Developing Posterior Contours Flashcards
What do biological contours do
Stimulate natural healthy teeth
Protect the supporting tissues
Maintain the health of gingiva + periodontum
Minimize trauma and irritiation to bony tissue
What do Improper Contours do
Early breakdown of supportive structures
Early loss of teeth
Biologic Contour Check List
Facial and LIngual convexities Mesial and sital concavities Transitional line Contact area and embrasures Cervical Curvatures Marginal ridges Tooth reduction
The greatest convexity on the axial surface of the crown
Crest of Curvature/ Height of Contour
What are the shapes a contour
Curved shape
Where are the curvatures unifrom when viewing a tooth from the mesial and distal aspect
the cervical and middle third
What does the proper degree of curvature allow for
Deflecting food over the gingival margin preventing irritiation
stimulation of soft tissue
What happens if the curvature is absent
Gingival tissue will driven Apically and will result in pathological changes
What happens if the curvature is too great
Gingiva is protected too much and loses gingival tone
Food and debris may back and lead to chronic inflammation
How far facial should something be contoured
1/2 mm facially beyond the CEJ
Where is the Height of Contour facially
in the cervical 1/3
How far should the lingual curve go
no more than 1/2 mm lingually beyond the CEJ
where si the Height of contour lingually
in the middle 1/3(except mandibular second premolars and molars which are3/4 to `1mm lingual
The tooth surface that is gingival to the height of contour and above the gingival crest
Emergence profile
The emergence profile
THe profile of the gingival 1/3 of a restoration as it emerges from the gingival crevice
What should the emergence profile look like
Be flat for 2-3 mm above the gingiva
What do Proximal surfaces look like
Always flat or slightly concave betwen the contact area and the CEJ to allow room for the Papillae
How many locations can the contact area have
Various locations
Function of Contact areas
Aids in proper development of the arches
Prevents food from packing between the teeth
Allows the teeth to be self cleaning (to some extent)
Prevents injury to the interproximal tissues
What do contacts points become as teeth mature
Contact areas
Why do contacts between teeth get wider wimeth ti
To wear as the teeth move during function
Where should the contact areas of all posterior teeth be
Buccal to the central fossa and in the occlusal 1/3
- exception (between max molar: junction of occlusal and middle 1/3 or middle 1/3 not occlusal 1/3)
- Exception (between max molars in middle 1/3 not buccal)
location of distal and mesial contacts in relation to one another
Distal contacts are more cervical (except mandibular premolars)
Where is the transitional line
Betweent he faciolingual convexities and proximal concavities
How should the transitional line angle contours look
Should blend the convexities and concavities without excessbulk or irregularity
What does improper contours of line angles hurt
The supporting tissues
Where are transitional line angles
Are strait between the proximal contact point and the CEJ
What happens if the Axial transitional line angles are too proximal
Teeth look wide AF
What are the two depressions that suround the marginal ridge
Occlusal embrasure
Proximal fossa
Shape of the marginal Ridges
Rounded elevated crests
Convex MD
Concave FL
height of MArginal Ridges
Adjacent ridges are the same height except between canines and premolars
What do you look at if both adjacent marginal ridges are missing, how do you determine height
The Opposing cusp
What part of the marginal ridge is wider
Facial is wider than the lingual half (converge from buccal to lingual)
- except mandibular 3 cusp 2nd premolar and maxillary first molar
Function of embrasures
Spillway for the escape of food during function
Maintain the tooth clean
Size of Buccal vs Lingual embrassure
Lingual embrasures are always larger except some maxillary molars
what does the cervical curvature relate to
The contour of the bony alveolar area
Shape of the cervical curvature
Occlusally at procimal
Apically at th facial and lingual
What is the biologic width
about 2 mm
why have a biologic width
The bone does not like to be close to the margin
What causes an over-contoured crown
Directly results from inadequate tooth reduction and causes a lack of room for biomaterials
What happens if the margins of a restoration are placed subgingival
Causes inflamation and reduction of gingival height
What kind of margin should you use for subgingival margins and why
A metal margin
easily tolerated by tissues
Zirconia if color is important because they are also compatible with tissues
How should contours in restorations be established
In harmony with the natural tooth structure
Problems with a guttered chamfer
unsupported enamel
How should the perio probe be for a chamfer
should fit just the tip
