NOT MOTRO Mandibular Movement

Lecture given on 8/14/2025

what are the movements of the mandible controlled by?

TMJ, muscles of mastication, ligaments, occlusion (tooth contacts)

rotation of the mandible

the process of turning around an axis, occurs when the mandible opens or closes like a hinge

what motions of the mandible can be done with only rotational movement?

chewing (grinding/small bites), speaking, early jaw opening without displacing the condyle

what is the approximate opening when the mandible is rotated ONLY?

20-25mm

translation of the mandible

occurs when the condyles move forward and downward and sideways along the articular eminence

the teeth, condyle, and rami all move in the same direction and to the same degree

why is the translational movement of the mandible important, when thinking clinically?

designing dentures, treating TMJ disorders, planning full-mouth rehabilitation

which type of mandibular movement occurs when the mandible moves forward in protrusion?

A) rotational

B) border

C) functional

D) translation

D) translation

which type of mandibular movement occurs during maximally opening?

A) rotational

B) border

C) functional

D) translation

E) A & D

E) A & D

describe the horizontal (transverse) plane, and what mandibular movements occur in this plane?

top to bottom view

protrusive, retrusive, lateral (right/left)

describe the sagittal plane, and what mandibular movements occur in this plane?

side view (left/right)

opening, closing, protrusion, retrusion

describe the frontal (vertical) plane, and what mandibular movements occur in this plane?

front to back view

side to side (lateral) movements, opening, closing

*border movements

maximum range a mandible can move

*what is an example of a border movement?

yawning

*what are border movements limited by?

ligaments, morphology of the TMJ > occulusal surface of teeth, muscles

*functional movements

within the border movement, determined by neuromuscular system

*where do border movements start?

CR position

*where do functional movements start?

ICP or MIP

*what shape is formed by mandibular movements in the frontal plane?

shield

*what shape is formed by mandibular movements in the horizontal plane?

rhomboid

*what shape is formed by mandibular movements in the sagittal plane?

beak

which plane is used to assess right and left lateral border movements?

A) sagittal plane

B) vertical plane

C) horizontal plane

D) transverse plane

C) horizontal plane

border movements are constrained by…

A) saliva flow

B) chewing habits

C) ligaments, morphology of TMJs, occlusal surface of teeth, and muscles

D) airway position

C) ligaments, morphology of TMJs, occlusal surface of teeth, and muscles

which of the following is not a border movement?

A) maximum protrusion

B) maximum opening

C) chewing cycle

D) edge to edge contact

C) chewing cycle

border movements always start in MIP

A) true

B) false

C) huh?

B) false

which movement is limited by the anatomy of the TMJ and ligaments?

A) functional

B) chewing

C) phonetic

D) border

D) border movements

border movements in horizontal plane is

A) tear shaped

B) heart shaped

C) rhomboid shaped

D) triangle shaped

C) rhomboid shaped

what shape is formed by mandibular movements in the frontal plane?

A) diamond

B) circle

C) shield

D) square

C) shield

which of the following factors does influence border movements?

A) ligaments

B) TMJ anatomy

C) tooth anatomy

D) all of the above

D) all of the above

stage 1 of posterior opening border movement

pure rotation from CR to terminal hinge axis

up to 20-25mm opening (incisal edge to edge)

stage 2 of posterior opening border movement

translation of condyles anteriorly and inferiorly

ends at maximum opening (40-60mm)

anterior opening border movement

begins with closing from maximum opening, guided by muscles and ligaments

condyles remain in a forward (anterior) position during early closure

not a pure hinge movement, it produces a curved border

what is anterior opening border movement controlled by?

inferior lateral pterygoid muscle contraction

the tightening of which ligament causes posterior condylar movement during anterior opening border movement?

stylomandibular ligament

posterior and anterior opening border movements are determined (or limited) primarily by…

ligaments and the morphology of the TMJs

anteiror opening border is formed between…. and is determined by…

maximum opening and maximum protrusion

muscles and ligaments

what is the superior contact border movement limited by?

tooth contacts (occlusal and incisal surfaces of the teeth), not ligament or muscles

what influences superior contact border movement?

amount of variation between CR and MIP, steepness of the cuspal inclines of the posterior teeth, overbite/overjet (vertical and horizontal overlap), lingual morphology of maxillary anterior teeth, general interarch relationship of the teeth

where does superior contact border movement end?

maximum protrusion

t/f changes in teeth like wear and alterations can alter the superior contact border movements

true

what is the common slide to CR to ICP in superior contact border movement?

1 to 1.25mm

functional movements in the sagittal plane begin around ____ and extend ____ and ____

ICP, downward, forward

functional movements in the sagittal plane are controlled by?

neuromuscular system, not ligament or bone

if your patient is sitting upright, what is their mandible resting location, closure path, and tooth contact?

2-4 mm below ICP

direct to ICP

normal

if your patient is sitting back at a 45 degree angle, what is their mandible resting location, closure path, and tooth contact?

mandibule is retruded

posterior to ICP

back tooth contact

if your patient is sitting forward at a 30 degree angle, what is their mandible resting location, closure path, and tooth contact?

mandible is slightly forward

anterior to ICP

front tooth contact

which of the following movements is included in sagittal plane border movement?

