Temporary Filling Materials
Temporary fillings are used for the hermetic sealing of the prepared carious cavity. Depending on the clinical objective, the period of their wear varies from 24 hours to one year.
The main indications for their placement are:
- Isolation of medications during caries treatment.
- Differential diagnostics of pulp conditions (control fillings).
- Filling of primary teeth.
- Creation of insulating barriers.
- Short-term fixation of orthopedic appliances.
- Temporary obturation of root canals.
According to their chemical structure, these agents are divided into three groups: zinc-eugenol, non-eugenol (zinc sulfate), and light-cured.
Comparative Characteristics of Non-Eugenol Cements
In domestic dentistry, zinc sulfate preparations are actively used: dentin paste and artificial water dentin. They differ in both composition and working technique.
- Dentin paste. A single-component mass consisting of zinc oxide and sulfate, kaolin, and vegetable oils (clove, apricot, peach). Does not require manual mixing. It is placed into the cavity with a plastic instrument, compacted with a condenser or cotton pellet, and hardens in about 2 hours under the influence of saliva and body temperature.
- Artificial dentin. A powder without the addition of oils. It is mixed on a rough glass slab with distilled water using a metal spatula for exactly 30 seconds. It hardens in just 1 minute, but is significantly inferior to paste in mechanical strength.
| Characteristic | Dentin paste | Artificial dentin |
|---|---|---|
| Presence of oils | Present | No |
| Preparation | Ready to use | Mixed with water |
| Setting time | 2 hours | 1 minute |
Clinical limitation: Slow-setting cements (including certain zinc-eugenol masses that set in 6–8 hours) must not be used to isolate necrotizing pastes. Due to the long setting time, the toxic substance may leak out and cause a chemical burn of the oral mucosa.
Delayed Fillings and Therapeutic Liners
If a defect needs to be sealed for a period of up to one year, delayed fillings are placed. In such cases, more reliable cements are used: zinc phosphate, polycarboxylate, glass ionomer, or polymer materials (for example, Comstan).
When treating deep caries or in case of accidental pulp exposure, it is necessary to use a therapeutic liner. It prevents irritation of nerve endings during preparation and protects tissues from bacterial toxins.
According to their mechanism of action, liners are divided into:
- Biological — combat microorganisms and relieve inflammation (contain enzymes, vitamins, antibiotics, corticosteroids).
- Odontotropic — stimulate the synthesis of secondary dentin.
- Combined — most often calcium hydroxide preparations.
Calcium Hydroxide-Based Preparations
Calcium hydroxide cements play a key role in the treatment of pulpitis and deep caries. Their pronounced therapeutic effect is based on a powerful alkaline reaction (pH up to 12.0), which stops inflammatory acidosis, destroys bacteria, and stimulates the production of new dentin.
The properties of the liner largely depend on the type of carrier:
- Aqueous carrier. Leaves a thin and brittle film after water evaporation. Requires mandatory coverage with a durable sealing layer.
- Polymer carrier. Creates a dense and reliable barrier. Can be applied for a period of more than 1 month and safely left under a permanent restoration.
Modern liner materials are applied spot-wise onto the projection of the pulp horns. They are available as two-component (base and catalyst for chemical curing) or single-component (light-cured masses capable of isolating the entire cavity floor).
Briefly: answers to topical questions
What are the physical and mechanical properties of glass ionomer cements?
The physical and mechanical properties of glass ionomer cements include a number of positive and negative characteristics.
Positive properties include:
- Thermal conductivity — the lowest among all filling materials (~0.198 mm²/s).
- Resistance — they are resistant to acid exposure.
- Modulus of elasticity — low, which compensates for internal stress during composite shrinkage.
- Adhesion — chemical bonding to dentin via hydrogen and ionic bonds.
- Shrinkage — low polymerization shrinkage.
- Esthetics — satisfactory aesthetic characteristics and color stability.
- Radiopacity — characteristic of most materials in this group.
Negative properties include moisture sensitivity during the setting phase, slow setting, and the risk of surface overdrying, which leads to a deterioration of physical and mechanical properties.
The "PP — DD" rule: Paste — Simple (ready immediately, sets slowly); Dentin — Long preparation (needs mixing, but sets quickly).
Class and exam questions
Can zinc oxide-eugenol cement be placed over arsenical paste?
No, this is strictly contraindicated. Zinc-eugenol compositions set within 6–8 hours, which can cause the toxic substance to seep through and induce a chemical burn of the oral mucosa.
How does artificial dentin differ from dentin paste?
The powder of artificial dentin does not contain vegetable oils, so it must be mixed with distilled water. It sets faster (in just 1 minute), but has lower strength compared to paste.
What is the therapeutic effect of calcium hydroxide?
It has a high pH level (up to 12.0), which provides a prolonged antiseptic effect, neutralizes the acidic environment during inflammation, and stimulates the formation of secondary dentin by the pulp.
What else to study on this topic
- Mechanisms of secondary dentin formation under the influence of odontotropic agents.
- Specifics of using glass ionomer and zinc phosphate cements for delayed fillings.
- Technique of spot application of liner materials to the projection of the pulp horns.
- Features of mixing two-component chemically cured liners.
- Interaction of biological liner components (corticosteroids, antibiotics, and enzymes) with dental tissues.
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