Lecture 18 & 19- Abrasives and Temporary Crowns Material (Slides)

8/3/2019 Lecture 18 & 19- Abrasives and Temporary Crowns Material (Slides)

1/57

1

Auxiliary dentalmaterials and

temporary crowns

Auxiliary dentalAuxiliary dentalmaterials andmaterials and

temporary crownstemporary crownsDental materialsDental materials

Dent 305Dent 305


2/57

2

Objectives of polishing

and finishing Esthetics

Smoothening of rough edges andsurfaces

Remove excess material

Reduce corrosion and breakdown


3/57

3

Finishing and polishing Is to use a diminishing series of

abrasives on a surface to contourthen smooth and bring a shine to the

surface


4/57

4

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


5/57

5

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.


6/57

6

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


7/57

7

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


8/57

8

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


9/57

9

Delivery design of

abrasives Paste abrasives

Loose abrasives

Coated abrasives

Bonded abrasives


10/57

10


11/57

11

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


12/57

12


13/57

13

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


14/57

14


15/57

15

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


16/57

16


17/57

17

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


18/57

18

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


19/57

19

3. Silicon carbide Hard and efficient abrasive with a 9-

10 on the Moh scale Comes as coated disks and bonded

rotary devices


20/57

20

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)


21/57

21

5. Sand Composed of quartz and silica

Rates 7 on Moh scale

Coated disks and strips


22/57

22

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.


23/57

23


24/57

24

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


25/57

25

Preparations used for

abrasionA. Prophylaxis paste, Composition:

Pumice, tin oxide

Lubricants

Preservatives Flavoring agents

Coloring agents Therapeutic agents such as fluoride


26/57

26

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


27/57

27

Continue, The most fine paste should be

selected and well lubricated to polishand remove stains and soft deposits


28/57

28

B. Tooth paste (dentifrices)

Contain abrasives to clean tooth

surface and prevent plaqueaccumulation

Contain : 20-40% abrasives

Coloring and flavoring agents

Therapeutic agents (fluoride)


29/57

29

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


30/57

30

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


31/57

31

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


32/57

32

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


33/57

33



34/57

34


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


35/57

35

Continue,

Polishing: done by

using bonded ,coated or looseabrasives (20-

submicron particlesizes)


36/57

36



37/57

37


composite


38/57

38


39/57

39

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


40/57

40

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


41/57

41

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.


42/57

42

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


43/57

43

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


44/57

44

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


45/57

45

Safety and infection


46/57

46

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


47/57

47

Continue, Preprocedure antimicrobial

mouthrinses are recommended Protective eye wear for patients

High volume suction Sterilize used devices and use dry

and fresh pastes.


48/57

48

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


49/57

49

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


50/57

50

Prepared tooth and temporaryrestoration

General outlines of the procedure:


51/57

51

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


52/57

52

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


53/57

53

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


54/57

54

Properties


55/57

55

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


56/57

56

Properties Biocompatibility: monomer is irritant.

Solution to protect freshly cutdentine?

Mechanical properties: fracture iscommon in thin areas.

Appearance: available in shades


57/57

57

Reference: Dental materials, clinical

applications for dental assistants anddental hygienists. Chapter 9

Applied dental materials. Chapter 26

Lecture 18 & 19- Abrasives and Temporary Crowns Material (Slides)

Documents

Transcript of Lecture 18 & 19- Abrasives and Temporary Crowns Material (Slides)