Dental Caries and Cavity Classifications

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Questions and Answers

What is the importance of having the axial wall parallel to the tooth long axis in cavity preparation?

It allows for effective instrumentation up to the depth of the proximal portion.

Describe the recommended approach for beveling the enamel on the buccal wall in upper premolar cavities.

Beveling removes undermined enamel and achieves a 90° cross-sectional area.

What are two clinical considerations to protect the adjacent tooth during cavity preparation?

Using a matrix band and applying a rubber dam are effective protective measures.

Why is it preferable to complete the proximal outline before breaking the marginal ridge?

It provides a guide for proximal design and protects the adjacent tooth from rotary instruments. Signup and view all the answers

What changes should be made to the gingival floor for achieving a 90° cross-sectional area?

The gingival floor should be slightly slanted gingivally. Signup and view all the answers

What is the recommended distance of the gingival floor above the gingival crest in relation to the pulpal floor?

The gingival floor should be 0.25 - 0.5 mm above the gingival crest and parallel to the pulpal floor. Signup and view all the answers

How far should the axial wall be from the DEJ for adequate restoration bulk?

The axial wall should be 1.5 - 2 mm away from the DEJ. Signup and view all the answers

What is the minimum width of the cavity isthmus portion bucco-lingually recommended?

The minimum width of the isthmus portion should be about ¼ the inter-cuspal distance. Signup and view all the answers

What shape is suggested for the proximal portion of the cavity in the context of retention form?

The proximal portion should have an inverted truncated cone shape. Signup and view all the answers

What preparation technique is recommended for creating axial retention in cavity walls?

Cavity walls should be prepared to be slightly converging occlusally to create mechanical undercuts. Signup and view all the answers

Name a technique used to ensure retention along with a proximal dovetail in molars.

The occlusal lock technique is used to provide retention along with a proximal dovetail. Signup and view all the answers

What is the role of proximal axial grooves in cavity preparation?

Proximal axial grooves are cut into the axio-buccal and axio-lingual line angles to enhance retention without risking pulp exposure. Signup and view all the answers

What is the primary purpose of the convenience form in cavity preparation?

The convenience form is designed to provide accessibility to the proximal portion of the cavity. Signup and view all the answers

What shape does caries typically spread in within enamel and dentin?

Caries spreads in a conical pattern within both enamel and dentin. Signup and view all the answers

What is the role of bite-wing x-ray films in the diagnosis of caries?

Bite-wing x-ray films are necessary for the correct diagnosis of caries, as they help identify lesions that are difficult to detect visually. Signup and view all the answers

Describe the occlusal portion of a Class II cavity preparation.

The occlusal portion of a Class II cavity preparation is the same as that of a Class I cavity. Signup and view all the answers

What characterizes the isthmus portion of a Class II cavity preparation?

The isthmus portion is the narrowest connection between the occlusal and proximal portions of the cavity. Signup and view all the answers

What considerations must be made for the proximal portion of a Class II cavity?

The proximal portion must involve all carious enamel and dentin and ensure the cavity margins are in a self-cleansable area. Signup and view all the answers

What effect does caries have on the marginal ridge and how does it spread?

Caries tend to undermine the marginal ridge early and spread occlusally along the dento-enamel junction. Signup and view all the answers

What is the importance of ensuring the cavity margins are in self-cleansable areas?

Ensuring cavity margins are in self-cleansable areas helps to prevent caries recurrence. Signup and view all the answers

What factors determine the outline form of the isthmus in Class II cavity preparation?

