Oral microbes and its environment : a review article / Wan Nordini Hasnor Wan Ismail, Fathilah Abdul Razak and Zubaidah Haji Abdul Rahim

The ecosystem within the oral cavity is unique as it is a result of interactions between components such as the oral fluids and oral microorganisms with structures of the oral soft and hard tissues. The soft structures are represented by the mucous membranes while the hard surface is represented by the teeth. Both the soft and hard tissue structures influence the distribution of microbes in the mouth. Some surfaces like those at the gingival junction protect their microbial inhabitants from any physical forces or/and chemical interactions, whereas other surfaces like the lingual incisal surface do not. Thus, the oral cavity represents a host environment that possessed features that support the establishment and growth of a great diversity of microbes. The cheek mucosa, the tongue, the gingival crevice and the tooth surface provide sites with different physicochemical and nutritional microenvironment that allows for the adherence and growth of selective microorganisms

The preliminary cytotoxicity study: anti-proliferative activity of aqueous extract of clinacanthus nutans, strobilanther crispa and pereskia bleo on oral squamous carcinoma cells orl-48 / Rahayu Zulkapli and Fathilah Abdul Razak.

This in vitro study was carried out to screen the aqueous extracts of selected local plants (clinacanthus nutans, strobilanther crispa and pereskia bleo) known locally to possess anticancer properties for cytotoxic activity. Method: The antiproliferative activity on human oral squamous cell carcinoma, ORL-48 was assessed based on a colorimetric assay using neutral red dye. Result: Clinacanthus nutans exhibited an IC50 of 49.8 ± 0.02 µg/mL on ORL-48 cells, while Strobilanther crispa and Pereskia bleo showed no antiproliferative response. Conclusion: The aqueous extract of clinacanthus nutans, strobilanther crispa and pereskia bleo does not possess anti proliferative activity towards oral squamous carcinoma cells ORL-48

Vitamin E (-Tocopherol) Exhibits Antitumour Activity on Oral Squamous Carcinoma Cells ORL-48

Cancers involving the oral cavity, head, and neck regions are often treated with cisplatin. In cancer therapy, the main target is to eliminate unwanted cancerous cells. However, reports on the nonselective nature of this drug have raised few concerns. Incorrect nutritional habits and lifestyle practices have been directly linked to cancer incidence. Nutrients with antioxidant activity inhibit cancer cells development, destroying them through oxidative stress and apoptosis. -tocopherol, the potent antioxidant form of vitamin E is a known scavenger of free radicals. In vitro study exhibited effective antitumor activity of -tocopherol on ORL-48 at 2.5 +/- 0.42 mu g/mL. Cisplatin exhibited stronger activity at 1.0 +/- 0.15 mu g/mL, but unlike -tocopherol it exhibited cytotoxicity on normal human epidermal keratinocytes at very low concentration (<0.1 mu g/mL). Despite the lower potency of -tocopherol, signs of apoptosis such as the shrinkage of cells and appearance of apoptotic bodies were observed much earlier than cisplatin in time lapse microscopy. No apoptotic vesicles were formed with cisplatin, instead an increased population of cells in the holoclone form which may suggest different induction mechanisms between both agents. High accumulation of cells in the G0/G1 phase were observed through TUNEL and annexin V-biotin assays, while the exhibition of ultrastructural changes of the cellular structures verified the apoptotic mode of cell death by both agents. Both cisplatin and -tocopherol displayed cell cycle arrest at the Sub G0 phase. -tocopherol thus, showed potential as an antitumour agent for the treatment of oral cancer and merits further research

The potential use of chlorhexidine (CHX) and hexetidine-containing mouth rinse in maintaining toothbrush sterility

