Dental Materials and Mixing Techniques
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Questions and Answers

What are the potential effects of using a temporary filling material if the cavity extends below the gums?

It may irritate the gums.

Why is it important to follow the manufacturer’s P/L ratio instructions when mixing dental cement?

Adhering to the P/L ratio ensures optimal consistency, flow, and minimizes irritation to the pulp.

Describe the correct process of incorporating powder into liquid when mixing dental cement.

The powder should be added to the liquid in small increments to achieve the desired consistency.

What steps should be taken to ensure a good working time when mixing dental cement?

<p>The glass slab and spatula should be clean and cool during mixing, and the mixing should begin with the powder.</p> Signup and view all the answers

What should be done to prevent cement from adhering to the spatula during application?

<p>The spatula can be dipped in powder before use.</p> Signup and view all the answers

What effect does the reaction between zinc oxide powder and ortho-phosphoric acid have upon mixing?

<p>An exothermic acid-base reaction occurs, initially resulting in a pH of 3.5.</p> Signup and view all the answers

What is the primary purpose of a dental base material in cavity preparation?

<p>The primary purpose is to protect the pulp by providing thermal insulation and absorbing occlusal forces.</p> Signup and view all the answers

What are the main disadvantages of using zinc phosphate cement as a temporary filling material?

<p>It is brittle, lacks adhesion, and is soluble in oral fluids.</p> Signup and view all the answers

Why should a cavity base material be bacteriostatic or bactericidal?

<p>It should be bacteriostatic or bactericidal to prevent the increase of bacteria in the cavity.</p> Signup and view all the answers

List two clinical advantages of zinc phosphate cement.

<p>It can be easily manipulated and provides adequate clinical resistance at a low powder/liquid ratio.</p> Signup and view all the answers

In what scenarios is zinc phosphate cement indicated for use?

<p>It is indicated for temporary sealing of cavities and as a base material for permanent fillings.</p> Signup and view all the answers

What are the two commonly used cavity base materials mentioned?

<p>The two commonly used materials are zinc phosphate cement and glass ionomer cement.</p> Signup and view all the answers

When is it sufficient to use only a cavity liner instead of a full base material?

<p>It is sufficient when the remaining dentin thickness is more than 2 mm.</p> Signup and view all the answers

What is the contraindication for the use of zinc phosphate cement in certain teeth?

<p>It is contraindicated for teeth with little dentin tissue, as it can irritate the pulp.</p> Signup and view all the answers

What protective barrier does a cavity base material provide against chemical irritants?

<p>It provides a barrier against chemical irritants like phosphoric acid and acrylic monomers.</p> Signup and view all the answers

What happens to the acidity of zinc phosphate cement after it is mixed?

<p>The acidity decreases significantly within one hour after mixing.</p> Signup and view all the answers

How does a cavity base material protect the pulp from galvanic currents?

<p>It protects the pulp by preventing electrical currents generated by restorations made of different metals.</p> Signup and view all the answers

Why is zinc phosphate cement not preferred as a temporary filling material?

<p>It wears out quickly and is easily exposed to plaque accumulation.</p> Signup and view all the answers

How does zinc phosphate cement play a role in orthodontics?

<p>It is used in bonding orthodontic bands and securing crowns, bridges, and inlays.</p> Signup and view all the answers

What property must a cavity base material have to resist external forces?

<p>A cavity base material must be resistant to chewing pressures.</p> Signup and view all the answers

Why is it important for cavity base materials to be radiopaque?

<p>It is important so that their borders can be clearly identified on radiographs.</p> Signup and view all the answers

What are the three types of glass ionomer cement (GIC) classified based on their applications?

<p>Type I is luting cement for crowns and bridges, Type II is restorative cement for aesthetic fillings, and Type III is used as liners and bases.</p> Signup and view all the answers

Describe the mechanism of adhesion of glass ionomer cement to tooth structure.

<p>The adhesion of glass ionomer cement to teeth is achieved through both mechanical and chemical bonding.</p> Signup and view all the answers

List two advantages of using glass ionomer cement in dental restorations.

<p>The advantages include fluoride release properties and thermal compatibility with tooth structure.</p> Signup and view all the answers

Identify two disadvantages of glass ionomer cement.

<p>Disadvantages include poor mechanical properties and low esthetics due to lack of translucency.</p> Signup and view all the answers

What precautions should be taken when the distance to the pulp is less than 0.5 mm?

<p>A calcium hydroxide primer made of glass ionomer material should be used to protect the dentin surface.</p> Signup and view all the answers

How do occlusal forces and porosities affect the longevity of glass ionomer cement restorations?

<p>Occlusal forces and porosities can lead to increased wear and potential failure of the restorations over time.</p> Signup and view all the answers

Explain the relationship between the size of glass ionomer cement particles and wear rate.

<p>Larger glass ionomer cement particles are associated with decreased wear rates.</p> Signup and view all the answers

What factors influence the solubility of glass ionomer cement at the margins?

<p>The solubility depends on the amount of cement present at the margins.</p> Signup and view all the answers

What is the purpose of applying 10% polyacrylic acid during tooth preparation?

<p>It increases the surface energy and wettability of the tooth, which improves chemical bonding.</p> Signup and view all the answers

How should the powder and liquid components of the restoration be mixed?

<p>The powder should be divided into two equal increments and mixed with the liquid immediately within 20-30 seconds.</p> Signup and view all the answers

What is the recommended time frame for application of glass ionomer cement after it is mixed?

<p>The application time is 2-3 minutes.</p> Signup and view all the answers

Why should the spatula be dipped in alcohol during the cement application process?

<p>To prevent the glass ionomer cement from sticking to the spatula, making removal easier.</p> Signup and view all the answers

What materials can be used to protect the setting cement during its initial setting phase?

<p>A matrix band, varnish, cocoa butter, or vaseline can be used for protection.</p> Signup and view all the answers

What steps are involved in the initial finishing of a glass ionomer cement restoration?

<p>Initial finishing involves the removal of gross excess material with a sharp hand instrument.</p> Signup and view all the answers

In which types of carious lesions are glass ionomer cement restorations indicated?

<p>They are indicated for class III and class V carious lesions, as well as root caries.</p> Signup and view all the answers

What is the importance of covering the setting cement with a matrix band during initial setting?

<p>It helps to protect the cement from moisture, ensuring proper setting.</p> Signup and view all the answers

What components are added to conventional glass ionomer to create hybrid ionomer or resin-modified glass ionomer cement?

<p>Resins like bisphenol A-glycidyl dimethacrylate or urethane dimethacrylate and photoinitiators are added.</p> Signup and view all the answers

Describe the dual-reaction curing mechanism of hybrid ionomers.

<p>It consists of acid-base and polymerization reactions that occur simultaneously upon mixing the powder and liquid.</p> Signup and view all the answers

What is the 'umbrella effect' in the context of hybrid ionomers?

<p>The 'umbrella effect' refers to the resin protecting the acid-base setting reaction from moisture contamination.</p> Signup and view all the answers

How does the ionic activity of hybrid ionomers compare to conventional glass ionomer cements?

<p>The ionic activity of hybrid ionomers is reduced due to the presence of resin.</p> Signup and view all the answers

What impact does the pH difference between resin-modified glass ionomer and conventional GIC have on pulp irritation?

<p>The initial pH of the hybrid ionomer is higher (pH=3.5), which reduces pulp irritation compared to conventional GIC (pH=2).</p> Signup and view all the answers

Which mechanical properties of hybrid ionomer cement are superior to conventional GIC?

<p>Wear resistance, fracture toughness, flexural strength, and diametral tensile strength are superior.</p> Signup and view all the answers

Explain why the fluoride release from hybrid ionomers is lesser than that from conventional GIC.

<p>The presence of resin reduces the ionic activity, leading to a lesser bonding tendency and fluoride release.</p> Signup and view all the answers

What are the main components of the liquid used in resin-modified glass ionomer cement?

<p>The liquid is an aqueous solution of polyacrylic acid and 10% 2-HEMA.</p> Signup and view all the answers

Flashcards

What is a dental base?

Dental base materials are placed on the floor of a cavity preparation to protect the pulp from various factors.

What are the properties of dental base materials?

A dental base should be bacteriostatic/bactericidal, non-toxic, hermetically seal the cavity, provide thermal insulation, protect from chemical irritants, prevent electrical/galvanic currents, be resistant to chewing, and be radiopaque.

How does a dental base provide thermal insulation?

One of the main functions of a dental base is to insulate the pulp from temperature changes, especially when using metal fillings like amalgam.

How does a dental base protect from chemical irritants?

Dental bases are sometimes needed to shield the pulp from chemicals present in some filling materials, such as phosphoric acid in silicates or acrylic monomers in resins.

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How does a dental base protect from electrical currents?

Dental bases can help prevent pulp damage caused by electrical currents generated when different metal restorations are in contact in the mouth.

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Why should a dental base be resistant to chewing forces?

Dental bases should be strong enough to withstand chewing forces and prevent the restoration from collapsing or cracking.

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Why should a dental base be radiopaque?

Dental bases should be radiopaque so that they can be easily seen on x-rays.

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What are some common dental base materials?

Commonly used dental base materials include zinc phosphate cement and glass ionomer cement.

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Zinc Phosphate Cement

A dental material that sets through an acid-base reaction between zinc oxide powder and phosphoric acid liquid.

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Powder Composition of Zinc Phosphate Cement

Zinc oxide, magnesium oxide, bismuth oxide, silica, and zinc are the key ingredients in the powder component of this cement.

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Liquid Composition of Zinc Phosphate Cement

Orthophosphoric acid and water make up the liquid component, creating an acidic environment that reacts with the powder.

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Exothermic Reaction of Zinc Phosphate Cement

The mixing of the powder and liquid initiates a chemical reaction, generating heat.

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pH Change of Zinc Phosphate Cement

Initially acidic, its pH decreases over time, reaching neutrality after 24 hours.

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Indications of Zinc Phosphate Cement

Used for temporary fillings, as a base material, and in bonding procedures like orthodontic bands and crown placement.

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Disadvantages of Zinc Phosphate Cement

Surface wear, lack of adhesion, and solubility in saliva are some drawbacks.

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Contraindications of Zinc Phosphate Cement

Its acidic nature makes it unsuitable for deep cavities, as it can irritate the dental pulp.

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Glass Ionomer Cement (GIC)

A type of dental cement known for its fluoride release and ability to bond to tooth structure.

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Type I GIC

The type of GIC used for cementing crowns and bridges.

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Type II GIC

The type of GIC used as restorative material for fillings.

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Type III GIC

The type of GIC used for liners and bases.

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Chemical Bonding in GIC

The ability of GIC to chemically bond to tooth structure, thanks to the presence of polyacrylic acid.

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Caries Preventive Action of GIC

The advantage of GIC that contributes to tooth protection and prevents decay.

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Factors Affecting GIC Longevity

The longevity of GIC restorations can be affected by factors like occlusal forces, porosities, and moisture.

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GIC for High-Caries-Risk Patients

The release of fluoride from GIC makes it beneficial for patients with a high risk of tooth decay.

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Dental Cement Consistency

The consistency of dental cement can influence its effectiveness in cavity filling. A putty-like consistency is suitable for cavity lining, while a more fluid mix is needed for luting, ensuring proper flow and bonding.

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Powder-to-Liquid Ratio (P/L)

The powder-to-liquid ratio (P/L) determines the thickness and setting time of dental cement. A low P/L ratio results in higher acidity, weaker mix and potential irritation to the pulp. A high P/L ratio leads to a thicker mix, faster setting time, and less working time.

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Mixing Dental Cement

Mixing dental cement correctly is crucial for its successful use. The mixing process should be slow, using a cool, dry glass slab, and adding powder to the liquid in small increments to achieve the desired consistency.

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Avoiding Gum Irritation

Improper manipulation of dental cement can cause irritation to the gums, especially when filling cavities extending below the gum line. The cement should be applied in small pieces, evenly coating the cavity walls to avoid excess residue.

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Working Time of Dental Cement

Working time of dental cement is typically 2-3 minutes. It is important to ensure the glass slab is clean and dry, and to use clean dry instruments for handling the cement during placement.

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What is Glass Ionomer Cement (GIC)?

Glass ionomer cement (GIC) is a dental material that releases fluoride and bonds chemically to tooth structure. It's used for filling cavities, restoring damaged teeth, and bonding indirect restorations like crowns.

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What are some common uses for GIC?

GIC is often used for restoring class III and class V cavities, as well as for tunnel restorations. It can also be combined with resin composite in a 'sandwich' technique for larger restorations.

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Why is GIC used for luting indirect restorations?

GIC is a popular choice for luting indirect restorations, such as crowns and bridges, because it bonds directly to the tooth structure and releases fluoride to protect the surrounding area.

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What other applications does GIC have in dentistry?

GIC is also used for bonding post and core systems, orthodontic bands, and brackets to teeth.

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How is the tooth surface prepared for GIC application?

Before applying GIC, a pumice slurry is used to clean the tooth surface, followed by conditioning with 10% polyacrylic acid to increase surface energy and improve bonding.

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How is GIC placed and adapted in the cavity?

After mixing the powder and liquid, the GIC is carefully placed in the cavity preparation using a cement carrier and adapted with a condenser.

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Why is moisture protection crucial during the initial setting of GIC?

After placing the GIC, it needs to be protected from moisture during its initial set with a matrix band and then later with varnish, cocoa butter, or vaseline. This is because GIC is sensitive to moisture for the first 24 hours.

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When and how is GIC finished and polished?

Once the GIC is set, it can be finished and polished. Initial finishing involves removing excess material, while final finishing is done after 24 hours.

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What is resin-modified glass ionomer cement (RM-GIC)?

A type of dental cement that combines the properties of traditional glass ionomer cements (GICs) and resin composites.

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What are the components of RM-GIC?

RM-GICs contain both powdered glass and a liquid solution of polyacrylic acid, similar to conventional GICs. They also include resins like bisphenol A-glycidyl dimethacrylate and photoinitiators.

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How does RM-GIC set?

RM-GICs set through two reactions: an acid-base reaction between glass and polyacrylic acid and a polymerization reaction of the resins. This dual curing mechanism provides both initial strength and long-term durability.

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What is the 'umbrella effect' in RM-GIC?

The setting reaction of RM-GICs is initiated by either chemical or light activation, which protects the underlying acid-base reaction from moisture contamination. This is referred to as the 'umbrella effect'.

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How does RM-GIC bond to the tooth?

RM-GICs are known to bond to tooth structure chemically. However, the presence of resin in the material slightly reduces the ionic bonding strength compared to conventional GICs.

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What is the fluoride release from RM-GIC like?

Although RM-GICs release fluoride, which helps prevent cavities, the rate of release is slightly lower than conventional GICs. The amount and type of resin can influence the rate of fluoride release.

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Is RM-GIC gentler on the pulp?

Because the initial pH of RM-GICs is higher than conventional GICs (pH 3.5 vs. pH 2), they generally cause less irritation to the pulp compared to traditional GICs.

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How do the properties of RM-GICs compare to GICs?

RM-GICs exhibit superior properties than conventional GICs in terms of wear resistance, fracture toughness, and flexural strength. However, their compressive strength is generally lower. They also offer better translucency compared to conventional GICs.

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Study Notes

Cavity Base Materials

  • Dental base is a material placed on the cavity floor, acting as a relatively thick layer.
  • Its purpose is to protect the dental pulp by providing thermal insulation from temperature changes and absorbing occlusal forces.
  • It can also be used to line out undercut areas of indirect restorations like gold or composite inlays.

Types of Base Materials

  • Zinc phosphate cement and glass ionomer cement are commonly used.

Properties of Cavity Base Materials

  • Bacteriostatic/bactericidal: Prevents bacterial increase.
  • Non-toxic: Should not harm hard or soft tissues.
  • Hermetic sealing: Prevents microleakage and secondary caries.
  • Thermal insulation: Protects the pulp from temperature changes.
  • Adhesion to tooth structure: Bonds to the tooth and fillings.
  • Resistance to chewing pressure: Resists breakage and cracking.
  • Radiopaque: Visible on radiographs for border detection.
  • Suitable working time and setting time: Must harden quickly at mouth temperature.

Additional Considerations

  • Protective barrier: Prevents chemical irritants from filling materials.
  • Electrical/galvanic current protection: Prevents current from different metals in the mouth.
  • Resistance to chewing pressure and damage.
  • Radiopaque to assess margins
  • Proper adhesion and bonding to adjacent materials and tooth.
  • Sufficient working time and fast hardening time.

Zinc Phosphate Cement

  • Powder: Zinc oxide, magnesium oxide, bismuth oxide, silica
  • Liquid: Orthophosphoric acid, water
  • Acidic (pH 3.5) during mixing, which decreases within an hour.
  • Complete neutralization within 24 hours.
  • Not preferred as a temporary filling because of quick surface breakdown and plaque accumulation.

