Q6-Developing Posterior Contours Flashcards
The biological contours help to achieve these goals involving the teeth and tissues
stimulate natural, healthy gums
protect supporting tissues
maintain the health of the gingiva and attachments
minimize trauma and irritation to bony tissues
Improper contours can result in these issues
often induce early breakdown of supportive structures
result in early loss of teeth
The facial and lingual convexities relate to this
crest of curvature = height of contour
Where is the greatest convexity (or bulge) of the crown
on the axial surfaces
When viewed from the medial or distal, crowns have rather uniform curvatures in which areas
cervical third and in the middle thirs
The proper degree of curvature will do what
deflect food over the gingival margin preventing irritation
True or False
The proper curvature will allow some stimulation of soft tissue
True; massaging of the gingiva while chewing will help to stimulate the soft tissues
What will happen if the proper curvature is absent
the gingival tissue will be drivel apically and this will result in pathological changes
What will happen if the proper curvature is too great
The gingiva will be protected too much and lose its gingival tone
food and debris may pack under the area and result in chronic inflammation of the gingiva
Where is the facial height of contour
in the cervical third
What is the dimension of the facial height of contour
no more than 1/2 mm facially beyond the CEJ
Where is the lingual height of contour
in the middle third
What is the dimension of the lingual height of contour
no more than 1/2 mm lingually beyond the CEJ
What are the exceptions to the lingual height of contour
mandibular second premolars and molars
they extend 3/4 to 1 mm lingual
due to the lingual tilt
What is the emergence profile
tooth surface that is gingival to the height of contour and above the gingival crest
What describes the angle of the emergence profile
the profile of the gingival third of a restoration as it emerges from the gingival crevice
Where is the area of the emergence profile
should be flat for 2-3mm above the gingiva
Due to the interdental papillae, what does this do for the proximal surfaces
proximal surfaces are ALWAYS flat or slightly concave between the contact area and CEJ to allow room for the papillae
What is the contact area of a tooth
the area of the mesial or distal surface of a tooth which touches its neighbors
similar to a ball or ball point contact
can have various locations
What are the 4 basic functions of a contact area
aids in proper development of the arches
prevents food from packing between the teeth
allows teeth to be self cleaning
prevents injury to the interproximal tissues
True or False
The contact areas become contact points as we age
False; the contact POINTS become contact AREAS as we age
What causes the contacts to become more broad
due to wear as the teeth move during function
Contact area of all posterior teeth should be where
buccal to the central fossa and in the occlusal third
What is the exception to having the contact in the occlusal third
between maxillary molars
in the junction of the occlusal and middle third or middle third
What is the exception to having the contact buccal to buccolingual center
between maxillary molars; in the middle third (large lingual)
True or False
Mesial contacts are more cervical than distal contacts
False; distal contacts are more cervical than mesial contacts
What is the only tooth where the mesial contacts are more cervical
mandibular first premolar
Where would you find the axial transitional line angle
between the faciolingual convexities and proximal concavities
Improper transitional line angles can present what
a hazard to the supporting tissues
True or False
Transitional line angles are straight between the proximal contact point and the CEJ
True
This is on the occlusal surfaces of the teeth at the proximal border; a ridge like structures neighbored by two depressions
marginal ridges
What forms a marginal ridge
two depressions; occlusal embrasure and proximal fossa
it is concave in shape
Marginal ridges have what type of crests, are shaped which ways MD/FL, and the adjacent ridges relate how
rounded elevated crests
convex MD
concave FL
adjacent ridges are at the same height (opposing cusp to contact)
What are the exceptions to a normal marginal ridge
premolars and canines
Marginal ridges converge from ______ to _______
buccal to lingual (buccal 1/2 wider than lingual 1/2)
In which tooth is it not true that the facial is wider than the lingual
maxillary first molar
What is an embrasure space
The āVā shaped space extending outward from the contact area of the teeth
also known as a spillway space
What are the 2 main functions of the embrasure space
a spillway for the escape of food during function
helps to keep the teeth clean
Which embrasure space is always larger, buccal or lingual
lingual space is always larger
Cervical curvature/cervical line extends where
it curves occlusally at the proximal and apically at the facial and lingual
What does the cervical curvature relate to
the contour of the bony alveolar bone
If the cervical margin is within this distance to the alveolar bone, then the bone will begin to recede
1.5-2.0mm
An over-contoured crown results from what and causes what
inadequate tooth reduction and it can cause a lack of room for biomaterials
What can result if a margin of a restoration is placed subgingival
inflammation and reduction of gingival height
When placing a sub gingival margin it is wise to use what material
a metal margin; it is easily tolerated by the tissues
True or False
It is important to always establish contours in restorations which are in harmony with the natural tooth structure
True
