Introduction To Restorations Luting And Pulp Therapy Notes

Introduction To Restorations Luting And Pulp Therapy

This chapter serves as an introduction to restorative dentistry, including cement, liners, and varnish. An emphasis is also placed on the effect of these materials on the pulp.

Restorations

Tooth material is often lost as a result of caries and trauma. A restoration is a material that substitutes the missing tooth structure and restores the form and function of the tooth.

Types Of Restorations

Restorations may be classified in several different ways.

• Temporary, intermediate, and permanent
• Direct and indirect
• Esthetic and nonesthetic

Read And Learn More: Basic Dental Materials Notes

Temporary Restorations

• Temporary restorations are often required before the placement of a permanent restoration. Materials used for temporary restorations are expected to last for only a short period, a few days or a few weeks Restoration of a tooth.at most.
• They serve as an interim restoration while the pulp heals; and/or till the permanent restoration can be fabricated and inserted. At one time gutta-percha (temporary stopping).
• a thermoplastic gum that is used to fill root canals was popular for this purpose. However, it did not adapt well to the cavity walls, microleakage ensued and sensitivity was a common occurrence.

• Because of its excellent initial sealing ability and kind pulpal response, zinc oxide eugenol (ZOE) is the cement of choice for temporary restorations.
• This material is particularly useful when a sedative treatment is required until the pulp has healed well enough for the permanent restoration to be placed. The Type 1 ZOE is very popular for sedative treatment, temporary coverage, and temporary cementation. Type 3 ZOE is used for temporary restorations.

Intermediate Restorations

• Intermediate or holding type of restoration is particularly used in pedodontics. For example, in rampant caries, it is desirable to remove all the caries quickly to change the oral health and arrest the caries process. Once the initial ‘clean up’ has been done, the dentist can proceed with the placement of the permanent restorations.
• The interval between the removal of the caries and the completion of the final restorative work may take several months. During this time teeth are protected with a desirable intermediate restoration.
• Conventional zinc-eugenol cement used as temporary restorations is deficient in toughness. They have inadequate strength and abrasion resistance to serve for a longer period. As a result polymer reinforced cement (IRM) is used.
• Earlier Type 2 zinc phosphate and Type II or Type 3 zinc silico-phosphate cements were used. However, these materials were irritating to the pulp and required more precise cavity preparation and placement time.
• They are now replaced by improved ZOE formulations. The combination of surface treatment and polymer reinforcement results in good strength, and improved abrasion resistance and toughness. They can last for a period of one year or more.

Requirements Of A Temporary Filling Material

• It should have adequate strength to last a few weeks but is weak enough to be dislodged easily.
• It should be easy to insert and remove.
• It should have an adequate seal.
• It should have antibacterial properties.
• It should have a therapeutic effect (pain relief, healing, etc.) on the pulp.
• It should have cariostatic properties.

Permanent

• The term permanent is not an absolute term. However, it serves to denote any material that is expected to last much longer than the temporary and intermediate restorations. Therefore, it is expected to have improved properties than the temporary and intermediate restorations.
• Examples of permanent restorative materials are direct filling gold, amalgam, composite resins, glass ionomer cement, as well as porcelain, composite, and cast metal inlays and onlays.
• The length of time each material lasts varies on the technical skills of the operator, the material itself, and other patient-related factors. A well-made amalgam restoration would probably last a lifetime or more.
• On the other hand, the composite restoration might have to be replaced much earlier as a result of wear, fracture, or discoloration.

Direct And Indirect Restorations

• Direct restorations These are materials used to build and restore the tooth structure directly in the mouth. They are usually placed in increments. They are usually soft and plastic when initially placed and harden later with time. Examples are amalgam, direct filling gold, composite (can be used both directly and indirectly), and glass ionomer.
• Indirect restorations These are usually fabricated outside the mouth on models of the tooth and then cemented into place in the mouth. Examples of indirect restorations are porcelain, composite, and cast metal inlays and onlays.

Esthetic And Nonesthetic

The terms esthetic and nonesthetic are again relative.

