Cavity Preparation Class I Quiz

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Questions and Answers

What surfaces are involved in Class I cavities?

Only the occlusal surfaces of molars

The distal surfaces of all teeth

Only the facial surfaces of maxillary anterior teeth

Occlusal surfaces of molars and premolars, and the occlusal 2/3 of buccal and lingual surfaces of molars (correct)

Which step is NOT involved in the manipulation of amalgam?

Trituration

Condensation

Finishing and Polishing

Archiving (correct)

What is the recommended initial depth when entering a Class I cavity?

1.2 mm

2.0 mm

1.5 mm (correct)

1.0 mm

What characteristic is typical of Class I cavity lesions?

A conical spread in enamel and dentin Signup and view all the answers

Which bur is recommended for creating a conservative Class I preparation?

No. 245 bur Signup and view all the answers

What should guide the outline form of a Class I cavity preparation?

The extent of caries and the need to eliminate pits and fissures Signup and view all the answers

Which is not an indicator suggesting susceptibility to caries in pits and fissures?

A smooth, sealed surface Signup and view all the answers

What is the function of a sealer in cavity preparation?

To provide a protective barrier Signup and view all the answers

What is the primary purpose of having a relatively flat pulpal floor in the resistance form?

To provide a stable seat for the restoration Signup and view all the answers

What minimum depth is required for adequate thickness of the restoration?

1.5 mm Signup and view all the answers

In what situation is a liner or base recommended for pulp protection?

In deeper carious excavations with thin remaining dentin Signup and view all the answers

What tool is commonly used to remove carious dentin in moderate to deep cavities?

Spoon excavator or round bur Signup and view all the answers

Which term describes the required shape of the cavo-surface margins for effective restoration?

Well defined and well supported Signup and view all the answers

What is the main function of the resin-modified glass-ionomer (RMGI) base?

To insulate the pulp from thermal changes Signup and view all the answers

What is an essential characteristic of enamel walls in cavity preparation?

They must meet the tooth surface at a right cavo-surface angle Signup and view all the answers

What preparation shape aids in providing primary retention form?

Slight occlusal convergence of external walls Signup and view all the answers

What is the primary purpose of the occlusal convergence of the facial and lingual preparation walls in cavity preparation?

To facilitate better retention form for the cavity Signup and view all the answers

How should the bur be oriented during cavity preparation according to the content?

Parallel to the long axis of the tooth crown Signup and view all the answers

What is a crucial consideration when designing the outline form of the cavity preparation?

Including only defective occlusal pits and fissures Signup and view all the answers

What is the recommended cavosurface angle for optimal amalgam margin strength?

90 to 100 degrees Signup and view all the answers

Which bur is primarily used for the preparation of buccal or palatal pits?

No. 245 bur Signup and view all the answers

What is the effect of having angular irregularities in the outline of a cavity preparation?

They increase the risk of fracture during condensation Signup and view all the answers

Where should the mesial and distal margins of a cavity preparation be placed?

Midway between the bottom of the proximal fossae and the crest of the proximal ridges Signup and view all the answers

What should be done after cleaning and debriding the cavity?

Dry the cavity with air Signup and view all the answers

What is the appropriate axial depth if retentive locks are required?

0.5 mm inside the DEJ Signup and view all the answers

What is the recommended cavity width relative to intercuspal distance?

1/4 - 1/3 the intercuspal distance Signup and view all the answers

How should groove extensions be managed in cavity preparations?

Narrowed as much as possible to preserve strength Signup and view all the answers

What purpose does rounding the axio-pulpal line angle serve?

To provide bulk to the restoration Signup and view all the answers

What is the goal when eliminating weak walls of enamel in cavity preparation?

To join outlines that are less than 0.5 mm apart Signup and view all the answers

In preparing compound Class I cavities, what should be done when the caries is still gingival to the pulpal seat?

A step is indicated Signup and view all the answers

What is the recommended direction for the axial wall to follow?

Parallel to corresponding external tooth surface Signup and view all the answers

What should be checked using a sharp explorer during the cavity preparation?

The details of the prepared cavity Signup and view all the answers

Study Notes

Class I Cavity Preparation for Amalgam

Class I cavities are pit and fissure type cavities
They involve occlusal surfaces of molars and premolars
They also involve the occlusal two-thirds of buccal and lingual surfaces of molars
Palatal pits in maxillary anterior teeth are also involved in Class I cavities
Pits and fissures are susceptible to caries due to imperfect enamel lobe coalescence
These areas are retentive for food, promoting caries production
Class I cavities lesions start small and may remain unnoticed until substantial size
The lesions spread conically in both enamel and dentin, enamel spreading towards the surface and dentin towards the pulp
Class I cavities can be simple occlusal, compound (two surfaces), or complex (more than two). Specific types include occluso-buccal, occluso-lingual / occluso-palatal, and occluso-bucco-lingual.

Clinical Procedures

Cavity preparation for amalgam
Application of sealer (varnish)
Matrixing (when necessary), vital in compound and complex cavities
Amalgam manipulation involving: selection and proportioning of alloy and mercury, trituration, condensation, carving, and finishing and polishing.

Cavity Preparation Steps

Outline form and initial depth
Resistance and retention forms
Convenience form
Decay removal
External cavity wall finishing
Cavity toilet

Class I Simple Occlusal Cavity Outline Form

The outline form of Class I cavities should be conservative, involving cleansable areas
The outline is governed by the extent of caries in enamel and dentin, and the necessary extension to eliminate pits and fissures
It varies according to the number of cusps and orientation of pits and fissures.

