Post on 06-Apr-2018
8/3/2019 Lecture 18 & 19- Abrasives and Temporary Crowns Material (Slides)
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Auxiliary dentalmaterials and
temporary crowns
Auxiliary dentalAuxiliary dentalmaterials andmaterials and
temporary crownstemporary crownsDental materialsDental materials
Dent 305Dent 305
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Objectives of polishing
and finishing Esthetics
Smoothening of rough edges andsurfaces
Remove excess material
Reduce corrosion and breakdown
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Finishing and polishing Is to use a diminishing series of
abrasives on a surface to contourthen smooth and bring a shine to the
surface
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What affects abrasion?1. Size, irregularity, and hardness of
particles: Diamonds are the most abrasive
material in dentistry. Their rate ofabrasion depends on particle size,pressure used and speed of rotating
device. The larger and coarser the particle,
the more abrasive it will be
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Continue, Hardness is the ability ofthe material to resist
abrasion. If the polished surface is
harder than the abrasive,
minimum finishing orpolishing will occur
Moh scale.
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Continue, Abrasive particles are classified
from coarse to fine depending ontheir size (grit) measured in microns
Coarse: 100 m and above Medium: 20-100 m
Fine: 20-submicron size
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2. Numbers that contact the surface:
1. The more concentrated the abrasiveparticles on the surface, the moreabrasive they are.
2. Lubricants such as saliva and water areused to dilute the abrasive material
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3. Speed and pressure:1. The higher the speed and pressure the
greater the abrasive effect2. Lack of proper control over speed andpressure during abrasion may lead to:
1. Excessive and uncontrolled removal ofmaterial or tooth structure
2. Excess heat production
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Delivery design of
abrasives Paste abrasives
Loose abrasives
Coated abrasives
Bonded abrasives
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Loose abrasives Powders and pastes
Coarse, medium, fine, superfine grit sizes
Applied by brushes, wheels, cups, soft
pads The proper grit and dilution should be
considered to determine the amount of
polishing required
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Bonded abrasives They are rotary instruments that have an
abrasive particle uniformly incorporated ina binder to form the shape of the devise.
Comes in many forms, points, disks, cups Usually used for intermediate and initialfinishing
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Coated abrasives Finishing strips and rotary disks
The abrasive particles are secured toone side of the disk with an adhesive
A mandrel is used to attach thedisks on
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Materials used in
abrasion1. Diamond:
1. hardest material and can abrade anysurface
2. Expensive and not usually disposable
3. Used as bonded abrasives and can bereused several times before they wear
4. Fine particle diamond paste is used topolish composite and porcelain
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2. Carbide finishing burs Come in different shapes and number
of cutting flutes (7-30) The higher the number of flutes, the
finer the finish
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3. Silicon carbide Hard and efficient abrasive with a 9-
10 on the Moh scale Comes as coated disks and bonded
rotary devices
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4. Aluminum oxide Manufactured as white powder
Used in: Bonded and rotary abrasive devices
Sandblasting restorations beforecementation
Also aluminum oxide impregnated rubberwheels are widely used (Burlew wheels)
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5. Sand Composed of quartz and silica
Rates 7 on Moh scale
Coated disks and strips
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6. Silicon dioxide: mainly used in
prophylaxis pastes and ranks 6-7 onMoh scale7. Pumice: manufactured as a loose
abrasive from volcanic silica and isextremely fine
8. Rouge: iron oxide found in blockform run on a rag wheel to polishprecious and semiprecious alloy in
lab.
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9. Tin oxide: fine abrasive and used topolish enamel and restorations. Isfound as powder mixed with water
or glycerin.
10. Calcium carbonate: found inprophylaxis paste and dentifrices
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Preparations used for
abrasionA. Prophylaxis paste, Composition:
Pumice, tin oxide
Lubricants
Preservatives Flavoring agents
Coloring agents Therapeutic agents such as fluoride
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Continue,
The paste is diluted with a lubricantto control abrasiveness and frictional
heat generated, and to preventhardening of the particles.
