Operative Flashcards
Operative Dent Definition
The science and art in dentistry that studies the prevention, diagnosis, treatment of defects in enamel and dentin
Carious vs. Non Carious
C
- bacterial infection
- diseased tissue has to be removed
- precise Cavity preparation
NC
-loss of surface tooth structure due to mechanical or chemical factors
Exs) attrition, abrasion, erosion, abfraction
Direct Restoration vs Indirect Restoration
Direct-
Dental material placed in a soft state directly in a cavity preparation to restore contour before it sets hard
Indirect-
A restoration fabricated outside the oral cavity then cemented or bonded to the tooth
-generally sent to the lab to be made
-CADCAM tech
Rotary Speeds for Handpieces
Slow/Low Speed
-<12,000 rpm (less friction/heat generation)
-no water coolants
-less efficient, more controlled removal
-need to tell patient they will feel a lot of vibrations
-has interchangeable attachments
Uses:
-deep caries excavation in close proximity to the pulp to avoid pulp exposure
-cleaning external surface of teeth (coronal polishing)
-finishing or polishing procedures
Medium Speed
- 12,000-20,000 rpm
- infrequently used and not used at OSU
High Speed
->200,000 rpm
-generates a lot of heat so water coolants are needed
-most cutting efficiency–>less vibration and pressure leading to less patient discomfort
-attachments are not interchangeable like the slow speed
Uses:
-teeth preparations
-removal of old restorations
Delivery Tubing System
-4 hole connector line (most common)
- large nut–> high speed
- small nit –> slow speed
Coupler
- attached the hand piece to the delivery unit and supplies air and water to the hand piece
- the 4 hole line receives the handpiece coupler
- fixed or moveable(360 swivel)
Slow Speed Parts
- Slow Speed Motor
- Nose cone/straight attachment (used for extra oral things like trimming casts or crowns)
- long shank type bur/straight bur
- Contra-angled Attachment (used for harder to reach places)
Slow Speed Heads
2-Latch type (RA) Head
- accepts only latch end burs
- latch end burs larger in diameters than friction grip burs
- Swing latch; Push button Latch; Spring Latch
Friction grip head
-uses friction grip type bur (smaller diameter and shorter shanks that latch type)
-two mechanisms
A: friction generated from an internal spring assembly (push button)
B: a special tool using force to overcome and generate friction (bur tool type)
Components of Rotary Instruments
Head
- the working part of the instrument
- consist of either blades or abrasive particulate surfaces
- many shapes and sizes
Shank
- straight/long shank (nose cone)
- latch design (slow speed contrangled latch type)
- friction grip design (slow speed contrangle firction grip head and high speed)
Neck
- not too bulky to avoid interfering with operator’s visibility
- not too narrow to become a weak link between the head and the shank
Bladed Instruments
Composition of Bladed Instruments vs Diamond Instruments
-the greater number of blades the smoother the finish
- Excavating/ cutting burs (blades 6 or 8)
- Finishing burs (blades 10-20)
- color coded: 10-12 (red); 16-20 (yellow); 30 (white)
Comp Bladed
-carbide for blade cutting
-blades…tungsten carbide blanks ground to the desired shape. Stronger and harder than stainless steel but brittle
-tungsten carbide head is attach to the steel bench and shank by welding and brazing
Uses: INTRAcoronal preps
Comp Diamond -diamond for abrasive cutting -metal blank on which small diamond particles are held together within a softer matrix -color coded for degree of abrasiveness -Yellow: superfine -Red: fine -Blue: medium -Green: coarse -Black: supercoarse (We will use blue and green for crown preps) Uses: EXTRAcoronal preps
Pear Shaped Bladed Head Design
Used for Intracoronal Preps
330
- Length: 1.5mm
- Taper: 8 degrees (inversion walls)
- Diameter: 0.8mm
245
- Length: 3mm
- Taper: 4 degrees
- Diameter: 0.8mm
Round Spherical Head Design
1/4 - 11
1/4 = 0.5mm
4(full) = 1.4mm
Plain Cylindrical Fissure Blade Head
-creates parallel walls
-55-59
(Designate 200 series for rounded corners)
Plain tapered fissure
We use 169
- narrowing at the distal end of blade
- creates divergent walls
End Cutting
- designate a 900 (we use 956)
- no side blades
- used to smooth floor
- end only carries the cutting blades
