Download Periodontal rationale for transverse skeletal normalization

CONTINUING EDUCATION
Periodontal rationale for transverse skeletal
normalization
Drs. Ryan K. Tamburrino, Shalin R. Shah, and Daniel L.W. Fishel strive to objectively measure and optimize
the skeletal transverse dimension
T
he goals of orthodontic treatment
are well established for the sagittal
and vertical dimensions in terms of how
the teeth and jaws should relate, fit, and
work together. Diagnostic and treatment
strategies focusing on these dimensions
are the topic of many orthodontic
symposiums, conferences, and research
papers.
However,
the
transverse
dimension is often missing from generally
accepted and performed patient analyses
and discussions. Additionally, well-defined
criteria for determining if there is a need
for correction based on objective means,
instead of subjective, frequently are not
used.
As there are treatment goals for the
final tooth positions based on sagittal and
vertical skeletal dimensions, there must be
a set of defined goals for the transverse. For
the posterior teeth, these would be to have
them upright and centered in the alveolus
Educational aims and objectives
The aim of this article is to discuss treatment goals to optimize the skeletal
transverse dimension.
Expected outcomes
Orthodontic Practice US subscribers can answer the CE questions on page
XX to earn 2 hours of CE from reading this article. Correctly answering the
questions will demonstrate the reader can:
• Identify the skeletal transverse discrepancy.
• Gain an understanding of the numerical measurement relationships for
the width of the maxilla or the mandible.
• Realize potential compromise to the periodontium resulting from
certain tooth movements in the presence of a skeletal disharmony.
• Realize the consequences of attempted tooth position normalization,
without skeletal correction, and their effect on long-term periodontal
viability.
• Realize that over time and in susceptible patients, some negative
sequelae may occur depending upon certain factors.
• Recognize the importance of objectively measuring and optimizing
the skeletal transverse dimension in conjunction with comprehensive
orthodontic treatment whenever possible.
Ryan K. Tamburrino, DMD, a native of
Pittsburgh and co-founder of the Center for
Orthodontic Excellence, graduated from Duke
University with a double major in biomedical
engineering and mechanical engineering/
materials science. He then attended the University of
Pennsylvania for dental school and stayed an additional
2 years for specialty training in orthodontics. During
his orthodontic training, Dr. Tamburrino concurrently
completed additional training in advanced orthodontic
diagnosis, functional occlusion, and TMJ health with
the AEO/Roth-Williams Group and the Andrews™ Six
Elements courses.
Shalin Raj Shah, DMD, MS, received his
Certificate of Orthodontics and Masters of
Science in Oral Biology from the University
of Pennsylvania and is a Diplomate of
the American Board of Orthodontics. He
is also a graduate of the University of Pennsylvania
College of Arts and Sciences and School of Dental
Medicine. Currently, Dr. Shah is Clinical Associate of
Orthodontics at the University of Pennsylvania and is
in private practice (Center for Orthodontic Excellence)
in Princeton Junction, New Jersey, and Philadelphia,
Pennsylvania.
Daniel L.W. Fishel, DMD, is a dual-trained
specialist in orthodontics and periodontics.
He maintains multiple practices in south
central Pennsylvania. His practice philosophy
focuses on providing orthodontic results that
decrease periodontal susceptibility, primary though
skeletal growth modification.
X Orthodontic practice
Figure 1: Ideal posterior dental treatment goals — teeth upright and centered in the
alveolus, and well-intercuspated
in addition to being well-intercuspated with
proper arch coordination, as shown in
Figure 1.
When there is a skeletal transverse
discrepancy, oftentimes this is recognized
by a posterior dental crossbite. However,
many times there is no posterior dental
crossbite, but the maxillary posterior
teeth are tipped buccally, and mandibular
posterior teeth are inclined lingually to
compensate for the skeletal disharmony.
This compensated dental arrangement
opens the patient to a higher likelihood for
non-working interferences from plunging
palatal cups, centric prematurities,
and functional shifts, in addition to
placing off-axis forces on the dentition.
“Decompensation,” which uprights and
centers the teeth in the alveolus, then
reveals the underlying “skeletal crossbite”
and amount of skeletal correction required,
as shown in Figure 2.
Coronal cuts of untreated patients,
where the posterior teeth were upright in
the alveolus, centered in the alveolus, and
well intercuspated were examined for the
Volume 5 Number 3
relationship between the jaws.1 When the
width of the maxilla and mandible were
measured, it was consistently shown that
these “normal” patients, which met the
stated transverse goals, had a maxilla that
was roughly 5 mm wider (measured at MxMx) than the mandible (measured at MGJMGJ), as shown in Figure 3. There is no
exact numerical measurement for the ideal
width of either the maxilla or the mandible.
