Natural Conservative Dentistry: An Alternative Approach to Solve Restorative Problems

Natural Anti-cariogenic Agents

Fatma Hussein¹, *

¹ Department of Operative Dentistry, Faculty of Dental Medicine for Girls, Al-Azhar University, Cairo, Egypt

Abstract

Tooth decay is primarily caused by demineralization resulting from acids secreted by bacteria, especially Streptococcus mutans and lactobacillus, which ferment dietary carbohydrates. This occurs in plaque biofilms, which attach to the surfaces of the tooth and become laden with bacteria. Thus, over time, dental caries result from the interaction of three main contributing factors: a diet containing carbohydrates, caries-producing bacteria, as well as sensitive tooth structure. The use of an antibacterial strategy for treating caries has evolved as a result of (1) identifying certain types of the oral microbiome as the main cariogenic flora and (2) increasing the knowledge of the specific ecology of these cariogenic florae. Combined with this concept, control, and prevention of caries have been sought by reducing the number of bacteria colonizing. Reducing bacterial populations or completely eradicating them from the oral flora would provide an additional reason to prevent dental caries. Several undesirable side-effects of conventional antimicrobial agents include tooth discoloration and the emergence of bacterial resistance. These side effects stimulate the search for alternative natural anti-microbial agents.

Keywords: Acid production inhibition, Bacterial adherence, Control of biofilm, Dental plaque, Extracellular-Polysaccharides synthesis, Ecology, Fruit extract, GTF, Glucosyltransferases, Herbal extract, Natural antimicrobial agents, Pathogenesis of caries, Probiotics, Plant extract, Streptococcus mutans, Sweetener, Sugar substitute, Spices.

* Corresponding author Fatma Hussein: Department of Operative Dentistry, Faculty of Dental Medicine for Girls, Al-Azhar University, Cairo, Egypt; E-mail: [email protected]

INTRODUCTION

Dental caries is caused by the interaction of specific bacteria and their metabolites with components of saliva and diet containing carbohydrates on tooth surfaces. The synthesis of extracellular polysaccharides in the biofilm matrix, acid production, and the low pH at the tooth-biofilm interface are the main modulating

animus factors regulating the pathogenesis of caries. While many micro-organisms may be included in the pathogenesis of the carious process. Streptococcus mutans have a significant role in the formation of toxic biofilm [1-4]. This bacterium efficiently metabolizes sucrose for the synthesis of extracellular polysaccharides via the activity of glucosyltransferases (Gtfs), and Fucosyltransferases bind to the surface of saliva-coated tooth enamel. Bacteria tenaciously adhere to the dextran-coated surface. It is both acid-producing and acid-resistant.

The extracellular polysaccharides are mainly composed of glucans that are formed by Gtfs enzymes in salivary pellicles (almost all GtfC) and that bind to the bacterial cell surface (almost all GtfB) among sucrose. In situ formed glucan provides the following functions binding sites for Streptococcus mutans, the matrix holds microbial cells together to form co-aggregated cell clusters called micro-colonies [5]. If these microcolonies are regularly exposed to a diet containing carbohydrates and not removed from the tooth surface (especially sucrose), Streptococcus mutans and other acid-producing and tolerant bacteria in the biofilm will ferment sucrose to organic acids [5].

Chemotherapeutic Strategies to Control Biofilm

Biologically active chemical agents on biofilm components may be promising for preventing or reducing the frequency of the caries process. Such components may have the following mechanism: (1) block Gtfs adhesion to the salivary pellicle, (2) inhibit the secretion of extracellular-polysaccharides, (3) modify the composition of extracellular polysaccharides matrix, (4) inhibit bacterial colonization, (5) disrupt acid formation and adaptation process, (6) suppress the growth of oral microorganisms, and (7) modify the biofilm ecology and biochemistry. Chlorhexidine, triclosan, and essential oils (e.g., Listerine) are broad-spectrum nonspecific microbicides, they are the most commonly used types. The research focused on chemotherapeutic strategies focused on decreasing the expression of Streptococcus mutans virulence factors without the destruction of the pathogen.

