Dental Materials: Amalgam Restorations

Selection of Restorative Materials

• Clinical dentistry relies on a thorough understanding of clinical techniques and the underlying biological, chemical, and physical principles.
• Restorative success hinges on the proper selection of materials. The final restoration's quality is directly tied to the material's properties.

Requirements for an Ideal Restoration

• Adaptability to Cavity Walls and Margins: The material must closely adhere to the cavity walls and margins without gaps to prevent further oral complications.

• Great Strength: The material must withstand the various functional stresses (including tensile, compressive, shear, and impact) in the oral cavity, whether static or dynamic.

• Dimensional Stability: The restoration must maintain a consistent size and shape, resisting expansion or contraction during setting or due to temperature changes in the mouth. Expansion could result in overhang and fracture, while contraction can cause marginal leakage or looseness.

• Biologic Compatibility: The material should not harm adjacent structures (gingival tissues) and the pulp. Maintaining pulp vitality is vital. Factors influencing biologic reaction include the pulp condition, dentin thickness,the pulp's reparative power, the materials' chemical makeup, restorative technique, and its behavior within the oral cavity.

• Insolubility: The material must not dissolve or break down in the oral fluids regardless of their pH levels

• Harmonious Color: The material should match the tooth's natural color (enamel and dentin combination) for a natural appearance.

• Low Thermal Conductivity: Resistant to undesirable thermal changes within the oral environment.

• Convenience of Manipulation: The material should be easy to apply and mold without complicated procedures or specialized equipment; it should not be sensitive to variations in the operator's skill.

• Stop Lesion Progress: The restoration should prevent further deterioration of the tooth by arresting caries, erosion, abrasion, attrition, or fracture.

• Restore Normal Function: The restored tooth should resume normal functionality.

• Restore Speech Defeccts: The restoration should restore or improve speech if it was affected by diastema or chipping.

• Integrity of the Dental Arch and Periodontium: The restoration should have proper anatomy, contours, and contacts to maintain the integrity of the dental arch and structures surrounding the tooth.

Types of Restorative Materials

• Restorative materials are categorized as:

  • Permanent
    • Metallic
    • Non-Metallic
  • Temporary

• Direct Restorations: Materials applied directly to the tooth while in a pliable state, which allow carving and finishing. Examples include amalgam, composite resins, glass ionomer materials, and intermediate restorative materials.

Amalgam

• Advantages:

  • Superior adaptation to cavity walls, improving with aging.
  • High compressive strength, withstanding occlusal forces.
  • Adequate form stability due to insolubility, wear resistance, and low creep in modern alloys that allows it to maintain surface polish, and interproximal contact.
  • Low coefficient of thermal expansion, reducing marginal leakage via reduced marginal percolation.
  • Easy to manipulate and mold, making it readily accessible and efficient.
  • Cost-effective, a key factor in affordability.

• Disadvantages:

  • Unesthetic appearance.
  • Requires mechanical retention methods within the cavity (not adhesive).
  • Environmental and occupational concerns with mercury exposure.
  • Possible thermal and galvanic shocks to pulp causing irritation, and permanent discoloration of the tooth and gingiva.

• Indications:

  • Suitable in some situations, like individuals of all ages.
  • Suitable for small and medium class I & II cavities (not subjected to tensile loads).
  • Ideal in stress-bearing areas of the mouth.
  • Preferable when personal oral hygiene is poor, moisture control is problematic, or cost is a prime consideration.

• Contraindications:

  • When esthetics is a top concern.
  • History of allergy to mercury or other amalgam components.
  • Extensive lesions, particularly undermining cusps (for which gold might be better).
  • Rampant caries (where a glass ionomer may be more suitable).
  • Situations requiring better esthetics.
  • Presence of opposing metallic restorations should also be assessed to avoid galvanic activity

• Requirements for Placing Amalgam:

  • 90-degree cavo-surface angles (butt joint).
  • Appropriate depth.
  • Enough macro-mechanical retention.

• Failure:

  • Improper cavity preparation or application and improper polishing
  • Excessive caries involving multiple surfaces
  • Improper zinc amalgam expansion
  • Inadequate pulp protection
  • Inadequate matrix application
  • Incorrect material preparation.

Composite Resin

• Advantages:

  • Excellent adhesive properties, often preferred for esthetic restorations.
  • Natural appearance.
  • Reasonable durability and wear resistance.
  • Minimal tooth preparation required.
    • Easily shaped to the anatomy of a tooth.
    • Repairable.
    • Command set system.

