Restorative Skills Flashcards
why are cavities restored ?
to restore integrity, function and aesthetics
what do extensive amalgam restorations involve ?
rebuilding cusps, provide auxiliary retention
how do EAR’s compare to cast restorations ?
EAR’s are less invasive, expensive and time consuming
what is retention form ?
the features of the cavity that prevent withdrawal of the restoration in the long axis of the preparation
what is resistance form ?
the features preventing dislodgement of the restoration under all other forms of loading
what is auxiliary retention ?
supplementary retention required for extensive restorations
how is auxiliary retention achieved ?
cavity design features, pins, adhesives
how is additional resistance form achieved in EAR’s ?
boxes, axial grooves, slots, pits
what should the dimensions of slots and pits be in EAR’s ?
depth no greater than 1mm, width slightly greater than diameter of instrument used
what are the 3 types of pins used in EAR’s ?
cemented pins, friction grip pins, self threading pins (most retentive)
when should a pin be used in an EAR?
1 pin for each missing cusp, line angle and proximal surface
specifically where should pins be placed ?
1-2 mm inside DEJ
2mm into dentine
2mm into amalgam
2mm from opposing tooth (upper/lower)
what are the disadvantages of using pins in EAR’s ?
weaken tooth structure and the restoration
possible fracture of tooth structure
internal stresses
incorrectly placed pins can perforate the pulp or periodontal tissues
pins too close to pulp will cause post op sensitivity
which adhesives can be used to retain EAR’s?
4META (amalgambond)
MDP (panavia)
what are the advantages of using adhesives to retain EAR’s ?
increase retention
conserve sound tooth structure
in which 2 ways can restorations fail ?
new disease - secondary/recurrent caries
technical failure
what are the disadvantages of replacing defective EAR’s?
inadvertent removal of tooth structure,
increased cavity size,
risk of damage to pulp,
development of clinical symptoms
why is to often better to repair EAR’s rather than replace them ?
conservative, quicker, cheaper, LA may not be required
which bur is used to prepare a class III cavity ?
520 round bur
what are the advantages of bevelling enamel margins in class III cavities ?
provides larger surface area for bonding,
reduces micro-leakage,
cross cuts prisms and gives better etch pattern,
blends composite onto surrounding tooth surface
what are the disadvantages of bevelling enamel margins in class III cavities ?
damage to adjacent tooth,
lacerate gingivae,
increase in subsequent cavity size
what are the clinical recommendations for bevelling enamel margins in class III cavities ?
if labial margin of cavity is visible
when is a class IV restoration indicated ?
trauma resulting in fracture of the crown, progress of a class III to involve the mesial edge
what angle do incisors fracture across the crown after trauma ?
45 degrees
what are the problems following trauma ?
root fracture may have occurred,
adjacent and opposing teeth may also have been fractured
how should the labial margin of a class IV be prepared ?
a D and Z bur is used to create a scalloped bevelled margin 1mm in width
where do class V cavities develop ?
cervical third of all tooth types
why may a class V restoration be required ?
caries due to poor plaque control,
abrasion due to inappropriate tooth brushing methods,
abfracture - occlusal stresses concentrate at the thin enamel near the enamel cementum junction causing fracture of the brittle enamel
what should be used to prepare the class V cavity before filling and why ?
oil and glycerine free prophylaxis paste to optimise the bonding of the filling material,
paste should also be free of fluoride as this may adversely affect bonding of the filling material
what is in a compomer ?
aluminosilicate glass and acid polymerisable resin
what is the resin in a compomer ?
tetra carboxylic acid butane polymerised by hydroxyethyl methacrylate
what can improve the bond strength of compomer to enamel ?
non rinse conditioner (NRC),
phosphoric acid etchant
what is NRC?
mixture of maleic and polyacrylic acids
how should enamel and dentine be prepared for compomer bonding ?
etched using total etch technique and bonding resin applied
what increments should compomer be cured in ?
