Download Don H. Dau, D.M.D. Saint Louis University in Partial Fulfillment

PERIODONTAL EFFECTS OF THE MAGNETAINER™
COMPARED TO FIXED RETENTION
Don H. Dau, D.M.D.
A Thesis Presented to the Graduate Faculty of
Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2015
© Copyright by
Don Hoang Dau
ALL RIGHTS RESERVED
2015
i
COMMITTEE IN CHARGE OF CANDIDACY:
Associate Clinical Professor, Donald R. Oliver,
Chairperson and Advisor
Associate Professor Ki Beom Kim
Professor Douglas Miley
ii
I dedicate this work to my parents, my brother, and my
sister.
They have supported me throughout my life, and
without them, I would not be where I am today.
iii
ACKNOWLEDGEMENTS
This project would not have been possible without the
mentorship of Drs. Donald Oliver, Ki Beom Kim, and Douglas
Miley.
Thank you for your support and guidance.
Thank you to Drs. Gene and Aron Dellinger for your
assistance with the sample for the MagneTainer™ group.
Thank you to Dr. Randall Brown for your assistance
with the sample for the bonded lingual retainer group.
Thank you to Dr. Heidi Israel for your assistance with
the statistical analysis.
iv
TABLE OF CONTENTS
List of Tables......................................vii
List of Figures....................................viii
CHAPTER 1:
INTRODUCTION..............................1
CHAPTER 2:
REVIEW OF THE LITERATURE
Stability and Relapse............................4
Removable Retention..............................6
Hawley Retainers............................6
Vacuum-Formed Retainers.....................7
Patient Compliance..........................8
Fixed Retention..................................9
Periodontal Implications of Fixed Retainers.....10
Magnets.........................................13
Magnet Properties and Types................13
Biological Considerations..................15
Corrosion Products.........................15
Magnetic Fields............................17
Statement of Thesis.............................19
Literature Cited................................20
CHAPTER 3:
Journal Article
Abstract........................................26
Introduction....................................28
Materials and Methods...........................32
Error Study.....................................35
v
Statistical Analysis............................35
Results.........................................36
Discussion......................................39
Conclusion......................................41
Literature Cited................................42
Appendix.............................................47
Vita Auctoris........................................48
vi
LIST OF TABLES
Table 2.1
Criteria for the Gingival Index System.......11
Table 2.2
Criteria for the Plaque Index System.........12
Table 3.1
Criteria for the Gingival Index System.......34
Table 3.2
Criteria for the Plaque Index System.........34
Table 3.3
Mean, standard deviation, and standard of
error for the GI score, PI score, Calculus
score, brushing frequency, and flossing
frequency....................................36
Table 3.4
Mann-Whitney U test for significant
differences between the variables............37
Table 3.5
Frequency of brushing difficulty for both
groups.......................................37
Table 3.6
Mann-Whitney U test to camper difficulty of
flossing with GI score, PI score, Calculus
score, brushing frequency, and flossing
frequency....................................38
Table 3.7
Spearman’s correlation for GI score, PI
score, Calculus score, brushing frequency,
and flossing frequency.......................38
Table 3.8
Independent t-tests for significant
differences in probing depths................39
vii
LIST OF FIGURES
Figure 1.1
The MagneTainer™ in place on a patient......3
Figure A1
Questionnaire Given to Patients............47
viii
CHAPTER 1:
INTRODUCTION
Orthodontic supervision does not end once the
appliances have been removed.
Orthodontists and patients
alike are concerned about the anticipated degree of
stability following active orthodontic treatment, and it
has been suggested that lifetime retention is necessary to
maintain satisfactory alignment after treatment in many
patients.1 As part of routine orthodontic protocol, a
retention period after treatment is done with removable
retainers, fixed retainers, or a combination of both.
Perfect alignment after orthodontic treatment is
unrealistic over a lifetime, and literature has shown that
relapse following orthodontic treatment is both
unpredictable and unavoidable.1-5
The challenge that many
orthodontists find in retention is that it is impossible to
predict which cases will undergo relapse and to what degree
it will occur.6
The words relapse, physiologic recovery,
rebound, post-retention settling, and other similar terms
have been used by orthodontic practitioners to describe the
changes that occur after orthodontic appliances have been
removed.7
Relapse can occur anywhere in the dentition, but one
of the more evident areas of potential instability is the
1
lower anterior region. Fixed retention was introduced to
help improve post-treatment stability of the lower anterior
teeth.
Fixed retention in this area involves a wire that
transverses the lingual surfaces of mandibular anterior
teeth.
While the main advantages of fixed lingual
retention are the esthetic value and virtually compliance
free nature, one of the major disadvantages is the tendency
for plaque and calculus accumulation over time.8
As a
result, there may be a negative effect on the periodontal
health.9
The MagneTainer™ is being introduced as an alternative
to traditional fixed lingual retention.
The MagneTainer™
was developed by Drs. Gene and Aron Dellinger of Ft. Wayne,
Indiana. It utilizes neodymium-iron-boron magnets that are
bonded on all the marginal ridges from the mesial of the
lower canine to the mesial of the contralateral canine as
seen in Figure 1.1.
The magnets maintain the alignment of
the lower anterior teeth and allow patients to floss
straight down the contact without any additional flossing
auxiliaries.
With the trend of using fixed lingual retainers for
long-term retention, it is important to understand the
effects that they may have on the periodontal tissues.
The
purpose of this study is to compare the periodontal health
2
of the mandibular anterior teeth retained with the
MagneTainer™ versus a conventional fixed lingual retainer.
