Dental amalgam 3-Reactions 1-Collection and different definitions phases 4-Failure 2-Composition Of dental B} manipulation Amalgam &types A} Cavity preparation

Definitions & collections

Amalgamis an alloy of mercury (no definite alloy)

Dental amalgam alloyan alloy of silver-tin alloy or silver copper - tin or silver-tin-copper-zinc or indium and may be other elements e.g. palladium , platinum or traces of gold

Definitions & collections

Dental amalgamis alloy of mercury , silver, copper, tin and other elements .

Amalgamation (trituration),it is a process of mixing of liquid mercury with one or more metals or alloys to form an amalgam mass .It may be manual or mechanical processing .

Composition of dental amalgam Dental amalgam means alloy of silver, tin, copper, zinc , may be indium and plus mercury.

MercuryIs the only metal which present in a liquid state must be triple distilled and pure mercury. Mercury have a tendency to form globules due to it's high surface tension have a high vapor pressure at room temperature, if inhaled , highly toxic for persons lead to paraesthesia , joints pain , loss of hearing and may be death.

Some alloys may be contain a 3% mercury and formed what is called pre-amalgamated alloys Such alloys has a slightly higher physical-mechanical properties and amalgamated more rapidly than the conventional one .

Alloys of dental amalgam contain zinc in excess of 0.01% , it called zinc containing amalgam alloys while that containing 0.01% or less it is consider alloys free of zinc ( zinc free amalgam alloys ) which is being used at areas where can not avoid contamination by oral fluids and gingival fluids and saliva

Silvermain component of the alloy about 63-72 % by weight , present in form of intermetallic compound with tin element form what is called gamma one ( y ) phase (Ag3Sn)

will lead to expansion of the set amalgam , increase the strength properties reduce the flow and creep and increase corrosion resistance of the set dental amalgam

Tin elementan important element as silver, about 26.8% by weight not more or less due to ??!!!!!!

If it is more than the savelevel, has a bad effect on the physical-mechanical properties ,

While less than save level, form (Beta ) phase which is solid solution of tin in silver i.e. free tin elements present instead of presence in form of y phase, more liable to unit with mercury and form a component that has a bad effect.

Tin has a great affinity to mercury so help in amalgamation process of alloy particles. tend to reduce strength properties of amalgam increase flow and creep and give contraction

Copperit's concentration is varying from 0 - 6 % in case of low copper amalgam alloys , while in case of high copper alloys it is 9 - 20 % or 13 - 33 % according to the type of the alloys

it's rule is increase the strength properties , reduce the creep and flow , give slight expansion but it is increase the tarnish and corrosion liability of the set amalgam fillings .

Zincit's concentration is 0 - 2 % act as scavenger for oxide films present on alloy particles during manufacturing. improve plasticity and workability of amalgam mass

has a great disadvantage, if there is contamination occur lead to formation of zinc oxide and hydrogen gases, lead to sever delayed expansions, sever tarnish and corrosion with sever pain and discomfort for patient and dentin hypersensitivity and extruded of filling from cavity .

Indiumcan replace zinc element in alloys concentration is about 0 - 5 % enhance mechanical properties increase tarnish & corrosion resistance .

Palladiumwhich is a noble metal added to alloy about 0 12% to increase the tarnish &corrosion resistance. increase the strength properties . reduce the flow and creep .

powder of alloy, manufacturedby either milling of cast ingot and produce lathe cut particles or fine cut particles or coarse cut one . Or by atomizing technique of liquid alloy by spray & aerosol it in a closed chamber containing gas under definite pressure, particles of molten alloy precipitate in form of spherical

Clinical information

The powder of dentalamalgam alloys may be supplied as a pellets or pills or it is supplied in ready mad capsules containing the powder and the mercury

Powder of lathe cut alloys or admix between lathe cut particles alloy plus spherical tend to resist condensation pressure better than dental amalgam made from entirely spherical particles alloy in which mass of amalgam escape under condensation pressure and not liable for condensed properly against cavity walls.

