Amalgam Restorations PDF

AMALGAM RESTORATIONS Mercury Hygiene & Safety OBJECTIVE: Discuss the importance of mercury hygiene and list recommendations to ensure proper handling. Like many other materials, mercury can be potentially toxic (have bad health effects) if not managed correctly. Metallic mercury is absorbed m...

AMALGAM RESTORATIONS Mercury Hygiene & Safety OBJECTIVE: Discuss the importance of mercury hygiene and list recommendations to ensure proper handling. Like many other materials, mercury can be potentially toxic (have bad health effects) if not managed correctly. Metallic mercury is absorbed most readily when the vapor is breathed into the lungs, but is poorly absorbed when ingested, or placed on the skin. When dental amalgam is mixed and placed correctly, the mercury reacts with the alloy so it is chemically tied up, and vapor release has not been found at toxic levels in humans. Many studies, most recently those presented in the 1990’s by the National Institute of Health, National Institute for Dental Research and the Federal Drug Administration, concluded that amalgam is not a significant health hazard to humans. Note, however, that a mild hypersensitivity (allergy) to mercury has been identified in a very few individuals. Even though toxicity from amalgam restorations has not been shown to be a health hazard, office personnel must be aware that amalgam, over time, could be a potential source of mercury toxicity both to the environment and to office staff exposed to dental amalgam frequently, if it is not handled correctly. The American Dental Association has developed office guidelines for mercury hygiene as follows: Train all office personnel on mercury hygiene practices. Work in well ventilated spaces, and clean air filters often. Periodically check mercury vapor levels (especially after spills) with a device called a dosimeter or mercury vapor analyzer. Use pre-capsulated alloys; do NOT use bulk mercury. Build/maintain an office environment that is conducive to cleaning up mercury spills with NO carpets, seams or absorbent coverings. Clean up mercury spills using trap bottles, tape or freshly mixed amalgam to pick up droplets. Do NOT vacuum, which would break up the droplets into smaller droplets, and increase the surface area releasing even more mercury vapor. Use water and high volume evacuators to keep down mercury vapor when removing or finishing amalgam restorations. Manage mercury waste: o Use traps to retain and recycle amalgam; do NOT rinse the trap over a drain in the sink; do NOT flush down the toilet or drain. o Store/dispense of old amalgam in sealed containers according to local regulations. o Recycle by placing scrap in wide mouth air-tight containers marked “Amalgam Waste for Recycling”. TRITURATION EFFECT: Trituration refers to the production of a homogeneous material through mixing. Dental amalgam is formed by combining particles of an alloy with mercury. (The amalgamator mixing speed and mixing time affect the characteristics of the amalgam. Trituration time, if correct, results in a cohesive ball of velvety, shiny amalgam. Physical properties can be negatively affected by improper trituration. When considering the properties of dental amalgam after trituration, compare it to the liquid and powder mix of water with dental plaster, only for amalgam, the mercury is the liquid and the alloy particles are the powder. If amalgam is under-triturated (not mixed enough), it will appear dry and grainy, (not cohesive). This porosity will contribute to corrosion, less strength, and other undesirable properties. If it is over-triturated (continued mixing even after it has already started to set up), the amalgam will be hot, crumbly, quick setting, but properties are not affected as much as under-trituration. Different amalgamator brands have varying speeds, and therefore may require different times for trituration of the same brand of amalgam. For the best results, the manufacturer’s directions should be followed. Figure: The amalgam mass should appear as a shiny mass. Left : The diaphragm from inside of the capsule (in the cotton forceps) may need to be separated from the amalgam. The amalgam can be set on a squeeze cloth, or in a dappen dish. Right : When picking up increments of amalgam with the carrier, the carrier should penetrate the amalgam without having it crumble. (If the mass of amalgam crumbles, it is too dry.) EFFECT OF CONDENSATION: Adequate condensation is needed to decrease voids between amalgam layers, thus improving all properties, and decreasing corrosion. This is especially true for lathe cut or admixed amalgams. The force applied to the amalgam is related to the diameter of the condenser nib. If the same hand pressure were used to condense an amalgam with a small diameter condenser nib, much more force would be applied against the amalgam than if the EFDA used a large diameter condenser nib. (Compare