1. DESIGNING AND PLANNING
DESIGNING AND PLANNING
CROWN AND BRIDGES
CROWN AND BRIDGES
Presented By;
Presented By;
DR FAHD KHALID
DR FAHD KHALID
2. Why replace missing teeth?
Why replace missing teeth?
The need for replacing missing teeth is obvious
The need for replacing missing teeth is obvious
to the patient when the edentulous space is in
to the patient when the edentulous space is in
the anterior segment of the mouth, but it is
the anterior segment of the mouth, but it is
equally important in the posterior region.
equally important in the posterior region.
It is tempting to think of dental arch as a static
It is tempting to think of dental arch as a static
entity, but that is certainly not the case.
entity, but that is certainly not the case.
It is in a state of
It is in a state of dynamic equilibrium
dynamic equilibrium, with the
, with the
teeth supporting each other .
teeth supporting each other .
4. TREATMENT PLANNING
TREATMENT PLANNING
AIMS
AIMS -Control and prevent further active disease.
-Control and prevent further active disease.
- Be efficient and effective yet involve only minimum
- Be efficient and effective yet involve only minimum
operative intervention.
operative intervention.
- Satisfy the patient’s expectations and
- Satisfy the patient’s expectations and
requirements.
requirements.
- Result in optimum outcome and long-term
- Result in optimum outcome and long-term
benefits.
benefits.
- Involve minimum psychological trauma.
- Involve minimum psychological trauma.
- Facilitate any further treatment, which may be
- Facilitate any further treatment, which may be
required.
required.
- Take account of long-term maintenance
- Take account of long-term maintenance
- To decide on the design and material(s) to be
- To decide on the design and material(s) to be
- used in the construction of the crown or bridge
- used in the construction of the crown or bridge.
.
5. Criteria for selecting a bridge
Criteria for selecting a bridge
design
design
No firm rules can be given for selecting any particular
No firm rules can be given for selecting any particular
design.
design.
Bridge design is complex, poorly researched and
Bridge design is complex, poorly researched and
dominated by personal opinion derived from clinical
dominated by personal opinion derived from clinical
experience, or lack of it.
experience, or lack of it.
In recent years, clinical evidence has been accumulating
In recent years, clinical evidence has been accumulating
suggesting that many of the early rules of bridge design
suggesting that many of the early rules of bridge design
should no longer be applied.
should no longer be applied.
However, this evidence is not yet sufficiently clear-cut for
However, this evidence is not yet sufficiently clear-cut for
new, firm rules to be established, leaving today's
new, firm rules to be established, leaving today's
dentists,, in a state of confusion
dentists,, in a state of confusion .
.
6. Design
Design
The design should:
The design should:
Be as simple and conservative as possible, yet sufficient to satisfy physical
Be as simple and conservative as possible, yet sufficient to satisfy physical
and mechanical requirements.
and mechanical requirements.
Care needs to be taken when using multiple, linked abutments to provide
Care needs to be taken when using multiple, linked abutments to provide
adequate resistance to the
adequate resistance to the leverage forces
leverage forces exerted during function with long
exerted during function with long
span bridges.
span bridges.
Enhance occlusal relationships and function, yet minimise adverse loading.
Enhance occlusal relationships and function, yet minimise adverse loading.
Encourage optimum tissue response and effective oral hygiene
Encourage optimum tissue response and effective oral hygiene
maintenance.
maintenance.
Particular attention needs to be paid to the maintenance of
Particular attention needs to be paid to the maintenance of embrasure
embrasure
spaces
spaces to facilitate oral hygiene.
to facilitate oral hygiene.
Be realistic in terms of being attainable clinically, and with due regard to
Be realistic in terms of being attainable clinically, and with due regard to
technical expectations.
technical expectations.
7. Cont;
Cont;
Treatment planning and design may be facilitated by:
Treatment planning and design may be facilitated by:
Having demonstration models and illustrated case histories to discuss with
Having demonstration models and illustrated case histories to discuss with
patients.
patients.
The use of duplicate study casts to simulate preparations, and for the
The use of duplicate study casts to simulate preparations, and for the
purposes of diagnostic wax-ups.
purposes of diagnostic wax-ups.
Communication with the technician who will
Communication with the technician who will construct the crown or bridge.
construct the crown or bridge.
Before finally agreeing to a particular treatment strategy, patients should be
Before finally agreeing to a particular treatment strategy, patients should be
made aware of the
made aware of the implications,
implications, possible sequelae
possible sequelae and
and anticipated life
anticipated life
expectancy of the work
expectancy of the work.
.
In addition, patients must understand and accept that the success of the
In addition, patients must understand and accept that the success of the
treatment will be highly dependent on their subsequent commitment to
treatment will be highly dependent on their subsequent commitment to oral
oral
health care
health care maintenance.
maintenance.
