Written by Jay Marlin, DMD Sunday, 30 April 2006 19:00
Figure 1. Obtura unit.
|Figure 2. Correct consistency as demonstrated by the long, fine strand of gutta-percha immediately prior to canal injection.|
ProFile series 29 0.06 Ni-Ti instruments (DENTSPLY Tulsa) used in a light touch, crown-down method provide an excellently shaped canal with a constriction at the apex and a flare at the orifice. ProTaper series 29 0.06 files (DENTSPLY Tulsa) used circumferentially in a crown-down technique also provide the needed shape. The ProTapers cut with a light, circumferential motion more efficiently coronally than the ProFile, allowing deeper penetration of the smaller sizes approaching the apex.
RC-Prep (Premier Dental Products) is used in the pulp chamber as a lubricant with Ni-Ti files, and as a mild chelating agent to help remove the smear layer. The new Obtura (Figure 1) has precise temperature settings required for gutta-percha flow through the 20-gauge and 23-gauge needles.
Figure 3. Endex apex locator.
Access is accomplished, orifices located, and the largest two Ni-Ti files are used to open the orifices of the canals. Canals are irrigated with sodium hypochlorite (NaOCl), and the pulp chamber is filled with RC-Prep. An appropriately sized instrument that can negotiate the apex is measured with an apex locator such as the Endex (Osada Electric; Figure 3). Measurement is compared with digital x-ray determination. If this measurement agrees within 1 mm of the apex locator, it is considered correct; otherwise, a radiograph of the instrument is taken. Once length is determined, 1mm is deducted, and this measurement is used as the working length. When the preparation is complete, it will be 1 mm longer than the working length, since the glide path and completed preparation removes the irregularities.
|Figure 4a. A 23-gauge needle correctly located in the middle third of the prepared bicuspid canal.||Figure 4b. The 20-gauge needles fit in the apical third of one mesial and distal canal. Due to the preparation needed in the distal canal, the needle reaches the lowest portion of the middle third of the distal canal.|
Figure 4c. Injection of gutta-percha between apical preparation and needle.
|Figure 4d. Injection of gutta-percha half the distance between depth of needle placement and apical preparation.|
One drop of loose sealer is placed 1 mm short of the apical preparation. Using a needle that fits in the middle third of the canal (Figures 4a and 4b), the Obtura is heated to the correct gutta-percha temperature so that it can be stretched to a fine, hair-like strand (Figure 2). Excess gutta-percha is removed from the needle tip, and it is rested to its extent in the middle third of the canal. Next, with no pressure on the needle, the flowable filling material is introduced into the canal until the needle rises 2 mm from its resting position. Injection is stopped, and the needle is then removed. The gutta-percha flows half the distance between the tip of the needle and the prepared apical constriction, leaving 2 to 4 mm of distance for the condensers to complete the flow as gutta-percha solidifies (Figures 4c and 4d).
Figure 5a. Completion of condensation and back-filling. Note apical accessory canal.
Figure 5b. Completion of root canal filling.
Figure 5c. Six-month postoperative recall showing apical healing.
|Figure 5d. Healing at 6-month recall showing extent of bone regeneration and accessory canals visible with this angulation.|
The No. 8 Schilder plugger is dipped in alcohol and introduced into the canal with firm vertical pressure short of the prefit reference point until the filling material feels solid. Rotate the condenser on its axis and remove. With the No. 25 finger plugger dipped in alcohol, the same motion is used until the gutta-percha is solid, then rotated on its axis and removed. The same motion is repeated with the No. 20 finger plugger. At this time the No. 25 is reintroduced, pushing gutta-percha circumferentially from the walls into the center of the canal. The Schilder plugger is likewise used and a radiograph taken. With the apex and accessory canals filled, the remainder of the canal is back-filled with the Obtura and condensed (Figures 5a to 5d).
|Figure 6a. Molar with periapical areas and mid-root lucency at the distal surface of the mesial root. Patient was referred due to blockages in mesial and distal canals.||
Figure 6b. Radiographic bone fill at 6-month recall.
Figure 7. Canine with Rapid-Flow Filling of bifid apex and lateral canal.
|Figure 8a. Wisdom tooth with No. 8 instrument demonstrating severe curvature of distal canal. Note the radiolucency at the base of the distal convexity.|
|Figure 8b. Recall of tooth in Figure 8a. Mesial canals filled with lateral condensation. Distal canal filled with Rapid-Flow Filling Technique to apex showing accessory canal into previous radiolucent area. First use of Rapid-Flow Filling Technique. (Image courtesy of Dr. David Melrod.)|
The Rapid-Flow Filling Technique is a 3-dimensional filling process that results in a solid impression of the root canal system and all its irregularities. Cones are not required, since the gutta-percha is plasticized outside the tooth, introduced into the canal preparation, which serves as a mold, and held under pressure during solidification. The technique is similar to the manufacturing of plastic products we use every day. Due to the unique heat-retentive flow characteristics of gutta-percha, adequate time is available to fill the properly prepared root canal completely and compact the material as it solidifies. Forcing the gutta-percha into the canal intricacies is a normal advantage of this obturation method. Often, the complete filling procedure is completed in less time than is required to fit a cone.
With experience, the dentist will adapt the Rapid-Flow Filling Technique to a great variety of cases (Figures 6a to 8b).
The Rapid-Flow Filling Technique has become an obturation method utilized by practitioners who avail them-selves of the technical ad-vancements in endodontics. Practitioners in general practice residencies and endodontic residency programs as well as endodontists have mastered the technique with minimal direction. Consistently accurate apex locators show apical constrictions that terminate at or just short of the apical foramen. Ni-Ti in-strumentation provides ideal shapes with apical constrictions. Gutta-percha with controlled temperature ranges and the new Obtura allow introduction of filling material at the correct temperature and consistency. With the Rapid-Flow Filling Technique, condensation and obturation are the same as other established warm gutta-percha techniques4 in significantly shorter chair time.
1. Grossman LI. Endodontic Practice. 6th ed. Philadelphia, Pa: Lea & Febiger; 1965:339.
2. Callahan JR. Rosin solution for the sealing of the dentinal tubuli and as an adjuvant in the filling of root canals. J Allied Dent Soc. 1914;9:53-63.
3. Schilder H. Filling root canals in three dimensions. Dent Clin North Am. Nov 1967;723-744.
4. Torabinejad M, Skobe Z, Trombly PL, et al. Scanning electron microscopic study of root canal obturation using thermoplasticized gutta-percha. J Endod. 1978;4:245-250.
Disclosure: Dr. Marlin has a royalty involvement with Obtura for their needles.
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