Fuse Nib
However, as a filling material
INTRODUCTION
Several types of dental restorative materials are currently available. They are usually grouped into categories such as materials of silver amalgam, gold molded, the tooth colored materials, dental porcelain, Porcelain fused to metal and gold directly.
Golds are the direct restorative materials or which are manufactured for compaction directly in the prepared cavities. Direct gold restorations can last a lifetime if attention to detail art restoration and appropriate home care. The longevity of gold restoration is the direct result of these two superb biocompatibility of gold with the oral environment and excellent marginal integrity.
RANKING
1. Foil
a) Units
- Cohesive
- Non-coherent
b) ropes
c) Cylinders
d) Laminated
e) Platinum
2. Electrolyte precipitate
a) gold mat
b) Aluminum Matte
c) Gold alloy calcium
3. Gold dust
Gold Leaf
Gold Leaf is the oldest of all restorative materials.
Gold leaf is in the form
Flat square sheets of different thicknesses.
- Standard # 4 wt. 4 grain (0.259 g) 0.51 um thick
- Standard No. 3 wt. 3 grains (0.194 g) 0.38 um thick
These sheets may be cut into eighths, sixteenths, sixty-fourths, etc., and then compressed into pellets or cylinders fig I.
After pellets of gold are rolled, they may be easily stored in a box of gold leaf, which is divided into sections labeled with different sizes of pellets.
Platinum Gold Leaf
Leaf gold platinum in manufacturing by rolling a sheet of aluminum machined plate between two sheets of gold. This sandwich is thinned by rolling to a desired thickness. This material creates a surface restoration is more difficult than the classical gold foil after compaction, and is used for the restoration of the tooth surfaces subject occlusal wear heavy such as tips of cusps of posterior teeth.
PREFORM gold leaf
Today, strings and actuators are available in preformed shapes. Both are made of sheet No. 4 was "carbonized."
By placing gold leaf between two sheets of paper to ignite in a closed container, charred sheet can be obtained. In turn, the paper is destroyed, but the gold leaf is left intact, except that it is "burned". This is due to scalding paper while in the oxidizer vessel sealed securely. After the carbon is removed, it is found that gold exhibits superior welding property.
Gold Leaf
Cohesive Gold Leaf
For welding cold, gold should have a clean surface, free of impurities. Gold draws gases, eg oxygen, its surface and a film absorbed gas prevents the cohesion of different increments of gold during their compaction. The manufacturer, therefore, provides the gold leaf virtually free of surface contaminants. This type of gold is known as the cohesion of gold leaf.
Not Cohesive Gold Leaf
The manufacturer shall submit the sheet to a volatile agent such that ammonia is absorbed on the surface of gold. This acts as a protective film which prevents the adsorption of non-volatile gas and premature cohesion of granules in the container. Ammonia-treated foil is known as non-cohesive gold foil.
But solidarity can not also have absorbed agents such as iron salt or an acid gas (sulfur or phosphorus-containing groups) on its surface. The film is easily removed volatile by heating, thus renewing the joint nature of the leaf.
Not Cohesive gold is rarely used today, but may be used to build the bulk of direct gold restorations.
INDICATIONS
- Class I small lesions caries in pits and fissures of posterior teeth and lingual surfaces of anterior teeth.
- Class V cavities on the buccal surfaces of teeth.
- Class III small cavities on the proximal surface of anterior teeth.
- Class II cavity surface, slender proximal caries in posterior teeth where the marginal ridges are not subject to large forces occlual.
- Class VI to restore the incisal or cusp.
- Repair of cast gold restorations.
CONTRAINDICATIONS
- It can not be used in teeth with pulp chambers very large.
- It can not be used in teeth periodontally severely weakened.
- Cons-indicated in patients with disabilities who are unable to sit for long dental appointments for the required procedures.
- Canal filled teeth because these teeth are fragile.
BENEFITS
- Gold is resistant to tarnishing and corrosion.
- Gold has biocompatibility.
- Gold has good mechanical properties.
DISADVANTAGES
- Direct filling gold restorations are adhesive to tooth structure. Therefore, they can not operate to strengthen the tooth structure in a manner similar to that of composite or porcelain restorations.
- Gold leaf is of poor quality of aesthetic restorative material.
- Gold leaf cause pulpal sensitivity to thermal stimuli, because gold high thermal conductivity.
- Manipulation of gold leaf is a difficult operation.
- Gold is a very expensive metal.
PROPERTIES
- Direct gold is essentially 100% gold. Pre-alloy with other elements would reduce the weldability and ductility at room temperature. However, another element may be incorporated (platinum or calcium) indirectly in the final structure by superimposing them on gold in forms such as gold leaf.
- Restoration of leaf Gold is denser than gold or matte gold dust and newer gold leaf have fewer assets to bending than gold matte gold powder.
- Density of gold leaf ranges 14.3-15.9 g/cm3.
- Flexural averages from sheets Gold = 265-296 MPa.
- Hardness of the gold leaf is about 69 KHN.
Clinical Features
- It retains a good surface.
- The restoration can be completed in one visit.
HANDLING
There are two processes involved in direct manipulation of gold restorations filling. (1) degassing (2) compaction
Degassing or annealing
The gold filling is received directly by the dentist in a consistent state, except for non-cohesive gold. However, during storage and packaging, they absorb gases in the atmosphere. Adsorbed gases or prevent the merger. Therefore it is necessary to heat the sheet or the ball immediately before it is brought into the cavity. This heating process that removes greenhouse surface (oxygen, nitrogen, ammonia, moisture or sulfur dioxide) and provides a clean surface or desorbed is called degassing.
Gold Leaf is stored in sealed containers, so it is recommended that the operator must wear fingertip Chamoi protect gold contamination.
Degassing is done by heating the gold leaf
- In a bulk in a mica plate on a flame or an electric or annealing
- By heating each piece of gold on pure ethanol flame.
Electric Annealing
The electric motor "annealing" is maintained at a temperature of 340oC and 370 º C.. The time required varies from 5 to 20 minutes depending temperature and the amount of gold on the shelf.
Disadvantages of electric annealing are:
- May pellets stick together, If the tray is moved.
- The draft in May effect the uniformity of heating.
- Greater exposure to contamination.
Flame desorption
The fuel for the flame is pure ethanol. Each piece is individually listed and went into kernel Internal blue flame at the end of a sheet passing instruments and held just before gold becomes dull red, the instrument is withdrawn from the flame. After a few seconds, allowed to cool, gold is placed into the cavity.
Advantages of the desorption of flame are:
- Ability to select a piece of gold the size desired.
- Less exposure to contamination from the degassing time and use.
Underheating: should be avoided. Because it does not remove adequately impurities and results in incomplete cohesion.
Overheating: is avoided as it may cause gold to become brittle or melt and make it unstable.
Compaction
Direct-ors must fill be compressed during insertion in the preparation of the tooth. Compaction is the form of malleting forces that are delivered with a mallet in hand used by the assistant or by a mallet or electro-pneumatic hammer used by the dentist. Malleting success of the gold leaf may be reached with one of the devices currently available. Some operators prefer electromallet or pneumatic hammer as a dental assistant is not required for the procedure.
Compaction begin when a gold coin is placed in a tooth preparation. Gold is the first pressure placed by hand, then a capacitor of appropriate size is used to start malleting in the center of mass (often this is done while the first increment is held in position by operating an instrument). Each succeeding step overlaps condenser (half) the previous one, because the condenser is moved towards the periphery. The movements of gold under the pen opposite the condenser, the compaction function as malleting product.
Compaction is the most effective product directly in the face NIB. Some compaction also occurs by lateral movement of gold against the walls surrounding the preparation. The result of compaction is to remove most of the empty space within each slice of gold, to compact the gold line and point angles and against the wall and attach gold previously placed through the process of cohesion. The line strength is important when gold is compacted. The line of force is the direction through which power is delivered (ie, the direction in which the condenser is intended).
The Electro-Mallet is an acceptable means If the instructions for the condenser maufacturer intensity Mallet followed. Correct hand malleting technique requires a light, bouncing under hammer for the condenser, rather than delivering blows.
Gold Leaf compacts easily because of its shape and therefore produces a mass with linear chains isolated microporosity. Because the thin folds of Pellet or weld together, the remaining channels of microporosity does not seem to be completely confluent with one another.
About the Author
Dr. Rohit Anand
M.D.S (Pedodontics with preventive dentistry)
Lucknow (U.P.), INDIA.
US $144.00
