Presentation on theme: "DIRECT FILLING GOLD Dr. Zameer pasha Lecturer, college of dentistry AlZulfi, Majma’ah University."— Presentation transcript:
DIRECT FILLING GOLD Dr. Zameer pasha Lecturer, college of dentistry AlZulfi, Majma’ah University.
O BJECTIVES General principles for cavity preparation Degassing (desorbing) Compaction General principles for restoration
G ENERAL PRINCIPLES FOR CAVITY PREPARATION FOR DFG OUTLINE FORM ------- The outline should be smooth and designed to be esthetically pleasing.
R ESISTANCE FORM flat pulpal floors perpendicular to the occlusal forces. Walls must be smooth and flat. Enamel walls must be supported by sound dentin.
R ETENTION FORM Parallel or slight occlusal convergence of the facial & lingual walls. Sharp internal line angles resist the movement of the restoration.
C ONVENIENCE FORM Convenience form for direct gold cavity preparation requires suitable access and a dry field. Width of cavity preparation should be minimal. Separators may be used to provide convenience access for class III cavity preparation. Sharp internal line and point angles in dentin serve as convenient starting points for compacting of direct gold restoration. Removing remaining caries. Finishing cavity walls, debridement and pulp protection.
F LAME DESORPTION / DEGASSING Fuel- alcohol or gas. Heating each piece directly in the open flame Time 5 – 20 min. Alcohol– pure methanol or ethanol without colorants or additives. Advantages — Ability to select piece of gold of desired size. Less exposure to contamination between degassing and use. Less damage to oversintering.
DEGASSING Incomplete cohesion. Pitting and flaking of the surface. Oversintering and possibly contamination from tray, instruments or flame. Incomplete cohesion Embrittlement Poor compaction UNDERHEATINGOVERHEATING
COMPACTION Hand mallet. Pneumatic vibratory condensers. Electrically driven condensers.
CONDENSERS Conventional– single pyramid shaped face Current instrument- series of small pyramidal serrations on the face. Serrations- exert lateral forces on their inclines in addition to providing direct compressive forces. Cut through the outer layers to allow air trapped below surface to escape.
CONDENSERS Size The lower limit is based on possible penetration by points of smaller size, which cause holes in the metal rather than weld it. 0.5 mm and 1 mm.
P RESSURE APPLICATION Conventional--- mallet Recent--- by hand. Mechanical gold foil condensers— Consists of points that are activated by light blows that are repeated with frequency that ranges from 360 to 3600 per minutes. Vibrations can be produced either pneumatically or electrically. Advantages--- greater comfort to patient and rapid.
DENSITY Direct gold restoration is characterized by an uniform density. The greatest strength is in the most dense area and the weakest part is the porous area, where layers or crystals are not closely packed. Voids on the restoration surface increase the susceptibility to corrosion and plaque deposition. Voids on the restoration tooth interface may cause gross leakage and secondary caries development.
DENSITY Density of compacted gold restoration is influenced by- size and shape of condenser face. Dimensions of prepared cavity. Dynamics of the compacting system and skill of the operator.
GENERAL PRINCIPLES FOR DIRECT FILLING GOLD RESTORATION 1. Build up of restoration. A) Tie formation- this involves connecting two opposing point angles or starting points filled with gold with a transverse bar of gold. This “tie” forms the foundation for any restoration in direct gold.
GENERAL PRINCIPLES FOR DIRECT FILLING GOLD RESTORATION B) Banking of the walls: This consists of covering each wall from its floor or axial wall to the cavosurface margin with the direct gold material. Banking should be done simultaneously on the surrounding walls of the preparation. C) Shoulder preparation: This consists of connecting two opposing walls with the direct gold material to completely fill up the restoration.
2. Surface hardening of the restoration The rectangular condenser is used with the highest possible condensation pressure in all directions on the surface of the restoration to strain harden the surface gold.
3. Burnishing This is done with a suitable burnisher moving from the gold to the tooth surface. This enhances the surface hardening and also produces good marginal adaptation of the gold. 4. Margination: This step uses sharp gold knives to remove excess gold from the surface to the tooth.
5. burnishing: It is important to burnish the surface of gold restoration after margination so as to eliminate marginal discripencies and to strain harden the surface. 6. Contouring : This step uses knives, files or finishing burs to create the proper occlusal anatomy.
7. finishing and polishing : Direct gold restorations require very little finishing if the previous steps are properly done. It can be done by using tin oxide powder on soft bristle brushes or rubber cups. 8. final burnishing: This is done after polishing to make the surface of the restoration smooth and free from voids.
CONCLUSION The technique skill of the dentist is of paramount importance to the success of the direct gold restorations. A direct gold restoration of poor quality can prove to be one of the most inferior of all clinical restoration.
REFERENCES Philip’s Science of dental materials 11 th edition by Kenneth J. Anusavic