(1) The study analyzed bone biopsy samples from 8 patients who underwent corticotomy to accelerate tooth movement as part of orthodontic treatment. (2) Bone samples were taken before surgery and 90 days after from both the corticotomized and non-corticotomized sites and analyzed histologically. (3) The results found higher levels of primary bone formation and osteocyte counts in the corticotomized sites 90 days after surgery compared to the non-corticotomized sites, suggesting corticotomy promotes reversible bone injury and remodeling without long-term harm.

1. PRESENTED BY
SAI KIRAN.K
ANGLE ORTHODONTIST, VOL 88, NO 2, 2018

2.  INTRODUCTION:
 Corticotomy was used as a surgical procedure to accelerate tooth movement.
 These events constitute a temporary stage of bone remodeling that results in the
reconstruction of injured sites to their normal state, known as the ‘‘regional
acceleratory phenomenon’’ (RAP).
 Corticotomy was used as a surgical procedure to accelerate tooth movement.

4.  It can be hypothesized that shallow perforations on the buccal cortical plate of the
mandible result in temporary bone injury and do not cause permanent harm to
patients.
 The aims of this study were to :
(1) analyze histologic findings of bone remodeling at baseline and 90 days after
corticotomy in corticotomized and non-corticotomized sites and
(2) provide scientific data to determine whether bone conditions in corticotomized
subjects are unaltered 3 months after surgery.

5.  MATERIALS AND METHODS:
 A sample of eight adult patients (three men, five women; mean age = 40.2 years) with
bilaterally tipped mandibular second molars were identified from the orthodontic
clinic at Rio de Janeiro State University.
 Patients were excluded if any of the following conditions were present:
 autoimmune disease,
long-term use of medication 3 months before the beginning of the study (nonsteroidal
anti-inflammatory, cortisone, immune suppressive, and, bisphosphonate drugs),
probing depth values exceeding 4 mm.
pregnant or lactating women

6.  Patients presented with bilaterally inclined mandibular second molars
 Corticotomy was randomly assigned to either the left or right quadrant using open
access software.
 Treatment were to upright teeth and prepare the open space generated by the missing
molars for future implant insertion.
 Orthodontic biomechanics consisted of a cantilever inserted into the inclined
mandibular molars and ligated mesially to anchor teeth.
 A week before the corticotomy, 0.017 * 0.025 inch cantilevers with an L loop
incorporated were fabricated at chairside and stored for the next appointment.

8.  A 0.019*0.025 inch stainless steel archwire was used to provide anchorage in the
lower arch.
 Patients returned the next week for corticotomy, bone harvest, and cantilever
activation on both lower quadrants.
 Full-thickness flaps were elevated from the edentulous space to the distal aspect
of the second molars.
 10 to 12 perforations were made in the cortical plate using a round bur with a
high-speed handpiece under abundant irrigation.

9.  The depth of the perforations approximated the width of the buccal cortical plate.
 Mandibular bone blocks were harvested using a trephine bur in a location mesial
to the mandibular second molars.
 Immediately after surgery, cantilevers were bilaterally inserted into each second
molar tube and hooked between the canine and the premolars.
 Bone biopsies were harvested in both groups at two time points: baseline and 90
days after surgery.

10.  The extracted bone was stored in 10% buffered formalin at room temperature.
 The following parameters were collected:
(1) ratio between secondary and primary bone,
(2) ratio between inorganic and organic bone,
(3) quantity of osteocytes, and
(4) reversal lines of bone remodeling.

11.  Since data were clustered, the mean deviation was obtained using a generalized
estimating equation with an identity link function.

12. • RATIO BETWEEN SECONDARY AND PRIMARY BONE:
• The test group exhibited 87% and 71% of secondary bone at T0 and T90,
respectively, whereas the control group exhibited 73% and 86% of
secondary bone at T0 and T90, respectively.
• At 90 days after surgery, there was a 16% increase of primary bone in the
test group and a 13% decrease of primary bone in the control group.
• The difference between the two groups was significant (P =.05).
• Data suggested that up to 3 months after intentional injury the coupling
phenomenon remained active with a high probability of new bone
formation.

13.  QUANTITY OF OSTEOCYTES:
 The test group exhibited a mean of 92.6 and 99.2 osteocytes at T0 and T90,
respectively.
 Control group displayed a mean of 100.8 and 76.5 osteocytes at T0 and T90.
 The osteocyte count in the test group was significantly greater than in the control
group (P = .039).
 RATIO BETWEEN INORGANIC AND ORGANIC BONE:
 Both groups exhibited a reduction in the inorganic proportion at T90, with a decrease
of 2% and 3% in the test and control groups, respectively.
 The difference between the two groups was not significant (P =.105).

14.  REVERSAL LINES OF BONE REMODELING:
 The test group exhibited a mean of 71.1 and 75.2 reversal lines identified at T0
and T90, respectively.
 In the control group showed a mean of 77.8 and 76.2 reversal lines identified in a
20* magnification at T0 and T90, respectively.
 Ninety days after surgery, there was an increase of 4.06 reversal lines in the test
group, and a mild decrease of 1.64 reversal lines in the control group.
 The difference between the two groups was not significant (P = .924).

15.  The surgical approach included cortical perforations in the buccal plate without
reflection of a lingual flap and vertical cuts.
 A more invasive approach does not necessarily mean more tooth movement.
 The current study showed that levels of primary bone and osteocytes increased
significantly in corticotomized patients at the 90-day follow-up.
 Alterations in the inorganic portion and reversal lines were mild and insignificant
in both groups, suggesting that the baseline characteristics of these two features
were preserved.

16.  Animal research conducted by Baloul et al. and Teng and Liou suggesting that an
accelerated bone turnover is still active 3 months after surgery.
 In this study, there was a noticeable difference between the quantity and quality
of bone biopsies despite the standardized harvesting protocol.
 With dense and compact bone, it was difficult to disrupt the cortical barrier there
was a high risk of fracturing the specimen into multiple small pieces during
extraction.
 The second bone biopsy was planned according to evidence suggesting that RAP
effects subside 3 months after surgery. Therefore it was safe to evaluate tissue
repair in specimens harvested in that period.

17.  CONCLUSIONS:
 Based on the findings of this study, it is possible to conclude that corticotomy
surgeries performed in adult patients promote a reversible and transient bone
injury.

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