8. Selection of the Type of Prosthesis
Selection of the Type of Prosthesis
Missing teeth may be replaced by one of
Missing teeth may be replaced by one of
three prosthesis;
three prosthesis;
A
A removable partial denture
removable partial denture (RPD)
(RPD)
T
Tooth-supported fixed partial denture
ooth-supported fixed partial denture
(
(FPD)
FPD)
or an
or an Implant-Suppted fixed partial
Implant-Suppted fixed partial
denture
denture.
.
Several factors be weighed when choosing the
Several factors be weighed when choosing the
type of prosthesis used in any given situation
type of prosthesis used in any given situation
9. Selection of the Type of Prosthesis
Selection of the Type of Prosthesis
Removable Partial Denture
Removable Partial Denture
Span length
Span length
Posterior Spans greater than
Posterior Spans greater than
two teeth
two teeth
Anterior spans longer than 4
Anterior spans longer than 4
incisors
incisors
Canine + 2 or more contiguous
Canine + 2 or more contiguous
teeth
teeth
Span configuration
Span configuration
No distal abutment
No distal abutment
Multiple or bilateral edentulous
Multiple or bilateral edentulous
spaces
spaces
Fixed Partial Denture
Fixed Partial Denture
Posterior span: 2 or fewer
Posterior span: 2 or fewer
Incisors: 4 or fewer
Incisors: 4 or fewer
Usually has distal abutment but
Usually has distal abutment but
can be used with short cantilever
can be used with short cantilever
pontic
pontic
10. Selection of the Type of Prosthesis
Selection of the Type of Prosthesis
RPD
RPD VS
VS FPD
FPD
Abutment alignment
Abutment alignment
Tipped abutments can be tolerated
Tipped abutments can be tolerated
Widely divergent abutment alignment
Widely divergent abutment alignment
Abutment condition
Abutment condition
Short clinical crowns
Short clinical crowns
Insufficient abutments
Insufficient abutments
Occlusion
Occlusion
More adaptable to irregularities in a
More adaptable to irregularities in a
healthy opposing natural dentition
healthy opposing natural dentition
Less than 25° inclination can be
Less than 25° inclination can be
accommodated by preparation
accommodated by preparation
modification
modification
Good if abutments need crowns
Good if abutments need crowns
Non vital teeth can be used if there is
Non vital teeth can be used if there is
sufficient coronal tooth structure
sufficient coronal tooth structure
Favorable loading (magnitude,
Favorable loading (magnitude,
direction, frequency, duration)
direction, frequency, duration)
12. Selection of the Type of Prosthesis
Selection of the Type of Prosthesis
Periodontal condition
Periodontal condition
Can use alternate (secondary
Can use alternate (secondary
abutments) when primary
abutments) when primary
abutments are weakened
abutments are weakened
Ridge form
Ridge form
Gross tissue loss in residual
Gross tissue loss in residual
ridge
ridge
Good alveolar bone support
Good alveolar bone support
Crown-root ratio 1:1 or better
Crown-root ratio 1:1 or better
No mobility
No mobility
Favorable root morphology
Favorable root morphology
Moderate resorption No gross
Moderate resorption No gross
soft tissue defects
soft tissue defects
14. Abutment Evaluation
Abutment Evaluation
Every restoration must be able to withstand the constant occlusal
Every restoration must be able to withstand the constant occlusal
forces to which it is subjected.
forces to which it is subjected.
This is of particular significance when designing and fabricating a
This is of particular significance when designing and fabricating a
fixed partial denture
fixed partial denture
Since the forces that would normally be absorbed by the missing
Since the forces that would normally be absorbed by the missing
tooth are transmitted, through the pontic, connectors, and retainers,
tooth are transmitted, through the pontic, connectors, and retainers,
to the abutment teeth
to the abutment teeth ???
???
Abutment teeth are therefore called upon to with
stand the forces
Abutment teeth are therefore called upon to with
stand the forces
normally directed to the missing teeth, in addition to those usually
normally directed to the missing teeth, in addition to those usually
applied to the abutments.
applied to the abutments.
15. Abutment Evaluation cont;
Abutment Evaluation cont;
Whenever possible, an abutment should be a
Whenever possible, an abutment should be a vital tooth
vital tooth.
.
Tooth that has been endodontically treated and is asymptomatic,
Tooth that has been endodontically treated and is asymptomatic,
with radiographic evidence of a good seal and complete obturation
with radiographic evidence of a good seal and complete obturation
of the canal, can be used as an abutment
of the canal, can be used as an abutment
How ever, the tooth must have some sound, surviving coronal tooth
How ever, the tooth must have some sound, surviving coronal tooth
structure to insure longevity.
structure to insure longevity.
