Salvadora persica (MISWAK) : an effective way of killing oral pathogens

Abstract: Mechanical removal of dental plaque is regarded as an effective means of controlling the progression of dental caries and periodontal disease. The habitual use of chewing sticks (Miswak) as an oral hygiene method is still wildly spread throughout parts of Asia, Africa, and the Middle East. Thus, the World Health Organization recommends and encourages the use of chewing sticks as an effective oral hygiene tool in areas where it is customary. As Salvadora persica (Arak) is one of the most important species still used around the world, the main aim of this thesis was to test the hypothesis that Salvadora persica Miswak offers a unique combination of mechanical and chemical supragingival plaque control. This thesis was based on two parts. A clinical part (Papers I & IV) investigated the effect of rinsing with Miswak extract on plaque pH after acidogenic challenge, and the effect of fresh and deactivated Miswak sticks on dental plaque and gingival inflammation in patients with gingivitis. A laboratory part (Papers II & III) tested the antibacterial activity of Miswak pieces and Miswak essential oil obtained by steam distillation against some Gram positive/negative bacteria. Through Gas Chromatography-Mass Spectrometry and Medium Pressure Liquid Chromatography the main antimicrobial component/s of Salvadora persica Miswak was specified and characterised. The main findings were both fresh Miswak and essential oil Miswak extract had a strong antibacterial activity against Gram negative bacteria including some oral pathogens such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. Benzyl isothiocyanate (BITC) was the main antimicrobial component of Miswak. Bacterial cell membrane exhibited protrusions upon treatment with Miswak oil and commercially available BITC. Rinsing with Miswak extract, compared with water rinsing, resulted in protracted elevation of plaque pH (>6.0). Both fresh and deactivated Miswak reduced dental plaque and gingival inflammation. The decrease was statistically significant with active Miswak but was not with deactivated Miswak. The positive clinical effects of Miswak on plaque pH, plaque and gingival indices, as well as the immediate strong antibacterial activity demonstrated in the laboratory experiments suggested that Miswak could be beneficial for oral health. Further laboratory and clinical investigations of antiviral and antifungal activities together with the effect on periodontal inflammation need to be performed. The cytotoxic activities of fresh Miswak and Miswak oil need to be evaluated before the development of oral applications becomes a future reality.