Principles of Tooth Prep & Handpieces & Burs PDF

Dfpd311: prosthodontics 1 PRELIMS: LECTURE 3 and 4: INDIVIDUAL TOOTH PREPARATION & HANDPIECE AND BURS LECTURE BY: DR. RAMONCITO VALDEZCO - DEPARTMENT OF CLINICAL DENTAL SCIENCES 3rd YEAR: 2ND SEMESTER – S.Y. 2022 - 2023 INDIVIDUAL TOOTH PREPARATION...

Dfpd311: prosthodontics 1 PRELIMS: LECTURE 3 and 4: INDIVIDUAL TOOTH PREPARATION & HANDPIECE AND BURS LECTURE BY: DR. RAMONCITO VALDEZCO - DEPARTMENT OF CLINICAL DENTAL SCIENCES 3rd YEAR: 2ND SEMESTER – S.Y. 2022 - 2023 INDIVIDUAL TOOTH PREPARATION FACTORS AFFECTING RETENTION AND RESISTANCE FORM PRINCIPLES OF TOOTH PREPARATION I. AXIAL WALL HEIGHT I. MECHANICAL PRINCIPLES ® Function ® Restoration must stay in the abutment when the patient masticates or speak ® Primary source of retention for the crown and bridge are the opposing walls and not the cement (cements are soluble to oral fluids) ® Three types of forces that can be directed against the restoration during function ® 4 walls parallel to the long axis of the tooth ® Buccal, lingual, distal, mesial TIPPING FORCE ® Occlusocervical height – axial wall height ® Less than 2mm will offer a very limited interocclusal distance between the preparation and opposing natural tooth à there will be thin crown ® Tipping force from the buccal à the crown will be displaced towards the lingual/palatal ® Tipping force from the lingual à the crown will be displaced towards the buccal ® Fulcrum- there will be leverage ® Manner of displacement – from fulcrum ® Horizontal forces ® Axis of rotation: direction in which the crown will be ® Tend to remove the restoration buccally or lingually removed from the tooth preparation ® Which crown will be removed? preparation 1 or preparation TWISTING OR ROTATIONAL FORCE 2? Preparation 1 will be dislodged because its axial wall height is lower (axis of rotation is free and no tooth block) II. TAPER OF PREPARATION ® Tend to rotate the crown or dislodge ® Only happen in a single unit restoration (for crowns) ® Mandibular second premolar can be rotated because it has ® Same axial wall height but the axis of rotation of 1 is free naturally rounded crown and no tooth block while in 2 there is blockage ® Over taper in preparation 1 PATH OF INSERTION FORCES ® Don’t make a straight or diverging axial wall ® Slight converging towards occlusal ® Ideal taper of the preparation is 3-5 degrees ® Less retention if over 3-5 degrees III. CIRCUMFERENTIAL IRREGULARITY ® Vertical ® Apically directed: removed towards the apex (hard bolus of food) ® Occlusally/incisally directed: removed towards the occlusal (sticky foods) ® Irregular shaped of the crown must be maintained ® Rotational forces will be blocked by the circumferential irregularities ® If crown is rounded à it will twist/rotate and be removed C.C. SANTOS [DMD 3-Y2-3] 1 Dfpd311: prosthodontics 1 PRELIMS: LECTURE 3 and 4: INDIVIDUAL TOOTH PREPARATION & HANDPIECE AND BURS LECTURE BY: DR. RAMONCITO VALDEZCO - DEPARTMENT OF CLINICAL DENTAL SCIENCES 3rd YEAR: 2ND SEMESTER – S.Y. 2022 - 2023 IV. OCCLUSAL IRREGULARITY Beveled shoulder chamfer ® Marginal ridges can be removed (mesial and distal) ® Occlusal irregularities of the normal anatomy of the crown should be followed shoulder V. STRUCTURAL DURABILITY VI. FINISH LINE REQUIREMENTS shoulder ® The point at which the preparation terminates on the tooth surface. It is the junction between the prepared and Knife edge unprepared portion of the tooth ® Purpose: marginal seal so that food debris, oral fluids, and bacteria will not enter the crown ® Always check the finish line of the preparation by looking at ® Poor marginal seal will lead to foul breath and the occlusal demineralization ® Types of finish line: A. Knife edge § A very thin finish line § Used for mandibular incisors because they are small B. Chamfer finish line § Obtuse angle gingival termination § Rounded § Used for metal restorations C. Shoulder finish line § Right angle gingival termination § Ledge/flat § Has corners § Used in porcelain crowns II. BIOLOGIC PRINCIPLES ® Should be compatible with the tissues à do not cause injury D. Beveled shoulder finish line to the pulp and supporting structures § Same with shoulder but has a small beveled ® Preservation of tooth structure (pulp might be hit if more than 2mm and will result to pulpal irritation) ® Speed of reduction (reduced the tooth intermittently – stop every 10 seconds to avoid heat generation) ® Instruments age and use of pressure (don’t use dull instrument; do not exert pressure because it will create friction and heat generation) ® Use of coolants (there should be air and water) ® Periodontal consideration (avoid lacerating the marginal gingival area) § Supra-gingival finish line – located above the gingival gingiva § Equal gingival finish line – the finish line is exactly located at the level of marginal gingiva § Sub-gingival finish line – located within the sulcus III. ESTHETIC PRINCIPLES ® Same color, form, size, shape ® Under reduction à bulky crown o bridge C.C. SANTOS [DMD 3-Y2-3] 2 Dfpd311: prosthodontics 1 PRELIMS: LECTURE 3 and 4: INDIVIDUAL TOOTH PREPARATION & HANDPIECE AND BURS LECTURE BY: DR. RAMONCITO VALDEZCO - DEPARTMENT OF CLINICAL DENTAL SCIENCES 3rd YEAR: 2ND SEMESTER – S.Y. 2022 - 2023 HANDPIECE AND BURS ® Rotary instruments are used to complete different functions § Contraangle