Rotary instruments for dentistry students

Rotary Instruments

1. Rotary
instruments

2. OperatingSpeedrangesanduses:
1.Regular,loworconventional
speed:(2.000to10000rpm).
2.Higherorintermediatespeed
(10.000to100.000rpm).
3.Ultraorsuperspeed(above
100.000rpm)isaccomplished
withtheairturbine.
Rotary instruments

3. CuttingPoints:
Thesmallestunitandtheoneactuallyremoving
toothstructures,maybeoneoftwo:
1.Bur 2.Stone.
Rotary instruments

4. Burparts:
Shank:
Theshankissecuredtothehandpieceforthepurpose
ofdrivingthebur.
Rotary instruments

5. Shaft:
TheShaftconnectstheheadoftheburwiththe
shank.
Head:
Thispartoftheburdoesthecuttingbythemeansof
thesmallbladeslocatedonthemetal.
Rotary instruments
shaft

6. Bursareclassifiedaccordingtotheirshanks
into:
Rotary instruments
1.Thefriction-gripburis
usedfortheultra-
speedairturbine.
2.Thelatchtype:are
usedforregularand
medium-speed
instruments.

7. Round bur
1.Gainigaccess.
2.Excavation of caries.
Rotary instruments

8. Inverted cone bur
1.Extension of cavity outline form
2.Flattening of pulpalfloor
Rotary instruments

9. 1.Maybeusedinsteadofthe
invertedconeburinmaking
extensionofcavitywallsto
obtainoutlineform.
2.Finishingofcavitywallsand
marginstoformsweeping
curves.
Fissure Bur
Rotary instruments

10. 1.Taperedafew
degreesinorderto
placewallinclinations
forthecastgoldinlay.
2.Thebursareselected
toproducegroovesfor
retentionoftheproximal
amalgam andinlay
restorations.
Rotary instruments
Tapered Fissure
Bur

11. Thebladesareshorterandcloser
togetherthaninotherburs.
Theyareusedforfinishingand
polishingofmetallicrestorations.
Rotary instruments
Finishingbur

12. Designofdentalbur:
Theburheadmaybe
dividedinto6or8blades
(alsocalledteeth,flutes).
Eachfluteorbladehasa
leadingside“Face”,anda
trailingside“Back”with
anangleinbetween,called
the“fluteAngle”orblade
angle.
Bur Design
Clearance
angle

13. ClearanceAngle:
Itistheanglebetweenthe
backofthebladeandthe
“work”
Itactstodecreasethe
frictionbetweentheback
ofburbladeandthework
ortoothtissuesduring
cutting,andtherefore,
decreaseheatgeneration.
Bur Design
Clearance
angle

14. ClearanceorChipSpace:.
Thespacebetweeneachtwo
successiveblades
Aspacewherethechips
formedduringthecutting
procedurescollectandget
eliminated.
Toosmall,theformedchips
willremainin-betweenthe
burblades,causingits
clogginggenerationofmore
heatand lossof
effectiveness.
Bur Design
Clearance
angle

15. Bur Design

16. RakeAngle:
Ananglecreatedbetweenthefaceofthebladewiththe
radiusofthebur.
Therakeanglemaybepositive,Zero(radial),and
negative,dependingonwhethertheradiallineisahead,
over-lying.Ortailingthefaceofthebladerespectively.
Bur Design

17. Radius
wheretheradiallineisaheadtothe
faceoftheblade.
Apositiverakeangleenablestheblade
tocutmoreeffectively.
makingtherakeanglemorepositive
canonlybeattainedbythinningoutthe
blade.
Thiswillcausethebladetobecome
weakandtoturnandloseits
effectivenessquitemorerapidly.
Bur Design

18. Bur Design
ZeroRakeAngle:wherethe
radiallineisover-lyingtheface
oftheblade.
Apositiverakeangleenables
thebladetocutmoreeffectively
thanazeroone.

19. Bur Design
Radius
Negativerakeangle:wherethe
radiallineistailingthefaceof
theblade.
Apositiverakeangleenables
thebladetocutmoreeffectively
thananegativeone.

21. Cuttingefficiency:
Itistheabilityoftheinstrumenttoremovea
maximumamountoftoothtissueswithaminimumof
effortandtimeinvolved.
Cutting efficiency
Factors influencing the cutting efficiency of burs:
1.Bur design.
2.Composition of the bur.
3.Tissues to be cut.

22. 1.Burdesign:
Thenumberofblades.
Cutting efficiency
Themorepositivetherakeanglethemore
effectiveistheburincutting.