effect of different intra orifice barriers and bleaching agents on the fracture resistance of endodontically

effect of different intra orifice barriers and bleaching agents on the fracture resistance of endodontically

1. Effect of Different Intra orifice Barriers and Bleaching Agents on the Fracture Resistance of Endodontically Treated Anterior Teeth Siavash Savadi Oskoee , DDS, MS, Mahmoud Bahari , DDS, MS JOE, November 2018. JOURNAL CLUB PRESENTATION BY DR. ABDUL KADIR MDS 3 RD YEAR DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS

2. INTRODUCTION Currently, bleaching methods are used for correcting internal discoloration. Hydrogen peroxide (HP) is an active ingredient of modern bleaching agents (BAs) that can be directly applied or produced by the chemical decomposition of carbamide peroxide (CP) or sodium perborate (PB).

3. Although numerous studies have shown that bond strength to the tooth structure decreases after bleaching, there is great controversy regarding the negative effects of BAs on the fracture resistance (FR) of endodontically treated teeth (ETT). Bonfante et al showed that the FR of ETT bleached with CP 37% did not change after 21 days. On the other hand, Pobbe Pde et al showed that the FR in ETT decreases after 2 sessions of bleaching with HP 38% activated by a light-emitting diode laser system,

4. Required features for an ideal IOB include easy placement, bonding to the tooth structure, a microleakage seal, easy distinction from the natural tooth structure, and noninterference with the final restoration. Glass ionomers are one of the agents with these features that are routinely used. Mineral trioxide aggregate (MTA) is another agent suggested that is highly biocompatible and capable of osteogenesis ; however, there are no reports on the ability of MTA regarding the reinforcement of the tooth structure,

5. Calcium-enriched mixture (CEM) is a recently introduced product as the substitute for MTA; this product also has an antibacterial property similar to calcium hydroxide and better than MTA. CEM cement has a lower toxicity, greater biocompatibility, and higher potential for inducing hard tissue formation in vital pulp therapy.

6. METHODOLOGY

7. FR MEASUREMENT Teeth were mounted in self-cured acrylic resin 2 mm below the cementoenamel junction inside a cylinder with a diameter of 1.5 cm and a height of 2.5 cm. The FR was measured with a universal testing machine (Hounsfield test equipment, Model H5K5; Analytical Laboratory Services, Surrey, UK) above cingulum at a crosshead speed of 5 mm/min at a 130 angle with the long axis of the root.

8. Fracture resistance measurement with a chisel-like and nonsharp blade at a 130 angle with the long axis of the root.

9. STATISTICAL ANALYSIS Data were analyzed with the 2-way analysis of variance test using SPSS Version 17 statistical software (SPSS Inc , Chicago, IL).

10. RESULTS

11. DISCUSSION External root resorption has been reported in some cases after the intracoronal bleaching process because of the penetration of the BA into the dentinal tubules, the change in pH, and its passage from the cementum into the periodontal ligament tissues. This reaction results from the presence of HP by releasing radical oxygen and ultimately reducing the physical properties of the hard tissues. In order to prevent this, various methods have been proposed, the most valid and most effective of which is the use of IOBs to prevent the penetration of the BA into the periodontal ligaments.

12. According to Gupta et al (19), fiberreinforced composite resin, RMGI, MTA, and nanocomposite resins as IOBs significantly increased the FR of ETT compared with the control group (without an IOB), which had the highest resistance in the RMGI group and the lowest in the MTA group. In another study, it was also concluded that RMGI and flowable composite resin are effective IOBs that increase the FR of ETT

13. The reason for the high FR in RMGI applications compared with other agents that was reported in several studies is because of the characteristics of this agent. RMGI has a high flexural strength and an elastic modulus (10–14 GPa ) close to the dentin. Therefore, the material can withstand a large amount of stress before transmitting the load to the root. In addition, its chemical bond to the dentin surface creates a greater resistance in the dentin-cement interface.

14. MTA is accepted as an IOB because of its adequate sealing and adaptation, high pH, and adequate radiopacity . Although this agent produces a perfect seal against microleakage , in the present study and other studies, it has been qualified as a weaker IOB in respect to the FR than RMGI and composite resin because of the lack of bonding to dentin , stiffness at high pressure , and weakness under tension despite its optimal elastic modulus.

15. CONCLUSION Considering the limitations of this in vitro study, it can be concluded that the effect of different BAs was significant on the FR, but the effect of the IOB and the interactive effect of the BA and the IOB were not significant. In addition, HP and PB caused a significant reduction in the FR compared with the control group, but the CP was not significantly different from the control group.

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