Operative Final Flashcards
what is the goal of restorative dentistry?
carefully remove the diseased tissue (cavity) in a precise manner and replace the missing part with a restorative material (restoration)
where do cavities occur?
the disease occurs most frequently in specific locations
occlusal pits and fissures of posterior teeth
interproximal areas- between teeth below contact area
smooth surfaces of facial and lingual surface
what is class 1 cavity?
Found in pits and fissures of: occlusal surfaces of premolars and molars; buccal or lingual pits of the molars; lingual pit near the cingulum of the maxillary incisors.
what is class 2 cavity?
Found on the proximal (mesial and distal) surfaces of premolars and molars.
what is class 3 cavity?
Found on the proximal (mesial and distal) surfaces of incisors and canines.
what is class 4 cavity?
Found on the proximal surfaces of incisors and canines, but also will involve the incisal edge.
what is class 5 cavity?
Found on gingival third (the area near the gingiva) of the facial or lingual surfaces of any tooth.
what are the instruments used to modify tooth structure?
powered cutting equipment and hand cutting instruments
what are powered cutting equipments?
rotary (routinely used since 60s)
laser (recent FDA approval for preparing teeth
air abrasion
what is a rotary powered cutting equipment?
handpiece
what is a handpiece?
device for holding rotating instruments, transmitting power to them, and for positioning them intraorally
- straight
- angle
what are the properties of a high speed handpiece?
> 200,000 rpms (high pitch sound)
air driven turbines
most efficient at removing tooth structure
sprays water coolant to avoid tooth damage (heat)
type of angled handpiece
what are the properties of a slow speed handpiece?
rotates <12000 rpms less efficient, more controlled removal used to refine preparation, -controlled caries removal -finishing and polishing causes vibration (patient discomfort) can be used as an angled or straight air or electric driven
what are the properties of intermediate speed handpiece?
>12000 and <200000 rpms we use 20000 rpm motor similar characteristics to slow speed air or electric powered water or no water coolant
what are the rotary cutting instruments?
dental burs (carbide burs)
diamond burs
other abrasive instruments like dental stones
fit into rotary equipment (handpieces)
what are burs?
all rotating cutting instruments that have bladed cutting heads
burs are made of carbide steel- carbide is stiff, strong and brittle
used for finishing metal restorations, surgical removal of bone and tooth preparation
what are the common features of burs?
head, neck and shank
what is the head of a bur?
the working part of the instrument
consist of either bladed or abrasive cutting surfaces
comes in many shapes and sizes
what are the 5 bur head shapes?
round, inverted cone, straight fissure, tapered fissure, pear
what is the standard carbides?
6 fluted- cut into the tooth more
what are the finishing carbides?
10, 12, 20, 30 fluted
more flutes smoother finish
what is the shank of the bur?
fits in the hand piece
controls the alignment and concentricity
3 shank design
what are the 3 shank designs?
friction grip used in both high and low speed angled- 1.59mm wide, 12.7mm long
latch type used in low speed angled only- 2.35mm wide, 13.2mm long
and straight used in low speed straight- 2.35mm wide, 31.7mm long
what is the neck of the bur?
connects the head to the shank
tapered to give better visibility
what are diamond abrasive instruments?
diamond points or abrasive
various shapes like burs
more abrasive than carbide
line angle
2 walls intersect
point angle
3 walls intersect
what are the internal walls?
axial - parallel to long axis of the tooth
and pulpal- perpendicular to the long axis of the tooth and occlusal of the pulp
what are the external walls?
prepared surface that extends to the external tooth surface
facial, lingual, mesial, distal, gingival
laser equipment
produces beams of coherent and very high intensity light
currently units are expensive and used mainly for soft tissue procedures (such as cutting and coagulation and gingivectomies) or hard tissue surface modification
generally not used for tooth preparations due to high amounts of heat generated, and inefficiency at removing large amounts of tooth structure
special safety precautions required when using a laser
air abrasion unit
used for removal of superficial enamel defects or stains, debriding pits and fissures for sealent placement, roughening of surfaces (enamel, metal or porcelain) to be bonded or luted
cannot produce well-defined preparation wall and margin details that can be achieved by conventional rotary cutting techniques
how does air abrasion unit work?
by transfer of kinetic energy from a stream of powder particles onto tooth structure or restoration, producing a fractured surface layer, which results in roughness for bonding or disruption for cutting
is roughening a surface with air abrasion is a substitute for acid etching technique?
