4. DH170 LO4: Class and Design of Perio Instruments

What is the primary focus of Learning Outcome 4 (LO 4) in Dental Hygiene Principles 1 (DH 170)?

To explain instrument design and select appropriate instruments to be utilized in basic periodontal instrumentation.

List the three main structural parts of a periodontal instrument.

1. Instrument Handles, 2. Instrument Shanks, and 3. Instrument Working-Ends.

What is a key factor addressed by ergonomic instrument design?

Instruments with ergonomic design help prevent musculoskeletal injury during instrumentation.

What handle characteristics must clinicians consider to prevent musculoskeletal injury?

Instrument weight, handle diameter, taper, and texture.

Define Pinch Force.

The force used to grasp the handle during instrumentation.

What consequence does repetitive forceful pinching have, and what exacerbates muscle cramping?

It can be a risk factor for carpal tunnel syndrome; more pinch force causes muscle cramping.

List the recommended characteristics for an ideal instrument handle.

Lightweight, large diameter, tapered, and possessing raised texturing.

What handle characteristics should be avoided?

Heavy, solid metal, small diameter, nontapered, and no texturing.

When is a periodontal instrument considered balanced?

A periodontal instrument is balanced if the working-end is centred with the midline of the handle.

What is the significance of using an instrument that is NOT balanced?

It is difficult to use and stresses the muscles of the hand and arm.

Why are the shanks of most periodontal instruments bent in one or more places?

To facilitate placement of the working-end against the tooth surface.

How can a clinician determine if an instrument has a simple shank or a complex shank?

If the working-end toe (or tip) is facing the clinician, a simple shank will appear straight; a complex shank will have side-to-side bends.

Which shank type is adequate for anterior teeth, and which is required for posterior teeth?

A simple shank is adequate for anterior teeth. A complex shank is needed for posterior teeth to allow reach to the mesial (M) and distal (D) root surfaces.

Define the Functional Shank.

The functional shank begins below the working-end and extends to the LAST bend in the shank nearest the handle.

Define the Lower Shank (also called the Terminal Shank).

The portion of the functional shank nearest to the working-end; it begins below the working-end and extends to the FIRST bend in the shank.

Why is it important to identify the Lower Shank?

It is an important visual clue for selecting the correct working end.

What characterizes "After Fives" or specialized instruments with extended lower shanks, and what is their purpose?

They have lower shanks that are 3 mm longer than standard shanks; they are designed for use in deep periodontal pockets.

How are Mini Gracey Blades different from standard blades, and when are they used?

Mini Gracey Blades are 50% shorter and 10% thinner; they are used for narrow teeth and/or narrow pockets.

What determines the strength of an instrument shank?

The type of metal the shank is made of, and the diameter of the shank.

Which shank type removes heavy calculus deposits?

A rigid shank removes heavy deposits.

What is Tactile Sensitivity?

The clinician’s ability to feel vibrations transmitted from the instrument working-end with his or her fingers (as they rest on the shank and handle).

Which characteristic of a shank is desirable for explorers, and why?

Flexible shanks are desirable for explorers because they enhance the amount of tactile information transmitted to the clinician’s fingers, which rely on the sense of touch to detect calculus deposits.

What primarily determines an instrument’s function?

The design of its working-end .

List the five parts of an instrument working-end.

1. Face, 2. Back, 3. Lateral surfaces, 4. Cutting edges, and 5. Toe or tip .

Where is the cutting edge formed?

The cutting edge is a sharp edge formed where the face and lateral surfaces meet .

What is the difference between a Toe and a Tip on a working-end?

A rounded toe is formed when the cutting edges meet on some working-ends; a pointed tip is formed when the cutting edges meet on others .

What does the cross section of a working-end determine?

It determines whether the instrument can be used SUBgingivally (beneath the gingival margin) or is restricted to SUPRAgingival use .

Which cross section is restricted to supragingival use?

Working-ends that are triangular in cross section .

Which cross section may be used both supra- and subgingivally?

