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Functional occlusion and orthodontics: a contemporary approach
FUNCTIONAL OCCLUSION AND ORTHODONTICS:
A CONTEMPORARY APPROACH
Oclusão funcional e ortodontia: uma abordagem contemporânea
Marco A. L. Feres 1
Marines Q. Portella 2
Renata C. L. Feres 3
Abstract
The authors have undertaken a deep review on funcional occlusion, from historical to contemporary
concepts. Also the interrelationship between occlusion and orthodontic treatment was described, proposing
objectives that should be achieved to establish good harmony with the stomatognatic system.
Keywords: Functional occlusion; Orthodontics; Treatment goals.
Resumo
O primeiro objetivo deste trabalho foi realizar uma revisão de literatura sobre oclusão estática e dinâmica,
revisando desde conceitos históricos até os conceitos mais aceitos atualmente. O segundo objetivo foi unir
estes conceitos com o tratamento ortodôntico, definindo, a partir daí, como o ortodontista deve tratar seus
casos, assegurando a harmonia de todo o aparelho estomatognático.
Palavras-chave: Oclusão funcional; Ortodontia; Objetivos de tratamento.
1
2
3
Professor Adjunto, Disciplina de Oclusão, PUCPR; Disciplina de Ortodontia, UFPR; Título de
Notório Saber em Ortodontia, UFPR.
Endereço: Rua Imaculada Conceição, 1.155 - Prado Velho - Curitiba, PR
Especialista em Ortodontia; Mestre em Morfologia Aplicada/DTM
Mestre em Ortodontia.
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Marco A. L. Feres; Marines Q. Portella; Renata C. L. Feres
Evolution of a concept
The word “occlusion” comes from the latin expression occludere which means “ to close”.
According to Galvão (1) this term is related to the
estatic or dynamic arrangements that exist between opposed teeth. Occlusion also means the functional relationships of all components of the mastigatory system, such as bone, TMJ, muscles and
supporting tissues.
Other authors (2,3) state that the initial
concept of occlusion was related to fixed relations
of the jaws, but a correct analysis has to take into
consideration all tissues involved, including the
TMJ, as well as all stimuli that derives from the
oclusal contacts like curve of Spee, cusps height,
condilar guidance and the occlusal plane.
Primary studies on occlusion include the
area of prosthodontics (4, 31) because early specialists needed to know how teeth should get in
contact. Therefore the development of the concepts of occlusion are directed related to the evolution of articulators. Since Phillip Pfaff in Germany
in 1756 (1) has “registered the bite” thus obtaining
plaster models, many other pioneers studied dental contacts through the use of articulators (4,5),
including parameters to the position of the condyles into the fossae and the concept of “balanced
occlusion” .
As time occurred, some of early concepts
became tested principles thus originating philosophies, the main ones consisting of the “balance”
and the “non-balanced” occlusion. The first followed principles of Bonwill (5),Monson (6), Wadsworth (7), Gysi(8) and others, and its main foundation included multiple contacts of opposing teeth both in centric as well as excentric mandibular
movements.
In 1926 a new and organized school of
occlusion was criated, the Gnatological Society of
Califórnia (9, 10), defining gnatology as the science that treats the biology of the masticatory “apparatus” . This masticatory system should be considered as a functional unit, thus providing: 1. the
coincidence between centric relation (CR) and centric occlusion (CO); 2. a well balanced occlusion
during slidind movements, with bilateral multiple
balanced contacts (11).
In 1950 (12), opposed to the “gnatological principle”, eroded the concept of the “long
centric” (12), which would mean freedom of man-
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dibular closure, both in CR or CO, consisting on
the Pankey-Mann Philosophy of Occlusal Reabilitation.
Ramjord and Ash (13) proposed the “functional occlusion” approach meaning an individual
attention to the demands of each patient, emphasizing the health of the masticatory system over
any specific occlusal configuration.
Dawson (14) stablished criteria for an ideal
occlusion running from selective grinding to complete occlusal reconstruction. He recommended
disoclusion in the balance side as well as group
function in the working side.
“Normal” and “ideal” occlusion
Normal occlusion has referenced diagnosis and treatment planning in Orthodontics,
but many times this concept has been misunderstood with ideal occlusion. This late aspect is
seldom seen, thus Profit and Ackermann (15)
prefer the term “imaginary ideal” meaning the
one that provides all physiological functions of
the masticatory system while preserving the health of all structures related. According to Ash
and Ramjord (17), the perfect idea of 138 occlusal contacts of all 32 teeh is rarely founded. In
other study (18) the same authors state that the
concept of normality in any biological system
presupposes a physiological “break” for adaptation around those values that are considered
normal.
Angle (19) has set the normal occlusion conditions with emphasis on the first molar
relationship, stating that the mesiobuccal cusp
of the upper first molars should occlude on the
occlusobuccal groove of the lower first molars.
Graber (20) and Moyers(21) stated that normal
occlusion includes oclusal contacts, teeth alignment and good relationship to the bony structures.
Beyron (22) refers to ideal or optimum
including function, health and confort, not only
esthetics and anatomy.