Strategies to control the biofilm are based on the disturbance of EXPs synthesis on the surfaces. Extracellular polysaccharides matrix may act as an adsorbent, thereby reducing antimicrobials that can interact with biofilms. Therefore, extracellular polysaccharide-inhibiting materials enhance the efficacy of antibacterial agents on plaque biofilm [6].

Effect of Natural Agents on Caries-producing Pathogens and Streptococcus mutans Physiology

Natural agents remain the main source of promising therapeutics for the management of human diseases [7, 8]. Research on the use of natural agents to inhibit or cure dental caries received limited regard in medicine. The biological effects of natural agents are as follows:

(i) Sugar substitute.

(ii) Inhibit exopolysaccharide synthesis.

(iii) Inhibit intracellular-polysaccharide synthesis, and decrease acid production.

(iv) Inhibition of bacterial adherence.

(v) Antibacterial effect: inhibit metabolism and growth of acid-producing and tolerated species.

(vi) Enhance salivary buffering capacity.

(vii) Improve acid resistance of enamel.

Classifications of Natural Anti-cariogenic Agents

1-Plant extract

2-Spices

3-Fruit extract

4-Sweetener

5-Natural micro-organisms (probiotics)

PLANT EXTRACTS

Due to their high content of antimicrobial agents, medicinal plants are useful in the management of different diseases, including bacterial diseases. Many phytochemicals, including antimicrobials, are derived from edible plants and have been shown to have antibacterial properties against Streptococcus mutans [8].

Tea (Camellia Sinensis)

Tea is a worldwide beverage made of Camellia sinensis plant leaves. According to the manufacturing process, there are three main types of tea [9], as represented in (Table 1).

Green Tea

Green tea is made by frying or steaming fresh leaves and then drying them to suppress the active enzymes. Chemically, it has many components, such as; polyphenolic catechins, epigallocatechin-gallate, epigallocatechin, caffeine, and vitamin C [9].

Table 1 Different types of tea, manufacturing, processing, and their chemical composition.

Black Tea

It is made by crushing the leaves of withered tea, enhancing enzyme-mediated oxidation reactions to initiate the fermentation procedures, and synthesizing oligomers. The black type of tea contains a lower monomer content compared to the green type, it also contains Theaflavins, thearubigins, and the content of fluorine is five times higher than that of green tea [9].

Oolong Tea

A partially fermented product contains certain amounts of catechins and oligomerized catechins [9].

Anti-cariogenic Effect of Tea

1- Anti-streptococcal (bactericidal): the bactericidal effect against Streptococcus mutans and Streptococcus sobrinus, the minimum inhibitory concentration of catechins 50-500% mg/l, flavored compounds in green tea also found inhibitory activity, the total flavor 7mg/l [10].

2- Inhibition of adhesion: It inhibits Streptococcus mutans adherence to saliva-coated tooth surfaces. The prevention of bacterial adherence to teeth decreases the hydrophobicity, which induces cellular aggregation of bacterial biofilm, easily washed by saliva.

3- Inhibition of glucosyltransferases, thereby reducing the synthesis of viscous glucan.

4- Inhibition of bacterial amylases: black and green tea repress amylase activity from Streptococcus mutans, black tea is more active than green tea due to the high molecular weight of polyphenols.

5- Enhancing the anti-acidity of teeth: About 300 ppm of fluoride was extracted into the tea infusion. Fluoride found in the enamel in the form of fluorapatite is known to enhance the acid resistance of the enamel, and the aluminum content of tea can increase the acid resistance of the enamel [10].

Anti-cariogenic Effect of Green Tea

The main anti-caries effects have been reported to be attributed to catechin, epigallocatechin gallate, and epigallocatechin, which have the following functions:

1-Inhibit Glucosyltransferases mechanism, hence reducing caries index in rats infected with Streptococcus mutans [10].

2- Catechins inhibit the growth and viability of bacteria, GTF activity, and amylase salivary activities [10].

3- EGCg reduces MGS and acid formation by bacteria in dental plaque [10].

