Finite element analysis in orthodontics /certified fixed orthodontic courses by Indian dental academy

APPLICATION OF FINITE
ELEMENT ANALYSIS IN
ORTHODONTICS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

AJO June 1985
• Melvin moss and co workers did a study on
craniofacial growth using FEA.
• FEA differs from traditional cephalometry
in that its descriptions and analyses are
invariant; that is, they are independent of
any method of registration and
superimposition.

• Growth study of the rat skull was done
using two-dimensional FE model.
• cranial structure were considered as
contiguous finite elements.

• In growth the deformations are not due to
stresses but are produced by cell division,
cell growth, and production of extra cellular
matrices (that is, by adding mass).
Accordingly, a growth strain is the
measurable deformation of a biologic body
resulting from its growth.

• It is assumed that the growth description of
any single element is valid for all of the
points within the continuum of that same
element in the present study of skulls.

• This approximation can be remedied
simply by supplying more detailed input
data.In FEM the finer the discretization of
the body (that is, the smaller the individual
finite elements and the more of them in a
given body), the more closely the resulting
numerical results will approximate the
reality of the growth behavior at each point.

• Growth tensors are used to describe
displacement occurring due to growth at
any node.It may be regarded as specifying a
transformation of coordinates from one
stage of growth to another.

• intersphenoidal synchrondrosis, basion, tip of the
external occipital crest,bregma,anterior nasal
point,prosthion,tip of the maxillary palatal
alveolar crest,tip of the maxillary incisor tooth,tip
of the mandibular incisor tooth,infradentale (tip of
labial mandibular alveolar crest),tip of lingual
mandibular alveolar crest,menton (tip of mental
protuberance,gonion and condylion.

• Three-noded, triangular, finite elements were
selected for rat skull.
• Finite element methods are able to provide, for the
first time, absolute quantitative descriptions of
cranial skeletal shape and shape change with local
growth significance, independent of any external
frame of reference, and, by so doing, eliminate the
principal source of methodological error in
customary roentgenographic cephalometry.

• Finite element methods uniquely describe
growth locally. This is to be understood as
stating that, given the coordinate
information defining the location of the
nodes of a series of individual finite
elements at successive times, the FEM
provides an invariant description of the
time-related shape changes of each finite
element of a given structure independently
of the coordinate system used and referred
to its own initial boundaries.www.indiandentalacademy.com

AJO DEC 1987
• Three-dimensional finite element analysis for
stress in the periodontal tissue by orthodontic
forces done by Kazuo Tanne and coworkers.
• The force systems that are used on an orthodontic
patient can be complicated. FEM makes it possible
to analytically apply various force systems at any
point and in any direction.

• A three-dimensional finite element model
was constructed on the average anatomic
shape of the Japanese first premolar. This
model was divided into 240 isoparametric
elements under the preprocessing check of
SUPERB, which was the three-dimensional
analysis program.

• Buccolingually directed forces were
analytically applied at the midpoint of the
buccal surface of the crown.
• The stresses were determined at the surface
of the root and the alveolar bone. In
addition, stress was defined midway in the
PDL. These stresses were established at
four occlusogingival levels.

• During tipping movement, stresses
nonuniformly varied with a large difference
from the cervix to the apex of the root. On
the other hand, in case of movement
approaching translation, the stresses
induced were either tensile or compressive
at all occlusogingival levels with some
difference of the stress from the cervix to
the apex.

AJO dec 1995
• Ceramic bracket design: An analysis using
the finite element method done by
Joydeep Ghosh, R.S.Nanda and coworkers.
• This investigation was designed to generate
finite element models for selected ceramic
brackets and graphically display the stress
distribution in the brackets when subjected
to arch wire torsion and tipping forces.

• Three-dimensional computer models of the
brackets were constructed and loading
forces, similar to those applied by a
stainless steel arch wire in torsion and
tipping necessary to fracture ceramic
brackets, were applied to the models. Stress
levels were recorded at relevant points
common among the various brackets.

• High stress levels were observed at areas of abrupt
change in geometry and shape.The brackets with
an isthmus connecting the wings seemed to resist
stresses better than the one bracket that did not
have this feature.The Starfire bracket ("A"
Company, San Diego, Calif.) showed high stresses
and irregular stress distribution, because it had
sharp angles, no rounded corners, and no isthmus.

FEA CAN ALSO BE APPLIED
TO STUDY
• Orthopedic forces.
• Bone modeling.
• Changes in soft tissue profile.
• Bond strengths and Debonding forces.
• Mechanics of appliances.
• Cephalometric analysis.

