Finishing and cementation/ dental education in india

FINISHING AND CEMENTATION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents
Introduction
Procedures
Abrasives
Zones of the casting
Cementation
Ideal requirements
Types
Conclusion
References

The unpolished surface is relatively
rough, and a series of finishing
procedures are needed to produce a
highly polished surface to limit the
accumulation and retention of plaque
and facilitate maintenance the health
the supporting periodontal tissues.

Cast metal restorations needs a series of
finishing procedures before try in and
cementation.
1. Preliminary procedures
2. Try in and adjustment
3. Pre cementation polishing
4. Cementation and
5. Post cementation polishing.

ABRASIVES AND POLISHING MATERIALS
Abrasion : It is the smoothening of
rough surface before preparing it for
polishing. The smoothening is carried
out by cutting action.

COMMON ABRASIVES USED
1. Diamond: chips are bound to a metal
shape by ceramic bond or
electroplating.hardest of all abrasives used
on enamel or porcelain.

2. Silicon carbide: basic material for
carborundom. It is sintered or pressed with
a binder into grinding wheels or discs.

3. Emery: it is a mixture of aluminium oxide
and iron oxide.Hard and black natural mineral
can be used on gold and porcelain.

4. Garnet: several minerals having similar
properties.used for grinding plastics and metal
alloys.
5. Sand paper: form of quartz,rounded or
angular in shape.they are typically bonded to
Paper discs for grinding metals and plastics.

6. Aluminium oxide:common abrasive used in
dentistry in the form discs and strips.
It is also impregnated into rubber wheels and
points. Used to adjust enamel or finish metal
alloys and ceramic materials

Zone-1 Internal margins:
Objective: To minimize any dissolution of the
luting agent, a 1mm wide band of metal
must be obtained that is closely adapted to
the tooth surface.

Here we should inspect the internal portion for
small nodules or bubbles and should be
removed with a hand piece using round
bur,but care should be taken to avoid damage
to the margin and annoying remakes.

Zone-2 Internal
surface:
Objective: is that no
contact should exist
between the disc and
the internal surface of
the casting.
It should be
examined for the
nodules.

Nodules should be
removed with a round
bur and carefully seated
on the die.
Force should not be
applied as any nodule
present may scratch the
die and this will result in
a restoration with poor
margins and poor
prognosis.

In the areas of the nodule, deliberate
removing of slightly greater amount of
alloy is recommended and should be
removed in one single step.

Marking agents
Several agents are commercially
available to facilitate identifications seating
interference between the casting and die.
1.Water soluble dies eg;ligna mark.
2.Solvent based dies eg;accufilm
3.Powdered sprays eg;occludent
4.A suspension of rouge in chloroform.

Zone-3 The sprue:
Objective; Is to establish proper coronal
morphology and function.
A corborundum separating disk is used
to cut the sprue
Cutting should be done circumferentially
Excess in the area of the sprue
attachment is removed with the disk, and
the area is refined with stones and
sandpaper disks

Zone-4 Proximal
contacts
Objective: is to adjusted
so that they will be in
correct when evaluated
in the mouth.
Proximal contacts on the
stone cast can be
achieved by careful
scraping of the adjacent
teeth with a blade.

Articulating strips between adjacent castings
or between the castings and the adjacent
tooth is helpful, as it allows the areas where
binding contact occurs to be adjusted
through grinding.

Connectors
The connectors require
special attention when
fixed partial denture is
finished
Periodontal health is
compromised if they are
not properly contoured
and finished.
Parabolic configuration

Rotary instruments
such as rubber
wheels, which
allows access to the
cervical margin are
used so that they do
not jeopardize the
margins

Zone-5 Occlusal
surface
Objective is to re-establish
Occlusal contacts in static and
dynamic relationship to the
opposing arch.
Occlusal contacts are
checked with Mylar
articulating strips.
Occlusal prematurities are a
result of excessive heavy
contact on the wax pattern as
the wax is subject to elastic
recovery.

