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FINISHING AND POLISHING
DR V.VASUNDHARA FINAL YEAR MDS
Introduction Benefits of finishing and polishingGoals of finishing and polishingDefinitionPurpose of finishing and polishingRequirements of finishing and polishingAbrasive motionSpeeds used in finishing and polishingClassification of abrasivesTypes of the abrasives
Methods used to asses the effectiveness of finishing and polishing
Finishing and polishing
Amalgam
Composite
GIC
DFG
Biological hazards of finishing and polishing
Conclusion
References
INTRODUCTION Finishing, polishing of dental restorations are important aspects of clinical procedures that enhance both aesthetics and longevity.
Residual surface roughness associated with improper finishing and polishing can cause plaque accumulation, gingival irritation, increased surface staining poor or suboptimal aesthetics.
Finishing and polishing process require a stepwise approach introducing finer scratches to the surface of the substrate in order to methodically remove the deeper scratches
Finishing and polishing are both wear processes but they differ in intent and degree
Benefits of finishing and polishing
a. Minimal irritation of soft and hard tissues
b. Simulates natural tooth surface aesthetics
c. Less likely to trap food debris and plaque
d. Reduced potential for corrosions
e. More hygienic
Goals of finishing and polishing
a. Obtain desired anatomy
b. Proper occlusions
c. Reduction of roughness, gouges and scratches
d. Surface should be well tolerated by oral tissue
e. Resist bacterial adhesion and excessive plaque accumulation
f. When plaque deposits exists they should be easily removable by tooth brushing and flossing
To obtain surface qualities series of procedural steps are conducted they are
Bulk reduction
Cutting
Grinding
Abrasion (finishing and polishing)
Definition :-Bulk reduction - removal of unwanted large portion or material of the tooth or appliances quickly. This is done by cutting and grinding.
Cutting – process of removing material from the substrate by use of a bladed bur or a abrasive embedded in a binding matrix on a bur or disk.
Grinding – Process of removing material from a substrate by abrasion with relatively coarse particles.
Abrasion
“A process of wear whereby a hard rough surface ( like a sand paper disk ) or hard irregular shaped particles ( like those in a slurry ) plough grooves in a softer material and cause materials from these grooves to be removed from the surface”.
Finishing and polishing are 2 abrasive procedures commonly used in dentistry
Finishing – Process of removing surface defects or scratches created during the contouring process through the use of cutting or grinding instruments or both.
Polishing – Process of providing luster or gloss on a material surface.
Other finishing methods
Electropolishing : as base metal alloy castings have very hard surface, polishing is quite tedious.
Also it is quite difficult to polish the irregular surface of cast RPDs and FPDs. In such cases electropolishing method is preferred
The finished article is suspended in an electrolyte like sulphuric acid solution. Cast metal act As the anode and a copper plate as cathode, small current of 2-5 amp is passed through it for 1-2 hr.
The projecting particles of the surface get detached due to higher potential difference and the surface become smooth and glossy
Glazing- it is not possible to polish ceramic article and composite resins easily. Self glazing and add on glazing technique are used for ceramics the glazed articles have better surface integrity ( no surface cracks). Which improves its flexure strength from 78 mpa to 138 mpa.
Purpose of finishing and polishingProvides 3 benefits of dental care- Oral health Oral function Esthetics
Oral health A well contoured and polished restoration promotes oral health by resisting the accumulation of food debris and pathogenic bacteria.
This is accomplished through reduction in total surface area and reduced roughness of the restoration.
Smoother surfaces have less retention areas and are easier to maintain in a hygienic state.
Oral function A highly polished restoration show a very less tarnish and corrosion
Oral function is enhanced with a well polished restoration because food glides more freely over occlusal and embrasure surfaces during mastication and minimizes the wear rates
Rough surfaces will develop high contact stress that can cause the loss of functional and stabilizing contacts between teeth.
Aesthetics Finishing and polishing gives lusture to visible surface of restoration thus increases the optical property of materials.
A high mirror like polish is preferred in highly visible areas such as the labial surfaces of the maxillary anterior teeth
These surfaces are not subject to high contact stresses and they are easily accessible for cleaning.
Important anatomic features and texture may be added to these area without affecting oral health or function.
Requirements of abrasive instrument
a) Have the right particle size
b) Not produce deep scratches, which cannot be removed easily in subsequent steps
c) Possess sharp edges and breakdown in a manner to expose new sharp edge particles
d) Not gouge substrate
e) Be strong enough to not permanently deform under load or high temperatures
Abrasive motion Abrasive motion can be classified as
1.Rotary- burs
2.Planar- disk
3.reciprocal motion.
ROTARY
In rotary motion, the bur in a high speed hand piece rotates in a clockwise direction.
Planar motion
Are used in disks removes material along a plane. Planar motion should preferably be done in one direction to obtain a smoother surface.
Reciprocal motion
Is produced by two different motions at the same time: part cyclic and part up and down motions.
This is useful to access interproximal arears to remove overhangs, to finish sub-gingival margins without creating ditches, and to create embrasures.
