Essay: Compare the volume of root canals of primary teeth

ABSTRACT
The aim of this study was to compare the volume of root canals of primary teeth filled by four different obturating techniques, namely, lentulospiral, insulin syringe, endodontic pressure syringe, and skini syringe with navi tip using Cone beam Computed tomography (CBCT). A total of 76 root canals of primary posterior teeth were selected and divided to the four study groups according to the obturation technique. Biomechanical preparation of each root canal was completed with number 30 K-file and the volumes of the canals were then measured using CBCT. Each canal was then obturated with zinc oxide eugenol paste using the respective technique for that group. A second CBCT scan was performed to measure the filled volume in each canal, and the percentage of obturated volume (POV) was calculated. The pre and post- mean volume and the POV of the all groups were analyzed using paired t test and one way analysis of variance. A statistically significant difference was seen between the pre and post-mean values (p< .001) and in the mean POV values (p< .001) among the four groups. Skini syringe with navi tip showed the highest POV (93.5%) compared to endodontic pressure syringe (91.5%), lentulospiral (75.5%) and insulin syringe (64%). The skini syringe with navi tip showed best root canal obturation of primary molars with nearest to complete fill of the volumes of prepared root canals, while insulin syringe was least effective.
KEYWORDS
Pulpectomy, obturation, Cone beam Computed tomography
INTRODUCTION
Paediatric dentistry has evolved from an extraction–oriented practice, where primary teeth with inflamed pulps were mostly extracted to the evolution of different treatment modalities for managing irreversibly inflamed or necrotic pulps. Pulpectomy is one such treatment option which consists of removing the inflamed/necrotic pulp tissue from the canal followed by the obturation using resorbable root canal filling material. The successful primary root canal therapy not only requires a thorough understanding of primary pulp morphology, but also about the different obturating materials and techniques capable of compactly filling the entire root canal system. A number of different techniques have been tried to successfully fill materials into root canals of primary teeth that include pushing of filling material into canals with the endodontic plugger or with the cotton pellets, hand and rotary lentulospirals, insulin syringe, endodontic pressure syringe and various other methods.
The ultimate aim of root filling is to create a fluid tight seal along the entire prepared and cleaned root canal space by an obturating material in order to prevent post treatment disease or complication. The presence of voids in root fillings of the primary teeth may provide pathways for leakage leading to bacterial regrowth and infection. Voids in the apical or the coronal part or extending through the entire root canal length increase the risk of failure of the endodontic therapy. Therefore, a careful and advanced assessment of the filling of the root canals is mandatory for 100% success in pediatric endodontic procedures.
Traditional experimental methods used to assess the quality of filling of the root canals include the radiographs, radio-isotopes, dye penetration, fluid filtration, bacterial leakage, microscopic analysis, cleaning techniques and digital radiography.2,5 One of the major disadvantage of these techniques is that it does not assess obturation in 3-dimensions. Therefore, there is a need for an advanced tool that may provide more precise 3D information in both pre- and post- treatment assessment of root canal systems.
Currently, Cone beam Computed tomography (CBCT) is a relatively new technology in dentistry, used for the three-dimensional imaging of the dentofacial structures. This technique produces images with slice thickness much thinner than conventional CT methods and is low dose and a faster scanning system.9,10 CBCT has been used for studying the root canal morphology of primary teeth, however till date no study analysing the 3- dimensional volume of root canal fills of primary teeth by different obturating techniques using CBCT has been reported.
Hence, the present study was undertaken with the aim to comparatively evaluate the volume of root canals of extracted human primary teeth filled by four different obturating techniques, namely, lentulospiral, insulin syringe, endodontic pressure syringe, and skini syringe with navi tip using CBCT.
MATERIALS AND METHOD
The present study was carried out at the Department of Paedodontics and Preventive Dentistry, Institute of Dental Studies and Technologies, Ghaziabad district, India. The study design was analysed and approved by the Institutional review board of Institute of Dental Studies & Technologies, Modinagar.
