**1. Introduction**

Herbs is defined as "any plants that lack the woody tissue characteristic of shrubs or trees" [1–7]. Several herbs have shown positive effects against a variety of inflammatory medical problems, such as dysphagia, gastric ulcers, wound healing, and sore throat. It is the core component of the complementary and alternative medicine (CAM) [1–7]. It has been used to manage blood problems and eliminate waste, stimulate body and blood circulation, minimize irritation [1–7]. It has several forms such as tablets, syrups, or it can be used externally as a dressings, or topical application [1–7].

Herbs could have a potential beneficial effect in the dental field, such as with gum swelling, specifically, and in oral healthcare overall. However, few studies have scientifically reviewed these topics. In this chapter, the most common herbal supplements that can be used in dentistry (i.e., neem, ginger, clove, aloe vera, eucalyptus, garlic, miswak, turmeric, tulsi, charcoal, and cinnamon) are reviewed. Evidencebased findings will be presented to support or refute the use of these agents in oral care.

### **2. Most common herbs used in dentistry**

#### **2.1 Aloe Vera**

Aloe vera is effective in periodontal disease conditions [1]. It is available in several forms, such as a mouthwash, toothpaste, or gel [1]. In a recent systematic review, aloe vera as a mouthwash was effective in all included studies in reducing plaque and gingival inflammation (**Table 1**, [2]). Moreover, aloe vera had no or very minimal side effects compared to other chemical mouthwashes [2]. It has a strong detoxifying agent, a neuro-sedative properties and immune booster [1, 2]. It can act as a mercury scavenger and antioxidant. It accerlated healing after surgical extraction including the third molar [1, 2].

Aloe vera toothpaste is another form that is effective on periodontal index and gingival scores and that can be used as an alternative to traditional toothpaste [3]. Aloe vera gel has inhibitory activities on some cariogenic organisms (*Streptococcus mutans*) [4], such as periodontopathic (*Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis*) and an opportunistic periodontopathogen (*Bacteroides fragilis*) [4]. It can be used as intracanal medicaments against *Enterococcus faecalis* (**Table 1**, [5]). It can be used to manage antiviral infection such as herpes simplex and herpes zoster, or as an antifungal agent against *candida albicans* [3–5].

There are several other uses for aloe vera such as aid in chemical burns, dry sockets, relief of aphthous ulcers, canker sores, lichen planus, pemphigus, desquamative gingivitis, migratory glossititis, and burning mouth syndrome [1–5]. It can helps in reducing the information related to ill-fitting dentures [1–5]. It can also be used in peri-implant mucositis and peri-implantitis [1–5].

#### **2.2 Ginger**

Ginger, which is scientifically named *Zingiber officinale roscoe*, can be used as a pain killer and is as effective as ibuprofen [6]. It can be used as an alternative for ibuprofen [6]. Combined with non-surgical periodontal therapy in chronic periodontitis cases among the type 2 diabetes population, ginger can help [7]. The reducing colony forming unit (CFUs/uL) of *S. mutans* is comparable to other oral rinses, such as chlorhexidine, and is also effective against *Lactobacillus* (**Table 1**).

Ginger may be a promising anti-cariogenic against *Streptococcus mutans* and *Streptococcus sobrinus* [7]. It contains phenolic compounds such as gingerol and shogaol, hydrocarbons, and oleoresins. These compounds have been investigated and shown to be effective anti-inflammatory, anti-bacterial, and antioxidant agents in oral microorganisms, which can help in disease prevention [8]. Moreover, ginger can help to reduce costs and side effects, and can introduce a safe inhibitory agent compared to conventional mouthwash [9]. It can be used also as an intracanal dressing, and in cases with recurrent apthous stomatitis and denture stomatitis [6–8]. However, it can lead to gastrointestinal irritation, heartburn, or diarrhea [6–8]. It can interfere with warfarin and inhibit platelet aggregation [6–8].

