OBTURATION TECHNIQUES l Preclinical Endodontics MCQs

OBTURATION TECHNIQUES l Preclinical Endodontics MCQ  (multiple choice question) for dental students

Obturation techniques

 

•           Broadly speaking, techniques of filling canals with gutta-percha can be divided into three main groups:

 

1.  Use of cold gutta-percha.
2.  Use of heat-softened gutta-percha.
3.  Use of solvent-softened gutta-percha.

 

Cold gutta-percha techniques

• Cold gutta-percha techniques are generally simple to master as they are not complicated by needing to soften the material with heat or solvents; neither do they require expensive and often complicated devices or equipment. However, it should be clear that cold gutta-percha cannot be compacted into irregularities within the canal system, with the result that this role must be fulfilled entirely by sealer.
•          Cold gutta-percha can be used in a number of techniques:

1.                 Full-length single point.
2.                 Apical (sectional) single point.
3.                 Lateral condensation.

 

Full-length single point:

•      With the advent of the standardized preparation technique, the method of filling canals with a single full-length gutta-percha point and sealer became popular. The theory behind the technique was simple and attractive; the canal was prepared to a round cross-sectional shape of standard size by use of reamers and then obturated by a gutta-percha point of matching diameter. However, it soon became 

• apparent that a round canal shape was rarely a chivied, especially in curbed canals, and that single –point obturation was less likely to be used, it would rely inevitably on substantial amounts of sealer to fill the gaps, resulting in increase leakage. It was also clear that discrepancies in size and taper between points and equivalent numbered instruments were prevalent.

Current canal preparation techniques which aim to flare canal to produce a flowing conical funnel shape cannot be filled adequately with a single-point technique using zinc oxide or calcium hydroxide-based sealers, and therefore should not be attempted.

Apical (sectional) single point:

• In a tooth scheduled for restoration with a post crown, substantial part of the canal must be available to accommodate the post. The apical 4-5 mm of a point was cut off and then mounted on the end of a file before being introduced into the canal. Once the gutta-percha point seated at the end–point of preparation the file was rotated, detached from the gutta-percha and removed. The technique was unpredictable and suffered from the same problems as the full-length point technique in terms of lack of fit. Therefore, use of an apical (sectional) single point is not recommended.

Lateral condensation:

• Lateral condensation of cold gutta-percha is taught and practiced throughout the world and is the technique of choice for many clinicians. It is simple and rapid to carry out, can be used in virtually all cases and is the standard against which many new techniques are compared. 

• Lateral condensation involves the placement of a master (primary) point at the end-point of preparation followed by the insertion of additional (accessory) points alongside. The use of a standardized master point provides a predictable apical fit, whereas the accessory points obturated the space produced as a result of the flared canal shape. The resultant filling consists of numerous points cemented together and to the canal wall by sealer; it does not result in a merging of the points into a homogeneous mass of gutta-percha.

•           A spreader is interested alongside the master point to improve the adaptation of the master point at the end-point of preparation and to create the space for accessory points. When inserted to within 1mm of the end-point of preparation, the spreader compacts effectively the master point apically and laterally, resulting in considerably less leakage than if the spreader had only entered part-way into the canal. In fact, the necessity to advance the spreader well into the canal is the only reason why canals are flared; a narrow, parallel canal shape would not allow a spreader to advance sufficiently to influence the adaptation of the apical region of the master point. Narrow preparations also predispose to the unwanted removal of the master point upon withdrawal of the spreader as it tends to pierce the master point rather than lie alongside it.

The requirements for successful lateral condensation are therefore:

1. A flared canal preparation with a definite apical stop.
2. A well-fitting master gutta-percha point of standard size and taper.
3. A series of spreaders of the appropriate size and shape.
4. An assortment of accessory points which match the size and taper of spreaders.
5. An appropriate sealer.

Well-fitting master point. 

•           The master cone must fit to the full length of the preparation, be tight at the end-point of preparation, and it must be impossible to force it through the foramen.
•           The size of the master cone is guided by the master apical file used in the final preparation of the apical stop or matrix. The selected gp point is held with tweezers at a length equivalent to the working distance and then inserted into the canal. Ideally, the point should:

1. Pass down to the full working distance so that the beaks of the tweezers touch the reference point.
2. Be impossible to push beyond this position, i.e. through the foramen.
3. Fit tightly at the end-point of preparation, giving some resistance to withdrawal (tug back).

• The tweezers are squeezed slightly so as to notch the point and are then released leaving the point in situ. A radiograph is then exposed to confirm its position in relation to the end-point of preparation and the radiographic apex. Theoretically, if the original estimate of the working distance was corrected, the point should be in the appropriate position and canal obturation can proceed. Some authorities condense the master point with a spreader prior to taking the radiograph in order to ensure that it reaches the end-point of preparation.

Selection of spreaders and accessory gutta-percha points: 

•             Once the master apical point has been selected, it is important to select and try-in the spreader in order to insure that it can pass down the canal to within 1 mm of the end-point of preparation. Spreaders should be precurved in curved canals and a rubber stop used to identify the length of insertion. To eliminate the risk of root fracture, excessive condensation pressure should be avoided by the use of finger spreaders.
•           Spreaders are either manipulated with fingers (like files) or have long handles. The working part can have a non-standardized taper or standardized international organization for standardization (ISO) 0.02 taper, the same as most files. Non-standardized spreaders have relatively small diameters at the tip but a range of tapers from extra-fine through
• fine, medium to large; some manufactures use letters rather than words to denote the degree of taper, e.g.    A-D. Spreaders with a standardized taper are manufactured with ISO diameters such as size 20 up to size 40.The choice of spreader design, that is, with non-standardized taper, is determined by operator preference and the type of accessory points to be used. When non-standardized spreaders are used the points should be non-standardized; however, standardized spreaders require standardized accessory gutta-percha points. In this way the space created by the spreader will be filled by the point. It is important to realize that space created by standardized spreader cannot be filled adequately with a non-standardized point. It is sound clinical practice to