The Effect of Root End Cavity Preparation Using Er,Cr:YSGG Laser, Ultrasonic Retrotip, and Bur on the Apical Microleakage of Retrograde Cavity Filled with MTA Plus.

AIM: The sealing ability of the retrograde material is greatly affected by the technique used for root end preparation. Advances in retrograde preparation techniques such as lasers has shown to provide an efficient outcome. The study was to evaluate and compare the effect of various techniques of retrograde cavity preparation on apical microleakage.
MATERIALS AND METHODS: Forty-five single rooted teeth were decoronated. Biomechanical preparation was carried out up to size F2 ProTaper system and obturated. Glass-ionomer cement was used as an access restorative material. The apical root resection was done at 3 mm from the apex at angulation of 90° to the long axis of the root. The allocation of the samples was done into three groups of 15 each. Group A: Retrograde cavities prepared using conventional round bur; Group B: Retrograde cavities prepared using ultrasonic retro preparation diamond tip; and Group C: Retrograde cavities prepared using "Erbium, chromium: yttrium, scandium, gallium, garnet" (Er,Cr:YSGG). The retrograde cavities hence prepared were filled with MTA Plus. Nail varnish was used to coat the samples except at the apical end. Samples were immersed in methylene blue for 24h. Stereomicroscope was used for examination of the sectioned teeth. The data were analyzed using one-way analysis of variance (ANOVA) and post hoc Tukey test.
RESULTS: Results showed very highly significant difference between laser and bur (P value = 0.001).
CONCLUSION: Retrograde preparation with Er,Cr:YSGG showed significantly less microleakage when compared to the use of ultrasonic retrotip and burs. Copyright:

INTRODUCTION

The complexities that remain after conventional endodontic treatment can be solved many a times by retrograde surgery. Placement of an impervious seal following root end resection prevents leakage from the canal system into the periapex. Success rate of retrograde cavity preparation of traditional apical surgery done with burs is approximately 60%.[1] Surgical endodontic therapy comprises exposure of the involved apex, resection of apical end, preparation of a cavity, and restoring the same with a filling material.[2]

Burs have been normally used for the preparation of retrograde cavities. However, newer preparation techniques include the use of ultrasonics and lasers.[3] Use of ultrasonic tips for retrograde preparation was initiated by 1976; availability of microsurgical tips to be used in ultrasonic devices became easily accessible around 15 years ago.[4] Development of ultrasonic tips for apical surgery has raised the success rate up to 90%.[5] Smaller dimensions of these microsurgical tips improved accessibility to the resected retrograde cavities.[6]

“Erbium, chromium: yttrium, scandium, gallium, garnet” (Er,Cr:YSGG) laser has shown to be more effective than ultrasonic tips in root end preparation.[7]

Mineral trioxide aggregate (MTA) as a retrograde material has excellent adaptation to cavity walls, good biocompatibility, and least solubility. Studies conducted previously have shown excellent success rates for MTA, ranging from 90% to 92%.[8] The study was conducted to compare and evaluate three techniques of retrograde cavity preparation and their effects on apical microleakage.

MATERIALS AND METHODS

Forty-five single-rooted teeth with single canal were collected, decoronated, and the working lengths were determined. Cleaning and shaping of the canals were done up to size with F2 ProTaper system. Obturation was done using AH Plus sealer and gutta-percha. Glass–ionomer cement was used to seal the access cavities. A 3-mm depth of the root apex was resected at 90° to the long axis of the root using a straight fissure bur in a high speed handpiece with water coolant.

Samples were allotted into the following three groups of 15 each:

Group A: Retrograde cavities of 3-mm depth were prepared using conventional round bur

Group B: Retrograde cavities of 3-mm depth were prepared using ultrasonic retro preparation diamond tip (SybronEndo, Sybron Endo Corporation, Orange, CA, USA; BK3-R) retrotip attached to EMS minipiezon scaler pre-set to Endo setting program for ultrasonics

Group C: Retrograde cavities of 3-mm depth were prepared using “Er,Cr:YSGG laser” (Waterlase MD Laser; BioLase Technology, Unicorn Denmart Limited, New Delhi, India) with parameters: 4 W, 55% water, and 65% air in noncontact mode

MTA Plus was used to fill the retrograde cavities and was allowed to set for 55 min. Nail varnish was used to coat the samples except the resected root end and apical 2 mm. All samples were then submerged in methylene blue dye for 24h.

Longitudinal sectioning of the samples was carried out into two halves, and they were examined under a stereomicroscope. The digital image was viewed on the computer, and the extent of microleakage was marked and measured using Motic Plus 2.0 software [Figure 1A–C].

Figure 1

(A) Group A: Stereomicroscopic evaluation of the root end preparation done by bur. (B) Group B: Stereomicroscopic evaluation of the root end preparation done by an Ultrasonic retrotip. (C) Group C: Stereomicroscopic evaluation of root end preparation using Er,Cr:YSGG laser

Statistical analysis

Data were analyzed using one-way analysis of variance (ANOVA). In case of significant differences between the groups, a post hoc Tukey test was used.

RESULTS

Mean microleakage of burs group was 2.016 ± 0.925, ultrasonic group was 1.117 ± 0.755, and laser group was 1.003 ± 0.454, showing that laser group has least microleakage values [Table 1]. Microleakage results showed very highly significant difference between laser and bur (P value = 0.001), and highly significant difference between burs and ultrasonics (P value = 0.005) [Table 2].