• Disadvantages:

  • Sensitive to technique.
  • Expensive compared to some other options.
  • Some time-consuming procedures.
  • Postoperative sensitivity due in part to polymerization shrinkage and resultant microleakage
  • Hydrolytic instability.
  • Limited wear-resistance for high stress areas.

• Issues:

  • Volumetric contraction and associated microleakage from thermal changes.
  • Monomers and heat generated during polymerization can harm the pulp.

• Indications:

  • Suitable for diverse situations, such as:
    • Core buildup, and class I, II, III, IV, V, and VI restorations.
    • Sealants and a variety of conservative restorations.
    • Esthetic procedures including veneers, and tooth contour modifications..

• Cavity Preparation:

  • Conservative outline with small extensions.
  • Rounded rather than sharp line and angles to accommodate the restorative material.
  • Beveled cavo-surface angles of 0.5-1 mm.
  • Proper wall preparation regarding material compatibility

• Failure

  • Incomplete removal of decay
  • Improper etching or bonding technique.
  • Lack of moisture control (dentin/composite).
  • Issues concerning composite placement
  • Inadequate finishing and polishing
  • Debonding

Glass Ionomer Cement

• Advantages:

  • Excellent chemical bonding with tooth structure.
  • Biocompatible.
  • Anti-cariogenic and fluoride releasing.
  • Relatively less technique sensitive than other materials.
  • Minimal cavity preparation.
  • Good marginal sealing.
  • Less dimensional change compared to other restorative materials.
  • Variety of modification options.
  • Acts as a fluoride reservoir

• Disadvantages:

  • Brittle and susceptible to erosion and wear.
  • Lower fracture resistance and wear resistance.
  • Less esthetic due to opacity.
  • Requires moisture control.
  • Reduced compressive strength
  • Water sorption can occur.,

• Issues:

  • Intimate adaptation for minimizing microleakage can sometimes become an issue.

• Indications:

  • Restoration of permanent teeth (class V, III, small class l), root caries, erosion, and abrasion.
  • Restoration of deciduous teeth.
  • Used for luting cement.
  • Preventive restoration of pits and fissures.
  • Important restorative material options used in primary posteriors (small occlusal and interproximal cavities).

• Contraindications:

  • Stress-bearing areas.
  • Cuspal replacement cases.
  • Situations requiring high degrees of esthetics.

Factors influencing material selection

• Material factors: Properties of the available restorative options.

• Patient factors: Patient's general health, oral hygiene, and personal factors

  • Age: Young patients may cope worse with extensive procedures, while older patients may need more suitable options for their physical conditions.
  • Gender: Male patients prefer stronger, more lasting restorations, while female patients tend to prioritize esthetic features.
  • Occupation: Patients with demanding jobs may favor restorations that are easy to maintain or that provide strength, whereas patients with exposure to substances that impact oral health might need more durable restorations.
  • Physical condition: This ranges from factors like their physical health to their ability to tolerate long procedures, and it should be considered for restoration planning.
  • Educational background: Education can impact how patients understand and cooperate with a restoration plan.
  • Psychological conditions: The dentist should also be considering the patient's psychological state when providing restorative options.
  • Habits: Habits like smoking or alcohol abuse can affect the material selection.
  • Economic condition: Cost and availability of restorative options can impact patient choice.

• Oral cavity factors: Include high caries incidence, oral hygiene, and malocclusion, etc

  • Oral hygiene: Patients with good oral hygiene can be restored with more types of restorative alternatives than those with poor oral hygiene.
  • Caries issues: Extensive caries may cause problems with restorative options, and short term procedures might be helpful, particularly in patients needing a long treatment plan.
  • Occlusal conditions: Occlusal condition can be a critical factor when determining the optimal restorative restoration; a better-planned and selected restorative procedure can result in patient comfort.

• Cavity Factors: These include the size, shape and location of the cavity along with the tooth's structure and pulp vitality.

• Tooth factors: These include factors including the tooth's condition and structure.

• Operator factors: The operator's expertise and knowledge of available restorative materials, their ability to perform restorative techniques successfully, and to provide adequate patient follow-up.

Success and Failure factors

• Material: The quality and suitability of the chosen material are essential.
• Contamination during restoration: Careless handling or improper timing during procedures can lead to issues.
• Technical expertise: The skill and knowledge of the operator impact the success of the restoration.
• Oral hygiene: Patients' oral hygiene practices before, during, and after the restoration directly impact restoration longevity.
• Dietary habits: Foods and substances can impact the longevity and effectiveness of restoration.

Test your knowledge on the properties, advantages, and contraindications of using amalgam in dental restorations. This quiz covers essential criteria for restorative materials and their adaptability. Perfect for dental students and professionals seeking to refresh their understanding of amalgam applications.