Azer Flashcards
what is prosthodontics?
dental specialty that deals with restoring missing oral and paraoral structures
mandibular movements in sagittal plane
rotation and translation
where does rotation occur around?
terminal hinge axis or transverse horizontal axis (THA)- imaginary line connecting the centers of the two condyles
what distance is rotational movement limited to?
20-25mm of incisal separation before the mandible start to translate
mandibular movements in horizontal plane
whole mandible- straight protrusive
lateral movement of mandible
what happens in lateral movement of the mandible?
non-working condyle travels forward and medial
working condyle exhibits slight lateral translation (bennett movement)- may be slightly forward or backward
mandibular movements in frontal plane
straight protrusive movement- both condyles move downward as they slide along the eminences.
lateral movements- non-working condyle will move downward and medial
working condyle- rotate and move lateral and upward or lateral and downward
range of mandibular movements
envelope of motion
what is centric relation arc of closure?
when mandible is guided to centric relation, the arc traced by the point between 2 mandibular centralincisors
when is mandible in centric relation?
at any point along the centric relation arc of closure
what is the definition of centric relation?
maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discks, with the complex in the anterior-superior position against the shapes of the articular eminencies. this position is independent of tooth contact. restricted to a purely rotary movement about the transverse horizontal axis
centric occlusion
if mandible is manipulated upward on the centric relation arc of closure until tooth contact occurs
what happens to 90% of the population?
co contact occurs between only one or two maxillary and mandibular teeth.
what are contacts points referred to as?
initial points of contact
contacting surfaces located on distal incline of the mandibular tooth and mesial inclines of maxillary teeth
what happens if the mandible closes further past centric occlusion?
it must slide out of CR along a path dictated by the inclines of the contacting posterior teeth. mandible continues to close and slide forward or laterally until all the teeth intercuspate together as best as they can.
reaches maximal intercuspation (MI)
what is centric slide? what is its significance?
slide btween CO and MI. if initial point of contact (CO) coincides with MI, restorative treatment is made relatively easy. if there is a slide- it is necessary to determine whether corrective occlusal therapy is needed before restoreative treatment is accomplished
what is protrusive movement?
starting from MI position, the mandible can be protruded keeping tooth contact. mandible has to open as mandibular anterior teeth ride down along the lingual concavity of the maxillary anterior teeth until they reach an end to end position.
tracing on sagittal plane is dictated by the shape and position of the maxillary anterior teeth (vertical and horizontal overlap)
as the mandible continues to move forward and the anterior teeth clear, the contacting posterior teeth dictates its path. the mandible continues to close and slide forward until maximum protrusive superior position is reached. from thiss position, the mandible can undergo a wide opening movement to its max opened position. max opening may range up to 50-60mm measured between maxillary and mandibular incisors. the mandible can now close back with translation and rotation to its centric relation arc of closure.
habitual arc of closure
patient is instructed to close patient close mouth from the maximum open position. line not reproducible because it is not a border position.
are border movements of the mandible reproducible?
yes
where is the physiologic rest position?
lies on habitual arc of closure. the position that the mandible assumes when all muscles are at a state of equal relaxation. characterized by the teeth being separated by the interocclusal rest distance or space
how is the interocclusal rest distance or space determined?
using two arbitrary reference points on each side of the maxlliary and mandibular teeth or attached gingiva or the skin over the mandible and cranium. distance between these two reference points with the teeth in MI is the vertical dimension of occlusion (VDO). the distance between these two points with the mandible in physiologic rest position is the vertical dimension at rest (VDR)
interocclusal rest distance=VDR-VDO