Dental amalgam made from

particles alloys has a good advantage over lathe cut that , it required a less amount of mercury percentage by weight for the proper amalgamated mass with better properties

On other hand , spherical

it's high compressive strength if it is properly manipulated. it's indestructibility in the oral fluids , have a good adaptation to the cavity walls and margins ,

posses a low thermal coefficient of expansion and not required sensitive techniques

it is dimensionally stable if it is properly manipulated from the first step of alloy / mercury ratio . capability to give &maintain a good polished , smooth and lustrous surfaces if properly manipulated

easy in it's manipulation cheap in relation to the other advanced materials .

it posses unharmonious color tendency for tarnish liability and tendency for discolored tooth structure by aging, So limit for restoration of posterior teeth where esthetic is not essential,

it posses a very low tensile, shear strengths. it posses a very low edge strength

liability to dimensionally unstable before and during it is being set and hard due to improper manipulation or subjected to contamination by water or sweat or saliva .

as it is metallic restorations, high thermal conductivity as the amalgam materials is vesicle-elastic , subjected to creep under the functional stresses

In case of the low copper alloys,Ag-Sn alloy particles begin dissolve into mercury , and at the same time mercury diffuses into alloy particle , react with (Ag) to form (Ag3Hg3 y1 phase) and with (Sn) to form (Sn8Hg y2) phase with remaining alloy particles of ( y )gamma which considered strongest phase of set amalgam.

AMALGAMATION AND RESULTING STRUCTURE

AMALGAMATION AND RESULTING STRUCTURE

In case of the low copper alloys, Ag3Sn (y) + Hg___Ag3Hg3 (y1) + Sn8Hg (y2) + unreacted (y) + My be free less mercury.

AMALGAMATION AND RESULTING STRUCTURE

(y1) phase act as a matrix which bind and collected and attracted the other phases of dental amalgam, while (y2) is the weakest phase and not preferable in the matrix .

In case of the admix alloy , -2/3 conventional lathe cut low copper alloy particles . -1/3 spherical eutectic silver-copper alloy particles . Percent of copper 9-22% by weight

When mercury react with alloy powder (y) + AgCu + Hg _______ (y1) +(y2) + (y) + AgCu (y2) Sn8Hg + AgCu______(y1)+ eta phase(Cu6Sn5) So there always breakdown of formed (y2) phase which is the weakest phase in the dental amalgam

Unicompositional alloy type there is one composition alloy particles not more, a tertiary one formed of silver, copper and tin total concentration of copper content about 13 - 33 % by weight .

When mercury react with the alloy (y) + (E) phase (Cu3Sn)+Hg __(y1) + eta phase (Cu6Sn5) + (y) and (E) (E) phase Cu3Sn is EPSILON phase

Dental amalgam alloys types and classification

I. According to Number of Alloyed Metals binary alloys (silver-tin) ternary alloys (silver-tin-copper) quaternary alloys (silver-tin-copper-indium).

II. According to Whether Powder Consists of Unmixed or Admixed Alloys one alloy. Others have more one alloy.

III. According to Shape of Powdered Particles The alloy particles may have a spherical shape. or irregular shapes ranging from spindles to shavings or Spheroidal.

IV. According to Powders Particle Size alloys may be macro-cut micro-cut, fine cut, coarse cut. etc.

V. According to Copper Content of Powder alloys with a copper content of 4-6% or less are called low copper alloys. Those containing more than 10% considered high-copper alloys.

In concentrations below 4% copper can be an admixture without adverse effect on alloy properties.

VI. According to Addition of Noble Metals such as palladium, gold, or platinum. palladium has proven to be the most effective noble metal addition to modern amalgam alloys.

According to present of zinc element or not 0.01% less or more

Whether alloy supplied as powder form or pellets or pills

It is pre-amalgamated with 3% of mercury or not

Generations of dental amalgam alloys

MANIPULATIVE CONSIDERATIONS OF DENTAL AMALGAMResponsible for 50% of F&S of final amalgam restorations

I

Preparation of operative field

&Respective tooth before insertion of amalgam

A proper manipulation of dental amalgam resulting restorations lasts an average 12 - 15 years . Manipulative characteristics are extremely important and a matter of personal preference .

Higher copper alloys systems are now material of choice due to improved physical properties.

MANIPULATIVE CONSIDERATIONS OF DENTAL AMALGAM

II

o alloy / mercury ratio &proportioning

oTriturating process & mixing

alloy / mercury ratio & proportioning

Recommended to use an mercury sufficient to coat all particles of alloy.

to achieve restorations with smooth , homogenous , coherent , plastic , shiny and lustrous mixes without any excess.

Hg Approximately, 50% wt , with lesser amount approximately 42% wt being used with spherical shape type alloys . Recommended ratio of alloy / mercury , varies for different alloy compositions, particle size, and shapes.

Recommended ratio for lathe cut, low copper alloy is 1 - 1 or 50 % wt mercury while with spherical and high copper alloys recommended amount of mercury is closure to about 42 % wt .

Keeping in mind that, too little amount of mercury impairs the physical and mechanical properties of the final dental amalgam restorations as an excessive quantity of mercury.

oTriturating process & mixing

Process of mixing between alloy and mercury and allow for the reaction to form a homogeneous, coherent, plastic, smooth, shiny and lustrous mass .

oTriturating process & mixingDuring trituration procedure, there is rubbing of oxide films covered alloy particles and allow for active surfaces to react with mercury .

PROCEDURES

Originally, alloy and mercury were triturated by manual procedure. Mechanical amalgamation using dental devices called amalgamator and amalgamizer.

Time required for

amalgamation of various alloys differs from one alloy to other . Usually spherical type alloys required less time than do the lathe cut alloys And on the other hand , the larger alloy amount required slightly longer mixing time than smaller one.

Keep in mind that avoid under triturating mix which is dull mix . not homogenous , not coherent , not smooth and there is free particles of alloy and free mercury .

Some authors reported that, it is advice to do proper trituration with slight over trituration which give a good strength properties with slight expansion .

A. The Original Gamma Phase Phases of dental (Ag3Sn). amalgamation B. The Gamma-1 Phase ( silver-mercury phase. or Ag2Hg3). C. The Gamma-2 Phase, tinmercury phase (Sn8Hg). D. The Mercury Phase, unreacted, residual mercury.

E. The Voids (Pores) Phase . F. The Trace Element Phases, in which copper and zinc might be found either separate phases or combined (alloying) With tin, silver or mercury. G. The Inter-phases

oMulling (milling) oExpression ofexcess mercury

Mulling (milling)

Done manually by slightly rubbing of mass in rubber finger to increase plasticity OR mechanically 3 seconds, NEVER do that against bare fingers to avoid contamination by sweat (source of water) .

Expression of excess mercury Used of a clean piece of gauze and do gentle squeezing for amalgamated mass after mulling procedure to eliminate excess mercury present . This step is recommended with manual trituration and when used amalgamators with loaded alloy and mercury .

While ready made capsules with alloy and mercury after amalgamation not need for expression of mercury due to has the exact proportioning

o Condensation& packing

A process of packing and condensation of amalgamated mass into prepared cavities piece by piece or increment by increment against cavity walls and margins, to increase density and way to remove or eliminate excess mercury if present .

For thorough amalgam condensation:

(1)- Only fresh mixes should be used, when mix is more than 3-5 minutes old, must be discarded. (2)-The restoration must be built from successive small increments.

(3)- Great condensation pressure is required and should be directed towards walls and margins of cavity to achieve better adaptation and more density. (4)- Condensation be done between rigid cavity walls, and if a wall is missing it is compensated with a rigid and strong matrix band .

(5)- A proper size and design condensers must be used. (6)-Condensation should be completed under clean and dry conditions.

Amalgam may be condensed by hand condensation technique or mechanically with equally good results.

Burnishing or Surfacinga large rounded burnisher is used in light strokes proceeding from amalgam surface to the tooth surface on occlusal and other portions of restoration.

This process has four objectives-:I. a continuation of

condensation, in that it will further reduce size and number of voids of amalgam. 2. It brings any excess mercury to the surface.

3. It will adapt amalgam further to cavosurface anatomy. 4. It conditions the surface amalgam to carving step.

If any defect in amalgam at the margins is discovered, addition of a fresh mix is indicated, provided the area has not been contaminated by moisture.

o Carving & shaping

oFinishing & polishing

Carving & shaping

Fast setting dental amalgam can be soon carved after condensation.

While slow setting dental amalgam can be carved after about 4 -7 minutes . Objective of carving is to stimulate anatomy and fine details

So clinically , at what time

can do carving , when there is tactile and hearing metal sound between sharp instrument and surface of amalgam . Carving must be done with sharp instruments.

Carving should be done in one direction from tooth surfaces to center of filling never vice versa , carving can be done any direction except from filling toward tooth surfaces and cavity walls and margins subother wise margins defects will resulted.

In case of compound cavities and using matrix band and retainer , the occlusal surface is first carved and established the occlusal anatomy. Do not leave any flashes beyond the cavo-surface margins . After occlusal surface is carved, dental matrix and wooden wedge is removed.

By using dental carvers and explorers , doing proximal contouring. Occlusion checked by using articulator papers and remove any premature contact areas , which also can be detected as a highly shiny areas within the dull amalgam surfaces .

patients were instructed not to use that side of mouth for at least 6 - 8 hours to avoid accidental fracture of amalgam restorations , also to come back at least after 24 hours to dental clinic to do finishing and polishing of restorations .

Wards

Frahms

Frahms

Wards

Finishing and Polishing

Finishing can be defined asprocess which continues the carving objectives,Removes flashes and overhangs and corrects minimal enamel discrepancies.

Polishing is the process whichremoving scratches and irregularities from the surface.

To creates a corrosion resistant layer

Objectives as important as

condensation, and continue objectives of carving. Amalgam flashes that was left behind after carving is removed.

major overhangs are removed. thus assuring continuity between tooth surface and amalgam surface.

conversion of superficial amalgam into a relatively inert layer galvanically. This minimizes electrolytic corrosion which is a normal phenomenon due to Complex, multiphasic nature of amalgam materials. removal of superficial scratches and irregularities.

Principles and procedures for finishing and polishing amalgam restorations Usually, 24 hours should pass after amalgam insertion. However, some newer alloys can be polished after 8-12 hours.

still others require only a 30-minute wait after insertion.

re-moval of gross overhangs and flashes using periodontal files and finishing burs.

Care should be taken not traumatize periodontuim.

removing Premature contact shiny areas in the amalgam.

polishing Removing superficial scratches and irregularities is done using descending grade abrasives. The combination of frictional heat and pressure with these materials achieves the desired results.

The final polishing obtaining a metallic luster, is always done with a polishing agent (e.g.. precipitated chalk, tin or zinc oxide) applied with a rubber cup.

One should bear in mind throughout these procedures that over-abrading can cause a loss of anatomy or contact or contour. Too much friction can produce overheating, which may endanger P-D organ as well as adversely affect mechanical properties of amalgam.

Wards

Frahms

Frahms

Wards

Objectives of restorations

o eliminate dental caries o avoid completely progressof dental caries .

o avoidance of recurrenceof dental caries.

o finally it is important toestablish functions and esthetic of restored tooth or teeth.

success and failure of any ~Degree of lesion restorative and failure WORK depend success selection of involvement. I- proper upon : of restorative restorative material . ~ Skillfulness of operator

FILLING II- proper cavity ~ Physical-mechanical MATERIALS preparation properties of material.

III- proper manipulation of material

Failures of amalgam restorations can be clinically manifested as marginal disintegration and breakdown . isthmus fracture . recurrence of caries . pulp affection .

discoloration . dislodgement of amalgam gingival & periodontal affections .

Isthmus fracture & or marginal Which is related to compound disintegrations: and complex cavities of amalgam fillings

Definition isthmus an imaginary area incompound or complex cavities connected two main parts of the restoration . Considered most weakened area subjected to fractured if not over-come and prevention during cavity preparation and manipulation of filling .

stresses Responsible for Tensile and shear stresses responsiblefactors of fracture at isthmus portion of fracture COMPOUND & complex CLASS I & II CAVITIES of amalgam restorations also compressive stresses ; if converted to undesirable tensile and shear stresses (UNFAVORABLE TORQUE FORCES) and this is can be done when there is improper cavity preparation and design .

stresses Responsible for fracture

The compressive strength of amalgam is about 45,000 - 72,000 Psi, while tensile is about 20 - 25 % of the compressive. So if applied forced is beyond tolerance capacity of amalgam restoration, fracture will happened.

o production of unfavorablestresses on surface area of amalgam filling; which due to presence of improper cavity preparation & improper manipulation of dental amalgam.

fracture result due to the following

fracture result due to the following o reduction of strength properties of dental amalgam; which commonly due to improper manipulation of dental amalgam ONLY .

So during cavity preparation @ during obtaining outline avoid the following to prevent form of compound or isthmus fracture complex class I & II . :IN GENERAL SPEAKING

prepare CAVITY WALLS AND MARGINS parallel torespective tooth surfaces

preparingocclusal surface PULPAL FLOOR parallel toat right angle to long axis of tooth, except at lower premolars, parallel to GINGIVAL WALL

Gingival wall also have enough width about 1.5 - 2mm varying from premolars and molars and flat, regular and at right angle to long axis of tooth, parallel to pulpal floor and occlusal surface of tooth .

AXIAL both pulpal floorat right WALL prepared angle to andgingival wall, parallel to long axis of tooth with slight slanting occlusally to give a great chance for bulky of amalgam at isthmus portion. But it is better to do axial wall parallel to long axis of tooth to avoid?

AXIO-PULPAL LINE ANGLE is being rounded or beveled or slightly slanted not sharp which lead to concentration of unfavorable forces during function at isthmus portion and fracture of dental amalgam

PRESENCE OF GINGIVAL WALL OR SEAT with enough width and proper direction itself is very important because of , in the absence, easily fractured of amalgam filling at isthmus area .

ISTHMUS AREA should be prepared with enough depth and width specially width to avoid pulp injury. As amalgam is over-come fracture at isthmus area when there is bulky restoration

ISTHMUS AREA

BUCCAL AND LINGUAL WALLS AT ISTHMUS should be running in a sweeping curve around buccal and lingual cusp plans of affected tooth and not across cusps themselves to AVOID.?

BUCCAL AND LINGUAL WALLS AT ISTHMUS must be meeting proximal surface of tooth at right angle (90*) to AVOID presence of? BY.?

@ during obtaining retention &

resistance form of class II cavity preparation, as amalgam have an inadequate tensile & shear strengths, each part of compound class II cavity should have it's own retention & resistance forms

@ @ during finishing of the

cavity walls and margins, through which they should be flat, regular, smooth and parallel to the respective tooth surfaces to avoid the production of unfavorable stresses upon amalgam surfaces during function.

What about manipulation of amalgam and relation TO (production) of unfavorable forces & (reduction) of strength properties of amalgam

1- alloy / mercury ratio , all particles of amalgam alloy should be covered by adequate amount of mercury without residue or excess because excess mercury or inadequate amount lead to amalgam mass with lowered strength properties.

2- trituration or amalgamation process should be done properly with final mass being homogenous plastic, shiny, luster, smooth and coherent mass to assure that the final amalgam restoration has a good strength properties

3- mulling and expression of excess mercury which deals with increase homogeneity and plasticity and increase density, remove voids, and any residual mercury removed, all of these conditions lead to amalgam with an adequate strength properties.

4- condensation @ doing of condensation within 5 minutes @ using suitable sizes and shapes of condensers and pressure @ Doing condensation within a complete dryness condition

@ Doing condensation of amalgam increment by increment @ Avoid the lamination between the condensed layers

@ Be sure that every condensed layer of amalgam is left shiny (no excess mercury) otherwise if dull lead to no cohesion occur between that layer and the next i.e. there is lamination. @ Doing over filling to assure that all cavity walls and margins are covered by filling

5- carving 1- by using sharp hand instruments not dull to avoid stimulation of floating of mercury . 2- Avoid excessive or over carving and removal of amalgam

3- Avoid leaving any premature contact areas or prematurely of high points which lead to excessive concentration of unfavorable forces on the surfaces of amalgam restoration

4- Avoid doing of deep fissures and angular grooves within restoration . 5- Doing amalgam carving after it has been partially set and clinically can be detected by hearing of metal sound by passing a sharp carver.

N.B During asking patient .for feeling about occlusion, do simply and gently not firmly without strokes

6- during finishing and polishing step Done carefully to avoid heat generation which stimulate mercury to leave amalgam body and come to surface accompanied by undesirable effect on strength properties of amalgam .

7- during removal of the matrix band should be done in a buccal or lingual direction never in occlusal one to avoid completely fracture of marginal ridges, impairing the contact areas and may be fracture occur at the isthmus area .

8- finally ask the patient never to use the side of amalgam filling at least for 8 hours until the amalgam mass had been completely set and hardened .

recurrence of caries .

The prevention of the recurrence of decay can be established by: proper selection of the restorative filling material Do not forget that there are several factors influencing this selection.

obtaining proper cavity preparation by following the general principles of cavity preparation. proper manipulation of restorative filling material .

HOW IMPROPER SELECTION AFFECTED RECURRENCE DECAY? There are numerous factors influencing the selection One related to the material choice itself in relation to ideal requirements. one related to tooth condition which restored. and lastly factor related to the operator.

factors related to patient

In case of bad oral hygiene and high caries index Also in case of acute rampant caries dentist should be know every thing about metallurgy, advantages and disadvantages and indication and followed the manufacturer's instruction

HOW IMPROPER CAVITY PREPARATION LEAD TO RECURRENCE OF DECAY. By following two important concepts Biological principle of avoidance recurrence of decay Mechanical principles

During obtaining proper outline form

remove all the carious dentin found specially that laterally spreading at dentino-enamel junction and toward lateral cavity walls all cavity walls and margins should be extended to the self cleansable areas if there is two separate cavities in one tooth

cavity walls and margins should be running in sweeping curve around the cusps

all pits and fissures and grooves should be included supplied the prepared cavity with suitable and right cavosurface angle.

all short and loose enamel prisms at the enamel walls should be removed remove all the undermined enamel

Improper application of all means of resistance and retention form, one of character of prepared cavity to amalgam filling that, each part of compound cavities must have it's own resistance and retention form

the presence of gingival seat is very important with other means of resistance &retention form, box shape , undercuts dove tails

Also do not carry cavity walls and margins to the stress bearing areas about 8-15kg load cycle are applied and the filling not apple to withstand without marginal disintegration and breakdown at the tooth / restoration interface and creation of recurrence of caries occur .

improper removal of remaining carious dentin the final floor of the cavity which performed just below the DEJ by about 0.5mm should be formed of sound and hard not discolored dentin

but sometimes in case of deep carious cavities, this dentin floor was carious and soft and discolored so what we do?.

do not forget that, controversy

may occur i.e. leaving of the residual caries lead to recurrence of decay under the filling material due to for any reason there is activation of microorganisms and the process of caries proceeding .

improper finishing of the enamel walls and marginsall detected under-mined enamel short or loose enamel rods or prisms must be removed specially at the stress bearing areas of the prepared cavity

prepared walls of cavity flat, regular and smooth, so attaining an excellent relation- ship of adhesion property at the restoration / tooth inter-face supplied cavity with proper and suitable cavo-surface angle

proper toilet and using the cavity cleaners specially before application of chemically adhesive filling materials clean cavity from any debris, saliva, blood or even smear layer of the smear unit to enhance an excellent adhesion between filling and tooth to reduce or diminish microleakage

In case of amalgam it is suitable to do cleaning of the cavity by jets of air and water and using probe to remove the chips if present then dry the cavity by gentle air jets and avoid desiccation of dentin.

SO DO NOT FORGET IMPORANT RULE OF GENERAL PRINCIPLES OF CAVITY PREPARTION TO DIMINISH OR REDUCE THE RECURRENCE OF DECAY .

THE RULE OF IMPROPER MANIPULATION OF THE FILLING MATERIAL FOR RECURRENCE OF CARIES : Specially during condensation, Carving, Finishing and polishing

see the knowledge about biological principles of cavity preparation as regard to the protection of pulp and dentino-pulpal organ .

biological influence of the restorative procedures on the dentino-pulpal organ

before packing and condensation of the restorative materials

It has been repeatedly warned that , poor restorations and restorative procedures have a high risk factor among causes of gingival and periodontal affections .

strongly related to operative procedures cavity preparation and manipulation of the restorative fillings

during the operative phase, should preserve and conserve the dentinopulpal organ faulty restorations

disharmony of the occlusion or traumatic occlusion .

So restorations that cause gingival & periodontal inflammation are: faulty and disharmony of occlusion . faulty inter-proximal embrasures or spill ways.

faulty inter-proximal contact areas either plus or minus faulty axial contours of the axial surfaces of the tooth .

presence of the gingival over-hanging or over extended margins of the restorations .

Do not forget that , class V restorations when poorly done act as a matrix for the accumulation of oral dental plaques and the result will be continuous and constant inflamed of gingival and periodontal tissues.

Post operatively, a bit-wing X - ray films taken to be sure that all work and procedures was done properly .

Also , a complete check up of the gingival sulcus or crevice for loose particles of amalgam or any other foreign bodies which can cause acute gingivitis and / or periodontitis