Polycarbonate Crowns in Pedodontics

Polycarbonate crowns are commonly used in pediatric dentistry, particularly for managing anterior teeth affected by nursing bottle caries. These crowns serve as temporary fixed prostheses for primary teeth, providing a functional and aesthetic solution until the natural teeth exfoliate. This lecture will discuss the indications, contraindications, and advantages of polycarbonate crowns in pedodontic practice.

Nursing Bottle Caries

• Definition: Nursing bottle caries, also known as early childhood caries, is a condition characterized by the rapid demineralization of the anterior teeth, primarily affecting the labial surfaces.
• Progression: The lesions begin on the labial face of the anterior teeth and can lead to extensive demineralization, affecting the entire surface of the teeth.
• Management Goal: The primary objective is to stabilize the lesions without attempting a complete reconstruction of the coronal anatomy.

Treatment Approach

1. Preparation of the Lesion:

   • The first step involves creating a clean periphery around the carious lesion using a small round bur.
   • Care should be taken to leave the central portion of the affected dentin intact to avoid pulp exposure.
   • This preparation allows for effective ion exchange with glass ionomer materials, facilitating a good seal.

2. Use of Polycarbonate Crowns:

   • Polycarbonate crowns are indicated as temporary crowns for deciduous anterior teeth that will eventually exfoliate.
   • They provide a protective covering for the tooth while maintaining aesthetics and function.

Contraindications for Polycarbonate Crowns

Polycarbonate crowns may not be suitable in certain situations, including:

• Severe Bruxism: Excessive grinding can lead to premature failure of the crown.
• Deep Bite: A deep bite may cause undue stress on the crown, leading to potential fracture or dislodgment.
• Excessive Abrasion: High levels of wear can compromise the integrity of the crown.

Advantages of Polycarbonate Crowns

Polycarbonate crowns offer several benefits in pediatric dentistry:

• Time-Saving: The application of polycarbonate crowns is relatively quick, making them efficient for both the clinician and the patient.
• Ease of Trimming: These crowns can be easily trimmed to achieve the desired fit and contour.
• Adjustability: They can be adjusted with pliers, allowing for modifications to ensure proper seating and comfort for the patient.

Tooth Replantation and Avulsion Injuries

Tooth avulsion is a dental emergency that occurs when a tooth is completely displaced from its socket. The success of replantation, which involves placing the avulsed tooth back into its socket, is influenced by several factors, including the time elapsed since the avulsion and the condition of the periodontal ligament (PDL) tissue.

Key Factors Influencing Replantation Success

1. Time Elapsed Since Avulsion:

   • The length of time between the loss of the tooth and its replantation is critical. The sooner a tooth can be replanted, the better the prognosis for retention and vitality.
   • Prognosis Statistics:
     • Replantation within 30 minutes: Approximately 90% of replanted teeth show no evidence of root resorption after 2 or more years.
     • Replantation after 2 hours: About 95% of these teeth exhibit root resorption.

2. Condition of the Tooth:

   • The condition of the tooth at the time of replantation, particularly the health of the periodontal ligament tissue remaining on the root surface, significantly affects the outcome.
   • Immediate replacement of a permanent tooth can sometimes lead to vitality and indefinite retention, but this is not guaranteed.

3. Temporary Measure:

   • While replantation can be successful, it should generally be viewed as a temporary solution. Many replanted teeth may be retained for 5 to 10 years, with a few lasting a lifetime, but others may fail shortly after replantation.

Common Avulsion Injuries

• Most Commonly Avulsed Tooth: The maxillary central incisor is the tooth most frequently avulsed in both primary and permanent dentition.
• Demographics:
  • Avulsion injuries typically involve a single tooth and are three times more common in boys than in girls.
  • The highest incidence occurs in children aged 7 to 9 years, coinciding with the eruption of permanent incisors.
• Structural Factors: The loosely structured periodontal ligament surrounding erupting teeth may predispose them to complete avulsion.

Recommendations for Management of Avulsed Teeth

1. Immediate Action: If a tooth is avulsed, it should be replanted as soon as possible. If immediate replantation is not feasible, the tooth should be kept moist.

   • Storage Options: The tooth can be stored in:
     • Cold milk (preferably whole milk)
     • Saline solution
     • Patient's own saliva (by placing it in the buccal vestibule)
     • A sterile saline solution
   • Avoid: Storing the tooth in water, as this can damage the periodontal ligament cells.

2. Professional Care: Seek dental care immediately after an avulsion injury to ensure proper replantation and follow-up care.

1. Crown Dimensions

• Primary Anterior Teeth: The crowns of primary anterior teeth (incisors and canines) are characterized by a wider mesiodistal dimension and a shorter incisocervical height compared to their permanent counterparts. This means that primary incisors are broader from side to side and shorter from the biting edge to the gum line, giving them a more squat appearance.

• Primary Molars: The crowns of primary molars are also shorter and narrower in the mesiodistal direction at the cervical third compared to permanent molars. This results in a more constricted appearance at the base of the crown, which is important for accommodating the developing permanent teeth.

2. Root Structure

• Primary Anterior Teeth: The roots of primary anterior teeth taper more rapidly than those of permanent anterior teeth. This rapid tapering allows for a more pronounced root system that is essential for anchoring the teeth in the softer bone of children’s jaws.

• Primary Molars: In contrast, the roots of primary molars are longer and more slender than those of permanent molars. This elongation and slenderness provide stability while also allowing for the necessary space for the developing permanent teeth beneath them.

3. Enamel Characteristics

• Enamel Rod Orientation: In primary teeth, the enamel rods in the gingival third slope occlusally (toward the biting surface) rather than cervically (toward the root) as seen in permanent teeth. This unique orientation can influence the way primary teeth respond to wear and decay.

• Thickness of Enamel: The enamel on the occlusal surfaces of primary molars is of uniform thickness, measuring approximately 1 mm. In contrast, the enamel on permanent molars is thicker, averaging around 2.5 mm. This difference in thickness can affect the durability and longevity of the teeth.

4. Surface Contours

• Buccal and Lingual Surfaces: The buccal and lingual surfaces of primary molars are flatter above the crest of contour compared to permanent molars. This flatter contour can influence the way food is processed and how plaque accumulates on the teeth.

5. Root Divergence

• Primary Molars: The roots of primary molars are more divergent relative to their crown width compared to permanent molars. This divergence is crucial as it allows adequate space for the developing permanent dentition, which is essential for proper alignment and spacing in the dental arch.

6. Occlusal Features

• Occlusal Table: The occlusal table of primary molars is narrower in the faciolingual dimension. This narrower occlusal surface, combined with shallower anatomy, results in shorter cusps, less pronounced ridges, and shallower fossae. These features can affect the functional aspects of chewing and the overall occlusion.

• Mesial Cervical Ridge: Primary molars exhibit a prominent mesial cervical ridge, which serves as a distinguishing feature that helps in identifying the right and left molars during dental examinations.

7. Root Characteristics

• Root Shape and Divergence: The roots of primary molars are not only longer and more slender but also extremely narrow mesiodistally and broad lingually. This unique shape contributes to their stability while allowing for the necessary divergence and minimal curvature. Additionally, primary molars typically have little or no root trunk, which is a stark contrast to the more complex root structures of permanent molars.

CARIDEX and CARISOLV

CARIDEX and CARISOLV are both dental products designed for the chemomechanical removal of carious dentin. Here’s a detailed breakdown of their components and mechanisms:

CARIDEX

• Components:

  • Solution I: Contains sodium hypochlorite (NaOCl) and is used for its antimicrobial properties and ability to dissolve organic tissue.
  • Solution II: Contains glycine and aminobutyric acid (ABA). When mixed with sodium hypochlorite, it produces N-mono chloro DL-2-amino butyric acid, which aids in the removal of demineralized dentin.

• Application:

  • CARIDEX is particularly useful for deep cavities, allowing for the selective removal of carious dentin while preserving healthy tooth structure.