Green tea inhibits the adhesion of Streptococcus mutans, Porphyromonas. gingivalis, and Streptococcus sobrinus. Bacteria adhere to the tooth surface to form a glycocalyx film, hence plaque formation. Glucan formed in the film from sucrose by the activity of glucosyltransferases enzyme, controls bacterial adhesion [11-13]. Camellia sinensis. leaves extract contains polyphenols, which are active against different types of microorganisms. Previous studies reported that polyphenolic catechins in green tea, such as; epigallocatechin gallate and epicatechin gallate, suppress gram-positive and gram-negative bacteria [11-13].

The antibacterial effect of green tea was higher than that of antibiotics. The tea polyphenols significantly reduced the bacterial count of Streptococcus mutans after 5-10 minutes of exposure, it suppresses dextran and levan formation from sucrose by Streptococcus mutans [13]. Inhibition zones against Streptococcus mutans using EGCG extract were recorded at different concentrations of EGCG extract [14].

Anti-cariogenic Effect of Black Tea

The anti-cariogenic effect of black tea is linked to its polymer polyphenols (Theaflavins and Thearubigins), which were found to inhibit dental plaque, decrease the PH of dental plaque, and inhibit cariogenic microflora. Moreover, the anti-cariogenic effect of polyphenols in tea and the antibacterial activity may be attributed to the fluoride, as black tea contains more fluoride than green tea [15]. Both types of tea (green-black), presented the largest zone of inhibition at concentrations of 400mg/ml in comparison to 0.2% chlorhexidine. Black tea showed higher antibacterial activity than green tea [15]. On the other hand, green tea showed the lowest inhibitory zone compared to chlorhexidine, pomegranate, and ginger [16].

Coffea rubiaceae (Coffee)

There are eighty types of coffee, the common types are called Coffea arabica, and Coffea canephora. The chemical profile of the green type depends on the variety, fruit maturity, agricultural practices, primary and secondary processing procedures, and the condition of storage [17].

Chemical Composition

Different types of coffee and their compositions are represented in Table 2.

Anti-cariogenic Activity of Coffee

In a previous study, the authors reported that coffee components inhibited the glucosyltransferase synthesis by caries producing micro-organisms. They related that inhibition to the polyphenols action, secondary metabolites are thought to be involved in photochemical defense against predators [18]. The antibacterial effects of polyphenols are linked to their capability to suppress bacterial by-products [19].

Catechin inhibits different types of bacterial species; they produce H2O2 and alter bacterial cell membrane permeability [19]. Caffeic acid, 5-caffeoylquinic, and polyphenols found in coffee inhibited the growth of Streptococcus mutans [19]. Furthermore, natural components like Trigonelline, Caffeine, and Alpha-Dicarbonyl compounds have an inhibitory effect against Streptococcus mutans [20]. Coffee has an anti-cariogenic effect; it has an inhibitory effect on the growth of Streptococcus mutans [21]. The anti-cariogenic potency of a substance through its antibacterial effect by inhibiting the metabolites of Streptococcus mutans, as well as their physicochemical activity by inhibiting the demineralization and enhancing the minerals’ participation in the tooth [22].

Table 2 Different types of coffee and their composition.

Myrtus Communis Linn (Myrtaceae), (Myrtle)

Myrtus communis L grows spontaneously in the Mediterranean area. Ethanol extract type is used in the preparation of alcoholic beverages in the Mediterranean regions.

Chemical Composition of Myrtus communis L. Extracts

The major secondary products of Myrtle are polyphenols and essential oils. They are rich in volatile flavonoids, tannins, anthocyanins, fatty acids, and terpinolene, tannins, and flavonoids [23]. The leaves and flowers contain essential oils, phenolic acids, flavonoids, and tannins. The berry consists of tannins, anthocyanins, and fatty acids. Its content depends on the extraction solvent used. The popular components that are usually found in Myrtle leaves and flowers are α-pinene and 1,8-cineole [24, 25].

