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Dental Materials 2
Dental Materials Test 2
| Question | Answer |
|---|---|
| where is dental amalgam popular to place on? | posterior teeth or areas that are difficult to isolate |
| what are amalgam alloy? | metals that are a combination of several elements, one of which is mercury (Hg) NOT EQUAL silver- tin (Ag-Sn) powdered metal BEFORE it is mixed with liquid mercury |
| what is dental amalgam | made by mixing approximately equal parts (by weight) of powdered metal alloy (amalgam alloy) and liquid mercury (Hg) the RESULT of mixing the powdered metal alloys with liquid mercury |
| elemental components of dental amalgam | silver and tin (predominately copper and zinc (small amount) Mercury |
| how do you form dental amalgam? | Silver, tin, copper and zinc + mercury in high speed shaking motion = chemical reaction to form dental amalgam |
| how long does it take dental amalgam to become hard? | 24 hours, it can be polished at this time |
| freshly mixed amalgam has a putty like consistency for.. | 4-5 minutes and is easy to manipulate |
| low copper or conventional amalgam composition | Ag: 68-70% Sn: 26-27% Cu: 4-5% |
| High copper or modern amalgam alloy composition | Ag: 40-70% Sn: 22-30% Cu: 13-30% |
| zinc containing dental amalgam has how much % zinc? | less than 2% zinc |
| zinc free dental amalgam has how much % zinc? | less than 0.01% zinc |
| why is silver put in dental amalgams? | causes setting expansion and increases strength and corrosion resistance |
| why is tin put in dental amalgams? | causes setting contraction and decreases strength and corrosion resistance |
| the expansion effects of the silver in the alloy offset... | the contraction effects of the tin balanced formula |
| why is zinc put in dental amalgam? | causes significant, long term and clinical unacceptable expansion of amalgam when it is contaminated with moisture longer clinical life expectancy than non zinc amalgam |
| low copper or tradition convention alloys produce... | weak Y2 phase and are most corrosion prone |
| high copper alloys produce amalgams with... | higher strength, less corrosion, better longevity at the margins eliminates weak Y2 phase which increases strength and decreases marginal breakdown |
| what are lathe cut type dental amalgam | irregular shaped particles |
| what are spherical type dental amalgam | spraying molten alloy into an inert gas |
| what are admixed type dental amalgam | dispersion type or blended alloy mixture of lathe cut and spherical |
| admixed alloys produced dental amalgam that is | grater packing/condensation forces during placement than amalgam with spherical particles alone |
| spherical amalgams produce dental amalgam that is | requires less mercury and set somewhat faster |
| proper mixing of dental amalgam is important because | so it does not contain voids and lack of appropriate contacts proper mixing and condensation will decrease porosity and void |
| what are the three phases of amalgamation? | first phase: gamma phase (Y) second phase: gamma-1 phase (Y1) third phase: gamma 2 phase (Y2) |
| what happens in first phase: gamma phase (Y) | silver alloy phase strongest and less corrosion |
| what happens in second phase: gamma 1 phase (Y1) | consisting of mercury reacting with silver strong corrosion resistant (not as much as gamma phase) |
| what happens in third phase: gamma 2 phase (Y2) | consisting of mercury reacting with tin weak and corrosion ready |
| what is not present in high copper amalgam? | no Sn-Hg (Y2) phase |
| what is not present after amalgam is set in restorations | no free (unreacted) mercury |
| when does mercury no longer have toxic properties? | mercury reacted with silver or tin |
| what happens if amalgam is heated beyond 80 C or 176 F | liquid mercury can form on the surface of the amalgam it's vapor can present a health hazard |
| amalgam is a thermal _____ | conductor |
| enamel and dentin are thermal ____ | insulators |
| dimension changes are affected by... | mercury/alloy ratio, trituration, condensation techniques |
| what is usually for dimension changes in amalgam | initial contraction followed by slight expansion |
| high copper amalgam has what in regards to dimensional changes | less initial shrinkage, more stable |
| what occurs only in zinc containing amalgams | excessive expansion, delayed expansion, |
| what causes excessive expansion in zinc containing amalgams | due to hydrogen gas produced by electrolytic reaction between zinc, saliva and other constituents metals in amalgam, gas release causes delayed amalgam expansion |
| what are the properties of strength in amalgams | high compressive strength, low tensile strength and shear strength |
| excessive contraction of amalgam leads to... | leads to leakage and post op sensitivity |
| excessive expansion of amalgam leads to... | post op sensitivity |
| what is the minimum bulk amalgam needs to withstand occlusal force | 1.5 mm, measured by bur 330 |
| lower creep values = | better deep resistance superior resistance to marginal fracture, better material |
| what amalgam has a higher strength 15 minutes after placement into the cavity? | spherical high copper amalgams |
| what does creep mean? | dimension change under loading deformation during chewing |
