Transcript ideal abutment

EVALUATION AND
SELECTION OF ABUTMENTS
CONTENTS
Definition
Function & Ideal Abutment
Types Classification
Factors or Criteria for selection of an abutment
Special problems ( Abutment)
Reference
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
IDEAL ABUTMENT
 IDEAL CROWN ROOT RATIO
 ADEQUATE THICKNESS OF ENAMEL AND
DENTIN
 ADEQUATE BONE SUPPORT
 ABSENCE OF PERIODONTAL DISEASE
 PROPER GINGIVAL CONTOUR
CLASSIFICATION OR TYPES OF
ABUTMENTS
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ABUTMENT
PIER ABUTMENT
CANTILEVER ABUTMENT
ADDITIONAL ABUTMENT
DISTANT ABUTMEN
IMPLANT 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.
CANTILEVER ABUTMENT
DISTANT ABUTMENT
The posterior or distal abutment which retain and
 The abutments which retain and
support the lone pontic in anterior region.Usually
support the pontic only on one side.
used in diastema cases
 Can be one or more in number.
IMPLANT ABUTMENT
CRITERIA (FECTORS)FOR SELECTION OF AN ABUTMENT
CRITERIA
TOOTH
LOCATION
POSITION
FORM
CONDITION
ROOT
CROWN ROOT
RATIO
ROOT
CONFIGURATION
GINGIVOPERIODONTAL
COMPLEX
GINGIVA
PERIODONTIUM
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
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
Tooth
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).
Area mm2
Ranking
Mandibular
Area mm2
Ranking
Central
139
7
103
8
Lateral
112
8
124
7
Canine
204
3
159
4
First premolar
149
5
135
6
Second
Premolar
140
6
135
5
First molar
335
1
352
1
Second molar
272
2
282
2
Third molar
197
4
190
3
LONG-SPAN FIXED PARTIAL DENTURE
Short spans are rigid.
Two tooth pontic span
will bend 8-times
A three tooth pontic span bends 27times as much as a single pontic
.
Thick pontic
Thin pontic
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.
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
Canine replacement
Fixed partial dentures replacing canines can be difficult because the
canine often lies outside the interabutment axis.
Maxillary
forces are transmitted outward
(labially) on the maxillary arch,
against the inside of the curve (its
weakest point).
Mandibular
On the mandibular canine, the
forces are directed inward
(lingually), against the outside
of the curve (its strongest
point)..
PIER ABUTMENT
.
CANTILEVER ABUTMENT
Badly mutilated Abutment
RCT & restore with post & core build –up.
post
Cast post
Pre – fabricated posts
core
crown
REFERENCES
• SHILLINGBURG- Fundamentals of Fixed Prosthodontics(3RD ED.)
• ROSENSTEIL-Contemporary Fixed Prosthodontics(3RD ED.)