: The first premolar on the CF side moved significantly more rapidly (P 0.05). Histologic findings
showed more active and extensive bone remodeling on both the compressive and tension sides in the CF
group. Conclusions: The CF technique doubled the rate of orthodontic tooth movement. Histologically, the
more active and extensive bone remodeling in the CF group suggested that the acceleration of tooth move-
ment associated with corticotomy is due to increased bone turnover and based on a regional acceleratory
phenomenon. (Am J Orthod Dentofacial Orthop 2009;136:570-7)
O
rthodontic treatment usually lasts 1 to 2 years,
and even more time is required for extraction
cases. To shorten the time for orthodontic tooth
movement, various attempts have been made. These at-
tempts fall into 3 categories. The first is local or sys-
temic administration of medicines.1-4
The second
category is mechanical or physical stimulation such as
direct electrical current5
or a samarium-cobalt magnet.6
The last category is oral surgery, including dental dis-
traction,7
alveolar surgeries to undermine interseptal
bone,8
and alveolar corticotomies, which have been
used to correct malocclusions for over 100 years.
Kole9
used a combined interradicular corticotomy and
supra-apical osteotomy technique for rapid tooth move-
ment. Duker,10
in 1975, duplicated Kole’s technique in
a report of alveolar corticotomies using beagle dogs. By
using only labial and lingual corticotomy cuts to cir-
cumscribe the roots of the teeth, Generson et al11
in
1978 revised Kole’s technique and reported successful
results with a 1-stage corticotomy-only technique with-
out the supra-apical osteotomy. Gantes et al12
in 1990
also reported rapid tooth movement and reduced treat-
ment time. In 2001, Wilcko et al13
reported a revised
corticotomy-facilitated (CF) technique that included
periodontal alveolar augmentation, called accelerated
osteogenic orthodontics; it demonstrated acceleration
of treatment to one third of the usual time.14
Anchorage control is a fundamental concept in
orthodontic treatment.15
Various types of miniscrews
were introduced for different orthodontic applica-
tions.16,17
In 2003, Kyung et al18
introduced Absoan-
chor titanium miniscrews, which were specifically
designed for orthodontic use. Specific implant heads
were introduced to facilitate easier attachment to ortho-
dontic appliances; they are small enough to be placed in
any area of the alveolar process. These miniscrews can
be immediately loaded, and their effectiveness as
anchor units has been satisfactory.
The previous evaluations of the CF technique were
mainly based on case reports and clinical evidence
rather than on detailed histologic investigations.13,14,19
This study was designed to answer the following ques-
tions. Compared with the standard tooth-movement
technique (S), to what extent will the CF technique
From the Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
a
Professor and chairman, Orthodontic Department.
b
Lecturer, Orthodontic Department.
c
Lecturer, Oral Biology Department.
d
Lecturer, Oral and Maxillofacial Surgery Department.
e
Assistant lecturer, Orthodontic Department.
The authors report no commercial, proprietary, or financial interest in the prod-
ucts or companies described in this article.
Reprint requests to: Yehya Ahmed Mostafa, 52 Gameat El-Dowal E-Arabia St,
Mohandeseen, Giza, Egypt; e-mail, mangoury@usa.net.
Submitted, July 2007; revised and accepted, October 2007.
0889-5406/$36.00
Copyright Ó 2009 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2007.10.052
570

2. speed up tooth movement? What is the histologic expla-
nation of the difference between the 2 techniques?
MATERIAL AND METHODS
Six dogs (ages, 6-9 months) were kept for this study
in a well-controlled animal facility. They were caged in-
dividually and fed soft dog chow and water. All exper-
imental procedures, including surgical and clinical
examinations, were performed aseptically by using so-
dium pentobarbital (25 mg per kilogram of body
weight) for intramuscular anesthesia. Intravenous injec-
tions of penicillin were given for 3 days postsurgically.
The dogs were humanely killed with intravenous injec-
tions of pentobarbital (50 mg per kilogram). All proce-
dures were approved by the Animal Ethics Committee
of Cairo University.
The following surgical procedures were performed.
1. Absoanchor miniscrews (Dentos, Daegu, Korea)
were used. The small head type (diameter, 1.2
mm; length, 8 mm) was selected for this study.