| what amalgam has the best creep value? | high copper amalgams have lower creep values than low copper amalgams and better resistance to marginal fracture |
| what amalgam has best resistance to marginal fracture? | high copper amalgams are superior to low copper amalgams |
| what can be added to amalgams to decrease tarnish? | palladium |
| what is tarnishing of amalgams? | oxidation that attacks surface of amalgam and extends slight below the surface, results from contact with oxygen, chloride and sulfide in the mouth |
| what is corrosion | same way iron rusts, occurs both on the surface and the interior of restoration degradation by electrochemical process which can result in bulk degradation and failure of restoration |
| surface corrosion can lead to... | discolored amalgam restoration and pitting |
| internal corrosion may lead to.. | marginal breakdown and fracture |
| what phase of amalgamation is most susceptible to corrosion? | Y2 |
| what can reduce the tendency for corrosion in amalgam? | careful finishing and polishing of amalgam restoration careful packing can resist |
| what is resistance to corrosion? | gold alloy is far superior than amalgams |
| what is galvanic corrosion | occurs when dissimilar metal restorations on adjacent teeth or opposing teeth come into contact in a wet environment electrical current flows between the two metals as saliva acts as electrolyte solution and oxidation (corrosion) of one of the metal |
| what are the symptoms of galvanic corrosion? | discomfort/pain by electrical stimulus metallic taste fracture of amalgam restoration |
| what are the best properties of amalgam when compared to composite? | strength, wear resistance, longevity |
| what are the best properties of composite when compared to amalgam? | esthetics, marginal seal |
| high ratio or more mercury yields what kind of amalgam? | wetter mix, decreased strength, decreased creep value, increased setting expansion and longer setting time |
| what does amalgam look like when it is excessively triturated | mix will have soupy, wet appearance, difficult to remove from the capsule, faster setting |
| insufficient trituration causes amalgam to be... | crumbly or dry, difficult to manipulate, reduction in strength |
| what does perfectly triturated amalgam look like? | rounded with smooth shiny surface |
| what is not used in dental settings for mercury composition chemistry | organic mercury compounds alky mercury salts (methyl mercury) |
| pharmaceutical uses for mercury | antibaterial agent, laxatives, diuretics, skin antiseptics, ointments |
| industrial uses for mercury | batteries, components of machines, reaction processes |
| what are the dental uses for mercury | amalgams |
| melting point of mercury boiling point of mercury | 38.9, liquid metal at room temperature 356.9 boiling point |
| what mercury is used in dental amalgam? | NOT organic inorganic mercury |
| what is the threshold value for workers in mercury industry? | 350 to 500 ug per day |
| what is the threshold limit value for national instate for occupational safety and health (NIOSH)? | 0.05 mg/m3 (in the air) for 8 hours per day 40 hours per week |
| who sets the limit value for mercury? | national institute for occupational safety and health (NIOSH) |
| what is an amalgam tattoo | amalgam particles embedded in oral tissue discoloration occurs |
| how can you clean up spilled mercury? | narrow bore tubing connected to a low volume aspirator to dental unit strips of adhesive tape sulfur powder for droplets that cannot be reached |
| what is an isthmus in dental structures? | facial lingual width between cusps, space between facial and lingual axial walls should be convergent in order to better hold amalgam restoration |
| what is a dovetail in dental structures? | mesial and distal margins should parallel the external tooth structure (marginal ridges helps lock amalgam into the preparation |
| what is a cavosurface margin in dental structures? | the edge of cavity preparation, where the preparation meets the uncut tooth surface |
| what is an isthmus in dental terminology? | Facial and lingual width (between cusps) space between facial and lingual axial walls should be convergent to hold amalgam restoration |
| what is a dovetail in dental terminology? | mesial and distal, should parallel the external tooth structure (marginal ridges) helps lock amalgam into the preparation should be divergent in inclination in order to avoid undermining medial distal marginal ridges |
| what should be convergent in dental terminology? | isthmus |
| what should be divergent in dental terminology? | dovetails |
| what is a cavosurface margin in dental terminology? | the edge of cavity preparation where the preparation meets the uncut tooth surface |
| what are GV Black's steps in cavity preparation? | establish outline form obtain resistance form and retention form obtain convenience form remove carious dentin finish the cavity wall cleanse the cavity |
| what mm should cavity prep be? | extends pulpally to a depth of 0.5 mm into dentin amalgam needs 1.5 mm depth to resist fracture |
| what is the rational for finishing and polishing amalgams? | remove tarnish, corrosion, smooths the amalgam, decreases plaque retention, removes excess amalgam, increases patient comfort, improves appearance, improves functional life |