Speeds used in finishing and polishing
Rotary speeds are in 3 basic ranges and are measured in revolutions per min (rpm)
1. low speed or slow speed: speed below 12,000 rpm provides better tactile sensation and procedure lesser heat when used for cleaning teeth, caries excavation and during polishing procedure
2. medium speed or intermediate speed: a speed of 12,000-2,00,000 rpm can be used for contouring.
3. high speed or ultra high speed: speed above 2,00,000 rpm is used for cutting teeth and removing old restorations because these instruments remove tooth structure faster with lesser pressure, vibration and heat generation, increasing patient comfort and operator efficiency. High speeds can be used for gross finishing and countering of the restoration.
Classification of abrasives.
ABRASIVE
VITREOUS BONDING
RUBBER BONDING
RESINOID BONDING
BONDED NON BONDED
SINTERED BONDING
DISPERSED IN WATER SOLUBLE
MEDIUM
POLISHING PASTES
COATED
Based on the abrasive grits
Coarse (125-150μm)
Medium coarse (90-100μm)
Medium fine (88-125μm)
Fine (60-74μm)
Super fine (38-44μm)
Abrasive grits – Abrasive grits are derived from materials that have been crushed and passed through a series of mesh screens to obtain different particle size ranges.
Sturdevant et al : The art and science of operative dentistry; 5thedition,Elsevier Publication
Colour coding of burs
According to Hardness
a) Hard abrasive - Diamond, Silicon carbide.
b) Medium abrasive - Pumice, Silicates, Zirconates.
c) Soft (Polishing) abrasive - calcites
( Robert g Craig)
According to use
a) Finishing abrasive.
b) Polishing abrasive.
c) Cleansing abrasive.
(Craig, Obrien, Powers)
Nuckles DB: Status report on rotary diamond instruments, council ondental materials and devices. J Am Dent Assoc 97: 233-235, 1978
Based on availability
Paper / plastic coated
Stainless steel coated strips
Bonded stones
Powder form
Cake form
Rubber impregnated
Paste from
Bonded abrasive Bonded abrasives consist of abrasive particles that are coated on a binder to form a grinding tool. The binder holds the abrasive during cutting, grinding or polishing.
It should not allow clogging of grinding debris between the particles since the particles will lose their cutting efficiency.
the methods used to bond the abrasives:
Sintering : the particles are fused together to make the whole cutting tool. Sintered abrasives have the strongest bonding and last longer.
Vitreous bonding: the abrasives are first mixed with a glassy or ceramic matrix material, then cold pressed to the shape of the instrument and fired to fuse the abrasives and the binder.
Resin-bonded abrasives: here the abrasives are cold pressed with resins and then the resin is cured. Heat curing of the resin yields a binder with low porosity.
Rubber-bonded abrasive: these are made similar to resin-bonded abrasives; here the abrasives are bonded with rubber and used for final polishing.
Non bonded abrasives Loose abrasives are polishing pastes contain a fine particle size distribution of either aluminum oxide or diamond particles dispersed in water soluble vehicle, such as glycerin
Aluminum oxide particles pastes are designed for final polishing of composite resin materials
Particles size ranging from 0.3µm to 1µm Diamond polishing pastes contain loose abrasive diamond particles in size range less than 10µm.
Effective particles size distributions of diamonds polishing pastes size range 0.3µm to and 1µm.
Indicated for final polishing of adjusted porcelain and ceramic materials.
Binders for diamond abrasives are manufactured specially to resist abrasive particles loss
diamond is hardest particle and bonded to metal wheels and been blanks with special heat resistant resins such as polyamides.
Super coarse and fine grades are then plated with nickel
Nickel plating provides improved properties and acts as a heat absorber.
Titanium nitride coatings are given to extend the longitivity.
Finishing diamonds for composites contain particles 40um or less in diameter.
Diamond burs should be used with copious amounts of water spray and rotational speed less than 50,000 rpm.
Disadvantages of abrasive pastes are
1. Relatively thick and cannot gain access into embrasures.
2. Paste tend to splatter off the instrument
3. Heat generation occurs due to insufficient coolant used or when intermittent polishing.
Application Of Nanotechnology In Abrasives
Nanotechnology introduced nano silica abrasives by chemical- mechanical planarization process.
Particle size of nano silica ranges from 10-90nm and is spherical in shape.
It has been reported that polishing with nano-silica provides high polishing and low surface roughness . Also polishing of teeth with nano silica helps in prevention of damage caused by cariogenic bacteria.
Roulet JF, Roulet-Mehrens TK: The surface roughness of restorativematerials and dental tissues after polishing with prophylaxis and polishingpastes. J Periodontology 1982 Vol 53, 257-266
Abrasive disks and strips: Are fabricated by securing abrasive particles to flexible backing material (heavy weight paper, metal or nylon) with a suitable adhesive material.
Supplied as disks and finishing strips
Moisture resistant
COATED
Mechanism of grinding ABRASIVE
THREE BODY WEARTWO BODY WEAR
TWO BODY WEAR: here the abrasive is bound to the instrument and is used to polish the specimen surface. No other abrasive is used.
Eg; trimming, abrading burs, bonding abrasives, coated abrasive.
THREE BODY WEAR - here the abrasive is free a loose slurry between polishing substrate and surface of the specimen to be polished,
Eg; polishing paste as aluminun oxide, diamond. And tooth paste.
