The antibacterial activity of acacia gum was assessed using fresh isolates and reference strains of Actinobacillus actinomycetemcomitans, Capnocytophaga spp., Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. A fine aqueous suspension of gum was produced by sonication and then a soluble fraction isolated by centrifugation and membrane filtration. These preparations were incorporated into columbia agar at doubling concentrations. Growth of P. gingivalis and P. intermedia cultures on the agar was inhibited by whole gum sonicate at concentrations of 0.5-1.0% w/v. Both species showed reduced susceptibility when horse blood was present in the agar. The gum soluble fraction did not inhibit growth of any bacterial culture. The effect of acacia on bacterial proteases was examined with cell sonicates from log phase broth cultures. Enzyme activities were determined by fluorimetric assay with various synthetic peptide substrates. Most protease activities reduced in the presence of 0.5% w/v gum sonicate, with the trypsin-like activities of P. gingivalis and P. intermedia proving most sensitive. The gum soluble fraction was nearly always less inhibitory than the sonicate. The action of acacia gum against suspected periodontal pathogens and their enzymes suggests that it may be of clinical value.

Protease activities in cell sonicates of defined bacterial strains were examined using peptide substrates and class-specific inhibitors. Capnocytophaga spp. all produced serine dipeptidyl peptidase activity and arginine/lysine, elastase- and chymotrypsin-like enzymes with some metalloprotease characteristics. The elastase-like activity was strongest in Capnocytophaga sputigena, but the others were greatest in Capnocytophaga gingivalis. The latter also had a separate arginine-specific enzyme which appeared not to be present in the other two species. Porphyromonas gingivalis showed serine dipeptidyl peptidase activity and very strong arginine and lysine cysteine protease activities. Prevotella spp. had inhibitor-resistant dipeptidyl peptidase activity and arginine cysteine protease activity that was much weaker but biochemically similar to P. gingivalis. Treponema denticola possessed a strong trypsin-like serine protease activity as well as very weak dipeptidyl peptidase and chymotrypsin-like activities that were sensitive to some cysteine protease reagents. Actinobacillus actinomycetemcomitans showed a novel alanine- and lysine-specific activity, but its nature was unclear.

Chewing sticks or Meswaks are used for teeth cleaning in many parts of the world. They contain substances that may reduce caries and periodontal disease. The present study consisted of 2 parts. In a short-term experiment, volunteers chewed on an inert eliciting agent (pyrogen-free rubber) and then a piece of Meswak, each for 5 min. For the medium-term experiment, volunteers brushed with either Meswak or a conventional toothbrush 5 x a day for 2 weeks. Saliva produced immediately after chewing Meswak showed statistically significant increases in calcium and chloride, but decreases in phosphate and pH as compared with controls. In the medium-term experiment, saliva samples collected 4 h after the last use of Meswak or toothbrush showed no significant differences in any of the components examined (calcium, magnesium, chloride, phosphate, IgA, IgG, lactate dehydrogenase and aspartate transaminase). Gingival and plaque indices, however, were significantly lower after brushing with Meswak. Salivary calcium promotes mineralization of tooth enamel and chloride inhibits calculus formation. Our results thus indicate that Meswak releases substances into saliva that could improve oral health. Calcium and chloride values were similar to those of controls after 4 h and thus frequent use of Meswak may be necessary to maintain a favorable salivary environment.

The gum of Acacia Arabica is described in the British pharmacopoeia as a source of useful medicaments. It is believed to be of value for treating gingivitis and for reducing plaque. 2 blind crossover trials were carried out to evaluate the antiplaque potential of Acacia gum compared with sugar free gum. In trial 1, the mean gingival and plaque scores were lower after 7 days of using Acacia compared with sugar-free gum but the differences were insignificant. In trial 2, daily photographic assessment of erythrocine-stained plaque showed lower scores after Acacia gum compared with sugar-free gum. The total difference in scores for each day from each individual between the 2 treatments was highly significant (p less than 0.05). This implies the presence of substances in Acacia gum which, compared with ordinary gum, primarily inhibit the early deposition of plaque.

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