Teeth that have been
Teeth that have been pulp capped
pulp capped in the process of preparing the
in the process of preparing the
tooth should not be used as FPD abutments unless they are
tooth should not be used as FPD abutments unless they are
endodontically treated. There is too great a risk that they will require
endodontically treated. There is too great a risk that they will require
endodontic treatment later, This is a situation that is better handled
endodontic treatment later, This is a situation that is better handled
before the fixed partial denture is made.
before the fixed partial denture is made.
Supporting tissues should be healthy, not inflamed and teeth should
Supporting tissues should be healthy, not inflamed and teeth should
not exhibit mobility
not exhibit mobility
16. Abutment Evaluation/ cont;
Abutment Evaluation/ cont;
Factors
Factors
The roots and their supporting tissues should be
The roots and their supporting tissues should be
evaluated for three factors
evaluated for three factors:
:
1. Crown-root ratio
1. Crown-root ratio
2. Root configuration
2. Root configuration
3 Periodontal ligament area
3 Periodontal ligament area
17. 1.
1. Crown-Root Ratio
Crown-Root Ratio
This ratio is a measure of the length of tooth
This ratio is a measure of the length of tooth
occlusal to the alveolar crest of bone compared
occlusal to the alveolar crest of bone compared
with the length of root embedded in the bone
with the length of root embedded in the bone.
.
18. Crown-Root Ratio
Crown-Root Ratio
The
The optimum
optimum crown-root ratio for a tooth to
crown-root ratio for a tooth to
be utilized as a fixed partial denture
be utilized as a fixed partial denture
abutment is
abutment is 2:3
2:3
A ratio of
A ratio of 1:1
1:1 is the
is the minimum
minimum ratio that is
ratio that is
acceptable
acceptable
19. 2.
2. Root Configuration
Root Configuration
This is an important point in the assessment of an
This is an important point in the assessment of an
abutment's suitability from a periodontal standpoint
abutment's suitability from a periodontal standpoint
Teeth that are broader labiolingually than they are mesiodistaly are
Teeth that are broader labiolingually than they are mesiodistaly are
preferable to roots that are round in cross section
preferable to roots that are round in cross section
20. Root Configuration/ Cont;
Root Configuration/ Cont;
Multirooted posterior teeth with widely separated roots
Multirooted posterior teeth with widely separated roots
will offer better periodontal support than roots that
will offer better periodontal support than roots that
converge, fuse, or generally present a conical
converge, fuse, or generally present a conical
configuration
configuration
21. 3.
3. Periodontal Ligament Area
Periodontal Ligament Area
Another consideration in the evaluation of prospective
Another consideration in the evaluation of prospective
abutment teeth is the root surface area, or the area of
abutment teeth is the root surface area, or the area of
periodontal ligament attachment of the root to the bone.
periodontal ligament attachment of the root to the bone.
Larger teeth have a greater surface area and are better
Larger teeth have a greater surface area and are better
able to bear added stress
able to bear added stress
In a statement designated as “Ante’s Law” by
In a statement designated as “Ante’s Law” by
Johnston et al,
Johnston et al, the root surface area of the abutment
the root surface area of the abutment
teeth had to equal or surpass that of the teeth being
teeth had to equal or surpass that of the teeth being
replaced with pontics.
replaced with pontics.
22. PDL Area
PDL Area
The combined root surface area of
The combined root surface area of
the second premolar and the
the second premolar and the
second molar
second molar (A2p+A2m
(A2p+A2m,) is
,) is
greater than thai of ihe firsi molar
greater than thai of ihe firsi molar
being replaced (A1m)
being replaced (A1m)
(Ac A1p A2p A1m A2m9)
23. Contradiction / Antes Law
Contradiction / Antes Law
Examples;
Examples; Lorries/Trucks-
Lorries/Trucks- old concept
old concept
Opposing dentures
Opposing dentures
24. There is evidence that teeth with very poor periodontal
There is evidence that teeth with very poor periodontal
support can serve successfully as fixed partial denture
support can serve successfully as fixed partial denture
abutments in carefully selected cases.
abutments in carefully selected cases.
Teeth with severe bone loss and marked mobility have
Teeth with severe bone loss and marked mobility have
been used as fixed partial denture and splint abutments.
been used as fixed partial denture and splint abutments.
Elimination of mobility is not the goal in such cases, but
Elimination of mobility is not the goal in such cases, but
rather the stabilization of the teeth in a status quo to
rather the stabilization of the teeth in a status quo to
prevent an increase of mobility.
prevent an increase of mobility.
27. Biomechanical Considerations
Biomechanical Considerations
In addition to the increased load placed on
In addition to the increased load placed on
the periodontal ligament by a long-span
the periodontal ligament by a long-span
fixed partial denture, longer spans are less
fixed partial denture, longer spans are less
rigid.
rigid.