When summarizing most author’s opinions we come o the conclusion that an “ideal”
occlusion shall pursuit :
• neuromuscular harmony
• oclusal stability
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• health periodontium
• accepted esthetics
• good masticatory function
• normal phonetics
• absence of parafunctional habits
• no TMJ pathological evidence
• oclusal loads distributed along the vertical axis of teeth.
• adequate anterior guidance
• good bilateral balance
• minimum muscular tension plus maximum efficiency.
• minimum dental wearing
During all functions of the masticatory
system, the mandible assumes a variety of positions from centric to excentric movements. In
order to analyse all the aspects involved we
should consider occlusion from maximum intercuspation to all mandibular movements.
Maximum Intercuspal Position (MIP)
According to Lee (23) this position is
reached over 5000 times a day during the masticatory cycle, with occlusal forces varing individually. Okeson (24) states that total force
loaded daily during chewing and deglutition
may reach 8600 kg, decreasing at night.
Orthlieb e Laplanche (25) describes
MIP as the oclusal position with the greatest
interarches contacts with maximum intensity
of isometric contractions. It is important to emphasize that such independs on the position
of the condyles into the glenoid fossae.
Ash and Ramjord (17) describes MIP
as a tooth to tooth relationship, guided by its
occlusal surfaces. This position may vary according to changes in these oclusal surfaces.
The same authors refer to MIP as “intercuspal”,” dental”, “acquired centric” or simply
“habitual centric”. It is important to emphasize that the expression Centric Occlusion (CO)
became elected in the literature when referring to MIP.
Authors (25) focus on the fact that all
teeth should participate of these contacts, while
failure in achieving so may be caused by muscular habits, eruption problems of skeletal imbalance.
Functional occlusion and orthodontics: a contemporary approach
Centric Relation (CR)
It is a key reference to analyse and
reconstruct the masticatory system. It is a
position that is achieved when the operator
takes the condyles and disc to the anterior
wall of the fossae. Such position is disc oriented and is a very useful reference to check or modify interarches relationships.
According to Ash (17) MIP rarely coincides with CR. For some authors (16,26,27)
the best condyle-fossa relationship is the
one achived in CR . During many years, RC
was describe as the most retruded position
of the mandible, from which lateral movements could be undertaken (28, 29, 30, 31)
.
After laminagraph studies (32) this
concept changed dramactically, with outlined condyles well seated into the fossae.
Later on, Dawson (33) defined CR as the
upper position that could be reached by yhe
condyles into the mandibular fossae.
Eletromiografical studies (34, 35) related that the physiological position of the
condyles, determined by musculature, is superior and anterior, against the posterior slope of the articular eminence. Okeson (37)
refers to the ideal position of the condyle
into the fossae as “orthopedic stability of
the mandible” or “muscular – skeletal stability” .
Authors (38) founded great stability
in condyles when in this upper/anterior position, in close contact with the disc. Under
these circunstances, the compression forces
produced by muscles are well tolerated once
the disc is basically formed by dense colagenous tissue with no innervation or irrigation in the central zone. On the other hand,
continuos forced derived to other areas of
the disc may result in damage of the tissues involved.
Masticatory forces should be distributed along the vertical axis of teeth, thus
being well tolerated by all periodontal tissues while involving a maximum number of
horizontal and oblique fibers. Through this
approach the impact of masticatory loads is
uniformed distributed along all supporting
tissues. (22,18)
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Marco A. L. Feres; Marines Q. Portella; Renata C. L. Feres
Mandibular movements
During ideal mandibular movements two
factors are of umost importance : freedom of movement and “economy” of muscular energy. These
conditions are provided by anterior guidance in
protrusive movements and by canine protection
or group function in lateral excursions.
According to Fantini (39) one must
differenciate total from partial group function, the
latest meaning that not all teeth in the working
side are involved with the disoclusion process.
Neverthless, many patients include only the canines and bicuspids in such gnatological approach.
In “ideal” occlusions anterior guidance
orients mandibular movements and shall be able
to provide MIP without articular or neuromuscular
accommodation, which by all means represents
“economy” in muscular energy .
According to Kahn (40), canine guidance
is the main mechanism to disoclude posterior teeh
from the working side. On the other hand, the key
factor for disoclusion in the balance side is the
sliding movement of the condyle through the posterior slope of the articular eminence. The canine
protected occlusion concept (41,42,43) is based
upon the fact that the canine tooth is the most
appropriate element to guide mandibular lateral
excursion due to crown morphology, root and
periodontal strength plus superior proprioceptive
mechanism.
Other authors (44) did some eletromiografical studies on elevator muscles relating them
to group function or canine protection. Results
demonstrated in group function there was a clear
reduction in muscle action when compared to intercuspal position, mainly to the temporal muscle
from the balance side. When analyzing canine protected occlusions, reduction in muscle activity was
greater than in group function.
According to Lee (23) canine guidance is
optimum to :
• avoid excentric lateral interferences of
posterior teeth.
• provide freedom of condilar movements.
• orient mandibular closure in a more
vertical pattern.