Figure 1.1:
The MagneTainer™ in place on a patient
3
CHAPTER 2:
REVIEW OF THE LITERATURE
Stability and Relapse
The orthodontic literature has shown that relapse
following orthodontic treatment is both unpredictable and
unavoidable.1-5
The challenge that many orthodontists find
in retention is that it is impossible to predict which
cases will undergo relapse and to what degree it will
occur.6
The words relapse, physiologic recovery, rebound,
post-retention settling, and other similar terms have been
used by orthodontic practitioners to describe the changes
that occur after orthodontic appliances have been removed.7
Longitudinal studies have shown that during the posttreatment period, there is a trend towards decreased arch
length, decreased arch width, increased overbite, increased
overjet, and increased mandibular anterior crowding.4,
7, 10-12
Horowitz and Hixon stated that orthodontics may alter
the course of the continuous physiologic changes, however,
following the mechanotherapy and retention period
restraint, the developmental maturation process resumes.13
In order to understand post-retention stability and
relapse, it is important to examine the maturation of
untreated normal occlusions.
Sinclair and Little examined
untreated cases from the mixed-dentition phase to early
4
adulthood and found a decrease in arch length, a small
decrease in inter-canine width, minimal change in
intermolar width, minimal change in overjet and overbite,
and an increase in incisor irregularity.7
Changes that
occur in the untreated dentition are less than that seen in
treated cases post-retention.7
Eslambolchi et al. examined longitudinal changes in
mandibular incisor alignment in treated and untreated
patients.
They found that treated and untreated patients
had similar long-term changes.
Intercanine width,
interfirst premolar width, arch length, anterior space, and
total space significantly decreased while Little’s
irregularity index significantly increased in both groups.14
Blake and Bibby examined 15 potential factors of
stability that included arch form, periodontal tissues,
mandibular incisor dimensions, neuromusculature balance,
growth, post-treatment results, third molars, original
malocclusion, extraction treatment, expansion, and nonextraction treatment.15
They concluded that orthodontist
should aim to remove the primary burden of preventing
relapse from the patient by maintaining treatment goals
that follow well-documented principles such as maintaining
lower intercanine width and lower arch form.15
5
Even though there are many studies describing possible
pretreatment factors leading to relapse, most attempts have
been unsuccessful at showing any reliable predictors of
stability.16-18
Ormiston et al. found that the initial
severity of the malocclusion was correlated with the postretention instability.18
Despite orthodontists’ best
efforts, the best way to maintain satisfactory alignment
post-treatment is through an indefinite period of
retention.1
One of the more unstable and unpredictable areas
during the retention period is the lower anterior region.1921
According to Zachrisson, long-term retention of the
lower anterior segment may be necessary in order to prevent
or reduce unwanted post-treatment changes.22
Removable Retention
The two main forms of removable retention utilized by
orthodontists are Hawley retainers and vacuum formed
retainers.
Each of these has their own respective
advantages and disadvantages; however, one commonality
between the two is that they rely heavily on patient
compliance.
Hawley Retainers
Charles Hawley designed the Hawley retainer in 1919.
Hawley designs have evolved throughout the years, but the
6
current basic design includes a labial bow that contacts
the anterior teeth and an acrylic plate that rests behind
the teeth.
Hawley retainers are known for their durability
and adjustability during the retention period.
They allow
for relative vertical movement of the posterior teeth
during retention, and this allows for post-treatment
settling of the dentition.23
When compared to wearing
vacuum-formed retainers, the use of Hawley retainers
results in more occlusal contacts because the retainer does
not involve occlusal coverage.23
Vacuum-Formed Retainers
Vacuum-formed retainers were introduced in 1971.24
Their popularity has grown due to their esthetic qualities,
ease of fabrication, and lower costs.6,
21, 25
The drawbacks
of vacuum-formed retainers include occlusal wear of the
appliance, cracking, reduced vertical settling, and
adjustability of the appliance.6,
23
Various studies have shown that vacuum-formed
retainers are effective as Hawley retainers in maintaining
orthodontic corrections.6,
21, 26
Barlin et al. examined
eighty-two patients who were randomly assigned either a
Hawley or a vacuum-formed retainer.6
After a 12-month
period, there was no difference in the measured arch width,
arch length, or modified Little’s index.6
7
Two studies have shown, however, that vacuum-formed
retainers are more effective in maintaining mandibular
incisor positions during retention when compared with
Hawley retainers.21,
27
Despite the statistically
significant results of these studies, they can be
considered clinically insignificant unless it relates to a
single tooth displacement in the mandibular arch.21
Patient Compliance
The retention phase is placed in the hands of the
patient once they are given a retainer.28
The desire to
keep the teeth aligned after years of orthodontic treatment
now depends on the patient.
Every orthodontist has a
different retention protocol, but the end goal is the same.
A survey of two thousands orthodontists was conducted and
it was found that most orthodontists prescribed less than 9
months of full-time wear and advised life-long part-time
wear.28
Despite that which is prescribed and how much emphasis
is placed on the need for retention, patient behavior can
vary.
A survey of 428 retention patients showed that 20%
of patients were not wearing their retainers after 2 years,
but 45% were wearing them every night and 80% at least 1
night per week.29
They did not find age or sex to influence
the levels of compliance.29
8
Fixed Retention
Fixed lingual retainers are the main alternatives to
traditional removable retainers, especially in the lower
anterior region. Traditionally, bonded mandibular canineto-canine retainers are made from single stranded or multistranded wires bonded to the lingual surfaces of the lower
anterior teeth. Their popularity has grown because they are
esthetically pleasing, virtually free of patient
compliance, and reliable as part of the retention phase.
The major shortcomings include the time consuming placement
procedure, bond failures, stress fractures, and the
tendency for plaque and calculus accumulation.30
One of the main advantages of fixed lingual retainers
is that they are reliable in maintaining post-retention
stability due to their almost compliance free nature.
