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Conservative Dentistry

Primary Retention Form in Dental Restorations

Primary retention form refers to the geometric shape or design of a prepared cavity that helps resist the displacement or removal of a restoration due to tipping or lifting forces. Understanding the primary retention form is crucial for ensuring the longevity and stability of various types of dental restorations. Below is an overview of primary retention forms for different types of restorations.

1. Amalgam Restorations

A. Class I & II Restorations

  • Primary Retention Form:
    • Occlusally Converging External Walls: The walls of the cavity preparation converge towards the occlusal surface, which helps resist displacement.
    • Occlusal Dovetail: In Class II restorations, an occlusal dovetail is often included to enhance retention by providing additional resistance to displacement.

B. Class III & V Restorations

  • Primary Retention Form:
    • Diverging External Walls: The external walls diverge outward, which can reduce retention.
    • Retention Grooves or Coves: These features are added to enhance retention by providing mechanical interlocking and resistance to displacement.

2. Composite Restorations

A. Primary Retention Form

  • Mechanical Bond:
    • Acid Etching: The enamel and dentin surfaces are etched to create a roughened surface that enhances mechanical retention.
    • Dentin Bonding Agents: These agents infiltrate the demineralized dentin and create a hybrid layer, providing a strong bond between the composite material and the tooth structure.

3. Cast Metal Inlays

A. Primary Retention Form

  • Parallel Longitudinal Walls: The cavity preparation features parallel walls that help resist displacement.
  • Small Angle of Divergence: A divergence of 2-5 degrees may be used to facilitate the seating of the inlay while still providing adequate retention.

4. Additional Considerations

A. Occlusal Dovetail and Secondary Retention Grooves

  • Function: These features aid in preventing the proximal displacement of restorations by occlusal forces, enhancing the overall retention of the restoration.

B. Converging Axial Walls

  • Function: Converging axial walls help prevent occlusal displacement of the restoration, ensuring that the restoration remains securely in place during function.

Carisolv

Carisolv is a dental caries removal system that offers a unique approach to the treatment of carious dentin. It differs from traditional methods, such as Caridex, by utilizing amino acids and a lower concentration of sodium hypochlorite. Below is an overview of its components, mechanism of action, application process, and advantages.

1. Components of Carisolv

A. Red Gel (Solution A)

  • Composition:
    • Amino Acids: Contains 0.1 M of three amino acids:
      • I-Glutamic Acid
      • I-Leucine
      • I-Lysine
    • Sodium Hydroxide (NaOH): Used to adjust pH.
    • Sodium Hypochlorite (NaOCl): Present at a lower concentration compared to Caridex.
    • Erythrosine: A dye that provides color to the gel, aiding in visualization during application.
    • Purified Water: Used as a solvent.

B. Clear Liquid (Solution B)

  • Composition:
    • Sodium Hypochlorite (NaOCl): Contains 0.5% NaOCl w/v, which contributes to the antimicrobial properties of the solution.

C. Storage and Preparation

  • Temperature: The two separate gels are stored at 48°C before use and are allowed to return to room temperature prior to application.

2. Mechanism of Action

  • Softening Carious Dentin: Carisolv is designed to soften carious dentin by chemically disrupting denatured collagen within the affected tissue.
  • Collagen Disruption: The amino acids in the formulation play a crucial role in breaking down the collagen matrix, making it easier to remove the softened carious dentin.
  • Scraping Away: After the dentin is softened, it is removed using specially designed hand instruments, allowing for precise and effective caries removal.

3. pH and Application Time

  • Resultant pH: The pH of Carisolv is approximately 11, which is alkaline and conducive to the softening process.
  • Application Time: The recommended application time for Carisolv is between 30 to 60 seconds, allowing for quick treatment of carious lesions.

