Direct Filling Gold
Question 1. Describe the direct filing gold.
Answer:
Pure gold can be used as a restorative material. It is the noblest metal and rarely tarnishes in the oral cavity. Gold in its pure form is very soft. Its malleability and lack of surface oxide layer permit increments to be welded in the oral cavity. This unique characteristic of gold to be welded at room temperature (cold welded) allows gold to be used as a direct filing gold.
Read And Learn More: Dental Materials Question And Answers
Following are the forms of direct gold filing:
1. Foil (Fibrous gold):
- Sheet
- Cohesive
- Non-cohesive
- Ropes
- Cylinders
- Laminated
- Platinized.
2. Electrolytic precipitate (mat gold):
- Mat gold
- Mat foil
- Alloyed or gold-calcium alloy
3. Granulated gold (encapsulated powder gold).
Gold Foil of Direct Gold filing
Gold is malleable. A cast ingot of 15 mm thickness is beaten to the submicroscopic thickness of 15 to 25 µm. This is known as gold foil. Gold foils are made from pure metal by beating and rolling. Beating produces lightweight foils and rolling produces heavy-weight foils.
Fibrous gold is supplied in the form of sheets about 4 inches square which range in numbers 2, 3, 4, 5, 6, 8, and 10. Higher numbers are rolled by manufacturers from an ingot, while lower numbers are beaten by machinery. These numbers are indicative of the number of grains in the sheet, for example, No.5 gold sheet contains 5 grains. Gold foil or fibrous gold is available in the form of sheets, rolls, cylinders, and pellets of various sizes. Sheets of gold foil are of two types, i.e. cohesive and non-cohesive.
1. Cohesive Gold Foil:
- Cohesive gold is also known as sticky gold.
- This is the gold foil that the manufacturer supply to the dentist is free from any surface contaminant and can be placed directly in cavity preparation known as cohesive gold.
- Although it is free from surface contaminants some of the gases are still adsorbed during storage so degassing is required.
Various types of cohesive gold foils are:
- Soft type: This gets annealed before trimming and is treated in ammonia fumes for reducing the cohesion. As this type is cut and rolled in desired sizes, ammonia gas is driven off
- Dead soft type: This is not annealed and is soft. This is less cohesive than soft type.
- Extra or special soft: This is deliberately alloyed by a trace of silver for limiting cohesiveness. This is moderately cohesive after annealing.
- Platinized soft gold foil: In this, a sheet of pure platinum foil is sandwiched between two sheets of pure gold foil and then malleated again till the original thickness is established. Platinum increases hardness and wear resistance.
2. Non-cohesive Gold Foil:
- Non-cohesive gold foil is subjected by the manufacturer to a volatile agent such as ammonia which is adsorbed on the surface of gold.
- This adsorption of ammonia gas on the surface of gold prevents gold foil from adhering.
- Non-cohesive gold is rarely used currently but it can be used to build up the bulk of direct gold restoration.
- Non-cohesive gold can also be used with cohesive gold for beginning restoration on the gingival wall in the proximo occlusal cavity or on the pulpal wall in occlusal cavities as a timesaver.
Electrolytic Precipitated Gold
- Crystalline gold powder is formed by electrolytic precipitation. The powder is formed into strips and shapes by sintering.
- Electrolytic precipitated gold is available as mat gold, mat foil, and alloyed electrolytic precipitate.
- Mat Gold: Mat gold is electrolytically precipitated gold sandwiched between sheets of foil and then formed into strips. Strips can be cut by the dentist into the desired size. It is used to build up the bulk of the restoration, as it can be more easily compacted and adapted to the cavity. However, mat gold has lots of voids and results in a pitted external surface. Therefore, foil gold is used to cover the mat gold and form the surface of the restoration.
- Mat Foil: It is a sandwich of electrolytic precipitated gold powder between sheets of No. 3 gold foil. The sandwich is sintered and cut into strips of differing widths. The dentist can then cut these to desired lengths. Mat was sandwiched between foil sheets and tried to eliminate the need to veneer the restoration with a layer of foil. This type is no longer marketed.
- Alloyed Electrolytic Precipitates: A form of electrolytic gold is an alloy of gold and calcium (0.1% by wt) called ‘Electraloy RV’. For greater ease of handling, the alloy is sandwiched between two layers of gold foil. Calcium produces stronger restorations by dispersion strengthening which locks in cold work strengthening. Thus, alloying with calcium changes the crystalline structure and makes it harder and stronger.
