The Ability of Three Different Protocols in Removing Biroceramic- and Resin based Sealers from Simulated Internal Root Resorption Cavities: An in vitro Study

The endodontic therapy is considered successful when it achieves certain criteria that include the absence of periapical radiolucency, root lling extending to 2 mm within the radiographic apex, root lling with no voids, and a satisfactory coronal restoration1. However, root canal failure could occur in a percentage of 15 - 22%, and the non-surgical root canal retreatment stays the treatment of choice as a conservative way to control the post-treatment disease2. In non-surgical root canal retreatment removing all of the old root lling material is essential to improve the chances of success because this material could make a mechanical barrier that potentially retains the bacteria responsible for the case failure and also hinders the contact of irrigating solutions and intracanal dressings to the root canal walls3. Sealers are used to obturate the root canal irregularities and to ll the voids between the root canal lling and the canal walls4. Many new sealers have been introduced in the market; most commonly used are the resin-based and the bioceramic based sealer, the retreatability of these sealers is still not fully known5. In canal irregularities and atypical root canal system, faces a further challenge in the effective removal of the root canal lling. Internal root resorptions are a pathological condition caused by the inammatory reaction of the pulp cells leaving a resorptive cavity, the limitations of conventional non-surgical retreatment protocols require a more effective approach to fully remove the root canal llings6. improve the removal of Ca(OH)2 from oval canals and reduce the bacterial count in the root canal system8, XP-Endo Shaper (FKG Dentaire) has the same titanium alloy as XP-endo Finisher and according to the manufacturer, this alloy has the ability to adapt to the morphology of the root canal and could expand to reach all canal walls.


Introduction
The aim of this in vitro study is to compare XP-endo shaper, XP-endo nisher, and Passive Ultrasonic Irrigation cleaning e cacy of two root canal sealers (resin and bioceramic based) in internal root resorption cases, to determine the better clinical approach. so the PICO questions ..
In retreatment cases to teeth with internal root resorption that had been obturated with either resin-or bioceramic based sealers. Do XP-endo shaper, XP-endo nisher, or PUI differ in cleaning e cacy? · Population: Single rooted mandibular premolars with simulated internal root resorption · Intervention (1): XP-endo shaper retreatment to teeth obturated with resin-based sealer · Intervention (2): XP-endo shaper retreatment to teeth obturated with bioceramic based sealer · Intervention (3) Procedure 1. Crowns will be removed using a sterile diamond disk to standardize root length to 18 mm.
2. Access cavity will be prepared using sterile diamond burs, the pulp will be extirpated using #10 Kles then #15 K-le will be used to determine working length 1mm short from the length the le was visible from the apical foramen.
3. The root canal will be mechanically prepared to the size #35:0.06 with NaOCl 5.25% irrigation with a 27-gauge needle 1mm short from the working length.
4. Final irrigation 5 mL of distilled water then drying with paper points 5. Simulated internal root canal resorption will be prepared according to Topçuoğlu et al [1].
6. Specimens will be xed in modi ed silicon (hydrorise, Zhermack, Italy) in an eppendorf tube for proper bonding later.
7. After setting of silicone the specimen will be removed, and two longitudinal grooves along the root will be prepared on both the buccal and lingual sides, then the specimen is to be split along its long axis using a chisel.
8. Standard cavities on both segments are to be made, 5 mm from the apex with 0.8 mm depth and 1.6 mm diameter using sterile diamond burs under water cooling. 9. 7 random specimens will be kept as a negative control group with no further treatment 10. 36 random specimens, the cavities will be lled with resin-based sealer and assigned to group A 11. 36 random specimens, the cavities will be lled with bioceramic sealer and assigned to group B 12. Then the two halves of each specimen will be bonded back together using superglue and remounted back in the silicon impression for proper positioning and the access cavity will be sealed with a temporary lling.
13. Specimens will be stored at 37º C at 100% humidity for 1 week.
14. The trial will be conducted on each group 15. After restoring specimens at 37º C at 100% humidity for 1 week, each specimen will be split again. 16. Two digital images -one for each half-under a light microscope (Inverted Laboratory Microscope Leica DM IL LED, Leica Microsystems©, Wetzlar, Germany) would be evaluated using the classi cation described by Van der Sluis et al [2]: Score 0: the cavity is free of debris.
Score 1: less than half of the cavity is lled with debris.
Score .2: more than half of the cavity is lled.

Troubleshooting
After restoring specimens at 37º C at 100% humidity for 1 week, each specimen will be split again.
Two digital images -one for each half-under a light microscope (Inverted Laboratory Microscope Leica DM IL LED, Leica Microsystems©, Wetzlar, Germany) would be evaluated using the classi cation described by Van der Sluis et al: