Properties And Uses of dental Fillings
1. Amalgam Fillings
After a short period of time, the filling the surface is polished with amalgam finishing burs or ball burnisher, Abrasive strips and discs, brushes, pumice, and glycerin, or zinc oxide in alcohol, to ensure a final smooth finish.
Carving is very important during amalgam fillings because it helps remove excess amalgam and restores the tooth to its original anatomical form, this being best for maximum functional efficiency. Formation of a marginal ridge prevents food from reaching and damaging the gingivae.
Carving also attains a level joint between tooth enamel and amalgam. If this were not done food would catch in this region, stagnate, and lead to recurrent decay, as well as gingivitis if at gum level.
What requirement for successful amalgam filling or restoration?
- Use the correct ratio of alloy and mercury according to the manufacturer’s instructions.
- Careful and thorough trituration.
- Immediately pack into the cavity.
- Condense with heavy pressure to ensure the removal of excess mercury.
- Carve to the correct anatomical form.
- Polish to ensure a smooth surface, with no edges between tooth and amalgam.
Whereas it is quite simple to pack amalgam into a simple class 1 cavity, it is not so easy to do this in class II. A matrix band placed around the tooth replaces any missing wall and prevents filling material leaving the cavity, even with maximum condensing pressure. Various types of matrix holders and the band may be obtained (each with a different use)
Uses of amalgam
- Posterior fillings where aesthetics are of less importance.
- Anterior fillings in mouths highly susceptible to caries, where other materials are rapidly attacked.
Properties of amalgam
- Silver 68 percent
- Tin 26 percent
- Copper 5 percent
- Zinc 1 percent
The function of each is:
- Silver: strength, color, correct expansion.
- Tin: ease of manipulation, increased flow, slower setting time.
- Copper: hardens, increased setting time.
- Zinc: increased dimensional stability, ease of work.
It is essential to use the correct proportions of alloy and mercury in accordance with the manufacturer’s instructions otherwise incorrect properties will be obtained. Excess mercury causes weak amalgam with excessive expansion. Insufficient mercury causes brittle amalgam, rapid setting, lack of plasticity, and excessive contraction. It is therefore difficult to handle and pack into a cavity.
What are the techniques of amalgamation?
- Trituration of alloy and mercury with a pestle and mortar or Amalgamator until the silvery mass clings to the side of the glass mortar, ln case of Amalgamator the pestle should be held in a ‘pen grip’ and put inside the Amalgamator and mixed.
- By kneading them in a thick rubber finger stall.
- By vibrating them in an automatic Amalgamator, for which purpose the constituents may be obtained pre-dispensed in capsules.
This, in turn, causes pain, due to pressure on dentine overlying the pulp.
|Source: “Dr. Gary Walton” – under creative commons license.|
What is the Equipment required for amalgam fillings? :
- Diagnostic kit-mirror, probe, tweezers.
- Handpiece and burs.
- Excavators and chisels.
- Amalgam pluggers
- Plastic instruments.
- Amalgam carvers.
- Matrix holders and bands.
- Saliva ejector.
- Chip syringe.
- Amalgamator or pestle and mortar.
A lining is always placed over exposed dentine to prevent free acid in the silicate cement from irritating the pulp. For silicates, the matrix takes the form of a celluloid strip, which may be held in position with a special clamp.
Silicate is placed into the cavity with a plastic instrument and a strip lightly smeared with petroleum jelly is used to compressed it tightly into position. After the filling has set hard the strip is easily removed, the petroleum jelly acting as a separating medium.
Excess material is removed with a scalpel blade and white stones smeared with petroleum jelly, and a coating of varnish is applied. This stops uptake of moisture and stains before the final set has taken place. After twenty-four hours the filling is polished with fine stones, Disks, And strips, all greased with petroleum jelly.
Uses of silicate fillings
- Semi-permanent restorations in the front of the mouth as the color and translucency match the natural tooth substance.