no
what is a round bur?
spherical, used for initial penetration into the tooth, caries removal, retentive groove and holes
what is an inverted cone bur?
shape of a tapered cone, with the apex toward the bur shank; particularly suited to provide undercut in a preparation
what is a straight fissure bur?
elongated cylinder
what is a tapered fissure bur?
slightly tapered come, with apex directed away from the bur shank, used to prepare teeth for indirection restoration (inlays, crowns) which require some taper in tooth preparation
what is a pear shaped bur?
similar to inverted cone in that it is easy to produce undercuts in preparations, but has rounded ends and longer head; can be used for amalgam tooth preparations
what is the rake face?
side of the blade towards which the bur is cutting
what is the clearance face?
side of the blade away from which the bur is cutting
what is the rake angle?
angle between the rake face and the radius of the head diameter, most important design characteristic of a bur blade, when cutting hard brittle materials, a negative rake angle minimizes fractures of the cutting edge, increasing tool life
what is the edge angle?
basically the angle between the rake face and clearance face, increasing edge angle reinforces the cutting edge, and reduces likelihood for fracture of the blade’s edge
what is the clearance angle?
angle between the clearance face and tooth surface.
what are the normal angles of carbide burs?
carbide bur blades normally have slight negative rake angles, edge angles of approx 90 degrees and low clearance angles
how many blades on excavating burs?
6-10
how many blades on burs for finishing procedures?
12-40 blades. the greater the number of blades the smoother the cutting at low speeds
what are diamond abrasive instruments?
involves abrasive rather than blade cutting
cutting occurs at a large number of points where individual hard particles protrude from a matrix, instead of along a continuous blade edge
have long life and very effective at cutting dentin and enamel
what are the three parts of diamond abrasive instruments?
metal blank, metallic bonding material, powdered diamond abrasive
what are metal blanks?
resembles a bur without blades, has a head, neck and shank
what are the powdered diamond abrasive?
comes in 4 grits (particular size)
coarse medium fine and very fine
what size is the coarse diamond?
125-150um
what size is the medium diamond?
88-125um
what size is the fine diamond?
60-74um
what size is the very fine diamond?
38-44um
what are metallic bonding materials?
holds diamond powder onto the blank
what are other abrasive instruments used for?
restricted to shaping, finishing, and polishing restorations in the clinic and laboratory
similar to diamonds, cutting surfaces of the head consist of abrasive particles held in a continuous matrix of softer material
what are the two categories other abrasive instruments are divided into?
molded instruments and coated instruments
what is brittle fracture?
associated with crack production usually from tensile loading. high speed cutting of enamel proceeds by brittle fracture
what is ductile fracture?
involves plasmic deformation of material usually proceeding by shear forces. low speed cutting usually proceeded by plastic deformation before tooth structure fracture
what is bladed cutting used for?
burs are generally preferred for cutting ductile material like dentin
used for intracoronal tooth preparation and end cutting
what is abrasive cutting used for?
diamonds are most efficient when used to cut brittle materials; superior to burs for enamel removal
due to producing a rougher tooth surface, diamonds may be preferred when preparing teeth for bonded restorations (roughened surface increases bonding potential); used primarily for extracoronal preparations
what are some of the precautions with high speed cutting?
damage to tooth from heat- need coolant (air water syringe) for vital teeth
damage to soft tissue from lack of control- can be due to operator, or sudden movement by patient
eye protection- safety glasses always indicated when rotary instruments are in use
inhalation precautions- aerosols and vapors are created when cutting tooth structure and restorative materials, this is a health hazard; need to use intraoral evacuation and wear mask
ear protection- high speed handpieces can produce high noise levels; variation in noise levels among handpieces by sam manufacturer, effect of excessive noise depends on amount of exposure time, earplugs can be used
what are the non cutting hand instruments?
mirrors, explorers, probes, condensers
what are the cutting hand instruments?
excavators
chisels
what are the instrument design of hand instruments
handle, shank, blade
what are the excavators?
(ordinary hatchets, hoes, angle formers, spoons)
what are the chisels?
(enamel hatchets, gingival margin trimmers, straight chisels, curved chisels, bin-angle chisels)
what is the shank of hand instrument?
connects handle to the blade. shank angles can be mon-angle (one), bin angle (two), triple angle (three)
what is the blade of hand instrument?
working end of the instrument
what is the instrument formula?
describes dimensions and angles of the working end, placed on the handle using 3 or 4 numbers
what are the numbers in the 4 number code?
