Total bacterial eradication from the root canal system is a major goal of endodontic treatment. More than one procedure should be combined to eliminate bacterial infection. These procedures include the use of efficient irrigating solutions such as sodium hypochlorite (NaOCl) or hydrogen peroxide (H2O2) during cleaning and shaping in addition to the intracanal medicament that contains antimicrobial agents such as calcium hydroxide (Garcez et al. 2007; Bonsor et al. 2006).
The use of intracanal medicaments is often mandatory to eliminate bacteria from root canals in order to stop their ingress, prevent their growth, and cut off their source of nutrients (Siqueira et al. 2001).
For root canal system disinfection, calcium hydroxide is the most widely used intracanal medicament (Mustafa et al. 2012); when applied for at least 7 days, elimination and/or reduction of the populations of living bacteria even after cleaning and shaping could be achieved (Mohammadi et al. 2012). Direct contact of calcium hydroxide (pH is about 12.5) with the mostly found bacterial species in infected root canals leads to its elimination after short period of time (BystroÈm and Sundqvist 1985). The antimicrobial activity of calcium hydroxide could be attributed to hydroxyl ions release in an aqueous environment. Hydroxyl ions are highly oxidant free radicals that show extreme reactivity, reacting with several biomolecules (Freeman and Crapo 1982). This reactivity is high and indiscriminate, so this free radical rarely diffuses away from sites of generation.
According to Siqueira et al. (1999), their lethal effects on bacterial cells are probably due to the following mechanisms: (1) damage to the bacterial cytoplasmic membrane; (2) protein denaturation; and (3) damage to the DNA.
It was shown that bond strengths between root canal dentine and resin‐based sealer was decreased due to presence of calcium hydroxide remnants (Barbizam et al. 2008). Ca(OH)2 remnants were also shown to have interfered with the sealing ability of a silicon‐based sealer (Contardo et al. 2007). Calcium hydroxide based intracanal medications also contributed to the increased apical leakage of root canals filled with gutta percha and zinc oxide–eugenol sealer (Kim and Kim 2002) which can be explained by the accelerated setting of the sealer (Margelos et al. 1997).
Therefore, it was then mandatory to study new antimicrobial agents targeting these bacteria to achieve a higher success rate in endodontic treatments thus predicting a better prognosis for the tooth.
Nowadays, new natural products and various plants have been used as a source of medicine. That’s why, many studies are being carried out to investigate these new products’ properties (Mistry et al. 2014). Moringa oleifera is known as miracle tree because all the parts of the tree (leaves, pods, seeds, roots, flowers) can be utilized for nutritional and pharmacological benefits.
According to a study conducted by Shetty et al. (2019), Moringa oleifera and Azadirachta indica demonstrated an antibacterial effect against Enterococcus faecalis. They concluded that these natural products could be used effectively as antimicrobial agent in root canal therapy.
During the first 24 and 48 h, Moringa oleifera had an antibacterial effect against E. faecalis. Olson and Fahey showed that the chemical compound named 4-(4′-O-acetyl-α-L-rhamnopyranosyloxy)-benzylisothiocyanate is responsible for the antibacterial effect of Moringa oleifera. Its action mechanism depends on inhibition of essential cellular membrane enzymes (Olson and Fahey 2011; Martin et al. 2013). Jung’s study showed that even with concentrations of 600 mg/ml, extract of Moringa oleifera showed no cytotoxic effect against a cellular line Cos-7 (Jung 2014).
In a previous study, Khallaf et al. (2020) used Moringa oleifera as an irrigant solution during instrumentation and compared it to NaOCl and chlorhexidine regarding its effect on dentin microhardness and its smear layer removal ability. It was confirmed that Moringa oleifera when used as an irrigant alone or in combination with chlorhexidine had a similar effect in removal of remaining debris as NaOCl and chlorhexidine. Different formulations of Moringa oleifera used in this previous study increased the dentin microhardness all over the canal. They concluded that Moringa oleifera is a promising irrigant solution.
Concerning, the evaluation of remnants of the intracanal medicaments in root canals after irrigation, our results showed that in the apical part of root canals, there was significantly higher remnants of Ca(OH)2 left compared to Moringa oleifera leaf and roots. Metapex is oil-based calcium hydroxide paste. According to manufacturers, the main ingredients of Metapex that we used in our study are calcium hydroxide 30.3%, iodoform 40.4%, silicone oil 22.4%, others 6.9%. This mixture can be filled in the root canals using disposable tips, filled with the material. Previous findings suggested that oil-based Ca(OH)2 pastes were more difficult to remove than Ca(OH)2 mixed with distilled water (Lambrianidis et al. 1999; Nandini et al. 2006).
No significant difference was found between Ca(OH)2 and Moringa oleifera leaf and root in the coronal part and this may be due to the ease of flushing of intracanal medicament from the coronal part.
In our study, three points microhardness measurements were recorded for the root canal dentin (coronal, middle and apical third). A Mean Vickers hardness number.
(VHN) was calculated for each specimen third (Hasheminia et al. 2009). Dentin microhardness is directly related to tubular density that differs from an area to another on the root dentin surface. Therefore, the current study design followed Pashley et al. (2004), who declared that as the tubular density increases, dentin microhardness decreases.
Vickers microhardness tester was selected for this study as it permits to evaluate surface changes of deeper dental hard tissues. Other hardness tester such as Knoop are only restricted to evaluate the microhardness of only the superficial dentin at 0.1 mm and not advocated for deep dentin (Fuentes et al. 2003).
The decrease in dentin microhardness facilitate root canal instrumentation but it may lead to weakening of the root structure that may end up into fracture of the endodontically treated tooth (Baghdadi and Hassanein 2004).
The results of our study showed that in total, there was no statistically significant difference in microhardness values between Moringa oleifera leaf, Moringa oleifera roots and Ca(OH)2. This could be explained by the finding that Moringa oleifera has a remineralizing effect, as confirmed by Nagib et al. (2016) They also stated that different formulations of Moringa oleifera were capable of increasing the dentin microhardness in the three thirds of the canal.
These results are very encouraging to pursue further researches on the properties of this natural product and its effect when used in root canal treatment. The aim of studies in this field is to create new treatments based on natural substances that would lead to a better prognosis.