The study was carried out with the aim of demonstrating quantitatively the presence of microorganisms adhered to toothbrush bristles and to determine the potential of using antimicrobial agent (such as chlorhexidine gluconate (CHX) and hexetidine (HX)) in commercialized mouth rinses to reduce microbial contamination. The study was carried out by enumerating the total colony counts of bristles-adhered microbes after three weeks of normal oral hygiene followed by rinsing the toothbrushes with CHX, HX, tap water and deionized water independently following a strict planned schedule. Rinsing toothbrush with tap water was included in the study as a control due to the normal way of cleaning toothbrush after use in every home. Whereas, sterilized deionized water do not contain any ions, minerals and is microbes-free. The total colony counts of microbes obtained from the toothbrush rinsed with tap water, deionized water, CHX and HX were 62.6×106 CFU mL-1, 74.4×106 CFU mL-1, 2.4×106 CFU mL-1 and 7.6×106 CFU mL-1, respectively. Staphylococcus aureus, Actinomyces naeslundii and Clostridium sp. were isolated from toothbrush rinsed with tap water. Staphylococcus aureus and Peptostreptococcus sp. were obtained from toothbrush rinsed with deionized water. Actinomyces sp. and Clostridium sp. were recovered from toothbrush rinsed with CHX and only Staphylococcus aureus was obtained from toothbrush rinsed with HX. Although toothbrush rinsed with mouth rinses containing antimicrobial agent such as CHX and HX still harbour microorganisms, but the microbial load has been very much lowered compared to the control toothbrush. Thus, this indicates that toothbrush rinsing with mouth rinse after the normal oral hygiene is very convenient and cost effective to reduce toothbrush contamination

Antiproliferative activity of aqueous extract of Piper betle L. and Psidium guajava L. on KB and HeLa cell lines

The aim of the present study was to assess the effect of the aqueous extracts of Psidium guajava and Piper betle plants on the proliferation of cancerous cell lines, that is, KB and HeLa cell line. Using the neutral red cytotoxicity assay, the IC(50) of P. guajava and P. betle were determined at 29.0 +/- 0.4 and 29.5 +/- 0.3 mu g/ml, respectively, indicating both plant extracts equally potent for the treatment of cancerous oral epidermal lesions. However, a less potent anti-proliferative activity was recorded by P. guajava towards HeLa cell line with an IC(50) of 51.0 +/- 0.6 mu g/ml, whereas P. betle extract did not affect the proliferation of HeLa

Effect of phenotypic switching on the biological properties and susceptibility to chlorhexidine in Candida krusei ATCC 14243

Phenotypic switching is characterized as a virulence factor of Candida spp. This study was carried out to evaluate the phenotypic switching ability of C. krusei ATCC 14243 and to determine its effect on the biological properties, adherence capacity and susceptibility towards chlorhexidine digluconate (CHX). To induce switched generations C. krusei was cultured under nitrogen-depleted growth conditions by adding phloxine B. These phenotypically switched colo- nies were designated as the 1st generation. Subsequent sub-culturing was per- formed to produce the 2nd, 3rd and 4th switched generations. The recovery of the 3rd generation was the highest at 85.7% while that of the 4th generation was lower at 70.8%, and the recovery of the 1st and 2nd generations gradually reduced to 46.6% and 36.4%, respectively. All generations of C. krusei were susceptible towards CHX. The unswitched C. krusei was the most susceptible but the least adherent to coated hard surfaces. The 2nd generation was the least susceptible, but with the highest adherent ability. The minimum inhibition concentration and minimal fungicidal concentration of C. krusei of all genera- tions were determined at 0.4 mg mL 1. These observations suggest that the switching activity of C. krusei induces changes to its biological properties and susceptibility towards CHX

Muscle spindles provide servo-assistance to jaw-closing muscles for chewing hard foods

The fundamental pattern of chewing induced by the network of neurons called central pattern generator has been reported to be modified by the information arising from the various oro-facial sensory receptors including muscle spindles of jaw closing muscles. The cell bodies of primary afferent neurons from these muscle spindles lie in mesencephalic trigeminal nucleus (MTN) in the brainstem. The aim of the study was to understand whether muscle spindles from jaw-closing muscles play any role in hard food chewing. Single neuronal discharge of muscle spindle afferents was recorded from the MTN simultaneous with jaw-movement and electromyograpic (EMG) activities of the left masseter (jaw-closing) muscle during chewing soft and hard foods (apple and pellet) in awake rabbits. Ten consecutive chewing cycles were taken for analysis. Discharge of nineteen muscle spindles from seven rabbits was successfully recorded. Muscle-spindle discharge was significantly higher during the closing phase of jaw-movement for the hard food chewing than for the soft food. The jaw-closing muscle EMG activity was significantly higher during hard food chewing compared to soft food. The spindle discharge was higher when the masseter muscle activity was greater for chewing hard food. Significant positive (r=0.822, p=<0.001) correlation was found between the difference of muscle activity between apple and pellet and the difference of spindle discharge between apple and pellet. Above findings suggest that the increase of spindle discharge during hard food chewing may play a role for facilitating jaw-closing muscle activities and thereby provides servo-assistance to jaw-closing muscles to compensate the hardness of food

