1. EVALUATION AND SELECTION OF ABUTMENTS

2. CONTENTS Definition Function & Ideal Abutment Types Classification
Factors or Criteria for selection of an abutment
Special problems ( Abutment)
Reference

3. ABUTMENT
A tooth, a portion of a tooth or that portion of a dental implant that serves to support and/or retain a prosthesis.
FUNCTION OF AN ABUTMENT
To Retain
To Support
Take up functional and parafunctional load

4. IDEAL ABUTMENT IDEAL CROWN ROOT RATIO
ADEQUATE THICKNESS OF ENAMEL AND DENTIN
ADEQUATE BONE SUPPORT
ABSENCE OF PERIODONTAL DISEASE
PROPER GINGIVAL CONTOUR

5. CLASSIFICATION OR TYPES OF ABUTMENTS
PIER ABUTMENT
CANTILEVER ABUTMENT
ADDITIONAL ABUTMENT
DISTANT ABUTMEN
IMPLANT ABUTMENT

6. PIER ABUTMENT ADDITIONAL ABUTMENT
It is the abutment which is used in addition to the primary abutments in case of a long edentulous span, or if the primary abutment is weak.
PIER ABUTMENT
It is a natural tooth located between
terminal abutments that serve to
support a fixed or removable prosthesis.

7. IMPLANT ABUTMENT DISTANT ABUTMENT
The posterior or distal abutment which retain and support the lone pontic in anterior region.Usually used in diastema cases
CANTILEVER ABUTMENT
The abutments which retain and support the pontic only on one side.
Can be one or more in number.
IMPLANT ABUTMENT

8. CRITERIA (FECTORS)FOR SELECTION OF AN ABUTMENT

9. CROWN TO ROOT RATIO
This ratio is a measure of the length
of the tooth occlusal to the alveolar
crest of the bone compared with the
length of the root embedded in the bone.
The optimum crown to root ratio is
2:3,but the minimal ratio required is 1:1.
ROOT CONFIGURATION
Roots that are broader labio-lingually rather than mesio-distally are preferred to roots which are round in
cross section. Multirooted posterior teeth with widely seperated roots
offer better support than roots that converge, fuse or have a conical configuratio

10. Periodontal ligament area-(Ante’s law)-combined pericemental area of all abutment teeth supporting a fixed dental prosthesis should be equal to or greater in pericemental area than the tooth or teeth to be replaced
Maxillary
Mandibular
Tooth
Area mm2
Ranking
Central
139 7
103 8
Lateral
112
124
Canine
204 3
159 4
First premolar
149 5
135 6
Second Premolar
140
First molar
335 1
352
Second molar
272 2
282
Third molar
197
190
The combined root surface area of the second premolar and the second molar (A2p+A2m) is greater than that of the first molar being replaced (A1m).

11. LONG-SPAN FIXED PARTIAL DENTURE .
Two tooth pontic span will bend 8-times
A three tooth pontic span bends 27-times as much as a single pontic
Short spans are rigid.
Thick pontic
Thin pontic

12. SPECIAL PROBLEMS
ARCH CURVATURE There is a common problem in replacing all four maxillary incisors occurs because the pontics lie outside the interabutment axis line and thus acts as a lever arm, which can produce a torquing movement. In order to offset the torque, additional retention is obtained in the opposite direction of the lever arm and at a distance from the interabutment axis equal to the length of the lever arm.

13. Tilted molar abutment Some possible solutions to these problems are: Preparation modifications:
Tilting is slight –
recontouring of mesial surface of 2nd molar
Tilting is severe –
orthodontic correction
Proximal half crown
A telescopic crown
Non rigid connector

14. Fixed partial dentures replacing canines can be difficult because the
Canine replacement
Fixed partial dentures replacing canines can be difficult because the
canine often lies outside the interabutment axis.
Mandibular
On the mandibular canine, the forces are directed inward (lingually), against the outside of the curve (its strongest point)..
Maxillary forces are transmitted outward (labially) on the maxillary arch, against the inside of the curve (its weakest point).

15. PIER ABUTMENT .
CANTILEVER ABUTMENT

16. Badly mutilated Abutment
RCT & restore with post & core build –up.
post
Cast post
Pre – fabricated posts
core
crown

17. REFERENCES SHILLINGBURG- Fundamentals of Fixed Prosthodontics(3RD ED.)
ROSENSTEIL-Contemporary Fixed Prosthodontics(3RD ED.)