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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 15  |  Issue : 2  |  Page : 251-254

An in vitro assessment of effect on microhardness of dentin using vicker's hardness method


1 Department of Conservative and Endodontics, SPDC, DMIMS, Wardha, India
2 Department of Conservative and Endodontics, Swargiya Dadasaheb Kalmegh Smruti Dental College, Nagpur, Maharashtra, India

Date of Submission04-Feb-2020
Date of Decision10-Feb-2020
Date of Acceptance08-Mar-2020
Date of Web Publication21-Dec-2020

Correspondence Address:
Dr. Rakhi Chandak
Swargiya Dadasaheb Kalmegh Smruti Dental College, Nagpur, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdmimsu.jdmimsu_35_20

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  Abstract 


Aim: this study was conducted to compare the effects of different intracanal medicaments on microhardness of dentin. Materials and Methods: The dentin disc of third molars (n = 45) was obtained and was randomized into three groups. Group metapex, modified triple antibiotic paste (MTAP), and control group according to the medicaments used. Teeth were incubated in 100% humidity for 7 days. For each group, teeth were subjected to microhardness testing. The one-way analysis of variance test was used to check mean differences among the groups. Post hoc analysis was done using Tukey's Honest Significant Difference test. Results: Significant differences (P < 0.001) in mean microhardness of dentin between the control group and medicament group. The intergroup comparisons of metapex and MTAP group did not show any statistically significant variations (P > 0.05) in mean microhardness of dentin after the 7th day of application. Conclusion: Under the condition of this study, MTAP affects the microhardness of dentin adversely compared to the metapex.

Keywords: Chlorhexidine gel, intracanal medicaments, metapex, microhardness of dentin, modified triple antibiotic paste


How to cite this article:
Chandak M, Modi R, Gogiya R, Chandak R, Ikhar A, Mankar N. An in vitro assessment of effect on microhardness of dentin using vicker's hardness method. J Datta Meghe Inst Med Sci Univ 2020;15:251-4

How to cite this URL:
Chandak M, Modi R, Gogiya R, Chandak R, Ikhar A, Mankar N. An in vitro assessment of effect on microhardness of dentin using vicker's hardness method. J Datta Meghe Inst Med Sci Univ [serial online] 2020 [cited 2021 Jan 24];15:251-4. Available from: http://www.journaldmims.com/text.asp?2020/15/2/251/304258




  Introduction Top


Root canal treatment (RCT) may necessitate eradicating most bacteria from the canal during biomechanical preparation. The placement of intracanal medicament is recommended as a significant step to alleviate the microbial load before the root canal filling.[1] Biomechanical preparation and irrigation protocol in the RCT has shown to significantly decrease the count of bacteria in infected canals, however, it is difficult to accomplish total disinfection in many cases. Persistent bacteria in obturated canal may proliferate and invade in the complex root canal system. These bacteria remain unaffected by chemomechanical preparation, therefore, the placement of intracanal medicament is an imperative procedure.[2]

In root canal therapy, medicament has a significant role in removal of active exudation and removal of the necrotic pulp. The type of medicament to be used is determined by the diagnosis of the tooth condition, microorganism involved, their growth, and survival.

Endodontic irrigants also have a vital role in endodontics in the removal of the organic and inorganic components as well it alters the other properties such as microhardness, permeability, and solubility.

Triantibiotic paste was initially developed by Hoshino and colleague in the year 1996, who had done a study and demonstrated that triple antibiotic paste decontaminates  Escherichia More Details coli-infected dentin.[3] Triantibiotic paste is a combination of three medicaments, which are metronidazole (nitroimidazole compound), ciprofloxacin (synthetic fluoroquinolone), and minocycline (semisynthetic derivative of tetracycline).

In various studies, minocycline has shown various other disadvantages, such as tooth discoloration and demineralizing effect on dentin. It also lowers the pH of the medicament mixture. Another antibiotic which can be replaced is clindamycin, which is effective against various endodontic pathogens. It is a modified triple antibiotic paste (MTAP) consisting of metronidazole, ciprofloxacin, and clindamycin can be used as an intracanal medicament.

