prep principles, margin designs, and treatment considerations for FDP's Flashcards
what is the objective of tooth preparations
Conserve tooth structure Preserve pulpal vitality Retention and resistance Adequate reduction for: - physiologic tooth contours - resist deformation
what are the primary factors of retention
Taper (TAC)
Length (OC)
surface area (diameter, FL, MD)
what does the total axial convergence come from
the sum of the taper of 2 opposing preparation walls
what is the reduction needed for anterior preparations
Incisal greater than 2 mm facial:1.5mm facial Margin: 1.2mm lingual reduction: 1mm Lingual wall: .5mm
why do a metal collar
Posterior teeth not in the esthetic zone
secondary on mandibular teeth
what is the benifit of the sloped shoulder
Can be used with any preparation style and hides the metal
- beter esthtics
- less intrusivion into gingival crevice
- simple lab construction
disadvantages of sloped should
Difficult to prep greater marginal creek Rough marginal area potential gray line Lab tends to overcontour
advantages of porcelain butt margin
- Optiumum esthetics
- Glazed porcelain at margin=less palque
Margin need not be buried in gingival crevice
what are the absolue indications for a porcealin butt margin
Minimal sulcus depth of 1mm
thin labial tissue
High smile line
what are the real indications for a porcelain butt margin
Margins in the esthetic zone
where is the esthetic zone
where the patient says it is
disadvantages of shoulder(butt)
Higher lab cost
more difficult lab procedue
more difficult preparation
Ante’s Law
the total periodontal membrane area of the abutment teeth must equal or exceed that of the teeth to be replaced.
- excessive span length is a contraindication for fixed dental prosthesis
what can horizontal bone loss do
Results in a considerable loss of bone support because of root morphology
where must retention be extended for a distance
At a similar sitance from the axis of the primary abutment teeth to the distanceof the lever arm that the pontic exerts
what is a cantilever pontic
when the pontic is attached to only one abutment tooth
what is the reduction for metals and porcelain
.5 for metal
1 for porcelain
1.5 for metal Fused to porcelain
what is the ideal taper
6 degrees
for what teeth is it nice to have a metal collar
for long teeth
what type of FPD doesn’t have metal
Anterior zirconia
what is a disappearing margin
metal comes all the way to the axial surface of the prep
- all the way to the margin
what is the ideal crown to root ratio according to Ante’s law
2:3
how many teeth should you use per pontif
One tooth on each side per pontif
what should you use if there is a long gap between teeth for a pontif
use a non-ridgid connector to avoid uncementation or fracture
can you do a bridge on the cnetral incisors
Use the laterals and the canines(very strong tooth root)
- prefer to do implants though
