ORIGINAL ARTICLE

Effect of piezocision on root resorption

associated with orthodontic force: A
microcomputed tomography study
Braydon M. Patterson,a Oyku Dalci,a Alexandra K. Papadopoulou,b Suman Madukuri,c Jonathan Mahon,c
Peter Petocz,d Axel Spahr,b and M. Ali Darendelilera
Sydney, Australia, and Thessaloniki, Greece

Introduction: The purpose of this study was to investigate the effect of piezocision on orthodontically induced
inflammatory root resorption. Methods: Fourteen patients were included in this split-mouth study; 1 side was
assigned to piezocision, and the other side served as the control. Vertical corticotomy cuts of 4 to 5 mm in
length were performed on either side of each piezocision premolar, and 150-g buccal tipping forces were
applied to the premolars. After 4 weeks, the maxillary first premolars were extracted and scanned with
microcomputed tomography. Results: There was a significantly greater total amount of root resorption seen
on the piezocision sides when compared with the control sides (P 5 0.029). The piezocision procedure resulted
in a 44% average increase in root resorption. In 5 patients, there was noticeable piezocision-related iatrogenic
root damage. When that was combined with the orthodontic root resorption found on the piezocision-treated
teeth, there was a statistically significant 110% average increase in volumetric root loss when compared with
the control side (P 5 0.005). Conclusions: The piezocision procedure that initiates the regional acceleratory
phenomenon may increase the iatrogenic root resorption when used in conjunction with orthodontic forces. Pie-
zocision applied close to the roots may cause iatrogenic damage to the neighboring roots and should be used
carefully. (Am J Orthod Dentofacial Orthop 2017;151:53-62)

O
rthodontically induced inflammatory root supporting alveolar bone, and tissues with differing
resorption1 is defined as the loss of dental hard cell populations and differing remodeling capabilities.6
tissues caused by clastic cellular activity.2 It is During tooth movement, the production of hyalinization
an undesirable and often unpredictable side effect of or- regions in the periodontal tissues occurs particularly
thodontic tooth movement,3,4 with a complex and upon the application of heavy forces.7,8 The removal
multifactorial etiology.5 of these hyalinization zones by osteoclasts has been
Orthodontic tooth movement relies on the compli- associated with orthodontic root resorption.9,10
cated changes that occur in the periodontal ligament, Corticotomies have been discussed in the orthodontic
literature as a means for accelerating the rate of tooth
a
movement for over 100 years.11 Initially, it was believed
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney
Dental Hospital, Sydney South West Area Health Service, Sydney, Australia. that corticotomies accelerated tooth movement because
b
Discipline of Orthodontics, Faculty of Dentistry, University of Sydney, Sydney of segmentation of alveolar bone and the en-masse move-
Dental Hospital, Sydney South West Area Health Service, Sydney, Australia; ment of the teeth and associated block of bone. More
Department of Oral Surgery and Implantology, Aristotle University of Thessalo-
niki, Thessaloniki, Greece. recent research has used corticotomies as a means of
c
Discipline of Periodontics, Faculty of Dentistry, University of Sydney, Sydney accelerating the rate of bone turnover.11-13 Corticotomy
Dental Hospital, Sydney South West Area Health Service, Sydney, Australia. accelerates orthodontic tooth movement via the
d
Department of Statistics, Macquarie University, Sydney, Australia.
All authors have completed and submitted the ICMJE Form for Disclosure of activation of a regional acceleratory phenomenon
Potential Conflicts of Interest, and none were reported. (RAP).14-16 The RAP effect usually commences within a
Financial support from the Australian Society of Orthodontists Foundation for few days of injury, peaks at 1 to 2 months, and lasts for
Research and Education.
Address correspondence to: M. Ali Darendeliler, Discipline of Orthodontics, Fac- 2 to 4 months, with up to 6 to 24 months reported in
ulty of Dentistry, University of Sydney, Sydney Dental Hospital, Level 2, 2 Chalm- the literature.11,17-19 This normal healing process
ers St, Surry Hills, NSW 2010, Australia; e-mail, ali.darendeliler@sydney.edu.au. involves the acceleration of growth, remodeling,
Submitted, November 2015; revised and accepted, June 2016.
0889-5406/$36.00 metabolism, healing, inflammation, perfusion, cell
http://dx.doi.org/10.1016/j.ajodo.2016.06.032 turnover, and repair of microdamage.20,21
53
54 Patterson et al

