Sealing ability of three root-end filling materials prepared using an erbium: Yttrium aluminium garnet laser and endosonic tip evaluated by confocal laser scanning microscopy.

AIMS: (1) To compare the sealing ability of mineral trioxide aggregate (MTA), Biodentine, and Chitra-calcium phosphate cement (CPC) when used as root-end filling, evaluated under confocal laser scanning microscope using Rhodamine B dye. (2) To evaluate effect of ultrasonic retroprep tip and an erbium:yttrium aluminium garnet (Er:YAG) laser on the integrity of three different root-end filling materials.
MATERIALS AND METHODS: The root canals of 80 extracted teeth were instrumented and obturated with gutta-percha. The apical 3 mm of each tooth was resected and 3 mm root-end preparation was made using ultrasonic tip (n = 30) and Er:YAG laser (n = 30). MTA, Biodentine, and Chitra-CPC were used to restore 10 teeth each. The samples were coated with varnish and after drying, they were immersed in Rhodamine B dye for 24 h. The teeth were then rinsed, sectioned longitudinally, and observed under confocal laser scanning microscope. STATISTICAL ANALYSIS USED: Data were analyzed using one-way analysis of variance (ANOVA) and a post-hoc Tukey's test at P < 0.05 (R software version 3.1.0).
RESULTS: Comparison of microleakage showed maximum peak value of 0.45 mm for Biodentine, 0.85 mm for MTA, and 1.05 mm for Chitra-CPC. The amount of dye penetration was found to be lesser in root ends prepared using Er:YAG laser when compared with ultrasonics, the difference was found to be statistically significant (P < 0.05).
CONCLUSIONS: Root-end cavities prepared with Er:YAG laser and restored with Biodentine showed superior sealing ability compared to those prepared with ultrasonics.

INTRODUCTION

The major goals of root canal treatment are to clean and shape the root canal system and fill it with a three-dimensional obturation.[1] When nonsurgical endodontic treatment is not successful, surgical endodontic therapy is indicated which involves exposure of the apex, resection of the apical end of the root, root-end preparation, and insertion of a root-end filling material.[2] Root-end preparation using burs have the inbuilt disadvantages including limited operative field and root-end bevel, which increases the number of exposed dentinal tubules on the root-end surface. Ultrasonic devices have been advocated to overcome such limitations.[3]

Laser technology is being used in all fields of dentistry, particularly in endodontics. The favorable results of high-power lasers are decrease in dentine permeability and cavity preparation without vibration.[4]

Mineral trioxide aggregate (MTA) is a hydraulic cement and it sets in the presence of water. When used as a root-end filling material, there is complete regeneration of the periradicular periodontium.[5] It has been generally accepted that MTA has osteoinductive and osteoconductive ability.[6]

Two new materials which might potentially provide the necessary properties of an optimal root-end filling material are Biodentine and Chitra-calcium phosphate cement (Chitra-CPC).

The aim of the present in vitro study is

To find an optimal root end filling material

To find an efficient technique of root end cavity preparation.

The objectives of the study were to

Compare the sealing ability of MTA, Biodentine and Chiitra-CPC when used as root end filling material evaluated under Confocal Laser Scanning microscope Using Rhodamine B dye.

To compare the seal of root ends prepared using an ultrasonic retroprep tip and an Er: YAG Laser using 3 different root end filling materials.

MATERIALS AND METHODS

Eighty mandibular first premolar teeth with single canals were collected and stored in saline. After decoronation, the length of each canal was determined where a size 15 K-file exited the apical foramen and working length was calculated 0.5 mm short of this position.

Biomechanical preparation of the root canals was done up to size F2 ProTaper instrument (Denstply, Maillefer). Root canals were obturated with gutta-percha and AH Plus sealer. After removal of 2 mm of the filling material, the access cavity was sealed with light-cured glass ionomer cement. Apical root resection was then performed by removing 3-4 mm of the apex at 90° to the long axis of the root with a straight fissure bur in a high-speed handpiece with water coolant.

The teeth were randomly allocated into two control groups of 10 teeth each and experimental groups of 60 teeth each. In half of the samples, the apical cavity was prepared using an ultrasonic retropreparation diamond tip (Sybron Endo; BK3-R) with water coolant. In the rest of the samples, apical cavity preparation was performed using an Er:YAG hard tissue laser (Fidelis Laser; Fotona (400 mJ, 10 Hz)) in noncontact mode.

Group I

Endosonic tip used for root-end preparation.

Subgroup IA: The root-end cavities prepared using endosonics were filled with MTA.

Subgroup 1B: The root-end cavities prepared using endosonics were filled with Biodentine.

Subgroup IC: The root-end cavities prepared using endosonics were filled with Chitra-CPC.

GROUP II

Er:YAG laser used for root-end preparation.

Subgroup IIA: The root-end cavities prepared using Er:YAG laser were filled with MTA.

Subgroup IIB: The root-end cavities prepared using Er:YAG Laser were filled with Biodentine.

Subgroup IIC: The root-end cavities prepared using Er:YAG laser were filled with Chitra-CPC.

All the specimens were covered with two layers of nail varnish except for the apical surfaces. The control groups were divided into two groups of 10 teeth each.

Group III

Negative control: In 10 teeth, the entire root surface was coated with two coats of nail varnish to act as negative controls.

Group IV

Positive control: The remaining 10 teeth were not filled with any root-end filling material to act as positive controls.

