Dental materials 3

Galvanism

When 2 dissimilar metals make contact in the mouth and an electric current is created

Mercury 5

A dense metal that is liquid at room temp Powder and mercury are sealed in to a disposable capsule A small cylinder called a pestle maybe added to facilitate mixing of the amalgam Pre capsulation reduces the risk that mercury vapor will contaminate the dental operatory Provides the proper ratio of alloy powder to mercury limits handling of pure mercury by the dental team produces amalgams was consistent physical properties and keeps the mercury clean

Dental amalgam 6

A mixture of sliver alloy with mercury Mercury is 50% or less Sometimes small amount of zinc (which acts as antioxidant) Can contain low amounts of copper (>7%) or high amounts of copper (10%-30%) to reduce corrosion The powder has either round of irregular particles A freshly mixed mass is plastic for several minutes and it can be package into cavity preparation and carved to the desired shape

Amalgam transfer 3

After trituration the amalgam must be transferred and condensed into the cavity prep The amalgam transferred from the mixing capsule to a mixing well using an amalgam carrier Generally two ends one smaller than the other

Condensation in an amalgam 8

Amalgam is pressed against cavity walls and floor in small increments To reduce voids Obtain maximum adaption to cavity prep To minimize mercury content Accomplished manually Hand condensers are far more common and come in a variety of shapes and sizes Selected in basis of type of amalgam the shape and size of the cavity prep and the stage of condensation The amalgam wall must be condensed using overlapping steps and lateral condensing to adapt to cavity walls

Safety for pt. 4

Amalgams has been used in dentistry for 175 years Ingestion of mercury from dental amalgam is less than from food water and atmosphere Allergic reactions to mercury are low less than .1% manifest as skin reaction Once mercury is mixed with the alloy little or no mercury remains on reacted because the Mercury is reacted mercury is unable to be released from the amalgam it no longer has a toxic property of unreactive mercury

Less failures with 2

Amalgams than any other restorative materials Strong durable cheap and easy to use

Coefficient of thermal expansion

An index which indicates how one material reacts to temperature extremes in relation to another

Action of silver alloy with mercury 9

Called amalgamation And lower copper amalgams the chemical reaction produced a tin mercury product called gamma-2 high copper amalgams have eliminated the gamma two product increasing resistance to corrosion and marginal breakdown The hardening of the amalgam occurs before all of the original alloy particles dissolve The set amalgam contains much of the original sliver alloy particles surrounded by new products In the set mass of most contemporary amalgams the original particles comprise more than 50% of the volume Once amalgamation is complete little or no Mercury remains unreacted Minute amounts of mercury vapor are released from dental amalgams as a result of chewing Higher releases may occur during the setting reaction during removal of old amalgams or if the amalgam is heated above 80 C

Heat from polish2

Can injure the pulp damage odontoblasts cause pain and release of mercury that results in a Dull cloudy appearance Excessive heat can also increase susceptibility to break down and corrosion

Amalgam corrosion 7

Chemical reaction that penetrate into the body of the amalgam Corrosion will eventually lead to failure of the restoration ⭐️ products of corrosion can fill the tooth/ amalgam interface and decrease mirco leakage resulting in minimal recurrent decay around amalgam margins Surface corrosion can lead to discoloration and pitting Internal corrosion can lead to weakened amalgam marginal breakdown and fracture - beyond clinical detection All oral contaminants such as blood saliva corrode metallic restorations

Class oration of caries (GV BLACK) 6

Class I- pits and fissures Class II- interproximals of posterior teeth Class III- interproximals of anterior teeth Class IV- interproximals and incisal edge of anterior teeth Class V- cervical, lingual, gingival 1/3 Class IV- cusp tips and or incisal edge

Manipulation of amalgam 2

Clinical success of an amalgam restoration depends on greatly on the appropriate manipulation of the amalgam during placement Divided into four steps: mixing, condensing, carving and finishing

Marginal irregularities under contoured

Deficiency of amalgam between the margin of the amalgam and the tooth (opposite of overhang)

Marginal irregularities: open Margin cause 2

Delay of condensation following trituration amalgams begins to set and is difficult to condense Amalgam inserted into the cavity prop at one time is too large

Contraction or shrinkage of amalgam 2

Dimensional change is negative if the amalgam contracts Can cause gross leakage around the amalgam

Marginal irregularities: open margin

Distinct space between wall amalgam and the wall of cavity prep

Amalgam carving 3

Done with a variety of hand instruments May start 2-3 min after mixing and should cease when amalgam becomes hard(5-10 min) Carving after an amalgam is set may cause fracture of the amalgam

Properties of amalgam: desirable features 3

Durable and strong Compressive strength is similar to enamel Relatively inexpensive

Adequate force

During condensation adapts amalgam to the prepared cavity increases strength and decreases creep, reduces voids works Mercury to surface of restoration

Dental amalgam alloy3

Fine powder composed of sliver tin and copper (40%-70%) Sliver is a bad metal subsceptibe to corrosion Sliver alloy portion is predominantly sliver and Tin

Safety precautions for handing mercury

Follow ADA recommendations

Marginal irregularities: ditch or groove

Gap on occlusal surface where either flash broke off or contraction of the amalgam caused the restoration to pull away from the tooth

Finishing and polishing 2

Generally are preformed at least 24 hours after placement If spherical high copper amalgam is used polishing may be done at the time of placement

Properties of amalgam: undesirable features 5

High thermal conductivity Dimensionally creep unstable Requires tooth support Fracturable by excessive force Delayed expansion if contaminated by saliva

Toxic mercury 5

Highly toxic to kidneys and central nervous system It is slowly illuminated from the body so even if the daily exposure is small it can build up in the body faster than it is eliminated An eyedropper size amount of mercury contains enough mercury to saturate air in a typical operatory Mercury vapor has no color Oder or taste and poses the most significant danger because of the lungs absorb the vapor Proper precautions should be taken to limit exposure to the patient and dental team

Triturate

Mix

Transfer and condensation must occur2

Immediately after mixing and before amalgam sets The cavity prep is generally over packed and carved back to final contours

The amalgam surface2

Is contoured until they are smooth (congruous) with the tooth Produce correct anatomy (sculpt amalgam)

Alloy

Mixture of 2 or more metals

What to avoid during condensation 3

Moisture before and during If saliva contamination occurs delayed excessive expansion of amalgam could result especially if Zinc is present in the alloy Also could result in corrosion loss of strength voids and premature failure

Amalgam strength9

Needs proper enamel support to withstand forces of mastication Must be high enough to resist forces placed in mouth Insufficient strength may result in bulk it marginal fracture Both tensile and compressive forces occur in the mouth If amalgam is subjected to chewing before sufficient strength them fracture or crack Avoid chewing for 8 hours Develops over 24 hrs Not good condensation results in voids which weaken the set mass Mixing for too long or too short weakens the final strength

Marginal irregularities: flash cause 2

Occlusal class results from improper carving Proximal flash can result from improperly placed wedge or from not using a wedge at all

Marginal irregularities: overhang4

Over contour Excess amalgam Creates a plaque trap and hinders plaque removal inflammation Over hangs are detected with an explorer

Sliver alloys for amalgams 2

Particles can be a regular or spherical it a mixture of the two A mixture of particles is called an admixed amalgam

Mircoleakage/percolation

Passage of oral fluids/ bacteria into and out of tooth structure due to a marginal gap or failure of the marginal seal

Where are amalgams limited to? Why?5

Posterior teeth Grey color More esthetic porcelain or composite restorations also are common for posterior restorations Turned his have problems such as expense shorter longtivity or difficult placement Amalgams are retained by undercuts and the roughness of cavity prep

Mercury mask2

Pre capsulated amalgam Use high volume excuse ion during placement and removal of amalgam restorations

Marginal irregularities: over hand cause 2

Proximal overhangs usually result from improper placement of the matrix band and wedge They can also be caused from errors in manipulation carving and or finishing

Marginal irregularities under contour cause 2

Proximal surfaces improper placement of matrix band or wedge of both Occlusal surfaces incorrect carving

Tarnish and corrosion...

Rate can be reduced by careful polishing and finishing of amalgam

Amalgamation

Reaction of the sliver alloy with the Mercury

Final amalgam finishing 2

Removal of marginal irregularities to produce margins are continuous with the adjoining tooth structure and contours Smooth roughness of amalgam

Margination

Removal of over hangs

Marination 4

Removal of overhangs Note if the overhang in large the restoration should probably be removed and replaced Manuel instruments: amalgam knife, files, finishing stripes, scales Power driven instruments

Admixed amalgam

Require greater condensation forces

Spherical amalgam

Require less Mercury and set somewhat faster

For class II, III, IV (interproximals)

Restorations where the cavity prep is not completely surrounded by the tooth a matrix band is used as a wall to pack restorative material against The matrix band is held in place with a retainer ⭐️most common is the tofflemire retainer An interproximal wedge angular shaped wooden of plastic stick is inserted between the teeth after placement of the matrix band braces matrix band tightly against

Shear force

Sliding the top of an object over the bottom parts are forced to slide against each other

Dental amalgam copper 4

Sliver alloys used for dental amalgam had low amounts of copper High copper alloys produce amalgams with higher strength, less corrosion, less creep, better marginal integrity, and better longevity at the margins Require less Mercury Today's high copper amalgams are also essentially free of zinc

Amalgam creep4

Slow change or deformity in the shape from compression Resulting in the restoration protruding from the cavity prep marginal deterioration fracture at the restorative margins or distortion Repeated chewing forces cause creep Associated with breakdown of marginal integrity

Creep

Slow dimensional change by compression

Over Triturate 2

Soupy and may adhere to the inside of the capsule Poor strength and creep and may have poorer corrosion properties

A polishing agent 2

Such as fine pumice or Silux or rubber abrasive points is used to smooth the alloy surface A high luster on the surface is created with a very fine abrasive paste or rubber abrasive point

Amalgam tarnish 4

Surface phenomenon Chemical reaction between the amalgam and oral cavity is restricted to the amalgam Removable surface discoloration Does not affect the internal integrity of the restoration

Improperly handled Mercury 2

System absorption through the skin Inhalation of mercury vapor and airborne particles

Tensile and compressive strength in amalgams 2

Tensile strength and shear are low (stronger in composites) Compressive strength is high

Dimensional change in amalgams 3

The contraction or expansion of amalgam In general most amalgams expand and contract slightly during setting Most modem amalgams exhibit slight contraction at the end of 24 hours

Comprehensive force strength

The force at which a material breaks under pressure

Tensile force/strength

The force exerted to stretch material to the point of fracture

Final amalgam polishing 8

The surface is smooth to a high luster To reduce the likelihood of biofilm retention corrosion tarnish Use a sequence of her braces from coarse to finest Final polish in mouth with 10 oxide Polishing amalgams increases the longevity of the restorations Polish and a wet field to reduce heat Except for fast setting high copper Amalgams that can be polished 8-12 min after placement, 24 hours should pass before final polishing an amalgam AVOID CONTACT AREAS WITH ANY ABRASIVE

Marginal irregularities: flash2

Thin layer of amalgam that extends over the margin of the cavity prep Flash can break off and produce irregular margins

Limiting exposure to mercury 5

Toxic Mercury may gain access through skin on contact through ingestion or through the lungs as a vapor Is never touched even with gloves hands A masher be worn to decrease exposure to particulate amalgam Scrap should be stored in containers with x-ray x fixer caped tightly and kept cool

Mixing the amalgam 3

Trituration is accomplished mechanically with an amalgamator Agitate the capsule containing the sliver alloy and the Mercury at a high speed Use of pre capsulation amalgam is mandatory

Expansion in amalgams 3

exert pressure on the pulp can cause sensitivity Cause protrusion of restoration from the cavity Chase fracture of surrounding tooth structure

Under trituration 2

under triturated has a dull crumbly look Will have poor compressive and tensile strength