Chapter 5: Criteria for Optimum Functional Occlusion
The relationship of the maxillary and mandibular teeth when they are in functional contact during activity of the mandible.
The first significant concept developed to describe optimum functional occlusion was (...), which was developed primarily for complete dentures and advocated bilateral and balancing tooth contacts during all lateral and protrusive movements.
bilateral balanced occlusion
After much debate regarding the desirability of balanced occlusion in the natural dentition, the concept of (...) was developed, which suggests that laterotrusive as well as protrusive contacts should occur only on the anterior teeth.
unilateral eccentric contact
The science of mandibular movement and resultant occlusal contacts.
In the 1970s, the concept of (...) emerged, which suggests that if the masticatory system is functioning efficiently and without pathology, the occlusal configuration is considered physiologic and acceptable regardless of specific tooth contacts.
dynamic individual occlusion
How many areas occur when the elevator muscles contract to raise the mandible such that contact is made?
three (two TMJs and the teeth)
The term (...) is generally considered to designate the position of the mandible when the condyles are in an orthopedically stable position.
centric relation (CR)
Earlier definitions described CR as the most (...) position of the condyles, which is the position determined mainly by the ligaments of the TMJ.
Today the term centric relation has been suggested to mean that the condyles are in their most (...) position in the articular fossae.
The articular disc plays an important role ind determining centric relation. True or false?
False. The disc separates, protects, and stabilizes the condyle during functional movements; it does not, however, determine positional stability of the joint
The ligments play an important role in determining centric relation. True or false?
False. Ligaments do not actively participate in joint function; they are present to act as limiting structures for certain extended or border joint movements.
The optimum orthopedically stable joint position of the TMJ is determined by the (...), which pull across the joint and prevent dislocation of the articular surfaces.
Muscles stabilize joints. Therefore every mobile joint has a (...) position.
musculoskeletally stable position (MSS)
When pursuing the most stable position for the TMJs, the muscles that pull across the joints must be considered. What are the major muscles that stabilize the TMJs?
elevator muscles (masseter, medial pterygoid, and temporalis)
The direction of the force placed on the condyles by the masseters and medial pterygoids is (...).
Tonus in the (...) muscle positions the condyles anteriorly against the posterior slopes of the articular eminences.
inferior lateral pterygoid
The (...) aspect of the mandibular fossa is composed of very thin bone that is not developed to support loading, however, the (...) is composed of dense bone able to withstand these forces.
superior aspect; articular eminence
Optimum joint relationship is achieved only when the (...) are properly interposed between the condyles and the articular fossae.
The complete definition of the most orthopedically stable joint position, is when the condyles are in their most (...) position in the articular fossae, resting against the (...) with the discs (...).
superoanterior; posterior slopes of the articular fossae; properly interposed
The most orthopedically stable joint position is the position the condyles assume when the elevator muscles are activated with no occlusal influences. It is therefore also considered to be the most (...) position of the mandible.
Why isn't the most superoposterior position for the condyle considered a physiologically or anatomically sound position?
In this position, force can be applied to the posterior aspect of the disc, inferior retrodiscal lamina, and retrodiscal tissues.
Why isn't most anteroinferior position of the condyle considered the as most physiologic or functional position?
It requires contraction of the inferior lateral pterygoid muscles (i.e. it is a “muscle stabilized” position, but not a “musculoskeletally stable” position).
From an anatomic standpoint, the most orthopedically sound position is when the condyles are in their most (...) position, resting on the discs against the (...).
superoanterior; posterior slopes of the articular eminences
When closure of the mandible in the MS position creates an unstable occlusal condition, the (...) quickly feeds back appropriate muscle action to locate a mandibular position that will result in a more stable occlusal condition.
When only right side occlusal contacts are present, activity of the elevator muscles tends to pivot the mandible using the tooth contacts as a fulcrum. The result is an increase in joint force to the (...) TMJ and a decreased force to the (...) TMJ.
For mandibular and condylar stability, there must be (...) occlusal contacts.
As the number of occluding teeth increases, the force to each tooth (...).
Understanding the progression of these illustrations leads to the conclusion that the optimum occlusal condition during mandibular closure requires (...) contact of all possible teeth.
even and simultaneous
The criteria for optimum functional occlusion are described as:
- (...) contact of all possible teeth
- when the condyles are in the most (...),
- resting against the (...),
- with the discs (...).
- even and simultaneous
- superoanterior position
- posterior slopes of the articular eminences
- properly interposed
Orthopedic stability exists when the (...) position of the condyles coincides with the (...) position of the teeth.
musculoskeletally stable position (CR); maximum intercuspal position (MICP)
Since the teeth are constantly receiving occlusal forces, a (...) is present between the root of the tooth and the alveolar bone to help control these forces.
periodontal ligament (PDL)
The PDL is composed of collagenous connective tissue fibers that run (...) from the cementum to the bone.
