Abstract

Dental caries is a common disease in human population which has a multifactorial etiology. A major cause of the disease is believed to be commensal bacteria which exist in dental plaque, particularly oral Streptococci. Our study is aimed at investigating the effects of aqueous, alcoholic and etheric, extracts as well as essence of four medicinal plants (Thymus vulgaris L., Melissa officinalis L., Rhus corriaria L. and Magnolia grandiflora L.) on Streptococcus mutans L. (ATCC-1 27607) and Streptococcus sanguis L. (PTCC-1449). None of the aqueous extracts had an effect on either S. mutans or S. sanguis. However, ethanol extract of M. officinalis had a minimal inhibitory concentration (MIC) of 310 µg/ml on both pathogens.  R. corriaria had a MIC and a minimal bactericidal concentration (MBC) of 250 µg/ml on S. mutans and S. sanguis. Plant essence demonstrated superior effect than aqueous and alcoholic extracts. M. grandiflora had a MIC of 1/5200 ml and MBC of 1/3200 ml on S. mutans. The MIC and MBC was 1/5200 ml and 1/2400 ml respectively on S. sanguis.  T. vulgaris had a MIC of 1/2000 ml and a MBC of 1/1200 ml on S. mutans. The plant essence inhibited S. sanguis up to 1/400 ml but no MB effect on S. sanguis. Essence of M. officinalis had a MI effect on both S. mutans and S. sanguis up to 1/1200 dilution but no MB effect on the pathogens.

Key words: aqueous extract, alcoholic extract, dental plaque.