Screws were placed bilaterally between the roots
of the maxillary third premolar and the maxillary
first molar. They were placed above the gingival
margin by approximately 5 mm. With the self-tap-
ping technique, the following were done: an inden-
tation of 0.9 mm with a pilot drill was made near the
screw with water cooling, and the miniscrew was
placed by using a long miniature screwdriver.
2. The maxillary second premolar was extracted
bilaterally.
3. On the right side of the maxilla, a labial full-thick-
ness mucoperiosteal flap was reflected (CF group).
Two vertical and 1 horizontal corticotomy cuts
were made mesially, distally, and apically, respec-
tively, in the area of future tooth movement
(Fig 1). The vertical corticotomy cuts were made
1 mm apical to the alveolar crest and extended
apically to the level of the root apices. Small cor-
ticotomy perforations were drilled in the buccal
cortical bone. There were 8 to 10 perforations ac-
cording to the alveolar process area in each dog.
These perforations were made to obtain additional
bleeding points. The corticotomy cuts and perfora-
tions were made with a #2 long-shank round bur
in a high-speed hand piece with copious water ir-
rigation and extended barely into the spongy bone.
The following orthodontic procedures were per-
formed on both the right maxillae (CF group) and the
left maxillae (S group).
1. A horizontal cervical groove was made encircling
the first maxillary premolar below the height of
contour by using a 1-mm round bur on a low-speed
micromotor.
2. A 0.016-in ligature wire was tightened around the
horizontal cervical groove on the first premolar.
The pigtail was formed into a hook for the attach-
ment of the eyelet of the coil spring.
3. A nickel-titanium closed-coil spring was stretched
between the hook on the first premolar and the
head of the miniscrew to distalize the first premo-
lars. The force from the coil was 400 g. Measured
with a force gauge, it was equal bilaterally. Load-
ing of the miniscrew began immediately after
placement (Fig 2).
4. The distance between a vertical notch on the cervical
area of the first premolar and another notch placed
similarly on the third maxillary premolar was re-
corded weekly byusinga Boley gauge. The measure-
ments were made to the nearest 0.1 mm (Fig 3).
Fig 1. Vertical and horizontal corticotomy cuts and per-
forations on the corticotomy side with the miniscrew in
position.
Fig 2. Retraction force applied on the first premolar and
anchored to the miniscrew through the nickel-titanium
coil spring.
American Journal of Orthodontics and Dentofacial Orthopedics Mostafa et al 571
Volume 136, Number 4

3. For the histologic procedures, the first dog was
killed after 1 week of force loading, and another dog
was killed each week thereafter. Each maxilla was dis-
sected free, and soft tissue was immediately removed.
The maxillary segments, including the first premolar
and the extraction socket, were dissected. The speci-
mens were processed as described by Callis.20
After
complete decalcification, the specimens were embed-
ded in paraffin with a convential technique and sec-
tioned mesiodistally (6 mm thick). The sections were
stained with hematoxylin and eosin for routine exami-
nation and Masson’s trichrome for collagen detection.
Statistical analysis
Within-group differences in tooth movement for
the first 4 weeks were analyzed by using the paired
t test. Intergroup differences were analyzed with the
unpaired t test. The values of the first 4 weeks only
were analyzed because of the small sample size in
the fifth and sixth weeks (2 and 1 maxillae) in each
group, respectively. Values of P 0.05 were
considered statistically significant.
RESULTS
The mean values for movement of the first premo-
lars from the first to the fourth weeks starting from
day 0 in each group are shown in Table I. There was sig-
nificant movement (P0.05) in the first 4 weeks in both
groups. In the fifth week, a small amount of movement
(0.5 mm) occurred in the S group, but there was none in
the CF group; no movement was found in the sixth week
in either group. There were also significant differences
in tooth movement between the 2 groups in the first 4
weeks and in the total amount of tooth movement, as
shown in Table II. The mean value of tooth movement
in the first 4 weeks in the CF group was 4.67 6 0.58
mm. This value was twice that of the S group (2.33 6
0.58 mm). The tooth displacement curve of the first pre-
molar (Fig 4) was similar to the classic tooth displace-
ment curve described by Reitan.21
Both groups
followed the curve, but, in the CF group, the tooth
movement values were approximately double those of
the S group.
