lectures Flashcards
what are dental stones made of
dental gypsum
how are articulators deisgned
to look like and act like that of the normal jaw (TMJ)
how does the jaw move during protrusions
forward and downward so we shoot for a 30 degree angle for the articulator eminence
how does the universal occlusal mounting stand mount the maxilary cast
to bodwins equalateral triangle
The geometric (Non-anatomic) school of articulator design
School of articulator design that denied the existance of condylar axes and disregarded
the condylar paths as influences on occlusion and instead claimed that the articulation of teeth guides the mandible during mastication
what are features of articulators from the condylar (Anatomic) school of thought
Adjustable condylar guides
Average value instruments
Bonwill triangle theory
The size of the mandible is equal to 10 cm (4 inches) from condyle to
condyle and from each condyle to the incisor point.
what forms the balkwill angle
Is formed between the occlusal plane and Bonwill triangle (~26˚)
Curve of spee
“The relationship between the curved arrangements of the occlusal planes of natural teeth and the corresponding curves of the condylar paths.”
The molar masticatory surfaces lie on the same arc of a circle. Theposterior continuation of which touches the most anterior point of the condyle.
curve of spee
where is the location of the axis of the curve of spee
The location of the axis of that cylinder’s curvature is at the level of the horizontal mid-orbital plane.
what did carl Christonson discover
the space between the maxilla and mandible during protrusion
how did monson describe a method for setting denture teeth
used bonwill’s equilateral triangle conforming to the surface of a sphere
where is monson center of rotation
4inches from the 3 corners of the bonwill triangle to create a radius of a sphere
describe the curve of wilson
In the theory that occlusion should be spherical, the
curvature of the cusps as projected on the frontal plane expressed in both arches; the curve in the lower arch being concave and the one in the upper arch being
convex.
Rupert E. Hall’s Conical Theory of Mandibular Movement (describes the modern articulator)
The external occipital protuberance was considered as the anatomic rotation center of mandible.
what gives the anatomic and functional harmony in the occlusal stability
balance between elevator and depressor muscles
stongest muscle in the body
masseter (80Kg of force
muscles of mastication
masseter digastric temporalis lateral pterygoid medial pterygoid
where does the temporalis insert
inserts to coranoid process of mandible and anterior ramus
lateral pterygoid inserts
in condylar process and disks
action of lateral pterygoid
protrussion
move jaw sideways
what muscle must be past through to get to the lingual nerve
the medial pterygoid
the biconcave disk for the head of the condyl for friction
joint capsul/disk
parts of the conyl
has a medial and lateral pole
the working side for lateral movements of the mandible``
pivoting side
Bennett’s movement
A cone shapped structure where the pivoting/working condyl can go
what muscle aids with opening the mouth
lateral ptyergoids and the digastic muscle
what is the shape of chewing
teardrop fassion
bennett’s side shift
mandibular lateral translation
ulf posselt’s envelope of motion
arch of rotation then arch of translation then protrude and close at the same time CO->MI then slips over the anterior teeth and connects to full protrusion
function of anterior teeth
anterior guidance perform initial acts of mastication speech lip support esthetics
what dictates anterior guidance
- Position of the incisal edge of the mandibular anterior
teeth relative to the lingual surfaces of the maxillary
anterior teeth - Changes in morphology of the lingual surfaces of
maxillary anterior teeth. - Length of mandibular incisors or canines
3 functions ofthe anterior guide table
- When anterior teeth are prepared, the angulation of the custom
guide provides anterior guidance in place of the anterior teeth. - 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. - Reduce the amount of wear of the stone casts during excursive
movements made on the articulator.
what does the frankfort horizontal plane define
defines the horizontal plane of the skull so that other measures can be made more accurately
what defines the frankfort horizontal plane
the external acoustic meatus and the base of the eyeball (but normally defined by bones)
how is the frankfort horizontal plane separated from the occlusal plane
by 10 degrees
what is used to estimate the frankfort horizontal plane
the ala-tragus plane (camper’s plane)- based on soft tissue
articulators that allow opening
plane line articulator
bennett’s angle
the angle between the protrusion and medial wall on the non-working side as the condyl moves medially on the horizontal plane
fissur’s angle
the downward pathways of the condyl in protrusion vs non-working expression in the sagital plane
what is used to record mandibular movements
the pantograph
how should occlusal cusps and ridges be defined
The cusps and ridges of the occlusal surfaces should be shaped to allow even contact with the opposing teeth while stabilizing the teeth and directing forces along their long axes.
where is the arbitrary hinge axis for an earbow transfer
13mm anterior to tragus on tragus-canthus line
how do you find the kinematic hinge axis
pinpoint actual axis by means of pantograph
Hanau’s formula for bennett’s angle
L=H/8 +12
L=lateral angle
H=horizontal angle
why use ear bow transfer
- relates maxillary cast to termial hinge axis (manibular condyles
- orients the maxillary cast correctly in space using a 3rd point of reference(occlusal plane)
- is aligned parallel to the interpupillary line (reference)
- permits mounting of the maxillary cast on a semi-adjustable articulator
- the mandibular cast is mounted using a centric relation record
where is the habitual arc of closure
within the boarder movement
location of physiological rest position
right below MI (2-3mm)
what do the superior and inferior heads of the lateral pterygoid attach to
superior: articular disk
Inferior: neck of mandible
where do cusps normally go
mandibular cusp in the mesial fossa of the maxillary tooth( tooth to tooth) (wrong: tooth to two teeth)
if occlusion is tooth to two teeth
mandible is too far forward
what is the optimal joint relationship in the TMJ
Optimal joint relationship is achieved only when the articular disks are properly interposed between the condyles and the articular fossae (CR).
In this position, the articular surfaces and tissues of the joints are aligned such that forces applied by the masculature do not create any damage.
what helps with dealing with pressure forces
osseous tissues not good, so periodontal ligaments help to control these forces
Class 1 lever
fulcrum between load and effort
class 2 lever
load between fulcrum and effort
class 3 lever
effort between load and fulcrum
effects of tooth loss
supraeruption- when the opposite tooth to a removed tooth overgrows tilting loss of contact loss of posterior tooth support loss of vertical dimension flaring of anterior teeth non-working interferences
goal of occlusal treatment
- direct occlusal forces along the long axes of teeth(stable posterior contacts)
- In MI position, all mandibular teeth should contact their maxillary opponents at the same time and with same intensity (CO-MI)
- to furnish a smooth prtrusive path guided by the anterior teeth without any interference from occlusal contacts between the posterior teeth (Posterior disclusion)
- working contacts (canine guidance/group function) should be prevented from contacting by non-working interferences
goals of occlusal equilibration
- improve functional esthetic relationships between maxillary and mandibular teeth
- eliminate TMD
what evidence is neccessay to alter occlusion
evidence exists to support that the occlusal condition is an etiological factor
treatment planning for occlusal therapy
- selective grinding
- fixed prosthodontics
- orthodontic therapy
- orthognathic surgery-move entire jaw
rule of thirds
cusp touches 1/3 near fossa: selective grinding
cusp touches middle 1/3 of incline: fixed prosthodontics
cusp touches the other cusp of opposing tooth: Orthodontic treatment
what factors influence treatment planning
symptoms Condition of the dentition systemic health esthetics finances
what determines if selective grinding can be accomplished within the confines of the enamel
the shorter the slides
being verticle slides (horizontal makes it difficult to eliminate within the confines of the enamel
why do selective grinding on diagnostic casts
done first so you can see the final results
Grinding for Non-working interferences
BULL
Grinding for opening protrsive interferneces
DUML
grinding for opening working interferences
LUBL