this to having a woman step on your hand while she is wearing flat soled shoes versus spike high heel shoes. For the same weight woman, the small diameter of the high heel would certainly apply more force to your hand! ) EFFECT OF BURNISHING: Burnishing the amalgam (lightly rubbing with a smooth ended instrument) immediately after carving improves surface properties by reducing surface voids. EFFECT OF AMOUNT OF MERCURY: The correct amount of mercury is critical to obtaining the best amalgam properties. If too much mercury is present, the amalgam will not have its best strength (just like plaster would not be as strong if too much water was used.) It will also set slower. This amalgam would also exhibit increased setting expansion, increased corrosion, and increased creep. Therefore, care must be taken that the correct ratio of mercury is used in the capsule (preferable pre- capsulated), and the mercury rich layer (plash) should be removed upon condensation of the material. Amalgam Evaluation Criteria (general; used by the Commission on Dental Testing) When evaluating a restoration, each category may be assigned one of four ratings: R-3, S-2, T-1 or V-0. Very generally, a rating of “R” means that criteria is essentially perfect, rating of “S” means there are minor deficiencies in that criteria, a “T” means there are substantial deficiencies, and a “V” indicates that the criteria exhibits gross deficiencies. EVALUATION CATEGORIES for ALL amalgam restorations Occlusion Interproximal Contact/Contour Occlusal/Incisal Anatomical Detail Marginal integrity Surface texture (smoothness) Evaluation Criteria for Amalgam: Anatomical Detail ANATOMICAL FORM (occlusal, incisal and interproximal) of an amalgam RATING CRITERIA for amalgam 3-R The Restoration reproduces physiological contours of the tooth (including [perfect or nearly perfect] embrasures). Surfaces, cusp planes, marginal ridges, axial and proximal contours are continuous with natural tooth surfaces. Major anatomical features produced the normal anatomical and functional forms of the tooth 2-S Restoration reproduces the physiological contours with slight variation from [slight problems but acceptable] normal. Minor correction of anatomical features is necessary Major anatomical features resemble normal tooth anatomy Embrasure form does not adequately reproduce normal function. 1-T Proximal and axial contours are too flat or too full and not continuous with [decided problems; minimally acceptable] existing natural tooth surfaces. Anatomy significantly lacks definition. Requires major correction. 0-V Proximal and axial contours are concave and/or completely inconsistent with [gross failure; not acceptable] normal tooth contours. Restoration jeopardizes the gingival health of the patient. Anatomy totally lacks definition; or excessive depth. Surface grossly over/under contoured Restoration requires replacement. TERMS TO DESCRIBE POOR RESTORATION CONTOURS: Overcontoured: the restoration is contoured too much (has too much contour; is too fat). This is often the result of not carving enough amalgam away, so may also be called undercarved. Since it could also result from placing too much amalgam, it can also be called overfilled  Undercontoured: the restoration is contoured too little (has too little contour; is too flat or concave when it should be convex). This is often the result of carving too much of the restoration away, so it may also be calledovercarved. This could also result from not filling the preparation enough and be called underfilled. Evaluation Criteria for Amalgam: Margins RATING CRITERIA for amalgam R-3 Cavosurface is not detectable or scarcely detectable with explorer. [perfect or nearly perfect] S-2 There is evidence of slight excess< 1.0 mm visually or deficiency ( 1.0mm or severe deficiencies >0.2mm, voids, open margins when the unacceptable] explorer passes over it TERMS TO DESCRIBE POOR AMALGAM RESTORATION MARGINS: Figure: Use an explorer tip to lightly crisscross the cavosurface in order to evaluate the entire margin. A “catch” or “bump” must be determined to be either over-extended, a submarginal area, or an open margin. Submarginal (or under-extended): The restoration is not at the same level as the tooth cavosurface, so tooth structure must be removed to make it flush. IF the filling is over two-tenths (0.2) mm submarginal, it is not acceptable due to the amount of tooth that would have to be removed to make it flush. Figure: Submarginal amalgam margin. Overextended or excess: The restoration extends beyond the cavosurface margin of the preparation.Filling material must be removed to make margins flush. If this excess occurs at a proximal gingival margin, it is also called an overhang Figure: Overextended/excess amalgam. Flash extends beyond the margins. Flash is another form of excess amalgam. It extends beyond the margins of the preparation (see arrows). There may