• Biomechanical effect of anteriorly directed
extraoral forces on the craniofacial
complex: A study using the finite element
method
• Kazuo Tanne and coworkers.
• 1989 March AJO.

• This study was designed to investigate the
biomechanical effect of protractive maxillary
orthopedic forces on the craniofacial complex by
use of the three-dimensional finite element method
(FEM). The three-dimensional FEM model was
developed on the basis of a dry skull of a young
human being. The model consisted of 2918 nodes
and 1776 solid elements.

• An anteriorly directed 1.0-kg force was
applied on the buccal surfaces of the
maxillary first molars in both a horizontal
parallel direction and a 30° obliquely
downward direction to the functional
occlusal plane.

• The nasomaxillary complex showed a
forward displacement with upward and
forward rotation in a horizontal protraction
case, whereas a downward force produced
almost translatory repositioning of the
complex in an anterior direction. High
stress levels were observed in the
nasomaxillary complex and its surrounding
structures. www.indiandentalacademy.com

• The role of the periodontal ligament in bone
modeling: The initial development of a
time-dependent finite element model
• John Middleton, Malcolm Jones,Adrian
Wilson.
• 1996 Feb AJO.

• In this study, the stresses and strains within
the periodontal ligament and surrounding
bone, consequent to orthodontic loading of
a tooth, were investigated by application of
the finite element method.

• The results suggest that the remodeling process
may be controlled by the periodontal ligament
rather than the bone. In the finite element model,
bone was found to experience a low strain of 1 ×
10-5, whereas the periodontal ligament
experienced a strain of 0.1 when the "tooth model"
is loaded. This value is above the threshold
necessary to initiate the remodeling process.

• An evaluation of the changes in soft-tissue
profile form induced by orthodontic therapy
• C. L. B. Lavelle and Roberto S. Carvalho.
• 1989 Dec AJO.

• In view of the growing concensus that
traditional cephalometric appraisals yield
data of dubious scientific value, the changes
in soft-tissue profile forms were evaluated
by FEM. This involved dividing the soft-
tissue profile form into a series of triangular
finite elements.

• the changes in soft-tissue profile form were
evaluated by computing the degree of
distortion in each triangle after treatment
(target element) compared with the triangle
before treatment (reference element) in
terms of specific size and shape parameters.

• In a comparison of samples of patients with
Class I and II malocclusion, varying
patterns of facial profile change were noted,
depending on the parameters analyzed. The
results, therefore, showed that although
such technique offers great cephalometric
potential, further investigation is required to
identify more appropriate points.

• Use of Finite Element Analysis in
Assessing Stress Distribution During
Debonding
• P. EMILE ROSSOUW, EUGENE
TERBLANCHE.
• 1995 Nov JCO.

The present study was designed
to:
• 1. Evaluate stress distribution around
orthodontic attachments during debonding
with various types of forces.
• 2. Develop recommendations for bonding in
clinical practice.
• 3. Generate a computer model for testing
bonding and debonding procedures in the
laboratory.

• To develop a finite element model of a
tooth, a human canine was meshed from
dentin to enamel. An average buccal tooth
curvature was calculated for the model.

• A composite resin (Concise) and a stainless
steel bracket (Ormesh) were added to the
model, including material properties such as
the yield stress of the composite, Young's
modulus of elasticity, etc.

• Stresses induced by edgewise appliances in
the periodontal ligament – a finite element
study
• By Niall McGuinness and coworkers.
• Angle orthodontist 1992 vol 1.

• Finite element technique was used to
determine the stress induced in the
periodontal ligament in three dimensions
when a maxillary canine tooth is subjected
to an orthodontic force similar to that
produced by an edgewise appliance.

• The maximum stress induced at the cervical
margin of the periodontal ligament was
0.072 N/mm2, while the maximum stress
induced at the level of the apical foramen
was 0.0038 N/mm2. The findings suggest
that even with ‘perfect’ edgewise
mechanics it would be difficult to obtain
canine movement by pure translation or
‘bodily movement.’

• Finite element-based cephalometric analysis
• By Glenn T. Sameshima and Michael
Melnick.
• Angle orthodontist 1994 vol 5.

• The CEFEA program used in the study utilises
the color graphics display of computers to show
size change, shape change, and angle of maximum
change. These are pictured as colored triangles of
clinically relevant regions between pre- and mid-
or post treatment lateral headfilms. The program is
designed to have features of interest in both
clinical practice and research.

THANK YOU
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Finite element analysis in orthodontics /certified fixed orthodontic courses by Indian dental academy

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Finite element analysis in orthodontics /certified fixed orthodontic courses by Indian dental academy