Lecture midterm Flashcards
two cavities should not be combined unless the separating ridge is less than
0.5mm
when can you extend into the oblique ridge of 1st maxillary molars
if its undermined by caries
isthmus width should not exceed ____ intercuspal distance
1/3
what depth into dentin should a cavity prep be
0.2-0.5mm
why do we prep cavities with converging buccal and lingual walls?
follows direction of enamel rods
how much of the marginal ridge should be conserved
1.6mm
prevents dislodgment of the restoration by lifting or tipping
retention form
increased surface area helps to increase friction for what cavity prep feature
retention form
opposing walls slightly converging is what type of prep feature
retention form
sufficient access to the cavity is what type of prep feature
convenience form
why is convince form import for visibility
removal of all decay
needs for access to the prep for instruments
convenience form
important prep feature to achieve the best marginal seal
finishing
removing jagged edges or rough outline is what type of prep feature
finishing
the final step before the prep receives restorative material
Debridement
rising the cavity with air/water spray and high suction
Debridement
removes smear layer from cavity prep
Debridement
dental shavings on cavity preparation
smear layer
remove moister (blood & saliva) from prep
Debridement
the junction between the external walls of the cavity preparation and the uncut tooth structure
cavosurface margin
the shape of the cavity preparation
outline form
what are the three factors that govern outline form
conservation of tooth structure
location & extend of caries
position of pits & fissures
unnecessary loss of healthy tooth structure
extension for prevention
preservation of remaining tooth structure- minimal extension
conservative approach
removal of carious area and any weak enamel
outline form
Helps the restoration to withstand the forces directed towards the long axis of the tooth
resistance form
primary resistance features
removal or undermine enamel flat floor adequate depth well defined line angles type of restorative material
cavosurface margin should not terminate on unsupported enamel
resistance form
minimum amalgam thickness to withstand forces
1.5mm
what makes the amalgam margin angle & smoothness so important
low edge strength
taper of a 330 bur
8 degrees
tapper of a 245 bur
4 degrees
what shape burs are 229-330
pear
length of 330 bur
1.5mm
length of 245 bur
3.0mm
diameter of 330
0.8mm
diameter of 245
0.8mm
not efficient at cutting ductile material (dentin)
abrasives / Diamond
recommend for intracoronal preparations
bladed cutting
force applied perpendicular to cutting edge
direct cutting
force applies parallel to the cutting edge
indirect cutting
can do lateral and direct cutting
enamel hatchet
cutting edge makes an angle to the long axis of the blade
marginal trimmer
what is a lesion caused by mechanical factors
none carious lesion
what rotary instrument runs at 12,000 - 20,000 rpms
Medium speed
type of bur that is used for extracoronal preps
diamond
In OSU’s lab do we use negative or positive rake angle burs?
negative
These burs are efficient at cutting but get clogged and break easily
Postive rake angle
Bur cuts by shearing layers of tooth structure
Bladed
Bur cuts by removing a mono layer
Diamond
The hard but brittle material that is used to make bladed burs
tungsten carbide
A bigger ____ angle created less friction on the tooth
clearance
Not for cutting just refining the cavity prep
Hand instruments
In hand instruments creates balance and directs the forces onto the cutting angle
contra angle
why don’t we use mono angle instruments in the mouth
forces out of balance
Rotary instrument that turns at a rate below 12,000 rpms
slow speed
Rotary instrument that turns at a rate above 20,000 rpms
high sleep
Besides cavity preps what is another use for the high speed instrument
removing old restorations
why is the neck of the bur constricted
visibility
A large number of blades on a bur give the prep a. . . .
smooth finish
dental Material is place in a soft state and contoured before it sets
Direct restoartion
Restoration is fabricated outside of the oral cavity then cemented or bonded to the tooth
indirect restoration
The clearance face is in front of the axis line (of the bur)
postive
how many surfaces does a compound cavity prep involve
2
how many surfaces does a complex cavity prep involve
3
what is a class 1 prep?
Pits and fissures
what angle should the cavosurface margin be?
90 degree
Cariesclassification: occlusal surface of premolars and molars; buccal or lingual pits/ fissures of the molars; lingual pit near cingulum of maxillary incisors
Class I
Caries classification: Proximal surface (mesial and/ or distal) of premolars and molars
Class II
Caries classification: Proximal surface (mesial and/ or distal) of incisors and canines
Class III
Caries classification: Proximal surface of incisors and canines but also the incisal edge
Class IV
Caries classification: Gingival third of the facial or lingual surface on any tooth
Class V
Caries classification: involve the inciscal edges of anteriors or cusp tips of posteriors
Class VI
cutting motion from beveled to non beveled edge of a hand instrument
Lateral / indirect cutting
Cavity prep principle: smooth pulpal and gingival floor provides
resistance form
Removing undermined enamel from the cavity preparation provides
resistance form
Ideal isthmus width is ______ of the intercupsal distance
1/4 - 1/3
Ceramics are
brittle
ceramic mimic what part of the tooth
enamel
gold is
ductile
Gold mimic what part of the tooth
dentin
Dentin provides ____ that helps to adjust to condensing
elasticity
why do we drill 0.05mm into dentin
elastic recoil
The dove tail feature is
retentive
Minimum isolation for a rubber dam is ____ posteriorly and _____ anteriorly
1, 2
All line angles of a class V prep are
divergent facially
The prongs of a clamp on the rubber have to be touching _____ line angles
all four
The tip of the hole back should be placed in ___ during carving
central groove
Is done because the softest phase of amalgam stays on top
overfilling
what needs to be done with the top layer of over filled amalgam
carved away
Why is the top phase of the amalgam filling softer
mercury rich
What need to be done if the amalgam filling has an open margin
redone
What need to be done if the amalgam filling is submarginal
enameloplasty
Are open margins sealed?
No
Are submerging sealed
just shy (.2)
Has to be removed from the filling with a finishing bur
flash
Admix - blend of lathe cut and spherical particles
Permite C
When the membrane of the amalgam capsule is ruptured what happened
mercury in contact with alloy
Process by which mercury is allowed to react with the alloy powder
Trituration
Trituration
Amalgamation
How long should the amalgamator be set
7/8 seconds
Amalgam that is soupy, difficult to remove
Over Trituration
Excess matrix is formed in
Over Trituration
Soft shiny, warm
proper mix
Amalgam that is grainy, is dull and crumbles
Undertrituration
under triturated amalgam has
reduced strength
under triturated amalgam is
hard to handle
Amalgam that has optimal properties
proper Trituration
The process of compressing the allot into the tooth preparation and eliminating voids
condensation
Force / area =
pressure
A shiny rich mercury phase viable and you’ll head a crunch
adequate condensing
From the center to periphery
condensing
Which end of the condenser should be used as you approach the external surface of the tooth
large
In what time frame (for permite C) should condensing be completed?
3-4 minutes
Should the last increment of amalgam extend over the preparation?
yes (1mm)
How should amalgam be added to the cavity preparation
in increments
using the round face of the condenser either perpendicular to the long axis or axis at 45 degrees
vertical strokes
using the side of the condenser either parallel to the long axis of at 45 degrees
lateral storkes
Type of stroke used solely in class I preps with extensions or in proximal boxes
lateral / horizontal strokes
over filling is done to extract ____ from the preparation
mercury
over filling helps to
seal the margins
What can form if condensing goes beyond 3-4 minutes
cracks in matrix
used between condensing and final carving
anatomical burnisher
Carving instruments should always be resting
partially on tooth structure
Used to define the developmental grooves
push stroke
High gentle pressure moving the carver parallel to the margins
pull stroke
Motion from tooth structure to amalgam
push stroke
Carving is done of two planes for this prep
Class V
What are the two planes of carving for the Class V prep
gingival and occlusion
Over-contoured cusps, shallow central groove, shallow fusses and high occlusal contract are a result of
under carving
Deep central groove, steep triangular ridges, deep marginal fossas are result of
over carving
Break between tooth and the amalgam restoration / not continuous
open margin
The seal between the alarm and the enamel is not broken (<0.2mm)
submarginal
if the gap is marginal > 0.2mm
restoration needs replaced
When the patient bites down this will be broken easily
flash
If the tip of the explore catches from tooth to amalgam and not from amalgam to tooth structure at the margins
flash
Marginal voids due to inadequate condensation
open margins
How do you fix open margins
re do
Tip of the explorer catches when moved in both directions across the margin
open margin
Tip of the explorer catches when moved form amalgam to tooth but not from tooth to amalgam at the margin
submarginal
Serves to substitute to conventional polishing, can help to improve marginal integrity
post carve burnishing
A moist cotton tip applicator to clean the surface from minute scrap and debris
Cleaning surface
Should occlusion be checked before after removal of rubber dam
after
Ideal occlusion mark are on the _____ cusps and the _____
functional, marginal ridge areas
Clinically gingival clearance for a proximal box
0.5mm
In typodonts the proximal contacts are more
occlusal
In a class V prep the wall that runs parallel to the root axis is the
axial wall
the diameter of the 1/4 round is
0.5mm
The distance from the external surface to the axial wall
axial depth
Axial depth on the crown of a Class V prep
1.0 -1.25mm
Axial depth on the root of a Class V prep
0.75mm
What is the primary mechanical retention of a class V prep
there is none
Because there is no primary mechanical retention of a class V prep we add
retention grooves
The incised, gingival, mesial and distal walls of a class V prep are all
divergent
What is the retention groove call
auxiliary/ secondary retention