Advantages of Zinc Phosphate Cement

  • Quick hardening
  • Sufficient clinical resistance even at a low powder/liquid ratio
  • Easy to manipulate

Disadvantages of Zinc Phosphate Cement

  • Pulpal irritation
  • Lack of antibacterial properties
  • Brittleness
  • Lack of adhesion
  • Solubility in oral fluids

Indications for Cavity Base Materials

  • Temporary sealing of cavities in permanent and deciduous teeth.
  • Base material in cavities of deciduous and permanent teeth to ensure placement of permanent filling.
  • Used in bonding of orthodontic bands, crowns, bridges, inlays, and for decayed teeth prior to crown-bridge fabrication.

Contraindications for Cavity Base Materials

  • Deep caries with minimal dentin tissue exposed
  • Teeth with sensitive pulps
  • If used as a temporary filling, may irritate gums if the cavity extends below the gum line.

Manipulation of Zinc Phosphate Cement

  • Powder/liquid ratio: Follows manufacturer instructions.
  • Mixing: Mixing procedure should begin from powder to liquid and spatulated on a cool, dry glass slab in increments to prevent heat generation and increase working time.
  • Application: Applied as small pieces to the cavity and subsequently coated on walls.
  • Working time: 2-3 minutes

Glass Ionomer Cement

  • Powder: Fluoroaluminasilicate glass, aluminum oxide, calcium fluoride, aluminum fluoride, and silicon oxide
  • Liquid: Polyacrylic acid, tartaric acid, taconic acid, and distilled water

Classification of Glass Ionomer Cement

  • Type I: Luting cement for crowns and bridges
  • Type II: Restorative cement for aesthetic fillings
  • Type III: Liner and base materials

Resin-Modified Glass Ionomer Cement

  • Hybrid material between traditional glass ionomer cement and resin composite.
  • Composition: Powder (fluoro-aluminosilicate glass, light, and chemical initiators), liquid (aqueous solution of polyacrylic acid and 10% 2-HEMA).

Setting Reaction of Resin-Modified Glass Ionomer Cement

  • Dual-reaction curing mechanism (acid-base and polymerization).
  • Polymerization reaction starts from the mixing of liquid and powder with chemical and light initiations.
  • "Umbrella effect": Reaction protects against moisture contamination, providing greater initial strength.
  • Acid-base reaction is the determining factor for the final strength of the material.

Advantages of Resin-Modified Glass Ionomer Cement

  • Chemical bonding to tooth structure
  • Caries preventive action
  • Thermal compatibility with tooth structure
  • Mild pulp response
  • Tooth colored restorative material
  • Easy manipulation
  • Longer working time
  • Superior wear resistance, fracture toughness, flexural and diametral tensile strength compared to conventional GIC

Disadvantages of Resin-Modified Glass Ionomer Cement

  • Lower mechanical durability compared to composites
  • Less aesthetic compared to composites
  • Moisture sensitive during setting

Indications for Resin-Modified Glass Ionomer Cement

  • Class V restorations
  • Restoration of non-carious cervical lesions
  • Class I and II restorations in primary teeth
  • Liner/base under composite restorations (sandwich technique)

Manipulation of Resin-Modified Glass Ionomer Cement

  • Polymerized by light
  • Incremental layering techniques for reduced polymerization shrinkage
  • Polishing can be done immediately but 24 hours is preferred.

Restoration Procedure

  • Cleaning: Apply pumice slurry to the tooth surface.
  • Conditioning: Apply 10% polyacrylic acid to the tooth surface for 10 seconds.
  • Placement: Apply mixed GIC to the cavity using a condenser or cement carrier.
  • Protection of cement: Cover with matrix band or varnish during setting and apply varnish, cocoa butter, or petroleum jelly after the first 24 hours.
  • Finishing and polishing: Removal of excess material and final finishing.

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Description

This quiz covers critical concepts related to dental temporary fillings, cement mixing techniques, and the properties of various dental materials. It explores the importance of following manufacturer's guidelines, the benefits and disadvantages of using zinc phosphate cement, and the role of cavity base materials. Test your knowledge and understanding of these essential dental practices.

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