Assessment of Antifungal Activity of Bakuchiol on Oral-Associated Candida

Bakuchiol is an active component of Psoralea glandulosa and Psoralea corylifolia, used in traditional Chinese medicine. The study aimed at investigating the antifungal activity of bakuchiol on planktonic and biofilm forms of orally associated Candida species. The antifungal susceptibility testing was determined by the broth micro dilution technique. Growth kinetics and cell surface hydrophobicity (CSH) of Candida were measured to assess the inhibitory effect of bakuchiol on Candida planktonic cells. Biofilm biomass and cellular metabolic activity were quantitatively estimated by the crystal violet (CV) and the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) assays. All Candida strains have been shown to be susceptible to bakuchiol with the MIC ranges from 12.5 to 100 μg/mL. Significant decrease in specific growth rates and viable counts demonstrates the inhibitory effect of bakuchiol on Candida planktonic cells. A brief exposure to bakuchiol also reduced CSH of Candida (P<0.05), indicating altered surface properties of yeast cells towards hydrophobic interfaces. Biofilm biomass and cell metabolic activity were mostly decreased, except for C. glabrata (P=0.29). The antifungal properties of bakuchiol on Candida species in this in vitro study may give insights into the application in therapeutic strategy against Candida infections

Assessment of Antifungal Activity of Bakuchiol on Oral-Associated Candida spp

Bakuchiol is an active component of Psoralea glandulosa and Psoralea corylifolia, used in traditional Chinese medicine. The study aimed at investigating the antifungal activity of bakuchiol on planktonic and biofilm forms of orally associated Candida species. The antifungal susceptibility testing was determined by the broth micro dilution technique. Growth kinetics and cell surface hydrophobicity (CSH) of Candida were measured to assess the inhibitory effect of bakuchiol on Candida planktonic cells. Biofilm biomass and cellular metabolic activity were quantitatively estimated by the crystal violet (CV) and the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) assays. All Candida strains have been shown to be susceptible to bakuchiol with the MIC ranges from 12.5 to 100 g/mL. Significant decrease in specific growth rates and viable counts demonstrates the inhibitory effect of bakuchiol on Candida planktonic cells. A brief exposure to bakuchiol also reduced CSH of Candida ( &lt; 0.05), indicating altered surface properties of yeast cells towards hydrophobic interfaces. Biofilm biomass and cell metabolic activity were mostly decreased, except for C. glabrata ( = 0.29). The antifungal properties of bakuchiol on Candida species in this in vitro study may give insights into the application in therapeutic strategy against Candida infections

Gaining more insight into the determinants of candida species pathogenicity in the oral cavity

Candida infection (candidiasis) is potentially life threatening and can occur in almost all anatomical sites, including the mouth. Candida species are in fact the most common fungal pathogens isolated from the oral cavity and frequently cause superficial infections such as oral candidiasis and denture-associated erythematous stomatitis. Whilst systemic dissemination of Candida from intraoral foci is rare and largely due to severe deficits of the host immune defenses, the development of localized oral candidiasis is most commonly related to a variety of non-immune determinants such as Candida virulence factors and permissive oral microenvironment. In particular, phenotypic switching and dental biofilm have emerged as major determinants for the pathogenicity of Candida and are currently the subject ofintense research. An understanding of the molecular aspects underlying the biological behavior of Candida will be the key to the development of effective preventive as well as therapeutic measures for invasive and oral candidiasis