3mm
what happens once the finished compomer restoration absorbs water ?
the glass ionomer reaction proceeds via the ionised pendant groups of carboxylic, these will react with the filler particles of alumina silicate glass
this allows some ionic interchange with the tooth surface for bonding and also release fluoride
what are the indications for a porcelain crown ?
heavily restored tooth, trauma resulting in fracture, hereditary and acquired hypoplasia, tooth wear, alter size and shape of tooth, in combination with bridges and partial dentures, improve appearance of anterior teeth
what are the alternative treatments to porcelain crowns ?
bleaching discoloured teeth,
restore with tooth coloured filling materials,
veneers
what bur should be used for the incisal reduction in a porcelain crown ?
554
how much incisal reduction should be created for a porcelain crown ?
1-2mm
which bur should be used for the labial reduction in a porcelain crown ?
5013
what is the depth of the labial reduction on a porcelain crown ?
1mm
which bur is used for the axial reduction in a porcelain crown ?
5013
what should the diverging angle of the sides of the porcelain crown prep be ?
3-6 degrees
what is the finish line for a porcelain crown ?
1mm shoulder
which bur should be used to complete the palatal reduction for a porcelain crown ?
5013 bur
which bur is used to complete the cingulum reduction for the porcelain crown ?
285 rugby ball bur
what is the difference between a temporary and provisional crown ?
temporary crown - short term while permanent crown made
provisional crown - lasts for longer period while other assessment of teeth carried out
what are the requirements of temporary restorations?
biological,
mechanical,
aesthetic
what are the biological requirements of a temporary crown ?
protect prepared dentine,
prevent gingiva overgrowing prep margins,
prevent over eruption or tilting of prepared tooth
what are the indications for PFM crowns ?
heavily restored tooth,
porcelain crown repeatedly fractures,
occlusion is unfavourable - deep overbite and minimal overjet,
in conjunction with bridge or partial denture construction
what is the reduction of the functional cusp for a PFM?
1.5mm
what is the reduction of the non functional cusp for a PFM ?
1mm
which bur is used to complete the occlusal reduction for a PFM ?
554
what is the buccal finish line for a PFM ?
1.3 mm shoulder
what is the palatal/lingual finish line for a PFM?
champher
which bur is used to complete the chamfer ?
877K
what are the advantages of the wingless PFM design ?
easier to prepare,
less chance of leaving undercut
what are the disadvantages of the wingless PFM design ?
less resistance form,
not as conservative of tooth structure
how many mm clearance should dentine pins be placed from the edge of the tooth?
3mm
how much dentine should surround the pin ?
1mm
what thickness of dentine is required for pin placement ?
2.5mm
Describe the international caries detection and assessment system
0 sound tooth surface 1 first visual change in dry enamel 2 distinct visual Change I wet enamel 3 localised enamel breakdown 4 underlying dark shadow from dentine 5 district cavity with visible dentine 6 extensive distinct cavity
Describe the criteria for scoring bite wing radiolucencies
C0 no radiolucencies
C1 radiolucency evident in outer half of enamel
C2 radiolucency evident in inner half of enamel
C3 radiolucency extends beyond adj
C4 radiolucency evident within outer third of dentine
C5 radiolucency extends to inner third of dentine, may reach pulp
When is pulpal extirpation indicated ?
Alleviation of pain of pulpitis or acute peri apical periodontitis and stabilise tooth in short term
When is indirect pulp cappings or stepwise technique indicated ?
Where likelihood of pulpal exposure eg 3/4 of dentine thickness demineralised
Why are restorations polished ?
Improve marginal integrity and longevity
Less destruction to opposing dentition,
Minimise plaque and gingival irritation,
Eliminate overhangs
Increased reflective and refractive index
What is the order of polishability of composites ?
Least Microhybrids, Nanohybrids, nanofills Microfills Most
What do high speed abrasives produce ?
Quick abrasion,
High heat,
Little wear of abrasive,
Smooth surface
What do low speed abrasives produce ?
Slower abrasive action,
Less heat,
Wear of abrasive particles,
Deeper scratches
What are the types of dental abrasives ?
Emery, Garnet, Pumice, Keiselguhr, Carbides, Diamond, Sand
What does polishing produce ?
Smooth reflective surface,
Beilby layer,
Surface flow
What are the types of polishing agents ?
Whiting, Rouge, Tripoli, Tin oxide, Chromium oxide
What is burnishing ?
Smoothing by rubbing metal against metal