The adjustments are
done with flame
shaped finishing
burs.The entire
ridge or cusp should
be redeveloped
rather than grinding
only the point of
interference.
After refinement of
the Occlusal
contacts ,they
should be altered
with extensive
polishing.

Zone-6 Axial walls
Objective: The axial walls
should be smoothly
contoured and polished so
that the patient can carry out
plaque control.
Surface defects are removed
by grinding with abrasive
particles
Polishing should be carried
out by using the abrasives in
a sequence. The finer
abrasive should be used last
because the coarser grits
will remove material
efficiently www.indiandentalacademy.com

Zone-7- External
margins
Objective: for the
restorations longevity.
Cavo-surface margins
should be finished
directly on the tooth.
Those parts that
cannot be finished on
the tooth should be
finished on the disc
The edges of the
margin should not be
distorted

A fine grit stone is used to remove casting
roughness, followed by soft rubber wheel and
finally by rouge or a brush, during all these
procedures, the casting should be supported by
the finger.

Once the laboratory procedures are completed the
restoration should be evaluated in the patient’s mouth
before final finishing and cementation
•It should be evaluated for the following:
1.Proximal contacts
2.Margin integrity
3.Stability
4.Internal fit
5.External contour
6.Occlusion
7.Surface finish

Proximal contacts
Proximal contacts should be like those of natural
teeth
Use of floss is a convenient method to compare
the contacts
If the floss does not pass, the contact is too tight
Ideal contact should allow for positional stability of
the abutments and adjacent teeth as well as easy
maintenance of the supporting structures

EXCESSIVE
TIGHTNESS.
1. Metal restorations
Adjustments are made with
rubber wheel. The satin
finish produced helps to
identify where binding
occurs because a shiny
spot will appear where
adjustment is necessary.

2.porcelain
restorations
If high proximal
contact in unglazed
porcelain is easily
adjusted with cylindrical
mounted stone. Area
identified by red pencil.
If adjustment of glazed
porcelain is needed, it
can be polished with
diamond impregnated
silicone points or
diamond polishing paste

Deficiency
Usually corrected by soldering.
Armamentarium:
Soldering tweezers
Gold solder
Paste flux
Bunsen burner
Antiflux and polishing armamentarium

1. Roughening the area with disk
2. Adding antiflux- granite
3. Roughened surface is painted with flux
4. Then the casting is held on the bunsen
flame at the height of the reduction
portion of the flame

5. As the solder heats up it starts to fuse
and rapidly spread. It should be tipped
to help the solder flow in the desired
direction.
6. Proximal contact is then readjusted.

Porcelain restorations
Deficient porcelain contact requires
additional fixing, it is at bisque stage.
If restoration has been completely
finished, add on or convection
porcelain can be used

Margin integrity
The completed
restoration should go
into its place without
binding and the best
adaptation should be at
its margins.
A sharp explorer moved
from restoration to tooth
and from tooth to
restoration can be
evaluated for marginal
adaptation.

Stability
The restoration should be checked for
stability. It should not rock or rotate, any
degree of instability is likely to cause failure
during function.

Occlusion
The occlusion contact with the
opposing teeth is carefully
checked.any undesirable
eccentric contacts as well as
centric interferences must be
identified.
Use of two different colored
ribbon tapes or articulating
paper is used for excursive
movements and centric
contacts. Ant interferes are
then corrected with diamond
or white stone

Ceramic restorations
Ceramic restorations need certain additional
steps during evaluation to satisfy esthetic,
biologic and mechanical requirements.
Contour, surface characteristics and color
match.

Contour
The contours of the gingival third is verified
Excessive bulk may be associated with
periodontal disease
When adjustment is necessary porcelain and
metal should not be grounded together.

If at all grinding both is
absolutely necessary, the
direction of grinding is
parallel to the metal-
ceramic junction.
The incisal edge should be
checked for proper position
and shape
This is the key for good
esthetics and function.