All the samples were wrapped in wet pieces of gauze and stored in 100% humidity for 24 h. The samples were then totally immersed in 0.2% aqueous solution of Rhodamine B fluorescent dye for 24 hours. Using a diamond disc each root was longitudinally sectioned into two halves. The depth of dye penetration was examined under confocal laser scanning microscope.

RESULTS

Very high significant differences were observed between the groups (P-value < 0.05). The positive control group had the highest dye penetration, while the negative control group showed the least penetration. Comparison of microleakage showed maximum peak value of 0.45 mm with a standard deviation of 0.15 for Biodentine, 0.85 mm with a standard deviation of 0.09 for MTA, and 1.05 mm with a standard deviation of 0.11 for Chitra-CPC. Among the three materials, Biodentine showed less microleakage followed by MTA and Chitra-CPC.

Comparison of microleakage showed maximum peak value of 0.8627 mm with a standard deviation of 0.2533 for ultrasonics and 0.7103 mm with a standard deviation of 0.2918 for lasers [Table 1]. Among the treatment using ultrasonic and laser, laser showed less microleakage [Figures 1 and 2]. Two-way analysis of variance (ANOVA) was carried out to check whether there is any significant difference between the materials (A, B, and C) and the treatment (I and II) and their combinations. Results of the test indicated that there was significant difference among the three materials A, B, and C (P < 0.05) [Table 2].

Table 1

Descriptive statistics for sealing ability for material and the treatment

Figure 1a, b, c

Microleakage visualized under CLSM

Figure 2

(a) Microleakage visualised under CLSM (b) Microleakage visualised under CLSM (c) Microleakage visualised under CLSM

Table 2

Descriptive statistics for sealing ability with respect to the type of material

Among the treatment (I and II) also there was significant difference (P < 0.05). But the combination of treatment and material was not statistically significant (P > 0.05) [Table 3].

Table 3

ANOVA Table

DISCUSSION

Apical seal of root-end filling materials is the single and most important factor in achieving success in surgical endodontics.[7]

Root-end cavity preparation techniques require the use of ultrasonic instruments and lasers.[5] The advantages of ultrasonic preparation are smaller dimensions and improved access to the resected root-end cavity. When compared to burs, laser has the following advantages: No vibration or discomfort, minimal pain, and less bacterial risk of trauma to adjacent tissues.

In the present study the amount of dye penetration was found to be lesser in root ends prepared using Er:YAG laser when compared to ultrasonics. This may be due to better preservation of the integrity of root-end cavities from the standpoint of dentinal chipping.

The difference was found to be statistically significant (P < 0.05). This was in concurrence with the findings of Karlovic et al., in which the cavities prepared with Er:YAG laser had significantly lower microleakage.[8]

Despite the favorable properties of MTA it has several disadvantages. It has a long setting time and its potential to cause coronal discoloration.[9]

In the present study MTA showed a mean microleakage of 0.85 mm, which was much less than Chitra-CPC (1.05 mm) but greater than that of Biodentine (0.45 mm). The difference was found to be statistically significant (P < 0.05). The slow setting reaction of MTA might be the reason for the increased depth of microleakage seen in the present study. This was not in concurrence with the findings of Xavier et al., where MTA showed superior sealing ability compared to other root-end filling materials.[10]

CPC is considered as excellent alloplastic material for osseous augmentation.[11] The set mass of CPCs is hydroxyapatite, the basic inorganic component of bone and teeth. The material has the property of osteotransductivity (i.e., active resorption at bony sites, facilitating bone remodeling).[12]

A novel indigenous formulation of CPC has been developed at the Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Thiruvananthapuram which was named ‘Chitra-CPC’. Compared to conventional CPC it has enhanced viscous and cohesive properties. Chitra-CPC could be mixed in varying consistencies, from moldable putty to injectable paste.[12]

However, in the present study, Chitra-CPC showed a mean microleakage of 1.05 mm which was greater than that of MTA (0.85 mm). The difference was found to be statistically significant (P < 0.05).

Biodentine is similar to MTA in basic composition. The powder consists of tricalcium, dicalcium silicate, calcium carbonate, and zirconium dioxide. The liquid consists of calcium chloride in aqueous solution with an admixture of polycarboxylate. Biodentine has a setting time of 12 min. Calcium hydroxide is formed during the setting of the cement.[13]

Biodentine bonds chemomechanically with the tooth. This has high compressive and flexural strength.[14] Its sealing ability, when in contact with dentin, has been confirmed in vitro with a very low silver nitrate penetration. Tricalcium silicate-based cements do not leach any contaminants, thus are considered safer for use as root-end filling materials.[15]

In the present study, Biodentine showed a mean microleakage of 0.45 mm which was much lower than MTA (0.85 mm) and Chitra-CPC (1.05 mm). The difference in microleakage values was found to be statistically significant (P < 0.05). Thus, Biodentine might be considered as a promising material for use as a root-end filling material.

A confocal microscope creates sharp images of a specimen. This is achieved by excluding most of the light from the specimen that is not from the microscope's focal plane. The image has better contrast and less haze than that of a conventional microscope. The confocal microscope does not require a specific sectioning technique and no artifacts produced when compared to scanning electron microscope.[16]

CONCLUSION

Within the limitations of the present study, it can be concluded that Biodentine is a better material to prevent apical microleakage in comparison to MTA and Chitra-CPC.

Root-end preparation with Er:YAG laser exhibited lesser amount of dye penetration when compared to ultrasonics. This may be due to absence of chipping during root-end cavity preparation with Er:YAG Laser. Further in vivo studies are needed to correlate with the finding of the present study.