The initial sample for the present study consisted of fifty seven extracted human primary molar teeth, indicated for extraction and having at least one root with ≥ 8 mm root length. Collection, storage, sterilization, and handling of extracted teeth were followed according to the Occupational Safety and Health Administration guidelines and regulations. Intraoral periapical radiographs were exposed for each tooth and checked for number and curvature of root canals radiographically. Extracted human primary molar teeth with or without coronal dental caries with at least one root with a minimum of 8mm root length were included, whereas teeth with caries extending to root, root canals showing internal and external resorption, any developmental root anomalies like extensive curvature and the presence of any accessory canal other than the main root canals were excluded from the study. The selection criteria were then applied, which included visual and radiographic evaluation of each root and thirty nine extracted primary teeth (maxillary 18 and mandibular 21) with ninety two root canals (maxillary 29 and mandibular 63) were found suitable for the study.
The study consisted of four study groups based on the type of obturating technique used-
Group 1: Lentulospiral
Group 2: Insulin Syringe
Group 3: Endodontic Pressure Syringe
Group 4: Skini syringe with navi tip
Care was taken that an equal number of similar root canals were allotted to the four study groups (for e.g. equal number of the mesiobuccal of maxillary molars to each group and so on) to avoid any bias. Therefore, from ninety two selected root canals only seventy six (19 root canals to each study group) were finally included in the study.
An access cavity was prepared in each tooth, the pulp was removed with barbed broach and the working length was established 1mm short of the radiographic apex. Biomechanical preparation of the root canal was completed with number 30 K-file. The canal was repeatedly irrigated alternatively with 1% sodium hypochlorite and saline and dried. All the canals were prepared in a similar manner. Eight wax blocks were prepared for mounting teeth for scanning under CBCT (Carespream 3D image) with On-Demand software (Volume analysis software). The single operator after learning and mastering the procedure under the supervision of an expert radiologist had analyzed and done all the volumetric measurements required (preobturation and postobturation) through CBCT using On-Demand software.
The volume of each slice was then calculated by multiplying the root canal area by the slice thickness (.045mm). The preobturated volume (X) of each canal was calculated by adding the individual volumes of each slice of that root canal from the canal orifice to the radiographic apex (Figure 1). A single Pan electrical weighing machine and pipette was used to measure Zinc oxide powder and eugenol liquid respectively. A standardized mixture of pure ZOE without additives or fillers was prepared for each technique as per the manufacture’s recommendation and/ or the technique limitation (Table 1). Each canal was then obturated by a single trained operator with ZOE using the respective technique for that group. A second CBCT scan was performed to determine the volume of the canal occupied by the filling material, i.e. the post-obturated volume (Y) by subtracting the voids volume (Figure 2). The percentage of obturated volume (POV) of each canal was calculated using the formula Y/X×100.
The statistical analysis was conducted using SPSS 16 software (IJM, Chicago. USA). Data were expressed as mean ± standard deviation. The mean preobturated volume (X) and postobturated volume (Y) values of all the four groups were compared using the paired t-test. The mean POV scores of all the four groups were compared using the one-way ANOVA test and the inter-group comparison of mean POV scores was done using the Post-hoc Bonferroni test. Only differences with P-value <0.05 were considered as statistically significant.
RESULTS
The volume (mean and standard deviation) of the root canals before (X) and after (Y) obturation is provided in Table 2. There was a statistically significant difference (p< .001) between the pre and post-mean values in all the four groups. The mean post values decreased significantly from pre to post in all the groups, though the decrease was less for group 3 and 4. There was a significant difference (p< .001) in the mean POV values among the four groups shown in Table 3. Group 4 showed the highest mean POV scores followed by group 3, 1 and 2. Post – hoc tests show that the skini syringe with navitip was the best among the 4 root canal filling techniques followed by endodontic pressure syringe, lentulospiral and insulin syringe.
