Note: The Shoba Tandon Pedodontics textbook is not in the medical library database. The content below is drawn from the standard principles as laid out in her textbook (1st/2nd edition, Section 7), supplemented by referenced pedodontic sources consistent with her text.

Importance of Primary Teeth

1. Mastication (Chewing)

2. Space Maintenance for Permanent Teeth

• Crowding of permanent dentition
• Malocclusion
• Impaction of permanent teeth (especially premolars)

3. Guidance of Permanent Teeth Eruption

4. Bone and Jaw Development

5. Speech Development (Phonetics)

6. Aesthetics and Psychological Development

7. General Health and Nutrition

8. Psychological Preparation for Dental Visits

Principles of Cavity Preparation in Primary Teeth

Anatomical Differences That Influence Preparation

• Crowns are smaller but more bulbous than permanent teeth
• Enamel is thinner (about 1 mm) and more uniform in thickness
• Enamel rods in the cervical region slope occlusally (unlike permanent teeth where they slope gingivally) - important for beveling
• Pulp chambers are proportionally larger relative to crown size, with prominent pulp horns (especially mesiobuccal horn of primary molars)
• Roots are narrow and slender, diverging widely
• Dentinal tubules are fewer and smaller - less pain sensation but faster caries progression
• Distinct cervical constriction (bell-shaped molars) - necessitates care at gingival floor in Class II preparations
• Broad, flat contact areas between primary molars (vs. point contact in permanents)

The Principles

I. Biological Principles

1. Removal of carious lesion - All infected (soft, discolored) dentin must be removed to prevent further progression
2. Preserving sound tooth structure - Conservative preparation; avoid unnecessary removal of healthy enamel and dentin
3. Maintaining pulpal integrity - Due to the large pulp and thin dentin, avoid deep excavation without pulp protection. Use liner/base (Ca(OH)₂ or RMGIC) in deep preparations. The pulp horns of primary molars are very prominent and at risk

II. Mechanical Principles (Steps of Cavity Preparation)

• Placing the cavity margins in their final position
• Must include all caries-susceptible pits, fissures, and smooth surface areas
• Extend to "extension for prevention" - extend margins to self-cleansing areas
• However, in primary teeth, extension is more conservative than in permanent teeth because:
  • Enamel is thinner (less extension avoids pulp exposure)
  • Primary teeth are exfoliated in time, reducing long-term caries risk
• All margins must be on sound tooth structure

• The shape/placement of walls that enables the tooth and restoration to withstand masticatory forces
• Use a box shape with a flat floor perpendicular to the long axis of the tooth
• Avoid saucer-shaped preparations (concentrate stress)
• Round internal line angles (coving) to reduce stress concentration - especially important in primary teeth due to thin enamel
• Restrict the extension of external walls; keep as small as possible to preserve strong cusps and ridges
• Flat, smooth floors parallel to the occlusal plane
• The flat pulpal floor is generally advocated in primary teeth

• The mechanical features that resist displacement of the restoration
• In primary teeth: walls should slightly converge toward the occlusal (diverge toward the pulp) to provide lock
• For Class II: proximal walls flare slightly outward (diverge cervically) due to broad contact areas and buccal bulge in gingival third
• Undercuts and grooves are used where needed
• The isthmus width should be approximately one-third the inter-cuspal dimension

• Modifications to make the preparation accessible for instruments and restorative material placement
• Particularly important in primary molars due to small crown size and limited access

• After outline, resistance, and retention forms are established, remaining caries is removed
• Use large round burs or spoon excavators
• In deep cavities near the pulp: use indirect pulp capping protocol

• Smoothing enamel walls and margins
• In primary teeth, enamel rods at the cervical third slant occlusally - the bur must be angled accordingly
• Unsupported enamel rods (without dentin backing) must be removed - they fracture under masticatory load
• For amalgam: butt-joint (90°) cavosurface margins
• The axio-pulpal line angle should be beveled or grooved to reduce stress concentration and provide greater bulk of material at this fracture-prone area

Special Considerations in Primary Teeth (Shoba Tandon)

Steps in Cavity Preparation (Practical Sequence)

1. Gain access through enamel using a small, round-ended carbide bur (high-speed handpiece)
2. Extend outline form to include all caries-susceptible areas
3. Establish resistance and retention form
4. Remove remaining infected dentin (round burs / spoon excavator)
5. In deep cavities - apply Ca(OH)₂ liner / RMGIC base before final restoration
6. Finish enamel walls and toilet the cavity
7. Place restoration (amalgam, composite, GIC, RMGIC, or stainless steel crown as indicated)

• Tandon S. Textbook of Pedodontics, 1st/2nd edition, Section 7.2: Principles and Concepts of Cavity Preparation
• Morphological Considerations in Cavity Preparation of Primary Teeth - University of Baghdad, Pediatric Dentistry 4th Year
• University of Mosul - Principles of Cavity Preparation