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Effect of cyclooxygenase inhibitors on rat root resorption and tooth movement

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Effect of cyclooxygenase inhibitors on rat root resorption and tooth movement

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EFFECT OF CYCLOOXYGENASE INHIBITORS ON RAT ROOT

RESORPTION AND TOOTH MOVEMENT
by
Timothy D. Brunson, DDS
____________________________________________________________________
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(CRANIOFACIAL BIOLOGY)
May 2008
Copyright 2008 Timothy D. Brunson, DDS
ii

DEDICATION

To My Wife and Kids:
Megan Brunson
Cole Brunson
Chloe Brunson
Sadie Brunson
Dallas Brunson
iii

ACKNOWLEDGEMENTS
A special thank you to:

Dr. Zeichner-David

Dr. Sameshima

Dr. Shuler

Morrell Family

iv

TABLE OF CONTENTS

Dedication ii
Acknowledgements iii
List of Tables v
List of Figures vi
Abstract vii
Chapter 1: Introduction 1
Chapter 2: Review of Literature 6
Chapter 3: Hypothesis 29
Chapter 4: Materials and Methods 31
Chapter 5: Results 35
Chapter 6: Discussion 51
Chapter 7: Assumptions 53
Chapter 8: Limitations 54
Chapter 9: Summary 55
Chapter 10: Conclusions 56
Bibliography 57

v
LIST OF TABLES
TABLE1: Descriptive Statistics 39
TABLE 2: Analysis of Variance & Post Hoc, Total Resorption 40
TABLE 3: Analysis of Variance & Post Hoc, Mesial Root Compression Surface 41
TABLE 4: Analysis of Variance & Post Hoc, Mesial Root Tension Surface 42
TABLE 5: Analysis of Variance & Post Hoc, Distal Root Compression Surface 43
TABLE 6: Analysis of Variance & Post Hoc, Distal Root Tension Surface 44
TABLE 7: Analysis of Variance & Post Hoc, Tooth Movement 45

vi
LIST OF FIGURES
FIGURE 1: Screen Capture Image Pro Plus 34
FIGURE 2: Box Plots Root Resorption & Tooth Movement 46
FIGURE 3: Drug and Dosage Resorption Means 47
FIGURE 4: Bar Graph Root Resorption & Tooth Movement 48
FIGURE 5: Histological Slide Samples 49
FIGURE 6: Tooth Movement Plots 50

vii
ABSTRACT

Purpose: The purpose of this study was to compare the effects of ibuprofen,
a conventional NSAID, and celebrex, a COX-2 specific inhibitor, on tooth
movement and root resorption. Methods: 49 female wistar rats were placed into 5
groups: (1) control (no dosage), (2) high dose celebrex (80mg/kg body weight), (3)
high dose ibuprofen (50 mg/kg), (4) low dose celebrex (40 mg/kg), and (5) low
dose ibuprofen (25 mg/kg). Rats were anesthetized by IP injection of Phenobarbital
(0.1 mg/gm body weight), and a force of 80 grams was applied to the maxillary left
first molars using a nickel titanium closed-coil spring. Tissue samples analyzed by
light microscopy, and areas of resorption were quantified. Results: Ibuprofen and
celebrex reduced resorption compared to control. High dose celebrex caused a
reduction of tooth movement. Conclusions: There is minimal advantage in using
selective COX-2 inhibitors to limit resorption; however, treatment time may be
lengthened.

1
Chapter 1: INTRODUCTION

Tooth movement depends on a delicate balance between bone formation

and
bone resorption, in which bone forming osteoblasts and bone resorbing

osteoclasts
play essential roles.
19-22
Tipping this balance in favor

of osteoclasts leads to
pathologic resorption. Several theories exist to explain the process of resorption
including the involvement of the inflammatory process. The ligand receptor activator
of NF B (RANKL) has been identified

as a member of the membrane-associated
tumor necrosis factor

ligand family, and is an important regulatory molecule of
osteoclastogenesis.
23,24
It has been

reported that RANKL

was detected in osteoblasts
and periodontal ligament (PDL) cells

during experimental tooth movement.
18,25

Osteoprotegerin (OPG) is

a secreted tumor necrosis factor (TNF) receptor member
that

functions as a decoy receptor for RANKL, thereby inhibiting

these processes and
accelerating osteoclast apoptosis.
26,27
It has been shown that OPG

gene transfer to
periodontal tissue inhibited RANKL-mediated

osteoclastogenesis and inhibited
experimental tooth movement.
26,27,28
Thus, the signaling and regulation of the
expression of RANKL

and OPG in PDL may play critical roles in bone remodeling
during

orthodontic tooth movement.
27
However, very little is known about

the
relationship between external apical root resorption and

the production of these
modulators during orthodontic tooth

movement.
26,28-29

Cyclooxygenase 2 (COX-2) is one of the strongly

induced genes following
RANKL stimulation in osteoclast precursors.
26
COX-2 is known to be expressed at
very low levels and is strongly

induced by pro-inflammatory stimuli, including
2
lipopolysaccharide

(LPS), as well as by several activated oncogenes.
23-26,36
The
significance

of COX-2 in inflammation is highlighted by the observation that

COX-2
inhibitors block the synthesis of prostaglandin (PG) E
2

(PGE
2
) and, as a result,
inhibit inflammation.
30,59
In bone, PGE
2
is produced mainly by osteoblasts and acts
as

a potent stimulator of bone resorption.
2
The production of

PGE
2
by osteoblasts is
regulated by several cytokines, including

interleukin 1 (IL-1) and IL-6.
26
Because
the rate-limiting

step in PGE
2
synthesis is catalyzed by COX-2, the fact that

osteoclast precursors express COX-2 by RANKL stimulation led

us to the
investigation of COX-2 inhibitors on tooth movement and root resorption.
29
Root resorption can occur in response to numerous stimuli such as trauma,
tumors, infection or mechanical forces.
1-3
Root shortening as a result of apical root
resorption is an

undesirable consequence of orthodontic treatment.
4-6
Upon
radiographic

examination, 48% of orthodontically treated patients show some degree
of loss

in root length.
3,8-9
The

maxillary incisors have been regarded as the most
susceptible

to root resorption, especially those with blunt or pipette-shaped

roots.
10-13

Patient characteristics such as type of malocclusion, gender, ethnicity,

age, root
morphology, dental anomalies, and previous trauma

have been suggested as possible
risk factors.
6, 10-12
There is some

controversy as to whether the age of the patient is
related

to orthodontically induced resorption.
13-15
The amount and type of tooth

movement are also determinants of root resorption.
14,16
As for the type of tooth

movement, intrusive force has been suggested as the most detrimental

to the root in
some studies.
6,7,14

3
Beyond examining root morphology, considering ethnicity, or a family
history of root resorption; there is currently no accurate method to predict when,
where or to what extent resorption will occur, and there is no treatment modality to
stop the external resorption once it is radiographically evident.
4,7
The radiographic
appearance of resorption is usually the first clinical indication that the process is
occurring and extensive, possibly unrepairable damage already begun.
17-18

Non-steroidal anti-inflammatory drugs (NSAIDS) are among the most widely
used of all therapeutic agents.
42-45
There are now more than 50 NSAIDS on the
market, all with varying degrees of therapeutic and side effects. These drugs have
anti-inflammatory, analgesic, and antipyretic properties that play a vital role in the
treatment of the inflammatory process. Traditional NSAIDS such as aspirin,
Ibuprofen, Aleve and other prescription drugs act by interfering with the synthesis of
prostaglandins, chemical mediators released when tissue is injured. While their
individual physiological roles may vary, prostaglandins are clearly implicated in the
inflammatory process. It is possible that the administration of anti-inflammatory
drugs could have a protective effect, inhibiting or slowing resorption.
27,28

COX-1 is

thought to produce PGs important for homeostasis and certain
physiological

functions and is expressed constitutively in most tissues and

cells,
although it can be induced in some cell lines under

certain conditions. A second,
inducible, form of COX was

hypothesized to exist on the basis of the finding of a
glucocorticoid-regulated

increase in COX activity observed in vitro and in vivo in
response

to inflammatory stimuli.
28,29
The isolation of a distinct

gene and enzyme for
COX-2 confirmed this hypothesis and led to

the supposition that selective inhibition
4
of inducible COX-2 would

be anti-inflammatory, while preserving the physiological
functions

of COX-1 derived PGs. This hypothesis was corroborated by the

discovery
and synthesis of anti-inflammatory compounds that selectively

and potently inhibit
COX-2 but not COX-1.
32-34

As with all pharmacologic agents, non selective NSAIDs can result in
various side effects. The frequency of side effects varies between the drugs. The
most common side effects are nausea, vomiting, and diarrhea decreased appetite,
rash, dizziness, headache, and drowsiness.
30,33
NSAIDs may also cause fluid
retention, leading to edema. The most serious side effects are kidney failure, liver
failure, ulcers and prolonged bleeding after an injury or surgery. In certain
individuals with specific medical conditions, selective NSAIDs can be
contraindicated due to potentially dangerous side effects, however for healthy
individuals, these drugs may provide the therapeutic benefit without the potential
side effects of non selective NSAIDS.
29
The substantial GI risk associated with the
use of traditional nonselective NSAID therapy, coupled with the understanding that
COX-2 is associated with the development of prostaglandins that produce pain and
inflammation, led researchers to develop new agents with greater COX-2
selectivity.
30,32-35
A selective COX-2 inhibitor would have a similar ability to reduce
pain and inflammation as a traditional NSAID but would not have any adverse
effects on GI mucosa that can be linked to the inhibition of COX-1 activity.

