prostho midterm quiz

Rotary Instruments

are used to complete different functions in the cutting, polishing, and finishing of tooth structure and the restoration process

1940

Introduction of rotary instruments

 Belt-driven handpiece

 Development of diamond cutting burs

1950

Invention of tungsten carbide

Development of the air-driven turbine handpiece

Handpiece

is the most frequently 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

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 backward motion

Long-Shank Laboratory Bur

Prophylaxis Angle Attachments

Low-Speed Attachments: Straight Attachments

Latch-Type rotary instruments

mandrel

Low-Speed Attachments: Contraangle Attachments

Prophylaxis Angle

Used during polishing procedures to hold the prophylaxis cup and bristle brush

Two types

• plastic disposable prophy angle

• metal prophy angle

High-Speed Handpiece

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

Ultrasonic Handpiece

Attaches to the dental unit

 Powered by electricity

 Primarily used for prophylaxis appointments

 Attachments similar in appearance to scaling instruments

 Delivers a pulsating spray of water

Magnetostrictive Ultrasonic Scaler

Vibrations range from 24,000 to 42,000 cycles per second

Piezoelectric Ultrasonic Scaler

Vibrations range from 29,00 to 50,000 cycles per second.

Sonic Ultrasonic Scaler

Vibrations range from 2500 to 7000 cycles per second.

Laser Handpiece

Laser light beam, conducted through a fiberoptic cable, instead of rotary instruments

Resemblance to a standard handpiece

Water-coolant system

Air-coolant system

Laboratory Handpiece

Operates at speeds as high as 20,000 rpm

Uses lab burs

Straight

Latch

Friction

Three basic parts to a rotary instrument

Dental Burs

Rotary instruments with sharp cutting head

PARTIAL VENEER CROWN

Restoration that covers only a portion of the clinical crown

Three Quarter Crown

Seven Eight Crown

Reverse Three Quarter Crown

Mesial Half Crown

TYPES OF PARTIAL VENEER CROWN

Incisal Reduction

Using the donut shape or round end tapering diamond reduce the edge by at least 1.0 to 1.5 mm

LINGUAL REDUCTION

Use football or donut shaped diamond and reduce approximately 0.7 to 1.0 m

CINGULUM REDUCTION

Lingual Chamfer

0.5 mm

PROXIMAL REDUCTION

Using a round end and thin tapered diamond, reduce the proximal by moving the bur from lingual to facial, do not break contact

OCCLUSAL PREPARATION

Using a round end tapered diamond, reduce the inner incline of buccal cusp and both inner and outer incline of lingual cusp by at least 1.5 to 2.0 mm

AXIAL WALL PREPARATION

Using the round end tapered diamond reduce the axial walls by 0.5 mm. and establish a supra gingival chamfer finish line

PROXIMAL PREPARATION

Reduce the proximal surface by moving the bur from lingual to facial surface

FACIOLINGUAL PREPARATION

Reduce the lingual surface to develop a chamfer 0.5 mm. in depth at the cervical finish line, break distal contact and reduce the distofacial surface.

AXIAL GROOVES

3 mm. long

0.5 mm. depth

57-010

Bur for incisal reduction

7404-014

Bur for lingual clearance

850-012

Proximal Reduction

HYDROPHILIC

READILY WETTABLE BY GYPSUM

HYDROPHOBIC

RESISTANT TO WETTING

Rubber Impression

Polysulfide rubber, condensation silicone, polyether, addition silicone

Polysulfide rubber

Dimensional stability less than polyether and addition silicone, long setting time

Condensation silicone

Odorless, dimensional stability less than polysulfide

Polyether

Addition polymerization

Addition silicone

Dimensionally stable, delayed pouring