Calcium hydroxide is recommended as intracanal dressing due to its biological properties such as high alkalinity, antimicrobial activity, inhibits tooth resorption, and tissue dissolving capability that improves the clinical situations. However, several studies suggested to ameliorate the properties of calcium hydroxide by mixing it with other substances such as silicon oil-based calcium hydroxide with 38% iodoform.[4] Iodoform is lemon yellow color bright hexagonal crystal. It has a less solubility in water compared to alcohol and ether. After decomposition, iodine produces elementary iodine, and its action is by oxidizing essential enzymes and precipitating proteins.[5]

There is a strong correlation between the bond strength and microhardness of dentin. Hence, the behavior of dentin/restoration is best predicted by microhardness. Small alterations in microhardness can disrupt the distribution of stresses, so the location of failures can also be determined.[6] Hence, the current study was carried out to establish the effect of different intracanal medicaments on microhardness of radicular dentin using Vicker's microhardness test (VHN). The resistance to deformation of dentin, which is caused by indenting stylus, can be measured by microhardness testing. This gives information about the effect of medicament on the mechanical properties of dentin.[7]


  Materials and Methods Top


Sample selection

Forty-five freshly extracted third molars were selected and stored until use. Caries-free human third molar and teeth with sufficient dentin thickness and width were selected. Carious teeth, cracked teeth, and malformed teeth were excluded from the study.

Crown was sectioned, and dentin disc was obtained from each sample to obtain a standardized disc of 1.5 mm, then each sample was irrigated with 20 ml of 1.5% sodium hypochlorite (NaOCl).

Sample classification

Sample preparation

Teeth were randomly divided into three groups (n = 15) according to the medicament used: group metapex, group MTAP, and control group (with no medicament).

For each of the medicament group, the radicular side of each dentin disc was treated with the medicament by applying with either 0.1 ml of MTAP or calcium hydroxide-based intracanal medicament using a disposable syringe to cover the entire surface of radicular dentin. The amount of the intracanal medicament applied was 0.1 ml, which was enough to cover the radicular surface of the dentin disc.

Vicker's hardness testing

On the 30th day, VHN values were determined (kg/mm2) at a load of 50 g indentation for 10 s. The load was divided by the area of indentation. Three indentations were performed in the middle of the radicular dentin of each specimen. The long axis of indenter was kept perpendicular to the radicular surface. The three measurements were taken on the most distal part of the central area, that is, 1000 μm away from the pulpal space. Load impression can be applied to brittle materials without cracking. The mean of the three indentations was taken as the final reading in VHN.

Statistical analysis

The one-way analysis of variance test was used to check mean differences among the groups. Post hoc analysis was done using Tukey's Honest Significant Difference test.

Ethical Approval

Ethical approval for this study (DMIMS(DU)/IEC/2017-18/6733) was provided by the Ethical Committee of Datta Meghe Institute of Medical Sciences (Deemed to be University) on 27/9/2017.


  Results Top


The control group had the highest mean microhardness of dentin followed by MTAP group and metapex group and showed statistically significant differences (P < 0.001) in mean microhardness of dentin. The intergroup comparisons of metapex and MTAP group did not show any statistically significant variations (P > 0.05) in mean microhardness of dentine after the 7th day of application.

Comparison of mean microhardness of dentin after the 7th day of application of three intracanal medicaments


  Discussion Top


Microorganisms have significant role in the pulpal and periradicular diseases. The eradication of these microbes from the infected root canals is rigorous. Instrumentation alone cannot eradicate the microbes from the complex canal anatomy. Hence, a certain kind of disinfection is required to kill and eliminate the microbes from the root canal.[8] Intracanal medicaments used in endodontics have various significant purposes, which include eradication of the remaining microbes, to maintain the canal entity inert, and to prevent postoperative pain. However, apart from this, alteration in mechanical and chemical properties of root dentin occurs due to the use of the disinfectant protocol in endodontic therapy. This causes change in microhardness, solubility, and permeability due to the change in inorganic/organic ratio of dentin structure.[9]

Microhardness is defined as the resistance to local deformation. These tests are based on the induced permanent surface deformation that remains after the removal of the load.[10] Hardness measurements can be coordinated with other mechanical properties such as yield strength, modulus of elasticity, and fracture resistance. A strong correlation exists between the bond strength and microhardness of dentin. Hence, microhardness provides the initial step to determine the results of dentin/restorations interface and the locations of failures.

