Instruments in Fixed Prosthodontics (October 6 University) PDF

INSTRUMENTS in Fixed Prosthodontics by Dr. Sara Alaa El Din Lecturer of Fixed Prosthodontics ILOs for this lecture: List various instruments used in field of fixed prosthodontics and their individual use. Methods of sterilization Compare between different instrume...

INSTRUMENTS in Fixed Prosthodontics by Dr. Sara Alaa El Din Lecturer of Fixed Prosthodontics ILOs for this lecture: List various instruments used in field of fixed prosthodontics and their individual use. Methods of sterilization Compare between different instruments and their use in fixed prosthodontics to choose the proper instrument for each preparation design. Use the appropriate instrument during tooth preparation and finish line preparation.  Dental Instrument Definition Tool or device used to provide dental treatment  1-Diagnostic instruments Instruments are classified 2-Cutting according to their instruments uses: 3-Restoring instruments  1-Hand cutting instruments 2-Rotary cutting Cutting instruments instruments are classified into: 3-laser equipment 4-Other equipment(air abrasion) A-Hand cutting instruments These are light weight handheld instruments constructed from stainless steel, carbon steel, carbide or other alloys(Ni,Cr,Co). Carbon steel(increase hardness and decrease tarnish and corrosion. Stainless steel(resist tarnish and corrosion). Carbide(improve cutting efficiency and durability).  They possess numerous designs for varied purposes as (probes, excavators, carvers, Hand cutting instrument chisel). composed of three parts: Hand le shaft Blade(working point ,working end)  B-Rotary cutting instruments These include a wide variety of small tools held and operated by : Electric motor driven or Air driven (air or water turbine hand piece) Hand piece: device holding instruments, transmitting power to them and for positioning them intraorally. Air driven hand piece is the most popular type. Hand piece are classified according to shape 1-Straight hand piece 2-Contra angle hand piece  Rotary speed range Rational speed of an instrument is measured in revolution per minute. Speed ranges are generally recognized : Low or Slow speeds below 12,000 rpm Medium or Intermediate speeds 12,000 to 200,000 rpm High or Ultra high speeds above 200,000 rpm Low speed cutting High speed cutting Requires a relatively heavy force Faster with less pressure, less vibration application Produce vibrations Better control Several teeth can be treated at the same appointment Used for Less apprehensive to the patient because of low vibration Preparation of grooves and Pinholes Cleaning teeth Finishing and polishing Rotary Cutting Instruments Consists of Three Parts: 1-Shank: 1-Long shank: used in straight hand piece. 2-Short latch shank : used in latch contra angle handpiece. 3-Friction grip shank: ultra high speed handpiece. 2-Neck: Is the intermediate portion of an instrument that connects the head to the shank. 3-Head: Is the working part of the instrument, the cutting edge or points which perform the desired shaping of tooth structure.  Rotary instruments are further divided into: 1. Burs: cutting or shaving action (bladed). 2. Abrasives: remove tooth structure by abrading the surface. a. Diamond stones. b. Discs. 1. Burs : cutting burs and finishing burs ·They are made of either steel or tungsten carbide. ·Burs possess blades that shear tooth structure. ·They are best used for making precise intra-coronal preparation features (grooves, boxes & pinholes). ·They are also used for smoothening surfaces in enamel & dentin. Grooves: are placed using a tapered fissure bur with square end. Boxes: are placed with a straight fissure burs that are parallel walled.  Pinholes: a 1/2 round bur first used to the required depth & then refined to the final tapered form using a tapered fissure bur.  Cutting burs are made with (6- 8) blades. ·Finishing burs possess 12 blades or even more. Burs commonly used in fixed prosthodontic preparations are: Straight or tapered fissure burs →long & short. End cutting burs →repositioning finish lines as it is a cylindrical fissure bur. its only cutting surface is at its end.  Number 1/2 round bur → initial pinhole access Number 4 or 6 round bur → for removal of deep caries. 