Mandibular Movements Flashcards
___ is the dental specialty that deals with restoring missing oral and para-oral structures.
Prosthodontics
___ ___ involves restoring teeth by non-removable artificial substitutes.
Fixed prosthodontics
The complex 3-dimensional mandibular movement can be broken down into two basic components, ___ and ___.
rotation; translation
In the sagittal plane, the mandible is capable of ___ and ___.
rotation; translation
Rotation occurs around the ___ ___ ___ or ___ ___ ___ (THA), which is an imaginary line connecting the centers of the two condyles.
terminal hinge axis; transverses horizontal axis
In the sagittal plane, the rotational movement is limited to about __-__ mm of incisal separation before the mandible begins to translate.
20-25
T/F. Mandibular movement around the sagittal axis occurs when one condyle moves superiorly while the other remains in the terminal hinge position.
False. One condyle moves INFERIORLY. This inferior displacement of the condyle is limited naturally by the ligaments and musculature of the TMJ.
What types of motions are produced by horizontal axis rotation?
opening and closing
In the horizontal plane, the whole mandible can make a straight ___ movement.
protrusive
In lateral movement of the mandible, the non-working condyle travels ___ and
___. The working condyle exhibits slight ___ translation (Bennett movement). This may be slightly forward or slightly backward.
forward; medial; lateral
In a straight protrusive movement, both condyles will move ___ as they slide along the eminencies
downward
Explain lateral movements in frontal plane of the non-working and working condyles.
In lateral movements, the non-working condyle will move downward and medial. The working condyle, however, will rotate and move lateral and upward or lateral and downward.
Ulf Posselt described this range of movement in the ___ planes of orientation using a starting reference point between the two mandibular ___ ___. This range of movement is also referred to as the “__ __ __.”
three; central incisors; envelope of motion
Pure rotational opening can occur until the anterior teeth are __-__ mm apart.
20-25
T/F. Pure rotational opening occurs with translation of the condyles.
False. The mandible can be lowered (mouth opening) in a pure rotational movement without translation of the condyles.
What happens during the second rotational movement during opening?
The condyle is translated down to the articular eminence when the mouth rotates open to its maximum limit.
During the second stage of opening, the condyles move ___ and ___ while the anterior portion of the mandible moves ___ and ___.
anteriorly; inferiorly; posteriorly; inferiorly
T/F. The second stage of opening involves rotation and translation.
True
What is the maximum opening range?
50 to 60mm when measured between the incisal edges of the maxillary and mandibular teeth
If the mandible is manipulated upward on the centric relation arc of closure until tooth contact occurs, the mandible is now said to be in ___ ___.
centric occlusion (CO)
What muscle is involved in the closure of the mandible?
inferior lateral pterygoids (which keep the condyles positioned anteriorly)
T/F. Superior contact movements are determined by the characteristics of the occluding surfaces of the teeth.
True.
In approximately __% of the population, this contact occurs between only one or two maxillary and mandibular teeth
90
Contacting surfaces are located on the ___ inclines of the mandibular tooth (teeth) and the ___ inclines of the maxillary tooth (teeth).
distal; mesial
Forces applied to the teeth when the condyles are in centric relation (CR) will create a superoanterior shift of the mandible to the ___ ___.
intercuspal position (maximal intercuspation)
The slide between CO and MI is referred to as “__ __.”
centric slide
In intercuspal position or at MI, the opposing anterior teeth are in contact. When the mandible is protruded from MI, contact between the ___ edges of the mandibular anterior teeth and the ___ inclines of the maxillary anterior teeth results in an anterorinferior (opening) movement of the mandible.
incisal; lingual
The mandible has to open as the mandibular anterior teeth
ride down along the lingual concavity of the maxillary anterior teeth until they
reach an __-to-__ (__-to-__) position.
end-to-end; edge-to-edge
What dictates the path of the mandible as it continues to move forward and clear the anterior teeth?
the posterior teeth
If from the maximum open position the patient is instructed to close, what path will the mandible trace?
the path of the habitual arc of closure
T/F. The physiologic rest position of the mandible lies on the habitual arc of closure.
True.
What is the position that the mandible assumes when all muscles are at a state of equal relaxation?
physiologic rest position
Define the vertical dimension of occlusion (VDO) and vertical dimension at rest (VDR)
It is the distance between two arbitrary reference points on each side of the maxillary and mandibular teeth when the teeth are separated by the interocclusal rest distance or space. This distance at physiologic rest position
What are the four muscles of mastication? What muscle is an accessory muscle?
masseter, temporalis, lateral and medial pterygoid muscles
digastric
Explain the Bennett’s side shift.
Because the condyles are oblong and not spherical, the center will shift and will take the condyle slightly out of the cone of Bennett.
This causes a mandibular lateral translation
what are the functions of anterior teeth?
anterior guidance, perform initial acts of mastication, speech, lip support, esthetics
which types of bites have no anterior guidance?
class III (end to end), class III, anterior open bite
Anterior guidance includes what two subcategories?
incisal guidance and canine guidance
What are the two types of occlusal schemes?
anterior guidance and group function
what factors determine the anterior guidance?
the lingual concavities of the maxillary anterior teeth as well as the vertical and horizontal overlap of maxillary and mandibular anterior teeth.
If the relationship of the maxillary and mandibular canines determines the lateral jaw movement, the term ___ ___ is used in reference to the path during lateral movement.
canine guidance
What serves to guide the diclusion of posterior teeth?
The inclination of the articular eminence of the TMJ and the morphology of the lingual surfaces of anterior teeth
what are the three posterior determinants of mandibular movements?
- inclination of articular eminence
- medial wall of glenoid fossa
- intercondylar distance
What are the two anterior determinants of mandibular movements?
- horizontal overlap of anterior teeth
2. vertical overlap of anterior teeth
what are the other determinants of mandibular movements?
- occlusal plane
- curve of spee
- neuromuscular response
Anterior guidance is dictated by the position of the ___ edge of the mandibular anterior teeth relative to the ___ surfaces of the maxillary anterior teeth.
incisal; lingual
Anterior guidance is dictated by changes in morphology of the ___ surfaces of maxillary anterior teeth.
lingual
Anterior guidance is dictated by the length of mandibular ___ or ___
incisors or canines
For incisal guidance, immediate disclusion of posterior teeth takes place on mandibular ___.
protrusion
For canine guidance, immediate disclusion of posterior teeth takes place as soon as the ___ movement begins.
lateral
What function occurs when the mandibular buccal working cusps travel downward, forward, and lateral in contact with the lingual inclines of the maxillary buccal cusps, simultaneously with the canines?
group function
One use of the incisal guide table is to ___ an existing guidance prior to preparing teeth.
record
Another use of the insical guide table is to ___ wax patterns, which may be abraded during movements of the articulator
protect
T/F. When only posterior teeth are to be replaced, the angulation of
the guide serves to estimate the buccolingual and mesiodistal
cusp angles, so as to avoid interferences in both protrusive and non-working excursions.
True