• Esthetic An esthetic material is something pleasing to an individual. At one time gold fillings and crowns were considered esthetic. Today, however, an esthetic material implies any material that is capable of reproducing the color and appearance of a natural tooth. Examples are resin-based composites, glass ionomer, and porcelain restorations.
• Nonesthetic Currently, it denotes any material that is not tooth colored. This includes amalgam, direct filling gold, and metal inlays and onlays.

Luting

• Luting or cementation is the process by which crowns, restorations, and other devices are fixed or attached to tooth structure using an intermediate material called cement. Cements have multiple uses.
• For example, glass ionomer can be used as a base, luting agent, and restorative material. Besides attaching the restoration a luting agent must also seal the space between the restoration and the tooth structure to prevent caries and chemical and bacterial irritation of the tooth and pulp.

Types

• Temporary cementation
• Permanent cementation

Temporary Cementation

• Temporary cementation of crowns and fixed partial dentures (FDP) are often required. Temporary crowns and FDPs are required to stay in place only until the permanent structure is ready. Therefore, it must be weak enough to be easily removed when the permanent structure is ready for cementation.
• In addition, this cement should have some soothing effect on the pulp of the freshly, prepared vital tooth, which would have been traumatized during the preparation. Permanent structures (e.g. crowns or FDPs) are also sometimes cemented temporarily. This allows the patient to take it for a home trial or to observe the pulpal response.
• Once the patient and dentist are satisfied with the results, the restoration is removed and The luting agent attaches as well as seals the space between the restoration and tooth structure. cemented permanently. An example of such a temporary bonding cement is a zinc oxide eugenol-based cement (Temp Bond).

Permanent Cementation

• A permanent cementing material on the other hand should be strong and insoluble in oral fluids. It would also be advantageous if it had some chemical bonding to the tooth structure. In addition, it should be fluid enough to flow well to ensure the complete seating of the restoration.
• Examples of permanent cementing materials are zinc phosphate cement, glass ionomer cement, resin cement, polycarboxylate cement, etc.

General Requirements Of Luting Materials

• They should be nontoxic and nonirritant to pulp and tissues.
• They should be insoluble in saliva and liquids taken into the mouth.
• Mechanical properties: These must meet the requirements for their particular applications, e.g. a cement base should develop sufficient strength rapidly to enable a filling material to be packed on it.
• Protection of the pulp from insults.
  • Thermal insulation, a cement used under a large metallic restoration should protect the pulp from temperature changes.
  • Chemical protection should be able to prevent penetration into the pulp of harmful chemicals from the restorative material.
  • Electrical insulation under a metallic restoration to reduce galvanic shock.
• Optical properties: For the cementation of translucent restorations (e.g. porcelain) the cement should match the color and translucency of the tooth substance.
• Dental cements should ideally be adhesive to both tooth structure and restorative material (gold alloys, porcelain, etc.), but not to dental instruments.
• They should be bacteriostatic in a cavity with residual caries.
• They should have an obtundent (soothing) effect on the pulp.
• Rheological properties: A luting cement should have sufficiently low viscosity to give a low film thickness.

Pulp Capping

Pulp capping is the process of placing a specialized agent in contact with or near the pulp to encourage the formation of new dentin (secondary dentin) and promote the healing of the pulp. Before the discovery of pulp capping agents, pulp exposure often led to irreversible pulpitis or pulpal infection and ultimately pulp necrosis.

Thanks to these pulp capping agents, it became possible to treat pulpal tissue which otherwise would have had to undergo root canal therapy. An example of a pulp-capping agent is calcium hydroxide cement.

Criteria For Pulp Capping

Are all exposed pulps suitable for pulp capping therapy? The answer is no. The dentist has to apply certain criteria and select his cases carefully.

• The pulp should be healthy and noninfected.
• The area of exposure should be no more than 0.5 mm.
• Following exposure the dentist should make all attempts to immediately isolate the tooth and prevent contamination.