Pressure stimulates osseous (...), while tension (pulling) stimulates osseous (...).
When a tooth is contacted on a cusp tip or a relatively flat surface such as the crest of a ridge or the bottom of a fossa, the resultant force is directed (...) through its long axis, where it can be efficiently dissipated by the fibers of the PDL.
When a tooth is contacted on an incline, the resultant force is not directed through its long axis but rather a (...) component is incorporated that tends to cause tipping. The fibers of the PDL are not properly aligned to control this force.
The process of directing occlusal forces through the long axis of the tooth is known as (...).
Axial loading can be achieved by two methods. What are they?
- development of tooth contacts on either cusp tips or relatively flat surfaces that are perpendicular to the long axis of the tooth
- development of tooth contacts such that each produces three contacts surrounding the cusp tip (tripodization)
Each tooth should contact in such a manner that the forces of closure are directed through the (...).
long axis of the tooth
The amount of force that can be generated between the teeth depends on the distance from the temporomandibular joint and the muscle force vectors. Much more force can be generated on the (...) teeth than on the (...) teeth
When heavy forces are applied to an object on the posterior teeth, the mandible is capable of shifting (...) to obtain the occlusal relationship that will best complete the desired task. This shifting of the condyles creates an unstable mandibular position.
downward and forward
The damaging horizontal forces of eccentric movement must be directed to the (...) teeth, which are positioned farthest from the fulcrum and the force vectors.
When all the anterior teeth are examined, it becomes apparent that the (...) are best suited to accept the horizontal forces that occur during eccentric movements.
Why are the canines best suited to accept the horizontal forces?
- they have the longest and largest roots (best crown/root ratio)
- they are surrounded by dense compact bone (tolerates forces better)
When the mandible is moved in laterotrusive excursion, the canines should contact to disocclude the posterior teeth. This condition is described as (...).
Many patients’ canines are not in the proper position to accept the horizontal forces; in a study by Panek, et al. only about (...)% of the general population have bilateral canine guidance.
The most favorable alternative to canine guidance is called (...), in which several of the teeth on the working side contact during the laterotrusive movement.
What are the most desirable teeth for group function?
canine, premolars, and possibly the first molar
In group function, any laterotrusive contacts more posterior than (...) are not desirable because of the increased amount of force that can be created as the contact gets closer to the fulcrum (TMJ).
the mesiobuccal cusp of the first molar
It is reported that 41% of the general population have group function guidance in the 20 to 30 age group and this percentage increases to 68% in the 50 to 60 age group. What is the most likely explanation for this?
When group function guidance is desirable, the (...) contacts are utilized; (...) contacts are not desirable during eccentric movement.
(...) contacts need to provide adequate guidance to disocclude the teeth on the opposite side of the arch immediately; (...) contacts can be destructive because of the the forces that can be applied to the joint and dental structures.
The anterior teeth are not positioned well in the arches to accept heavy occlusal forces because their (...) makes axial loading nearly impossible.
When the mandible moves forward into protrusive contact, damaging horizontal forces can be applied to the teeth. As with lateral movements, the (...) teeth can best receive and dissipate these forces.
The (...) teeth function most effectively in stopping the mandible during closure; the (...) teeth function most effectively in guiding the mandible during eccentric movements.
Posterior teeth should contact slightly more heavily than anterior teeth when the teeth are occluded in the ICP. This condition is described as (...).
mutually protected occlusion
In the normal upright head position well as the alert feeding position, the contacts between the posterior teeth should be (...) than those of the anterior teeth.
If an occlusal condition is established with the patient reclined in a dental chair, the resultant occlusal condition may be oriented slightly too far (...).
When heavy anterior tooth contacts occur, the anterior teeth must be reduced until the posterior teeth again contact more heavily during normal closure. This concept is called the (...).
anterior envelope of function
When there is a loss of posterior occlusal support because of caries or missing teeth, the maxillary anterior teeth gain heavy occlusal contacts. These heavy anterior contacts often lead to (...) of the maxillary anterior teeth.
labial displacement or flaring
What are five criteria for optimum functional occlusion? (long answer)
- The condyles are in the most superoanterior position, against the posterior slopes of the articular eminences with the discs properly interposed.
- All tooth contacts provide axial loading of occlusal forces.
- In laterotrusive movement, tooth-guided contacts on the laterotrusive (working) side disocclude the mediotrusive (nonworking) side immediately.
- In protrusive movement, tooth-guided contacts on the anterior teeth disocclude all posterior teeth immediately.
- In the upright head position and alert feeding position, posterior tooth contacts are heavier than anterior tooth contacts.