Crown & Bridge

Lecture 2 Dr Farid

Fixed Partial Denture

Indications

A) General:

1- Psychological: The FPDs are rapidly tolerated by patients than RPDs

2- Systemic: as in epileptic patients (attack of unconsciousness), the FPDs
have adequate strength & retention, while in RPD, there is a potential for
fracture or inhalation.
3- Orthodontic consideration: FPDs are indicated for stabilizing the
orthodontic results (e.g., FPD used to replace missing lateral incisor after
diastema between two centrals has been closed).
4- Speech: RPDs are bulky, which cause difficulty in speech. In contrast,
in FPDs, the size of pontics are similar to the missed teeth which rarely cause
difficulty in speech.
5- Periodontal reasons: FPDs can stabilize teeth with minor mobility using
fixed splint (bridge), to prevent further movement that leads to drifting or
over extrusion with more loss of bony support, additionally, to ensure that
the mastication forces are eventually distributed over several teeth rather
than overloading on a tissue that is seriously weakened by the disease.

B) Local:

1) The bridges are indicated wherever there are properly distributed healthy
teeth that serve as abutments.

 Vital tooth or endodontically treated with no radiographic evidence of

pathology

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  Adequate crown/root ratio

 Good periodontal condition

 Root configuration & angulations

2) Tooth suitable as abutment which require cast restoration (the same tooth
lie adjacent to edentulous space & suitable as abutment).

3) Unfavourable angulations of teeth for removable prosthesis (badly tilted

teeth).

4) It is advisable to restore edentulous space with fixed rather than RPD,

because the force of occlusion transmitted to periodontium, then to the
alveolar bone (natural), while in the RPD the occlusal force is transmitted to
muco-periostium, and then the underlying bone (which is not designed for
this function).

Contraindications:

A- General:

1- Uncooperative patient: difficult to achieve satisfactory result.

2- Social problem: FPDs are more expensive than RPDs. Usually the patient
must be given what he wants, which makes him sometimes unsatisfied for
the results.
3- Occupation: boxers, hockey players, and pipe smokers are not advisable for
FPDs (fracture of teeth or restorations)

4- Poor oral hygiene: The bad attitude toward dentistry limit the decision to
make FPDs unless the patients are positively motivated before treatment.

5- Age: FPDs are preferred to be done after the age of 18 yrs. especially in the
posterior region due to the large pulp size or teeth are not fully erupted. They
are not indicated for elderly patient when there is a lack of resilience of the

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 periodontal membrane or teeth attrition which increase the size of occluding
surfaces.

B- Local:

1- Absence of distal abutment.

2- A considerable bone loss in the visible area of the mouth.

3- Long span.

4- Abutment related factors (tooth not suitable as abutment: length, shape,

caries, and periodontal support).

Advantages of the bridges: They improve appearance, function, & speech.

They maintain the occlusal stability, provide periodontal splinting, and restore
occlusal vertical dimension.

Disadvantage of the bridges: They may induce tooth & pulp damage,
potential secondary caries, periodontal problem added to the high cost.

Comparison & advantages of fixed bridges over RPDs:

1) More stable & comfortable because it covers less tissue surface (there is no
acrylic base, flanges or clasps).

2) More aesthetics.

3) More stable occlusion with even distribution of the occlusal forces.

4) Provide a splinting action, while the RPDs push the teeth and cause mobility.

5) Easier cleaning using tooth brushes and dental floss (when there is a point
contact between pontic & the underlying tissue), in contrast, the RPD must
be removed to be cleaned.

6) Do not irritate tissues or apply pressure on them.

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7) Psychological patients can easily tolerate FPD rather than removable one.

8) The FPDs are preferred for handicapped, epileptic patients, and patient with
Parkinson disease due to the possibility of fracture or inhalation of the RPD.

9) No speech difficulty in FPDs

10) Badly tilted abutment teeth may interfere with the construction of PD (due
to the presence of undercut that lead to food stagnation). A telescopic bridge
with metal coping, or fixed-movable bridge or proximal half-crown can be
used.

