developing posterior contours Flashcards
what are biologic contours
stimulate natural, healthy teeth
protect the supporting tissues
maintain the health of gingiva and attachments
minimize trauma an irritation to bony tissue
what are improper contours
often induce early breakdown of supportive structures
result in early loss of teeth
facial and lingual convexities
crest of curvature=height of contour
contours of tooth are curved
from mesial and distal, crowns have rather uniform curvatures in the cervical and middle third
4 roles of protective contours
- proper degree of curvature will deflect food over the gingival margin preventing irritation
- proper curvature will allow some stimulation of soft tissue
- if the curvature is absent, the gingival tissue will be driven apically and this will result in pathological changes
- if the curvature is too great, the gingiva is protected too much and loses gingival tone. food and debris may pack under this area and result in chronic inflammation of gingiva
facial contours
no more than 1/2 mm facially beyond cej
height of contour in cervical third
lingual contours
no more than 1/2 mm lingually beyond cej
height of contour middle third
lingual contour exception
mandibular second premolar and molars- 3/4 to 1 mm lingual
emergence profile
tooth surface that is gingival to height of contour and above the gingival crest
should be flat for 2-3mm above the gingiva
proximal contours
proximal surfaces are always flat or slightly concave between the contact area and the cej to allow room for the papillae
contact area
the area of the mesial or distal surface of a tooth which touches its neighbors, similar to ball to ball point contact. can have various locations
basic functions of contact area
- aids in proper development of arches
- prevent food from packing between teeth
- allows the teeth to be self- cleaning
- prevents injury to the interproximal tissues
posterior contact points
the contacts get broader with time due to wear as the teeth move during function
contact areas of all posterior teeth
buccal to the central fossa and in the occlusal third
distal contacts more cervical than mesial contacts
exception to occlusal third contact area
maxillar molars- junction of occlusal and middle third or middle third
exception to buccal to buccolingual center
between max molars, in middle third
exception to distal contact more cervical than mesial
mandibular first premolars
transitional line angles
between faciolingual convexities and proximal concavities
contours of this area should blend convexities and concavities without excess bulk or irregularity
improper contour present hazard to the supporting tissues
straight between the proximal contact point and cej- exception max 1st premolar
marginal ridges
ridge like structure neighbored by 2 depression
one- occlusal embrasure
other- proximal fossa
rounded and elevated crests
convex md and concave fl
adjacent ridges at same height except canines and premolars
converge from buccal to lingual (facial half wider than lingual half)
embrasures
v shaped space extending outward from the contact areas of the teeth
spilllway space
lingual embrasures are larger than buccal
functions of embrasure
spillway for the escape of food during function
help maintain the tooth clean
cervical curvature
margins of restoration often end at the cervical line or cej. line curve occlusaly at the proximal and apically at the facial and lingual. curvature relates to the contour of bone alveolar area
biologic width
1.5 to 2mm
tooth reduction
overcontoured crown results directly from the inadequate tooth reduction and causes a lack of room for biomaterials
placing margins of restorations subgingival can cause inflammation and reduction of gingival height
subgingival margins
use metal margin