Powdered Gold
- Powdered gold is also known as EZ gold. It is known as EZ gold because its manipulative characteristics are similar to very stiff amalgam and is more sticky than gold foil.
- Powdered gold is a blend of atomized and precipitated powder that is embedded in a wax-like organic matrix.
- This is available in pellets of various sizes which are mixed with wax and are enclosed in gold foil No. 3 wrappers and packed for their usage.
- The usage of pellets of powdered gold increases cohesion at the time of compaction and decreases the time needed for placing the restoration.
- Commercially available pellets of powdered gold wrapped in a gold foil are known as Golden.
- The ratio is 95% powder and 5% foil. It is provided in a cohesive form. The powdered particles are mixed with soft wax and held in a No. 3 gold foil.
- The gold foil acts as a container for the powdered particles and facilitates their condensation.
- Each pellet contains approximately ten times more gold than a pellet of gold foil of comparable size.
- The hand method of compaction is better than mechanical compaction for powdered gold.
Applications of Direct Filling Gold:
- Pits and small class I restorations.
- For repair of casting margins.
- For class II, class V, and class VI restorations.
- Repair of cement vent holes and perforation in the gold crown.
Disadvantages of Direct Filling Gold:
- Poor esthetics (it is not tooth-colored)
- High coefficient of thermal conductivity
- Manipulation is difficult
- The problem of temperature sensitivity if not insulated with base.
Advantages of Direct Filling Gold:
- Tarnish and corrosion resistance
- Good mechanical properties
- Good biocompatibility.
Contraindications of Direct Filling Gold:
- In disto-occlusal cavities in molars
- Teeth with large pulp chambers
- In periodontally weak teeth with poor prognosis
- In low socioeconomic status individuals
- In root canal filed teeth as they are brittle
- In handicapped patients who are unable to sit for long dental appointments needed for this procedure.
- If the skill of the operator is questionable.
Manipulation of Direct Filling Gold
Manipulation of direct filing consists of the following steps:
- Desorbing or degassing
- Compaction.
1. Desorbing or Degassing:
- The heating process which removes surface gases and ensures a clean surface is known as degassing or desorbing
- Degassing removes the surface gases like oxygen, nitrogen, ammonia, moisture, or sulfur dioxide which may be present due to improper storage.
- Direct filing gold may be heated by one of two methods as follows:
- In bulk on a tray heated by either a gas-flame or electricity
- Piece by piece, in a well-adjusted alcohol flame
In practice all but the powder gold may be desorbed on a tray:
- An electric annealer should be maintained at a temperature between 340°C (650°F) and 370°C (700°F). The time required varies from 5 to 20 minutes depending on the temperature and the quantity of gold on the tray.
- Powder gold must be heated in a flame to ensure the complete burning away of the wax.
- In flame desorption, there is picking up each piece individually, heating it directly in the open flame, and placing it in the prepared cavity.
- The fuel for the flame may be alcohol or gas, but alcohol is preferred as there is less danger of contamination. The alcohol should be pure methanol or ethanol without colorants or other additives.
- Underheating could not adequately remove the impurities and thus results in incomplete cohesion, pitting, and flaking of the surface while overheating leads to overwintering and possible contamination from the tray, instruments, or flame.
- This results in incomplete cohesion, embrittlement of the portion being heated, and poor compaction characteristics.
2. Compaction:
The gold is compacted by following methods, i.e.
- Hand mallet
- Condensors
- Mechanical condensors.
- Hand Mallet: Earlier gold was compacted entirely with a mallet.
- Starting points are cut in the prepared cavity.
- The first pieces of foil are wedged into these areas and compacted.
- The condenser is placed against the foil and struck sharply with a small mallet.
- Subsequently, additional foil is wedged in the same manner, till the cavity is filed.
- Each increment of gold must be carefully ‘stepped’ by placing the condenser point in successive adjacent positions.
- This permits each piece to be compacted over its entire surface so that voids are not bridged.
- Condensers:
- The original foil condensers had a single pyramid-shaped face, but current instruments have a series of small pyramidal serrations on the face.
