Materials for making fillers. Their positive and negative properties

Topic 36: “Solid filling materials (fillers) for root canals. Their varieties, positive and negative aspects. Modern technology, their common characteristics”.

Requirements for materials for obturation of root canals:

1. It should be easily introduced into the canal.

2. It should seal the canal laterally as well as apically.

3. It should not shrink after being inserted.

4. It should be impervious to moisture.

5. It should be bacteriostatic or at least not encourage bacterial growth.

6. It should be radiopaque.

7. It should not stain tooth structure.

8. It should not irritate periapical tissue.

9. It should be sterile, or quickly and easily sterilized before insertion.

10. It should be easily removed from the root canal if necessary.

Instruments for root canal filling:
1. Spreadersare pointed instruments used to move gutta-percha laterally and to create space for additional cones. They are used in lateral condensation.	2. Pluggersare flat-tipped instruments used to condense and force gutta-percha apically. They are specially designed and sized so that they will provide a more accurate fit in those canals that have been enlarged into a funnel form.
Function.Used to condense gutta percha into the canal during obturation.Finger instrument with a smooth, pointed, tapered working end.Disposed of in the sharps’ container. Varieties. Can be of the hand instrument type (lateral condenser).	Function.Hand instrument, working end is flat to facilitate plugging or condensing the gutta percha after the excess has been removed by melting off with a heated instrument. Varieties.Different sizes of working ends are available. Available as hand or finger instruments.

Materials for making fillers. Their positive and negative properties.

Gutta-percha, a semisolid material, is the most widely used and accepted obturating material. Gutta-percha is a natural product that consists of the purified coagulated exudate of mazer wood trees (Isonandra percha) from the Malay Archipelago or from South America. Gutta-percha does not adhere to the canal walls, regardless of the filling technique applied, resulting in the potential for marked leakage. Therefore, it is generally recommended that gutta-percha (used cold or heated) is used together with a sealer. For an optimal seal the sealer layer should generally be as thin as possible.

Gutta-percha exists in two crystalline forms (α and β) and melted in an amorphous form: α - sticky and fluid mass, softens at relatively low temperatures; β - more flexible, elastic form used for making pins.

They possess biologically inert, do not irritate tissue periodontal antimicrobial properties, biocompatibility to tooth and periodontal plastic and radiopaque.

Gutta-percha pins shortcomings: lack of adhesion to dentin and therefore always applied to sillers; pins of small size is not rigid, making it difficult for their introduction, especially in curved root canals.

Typical composition of gutta-percha cones.
Components	Composition (%)
Zinc oxide
Metal sulfates ( radiopacity )
Gutta-percha
Additives like colophony (resin, mainly composed of diterpene resin), pigments or trace metals

Silver pins in root canal filler is used for about 50 years. Negative qualities, which prevent their widespread use is corrosion in liquid media to form toxic to the cells and tissues of the oxides of silver, discoloration of the tooth after obturation, the inability to adapt to the shape of the channel because of the hardness of the hard rounded tip, which can not replicate the anatomy of terminal holes, circular, almost never occurs in a natural channel. Used in small direct channels with a circular cross section.

Titanium pins as obturating material for root canals proposed about 20 years ago. Resist corrosion, but have all the other disadvantages silver points.

Fiberglass pins have such unique features as: flexibility, elasticity, strength and ability to withstand long-term load. Fiberglass pin fixed in the dental root canal on a permanent material. The method of entering the pin into the canal is passive. One of the important qualities of fiberglass pins is their aesthetic characteristics. Restorations performed on fiberglass pins, highly aesthetic (the pin is not visible in the restoration).

Obligatory condition for the use of primary filling solids is to use them with the hardening pastes - endo sealants (sealers). This is necessary for tight closure of the apical foramen and prevent micro leakage at the "pin / canal wall."

Root filling techniques

1. Solid core techniques • Single cone – Simple – Quick – Good length control – Round standard preparation required • Lateral compaction – Good length control – Not one compact mass of gutta-percha – Time-consuming technique – Supposed risk of root fracture

2. Softened core techniques • Warm lateral compaction – Moderate length control – Time-consuming technique – Heat may damage periodontium • Warm vertical compaction – Poor length control – Sealer extrusion – Heat may damage periodontium • Injection-molded gutta-percha – Quick technique – Poor length control – Heat may damage periodontium •Thermomechanical compaction – Quick technique – Poor length control – Heat may damage periodontium – Instrument fracture risk • Core carrier – Quick technique – Sealer extrusion – Gutta-percha may be stripped off carrier in curvature – Difficult to remove for retreatment – In combination with posts, inconvenient technique • Chloroform–resin – Quick technique – Potential health hazard effects on dental personnel with long-term use.

