5- Instruments

General Classification of Operative Instruments

Diagnostic Instruments

  • Examples: Mouth mirrors, explorers.

Cutting Instruments

  • Hand Cutting Instruments: Hatchets, chisels.

  • Rotary Cutting Instruments: Burs, stones.

Condensing Instruments

  • Types: Hand and mechanical plastic instruments.

Finishing and Polishing Instruments

  • Hand Instruments: Interdental finishing strips.

  • Rotary Instruments: Finishing burs, rubber cups.

Isolation Instruments

  • Examples: Rubber dam, saliva ejector, cotton roll holder.

Miscellaneous Instruments

  • Examples: Tweezers, pliers, and others.

Hand Instruments

Parts of Hand Instruments

  • Three Parts:

    • Handle/Shaft: For gripping, may have various designs for control.

    • Shank: Connects working end to handle, can be straight or angled.

    • Working Part: Carries out specific functions.

Handle or Shaft

  • Design: Straight, smooth, serrated for better grip.

  • Identifying Marks: Include serial number, designer name, and specific identifying marks.

Shank

  • Function: Attaches the working end to the handle; tapers down to starting point of working part.

Types of Shank Angles

Importance of Contra-Angling

  • Enhances accessibility, balance, and vision during procedures.

Shank Types:

  • No Angle: Straight shank.

  • Mono-Angle: One angle shank.

  • Bin-Angle: Two angles shank.

  • Triple Angle: Multiple angles shank.

Instrument Formula

  • Four Number Formula:

    1. Width of Blade

    2. Angle of Cutting Edge

    3. Length of Blade

    4. Angle of Blade

Chisels and Excavators

Types of Chisels

  • Straights and Angled

  • Used primarily for cutting enamel.

Excavators

  • Used for dentin cutting, vary in thickness and shape.

Instrument Grasping Techniques

Types of Grasp

  • Pen Grasp: Commonly used, held similar to writing.

  • Palm & Thumb Grasp: Often used for posterior teeth.

Purpose of Rests

  • Stabilize working hand, prevent soft tissue injury.

Guards and Sharpening

Importance of Guards

  • Protect soft tissues during procedures.

Sharpening Instruments

  • Devices Used: Arkansas stones, abrasive disks.

  • Importance: Enhances efficiency, reduces force, minimizes patient discomfort.

Advantages of Hand Instruments

  • Conservative cutting, reduced heat, efficient cutting, smoother finishes, longer lifespan.

Power Cutting Instruments

Types

  1. Rotary Equipment: Common for substantial tooth structure removal.

  2. Ultrasonic Equipment: Removes tooth material via ultrasonic energy.

  3. Air Abrasion Equipment: Uses high-pressure gas to remove material.

  4. Water Lase Equipment: High-intensity light removal.

Rotary Instruments Overview

Operation Speed Ranges

  • Various speeds for different surgical needs: Low (2,000-10,000 rpm), Intermediate (10,000-100,000 rpm), and High Speed (above 100,000 rpm).

Bur Classification

  • Cutting Points: Burs (flutes, blades) and stones (grits).

Bur Design and Cutting Efficiency

Clearance Angle

  • Reduces friction and heat during cutting.

Factors Affecting Efficiency

  • Bur design, material, pressure, speed, and the tissue being cut.

Heat Generation in Rotary Cutting

Causes of Heat Generation

  • Increased speed, pressure, area of cutting, and time can elevate heat levels.

Effects of Heat Generation

  • Potential risks include thermal pulp irritation and discomfort for both patient and operator.

Control of Heat Generation

Strategies

  • Decrease frictional heat by managing speed, pressure, and area.

  • Use cooling methods like air-water sprays.

Eccentricity in Rotary Tools

Definition

  • Described as the displacement of the rotary tool’s axis exceeding 0.025 mm.

Effects of Eccentricity

  • Reduced cutting efficiency, increased heat generation, and discomfort.

Diamond Burs

  • Different grades for cutting and polishing surfaces.

References

  • Operative Dentistry: Modern theory and practice.