Anti-cariogenic Effects

The antimicrobial effect of Myrtle extract has been attributed to polyphenolic compounds and flavonoids. Myrtle has no significant effect on gram-negative bacteria; the antibacterial effect of this extract against gram-positive bacteria is associated with active compounds such as Mirtocomolone A and B [26]. Gram-negative bacteria that have an outer membrane of glycolipid polysaccharide and some channels involved in the transport of substances, which are resistant to antibiotics, hydrophilic dyes, and toxins [27]. High concentrations of Myrtle extract and essence have antimicrobial properties against antibiotic-resistant strains of Staphylococcus aureus [28]. Streptococcus mutans showed the highest susceptibility to ethanol extract, which has the highest extractive and phenolic compounds, which may explain the antibacterial activity of Myrtle extract [26]. Extracted alcohol is a polar compound; therefore, the more sensitivity of gram-positive bacteria was related to the extract polarity, as polar substances penetrate more easily through the membranes of Gram-positive cells (i.e. Streptococcus mutans) [26]. The MIC and MBC of Myrtle ethanol extract were 3.12 mg/mL and 6.25 mg/mL, respectively [28].

Neem (Azadirachta indica)

Azadirachta indica is named the Indian neem, margosa tree, and Indian lilac. It contains essential ingredients such as; alkaloid margosine, resins, gums, chlorides, fluorides, silica, sulfur, tannins, oils, flavonoids, and calcium [29].

Antimicrobial Activity of Neem

Neem contains fluoride with its anti-caries effect and silica, which acts as abrasive. Neem plant belongs to Gallotannins. In the early stage of plaque formation, Gallotannins inhibit the association of biofilm-producing pathogen with the tooth surface, increasing the physical removal of bacteria in the mouth through aggregate formation, potent inhibition of the Glucosyltransferases activity, and reduction of bacterial adhesion [30]. Neem extract inhibited streptococci colonization to the surfaces of the tooth. It was reported that 5% of neem extract showed no antibacterial effect [30].

Babool Chewing Sticks (Datun)

Babool has similar effects to neem. Babool's antibacterial activity is related to hydrophilic ingredients; polyphenols, (polysaccharides), and tannin. Accumulating evidence supports the relatively high content of bioactive secondary compounds in plants of the genus Acacia [31]. The antimicrobial activity of Babool extract increased by increasing the extract concentration.

There was no antibacterial effect observed using 5% of babool extract. On the other hand, there was an antibacterial effect observed with 10% of the extract [30]. This was supported by the finding of previous research, which showed no antimicrobial effect of babool’s extract on Streptococcus mutans [32].

Tulsi (Ocimum sanctum)

Ocimum sanctum (Fig. 1) is native to India. Tulsi extract treats different diseases such as; diabetes mellitus, arthritis, bronchitis, and skin diseases, its antibacterial effect was evaluated against different types of microorganisms such as; Staphylococcus aureus, Klebsiella, Candida albicans, E. coli, and Proteus sp.

Fig. (1))

Tulsi, Ocimum sanctum.

Composition

Eugenol is the active component in tulsi, it is mainly accountable for their therapeutic effect, other important compounds such as; ursolic acid, and carvacrol [33].

Anti-cariogenic Effect

The antibacterial effect of O. sanctum is linked to its components. O. sanctum leaves extract showed maximum antimicrobial activity against cariogenic bacteria at the 10% concentration level, although 5-2.5% were also effective. 10% of the extract showed potent antibacterial activity against Streptococcus mutans and Streptococcus sanguis with 10% extract [34]. On the other hand, a previous study recorded the maximum antimicrobial potential against Streptococcus mutans at 4% concentration and a zone of inhibition of 22 mm [35].

Miswak Chewing Sticks (Twigs of Salvadora persica)

Miswak is known as a cleaning stick, people use it to clean teeth and gums. These sticks are chewed or tapered at one end till they are worn down into a brush. They are used to clean the teeth in a similar way to the toothbrush [36].

Technique of Handling

During cleaning your teeth and mouth with Miswak, the stick is held in one hand as a pen-like grip, and the end of the brush with an up-and-down or rolling motion. Two-finger/five-finger grasping techniques have been described in the literature. The stick fails when the brushed edge crumbles after a few times of use [37].

