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