Removal of surface can also be achieved by EROSION Hard particles impacting a substance surface , carried by either a stream of liquid or a stream of air. Eg : Hard particle erosion occurs when SAND BLASTING a surface
Sandblasting
- Its used to clean the alloy surface
- To achieve both microretentive topography and increased surface area
- Pickling
Pickling is a procedure of heating the discoloured casting in an acid such as 50% hydrochloric acid. The HCL removes the oxide coating as well as any residual investment.
ElectropolishingElectrolytes –
1. Ethylene glycol – 80%
Conc Sulphuric acid – 15%
Water – 5%
2. 3parts of Phosphoric acid
1 part of glycerine
1 part of water
Mechanism of finishing and polishing
Instruments used for finishing and polishing
Fluted carbide burs
Diamond burs
Stone burs
Coated abrasive discs
Coated abrasive discs
Coated abrasive strips
Polishing paste
Polishing cups
Polishing points
Polishing wheels
Natural abrasives
Arkansas stones, chalk, corundum diamond, garnet, pumice, quartz, sand, Tripoli, and aluminum and silicate.
Remnants of living-organisms
kieselghur and cuttle Manufactured abrasives
synthesized materials, that are generally preferred because of their more predictable physical properties. Eg silicon carbide, Aluminum oxide, Synthetic diamond, Rouge, Tin oxide
Anusavice
1. Arkansas Stone :
Semi-translucent , light grey , siliceous sedimentary rock emended in Arkansas
Contains mico-crystalline quartz .
Small pieces are attached to metal shanks and trued to various shapes for fine grinding of tooth enamel and metal alloys.
2. Chalk :
mineral form of calcite
contains calcium carbonate
used as a mild abrasive paste to polish enamel, gold fillings
3.Corundum :
Largely replaced by alpha aluminium oxide due to its superior physical properties .
Available as bonded abrasive and is used primarily to grind metals.
4.Diamond :
Transparent colorless mineral composed of carbon
Called SUPER-ABRASIVE because of its ability to abrade any known substance .
Hardest substance known .
Used on ceramic and resin based composite materials.
Supplied as – bonded abrasive , diamond abrasive pastes , abrasive strips .
5. Emery :
Consists primarily of a natural oxide of aluminium called corundum.There are various impurities present , such as iron oxide which also act as abrasives .Usually bound to paper discs and can be used on gold or porcelain.
6. Garnet :
Includes several minerals , which posses similar physical properties and crystalline form like silicates of Al,Co,Mg, Mn. Usually coated on paper or cloth with a binder. Cuts both metal and porcelain.
7. Pumice :
Highly siliceous material of volcanic origin .
Suitable for use as an abrasive or a polishing agent according to its particle size .Can be used for many operations from smoothening of denture bases to the polishing of teeth in the mouth.
8. Quartz :
The particles are pulverized to form sharp angular particles , which are useful in making coated discs . Used to finish metal alloys.
9. Sand :
-It’s a mixture of small mineral particles predominantly composed of silica.
-Sand blasting
-Coated abrasives
10. Tripoli :
It’s a siliceous rock
Mild abrasive and polishing agent
Used for polishing metal alloys.
11. Zirconium silicate :
Occurs in nature as Zircon .
Is ground to various particle sizes and used as a polishing agent
It is used as a constituent of dental prophylactic pastes and in abrasive impregnated polishing strips and discs .
13.Kieselguhr :
It is composed of siliceous remains of minute aquatic plants know as diatoms .
It is an excellent mild abrasive and polishing agent .
12. Cuttle :
A fine , relatively soft polishing agent made from calcified internal shell of cuttle fish .
It is used on paper discs for polishing of metal margins .
Manufactured abrasivesSilicon carbide :
First of the synthetic abrasives to be developed .
It is the basic material of carborundum
Supplied as an abrasive in coated discs, vitreous bonded and rubber bonded instrument.
Rouge:
It is a fine red powder composed of iron oxide.
Its blended in cake form.
Excellent polishing agent for gold and noble metal alloys.
Aluminium oxide:
Its widely used in dentistry to make bonded abrasives,coated abrasives and air propelled grit abrasives.
Sintered aluminium oxide is used to make white stones which are used for finishing metal alloys.