Fig 3. Measurement of the distance between vertical
grooves on the first and third premolars with the Boley
gauge.
Table I. Paired t test showing mean differences in tooth
movement in each group in the first 4 weeks starting
from day 0
Group Time Mean 6 SD (mm) P value
S D0-W1 0.92 6 0.20 0.00011‡
S D0-W2 1.80 6 0.57 0.00212†
S D0-W3 2.33 6 0.58 0.01980*
S D0-W4 2.33 6 0.58 0.01980*
CF D0-W1 2.00 6 0.55 0.00029‡
CF D0-W2 3.30 6 0.84 0.00091‡
CF D0-W3 4.25 6 0.65 0.00095‡
CF D0-W4 4.67 6 0.58 0.00506†
D0, Day 0; W, week.
*Significant: P0.05; †
Significant: P0.01; ‡
Significant: P0.001.
Table II. Unpaired t test showing the mean differences in
tooth movement between the 2 groups in the first 4
weeks
Week Dogs (n) Mean difference 6 SD (mm) P value
1 6 1.08 6 0.24 0.00108†
2 5 1.50 6 0.45 0.01065*
3 4 1.92 6 0.47 0.00979†
4 3 2.33 6 0.47 0.00776†
*Significant: P 0.05; †
Significant: P 0.01.
0.0
1.0
2.0
3.0
4.0
5.0
0 1 2 3 4 5 6
Weeks
TOOTHMOVEMENTINmm
S
CF
Fig 4. Tooth displacement curve of the first premolar in
the 2 groups.
572 Mostafa et al American Journal of Orthodontics and Dentofacial Orthopedics
October 2009

4. The histologic findings on the compressive side
were the following. During the first and second weeks,
the periodontal ligament (PDL) of the CF group wid-
ened, and the interseptal bone resorbed, leaving only
sporadic bone areas scattered in the PDL. As a result,
the PDL joined the extraction socket that was filled
with many dilated blood vessels. On the other hand,
the PDL of the S group narrowed, and the fiber bundles
were condensed and arranged haphazardly. Thin inter-
septal bone was seen surrounded by an osteoblastic
layer (Fig 5). Neither group had root resorption.
During the third and fourth weeks, the CF group’s
PDL fibers were a mature type and arranged somewhat
regularly. The extraction socket was filled by thick wo-
ven bone with many reversal lines. The PDL of the S
group narrowed and included both mature and immature
collagen fiber bundles. The continuation between the
PDL and the extraction socket was still noticed in the
CF group, whereas the alveolar bone in the S group re-
verted to a nearly normal condition, entrapping wide
marrow spaces. Direct bone resorption was indicated
by many Howship’s lacunae (Fig 6).
After the sixth week, there was direct resorption on
the bone surface in the CF group as evidenced by the
many osteoclasts. Dilated blood vessels were noticed
especially at the bone surface. The woven bone in the
extraction socket was resorbed and replaced by lamellar
bone. In the S group, fewer osteoclasts were seen. The
PDL turnover was localized in the intermediate zone
where hyalinization was noticed. The regenerative
bone tissue refilled the extraction socket and was still
the woven type (Fig 7).
On the tension side, the periodontium widened, and
dilated blood vessels were seen during the first and the
second weeks in the CF group. Newly formed bone with
numerous osteocytes and wide marrow spaces were no-
ticed. The newly formed woven bone in the S group was
thinner and more regular than that in the CF group.
Areas of collagen fiber degeneration were seen in the
CF group near the bone surface. In the S group, these
findings were not observed (Fig 8).
During the third and the fourth weeks, the PDL fibers
in the CF group were arranged haphazardly, and mature
collagen fiber bundles were observed interlaced with
immature ones, especially in the intermediate zone.
On the other hand, the collagen fiber bundles in the S
group consisted of mature fibers, and the formed bone
was thinner compared with that in the CF group (Fig 9).
After the sixth week, the collagen fiber bundles had
a normal appearance in both groups. The newly formed
bone in the CF group was bulky and lamellar. Many oste-
oblasts were noticed on the bone surface. Woven bone
withwidemarrowspaceswasseenintheSgroup(Fig10).
