fixed prosthodontics Dental Rotary Instruments

Instruments used for tooth preparation The dental instruments used for tooth praeparation are a rotary cutting or abrading instrument . Rotary instrument are tools held and operated by a hand piece (air turbine) or by electric motor (micromotor) Air turbine is : - A high speed rotation 40,000 – 100,000 r.p.m -Ulra – high speed rotation 100,000 – 500,000 r.p.m and micromotor is low speed rotation 3000 – 4000 r.p.m

Air turbine

micromotor

Dental units

Dental instrument It’s the tool or device used for a specific type of dental work or procedure in prosthodontics These instruments used for cutting and reducing the hard tissue of tooth Dental instruments divided to types : 1- diagnostic ( probe , twisser , mirror) 2- cutting (hand , rotary ) 3- restoring ( ammalgam condensor , excavator , …..etc.)

Hand instrument made from stainless steel and consist of three part : Cutting instruments Rotary instruments Hand instrument ( chisel , hatchet , hoes excavator , angle former , gingival trimmer . Hand instrument made from stainless steel and consist of three part : 1- handle , 2-shank 3- blade

Blade (cutting edge) Shank Handle (shaft)

Rotary instruments divided to : Cutting abrasive Carbide burs 1-Diamond burs 2- Discs 3- stones 4- rubber wheels Made from 1- tungsten carbide 2- steel carbide

Rotray instruments consist of three parts : 1- shank 2- neck (shaft) 3- head Shank design 1 – long shank – used for straight hand piece (low speed) shaft Shank head

2- short latch shank – used for contra-angle (low speed) 3- friction grip shank - used for high speed hand piece head shank shaft

Dental burs According shank According to shape According to composition friction grip short shank long shank short latch Round Flat Fissure Wheel Football Pear Bud Diamonds Tungsten Steel carbide

Carbide burs Burs possess blades that shear (cut) tooth structure . They are used for making precise intracoronal preparation features such as placing groove ,and boxes . And they are used for smoothing surface in enamel and dentin They are not used for bulk reduction because to producing undulations on the tooth surface 1- Twelve-fluted carbide bur Its used for highly smoothing of prepared surfaces of tooth Because of its blades in a diagonal to the instrument shaft Its have a torpedo shape

Twelve-fluted carbide bur

2- Plain fissure bur Its tapered and cylinder shape its used for palcing groove and boxes and they also used for finishing of preparation (smoothing) Groove seating

Diamond durs These are made from diamond chips bonded to blanks (heads) . Diamond burs used for griding enamel and dentin surfaces Diamond burs may divided according to : 1- coarseness ( medium grit - fine grit ) 2- shape Medium grit Fine grit

1- Tapered round-ended bur Use ; For axial reduction (buccal –lingual – mesial – distal ) with 6 grades taper And for chamfer finish line 0.5mm Indication : 1- full metal crown 2- palatal surface of full ceramic crown

Depth marking Axial reduction Chamfer forming

2- Tapered flat-ended bur Use : Axial reduction with their surfaces anf form shoulder finish line Indications 1- full ceramic crown 2- facial surface of metal ceramic crown

3- Long needle bur Use : For interproximal initial access without causing injury to adjacent tooth and to form knife – edge (chisel) finish line )

4 – torpedo bur Used for formating the bevel shoulder finish line in full ceramic and netal-ceramic crowns

5 – wheel-shaped bur Used for reduction of occlusal surface , for reduction incisal edge reduction and also used for reduction of palatal fossa of anterior teeth

6 – football-shaped bur Used for occlusal reduction and for reduction of palatal fossa of anterior teeth

7- depth marking burs Depth marker Round bur o.16 , o.15

Burs kit of tooth preparation

Discs and rubber wheels

Plaster (stone) cuters Fine fissue bur

Diamond disc Wheel stone Felt wheel Stones

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