5
Previous studies in our laboratory resulted in the creation of a rat animal
model for root resorption using orthodontic tooth movement. When forces of 80
grams or greater were applied to the first molars, root resorption takes place in as
little as five days.
With our greater understanding of NSAIDs, and the potential benefits of
newly developed selective inhibitors, health care professions will see a dramatic
increase in the usage of these drugs. Currently, little literature exists on the effects of
these new drugs on tooth movement or root resorption.
Purpose of the Study
• Determine and compare the effect of selective and non-selective COX inhibitors
on root resorption
• Determine and compare the effect of selective and non-selective COX inhibitors
on tooth movement
• Determine if there is a drug dose dependant interaction with root resorption
and/or tooth movement

6
Chapter 2: REVIEW OF THE LITERATURE

Biology of Prostaglandins and the COX Pathway

Prostaglandins, leukotrienes, and related substances are called eicosanoids
because they are derived from 20-carbon essential fatty acids.
31
These substances are
extremely potent, endogenous, regulatory substances that are synthesized and
released for immediate, local action. For eicosanoid synthesis to occur, arachidonic
acid (eicosanoid precursors) first must be mobilized from membrane phospholipids
by the enzyme phospholipase A
2
.
30,33-34

After mobilization, arachidonic acid is oxygenated by four distinct pathways:
COX, lipoxygenase, P450 epoxygenase, and isoprostane pathways.
32
The COX
pathway is the rate-limiting step and has two distinct activities: endoperoxide
synthase activity that oxygenates the arachidonic acid to form the cyclic peroxide
prostaglandin G
2
, and peroxidase activity that converts prostaglandin G
2
to
prostaglandin H
2
, a common precursor for all prostanoids. Prostaglandin H
2
then is
converted by specific enzymatic pathways, including prostacyclin synthase,
thromboxane synthase, and isomerase, to yield three groups of cyclic prostanoids:
prostacyclin (prostaglandin I
2
), thromboxane A
2
, and prostaglandins (e.g.,
prostaglandin E
2
), respectively.
32-33

The two isoforms of the COX enzyme, COX-1 and COX-2, are coded by the
COX-1 and COX-2 gene, respectively. These two isoenzymes share about 60% gene
homology; however, substantial differences exist between the gene and promoter
structures of COX-1 and COX-2.
34,59
7
The most important difference between the two isoforms is their pattern of
tissue expression and regulation.
31,34-35
Cyclooxygenase-1 is expressed constitutively
in virtually all tissues, most notably platelets, endothelial cells, gastrointestinal tract,
renal microvasculature, glomerulus, and collecting ducts. Its expression can increase
2-4-fold under stimulatory conditions and is not affected by glucocorticoids.
30,34
Conversely, COX-2 is normally undetectable in most tissues under basal conditions,
but its expression in many cell types, including macrophages, fibroblasts,
chondrocytes, and epithelial and endothelial cells, is augmented 10-80-fold on
stimulation with inflammatory cytokines, growth factors, or endotoxins.
34-37
The History and Controversy of Cyclooxygenase Inhibitors
Historically, anti-inflammatory drugs originate from the discovery of plant
extracts that were applied for the relief of pain, fever and inflammation. When
salicylates were discovered to be the active components of Willow Bark, this
enabled these compounds to be synthesized and acetyl-salicylic acid or Aspirin was
developed. Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to treat
inflammation and pain.
29,42
The cardinal signs of

inflammation; including edema,
hyperalgesia, and erythema, develop

as an acute response to a local inflammatory
insult. These symptoms

result from the action of inflammatory agents such as
bradykinin,

histamine, neurokinins, complement, and nitric oxide, which can

originate locally or from cells that infiltrate the site of insult.
42
Elevated levels of
prostaglandins (PGs) are also

produced during inflammation and enhance or prolong
signals

produced by pro-inflammatory agents, but alone do not cause inflammation.
8
NSAIDs reduce or prevent the production of PGs by direct

inhibition of the
cyclooxygenase (COX) enzymes. The

observation that NSAIDs inhibit COX activity
attests to the contribution

of PGs to inflammation.
COX-1 is

thought to produce PGs important for homeostasis and certain
physiological

functions and is expressed constitutively in most tissues and

cells,
although it can be induced in some cell lines under

certain conditions.
31,42
A second,
inducible, form of COX was

hypothesized to exist on the basis of the finding of a
glucocorticoid-regulated

increase in COX activity observed in vitro and in vivo in
response

to inflammatory stimuli. The isolation of a distinct

gene and enzyme for
COX-2 confirmed this hypothesis and led to

the supposition that selective inhibition
of inducible COX-2 would

be anti-inflammatory, while preserving the physiological
functions

of COX-1 derived PGs.
42
This hypothesis was corroborated by the

discovery and synthesis of anti-inflammatory compounds that selectively

and
potently inhibit COX-2 but not COX-1.
43
In contrast,

NSAIDs inhibit both forms of
COX at approximately equivalent concentrations. Selective inhibition of COX-2
only partially reduces

the level of PGs at sites of either acute or chronic
inflammation,

in comparison to NSAIDs, which reduce PGs to undetectable
levels.
44,45
Therefore, COX-1 may contribute significantly

to the total pool of PG at a
site of inflammation. To date, the

contribution of COX-1 to inflammation has not
been clearly established.
30,42
The substantial GI risk associated with the use of
traditional nonselective NSAID therapy, coupled with the understanding that COX-2
is associated with the development of prostaglandins that produce pain and
inflammation, led researchers to develop new agents with greater COX-2 selectivity.
9
A selective COX-2 inhibitor would have a similar ability to reduce pain and
inflammation as a traditional NSAID but would not have any adverse effects on GI
mucosa that can be linked to the inhibition of COX-1 activity.

These agents also
must not inhibit platelet function.
The search for COX-2-specific durgs resulted in promising candidates such
as valdecoxib, celecoxib, and rofecoxib (marketed under the brand names Bextra,
Celebrex, and Vioxx respectively).
30,42
Valdecoxib and rofecoxib are about 300
times more potent at inhibiting COX-2, than COX-1, suggesting the possibility of
relief from pain and inflammation, without gastrointestinal irritation, and promising
to be a boon for those who had experienced such adverse effects previously.
Celecoxib is approximately 30 times more potent at inhibiting COX-2 than COX-1.

30,37,42

Although individual reactions to particular NSAIDs vary, in general the
efficacy of COX-2 inhibitors has proved similar to that of other NSAIDs, as
expected since both classes of drug inhibit the desired target, the action of COX-2
prostaglandins. The drugs effectiveness is similar to that of traditional NSAIDs such
as ibuprofen, diclofenac, or naproxen.
30,31,42

Celebrex and Vioxx were introduced in 1999 and rapidly became the most
frequently prescribed new drugs in the United States. By October 2000, their US
sales exceeded 100 million prescriptions per year for $3 billion, and were still rising,
sales of Celebrex alone reaching $3.1 billion in 2001.
30
A Spanish study found that
between January 2000 and June 2001, 7% of NSAID prescriptions and 29% of
NSAID expenditures were for COX-2 inhibitors.
30,42
Over the period of the study,
10
COX-2 inhibitors rose from 10.03% of total NSAIDs prescribed by specialty
physicians to 29.79%, and from 1.52% to 10.78% of NSAIDs prescribed by primary
care physicians (98.23% of NSAIDs and 94.61% of COX-2 inhibitors were
prescribed by primary care physicians).
42.46,47
For specialty physicians, rofecoxib and
celecoxib were third and fifth most frequently prescribed NSAIDs but first and
second in cost, respectively; for primary care physicians they were ninth and twelfth
most frequently prescribed NSAIDs and first and fourth in cost.
42,44,46

The cause of the rapid widespread acceptance of Celebrex and Vioxx by
physicians was the publication of two large trials in JAMA, the Celecoxib Long-term
Arthritis Safety Study (CLASS) study, and the Vioxx Gastrointestinal Outcomes
Research (VIGOR) study.42,43 Both publications concluded that COX-2 specific
NSAIDs were associated with significantly fewer adverse gastrointestinal effects. In
the CLASS trial comparing Celebrex 800 mg/day to ibuprofen 2400 mg/day and
diclofenac 150 mg/day for osteoarthritis or rheumatoid arthritis for six months,
Celebrex was significantly associated with fewer upper gastrointestinal
complications (0.44% vs. 1.27%, P=0.04), with no significant difference in incidence
of cardiovascular events in patients not taking aspirin for cardiovascular
prophylaxis.
42-45
In the VIGOR trial testing Vioxx 50 mg/day versus naproxen for rheumatoid
arthritis, Vioxx reduced the risk of symptomatic ulcers and clinical upper
gastrointestinal events (perforations, obstructions and bleeding) by 54%, to 1.4%
from 3%, the risk of complicated upper gastrointestinal events (complicated
perforations, obstructions and bleeding in the upper gastrointestinal tract) by 57%,
11
and the risk of bleeding from anywhere in the gastrointestinal tract by 62%.
42,43
An
enormous marketing effort capitalized on these publications; Vioxx was the most
heavily advertised prescription drug in 2000, and Celebrex the seventh, according to
IMS Health.
43,47
The COX-2 controversy began on September 30, 2004 when Merck & Co.
voluntarily withdrew Vioxx from the market.
42,43,45,46
They had been testing Vioxx
for anti-cancer properties in their APPROVe (Adenomatous Polyp Prevention on
VIOXX) trial.
46
Unfortunately, patients who were on Vioxx for more than 18
months began to show an increased frequency of serious cardiovascular problems.
42

