developing posterior contours

Question 1

what are biologic contours

Answer 1

stimulate natural, healthy teeth
protect the supporting tissues
maintain the health of gingiva and attachments
minimize trauma an irritation to bony tissue

Question 2

what are improper contours

Answer 2

often induce early breakdown of supportive structures

result in early loss of teeth

Question 3

facial and lingual convexities

Answer 3

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

Question 4

4 roles of protective contours

Answer 4

1. proper degree of curvature will deflect food over the gingival margin preventing irritation
2. proper curvature will allow some stimulation of soft tissue
3. if the curvature is absent, the gingival tissue will be driven apically and this will result in pathological changes
4. 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

Question 5

facial contours

Answer 5

no more than 1/2 mm facially beyond cej

height of contour in cervical third

Question 6

lingual contours

Answer 6

no more than 1/2 mm lingually beyond cej

height of contour middle third

Question 7

lingual contour exception

Answer 7

mandibular second premolar and molars- 3/4 to 1 mm lingual

Question 8

emergence profile

Answer 8

tooth surface that is gingival to height of contour and above the gingival crest
should be flat for 2-3mm above the gingiva

Question 9

proximal contours

Answer 9

proximal surfaces are always flat or slightly concave between the contact area and the cej to allow room for the papillae

Question 10

contact area

Answer 10

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

Question 11

basic functions of contact area

Answer 11

1. aids in proper development of arches
2. prevent food from packing between teeth
3. allows the teeth to be self- cleaning
4. prevents injury to the interproximal tissues

Question 12

posterior contact points

Answer 12

the contacts get broader with time due to wear as the teeth move during function

Question 13

contact areas of all posterior teeth

Answer 13

buccal to the central fossa and in the occlusal third

distal contacts more cervical than mesial contacts

Question 14

exception to occlusal third contact area

Answer 14

maxillar molars- junction of occlusal and middle third or middle third

Question 15

exception to buccal to buccolingual center

Answer 15

between max molars, in middle third

Question 16

exception to distal contact more cervical than mesial

Answer 16

mandibular first premolars

Question 17

transitional line angles

Answer 17

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

Question 18

marginal ridges

Answer 18

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)

Question 19

embrasures

Answer 19

v shaped space extending outward from the contact areas of the teeth
spilllway space
lingual embrasures are larger than buccal

Question 20

functions of embrasure

Answer 20

spillway for the escape of food during function

help maintain the tooth clean

Question 21

cervical curvature

Answer 21

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

Question 22

biologic width

Answer 22

1.5 to 2mm

Question 23

tooth reduction

Answer 23

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

Question 24

subgingival margins

Answer 24

use metal margin