Material Material f/ pf/ p Chem. Chem. CompComp
Forms availableForms available usesuses
PumicePumice PolishingPolishing SilicaSilica Grit form, Rubber Grit form, Rubber bonded abrasivebonded abrasive
Acrylic, tooth Acrylic, tooth enamel, gold enamel, gold foil, amalgamfoil, amalgam
QuartzQuartz FinishingFinishing SilicaSilica Coated Abrasive Coated Abrasive disksdisks
Metal alloysMetal alloys
SandSand FinishingFinishing SilicaSilica Sand paper & Sand paper & powder form for powder form for sand blastingsand blasting
Metal alloys, Metal alloys, Acrylic resinAcrylic resin
TripoliTripoli PolishingPolishing SilicaSilica Bar formBar form Metal alloysMetal alloys
Zirconium Zirconium SilicateSilicate
Polishing Polishing SilicaSilica Coated abrasive Coated abrasive disks, stripsdisks, strips
Metal margins, Metal margins, tooth enameltooth enamel
CuttleCuttle PolishingPolishing Silica (white Silica (white Calcereous Calcereous powder)powder)
Coated abrasiveCoated abrasive Metal margins, Metal margins, Amalgam Amalgam restorationsrestorations
KieslghurKieslghur PolishingPolishing SilicaSilica Coated abrasiveCoated abrasive Amalgam Amalgam restorationsrestorations
Tin OxideTin Oxide PolishingPolishing Tin OxideTin Oxide Paste FormPaste Form High noble High noble metal alloysmetal alloys
Material Material f/ pf/ p Chem. CompChem. Comp Forms availableForms available usesusesArkansas stoneArkansas stone FinishingFinishing MicrocrystallMicrocrystall
ine quartzine quartzAttached to metal Attached to metal shanks shanks
Fine grinding of Fine grinding of tooth enameltooth enamel
ChalkChalk PolishingPolishing Calcium Calcium carbonatecarbonate
Paste formPaste form tooth enamel, tooth enamel, gold foil, gold foil, amalgam. amalgam.
CorundumCorundum Grinding. Grinding. Alpha Alpha aluminium aluminium oxideoxide
bonded abrasivebonded abrasive Grinding metal Grinding metal alloysalloys
DiamondDiamond Finishing and Finishing and polishingpolishing
Mineral of Mineral of carbon carbon
Bonded abrasive, Bonded abrasive, rotary instruments rotary instruments , abrasive strips , abrasive strips and polishing and polishing pastes pastes
Finishing and Finishing and polishing of polishing of porcelain and porcelain and ceramicsceramics
Emery Emery FinishingFinishing Grayish Grayish black black corundumcorundum
Coated abrasive Coated abrasive disksdisks
Finishing metal Finishing metal alloys and acrylic alloys and acrylic resin resin
Silicon CarbideSilicon Carbide CuttingCutting SilicaSilica Coated discsCoated discs MetalMetal
Aluminium OxideAluminium Oxide Finishing & Finishing & polishingpolishing
AlAl220033 Bonded abrasiveBonded abrasive Composites & Composites & PorcelainPorcelain
RougeRouge PolishingPolishing Iron oxideIron oxide Cake FormCake Form High noble alloysHigh noble alloys
Sequential use of abrasives
Philip & Baum et al: Operative dentistry. Saunders 2nd edition 1981,223-34
1)GROSS REDUCTION ,CONTOURING AND MARGINATION
This step involves use of abrasive elements of the coated or bonded variety with abrasive particles in the order of 100 microns or larger
That permits the efficient removal of the restorative materials , usually minimal removal of the tooth structure.
Diamond points, Tungsten carbide burs are used.
Instruments used for gross reduction and contouring
A) Diamonds The primary intended purpose for finishing diamonds is to contour, adjust porcelain and composites especially microfilled composites, which are prone for surface micro cracks when finished with finishing fluted carbide burs
They come in various grit size ranging from 5 to 60 microns
Diamond burs should always be utilized with water spray and at speeds less than 50,000 rpm.
B) fluted finishing burs
They are available in 8,12 , 16, 20 and 30 fluted bur designs The fewer the flutes , the more aggressive is the cutting They are used for finishing composites 30 fluted burs can be used to smooth, abrade porcelain surfaces before application of diamond polishing pastes
Several specific group of fluted finishing burs have been developed for finishing of composites known as esthetic trimming burs
Abrasive finishing discs
Coated abrasive discs are used
In the coarse and medium grit size can be used for bulk reduction or gross reduction
The coarse abrasive finishing and polishing disc is coated with 100 microns aluminum oxide particles
The medium grit is coated with 40 microns to 100 microns
The greatest ability to reduce composites , porcelain , can be obtained with the coarse disc ,whereas medium disc can also be used to reduce the bulk of the material
Advantage is it can access incisal edges, embrasures, and line angles which is not possible with rotary or bonded abrasives
Disadvantage of abrasive discs is they have tendency to flatten surface features and restoration contours, creating a less anatomic details
Instruments for inter mediate finishing and polishing Coated abrasive disc Available as finer grit discs and medium Bonded abrasive discs Fine diamond and multi fluted finishing burs
FINISHING AND POLISHING TECHNIQUES
The larger the abrasive particles, the deeper the scratch will be and conversely, the smaller the abrasive particle, the finer the scratch will be.
If the particle size of the abrasive is decreased sufficiently, the scratches finally become very fine and with extremely fine abrasives, they may disappear entirely.
The surface then acquires a smooth shiny layer known as a polish. The most recent theory is that polishing agents actually removes material from the surface, molecule by molecule and thus produces very smooth surfaces.
In the process fine scratches and irregularities are filled in by the fine particles being removed from the surface.
This microcrystalline layer is referred to as the POLISH Layer or BEILBY layer.
Beilby layer : sir George Thomas beilby proposed that when metal is polished, a film forms on the surface due to plastic flow of the metal. As in polishing due to heat generated, the crystalline surface is broken down to form a harder and denser surface layer.
Beilby layer explains hardness of the material under cold working
Advantages of highly polished surface
more resistant to cariogenic action than a surface which is not polished.
polished tooth surface is approximately 15% less soluble in acid than one with a rough surface.