Artun and coworkers found that fixed lower retainers
effectively maintained incisor alignment 3 years posttreatment and these results have been supported by other
studies as well.30-32
The effectiveness of fixed lingual
retainers at maintaining alignment is only possible as long
as the retainer is intact and does not have bond
failures.30,
32, 33
When failures occur, more incisor
irregularity is observed when compared to the retainers
that did not fail.30,
32, 33
9
Failures can be intrinsic because of poor bonding
technique, or they can be extrinsic due to wear or direct
trauma to the retainer.32
Bond failure rates as reported in
the literature range from 9% - 35%.30,
32, 33
Variation in
bond failure rates reported can be attributed to how bond
failures are recorded, whether a dentist fixed a bond
failure during a hygiene check, and the length of the
observation period.
Since patients with retainer failures
experienced more relapse than those without failures, it is
important to minimize bond failures in order to maintain
the effectiveness of lower lingual bonded retainers.30,
32
Lingual fixed retention may be compliance free in
regards to wearing a retainer, however, it is not
compliance free when it comes to care in food type
selection and oral hygiene.
Since the wire of a fixed
lower retainer transverses the lingual surfaces of the
mandibular anterior teeth, flossing and brushing can be
more difficult.
The result is a tendency for plaque and
calculus buildup around the area of the retainer.
Periodontal Implications of Fixed Retainers
The Gingival Index system was introduced in 1963 and
the Plaque Index system was introduced in 1964.34,
35
The
Gingival Index system is used as a method to assess the
gingival condition through qualitative changes in the
10
gingival soft tissue.36
Each tooth is broken down into four
areas that make up the circumference of the marginal
gingiva (buccal, mesial, distal, lingual).36
Each of the
four gingival areas is assigned a score from 0-3 based on
the criteria for the Gingival Index system as seen in Table
2.1.
The average of the scores of the four areas of a
tooth gives the GI for the tooth.
The average of all the
GI’s of the individual teeth examined gives the GI for the
individual.
Silness and Loe’s Plaque Index system is similar to
their Gingival Index system in that it is used to clearly
distinguish between the severity and location of soft
debris aggregate.35
The individual locations, individual
teeth, and overall individual scores are calculated similar
to that of the Gingival Index system.
The criteria for the
Plaque Index system can be seen in Table 2.2.
Table 2.1: Criteria for the Gingival Index System adapted
from Loe and Silness34
Criteria for the Gingival Index System
Score
0
Description
Normal gingiva
1
Mild inflammation – slight change in color,
slight edema. No bleeding on probing
2
Moderate inflammation – redness, edema and
glazing. Bleeding on probing
3
Severe inflammation – marked redness and edema,
ulceration. Tendency to spontaneous bleeding
11
Table 2.2: Criteria for the Plaque Index System adapted
from Silness and Loe35
Criteria for the Plaque Index System
Score
Description
0
No plaque in gingival area
1
A film
margin
plaque
across
2
Moderate accumulation of soft deposits within the
gingival pocket, on the gingival margin, and/or
adjacent tooth surface, which can be seen by the
naked eye.
3
Abundance of soft matter within the gingival
pocket and/or on the gingival margin and adjacent
tooth surface
of plaque adhering to the free gingival
and adjacent area of the tooth. The
may only be recognized by running a probe
the tooth surface
Loe and Silness’s Gingival Index and Plaque Index
systems have been used throughout orthodontic literature to
evaluate the quality of the gingiva.
Artun et al. compared
lower lingual fixed retainers and removable retainers
utilizing the Gingival Index and Plaque Index.30 At threeyear follow-up, they found no differences in the indices
and that plaque accumulation scored less frequently after 3
years in retention.30
Similarly another study found that
the Gingival Index scores demonstrated no detrimental
effects to the mandibular anterior gingiva after a 20-year
follow-up study.37
Heier and colleagues found that there
was slightly more plaque and calculus present in the fixed
retention group, however, this did not result in more
pronounced gingival inflammation than in the removable
retainer group.38
12
In contrast, Pandis and his coworkers reported greater
calculus accumulation, greater marginal recession, and
increased probing depths in patients with mandibular fixed
retention for long periods.39
Similarly, Levin et al. found
greater probing depths, bleeding on probing, and plaque
index in patients with fixed retention when compared to
patients without fixed retention.9
Other researchers also
found more plaque accumulation in those with bonded lingual
retainers compared to removable retainers.40
Magnets
Magnets are able to produce a measured force
continuously over a long period of time.41
Since magnets
can be made to attract or repel, they can be utilized to
exert their force without the need for direct contact.41
Orthodontists have utilized magnets in a variety of ways
that includes treatment of unerupted teeth, tooth movement
along archwires, expansion, correction of anterior open
bites, and functional appliances.41
With the introduction
of utilizing magnets for retention, it is important to
examine the potential biological effects that they may have
when used intraorally.