DISCUSSION
Much of the literature on CF orthodontics is based
on empirical evidence and case reports. Experimental
animal-based histologic studies, much needed to
Fig 5. Photomicrographs of the compressive sides after the second week. A, The CF group showing
sporadic bony area in the PDL (p) (thick arrows) and woven bone trabeculae surrounded by osteo-
blasts in the healing socket (thin arrows). Many dilated blood vessels in the extraction socket can
be seen (V). B, The S group showing haphazard fibrous arrangement of the PDL (p). Thin woven
bone trabeculae surrounded by osteoblasts can be seen in the extraction socket (arrows). a, Alveolar
bone. A, Hematoxylin and eosin stain, magnified 200 times; B, Masson’s trichrome stain, magnified
200 times.
American Journal of Orthodontics and Dentofacial Orthopedics Mostafa et al 573
Volume 136, Number 4

5. elucidate the tissue changes with this technique, are
rather few. This study was undertaken to investigate
the influence of corticotomy on tooth movement and
to compare tissue changes between the CF and the S
orthodontic techniques.
Our results showed that the CF technique signifi-
cantly accelerated tooth movement. The rate of tooth
movement in the CF group was twice that in the S group.
These results agree with those of Iino et al,22
who re-
ported significant acceleration of tooth movement in
their animal study. The findings of both animal experi-
ments corroborate the clinical observations of Wilcko
et al13,19
and Hajji,14
who reported significant reduc-
tions in treatment time with CF orthodontics.
In this study, we modified the technique to suit the
extraction case in the dog model; corticotomy cuts
were made mesially, distally, and apically to the extrac-
tion site to achieve bone activation, and, as recommen-
ded by Wilcko et al,13,19
corticotomy perforations were
used to increase the bleeding points at this area. Tooth
movement began immediately after corticotomy. On
the other hand, Iino et al22
used both labial and lingual
corticotomy cuts near the moving premolar. Tooth
movement was started 16 weeks after corticotomy.
Fig 7. Photomicrographs of the compressive sides after the sixth week. A, The CF group showing
lamellar bone (*). Many osteoclasts are obvious (arrows). B, The S group showing the area of hyali-
nization especially at the intermediate zone (h), and internal bone formation as a reaction to EARR
(arrows). a, Alveolar bone. A, Hematoxylin and eosin stain, magnified 200 times; B, Masson’s
trichrome stain, magnified 200 times.
Fig 6. Photomicrographs of the compressive sides after the fourth week. A, The CF group showing
trabeculae of woven bone surrounded by osteoblasts with many reversal lines (arrows). B, The S
group showing haphazard fibrous arrangement of the PDL (p). Scalloped bone surface faces the
PDL (arrows). a, Alveolar bone. A and B, Masson’s trichrome stain, magnified 200 times.
574 Mostafa et al American Journal of Orthodontics and Dentofacial Orthopedics
October 2009

6. Labial and lingual cuts might be justified in a mandible
with thick cortical plates. We believed that labial cuts
were sufficient in the dogs’ less dense maxillae. In addi-
tion, the cuts were made in the area of desired tooth
movement rather than around the moving tooth.
The acceleration of tooth movement in this study
was similar to that reported by Ren et al,8
who used
a surgical technique that depended on undermining
the interseptal bone in a premolar-extraction canine ex-
periment. Although in that study a corticotomy in the
Fig 8. Photomicrographs of the tension sides after the second week: A, the CF group and B, the S
group showing dilated blood vessels (V); the thick layer of woven bone is demarcated by reversal
lines in A with thinner bone in B (*) and is surrounded by osteoblasts. Areas of fibrous degeneration
are observed near the bone surface in A (*). a, Alveolar bone; c, cementum; p, PDL. A and B, Hema-
toxylin and eosin stain, magnified 200 times.
Fig 9. Photomicrographs of the tension sides after the fourth week: A, the CF group and B, the S
group showing widened periodontium. In A, mature and immature fibers interlace much more than
in B. A thick layer of woven bone is demarcated by reversal lines in A with thinner bone in B (*) and
is surrounded by osteoblasts. a, Alveolar bone; c, cementum; p, PDL. A and B, Masson’s trichrome
stain. magnified 200 times.
