Amalgam Repair Flashcards
What is the average survival for amalgam restorations?
11 to 12 years
Name 3 reasons amalgam is being phased out
- Composites are more aesthetic
- Composites have bonded techniques so are more conservative
- Minamata Convention on Mercury means reduction in environmental pollution
Describe EU regulations on amalgam as of July 2018
Restriction of amalgam use on children under 15, deciduous teeth and pregnant women unless deemed clinically necessary
Name 6 potential causes of failure of amalgam
- Recurrent caries
- Marginal ditching
- Excessive creep
- Bulk fracture
- Loss of retention
- Dependent on bucco-palatal width of amalgam
Describe 2 reasons amalgam stays in place
- Retention
2. Resistance
Describe retention in small amalgam restorations
Relies on undercuts in the tooth structure and frictional resistance from walls in preparation
Describe amalgam retention in large restorations
Additional retentive features created e.g undercuts, resulting in the destruction of sound tooth substance
Name 4 ways of providing retention for large amalgam restorations apart from undercuts
- Dentine pins
- Dentine slots
- Bonded amalgam
- Reconsider choice of restorative material
Describe dentine pins as a retentive feature of amalgam
- Self threading pins inserted into dentine floor of cavity
- 1-2 mm inserted into dentine with 2-4mm protruding above the cavity floor
- Amalgam packed around base of pins in small increments
- One cap per missing cusp
Describe the steps in placing a dentine pin
- Identify site for pin and drill locating hole with size 0.5 round bur in slow hand piece
- Identify correct size of pin
- Use matching twist drill to drill channel to full depth of drill in one movement
- Insert pin into prepared channel with speed reducing head
Name 5 disadvantages of dentine pins
- Induce high stress within tooth leading to crazing
- Very high temperatures generated on placement
- Risk of perforating pulp or ligament
- Insufficient occlusal clearance
- Special equipment required
Describe how dentine grooves, slots and pits are prepared
- Prepare slots 1mm deep, 2-4m long and 1mm wide in floor of cavity
- Avoid furcations and pulp horns
- Condense amalgam in small increments into slots
Describe 5 advantages of dentine slots, grooves and pits
- No special equipment required
- Less traumatic to pulp
- Dentine and enamel less stressed
- Reduced risk of perforating pulp
- Less risk of perforating PDL than pins
What is Nayyar core?
Amalgam core condensed 3-4mm into the coronal aspect of the root canals
What are bonded amalgams?
Technique which uses adhesive to bond amalgam to a cavity
Name 5 claimed advantages of bonded amalgams
- Decreased post op sensitivity
- Reduced microleakage
- Increased retention and margins
- Tooth reinforcement
- Decreased flexure of tooth tissue
What syndrome may bonded amalgam be particularly useful for?
Cracked cusp syndrome
Name 2 types of bonded amalgams available
- Panavia
2. Optiobond Solo
Describe the typical clinical steps when using bonded amalgams
- Isolate tooth with matrix band
- Etch all dentine and enamel of cavity
- Wash and lightly dry
- Apply adhesives (+/- light curing)
- Pack amalgam as usual and carve
Describe how bonded amalgams work
- Etching dentine opens up tubules enabling adhesive resin to flow into dentine
- Adhesive resin adheres to amalgam roughness micromechanically and 4-META adhesive
Describe a theory based on Brannstrom’s work as to why bonded amalgam can be used without a lining material without sensitivity
Brannstrom’s hydrodynamic theory of pain to get pain states fluid must flow within the tubules to stimulate odontoblasts, and as the resin blocks the tubules there is not response to hot or cold stimuli
Describe the clinical indications for bonded amalgam
- Not recommended for routine amalgam cavities (no evidence of benefit to balance increased cost)
- Useful for multi-surface amalgams to avoid use of pins
- Useful for amalgam repairs
Name 4 limitations of bonded amalgam
- Increased cost
- Technique sensitive
- Not in use long enough to permit adequate evaluation of performance
- Adhesion may break down over time
Describe 2 categories of composite alternatives to amalgam
- Direct Composite Restorations
2. Indirect Composite Restorations