Solid core technique.

Single cone. The single-cone technique consists of matching a cone to the prepared canal. For this technique a type of canal preparation is advocated so that the size of the cone and the shape of the preparation are closely matched. When a gutta-percha cone fits the apical portion of the canal snugly, it is cemented in place with a root canal sealer. Although the technique is simple, it has several disadvantages and cannot be considered as one that seals canals completely. After preparation, root canals are seldom round throughout their length, except possibly for the apical 2 or 3 mm. Therefore, the single-cone technique, at best, only seals this portion.

Cold lateral condensation. (Fig. 1) This is a commonly taught method of obturation and is the gold standard by which others are judged. The technique involves placement of a master point chosen to fit the apical section of the canal. Obturation of the remainder is achieved by condensation of smaller accessory points. The steps involved are:

Fig. 1 Cold lateral condensation of gutta percha

A. Master cone in place with finger spreader.

B. Accessory cone placed in space created by the finger spreader.

C. Accessory cones in place, completing the obturation process.

1. Select a gutta-percha master point to correspond with the master apical file instrument. This should fit the apical region snugly at the working length so that on removal a degree of resistance or 'tug-back' is felt. If there is no tug-back select a larger point or cut 1 mm at a time off the tip of the point until a good fit is obtained. The point should be notched at the correct working length to guide its placement to the apical constriction.

2. Take a radiograph to confirm that the point is in correct position if you are in any doubt.

3. Coat walls of canal with sealer using a small file.

4. Insert the master point, covered in cement.

5.Condense the gutta-percha laterally with a finger spreader to provide space into which accessory points can be inserted until the canal is full.

6. Excess gutta-percha is cut off with a hot instrument and the remainder packed vertically into the canal with a cold plugger.

Fig. 2.Cold lateral condensation of gutta percha. Sketch showing a cross-sectional cut through a root canal filled with a master cone and multiple accessory cones.

Softened core techniques.

Warm lateral condensation. As above, but uses a warm spreader after the initial cold lateral condensation. Finger spreaders can be heated in a flame or a special electronically heated device (Touch of heat) can be used (Fig. 3).

Fig. 3Demonstration of gutta-percha compaction with a hot instrument

Vertical condensation

In this technique (Fig. 4) the gutta-percha is warmed using a heated instrument and then packed vertically. A good apical stop is necessary to prevent apical extrusion of the filling, but with practice a very dense root filling can result. Time consuming.

Fig. 4 Diagram of the warm vertical condensation technique.

A. After a heated spreader is used to remove the coronal segment of the master cone, a cold plugger is used to apply vertical pressure to the softened master cone.

B. Obturation of the coronal portion of the canal is accomplished by adding a gutta-percha segment.

C. A heated spreader is used to soften the material.

D. A cold plugger is then used to apply pressure to the softened gutta-percha.

Thermomechanical compaction. This involves a reverse turning (e.g. McSpadden compactor or gutta-percha condenser) instrument which, like a reverse Hedstroem file, softens the gutta-percha, forcing it ahead of, and lateral to the compactor shaft. This is a very effective technique, particularly if used in conjunction with lateral condensation in the apical region, but requires much practice to perfect.

Thermoplasticized injectable gutta-percha (e.g. Obtura, Ultrafil) These commercial machines extrude heated gutta-percha (70-160°C) into the canal. It is difficult to control the apical extent of the root filling, and some contraction of the gutta-percha occurs on cooling. Useful for irregular canal defects, e.g. following internal root resorption.

Coated carriers (e.g. Thermafil). These are cores of metal or plastic coated with gutta-percha. They are heated in an oven and then simply pushed into the root canal to the correct length. The core is then severed with a bur. A dense filling results, but again apical control is poor and extrusions common. They are expensive and difficult to remove.

Once the filling is in place the tooth will need to be permanently restored, provided the follow-up radiograph is satisfactory. Fillings that appear inadequate radiographically may be reviewed regularly, or replaced, depending upon the clinical circumstances.

The Coronal Seal

Regardless of the technique used to obturate the canals, coronal micro leakage can occur through seemingly well-obturated canals within a short time, potentially causing infection of the periapical area. A method to protect the canals in case of failure of the coronal restoration is to cover the floor of the pulp chamber with a lining of glass ionomer cement after the excess gutta-percha and sealer have been cleaned from the canal. Glass ionomers have the intrinsic ability to bond to the dentin, so they do not require a pretreatment step. The resin-modified glass ionomer cement is simply flowed approximately 1 mm thick over the floor of the pulp chamber and polymerized with a curing light for 30 seconds. Investigators found that this procedure resulted in none of the experimental canals showing leakage.