4. Advantages

  • Minimally Invasive: Carisolv offers a minimally invasive approach to caries removal, preserving healthy tooth structure while effectively treating carious dentin.
  • Reduced Need for Rotary Instruments: The chemical action of Carisolv reduces the reliance on traditional rotary instruments, which can be beneficial for patients with anxiety or those requiring a gentler approach.
  • Visualization: The presence of erythrosine allows for better visualization of the treated area, helping clinicians ensure complete removal of carious tissue.

Glass ionomer cement is a tooth coloured material 
Material was based on reaction between silicate glass powder & polyacrylicacid.
They bond chemically to tooth structure & release fluoride for relatively long period

CLASSIFICATION 

Type I. For luting

Type II. For restoration 

Type II.1 Restorative esthetic 

Type II.2 Restorative reinforced

Type III. For liner & bases

Type IV. Fissure & sealent

Type V. As Orthodontic cement

Type VI. For core build up

Physical Properties

1. Low solubility
2. Coefficient of thermal expansion similar to dentin
3. Fluoride release and fluoride recharge
4. High compressive strengths
5. Bonds to tooth structure
6. Low flexural strength
7. Low shear strength
8. Dimensional change (slight expansion) (shrinks on setting, expands with water sorption)
9. Brittle
10.Lacks translucency
11.Rough surface texture

Indications for use of Type II glass ionomer cements 

1) non-stress bearing areas 

2) class III and V restorations in adults 

3) class I and II restorations in primary dentition 

4) temporary or “caries control” restorations 

5) crown margin repairs 

6) cement base under amalgam, resin, ceramics, direct and indirect gold 

7) core buildups when at least 3 walls of tooth are remaining (after crown preparation)

Contraindications 

1) high stress applications I. class IV and class II restorations II. cusp replacement III. core build-ups with less than 3 sound walls remaining

Composition

 

Factors affecting the rate or setting

1. Glass composition:Higher Alumina – Silica ratio, faster set and shorter working time.
2. Particle Size: finer the powder, faster the set.
3. Addition of Tartaric Acid:-Sharpens set without shortening the working time.
4. Relative proportions of the constituents: Greater the proportion of glass and lower the proportion of water, the faster the set.
5. Temperature

Setting Time

Type 1 - 4-5 min
type II - 7 min


PROPERTIES 

Adhesion :

- Glass ionomer cement bonds chemically to the tooth structure->reaction occur between carboxyl group of poly acid & calcium of hydroxyl apatite.
 
- Bonding with enamel is higher than that of dentin ,due to greater inorganic content. 

Esthetics :
-GIC is tooth coloured material & available in different shades.
Inferior to composites.
They lack translucency & rough surface texture.
Potential for discolouration & staining.

Biocompatibilty :

- Pulpal response to glass ionomer cement is favorable. 
- Pulpal response is mild due to 
- High buffering capacity of hydroxy apatite. 
- Large molecular weight of the polyacrylic acid ,which prevents entry into dentinal tubules. 

a) Pulp reaction – ZOE < Glass Ionomer < Zinc Phosphate 

b) Powder:liquid ratio influences acidity 

c) Solubility & Disintegration:-Initial solubility is high due to leaching of intermediate products.The complete setting reaction takes place in 24 hrs, cement should be protected from saliva during this period.

Anticariogenic properties :
- Fluoride is released from glass ionomer at the time of mixing & lies with in matrix.
Fluoride can be released out without affecting the physical properties of cement.

ADVANTAGE DISADVANTAGE

Beveling in Restorative Dentistry

Beveling: Beveling refers to the process of angling the edges of a cavity preparation to create a smooth transition between the tooth structure and the restorative material. This technique can enhance the aesthetics and retention of certain materials.

Characteristics of Ceramic Materials

  • Brittleness: Ceramic materials, such as porcelain, are inherently brittle and can be prone to fracture under stress.
  • Bonding Mechanism: Ceramics rely on adhesive bonding to tooth structure, which can be compromised by beveling.