The negative space
should be evaluated
(incisal embrasures)
The absence of
embrasures draws
attention to the
prosthesis
When viewed from the
incisal inter proximal
embrasures should be
as narrow and deep as
possible

Cementation
Cement: Binding agent used as a substance to
make objects to adhere to each other, or
something serving to firmly unite. GPT-8
Luting agent: Material that on hardening will fill
a space or bind adjacent objects. GPT-8

Cementation- The process of attaching
parts by means of cement or attaching a
restoration to natural teeth by means of
cement.GPT-7.
Luting materials play a central role in indirect
dentistry by aiding the retention of
restorations and in the prevention of leakage
at their margins.

The ideal luting material should be:
Bio- compatible with the tissues
Adhere to tooth surface and restoration either
chemically, mechanically or both.
Prevent leakage by producing a good marginal
seal
Have sufficient mechanical properties to resist
forces transmitted to the lute through the
restoration that is it should have high tensile and
compressive strength, high fracture toughness
and fatigue strength and a modulus of elasticity
which is appropriate for stress absorption

Be cariostatic
Be insoluble in the dilute organic acids
Resist water sorption
Be available in sufficient range of shades
Achieve optimal physical properties as quickly
as possible
Allow easy removal of excess and clean- up

It should have sufficiently low film thickness, so
that the restoration may seat fully.
Should have radio-opacity similar to or greater
than dentine
Additionally the luting cement should be
technique insensitive

They can be classified according to the material
from which they are formed and more generally,
as active and passive.

Active luting materials
They are bonded both to tooth and restoration
make the restoration and tooth synergistic and
there by play a role in the retention of the
restoration,as well as sealing its margins and
filling the space between restoration and tooth.

Passive luting materials
They merely fill the gap between the indirect
restoration and tooth, with no chemical
adhesion at the restorative or lute and or tooth
or lute interface.

PASSIVE LUTING MATERIALS
Zinc phosphate cement:
Oldest of the currently available luting materials
Powder- liquid material has zinc oxide as the
main constituent of the powder and liquid is an
aqueous solution of phosphoric acid.
Zinc oxide powder react with phosphoric acid to
form an insoluble phosphate

Setting time can be lengthened by mixing on a
chilled glass slab and working time can be
prolonged by adding small increments of
powder to the liquid
PH of freshly mixed cement is between 1.6 –
3.6.
Clean – up is relatively simple, as the setting
cement reaches a rubbery stage and can be
peeled off the restoration.
Compressive and tensile strengths are
adequate but the solubility of the set material is
high in solutions of lower ph.
Another major disadvantage is the lack of
adhesion to the tooth surface.

Zinc-polycarboxylate
Fore runner to glass ionomer cements
Introduced by SMITH in 1968, showed true
adhesive attachment by molecular bonding to tooth
structure.
Based on the reaction of zinc oxide and polyacrylic
acid to form zinc polyacrylate

Clean –up is difficult as it will stick to the mucosa
and should be removed as soon as possible after
placement.
They are as strong as zinc phosphate with higher
tensile strength, however, they are more soluble
than zinc phosphate and may absorb water.

Glass ionomer cements
The first glass ionomer cements were developed in
1978
These cements contain anion- leach able fluoro-
alumino-silicate glass which reacts with a water
soluble polymeric acid
The outer layer of glass particles are decomposed
leading to release of Ca+,Al+ and F- ions.thus the
set cement is therefore a core of unreacted glass
particles sheathed by a siliceous hydro gel bounded
together by the reaction products.

These materials also release fluoride. The value
of this fluoride release in cariostatic is
questionable.
These cements adhere to enamel and dentin and
contribute to the retention of the restoration. 20-
30% higher retention than zinc phosphate or zinc
polycarboxylate cement.
However these cements have been reported to
cause inflammatory response in pulpal tissue
under deep restorations
They have superior compressive strength but
their tensile strength is low and fracture
toughness is also low

Resin modified glass ionomer cements
These materials were developed to overcome some
of the short comings of traditional glass ionomer
cements
In addition to components of glass ionomer they
contain a monomer such as 2 hydroxy-ethyl
methacrylate (HEMA) or BIS-GMA.

