Dental Amalgam

Dental Amalgam

Chapter Overview

  • Overview of dental amalgam as a restorative material.

  • Protection of copyright and data mining rights noted.

Lesson 11.1: Dental Amalgam (1 of 3)

  • Main Components of Dental Amalgam:

    • Silver, tin, copper, and mercury are critical components of dental amalgam.

  • Particle Shapes in Dental Amalgam:

    • Lathe-Cut Alloys: Characterized by irregularly shaped particles that can create a thicker mass, resulting in higher condensation resistance.

    • Admix Alloys: A combination of lathe-cut and spherical particles, aimed for a balance of versatility and strength.

    • Spherical Alloys: Features spherical particles that facilitate smooth manipulation and quicker condensation.

  • Effects on Condensation Resistance: The particle shape affects the amalgam's handling characteristics, particularly under condensation pressure.

Lesson 11.1: Dental Amalgam (2 of 3)

  • Mixing Time:

    • Longer mixing times may enhance strength but could adversely affect manipulability; optimum time is critical for effective binding.

  • Advantages and Disadvantages:

    • Advantages:

    • Ease of manipulation

    • Durability

    • Cost-effectiveness

    • Disadvantages:

    • Aesthetic concerns (not tooth-colored)

    • Safety concerns regarding mercury content.

  • Safety: Discussion on the safety profile of amalgam as a restorative material and the mercury hygiene practices that must be followed in dental offices.

  • Recycling: Proper collection and processing of amalgam scrap for environmental considerations.

Lesson 11.1: Dental Amalgam (3 of 3)

  • Matrix Band for Class II Amalgam: Proper size selection of the matrix band is crucial to ensure adequate space and support during restoration.

  • Tofflemire Band Assembly: Correct assembly techniques are essential for final restoration quality.

  • Evaluation Criteria: A class II amalgam matrix setup must meet specific placement criteria to be effective.

  • Amalgam Placement: Students may assist with or perform amalgam placement in class II cavity preparations as per state regulations.

History of Dental Amalgam

  • Historical Use: Dental amalgam has been utilized for over 180 years.

  • Advantages:

    • Easy to manipulate, durable, and low-cost material.

  • Disadvantages:

    • Lacks aesthetic appeal and has raised safety concerns over time.

Alloys Used in Dental Amalgam

  • Composition: Dental amalgam alloys are silver-based mixtures predominantly featuring silver and tin, with copper and other metals added.

  • Classification: Alloys are categorized by the shape of their powder particles:

    • Irregular particles

    • Spherical particles

    • Admixed combinations of the two.

Setting Transformation (Amalgamation)

  • Process Details: The alloy in powder form is combined with liquid mercury, prompting a chemical reaction that results in amalgamation.

  • Initial Consistency: The amalgam must achieve a consistency suitable for shaping before hardening.

  • Setting Reactions: Amalgamation occurs in three key phases.

Phases of Amalgamation

  • Gamma Phase (ϒ):

    • Strongest phase with the least corrosion susceptibility.

  • Gamma 1 Phase (B31):

    • Intermediate in strength.

  • Gamma 2 Phase (B32):

    • Weakest phase that is prone to corrosion.

Properties of Amalgam

  • Critical Properties Include:

    • Strength

    • Dimensional changes, including delayed expansion

    • Creep and tarnish properties

    • Corrosion attributed to galvanic reactions

    • Thermal conductivity which affects comfort post-application.

Applications for Dental Amalgam

  • Suitable for:

    • Small-to-moderate intracoronal restorations.

    • Stress-bearing areas, typically on posterior teeth.

    • Large cavity preparations and replacing missing cusps.

    • Crown foundations and sealing root apices.

    • Situations where blood/saliva control is challenging during restorations.

Manipulation of Amalgam

Dispensing and Trituration

  • Dispensing Method: Use of pre-filled capsules for alloy and mercury.

  • Trituration: Analysis of proper mixing time essential to prevent packing and improper setting.

Working and Setting Time

  • Working Time: Time available for manipulation before the material begins to set.

  • Setting Time: Differentiation between initial and final setting times which is critical for treatment planning.

Placement and Finishing

  • Placement Techniques: Proper protocol for placement and condensation of amalgam.

  • Finishing: Includes instructions for polishing and applying cavity sealers to prevent microleakage, specifically noting the use of copal varnish.

Longevity of Amalgams

  • High-Copper Amalgams: Notable longevity due to reduced corrosion, improved strength, and marginal integrity compared to low-copper alternatives.

  • Clinical Indications for Replacement: Postoperative sensitivity, pain, and failures. Recognize common signs indicating the need for repair or replacement.

Allergy to Amalgam

  • Considerations regarding sensitivity to metals in amalgam and its implications for patient care.

Safety of Dental Amalgam

  • ADA Stance: Consistent support for the use of dental amalgam by the American Dental Association, confirming its safety with evidence that suggests it is not harmful to the general population.

  • Recommendations for clinicians on risk assessment regarding amalgam restoration choices with patients.

Concerns About Mercury Exposure

Patient Safety Practices

  • Use of rubber dams and high-volume evacuators to minimize exposure; special concerns for pregnant patients and young children.

  • Regulations around amalgam waste and the necessary environmental protections in dental practices.

Environmental Impact

  • Health risks and regulations regarding publicly owned treatment works (POTWs) and amalgam separators.

Restrictions on Amalgam

  • Historical Restrictions: Discussion of Japan's approach to banning amalgam use in pediatric and pregnant populations during the 1980s.

  • 93 countries commitment in 2013 to strategies for reducing amalgam utilization.

Dental Assistant Role

  • Responsibilities in patient education regarding amalgam use and safety.

  • Importance of adhering to manufacturer instructions for handling amalgam and staying updated on protocols.