Anterior Guidance, Envelope of Function, Restoration of Anterior Movements

anterior guidance

-the influence of the contacting surfaces of the anterior teeth that act to limit (guide) mandibular movements

anterior guidance discluding the posteriors

-watch for change in AG:

-incisors go from good AG to poor if in overjet (no longer protecting posterior contacts)

-if ants and posts in contact at the same time, the posteriors will win

5 requirements of a stable occlusion

-stable centric stops on all teeth

-anterior guidance in harmony with functional border movements

-disclusion of all posterior teeth in protrusive movements

-disclusion of non-working side when the mandible moves laterally

-noninterference of all posterior teeth on the working side

AG as a foundation of a mutually protected occlusion

-anterior teeth protect the posterior teeth in all mandibular excursive movements

-posterior teeth protect the anterior teeth from excessive pressure in MI

AG is principle determinant of

-posterior occlusal form

AG protects posteriors by

-discluding them and keeping the muscles peaceful

anterior guidance dictated by

-incisal edge position

envelope of function (EoF)

-three teeth have entirely different ones

-shape variations of EoFs is due to the different incisal edge positions of the uppers

-different incisal edge positions therefore also produce different AGs

EoF determined by

-how the teeth were guided into position during eruption by the tongue and lips

-(the neutral zone)

-mechanoreceptors in and around the teeth program the muscles for functional jaw movements

if incisal edges were moved labially

-there would be no interference with the EoM

-but there would be interference with the neutral zone, phonetics, and the lip closure path

-restoring anterior teeth requires understanding all these factors

envelope of function frontal view

-occurs within envelope of motion

envelope of function- chewing strokes

envelope of function- sagittal view chew strokes

EoF relationships

-muscles place the teeth

-maxillary tooth’s incisal edge forms shape of EoF

-upper part of EoF is the AG (which the lower incisal edge rides against)

EoF in restoring anterior teeth

-merely recording the outer limits of motion (EoM) would not supply the needed information for restoration of anterior teeth

-also need EoF

-EoF that controls the anterior relationship must be treated as a separate entity

-it must be recorded in the mouth, no articulator setting can produce it

-an articulator can reproduce it

-prepare the tooth, put temp crown on, see how it works in the mouth- pt will tell you based on feeling

first step in restoring anterior teeth

-properly mounted models

-facebow mounting with CR bite registration

properly mounted models

-facebow mounting with CR bite registration

the only way to determine the correct relationship of the lower incisal edges to the upper linguals

-mounted casts

-need 2 pictures of incisal shot from below of OJ being reduced

restoring anterior teeth- 2 considerations

1) posteriors must be gotten out of the way in order to see how anteriors couple

2) the lower incisal edge should have a definite labio-incisal angle

designing restorations

-refine and verify the lower incisal edge position

-if upper anterior position has not been determined, it must be done in combination with the lower determination

restoring anterior teeth- once the posteriors are not creating interferences,

-the AG can be visualized on the existing teeth or designed on restorations

restoring anterior teeth- designing the restorations

-establish centric holding stops (first rule of occlusion)

designing the restorations- lip support

-upper half of labial contour is in line with alveolar contour

-could be determined on the casts (IF casts properly record the vestibule)

designing the restorations- lip closure path

-must be determined in the mouth

-gingival contour guides, then tucks in to touch the lower lip wet/dry line

designing the restorations- esthetics

-determine incisal length

-use the smile line of lower lip

-important for phonetics of F and V sound

designing restorations- refining

-refine incisal edge position

-use F and V sounds

-incisal edge should contact the inner dry-wet line

-have patient phonate softly for this determination

designing restorations- adjusting for long centric

-pt laying down to seated position, ~0.5mm of freedom in CR exists

-can’t lock patient in CR

-follow the rules for AG after CR and incisal edges have been determined

steps to restoring anterior teeth

-communication to lab

-mounting on an articulator

-buccal indices

-written instructions

-photography

crow foot diagram

blue box diagrams

determining path of movement/contacts using blue box