attachment in the cutting polishing, and finishing of tooth structure and ¾ Latch-type rotary instruments the restoration process ¾ Mandrel THE EVOLUTION OF ROTARY EQUIPMENT ® Prophylaxis angle ® 1940s ¾ Used during polishing procedures to hold the § Introduction of rotary instruments prophylaxis cup and bristle brush § Belt-driven handpiece ¾ Two types § Development of diamond cutting burs 1. Plastic disposable “prophy” angle 2. Metal ‘prophy” angle ® 1950s § Invention of tungsten carbide § Development of the air-driven turbine handpiece DENTAL HANDPIECE ® The handpiece is the most frequent used piece of machinery in dentistry ® It provides power to a rotary instrument that is used to complete the actual cutting or polishing of tooth structure and castings LOW-SPEED HANDPIECE ® Design § Straight in appearance § Standard length and shorty § Speeds range from 10,000 to 30,000 rotations per minute (rpm) § Powers the rotary instrument in both a forward and a HIGH-SPEED HANDPIECE backward motion ® Design § One-piece unit with a slight curve § Operated by air pressure § Operates at speeds as high as 450,000 rpm § Maintains a water-coolant system § Friction-grip locking system for rotary instruments § Fiberoptic lighting ® Uses § Clinical – used inside the patient’s mouth ¾ Removal of soft decay and finishing of cavity preparations ¾ Finishing and polishing of restorations ¾ Coronal polishing and removal of stains ® Uses ¾ Porcelain adjustments § Removal of decay ¾ Root canal treatment § Removal of old or faulty restorations § Reduction of the crown portion of a tooth in preparation for a crown or bridge § Laboratory § Preparation of an outline and retention grooves for a ¾ Trimming and contouring of temporary crowns new restoration ¾ Trimming and relining of removable partials and § Finishing or polishing of a restoration dentures § Sectioning of a tooth during a surgery ¾ Trimming and contouring of orthodontic appliances ULTRASONIC HANDPIECE ® Attachments ® Design § Straight attachments § Attaches to the dental unit ¾ Long-shank laboratory bur § Powered by electricity ¾ Prophylaxis angle attachments § Primarily used for prophylaxis appointments C.C. 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RAMONCITO VALDEZCO - DEPARTMENT OF CLINICAL DENTAL SCIENCES 3rd YEAR: 2ND SEMESTER – S.Y. 2022 - 2023 § Attachments similar in appearance to scaling ® Disadvantages instruments § Cannot be used on teeth with existing restorations § Delivers a pulsating spray of water LABORATORY HANDPIECE ® Types of ultrasonic scaler ® Design MAGNETOSTRICTIVE à vibrations range from 24,000 to § Operates at speeds as high as 20,000 rpm 42,000 cycles per second § Uses laboratory burs PIEZOELECTRIC à vibrations range from 29,000 to § Greater torque than that of handpieces used intraorally 50,000 cycles per second SONIC ® Vibrations range from 2500 to HANDPIECE MAINTENANCE 7000 cycles per second ® General considerations § Wear personal protective equipment and follow ® Uses universal precautions § Removal of calculus § Clean debris from the external surface § Removal of stains § Clean the internal components of the handpiece § Removal of bonding materials from the tooth surface § Handpiece must eb dry before being packaged after orthodontic appliances are removed § Wrap the handpiece for sterilization § Removal of cement after orthodontic bands are removed § Sterilize the handpiece § Wipe the light port on the fiber-optic with an alcohol LASER HANDPIECE swab to remove any excess lubricant ® Design § Laser light beam, conducted through a fiberoptic cable, ROTARY CUTTING INSTRUMENTS instead of rotary instruments ® Three basic parts to a rotary instrument § Resemblance to a standard handpiece § Shank: portion that fits into the handpiece § Water-coolant system ¾ Straight shank § Air-coolant system ¾ Latch type shank ¾ Friction grip shank § Neck: portion of the rotary instrument that connects the shank and the head § Head: the cutting, polishing, or finishing portion ® Uses § Cauterizing soft tissue § Vaporizing decayed tooth structure ® Advantages § Usually painless § Generally no need for anesthesia § Speed of procedure C.C. 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RAMONCITO VALDEZCO - DEPARTMENT OF CLINICAL DENTAL SCIENCES 3rd YEAR: 2ND SEMESTER – S.Y. 2022 - 2023 DENTAL BURS ® Rotary instruments with sharp cutting head ® Uses: § Tooth preparation § Excavation of decay § Finishing cavity walls § Finishing restoration surfaces § Taking out old fillings § Finishing crown preparations § Separating crowns and bridges § Adjusting and correcting acrylic temporaries Carbide burs Round bur Flame/bullet ® Coarse grit shaped bur Long, tapered, flat-end bur ® Medium grit – for abrading ® Fine grit- for finishing/ smoothening of preparation Football shaped bur Long, tapered, rounded-end bur ® Carbide burs: used to cut tooth surface § Name based on the shape, length, end § Flat end – shoulder finish line § Round end- chamfer finish line § Sharp edge- knife-edge finish line ® Diamond burs: used to abrade tooth surface § Based on the shape, length, end Barrel- Football- shaped shaped diamond Round diamond diamond Long, Long, short, tapering tapering straight round end flat end flat end ® Thin-tapered diamond bur- used specifically for proximal preparation C.C. 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