DENTAL BURS Burs are rotary cutting instruments that have bladed cutting heads This includes instruments intended for such purpose as finishing metal restorations amp surgical removal of bone as well as those primarily intended for tooth preparation ID: 1020269
Download Presentation The PPT/PDF document "DENTAL BURS & OTHER MODALITIES OF TO..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
1. DENTAL BURS & OTHER MODALITIES OF TOOTH PREPARATION
2. DENTAL BURS Burs are rotary cutting instruments that have bladed cutting heads. This includes instruments intended for such purpose as finishing metal restorations & surgical removal of bone, as well as those primarily intended for tooth preparation.
3. HISTORICAL DEVELOPMENTEarliest burs were hand made and intented to be use with hand powered finger rings.These were made of stainless steel.Carbide burs introduced in 1947, have now replaced steel burs & steel burs are nowadays used only for some finishing procedures.
4. STEEL BURSSteel burs are cut from a blank steel stock by means of a rotary cutter that cuts parallel to the long axis of the bur. The bur is then hardened and tempered until its vicker’s hardness no. is 800Steel burs perform well at low speed but dull rapidly at high speed.Steel burs cut dentin more efficiently than enamel.
5. CARBIDE BURSTungsten carbide burs are product of metallurgy.The tungsten carbide powder is mixed with powdered cobalt under pressure & heated in vaccum. A blank is then formed & the bur is cut from it with a diamond tool.VHN – 1650-1700Carbide burs perform better than steel burs at all speeds & their superiority is greatest at high speeds.
6. DESIGN CHARACTERISTICSEach bur consist of three parts: 1.shank 2.neck 3.head
7. shankPart that fits in handpiece,accepts the rotary motion & provides a bearing surface to control the alignment & concentricity of the instrument.Design & dimensions vary with the hand piece.Acc. To ADA sp.No.23 there are 5 classes of shanks of which 3 are most commonly used: A.the straight hand piece shank B.the latch type contraangle handpiece shank C.the friction grip contraangle hand piece shank
8. Shank portion of straight hand-piece is a simple cylinder held in the hand-piece by a metal chuckRarely used
9. neckIt is intermediate portion that connects head with the shank.It transmits rotational & translational forces to the head.It tapers from a large cross-section(shank) to a smaller diameter immediately adjacent to the head.This improves access & visibility.
10. headHead is the working part of the instrument, the cutting edges or points that perform the desired shaping of the tooth structure.Its shape & material are closely related to its applications & technique of use.
11. BUR BLADE DESIGNThe actual cutting action of a bur occurs in very small region at the edge of the blade.Each blade has 2 sides- the rake face - the clearance face/trailing edge 3 Angles - the rake angle - the clearance angle - the edge angle Flute / chip space : is the space b/w successive bur teeth/blades.
12. BUR BLADE DESIGN
13. The optimal value of these angles depends upon the: -mechanical properties of blade material -mechanical properties of the material being cut -the rotational speed & diameter of the bur -the lateral force applied by the operator to the handpiece & to the bur.If land is present-primary & secondary clearance angle are presentIf back surface is curved – radial clearance angle
14. FACTORS AFFECTING THE CUTTING EFFICIENCY OF BURSRAKE ANGLE:more +ve the rake angle=greater cutting efficiencyRadial rake angle = more efficient than –ve rake angle+ve rake angle – chips are larger & clog the chip space-ve rake angle – cut chips move away from the bladeFor brittle materials- -ve rake angle desirableMaterials of low hardness eg.stainless steel should be used with –ve rake angle & hard materials eg.carbide burs can be used with +ve rake angle.
15.