- These serrations act as swaggers, exerting lateral forces on their inclines in addition to providing direct compressive forces.
- They also cut through the outer layers to allow air trapped below the surface to escape.
- Each increment of gold should be carefully stepped by lacing the condenser point in successive adjacent positions, as the compaction force is applied.
- The stepping may be more readily accomplished and standardized by mechanical condensers.
- Size of the Condenser Point:
- The diameter of circular points should be 0.5 mm and 1 mm. The size of the condenser point determines the effectiveness of compaction.
- The force distribution to the gold depends on the area of the point.
- Small condenser points are indicated in order to get the desired compaction without using forces that might damage oral structures.
- Pressure Application:
- The pressure was applied by the use of a special mallet. In recent years, there has been a tendency to apply condensation pressure by hand.
- Compaction with mechanical devices like electromagnetic or spring loading condensers is quite rapid and is accomplished with greater comfort for the patient.
3. Mechanical Condensers:
Electromagnetic or spring-loaded have provided a mechanical means of applying force. The mechanical devices consist of points activated by comparatively light blows that are repeated with frequencies that range from 360–3600/minute. Vibrations can be produced either pneumatically (air driven) or electrically. They are faster and more comfortable for the patient.
Question 2. Write a short note on forms of direct gold filing.
Answer:
Following are the forms of direct gold filing:
1. Foil (Firous gold):
- Sheet
- Cohesive
- Non-cohesive
- Ropes
- Cylinders
- Laminated
- Platinized.
2. Electrolytic precipitate (Mat gold):
- Mat gold
- Mat foil
- Alloyed.
3. Granulated gold (encapsulated powder gold)
Gold Foil of Direct gold filing:
Gold is malleable. A cast ingot of 15 mm thickness is beaten to the submicroscopic thickness of 15 to 25 µm. This is known as gold foil. Gold foils are made from pure metal by beating and rolling. Beating produces lightweight foils and rolling produces heavy-weight foils.
Fibrous gold is supplied in the form of sheets about 4 inches square which ranges in numbers 2, 3, 4, 5, 6, 8, and 10. Higher numbers are rolled by manufacturers from ingot, while lower numbers are beaten by machinery.
These numbers are indicative of the number of grains in a sheet, for example, No. 5 gold sheet contains 5 grains. Gold foil or fibrous gold is available in form of sheets, rolls, cylinders, and pellets of various sizes. Sheets of gold foil are of two types, i.e. cohesive and non–cohesive.
1. Cohesive Gold Foil:
- Cohesive gold is also known as sticky gold.
- This is the gold foil that the manufacturer supply to the dentist is free from any surface contaminant and can be placed directly in cavity preparation is known as cohesive gold.
- Although it is free from surface contaminants some of the gases are still adsorbed during storage so degassing is required.
Various types of cohesive gold foils are:
- Soft type: This gets annealed before trimming and is treated in ammonia fumes for reducing the cohesion. As this type is cut and rolled in desired sizes, ammonia gas is driven off
- Dead soft type: This is not annealed and is soft. This is less cohesive than soft type.
- Extra or special soft: This is deliberately alloyed by a trace of silver for limiting cohesiveness. This is moderately cohesive after annealing.
- Platinized soft gold foil: In this, a sheet of pure platinum foil is sandwiched between two sheets of pure gold foil and then malleated again till the original thickness is established. Platinum increases hardness and wear resistance.
2. Non-cohesive Gold Foil:
- Non-cohesive gold foil is subjected by the manufacturer to a volatile agent such as ammonia which is adsorbed on the surface of gold.
- This adsorption of ammonia gas on the surface of gold prevents gold foil from adhering.
- It is rarely used currently but it can be used to build up the bulk of direct gold restoration.
- It can also be used with cohesive gold for beginning restoration on the gingival wall in the proximo-occlusal cavity or on the pulpal wall in occlusal cavities as a timesaver.
Electrolytic Precipitated Gold
- Crystalline gold powder is formed by electrolytic precipitation. The powder is formed into strips and shapes by sintering.
- Electrolytic precipitated gold is available as mat gold, mat foil, and alloyed electrolytic precipitate.