Magnet Properties and Types
Magnets have magnetic fields around them that start
from one pole of the magnet and returns to the other pole
13
of the magnet.41
They produce flux, which is the change
induced by the magnet in the medium surrounding the
magnet.41
The flux produced causes magnets to attract or
repel other magnets and other materials containing iron.41
High-energy magnets were introduced in the 1970’s and
have the advantage of being able to produce high forces
relative to their size.41,
42
The increased magnetism is
attributed to the property of magnetocrystaline anisotropy,
which allows for single crystals to be preferentially
aligned along the long C-axis.41
Rare earth metals have
been incorporated into high-energy magnets and this has
significantly increased the magnetism.41,
42
Rare earth
magnets have high coercivity, which means that they can
resist demagnetization better.41,
43
The downsides to the
rare earth magnets include being brittle, having low
corrosion resistance, and suffering irreversible magnetic
loss when heated.41,
43
The two main rare earth magnets that
have been utilized in orthodontics are samarium-cobalt
magnets and neodymium-iron-boron magnets.44
Samarium-cobalt magnets are characterized by their
high saturation magnetism and high Curie temperature of
680°C.42,
44
A higher Curie temperature indicates that the
magnet can withstand high heat without demagnetization,
14
which is important when fabricating appliances in acrylic.42
They are more costly than other rare earth magnets.44
Neodymium-iron-boron magnets have very high magnetic
saturation, good resistance to demagnetization, and the
highest value of energy production.44
They are cheaper and
less brittle than samarium-cobalt magnets, but they also
have a lower Curie temperature at around 300°C.42,
44
Biological Considerations
Any new material used clinically should not produce
any side effects at a local or systemic level, and it is
important to have biological safety testing done to ensure
this as far as reasonably possible.45
Various studies have
been done to test the biological safety of magnets by
examining the effects of corrosion products and magnetic
fields produced by the magnets.46-48
Corrosion Products
Rare earth magnets are susceptible to corrosion and
tarnish intraorally over time and the corrosion products
can effect intraoral tissues.45-47
Corrosion is an
electromechanical process that results in a deterioration
of the metal and release of ions.45
Non-encapsulated
neodymium-iron-boron magnets have poor corrosion resistance
intraorally.49
Hopp et al. examined the effects of rare
earth magnets on mouse fibroblasts and found that uncoated
15
samarium-cobalt magnets have a strong tendency for
corrosion and exert a considerable cytotoxicity.50
They
also found that uncoated neodymium-iron-boron magnets have
a lesser tendency for corrosion and are only moderate
cytotoxic.50
Uncoated samarium-cobalt magnets have
demonstrated high to moderate cytotoxicity, while uncoated
neodymium-iron-boron showed negligible cytotoxicity.48
Evans and McDonald examined the effects of the
corrosion products of uncoated neodymium-iron-boron magnets
on the proliferation of human oral mucosal fibroblasts and
found that oral fibroblast attachment was not affected by
corrosion products.45
They did note that fibroblast
proliferation in the presence of corrosion products was
lower than the control but not completely inhibited.45
To prevent the corrosion of magnets intraorally, it
has been recommended that magnets be coated or hermetically
sealed to isolate them from the oral environment.48,
50, 51
Corrosion resistance of samarium-cobalt and neodymium-ironboron magnets can be enhanced when rare earth magnets are
hermetically sealed for use in dentistry.47
Noar et al.
found that a thin parylene coating is unlikely to withstand
intrao-oral forces, however, the shape of the magnets, the
manufacturing process in production, and the thickness of
the coating are important factors to consider with
16
intraoral magnets.52
Parylene coated samarium-cobalt and
neodymium-iron-boron magnets have shown negligible
cytotoxicity.48
Magnetic Fields
The effectiveness of magnets used intraorally relies
on the mechanical forces generated by magnetic fields.53
A
variety of in vitro, animal, and in vivo studies have been
done to see the potential effects magnetic fields may have
on intraoral tissues.
Linder-Aronson and Lindskog exposed cultured human
periodontal fibroblasts in a static magnetic field for five
weeks and found significantly and progressively impaired
attachment and growth.53
They concluded that a static
magnetic field itself is capable of influencing vital cell
functions but did not rule out the possibility of corrosion
products contributing to the cytotoxic and biological
effects.53
Conversely, Bondemark et al. found short-term exposure
to a static magnetic field in vitro did not cause any
cytotoxic effect on the cells.48
Researchers examining
human cultured cells and found that static magnetic fields
had no effect on cell morphology, cell growth, DNA content,
or DNA synthesis.54
17
Animal studies have shown negligible effects of
magnetic fields on surrounding tissue.55-57
When magnetic
appliances were placed in dogs for six months, no evidence
of tissue damage was observed clinically and
microscopically.57
Linder-Aronson and Lindskog examined tissue response
of magnets placed in monkeys for space closure and found a
lack of tissue effects of the magnets in respect to cell
and tissue reactions.55
They concluded that there were
negligible clinical side effects of orthodontic magnets.55
Szabo et al. examined tissue reactions of cobaltsamarium magnets by implanting them into the skulls of dogs
and pigs.56
Upon histological examination, they found
magnetic fields did not give rise to any tissue changes.56
There have been few in vivo studies done on the
effects of magnetic fields.
When human dental pulps and
gingival tissues were examined after exposure to static
magnetic fields in seven individuals, no change was
observed in the dental pulps or gingival tissues adjacent
to the magnets.58
Saygili et al. examined the effects of
magnetic fields on neighboring capillary circulation in 10
subjects and found that there was no effect on blood flow
when dental magnets were used.59
18
The evidence currently available from biological
safety testing suggests that the conceivable risks of
biological harm are neglible.41,
44
Statement of Thesis
This study is a prospective study to determine whether
patients with a MagneTainer™ have better periodontal health
when compared to patients bonded with traditional fixed
lingual retainers on the lower anterior teeth.
were gathered for this study.
Two samples
The first sample contained
32 patients that have the MagneTainer™ in place.
The
second sample contained 33 patients with bonded canine-tocanine fixed lingual retainers.
Periodontal health was evaluated on all patients using
a gingival index, plaque index, calculus index, and probing
depths.
All patients were given a questionnaire relating
to their oral hygiene habits.
The dependent variable was
the periodontal health of the patients.
The alternate hypothesis is that there will be a
difference in periodontal health in the MagneTainer™ group
when compared to the conventional bonded lingual retainer
group.
The null hypothesis is that there will be no
difference between these two groups.
19
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retainers. J Clin Orthod. 1998;32(2):95-7.
27.
Demir A, Babacan H, Nalcaci R, Topcuoglu T. Comparison
of retention characteristics of Essix and Hawley
retainers. Korean J Orthod. 2012;42(5):255-62.
28.
Valiathan M, Hughes E. Results of a survey-based study
to identify common retention practices in the United
States. Am J Orthod Dentofacial Orthop.