16. 2.Clearance angleGreater clearance angle – greater chip space-less edge angle-increased chance of fracture.To overcome this problem Clearance face is curved / landed.3.EDGE ANGLEMore the edge angle – less chances of blade fractureCardide burs are brittle- require greater edge angle
17. 4.No. of teeth/blades & their distributionNo. of teeth – 6-8Increase in no.of flutes-increased heat production & reduced cutting efficiency-good for finishing & polishingA fissure bur with straight flutes produces less temp. rise than one with spiral flutes5.FINISH OF THE FLUTESHighly finished flutes show greater efficiency
18. 6.Heat treatmentUsed to harden a bur made of soft steel. 7.DESIGN OF FLUTE DESIGN2 types of flute endThe relevation cut: flutes come together at the junctions near the diametrical cutting edge.The star cut: the end flutes come together in a common junction at the axis of the bur.The relevation type superior in direct cutting but in lateral cutting both equally efficient
19. 8.Bur diameterVolume of material removed vary with bur diameter os well as torque & energy supplied by power source9.DEPTH OF ENGAGEMENTDecrease in depth of engagement – increase in force intensity on bur & volume of material removed
20. 10.Influence of loadIt is force exerted by dentist on the tool headLoad = 1/rotational speed of the burFor low speed – 1000-1500gmFor high speed – 60-120gm
21. 11.Influence of speedRate of increase in cutting is greater b/w 30000 – 1,50,000rpmWith constant load,rate of cutting increases with rotational speed12.RUN-OUTRefers to the eccentricity or max. displacement of the bur head from axis of rotationwhile the bur turnsAverage value - .023mm
22. BUR CLASSIFICATION SYSTEM: Can be classified in no. of ways:a.)Acc. To the mode of attachment of handpiece -latch type -friction gripb.)Acc. To their composition -stainless steel -tungsten carbide -combinationc.)Acc. To their motion -right bur -left bur
23. d.)Acc. To the length of bur head -long -short -regulare.)Acc. To their use -cutting bur -finishing & polishing burf.)Acc. To their shape -round -inverted cone -pear shaped -wheel shaped -tapered fissure -straight fissure etc.
24. BUR SHAPES ROUND BUR:-used for initial tooth penetration & for placement of retentive grooves-Are numbered as ¼, ½, 1, 2 to 10
25. INVERTED CONE BUR:-head length is approx. the same as the diameter.-portion of rapidly tapering cone with the apex directed towards the bur shank-Used for providing undercuts in tooth prep-numbered as 331/4,331/2,34,35 to 39.
26. PEAR SHAPED BUR-slightly tapered cone with the small end of the cone directed toward the bur shank-normal length – for classI gold foil tooth prep.-long length(L=3W) – for tooth prep. for amalgam-numbered as- 229-333
27. STRAIGHT FISSURE BUR-used for amalgam cavity prep.-modified burs of this design are available-numbered as- 55-59TAPERED FISSURE BUR-slightly tapered cone with the small end of the cone directed away from the bur shank.-numbered as – 168,169-172
28. BUR SIZESOriginal numbering system by SS White dental manufacturing company grouped burs into 9shapes & 11 sizes½ , ¼ were later added for smaller instruments Crosscut was indicated by adding 5OO to the no. of the equivalent non-crosscut size eg.no.57 as 557End cutting bur was indicated by adding 900 to the equivalent size eg.no.57 as 957.Round nose fissure bur was indicated by adding 1 to the equivalent size of the fissure bur eg.no.57 as 157
29. MODIFICATIONS IN THE BUR DESIGNModifications in bur design were seen with the introduction of high speed handpieces:1.Size of the bur2.Reduced use of cross-cuts3.Rounding of sharp tip angles
30.
31.
32.
33. ABRASIVE INSTRUMENTS:Second major category of rotary cutting instruments.Small angular particles of hard substance held in matrix of softer material (binder).Binder can be ceramic,metal,rubber,shellac etc.Rubber & shellac are used for finishing & polishing.Cutting occurs at a large no. of points where hard particles protude from the binder.
34. Abrasive instruments can be grouped as: 1.Diamond Abrasives 2.Non-Diamond abrasives -Molded abrasive instruments silicon carbide(carborandum) Aluminium oxide -Coated abrasive instrument garnet quartz pumice
35. Diamond abrasive instrument:For dental use were introduced in 1942Their preference over tungsten carbide burs is based on their greater resistance to abrasion, lower heat generation & longer lifeConsist of three parts: - a metal blank - powdered diamond abrasive - bonding material
36.