11) Anatomical limitation of RPDs such as abnormally large tongue,

muscular disorder, mandibular tori (torous), and palatal surface tissue.

Classification of dental bridges (Types of bridge):

A. Depending on the materials used

1. Cast metal FPDs

2. Metal-ceramic FPDs

3. All-ceramic FPDs

4. Resin-veneered FPDs

B. Depending upon location: Anterior FPDs, and posterior FPDs

C. Depending on number of teeth: Two units FPDs, Three units FPDs.

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D. Depending upon the tooth reduction

1. Conventional (Conventional preparation) bridges:

where a substantial tooth reduction is necessary for the
abutment teeth.

2. Minimally-prepared bridges: (adhesive, acid etched,

resin-bonded bridge): These bridges are luted to the
unprepared or minimally prepared surfaces of the
abutments with resin adhesives.

3. Hybrid bridges: A combination of conventional & minimally

prepared teeth. The figure shows a Fixed-movable with a
minimal- retainer carrying the movable connectors

4. Implant-Supported FPDs: Bridges that are totally

supported by implant fixers, usually are not attached to the
adjoining natural teeth, which are either can be removed
by the dentist only, or can be removed by the patient for
cleaning or any other reasons.

5. Removable bridges: Bridges that are totally supported by teeth which differ
from the RPDs. They are either be removed by the dentist only, or can be
removed by the patient for cleaning or any other reason. They are designed
to overcome problems associated with long span FPD, such as Andrew s
bridge system that is indicated for edentulous ridges with sever vertical
defect. The prosthesis consists of a fixed & a removable component

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 Figure 1: Preoperative and post teeth reduction for porcelain fused to metal
restorations

Fig. 2: Metal try-in, and waxed up trial denture for RPD

Fig 3. Post-operative Picture: Andrew's Bridge replacing

E. Depending upon the connectors (Basic bridge designs)

1. Fixed-fixed bridge:

- Preferred for long-span bridges.

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- Have rigid connector at both end of the pontic.

- Maximum retention & strength.

- All retainers are major which require extensive

tooth reduction.

- Unconservative, more destruction of the tooth

structure & trauma to the pulp

- Must have only one path of insertion (the

preparations of both abutments need to be parallel).

-The entire occlusal surfaces of both abutments must be covered with retainers
otherwise the occlusal forces will be directed on the unprepared area which
depress the tooth downward & break the connectors.

- All retainers must have approximately the same amount of retention reducing
the risk of dislodgement when the force is applied on weak retainers.

-. Abutment teeth are splinted together (adequate in case of mobile teeth).

- Cemented as one piece.

2. Fixed- mobile design:

- Have rigid connector (major) at the distal end of pontic & mobile (minor)
connector mesially.

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- More conservative to tooth structure than
fixed-fixed design, because minor retainers
need less tooth reduction.

- It allows minor tooth movement (lateral &

vertical).

- Limited to one missing tooth (limited length

of span).

- Parts of the bridge can be cemented

separately.

- Lab. construction is complex & difficult.

- Preparation of abutment does not need to be parallel.

- It is indicated to be used in divergent abutment teeth (unparallel), whenever

a pier abutment is present (complex bridge), and for aesthetic consideration
(class III inlay on distal of canine).

3. Simple cantilever:

- The support for the pontic at one end only.

- Pontic may attach to one or two retainer.

- Abutment tooth is either mesial or distal to the span.

- It is the most conservative design

- Limited cases, as in lateral incisor replacement using

the canine as abutment when the occlusion is favourable.

- The design can be used to replaced upper or lower first premolar & second
molar.

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4. Spring cantilever

-The pontic attach to a long metal arm (flexible bar) run into the palate &
terminate with rigid connector on the palatal side of a single retainer on upper
4 or pair 4 & 5.

- Tooth retained and tissue borne.

- Forces are absorbed by the springing of the arm and

by displacement of the soft tissue of the palate.