2. Abrasives: I. Diamond stones: ·These are made of diamond chips bonded to blanks (heads) machined to the desired shapes of the instrument. ·Each chip cuts away a minute quantity of tooth structure. ·Diamond stones are most effective for grinding enamel (2 or 3 times as fast as burs). Diamond stones may be divided according to : a. Size and coarseness of the chips : Coarse or medium: Used for rapid removal of the tooth structure. Fine grit: Used for smoothening of the prepared surfaces. Color Coding & Diamond Grit Size: b. Shape and size of the head : Tapered with round end : Use: ·Axial reductions (Buccal-lingual-mesial-distal) with their sided (6◦taper). ·Chamfer F.L with their ends 0.3mm. Indications: i. Cast metal restorations. ii. Palatal or lingual surface of veneered(PFM ) crowns. Tapered with flat end: Use: ·Axial reductions with their sides & Shoulder ·F.L with their ends. Indications : I. All ceramic crowns. ii. Facial surface of partial and full veneered crowns. Needle stone A) Long needle: Use: Interproximal initial access without causing injury to the adjacent tooth. Produces chisel (knife edge) F.L. Short needle : Use: For interproximal initial access in tight contact cases. Wheel diamond stone : Use: ·Palatal fossa of anterior teeth. ·Incisal edge reduction of anterior teeth. Occlusal surface reduction of molars & premolars. Tinker (Torpedo) Use: Bevel finish line or to make shoulder with bevel. Football (flame) stone: ·For the reduction of palatal fossa of anterior teeth.  Cylindrical stone : shaped like cylinders For accentuating (achieving) shoulder finish lines. Dental rotary instruments may be supplied as : A. Mounted type : ·Supplied with their mandrel firmly attached to the working points as all diamond stones & burs. B. Demounted type : These are mounted to a shank (mandrel), which carries a variety of interchangeable demounted rotary points. They are more economic than the mounted type. The mode of attachment between the working point & mandrel is a hole and screw in lock system or friction grip. II. Discs : These were used for proximal slicing or reduction of all types of preparations. supplied in mounted or demounted forms... used with conventional & standard speeds.  1. According to Material : Diamond or metal discs Classification used for proximal slicing in lab of Discs : Carborundum discs for removing sprues & sectioning F.P.D. Sand paper discs for finishing &smoothening preparation. 2. According to their Diameter: Small 3/8 " Medium 5/8 " Large 7/8 " 3. According to their Shapes: 1-Flat shaped disc 2-Cup shaped disc: for reduction of distal surface of mandibular posterior teeth 4. According to size of abrasives: Coarse, medium or fine depending on the particle size. 5-According to side of abrasive material: They also may be supplied as safe sided or double sided. Safe sided :abrasive material on one side Double sided: abrasive material on both sides for economic purposes. Various shapes of abrasives: ❑ Round and oval ❑ Inverted cone ❑ Barrel shaped ❑ Pear shape ❑ Wheel brush C. Lasers : Beam of high intensity light. Soft tissue treatment: Coagulation & hemostasis, Gingival retraction & crown lengthening may also be done.  Hard tissue treatment (surface treatment of metals, ceramics & enamel). Commonly used lasers are argon laser, Co2 & ND:YAG laser. D-Air abrasion Stream of abrasive particles projected at a tooth surface with pressure. Tooth abrasion without heat, vibration or noise. Disadvantages : No tactile sense Abrasive dust interferes with vision Difficult determination of cutting progress  Air Abrasive Equipment Uses: Stain removal Debriding pit and fissures prior to sealing Micromechanical roughness of surface to be bonded to (enamel, cast metal alloys, porcelain). Sterilization and Disinfection of Instruments : The goal is to protect ourselves and our patients from cross infection. Methods of Sterilization : 1. Steam Autoclave (steam under pressure) · Most reliable & effective method for destroying the pathogenic organisms. 2. Unsaturated Chemical Vapors : ·Effective for all metal instruments. Disadvantages: Odor and need ventilation 3. Dry heat: For instruments that can withstand very high temperature.  4. Chemical Solutions : For materials that cannot withstand heat sterilization. Not recommended for sterilizing metal dental instruments. To be effective, the solution must come in contact with the organism for several hours. References