37. On the basis of particle size diamond abrasive can be classified as: coarse : 125-150microm particle size medium : 88-125microm fine : 60-74 microm very fine : 38-44 microm-coarse & medium are used for gross cutting-fine & very fine are used for refining & finishing of tooth preparation.
38. Diamond abrasive head shape & sizesAvailable in shapes & sizes that corresponds to the burs except the smallest diameter bur.Due to lack of any standard & uniform nomenclature it can be selected visually to obtain the desired shape & size.
39.
40. Factors influencing the abrasive efficiency & effectivenessSize of the abrasive particlesShape of the abrasive particles- should be irregularDensity of the abrasive particles- refers to the no. of abrasive particles/areaHardness of the abrasive particles-should be greater than the hardness of the work.Clogging of the abrasive particlesSpeed & pressure
41. Disposable diamond abrasives:“ single patient use” bur is a recent introduction to risk of cross contaminationSome of the marketed disposable diamond burs are cobra, monosteryl, neo, patriot, SS white & spring.
42. Advantages of burs & abrasivesIt is familiar & well known procedure.Precision is obtained i.e. margins are clearly identifiable.It is easy to control the cutting.The practitioner has tactile perception of the extent of cutting.Debris can be removed by water lavage & use of suction.Practitioner’s vision while cutting is relatively good.
43. Disadvantages of burs & abrasivesCutting with these instruments usually causes painVibration usually cracks/fractures toothNoiseConstant use & sterilization can cause them to break downDull burs produce lot of heat & pulpal damageOvercutting if operator loses control or pt. moves inadvertently
44. EVALUATION OF CUTTINGMeasured in terms of effectiveness & efficiency.Cutting Effectiveness: is the rate of tooth structure removal(mm/min or mg/s).Effectiveness doesn’t consider side effects eg. heat, noiseCutting Efficiency: is the % of energy actually producing cutting
45. CUTTING MECHANISM:Rotary instrument cutting can be of 2 types:BLADED CUTTING: with bursABRASIVE CUTTING: with abrasives
46. 245 burMulti purpose or all in one bur.It is a non standard carbide bur that do not conform to the current ADA standard numbering system.It is a pear shaped long length bur.used for amalgam class II cavity preparation.No need to change the bur during cavity prep.
47. Site specific burs for conservative preparation in preventive resin restorationOriginally , smaller burs e.g no.1/2,1 round,331/2 inverted cone were recommended for preparing PRRs.Recently new burs that are thin enough to allow easy penetration into pits & fissures are introduced – FISSUROTOMY BURS (SS white burs, lakewood, new jersey)These burs allow the clinician to prepare the pit & fissure in many cases owing to the smaller surface area of the tip.
48. Fissurotomy burs are available in three configurations:1.Fissurotomy original(1.1mm wide by 2.5mm long)2.Fissurotomy micro NTF(0.7 mm wide by 2.5 mm long)3.Fissurotomy micro STF(0.6mm wide by 1.5mm long) other manufacturers have developed thin diamonds to mimic the fissurotomy shape
49. POLYMER BURRecently , a unique polymer instruments, the SMARTBUR has been introducedSMARTBURS are available in round shapes – RA no.2, RA no.4, RA no.6 with an innovative flute design.It has hardness less than healthy enamel & dentin but harder than carious dentin to remove carious tooth structure without damaging healthy tooth structure.
50. Polymer burs are used at slow rotary speed of 500-800rpm using light touch with a slow speed handpiece & a latch contra angle attachment.
51. PrecautionsPulpal precautions:-damage occur by exposure to vibration, heat,dessication.-it is hazardous to use them in prep. Deeper than .5-1mm from the pulp-for removal of dentin 2mm or more from the pulp carbide burs are efficient.Soft tissue precautions:Rubber dam, cotton rolls, retractors must be practiced to avoid soft tissue injury.
52. Eye precautions-Protective glasses are always indicated when rotary instrumentation is being usedInhalation precautions-Aerosols & vapors created by cutting tooth structure are a health hazard.-Use of evacuators, face mask, rubber dam protects the patient from inhalation.