Bending or deflection varies directly with
Bending or deflection varies directly with
the cube of the length and inversely with
the cube of the length and inversely with
the cube of the occlusogingival thickness
the cube of the occlusogingival thickness
of the pontic
of the pontic.
.
29. Occluso - Gingival Thickness
Occluso - Gingival Thickness
There will be 8 times as much
There will be 8 times as much
deflection 18X if the thickness is
deflection 18X if the thickness is
decreased by one-half.
decreased by one-half.
30. Biomechanical Considerations
Biomechanical Considerations
Double abutments
Double abutments are sometimes used as a means of
are sometimes used as a means of
overcoming problems created by unfavorable crown-root
overcoming problems created by unfavorable crown-root
ratios and long spans.
ratios and long spans.
There are several criteria that must be met if a
There are several criteria that must be met if a
secondary
secondary (remote from the edentulous space) abutment
(remote from the edentulous space) abutment
is to strengthen the fixed partial denture and not become
is to strengthen the fixed partial denture and not become
a problem itself.
a problem itself.
A secondary abutment must have at least
A secondary abutment must have at least as
as much root
much root
surface area
surface area and as favorable a crown-root ratio as the
and as favorable a crown-root ratio as the
primary
primary (adjacent to the edentulous space) abutment it is
(adjacent to the edentulous space) abutment it is
intended to bolster.
intended to bolster.
Example
Example;Canine_premolar
;Canine_premolar
Lateral_canine
Lateral_canine???
???
32. Tilted Molar Abutments
Tilted Molar Abutments
A common problem that occurs with some frequency is the
A common problem that occurs with some frequency is the
mandibular second molar abutment that has
mandibular second molar abutment that has tilted mesially
tilted mesially into the
into the
space formerly occupied by the first molar.
space formerly occupied by the first molar.
It is impossible to prepare the abutment teeth for a fixed partial
It is impossible to prepare the abutment teeth for a fixed partial
denture along the long axes of the respective teeth and achieve a
denture along the long axes of the respective teeth and achieve a
common path of insertion
common path of insertion
39. Fixed Partial Denture
Fixed Partial Denture
Configurations
Configurations
Fixed partial dentures can be categorized as either
Fixed partial dentures can be categorized as either
simple
simple or
or complex
complex, depending on the number of teeth to
, depending on the number of teeth to
be replaced and the position of the edentulous space in
be replaced and the position of the edentulous space in
the arch.
the arch.
The
The classic simple fixed partial denture
classic simple fixed partial denture is one that
is one that
replaces a single tooth.
replaces a single tooth.
Longer spans generally place greater demands on the
Longer spans generally place greater demands on the
skills of the dentist, on the resistance of the retainers,
skills of the dentist, on the resistance of the retainers,
and on the abutments and their periodontal support.
and on the abutments and their periodontal support.
40. Fixed Partial Denture Configurations
Fixed Partial Denture Configurations
The maximum number of posterior teeth that can be
The maximum number of posterior teeth that can be
safely replaced with a fixed partial denture is
safely replaced with a fixed partial denture is three,
three, and
and
this should be attempted only under ideal conditions.
this should be attempted only under ideal conditions.
An edentulous space created by the loss of four
An edentulous space created by the loss of four
adjacent teeth other than four incisors is usually best
adjacent teeth other than four incisors is usually best
restored with either a removable partial denture or an
restored with either a removable partial denture or an
implant-supported fixed partial denture
implant-supported fixed partial denture
41. Third molars as abutments
Third molars as abutments
Rarely can third molars be used
Rarely can third molars be used ‘as
‘as abutments, since they
abutments, since they
have been removed from the mouths of so many patients.
have been removed from the mouths of so many patients.
Even when they are present, . they frequently display
Even when they are present, . they frequently display
incomplete
incomplete eruption;
eruption; short, fused 'roots
short, fused 'roots, and a marked
, and a marked
mesial inclination
mesial inclination in the absence of a second molar.
in the absence of a second molar.
If a third molar is to be considered as a potential abutment,
If a third molar is to be considered as a potential abutment,
it should be upright, with little or no mesial inclination, have
it should be upright, with little or no mesial inclination, have
long, distinctly separate roots; and be completely erupted.
long, distinctly separate roots; and be completely erupted.
It must have a healthy cuff of attached, keratinized gingiva
It must have a healthy cuff of attached, keratinized gingiva
that completely surrounds the tooth.
that completely surrounds the tooth.
42. Simple Fixed Partial Denture
Simple Fixed Partial Denture
Missing
Missing:
: Maxillary second
Maxillary second
premolar
premolar
Abutments:
Abutments: First premolar and first
First premolar and first
molar
molar
Retainers:
Retainers: Three-quarter crowns
Three-quarter crowns
Ponltc:
Ponltc: Metal-ceramic
Metal-ceramic
Abutment-pontic root ratio
Abutment-pontic root ratio:
: 3.1
3.1
Considerations
Considerations:
: Facial defects or
Facial defects or
patient request will necessitate
patient request will necessitate
metal-ceramic retainers. Resin-
metal-ceramic retainers. Resin-
bonded retainers can be used if
bonded retainers can be used if
the abutments are caries free or
the abutments are caries free or
very minimally affected by caries.
very minimally affected by caries.
43. Complex Fixed
Complex Fixed Partial Dentures
Partial Dentures (one tooth)
(one tooth)
Missing
Missing:
: Maxillary canine
Maxillary canine
Abutments
Abutments:
: Central incisor, lateral
Central incisor, lateral
incisor, and first premolar
incisor, and first premolar
Retainers
Retainers:
: Metal-ceramic
Metal-ceramic
Pontic:
Pontic: Metal-ceramic
Metal-ceramic
Abutment pontic root ratio
Abutment pontic root ratio: 2
: 2 .3
.3
Considerations
Considerations:
: Restore the
Restore the
occlusion to group function. Use of
occlusion to group function. Use of
the two premolars and the lateral
the two premolars and the lateral
incisor as abutments is not
incisor as abutments is not
desirable because it places too
desirable because it places too
heavy a burden on the smaller
heavy a burden on the smaller
single abutment, the lateral
single abutment, the lateral
incisor. single implant supported
incisor. single implant supported
metal-ceramic crown might be
metal-ceramic crown might be
considered here
considered here
44. Simple Fixed Partial Denture
Simple Fixed Partial Denture
Missing: Mandibular second
premolar
Abutments: First premolar and first
molar
Retainers: Metal-ceramic crown on
premolar and full crown on molar
Pontic: Metal-ceramic
Abutment-pontic root ratio: 3,1
45. Complex Fixed Partial Dentures
Complex Fixed Partial Dentures
(more than two teeth)
(more than two teeth)
Missing
Missing:
: Both maxillary central incisors
Both maxillary central incisors
and one lateral incisor
and one lateral incisor
Abutments:
Abutments: Both canines and the
Both canines and the
remaining lateral incisor
remaining lateral incisor
Retainers:
Retainers: Metal-ceramic
Metal-ceramic
Pontics:
Pontics: Metal-ceramic
Metal-ceramic
Abutiment-pontic root ratio
Abutiment-pontic root ratio:
: 1.3
1.3
46. Missing
Missing;
;
AII maxillary incisors
AII maxillary incisors
Abutments:
Abutments: Canines and first
Canines and first
premolars
premolars
Retainers:
Retainers: Metal-ceramic
Metal-ceramic
Pontics;
Pontics;
Metal-ceramic
Metal-ceramic
Abutment-pontic root ratio
Abutment-pontic root ratio:
: 1,3
1,3
47. Complex fixed Partial denture
Complex fixed Partial denture
Missing;
Missing; Maxillary first and second
Maxillary first and second
premolar and first molar
premolar and first molar
Abutments:
Abutments: Canine and second
Canine and second
molar retainers
molar retainers
Pontics
Pontics: Metal-ceramic
: Metal-ceramic
Ab
Abutment-pontic root ratio
utment-pontic root ratio:
: 0.8
0.8
considerations:
considerations: This fixed partial
This fixed partial
denture can be made only if the
denture can be made only if the
clinical crowns of the abutments
clinical crowns of the abutments
are long and perfectly aligned. The
are long and perfectly aligned. The
occluso glngival dimension of the
occluso glngival dimension of the
edentulous space must be ample
edentulous space must be ample
to provide adequate rigidity. This
to provide adequate rigidity. This
fixed partial denture has a much
fixed partial denture has a much
better prognosis if the opposing
better prognosis if the opposing
occlusion is on a removable partial
occlusion is on a removable partial
denture. Canine guidance is
denture. Canine guidance is
important in this situation.
important in this situation.
49. PRINCIPLES OF TOOTH PREPARATION
PRINCIPLES OF TOOTH PREPARATION
The design of a preparation for a cast
The design of a preparation for a cast
restoration and the execution of that
restoration and the execution of that
design are governed by five principles:
design are governed by five principles:
1.
1. Preservation of tooth structure
Preservation of tooth structure
2.
2. Retention and resistance
Retention and resistance
3.
3. Structural durability
Structural durability
4.
4. Marginal integrity
Marginal integrity
5.