The frequency of heart attacks, strokes, and blood clots was 1.5% in patients
taking Vioxx compared to 0.78% in patients taking a placebo. Although this increase
is small it potentially represents a large number of people world-wide. It is not clear
why Vioxx causes cardiovascular problems. It may be due to increasing the patient's
blood pressure or by causing inflammation of blood vessel walls. It is also not clear
if the problems with Vioxx extend to the other COX-2 inhibitors.
43,47
Two large multicenter, double-blinded, outcome-based studies demonstrated
the efficacy of selective COX-2 inhibitors in the prevention of endoscopically
defined NSAID-associated gastropathy. The Celecoxib Long-Term Arthritis Safety
Study evaluated the use of celecoxib 400 mg twice daily, versus either ibuprofen 800
mg 3 times a day or diclofenac 75 mg twice daily for at least a 6-month period. The
results of this trial demonstrated a lower incidence of upper GI ulcer complications
in those patients assigned to celecoxib than in those assigned to traditional NSAIDs
(0.76% vs 1.45%, respectively), as well as a significant reduction in the combined
12
incidence of upper GI ulcer complications and symptomatic ulcers (2.08% vs 3.54%,
respectively). An important issue to note regarding the CLASS trial is that patients
were allowed to continue low dose cardioprotective aspirin (< 325 mg/day) during
the study. In fact, 21% of the patients in this trial continued to use low-dose aspirin,
and, when this subpopulation was evaluated, the gastroprotective benefits of
celecoxib over traditional NSAIDs disappeared.
45,46
The rationale for this finding is
that the addition of aspirin, a nonselective NSAID, to a selective COX-2 inhibitor
renders the combination nonselective, because both COX-1 and COX-2 are
inhibited. This issue potentially may have skewed the results of the study.
43,45,47

The second trial was the Vioxx GI Outcomes Research (VIGOR) study,
which compared rofecoxib 50 mg daily with naproxen 500 mg twice daily.
Rofecoxib produced a significant reduction in clinical upper GI events, versus
naproxen (2.1 and 4.5 events per 100 patient years, respectively), as well as
significantly reducing complicated upper GI events, such as perforation or
obstruction (0.6% and 1.4%, respectively), at 9 months. A major difference between
the CLASS and VIGOR studies was that the VIGOR study excluded all patients
taking aspirin.
30,36, 47

The gastroprotective benefits of rofecoxib in the VIGOR study have
unfortunately been tempered by the identification of potential CV risks. Patients
randomized to rofecoxib demonstrated a higher myocardial infarction (MI) rate
(0.4%) than those patients randomized to naproxen (0.1%). This finding resulted in
the hypothesis that selective inhibition of COX-2 will inhibit the synthesis of
13
prostacycline without altering the synthesis of thromboxane A2, thus potentially
creating a prothrombotic environment within the vasculature.
30,36,47,63

The data from the VIGOR study were then followed in 3 individual studies,
each with a differing COX-2 inhibitor that added to the evidence that COX-2
inhibitors were potentially associated with a great risk for cardiac toxicity. The
Adenoma Prevention with Celecoxib (APC) study was performed with 2035 patients
to evaluate the use of 2 different doses of celecoxib (200 and 400 mg twice daily) in
the prevention of adenomatous polyps in the colon and rectum. The study
demonstrated, however, that patients on celecoxib (both groups combined) had a
nearly threefold increased risk of adverse CV events, such as MI, stroke, and heart
failure.
30,36,42,47,63

The Adenomatous Polyp PRevention On Vioxx (APPROVe) trial evaluated
the use of rofecoxib 25 mg daily versus placebo in patients with a medical history of
colorectal adenomas. The study was discontinued early and showed an approximate
twofold higher incidence of thrombotic events (RR, 1.92; 95% CI 1.19-3.11) in
patients treated with rofecoxib.

In both of these trials, CV events appeared at ~18
months, suggesting increased risk with prolonged duration of therapy.
30,42,63

Studies also have demonstrated potential dose relationships with adverse CV
events. A retrospective cohort study using the Tennessee Medicaid database was
designed to assess event rates with traditional NSAIDs and selective COX-2
inhibitors. This study found that rofecoxib in doses of 25 mg or less per day did not
show a significant increase in CV events. Doses >25 mg per day, however, were
significantly associated with an increased risk.
30,36, 47,63

14
Efforts are currently underway to discover why cardiovascular reactions took
place with coxibs, identify safer coxibs, as well as elucidate the roles of COX-2 and
COX-1 in cardiovascular diseases and stroke in the hope that there may be some
basis for developing newer agents (e.g. nitric oxide-donating NSAIDs) to control
these conditions. The discovery of the COX isoforms led to establishing their
importance in many non-arthritic or non-pain states where there is an inflammatory
component to pathogenesis, including cancer, Alzheimer's and other
neurodegenerative diseases.
30,36, 47,63
The applications of NSAIDs and the coxibs in
the prevention and treatment of these conditions as well as aspirin and other
analogues in the prevention of thrombo-embolic diseases now constitute one of the
major therapeutic developments of the this century.
30,36, 47,63
Moreover, new anti-
inflammatory drugs are being discovered and developed based on their effects on
signal transduction and as anti-cytokine agents and these drugs are now being
heralded as the new therapies to control those diseases where cytokines and other
nonprostaglandin components of chronic inflammatory and neurodegenerative
diseases are manifest. To a lesser extent safer application of corticosteroids and the
applications of novel drug delivery systems for use with these drugs as well as with
NSAIDs also represent newer technological developments of the 21st century. What
started out as drugs to control inflammation, pain and fever in the last two centuries
now has exploded to reveal an enormous range and type of anti-inflammatory agents
and discovery of new therapeutic targets to treat a whole range of conditions.

30,36,42,47,63

15
Origin and Role of Osteoclasts

Osteoclasts are multinucleated cells formed by the fusion of mononuclear
progenitors of the monocyte/macrophage family.
26,59,64
They

are the principal, if not
exclusive, resorptive cell of bone,

playing a central role in the formation of the
skeleton and regulation

of its mass. Bone-forming cells, or osteoblasts, have an
equally

important role in the regulation of bone mass.
26,64

In vitro maturation of macrophages into osteoclasts requires the presence of
marrow stromal cells

or their osteoblast progeny.
59,64
These accessory cells express
two molecules

that are essential to promote osteoclastogenesis:

macrophage colony-
stimulating factor (M-CSF) and receptor for

activation of nuclear factor kappa B
(NF- B) (RANK) ligand (RANKL)

(also known as OPGL and TRANCE). M-CSF,

which is imperative for macrophage maturation, binds to its receptor,

c-Fms, on early
osteoclast precursors, thereby providing signals

required for their survival and
proliferation.
26,27,59,64

Although M-CSF is a secreted product, osteoclastogenesis requires contact
between osteoclast precursors and stromal cells

or osteoblasts. Thus, stromal cells
and osteoblasts

synthesize a surface-residing molecule, essential for
osteoclastogenesis,

whose identity long remained enigmatic.
26,59,64
In 1997, it was
found

that overexpression or administration of a protein, eventually

termed
osteoprotegerin (OPG), blunts osteoclastogenesis in mice.

Similarly, animals lacking
OPG have accelerated osteoclastogenesis

and develop severe osteoporosis. OPG is
now known

to be a soluble "decoy" receptor that competes with RANK for RANKL.

64,65
The presence of RANK on osteoclasts and their precursors

suggested that
16
osteoclast-differentiating factor,

residing on stromal cells, may be RANKL, which
proved to be the

case. RANKL is also expressed in abundance by activated

T
lymphocytes.
59,64,65
These cells can directly trigger osteoclastogenesis

and are
probably pivotal to the joint destruction seen in rheumatoid

arthritis. It is the balance
between the

expression of the stimulator of osteoclastogenesis, RANKL, and

of the
inhibitor, OPG, that dictates the quantity of bone resorbed. Moreover, complete
osteoclastogenesis can now be

achieved in vitro with pure populations of
macrophages exposed

only to M-CSF and RANKL. The number of osteoclasts

in
these cultures can be modulated by varying the concentrations

of these molecules.

64,65
Thus, agents that induce M-CSF expression

cause osteoclast precursors to
proliferate. In fact, this may

be a central pathogenetic mechanism in human
osteoporosis.

RANKL stimulates the pool of M-CSF-expanded precursors to commit

to the osteoclast phenotype.
65

The importance of RANKL in osteoclast differentiation emphasizes the
central role played by stromal cells and osteoblasts

in the process. In fact, stromal
cells and osteoblasts are the

targets of most osteoclastogenic agents that exert their
effect

by enhancing RANKL expression and thus increasing the quantity

of this
molecule relative to that of OPG. One such agent is parathyroid

hormone (PTH).
Disorders of excess PTH are characterized

by accelerated osteoclastogenesis, yet
osteoclasts lack high-affinity

PTH receptors. PTH is now known to interact with
receptors on

osteoblasts and on certain stromal cells that produce the
osteoclastogenic

factor RANKL. Similarly, 1,25-dihydroxyvitamin D
3,

the
biologically active form of vitamin D
3
, which was previously

believed to exert its
17
osteoclastogenic effect by directly promoting

osteoclast precursor differentiation,
probably acts by inducing

stromal cell and/or osteoblast expression of RANKL.

RANKL and RANK are members of the tumor necrosis factor (TNF) and
TNF receptor superfamilies, respectively.
26,64,65
This observation

is consistent with
clinical data indicating that inflammatory

lesions of bone are characterized by
abundant osteoclast proliferation.

Indeed, TNF is a potent osteoclastogenic agent and
appears to

mediate orthopedic implant loosening, a disorder accompanied by

local
secretion of TNF. Furthermore, systemic

administration of bacterial
lipopolysacharide, which is likely

to be an important pathogenetic factor in the
alveolar bone loss

seen in periodontitis, prompts rapid osteoclastogenesis through

the
p55 TNF receptor. The p75 TNF receptor, by

contrast, is anti-osteoclastogenic. Thus,
the

two TNF receptors may reciprocally regulate osteoclastogenesis.