The corticotomy-induced RAP response accelerates

tooth movement by producing temporary demineraliza-
tion/osteopenia in the bone surrounding the roots of
activated teeth. These teeth that have been activated
by corticotomies experience more rapid and extensive
alveolar bone and periodontal ligament turnover.22
The literature has demonstrated that corticotomies can
increase the rate of orthodontic tooth movement by up
to 2 to 3 times the normal rate.23,24
There is only limited evidence in the orthodontic Fig 1. Appliance design with 0.017 3 0.025-in beta-
literature that demonstrates a statistically significant titanium alloy buccal tipping springs.
reduction in the amount of root resorption with the
use of corticotomy procedures, when compared with first premolar and canine or second premolar. There
normal tooth movement.25,26 was concern that randomization might result in iatro-
Piezocision is a more conservative and less invasive genic damage to the teeth when performing the piezoci-
variation of the traditional corticotomy tech- sion procedure, so the side with the least risk of causing
nique.12,27,28 It involves the use of an ultrasonic root damage was selected.
cutting instrument to make the corticotomy incisions, The subjects had partial fixed appliances placed on
without the need for raising a soft tissue flap. It has the maxillary first premolars and first molars bilaterally.
been claimed that piezocision can produce comparable Self-ligating 0.022-in SPEED brackets and tubes were
rates of accelerated tooth movement to more used (Strite Industries, Cambridge, Ontario, Canada).
conventional corticotomy procedures.12 Buccal tipping forces (150 g) were applied to the maxil-
The aim of this pilot study was to investigate the ef- lary first premolars by 0.017 3 0.025 Beta III Titanium
fect of piezocision on root resorption when 150-g buccal (3M Unitek, Monrovia, Calif) cantilever springs. The
tipping forces were applied to maxillary first premolars springs were inserted into the maxillary first molar and
for a 4-week period. A qualitative and quantitative first premolar brackets and bypassed the maxillary sec-
assessment of the degree of root resorption was per- ond premolar (Fig 1).
formed by microcomputed tomography scanning of The force produced by the springs was calibrated
the extracted premolars. with a strain gauge (Dentaurum, Ispringen, Germany)
and customized to each premolar. Once the springs
were fitting well and generating 150 g of force, they
MATERIAL AND METHODS were taken out of the brackets to allow unimpeded ac-
The sample consisted of 28 maxillary first premolars cess to the surgical site. In addition, occlusal stops
that were extracted bilaterally from 14 patients. There (Transbond Plus Light Cure Band Adhesive; 3M Unitek)
were 6 male and 8 female patients (mean age, 16 years were placed onto the mesiopalatal cusps of the maxillary
2 months; range, 13 years 1 month to 19 years 0 month). first molars to prevent occlusal interferences and allow
They required the extraction of maxillary first premolars uninhibited tipping of the maxillary first premolars dur-
as part of their orthodontic treatment. Ethics approval ing the experiment.
was granted by the Sydney Local Health District, RPAH At the same appointment, the piezocision procedure
Zone (ethics approval numbers X13-0371 and HREC/ was performed on 1 maxillary first premolar. A surgical
13/RPAH/519). The patients were carefully selected ac- setup was used for all subjects, with a sterile field of
cording to previously described strict inclusion criteria, operation. Local anesthetic was administered (Ligno-
and written informed consent was obtained.29 span lidocaine hydrochloride 2%, 1:100,000 Adr; Septo-
After the collection of pretreatment records, the sub- dont, France), and then a soft tissue laser (Picasso; AMD
jects had a baseline periodontal checkup for standard- Lasers, Indianapolis, Ind) was used to produce 2 buccal
ized periodontal measurements and oral hygiene vertical interproximal incisions into the gingiva/mucosa,
control before the experiment. one on the mesial side and one on the distal side of the
Using a split-mouth study design, we allocated the first premolar. The incisions were made apical to the
maxillary first premolars to 1 of 2 groups for each partic- interdental papilla, 5 to 7 mm long. A piezocision blade
ipant. One side was chosen to have the piezocision pro- (VarioSurg Ultrasonic Bone Surgery System; NSK-
cedure performed, with the other side acting as the Nakanishi, Tochigi, Japan) was then inserted into the
control. In some participants, it was apparent that there soft tissue incision, as per the technique of Dibart
was limited interradicular space between the maxillary et al12 and Dibart and Dibart.27 The piezocision blade