CARISOLV

• Components:

  • Syringe 1: Contains sodium hypochlorite at a concentration of 0.5% w/v (which is equivalent to 0.51%).
  • Syringe 2: Contains a mixture of amino acids (such as lysine, leucine, and glutamic acid) and erythrosine dye, which helps in visualizing the removal of carious dentin.

• pH Level:

  • The pH of the CARISOLV solution is approximately 11, which helps in the dissolution of carious dentin.

• Mechanism of Action:

  • The sodium hypochlorite in CARISOLV softens and dissolves carious dentin, while the amino acids and dye provide a visual cue for the clinician. The procedure can be stopped when discoloration is no longer observed, indicating that all carious dentin has been removed.

Growth Spurts in Children

Growth in children does not occur at a constant rate; instead, it is characterized by periods of rapid increase known as growth spurts. These spurts are significant phases in physical development and can vary in timing and duration between individuals, particularly between boys and girls.

Growth Spurts: Sudden increases in growth that occur at specific times during development. These spurts are crucial for overall physical development and can impact various aspects of health and well-being.

Timing of Growth Spurts

The timing of growth spurts can be categorized into several key periods:

1. Just Before Birth

   • Description: A significant growth phase occurs in the fetus just prior to birth, where rapid growth prepares the infant for life outside the womb.

2. One Year After Birth

   • Description: Infants experience a notable growth spurt during their first year of life, characterized by rapid increases in height and weight as they adapt to their new environment and begin to develop motor skills.

3. Mixed Dentition Growth Spurt

   • Timing:
     • Boys: 8 to 11 years
     • Girls: 7 to 9 years
   • Description: This growth spurt coincides with the transition from primary (baby) teeth to permanent teeth. It is a critical period for dental development and can influence facial growth and the alignment of teeth.

4. Adolescent Growth Spurt

   • Timing:
     • Boys: 14 to 16 years
     • Girls: 11 to 13 years
   • Description: This is one of the most significant growth spurts, marking the onset of puberty. During this period, both boys and girls experience rapid increases in height, weight, and muscle mass, along with changes in body composition and secondary sexual characteristics.

Stainless Steel Crowns

Stainless steel crowns (SSCs) are a common restorative option for primary teeth, particularly in pediatric dentistry. They are especially useful for teeth with extensive carious lesions or structural damage, providing durability and protection for the underlying tooth structure.

Indications for Stainless Steel Crowns

• Primary Incisors or Canines:
  • SSCs are indicated for primary incisors or canines that have extensive proximal lesions, especially when the incisal portion of the tooth is involved.
  • They are particularly beneficial in cases where traditional restorative materials (like amalgam or composite) may not provide adequate strength or longevity.

Crown Selection and Preparation

1. Crown Selection:

   • An appropriate size of stainless steel crown is selected based on the dimensions of the tooth being restored.

2. Contouring:

   • The crown is contoured at the cervical margin to ensure a proper fit and to minimize the risk of gingival irritation.

3. Polishing:

   • The crown is polished to enhance its surface finish, which can help reduce plaque accumulation and improve esthetics.

4. Cementation:

   • The crown is cemented into place using a suitable dental cement, ensuring a secure fit even on teeth that have undergone significant carious structure removal.

Advantages of Stainless Steel Crowns

• Retention:
  • SSCs provide excellent retention and can remain in place even when extensive portions of carious tooth structure have been removed.
• Durability:
  • They are highly durable and can withstand the forces of mastication, making them ideal for primary teeth that are subject to wear and tear.

Esthetic Considerations

• Esthetic Limitations:

  • One of the drawbacks of stainless steel crowns is their metallic appearance, which may not meet the esthetic requirements of some children and their parents.

• Open-Face Stainless Steel Crowns:

  • To address esthetic concerns, a technique known as the open-face stainless steel crown can be employed.
  • In this technique, most of the labial metal of the crown is cut away, creating a labial "window."
  • This window is then restored with composite resin, allowing for a more natural appearance while still providing the strength and durability of the stainless steel crown.