Year : 2008 | Volume
: 26 | Issue : 2 | Page : 49--52
Comparison of digital radiography, decalcification, and histologic sectioning in the detection of accessory canals in furcation areas of human primary molars
P Poornima, VV Subba Reddy
Departments of Pediatric Dentistry, Oral Medicine and Radiology, College of Dental Sciences and Hospital, Davangere-577 004, Karnataka, India
Department of Pediatric Dentistry, College of Dental Sciences and Hospital, Davangere-577 004
Although the terms lateral secondary and accessory canals are often used interchangeably they mean different things. The accessory canal is derived from the secondary canal branching off to the periodontal ligament in apical sections. Different methodology was used to study the accessory canals. Decalcification method appeared to the important in studying the accessory canals as compared to digital radiography and histological sectioning.
|How to cite this article:|
Poornima P, Subba Reddy V V. Comparison of digital radiography, decalcification, and histologic sectioning in the detection of accessory canals in furcation areas of human primary molars.J Indian Soc Pedod Prev Dent 2008;26:49-52
|How to cite this URL:|
Poornima P, Subba Reddy V V. Comparison of digital radiography, decalcification, and histologic sectioning in the detection of accessory canals in furcation areas of human primary molars. J Indian Soc Pedod Prev Dent [serial online] 2008 [cited 2020 May 30 ];26:49-52
Available from: http://www.jisppd.com/text.asp?2008/26/2/49/41615
The close interrelationship between the pulp and the periodontal ligament has been recognized in the dental literature for a very long time. ,, Communication between the pulp and the periodontal ligament takes place via the apical foramen, lateral and accessory canals in the apical and coronal parts of the roots. Despite careful selection of cases and the use of correct procedures, pulp treatment occasionally fails. Failure is often due to the presence of aberrant pulpal periodontal connections whose adequate treatment is very difficult because of physiological bone resorption.
Accessory canals result due to a localized failure in the formation of Hertwig's sheath during the embryonic stages of tooth formation. This defect is probably due to the persistence of abnormally placed blood vessels reaching the pulp, which is more common in the furcation region. This was demonstrated by Hess et al. as early as 1925 by injecting India ink into the pulp chamber. A variety of techniques, ,,, including radiographic studies, microscopic studies, grinding of teeth, sectioning, iontophoresis, injections, metal filling of pulp cavities and corrosion, plastic embedding, have been used to study the anatomy of the root canal system. However, the documentation of accessory canals in the furcation areas of primary molars is scanty  and the reports are contradictory. Hence, a in vitro study was planned to know the prevalence of accessory canals in molars and to compare the efficiency of digital radiography, decalcification, and histological sectioning in detection.
The present study was conducted on 100 extracted primary molars collected from the Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere. Only teeth with root resorption not involving more than one-third of the apical aspect of any root were included in the study. The teeth selected for the study were stored in normal saline. Endodontic access openings were made using a round bur and pulp tissue was removed using a standard spoon excavator. Root canal contents were extirpated using barbed broach; complete debridement of root canals was done using files No. 8 to 25, with copious irrigation using 5.2% sodium hypochlorite. The teeth were placed in separate bottles containing normal saline and were labeled.
Three different methods were used to study the accessory canals, viz, digital radiography, decalcification, and histologic sectioning.
All the teeth were imaged buccolingually with digital radiography. An average of 25 teeth were examined daily. To eliminate intraexaminer variability, before the examination of the 25 teeth.
The specimens were decalcified for 3 days in 5% nitric acid at room temperature. The solution was changed daily and agitated by hand three times each day. After completion of decalcification, the teeth were rinsed in running tap water for 4 h. Then, the teeth were dehydrated using a series of ethyl alcohol rinses, i.e., 80% solution for 12 h, followed by 90% solution for 1 h and, finally, three 100% alcohol rinses for 1 h each. The dehydrated teeth were then placed in methyl salicylate (for approximately 2 h) till the teeth became transparent [Figure 1].
India ink was injected into the pulp chamber, using a 24-gauge needle and a Luer-Lok plastic disposable syringe. The ink was then drawn through the canal system by applying negative pressure to the apical end of the tooth with the use of heavy suction. The excess ink was removed from the surface of the root with gauze soaked in alcohol and the teeth were returned to the methyl salicylate solution until needed [Figure 2]. The teeth were examined under a stereomicroscope under 10× magnification.
All decalcified teeth were mounted in acrylic stubs and were sectioned with a hard-tissue microtome. A series of sections, each of 100-µm thickness, were taken from the internal furcation area to the external furcation area and were mounted on slides using DPX (mounting media). The specimens were then examined under a polarized microscope at 4× magnification [Figure 3].
Out of the 100 primary teeth studied for prevalence of patent accessory canals, 9% showed canals on digital radiography, 26% in decalcification, and 39% in histological sectioning. The number of canals seen in each tooth ranged from 0 to 5. Multiple canals were best seen by sectioning, followed by decalcification; they were not seen on digital radiography.
[Table 1] shows the number and the percentages of molars showing accessory canals by the three different methods. For the maxillary first molars, decalcification was significantly ( P = 0.004) better than digital radiography, but the difference between the two methods was not significant for the maxillary second molars and the mandibular first and second molars. Sectioning proved to be better than digital radiography in identifying accessory canals in a significantly higher number of maxillary first and second molars and mandibular first molars but not in mandibular second molars. There was no significant difference between decalcification and sectioning in any of the molars.
[Table 2] shows the number and percentages of maxillary and mandibular primary molars showing accessory canals in the three different methods. Comparing digital radiography with decalcification, we found the latter to be significantly ( P P P et al .  found patent accessory canals in 59% of molars. This variation may be due to the methodology used. In our study, radiopaque dye was not injected into the pulp cavity and radiographs were not taken at different angles.
The decalcification technique used in the present study was the method advised by Robertson and is a modification of the method described by Brain. , Our study showed that the prevalence of accessory canals in maxillary molars was 28.88% and in mandibular molars it was 23.63%. The overall prevalence in primary molars was 26%. Similar studies done by Vertucci et al.  using a dissecting microscope found that 46% of teeth studied exhibited lateral canals in the furcation region. In contrast, in our study, where we used a polarized microscope, only 26% of teeth exhibited accessory canals. De Deus  studied 1140 transparent teeth and found that 27.4% of teeth demonstrated lateral secondary accessory canals, which was similar to our study.
The third method we studied was histological sectioning. This showed accessory canals in 39% of teeth. Scanning Electron Microscopic (SEM) investigation of furcation areas of 20 primary molars found 20% of canals in the internal furcation surface and 50% on the external furcation surface. Even though SEM investigation provides detailed information, it does not provide information on patency of canals.  Paras et al .  did a study by perfusing low-viscosity latex using positive and negative vacuum pressure and demonstrated accessory canals in only one tooth out of 20. On the other hand, Moss  found accessory canals in 20% of the specimens. Our study showed 39% of primary molars with accessory canals. These variations may be due to the differences in sample sizes and the methods used.
In present study, digital radiography was less effective than decalcification and sectioning in identifying accessory canals in maxillary molars. This could because no overlapping of the palatal root when the tooth is exposed buccolingually, which obscures the presence of canals. The total number of accessory canals seen with decalcification was only 30, whereas with histological sectioning 59 could be seen. This difference may have been be due to failure of the dye in penetrating through the smaller canals; these smaller canals were better shown in sectioning.
The prevalence of accessory canals in the furcation region of primary molars was seen to be high in histological sectioning followed by decalcification and radiography. On comparing the different methods, decalcification was found to be significantly better than digital radiography. The difference between digital radiography and sectioning was highly significant. Although there was no significant difference between decalcification and sectioning when individual groups of molars were considered, there was significant difference seen when the primary molars were considered as a whole.
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