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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 6  |  Issue : 1  |  Page : 3-7

Dentinal crack formation after different obturation techniques


Department of Endodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey

Date of Web Publication12-Mar-2019

Correspondence Address:
Nazife Tugba Azmaz
Department of Endodontics, Faculty of Dentistry, Selcuk University, Konya
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjos.SJOralSci_2_18

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  Abstract 


Introduction: The aim of this investigation was to compare the incidence of dentinal crack after different obturation techniques.
Materials and Methods: Fifty-five mandibular teeth with mature apices and straight root canals (>5°) that had been extracted for periodontal reasons were selected and stored in distilled water until use. The teeth were randomly assigned to five groups of 15 teeth each. The groups were as follows; (Group 1) no canal preparation, (Group 2) canal preparation, (Group 3) canal preparation and obturation with cold lateral condensation technique, (Group 4) canal preparation and obturation with warm vertical condensation (WVC) technique, and (Group 5) canal preparation and obturation with single-cone (SC) technique. Afterward, the teeth were horizontally sectioned at 3, 6, and 9 mm from the apex with a low-speed saw under water cooling. All slices were then viewed through a stereomicroscope at ×25 magnification and pictures were taken. The presence of dentinal crack was noted and analyzed using the Chi-square test.
Results: The Group 1 had no dentinal crack. All the other groups resulted in dentinal crack. Groups 3 and 4 produced significantly more dentinal crack than the other groups in the 6 and 9 mm sections (P < 0.05). The Groups 3 and 4 produced significantly more dentinal crack in the 6 and 9 mm sections than 3 mm sections (P < 0.05).
Conclusion: Under the conditions of this study, after root canal filling with the cold lateral and WVC techniques determined more dentinal cracks than the only preparation and SC technique. The SC technique seems to be an appropriate obturation technique.

Keywords: Cracks, dentinal damage, obturation technique, root canal filling, root canal instrumentation, root fracture


How to cite this article:
Aydinbelge HA, Azmaz NT, Yilmaz MO. Dentinal crack formation after different obturation techniques. Saudi J Oral Sci 2019;6:3-7

How to cite this URL:
Aydinbelge HA, Azmaz NT, Yilmaz MO. Dentinal crack formation after different obturation techniques. Saudi J Oral Sci [serial online] 2019 [cited 2019 May 20];6:3-7. Available from: http://www.saudijos.org/text.asp?2019/6/1/3/254028




  Introduction Top


Vertical root fracture (VRF) is a problem of particular clinical significance because it indicates a hopeless prognosis for the affected tooth. In some situations, a fractured tooth may be salvaged with root amputation or hemisection, but more often extraction is indicated. Because reports in the literature suggest an association between VRF and endodontic treatment,[1],[2] it has been speculated that the force of lateral condensation is primarily responsible for these fractures.[3] Analysis of the lateral condensation forces has identified the variables of spreader load,[4],[5] canal flare,[4] root and canal dimensions,[6] rate of strain,[7] and spreader design,[5] as contributing factors to VRF.

Many various materials have been used for obturation of the root canal system, the most common being gutta-percha combined with a sealer. Different techniques have been suggested to achieve the best adaptation of gutta-percha to the canal walls.[8] Cold lateral condensation (CLC) is one of the most widely used techniques and has become a standard method for obturation of the root canal space.[9] However, the final filling is composed of a large number of gutta-percha cones tightly pressed together and joined by frictional grip and cementing substance, rather than a homogeneous mass of gutta-percha.[10] The resulting fill in such cases would lack homogeneity and has to rely on sealer to fill the voids and thus would have a poorer prognosis.[11],[12]

Warm vertical condensation (WVC) of gutta-percha can provide a high-density filling and better sealing at all portals of entry between the root canal and the periodontium.[13],[14] This technique allows the placement of a homogeneous mass of gutta-percha into the canal system with the carrier as a means of compaction.[15] This technique can be more effective in filling lateral canals than CLC.[16] The BeeFill 2 in 1 system (BeeFill 2 in 1 VDW, Münich, Germany) that includes downpack and backfill equipment in one unit is a variation of WVC.[17] In this system, heated pluggers are used to thermoplasticize and downpack the filling material at the apical third. The remaining part of the canal is backfilled with thermoplasticized filling material and then condensed vertically with pluggers. In addition, these techniques (CLC and WVC) are time consuming.

The single-cone (SC) technique has later been revived, with the introduction of greater taper gutta-percha cones that closely match the shape of rotary nickel–titanium instruments and that technique has gained rapid acceptance.[18] According to our knowledge, there are no adequately data in the literature about the effect of greater taper gutta-percha cones that closely match the shape of rotary nickel–titanium instruments on the occurrence of cracks on root canal wall. Thus, the aim of this investigation was to compare the incidence of dentinal crack after different obturation techniques. The null hypothesis was that there would be no differences in crack formation among the groups.