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Patterson et al 55

Fig 2. Vertical interradicular piezocision corticotomy

cuts.

was used to produce a vertical corticotomy cut into the

buccal cortical plate, mesial and distal to the buccal root
of the maxillary first premolar. Each alveolar bone corti-
cotomy cut was 4 to 5 mm long and made to a depth of 2
to 3 mm. When the maxillary first premolar root was
close to the canine or second premolar root, the depth
of the corticotomy cut was reduced to prevent iatrogenic Fig 3. Binary axial image slice of root specimen.
root damage. Once the piezocision procedure had been
completed, no suturing was required for the vertical each tooth specimen. This microcomputed tomography
soft tissue incisions (Fig 2). unit produces high-resolution 3-dimensional images
The calibrated beta-titanium alloy springs were re- from multiple 2-dimensional (2D) x-ray shadow trans-
placed into their corresponding brackets and left in place mission images of the specimen at differing angulations.
for the 4-week experimental period, with no reactivation. The teeth were scanned individually, from a position
All surgical procedures were performed by 1 clinician just apical to the cementoenamel junction to the root
(S.M.) from the periodontology department. All ortho- apex. Specimens were scanned 180 around the vertical
dontic procedures were performed by 1 clinician (B.P.) axis, with image resolution set at 17.6 mm.
from the orthodontics department, both from the Uni- The image data from the SkyScan unit was then re-
versity of Sydney. constructed with its own proprietary software, NRecon
Two weeks after the piezocision procedure, standard- (version 1.6.9.18; Bruker). This program relies on a
ized periodontal parameters were retaken, and the sub- modified Feldkamp cone-beam algorithm to produce
jects were checked for any issues regarding the slice-by-slice axial reconstruction.31 The settings for
piezocision procedure. NRecon were standardized for all images. The recon-
After 4 weeks of buccal tipping force application, the structed slices were saved in 16-bit tagged image file
partial fixed appliances and occlusal stops were format (TIFF).
removed. Final standardized periodontal measurements Root resorption crater detection and quantification
were taken. The maxillary first premolars were carefully were performed using the imaging software program
extracted by 1 operator (B.P.) to ensure that minimal Fiji (version 2.0.0-rc-15/1.49k; available at http://
damage occurred to the root surfaces. The teeth were imagej.net/Contributors),32 along with a custom macro
not luxated; only forceps were used. (Enigma; Australian Centre for Microscopy and Micro-
The extracted first premolars were then stored and analysis, University of Sydney). All axial slices of the im-
prepared according to previously established proto- age stack for each specimen were manually examined for
cols.29,30 The teeth were stored in deionized water resorption craters. Each image slice needed to be con-
(Milli Q; Millipore, Bedford, Mass). An ultrasonic bath verted to a binary image (black and white) before crater
was used for 10 minutes to allow the removal of soft calculation (Fig 3).
tissue and periodontal fragments from the root Once a crater was detected, it was highlighted with a
surface. Any residual periodontium was carefully clipping tool and duplicated into its own image
removed with damp gauze. Disinfection was achieved sequence to allow Enigma to calculate the volume of
by placing the teeth into 70% isopropyl alcohol for each crater in cubic millimeters. All measurements
30 minutes, followed by bench drying at room were carried out by 1 operator (B.P.) to reduce error
temperature (23 C 6 2 C) for at least 48 hours. and bias. Craters were categorized as located on the
A desktop x-ray microtomograph machine (SkyScan buccal, palatal, mesial, or distal surface, with the 3 ver-
1172; Bruker, Aartselaar, Belgium) was used to scan tical location designated as the cervical, middle, or apical

American Journal of Orthodontics and Dentofacial Orthopedics January 2017  Vol 151  Issue 1
56 Patterson et al

Fig 4. Three-dimensional image reconstruction with buccal and palatal views of a nonpiezocision
maxillary first premolar.

third of the root. Total root resorption volume was also Overall, more root resorption was seen on the piezo-
recorded for each tooth. cision teeth than on the control teeth (Fig 5).
For 3-dimensional image reconstruction (Avizo Fire For the total volumes of root resorption cratering per
version 8.1.0; Konrad-Zuse-Zentrum, Berlin, Germany) tooth, the piezocision teeth averaged 0.435 mm3, and
was used to create and view selected specimens (Fig 4). the control teeth averaged 0.302 mm3. This resulted in
the piezocision procedure producing an average of
Statistical analysis 0.133 mm3, or 44%, more root resorption than did the
corresponding control teeth. The difference was statisti-
The SPSS statistics program (version 21; IBM, Ar-
cally significant (P 5 0.029). Only 4 participants demon-
monk, NY) was used for statistical analysis. Paired t tests
strated less total root resorption with the piezocision
were used to determine whether there were any statisti-
procedure when compared with the contralateral control
cally significant differences in the data of the
teeth (Table I).
piezocision-related root resorption compared with the
The root resorption data were also assessed in terms
nonpiezocision root resorption. This included
of distribution on the buccal, palatal, mesial, and distal
comparing the total resorption crater volume per tooth
surfaces for each tooth. The piezocision teeth demon-
for each root surface (buccal, palatal, mesial, and distal)
strated marginally more root resorption on the buccal,
and for each vertical third (cervical, middle, and apical).
palatal, mesial, and distal surfaces when compared
All analyses were assessed with P \0.05 considered sta-
with the control teeth. However, no results had statistical
tistically significant.
significance (Table II).
The root resorption crater volumes of 6 randomly
When we examined the root resorption crater distri-
selected teeth were remeasured to determine the overall
bution on the cervical, middle, and apical thirds of the
standard error of the measurements and the coefficient
teeth, the piezocision-treated teeth exhibited more
of variation.
root resorption in all vertical thirds than did the control
teeth, but these results were not statistically significant
RESULTS (Table III).
All 14 patients completed the study, with all 28 pre- During the assessment of each maxillary first pre-
molars deemed eligible for assessment and inclusion in molar with the microcomputed tomography machine,
the study. we noted that 5 participants had considerable

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Patterson et al 57

Fig 5. Total resorption per tooth (piezocision, control, and piezocision 1 damage).

the damage crater that corresponded to the piezocision

Table I. Total volumetric root resorption loss per
blade configuration, whereas orthodontic root resorp-
tooth (including piezocision damage)
tion craters had a much shallower and broader form
Total resorption (Fig 6).
per tooth (mm3) Since the piezocision instrument essentially created
Piezocision Damage 1
Piezocision Nonpiezocision damage piezocision iatrogenic root resorption cratering, the results for total
Subject side side (mm3) side (mm3) root resorption volume per tooth were recalculated as a
1 0.455 0.447 0 0.455 second data set to include the volumetric damage
2 0.122 0.176 0.725 0.847
values. Adding the iatrogenic damage and orthodontic
3 0.263 0.170 0.212 0.475
4 0.395 0.180 1.116 1.511 root resorption values together resulted in an average
5 0.340 0.381 0.547 0.886 total volume for each piezocision tooth of 0.633 mm3.
6 0.315 0.267 0 0.315 When compared with the average value for the control
7 0.157 0.153 0.173 0.330 teeth (0.302 mm3), there was an additional
8 0.717 0.399 0 0.717
0.331 mm3, or 110% more, volumetric root loss. This
9 0.396 0.422 0 0.396
10 1.109 0.710 0 1.109 result was highly significant (P 5 0.005).
11 0.551 0.320 0 0.551 The repeated measurements on the 6 randomly
12 0.121 0.295 0 0.121 selected premolars resulted in an overall standard error
13 0.445 0.127 0 0.445 of measurement of 0.012 mm3 and a coefficient of vari-
14 0.711 0.180 0 0.711 ation of 4.7%.
Total 6.095 4.228 2.772 8.867
Mean 0.435 0.302 0.198 0.633
SD 0.271 0.161 0.350 0.365 DISCUSSION
The effect of corticotomy procedures on orthodonti-
iatrogenic root damage from the piezocision surgical cally induced inflammatory root resorption has been as-
procedure. The shape of the piezocision-related dam- sessed briefly in previous studies.25,26,33,34 The general
age was clearly differentiated from the orthodontically consensus from the limited data in the literature
induced inflammatory root resorption. Iatrogenic pie- indicated that either corticotomy procedures did not
zocision damage appeared as long, narrow, and deep result in more root resorption than conventional
vertical defects, with a sawtooth shape of the floor of orthodontic treatment,33 or there was actually less root

