Lecture 8 Static Forces of Occlusion Flashcards
what are static factors of occlusion
characteristics shared by the teeth when they are stationary
what do alignment and occlusion of the dentition determine
-the tooth position
- intra-arch alignment
- inter arch alignment
what factors and forces determine the tooth position
-labiolingual alignment
- mesiodistal alignment
- vertical position
-muscles
-genetics
-habits
what muscles are involved in tooth position
cheeks,lips and tongue
- neutral zone
what do genetics determine about tooth position
size and shape of the arch and teeth ->available space
what maintains tooth position
- interproximal contacts
- occlusal contacts
what does mesial drift affect
alveolar bone and gingival fibers
what is intra arch tooth alignment
the relationship of the teeth to each other within the dental arch
what is the plane of occlusion defined as
plane that curves to fit the occlusal surfaces and incisial edges of all the teeth
describe the plane of occlusion
- not flat
- concave on the mandible
- convex on the maxilla
- teeth positioned in the arches at varying degrees of inclination
what is the angulation of the teeth determined by
the long axis of the tooth (crown and root)
what planes are there in angulation of the teeth
-sagittal plane
- frontal plane
describe the angulation of mandibular teeth in the sagital plane
- anterior teeth: labially inclined 20 degrees
- premolars: mesially inclined 6 degrees
- molars: mesially inclined 10-15 degrees
describe the angulation of the maxillary teeth in the sagittal plane
- anterior teeth: labially inclined- central incisor greatest at 28 degrees
-premolars: mesially inclined 9 degrees - molars: mesially inclined 12 degrees- crowns of the maxillary molars tilted distally and labially
describe the angulation of mandibular teeth in frontal plane
-anterior teeth: vertical inclination 0 degrees
- premolars: 1st premolar- labial inclination of 9 degrees. 2nd premolar- lingual inclination of 9 degrees
-molars: lingual inclination of 20 degrees
describe the angulation of maxillary teeth in the frontal plane
- anterior teeth: incisors: distal inclination 2-6 degrees. canine- mesial inclination of 17 degrees
-premolars: slight buccal inclination of 5 degrees - molars: buccal inclination of 20 degrees
what is the curve of spee
- antero posterior curvature of the occlusal plane
-concave in the mandible, convex in the maxilla
what is the curve of wilson
-medio lateral curvature of the occlusal plane
- concave in the mandible, convex in the maxilla
what is the net effect of angulation on posterior teeth
-when they occlude they are loaded axially
-designed to take heavy loads and support the occlusal vertical dimension
what is the net effect on angulation on anterior teeth
-when they occlude they are not loaded through their long axis
- not designed for loading
what is the occlusal table
the area defined by the cusp tips and the mesial and distal cups ridges/arms
occlusal table is _____% of the buccolingual width of the tooth
50-60%
what does the occlusal table facilitate
axial loading
what are the inclines of the occlusal table and describe each
-inner incline: inclines inside the buccal and lingual cusp ridges
- outer inclines: inclines outside the buccal and lingual cusp ridges
what is interarch tooth alignment
the relationship of the teeth in one arch to those in the other arch
what are the different way to describe arch shape and size
- U shaped/square/ tapering
- symmetrical, smooth in outline
which arch is wider
maxillary
which arch is longer
maxillary
what is the length of each arch
-maxillary: 128 mm long
- mandibular: 126 mm long
what is the net effect of normal arch width
- the buccal cusps of the mandibular posterior teeth and the lingual cusps of maxillary posterior teeth occlude with the opposing central fossa areas
- minimize trauma to soft tissue
-supporting/centric/functional/ stamp cusps - guiding/non-centric/balancing/shearing cusps
what is the bucco-occlusal line
imaginary line drawn through the buccal cusp tips of the mandibular teeth
what is the linguo occlusal line
imaginary line defined by joining the lingual cusp tips of the maxillary teeth
what is the central fossa line
imaginary line that follows the central grooves and fossa of all the posterior teeth
what are the interarch relationships
- bucco occlusal line of the mandible occludes in the central fossa line of the maxilla
- linguo occlusal line of the maxilla occludes in the central fossa line of the mandible
a crossbite is the opposite of what relationship
the ideal interarch relationship
what is a crossbite defined as
-the bucco occlusal line of the maxilla occludes with the CF line of the mandible
- the LO line of the mandible occludes with the CF line of the maxilla
what is the net effect of arch length discrepancy
-tooth to tooth vs tooth to two teeth relationships
- cusp- marginal ridge vs cusp-fossa relation
what are the common occlusal relationships of the posterior teeth
- relationship between the maxillary and mandibular first molars
- angles class 1 is ideal occlusion from an orthodontic perspective
what is defined in the angles class 1 molar relationship
- MB cusp of the maxillary first molar is aligned directly over the buccal groove of the mandibular first molar
- MB cusp of the mandibular first molar occludes in the embrasure area between the maxillary second premolar and first molar
- ML cusp of the maxillary first molar occludes in the central fossa area of the mandibular first molar
what is defined in the angles class II molar relationship
-MB cusp of the maxillary first molar is situated over the embrasure between the mandibular second premolar and first molar
- MB cusp of the mandibular first molar occludes in the central fossa of the maxillary first molar
- DL cusp of the maxillary first molar occludes in the central fossa of the mandibular first molar
what is defined in the angles class III molar relationship
-MB cusp of the maxillary first molar is situated over the embrasure between the mandibular first and second molar
- DB cusp of the mandibular first molar occludes in the embrasure between distal marginal ridge of the maxillary second premolar and the mesial marginal ridge of the maxillary first molar
- ML cusp of the maxillary first molar is situated in the mesial pit of the mandibula r second molar
what is vertical overlap is class I
-distance the maxillary anterior teeth overlap the mandibular anterior teeth in a veritical direction
- usually 2-4 mm
what is horizontal overlap in class I
-distance the maxillary anterior teeth overlap the mandibular teeth when measured in a horizontal direction
- 2-4mm
what is division 1 of class II anterior teeth
-great vertical overlap, the mandibular teeth contact the gingival third of the maxillary anterior teeth- “Deep bite”
what is division 2 of class II anterior teeth
-maxillary incisors are lingually inclined
- laterals overlap the centrals labially
describe the class III anterior tooth relationships
-end to end relationship
- mandibular anterior teeth are so far forward overlapping maxillary anterior teeth