2010;137(2):170-7; discussion 7.
29.
Kacer KA, Valiathan M, Narendran S, Hans MG. Retainer
wear and compliance in the first 2 years after active
orthodontic treatment. Am J Orthod Dentofacial Orthop.
2010;138(5):592-8.
30.
Artun J, Spadafora AT, Shapiro PA. A 3-year follow-up
study of various types of orthodontic canine-to-canine
retainers. Eur J Orthod. 1997;19(5):501-9.
31.
Edman Tynelius G, Petren S, Bondemark L, LiljaKarlander E. Five-year postretention outcomes of three
retention methods--a randomized controlled trial. Eur
J Orthod. 2015;37(4):345-53.
32.
Renkema AM, Renkema A, Bronkhorst E, Katsaros C. Longterm effectiveness of canine-to-canine bonded flexible
spiral wire lingual retainers. Am J Orthod Dentofacial
Orthop. 2011;139(5):614-21.
22
33.
Dahl EH, Zachrisson BU. Long-term experience with
direct-bonded lingual retainers. J Clin Orthod.
1991;25(10):619-30.
34.
Loe H, Silness J. Periodontal Disease in Pregnancy. I.
Prevalence and Severity. Acta Odontol Scand.
1963;21:533-51.
35.
Silness J, Loe H. Periodontal disease in preganancy.
II. Correlation between oral hygiene and periodontal
condition. Acta Odontol Scand. 1964;22:121-35.
36.
Loe H. The Gingival Index, the Plaque Index and the
Retention Index Systems. J Periodontol.
1967;38(6):Suppl:610-6.
37.
Booth FA, Edelman JM, Proffit WR. Twenty-year followup of patients with permanently bonded mandibular
canine-to-canine retainers. Am J Orthod Dentofacial
Orthop. 2008;133(1):70-6.
38.
Heier EE, De Smit AA, Wijgaerts IA, Adriaens PA.
Periodontal implications of bonded versus removable
retainers. Am J Orthod Dentofacial Orthop.
1997;112(6):607-16.
39.
Pandis N, Vlahopoulos K, Madianos P, Eliades T. Longterm periodontal status of patients with mandibular
lingual fixed retention. Eur J Orthod. 2007;29(5):4716.
40.
Johnsson AC, Tofelt LN, Kjellberg H. Subjective
evaluation of orthodontic treatment and potential side
effects of bonded lingual retainers. Swed Dent J.
2007;31(1):35-44.
41.
Noar JH, Evans RD. Rare earth magnets in orthodontics:
an overview. Br J Orthod. 1999;26(1):29-37.
42.
Ravindran KV. Review Article: Role of magnets in
orthodontics—a review. Indian J Dent. 2011;2:147-55.
43.
Bondemark L, Kurol J, Wennberg A. Biocompatibility of
new, clinically used, and recycled orthodontic
samarium-cobalt magnets. Am J Orthod Dentofacial
Orthop. 1994;105(6):568-74.
23
44.
Sukh R, Tandon P, Singh A, Singh GP. Role of Magnets
in Orthodontics and Dentofacial Orthopedics: A
Comprehensive Review. Trends in Biomaterials &
Artificial Organs. 2013;27(3):131-7.
45.
Evans RD, McDonald F. Effect of corrosion products
(neodymium iron boron) on oral fibroblast
proliferation. J Appl Biomater. 1995;6(3):199-202.
46.
Drago CJ. Tarnish and corrosion with the use of
intraoral magnets. J Prosthet Dent. 1991;66(4):536-40.
47.
Kitsugi A, Okuno O, Nakano T, Hamanaka H, Kuroda T.
The corrosion behavior of Nd2Fe14B and SmCo5 magnets.
Dent Mater J. 1992;11(2):119-29.
48.
Bondemark L, Kurol J, Wennberg A. Orthodontic rare
earth magnets--in vitro assessment of cytotoxicity. Br
J Orthod. 1994;21(4):335-41.
49.
Yiu EY, Fang DT, Chu FC, Chow TW. Corrosion resistance
of iron-platinum magnets. J Dent. 2004;32(6):423-9.
50.
Hopp M, Rogaschewski S, Groth T. Testing the
cytotoxicity of metal alloys used as magnetic
prosthetic devices. J Mater Sci Mater Med.
2003;14(4):335-45.
51.
Mancini GP, Noar JH, Evans RD. The physical
characteristics of neodymium iron boron magnets for
tooth extrusion. Eur J Orthod. 1999;21(5):541-50.
52.
Noar JH, Wahab A, Evans RD, Wojcik AG. The durability
of parylene coatings on neodymium-iron-boron magnets.
Eur J Orthod. 1999;21(6):685-93.
53.
Linder-Aronson A, Lindskog S. Effects of static
magnetic fields on human periodontal fibroblasts in
vitro. Swed Dent J. 1995;19(4):131-7.
54.
Sato K, Yamaguchi H, Miyamoto H, Kinouchi Y. Growth of
human cultured cells exposed to a non-homogeneous
static magnetic field generated by Sm-Co magnets.
Biochim Biophys Acta. 1992;1136(3):231-8.
55.
Linder-Aronson A, Lindskog S, Rygh P. Orthodontic
magnets: effects on gingival epithelium and alveolar
bone in monkeys. Eur J Orthod. 1992;14(4):255-63.
24
56.
Szabo G, Miklos L, Suba Z, Csendes P. Long-term tissue
tolerance of titanium-encapsulated cobalt-samarium
implants. J Long Term Eff Med Implants. 1992;1(4):34755.
57.
Cerny R. The reaction of dental tissues to magnetic
fields. Aust Dent J. 1980;25(5):264-8.
58.
Bondemark L, Kurol J, Larsson A. Human dental pulp and
gingival tissue after static magnetic field exposure.
Eur J Orthod. 1995;17(2):85-91.