American Journal of Orthodontics and Dentofacial Orthopedics January 2017  Vol 151  Issue 1
58 Patterson et al

3
Table II. Total volume of root resorption per surface (mm )
t test,
Tooth surface Piezocision Mean SD Nonpiezocision Mean SD P
Buccal 2.052 0.147 0.099 1.318 0.094 0.075 0.072
Palatal 0.824 0.059 0.059 0.599 0.043 0.038 0.298
Mesial 1.911 0.136 0.116 1.361 0.098 0.091 0.313
Distal 1.309 0.093 0.117 0.951 0.068 0.077 0.295
Total 6.096 4.229

3
Table III. Total volume of root resorption per vertical third (mm )
t test,
Tooth third Piezocision Mean SD Nonpiezocision Mean SD P
Cervical 2.764 0.197 0.111 2.040 0.146 0.093 0.217
Middle 1.865 0.133 0.154 1.128 0.081 0.098 0.075
Apical 1.466 0.105 0.130 1.061 0.076 0.075 0.203
Total 6.095 4.229

Fig 6. Piezocision (red) and root resorption craters (blue) highlighted.

resorption.25,34 The accuracy of these studies could be orthodontics resulted in an average of 0.6 mm of apical
questioned, since most of them examined root root loss, whereas conventional orthodontics resulted in
resorption from periapical radiographs. Traditional 2D 1.5 mm of resorption. Cone-beam computed tomo-
radiography has multiple issues when it comes to graphs have been reported to allow better detection of
diagnosing and assessing orthodontic root resorption, root resorption than do 2D films.36 However, they have
including superimposition of adjacent structures, not been used extensively in root resorption studies,
magnification, the ability to assess root resorption only possibly because of concerns about unnecessary radia-
on mesial and distal root surfaces that are tion exposure of the subjects and the retrospective na-
perpendicular to the x-ray beam, and a general lack of ture of many root resorption studies.
reproducibility and sensitivity. These drawbacks of 2D This prospective clinical trial is the first study to use
imaging result in detecting only advanced root microcomputed tomography to examine the effects of
resorption and apical root loss.35 Abbas et al26 per- corticotomy-facilitated orthodontic procedures on the
formed a study that used cone-beam computed tomo- root resorption process. This is also the first study to
graphs and found that corticotomy-facilitated report a statistically significant increase in root

January 2017  Vol 151  Issue 1 American Journal of Orthodontics and Dentofacial Orthopedics
Patterson et al 59