  Materials and Methods Top


Seventy-five mandibular teeth with mature apices and straight root canals (>5°) that had been extracted for periodontal reasons were selected and stored in distilled water until use. Mesiodistal radiographs of the teeth were taken to verify the canal configuration, and only teeth with a single canal were included in the study. The coronal portions of all the teeth were removed by diamond coated bur with water cooling, leaving roots approximately 14 mm in length. All the roots were observed with a stereomicroscope (Novex, Arnhem, The Netherlands) with ×12 magnification to detect any preexisting external defects or cracks. Roots with such defects were excluded from the study. The teeth were randomly assigned to five groups of 15 teeth each.

The teeth in Group 1 had pulpal tissue removed using only a broach. The root canals length of all of the teeth in Groups 2–5 was measured by inserting a size 10 K-file into the canal until the tip of the file became visible at the apical foramen. The distance between the tip of the file and the reference plane was defined as the canal length. The working length (WL) was established by subtracting 1 mm from this length. Then, the root canals of all of the teeth in Groups 2–5 received canal preparation using the ProTaper Next rotary system (Dentsply Maillefer, Ballaigues, Switzerland), to an apical size of ×4 (40). A glide path was performed through a size 15 K-file. During the instrumentation, each canal was irrigated with 2 mL of 1% sodium hypochlorite solution (Caǧlayan Chemistry, Konya, Turkey) between each file.

Teeth in Group 2 received no canal obturation.

Teeth in Group 3 were obturated using gutta-percha and epoxy resin-based sealer (AH Plus, Dentsply DeTrey, Konstanz, Germany) with CLC. A size-40 master gutta-percha cone (Diadent, Seoul, Korea) so that it had tug-back at the WL was selected. The epoxy resin-based sealer was prepared according to the manufacturer's instructions. The master cone was lightly coated with the sealer and placed into the root canal until the WL was achieved. CLC was performed using standardized spreaders and auxiliary size-25 and size-20 gutta-percha cones. Auxiliary cones were added until the spreader could penetrate no more than 4 mm. Excess gutta-percha was removed with a heated instrument, and vertical condensation was applied with a cold plugger for 5 s at the canal orifice.

Teeth in Group 4 were obturated with WVC. The master cone was lightly coated with the sealer and placed into the root canal until the WL was achieved. The heat source (BeeFill 2 in 1 System, VDW; Aseptico, Woodinville, WA) was adjusted to 200°C, and the heater plugger of the BeeFill 2 in 1 system was advanced to 3 mm from WL. Then, the heater plugger was again used to place the auxiliary size-25 and size-20 gutta-percha cones. Auxiliary cones were added until the spreader could penetrate no more than 4 mm. Excess gutta-percha was removed with a heated instrument, and vertical condensation was applied with a cold plugger for 5 s at the canal orifice.

Teeth in Group 5 were obturated with SC technique. Confirm Fit Gutta-Percha Points for Protaper Next, Sz ×4 (Dentsply Maillefer, Ballaigues, Switzerland) so that it had tug-back at the WL was selected. The gutta-percha cone was lightly coated with the sealer and placed into the root canal until the WL was achieved. Excess gutta-percha was removed with a heated instrument and vertical condensation was applied with a cold plugger for 5 s at the canal orifice. During the experimental procedures, roots were covered with 4 mm × 4 mm gauze and kept moist to avoid drying. After filling all the canals, the roots were stored for 1 week at 37°C and 100% humidity to allow the sealers to set. All instrumentation and obturation were performed by one investigator.

After obturation, the teeth were horizontally sectioned at 3, 6, and 9 mm from the apex with a low-speed saw (Isomet 1000; Buehler, Lake Bluff, IL) under water cooling. All slices were then viewed through a stereomicroscope (Novex, Arnhem, The Netherlands) at ×25 magnification and pictures were taken.

Each specimen was checked by two operators and classified into two categories: “No cracks” and “cracks.”

  1. “No cracks” were root dentin without any lines or cracks on the external or the internal surface of the root [Figure 1]
  2. “Cracks” were defined if any lines, microcracks, or fractures were present in root dentin [Figure 2].
Figure 1: Crack

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Figure 2: No crack

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Chi-square test was used for statistical analysis of differences between the groups at a 95% confidence level (P < 0.05).


  Results Top


The quantity of each dentinal crack for each group at different section is shown in [Table 1]. The Group 1 had no dentinal crack. All the other groups resulted in dentinal crack. Groups 3 and 4 produced significantly more dentinal crack than the other groups in the 6 and 9 mm sections (P < 0.05). The Groups 3 and 4 produced significantly more dentinal crack in the 6 and 9 mm sections than 3 mm sections (P < 0.05). In the 3 mm section, there was no statistically significant difference among the groups (P > 0.05). The Groups 2 and 5 produced significantly fewer cracks than the Groups 3 and 4 in the 6 and 9 mm sections (P < 0.05).
Table 1: The quantity of each dentinal crack for each group at different section

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  Discussion Top


The results of the present study revealed that root canal instrumentation with the ProTaper Next rotary system and different obturation techniques can create dentinal cracks. Group 3 (canal preparation and obturation with CLC technique) and Group 4 (canal preparation and obturation with WVC technique) produced significantly more dentinal crack than the other groups in the 6 and 9 mm sections. There were significant differences among the groups. Hence, the null hypothesis was rejected.

The teeth extracted for periodontal reasons with minimal trauma were used in this study. Because the forces of extraction may also contribute to the observation of incomplete fractures.[19],[20]

In the current study, after the coronal portions of all the teeth were removed by diamond coated bur with water cooling, leaving roots approximately 14 mm in length, all the roots were examined under a stereomicroscope to detect any preexisting external defects or cracks. Roots with such defects were excluded from the study, and the roots were randomly assigned to groups. Therefore, that removing procedure not affect crack formation can be argued.

Previous ex vivo experiments studying the influence of endodontic procedures on root dentine mainly used one or other of the following methodologies: stress distribution, resistance to fracture, measurements, or observations of the presence of effects in tooth sections.[15],[20],[21],[22],[23],[24],[25] Stress distribution studies record stress transmission to dentine during different procedures using strain gauges,[21],[23],[24] or a photoelastic material.[15] Resistance to fracture is frequently measured to assess the weakening of the root after different procedures, and it applies an external force until the root fractures.[25] In the current study, the sectioning method was used that allowed the evaluation of the effect of root canal treatment procedures on the root dentine by direct inspection of the root canal wall and no external forces were applied.

The clinical situation is more complex because of the presence of the periodontal ligament that could further influence the distribution of forces. While some studies did not attempt to imitate bone or periodontal ligament,[20],[25] others have made various attempts to do so.[22],[24] However, Saw and Messer, 1995, stated that these attempts are insufficient to mimic the anatomical and biological aspects of tooth structure. Therefore, in the present study, we did not attempt to imitate bone or periodontal ligament using acrylic blocks and silicone impression material.

During the preparation and obturation, stress on the root canal walls may arise[17] and these can result as microcracks or craze lines[22] because of the repeated stress application by occlusal forces these microcracks and craze lines may develop into VRF.[19],[22] The presence of craze lines and incomplete cracks after instrumentation has been reported previously.[19],[26],[27] Shemesh et al. (2009; 2010) stated that root canal preparation with rotary nickel–titanium instruments can damage the dentine and create defects on root canal walls. Our results confirm the claim of Shemesh et al. (2009; 2010) that the significant increase in the appearance of defects after preparation alone was been when compared to the control group which did not undergo any treatment.

In this study, the root canals of all of the teeth in Groups 2–5 received canal preparation using the ProTaper Next rotary system to an apical size of ×4 (40). All instrumentation and obturation were performed by one investigator.

Thus, the effect of instrumentation was studied to equalize at the experimental groups.

Many clinicians continue to use lateral condensation technique as it does not require special or expensive equipment and is considered safe in controlling the apical extension of the filling.[28] However, previous studies documented that lateral condensation of gutta-percha can create cracks on the root canal walls[17] and that it is associated with an increased risk of VRF.[29],[30] However, laboratory stress distribution studies consistently conclude that the pressure applied during lateral compaction is insufficient to cause VRF.[24],[31] Thus, it remains unclear whether lateral compaction can cause VRF. Shemesh et al. (2009) compared lateral condensation and noncondensation filling with standard 0.2-tapered cones and reported that the total number of cracks after lateral condensation was higher than after noncondensation filling. Similarly, our study demonstrated that the number of dentinal cracks after lateral condensation was higher than after SC filling. In the CLC techniques, the force of lateral condensation or the direct contact of spreader to the root canal wall may be responsible for these cracks.

The WVC technique involves vertically condensation of a thermoplasticized filling material with pluggers. In this study, WVC technique was performed using the BeeFill 2 in 1 system. Telli et al. reported that root fractures are not likely to occur when WVC technique is performed skillfully. On the other hand, hydraulic forces during WVC could create pressure on the root canal walls and induce a wedging effect.[32],[33] In addition, the direct contact of a plugger at 200°C with the root canal wall could cause cracks on dentine surfaces in the WVC techniques.

Shemesh et al. (2010) stated that dentinal defects were observed in roots filled with gutta-percha and AH26 using the lateral condensation and continuous wave techniques. Similarly, in the present study, after root canal filling with the cold lateral and WVC techniques determined more dentinal cracks than the only preparation and SC technique in the 6 and 9 mm sections. The number of cracks with SC obturation was parallel to the only preparation and less than the other filling techniques. This may be due to the SC technique performing minimal pressure compared to the other filling techniques that create compaction forces on the root canal walls.

A recent study reported that root canal filling procedures can potentially propagate dentinal cracks in the apical region.[28] Despite this in the present study, after root canal filling with the cold lateral and WVC techniques produced significantly more dentinal crack in the 6 and 9 mm sections than 3 mm sections. This might be attributed to the forces in the middle and coronal third that originate from replacing the spreader and plugger in the canal.[34]


  Conclusion Top


Under the conditions of this study, after root canal filling with the cold lateral and WVC techniques determined more dentinal cracks than the only preparation and SC technique. SC technique which used greater taper gutta-percha cones that closely match the shape of rotary nickel–titanium instruments was shown less damage on the dentine. SC technique seems to be an appropriate obturation technique.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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