Dental Burs

DEPARTMENT OF CONSERVATIVE DENTISTRY & ENDODONTICS

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Seminar on

DENTAL BURS  BUR DESIGN,SHAPES,SIZES,  BURS FOR AMALGAM AND COMPOSITE

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Seminar on

DENTAL BURS  BUR DESIGN,SHAPES,SIZES,  BURS FOR AMALGAM AND COMPOSITE

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CONTENTS o

 Definition

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 Parts of bur

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 Purpose

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 Bur classification systems

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Classification of burs

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 Bur shapes

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 Bur blade design

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 Factors influencing cutting efficiency efficiency of burs

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Care with rotary instruments

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 Burs for amalgam

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 Burs for composite  Finishing and polishing polishing  Amalgam, Composite

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BUR:

Rotary cutting instrument with bladed cutting head PARTS OF A BUR:

Shank  Neck Head

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HISTORICAL DEVELOPMENT: 

Steel bur 1891



Carbide bur 1947

PURPOSE: 

 Tooth preparation



 Finishing a restoration



 Surgical removal of bone

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BUR CLASSIFICATION SYSTEMS:

 A. SHORT HAND DESIGNATION  B. FDI, ISO SYSTEM C. SIMPLIFIED NUMBERING SYSTEM A. Short hand designation : 

Arbitrary numerical codes for head size and shape E.g. : No.2 - 1mm round bur  No. 57 - 1mm straight fissure bur  No. 34 - 0.8mm inverted cone bur

B. F D I , I SO : 

 Head diameter in tenth of mm 6

C. S i mpli fied Number ing System f or dental bur s: 

First two alphabets - 'the shape of the bur' rd - round bur

fs  –  flame-shaped bur

 bd - bud-shaped bur,

ic -inverted cone bur,

 pr -pear-shaped bur,

wl - wheel-shaped bur,

sf - straight fissure bur,

fs - football-shaped bur,

tf - tapering fissure bur, ec - end-cutting bur, and ts - torpedo-shaped bur, eb - endo bur. 

Second parameter - 'maximum head diameter'. Diameter (in mm) is being multiplied by 10 to make it a whole number . 0.5 as 5, 0.6 as 6 7



Third parameter - 'maximum length of the bur head' This value is converted into a whole number by multiplying it by 10 and is included next to the previous number followed by a space to indicate separation. E.g. : 1.2 as 12, 3 as 30, etc.



Fourth parameter - 'material of the cutting head'. D (diamond), C (carbide), or S (steel) . Regular friction grip bur - 'FG' Short-shank friction grip bur -

'SS’

“Straight fissure diamond point with head diameter of 1.2 mm, head length 3.0 mm with a normal friction grip shank will have the designation 'SF 12 30 DFG” 8

CLASSIFICATION OF BURS: I.

According to their mode of attachment Latch type Frictional grip type

II.

According their composition Stainless steel Tungsten carbide Diamond

III.

According to head Bladed Abrasive 9

IV.

According to length of their head Long Short Regular

V.

According to their shapes Round Straight fissure Tapered fissure Inverted cone

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ROUND BURS: 

 ¼, ½, 1, 2, to 10 - Used for initial entry into the tooth, extension of the preparation, preparation of retention features, and caries removal.



No. 2, 4, and 6 and two lengths, regular and surgical, are used for endodontic access opening. 11

INVERTED CONE BURS:  

Numbered from 33 ¼, 33 ½, 34, 35, to 39. Cavity extension and occasionally for establishing wall angulations and retention forms.

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PLAIN CYLINDRICAL FISSURE BUR: 

They are numbered from 55 to 59.



The bur teeth  – straight, spiral

CROSS CUT CYLINDRICAL FISSURE BUR: 

555, 556 to 560.



Teeth - straight ,spiral.



Cylindrical fissure burs- Gross cutting, cavity extension and creation of walls. 13

PLAIN TAPERED FISSURE BUR: 

168, 169, to 172.