Working-ends that are semi-circular in cross section .

Describe the design characteristics of Sickle Scalers based on their cross section and related anatomy.

They have a triangular cross section, a pointed back, and a pointed tip; they are limited to SUPRAgingival use.

Describe the design characteristics of Curets based on their cross section and related anatomy.

They are semi-circular in cross section, possessing a rounded back and a rounded toe; they may be used SUPRAgingivally and SUBgingivally.

How are instruments identified by their names and numbers?

The Design Name indicates the school or person who designed the instrument; the Design Number identifies the working-ends (e.g., 1 and 2); and the Last Number indicates the type of handle (e.g., 7) .

What are the three classes of Calculus Removal Instruments?

1. Sickle Scalers, 2. Curets (Universal Curets and Gracey Curets), and 3. Periodontal Files (not common)

What is the primary use of Sickle Scalers?

To remove medium- to large-sized SUPRAgingival calculus deposits from crowns (they should NOT be used on roots).

How does the face of a sickle scaler relate to its lower shank?

The face of a sickle scaler is perpendicular to its lower shank (meaning the face is not tilted).

To achieve the correct 70-degree scaling angle with a sickle scaler, what action must the clinician take?

The clinician needs to lean the lower shank of the instrument slightly towards the tooth surface being worked on.

What is the primary use of Curets, and what characteristics allow this use?

Used to remove calculus deposits from the crowns AND roots without traumatizing tissue . This is possible because of their semi-circular cross section, rounded toe, and back .

Why are Universal Curets named as such?

Because they can be used on ALL SURFACES of posterior teeth .

How does the face of a Universal Curet relate to its lower shank?

The face is perpendicular to the lower shank, making the two cutting edges level with each other .

To achieve the correct 70-degree scaling angle with a Universal Curet, what action must the clinician take?

The clinician must tip the lower shank/handle slightly towards the tooth surface .

What is the most common brand name for Area-Specific Curets?

Gracey Curets .

Why are Gracey Curets called "area-specific"?

Because each instrument is limited to use on certain teeth and on certain surfaces .

What design feature makes Gracey Curets especially suited for instrumentation of root surfaces in periodontal pockets?

They have long, complex functional shanks .

What is the unique feature of Gracey Curet cutting edges compared to Universal Curets?

Gracey Curet cutting edges are curved to enhance adaptation around root concavities and furcations, while universal curets have parallel cutting edges .

How is the face of an Area-Specific (Gracey) Curet positioned relative to its terminal shank?

The face is tilted (sloped) in relation to the terminal shank.

Due to the tilted face of the Gracey Curet, which cutting edge is used for calculus removal?

Only the lower cutting edge is used for calculus removal; this edge is called the “working edge”.

What is the significant advantage of the working edge being lower and the nonworking edge being angled away from the tissue?

The nonworking cutting edge is angled away from the soft tissue wall of the pocket, which helps to protect the gingiva.

How is the 70-degree face-to-tooth angulation automatically achieved when using a Gracey Curet?

The face-to-tooth angle is automatically 70 degrees when the clinician ensures the terminal/lower shank is parallel to the tooth surface being instrumented.

What are the negative consequences if the angulation for calculus removal is too open (over 70 degrees)?

One cutting edge causes tissue trauma.

What are the negative consequences if the angulation for calculus removal is too closed (under 70 degrees)?

The cutting edge slides over the calculus.

What type of instrument is the Periodontal Probe, and what is its working-end shape?

It is an Assessment Instrument used to evaluate the health of periodontal tissues; it has a blunt, rod-shaped working-end .

What is the primary function of the Explorer 11/12, and what are its shank and cross-section characteristics?

Used to locate calculus deposits, tooth irregularities, and defective restoration margins; it has flexible shanks and is circular in cross section.

What is the function and design of Periodontal Files?

They are used to crush large calculus deposits and are characterized by having several cutting edges on each working-end.

What is the classification of instruments based upon?

The classification is based on the specific design characteristics of the working-ends