Contraindications

  • Cavosurface Margins: Beveling the cavosurface margins of ceramic restorations is contraindicated because:
    • It can weaken the bond between the ceramic and the tooth structure.
    • It may create unsupported enamel, increasing the risk of chipping or fracture of the ceramic material.

Beveling with Amalgam Restorations

Amalgam Characteristics

  • Strength and Durability: Amalgam is a strong and durable material that can withstand significant occlusal forces.
  • Retention Mechanism: Amalgam relies on mechanical retention rather than adhesive bonding.

Beveling Guidelines

  • General Contraindications: Beveling is generally contraindicated when using amalgam, as it can reduce the mechanical retention of the restoration.
  • Exception for Class II Preparations:
    • Gingival Floor Beveling: In Class II preparations where enamel is still present, a slight bevel (approximately 15 to 20 degrees) may be placed on the gingival floor. This is done to:
      • Remove unsupported enamel rods, which can lead to enamel fracture.
      • Enhance the seal between the amalgam and the tooth structure, improving the longevity of the restoration.

Technique for Beveling

  • Preparation: When beveling the gingival floor:
    • Use a fine diamond bur or a round bur to create a smooth, angled surface.
    • Ensure that the bevel is limited to the enamel portion of the wall to maintain the integrity of the underlying dentin.

Clinical Implications

A. Material Selection

  • Understanding the properties of the restorative material is essential for determining the appropriate preparation technique.
  • Clinicians should be aware of the contraindications for beveling based on the material being used to avoid compromising the restoration's success.

B. Restoration Longevity

  • Proper preparation techniques, including appropriate beveling when indicated, can significantly impact the longevity and performance of restorations.
  • Regular monitoring of restorations is essential to identify any signs of failure or degradation, particularly in areas where beveling has been performed.

Inlay Preparation

Inlay preparations are a common restorative procedure in dentistry, particularly for Class II restorations.

1. Definitions

A. Inlay

  • An inlay is a restoration that is fabricated using an indirect procedure. It involves one or more tooth surfaces and may cap one or more cusps but does not cover all cusps.

2. Class II Inlay (Cast Metal) Preparation Procedure

A. Burs Used

  • Recommended Burs:
    • No. 271: For initial cavity preparation.
    • No. 169 L: For refining the cavity shape and creating the proximal box.

B. Initial Cavity Preparation

  • Similar to Class II Amalgam: The initial cavity preparation is performed similarly to that for Class II amalgam restorations, with the following differences:
    • Occlusal Entry Cut Depth: The initial occlusal entry should be approximately 1.5 mm deep.
    • Cavity Margins Divergence: All cavity margins must diverge occlusally by 2-5 degrees:
      • 2 degrees: When the vertical walls of the cavity are short.
      • 5 degrees: When the vertical walls are long.
    • Proximal Box Margins: The proximal box margins should clear the adjacent tooth by 0.2-0.5 mm, with 0.5 ± 0.2 mm being ideal.

C. Preparation of Bevels and Flares

  • Primary and Secondary Flares:
    • Flares are created on the facial and lingual proximal walls, forming the walls in two planes.
    • The secondary flare widens the proximal box, which initially had a clearance of 0.5 mm from the adjacent tooth. This results in:
      • Marginal Metal in Embrasure Area: Placing the marginal metal in the embrasure area allows for better self-cleansing and easier access for cleaning and polishing without excessive dentin removal.
      • Marginal Metal Angle: A 40-degree angle, which is easily burnishable and strong.
      • Enamel Margin Angle: A 140-degree angle, which blunts the enamel margin and increases its strength.
    • Note: Secondary flares are omitted on the mesiofacial proximal walls of maxillary premolars and first molars for esthetic reasons.

D. Gingival Bevels

  • Width: Gingival bevels should be 0.5-1 mm wide and blend with the secondary flare, resulting in a marginal metal angle of 30 degrees.
  • Purpose:
    • Removal of weak enamel.
    • Creation of a burnishable 30-degree marginal metal.
    • Production of a lap sliding fit at the gingival margin.