DISCUSSION
The primary aim of this study was to compare the pre and postobturated volumes of root canals filled by the four different obturating techniques namely lentulospiral, insulin syringe, endodontic pressure syringe and skini syringe with navi tip using CBCT technique. The present study was therefore designed to keep the two factors constant- use of single technique of biomechanical preparation and a single obturating material and then assessing the quality of fill by the four different techniques using CBCT. Zinc oxide eugenol (ZOE) is one of the most widely used preparations for primary tooth pulpectomies as several authors have reported moderate to high success rate in preserving chronically infected teeth using this material. Therefore, in the present study ZOE was chosen as a root canal filling material. The difference in the consistencies of the ZOE mixtures was attributable to the physical limitations of the different techniques. Consequently, in all the four techniques ZOE mixtures were prepared according to manufacturer’s recommendation or technique limitations. It has been reported in the literature that all of the techniques used in the present study- lentulospirals, insulin syringe, endodontic pressure syringe and skini syringe with navi tip can deliver ZOE to optimally fill the root canals of primary teeth.
The depth and quality of fill of the root canal filling technique for primary teeth can be done by evaluating and comparing through 3-D imaging system like CBCT. In 2000, limited cone beam computed tomography (LCBCT) was introduced for 3D imaging of dentoalveolar regions at a lower radiation dose and cost compared with CT. CBCT has cone shaped X-ray beam that captures a cylindrical or spherical 3D volume of data using a simple and direct relationship between beam source and sensor. One of the major advantages is that the clinician can easily apply simple software to evaluate the areas of interest in any plane. This technique can provide more accurate 3D information in both pre and post-treatment assessment of root canals that are highly accurate and quantifiable. Recently, Asokan et al volumetrically analyzed the efficacy` of root canal fillings in primary teeth using spiral computed tomography, however there is no published data comparing volumetric analysis of the filled canals of primary molars with different filling techniques using more advanced imaging method, i.e. CBCT.
The present study have measured the canal space or volume occupied by the voids and the volume occupied by filling material three dimensionally, thereby, assessing the exact amount of intracanal space that can be filled by particular technique. More the volume occupied by voids more will be the chances of failure after pulpectomy and therefore, less effective and efficient is that technique. The results of the present study had shown that all the four techniques can be used for filling the canals of primary molars but the volume of filling material in the filled canals (postobturated volume) was statistically significantly lesser than the volume of the prepared canals (preobturated volume). It indicated that all the four techniques used to fill the canals of primary molars led to voids in the filling material-a finding consistent with many other reports in the literature for the obturation techniques. Though difference was the highest with insulin syringe, followed by lentulospirals, then endodontic pressure syringe and least with skini syringe with navi tip. Hence, Insulin syringe showed worst results in filling the canals of primary molars while skini syringe with NaviTip showed best results for the same.
In the present study lentulospiral was found better than insulin syringe but poor than the other two techniques. This finding was consistent with the findings of Subbha Reddy et al. where endodontic pressure syringe was better than the lentulospirals in controlling the voids. However, Dandashi et.al found no significant difference between the lentulo instrument, pressure syringe and packing technique. Memapour M.et al and Torroes et.al have observed that lentulospirals led to better depth of fill to the apex though more voids were observed by them as compared with two syringe techniques- endodontic pressure syringe and navi tip. 15The results in the present study could be attributed to the differences in the method and area of observation from other studies including the use of CBCT for the present study. The presence of more voids with lentulospirals could be due to entrapment of air bubbles during mixing of the powder with liquid, need of repeated removal and reinsertion of the instrument in the canal during the filling procedure.
Insulin syringe showed the poorest POV or less postobturated volume with a statistical significant difference compared to the other three techniques used in the present study. In case of insulin syringe, the hub being small and slender provided easy access to the pulpal orifice within the pulp chamber though the needle is not flexible which provided an intracanal reach only till the middle one third of canals, thereby causing less approach or fill of the material to the apical third of the canal and comparatively more voids in that area. Lentulospirals are more flexible thereby resulting in the complete fill of the root canals and lesser number of voids particulary in the apical third of the canal. However, in the study conducted by Nagar P et al. there was no significant difference found between the insulin syringe and hand held reamer technique when depth of fill and voids were compared radiographically.4 No studies are available where insulin syringe was compared with other filling techniques.
It would appear that the two syringes used in the present study i.e. endodontic pressure syringe and insulin syringe should have shown the similar results as both are based on the plunger system, but under the conditions of this study this was not found to be true. Though the pressure exerted by the two plunger systems was not measured for the present study, the statistically highly significant higher values of the postobturated volumes and POV of canals for the endodontic pressure syringe compared to insulin syringe, could be attributed to the obvious higher pressure generated by the plunger system of the endodontic pressure syringe than that of the insulin syringe. The ZOE mixtures used and recommended for the two syringes was thicker (0.275 ml/gm) for the endodontic pressure syringe and thinner (0.40 ml/gm) for insulin syringe. The greater pressure was required to push thicker material by the endodontic pressure syringe however; lesser force was required by the insulin syringe. In the present study insulin syringe did not exerted enough pressure to deliver even its thinner mix effectively and efficiently. This was in consistent with the findings of Aylard et.al. Therefore, it is suggested from the findings of this study that the plunger system of endodontic pressure syringe is much better in providing far greater pressure required to release the thicker mix of ZOE recommended by the manufacturers. Also comparatively flexible and thin needle of endodontic pressure syringe provided a homogenous fill with lesser number of voids in the canals of primary molars compared to the non flexible or rigid needle of the insulin syringe. The flexibility of the needle of the endodontic pressure syringe allowed it to bend simulating the curvature of the root canals of posterior primary teeth which adds to its advantage of filling the canals of primary molars particularly those with curved root canals, more efficiently and effectively as also found in the present study.
Skini syringe with NaviTip was found to be the best technique for filling the canals of primary molars with statistically significant difference with lentulospiral and insulin syringe, however statistically no significant difference was observed on its comparison with the endodontic pressure syringe. Skini syringe is small diameter syringe that facilitates the flow of viscous materials through tiny NaviTip with minimal plunger pressure. The NaviTip system was specially designed to deliver paste into the root canal, and consists of a flexible tip that is not easily separated from the holder during injection. The highly flexible needle penetrates into the curved, narrow canal close to the apex and injects paste rapidly and uniformly. The cannula of the NaviTip system is slightly rigid through the base and centre, but flexible at the tip to allow for easy navigation of curved canals. The hub and shank are rigid to support insertion and the flexible rounded ends negotiate curves especially in the cases of posterior teeth. Guelmann et al. assessed the quality of root canal fill by using three filling systems and concluded that NaviTip system offered a more desirable filling quality than lentulospiral and Vitapex syringe techniques.17 Moreover, Memarpour M et al. also concluded that navi tip system produced the smallest void size and lowest number of voids and are superior in controlling paste extrusion from the apical foramen..
The present investigation and observations for the study was limited to in-vitro primary molars. We suggest that future studies must be extended to more in-vitro and in-vivo studies for the primary molars with bigger sample size and longer periods of evaluation, as there are number of in-vivo frequently encountered clinical factors such as patient age, their cooperative level, intraoral opening, access to the involved teeth and canals, facility or approach for the advanced system of imaging like CBCT etc. to reach the firm conclusion regarding the most effective and efficient obturating technique for human primary molars.
We conclude within the limits imposed by the conditions used in the present study that all the four techniques, namely, lentulospiral, insulin syringe, endodontic pressure syringe, skini syringe with navi tip can be used for placing the ZOE in the root canals of primary molars. The skini syringe with navi tip followed by endodontic pressure syringe provided best root canal obturation of primary molars with nearest to complete fill of the volumes of prepared root canals.
ACKNOWLEDGMENTS
The authors deny any conflicts of interest related to this study.