Placement of Amalgam PDF

Placement of Amalgam 1 The technique for amalgam placement is basically the same, regardless of the type or classification of the preparation. 2 Amalgam is mixed (triturated) , carried to the preparation, and condensed into the cavity...

Placement of Amalgam 1 The technique for amalgam placement is basically the same, regardless of the type or classification of the preparation. 2 Amalgam is mixed (triturated) , carried to the preparation, and condensed into the cavity so that voids are eliminated and all areas of the preparation are filled. The amalgam is then carved to reproduce the portion of the tooth that is missing. 3 Spherical alloys produce an amalgam that requires -lower mercury-alloy ratio -less condensation force 4 The direction of the condensation force is extremely important for spherical amalgams They do not adapt to the cavity walls as well as lathe - cut or admixture amalgams. 5 In addition, the spherical materials generally have a shorter working time and demonstrate a faster set than the admixtures. 6  Trituration The trituration process includes the mixing of liquid mercury with dry amalgam alloy powder. - Hand trituration - Mechanical trituration 7 Electric amalgam mixers (also called amalgamators) are used for trituration process. 8 9 10 11 12 The duration and speed of trituration should be just enough to coat all alloy particles with mercury, to produce the amalgam matrix, and provide a plastic mix. 13 - Under-triturated amalgam appears dry and crumbly and sets too quickly. - Over-triturated amalgam appears wet, soft, hard to remove from the capsule, sets quickly. - Properly triturated amalgam has a shiny appearance, separates in a single mass from the capsule. 14  Condensation Condensation is the process of compressing and directing the dental amalgam into the tooth preparation with amalgam condensing instrument until the preparation is completely filled and overfilled with a dense of amalgam. 15 Objectives of the condensation : -To adapt amalgam to the cavity walls. -To remove excess mercury. -To increase the density of the restoration. 16 There is two type of condensation : -Hand condensation. -Mechanical condensation. 17 The field of operation must be kept absolutely dry during condensation. Immediate condensation done after each increment with sufficient pressure (3- 4 pounds) in vertical and horizontal direction starting with smaller condenser. 18 The force of adequate condensation should be ( 2 to 5 ) kg for a condensable amalgam (admixture or conventional). 19 The condensation force required for spherical amalgams will be considerably less, because heavy forces tend to push the spherical particles to the side and “punch through” the amalgam mass. 20 Amalgam should be condensed both vertically and horizontally or laterally (toward the walls of the preparation). 21 22  Mechanical condensation It differs from hand condensation such that it is performed by an automatic device. Less energy is required than hand condensation and the dentist feels less fatigue. 23  Precarve Burnishing After condensing the amalgam, and before carving procedures are initiated the amalgam may be further shaped occlusaly with a large egg-shaped or ball burnisher. 24  The round end burnisher is positioned on the unprepared enamel adjacent to the amalgam margin and pulled parallel to the margin, this removes any excess at the margin while not allowing the marginal amalgam to be overcarved. 25  Carving The objective of carving is to simulate the anatomy rather than to reproduce extremely fine details. - Carving should not be started until the amalgam is hard enough to offer resistance to the carving instrument. 26 The carving is performed by using various varieties of amalgam carvers avaiable. Carving is always from the tooth surface to the restoration surface. This is done to avoid removal of amalgam at the margins. 27 The dentist should try to develop  margins of amalgam that will leave a 90 degree angle at the margin of occlusal amalgam. 28  Burnishing Objectives : -To further decrease the size and number of voids. -To express excess Hg on the surface of the amalgam restoration. -To adapt amalgam to the cavo surface anatomy. 29 The burnishing performed using burnisher from amalgam to tooth. Final smoothing can be done with the help of moist cotton. 30 Check condenser fit 31 Overpacked 32 33 34 35 36 Class II restoration 37 38 39 40 41 42 Adjusting the Occlusion When the carving appears to be correct, the rubber dam is removed, and the occlusion is checked. This is accomplished with articulating ribbon, which marks the points of contact when the mandibular and maxillary teeth are brought together. 43 Articulating ribbon 44 The amalgam must be carved until contacts on the restoration occur togather with other centric contacts on that tooth and adjacent teeth. 45 46 Repair of Amalgam Restorations Main reasons: - Secondary caries. - Marginal defect. - Cusp fracture. 47  Replace or repair - lossof dental tissue. - increasing preparation. - cost. - time consuming. - potentially damage to pulp. 48  Benefit of repair - more conservative of tissue. - reduce risk of iatrogenic damage. - reduce need for the use of local anesthesia. - opportunity to enhanced patient experience. - saving in time. 49 Dentist were more likely to repair a : - restoration in a molar than premolar - restorations with single surfaces than multiple restoration surfaces. 50 The important factor related to the quality of the amalgam repair is the interfacial bond between the new and the existing amalgam. The surface of an old amalgam to be bonded should be roughened to remove corrosion and saliva contaminants. 51 When a freshly triturated amalgam is condensed directly onto the roughened surface of an existing amalgam , the flexural strength of the repaired structure can reach 50% of that of unrepaired amalgam. 52 If an amalgam fracture has occurred in the mesial box portion of a mesio- occlusodistal restoration, but the remaining disto-oclussal portion involves a very gingivally deep distal margin, 53 The most conservative and simplest treatment might be to replace only the mesio - occlusal portion of the restoration. 54