resorption produced by a corticotomy-facilitated ortho- has been established that the RAP effect increases the
dontic procedure when compared with conventional or- turnover rate of alveolar bone and the periodontal liga-
thodontics, as well as the documentation and ment,22 by increasing the activity of associated cells such
quantification of iatrogenic root damage produced by as osteoblasts, fibroblasts, cementoblasts, and osteo-
the piezocision instrument. By extracting the maxillary clasts.43 An enhanced bone turnover rate leads to an
first premolars, it was possible to obtain detailed infor- osteoporotic environment and a reduction in the resis-
mation about the root resorption craters and tance of teeth moving through alveolar bone.13,17 By
piezocision-related damage that would not have been reducing areas of pressure concentration and the
possible if the teeth had remained in the patient's mouth potential for hyalinization to develop, this could
and were examined with conventional 2D radiographic theoretically reduce the amount of root resorption
methods. associated with corticotomy procedures, but the
The piezocision procedure resulted in an increase in relationship between alveolar bone density and the
root resorption on all surfaces (buccal, palatal, mesial, root resorption process is not clear.44 Although some
and distal) and vertical thirds (cervical, middle, and api- studies have suggested that increased bone turnover
cal) when compared with the control side after the appli- and reduced bone density favor remodeling of bone
cation of orthodontic force for 28 days. However, only over root surface,45 other studies have shown that root
total root resorption values reached statistical signifi- resorption increased due to increased bone turnover.46
cance. There were considerable individual variations in Animal research has shown that after a corticotomy pro-
root resorption values among the participants, and this cedure, at 3 weeks postsurgery, the numbers of osteo-
was expected because of the impact of individual sus- clasts and the bone apposition rate tripled compared
ceptibility on the root resorption process.37,38 For both with the controls.47 The dramatic increase in trabecular
groups, root resorption was seen on the buccal and bone turnover was attributed to the increased osteoclast
palatal surfaces, in particular the buccal-cervical and activity and cell numbers associated with the RAP
palatal-apical regions; this was consistent with previous response. Teng and Liou48 found that interdental os-
studies that examined buccal tipping forces and root teotomy cuts between the third incisor and canine of
resorption.39-41 Resorption was also present on the beagle dogs resulted in a 2-fold postoperative increase
mesial and distal surfaces. It was likely that a mesial, in orthodontic tooth alignment. Indicative biomarkers
distal, or rotational component of force was imparted of bone remodeling showed significant increases in
on the maxillary premolars during tipping. This could regional levels when compared with the controls. In
be explained by the simple cantilever design of the more detail, gingival crevicular fluid levels of bone-
buccal beta-titanium alloy springs, and the relative po- specific alkaline phosphatase showed a continuous
sition and rotation of the maxillary first premolars in increase during the experimental period, whereas
relation to the dental arch. The increased mesial and C-terminal telopeptide of type I collagen levels dramat-
distal root resorption in the piezocision group compared ically increased at the beginning of the experiment and
with the control group could be explained by the ability then gradually decreased. The authors found that the
of corticotomy procedures to facilitate a RAP response in experimental dogs did not experience a systemic in-
areas not directly associated with the corticotomy. Teix- crease in the baseline bone turnover (measured by serum
eira et al42 performed an accelerated tooth movement alkaline phosphatase and C-terminal telopeptide of type
study on rats that involved placing 3 buccal cortical I collagen levels) when compared with the controls; this
bone perforations at a distance of 5 mm mesial to the highlighted that a RAP response only had a localized ef-
maxillary first molar. The bone perforation experimental fect on bone turnover. However, the extent of the inter-
group experienced accelerated tooth movement, in- dental osteotomy was addressed as a possible
creases in osteoclast numbers, significant reductions in determining factor for the intensity of bone turnover
bone volume fraction levels, and statistically higher and osteoporotic changes. Hence, it could be argued
levels of cytokine/cytokine receptor levels compared that in the presence of increased clastic cellular activity
with the untreated controls and the orthodontic force during increased bone turnover, an increase in the
only groups. These results demonstrated that a sufficient amount of root resorption may be expected.
localized RAP response was produced by cortical bone The RAP effect has also been associated with an in-
perforations that were not close to the experimental crease in the local inflammatory response.20 A study
teeth. that examined the effect of buccal cortical bone perfora-
The biologic mechanisms behind the acceleration of tions on the rate of maxillary canine retraction found
tooth movement via corticotomy procedures and their that within 24 hours of commencing canine retraction,
effects on root resorption are complex and unclear. It both control and experimental groups experienced an

American Journal of Orthodontics and Dentofacial Orthopedics January 2017  Vol 151  Issue 1
60 Patterson et al