1st number- width of blade (tenths of mm) - 13 =1.3mm
2nd number- primary cutting edge angle (measured from line parallel to long axis of instrument handle in clockwise centigrade)
3rd number- blade length (mm) 8=8mm
4th number- blade angle relative to long axis of the handle in clockwise centigrade
what are the numbers in the 3 number code?
1st number- width of blade (tenths of mm)
2nd number- blade length in mm
3rd number- blade angle relative to long axis of the handle in clockwise centigrade
what is the cutting instrument bevel?
on the end of the blade, most instruments have a single bevel that forms the primary cutting edge. 2 secondary cutting edges extend from the primary edge for the length of the blade
what is a bibeveled instrument?
ordinary hatchet,
have 2 bevels that form cutting edge
what is a double ended instrument?
instruments with blades and shanks on both end of the handle
what is an excavator used for?
used for removal of caries and refinement of internal parts of a tooth preparation (Ex. spoon)
what is a chisel used for?
used mainly for cutting enamel, such as planing walls or beveling a preparation
what are the functions of other cutting instruments?
knives: trimming excess material on restorations
files: trim excess restorative material
discoid-cleoid: for carving occlusal anatomy in unset amalgam restoration, can trim or burnish inlay/onlay margins
what is the modified pen grasp?
similar but not identical to pen grasp
pads of thumb, index and middle fingers contact instrument, tips of ring finger of ring and little fingers placed on nearby tooth as rest. middle fingers works with wrist and forearm to generate cutting or cleaving pressure
what is the inverted pen grasp?
same as mod pen grasp, but palm is faced more toward operator
what is the palm and thumb grasp?
limited use. handle is placed in the palm and grasped by all fingers except the thumb which serves as a rest on nearby tooth in the same arch or on a firm, stable structure
what is modified palm and thumb grasp?
can provide more ease of instrument movement and control against slippage than palm and thumb grasp; tip of thumb rests on tooth being prepared or adjacent tooth; may be used in maxillary arch with dentist operating at a rear chair position
what is dental caries?
an infectious microbiologic disease that results in localized dissolution of calcified tissues of teeth
what is the caries terminology?
location of primary caries and secondary (recurrent) caries
extent- incipient (reversible) and cavitated (irreversible) caries
rate- acute (rampant) and chronic (slow or arrested) caries
what are the 3 morphologic types of caries observed clinically?
lesions originating in enamel pit and fissures
lesions originating on enamel smooth surfaces
lesions originating on root surfaces
classfication of caries
system developed in early 1900s by Dr. GV Black
classification of caries and tooth preparation based on their location
what is class 6 cavity?
cusp tips of posterior or incisal edge of anteriors
what is the definition of tooth preparation?
mechanical alteration of a defective, injured or diseased tooth such that placement of a restorative material reestablishes normal form and function
what is the cavosurface margin?
junction of prepared wall with uncut tooth surface
what is a conventional preparation?
precise preparations resulting in uniform depths, particular wall and marginal forms (requirement for amalgam)
what is a modified preparation?
without specific depths, particular wall designs or retentive features (can be done for composite)
what is the principle of the outline form?
conservative preparation
margins on sound enamel
include defective enamel (pits and fissures)
depends on carious lesion or previous restoration
what is the principle of retention form?
features that lock or retain the amalgam in the tooth
slight occlusal convergence of prepared walls
facial and lingual only
what is the principle of resistance form?
features that prevent the enamel from fracturing as a result of occlusal forces
preservation of cusps and marginal ridges
pulpal floor flat and perpendicular to occlusal forces
rounded internal preparation angles
removing unsupported tooth structure
divergence of mesial and distal prepared walls
features that help the amalgam resist fracture and wear under function
what is the uniform and adequate thickness of amalgam?
1.5-2mm
what is the adequate depth of pulpal floor?
0.5mm in dentin
degree between marginal amalgam and cavosurface margin?