The Resorption Process
Resorption is a multistep process initiated by the proliferation of immature
osteoclast precursors, the commitment of

these cells to the osteoclast phenotype, and
finally, degradation

of the organic and inorganic phases of bone, dentin or cementum
by the mature resorptive

cells.
70.72,75,76
At first glance, the osteoclast resembles a
macrophage

formed in response to exogenous particulate matter. The osteoclast

is,
however, more complex and has a number of unique features

that permit it to
recognize and degrade mineralized tissues.
70.72,73,75,76
Most dramatic is

the
osteoclast's capacity to polarize on bone, and in so doing

to form a "ruffled
membrane." This complex infolding of the plasma

membrane juxtaposed to the
matrix is the osteoclast's resorptive

organelle and appears only when the cell is
18
attached to bone.
75,76
The ruffled membrane probably represents the transport of
acidifying

vesicles along microtubules and their polarized insertion into

the plasma
membrane, an event similar to exocytosis.
70-76

The realization that the osteoclast is a member of the monocyte/macrophage
family has prompted the development of techniques

whereby macrophages, derived
from many sources and at various

stages of maturation, can be induced to
differentiate into osteoclasts.
72,75,76
Like their in vivo counterparts, these in vitro-
generated

osteoclasts are capable of bone resorption.
66-69,70.72,75,76
When cultured on
bone

or dentin (another osteoclast substrate), osteoclasts create

resorptive lacunae
that are similar to the structures

formed when the cells degrade bone in vivo.

The
number and size of resorption lacunae formed in vitro are

a quantitative measure of
osteoclast activity.
70,78

The initial event in degradation is the attachment of osteoclasts to the target
matrix.
20,62,75,77
Once attached, the cell generates an isolated extracellular
environment

with the mineralized surface. The closeness

between osteoclasts and
bone, required for resorption, is reflected

by the "matrix attachment" or "sealing"
zone. This structure,

rich in filamentous actin, and largely devoid of organelles,

is
organized as a ring surrounding the ruffled membrane.
20,62,75,77
The F-actin in the
sealing zone localizes in plasma membrane

protrusions known as podosomes. In
addition to

F-actin, these structures contain proteins such as vinculin, talin,

and -
actinin, which link matrix-recognizing integrins to the

cytoskeleton. The appearance
of the podosomal ring,

like the ruffled membrane, parallels bone resorption.
23,24,77

19
Bone and dentin consists largely of type 1 collagen (>90%) and of
noncollagenous proteins containing a mineral phase of substituted hydroxylapatite.

76,77
Dissolution of the inorganic phase of bone precedes matrix degradation. Bone
demineralization involves acidification

of the isolated extracellular
microenvironment, a process mediated

by a vacuolar H
+
-adenosine triphosphatase
(H
+
-ATPase) in the cell's ruffled membrane, which is similar to the

proton pump in
the intercalated cell of the renal tubule.
23,24,77
It is possible, however, that one or
more subunits

of the osteoclast H
+
-ATPase are unique to this cell. Again, as in

the
intercalated renal cell, the intra-osteoclastic pH is maintained,

in the face of abundant
proton transport, by an energy-independent

Cl
-
/HCO
3
-
exchanger on the cell's
antiresorptive surface.
23,24,62
Finally, electroneutrality is preserved by a ruffled
membrane

Cl
-
channel, charge-coupled to the H
+
-ATPase.
62.77
The result of these ion
transporting

events is secretion of HCl into the resorptive microenvironment,

prompting a pH of ~4.5. This acidic milieu first

mobilizes bone mineral;
subsequently, the demineralized organic

component of bone is degraded by a
lysosomal protease, cathepsin

K.
23,55,62
The products of bone degradation

are
endocytosed by the osteoclast and transported to and released

at the cell's
antiresorptive surface.
23,24,77

The role of metalloproteinases in osteoclast function is less clear.
55,77
The
most compelling evidence that these enzymes participate

in the resorptive process
comes from the demonstration that bone

resorption is attenuated in mice carrying a
mutation in the site

in type 1 collagen that is targeted by neutral collagenases.
23,24,77

20
The functional cycle of the osteoclast consists of episodes of matrix
adherence followed by detachment and movement to a new

site of bone degradation.
23,24,77,78
Although the events

initiating bone resorption are reasonably well
understood, less

is known about the signals that arrest the process.
55
A provocative

argument holds that plasma membrane receptor sensing of high calcium

levels within
the resorptive space prompts the withdrawal of the

osteoclast from the bone surface
and the termination of resorption

at that site.
23,24

On the other hand, there is increasing evidence

that the bone-sparing effects
of antiosteoporosis agents such

as estrogen and bisphosphonates

reflect in part a
stimulation of osteoclast apoptosis.

In the case of estrogen, osteoclast death is
mediated by transforming

growth factor- (TGF- ), whereas bisphosphonates

promote apoptosis by inhibiting the melavonate pathway.
22,23,24,55,65,77

Physical contact between matrix and cell is required for osteoclastic
resorption, and it appears that

the recognition of bone by osteoclasts is controlled by
integrins.

1 integrins may participate by binding to type 1 collagen, but

the major
attachment molecule is v 3.
23,24,29,55
Blocking studies using

antibodies and
competitive ligands have established

that the v 3 integrin is essential for bone
attachment and resorption

in vitro, and the 3
-/-
mouse confirms the same in vivo.
29

Osteoclasts

from these mutant mice do not form actin rings, have abnormal

ruffled
membranes, and fail to effectively resorb bone in vivo.
62
Consistent with retarded
bone resorption, v 3-deficient mice

have low levels of blood calcium and increased
skeletal mass.
29,36,55,66,67,77

21
Although the v 3 integrin is pivotal to the resorptive process, its most
important function is probably not the formation

of a physical seal between the
osteoclast and bone.
23,62,77
It most likely

transmits bone matrix-derived signals,
ultimately prompting intracellular

events such as cytoskeletal organization (for
example, formation

of the ruffled membrane) that are pivotal to bone resorption.
62
This putative function of the integrin is in keeping with its

association, in the
podosome, with signaling molecules such as

c-Src and the FAK-like kinase Pyk-2,

both of which are activated upon v 3occupancy. Thus, v 3 may

be an attractive
target for anti-osteoporosis therapy.
62,77

Cyclooxygenase 2 (COX-2) is one of the strongly

induced genes following
RANKL stimulation in osteoclast precursors.
45
COX-2 is known to be expressed at
very low levels and is strongly

induced by pro-inflammatory stimuli, including
lipopolysaccharide

(LPS), as well as by several activated oncogenes.
45
The
significance

of COX-2 in inflammation is highlighted by the observation that

COX-2
inhibitors block the synthesis of prostaglandin (PG) E
2

(PGE
2
) and, as a result,
inhibit inflammation.
23,24,29,66,70,79
In bone, PGE
2
is produced mainly by osteoblasts
and acts as

a potent stimulator of bone resorption.
79
The production of

PGE
2
by
osteoblasts is regulated by several cytokines, including

interleukin 1 (IL-1) and IL-
6.
36,66
Because the rate-limiting

step in PGE
2
synthesis is catalyzed by COX-2, the
fact that

osteoclast precursors express COX-2 by RANKL stimulation led

us to the
investigation of COX-2 inhibitors on tooth movement and root resorption.

22
Orthodontic tooth movement is dependent on efficient remodeling of
bone.
23,24,34,35,79
The theories of orthodontic tooth movement remain speculative but
the histological documentation is unequivocal. Teeth appear to lie in a position of
balance between the tongue and lips or cheeks.
28,35,37,38
This zone is not completely
neutral since tongue forces are usually slightly greater than the lips or cheeks. The
periodontal ligament is thought to have an intrinsic force which has to be overcome
before teeth move.
23,24,38
A notable feature of periodontal disease, where this intrinsic
force is lost, is splaying, drifting and spacing of teeth. Similarly, if there is excessive
tongue activity the teeth tend to drift.
37

Very low forces are capable of moving teeth. Classically, ideal forces in
orthodontic tooth movement are those which just overcome capillary blood
pressure.
1-4
In this situation bone resorption is seen on the pressure side and bone
deposition on the tension side. Teeth rarely move in this ideal way. Usually force is
not applied evenly and teeth move by a series of tipping and uprighting movements.

21,56,48,49,71,73
In some areas excessive pressure results in hyalinization where the
cellular component of the periodontal ligament disappears.
71,73
The hyalinized zone
assumes a ground glass appearance but this returns to normal once the pressure is
reduced and the periodontal ligament repopulated with normal cells. In this situation
a different type of resorption is seen whereby osteoclasts appear to 'undermine' bone
rather than resorbing at the 'frontal' edge.
59,64

How mechanical forces stimulate bone remodeling remains a mystery but
some key facts are known. First, intermittent forces stimulate more bone remodeling
than continuous forces. It is likely that during orthodontic tooth movement
23
intermittent forces are generated as teeth come into occlusal contact. Second, the key
regulatory cell in bone metabolism is the osteoblast. It is therefore relevant to
examine what effects mechanical forces have on these cells. The application of a
force to a cell membrane triggers off a number of responses inside the cell and this is
usually mediated by second messengers. It is known that cyclic AMP, phosphates
and intracellular calcium are all elevated by mechanical forces. Indeed the entry of
calcium to the cell may come from G-protein controlled ion channels or release of
calcium from internal cellular stores. These messengers will evoke a nuclear
response which will either result in production of factors responsible for osteoclast
recruitment and activation, or bone forming growth factors. An indirect pathway of
activation also exists whereby membrane enzymes (phospholipase A2) make
substrate (arachidonic acid) available for the generation of prostaglandins and
leukotrienes. These compounds have both been implicated in tooth movement.
Biomechancial Orthodontic Tooth Movement
This theory simply states that mechanically distorting a cell membrane
activates PLA2 making arachidonic acid available for the action of cyclo and
lipoxygenase enzymes. This produces prostaglandins which feed back onto the cell
membrane binding to receptors which then stimulate second messengers and elicit a
cell response. Ultimately, these responses will include bone being laid down in
tension sites and bone being resorbed at pressure sites. It is not clear how tissues
discriminate between tension and pressure.
14,20,32,35,79

24
Piezoelectric, Bone Bending, and Magnetic Forces
There was considerable interest in piezoelectricity as a stimulus for bone
remodeling during the 1960s.
72
This arose because it was noted that distortion of
crystalline structures generated small electrical charges, which potentially may have
been responsible for signaling bone changes associated with mechanical forces.
72