Table 1

Mean microleakage values of each group

Groups	N	Mean	Std. deviation	Min.	Max.
Burs	15	2.016	0.925	0.99	3.69
Ultrasonic	15	1.117	0.755	0.28	2.70
Laser	15	1.003	0.454	0.57	2.41

N = number of samples in the group

Table 2

Post hoc Tukey test showing comparison values between the groups

Multiple comparisons
Dependent variable microleakage
Tukey honest significant difference
Group (I)	Group (J)	Mean difference (I – J)	P
Bur	Ultrasonic	0.89933	0.005hs
Bur	Laser	1.01293	0.001vhs
Ultrasonic	Laser	0.11360	0.907ns

Hs = highly significant, vhs = very highly significant, ns = not significant

DISCUSSION

The primary goal of retrograde root end surgery is to retain a tooth, which was previously endodontically treated, in which the lesion did not subside either by conventional therapy or by retreatment.

Apical root resection is a significant step in apical surgery, which aids in removing the pathologic process and anatomical variations, and gains access to the canal system. This study evaluated retrograde preparations carried out using burs, ultrasonics, and Er,Cr:YSGG laser. As maximum amount of apical canal anomalies and lateral canal system ramifications occur in the apical 3 mm,[9] hence root end resection of approximately 3 mm was carried out in this study.

According to Gilheany et al.,[10] there are two means, which lead to failures in the apical area of a root sealed with a retrograde filling. One being apical microleakage, and the other by free flow of fluids through open tubules at the resected root surface.

Previous studies have suggested a 90° bevel 3 mm from the apex also removes maximum amount of root ramifications while maintaining the length of the root. In our study, a 90° bevel was given for the same reasons.[10]

Microleakage of a retrofilling material is best assessed by dye penetration, if the material in question can obstruct the leakage of smaller molecules of the dye, then they would also be able to prevent infiltration of material such as bacteria and their by-products.[1112]

Tanomaru Filho et al.[13] concluded that the sealing ability of MTA when evaluated with 2% methylene blue dye solution was better when compared to 0.2% rhodamine B dye. Studies have proved that methylene blue is economical, easy to handle, has a better staining ability, and it has been proved that the molecular weight is lesser than bacterial toxins.[13]

Root end cavities prepared using ultrasonics have smaller dimension, provide better access and are comparatively conservative in nature when compared to cavities prepared by a micromotor handpiece and bur.[14] Main disadvantage of ultrasonics is cracks in the root canal walls.[15] Khabbaz et al.[16] compared bur, sonic, and ultrasonic for the root end cavity preparation and showed 7%–20% cracks with ultrasonic tips. Ishikawa et al.[17] showed that burs created 10% microcracks and ultrasonics caused 60%–80% microcracks when used for root end cavity preparation. However, O’Connor et al.[18] did not find much differences between the preparation with ultrasonic tips or handpiece in the sealing of retrofillings. In our study, ultrasonic retrotip showed less microleakage when compared to burs. This might be attributed to the fact that ultrasonic retrotip resulted in less smear layer formation in a retrograde cavity in comparison to a slow-speed handpiece.[19]

The “Er,Cr:YSGG” laser has been more efficient in cutting hard tissues. This laser cuts dentin with energized water molecules, keeping the temperature of the root surface low and therefore produces least thermal change.[7] Laser also makes the involved surface retentive, which would increase the bond between the sealing material and dentin.[3]

From the standpoint of chipping, hard tissue lasers have shown to preserve the integrity of retrograde cavities better than ultrasonic devices.[20] Lasers yield favorable results, including less crack formation, absence of vibration and pressure during retrograde cavity preparation, and the effective removal of debris and smear layer.[21] Koçak et al.[22] used burs, ultrasonics, and Er,Cr:YSGG laser in their study with fluid filtration method and concluded that Er,Cr:YSGG showed significantly lesser microleakage. In this study, we found that laser group showed the least microleakage when compared to ultrasonics and burs. This conclusion was reached due to an explanation that Er,Cr:YSGG laser causes micro-explosions of the water in dentin, resulting in the removal of smear layer, thus allowing retrograde filling material to penetrate into these tubules and decrease microleakage.[1523]

Success in surgical endodontics is achieved by obtaining a fluid impervious apical seal. The root sealing material selected should be biocompatible, have good strength, promote optimum healing, and its properties should not be altered by the presence of moisture. MTA Plus was used in this study as it has a setting time significantly shorter than ProRoot MTA.[24] According to Gandolfi et al.,[25] MTA Plus showed improved reactivity and prolonged capability to release calcium ions compared to ProRoot MTA. MTA Plus also showed a more alkaline local pH in comparison with ProRoot MTA.[25] MTA Plus was chosen in this study, considering its availability and lower setting time, and thus was a suitable replacement to conventional bioactive calcium silicate MTA-like cements.

CONCLUSION

With the available resources pertaining to this study, we can come to a conclusion that retrograde preparation carried out with Er,Cr:YSGG laser showed comparatively less microleakage when compared to the use of ultrasonic retrotip and burs, and thus in total would improve the quality of endodontic root end surgeries.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.