Instead, every patient is their own “normal”
using the baseline dimension of the
mandibular width. Since the mandibular
basal bone is unable to be affected with
conventional orthodontic means, it is the
orthodontist’s role to then normalize the
maxilla to it. Therefore, the difference of
width between the two, instead of the
baseline jaw dimensions taken individually,
is the important concept. While a difference
of 5 mm is the ideal goal (meaning maxillary
width - mandibular width = 5 mm), the
authors feel comfortable with dentally
camouflaging a skeletal difference of 2-5
mm. Any differences < 2 mm (meaning
the maxilla has smaller width compared
to what should be ideal for a that patient’s
mandible) may benefit from correction via
orthopedic, surgical, or other means, as
deemed appropriate on a case-by-case
basis.
While it is possible to achieve good
uprighting and intercuspation of the
posterior teeth in the presence of a skeletal
disharmony, a risk of doing so is potential
compromise to the periodontium. In an
attempt to upright and well intercuspate the
teeth in the presence of a discrepancy, the
amount of soft tissue and bone overlying the
roots becomes thinner (Figure 4) because
Volume 5 Number 3
Figure 3: Three examples of untreated cases with ideal posterior dental relationships. Note the skeletal
difference between the width of the jaws at the level of the first molar is 5 mm
Figure 4: Cartoon of creating upright and well-intercuspated posterior teeth in the presence
of a transverse skeletal mismatch. Note the reduced thickness of bone/soft tissue on the
buccal portion of the maxillary molar as the discrepancy becomes greater
Figure 5: Example showing posterior teeth uprighting in the presence of a significant
transverse skeletal disharmony of 7 mm. Note loss of attachment. There was buccal
displacement of the teeth and thinning of the attachment when normalizing the dental
archform on an underlying skeletal base disharmony
Orthodontic practice X
CONTINUING EDUCATION
Figure 2: Comparison of an ideal posterior relationship vs. one where a skeletal
transverse discrepancy is present. Decompensation of the teeth reveals the
maxillary skeletal deficiency
CONTINUING EDUCATION
Figure 7: Case example of teeth being buccally tipped to camouflage the skeletal
discrepancy
Figure 6: Examples of cases where no dental crossbite is present, but the clinician can
suspect a camouflaged transverse discrepancy due to the excessive lingual inclination of the
mandibular molars
the teeth will no longer be centered in the
alveolus. In mild discrepancies, the effects
of this dental positioning may not pose a
concern. However, in severe transverse
discrepancies, an attempt to normalize
the posterior dentition inclination and
intercuspation in light of the uncorrected
skeletal disharmony risks root fenestration
and clinically obvious attachment loss, as
shown in Figure 5.
Moderate
skeletal
discrepancies
are the most common missed situation
using just clinical observation and not an
objective analysis. However, a practitioner
can gain an appreciation for where an
underlying skeletal crossbite is present, in
the absence of a dental one, by looking
at the inclinations of the mandibular teeth
(Figure 6).
In these scenarios the consequences
of attempted tooth position normalization,
without skeletal correction, and their effect
on long-term periodontal viability may not be
immediately realized clinically. On debond
it may appear that the posterior teeth were
corrected with just using brackets, crosselastics, or expanded archwires. However,
because no overt attachment loss was
seen during treatment, the practitioner may
wrongly assume that no harm was done
to the patient or the periodontium is viable
and resilient for the long term.
Over time and in a susceptible patient,
as stated above, the gingival attachment
may be less resilient to normal stresses
placed on it due to the reduced bulk of
tissue versus the amount present in a noncompromised patient. There is now a higher
risk for mechanically induced periodontal
tissue loss, especially for those patients
X Orthodontic practice
Figure 8: Comparison of functional and parafunctional loads placed on the dentition7
who may have a thinner tissue biotype at
baseline. Therefore, the negative sequelae
of loss of attachment and recession may
not appear until years or decades later,
depending on the patient’s adaptability,
periodontal biotype, and genetic makeup.2
Anzilotti and Vanarsdall brought this
phenomenon to light.3 In their thesis, it
was suggested that those people who had
skeletal discrepancies more than 5 mm
from the ideal relationship were at a higher
risk for periodontal disease and gingival
recession than those with optimally related
skeletal bases. While there are many
biologic, intrinsic, and extrinsic factors
that lead to periodontal compromise,
thinned tissue will have less resistance
to sustain forces placed on it by normal
mechanical means, such as toothbrushing.
Compounding factors (occlusal trauma,4
biological pathogens,5 and so on), in
addition to a reduced tissue thickness,
may further exacerbate tissue loss.
The Anzilotti paper describes what
happens with attempted normalization
of tooth inclinations on a skeletal base
mismatch. In another scenario where
teeth are tipped to compensate for
a
significant
skeletal
discrepancy,
periodontal consequences can also occur.
Here, posterior teeth are not uprighted
but instead are tipped buccally via crosselastics or archwires in an attempt to
“eliminate the crossbite” or “broaden the
archform,” as shown in Figure 7.