The interest therefore in 'electricity' and bone was considerable.
72,73,75,77
Root Resorption
The ability to move teeth through bone is dependent on bone being resorbed
and tooth roots remaining intact.
9-12,
It is highly probable that all teeth which have
undergone orthodontic tooth movement exhibit some degree of microscopic root
resorption.
13,39-41,82
Excessive root resorption is found in 3-5% of orthodontic
patients. Some teeth are more susceptible than others, upper lateral incisors can, on
average, lose 2 mm of root length during a course of fixed orthodontic treatment.
4,7

There are specific features of appliances which can increase the risk of root
resorption. The following are considered risk factors: fixed appliances, class II
elastics, rectangular wires, orthognathic surgery.
4,7,81,82

There is conflicting evidence that the use of functional appliances cause less
resorption than fixed appliances and may be used to reduce increased overjet where
there are recognized risks of root resorption which include pre-existing features such
as: short roots, blunt root apices, thin conical roots, teeth which have been previously
traumatized.
9-12,80

What prevents roots from resorbing is not known but the following have been
suggested: Cementum has anti-angiogenic properties.
21,39,55,57,58
This means blood
25
vessels are inhibited from forming adjacent to cementum and osteoclasts have less
access for resorption.
21
Periodontal ligament fibers are inserted more densely in
cementum than alveolar bone and thus osteoclasts have less access to the cemental
layer. Cementum is harder than bone and more densely mineralized.
21,39,55

Pharmacology and Tooth Movement
It has been shown that PG inhibition results in slower tooth movement;
however, some movement still occurs. Therefore, PGs may not be the only mediators
of bone resorption associated with tooth movement.
31,82
Leukotrienes (LTs), cyclic
adenosine monophosphate, and collagenase may also affect tooth movement when
mechanical forces are applied on periodontal tissues.
82
Acetaminophen exhibits
weak inhibition of cyclooxygenase and is a weak anti-inflammatory agent. Anti-
inflammatory activity with acetaminophen can only be demonstrated at doses far
exceeding those used for typical analgesia.
31
Thus, it should have no adverse effect
on PG production and subsequent bone resorption associated with orthodontic tooth
movement, unlike NSAIDs. Studies were conducted to determine whether blocking
PG synthesis would inhibit osteoclast production and the normal orthodontic tooth
movement process. Chumbley and Tuncay
31
conducted one of the first studies
measuring tooth movement in relation to PG inhibition. Six of 12 mongrel cats
received 5 mg/kg/d of oral indomethacin. Closed-coil springs delivering 250G were
stretched between teeth, while distances between burr holes and between cusp tips
were measured with calipers to the nearest hundredth of a millimeter. Cats receiving
indomethacin exhibited significantly less tooth movement than the control group (p
26
< 0.05); therefore, the authors concluded that indomethacin slowed the rate of tooth
movement through probable PG inhibition. Mohammed et al.
82
also found significant
inhibition (p < 0.05) of tooth movement in rats receiving indomethacin; however,
Sandy and Harris
84
found that the NSAID flurbiprofen inhibited the appearance of
osteoclasts, but had no significant effect on tooth movement.
Based on these data, Wong et al. examined the influence of aspirin (65
mg/kg/d) on orthodontic tooth movement induced with light spring forces in six
guinea pigs. The authors concluded that these results may have varied from previous
reports because of differences in orthodontic forces applied in each study or due to
indomethacin effects on mediators other than prostaglandins. Although alterations in
PG activity and tooth movement have occurred with concomitant NSAID use, there
is no evidence of complete inhibition of the orthodontic tooth movement process,
either from short- or long-term use. Thus, PGs may not be the only mediators of
bone resorption associated with tooth movement. To further define the role of PGs
on the normal tooth movement process, LTs and their products (e.g., LTB4) have
been studied to determine their contribution to orthodontic tooth movement.
Although LTs and PGs are derived from arachidonic acid, they are synthesized
through separate pathways, lipoxygenase and cyclooxygenase, respectively.
It is believed that inhibition of one pathway potentiates an increase in
arachidonic acid conversion via the alternate pathway. Therefore, the modulation or
mediation of orthodontic tooth movement by LTs in addition to PGs is not unlikely.
The role of LTs and their interaction with PGs in mediating orthodontic tooth
movement were investigated in 132 rats.
82
The authors concluded that LTs, in
27
addition to PGs, might have future clinical applications for affecting orthodontic
tooth movement. Unlike NSAIDs, acetaminophen is inactive as an anti-inflammatory
agent in peripheral tissues and should have no adverse effects on PG biosynthesis
and subsequent bone resorption associated with orthodontic tooth movement.
The effect of acetaminophen on tooth movement was examined in rabbits (n
= 14).
82
Springs delivering 100G were ligated between the lower first molar and
incisor in experimental and control animals. Acetaminophen 1000 mg/d was given to
seven rabbits, and tooth movement was measured at 21 days. Results showed that
experimental animals exhibited 5.85 mm of tooth movement compared with 6.17
mm in the control group; this was not statistically significant. Further evidence was
demonstrated in a clinical trial comparing acetaminophen, ibuprofen, and
misoprostol, a synthetic PGE1 analog, to determine the degree and rate of
orthodontic tooth movement in guinea pigs. Guinea pigs were chosen because their
periodontal structures and incisors are easily manipulated by orthodontic
mechanotherapy, and the arrangements of their hard and soft tissues are more similar
to humans. Acetaminophen and ibuprofen were chosen because they are commonly
used as over-the-counter analgesics for the relief of minor dental discomfort. End
point results demonstrated significant differences (p < 0.001) between groups for
mean tooth separation. At day 11, the misoprostol group exhibited the greatest
degree of tooth separation (4.49 ± 0.49 mm), while those receiving ibuprofen had the
smallest.

28
Recently a group in Spain evaluated the effect of specific cyclooxygenase
inhibitors on tooth movement. The study compared the three most commonly
prescribed COX-2 specific drugs to determine if there were any differences. They
determined that the more potent COX-2 (Vioxx) inhibitors were prone to inhibiting
tooth movement, while less potent COX-2 inhibitors (celebrex) had a more minimal
effect on the movement of teeth.
This same group then evaluated the effect of specific COX-2 inhibitors
compared to non-specific COX inhibitors to determine if there is any benefit during
orthodontic treatment. The data shows that there is not a significant correlation
between either group of drug and better tooth movement; thus, they determined there
was no significant benefit to using specific or non specific COX inhibitors.
No literature has yet to evaluate whether there is a correlation between
dosage and effect on tooth movement. Nor has the effect on root resorption been
determined. By evaluating these factors a better understanding of how the drugs
impact the biologic process of tooth movement may be elucidated.

29
Chapter 3: HYPOTHESES

• Root resorption measurements significantly differ between non-selective
(Ibuprofen) and selective (Celebrex) NSAIDs.
• Root resorption measurements significantly differ between dosages of non-
selective (Ibuprofen) and selective (Celebrex) NSAIDs.
• Total tooth movement measurements significantly differ between non-
selective (Ibuprofen) and selective (Celebrex) NSAIDs.

30
NULL HYPOTHESES
• Root resorption measurements do not significantly differ between non-
selective (Ibuprofen) and selective (Celebrex) NSAIDs.
• Root resorption measurements do not significantly differ between dosages of
non-selective (Ibuprofen) and selective (Celebrex) NSAIDs.
• Total tooth movement measurements do not significantly differ between non-
selective (Ibuprofen) and selective (Celebrex) NSAIDs.

31
Chapter 4: METHODS AND MATERIALS

49 7-week old female Wistar rats were used for this study. All animals were
treated under conditions set according to protocols approved by the University of
Southern California Institutional Animal Care and Use Committee. The average
weight of the rats was between 105-115 grams, and the rats were anesthetized by
intraperitoneal injection of Phenobarbital (0.1mg/gm body weight). A nickel
titanium closed coil spring was attached to the cervical area of the incisors and left
first molar of the maxilla with 0.010 steel ligature wire. A notch in the middle third
of the distal surfaces of the incisors was placed with a low speed carbide bur to
prevent migration of the ligature wire. To prevent possible breakage, the surface of
the maxillary incisor was etched for 15 seconds with 37% phosphoric acid, washed
with water, primed and covered with self-cure composite (Ormco orthodontic
bonding kit). A continuous force of 80 grams was applied and checked using a
dynamometer (Dentaurum No. 040711, Newtown, PA.). The rats were maintained
on a soft diet to minimize appliance breakage. All animals were housed in facilities
maintained by the University’s vivaria. The rats placed into groups as follows:

Group 1 (No Drug):
• 16 rats were placed in this group and given no dosage of drug. The rats were
placed on a soft food diet and provided drinking water that was replaced daily.
Water and food intake was measured to ensure the rats were eating and drinking
regularly.
32
Group 2 (Low Dose Ibuprofen):
• 10 rats were placed on a soft diet and given water with Ibuprofen (25mg/kg body
weight). Sugar was added to offset the potential for bitterness of the drug to
ensure adequate drinking. Food and water intake was measured daily.

Group 3 (High Dose Ibuprofen):
• 10 rats were placed on a soft diet and given water with Ibuprofen (50mg/kg).
Sugar was added to offset the potential for bitterness of the drug to ensure
adequate drinking. Food and water intake was measured daily.

Group 4 (Low Dose Celebrex):
• 6 rats were placed on a soft diet and given water with Celebrex (40mg/kg). Sugar
was added to offset the potential for bitterness of the drug to ensure adequate
drinking. Food and water intake was measured daily.

Group 5 (High Dose Celebrex):
• 7 rats were placed on a soft diet and given water with Celebrex (80mg/kg). Sugar
was added to offset the potential for bitterness of the drug to ensure adequate
drinking. Food and water intake was measured daily.