- Facing gold crowns at the chairside
Properties of silicate fillings
- Silicates consist of a liquid and a powder.
- The powder is composed of silica, alumina, Flux, lime, zinc oxide.
- The liquid is phosphoric acid, water, aluminum, and zinc phosphates.
The liquid rapidly takes up or gives off water according to the humidity (water content of the atmosphere). It is important that the bottle should be kept tightly stoppered when not in use, as changes in water content affect the setting reaction. Unfortunately, silicates are not long lasting.
Some are supplied in pre-dispensed capsules. In this case, the liquid is contained in a membrane, which is ruptured just before use, by squeezing in a special press. This brings liquid and powder into contact, after which they are mixed in a mechanical mixer for about 10 seconds.
The technique of Silicate Fillings
- A thick glass slab is cooled with cold water and dried. Thick glass retains the coolness for a long period of time, allowing a longer mixing time.
- The required quantities of liquid and powder are placed on the slab. It is important to hold the dropper vertically to ensure that the correct amount of liquid is dispensed.
- The powder is divided into four sections, each approximately half the size of the next section.
- The largest pile of powder is speedily mixed into the liquid followed by rapid addition of the other three sections until a dough-like consistency is obtained. A maximum quantity of powder added in this way gives maximum strength and adaptability. As soon as setting begins, manipulation music is stopped.
- An agate or bone spatula may be used. A special glass slab is kept for silicates. Remnants of other materials could contaminate and interfere with the durability of silicate fillings.
As silicates are affected by moisture, a rubber dam is often placed on the tooth before inserting the filling.
Silicate mixtures are acidic and would affect the pulp if no lining were used.
What is the equipment required for silicate fillings?
- Shade guide
- Celluloid stripso
- Petroleum jelly
- Surface varnish
- Agate or stellite spatula
- Glass slab.
- Automatic mixer, if used.
- Rubber dam, clamps, forceps, punch, frame.
- Silk floss.
This kind of filling is very popular and commonly used in today’s dentistry, composite resin is made up of glass particles mixed with an acrylic resin.
These are used for class III and v fillings, and for restoring fractured incisors. Prior to filling, the cavity is lined, but not with zinc oxide Eugenol, as this stains composite and inhibits it’s setting reaction. Enamel around the edge of the cavity is etched with a 50 percent solution of phosphoric acid, to aid retention.
Composite is packed into the cavity with a plastic spatula and a polythene matrix band or crown former is used to hold materials firmly in place for about two minutes. The matrix is then removed, and excess material is cut away with a sharp blade.
Normally, a handheld “curing” light is used to set, or harden, the material once it has been placed. This gives the dentists a more working time for shaping and placement than other filling materials.
Ideally, no further excess should remain, but if necessary further material can be removed after six minutes. Diamond, carbide finishing burs, greenstone, and zirconium strips are all used. Finals finishing is done with fine silicone carbide paper barked discs and white Arkansas stones, using water or a special lubricant.
- Varieties of different color shades so the material can be matched to the tooth aesthetics
- There is an Increased in working time for the dental team to manipulate the material to suit the tooth structure
- No Mercury
- Composite resins are able to bond easily or stick to the tooth, which can lead to less tooth removal during preparation
- Very Easy to use for small and simple procedures under repairs and restorations
Uses of composite
- Restorations where aesthetics is of prime importance.
Properties of composite
- Two pastes
- Paste and liquid
- Powder and liquid
- Paste and powder.
What is the equipment required for composite fillings?
- Shade guide.
- Composite kit.
- Polythene matrices and crown formers.
- Plastic spatula.
- Sharp knife.
- Finishing discs, stones.
- Porcelain fillings are very good for large restorations where strength is needed. Porcelain is also excellent in aesthetically returning the tooth to its natural shape
- Longevity and stability
- CEREC porcelain dental fillings can be fabricated and placed all in one visit, on one day.