Have a tapered cylindrical head



Teeth -straight or spiral

CROSS-CUT TAPERED FISSURE BUR: 

699, 700 to 703.



Straight or spiral.

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PEAR-SHAPED BURS:  

229 to 333 A normal-length pear bur (length slightly greater than the width) - class I tooth preparations for gold foil.



A long-length pear bur (length three times the width)

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Tooth preparations for amalgam.

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ROUND BURS

Bur # Cutter Size 

FG 1

0.8 mm



FG 2

1.0 mm



FG 4

1.4 mm



FG 6

1.8 mm



FG 8

2.3 mm

PLAIN TAPERED FISSURE

Bur #

Cutter Size



FG 169L 0.9 x 5.2 mm



FG 170L 1.0 x 5.2 mm



FG 171L 1.2 x 5.2 mm 16

CROSS CUT TAPERED FISSURE

Bur #

Cutter Size



FG 669L 0.9 x 5.2 mm



FG 700L 1.0 x 5.2 mm



FG 701



FG 701L

1.2 x 4.2 mm 1.2 x 5.2 mm

INVERTED CONE

Bur #

Cutter Size



FG 35

1.0 x 0.9 mm



FG 36

1.2 x 1.0 mm



FG 37

1.4 x 1.2mm



FG 38

1.6 x 1.4mm



FG 39

1.8 x 1.5mm

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STRAIGHT FISSURE CROSS CUT

Bur #

Cutter Size



FG 556L

0.9 x 5.2 mm



FG 557

1.0 x 4.0 mm



FG 557L

1.0 x 5.2 mm



FG 558L

1.2 x 5.2 mm



FG 559

1.4 x 4.5 mm



FG 559L

1.4 x 5.2 mm



FG 560

1.6 x 4.5 mm

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BUR BLADE DESIGN:

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

Bur blade

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Blade angle

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Chip space or flute

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Rake angle:

* Negative - if the face is leading the radial line * Zero - if the radial line & face coincide * Positive - if radial line leads the face.

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Land:

- The plane surface immediately following the cutting edge Clearance angle: -

The angle between the back of the bur tooth and tooth being cut.

-

Eliminates rubbing friction of clearance face

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Provides stop to prevent bur edge from digging into the tooth Carbide burs: slightly negative rake angle 90 degree edge angle  Low clearance angle 21

 Modifications in bur design:  Reduced use of crosscuts: - Crosscuts produce unduly rough surface when used with high speed  Extended heads on fissure burs: - Light pressure needed for high speeds permits this modification  Roundening of the sharp tip angles - lower stresses - enhance strengthof tooth - facilitate adaptation of restorative materials

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Additional features in head design:  Head length  Taper angle   Neck diameter  Spiral angle  Cross cut

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FACTORS INFLUENCING THE CUTTING EFFICIENCY OF BURS 1. Rake angl e: 

 Positive the rake angle - more the cutting efficiency



Positive rake angle>radial rake angle>negative rake angle



But negative rake angle is used because of following reasons

- The size of bur tooth and tooth angle is more thus increasing its bulk and increased resistance to fracture - The cut chips moves directly away from the blade

- Positive rake angle-the chips are larger and tend to clog the chip space 24

2. Clearance angl e:

3. Number of teeth or blades and their distr ibuti on:

- For ideal cutting efficiency- 6 to 8. -As number of blades decreases, magnitude of force at each  blade increases & thickness of the chip removed by each flute increases. . Concentricity: 4 

-Measures how closely a single circle can be passed

through tips of all the blades

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5. Run out:

- The eccentricity or maximum displacement of the bur head from its axis of rotation while the bur turns. - Run out leads to inaccurate cutting and increased heat  production

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CARE WITH ROTARY CUTTING INSTRUMENTS