33
All animals were euthanized with CO2 after two weeks of initial placement of
orthodontic forces. The appliances were removed and the rats were decapitated.
Tooth movement was measured as the distance between first and second molars.
Whole palate samples were cut in half and fixed in 10% neutral buffered formalin,
NBF, for 24 hours. Tissues were washed with distilled water in vials for 2 hours with
four changes, and then decalcified with EDTA at 4ºC for 6 weeks. Tissues were
processed for paraffin embedding procedures and sagittal sections (5 microns) were
prepared using a microtome. Samples were stained with Hematoxylin and Eosin or
Mallory, and analyzed under light microscope.
Resorption lacunae were measured using imaging software (Image Pro Plus,
Media Cybernetics) to accurately quantify surface area. Software program is
calibrated to the magnification of the light microscope used to take JPEG images of
histological slide. Resorption lacunae were examined on four root surfaces: mesial
root compression surface, mesial root tension surface, distal root compression
surface, and distal root tension surface. Each root surface was further examined for
resorption lacunae in the apical third, middle third and coronal third.

34

FIGURE 1: Screen capture of histological slide. Measurement of resorption
lacunae using Image Pro Plus software.
35
Chapter 5: RESULTS

In order to characterize the effects of ibuprofen and celebrex (at multiple
dosages) on root resorption and tooth movement, 49 rats were prepared with
appliances that both move molars and induce resorption. Histologic slides were
analyzed and statistical analysis was completed.
Sample Characteristics
There were a total of 45 rats included in this study. The subjects were
divided into 5 groups based upon drug and dosage. Group 1 consisted of 14 rats and
received no dosage of drug. Group 2 consisted of 10 rats and received a low dosage
of ibuprofen. Group 3 consisted of 9 rats and received a high dosage of ibuprofen.
Group 4 consisted of 5 rats and received a low dosage of celebrex. Group 5
consisted of 7 rats and received a high dosage of celebrex. Measurements of
resorption were made on each individual root surface: mesial root compression,
mesial root tension, distal root compression and distal root tension. Total resorption
was calculated from these measurements for a total of 5 measurements per subject.
Tooth movement was also calculated for each subject. Table 1 outlines the
descriptive statistics for the sites measured. Figure 5 provides examples of
resorption lacunae found on histologic sections.
Total Resorption
Results of an analysis of variance, using Tukey’s HSD pos hoc showed a
significant statistical difference between Group 1 which received no dosage of drug
and all other groups. High dose groups were generally more effective in limiting
total resorption than low dose groups. However, no statistically significant
36
difference was noted between using ibuprofen or celebrex. Table 2 shows results of
analysis of variance and using Tukey’s Post Hoc, differences between groups are
evaluated for significance. Figure 1 shows box plots of resorption measurements.
Figure 2 plots the differences in resorption for each drug at each dose.
Mesial Root Compression Resorption
Resorption measurements for the mesial root compression surface were
analyzed for significance. Several significant findings emerged from the data. First,
there was a significant difference in resorption on the mesial compression surface
between Group 1 and all other groups. High dose celebrex (Group 5) was found
statistically to be significantly more effective in limiting resorption than all other
groups. Ibuprofen was less effective than celebrex in limiting resorption. Table 3
shows results of analysis of variance and using Tukey’s Post Hoc, differences
between groups are evaluated for significance. Figure 1 shows box plots of
resorption measurements. Figure 2 plots the differences in resorption for each drug
at each dose.
Mesial Root Tension Resorption
Resorption measurements for the mesial root tension surface were analyzed
and no statistical significance was found. There were no significant differences
found between any groups. Higher dose groups measurements were found to be
lower than the low dose groups; however, the difference was not significant. Table
4 shows results of analysis of variance and using Tukey’s Post Hoc, differences
between groups are evaluated for significance. Figure 1 shows box plots of
37
resorption measurements. Figure 2 plots the differences in resorption for each drug
at each dose.
Distal Root Compression Resorption
Resorption measurements for the distal root compression surface were
analyzed for significance. Ibuprofen Groups were found to be most effective in
limiting resorption, all other groups had similar effects on resorption, the celebrex
groups were found to be more effective than controls however any differences were
not significant. No correlation was found between dosage and effectiveness in
limiting resorption. Table 5 shows results of analysis of variance and using Tukey’s
Post Hoc, differences between groups are evaluated for significance. Figure 1
shows box plots of resorption measurements. Figure 2 plots the differences in
resorption for each drug at each dose.
Distal Root Tension Resorption
Resorption measurements for the distal root tension surface were analyzed
for significance. A significant difference was found between Group 1 and all other
groups. When compared to Group 1, all other groups were significantly more effect
in minimizing resorption, however, no differences were found between drugs or
dosage. Table 6 shows results of analysis of variance and using Tukey’s Post Hoc,
differences between groups are evaluated for significance. Figure 1 shows box plots
of resorption measurements. Figure 2 plots the differences in resorption for each
drug at each dose.

38
Total Tooth Movement
Total tooth movement of the first molar was measured in millimeters.
Results of the data show that compared to controls, only group 5 experienced
significantly less tooth movement. All other groups showed slightly less movement
than Group 1 (no drug) however any differences were insignificant. Dosage had no
difference in effect, and in general, ibuprofen had less impact on tooth movement
than celebrex. Table 7 shows results of analysis of variance and using Tukey’s Post
Hoc, differences between groups are evaluated for significance. Figure 1 shows box
plots of resorption measurements. Figure 2 plots the differences in resorption for
each drug at each dose. Figure 6 shows plot of tooth movement of samples in study,
and overall trends of a drug and dosage effect on tooth movement.

39
TABLE 1: Descriptive Statistics
TOTALRES
14 1.2847 .35918 .09599 1.0773 1.4921 .87 2.23
10 .6571 .07776 .02459 .6015 .7127 .56 .81
9 .2783 .08794 .02931 .2107 .3459 .13 .40
5 .4958 .05649 .02526 .4257 .5659 .41 .56
7 .1539 .06001 .02268 .0984 .2094 .09 .26
45 .6804 .48878 .07286 .5336 .8272 .09 2.23
1.00
2.00
3.00
4.00
5.00
Total
N Mean
Std.
Deviation Std. Error Lower Bound Upper Bound
95% Confidence Interval for
Mean
Minimum Maximum

MRCS
14 .9489 .13971 .03734 .8683 1.0296 .71 1.22
10 .6374 .07928 .02507 .5807 .6941 .53 .80
9 .2662 .08698 .02899 .1994 .3331 .12 .39
5 .4166 .06469 .02893 .3363 .4969 .32 .50
7 .1440 .05780 .02185 .0905 .1975 .09 .24
45 .5588 .32600 .04860 .4609 .6567 .09 1.22
1.00
2.00
3.00
4.00
5.00
Total
N Mean
Std.
Deviation Std. Error Lower Bound Upper Bound
95% Confidence Interval for
Mean
Minimum Maximum
MRTS
14 .0066 .00960 .00257 .0010 .0121 .00 .03
10 .0010 .00105 .00033 .0002 .0018 .00 .00
9 .0004 .00073 .00024 -.0001 .0010 .00 .00
5 .0008 .00084 .00037 -.0002 .0018 .00 .00
7 .0011 .00168 .00063 -.0004 .0027 .00 .00
45 .0026 .00594 .00088 .0008 .0044 .00 .03
1.00
2.00
3.00
4.00
5.00
Total
N Mean
Std.
Deviation Std. Error Lower Bound Upper Bound
95% Confidence Interval for
Mean
Minimum Maximum
DRCS
14 .0104 .01072 .00286 .0042 .0165 .00 .03
10 .0010 .00105 .00033 .0002 .0018 .00 .00
9 .0008 .00097 .00032 .0000 .0015 .00 .00
5 .0110 .00962 .00430 -.0009 .0229 .00 .02
7 .0021 .00441 .00167 -.0019 .0062 .00 .01
45 .0052 .00820 .00122 .0027 .0076 .00 .03
1.00
2.00
3.00
4.00
5.00
Total
N Mean
Std.
Deviation Std. Error Lower Bound Upper Bound
95% Confidence Interval for
Mean
Minimum Maximum
DRTS
14 .3189 .28611 .07647 .1537 .4841 .00 1.00
10 .0177 .00546 .00173 .0138 .0216 .01 .03
9 .0109 .00454 .00151 .0074 .0144 .01 .02
5 .0674 .01180 .00528 .0527 .0821 .05 .08
7 .0066 .00868 .00328 -.0015 .0146 .00 .02
45 .1138 .20961 .03125 .0508 .1768 .00 1.00
1.00
2.00
3.00
4.00
5.00
Total
N Mean
Std.
Deviation Std. Error Lower Bound Upper Bound
95% Confidence Interval for
Mean
Minimum Maximum
TOOTHMOV
14 1.8993 .31387 .08389 1.7181 2.0805 1.21 2.34
10 1.7280 .22049 .06973 1.5703 1.8857 1.34 2.03
9 1.6367 .18453 .06151 1.4948 1.7785 1.33 1.89
5 1.6540 .11261 .05036 1.5142 1.7938 1.52 1.80
7 1.2786 .16365 .06185 1.1272 1.4299 .98 1.51
45 1.6849 .30322 .04520 1.5938 1.7760 .98 2.34
1.00
2.00
3.00
4.00
5.00
Total
N Mean
Std.
Deviation Std. Error Lower Bound Upper Bound
95% Confidence Interval for
Mean
Minimum Maximum

40
TABLE 2: Analysis of Variance (Total Resorption)
Dependent Variable: TOTALRES
8.684
a
4 2.171 47.512 .000
13.169 1 13.169 288.194 .000
8.684 4 2.171 47.512 .000
1.828 40 4.569E-02
31.344 45
10.512 44
Source
Corrected Model
Intercept
GROUPS
Error
Total
Corrected Total
Type III Sum
of Squares df Mean Square F Sig.
R Squared = .826 (Adjusted R Squared = .809) a.
Tukey HSD
.6276* .08851 .000 .3748 .8804
1.0064* .09133 .000 .7455 1.2672
.7889* .11137 .000 .4708 1.1070
1.1309* .09895 .000 .8482 1.4135
-.6276* .08851 .000 -.8804 -.3748
.3788* .09822 .004 .0982 .6593
.1613 .11708 .645 -.1731 .4957
.5032* .10534 .000 .2024 .8041
-1.0064* .09133 .000 -1.2672 -.7455
-.3788* .09822 .004 -.6593 -.0982
-.2175 .11923 .375 -.5580 .1231
.1245 .10773 .776 -.1832 .4322
-.7889* .11137 .000 -1.1070 -.4708
-.1613 .11708 .645 -.4957 .1731
.2175 .11923 .375 -.1231 .5580
.3419 .12517 .067 -.0155 .6994
-1.1309* .09895 .000 -1.4135 -.8482
-.5032* .10534 .000 -.8041 -.2024
-.1245 .10773 .776 -.4322 .1832
-.3419 .12517 .067 -.6994 .0155
(J) GROUPS
2.00
3.00
4.00
5.00
1.00
3.00
4.00
5.00
1.00
2.00
4.00
5.00
1.00
2.00
3.00
5.00
1.00
2.00
3.00
4.00
(I) GROUPS
1.00
2.00
3.00
4.00
5.00
Mean
Difference
(I-J) Std. Error Sig. Lower Bound Upper Bound
95% Confidence Interval
Based on observed means.
The mean difference is significant at the .05 level. *.