Steps of Operative Procedure

Begin Class I occlusal preparation by entering the deepest or most carious pit with a No. 1/2 carbide bur at high speed with air-water spray.
Extend the cavity with a suitable size fissure bur (or alternatively, No. 245 bur).
Establish the proper depth of 1.5 mm (half the bur length). The initial pulpally depth is 0.2mm inside the DEJ or 1.5 mm from the central groove.
A No. 245 bur has a 3mm head length and 0.8mm tip diameter. The sides converge toward the bur shank, which creates occlusal convergence of facial and lingual walls for adequate retention.
Rounded internal line angles, created by the bur, make the tooth resistant to fracture from occlusal force.
Necessary cavity extensions through pits, fissures, and developmental grooves are made with bur at a right angle to the tooth surface and a parallel long axis to the tooth crown.

Designing the Outline Form

Include only faulty, defective occlusal pits, fissures, carious, and undermined enamel.
Extend around cusps to maintain tooth structure and prevent pulpal horns from being approached too closely.
Keep a minimum width in sweeping curves to prevent fracture.
Cavity width is kept 1/4 - 1/3 intercuspal distance terminating on smooth surfaces to maintain strength and function of cusps but wide enough for condensation.

Setting Mesial and Distal Margins

Positioned midway between proximal fossae and crest of proximal ridges.
Placed parallel to these ridges.
Mesial/distal walls are slanted or slightly diverging from the pulpal floor outward to avoid marginal ridge undermining.
Preserves marginal ridge strength.
Groove extensions kept narrow (mesio-distally) where possible to preserve cusp strength (but at least as wide as the narrowest condenser).
Eliminate any weak enamel walls that are less than 0.5mm apart.

Extending Outline Form

Include enamel undermined due to caries.
Use enameloplasty on shallow fissures to conserve tooth structure.
Establish an optimal conservative depth in pulpal wall.

Resistance and Retention Forms

Resistance achieved by boxing the preparation.
Relatively flat pulpal floor in sound tooth structure that resists forces and provides stable seat for the restoration.

Minimal Extension

Minimal external wall extension.
Strong ideal enamel margins.
Adequate depth to ensure restoration thickness.
Slight occlusal convergence of opposing external walls provides primary retention.

Convenience Form

Establish depth and width for restoration.
Although conserving tooth structure is crucial, convenience form may need extensive preparation to allow better access and visibility.

Removal of Carious Dentin

In small cavities, caries removal is during cavity extension.
In moderate/deep cavities, caries removal using large spoon excavators or round burs.
Resistance/retention form may improve with flat floor peripheral to the excavated area.

Pulp Protection

No liner/base in shallow cavities.
In deeper cavities (0.5- 1.0mm remaining dentin), apply a thin layer of light-cured RMGI (resin-modified glass-ionomer) base.
RMGI base insulates the pulp, bonds to dentin, releases fluoride, is strong, and resists condensation forces.

Enamel Wall Planning

Finish enamel walls free of loose/undermined enamel.
Trim walls to meet tooth surface at a right cavo-surface angle.
Use sharp chisels, hatchets, fissure burs or stones for cleaning.
Round all sharp corners in enamel, as they can contain short enamel rods.

Cavo-Surface Margins

Well-defined and well-supported
Easier for visualization and carving, with marginal integrity
Important to achieve approximate 90-100 degree cavo surface angle for amalgam at the margin (approximately 80-90 degrees).
A butt-joint marginal area allows strength for both.

Debridement and Inspection

A sharp explorer to check cavity details/loosen any debris
Flush cavity with water, then dry with air
Facilitates amalgam adaptation, optimizes restoration physical properties by eliminating voids.

Buccal/Palatal Pits Preparation

Shape varies from oval-round to oblong based on extent of caries
Walls consistently joined and are slightly convergent towards cavosurface margin
Axial wall follows buccal/lingual surface contour

Additional Considerations

No. 245, 330 or 169 bur can be used for preparation, dependent on lesion size
Retention grooves added as needed using No. 1/4 or 33 1/2 burs, per caries extent and wall angulation.

Compound Class I Cavities

Occluso-buccal/occluso-lingual cavity extensions through fissures towards respective surfaces
Dentin cutting at dentino-enamel junction using No.56 bur until the occlusal ridge is undermined and removed.
If caries is still gingival to the level of the pulpal seat, a step is indicated.
A #56 bur is used to cut dentin at the dentino-enamel junction with pressure & mesio-distal movement for gingival direction.

Axial Wall

Follows external tooth surface contour
0.5mm depth inside the DEJ is ideal for retentive locks, otherwise 0.2mm is permissible

Resistance & Retention Form

Round axio-pulpal line angle to prevent stress concentration, provide bulk, and maintain thickness
Axial wall direction is parallel to corresponding exterior surface. This prevents pulp exposure and creates uniform thickness
Retention grooves may be cut as needed in dentin, along axio-mesial or axio-distal line angles.

Buccal Fissure Extension

Facial occlusal fissure is continuous with facial surface fissure.
Extend through facial ridge onto facial surface. This procedure creates a tooth preparation appearance that has undergone extension through the ridge.
Facial surface portion of extension is cut with bur's side, to create sharper line angles (to improve appearance) via bur from the facial aspect and, another sharp angle through occlusal direction use No. 169 bur.
Further retention form ensured by preparing locks with No. 1/4 round bur and final tooth preparation.

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Description

Test your knowledge on Class I cavity preparations with this quiz. It covers essential concepts such as recommended depths, tools, and the characteristics of Class I cavities. Perfect for dental students and professionals looking to refresh their understanding of cavity management.