The outline form of the isthmus is determined by the size of the contact area: straight for small, uniform for normal, and reverse curve for broad contact areas. Signup and view all the answers

Study Notes

Caries Characteristics

Two cones with bases at the DEJ (dentino-enamel junction)
Cone-shaped spread in enamel, base at DEJ, small opening
Cone-shaped spread in dentin, base at DEJ
Rapid lateral spread at DEJ

Tooth Classes

Class 1:
- Maxillary first molar: Kidney shape (mesial cavity)
- Mandibular first molar: Bat shape
- Mandibular first premolar: Snake eye or butterfly shape
- Mandibular second molar: Plus shape
- Mandibular second premolar: Y shape
- Maxillary premolars: Butterfly shape

Class VI Lesions

Images depicting Class VI lesions are shown

Class II Cavity Preparation for Amalgam Restoration

Information provided in a slide header format

Class II Cavities

Definition: Smooth surface lesion on proximal surfaces of molars and bicuspids in the middle third of the tooth
Types: Simple, Compound, Complex (illustrated with images)

Caries Characterstics

Difficult to detect until a considerable size
Bite-wing x-ray film necessary for correct diagnosis
Spreads in enamel and dentin in a conical pattern
Spreads occlusally along the dento-enamel junction and under the marginal ridge early
Extends bucco-lingually and gingivally
Recurrence at buccal, gingival and lingual gingival line angles of the cavity margin is likely.

Class II Cavity Preparation: Design

Composed of three parts: Occlusal, Isthmus, and Proximal.

Isthmus Outline Form

Straight: small contact area
Uniform: normal contact area
Reverse curve: broad/wide contact area

Proximal Portion

Involvement of all carious enamel and dentin
Freeing the proximal surface lingually, buccally, and gingivally
Placing cavity margins in embrasures, self-cleansable
Buccal wall midway between contact and axial line angle, parallel to buccal surface of tooth
Lingual wall midway between contact and lingual axial line angle, parallel to lingual surface of tooth
Gingival floor between 0.25 - 0.5mm above gingival crest, parallel to pulpal floor and occlusal plane
Axial wall 1.5-2mm from DEJ for enough bulk

Resistance Form

Occlusal portion: Same as class I cavity
Isthmus portion: Minimal width (¼ intercuspal distance), roundation/beveling of axio-pulpal line angle, increase bulk at isthmus
Reverse Curve: Wide proximal contact area, conserve sound tooth structure, freeing undermined enamel with correct CSA 90°
Proximal Portion: Reverse curve approach, smooth, flat, parallel pulpal floor and occlusal plane, axial walls parallel, 1.5-2 mm from DEJ, uniform bulk

Retention Form

Axial Retention: Mechanical undercuts, cavity walls converging occlusally, inverted truncated cone shape of the proximal portion

Lateral Retention

Proximal dove tail (premolars and molars, prevention and retention also)
Occlusal lock
Proximal axial grooves (cut into axo-buccal and axolingual line angles-extended to gingival floor, wider internally and gingivally)
Pin retention in extensive cavities

Convenience Form

Cutting an occlusal cavity for accessibility to the proximal portion
Accentuation of cavity walls and margins
Roundation of line angles
Axial wall parallel to tooth long axis in occluso-gingival direction
Selection of suitable sized instruments

Finishing of Enamel Wall

Occlusal portion: Same as class I cavity
Isthmus portion: Enamel wall in direction of enamel rods (CSA 90°), Free from any loose, undermined, or friable enamel
Proximal portion: Buccal and lingual walls flared slightly outward to obtain 90° CSA, Gingival floor slanted slightly gingivally to obtain 90°; Reverse curve approach in buccal wall, undermining buccal wall enamel.
Beveling of undermined buccal enamel (CSA 90°)

Clinical Considerations

Complete proximal outline before breaking marginal ridge and proximal enamel plate
Guides for proximal design
Protects proximal surface of adjacent tooth from rotary instruments
Saves time and effort
Reduces heat generation

Protecting Neighboring Teeth and Ginigva

Using a matrix band around the neighboring tooth during cavity preparation
Using rubber dam to protect gingival tissues
Using a circular wedge during gingival floor preparation to protect gingiva

Class II Simple Proximal Cavity

Enough proximal access due to: missing adjacent tooth, wide embrasure due to senile gum recession, ridge intact and not undermined by caries

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Description

Test your knowledge on the characteristics of caries and different tooth classes. The quiz covers Class II cavity preparations for amalgam restoration and Class VI lesions. Enhance your understanding of dental anatomy and cavity classifications through this engaging assessment.