| when should conventional low copper amalgam be polished? | 24 hours to finish and polish |
| what is tarnish? | surface discoloration caused primarily from the formation of sulfide |
| what is corrosion? | chemical deterioration of the metal which usually begins as tarnish |
| when should high copper amalgam be polished? | can be polished as early as 8 minutes most researchers say wait 30 minutes ONLY POLISH, do not finish |
| what are the indications for amalgam finishing and polishing? | areas of flash, indistinct anatomy broad contact areas, rough pitta amalgam, tarnished or corroded amalgams, high areas on the occlusal surface of the amalgam |
| what are the contraindications for amalgam finishing and polishing? | open margins of restoration, open contacts, fractured restorations, large overhang, recurrent decay, excessively deep occlusal anatomy, reiterations in teeth scheduled to be extracted or crowed |
| when do you identify amalgams you would like to polish for appointments? | during dental charting |
| what is the armamentarium for finishing amalgam restorations? | low speed contra-angle stones, finishing bur, sandpaper discs, finishing strips |
| what is the finishing green stone used to remove? | removes excess amalgam on the occlusal surface |
| what is the finishing white stone used to remove? | removes small areas of excess amalgam around the margins of restorations also removes tarnish and corrosion |
| what does the large round bur used to remove? | smooth margins of the amalgam |
| what does the large pear bur used to remove? | smooth margins of restoration and incline planes on occlusion |
| what is an optional step in finishing | using the finishing stones |
| what is the flame bur used to remove? | used to finish inter proximal area remove excess amalgam fish class V amalgam restorations |
| what type of bur do you use ONNLY on a class V amalgam? | Flame bur |
| what does the small round bur remove? | define anatomy, place and redefine grooves |
| what does the garnet sandpaper disc do? | remove excess amalgam from large restorations that extend towards the buccal or lingual portion of the tooth |
| what does the cuttle sandpaper disc do? | smooth the amalgam |
| what is the order of use for the sandpaper discs? | carnet first cuttle second |
| what is a finishing strip used for? | fine abrasive strips that are used to smooth the inter proximal area of the tooth one end has a course abrasive and the other end fine abrasive |
| what is the armamentarium for polishing amalgams | prophy angle, contra-angle, occlusal bristle brushes, rubber cup, dapper dish, pumice, tin oxide, who fu polishing points |
| what are the precautions during finishing and polishing amalgam restorations? | overheating causes mercury to rise and alter amalgam appearance and more susceptible to surface changes reduces the strength of amalgam, can cause irreversible damage to pulp, avoid cementum and soft tissue, take your time |
| what do you use to finish on the class II amalgam restoration in inter proximal area? | flame tip bur sandpaper disc finishing strip |
| what do you use to finish on the class II amalgam restoration in occlsual area? | large round or pear shaped bur flam bur small round bur |
| what do you use to finish on the class I amalgam restoration | large round or pear shaped bur flame bur small round bur |
| how do you assess finished amalgam? | margins are smooth and flush with enamel no open margins or open contacts anatomy is present |
| What is the first procedure for amalgam polishing | pumice + brush rinse tooth pumice + rubber cup rinse tooth |
| what is the second procedure for amalgam polishing? | tin oxide + brush rinse tooth tin oxide + rubber cup rinse tooth interproximal tin oxide and dental tape |
| why do you rinse between each abrasive | to get the abrasive off, do not want to make it scratchy again |
| what must you give your patient after you are done with finishing and polishing? | must give the patient a fluoride treatment after amalgam polishing is complete because you could have removed the enamel by accident |
| how do you polish an amalgam? | Course--> brownie sho fu, rinse, greenie sho fu, rinse, super greenie sho fu, rinse |
| what is bis acryl? | chemical structure that is intermediate between acrylic resin and dental composite resin which contains fillers |
| how do you place a temporary crown? | prep tooth, use pre formed crown or template to fill with acrylic resin temporary material, place over prep tooth and press down, trim off excess at margin when resin is partially set |
| what does temporary mean in dental materials? | reiterations that are planned to be replaced in a short time a week to a month |
| what does interim mean in dental materials? | restorations that are planned to be replaced in a longer period removable partial denture, flipper |
| what are the ideal requirements for temporary restorative materials? | high mechanical strength, chemical stability, reliable marginal integrity, easy handling and removal, aesthetics, average cost, low toxicity |
| what are the types of provisional restorations | temporary restorations, Zinc oxide eugenol cememnts, custom acrylics, customized preformed crown forms, resin composites, caivit |