59.
Saygili G, Aydinlik E, Ercan MT, Naldoken S, Ulutuncel
N. Investigation of the effect of magnetic retention
systems used in prostheses on buccal mucosal blood
flow. Int J Prosthodont. 1992;5(4):326-32.
25
Chapter 3:
Journal Article
Abstract
Introduction:
Orthodontists have struggled with stability
and retention after orthodontic treatment, especially in
the lower anterior region.
The MagneTainer™ is a new
retainer design that utilizes magnets bonded to the lower
anterior teeth and is an alternative to traditional fixed
lingual retainers.
It is bonded on all the marginal ridges
from the mesial of the lower canine to the mesial of the
contralateral canine to maintain the alignment of the lower
anterior teeth and allows patients to floss straight down
the contact without any additional flossing auxiliaries.
Purpose:
The purpose of this study is to compare the
periodontal health of the lower anterior teeth retained
with the MagneTainer™ versus a conventional fixed lingual
retainer.
Materials and Methods:
The periodontal health
of 32 patients bonded with the MagneTainer™ and 33 patients
bonded with conventional fixed lingual retainers were
evaluated utilizing a modified Gingival Index, modified
Plaque Index, modified calculus index, and probing depths.
A questionnaire was also given to each individual to assess
their oral hygiene habits.
Results:
There were no
significant differences in the GI Score, PI Score, Calculus
Score, brushing frequency, and flossing frequency between
26
the two groups.
More patients found it easier to floss
with the MagneTainer™ than the conventional bonded lingual
retainer.
Conclusions:
There were no differences in the
periodontal health between the two groups.
Patients with
the MagneTainer™ found it easier to floss, however, it did
not result in them flossing more.
27
Introduction
Orthodontic supervision does not end once the
appliances have been removed.
Orthodontists and patients
alike are concerned about the anticipated degree of
stability following active orthodontic treatment, and it
has been suggested that lifetime retention is necessary to
maintain satisfactory alignment after treatment in many
patients.1
Perfect alignment after orthodontic treatment is
unrealistic over a lifetime and relapse is unavoidable.
The orthodontic literature has shown that relapse
following orthodontic treatment is unpredictable.1-4
The
challenge that many orthodontists find in retention is that
it is impossible to predict which cases will undergo
relapse and to what degree it will occur.5
The words
relapse, physiologic recovery, rebound, post-retention
settling, and other similar terms have been used by
orthodontic practitioners to describe the changes that
occur after orthodontic appliances have been removed.6
Longitudinal studies have shown that during the posttreatment period, there is a trend towards decreased arch
length, decreased arch width, increased overbite, increased
overjet, and increased mandibular anterior crowding.1,
6-9
Sinclair and Little examined untreated cases from the
mixed-dentition to early adulthood and found a decrease in
28
arch length, a small decrease in inter-canine width,
minimal change in intermolar width, minimal change in
overjet and overbite, and an increase in incisor
irregularity.6
Blake and Bibby examined 15 potential
factors of stability including arch form, periodontal
tissues, mandibular incisor dimensions, neuromusculature
balance, growth, post-treatment results, third molars,
original malocclusion, extraction treatment, expansion, and
non-extraction treatment.10
They concluded that
orthodontist should aim to remove the primary burden of
preventing relapse from the patient by maintaining
treatment goals that follow well-documented principles.10
Even though there are many studies describing possible
pre-treatment factors leading to relapse, most attempts
have been unsuccessful at showing any reliable predictors
of stability.11-13
Despite orthodontists’ best efforts, the
best way to maintain satisfactory alignment post-treatment
is through an indefinite period of retention.1
Relapse can occur anywhere in the dentition, but one
of the more evident areas of potential instability is the
lower anterior region.14-16
Long-term retention of the lower
labial segment is necessary to prevent unwanted posttreatment changes, and bonded lower lingual retainers have
29
been utilized to maintain the alignment of the lower
anterior teeth.17
Fixed lingual retainers have the advantages of being
esthetically pleasing, virtually free of patient
compliance, and reliable as part of the retention phase.
Many studies have found that they are effective at
maintaining incisor alignment post-treatment.18-21
The major disadvantages of fixed lingual retainers
include the time consuming procedure, bond failures, stress
fractures, and the tendency for plaque and calculus
accumulation.18
Since the wire of a fixed lower retainer
transverses the lingual surfaces of the mandibular anterior
teeth, flossing and brushing can be more difficult.
The
result is a tendency for plaque and calculus to build up in
the area of the retainer.22-25
A new form of fixed lingual retainer called the
MagneTainer™ (Ft. Wayne, USA) is being introduced as an
alternative to traditional fixed lingual retention.
The
MagneTainer™ was developed by Drs. Gene and Aron Dellinger
of Ft. Wayne, Indiana.
The MagneTainer™ utilizes neodymium
iron boron magnets that are gold plated and sealed inside a
stainless steel cover.
They are bonded on all the marginal
ridges from the mesial of the lower canine to the mesial of
the contralateral canine and allows patients to floss
30
straight down the contact without any additional flossing
auxiliaries. The MagneTainer™ has been shown to be as
effective as a conventional fixed lingual retainer in
maintaining incisor alignment at two years post-retainer
placement.26
Rare earth magnets were developed in the 1970s and are
known for their high coercivity and small size.27,
28
The
two main types of rare earth magnets are samarium cobalt
magnets and neodymium iron boron magnets.
Orthodontics has
utilized rare earth magnets in a variety of ways that
includes treatment of unerupted teeth, tooth movement along
arch wires, expansion, correction of anterior open bites,
and functional appliances.27
Various studies have been done
to test the biological safety of magnets by examining the
effects of their corrosion products and magnetic fields.28-43
The evidence currently available from biological safety
testing suggests that the conceivable risks of biological
harm are negligible as long as the magnets are isolated
from the intraoral environment either by being coated or
encased in a protective casing.27-43
With the trend of using fixed lingual retainers for
long-term retention, it is important to understand the
effects that they have on the periodontal tissues
surrounding the teeth.