not be any “catch” at the margins in either direction, since the excess may thin out and be undetectable to the explorer tip. It is identified by memorizing the shape of the original preparation, and realizing that the outline of the final amalgam is larger than what you remembered the preparation size to be. Open margins: The explorer catches in both directions as it drops into a fissure between the tooth and restoration A restoration with an open margin would need to be replaced.. Figure: Open margin (a gap or crevice). Place a Class I Amalgam Restoration OBJECTIVE: Demonstrate the correct placement, condensing, and carving of a Class I amalgam restoration. ACTIVITY: Place a small Class I amalgam restoration. Review of terminology for an OA. Recall that Class I decay is most often located on the occlusal surface of posterior teeth. Theb decay is removed from the pits and fissures. The four cavosurface margins and adjacent walls of this preparation are named mesial, distal, buccal and lingual. The fifth wall or floor is called the pulpal wall (over the pulp and parallel to the occlusal surface). Retention is obtained by the convergence toward the occlusal of the buccal and lingual walls of the preparation. 1. Obtain and set out armamentarium: cleoid discoid carver, hollenback carver anatomical burnisher, explorer, condenser, amalgam carrier, dappen dish. 2. Obtain good operator and patient position, and good light. 3. Evaluate (memorize) the shape of the preparation. 4. Set the triturator for the time and speed recommended by the manufacturer for the amalgam being used. Figure: For Permite amalgam, hold the capsule and press it firmly against the bench top in order to break the inner diaphragm that separates the mercury from the alloy.  Figure: Separate the two halves of the capsule holder in the amalgamator and seat both ends of the capsule securely into the concavities of the holder. Then close the cover on the amalgamator and triturate for the recommended time. 5. Place the first layer of amalgam with the amalgam carrier. While extruding the amalgam into the preparation, exert moderate pressure and spread it from distal to mesial forming a uniform layer. Remember that no matter how small the preparation, you should always use a minimum of two layers of amalgam. Figure: Place amalgam with the amalgam carrier. 5. Condense the first increment using the small nib condenser one layer at a time with overlapping strokes. Make sure the small nib fits in the preparation, and that you angle the direction of condensing strokes into the buccopulpal and linguopulpal retentive areas. (patting the amalgam with a larger condenser initially after placement before condensing, assists in keeping the amalgam in place during condensing) Figure: Left: Angle the condenser into the buccopulpal and linguopulpal retentive features. Right: Use a sliding stroke to assure complete adaptation of amalgam against all walls, and removal of all voids. 7. Overfill the amalgam and form the central groove depression: Divide the amalgam into a buccal half and lingual half, picturing the central groove running down the center of the preparation from mesial to distal.First, adapt the larger end (overfill) condenser on the buccal half of the amalgam with one end of the large condensing nib resting on and parallel to the buccal triangular ridge, while the other end of the nib is centered in the amalgam to begin forming the central groove depression. A series of strokes can be used to form the buccal half of the preparation, and each stroke should slide toward and over the unprepared tooth to assure excellent adaptation with no voids at each cavosurface, and should form flash so thin that is should flake off and expose the cavosurface margin.  Figure: Condensing amalgam with a large (overfill) condenser in order to form central groove and slide toward tooth (buccal half, then lingual) to thin flash for easy removal. 8. Next, repeat the condensing strokes on the lingual half, now resting the nib parallel to the lingual triangular ridge, one end of the nib overlapping tooth, and the other end centered over the same central groove that was formed buccally. Finally, condense and slide the amalgam toward the mesial and then distal cavosurfaces to adapt and thin the amalgam at these margins. At this point there should not be large amounts of flash beyond the cavosurfaces. Prior to the next step, gross excess only should be removed quickly with a discoid carver as described in step “e” below. 9. Form the grooves: Grooves on the occlusal surfaces of teeth are important because they permit food to squeeze out between the chewing surfaces while we eat. If all surfaces were flat, the ability to cut through and chew food efficiently would be greatly reduced. Therefore, reproducing these grooves, or food escapeways, is important to good dentistry. 