A) left lateral movement

B) superior contact border movement

C) gothic arch tracing

D) chewing

B) superior contact border movement

what shape is the functional component of the frontal plane?

tear drop shape

where do the functional movements of the frontal plane begin and end?

ICP (maximum intercuspation)

what are the steps during chewing in the frontal plane?

mandible opens downward

shift to the side with food

closes up to ICP as food is broken down

finishes with a quick midline shift back to ICP

what are the 4 components of border movements in the horizontal plane?

left lateral border movement

continued left lateral border movements with protrusion

right lateral border movements

continued right lateral border movements with protrusion

during left lateral border movement, which side is the working side, and which is the non-working side?

left- working side

right- non-working side

during left lateral border movement, where do the left and right condyles move?

left- stays in CR

right- anteriorly, medially, inferiorly

during left lateral border movement, which inferior lateral pterygoid muscle remains relaxed, and which contracts?

left- remains relaxed

right- contracts

during left lateral border movement, which condyle acts as the rotating condyle, and which is the orbiting condyle?

left- rotating

right- orbiting

during right lateral border movements, the right side is the…

____ side

right inferior lateral pterygoid muscle _____

right condyle ______ and acts as the _____ condyle

working side

remains relaxed

remains in CR

rotating condyle

after left lateral border movement, there is left lateral border movement with protrusion… what happens to the muscles?

the left inferior lateral pterygoid muscle contracts, along with the right inferior lateral pterygoid muscle that was already contracting

after left lateral border movement, there is left lateral border movement with protrusion.. the muscles move, so what happens to the condyles?

the left condyle moves anteriorly (forward) and to the right

the right condyle is already at its maximum anterior position and remains stationary

mandibular midline shift

happens after lateral border movement with protrusion, working side condyle moves to its maximum anterior position and the mandibular midline shifts back to align with the facial midline

functional movements always start in?

MIP (ICP)

if the mandible move towards the left:

A) left condyle is working condyle & rotating

B) left condyle is non- working condyle & rotating

C) left condyle is working & orbiting

D) enuf of this

A) left condyle is working condyle & rotating

if the mandible move towards left:

A) right condyle is working condyle & rotating

B) right condyle is non- working condyle & orbiting

C) right condyle is working & orbiting

D) enuf of this

B) right condyle is non- working condyle & orbiting

horizontal plane border movements begin from which position?

A) maximum opening

B) CR

C) functional rest position

D) ICP

B) CR

in horizontal border movement, which position is the most anterior?

A) maximum protrusion

B) CR

C) working side

D) postural position

A) maximum protrusion

what is the most posterior postition in horizontal border movement?

A) CR

B) ICP

C) maximum protrusion

D) rest position

A) CR

the shape of the horizontal border movement pattern is important in…

A) diagnosing TMD

B) speech therapy

C) designing occlusal appliances

D) detecting caries

C) designing occlusal appliances

gothic arch tracing

used for complete denture patients to find CR position

made using a static plate attached to maxilla and a stylus point attached to the mandible

*in gothic arch tracing, when the mandible is at maximum opening, the size of the gothic arch tracing is at its….

smallest

the gothic arch tracing is commonly used in which dental procedure?

A) extraction

B) tooth bleaching

C) complete denture recording

D) crown preparation

C) complete denture recording

posselt’s envelope of motion

combines mandibular movements in all 3 planes

can differ from person to person

what is the superior surface of posselt’s envelope determined by?

tooth contacts

what are the borders (other than superior) of posselt’s envelope determined by?

ligaments and joint anatomy

posselt’s envelope of motion

A) differs from person to person

B) is the combined border movements in 3 planes

C) A & B

D) none of the above

C) A & B

the posselt’s envelope in the sagittal plane represents

A) only rotational movements

B) only functional movements

C) border movements of the mandible

D) condylar displacement

C) border movements of the mandible

the posselt’s envelope in the sagittal plane is shaped like a…

A) circle

B) shield

C) beak

D) triangle

C) beak

what limits the anterior opening border movement?

A) occlusion

B) ligaments and joint anatomy

C) muscle fatigue

D) tongue position

B) ligaments and joint anatomy

functional movements during chewing in the sagittal plane usually occur

A) within the border movements

B) at maximum opening

C) beyond the occlusal limit

D) at the protruded position

A) within the border movements

the terminal hinge position occurs during

A) swallowing

B) first 20-25mm of opening

C) protrusive closure

D) functional chewing

B) first 20-25mm of opening

maximum opening distance in sagittal plane is typically

A) 40-60mm

B) 25-35mm

C) 10-20mm

D) 70-90mm

A) 40-60mm

which manidbular movement plane shows both downward and medial motion?

A) frontal

B) sagittal

C) transverse

D) occlusal

A) frontal

the working side condyle primarily

A) rotates

B) translates forward

C) moves medially

D) moves superiorly

A) rotates

the nonworking condyle moves

A) straight downard

B) anteriorly, medially, and inferiorly

C) posteriorly

D) only inferiorly

B) anteriorly, medially, and inferiorly

in the frontal plane, the envelope of motion is useful to

A) guide denture teeth positioning

B) check facial symmetry

C) align midline

D) balance the TMJ load

A) guide denture teeth positioning