The purpose of this study is to
31
compare the periodontal health of the mandibular anterior
teeth retained with the MagneTainer™ versus a conventional
fixed lingual retainer.
Materials and Methods
There were two groups for this study: a MagneTainer™
group and a conventional fixed lingual retainer group.
The
MagneTainer™ group was from Dr. Aron Dellinger’s
orthodontic practice in Ft. Wayne, Indiana.
The
conventional fixed lingual retainer group was acquired from
Saint Louis University Center for Advanced Dental Education
(St. Louis, MO) and Dr. Randall Brown’s orthodontic
practice (Evansville, IN).
The following inclusion criteria were used:
lingual
fixed retention, no cavities or restorations on mandibular
anterior teeth, no dental cleaning within one month, and
absence of smoking habits.
A total of 65 patients
participated in the study.
The conventional fixed lingual
retainer group had 33 patients and the MagneTainer™ group
had 32 patients.
All patients were seen at 2 months or
more after orthodontic appliances have been removed.
The
fixed lingual retainer group had lingual retainers bonded
on the canines.
The periodontal health of the lower anterior teeth
(canine to canine) was evaluated by one-examiner utilizing
32
a modified Gingival Index, modified Plaque Index, modified
calculus index, and probing depths.
Measurements were done
on each tooth in the following gingival six areas:
mesiobuccal (MB), buccal (B), distobuccal (DB),
mesiolingual (ML), lingual (L), and distolingual (DL).
An adaptation of Loe and Silness’s Gingival Index was
used to determine the GI score of each patient.44
tooth was measured at the six gingival areas.
Each
Each of the
six gingival areas were assigned a score from 0-3 based on
the criteria for the Gingival Index system as seen in Table
3.1.
The average of the scores of the six areas of a tooth
gave the GI for the tooth.
The average of all the GI’s of
the individual teeth examined gave the GI for the
individual.
An adaptation of Silness and Loe’s Plaque Index system
was used to determine the PI score of each patient.45
The
individual locations, individual teeth, and overall
individual scores were calculated similar to that of the
Gingival Index system.
The criteria for the Plaque Index
system can be seen in Table 3.2.
33
Table 3.1: Criteria for the Gingival Index System adapted
from Loe and Silness44
Criteria for the Gingival Index System
Score
0
Description
Normal gingiva
1
Mild inflammation – slight change in color,
slight edema. No bleeding on probing
2
Moderate inflammation – redness, edema and
glazing. Bleeding on probing
3
Severe inflammation – marked redness and edema,
ulceration. Tendency to spontaneous bleeding
Table 3.2: Criteria for the Plaque Index System adapted
from Silness and Loe45
Criteria for the Plaque Index System
Score
Description
0
No plaque in gingival area
1
A film
margin
plaque
across
2
Moderate accumulation of soft deposits within the
gingival pocket, on the gingival margin, and/or
adjacent tooth surface, which can be seen by the
naked eye.
3
Abundance of soft matter within the gingival
pocket and/or on the gingival margin and adjacent
tooth surface
of plaque adhering to the free gingival
and adjacent area of the tooth. The
may only be recognized by running a probe
the tooth surface
An adaptation of the Calculus Surface Index as
described by Ennever et al. was used for calculus
assessment.46
The total number of surfaces on which
calculus was detected will be the patient’s calculus score.
Probing depths were done from lower canine to lower
canine using a number 12 UNC periodontal probe.
34
Probing
depths were measured at the six gingival areas of each
tooth.
A questionnaire was given to each patient that related
to his or her oral hygiene habits (see Figure A1).
The
patients were asked how often they brushed per day, how
often they flossed, and if they found it difficult to
floss.
Error Study
Three patients were selected at random from the
control group and four patients were selected at random
from the experimental group to be re-measured.
All
variables in both samples had intra-class correlation
values of 90% or above.
Statistical Analysis
Independent samples Mann-Whitney U tests were done
using SPSS® software (IBM Corporation, Armonk, New York).
These tests were used to determine if there were any
differences between the two groups in regards to Gingival
Index Score, Plaque Index Score, Calculus Index, brushing
frequency, and flossing frequency.
An independent samples
Mann-Whitney U test was done to compare flossing difficulty
with Gingival Index Score, Plaque Index Score, Calculus
Index, brushing frequency, and flossing frequency.
Independent t-tests were used to compare the probing depths
35
between both groups.
Spearman’s correlation coefficients
were measured to determine the relationship between all
variables.
Results
The mean of values of the GI score, PI score, Calculus
score, brushing frequency, and flossing frequency can be
seen in Table 3.3. There were no significant differences in
the GI score, PI score, Calculus score, brushing frequency
per day, and flossing frequency per day across the two
retainer groups.
The results of these tests can be seen in
Table 3.4.
Table 3.3 Mean, standard deviation, and standard error of
the mean for the GI score, PI score, Calculus score,
flossing frequency per day, and brushing frequency per day.
Group
Mean
Standard
Std Error
Deviation
mean
Conventional
1.131
0.541
0.094
GI Score
Magnetainer™
0.940
0.441
0.078
Conventional
0.836
0.500
0.087
PI Score
Magnetainer™
0.688
0.372
0.066
Conventional
3.270
7.686
1.338
Calculus
Magnetainer™
2.380
4.210
0.744
Conventional
0.481
0.710
0.123
Flossing
Magnetainer™
0.358
0.428
0.076
Brushing
Conventional
1.850
0.508
0.088
Magnetainer™
1.880
0.609
0.108
36
Table 3.4 Independent samples Mann-Whitney U test were used
to compare the two retainer groups with GI score, PI score,
Calculus Index, flossing frequency per day, and brushing
frequency per day.