41
TABLE 3: Analysis of Variance (MRCS)
Dependent Variable: MRCS
4.155
a
4 1.039 104.162 .000
9.484 1 9.484 950.973 .000
4.155 4 1.039 104.162 .000
.399 40 9.973E-03
18.830 45
4.554 44
Source
Corrected Model
Intercept
GROUPS
Error
Total
Corrected Total
Type III Sum
of Squares df Mean Square F Sig.
R Squared = .912 (Adjusted R Squared = .904) a.
Dependent Variable: MRCS
Tukey HSD
.3115* .04135 .000 .1934 .4296
.6605* .04267 .000 .5386 .7823
.5323* .05203 .000 .3837 .6809
.8049* .04623 .000 .6729 .9370
-.3115* .04135 .000 -.4296 -.1934
.3490* .04588 .000 .2179 .4800
.2208* .05470 .002 .0646 .3770
.4934* .04921 .000 .3528 .6340
-.6605* .04267 .000 -.7823 -.5386
-.3490* .04588 .000 -.4800 -.2179
-.1282 .05570 .166 -.2872 .0309
.1444* .05033 .048 .0007 .2882
-.5323* .05203 .000 -.6809 -.3837
-.2208* .05470 .002 -.3770 -.0646
.1282 .05570 .166 -.0309 .2872
.2726* .05847 .000 .1056 .4396
-.8049* .04623 .000 -.9370 -.6729
-.4934* .04921 .000 -.6340 -.3528
-.1444* .05033 .048 -.2882 -.0007
-.2726* .05847 .000 -.4396 -.1056
(J) GROUPS
2.00
3.00
4.00
5.00
1.00
3.00
4.00
5.00
1.00
2.00
4.00
5.00
1.00
2.00
3.00
5.00
1.00
2.00
3.00
4.00
(I) GROUPS
1.00
2.00
3.00
4.00
5.00
Mean
Difference
(I-J) Std. Error Sig. Lower Bound Upper Bound
95% Confidence Interval
Based on observed means.
The mean difference is significant at the .05 level. *.

42
TABLE 4: Analysis of Variance (MRTS)
Dependent Variable: MRCS
4.269
a
4 1.067 104.714 .000
9.311 1 9.311 913.694 .000
4.269 4 1.067 104.714 .000
.408 40 1.019E-02
18.728 45
4.676 44
Source
Corrected Model
Intercept
GROUPS
Error
Total
Corrected Total
Type III Sum
of Squares df Mean Square F Sig.
R Squared = .913 (Adjusted R Squared = .904) a.

Dependent Variable: MRTS
Tukey HSD
.0056 .00230 .129 -.0010 .0121
.0061 .00237 .093 -.0006 .0129
.0058 .00289 .286 -.0025 .0140
.0054 .00257 .234 -.0019 .0128
-.0056 .00230 .129 -.0121 .0010
.0006 .00255 .999 -.0067 .0078
.0002 .00304 1.000 -.0085 .0089
-.0001 .00273 1.000 -.0080 .0077
-.0061 .00237 .093 -.0129 .0006
-.0006 .00255 .999 -.0078 .0067
-.0004 .00309 1.000 -.0092 .0085
-.0007 .00280 .999 -.0087 .0073
-.0058 .00289 .286 -.0140 .0025
-.0002 .00304 1.000 -.0089 .0085
.0004 .00309 1.000 -.0085 .0092
-.0003 .00325 1.000 -.0096 .0089
-.0054 .00257 .234 -.0128 .0019
.0001 .00273 1.000 -.0077 .0080
.0007 .00280 .999 -.0073 .0087
.0003 .00325 1.000 -.0089 .0096
(J) GROUPS
2.00
3.00
4.00
5.00
1.00
3.00
4.00
5.00
1.00
2.00
4.00
5.00
1.00
2.00
3.00
5.00
1.00
2.00
3.00
4.00
(I) GROUPS
1.00
2.00
3.00
4.00
5.00
Mean
Difference
(I-J) Std. Error Sig. Lower Bound Upper Bound
95% Confidence Interval
Based on observed means.

43
TABLE 5: Analysis of Variance (DRCS)

Dependent Variable: DRCS
9.583E-04
a
4 2.396E-04 4.797 .003
1.022E-03 1 1.022E-03 20.458 .000
9.583E-04 4 2.396E-04 4.797 .003
1.998E-03 40 4.994E-05
4.152E-03 45
2.956E-03 44
Source
Corrected Model
Intercept
GROUPS
Error
Total
Corrected Total
Type III Sum
of Squares df Mean Square F Sig.
R Squared = .324 (Adjusted R Squared = .257) a.

Dependent Variable: DRCS
Tukey HSD
.0094* .00293 .021 .0010 .0177
.0096* .00302 .023 .0010 .0182
-.0006 .00368 1.000 -.0112 .0099
.0082 .00327 .108 -.0011 .0176
-.0094* .00293 .021 -.0177 -.0010
.0002 .00325 1.000 -.0091 .0095
-.0100 .00387 .093 -.0211 .0011
-.0011 .00348 .997 -.0111 .0088
-.0096* .00302 .023 -.0182 -.0010
-.0002 .00325 1.000 -.0095 .0091
-.0102 .00394 .091 -.0215 .0010
-.0014 .00356 .995 -.0115 .0088
.0006 .00368 1.000 -.0099 .0112
.0100 .00387 .093 -.0011 .0211
.0102 .00394 .091 -.0010 .0215
.0089 .00414 .224 -.0030 .0207
-.0082 .00327 .108 -.0176 .0011
.0011 .00348 .997 -.0088 .0111
.0014 .00356 .995 -.0088 .0115
-.0089 .00414 .224 -.0207 .0030
(J) GROUPS
2.00
3.00
4.00
5.00
1.00
3.00
4.00
5.00
1.00
2.00
4.00
5.00
1.00
2.00
3.00
5.00
1.00
2.00
3.00
4.00
(I) GROUPS
1.00
2.00
3.00
4.00
5.00
Mean
Difference
(I-J) Std. Error Sig. Lower Bound Upper Bound
95% Confidence Interval
Based on observed means.
The mean difference is significant at the .05 level. *.

44
TABLE 6: Analysis of Variance (DRTS)

Dependent Variable: DRTS
.868
a
4 .217 8.142 .000
.284 1 .284 10.659 .002
.868 4 .217 8.142 .000
1.066 40 2.664E-02
2.516 45
1.933 44
Source
Corrected Model
Intercept
GROUPS
Error
Total
Corrected Total
Type III Sum
of Squares df Mean Square F Sig.
R Squared = .449 (Adjusted R Squared = .394) a.

Dependent Variable: DRTS
Tukey HSD
.3012* .06758 .001 .1081 .4942
.3080* .06974 .001 .1088 .5071
.2515* .08504 .039 .0086 .4943
.3123* .07556 .002 .0965 .5281
-.3012* .06758 .001 -.4942 -.1081
.0068 .07499 1.000 -.2074 .2210
-.0497 .08940 .981 -.3050 .2056
.0111 .08044 1.000 -.2186 .2409
-.3080* .06974 .001 -.5071 -.1088
-.0068 .07499 1.000 -.2210 .2074
-.0565 .09104 .971 -.3165 .2035
.0043 .08226 1.000 -.2306 .2392
-.2515* .08504 .039 -.4943 -.0086
.0497 .08940 .981 -.2056 .3050
.0565 .09104 .971 -.2035 .3165
.0608 .09557 .968 -.2121 .3338
-.3123* .07556 .002 -.5281 -.0965
-.0111 .08044 1.000 -.2409 .2186
-.0043 .08226 1.000 -.2392 .2306
-.0608 .09557 .968 -.3338 .2121
(J) GROUPS
2.00
3.00
4.00
5.00
1.00
3.00
4.00
5.00
1.00
2.00
4.00
5.00
1.00
2.00
3.00
5.00
1.00
2.00
3.00
4.00
(I) GROUPS
1.00
2.00
3.00
4.00
5.00
Mean
Difference
(I-J) Std. Error Sig. Lower Bound Upper Bound
95% Confidence Interval
Based on observed means.
The mean difference is significant at the .05 level. *.

45

TABLE 7: Analysis of Variance (Tooth Movement)

Dependent Variable: TOOTHMOV
1.843
a
4 .461 8.372 .000
107.425 1 107.425 1951.349 .000
1.843 4 .461 8.372 .000
2.202 40 5.505E-02
131.794 45
4.046 44
Source
Corrected Model
Intercept
GROUPS
Error
Total
Corrected Total
Type III Sum
of Squares df Mean Square F Sig.
R Squared = .456 (Adjusted R Squared = .401) a.