- The abutments are usually posterior teeth (tooth need restoration is better to
be used)

- Contraindicated in V-shape palate & in the lower arch

- It is indicated only for replacing missing upper incisor when the adjacent teeth
are sound, midline diastema, spacing of anterior teeth, or posterior teeth
need crown.

- Not advised for the lower arch due to the instability of the sub-mucosal tissue,
and a potential for plaque & calculus deposition.

5. Combination designs (Complex or compound bridge)

It is a combination of two or more of conventional designs incorporated in the

general design of bridge, such as:

- Fixed-fixed with simple cantilever.

- Fixed-fixed with fixed-mobile.

Benefits:

- Simplify the construction of the prothesis.

- Unfavourable angulation of abutments.

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- Simplify the preparation and conserve tooth tissues.

- Easily repaired after fracture.

- Precision retainers permit the separation of two or more components.

Fluid control and soft tissue management

Complete control of the environment of the operative site is essential during

restorative dental procedure. For the patient's comfort and safety, and for the
operator’s access and clear visibility.

Fluid control:
Depending on the location of the preparation in the dental arch, several
techniques can be used to create the necessary dry field of operation.

1- Rubber dam:

Rubber dam is the most effective of all isolation devices utilized in restorative
dentistry, but it has only limited direct application in the area of cast
restorations. It can be used during tooth preparation for inlays and onlays (if
the occlusal reduction is done before the dam is placed).

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2- High volume vacuum:

A high-vacuum suction type is extremely useful during the preparation

phases and is most effectively utilized within assistant when wielded by
acknowledgeable assistant, it makes an excellent retractor while the operator
uses a mirror to retract and protect the tongue.

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3- Saliva ejector:
The simple saliva ejector can be utilized effectively in some situations by the
lone dentist. It is most useful as an adjunct to high-volume evacuation, but it
can be used alone for the maxillary arch. The saliva ejector is placed in the
corner of the mouth opposite the quadrant being operated, and the patient's
head is turned toward it. It can also be used very effectively on the maxillary
arch for impression and cementation simply by adding cotton rolls in the
vestibule facial to the tooth being isolated. It can be used on the mandibular
arch while cotton roll holder positions cotton rolls facial and lingual to the teeth.

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Gingival Retraction
To displace free gingival tissue or to expose the margin of the
preparation, so that better impression could be taken. It is used when the
margin is sub gingival or with the level of gingival.

The objectives of the gingival retraction are:

1. Create access for the impression material to the area of preparation
that is located subgingivally.
2. Provide enough thickness of the impression material at the area of the
finishing line to prevent distortion of the impression.
3. Prevent sulcular hemorrhage and fluid seepage which interrupt the
flow of impression material.

Techniques of gingival retraction could be:

1. Mechanical.
2. Combination of mechanical and chemical (chemo-mechanical).
3. Surgical technique.

1- Mechanical: We apply pressure on the gingival to open the gingival

sulcus. May be done by:

A- Construction of temporary crown with long margin and leave it for half an
hour. Their effectiveness is limited because pressure alone often will not
control sulcular hemorrhage.

B- The most common way to do gingival retraction is by using retraction

cord which is special cord made of cotton comes either with or without
medicament (vasoconstrictor). The cord that is free from vasoconstrictor is
used as mechanical technique.

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 2- Chemomechanical: The cord contains vasoconstrictor (adrenaline). We
use it as mechanical and chemical retraction. By packing this cord in gingival
sulcus, between the tooth and the free gingival tissue using plastic instrument
(Ash no. 6) so that the cord physically pushes the gingival tissue away from
the finish line and the combination of the chemical action and pressure packing
help to control seepage of fluid from the wall of the gingival sulcus. We put the
retraction cord inside the gingival sulcus all around the tooth; it is left for 10
minutes.

3- Radial or surgical: done by using electrosurgical unit to remove gingival

tissues from finishing line or sometimes we do gingivectomy in case of
periodontal disease or inflammation.

Reference: Contemporary Fixed Prosthodontics

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