Irrigation plays a very crucial role in counteracting the problem such as complex anatomical structure which prohibits the complete removal of the microorganisms. NaOCl is the most frequently used irrigating solution, but it also has certain limitations of causing cytotoxicity, corrosion of instruments, and so on [Figure 1] and [Table 1].[11]
Figure 1: Comparison of mean micro-hardness of dentin after 7th day of application of three intra-canal medicaments

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Table 1: Comparison of mean micro-hardness of dentin after 7th day of application of three intra-canal medicaments

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No irrigating solution is considered optimal. Therefore, a combination of adjunct irrigant with a proper sequence is required to obtain successful results.[9] Another commonly used irrigating agent is ethylenediaminetetraacetic acid (EDTA), which dissolves the inorganic component. EDTA also provides additional advantages, such as helping in RCT procedures, ease of access for root canal armamentarium, and minimal or reduced corroding activities for instruments. In addition, it is also useful in preparing teeth with calcified canals.[7]

The higher concentration of NaOCl causes cytotoxic effect when extruded in the periradicular tissue. This leads to severe pain, immediate swelling, and exuberant bleeding. Furthermore, it is noted that NaOCl causes interference in the bonding of the resin-based sealer used in endodontic therapy.[11] The concentration of 1.5% NaOCl was used in the present study as per the recommendations by the current endodontic regenerative protocol by the American Association of Endodontics. Final irrigation with 17% EDTA was recommended during endodontic regeneration (Galler et al. 2011 and Miller et al. 2012). Chelating agent improved the chemomechanical debridement of the root canal by eliminating smear layer. However, it was also found to significantly reduce the radicular dentine microhardness (De-Deus et al. 2006) and root resistance to fracture (Uzunoglu et al. 2012).[8]

Calcium hydroxide is the commonly used intracanal medicament. The antibacterial effect of calcium hydroxide is maintained when the pH is high.[12] Various studies have been done to evaluate the effect of calcium hydroxide mixture with other substance, which will improve its properties. The additional factors that affect the outcome includes vehicle which alter the ionic dissociation, antimicrobial activity, and radiopacity. It also includes the consistency, which helps in filling of the canal. Silicon oil-based calcium hydroxide containing 38% of iodoform is commercially available as metapex.

Andreasen et al. (2002) theorized that the proteolytic action of Ca (OH) 2 could weaken a tooth up to 50%, and this weakness could lead to an increase in fracture. White et al. (2002) reported a 32% decrease in dentine strength after the use of Ca (OH) 2. They proposed that this was caused by breakdown of the protein structure and alkalinity of calcium hydroxide.

The use of antibiotics in endodontics was initially introduced by Grossman in 1951 as a combination of different antibiotics known as polyantibiotic paste. Triple antibiotic paste is a mixture of metronidazole, ciprofloxacin, and minocycline, the widely used intracanal medicament become popular and regular after its role revascularization. Metronidazole, it particularly effective against anaerobes and also has an antimicrobial effect against protozoa and anaerobic bacteria.


  Conclusion Top


Ciprofloxacin has an antibacterial action against Gram-negative bacteria while it has a limited role against Gram-positive bacteria. Minocycline is bacteriostatic and shows antibacterial activity against both Gram-positive and Gram-negative.[13] Among many advantages, it has some remarkable disadvantages, such as crown discoloration and demineralization effect on dentin due to its low pH. Hence to overcome these side effects, minocycline has been substituted with other antibiotics (Iwaya et al. in 2001, Thibodeau and Trope, in 2007). As clindamycin has been effective against endodontic pathogens, an MTAP was developed consisting of metronidazole, ciprofloxacin, and clindamycin. Lin et al.[6] evaluated the antibacterial outcome of clindamycin and tetracycline using a agar diffusion test in bovine dentin sample. The study results showed that the clindamycin showed a marked reduction in the number of bacteria in each dentin sample compared to tetracycline.

VHN has been used in our study for assessing the microhardness of teeth on the application of various remineralizing agents. This test gives accurate readings in both soft and hard materials, that is, it gives identical hardness numbers on similar materials at different loads, while other tests need arbitrary changing of scales. The decalcified teeth lose the inorganic components leading to decreased hardness, but the accurate readings of this test made it our choice of analysis for microhardness.[14]

Intracanal medicaments are capable of decreasing the microhardness of dentin. Irrigation protocol performed during treatment also affects the microhardness. Therefore, type and duration of medicament has a pivotal role in the maintenance of dentin microhardness.[15],[16],[17],[18],[19]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
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Estrela C, Estrela CR, Hollanda AC, Decurcio Dde A, Pécora JD. Influence of iodoform on antimicrobial potential of calcium hydroxide. J Appl Oral Sci 2006;14:33-7.  Back to cited text no. 4
    
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Parhizkar A, Nojehdehian H, Asgary S. Triple antibiotic paste: Momentous roles and applications in endodontics: A review. Restor Dent Endod 2018;43:e28.  Back to cited text no. 13
    
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