According to Roth (35), incisal guidance should be established by all six upper and
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eight lower anterior teeth, thus dividing protrusive load. Smooth anterior guidance are vital not
only to appropriate function during mandibular
excursions but are strongly related to occlusal stability after orthodontic treatment. He stresses that
excessive lateral load on the canines may result in
lingual movement of the lower cuspids with subsequential anterior crowding.
Ideal occlusion and orthodontics
Proper adaptation of all concepts of optimun occlusion into modern orthodontic therapy
demands basic atitudes related to diagnosis, treatment planning, mechanics, finishing and retention. As widely known, orthodontic treatment has
a very close relationship with all components of
the masticatory system, therefore the specialist
needs to be expertise in all aspects of functional
occlusion. The Angle’s classification is a good way
to start with, but in no way offers adequate parameters for defining treatment goals. Many occlusions presenting solid class I relationship may present several pathological aspects.
In order to achieve proper parameters,
Andrews (46) studied positions and interarch relationships of all crowns of 120 models presenting
“optimum” occlusions, which he called “The Six
Keys to Normal Occlusion” . His method allows
one to assess all pertinent aspects of the occlusion
from the labial and occlusal surfaces. These six
keys are :
• 1 – Anteroposterior relationship
• 2 – Crown angulation
• 3 – Crown inclination.
• 4 – No rotations
• 5 – Solid interproximal contacts
• 6 – Presence of Curve of Spee.
Yet according to Andrews (46), the six
keys are independent elements of the structural
system and consist in solid foundation for occlusal
assesment and treatment goals for most patients.
The modern concept of occlusion in orthodontics includes all TMJ components (49). Before aplliances removal it is essential to observe
mandibular movements and check for interferences. Testing the working side with canine guidance or group function thus providing no contacts in
Clin. Pesq. Odontol., Curitiba, v.2, n.2, p. 155-163, out/dez. 2005
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the balance side, as well as smooth anterior contacts in protrusive is of utmost importance to achieve good functional occlusion (50).
Case presentation
Functional occlusion and orthodontics: a contemporary approach
chform assimetry, anterior aesthetics and some difficulty in chewing. There was no significant medical history. His oral hygiene was good and he
had received routine dental care since early childhood. Despite presenting some interferences no
significant signs or symptoms of temporomandibular joint were related.
A15-year-old oriental boy was referred by
his general dentist for evaluation of crowding, ar-
Fig. 1 – Pre treatment photographs
Fig. 2 – Pre treatment models
Diagnostic and etiology
The patient showed a harmonic and
simetric face both from frontal and lateral,
with a slight convex profile. The occlusal relationship presented a Class I molar relationship, deep overbite, crowding in the incisal area . The upper arch showed a constricted “V” shape, with midline deviation to the
left. The following occlusal problems were
listed :
a) Too long and deep incisal guidance,
thus leading to an excessive anterior condilar displacement in protrusive; b) Contacts on the upper
lateral incisors in working side; c) Some interferences in the balance side, right and left.
Treatment objectives
Treatment objectives were primarily dentoalveolar, improving dental positions, midline
correction, overbite correction and a very accurate
interarch coordination. This last procedure is a key
factor to achieve a good functional occlusion, namely proper incisal guidance, desoclusion by canines in lateral movements and a final reciprocal
protected occlusion.
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Marco A. L. Feres; Marines Q. Portella; Renata C. L. Feres
Fig. 3 – Finishing procedures
Treatment progress
full time in the first year, changing to partial time
use after that.
Maxillary and mandibular .022” preajusted Edgewise mechanism / Roth prescription was placed. Initial alignment and leveling
were achieved with a sequence of thermoactivated niti wires. Vertical control and deep-bite
correction was achieved by using one set of
reverse Curve of Spee arches. After a sequence
of round stainless steel arches, proper arch form
and coordination was reached through rectangular .019” x .025” SS arches, with individual
torque control plus finishing detailing.
Appliances were removed after 22 months of active treatment. The patient was instructed to wear upper and lower Hawley retainers
Treatment results
The observed dentoalveolar alterations are
seen in postreatment figures. Little skeletal modifications occurred, as expected. Good teeth positions were achieved, with proper overjet and overbite, midline correction and nice upper and lower
arch forms. Important to note the solid intercuspal
relationship obtained as well as adequate incisal
guidance. The key factor in eliminating posterior
interferences was the strong canine contact in the
working side, sufficient enough to provide good
guidance and protection in lateral movements.
Fig. 4 – Post treatment photographs
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Functional occlusion and orthodontics: a contemporary approach
Fig. 5 - post treatment lateral movements
Conclusions
Good functional occlusion was achieved
in a moderate crowed Class I malocclusion, with
good patient cooperation. Timely and contemporary orthodontic procedures based on solid gnatological principles changed a poor functional occlusal environment into a nice, pleasant and functional interarch relationship, probably preventing
many potential problems in the years to come.
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Recebido em 20/8/2005; Aceito em 19/9/2005
Received in 8/20/2005; Accepted in 9/19/2005.
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