Mechanism of Cutting
Brittle vs Ductile Fracture
Brittle
- brittle material fractures by crack formation upon tensile loading
- enamel is brittle
- abrasive cutting: more efficient with brittle materials (microcracks) –>extracoronal preps (diamond burs)
- like dropping a plate
Ductile (will absorb more energy)
- plastic deformation of the material by shearing
- bladed cutting more efficient with ductile material (deform then shear)–> intracoronal preps in dentin
Blade Design
Angles
Rake face
- the surface that forms the chip
- the surface of the blade towards the direction of cutting (usually clockwise)
Clearance face
- surface the clears the chips
- away from the direction of cutting
ANGLES (look at pic on slide 43, lecture 1)
Edge angle
-between the rake and the clearance surfaces
Rake angle
-between the radial line and the rake face
Clearance angle
-the angle that provides clearance between the cutting edge and the tooth structure
Positive Rake Angle
- sharper than the negative
- when the radius (from cutting edge to axis of bur) is ahead of the rake face
- higher cutting efficiency
- larger chips produced
- chip space smaller; clogging of chip space
- always a chance to curve, fracture material if not adequate
- break easily
Negative Rake Angle
- when the rake face is ahead of the radius (from the cutting edge to axis of bur)
- decreased cutting efficiency
- smaller chips are produced= no clogging of the chip space
- cutting edge is spared (less liable to fracture) since carbide burs are brittle)
Clearance Angle
- the angle that provides the clearance
- prevents the blade from rubbing on the tooth surface
- bigger the clearance angle –> less friction –> dulling minimized –> bur life lengthened
Hand Instruments
- Examination Instruments
- Hand cutting instruments
- Restorative instruments
- Accessory instruments
Examination Instruments
Mirror
- non dominant hand
- reflects light
- for indirect vision
- retracts lips, cheeks and tongue for access
- protection of soft tissue: tongue, floor of the mouth
Explorer (Sheperd’s hook #23, Pigtail/cowhorn #2)
-pointed tip to enhance tactile sensation for caries detection
Periodontal Probe
- measures cavity depth
- “dental ruler”
Shank Design Principles
- balance
- concentration of the force onto the blade without rotation of the instrument
- out of balance: creates more torque
- balanced: concentrates forces on cutting edge
Black’s Instrument Formula
3 Unit Formula
1st Number - width of the blade in tenth of a mm (ex-10=1mm)
2nd number - length of blade in mm (ex- 7 =7mm)
3rd number - angulation of the blade to the long axis of the handle
-expressed in 100th of a circle
-always <50
Black’s Instrument Formula
Four Number Formula
The second number indicates the primary cutting edge relative to the long axis of handle (always greater than 50
1st- Width of blade
2nd (new)- primary cutting edge angle (>50)
3rd- blade length in mm
4th- blade angle relative to the long axis in centigrade
Restorative Instruments
- insert and carve the restorative material
- carrier
- condenser/plugger
- anatomical/acorn burnisher
Accessory Instruments
- articulating paper holder (miller forceps)
- scissors
-Amalgam well (accessory equipment)
Direct Cutting
-force is applied to perpendicular to cutting edge
-hold the instrument parallel to the wall planed at all time
-the cutting edge in contact with the wall being planed
Ex) enamel hatchet
Lateral Cutting
-indirect cutting/ lateral cutting/ scrapping: force is exerted is parallel to the cutting edge
-motion: from the beveled to the non beveled side (away from the bevel)
Ex) Enamel Hatchet and Gingival Margin Trimmer
Enamel Hatchet
- the cutting edge is parallel to the long axis of the handle
- direct and lateral cutting
- double ended instrument with right and left bevels
Chisel Family
A. Straight/ slightly curved/bin angled chisels (push motion)
B. Enamel Hatchet: direct cutting and lateral cutting
C. Gingival Margin Trimmer: lateral cutting
Gingival Margin Trimmer
- 4 unit formula
- the blade is curved and not milled in a single plane: curved blade accentuates the lateral cutting
- cutting edge makes an angle to the long axis of the blade
- lateral cutting: force is applied parallel to the cutting edge
Excavator Family
A. Ordinary hatchet
B. Hoes (pull)
C. Angle Former
D. Spoon