- Mat Gold: Mat gold is electrolytically precipitated gold sandwiched between sheets of foil and then formed into strips. Strips can be cut by the dentist into the desired size. It is used to build up the bulk of the restoration, as it can be more easily compacted and adapted to the cavity. However, mat gold has lots of voids and results in a pitted external surface. Therefore, foil gold is used to cover the mat gold and form the surface of the restoration.
- Mat Foil: It is a sandwich of electrolytic precipitated gold powder between sheets of No. 3 gold foil. The sandwich is sintered and cut into strips of differing widths. The dentist can then cut these to desired lengths. Mat was sandwiched between foil sheets to try to eliminate the need to veneer the restoration with a layer of foil. This type is no longer marketed.
- Alloyed Electrolytic Precipitates: A form of electrolytic gold is an alloy of gold and calcium (0.1% by wt.) called ‘Electraloy RV’. For greater ease of handling, the alloy is sandwiched between two layers of gold foil. Calcium produces stronger restorations by dispersion strengthening which locks in cold work strengthening. Thus, alloying with calcium changes the crystalline structure and makes it harder and stronger.
Powdered Gold:
- Powdered gold is also known as EZ gold.
- It is known as EZ gold because its manipulative characteristics are similar to very stiff amalgam and is more sticky than gold foil.
- Powdered gold is a blend of atomized and precipitated powder that is embedded in a wax-like organic matrix.
- This is available in pellets of various sizes which are mixed with wax and enclosed in gold foil N o. 3 wrappers and packed for their usage.
- The usage of pellets of powdered gold increases cohesion at the time of compaction and decreases the time needed for placing the restoration.
- Commercially available pellets of powdered gold wrapped in a gold foil are known as Golden. The ratio is 95% powder and 5% foil.
- It is provided in a cohesive form.
- The powdered particles are mixed with soft wax and held in a No. 3 gold foil.
- The gold foil acts as a container for the powdered particles and facilitates their condensation.
- Each pellet contains approximately ten times more gold than a pellet of gold foil of comparable size.
- The hand method of compaction is better than mechanical compaction for powdered gold.
Question 3. Write a short note on gold foil.
Or
Write a short answer on gold foil.
Answer:
Gold is malleable. A cast ingot of 15 mm thickness is beaten to the submicroscopic thickness of 15 to 25 µm. This is known as gold foil. Gold foils are made from pure metal by beating and rolling. Beating produces lightweight foils and rolling produces heavy-weight foils
Fibrous gold is supplied in the form of sheets about 4 inches square which ranges in numbers 2, 3, 4, 5, 6, 8, and 10. Higher numbers are rolled by manufacturers from ingot while lower numbers are beaten by machinery. These numbers are indicative of the number of grains in the sheet. for example. No. 5 gold sheet contains 5 grains.
Gold foil or fibrous gold is available in the form of sheets, rolls, cylinders, and pellets of various sizes. Sheets of gold foil are of two types, i.e. cohesive and non–cohesive
1. Cohesive Gold Foil:
- Cohesive gold is also known as sticky gold.
- This is the gold foil that the manufacturer supply to the dentist is free from any surface contaminant and can be placed directly in cavity preparation is known as cohesive gold.
- Although it is free from surface contaminants but some of the gases still adsorbed during storage so degassing is required.
Various types of cohesive gold foils are:
- Soft type: This gets annealed before trimming and is treated in ammonia fumes for reducing the cohesion. As this type is cut and rolled in desired sizes, ammonia gas is driven off
- Dead soft type: This is not annealed and is soft. This is less cohesive than soft type.
- Extra or special soft: This is deliberately alloyed by a trace of silver for limiting cohesiveness. This is moderately cohesive after annealing.
- Platinized soft gold foil: In this, a sheet of pure platinum foil is sandwiched between two sheets of pure gold foil and then malleated again till the original thickness is established. Platinum increases hardness and wear resistance.
2. Non-cohesive Gold Foil:
- Non-cohesive gold foil are subjected by the manufacturer to a volatile agent such as ammonia which is adsorbed on the surface of gold.
- This adsorption of ammonia gas on the surface of gold prevents gold foil from adhering.
- Non–cohesive gold is rarely used currently but it can be used to build up the bulk of direct gold restoration.
- Non-cohesive gold can also be used with cohesive gold for beginning restoration on the gingival wall in the proximo occlusal cavity or on the pulpal wall in occlusal cavities as timesaver.