E. Occlusal Bevels

  • Location: Present on the cavosurface margins of the cavity on the occlusal surface.
  • Width: Approximately 1/4th the depth of the respective wall, resulting in a marginal metal angle of 40 degrees.

3. Capping Cusps

A. Indications

  • Cusp Involvement: Capping cusps is indicated when more than 1/2 of a cusp is involved and is mandatory when 2/3 or more is involved.

B. Advantages

  • Weak Enamel Removal: Helps in removing weak enamel.
  • Cavity Margin Location: Moves the cavity margin away from occlusal areas subjected to heavy forces.
  • Visualization of Caries: Aids in visualizing the extent of caries, increasing convenience during preparation.

C. Cusp Reduction

  • Uniform Metal Thickness: Cusp reduction must provide for a uniform 1.5 mm metal thickness over the reduced cusps.
  • Facial Cusp Reduction: For maxillary premolars and first molars, the reduction of the facial cusp should be 0.75-1 mm for esthetic reasons.

D. Reverse Bevel (Counter Bevel)

  • Definition: A bevel given on the margins of the reduced cusp.
  • Width: Varies to extend beyond any occlusal contact with opposing teeth, resulting in a marginal metal angle of 30 degrees.

E. Retention Considerations

  • Retention Form: Cusp reduction decreases the retention form due to reduced vertical wall height. Therefore, proximal retentive grooves are usually recommended.
  • Collar and Skirt Features: These features can enhance retention and resistance form.

Early Childhood Caries (ECC) Classification

Early Childhood Caries (ECC) is a significant public health concern characterized by the presence of carious lesions in young children. It is classified into three types based on severity, affected teeth, and underlying causes. Understanding these classifications helps in diagnosing, preventing, and managing ECC effectively.

Type I ECC (Mild to Moderate)

A. Characteristics

  • Affected Teeth: Carious lesions primarily involve the molars and incisors.
  • Age Group: Typically observed in children aged 2 to 5 years.

B. Causes

  • Dietary Factors: The primary cause is usually a combination of cariogenic semisolid or solid foods, such as sugary snacks and beverages.
  • Oral Hygiene: Lack of proper oral hygiene practices contributes significantly to the development of caries.
  • Progression: As the cariogenic challenge persists, the number of affected teeth tends to increase.

C. Clinical Implications

  • Management: Emphasis on improving oral hygiene practices and dietary modifications can help control and reverse early carious lesions.

Type II ECC (Moderate to Severe)

A. Characteristics

  • Affected Teeth: Labio-lingual carious lesions primarily affect the maxillary incisors, with or without molar caries, depending on the child's age.
  • Age Group: Typically seen soon after the first tooth erupts.

B. Causes

  • Feeding Practices: Common causes include inappropriate use of feeding bottles, at-will breastfeeding, or a combination of both.
  • Oral Hygiene: Poor oral hygiene practices exacerbate the condition.
  • Progression: If not controlled, Type II ECC can progress to more advanced stages of caries.

C. Clinical Implications

  • Intervention: Early intervention is crucial, including education on proper feeding practices and oral hygiene to prevent further carious development.

Type III ECC (Severe)

A. Characteristics

  • Affected Teeth: Carious lesions involve almost all teeth, including the mandibular incisors.
  • Age Group: Usually observed in children aged 3 to 5 years.

B. Causes

  • Multifactorial: The etiology is a combination of various factors, including poor oral hygiene, dietary habits, and possibly socio-economic factors.
  • Rampant Nature: This type of ECC is rampant and can affect immune tooth surfaces, leading to extensive decay.

C. Clinical Implications

  • Management: Requires comprehensive dental treatment, including restorative procedures and possibly extractions. Education on preventive measures and regular dental visits are essential to manage and prevent recurrence.

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