increase in local inflammatory marker/mediator levels.49 lack of interradicular space around the maxillary first
However, the experimental side had statistically signifi- premolars. The surgical sites were carefully planned
cant higher levels of the measured cytokines (IL-1a, and assessed before the experimental period with photo-
IL-1b, TNF-a, and IL-6) and chemokines (CCL-2, CCL- graphs, study models, and parallel periapical radio-
3, CCL-5, and IL-8) when compared with the control graphs. Nevertheless, reduction in the depth of the
group. The induced RAP effect was responsible for the piezocision cuts in the buccal cortical plate had to be im-
elevated levels of inflammatory markers. Although the plemented in a few participants during the surgical pro-
cytokine and chemokine levels were higher in the exper- cedure to minimize damage to adjacent teeth. Also, the
imental group than in the control group after the 4-week width of the piezocision blade was less than 1 mm, which
experimental period, most of these values were not sta- was narrower than the diameter of surgical burs tradi-
tistically significant. Since orthodontic root resorption is tionally used in corticotomies. Despite taking these addi-
an inflammatory process, increased levels of inflamma- tional precautions, 5 participants experienced
tory mediators may increase root resorption.1 piezocision-related iatrogenic root damage on the
The literature generally agrees that treatment duration experimental premolars. The volume of piezocision
is positively correlated with root resorption, although damage was often comparable with the amount of
some recent cone-beam research disputes that link.50-53 corticotomy-facilitated orthodontic root resorption.
Makedonas et al54 could not find an association between Corticotomy-facilitated orthodontic techniques are
treatment duration and root resorption in a sample of 156 often indicated in patients with crowding, when
patients. Piezocision procedures reduce treatment dura- nonextraction-based accelerated tooth movement is
tion via accelerated tooth movement, so this should theo- desired.56 However, in crowding cases, when teeth and
retically lead to a reduction in total root resorption their roots are often displaced and close to each other,
during treatment when compared with slower conven- there would appear to be a risk of iatrogenic root damage.
tional orthodontics.12 In our study, the piezocision It could be argued that with further experience in cortico-
procedure resulted in more incidental root surface resorp- tomy procedures, a surgical operator would improve his
tion than did conventional treatment over the 4-week or her technique and ability to identify patients at risk
experimental period. Future research should involve the for root damage. However, in our study, it was clear
examination of the effect of piezocision on root resorp- that even with periodontists, some teeth experienced un-
tion over the complete course of treatment. This would wanted iatrogenic root damage. In terms of recommen-
possibly provide a more comprehensive perspective on dations for current clinical practice, it appears that
how the various biologic mechanisms of corticotomy- patient selection is important when performing a cortico-
facilitated tooth movement interact and influence the tomy procedure, where sufficient interradicular space is
overall root resorption process. required to minimize the risk of iatrogenic root damage.
The buccal tipping force of 150 g was chosen as a The long-term effects of the iatrogenic root damage
clinically relevant force that was intermediate when and the associated root reparative processes are currently
compared with light and heavy forces established in pre- unknown, so clinically it would be prudent to prevent cor-
vious root resorption studies at the University of ticotomy/piezocision damage as much as possible.
Sydney.39,40,55 These studies also established that a One limitation of our study was the small sample size.
4-week experimental period was sufficient to allow The size was based on previous root resorption research
detectable root resorption cratering to form, while re- with similar study designs.57,58 The split-mouth design
maining ethical and practical for the participants. The was chosen to improve the power of the study. Ideally,
piezocision surgical protocol used in this study was cho- an a priori sample size calculation would have allowed
sen because it had been shown in the literature to be the study to have a sufficient sample size to achieve
more conservative and safe, but a similarly effective adequate power. This was not possible since this was a
form of corticotomy procedure when compared with pilot study, and there were no previous studies that
other corticotomy techniques.12,28 At the postsurgical could provide data on the expected magnitude of
review appointment, the participants mentioned that change or standard deviations needed for a power calcu-
they experienced minimal discomfort from the lation. Although statistical significance was achieved
piezocision procedure. with the total root resorption figures, an adequate sam-
Difficulties with the piezocision technique occurred ple size may have allowed statistically significant results
during the study. Inadequate visual access of the inter- for the differences in root resorption for individual root
radicular cortical bone occurred because the soft tissue surfaces and vertical thirds. Randomization of each
incisions were relatively short and did not involve raising participant would have been preferable to reduce selec-
a mucoperiosteal flap. Another problem was the general tion bias. However, this may have produced iatrogenic

January 2017  Vol 151  Issue 1 American Journal of Orthodontics and Dentofacial Orthopedics
Patterson et al 61

