Dental materials: MTA

Chemical composition of MTA dental material

MTA is a mechanical mixture of 3 powdered ingredients:

• Portland cement (75%) • Bismuth oxide (20%) • Gypsum (5%)

Portland cement composition includes :

• Dicalcium silicate • Tricalcium silicate • Tricalcium aluminate •Tetracalcium aluminoferrite

Mineral Trioxide Aggregate

• Mineral trioxide aggregate is a biocompatible material with varied clinical applications in endodontics.

• MTA is mainly comprised of Portland cement, to which oxides such as bismuth oxide are added to confer radiopacity to the material.

• Portland cement consists of fine hydrophilic particles: Tricalcium silicate, Tricalcium aluminate, Silica oxide and Tricalcium oxide are the major components and few other mineral oxides are responsible for chemical and physical properties of MTA.

• The material offers an improvement over other materials especially in endodontic procedures involving root repair and bone healing.

Types of MTA

Considered types of MTA:

• Gray • White

FeO-present MTA FeO replaced with MgO

FeO- Black MgO-White (hue used matches the color of teeth)

6 steps of Manipulation: Mixing MTA

1. Prepared immediately before use.

2. To be kept always in closed containers free from moisture.

Powder : Water = 3:1

3. Glass or paper slab used for mixing - plastic / metal spatula.

4. Moisture required for setting.

5. When the mixture is in “dry sandy form” (thick consistency) - it is ready for application.

6. Working time: 5 minutes.

MTA Carriers

MAP System

(used for the delivery of MTA to the treatment site, ensuring accurate placement and minimizing contamination during procedures.)

Explain the 4 points on the reason of the Setting Time of MTA

1. MTA powder consists of fine hydrophilic particles.

2. Hydration of the powder results in a colloidal gel that solidifies to a hard structure in about 4 hrs- long setting time.

-*Usually an ideal potential root end filling material should set as soon as placed in root end cavity without significant shrinkage.

3. Insignificant shrinkage of the material following placement facilitates the dimensional stability of the material.

4. Short setting time implies less time for an unset material to be in contact with vital tissues. In general, the quicker a material sets the more significant the shrinkage.

-*However, MTA has a long setting time with less shrinkage

What are the setting reactions of MTA? Specifically in portland cement

Portland Cement

Reactants Products

Calcium Silicates = Calcium-silicate-hydrate

Calcium Aluminates = Calcium-aluminate-hydrate

Calcium oxide + Water = +Calcium hydroxide

Unreacted Bismuth Oxide = Unreacted Bismuth Oxide

7 Physical & Mechanical Properties of mta

• Colour grey/white • Odor: no specific odor • Radiopaque

• Physical State: solid (powder)

• Boiling Point: >1000ºC

• Setting Time : 2 hours 45 min– 4 hours

• Compressive Strength: immediately after setting 40 Mpa and increases to 70 Mpa 21 days after setting.

• pH: at start of mix it is 10.2 but rises to 12.5 after 3 hours. MTA has been shown to be capable of maintaining high pH for long periods of time.

• MTA contains 5% gypsum that expands during setting contributing to better adaptation.

Name the 4 Chemical Properties of MTA

• Solubility: solubility of MTA in water is about 0.1%-1.0%.

• Formation of CaOH: Calcium oxide present in MTA reacts with water.

• Hydroxyapatite matrix @ dentin-MTA-interface formed when Ca-ions react with tissue phosphates.

• Maintains its integrity, even in contact with water as its mainly composed insoluble matrix of silica gel.

What are the Biological Properties of MTA?

• Biocompatible

• Antibacterial properties (attributed to high pH)

• Induces reparative dentinogenesis

• Good sealing ability (seals the root canal system from apical and coronal leakage)

• Stimulates fibrous connective tissue and/ or cementum formation, covering the entire root end.

What is the Mechanism of Action of MTA

Calcium ions

1. high pH and inhibits bacterial growth

2. reacts with the tissue phosphates to form HA:

*Adsorption of serum protein and growth factors, promotes adhesion and proliferation of mineral issue forming cells

3. promotes cellular migration, differentiation, attachment and up-regulation of cytokines and bone protein

*Mineralisation of hard tissue

Clinical Applications of MTA (PRAOF)

Pulp capping , Perforations repair, Pulpotomy

Root fracture, Root-end filing, Resorptive defects

Apical plug, Apexification

Obturation

Furcation involvement

6 MTA Indications and MTA Contra-Indications

• To preserve pulp vitality

• Prevent pathological changes in the periradicular tissues

• Mechanical pulp exposures

• Carious pulp exposures with immature apices.

• Perforation repairs in roots or furcation

• It is also useful for perforating resorptive defects.

MTA Contra-Indications

• The material was initially not recommended for obturation of primary teeth that are expected to exfoliate but now gaining 19 acceptance.

MTA 8 Advantages and 4 Disadvantages

Advantages

• Biocompatible • Hydrophilic • Radiopaque

• Antibacterial activity • Excellent sealing properties

• Many varied applications • Dentinal bridge formation

• Least cytotoxic compared to other materials

Disadvantages

• Long setting time • Difficult to manipulate

• Technique sensitive (requiring operator expertise) • Material cost- Expensive