Advantages over Conventional Glass
Ionomers are:
Improved bio-compatibility
Better fluoride release
Improved adhesion to tooth and
Improved physical properties, specially tensile
strength
Clean- up is easy as it goes through a rubbery
phase.eg: Fujiplus,Fuji-cem and rely-X

Active luting agents
Resin based luting materials
These cements bond to the tooth by the cure of
dentin – bonding agent. These materials may also
be bonded to a ceramic surface which has been
rendered micro-mechanically retentive by treating
with acids such as hydrofloric acid, while bonding
to metal surfaces may be achieved by oxidising
ortin plating gold surfaces

Bonding is usually achieved with organo-
phosphates, HEMA or 4-META(4-methacryl
ethyl trimellitic anhydride)

Their physical properties include=
Excellent compressive and tensile strength and
fracture toughness
Low solubility in oral fluids
Low potential for microleackage when bonded to
a tooth by an intermediary bonding systems.
High bio-compatibility when used with dentin
bonding systems

CHOICE OF LUTING AGENT
Zinc – phosphate
1. Cast restorations
2. Normal conservatively prepared tooth

Zinc polycarboxylate cement
1. Recommended on retentive preparations with
minimal pulp irritation.
Eg: children with large pulp chambers.

Glass ionomer cement
Popular for luting cast restorations

Resin modified glass ionomer luting
agents
Most popular because low solubility and low
micro leakage and reduced post
cementation sensitivity.

Adhesive resin
Material of choice with all ceramic
restorations.

Cementation with zinc phosphate
The field must be dry
Isolated with cotton rolls
Protection of pulp by application of
varnish|dentin bonding agent
Mixing done by adding increments
Mixing done on a wide area

When the consistency is right,load the
cement on to the restoration.
Tell the patient to put force to the
Occlusal surface by closing on a plastic
wafer.
Once the cement has set remove the
excess with explorer.

Cementation with
polycarboxylate
Isolate the quadrant
Blot dry the tooth
Dispense proper powder-liquid ratio
Spatulation should be complete in 30
secs
Cement is coated on the inside of the
casting and seated on the tooth.

Cementation with glass
ionomer
Clean and dry the tooth
The preparation can be dried with
pumice to increase retention.
Powder liquid ratio is 3.4:1
Mixing should be fast,applied on to the
restoration and seat the crown.
Excess cement removed after it has
become brittle

Resin cements
For metal restorations
Air abrade the the inside of the crown,rinse it
and dry it.
Dentin activator is appliued for 10 secs
Base catalyst ratio is 4:1,to this 2 scoops of
powder is added and stirred gently for 5 secs
to produce a creamy mixture
Apply the cement onto the restoration and
placed over the tooth.10 mins is the setting
time.

Ceramic restorations
Crown is is silaned by applying the silane
agent onto the internal surface of the crown.
The prepared tooth is cleaned with pumice
washed and dried.
Etch the enamel,rinse for 30 secs
Apply primer to dentin and polymerize for 30
secs
Dispense equal amount of base and catalyst
mix for 20 secs,apply thin layer onto the
internal surface of the crown and seat the
crown
Light cure at marginal areas from
facial,lingual and Occlusal directions.

Conclusion
When a restoration is tried in the mouth
the proximal contacts,margin
integrity,and occlusion must be verified.
With metal ceramic restorations the
contour in the cervical third is critical for
the maintenance of health of supporting
structures.
Proper shaping of gingival and incisal
embrasures will improve the esthetics.

No matter what type of cement is used
for cementation,proper moisture control
is essential .
Cement should be protected from
moisture during initial set,and removal
of excess from the gingival sulcus is
critical for continued periodontal health.
Active luting, in which the material
bonds the restoration to the tooth is the
most desirable feature, which make the
resinbonded the material of choice but
they are technique sensitive.

References
Contemporary Fixed Prosthodontics-
Rosenstiel
Fundamentals Of Fixed Prosthodontics-
Shilling burg
Trends In Indirect Dentistry-Dental
Update 2005.

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