American Journal of Orthodontics and Dentofacial Orthopedics Mostafa et al 575
Volume 136, Number 4

7. strict sense was not performed, the similarity of findings
is remarkable. The anchorage loss was not measured in
this study because the first premolars were distalized on
miniscrews that give sufficient anchorage.18
We focused
on the influence of corticotomy on tooth movement and
the accompanying tissue changes.
Standard orthodontic tooth movement has 3 periods:
initial, lag, and postlag. In this experiment, the tooth dis-
placement curve of the first premolar was similar to the
classic tooth-displacement curve described by Reitan21
in
both groups. However, the initial movement in the first
and second weeks was faster in the CF group than in the
S group. This could have been due to the extensive alveolar
bone septum resorption in the CF group. In the S group,
therewas thin interseptal bone surrounded by an osteoblas-
tic layer. Ren et al8
also found interseptal bone resorption,
but after the third and fourth weeks of force application
(150 g). The difference in timing between the study of
Ren et al8
and ours, particularly in the CF group, was prob-
ably due to more extensive bone resorption and increased
osteoclastic activity caused by the corticotomy; this agrees
with the findings of Yaffe et al.23
The excessive applied
force (400 g) in that study could be another reason for
the more rapid bone resorption. However, the absence of
microscopic root resorption until the end of the sixth
week offorce application indicated that this load was toler-
ated by the dogs’ teeth, even though strong forces are
a cause of root resorption during orthodontic treatment.24
After the second week, greater osteoblastic activity
in the compressive side was found in the S group. This
probably was an attempt to revert to the resorbed alve-
olar bone and might have hindered tooth movement in
the S group.
The lag period, from the third to the sixth weeks in
this study, was associated with PDL compression and
destruction of its fiber arrangement and structure that
were replaced by immature fibers. This observation
was more obvious in the S group than in the CF group.
Many researchers have stated that the lag period is prob-
ably associated with hyalinization in the PDL.8,25-29
The PDL fibers in this study did not show hyalinization
except in small areas in the S group at the sixth week.
This might be due to the high vascularity from the ex-
traction socket, thus preventing the expected ischemia
to the PDL fibers. Von Bo¨hl et al28
stated that hyaliniza-
tion was found not only in the phase of arrest, between 4
and 20 days of force application, but also after 40 and 80
days of tooth movement. This suggested that the devel-
opment and removal of necrotic tissue was a continuous
process during tooth displacement rather than a single
event.
Although we did not study the postlag period, it
was expected from the reappearance of many osteo-
clasts on the alveolar bone surface in the sixth
week. Von Bo¨hl et al28
recorded such a postlag period
after 40 and 80 days of tooth movement.
Regarding the tension side, new bone formation was
similar in both groups except that osteogenesis was
more active in the CF group because of more extensive
stretching of the periodontium from the faster tooth
Fig 10. Photomicrographs of tension sides after the sixth week: A, the CF group and B, the S group
showing osteogenesis and PDL fibers reverted to normal arrangement. Thick lamellar bone is seen in
A (*); woven bone is seen with many reversal lines in B (*). a, Alveolar bone; c, cementum; p, PDL. A,
Hematoxylin and eosin stain, magnified 200 times; B, Masson’s trichrome stain, magnified 200 times.
576 Mostafa et al American Journal of Orthodontics and Dentofacial Orthopedics
October 2009

8. movement in this group. These results were similar to
those of Ren et al,8
except that the PDL fibers of the
CF group showed degeneration at the bone surface.
This observation could be because rapid movement in
the CF group led to degeneration of the collagen fiber
bundles, whereas steady, smooth movement in the S
group prevented this. The return to the normal arrange-
ment of the PDL fibers after the fifth and sixth weeks in
both groups might be due to the lag period that allowed
for this rearrangement. Not only was the thickness of the
newly formed bone different in both groups but also the
quality of the bone was different. In the CF group, the
bone became lamellar; in the S group, the bone was
the woven type with wide marrow spaces up to the sixth
week. This suggested a greater relapse tendency in the S
group.
CONCLUSIONS
The CF technique was found to double the amount
of tooth movement compared with the S technique. His-
tologically, there was more active and extensive bone
remodeling in the CF group. This suggests that the ac-
celeration of tooth movement associated with cortico-
tomy is due to increased bone turnover and based on
a regional acceleratory phenomenon.
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