10. Use an anatomical burnisher to form the pits and grooves. This must be accomplished when the amalgam is still very soft. Figure: Anatomical burnisher used in soft amalgam to form the pits and grooves. Purpose for carving: Carving should remove the mercury rich outer layer (plash) of the overfilled amalgam and leave behind a compact mass on the surface and at all cavosurface margins. On these relatively small amalgam restorations, carving is best accomplished after amalgam has set up just a little in order to avoid overcarving. The harder the amalgam, the more force is needed to remove the excess, so make each carving stroke effective. The goal of each carving stroke is to let “the tooth tell you” what contours to reproduce by letting the adjacent tooth contours guide the instrument (that is half on tooth and half on filling) when developing the restoration  contours. You can actually begin the carving stroke with the instrument entirely on tooth structure, feeling the convexity of the crown (mesiodistally) while paralleling the occlusal and gingival cavosurfaces. Repeat these carving strokes with each one moving closer to the amalgam until you have removed all flash. 11. Carve: Use a thin bladed carving instrument (like the Hollenback or Tharpe carver) to refine the amalgam shape and remove flash one cavosurface at a time. Remove Remaining Flash: By this time, you should have formed all major grooves in about 15-20 seconds. The restoration should be about 90% complete. Final carving is needed to remove the last remnants of flash and, as needed, to refine the grooves and smooth the ridges. Flash can be identified as any amalgam that you think has extended beyond the cavosurface outline that you memorized earlier, especially if the amalgam outline appears as a thin point of amalgam since all cavosurfaces are rounded. It is best removed using the disc-shaped discoid end of the cleoid-discoid carver, using strokes that run parallel to each margin. The key to the discoid carver is that it should never go far enough into the amalgam to obliterate the grooves you formed with the anatomical burnisher, and it should not extend into the amalgam so far that it removes amalgam within the margins. A: B: Figure: Left-A: Discoid carver removing flash that overlaps the unprepared tooth by running the discoid parallel to the margins; Right-B: Discoid carver too far into amalgam “scooping” it out at the margins resulting in over carving and thin amalgam. Remove mesial flash using a modified pen grasp and finger rest, by laying the discoid carver against the cavosurface next to the marginal ridge. Use short strokes from lingual to buccal (or buccal to lingual), beginning with the discoid entirely on the tooth to “feel” the tooth contour, and then repeating these short strokes while moving closer to the amalgam each time until flash has been removed. Remove distal flash using short, repeated strokes from lingual to buccal (or buccal to lingual). Remove buccal flash by using a modified pen grasp and finger rest, by laying the discoid carver against the buccal cavosurface while moving mesiodistally and reproducing the convex contours of the triangular ridge. Use short strokes from distal to mesial (or mesial to distal), at first resting completely on the tooth to “feel” the convex contour of the triangular ridge, and then repeating this stroke while moving closer to the amalgam each time until flash has been removed. Remove the lingual flash moving mesiodistally while paralleling the lingual cavosurface. 12. Define and deepen grooves as necessary while smoothing ridges: At this point the tooth contour and amalgam should be flush and have a reasonably continuous contour from tooth to filling. All major grooves should be visible. If the amalgam between the cavosurface and the grooves is lumpy or bumpy, or if the grooves need to be defined, use the claw-shaped cleoid end of the cleoid-discoid carver. The tip of the cleoid is pointed so can be used for defining grooves, while the side carving edge is flatter so it can actually rest on the tooth like the discoid carver to remove residual flash while simultaneously smoothing the adjacent amalgam, one cavosurface at a time. With the cutting edge of the cleoid carver at an angle parallel to the slope of the triangular ridge, use the tip to trace the central groove beginning at one pit and ending at the other, while simultaneously resting on adjacent tooth that guides you to form the convex contour of the triangular ridge. If the cleoid is angled too steeply into the amalgam, the anatomy will be too deep, and amalgam at the margins will be too thin. If the cleoid is not angled deeply enough into the amalgam, the anatomy will be too shallow and the amalgam is likely to be heavy in occlusion. Note: A Hollenback or Tharpe carver may also be used to define these grooves. Figure:Carving too deep resulting in thin amalgam margins that are brittle and can easily break. Next, very