Carbonized or Corrugated Gold Foil:
- Corrugated foil is obtained by placing the gold foil in between sheets of paper and igniting it in closed container.
- On igniting paper gets charred, but the gold foil remains unharmed except that it becomes corrugated. This is due to shriveling of paper while oxidizing in an airtight safe.
- The condenser is placed against the foil and struck sharply with a small mallet.
- Subsequently, additional foil is wedged in the same manner till the cavity is filed.
- Each increment of gold must be carefully ‘stepped’ by placing the condenser point in successive adjacent positions.
- This permits each piece to be compacted over its entire surface so that voids are not bridged.
Supply of Gold Foil:
- Flat square sheets (of varying thickness) in booklet form, 12 sheets (each 10 cm × 10 cm) per booklet.
- No. 4 wt 4 grains (0.259 gram) 0.51 um thick.
- No. 3 wt 3 grains (0.194 gram) 0.38 um thick.
- The number denotes the weight of the gold. Other sheets also available are Nos. 20, 40, 60, and 90. No. 3 foil is used to manufacture electrolytic and powder gold.
- Performed cylinders and ropes. These are made by cutting the No. 4 gold foil sheets into strips of varying widths (3.2,4.8, etc.) and then rolling and compressing them into pellets or cylinders. They may be carbonized
- A number of sheets of foil may be placed one top of each other to form laminated gold foil. One type of laminated foil is platinized foil which is a sheet of pure platinum foil sandwiched between two sheets of pure gold foil.
Question 4. Enumerate the tooth-colored restorative material
Answer:
Tooth-colored restorative materials are:
- Composite resin
- Glass ionomer cement
- Acrylic resin
- Porcelain.
Question 5. Write a short note on annealing and degassing.
Answer:
The effect associated with cold working (for example, strain, hardening) can be reversed by simple heating of the metal. The process is called annealing.
- The more severe the cold working the more readily annealing occur.
- Annealing generally comprises of three stages.
- Recovery: In the recovery stage, the properties of the cold worked metal begin to disappear before any significant changes are observed under microscopic examination.
- Recrystallization: When a severely cold worked metal is annealed, recrystallization occurs after recovery. This involves a radial change in the microstructure.
- Grain growth: The average grain size of the recrystallized structure depends on the initial number of nuclei. The more severe the cold working, the greater the number of such nuclei, and the grain size for the recrystallized metal can range from fie to fairly coarse.
- This grain growth process is simply a bounded energy-minimizing process.
- The annealing is a relative process, the higher the melting point of the metal, the higher is the temperature needed for annealing.
Degassing:
It is also called desorption.
- It is preferred over annealing because at no stage there is not any recrystallization or stress relief intentional
- The primary purpose is to produce an atomically clean surface and render the material cohesive and workable.
- For non-cohesive gold, degassing is done to remove protective ammonia film which is placed on the surface by the manufacturer.
Question 6. Write in detail about degassing and compaction methods of DFG.
Answer:
Degassing
- The heating process which removes the surface gases and ensures a clean surface is known as degassing or desorbing.
- Degassing removes the surface gases like oxygen, nitrogen, ammonia, moisture or sulfur dioxide which may be present due to improper storage.
- Direct filing gold may be heated by one of two methods as follows:
- In bulk on a tray, heated by either a gas-flame or electricity
- Piece by piece in a well–adjusted alcohol flame
In practice, all but the powder gold may be desorbed, on a tray:
- An electric annealer should be maintained at a temperature between 340°C (650°F) and 370°C (700°F). The time required varies from 5 to 20 minutes depending on the temperature and the quantity of gold on the tray.
- Powder gold must be heated in a flame to ensure the complete burning away of the wax.
- In flame desorption, there is picking up of each piece individually, heating it directly in the open flame, and placing it in the prepared cavity.
- The fuel for the flame may be alcohol or gas, but alcohol is preferred as there is less danger of contamination.
- The alcohol should be pure methanol or ethanol without colorants or other additives.
- Underheating could not adequately remove the impurities and thus results in incomplete cohesion, pitting, and flaking of the surface, while overheating leads to overwintering and possible contamination from the tray, instruments, or flame.
- This results in incomplete cohesion, embrittlement of the portion being heated, and poor compaction characteristics.
Compaction Methods:
The gold is compacted by following methods, i.e.