5. Preservation of the periodontium
Preservation of the periodontium
50. RETENTION AND RESISTANCE
RETENTION AND RESISTANCE
Retention; Prevents
Retention; Prevents removal of the restoration along the
removal of the restoration along the
path of insertion or long axis of the tooth preparation
path of insertion or long axis of the tooth preparation
Resistance; Prevents
Resistance; Prevents dislodgement of the restoration by
dislodgement of the restoration by
forces directed in an apical or oblique direction and
forces directed in an apical or oblique direction and
prevents any movement of restoration under occlusal
prevents any movement of restoration under occlusal
forces.
forces.
TAPER
TAPER
FREEDOM OF DISPLACEMENT
FREEDOM OF DISPLACEMENT
LENGTH
LENGTH
PATH OF INSERTION
PATH OF INSERTION
SUBSTITUTION OF INTERNAL FEATURES
SUBSTITUTION OF INTERNAL FEATURES
53. Path of Insertion
Path of Insertion
The
The path of insertion
path of insertion is an imaginary line along
is an imaginary line along
which the restoration will be placed onto or
which the restoration will be placed onto or
removed from the preparation
removed from the preparation.
.
It is determined mentally by the dentist before
It is determined mentally by the dentist before
the preparation is begun, and all features of the
the preparation is begun, and all features of the
preparation are cut to coincide with that line..
preparation are cut to coincide with that line..
It is of special importance when preparing teeth
It is of special importance when preparing teeth
to be fixed partial denture abutments, since the
to be fixed partial denture abutments, since the
paths of all the abutment preparations must
paths of all the abutment preparations must
parallel each other.
parallel each other.
54. Path of Insertion
Path of Insertion
For a preparation to be surveyed in the mouth, where direct vision is
For a preparation to be surveyed in the mouth, where direct vision is
rarely possible, a mouth mirror is used. It is held at an angle
rarely possible, a mouth mirror is used. It is held at an angle
approximately 1/2 inch above the preparation, and the image is
approximately 1/2 inch above the preparation, and the image is
viewed with one eye
viewed with one eye
55. PATH OF INSERTION
PATH OF INSERTION
The path of insertion must be
The path of insertion must be
considered in two dimensions:
considered in two dimensions:
faciolingually
faciolingually and
and
mesiodistally.
mesiodistally.
The facio
lingual orientation of
The facio
lingual orientation of
the path can affect the
the path can affect the
esthetics of metal-ceramic or
esthetics of metal-ceramic or
partial veneer crowns,
partial veneer crowns,
56. PATH OF INSERTION
PATH OF INSERTION
The mesiodistal inclination of
The mesiodistal inclination of
the path must parallel the
the path must parallel the
contact areas of adjacent
contact areas of adjacent
teeth. If the path is inclined
teeth. If the path is inclined
mesiaily or distally, the
mesiaily or distally, the
restoration will be held up at
restoration will be held up at
the proximal contact areas and
the proximal contact areas and
be "locked out"
be "locked out"
“Locked out"
Correct
Correct
58. 2.
2. Functional cusp bevel
Functional cusp bevel
Lack of a functional cusp
Lack of a functional cusp
bevel can cause a thin area
bevel can cause a thin area
or perforation in tile casting.
or perforation in tile casting.
Over inclination of
Over inclination of
the buccal surface
the buccal surface
will destroy
will destroy
excessive tooth
excessive tooth
structure while
structure while
lessening retention
lessening retention
The functional cusp bevel is
The functional cusp bevel is
an integral part of occlusal
an integral part of occlusal
reduction
reduction
Lack of functional cusp
Lack of functional cusp
bevel may result in over
bevel may result in over
contouring and poor
contouring and poor
occlusion
occlusion
59. Preservation Of The Periodontium And
Preservation Of The Periodontium And
Finish Line Placement
Finish Line Placement
60. ACCURATE IMPRESSIONS
ACCURATE IMPRESSIONS
Exact impression capture
Exact impression capture
will enable consistent,
will enable consistent,
precise communication.
precise communication.
Since the development of
Since the development of
clear, concise margins is
clear, concise margins is
paramount to the transfer
paramount to the transfer
of critical hard and soft
of critical hard and soft
tissue structures, the use
tissue structures, the use
of high-quality impression
of high-quality impression
materials will provide
materials will provide
dimensional stability and
dimensional stability and
accuracy.
accuracy.
61. Contact with Tray
Contact with Tray
Distortion of the final
Distortion of the final
impression may occur due
impression may occur due
to improper tray positioning.
to improper tray positioning.
