Lecture 12 Flashcards
Indications for Class II lesions?
Occlusal and proximal contacts, existing restorations
How to achieve tight contacts:
pre-wedge or ring, also promotes more conservative preparation
How to achieve ideal proximal wall contours:
anatomical sectional matrices
Why not to use a matrix band with resin composite:
it creates a flat proximal surface and can’t hold the matrix band in close adaptation to the adjacent tooth.
How to achieve intimate gingival margin seal:
good wedging or flowable composite
How to get matrix band in contact with adjacent tooth:
burnish the matrix
What to be cautious of when burnishing the matrix?
not to scratch the matrix band, use a round contoured instrument
True or False? Single placement of wedge is most effective.
F. Multiple wedging is better (reapplying seating pressure several times throughout procedure.
Beyond the initial damage why is the destruction of adjacent tooth structure so detrimental?
more likely the damaged surface will require subsequent restoration
Alternate method to protect proximal surfaces:
Interguard (Ultradent), FenderWedge (Garris Dental Solutions) for simultaneous preweding and protection of the adjacent tooth
Instrument for protecting proximal surfaces during preparation:
special diamond preparation tip, diamond abrasive only on one side of tip, sonic handpieces that fit dental unit couple or piezoelectric ultrasonic unit used for SRP
True or False? Pulp temperature increases more with ultrasonic preparation than with water-cooled rotary preparation.
F. Not greater than
How does sonic preparation adversely affect adhesion compared to rotary handpiece preparation with a carbide bur?
It does not
Methods to remove proximal wall in a Class II preparation:
safe-side diamond tip or spoon excavator to fracture and remove thinned enamel (fine-ri diamonds or carbide finishing burs for bevels)
When is a bevel not necessary on the F or L, proximal surface of a Class II preparation?
When preparation exits the external tooth surface at an obtuse angle
Benefit of bevel when using adhesive agent and resin composites:
more area for acid etching and bonding
Functional purpose of beveling in general:
to expose enamel rods transversely, more effective etching pattern.
True or False? Etching of longitudinal cut enamel rods will result in the most effective bond.
F. Transversely exposed rods (beveled Class III)
How do enamel rods exit tooth surfaces?
approximately right angles to external tooth surface
Why must an obtuse angle be formed in Class II preparation on proximal surface?
to expose ends of enamel rods
On which surface margins of the proximal box should bevels be placed?
F and L cavosurface margins (makes margins more accessible for finishing and polishing and reduces marginal leakage)
If the preparation exits tooth at an obtuse angle, should a bevel be placed?
no
When not to bevel:
within 1.0 1.5mm of CEJ (or apical to CEJ) or not an adequate band of enamel remaining
What type of enamel is found near the CEJ?
prismless
Why not to bevel near CEJ:
thinner enamel, beveling increases the potential for removing the little enamel that remains, acid etching of prismless enamel is ofter less effective
At what distance from the CEJ is adhesion no better than bonding to dentin?
within 1 mm of CEJ
Inverse or internal bevel:
leaving enamel that is not supported by dentin at the gingival cavosurface margin
When should enamel with no supporting dentin NOT be removed in preparation?
Class 2, at the gingival cavosurface margin
Why is leaving unsupported enamel indicated for Class 2 preparations at gingival cavosurface margins?
reduces microleakages compared to butt margin, better than making a margin on or near the CEJ
How does an inverse bevel help with adhesion?
exposes enamel rods for etching on their internal ends, better adhesion to the gingival margin
On which surface is a bevel not indicated?
occlusal, normal preparation: end-cut rods because of the orinetation of the enamel rods in cusp inclines
Benefits of not beveling on occlusal surface:
conserve tooth, decreases the surface area of the restoration, lessens the chance of occlusal contact on the restoration, eliminates thin area of resin composites that would be more susceptible to feature ad wear, and well-demarcated marginal periphery to which resin composites can be finished more precisely
Survivability of posterior resin composite restorations is the directly related to:
the proportion of the occlusal surface restored (increased be beveling)
Placing a glass ionomer, RMGI, or bonded composite under unsupported enamel will make the above enamel as strong as it was when supported by dentin.
F. weaker
What are cavity liners composed of?
calcium hydroxide
When to use cavity liner:
very close to pulp and if there is a possibility of a minute plural exposure
When to use cavity liner over extensive area of dentin:
DO NOT. provides no benefit both e pulp and decreases the surface area of dentin available for adhesion, dissolution of the liner during acid etching can interfere with a sound bond to enamel and dentin
When is a glass-ionomer liner indicated?
deeper preparation, gingival margin approaches or extends beyond the CEJ
Mechanical advantage to glass-ionomer liner:
bond to both tooth structure and overlying resin composites AND introduces less polymerization stress into tooth structure than resin composite
Long-term advantage of glass-ionomer liner for posterior restoration:
fewer secondary caries, release fluoride into adjacent tooth structure