80-100 degrees, 90 ideal
what is principle of convenience form?
preparation features that make the area more accessible or the procedure easier
ex. extension of walls to provide greater access for caries removal
extension of walls to ensure the preparation is wide enough to fit the smallest condenser to ensure adequate condensation of amalgam
330 bur
pear shaped, normal length
1.5mm long, 0.8 mm wide
recommended for most conservative amalgam prep
245 bur
pear shaped, elongated can be used for class 1 cavity prep mostly for proximal box formation in class 2 cavity prep 3mm long and 0.8 mm wide
169 bur
tapered fissure
256 bur
straight fissure
what is the bur angulation?
parallel to long axis of the tooth (man tilt toward lingual bc of lingual tilt)
but positioned for entry into distal pit, stop just short of cutting edge of but, enter mesial pit- connect the two through the central groove
what is appropriate pulpal floor depth?
- 5mm measured from central groove to pulpal floor (full length of 330 bur, half of 245)
- 0 mm from cavosurface margin
- 2-0.5 into dentin
mesiodistal divergence
incline bur distally to establish proper occlusal divergen to mesial and distal walls- 10 degree tilt
for proper dentinal support of marginal ridges
unsupported enamel rod at margin make it prone to fracture
class 1 cavity shape
butterfly or dog bone
preparation of class 1 extension
inclination of bur altered for correct axial wall depth
axial wall depth should be 1.5-2mm (0.2-0.5mm into dentin)
extend through buccal surface
extend buccal groove with side of the bur
refine line angles from facial aspect
sharpen line angles from occlusal aspect
what are the goals of isolation?
moisture control, retraction and access, patient safety, increase operator efficiency
what are absorbents?
cotton rolls, dri-angles, 2x2 gauze
what are suction devices?
high volume evacuator
saliva ejector
what are the advantages of rubber dam isolation?
dry, clean operating field improved access and visibility patient protection increases operating efficiency improved properties of dental materials
what are the disadvantages of rubber dam isolation?
time consuming, patient objection, interferes with access
what tooth do you not drill perpendicular to the long axis?
mandibular 1st premolar
what are the occlusal parameters of class 2 amalgam prep?
centered on pits and fissures direction- longaxis width- small condensor- 1mm depth- 1.5mm, 0.5 into dentin isthmus- parallel or converge marginal ridge areas- parallel or diverge
box parameters
2.5-3.0mm depth
1.0 axial wall height
width- 1mm-width of 8-9 hatchet
what do you want to bevel?
bevel enamel portion of gingival wall with enamel margin trimmer
bevel axiopulpal line angel with gingival margin trimmer
box clearance
ideal- 0.2-0.3 mm- buccal and lingual
idea-0.5 gingivally
1/3 of explorer tip
very tip of perio probe
retentive features of the box
box converge occlusally
retentive grooves by 169
burs for class 2
occlusal outline 330
box form 245
refine box- 169
what is the step 1 of initial tooth preparation?
outline form and initial depth
place margins where they will be in the final preparation
initial depth-0.2-0.8mm into dentin
measurements for tools gauging B-L clearance?
perio probe-0.5
23 sickle explorer- 0.75
8-9 hatchet- 0.6
pig tail explorer- 0.5
what is the step 2 of initial tooth preparation?
primary resistance form
what is primary resistance form?
shape that enables tooth and restorative materials to resist vertical forces in long axis of tooth flat floor flat walls rounded internal line angles thickness of material cap weak cusps
what is step 3 of initial tooth preparation?
primary retention form
what is primary retention form
resistance to tipping or lifting forces
converging walls of box and isthmus
what is step 4 of initial tooth preparation?
convenience form
what is convenience form?
shape or form that provides for adequate observation and accessibility
proximal extensions of clearance
what is step 5 of final tooth preparation
remove any remaining defective tooth or materials
what is step 6 in final tooth preparation?
pulp protection
what is step 7 in final tooth preparation?
secondary resistance and retention form
what is step 8 in final tooth preparation?
finish external walls
90 degree cavosurface margins
100 degrees or greater occlusal
sloped gingival margins
maxillary mod prep
OL extension of maxillary molar leaves DL cusp weakened and it is open capped with restorative material
what is the steps of manipulation of amalgam?