In order to ensure proper fit
In order to ensure proper fit
and capture, care must be
and capture, care must be
taken that:
taken that:
•
• Appropriate tray materials
Appropriate tray materials
are selected prior to
are selected prior to
Impression taking
Impression taking
•
• Correct tray seating
Correct tray seating
procedures are followed
procedures are followed
•
• Correct tray size and
Correct tray size and
shape are determined pre
shape are determined pre
operativeyI
operativeyI
62. IMPRESSION LEDGES
IMPRESSION LEDGES
•
• Improper tray
Improper tray
position
position
•
• Dislodging the tray
Dislodging the tray
from the material prior
from the material prior
to full setting
to full setting
63. PRELIMINARY CAPTURE
PRELIMINARY CAPTURE
A preliminary impression of the
A preliminary impression of the
preparations was captured
preparations was captured
without wash material.
without wash material.
Since the material is
Since the material is
thixotropic and does not
thixotropic and does not
provide sufficient contact with
provide sufficient contact with
the tooth, the margins were
the tooth, the margins were
Inaccurate. Inadequate time
Inaccurate. Inadequate time
between mixing and seating,
between mixing and seating,
rocking of the tray to achieve
rocking of the tray to achieve
proper seating, and tray
proper seating, and tray
movement following seating
movement following seating
will also result in accurate
will also result in accurate
margin capture
margin capture
64. DEFINITIVE IMPRESSION
DEFINITIVE IMPRESSION
The final impression
The final impression
demonstrates clear
demonstrates clear
margin detail, and the
margin detail, and the
tooth structures are
tooth structures are
evenly centered within the
evenly centered within the
material
material for
for accurate
accurate
communication.
communication.
The use of hydrophilic
The use of hydrophilic
and hydrophobic
and hydrophobic
materials may also enable
materials may also enable
fluid displacement for
fluid displacement for
definitive impression
definitive impression
capture without involved
capture without involved
hemostasis or retraction
hemostasis or retraction
techniques (in select
techniques (in select
Instances).
Instances).
65. Voids
Voids
Voids can be developed
Voids can be developed
within the impression due
within the impression due
to:
to:
Inadequate sulcus
Inadequate sulcus
retraction
retraction
The use of incorrect
The use of incorrect
syringing techniques
syringing techniques
around the preparation
around the preparation
A prolonged period
A prolonged period
between mixing and
between mixing and
seating of the impression
seating of the impression
material
material
66. Inadequate Margins
Inadequate Margins
Inadequate capture of the
Inadequate capture of the
gingival margin may
gingival margin may
occur due to:
occur due to:
Insufficient retraction of
Insufficient retraction of
the sulcus around the
the sulcus around the
preparation
preparation
Presence of moisture or
Presence of moisture or
bleeding
bleeding
Insufficient cord retraction
Insufficient cord retraction
and tissue displacement
and tissue displacement
67. TEARING
TEARING
Appropriate setting times must
Appropriate setting times must
be consistently observed to
be consistently observed to
avoid premature removal of
avoid premature removal of
the tray from the mouth and
the tray from the mouth and
subsequent tearing.
subsequent tearing.
Inadequate retraction of the
Inadequate retraction of the
sulcus and the presence of
sulcus and the presence of
moisture or bleeding around
moisture or bleeding around
the preparation may also
the preparation may also
cause some Impression
cause some Impression
materials to tear.
materials to tear.
71. Accurate Replica
Accurate Replica
Transfer of critical hard and soft
Transfer of critical hard and soft
tissue contours is possible when
tissue contours is possible when
the hard and soft tissue
the hard and soft tissue
architecture is accurately captured
architecture is accurately captured
during the impression-taking
during the impression-taking
procedure.
procedure.
72. OCCLUSAL REGISTRATION
OCCLUSAL REGISTRATION
The purpose of occlusal registration is to allow accurate
The purpose of occlusal registration is to allow accurate
mounting of casts.
mounting of casts.
A formal registration may not be required if a
A formal registration may not be required if a small
small
number of teeth
number of teeth are being restored and there are
are being restored and there are
sufficient remaining contacts on the unprepared teeth to
sufficient remaining contacts on the unprepared teeth to
allow the technician to establish adequately the
allow the technician to establish adequately the
intercuspal position (ICP).
intercuspal position (ICP).
In situations where patients have
In situations where patients have lost posterior occlusal
lost posterior occlusal
support
support, accurate occlusal registration may only be
, accurate occlusal registration may only be
recorded with the aid of laboratory fabricated registration
recorded with the aid of laboratory fabricated registration
plates with wax rims
plates with wax rims
73. OCCLUSAL REGISTRATION
OCCLUSAL REGISTRATION
Principal Positions
Principal Positions
When adopting a confirmative approach (i.e. the
When adopting a confirmative approach (i.e. the
crown or bridge is to be in harmony with existing
crown or bridge is to be in harmony with existing
jaw relationships), the intercuspal position
jaw relationships), the intercuspal position (ICP)
(ICP)
should be recorded.
should be recorded.