root damage in more participants; this needed to be 4. Levander E, Malmgren O, Eliasson S. Evaluation of root resorption
avoided as much as possible. Blinding of the outcome in relation to two orthodontic treatment regimes. A clinical exper-
imental study. Eur J Orthod 1994;16:223-8.
assessor (B.P.) did not occur in the study, because the
5. Weltman B, Vig KW, Fields HW, Shanker S, Kaizar EE. Root resorp-
periodontal department needed the buccal beta- tion associated with orthodontic tooth movement: a systematic re-
titanium alloy springs removed from the subjects for view. Am J Orthod Dentofacial Orthop 2010;137:462-76.
the piezocision surgical procedure. Therefore, when the 6. Meikle MC. The tissue, cellular, and molecular regulation of ortho-
buccal tipping springs were replaced postoperatively by dontic tooth movement: 100 years after Carl Sandstedt. Eur J Or-
thod 2006;28:221-40.
the operator, it became immediately apparent which
7. Bister D, Meikle MC. Re-examination of ‘Einige Beitrage zur The-
side had the piezocision procedure. A more homoge- orie der Zahnregulierung’ (some contributions to the theory of the
neous use of the piezocision technique with precise cor- regulation of teeth) published in 1904-1905 by Carl Sandstedt. Eur
ticotomy positions and depths would have strengthened J Orthod 2013;35:160-8.
the methodology of the study. Because of a general lack 8. Schwarz AM. Tissue changes incidental to orthodontic tooth
movement. Int J Orthod Oral Surg Radiogr 1932;18:331-52.
of interradicular space for the piezocision cuts, this was
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not possible without causing more unwanted iatrogenic ment on different alveolar bone types. Angle Orthod 1964;34:
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CONCLUSIONS Angle Orthod 1974;44:68-82.
11. Wilcko W, Ferguson D, Bouquot J, Wilcko M. Rapid orthodontic
The following conclusions can be made in this micro- decrowding with alveolar augmentation: case report. World J Or-
computed tomography study where the effects of the thod 2003;4:197-205.
piezocision surgical technique were examined in relation 12. Dibart S, Sebaoun JD, Surmenian J. Piezocision: a minimally inva-
to orthodontic root resorption with the application of a sive, periodontally accelerated orthodontic tooth movement pro-
cedure. Compend Contin Educ Dent 2009;30:342-4; 46, 48-50.
buccal tipping force for 28 days. 13. Wilcko WM, Wilcko T, Bouquot JE, Ferguson DJ. Rapid orthodon-
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Periodontics Restorative Dent 2001;21:9-19.
may increase iatrogenic root resorption when used 14. Frost HM. The regional acceleratory phenomenon: a review. Henry
with orthodontic forces. Ford Hosp Med J 1983;31:3-9.
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rogenic damage to neighboring roots and should be cians. Part II. Clin Orthop Relat Res 1989;294-309.
used carefully. 16. Frost HM. The biology of fracture healing. An overview for clini-
cians. Part I. Clin Orthop Relat Res 1989;283-93.
3. The use of piezocision as a standard procedure 17. Buschang PH, Campbell PM, Ruso S. Accelerating tooth movement
should be reconsidered and closely evaluated during with corticotomies: is it possible and desirable? Semin Orthod
comprehensive treatment. 2012;18:286-94.
4. Potential applications to increase the RAP effect 18. Frost HM. From Wolff's law to the Utah paradigm: insights about
without iatrogenic damage should be considered. bone physiology and its clinical applications. Anat Rec 2001;262:
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19. Lee W, Karapetyan G, Moats R, Yamashita DD, Moon HB,
ACKNOWLEDGMENTS Ferguson DJ, et al. Corticotomy-/osteotomy-assisted tooth move-
ment microCTs differ. J Dent Res 2008;87:861-7.
We thank Dr Matthew Foley from the Australian 20. Frost HM. Perspectives: bone's mechanical usage windows. Bone
Centre for Microscopy and Analysis at the Australian Mi- Miner 1992;19:257-71.
21. Frost HM. A 2003 update of bone physiology and Wolff's law for
croscopy and Microanalysis Research Facility at the clinicians. Angle Orthod 2004;74:3-15.
Australian Centre for Microscopy and Microanalysis at 22. Mostafa YA, Fayed MM, Mehanni S, ElBokle NN, Heider AM. Com-
the University of Sydney for scientific and technical parison of corticotomy-facilitated vs standard tooth-movement
assistance, and Fred Zahr for preparing the participants techniques in dogs with miniscrews as anchor units. Am J Orthod
for the piezocision procedure. Dentofacial Orthop 2009;136:570-7.
23. Aboul-Ela SM, El-Beialy AR, El-Sayed KM, Selim EM, El-
Mangoury NH, Mostafa YA. Miniscrew implant-supported maxil-
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