| what are the benefits of adequate temporary protection? | maintain patient comfort minimize lateral or occlusal drift seal to prevent unnecessary exposure to oral fluids sedate the pulp, prevent gingival inflammation maintain esthetic appearance, temporarily restore function |
| what is the liquid of IRM | oil of cloves |
| what is the powder in IRM | zinc oxide |
| how do you create zinc oxide eugenol? | zinc oxide and oil of cloves mixed together |
| ZOE can be used in, has what properties and interacts with what? | interim filling or cement material, it has anesthetic and antibacterial properties but can interfere with composite resin polymerization |
| IRM has a mixing time of... | 1 minute |
| IRM has a working time of... | 4 minutes |
| IRM has a setting time of... | 8 minutes |
| What are the properties of ZOE? | small protected areas only (cavity prep) sedative action, anti-inflammatory, thermal insulator, water accelerates set still doughy mix |
| What is another name for IRM | reinforced ZOE |
| what are the steps for preparing class II cavity prep with IRM | isolation prepare Tofflemire matrix system follow manufacture's instructions placement and contour remove matrix band check proximal and gingival margins check occlusion and make occlusion adjustments |
| how do you mix IRM? | shake IRM powder bottle, place one scoop of powder and one scoop of liquid on mixing pad, incorporate half of the powder into the liquid and fold it using heavy force, add remainder of powder until homogenous mass- then shape into ball |
| what should you do if the IRM sticks to the condenser? | place instrument into the powder and reapply it to adequately condense the material into the cavity |
| what is the cotton pellet used for in IRM? | use damp cotton pellet to accelerate time and smooth surface of restoration |
| what is the definition of an overhang? | area of a restoration where material extends outward beyond the cavosurface margin of the cavity preparation |
| what is the definition of margination? | the process of removing excess restorative material in order to establish a smooth cavosurface margin, smooth restorative surface and re-contour functional tooth anatomy |
| what is type I size in margination | small overhang barely perceptible slight catch with the explorer in at least one section of the tooth less than 0.5 mm with explorer jump |
| what is type II size in margination | moderately large overhang definiate explorer jump involves more than one side of the restoration clearly visible on a radiograph less than 3 mm but greater than 0.5 mm explorer jump |
| what is a type III size in margination | large gross overhang clearly apparent by exploring clearly visible on radiograph can see it clinically greater than 3 mm explorer jump usually requires replacement |
| what are the causes of amalgam overhangs? | during placement of restoration- wedge or matrix band improper craving expansion of amalgam (unter trituration, moisture, amalgam creep) patient management- in accessible area of the mouth |
| what are the effects of overhang? | gingival inflammation bone loss increased bleeding upon probing, probing depths changes in microflora increased dental caries hinders plaque removal |
| what are the contraindications for margination | open of deficient margins around restoration recurrent caries open contacts fractures in restoration type III overhangs |
| how can we detect an overhang? | radiograph: bitewing/PA clinically, tactile (CONVEXITY) |
| what are knives used for in margination? | shave away slight to moderate excess amalgam and to reach tight contact areas |
| what are files used for in margination? | refinement of the cavosurface margin, removes bulk, start with moderate file and follow up with fine file |
| what are curets used for in margination? | remove small amalgam overhangs and to smooth the amalgam |
| what are discs used for in margination? | recontour bulbous or borad inter proximal contact areas |
| how do you evaluate your margination | margins flush with tooth contact with adjacent tooth is present reproduces contour of original tooth no damage to hard or soft tissue no debris is present, inter proximal area is smooth |
| how do you assemble a Tofflemire retainer? | turn larger nut until locking vise short distance from retainer hold large nut and move small nut until spindle free of slot burnish proximal area of the band using large football and beaver tail fold matrix band forming loop, gingival edge smaller) |
| how do you position a tofflemire retainer? | position band in retainer so that slotted side of the retainer is always directly gingivally, Tofflemire is placed in buccal vestibule smaller of the nuts is turned clockwise to tighten spindle against band place on tooth, larger nut is turned |
| how is the wedge placed in the mouth | base of the triangle is placed gingival and the apex occlusally |
| how do you remove the Tofflemire retainer? | loosen small end of knob, place thumb on top of band and pull retainer occlusally remove wedge, remove band from inter proximal areas |
| how should an Tofflemire retainer placed on an MOD be removed? | one inter proximal area at a time |
Created by:
Chobchi
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