Historical and Religious Background

People in Arab countries before the emergence of Islam used Miswak. Miswak was used by Ancient Arabs to make their teeth white with shiny surfaces [38]. Prophet Mohammad (Peace Be Upon Him) practiced using miswak sticks before sleeping, after rising, after entering the house, before and after meals, during fasting, and before performing prayers and reading the holy book. The Prophet Mohammad (Peace Be Upon Him) said, "If I had not found it hard for my followers or the people, I would have ordered them to clean their teeth with Siwak (Miswak) for every prayer" [38]. Therefore, Islam has influenced the spread and practicing of chewing miswak sticks in different areas of the world.

Today, miswak sticks and toothbrushes are used by Muslims worldwide. Miswak promotes good oral health and efficient cleansing of teeth by different mechanisms, including: (i) mechanical action through miswak fibers, (ii) release of beneficial substances, such as trimethylamine, salvadorine, mustard oil, vitamin C, resins, flavodine, saponins, sterols, and fluoride. They have benefits due to the combination of mechanical and chemical effects [39-42], thus these bioactive substances of Salvadora persica have an important role in oral health [43].

-Sulfur has a bactericidal effect.

-Vitamin C helps in tissue healing and repair.

-Silica acts as an abrasive and helps remove discolorations from tooth surfaces.

-Tannins have an astringent effect, reduce clinically detectable gingivitis, and inhibit the mechanism of action of Glucosyltransferases, thereby reducing plaque and gingivitis.

-Resin forms a layer on tooth enamel and protects it against dental caries.

-Salvadorine is an alkaloid that exerts a bactericidal and antifungal effect and stimulates the gingival mucosa.

-Essential oils promote salivary flow; acting as a buffering agent.

-Chloride inhibits the formation of calculus and aids in removing stains from the tooth surface.

-Fluoride Miswak contains about 1.0μg/lg of fluoride, which has an anti-cariogenic effect and tooth remineralization potential.

-Benzyl isothiocyanate acts as a chemo-preventive agent, as an anticancer and has a toxic effect on the gene. It has antibacterial activity, and antiviral effect.

-Trimethylamine has an antibacterial, antiphlogistic, and gingiva-stimulating effect.

-N-benzyl-2-phenylacetamide prevents calculus formation, suppresses human collagen-induced platelet aggregation, and has inhibitory effect against Escherichia coli.

Anti-cariogenic Effect

It was reported that Miswak has strong anti-caries properties in a previous study, which showed that those who used Miswak had less plaque formation and caries progression than those who used artificial toothbrushes [44]. Miswak has been reported to have anti-caries effects due to its fluoride content [45]. Furthermore, the spicy taste of Miswak and its chewing mechanism increase the secretion of saliva, thus improving its buffering capacity [46]. Petersen and Mzee 1998 reported that dental caries' prevalence was higher in urban regions [47].

Miswak's aqueous extract significantly inhibited the growth of caries-producing bacteria [48]. The use of Miswak immersed in 0.5%-0.1% sodium fluoride for a day was found to be promising in preventing caries [49]. The regular use of fluoride-containing Miswak remineralizes white spot lesions in orthodontic patients [50]. Those findings were linked to bioactive compounds and the antibacterial agents released from miswak sticks. They inhibit bacterial growth and control aggregation of cariogenic Streptococcus. Mutans on tooth surfaces [51]. It was reported that toothpaste containing Miswak had the lowest minimum inhibitory concentration (MIC) against Streptococcus. Mutans, Lactobacillus, and Staphylococcus compared to the control without Miswak [52]. Miswak may be a

promising therapy to inhibit caries development, initial adherence, and subsequent biofilm formation by caries-producing microorganisms [53].

Effect on saliva

It has the mechanism to release components into saliva and influences oral health as it raises the pH of plaque [54].

Efficacy of Miswak on Oral Hygiene

It is an effective oral hygiene therapy. Various studies assessed the cleaning effect of Miswak. For patients with severe plaque accumulation, toothbrushes are more effective than chewing sticks for controlling plaque. However, chewable sticks are as effective as toothbrushes for patients with moderate plaque accumulation [55]. Miswak was effective for plaque removal, similar to tooth brushing. The reason is the synergetic effect of mechanical cleansing, increased salivary secretion, and the release of antibacterial components [56, 57].