#### **2.3 Clove**

The principal phenolic components of clove, which is known scientifically as *Syzygium aromatic (S. aromatic)*, are volatile oil, eugenol, and eugenyl acetate. It has some physical properties that have an adverse effect on surface roughness and



#### **Table 1.**

*The most common herbs used in dentistry and the dental application.*

hardness, as well as transverse strength [10–13]. A high dose of clove oil can cause serious problems, such as sore throat, vomiting, toxicity, damage to the kidney and liver, epilepsy, and difficulty breathing. In small doses, it can inhibit decalcification and promotes remineralization (**Table 1**, [14]). It can be used as a topical agent, as a benzocaine before needle insertion, and has similar pain scores [15]. The crude extract of *S. aromaticum* (clove) has shown inhibitory activity against periodontal oral pathogens, including *S. mutans* (**Table 1**, [16]).

Other potential dental uses include antibacterial activity against *Porphyromonas gingivalis and Prevotella intermedia* [13]. It minimize several cytokines and factors such as IL-6, COX-2 and TNF-α. It has antifungal activity against *Candida albicans* [10–16], and antiviral activity against *Herpes Simplex virus 1 and 2* [10–16]. It can be used as mouthwashes, toothpastes, topical agents and local drug delivery devices [10–16]. Clove and its components are generally considered as "safe". However, it has been demonstrated as a cytotoxic agent towards fibroblasts and endothelial cells in vitro studies [10–16]. Moreover, hepatotoxicity, generalized seizures and disseminated intravascular coagulopathy has been reported as severe side effects [10–16]. Other potential side effects include skin irritation, ulcer formation, contact dermatitis, tissue necrosis, and delayed healing [10–16].

#### **2.4 Cinnamon**

Cinnamon is commonly referred to *Cinnamon Zeylanicum* or *Cinnamon cassia*. It can be used as an endodontic irrigant to minimize the *E. faecalis*, which is comparable to 3% of sodium hypochlorite [17]. Cinnamon has good antimicrobial properties against cariogenic bacteria such as *S. mutans* and *Lactobacillus casei* [18], as well as fungicidal activity against *Candida tropicalis* and *Candida glabatra* (**Table 1**, [18]).

Chewing gum containing cinnamon may help in the management of halitosis cases by minimizing volatile sulfur compounds inside the oral cavity [19]. The toothpaste that contained *Cinnamomum zeylanicum* showed anti-bacterial activity against periodontal pathogens (**Table 1**, [20]). It can be used in the dental unit water lines, which minimized bacterial count [21].

There are potential side effects such as tooth discoloration with high exposure to cinnamon [17–21], allergic reaction such as swelling, inflammation, burning, soreness of the mouth and lips [17–21].

### **2.5 Garlic**

Several in vitro studies found that the inhibition of the growth of the periodontal pathogens can happen with the aqueous extract, allicin [22], and diallyl sulfide of garlic [23]. The targeted pathogens are *Aggregatibacter actinomycetemcomitans*, *P. gingivalis*, and *Fusobacterium nucleatum* (**Table 1**, [24]).

When used as an irrigant, it is an effective, safe, and natural product, and is comparable to sodium hypochlorite after using it for a period of 12 months following root canals of primary molars [25]. The maximum zone of inhibition against cariogenic bacteria, such as *Streptococcus mutans* and *Lactobacillus acidophilus*, was in hard neck garlic extract, followed by chlorhexidine mouthwash [26]. The methanolic component of garlic had no anti-bacterial effects on *S. aureus* and *P. aeruginosa* [27].

Unpleasant breath or body odor is the most common side effects of garlic use [22–27]. Other side effects include heartburn, burning in a mouth or throat [22–27]. Patients need medical advice before garlic use if he/she is taking the following medications: acetaminophen; birth control pills; or warfarin [22–27].

#### **2.6 Neem**

Neem is scientifically known as *Azadirachta indica* and can be used as an endodontic irrigation solution to minimize the *E. faecalis*, which is comparable to 3% of sodium hypochlorite [17]. It has antiviral, anti-bacterial (*S. mutans, S. faecalis, S. salivarius, S. mitis, and S. sanguis)*, anti-sclerotic, and anti-inflammatory properties. A local drug delivery system using 10% neem oil chip statistically reduced *P. gingivalis* and all clinical parameters in periodontal-diseased patients (**Table 1**, [28]).

The highly pure neem leaf extract has proven potential inhibition of oral epithelial cell carcinoma through downregulation of intra tumor pro inflammatory pathways [29]. However, it was less effective in plaque scores reduction among orthodontic patients compared to *Salvadora persica* miswak-based mouthwash [30]. It has Anticandidial activity against *C. albicans,* and it inhibits *S. mutans* and *E. faecalis* which cause root canal failure in endodontic procedure [17, 28–30].

#### **2.7 Miswak**

*Salvadora persicahas* have potential benefits in reduction of plaque, bacterial oral germs, cavity prevention, and halitosis [31]. It contains high amounts of calcium, chloride, phosphate, and thiocyanate, which, as a consequence, can affect saliva and oral health [32]. When used in the dentifrice, it can lead to significant reduction in plaque index scores compared to conventional dentifrice [33]. The miswak raw extract is effective against *Porphyromonas gingivalis* and *herpes simplex virus-1* in chronic periodontitis patients (**Table 1**, [34]).

The mouthwash form has been investigated as an effective method for plaque reduction [35]. It can also be used as a chewing gum, mouthwash, and chewing stick [31–35]. It has remineralization effects following dental caries. Miswak can accelerate the wound healing after oral/periodontal surgery or extraction. It has potential anticariogenic, whitening properties and orthodontic chain preservation [35].

#### **2.8 Turmeric**

Curcumin (Turmeric) has shown anti-bacterial, anti-tumor, antioxidant, antiinflammatory, and analgesic properties [36]. It can be used as a topical application, mouthwash, subgingival irrigant or local drug delivery system to treat periodontal diseases, with equivalent or even higher efficacy compared with chlorhexidine in periodontopathic bacteria reduction such as *Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis*, and *Tannerella forsythia* (**Table 1**, [36]).

The extract gel can be used as a treatment for erythematous areas, ulcers, and pain [37]. It can help in cases with oral submucous fibrosis, leukoplakia, lichen planus and it gave better results compared with the systemic form alone, or antioxidants (**Table 1**). It has anticancer activity as well [36, 37].

Although it considered safe, it may cause gastric irritation, nausea, diarrhea, allergic reaction, and interfering with blood-clot formation [36, 37].

#### **2.9 Tulsi**

Tulsi is released in several metabolites found in these plants, which have antimicrobial agents. It can be used in toothpaste or mouthwash [38]. It is similar to chlorhexidine in its antimicrobial property, and as an alternative in patients who cannot use chlorhexidine [39]. Tulsi extracts have antimicrobial activity against *A. actinomycetemcomitans, P. gingivalis*, and *P. intermedia*, with different inhibition zones (**Table 1**, [40]).

#### **2.10 Green tea**

Green tea and its principal compound (*flavonoid epigallocatechin-3-gallate*) are responsible for protective effects against several diseases and has anti-bacterial properties [41]. They can minimize bone loss in osteoporosis and periodontal disease cases by inducing apoptotic cell death of osteoclasts and osteoclasts-like cells (**Table 1**, [41]).

Green tea extract rich in epigallocatechin gallate minimizes alveolar bone loss in rats with periodontal disease [42]. It can be used in different forms, such as mouthwash, local drug delivery, and chewing gum. It has catechins that is anti-bacterial against *Streptococcus mutans*, *Streptococcus sobrin*, *P. gingivalis*, and *P. melaninogenicus* (**Table 1**, [42]).
