Clinical Application of Amalgam Flashcards
what is amalgam
“an alloy of mercury with another metal or metals”
Dentistry use silver amalgam (one of many)
3 direct restorative materials
- Amalgam
- Composite Resin
- Glass Ionomer & RMGI
4 indirect restorative materials
- Gold
- Other metals
- Ceramic
- Composite Resin - Ceromeric
2 possible indications for amalgam
- A direct restoration in moderate and large sized cavities in posterior teeth.
- Core build ups when the definitive restoration will be an indirect cast restoration such as a crown or bridge retainer
Amalgam is predominately on posterior teeth
amalgam contra-indications (4)
If aesthetics are paramount to patient
The patient has a history of sensitivity to mercury or other amalgam components
Where the loss of tooth substance is such that a retentive cavity cannot be produced
- Build up sub-structure, base material
Where excessive removal of sound tooth substance would be required to produce a retentive cavity.
10 advantages of amalgam
Durable
Good long term clinical
performance
Long lasting if placed under ideal conditions
- median survival 12 – 15 years (nothing beats, bar gold)
Long-term resistance to surface corrosion
Shorter placement time than composite
- Ultimately easier than composite, shorter placement time (1/4)
Corrosion products may seal the tooth restoration
Interface
Radiopaque
Colour Contrast
Economical
Less professional time
12 disadvantages of amalgam
Poor aesthetic qualities
Does not bond easily to tooth substance
Thermal diffusivity high (1.7cm2 /sec vs 0.0026cm2 /sec for dentine)
Cavity preparation may require destruction of sound tooth tissue
Marginal breakdown
Long-term corrosion at tooth restoration interface may result in “ditching” leading to replacement or repair
- Ditching around edges
- Water more likely to penetrate lead to secondary caries
Local sensitivity reactions
Lichenoid lesions
Galvanic response can occur
tooth discoloration
amalgam tattoo
concern about possible mercury toxicity
lichenoid lesions due to amalgam
Type IV hypersensitivity reaction
- Remove amalgam and replace with Gold or composite
galvanic response to amalgam
Battery effect from 2 different amalgams or more likely amalgam and a cast metal restoration
Complain tingling in mouth - rare
tooth discolouration due to amalgam
Corrosion products migrate into tooth surfaces which is porous (stain dentine) → Darkened tooth
When replace with tooth coloured restoration see a dark line where amalgam was previously
what is amalgam tattoo
Fine amalgam particles migrate into soft tissues
Differential diagnosis
- Biopsy, X-ray (seldom helpful)
Need to be sure it’s amalgam tattoo
- Been there for a long time
Suddenly appeared could be intra myeloma - rare
why has amalgam been in use for 100s of years (^)
Quick and Easy
Self-hardening at mouth temperature
Can be used in load-bearing areas of the mouth
Good bulk strength and wear resistance
Usually placed at one visit
Economical
- vs gold (historically)
- vs composite or indirect restorations (less professional time)
restoration sequence for amalgam
Caries risk, assessment and diagnosis
Likely material choice (in these examples: amalgam)
Informed consent
Caries access and removal
Cavity Design
Removal of deep caries
Cavity Toilet
Restoration placement
2 things to remember for cavity design for amalgam
retention form
resistance form
retention form in amalgam cavity design
Features that prevent the loss of the restoration in any direction
- Prevent the restoration being lost – straight up and down
In an occlusal direction significant undercut is not required, parallel or minimal undercut is all that is necessary.
- Caries is naturally wider in dentine than in enamel – so natural to have undercuts usually
resistance form in amalgam cavity design
Features that prevent loss of the material due to distortion or fracture by masticatory (occlusion) forces
- Bite on it – amalgam prone to move as not bonded to tooth
Ideally the cavity floor should be approximately parallel to the occlusal surface with sufficient depth of the cavity to give adequate mechanical strength (approx 1.5 – 2mm)
- Moves to dips in cavity floor
- Place lining in particularly deep parts of floor – don’t cut even
- Want smooth, so no deficit areas
The gingival floor of an interproximal box should be approximately 90o to the axial wall. If it is greater this→ a sloping inclined plane which makes the filling liable to slide out of the cavity.
- Need gingival box at 90 degrees so amalgam doesn’t slide/gradually creep out
should amalgam be used in pit and small fissure caries?
no
there is improved composite and glass ionomer with clinical evidence to suggest their use
can amalgam be used in moderate/large occlusal cavities?
yes, will last well
If caries involves most of the fissure system removal of the caries will result in a roughly parallel sided cavity of adequate depth for either composite or amalgam.
- May cut less tooth
silver amalgam is not first choice for occlusal caries generally
2 amalgam cavity design for interproximal caries
Self-retentive box preparation (minimal preparation box)
Proximo-occlusal preparation
amalgam interproximal cavity: self-retentive box preparation
Similar to composite
- Difference - inside edges taper out slightly (usually there from caries progression)
Don’t remove natural undercuts for composite
3 advantages of self-retentive box preparation
Less tooth tissue removed than with a proximo- occlusal preparation
Reduced amount of amalgam placed
Sound tooth tissue retained between proximal box and any occlusal cavity
2 disadvantages of self-retentive box preparation
Can be more technically demanding than proximo- occlusal preparation
Further treatment of any pit and fissure caries may be required
when should proximo-occlusal amalgam cavity preparation be used
- Not fall out
- Caries on occlusal dealt with
- But More tissue removed
3 advantages of proximo-occlusal amalgam cavity preparation
(Should be) Very retentive
Also treats any caries in pits and fissures
Less or no opportunity for future caries in pits and fissures
disadvantages proximo-occlusal amalgam cavity preparation
Destruction of tooth tissue for retention • Increased risk of weakening of the tooth
how to create additional mechanical retention for amalgam
Include grooves or dimples within the cavity design
Dentine Pin placement - titanium / stainless steel
- Pin use is controversial
- Used to increase retention in large non-retentive cavities.
dentine pins for mechanical retention
Can work well in large restorations and for cores beneath crowns.
Pins are self tapping screws
Place pin into dentine in the greatest bulk of the tooth.
- Place a hole with drill, smaller in diameter than pin, pin goes in half in half out, parallel to the long axis of the tooth
- Hard to place
Never in enamel or at the ADJ
- Fracture the enamel
Dentine can bend with screw
Avoid the pulp and periodontal ligament
Pack amalgam around the pin
old fashioned
initial problems with dentine pins
Stress in tooth around the pin.
Cracking of dentine,
Sensitivity of tooth due to temperature transference
long term problems with dentine pins
filling can leak but will not fall out because of the pin
→ secondary caries which can progress further into the tooth because of the pin
Caused by direct route from external silver amalgam into core of tooth
- May have a lining elsewhere but pathway at pin
never use pins with composite resins
adhesive technology for additional amalgam retention
Sealing (resin) + bonding restorations
- ScotchbondTM
- Prime&Bond®NT
Must be dual curing bonding agent
Bonding – Resin Cement e.g. PANAVIA®21 EX
Resin Modified GIC e.g. Vitrebond
Bond amalgam in
- Amalgam Bonds to dentine bonding agents with MDP
- Can pack in top of bonding agent
low strength 4-5MPa compared to 20MPa to enamel
Can use when wet
Ultimately no evidence for bonded amalgam survival over non-bonded
finishing of amalgam preparation
Ensure all caries is removed
Smooth and round internal line angles
Check and finish cavo-surface angles
Smooth cavity margins
5 concerns of moisture contamination in amalgam
Reduces Strength
Increases creep
Increases corrosion
Increases porosity
Critical but not as critical as in bonded composite restorations
- Can be used under water - cannot for composite
- Better to be dry - better strength, less creep, corrosion, less porosity
why do we need to seal dentine in amalgam
Because amalgam transmits temperature need to place a liner
ways to seal dentine for amalgam
- Cavity Varnishes
- Normally with RMGIC
- Can use DBA but this complicates the process
(Need to keep cavity dry – would composite be more appropriate?)
microleakage
Passage of fluid and bacteria in micro gaps (10 microns) between restoration and tooth
what 3 things can microleakage result in
- Pulpal irritation and infection
- Discolouration
- Secondary Caries
what can lead to microleakage
mechanical loading and thermal stress
Composite more dentine margins
Amalgam both dentine and enamel margins
how does micoleakage effect composite more than amalgam
Composite more dentine margins
Amalgam both dentine and enamel margins
3 roles of matrices
Recreate wall(s) of the cavity - Need to get smooth walls of restorations joining to tooth
Allows creation of proximal form and adequate condensation
- Pressure need to compact can cause filling of gap - impossible to clean
Confines amalgam to the cavity
4 properties of matrices
Should be < 0.05mm thick (better contact area)
Smooth and strong
Allow close adaptation especially at the cervical margin
Allow good contact with adjacent tooth
5 functions of wedges
Essential to produce adaptation of the matrix at the cervical margin, Buccal or lingual approach
Temporary tooth separation
Prevents excess amalgam gingivally
Aids proximal wall contour
Prevents movement of matrix band
(Wizard wedges, Anatomical wedges)
what does mixing time of amalgam effect (4)
Handling characteristics
Working time
Amalgam microstructure
Restoration longevity
what is condensation (with amalgam)
Vertical and lateral pressure needed (packing the amalgam)
very important
importance of good condensation of amalgam (4)
Expels excess mercury bringing it to the surface where it will be carved off
- Weakest form
Adapts material to cavity walls
Reduces layering (homogenous) - Sufficient force to avoid distinct layers between gunfulls – prevents voids
Eliminates voids
how to achieve optimal condensation (3)
Require correct size of instruments
- Easier to control initial increment with a large plugger (keep material in cavity) Smear into the cavity;
- Smaller plugger (if use initially will end up stuck to and removing from cavity); Overlapping axial strokes
Lateral as well as axial condensation
Spherical alloys require less force for condensation
inadequate amalgam condensation (4)
Lack of adaptation to cavity
- Spaces round the edge - food and plaque lead to secondary caries
Poor bonding between layers
- Weak due to voids
Inadequate mercury expression and consequently removal during carving
Inferior mechanical properties
where is the weakest form of amalgam
at the top, where it is expressed
what should you always do when placing amalgam
overfill the cavity
how do you remove the higher mercury content amalgam
carving
burnishing/finishing
use high volume aspiraion
carving amalgam
Recreate anatomical contour
- Marginal Ridge
- Inter-proximal contact areas
- Fissure Pattern
- Cusps and cuspal inclines
- Re-establishes occlusal contacts
finishing amalgam
Only if required to adjust anatomical contour after amalgam has set
- Amalgam finishing burs with water spray
Aspiration
Adverse effects of heat
Mercury risk?
Polishing considered unnecessary
- Free up mercury in material - greater risk.
- Head shakes - unpleasant procedure
corrosion
“detrimental change in the character of amalgam due to reactions in the mouth”
Associated with Gamma 2 phase (hardly any Gamma 2 phase amalgams on market most are Cu enriched) – but can be already placed in patient
corrosion in amalgam can cause
marginal breakdown with creep and ditching
how can corrosion of amalgam occur
Expansion of amalgam during corrosive process may assist in the development of a marginal seal
Most amalgam is now non-gamma 2, high copper, so less of a problem.
creep
“slow internal stressing and deformation of amalgam under stress”
Apply smaller force over a long period of time - material moves away
creep in amalgam
Copper incorporated to decrease creep
- Ag-Sn-Cu phase stronger (therefore less of an issue)
The greater the amount of creep the weaker the amalgam
Reduced creep should maintain marginal integrity
Correct cavo-surface angle is essential
why would you remove amalgam (3)
- Secondary caries
- Bulk fracture
- Removal of an amalgam core within an extracoronal restoration
how to remove amalgam
need: Dental dam, High volume aspiration
Minimal and selective cutting
- Don’t want to grind out like power
- Cut mesial to distal and then cross ways - bits will pop out as not bonded to tooth
Hand instruments
Operator and assistant protection
Easy to see that you have removed due to colour difference
when is the greatest amount of mercury released in dentistry
During Insertion
- Amount is proportional to the restorations` free surface area
During removal
- Vapour + particles
5 methods of mercury absorption
Vapour into lungs
Contact with skin
Gastro-intestinal tract
Gingiva and mucosa
Dentine and Pulp as metal ions (?)
how much mercury is absorbed from a filling?
Inorganic mercury vapour is released
- very slowly from an amalgam
- about 0.5 microgrammes/surface/day
490 amalgam surfaces would be required in a mouth to reach the exposure dose limit set by the WHO.
- Not possible to overcome safe dose in reality from dental care
Only about 15% of the mercury released is absorbed (0.08 microgrammes) from the lungs and GI tract.
Organic Mercury in food (tuna) is absorbed much more easily (About 90% of that ingested)
mercury hygiene
Usual protection for dental personel
Dental dam
High Volume aspiration
Amalgam traps – separators Spillage Kit (prevent Hg going into water system)
Correct disposal of waste amalgam Correct disposal of unused amalgam
where is 50% of mercury derived from
natural sources
- ocean evaporation
- geothermal activity
- rock erosion
in the USA 80% of mercury pollution is from burning fossil fuels for energy
<1% is from dentistry (small part)
mercury toxicity
Dental Amalgam can produce delayed hypersensitivity contact reactions on the skin and mucous membrane
Higher levels than found in dentistry can cause:
- Neuro-toxicity (mad hatter effect (used in top hats))
- Kidney dysfunction
- Reduced immunocompetence
- Effects on the oral and intestinal bacterial flora
- Effects on general health
- Foetal and birth effects
Can kill
how can dental amalgam effect human body
can produce delayed hypersensitivity contact reactions on the skin and mucous membrane
what is the Minamata convention of mercury
global treaty to protect human health and the environment from the adverse effects of mercury
- Governs use of all mercury containing products.
- Global treaty 128 countries signed up.
agreed in Geneva, Switzerland on Saturday, 19 January 2013 and adopted later that year on 10 October 2013 at a Diplomatic Conference held in Kumamoto (Minamata), Japan.
Ratified in June 2017
‘Regulation on Mercury’ is the EU plan for reducing mercury in the environment
what is the objective of the Minamata convention of mercury
to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds.
Trying to get rid of amalgam use
- Limit and phase out mercury use throughout world
implications of Minamata convention of mercury
15 Years Post Ratification (2032) There will be no mining for new Mercury
There will be no import or export of Mercury or Mercury containing compounds
what does the Minamata convention of mercury govern
Governs use of all mercury containing products.
- Known as Mercury-added products
After 2020 it will be illegal to manufacture or export any of these products:
• Batteries
• Switches
• Fluorescent lights
• Some cosmetics
• Antiseptics
• Barometers, thermometers, manometers etc. (can be replaced with LED)
Dental Amalgam is different it is subject to a phase down
Nowhere in the regulations does it suggest phase out
European Commission Regulation (EU) 2017/852 adopted when
May 2018
EU guidelines on Mercury use
what does Minamata convention mean for dentistry
Dental Amalgam is different it is subject to a phase down
Nowhere in the regulations does it suggest phase out
European Commission Regulation (EU) 2017/852 mean for dentistry in UK
Encapsulated Amalgam
- From January 2019
Already in use in the majority of practices in uk
Amalgam Separation
- Amalgam separation mandatory from 2021
- All amalgam separators installed from June 2017 must retain at least 95% of amalgam particles
- Part of practice inspection
All amalgam waste must be authorised waste management establishment
From July 2018 Silver amalgam should not be used in:
- Children under 15
- Pregnant Women
- Breastfeeding Women
Unless there is an appropriate reason for it’s use.
Essentially the decision to use the material will still be based on the dentist’s clinical judgement and the informed consent of the patient.
SDCEP guidelines June 2018 in regards to amalgam
Acknowledges that there is no justification on health grounds for not placing amalgam restorations.
o No reason for not placing
There is no justification for removal of sound amalgam restorations except in patients with a proven allergic reaction to constituents of the material.
o If sound no need to remove
limited itself to article 10(2)
From July 2018 Silver amalgam should not be used in:
- Children under 15
- Pregnant Women
- Breastfeeding Women
Unless there is an appropriate reason for it’s use.
Unless there is an appropriate reason for it’s use.
- Read “Unless there is a specific Dental Reason for it’s use.”
2 dental reasons for placing amalgam
- Lack of cooperation
- Inadequate moisture control
Dental reasons e.g.
14 year old MOD in upper 6 and cannot get dry as subgingival or cannot keep dam on long enough - use amalgam
It doesn’t matter how good you are at doing composite restorations. If it’s not dry, they don’t work
amalgam use in adult
As we stand there are no restrictions to the use of dental amalgam in the bulk of the adult population.
There is no prospect of a phase out of amalgam. There is a natural phase down happening.
In Scotland the main Phase down action is continuation of a preventative programme
- similar scheme in Ireland, England has nothing in place currently
Black Cavity Classification
Class I: Pit and fissure caries (occlusal)
Class II: Approximal caries (posterior teeth) (MO/DO)
Class III: Approximal caries (anterior teeth)
Class IV: Approximal caries involving incisal angle
Class V: Caries affecting cervical surfaces
Class VI: Caries affecting cusp tips (rare)
Arranged in how often they occur
Class I
Pit and fissure caries (occlusal)
Class II
Approximal caries (posterior teeth) (MO/DO)
Class III
Approximal caries (anterior teeth)
Class IV
Approximal caries involving incisal angle
Class V
Caries affecting cervical surfaces
Class VI
Caries affecting cusp tips (rare)