- Hand mallet
- Condensors
- Mechanical condensors.
- Hand Mallet: Earlier gold was compacted entirely with a mallet.
- Starting points are cut in the prepared cavity.
- The first pieces of foil are wedged into these areas and compacted.
- The condenser is placed against the foil and struck sharply with a small mallet.
- Subsequently, additional foil is wedged in the same manner till the cavity is filed.
- Each increment of gold must be carefully ‘stepped’ by placing the condenser point in successive adjacent positions.
- This permits each piece to be compacted over its entire surface so that voids are not bridged.
Condensers:
The original foil condensers had a single pyramid-shaped face, but current instruments have a series of small pyramidal ser-rations on the face. These serrations act as swaggers, exerting lateral forces on their inclines in addition to providing direct compressive forces. They also cut through the outer layers to allow air trapped below the surface to escape.
Each increment of gold should be carefully stepped by lacing the condenser point in successive adjacent positions, as the compaction force is applied. The stepping may be more readily accomplished and standardized by mechanical condensers.
- Size of the Condenser Point
- The diameter of circular points should be 0.5 mm and 1 mm.
- The size of the condenser point determines the effectiveness of compaction.
- The force distribution to the gold depends on the area of the point.
- Small condenser points are indicated in order to get the desired compaction without using forces that might damage oral structures.
- Pressure Application:
- The pressure was applied by the use of a special mallet. In recent years, there has been a tendency to apply pressure by hand.
- Compaction with mechanical devices like electromagnetic or spring loading condensers is quite rapid and is accomplished with greater comfort for the patient.
Mechanical Condensers:
Electromagnetic or spring-loaded have provided a mechanical means of applying force. The mechanical devices consist of points activated by comparatively light blows that are repeated with frequencies that range from 360–3600/minute. Vibrations can be produced either pneumatically (air driven) or electrically. They are faster and more comfortable for the patient.
Question 7. Write a short note on karat and fitness.
Answer:
Karat:
- It is also known as carat.
- It is the parts of pure gold in 24 parts of alloy, for example, 24 karat or 24K gold is pure gold (100%).
- 22 karat gold: 22 parts pure gold (91.67%) and 2 parts of other metals.
- An alloy with 50% gold is l2 K, whereas an alloy with 75% gold is 18K.
- The carat system is commonly applied to dental casting alloys.
Fineness:
- Fineness is the actual gold content in gold pieces.
- It is expressed in grams or troy ounces.
- Karat weight is a unit of fineness for gold equal to 1/24 part of pure gold in an alloy.
- Pure gold which is 1000 fie is 24 Karat and finess of 750 is 18 Karat.
- The finess is obtained by multiplication of the mass percentage of gold by l0.
- It is the parts per 1000 of pure gold, for example,
- Pure gold: 10000 files.
- 750 fie gold: 75% gold content
- Used to describe gold alloy soldiers.
- The symbol for fitness is F.
Question 8. Write a short note on powdered gold.
Answer:
- Powdered gold is also known as granular gold or encapsulated powder gold or EZ gold.
- It is known as EZ gold because its manipulative characteristics are similar to, a very stiff amalgam and is more sticky than gold foil.
- Powdered gold is a blend of atomized and precipitated powder that is embedded in a wax-like organic matrix.
- The average particle size of powdered gold is 15 µm.
- As a powder the material is impractical to manipulate, so is gathered into a conglomerate mass having a diameter of 1–3 µms.
- These masses are either sintered or lightly condensed to facilitate slight adhesion between the particles and ease of handling.
However, even on mild provocation, these masses tend to fall apart:
- This is available in pellets of various sizes which are mixed with wax and are enclosed in gold foil no. 3 wrappers and packed for their usage.
- The usage of pellets of powdered gold increases cohesion at the time of compaction and decreases the time needed for placing the restoration.
- Commercially available pellets of powdered gold wrapped in a gold foil are known as Golden.
- The ratio is 95% powder and 5% foil.
- It is provided in a cohesive form. The powdered particles are mixed with soft wax and held in a No. 3 gold foil.
- The gold foil acts as a container for the powdered particles and facilitates their condensation.
- Each pellet contains approximately ten times more gold than a pellet of gold foil of comparable size.
- The hand method of compaction is better than mechanical compaction for powdered gold.
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