53. LASER TOOTH PREPARATIONFirst introduced to dentistry in 1989.Introduction of yttrium-scandium-gallium-garnet(YSGG) allowed for the preparation of enamel, dentin & carious tooth structure.The YSGG laser cuts hard tissues using a pulsed high energy photonic laser beam at 2780nm.The focussed laser beam allows for precise tooth structure removal in T/t of carious lesions of all sizes.
54.
55. KINETIC CAVITY PREPARATIONThe concept of application of Kinetic energy in the field of dentistry was conceived as early as 1945, Dr.R.B.Black‘AIR ABRASIVE TECHNIQUE’ technique was invented in 1951 which is now modified and improved as Kinetic Cavity Preparation (KCP) system
56. THE COMPONENTS OF KCP UNIT1. Precision built device containing a source of suitable gaseous propellant and means of regulating its pressure.2. Reservoirs for containing abrasive materials. 3. An intricately designed disposable handpiece where tip is made up of sintered tungsten carbide with an inner diameter of 0.45mm.
57. 4. Device for recovering spent abrasive powder and debris5. Master switch for activation of the machine and Foot control. 6. The other components are: Movable cabinet, Gauges and dials for controls, a suction hood with an accessory.
58. Abrasive particles:The KCP system utilizes particles of alpha alumina.The particle size varies form 10-50u with an average size of 27u. It has a Mohs scale hardness of 9.04. Magnesium carbonate or dolomite is also used as abrasive but it is chosen for prophylaxis as it has properties of softness and less weight.
59. Propellant:Though compressed air can be used as a propellant, the gas propellant of choice is carbon dioxide because the former is not free from moisture. Carbon dioxide with average pressure of 700-1300 PSI which is being reduced to 80-45 PSI at the tip of the handpiece is used.The flow of gas is approximately 1/3 cubic foot/minutes.
60.
61. ADVANTAGES OF KCP SYSTEM:1. Performs conservative cavity preparation rapidly and precisely usually without anesthesia 2. Old filling materials like composites can be removed quickly. 3. Modifies enamel and doubles the bond strength of dentine thereby allowing a strong bond without acid etching.
62. 4. Facilitates the maintenance of a dry operating field.5. It eliminates objectionable features of vibration bone conducted noise, pressure and heat. By eliminating vibration, the KCP system also reduces the risk of microfracture and chipping which may lead to premature failures of the restoration. 6. It not only saves steps and time but also make it possible for a dentist to perform multiquadrant restorations in a single visit. A typical KCP takes just 20-30 seconds. This speed, combined with the elimination of LA in most cases maximize productivity
63. DISADVANTAGES OF KCP SYSTEM1.Use limited to areas of good vision.2.No Tactile sensation between the handpiece and tooth surface to act as a guide while cutting. 3. Precise angles and margins difficult to obtain. 4. Mirror surface was made useless in a short of time by rebounding the abrasive particles.5.Possible ill effects due to inhalation of abrasive particles
64. The drawbacks of Airbrasive Technique' can be eliminated as follows:1.Fibroptic light, halogen light improve the field of vision. 2.Though there is no sense of touch between the handpiece and tooth surface, the improved visibility can guide in cutting.3.Conservative cavity preparation need not have precise angles and margins.4. Scratch free mirror be used. 5. Extensive research regarding the ill effects of abrasive particles concluded that the amount of alumina particle inhaled is far below the detectable limits
65. INDICATIONS1.Mainly for MID, specially for composites without the use of acid etching.2.Sealant therapy.3.For pits & class I preparation4.Removal of old composites, amalgam filling, # porcelain facing & porcelain jackets.5.For removal of high points on crown6. To remove casting irregularities & to modify surface that will receive porcelain. It is done with 50u alumina particles for 30sec.7. For prophylaxis8. Moderate class II & V9. Access opening in Endo therapy10. As an adjunct to rotary instruments for all dental preparations.
66. IF“ THE ART OF BEING WISE IS THE ART OF KNOWING WHAT TO OVERLOOK WHAT NOT”Thank you