Clove (Syzygium aromaticum)

Clove (Fig. 2) is related to the Myrtaceae family; it is a dried and unopened inflorescence of clove tree, ranges about ½ - ¾ inch in length. It contains 14-20% essential oils. It is considered a strong irritant due to its high eugenol content. The chemical substances found in clove inhibit bacterial growth. Clove is considered like an antibiotic, which has a broad antibacterial activity to gram-positive and gram-negative bacteria [58].

Fig. (2))

Clove.

Composition

Clove extract contains many chemical components with many biological activities such as; free eugenol, eugenol acetate, caryophyllene, sesquetrepene ester, phenyl propanoid, beta-caryophyllene, eugenol and acetyl eugenol, tannins, flavonoids, and myricetin [60, 61].

Anti-cariogenic Effect

Essential oils are one of the essential constituents of clove, terpenoid is the main components of essential oils. They are slightly water-soluble. The antibacterial activity of terpenoids is linked to the ability to disrupt lipid structures [61]. Terpenoids lead to the disturbance of the membrane integrity, and inhibition of intracellular pH homeostasis (Ouattara et al., 1997) [61]. Rashad, 2008, evaluated the effect of clove extract, versus the effect of chlorhexidine gluconate and deionized water on acid secretion by the Mutans streptococci; Chlorhexidine showed the most percent of bacterial reduction followed by clove extract [62]. Clove can be added to fluoride-free toothpaste to enhance its inhibitory effect on bacteria associated with dental caries and periodontal disease [63].

Rosemary (Rosmarinus officinalis)

Rosemary (Fig. 3) is the medicinal plant of the Lamiaceae family [64]. It is native to the Mediterranean region and characterized by its sessile, curved edges, dark green leaves, and sharp smell [65].

Fig. (3))

Rosemary (Rosmarinus officinalis).

Composition and Anti-cariogenic Effect

Rosemary extract contains various bioactive substances such as; phenolic monoterpenes, diterpenes, flavonoids, and Caffeol derivatives [65]. The antimicrobial activity of rosemary is linked to the binding potential in adhesin of the cell wall of Streptococcus mutans; rosemary can be a potent aid in combating caries in dental products [66, 67].

SPICES

Garlic (Allium sativum)

For about 3,000 years, the Chinese and Egyptians have used garlic as a flavor-enhancing food and folk medicine. Garlic has a strong smell, strong taste, and significant physiologic effects, inducing tearing, sweating, and salivation [68].

Components of Garlic

Thioethers occur naturally in garlic in the form of diallyl sulfide. Chemical analyses of garlic revealed (1-3%) concentration of sulfur-containing compounds [69].

Protective Properties in the Oral Cavity

Garlic has two protective properties: antimicrobial activity and salivary secretion stimulation by garlic taste. Garlic decreases acid production by Streptococcus mutans. Furthermore, it inhibits their growth in the long term period for 14 days, whereas, in the short term period, within 24 hrs., the acid production is controlled with the salivary stimulation associated with the spicy flavor of garlic. The spicy flavor stimulates salivary flow [70]. Saliva which is stimulated with garlic contains high concentrations of bicarbonates, hence increasing the salivary buffering capacity, thus the ability to neutralize and clear acids in plaque, therefore, improving the salivary pH and increasing the enamel resistance to dental caries. Salivation stimulated by garlic consumption reduces the drop in plaque pH, which may lead to demineralization of tooth structure and increase the likelihood of remineralization [70]. Mouthwashes are considered as an alternative to chlorhexidine mouthwash [71].

Comparable Effect with other Agents

Garlic mouthwash was effective in a similar way to chlorhexidine, it minimized the decrease in salivary pH after a cariogenic challenge. Moreover, the best results were obtained when they were combined together to stimulate their synergistic effect [72]. Garlic with lime oral rinse has a significant antimicrobial effect; it significantly decreased the salivary count of Streptococcus mutans compared to chlorhexidine 0.12% mouthwash [73].