activation, trituration, placement, condensation, carving, finishing, polishing
activation of amalgam
preencapsulated mercury and alloy
under trituration
incomplete amalgamation
poor working quality
granular and crumbly
decreases final strength
over trituration
decreases final strength
overly warm and shiny
decreases working time
trituration
amalgamation
mixing of amalgam
want to follow manufacturer’s directions
placement
make a mental note of outline form before restore
aids later in carving amalgam to cavosurface margin
place with amalgam carrier
condensation
the process of compressing the alloy into the tooth preparation and eliminating all voids
5-10 lbs of pressure
steps of condensation
place first increment
start with smallest condenser
angle condenser into faciopulpal and linguopulpal line angles
use sliding stroke to ensure complete adaptation of amalgam against all walls and to prevent voids (lateral condensation)
switch to largest condenser as you reach margins
plash
excess mercury
want to bring to the surface (Weaker)
final increment of amalgam
condensing overfilled amalgam with large condenser to form central groove
slide condenser towards tooth (buccal/lingual) to thin out flash for easy removal
precarve burnisher
done with large burnisher
form of final condensation
use heavy strokes mesiodistal and faciolingual
ensures marginal amalgam is well condensed before carving
initial carving
anatomic burnisher
immediately after condensation while amalgam still soft
establish mesial and distal pits
central groove connecting the pits
carving
place partly on margin and partly on adjacent tooth surface
use light sketch like strokes parallel to margin
short, overlapping strokes from tooth to amalgam ending at grooves
base of groove should be rounded and not too sharp
shallow and not too deep
carve parallel to margins to prevent ditching and uses tooth as carving guide
deep occlusal grooves
SHOULD BE AVOIDED
THINS amalgam at the margins
prone to chipping
weaken restoration
ideal contour
no flash or excess amalgam
no over or under contour of amalgam
central groove rounded- not too sharp
ideal carving
reproduces grooves and fossae
restores form and function
restores ability to cut and chew food
flash
thin portions of restoration on the unprepared tooth surface
prone to fracture
overfilled or undercarved
flush
good margin
void
open margin
submarginal
underfilled or overcarved
check occlusion
use articulating paper in miller forceps to check occlusion
typical bullseye/halo/doughnut shaped marking
shows heavy occlusal contacts on new amalgam
adjust occlusion
carve all visible high spots (bumps and lumps)
carve away heavy contact area only
amalgam should not be carved out of occlusion
light occlusal contacts as shown by faint marking
class 2 restoration
missing at least one proximal wall
prevents adequate condensation of amalgam in this area
purposes of matrix bands
provides a wall against which one can condense amalgam
re-establish proximal contact of restoration with adjacent tooth
aids in isolation of preparation during the fill
provides containment of the amalgam
aids in prevention of voids
helps to shape the proximal contours
contra angle retainer
place lingually
straight retainer
place buccally
matrix band looks like ^
tip -occlusally
matrix band placement
narrower opening gingival
open end of retainer always faces the gingiva
functions of the wedge
adapts the gingival edge of the matrix band against the gingival cavosurface of the prep to prevent flash from squeezing out gingivally
separates the teeth slightly to compensate for the thickness of the band
helps stabilize matrix band
wedge placement
placed into the largest embrasure (usually lingual embrasure) almost always
base of the triangle goes gingivally
overhangs
excess filling beyond marginal preparations
equivalent of occlusal flash
result of poor matrix and wedge technique
burnishing the band
after placement, loosen spindle 1/4 turn to take tension off band
burnish band firmly against contact area of adjacent tooth
do not retighten band
open contact
will increase probing depths and pocketing
constant food impaction resulting from no contact due to poor (or no) wedge technique
steps of insert and carve amalgam
proximal areas
occlusal areas
overfill
anatomic burnisher
marginal ridges and occlusal embrasures
clear excess flash on occlusal
remove matrix band
evaluate facial lingual and gingival walls for flash or voids
define or deepen grooves and fossae and smooth ridges
remove rubber damn and evaluate occlusion
burnish
with largest condenser
with condenser resting on tooth and amalgam, slide condenser upward toward tooth to thin out excess and start to form central grooves
form marginal ridges
sickle explorer tip is placed parallel to occlusal surface and central groove with the tip touching the inside of matrix band loop
want marginal ridges to be rounded and same height as adjacent tooth
form occlusal embrasure
raise explorer tip to 45 degrees with the tip still touching the inside of matrix band
do not raise the angle of the exploere to 90 degrees since this will cause the end of the explor to ledge the soft amalgam in the proximal surface
cleoid discoid
cleoid define grooves
discoid define margins
evaluating facial lingual gingival walls for flash or voids
tip of hollenback aimed into the gingival embrasure space, shave the gingival half of the box surfaces from gingival to occlusal
define grooves fossae and smooth ridges
triangular fossae
central groove
facial and lingual grooves in molars
goals of amalgam
restore anatomy
marginal ridges equal in height to adjacent teeth
light functional occlusion