Dependent Variable: TOOTHMOV
Tukey HSD
.1713 .09715 .409 -.1062 .4487
.2626 .10025 .086 -.0237 .5489
.2453 .12224 .282 -.1038 .5944
.6207* .10861 .000 .3105 .9309
-.1713 .09715 .409 -.4487 .1062
.0913 .10781 .914 -.2166 .3992
.0740 .12851 .978 -.2930 .4410
.4494* .11563 .003 .1192 .7797
-.2626 .10025 .086 -.5489 .0237
-.0913 .10781 .914 -.3992 .2166
-.0173 .13087 1.000 -.3911 .3564
.3581* .11824 .033 .0204 .6958
-.2453 .12224 .282 -.5944 .1038
-.0740 .12851 .978 -.4410 .2930
.0173 .13087 1.000 -.3564 .3911
.3754 .13739 .067 -.0170 .7678
-.6207* .10861 .000 -.9309 -.3105
-.4494* .11563 .003 -.7797 -.1192
-.3581* .11824 .033 -.6958 -.0204
-.3754 .13739 .067 -.7678 .0170
(J) GROUPS
2.00
3.00
4.00
5.00
1.00
3.00
4.00
5.00
1.00
2.00
4.00
5.00
1.00
2.00
3.00
5.00
1.00
2.00
3.00
4.00
(I) GROUPS
1.00
2.00
3.00
4.00
5.00
Mean
Difference
(I-J) Std. Error Sig. Lower Bound Upper Bound
95% Confidence Interval
Based on observed means.
The mean difference is significant at the .05 level. *.

46

FIGURE 2: Box Plots

47

FIGURE 3: Means Drug Dosage

48
FIGURE 4: Resorption Bar Graphs, Tooth Movement Bar Graph
GROUPS
5.00 4.00 3.00 2.00 1.00
Mean TOTALRES
1.4
1.2
1.0
.8
.6
.4
.2
0.0
GROUPS
5.00 4.00 3.00 2.00 1.00
Mean DRCS
.012
.010
.008
.006
.004
.002
0.000
GROUPS
5.00 4.00 3.00 2.00 1.00
Mean MRCS
1.0
.8
.6
.4
.2
0.0
GROUPS
5.00 4.00 3.00 2.00 1.00
Mean DRTS
.4
.3
.2
.1
0.0
GROUPS
5.00 4.00 3.00 2.00 1.00
Mean MRTS
.007
.006
.005
.004
.003
.002
.001
0.000

49
FIGURE 5: Histologic Samples: Resorption Lacunae & Cross Section of Molar

50

FIGURE 6:Tooth Movement Plots & Graph of Resorption
DRTS
DRCS
MRTS
MRCS

51
Chapter 6: DISSCUSION

Forces applied on teeth trigger an inflammatory response involving pain
and/or discomfort and bone resorption, which constitutes the basis of tooth
movement. Analgesics, including several NSAIDs, have been largely prescribed for
alleviation of the symptoms felt by patients undergoing OT. Among others, PGs are
typical inflammatory and pain mediators which result from the degradation of
arachidonic acid. Its synthesis is mediated by two different COX isoenzymes. The
constitutive COX-1 does not exhibit dynamic regulation while COX-2 expression is
subject to regulation by several environmental conditions.
53

In recent years, COX-2-selective non-steroidal anti-inflammatory substances
have become widely available and their use more common. Coxib shows anti-
inflammatory properties, preserving the COX-1 pathway and therefore allowing the
natural production of some PGs important for their gastrointestinal protective role.
45

In analgesic treatment during orthodontic procedures, acetaminophen, a very weak
COX inhibitor, has been proposed as the drug of choice. NSAIDs have proved to be
inappropriate for treatment of discomfort and pain during OT since they tend to limit
or even block tooth movement due to interference with the accompanying
inflammatory process
31
. The importance of achieving good anti-inflammatory effects
with minimum interference of the COX-1 pathway has resulted in a wide variety of
coxibs being developed and made commercially available in recent years. Some of
these have been the object of debate and even withdrawn from the market due to
reports of unwanted cardiovascular and renal side effects.
52
Coxibs, promising minimal NSAID-typical toxicity with full anti-
inflammatory efficacy, have been used for treatment of orthodontic discomfort and
pain.
In the search for an NSAID treatment it was hypothesized that coxibs with
differences in COX-1/COX-2 selectivity ratio could affect, in a different manner, the
movement of teeth during tooth movement. The present study intended to compare
the effects of celebrex on orthodontic tooth movement to the traditionally used
NSAID, ibuprofen. The results seem to confirm to conclusions of de Carlos, F. who
determined there is no significant advantage in using COX-2 specific drugs. This is
compatible with the idea that factors depending on synthesis via COX-1 are involved
in the bone remodeling process during orthodontic tooth movement. However, it is
also possible that other differences between the drugs themselves (bioavailability,
half life, etc.) could account for the different effects of these two drugs.

53
Chapter 7: ASSUMPTIONS

There were several assumptions made for this study. Any individual variation
inherent in the rat sample will not significantly affect statistical outcomes. All
measurements were accurate and reproducible. Any distortion or magnification of
histological images is statistically insignificant.

54
Chapter 8: LIMITATIONS

There were several potential limitations to this study. There were a limited
number of rats assigned to each group. Ideally each group would have been assigned
more samples to enhance the statistical analysis of the data. A single time point of 14
days was used to evaluate resorption and tooth movement. Using multiple time
points could have shown more completely the effect of each drug on resorption and
tooth movement including ideal dosage and how long a drug can or should be used
while undergoing active treatment. In order to evaluate the effect of drug on
resorption, a heavy force of 80 grams was applied; assuredly this level of force
caused undermining resorption and could have had a significant effect on the type of
tooth movement observed and the measurements made. Using a coil spring to move
teeth uses forces away from the center of resistance and caused a tipping effect
rather than a translation movement. Micro CT imaging has become a viable option
for measuring volume of resorption. Using histological sections gives a 2-
dimensioanl image and a measurement of area. Using a micro CT for measurement
would be more accurate. Finally measurements were subject to human error.

55
Chapter 9: SUMMARY

Several previous studies have found that non selective NSAIDs tend to limit
tooth movement due to the inhibition of prostaglandins. This study sought to find if
the same outcome would occur using celebrex, a selective COX-2 inhibitor. As new
drugs are prescribed to potential orthodontic patients, it is imperative for the
practitioner to understand the effect that these drugs will have on treatment, and any
precautions that may be required. Currently there is very little orthodontic literature
on this new lineage of NSAIDs, and among the information available there is
variation in the conclusions regarding the effect of celebrex. This study was able to
compliment the conclusions of previous work. Because both selective and non
selective NSAIDs inhibit COX-2, albeit at varying degrees, they are both effective in
minimizing resorption. However, because COX-2 specific drugs are many times
more effective in blocking COX-2, they significantly slow orthodontic movement at
high doses. If a patient is prescribed celebrex for a long term condition, the treatment
time will likely be lengthened. This isn’t to say that there is not value in this drug; it
was much more effective in reducing resorption on the mesial root compression site,
where this study found to be the area most prone to resorption.

56
Chapter 10: CONLUSIONS

1. A significant reduction in root resorption was shown using either ibuprofen
or celebrex compared to controls. High dose was more effective than low
dose. However, overall, no significant difference was found between the
drugs.
2. Higher doses were generally more effective than low doses in reducing root
resorption.
3. Celebrex was more effective than ibuprofen in reducing resorption on the
mesial root compression surface. High dose effect was significantly more
effective than the low dose.
4. High dose celebrex significantly inhibited tooth movement compared to all
other groups.
5. There is minimal advantage in using celebrex on root resorption; however
treatment time may be lengthened.
A better understanding of the biochemical mediators of orthodontic tooth
movement and Future clinical application of PGs and LTs may result in
enhancement or retardation in the normal orthodontic tooth movement process.
Currently, based on animal studies, acetaminophen may be the most appropriate
choice for treating orthodontic-associated pain because it does not contribute to PG
inhibition and anti-inflammatory activity. However, the clinical significance of
chronic (i.e., >20 days) NSAID use on dental orthodontics is unclear; therefore,
long-term human data are needed to define the role of acetaminophen, NSAIDs (e.g.,
aspirin, ibuprofen, celebrex), and LT inhibitors on orthodontic tooth movement.
57
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Abstract (if available)

Abstract Purpose: The purpose of this study was to compare the effects of ibuprofen, a conventional NSAID, and celebrex, a COX-2 specific inhibitor, on tooth movement and root resorption. Methods: 49 female wistar rats were placed into 5 groups: (1) control (no dosage), (2) high dose celebrex (80mg/kg body weight), (3) high dose ibuprofen (50 mg/kg), (4) low dose celebrex (40 mg/kg), and (5) low dose ibuprofen (25 mg/kg). Rats were anesthetized by IP injection of Phenobarbital (0.1 mg/gm body weight), and a force of 80 grams was applied to the maxillary left first molars using a nickel titanium closed-coil spring. Tissue samples analyzed by light microscopy, and areas of resorption were quantified. Results: Ibuprofen and celebrex reduced resorption compared to control. High dose celebrex caused a reduction of tooth movement. Conclusions: There is minimal advantage in using selective COX-2 inhibitors to limit resorption

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Asset Metadata

Creator Brunson, Timothy D. (author)

Core Title Effect of cyclooxygenase inhibitors on rat root resorption and tooth movement

School School of Dentistry

Degree Master of Science

Degree Program Craniofacial Biology

Publication Date 02/29/2008

Defense Date 02/11/2008

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,root resorption,tooth movement

Language English

Advisor Zeichner-David, Maggie (committee chair), Moon, Holly (committee member), Paine, Michael (committee member), Sameshima, Glenn T. (committee member)

Creator Email tbrunson@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m1033

Unique identifier UC1291031

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Dmrecord 40014

Document Type Thesis

Rights Brunson, Timothy D.

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu