Clinical Amalgam Flashcards
what are the direct restorative materials
amalgam, composite resin, glass ionomer and RMGI
what are the indirect restorative materials
gold, other metals, ceramic
what are the contra-indications for amalgam
aesthetics, sensitivity to mercury, loss of tooth substance does not allow for retentive cavity, excessive removal of tooth substance would be required
what are the indications for amalgam use
direct restoration in moderate and large sized cavities in posterior teeth
what are the advantages of amalgam
durable, good long-term clinical performance, long lasting, resistance to surface corrosion, shorter placement time, radiopaque, economical
what are the disadvantages of amalgam?
poor aesthetic qualities, does not bond easily to tooth substance, thermal diffusivity, cavity preparation requires destruction of sound tissue, marginal breakdown, local sensitivity, lichenoid lesions, galvanic response, tooth discolouration, amalgam tattoo, mercury toxicity
what is the retention form of the cavity design
features that prevent the loss of the restoration in any direction
what is the resistance form of the cavity design?
features that prevent the loss of the material due to distortion or fracture by masticatory forces
how is a resistance form made?
cavity floor parallel to occlusal surface with sufficient depth of the cavity to give adequate mechanical strength
in what type of cavity would amalgam be acceptable for?
moderate to large occlusal cavities
what are the cavity designs for interproximal caries
self-retentive box preparation, proximo-occlusal preparation
what is a self-retentive box preparation
small undercuts made on buccal and lingual walls
what are the advantages of self-retentive box preparations
less tooth tissue removed, reduced amount of amalgam, sound tissue retained between proximal box and occlusal cavity
what are the disadvantages of self-retentive box preparation
more technically demanding than proximo-occlusal preparation, further treatment of any pit and fissure caries may be required
what is a proximo-occlusal preparation
take out the fissure as well as interproximal caries
what are the advantages of proximo-occlusal preparation
retentive, also treats pit and fissure caries, less or no opportunities for future caries in pits and fissures
what are the disadvantages of proximo-occlusal preparation
destruction of tooth tissue, increased risk of weakening the tooth
what sort of initial retention factors can you include?
grooves or dimples within cavity design, pin placement
how do you place a retentive pin?
self-tapping screws, place into dentine, avoid pulp enamel and ADJ, pack amalgam around pin
what are the initial problems with pins?
stress in tooth, cracking dentine, sensitivity of tooth due to temperature transference
what are the long-term problems with pins?
filling can leak but will not fall out due to pin so secondary caries caused which can go deeper into tooth
how do you finish an amalgam cavity?
ensure all caries is removed, smooth and round internal line angles, check and finish cavo-surface angles, smooth cavity margins
what is the effect of moisture contamination
reduces strength, increases creep, increases corrosion, increases porosity, critical but not as bad as composite restorations
what do you seal dentine with?
cavity varnishes, RMGIC, use DBA sometimes
what is microleakage
passage of fluid and bacteria in micro gaps between restoration and tooth
what does microleakage cause?
pulpal irritation, discolouration, secondary caries
how can microleakage occur?
due to mechanical loading and thermal stresses
what is the purpose of a matrix?
recreate cavity walls, allows creation of proximal form, allows adequate condensation, confines amalgam to the cavity, should be less than 0.5mm thick, smooth and strong, allow close adaption at cervical margin, allow good contact with adjacent tooth
what do wedges do?
produce adaptation of matrix at cervical margin, prevents excess amalgam gingivally, aids proximal wall contour, prevents movement of matrix band
what does mixing time affect?
handling characteristics, working time, amalgam microstructure, restoration longevity
what does condensation do?
expels excess mercury bringing it to the surface, adapts material to cavity walls, reduces layering, eliminates voids
what does using a large plugger allow?
controlling initial increment
what does inadequate condensation do?
lack of adaption to cavity, poor bonding between layers, inadequate mercury expression and removal, inferior mechanical properties
how do you remove mercury from surface amalgam
carving, burnishing, using high volume aspiration
what does carving do?
recreates anatomical contour
what does finishing do?
adjust anatomical contour after amalgam set
what can corrosion cause?
marginal breakdown with creep and ditching
what is creep?
slow internal stressing and deformation of amalgam under stress
which type of alloys do not exhibit as much creeo?
high copper
what do you need to remove amalgam restorations
dental dam, high volume aspiration, minimal cutting, selective cutting, hand instruments
when is the greatest amount of mercury released?
during insertion and removal of amalgam restorations
during insertions what is the amount of amalgam proportional to?
the restorations free surface area
where can mercury absorption occur?
vapour into lungs, contact with skin, GI tract, gingiva and mucosa
what can mercury toxicity cause?
neuro-toxicity, kidney dysfunction, reduced immunocompetence, effect on oral and intestinal bacterial flora, effects on general health, foetal and birth effects
what does the Minimata convention aim to do?
phase down dental amalgam
what is the consequence of the Minimata convention
aim for prevention, minimise amalgam use, promote mercury-free alternatives, promote research of mercury-free materials, encourage education of mercury-free alternatives, discouraging insurance policies favouring amalgam, encourage insurance policies favouring amalgam alternatives, only encapsulated amalgam, promote good environmental practices
which groups of people should amalgam not be used on?
children under 15, pregnant women, breastfeeding women
what is the SDCEP guidance regarding amalgam use?
no justification for removal of sound amalgam restorations except in patients with allergies
what are the main limitations for alternative amalgam placement
lack of cooperation, inadequate moisture control
what is Class 1 Caries?
pit and fissure
what is Class 2 Caries?
approximal caries for posterior teeth
what is Class 3 caries?
approximal caries for anterior teeth
what is Class IV caries?
approximal caries involving incisal angle
what is Class V caries?
cervical surfaces
what is class VI caries?
affecting cusp tips