1. Ensure good access & visibility by providing proper retraction, use of rubber dam, evacuation and good illumination of the working area 2. Use proper finger rests to guide the handpiece, support it & provide maximum control of the cutting instrument 3. Avoid uncontrolled or excessive removal of uninvolved tooth structure. In case of deep caries removal use slow speed round steel burs with intermittent, light pressure to  protect pulp. 4. Always use sharp burs of small dimensions, avoid use of dull or clogged burs 27

5. Use air-water spray to cool, moisten & clear the operating site. The spray lubricates, cleans & cools the cutting instrument, thus increasing its cutting efficiency & life 6. Care for the adjacent teeth and gingiva. Use retraction, wedge & rubber dam isolation. Use safe-ended burs while operating near the gingiva 7. Wear protective glasses for protecting the eyes. Use of face shields are valuable in preventing aerosol spatter 8. Ear plugs, anti-noise devices can be used to minimize unwanted sounds 9. Disposable masks filter out bacteria. Use of rubber dam & high volume evacuation near the tooth may minimize inhalation of vapors. 28

BURS FOR AMALGAM   No.

245 carbide bur - punch cut

  No

169L or No. 329 pear shaped carbide bur - extension into fissures

  No.

169L or No. 330 - small lesions

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  No

¼ or No. 33 ½ - retention grooves

  No.

¼ round bur or No. 169 - Retention locks

  No.

33 ½ or no. ¼ - retention coves in facio pulpal line angle

  No.

169 - sharpen line angles ,class VI tooth preparation

  No.

2 or no. 4 bur - slot preparation

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  No.

2 or no ½ or no. 1  –  entry cut for class III

  No.

½ - accentuate axio gingival line angle

  No.

2 or No. 4 round bur - infected dentin

  No.

¼ - incisal retention cove at axiofacioincisal point angle of class III



 No. 2 or No. 4 round carbide bur or suitable tapered fissure bur - class V

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BURS FOR COMPOSITE   No.

½ ,1 or 2 round bur  –  outline form for class III

  No.

¼ - retention groove and cove

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Flame shaped or round diamond instrument  –  bevel



Appropriate size round bur - class IV

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  No.

700, 701 or 271 tapered fissure carbide bur - Class V

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

Inverted cone bur - class I

  No.

330 or 245 - class II

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FINISHING AND POLISHING: FOR AMALGAM

Additional appointment Use: Reduce plaque accumulation Decrease gingival inflammation Secondary caries Better marginal adaptation Minimizes tarnish and corrosion Esthetically acceptable

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Procedure: Wait for 24 hr Finish with steel bur or stones High point - reduced with carborundum stones or finishing  burs Overhangs reduced by rhein trimmers, bard parker knives,  periodontal knives or gold foil knives

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Abrasives: 

Coarse

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Medium

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Fine



 Ultra fine

Finishing of cervical areas - fine water resistant strips in to and fro motion

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Restoration moist during polishing Low speeds, light intermittent pressure Polishing agents : 

Tin oxide

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Zinc oxide

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Chalk

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Pumice



Extra fine silex

Used with Polishing strips, brushes, rubber cups Hazards: 

Aerosols



High temperature 38

FOR COMPOSITE:

*Contour unpolymerized composite with hand instruments Excess at cavosurface margins - scraped with scalpel or sharp gold knife Gross contouring and finishing : 

 Alpine stone



 Diamond points

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fluted carbide burs

Use Low speed, Water stream, Little pressure, Lubricant 39

Abrasives : 

Aluminium oxide

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 Cuttle fish

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Silicon dioxide coated disks and strips

Class V  –  finishing bur of adequate shape Final lustre - polishing pastes 

Pumice

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Silica

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 Alumina

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 Tin oxide

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 Silicon carbide

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 Zirconium silicate 40

Mix abrasive with water or glycerin Carried with brushes, rubber cups, linen strips, dental tapes Low speed, light pressure Dental floss to inspect proximal surfaces Etch restoration and adjoining enamel Apply thin layer of glaze Glaze : film of unfilled polymers with a composition similar to resin matrix

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Silicone polishers

Alumina disks

Felt disks

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