Methods to asses the effectiveness of finishing systems and devicesThe most common to asses the effectiveness of finishing and polishing system and devices on dental restorative materials include aided and unaided visual evaluation
a.Profilometerb.Optical microscopec.SEM ( scanning electron microscope )d.reflectometer
Relying on one single analytical method to asses may lead to misleading results and conclusions
Visual methods are prone to errors as a result of the influence on shading and influence composition of the structure of the specimens under evaluation
SEM must be done carefully to provide sufficient contrast to observe surface topography and with low angle views to detect clearly variations in the surface smoothness
Profilometer asses surface roughness of a restorative material after finishing and polishing procedures
It’s a device that uses a diamond stylus of precise dimensions to trace a fixed linear distance over the surface
It produces a tracing and using digital analog hardware and software, also calculates the average surface roughness for the resultant tracing
All the three methods ( visual, SEM, and profilometer) are technique sensitive, but with care and attention to detail all three methods can yield reproducible and highly useful information about the finishing and polishing procedures
Profilo meter data must be obtained in a reproducible manner and with prior microscopic visual evaluation of the finished samples to ensure that then stylus tracings run perpendicular to the pattern of surface scratches produced on the surface of the specimen
when each method of analyses is done carefully and with reproducible results, all three methods should validate each other in confirming the efficacy of finishing and polishing devices
Factors affecting finishing & polishing• Hardness
• Shape
• Size
• Pressure
• Speed
• lubrication
Hardness Hardness is a measure of a materials ability to resist indentation
The greater the differences in hardness between the abrasive and the substrate, the more rapid and efficient the cutting and abrasion
Diamond Is the hardest abrasive 7000 to 10,000 KHN
Silicon carbide burs has 2500 KHN
Shape The irregular object has a tendency to dig into surface instead of roll across it therefore its cutting efficiency is enhanced by having numerous sharp edges
Size Larger particles abrade a surface more rapidly than smaller ones because the former plough deeper grooves or cuts into the surface.
The roughness of the grand or finished surface is directly related to the size of the abrasive particles.
The procedure for finishing and polishing involves a sequential reduction in the size of the abrasive particles, the scratches left in the surface by previous abrasive are removed and replaced by smaller and shallower scratches eventually the abrasive is so small that the scratchs are no longer visible
Pressure Great force cause more rapid removal of material by forcing the abrasive to cut deeper into the surface.
Greater pressure also create additional heat and raise the temperature within the substrate
The greatest concern with the use of pressure to enhance cutting efficiency in the danger of over abrading the substrate.
Speed The speed of abrasive also influences the cutting efficiency rates
The clinician must take more care to keep the cutting instrument under control
Higher speed create greater temperature and a greater danger of overcutting the object.
Lubrication Lubrication reduces the heat that is produced during cutting procedures
Lubricant such as water facilities the movement of the cutting edges into the surface and carries away debris that would otherwise clog the cutting edges
Both cooling and the removal of debris by the lubricant enhances the efficiency of the abrasion process and are integral to successful finishing of dental restoration.
AMALGAM RESTORATIONS
a) OBJECTIVES
•Finishing and polishing should be considered as important as condensation and it does continue the objectives of carving through this process.
• amalgam flash that was left behind after carving is removed.
•Major overhangs are removed and minor enamel under hangs are corrected thus assuring the continuity between tooth surface and amalgam surface
•polishing is the process, which creates a corrosion resistant layer by removing scratches and irregularities from the surface.
It will minimize fatigue failure of the amalgam under the cyclic loading of mastication.
This failure occurs in the form of surface cracks which propagate inwards.
If such cracks join together or subsequently connect with internal voids or flaws, they can precipitate gross fracture and increase corrosion and micro leakage.
The scratch and irregular free surface layer created by the polishing procedure minimizes the concentration cell corrosion and presents the adherence of plaque
b) PRINCIPLES
Finishing and polishing procedures are necessary 1. To complete the carving. 2. Refine the anatomy contour and marginal integrity. 3. Enhance the surface texture of the restoration. Finishing and polishing procedures for amalgam restorations are not attempted within 24 hours of insertion, since crystallization is not complete.
Polishing of high-copper amalgams is less important than with conventional amalgams because high copper amalgams are less susceptible to tarnish and marginal breakdown.
Some of the fast setting high copper amalgams can be polished about 8 to 12 minutes after placement because of their rapid development of strength.
c) RESULTS OF FINISHING AND POLISHING. The following conditions results from proper [finishing and polishing]:
1. Smooth and flush cavosurface margins. 2. Recreation of defined anatomy. 3. Decreased plaque retention. 4. Healthier surrounding tissue. 5. Higher resistance to tarnish and corrosion. 6. Increased longevity of the restoration. 7. Improved esthetics.
A. Evaluate Restoration.
1. Surfaces
Always examine the amalgam surfaces for functional anatomy and defects.
2. Margins
Using the explorer (or a periodontal probe with a small tip) in a zigzag motion, determine if the cavosurface margins have any excessive discrepancies.