By contrast, when a reorganised approach has
By contrast, when a reorganised approach has
been planned (i.e. the occlusal scheme is to be
been planned (i.e. the occlusal scheme is to be
modified), a record of the retruded contact
modified), a record of the retruded contact
position
position (RCP)
(RCP) is indicated.
is indicated.
However, in most situations, given satisfactory
However, in most situations, given satisfactory
completion of preparatory management, the
completion of preparatory management, the
occlusal registration should record the patient’s
occlusal registration should record the patient’s
ICP.
ICP.
79. TRY-IN
TRY-IN
Purpose
Purpose
To confirm the clinical acceptability of completed
To confirm the clinical acceptability of completed
or partially completed crown and bridge in terms
or partially completed crown and bridge in terms
of:
of:
Marginal adaptation
Marginal adaptation
Contacts and relationships with adjacent and
Contacts and relationships with adjacent and
opposing teeth
opposing teeth
Form and function
Form and function
Cosmetic qualities
Cosmetic qualities
Patient acceptance
Patient acceptance
80. TRY-IN
TRY-IN
Principles
Principles
Prior to an appointment for try-in, crowns and bridges
Prior to an appointment for try-in, crowns and bridges
should be
should be carefully inspected
carefully inspected together with the master
together with the master
casts, and when available, the impression of the
casts, and when available, the impression of the
preparations to confirm satisfactory completion of the
preparations to confirm satisfactory completion of the
laboratory work
laboratory work
Any
Any minor adjustments
minor adjustments or further laboratory instructions
or further laboratory instructions
are generally best completed while the patient is still
are generally best completed while the patient is still
present.
present.
If a crown or bridge is considered to be unsatisfactory at
If a crown or bridge is considered to be unsatisfactory at
try-in, the
try-in, the cause of the failure should be identified
cause of the failure should be identified before
before
proceeding to remake the defective restoration.
proceeding to remake the defective restoration.
81. Cont;
Cont;
PRINCIPLES
PRINCIPLES
Consideration should be given to
Consideration should be given to temporarily cementing
temporarily cementing
crowns and bridges which, for example, alter vertical
crowns and bridges which, for example, alter vertical
face height or change occlusal function despite satisfying
face height or change occlusal function despite satisfying
criteria for clinical acceptability.
criteria for clinical acceptability.
Having patients confirm the
Having patients confirm the comfort and their
comfort and their
acceptance
acceptance of the appearance of crowns and bridges
of the appearance of crowns and bridges
should be considered a routine element of try-in
should be considered a routine element of try-in
procedures.
procedures.
82. CEMENTATION/BONDING
CEMENTATION/BONDING
Technique
Technique
The preparations should be cleaned, isolated and,
The preparations should be cleaned, isolated and,
where indicated, primed and conditioned as required for
where indicated, primed and conditioned as required for
the luting system selected.
the luting system selected.
The final restorations must be fully seated within the
The final restorations must be fully seated within the
available working time, with evidence of the luting
available working time, with evidence of the luting
material having completely filled the
material having completely filled the
preparation/restoration interface.
preparation/restoration interface.
While it is highly desirable to have some excess luting
While it is highly desirable to have some excess luting
material present along the entire margin of the
material present along the entire margin of the
restoration, gross excesses of these materials are best
restoration, gross excesses of these materials are best
removed.
removed.
84. CEMENTATION/BONDING -TECHNIQUE
CEMENTATION/BONDING -TECHNIQUE
The restorations must not be allowed to move relative to
The restorations must not be allowed to move relative to
the underlying preparation(s) during the critical initial
the underlying preparation(s) during the critical initial
set/polymerisation of the lute.
set/polymerisation of the lute.
At this time special precautions may be required to
At this time special precautions may be required to
isolate and protect the luting material used
isolate and protect the luting material used
When set, the
When set, the excess
excess luting material
luting material should be removed
should be removed
using instruments and techniques least liable to cause
using instruments and techniques least liable to cause
damage.
damage.
During the removal of excess luting material it is of
During the removal of excess luting material it is of
particular importance to ensure that no excess is left in
particular importance to ensure that no excess is left in
interproximal or subgingival sites.
interproximal or subgingival sites.
85. CONCLUDING REMARKS
CONCLUDING REMARKS
The completion of crown and bridge to a high
The completion of crown and bridge to a high
standard is an exacting task for the whole dental
standard is an exacting task for the whole dental
team: clinician, technician, nurse and other
team: clinician, technician, nurse and other
support staff, as well as for the patient. This is
support staff, as well as for the patient. This is
one area where a dentist can rapidly make, or
one area where a dentist can rapidly make, or
lose, a name for her/himself within their
lose, a name for her/himself within their
practising area.
practising area.
I hope that you have found these guidelines a
I hope that you have found these guidelines a
useful and practical reminder of the standards
useful and practical reminder of the standards
that we are all trying to achieve
that we are all trying to achieve