Significance
GI Score
0.152
PI Score
0.265
Calculus Score
0.819
Brushing Frequency
0.775
Flossing Frequency
0.612
*
Tests were significant with a p-value of ≤0.05
When patients were asked if they found it difficult to
floss with their retainers, 84% of the MagneTainer™ group
found it not difficult while 30% of the conventional bonded
lingual retainer group found it not difficult.
seen in Table 3.5.
This can be
There was a significant difference in
the Plaque Index and flossing frequency per day when they
were compared with the perception of flossing difficulty by
the patient (see Table 3.6).
Table 3.5 The frequency of patients reporting whether or
not they found it difficult to floss
n
Difficult
Not Difficult
Conventional
33
23 (70%)
10 (30%)
Magnetainer™
32
5 (16%)
27 (84%)
37
Table 3.6 Independent samples Mann-Whitney U test were used
to compare the difficulty of flossing with GI score, PI
score, Calculus Index, flossing frequency per day, and
brushing frequency per day.
Significance
GI Score
.064
PI Score
.001*
Calculus Score
.504
Flossing Frequency
.047*
Brushing Frequency
.522
*
Tests were significant with a p-value of ≤0.05
The correlations for the variables can be seen in
Table 3.7.
The GI score was highly correlated with both
the PI score and flossing frequency.
The frequency of
flossing per day was slightly correlated with the GI score
and the PI score.
The difficulty of flossing was
correlated with the frequency of flossing and plaque score.
Table 3.7 Spearman’s correlation used to find relationships
among GI score, PI score, Calculus score, flossing
frequency per day, and brushing frequency per day.
GI
GI
PI
Calculus
Brushing
Flossing
*
Correlation
Significance
Correlation
Significance
Correlation
Significance
Correlation
Significance
Correlation
Significance
PI
.654
< .001*
1
.654
<.001*
.109
.552
-.343
.054
-.538
.001*
1
.166
.363
-.162
.377
-.427
.015*
Calc
.109
.552
.166
.363
1
.018
.920
.117
.616
Tests were significant with a p-value of ≤0.05
38
Brush
-.343
.054
-.162
.377
.018
.920
1
.364
.041*
Floss
-.538
.001*
-.427
.015*
.092
.616
.364
.041*
1
There were significant differences in the probing
depths for the following sites:
L, LL2-L, LR3-ML, LR3-L.
LL1-B, LR1-MB, LR3-B, LL3-
These results can be seen in
Table 3.8.
Tables 3.8 Independent t-tests were used to compare the
probing depths between both groups. Significant results
shown.
Group
Mean
Standard
Std Error Sig.
Deviation mean
Conventional
1.33
.479
.083
.047
LL1-B
Magnetainer™
1.13
.336
.059
Conventional
1.67
.540
.094
.021
LR1-MB
Magnetainer™
2.03
.695
.123
Conventional
1.67
.479
.083
.030
LR3-B
Magnetainer™
1.41
.499
.088
Conventional
1.52
.508
.088
.037
LL3-L
Magnetainer™
1.25
.508
.090
Conventional
1.52
.508
.088
.005
LL2-L
Magnetainer™
1.19
.397
.070
Conventional
2.03
.467
.081
.027
LR3-ML
Magnetainer™
1.78
4.20
.074
Conventional
1.58
.502
.087
< .001
LR3-L
Magnetainer™
1.16
.369
.065
Discussion
The periodontal health of the lower incisors and
canines were determined by utilizing a Gingival Index,
Plaque, and Calculus Index.
When these were compared for
each retainer group, there were no significant differences
between the conventional bonded lingual retainer group and
the MagneTainer™ group.
The type of retainer did not make
39
a difference in the overall periodontal health of the
patient.
The GI score and PI score were correlated with
flossing frequency.
The more the patients flossed, the
better their GI scores and PI scores were.
There was no
significant difference between the brushing habits between
both groups, however, this does not take into account how
well patients brush.
Better oral hygiene resulted in
better periodontal health regardless of the type of
retainer.
There were significant differences in probing depths
at six locations.
None of these differences were greater
than 0.5 mm when comparing the means.
These differences
can be considered clinically insignificant.
Patients with the MagneTainer™ in place found that it
was less difficult to floss than those with the
conventional fixed lingual retainer, however, patients with
the MagneTainer™ did not floss more often than those with
conventional fixed lingual retainers.
Periodontal health
was more dependent on the patient and their willingness to
brush and floss rather than the retainer type.
The MagneTainer™ makes it easier for the patient to
floss, however, it does not encourage patients to floss
more.
As a result, there were no significant differences
40
in Gingival Index, Plaque Index, and Calculus Index between
the conventional fixed lingual retainer group and the
MagneTainer™ group.
Conclusion
1. There were no significant differences in GI score, PI
score, and calculus score between the conventional
bonded lingual retainer group and the MagneTainer™
group. Thus there were no differences in periodontal
health between the two groups.
2. GI score and PI score were correlated with flossing
frequency
3. Patients with the MagneTainer™ found it less difficult
to floss than those with the conventional bonded
lingual retainer.
4. There was no significant difference in flossing
frequency per day between the MagneTainer™ group and
the conventional bonded lingual retainer group.
41
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APPENDIX
Figure A1: Questionnaire given to patients
regarding oral hygiene habits
47
VITA AUCTORIS
Don Dau was born in Portland, Oregon on November 29th,
1986 and was raised in Tampa, Florida.
brother and a younger sister.
He has an older
Don attended the University
of South Florida and graduated with a Bachelor of Science
in Interdisciplinary Natural Sciences in 2009.
Don
graduated dental school from the University of Florida in
2013.
He began his orthodontic training at Saint Louis
University in 2013.
48