Types of Pulp Capping

• Direct pulp capping
• Indirect pulp capping

Direct Pulp Capping

Direct pulp capping is the placement of the agent directly on the exposed pulp. Such a situation is often encountered during

• The excavation of deep carious lesions when the dentist accidentally exposes the pulp.
• Traumatic fractures of the tooth.
• Iatrogenic (caused by treatment) exposure during cavity preparation.
• Iatrogenic exposure during crown preparation.

Indirect Pulp Capping

• Secondary dentin formation can be induced even when the pulp is not exposed but is near exposure. When the calcium hydroxide is placed in the region of the near exposure, it can still induce new dentin formation. This is known as indirect pulp capping.

Indications

• Deep carious lesions close to the pulp.
• During excessive crown preparation, the pulp is often visible through the remaining dentin as a pinkish or reddish spot or area.
• Similar near exposures may be seen in cases of traumatic tooth fractures.

Bases

A base is a layer of cement placed beneath a permanent restoration to encourage recovery of the injured pulp and to protect it against numerous types of insults to which it may be subjected. The type of insults depends upon the particular restorative material.

It may be thermal chemical or galvanic. The base serves as a replacement or substitute for the protective dentin, that has been destroyed by caries or cavity preparation. Nonvital teeth do not require a base.

Types

They belong to two categories.

High strength bases

• These are used to provide thermal protection for the pulp, as well as mechanical support for the restoration.
• Examples of high-strength bases are zinc phosphate, Zinc polycarboxylate, glass ionomer, and reinforced ZOE cement.
• Some important properties of cement used as high-strength bases are strength, modulus of elasticity, and thermal conductivity.

Low strength bases

• Low-strength bases have minimum strength and low rigidity. Their main function is to act as a barrier to irritating chemicals and to provide therapeutic benefits to the pulp. Examples are calcium hydroxide and zinc oxide eugenol.

Properties

Thermal properties

• The base must provide thermal protection to the pulp. This property is important especially when the tooth is restored with metallic restorations.
• The thermal conductivity of most cement bases is similar to tooth structure and is in the range of recognized insulators such as cork and asbestos.
• For effective thermal protection, the base should have a minimal thickness of 0.75 mm. A thin wash of cement would not offer protection against thermal insults through metallic restorations.

Protection against chemical insults

• The cement base also serves as a barrier against penetration of irritating constituents (e.g. acids, monomers, etc.) from restorative materials. Calcium hydroxide and zinc oxide eugenol are most effective for this, especially in deep (close to the pulp) cavities. Polycarboxylate and glass ionomer bases are also used as chemical barriers in more moderate cavities.

Therapeutic effect

• Some bases are used for their therapeutic benefit to the pulp. For example, calcium hydroxide acts as a pulp-capping agent and promotes the formation of secondary dentin. Zinc oxide eugenol has an obtundent effect on the pulp.

Strength

The cement base must have sufficient strength to

• Withstand the forces of condensation. Fracture or displacement of the base permits the amalgam to penetrate the base and contact the dentin. Likewise, in deep cavities, the amalgam may be forced into the pulp through microscopic exposures in the dentin.
• Withstand fracture or distortion under masticatory stresses transmitted to it through the permanent restoration.
• Also, the cement base should develop sufficient strength rapidly to allow early condensation of amalgam. The minimum strength requirement of a base is between 0.5 and 1.2 MPa.

Clinical Considerations

The base is selected according to

• Design of the cavity
• Type of permanent restorative material used
• Proximity of the pulp to the cavity walls.

With amalgam, calcium hydroxide or zinc oxide eugenol cement is usually sufficient.

In the case of direct filling gold where the condensation pressure is higher, a stronger cement is indicated as a base.

With resin restorations, calcium hydroxide is the material of choice, as zinc oxide eugenol cements interfere with its polymerization. Glass ionomer cement can also be used as a base.

Liners And Varnish

Liners and varnishes are agents in a volatile solvent which when applied to a surface evaporates leaving behind a thin film. This film acts as a barrier that has different functions depending on the circumstance and the location where it is applied. These materials are discussed in more detail in the subsequent chapter.