short strokes can be used to define the triangular grooves and deepen the fossae as follows. Rest the cleoid carver against the part of the marginal ridge next to the grooves, with the tip angles enough into the amalgam to trace and deepen the buccal triangular groove up to the pit. Then change directions at the pit, and trace and deepen the lingual triangular groove up to the pit. **Caution must be taken to avoid going submarginal at the cavosurface where the carved groove meets tooth. The key to the cleoid is that the pointed TIP should NOT touch the amalgam unless you are defining or deepening a groove. Sometimes, access into the mouth makes using the cleoid next to all cavosurfaces difficult, so there is another technique that can be used to remove lumps or bumps without obliterating the grooves. Use the discoid carver in repeating very short “sketching” strokes that begin on the tooth but end at the groove, and move very lightly onto the amalgam to remove lumps and smooth the ridges. If the amalgam is still quite soft, DO NOT CARVE FROM SOFT FILLING TO TOOTH which is likely to produce submarginal areas. Each light discoid stroke from tooth to amalgam must end at the grooves since if these strokes cross over the grooves the grooves will disappear. These short carving strokes should extend off of the tooth ridges and onto soft amalgam. ***If these strokes are used on amalgam that is still soft, or if any pressure is placed on the tooth while “sketching” these strokes, the amalgam at the cavosurface can easily be overcarved, leaving a submarginal area that requires enamel removal, or if severe enough, redoing the restoration. Figure: Short, overlapping discoid carving strokes used to smooth the amalgam: Each overlapping stroke follows the contour of the tooth very lightly onto the soft amalgam and stops at the grooves previously formed by the anatomical burnisher. Discoid strokes that can remove flash while smoothing the triangular ridges by directing the strokes at right angles to the cavosurfaces as long as the strokes STOP AT THE GROOVES, and are LIGHT ENOUGH so they do not produce submarginal areas (which is very easy to do on newly placed, soft amalgam). Evaluate the final restoration: Evaluate the four major criteria of this Class I amalgam restoration Anatomy Margins Occlusion Smoothness Occlusion- FOR THE PURPOSE OF THIS EXERCISE, during the anatomy course, WE WILL NOT BE EVALUATING OCCLUSION Anatomy: Class I restoration should be continuous with adjacent tooth structure. Fossae, cusp ridges, and major and supplemental grooves should be similar to those in the intact typdont tooth. Margins: margins for this Class I restoration should be flush (cannot be detected by the tip of a sharp explorer as it crisscrosses over the margin in any direction). That is, there are no open margins, no submarginal areas, and no flash. Smoothness: There must be no pits, voids or unnecessary ripples in the amalgam. Evaluation Criteria for Amalgam: Surface/Finish RATING CRITERIA for amalgam Surface of amalgam is uniformly smooth and free of scratches, pits, ripples, R-3 irregularities; no evidence of modifying, recontouring or removal of tooth [perfect or nearly perfect] structure Surface of amalgam is not uniformly smooth, slightly rough, lacking finish, S-2 exhibits some slight scratches, small pits or ripples. Correctable by polish. [slight problems but clinically acceptable] Evidence of removal of enamel gloss and slight scuffing of tooth structure T-1 Surface exhibits significant irregularities, scratches, pits. [decided problems; minimally clinically Difficult to correct with finish and polish. acceptable] Moderate tooth damage, loss of contour – not into dentin. Surface is severely pitted, rough, scratched, and has voids – inadequate V-0 condensation and improper manipulation of the amalgam; [gross failure; clinically unacceptable] Not correctable by finish and polish. Severe tooth damage into dentin.  FIRST: SURVEY THE SCENE TRITURATE AND CARRY OBSERVE THE TRANSFER AMAL CONFIGURATION BRISKLY “The clock OF THE is ticking” PREPARATION SMALL, OCCLUSION ?? MANAGEABLE NOTE DEPTH, INCREMENTS EXTENSIONS, MARGINS EFDA COURSE I 2 EFDA COURSE I 3 PACK INITIAL INCREMENT QUICKLY ADD ADDITIONAL INCREMENTS VERTICAL AND WORK QUICKLY HORIZONTAL WHEN PACKING MOTION INCREMENTS MUST SMALLER BECOME INSTRUMENT FIRST HOMOGENOUS HEAVY PRESSURE LARGER WITH FINGER INSTRUMENTS SUPPORT HEAVY PRESSURE EFDA COURSE I 4 EFDA COURSE I 5 OVERPACK INITIAL CARVE Overpacking brings Let tooth structure mercury-rich guide carver when amalgam to surface possible (which is then carved Wait for prime away) consistency Minimizing residual Not too deep 2mm mercury results in Margins most critical stronger amalgam EFDA COURSE I 6 EFDA COURSE I 7 FINISH CARVE & SMOOTH GOALS: – REPRODUCE ANATOMY – AMAL EXTENDS PRECISELY TO CAVOSURFACE MARGIN-NO OVERLAP OR UNDERLAP – OCCLUSION EFDA COURSE I 9