Histological arrangement of the PDL
fibers show that vertical stresses to the
dentition can be well tolerated, but react
to lateral or off-axis forces with much less
resilience.6 For normal masticatory function
Volume 5 Number 3
with vertical chewing strokes, this dental
arrangement may still prove viable as long
as the forces placed on the dentition and
periodontium are physiologic and there is a
normal to thick tissue biotype present.
The threshold to the patient’s level of
periodontal adaptability is reduced when
the teeth are not upright in the alveolus.
Additionally, the potential for adverse effects
to the periodontium is increased when
compromised posterior tooth inclinations
are combined with parafunctional activity.
Okeson describes that the forces generated
through nocturnal parafunction can be 3-4
orders of magnitude higher than what is
generated through normal physiologic
masticatory function (Figure 8).7
In addition to vertical clenching, the
often co-present jaw eccentric motion
of bruxism places lateral forces on the
dentition. As mentioned previously, the
PDL fibers are oriented in such a fashion
so they exert tensile forces (osteoblastic
for orthodontic movement) upon alveolar
bone when a tooth is loaded along its
long axis. However, compressive forces
(osteoclastic for orthodontic movement)
dominate at the alveolar crest when nonaxial or lateral forces are exerted on the
tooth in function and parafunction.6 The
combination of increased force, lateral
direction of stress application, and high
area of stress concentration seen with
a hanging palatal cusp or non-working
interference is the worst combination to
have with in a parafunctionally susceptible
patient who has a reduced resilience of the
periodontium to withstand this stress.
OP
References
1. Simontacchi-Gbologah MS, Tamburrino
RK, Boucher NS, Vanarsdall RL, Secchi AG.
Comparison of Three Methods to Analyze the
Skeletal Transverse Dimension in Orthodontic
Diagnosis [thesis]. Pennsylvania: University of
Pennsylvania; 2010.
2. Vanarsdall RL. Periodontal-orthodontic Interrelationships. In: Graber LM, Vanarsdall RL, Vig
KWL, eds. Orthodontics: Current Principles and
Techniques. 5th ed. St. Louis, MO: Mosby; 2012:
807-843.
3. Anzilotti CL, Vanarsdall RL, Balakrishnan M.
Expansion and Evaluation of Post-Retention
Gingival Recession [thesis]. Pennsylvania:
University of Pennsylvania; 2002.
5. El-Mangoury NH, Gaafar SM, Mostafa YA.
Mandibular anterior crowding and periodontal
disease. Angle Orthod. 1987;57(1):33-38.
6. Carranza FA, Newman GA. Clinical
Periodontology. 8th ed. Philadelphia, PA: W.B.
Saunders Company; 1996.
7. Okeson JP. Management of Temporomandibular
Disorders and Occlusion. 5th ed. St. Louis, MO:
Mosby; 2003.
9. Hayes JL . In search of improved skeletal
transverse diagnosis. Part 2: A new measurement
technique used on 114 consecutive untreated
patients. Orthodontic Practice US. 2010;1(4);34-39.
10. Ricketts RM. Introducing Computerized
Cephalometrics. Rocky Mountain Data Systems;
1969.
11. Andrews LF, Andrews WA. Andrews analysis. In:
Syllabus of the Andrews Orthodontic Philosophy.
9th ed. Six Elements Course Manual; 2001.
8. Tamburrino RK, Boucher NS, Vanarsdall RL,
Secchi AG. The transverse dimension: Diagnosis
and relevance to functional occlusion. Roth
Williams International Society of Orthodontics
Journal. 2010;2(1):11-20.
4. Amsterdam MA, Vanarsdall RL. Periodontal
prosthesis: Twenty-five years in retrospect. Alpha
Omegan. 1975;67(3):8-52.
Volume 5 Number 3
Orthodontic practice X
CONTINUING EDUCATION
Figure 9: Exostosis development on the buccal of the maxillary teeth as a compensatory
adaptation to withstand excessive loading
Knowing this, the body is remarkable,
and often attempts to adapt to support
non-physiologic stresses via development
of exostoses along the buccal cortical
surfaces of the maxillary posterior teeth
and/or lingual cortical surfaces of the
mandibular posterior teeth. Coronal cross
section cuts through the posterior teeth
clearly show this development in Figure 9.
However, in dentistry and orthodontics
in general, we do not have the ability to
test for a patient’s adaptive capacity and
are unable to predict which patients will be
able to develop adaptations to non-optimal
situations and who will not. Especially in
a population whose adaptive capacity is
poor or compromised, continued nonphysiologic stress to the area can lead to
tooth mobility, secondary occlusal trauma,
and further attachment loss.4
The bottom line is that we do not
know which patients can withstand
transverse camouflage, and to what
periodontal limit they will be able to tolerate
a dental compromise. The goal, therefore,
is to objectively measure and optimize
the skeletal transverse dimension8,9,10,11
in conjunction with comprehensive
orthodontic treatment whenever possible.