Allium cepa (Onion)

Onion belongs to the Allium Cepa family. Since 6000 years ago, it was cultivated in the nile valley. Its chemical profile contains many minerals and few vitamins. It was used as a type of spicy food, and it also used in medicine. For medicinal purpose, it was recommended to use raw onion due to the fact that boiling it loses its effect [74].

Composition

Onions contain many active components such as; sulphur which can inhibit the inflammatory reactions of the tissue, another component is the thiosulfinate, which can dissolve thrombi and superoxide dismutase, which has ant-oxidative properties. Uronic acid, glucose, and arabinose, xylose, fructose, and galactose are the main components of union cell wall [74]. Alkyl cysteine sulphoxide is responsible for the taste and odor of onion, whereas, anthocyanin is responsible for the red, purple, and yellow colors of onion [75]. Onion is rich in many minerals such as; sodium, magnesium, calcium, phosphorus, and potassium. It was reported that flavonoid content of onion showed enhanced antibacterial, antifungal, and anti-viral activities [75].

Anti-cariogenic Effect

Onion extract showed significant inhibitory effect against Streptococcus mutans. The red type of onion showed a significant inhibitory effect compared to the yellow and green types. On the other hand, the green type showed the least significant inhibitory effects. It was reported that, the antibacterial activity of different types of onions increased as the concentration of the onions increased [76].

Nutmeg (Myristica fragrans)

Nutmeg (Fig. 4) is the seed of the tree, it has roughly egg-shaped and about 20 to 30 mm (0.8 to 1) in length and 15 to 18 mm (0.6 to 0.7) in width, 5-10 g in weight, mace is dried lacy reddish covering of the seed [77].

Fig. (4))

Nutmeg (Myristica fragrans).

Composition

Nutmeg contains 5%-15% volatile oils, the main components are camphene or Sabinene, Dipentene, Dlinalool, Dborneol, Terpineol, Geraniol, Myristiine, Macelignan, Safrole, Eugenol, and Isoeugenol. It suppresses bacterial adherence [77, 78].

Anti-cariogenic Effect

Surface hydrophobicity is an important property of nutmeg oils. It separates lipids in the cell membrane of bacteria and results in a permeable cell wall. Excessive loss or expulsion of the essential substances from bacterial cells leads to death [78]. The structural property of Gram-negative cell wall enteric bacteria is the key to their drug resistance. Gram-negative bacteria contain about 15-20% of polysaccharides and 10-20% of lipids in their cell wall, on the other hand, gram positive bacteria contain about 35-60% of polysaccharides and 0-2% of lipids. The polysaccharides and lipid contents of the cell wall affect the permeability of active components. Gram positive bacteria are more sensitive to the antimicrobials in spices compared to the gram negative bacteria [79]. Myristicin, Myristic acid, Trimyristin, Elemicin, and Safrole are essential oils extracted from nutmeg. These active components have good antimicrobial activity and were effective against endodontic microorganisms and can be used as an effective medicament in the treatment of endodontic infections [80].

Nigella sativa L. (Black Cumin)

Nigella sativa L. seeds (Fig. 5) contain a large amount of fixed oil with the main component of seed extract being thymoquinone.

Fig. (5))

Nigella sativa L, black cumin.

Composition and Anti-cariogenic Activity

Thymoquinone, Thymohydroquinone, and Dithymoquinces in Steviaone, and Thymol, carvacrol, nigellicine, Nigellimine-x-oxide, Nigellidine, and alpha Hedrin are the active substances in sativa [81]. Nigella sativa nanoemulsion showed similar antimicrobial activity against Streptoccocus Mutans, Streptococcus sobrinus, and Streptococcus Salivarius. In contrast, Enterococcus Faecalis and Lactobacillus. acidophilus were the most resistant and susceptible bacteria to Nigella sativa nanoemulsion. This is linked to the structural differences of the bacterial cells. This result may be related to that, Enterococcus Faecalis is an opportunistic bacterium that produces lactic acid, which is highly effective against antibiotic resistance. Therefore, its tolerance to nanoemulsion is predictable. The outer membrane of gram-negative bacteria reduces the penetration of Nigella sativa molecules (due to their molecular size) to a definite expansion and results in the death