The cavosurface margin is the area formed by the cavity wall and external tooth surface. Remember that a rough margin is a poor predictor of recurrent decay. The patient's risk for caries must also be considered
3. OcclusionEvaluate the patients occlusion.
a) Articulating paper
Insert articulating paper along the occlusal surface and have the patient tap his teeth together.
b) Determine intensity
Observe all markings to determine if they have the same intensity.
c) Reduce the amalgam if it exhibits
Premature contacts or "high spots".
Premature contacts are areas where the amalgam has been under carved and these will register a darker areas when checked with articulating paper.
d) Even intensity
Check these areas throughout the finishing procedure to ensure that occlusal markings of equal intensity are achieved.
4. Proximal contacts
Check proximal contacts with dental floss.
1. Hand instruments
a) Use a finishing knife and or dental file at the gingival and proximal margins to remove overhangs.
b) Use short, overlapping shaving strokes to prevent the amalgam from fracturing.
2. Finishing bur
a) A flame-shaped bur is recommended when the area is easily accessible.
3. Finishing discs
Discs come in varying sizes and grits. Select a size easily adaptable to the proximal surface.
b) Technique
Use short, overlapping strokes and move diagonally across the cavosurface margins.
c) Sequence
Discs are used in a sequence of more abrasive to less abrasive grits.
d) Embrasures
When using discs in embrasure areas, care must be taken not to damage the contact area or papilla.
4. Finishing strips.
a)Use fine or medium finishing strips after using discs, burs, knives or files.
b) Position the strip so that it is on both the tooth and the amalgam, and move in a back-and-forth motion.
c) Avoid the contact area when using finishing strips, and use caution in areas of the inter dental papilla and surrounding tissue.
Wider strips may be cut in half lengthwise to make narrow strips.
Procedures for amalgam polishing.
a) Pumice and tin oxide slurries.
This method is accomplished using a rubber cup, brush, and wheel brush. Prepare a slurry mix of pumice, and water in a dappen-dish.
Polish all surfaces of the restoration with a brush or cup and plentiful pumice. Remember, the pumice does the polishing, the cup only moves the pumice a smooth satin finish is accomplished The satin finish produced will exhibit a dull appearance.
Polish the proximal surface with medium and fine polishing strips. Rinse and dry the mouth. Prepare the wet mixture of tin oxide and alcohol in a dappen dish. Water or mouth wash is an acceptable substitute for alcohol.
Polish all surfaces of the restoration with a new, clean cup or brush and the tin oxide slurry.
An optimal final step may include using a soft wheel brush in a straight hand piece with tin oxide.
Continue to polish the amalgam until the tin oxide begins to dry and a high luster is achieved.
Rinse and dry the tooth.
Examine with mouth mirror and explorer.
b) Rubber cups and points impregnated with Abrasive particles
Abrasive-impregnated rubber cups and points are supplied in three colors: brown, green and yellow-banded green. Each color denotes different degree of abrasiveness.
In some instances they are referred to as "brownies", "greenie" and "super greenies".
use.
The cups are designed for use on the proximal surfaces, and the points are used on the occlusal surface.
Often, they are used interchangeably.
They should be operated at a relatively low speed, using light, intermittent strokes under wet conditions.
Advantages.
The cups and point will polish restorations quickly and tend to be less messy than using two slurries of different abrasives.
Disadvantages.
The cups and points wear quickly from use and autoclaving.
Eventually a metal surface is exposed that will scratch the amalgam surface.
The greatest disadvantage, however, is heat production.
The amalgam surface MUST NOT be heated above 140'F by the polishing procedure. Heat is generated rapidly with the use of abrasive impregnated rubber cups and points.
Finishing and polishing of composites
Once a composite has been cured, it must be finished and polished to produce the final surface.
This step removes the air-inhibited layer. It also removes the outer surface of the composite that is resin rich and actually is already a smooth surface.
However, this cannot be avoided. The anatomic contours of composites cannot be so well established before curing to avoid reshaping.
On the latter procedure, several investigations have shown that removal of the polymer-rich, outermost resin layer is essential to achieving a stain-resistant, more esthetically stable surface.
Lu H, Roeder LB, Lei L, Powers JM. Effect of surfaceroughness on stain resistance of dental resin composites. JEsthet Restor Dent 2005; 17: 102-109.
The trick to finishing and polishing is to gradually move from larger-to-smaller abrasive containing agents.
This will produce finer-and-finer scratches in the surface .
Available finishing kits containing disc, cups and points include Enhance finishing system (DENTSPLY Caulk), Fini (pentron) and CompoMaster (Shofu).
These are used in a slow- speed hand-piece with a dry field and light intermittent pressure (to avoid the build up of heat on the tooth as well as deterioration of the finishing material).
Prior to the finishing and polishing the surface must be contoured and be defect free by using diamond or carbide finishing burs.
Polishers Polishers are available as stand alone products and can also be purchased as kits containing discs, cups and points.
Available polishers include. PoGo one step diamond micro-polishers (DENTSPLY Caulk); Sof-Lex superfine polishing discs (3M Espe), which contain aluminium oxide; Astropol (Ivoclar); identoflex (centrix) and jiffy polishers ( Ultradent).
Use of PoGo has been found to result in less staining following immersion in coffee for seven days than use of a Sof-Lex brush
In a study comparing Sof-Lex, PoGo and Identoflex polishers on a hybrid and microhybride composites, it was found that the smoothest surface was obtained using PoGo and the hybrid composite.
Polishing pastes. An alternative polishing technique is to use a polishing cup together with a polishing paste made specifically for composites – such as Prima – Gloss (DENTSPLY Caulk) for microfilled composites- or a combination of fine and extra fine pastes for hybrid composites (such as use of Prisma – Gloss followed by Prisma- Gloss Extrafine).
Other polishing pastes available include CompoSite (Shofu) and Luminescence Plus (Premier Dental).
Liquid polish Liquid polishers (surface sealants) are low viscosity fluid resins that provide a gloss over composites resin restorations, improving final esthetics.
Objective of liquid polishers is to aid in creating a marginal seal, and they have the ability to fill micro-gaps. Liquid polishers reduce micro-leakage at composite margins.
Studies have found that use of a surface sealants following finishing an polishing reduces surface roughness and wear compared to control restorations receiving no surface sealant.
Shinkai et al. found 50% less wear with use of surface sealants. Has been effective for two years.
The finishing procedure for composite restorations will usually consist of three to four steps involving a number of instruments.
Gross reduction where excess restorative material is removed.
Contouring- includes the reproduction of the size, shape, grooves and other details of the tooth form. Re-establishing contact with adjacent teeth to a normal and functional form.
Finishing and polishing establishes an even, well-adapted junction between the tooth surface and the restoration and removes scratches to produce a visually smooth and shiny surface.
Chemical cured materials must be accurately timed to complete polymerization.
It has been suggested that before finishing the restoration it should be left undisturbed for a minimum of 10 minutes to allow the resin to completely polymerize.
This may aid in reducing surface trauma from the finishing process.
Sof-Lex Finishing and Polishing Discs
The original Sof-Lex finishing and polishing discs are made from a urethane coated paper that gives the discs their flexibility.
The system is comprised of four individual aluminum oxide grits ranging from coarse to superfine.
The discs are available in three sizes; 13mm (1/2 inch), 9mm (3/8 inch), and a 16mm (5/8 inch) size with a square brass eyelet.
Sof-Lex XT Finishing and Polishing Discs
The Sof-Lex XT (extra thin) finishing and polishing discs are made with a polyester film which is one third the thickness of the original paper discs.
The thinner discs are slightly stiffer and allow more precise refinement of embrasures.
These discs also have four individual aluminum oxide grits, ranging from coarse to superfine.
They are available in two sizes, 13mm (1/2 inch), or 9mm (3/8 inch).
Sof-Lex Finishing Brush
The Sof-Lex finishing brush is made from a thermoplastic polyester elastomer that contains aluminum oxide abrasive particles molded into a shape similar to a prophy brush.
The brush itself is detachable from a stainless steel mandrel. The Sof-Lex Finishing Brush is an easy to use, one-step, reusable brush developed for polishing the concave and convex anatomy found on posterior composite restorations.
The soft bristles will conform to the restoration as it travels across the surface resulting in a smooth polished finish.
Sof-Lex Finishing and Polishing Strips
The design of the Sof-Lex strips allows for easy interproximal finishing.
The strips are made of plastic and are coated with an aluminum oxide abrasive.
Sof-Lex strips are free of any abrasive coating at their centers for easy interproximal insertion.
Each strip contains two different grits; a coarse/medium, or a fine/superfine.
They are also color coded similar to the discs. The coarser grit on each strip is a darker color than its opposing side.
Directions for Use Place the disc on the mandrel by firmly pushing the eyelet portion onto the mandrel until the disc is secure and does not wobble.
The polishing motion should be constant and move from the bulk of the restoration toward the margins.
A back and forth movement over the composite/enamel margin is not recommended, as a white line may form.
Use light pressure when polishing; let the discs do the work. To produce a smoother, more uniform finish, keep the tooth, restoration, and disc dry while polishing.
Avoid touching the composite with the mandrel or disc eyelet because discoloration may occur.
This discoloration can be removed by repetition of the finishing steps
Skipping a grit size in the finishing sequence may compromise the quality of the restoration’s polish.
It is important to maintain a dry field when using this system. After rinsing, and before proceeding to the next grit sequence, dry the area.
Start with coarse discs to remove excess restorative material and establish preliminary anatomy. Rinse and dry surface before moving onto medium disc.
Use medium discs for advanced contouring,establishing marginal ridges and adjusting incisal edges.Rinse and dry before using the fine disc.
Follow with fine disc to further improve finish qualityand prepare surface for final polishing.
Conclude polishing with superfine discs for the mostdurable, smoothest, high gloss finish.
After contouring posterior composite, polish surfacewith Sof-Lex finishing brush at low speeds.
Use Sof-Lex strips for finishing proximal areas bygently inserting the center gapped area between teeth.Operating sequence of strips (coarse/medium,fine/superfine) is the same as discs.
Finishing and Polishing of Ceramics
Finishing and Polishing of Ceramics
Ideal surface for ceramic restoration is a polished and glazed surface
The production of a glazed layer through natural glaze or over glaze processes will not necessarily yield a smooth surface if initial ceramic surface has significant roughness
Polishing can improve strength within surface region of a ceramic prosthesis because it removes pores and micro cracks
Adequate cooling is important in vivo when finishing and polishing ceramic restoration
Using an air water spray and maintaining intermittent contact between restoration and rotary instruments are critical during operation
Continuous contact between restoration and rotary instruments should be avoided
Heat less stone like silicon carbide provide heat reduction and can be used as an alternative
Techniques Contour with flexible diamond disc diamond burs, heatless or polymer stones or greenstones
Finish with white stones or abrasives impregnated rubber disc, cups and points
Apply over glaze or natural glaze on ceramic if necessary
Glass Ionomer Cement
Conventional versions of glass ionomer ideally require a polymerization period of 24 hours before final contouring and polishing
After removing the matrix the restoration gross excess is shaved away with either no-12 surgical blade in bald parker handle or sharp knives of scalers
Major part of finishing and polishing should be accomplished by hand instruments to preserve the smooth surface
if rotary instruments are used care must be taken not to dehydrate the surface
Fine disks are used for final finishing
Micron finishing diamonds are used to contour
A fine grit aluminum oxide polishing paste applied with a prophy cup to smoothen the surface
FINISHING OF DIRECT FILLING GOLD
Once the final contour is been obtained
Cuttle discs are used in decreasing abrasiveness to ready the surface for final polishing
polishing is performed with fine pumice followed by tin oxide or white rouge applied with a soft rubber cup
the abrasives are therefore used dry so that the field kept may be clean and exact position of the rubber cup seen at all the times
sharp gold foil knife is used to remove of the excess in the region of contact
permitting a fine finishing strip or a steel matrix strip to pass through the contact area a pull cut shoosan or a gold knife may facilitate removal of excess gold facially
finishing is performed with the extra –narrow extra fine cuttle strip
final polishing is accomplished with a worn out cuttle
Finishing of Alloys
Alloys Very hard metals used in partial denture and porcelain fused to metal have value of 5 to 6 moh’s scale that is similar to enamel. These alloys can be finished with combination of stones, disks and wheels.
After casting has been cleaned of investment debris with water and a tooth brush, it is often soaked or pickled, in warm HCL acid to remove the surface oxide layer. Later small nodules of metal are removed with carborundum stone.
For a class two inlay, the proximal margins can be finished with the medium cuttle disk. This gives surface roughness of 0.3 to .0.5 µm.
The surface of casting can then be polished with rubber wheel impregnated in abrasive particles (e.g Alo or Sio) reduces surface roughness to level 0.10 to 0.15 µm.
Final polish can be achieved with Tripoli and rouge on rag wheel.
The final surface roughness of a casting polish in this manner would be on the order of 0.05 µm.
Finishing of stainless steel crown.
the crown form can be smoothed and polished with a cloth or chamois wheel on the dental lathe, using Tripoli polishing agent and jeweler’s rouge (iron oxide) .
Debris from the finishing process, accumulated inside the crown, can be removed with a wet cotton swab.
Biological hazards - 1. Production of aerosols Silicosis (also called as grinder's disease) occurs due to liberation of silica based abrasives used for finishing the restorations.
2. Cross contamination occurs due to the presence of aerosols in the clinical area for more than 24 hrs.
3. Production of vapours Toxic mercury vapours arise during finishing and polishing amalgam restorations as there is rise in temperature while using the abrasives (Mercury toxicity). Finishing of acrylic based materials with abrasives results in monomer release.
4.Soft tissue irritation some people develop allergies to some of the abrasive (cuttle , kieselguhr) which are used during finishing
Aerosols produced during finishing and polishing can be controlled by –Personal protectionAdequate ventilation
Conclusion Finishing and polishing techniques are important in preparing clinically successful restorations .
The process of abrasion is affected by properties of the abrasive and the material being abraded. Finishing and polishing begin with coarse abrasives and end with fine abrasives
Clinically it is easier to control the rate of abrasion by speed rather than the pressure. Care must be taken to avoid over finishing margins and contours of restorations and to avoid over heating.
A definite sequence should be adopted in finishing and polishing of each restoration.
References Anusavice K.J. “Phillips Science Of Dental Materials” 11th edition, Philadelphia,W.B. Saunders
Jack L. Ferracane, materials in dentistry. 2nd edition, Williams and wilkins
Craig R.G. “Dental Materials, properties and manipulation”. 8th edition
Text book of dental materials, mahalakshmi. 1st edition
Aydin A.K. “Evaluation of finishing and polishing techniques on surface roughness of chromium-cobalt castings.”J.P.D.,1991;65:763-767
Jeffries S.R. “The art and science of abrasive and finishing and polishing in restorative dentistry”. DCNA,1998;42(4): 613-628.
Kern M. ,Thompson V.P. “Effect of sandblasting and silicoating procedures on pure titanium”. J.Dent.,1994;22:300-306.
Morris F., Brudvik J.S. “Influence of polishing on cast clasp properties”. J.P.D.,1986;55:75-77.
Mc Cracken’s Removable partial denture prosthodontics. 11th edition, 2004.
Richard .Troxell “The polishing of Gold casting”J.P.D:1959:9:668-675.
Stewart, Rudd and Kuebker: Clinical Removable denture prosthodontics. 2nd edition, 2001.
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