7 - Class II Silver Amalgam Restorations: General Principles, Preparation Technique and Matrix Flashcards
what is defined as restorations that involve occlusal and interproximal surface of posterior teeth
Class II restoration
Class II carious lesions start [axial, gingival] to contact
gingival
what must decay break thru to require a restoration
must break thru DEJ
when to restore a class II lesion
- fractured restoration
- marginal integrity defective and cannot be remedied by polishing or enameloplasty
- overhang
- poor contour
- weak or nonexistant proximal contact
- lesion on opposite proximal surface from existing class II restoration and mesial lesion on tooth with exisitng DO restoration
occlusal outline form of Class II
- similar to Class I
- outline to converge under cusps and diverge in grooves and marginal ridges
proximal outline form of Class II
facial and lingual extensions determined by contact position w/ adjacent tooth
what contacts to break when creating Class II proximal box
facial, lingual, and gingival contact
in class II prep, ideally break proximal clearance by ___
0.5 mm - tine of tip of explorer
create ___ degree cavosurface margin in proximal box of Class II
90 degree
what is the resistance to fracture
resistance form
what is the apporpriate retention features to include proximal retension grooves and convergent proximal walls
retention form
an [acute, obtuse] cavosurface margin of enamel has potential for fracture
acute
a ___ degree enamel margin on occlusal surface will withstand occlusion
90 degree
the position of proximal facial and lingual extensions are dependent on what
the contact position
proximal caries is normally located ___
gingival to contact
T/F: in most teeth, caries will be facial to the facial-lingual midline in class II
TRUE
what must you do to the proximal surface to slightly undermine enamel and establish initial proximal and gingival extensions and in most cases create axial wall
trenching in pendulum swing motion
clearance between teeth in class II is what
tine of explorer - 0.5 mm
must see light or pink gingiva
the F-L dimension of the proximal box is greater at the ___ than the ___ to provide convergence/retention for the restoration
gingival seat; occlusal
from facial to lingual, should the axial wall follow the external contour of the tooth (convex)?
YES
from gingival axial line angle to axial pulpal line angle, the axial wall should lean where? why?
lean toward pulp
enamel is thicker closed to occlusal surface and thinner near gingival seat. therefore angle is obtuse
T/F: the axial pulpal line angle should be sharp
FALSE! should be rounded or beveled
what is a common cause of isthmus fracture of Class II amalgam
inadequate depth at isthmus area (e.g., pulpal floor)
T/F: axial-pulpal line must be beveled
TRUE!
sharp internal line angles that project into amalgam result in what
unfavorable force distribution resulting in amalgam fractures
what adds a little bulk to amalgam in area for strength
beveled axial-pulpal line angle
what parts of class II prep show retention
- occlusal walls under cusps converge
- proximal walls from gingival seat to occlusal
what aids in resistance form by decreasing effect of proximal box portion of silver amalgam torqueing away frmo occlusal portion during occlusal loading
proximal retention grooves
T/F: proximal retention grooves on clas II fade out as axial pulpal line angle is approached
TRUE
where are proximal retention grooves placed
1/2 mm inside DEJ
deeper at facial axial gingival and lingual axial gingival point angles and fade out occlusally
what determines size of proximal retention grooves in class II
distance between facial axial and lingual axial line angles
what must you do prior to starting class II prep
place wedge or guard
what makes room for working between teeth and creates better proximal contact w final restoration
wedge
when removing decay, do you move the entire affected wall to the depth of the lesion?
NO! remove tissue only in area of lesion. do not move entire affected wall or pulpal floor to depth of lesion
what is a more dangerous bur: 1 mm or 1/2 mm bur?
1/2 mm because it is smaller so easier to penetrate pulp
how to remove debris of instrumentation
washing with water
what is placed for saliva control and help maintain a clear surgical field
placement of rubber dam
do you place rubber dam before or after anesthesia is administered
after
what is used for hemorrhage control
- hemostatic agents
- epinephrine compounds
- matrix band and wedge
what part of class II prep is considered undermined or unsupported enamel
remaining hooks of enamel that form during preparation
what supplies the missing wall, gives something to condense against, and develops proximal contour of restoration
matrix system
what are the parts of tofflemire matrix system
- matrix retainer
- set screw
- rotating spindle
- slide
- head
- band
specifications of a matrix (6)
- easy to use
- convenient
- rigid
- versatile
- proper height
- can be contoured
matrix band is fitted into retainer so that the narrow/concave end of the loop is toward
gingival
the matrix band should imitate what
the shape of the tooth
what are the types of tofflemire retainer
- straight
- contra-angled
what side to place matrix retainer? exception?
- on buccal surface of tooth
- exception: if not buccal cusps for retainer to brace, switch to lingual
[outer, inner] nut holds matrix band to retainer
end/outter
matrix band tightened onto tooth by turning [inner/outer] nut
inner knurled screw/nut
where should the slots in the head of the matrix be directed
GINGIVALLY. NOT OCCLUSAL
primary function of a wedge
tooth separation - compensates for matrix band thickness to restore proximal contact
what adapts band against gingival seat
wedge
what provides gingival tissue retraction/protection
wedge
what aids in developing contour and minimize prep contamination by saliva and blood
wedge
how to make sure the band lies against the adjacent tooth
burnish the band using a condenser or ball burnisher. make sure the band is actually touching the next door tooth
how to remove tofflemire
- stabilize matrix band w/ finger to prevent SA fracture
- remove retainer leaving band and wedge in place
- while stabilizing band, remove wedge then carefully remove band