Supplied as coarse to superfine For polishing, the hardness of thepaste should be 1-2 points higher
than the polished surface
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Continue, The most fine paste should be
selected and well lubricated to polishand remove stains and soft deposits
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B. Tooth paste (dentifrices)
Contain abrasives to clean tooth
surface and prevent plaqueaccumulation
Contain : 20-40% abrasives
Coloring and flavoring agents
Therapeutic agents (fluoride)
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C. Denture cleansers Cleansers used by a tooth brush are used
to : Remove stains
Plaque accumulation
Food debris
Some cleansers are used by soaking
dentures in them to loosen debris anddeposits
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Denture cleansers Requirements:
Non toxic
Non abrasive Harmless to the components of the denture
Example materials: dilute alkaline or acid
preparations Prosthesis with metal parts should not be
soaked in acid solutions to prevent
corrosion
Fi i hi d li hi
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Finishing and polishing
procedures Consider the following:
Type and grit size of abrasive used The order in which the abrasives are used The desired anatomic features of the
restorations Tooth structure adjacent to the polished
restorations
Original contour should be recreated Contact areas should not be polished
M i ti d l
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Margination and removal
of flash Margination is the removal of excess
restoration to bring it flush with thecavosurface tooth structure. This
includes removal of: Feathered flash
overhang
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Finishing and polishing
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Finishing and polishing
amalgam After 24 hours after insertion
Steps that should be followed: Remove excess amalgam as indicated
Finishing: Abrasives used to removescratches and surface defects. Bondedand coated abrasives (>25 m),multifluted burs are used
Continue
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Continue,
Polishing: done by
using bonded ,coated or looseabrasives (20-
submicron particlesizes)
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Finishing and polishing
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Finishing and polishing
composite
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Gold alloys: finished and polishedusing Burlew wheels followed byrouge on a rag wheel.
Porcelain: finishing is done in the lab.Diamond burs are used to make
adjustments. Rubber points andwheels designed for porcelain areused. Diamond polishing paste is alsoused.
Polishing during an oral
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Polishing during an oral
prophylaxis Amalgam: benefits from polishing
using rubber cup or brush withprophy paste.
Composite: polished with aluminumoxide paste. May help in removingstains. Avoid ultrasonic scalers andprophy paste.
C sit ( ti ): st t ith
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Composite (continue, ): start with
fine paste, if not effective usecoarser abrasives and pay attentionto restoration margins and surface.use light pressure, light sweepingaction under water in less than 30
seconds.
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Gold and porcelain: use porcelainpolishing paste for porcelain andaluminum oxide for gold if surface of
these restorations is rough or hasscratches on it
Resin cement interface: treated ascomposite.
l h d
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Air polishing and abrasion
Use microparticles as a replacement
for rotary cutting and polishinginstruments
Air polishing: uses water, air, Nabicarbonate under pressure toremove stains and debris fromenamel surface.
b
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Air abrasion
Uses compressed air and 27-50 m
particles of aluminum oxide. Notrecommended for stain removal.Mainly used for:
Cast restorations before cementation Repair for porcelain and composite
Tooth surface before bonding
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Safety and infection
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Safety and infection
control Splatter from pastes can cause eye
damage Vapor and aerosols during finishing and
polishing can transmit diseases
Silica particles and mercury vapor arehealth risks
Personal protective equipments are needed
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Continue, Preprocedure antimicrobial
mouthrinses are recommended Protective eye wear for patients
High volume suction Sterilize used devices and use dry
and fresh pastes.
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Patient education Effective oral hygiene practice
Awareness of what causes staining Regular recall appointments
Advise on appropriate abrasiveagents that maybe used at home
Temporary crown and
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Temporary crown and
bridge resins Temporary coverage is needed
following tooth preparation. Why? Protect tooth vitality after enamel and
dentine removal Prevent gingival overgrowth
Prevent supra-eruption of opposing
tooth
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Prepared tooth and temporaryrestoration
General outlines of the procedure:
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General outlines of the procedure
Impression is taken prior to tooth preparation Tooth prepared
Temporary crown material mixed and placed in
impression or plastic crown then reseated Initial setting impression and material is
taken out. Final setting outside the mouth
Adjustments and finishing is made then crownis cemented
Requirements
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Requirements Non irritant Strong
Tooth colored Setting should not yield high temperatures Setting contraction not too high
Sufficient working time After seating, quick initial setting
(rubbery) for easy removal
Quick hardening outside the mouth
Available materials
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Type Dispensationmethod Composition
Acrylic Powder/liquid PMMA+ peroxide
MMA +activator
Acrylic Single paste (LC) PMMA+ monomer+ light activator
Higher
methacrylate
Powder/liquid PMMA+ peroxide
Isobutylmethacrylate + activator
Composite Paste/paste Multi-functional methacrylate +fillers+ initiators + activators
Composite Single paste (LC) Multi-functional methacrylate +fillers+ light activators
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Properties
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Properties
Setting characteristics: Composite materials: have a distinct rubbery
stage due to multifunctional monomer. Finalsetting maybe accelerated in hot water
Acrylic materials: rubbery stage not as distinct
Setting is exothermic Undergo shrinkage
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Properties Biocompatibility: monomer is irritant.
Solution to protect freshly cutdentine?
Mechanical properties: fracture iscommon in thin areas.
Appearance: available in shades
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Reference: Dental materials, clinical
applications for dental assistants anddental hygienists. Chapter 9
Applied dental materials. Chapter 26