Bjarne Svatun

The effect of stannous fluoride on human plaque acidogenicity in situ (Stephan curve)

A system employing an Ingold glass electrode was shown to give reliable measurements of pH drops in dental plaque in situ (Stephan curve readings). The system was used to demonstrate that mouthrinses of 0.2 per cent aqueous solutions of stannous fluoride reduced the pH drops markedly for at least seven hours. A reduction of the stannous fluoride concentration increased the pH drops and decreased the duration of the inhibiting effect. A commercial toothpaste containing stannous fluoride and stannous pyrophosphate had an effect similar to the 0.2 per cent mouthrinse. It was shown that tin accumulated in dental plaque after application of solutions containing stannous fluoride. About 40 per cent of the amount of tin present in the plaque immediately after the mouthrinse was still retained seven hours later. It is suggested that the reduction in acid formation may be caused by stannous ions adsorbing to the bacterial cell wall thus disturbing membrane transport mechanisms, or through inhibition of enzyme systems essential in the fermentation of sugars. The observed effect may be a part of the mechanism involved in the caries preventive function of stannous fluoride.

Plaque-inhibiting effect of dentifrices containing stannous fluoride.

The present study showed that the plaque inhibiting effect of aqueous solutions of stannous fluoride can be maintained in toothpastes. A commercial toothpaste containing 0.4 per cent of water soluble tin was effective whereas one containing 0.03 per cent showed no effect. The plaque inhibiting effect was shown in one study where the toothpastes were applied in cap splints and the plaque was scored after four days by the Plaque Index of Löe, and in another where the effect of locally applied pastes was monitored 24 hours later by the Gingival margin Plaque Index of Harrap. The present investigation supports the view that the stannous ion is essential in the plaque inhibition caused by stannous fluoride preparation. The exact mechanism is unknown but it is speculated that a change in the surface potential of oral bacteria through interaction with the stannous ion may be important.

Oral hygiene, periodontal health and need for periodontal treatment among institutionalized mentally subnormal persons i Norway

Oral hygiene, periodontal health and periodontal treatment needs were studied in the dentulous patients (n = 328) of a sample selected to be representative of all institutionalized mentally subnormal persons in Norway aged 5--45. The average oral hygiene and periodontal health was poor except for patients in a few institutions where the nurses were trained to clean teeth regularly. Increased age, epilepsy, Downs syndrome and a high degree of mental deficiency were all elements that apparently contributed to impairment of periodontal health and to increased treatment requirements. The preventive programs used in some institutions seemed to be effective. Still better results, however, could probably be obtained by the use of dental hygienists.

The effects of stannous and stannic ions on the formation and acidogenicity of dental plaque in vivo

The present study was concerned with the effect of stannous and stannic ions on the formation and acidogenicity of dental plaque in vivo. Five dental students participated in the study on inhibition of plaque formation. They rinsed for four days with 0.2% aqueous solution of either Sn2+ or Sn4+ and in addition 15% w/v sucrose to enhance plaque formation. The P1.I was recorded after each series. Another test panel participated in the study on inhibition of acid production. The pH of the plaque was measured in situ. The stannous ion showed marked inhibiting activity on plaque formation whereas the stannic ion showed only a slight effect. The stannous ion also showed an effect in reducing the acidogenicity of dental plaque whereas the stannic ion showed no such effect. These findings support the concept that the stannous ion reduces the metabolic activity of plaque by oxidation of thiol groups by affinity for these groups. This is not the case with stannic ions. It seems conceivable that the reduced metabolic activity in plaque is the main factor which causes plaque inhibition. The slight plaque inhibiting effect of the stannic ions may be caused by inhibition of adsorption as such as this ion has no direct effect on the metabolism of the plaque.

Uptake and retention of tin by S. mutans

The uptake of tin by S. mutans from stannous fluoride or stannous chloride solutions was determined by atomic absorption spectroscopy. The uptake occurred rapidly, and the microorganism was shown to have a greater capacity and higher affinity to uptake of tin than of other metal ions tested. In 10 mM solutions, bound tin amounted to 17.5 per cent of the cellular dry mass. The tin uptake was independent of cell metabolism. The cell bound tin could not be washed out with water or saline, but 84 per cent was removed by ethylenediaminetetraacetic acid solutions. When pH was lowered by low 2, increasing loss of bound tin occurred. It is suggested that the binding occurs to polyanionic structural polymers in the cell wall and the cell capsule.

Solubilization of hydroxyapatite at neutral pH by an anionic ionic exchange resin

Sucrose, induced dental plaque has been shown to contain high amounts of lipoteichoic acids, a bacterial anionic polymer with chemical properties similar to ionic exchange resins. The present study describes an in vitro experiment where a commercial resin Amberlite IR 120 was shown to dissolve hydroxyapatite at neutral pH. The resin binds calcium and the dissociation of the hydroxyapatite Ca5(PO4)3OH leads to 5Ca++ +3 PO4(-3) + OH- is driven to the right as long as the resin takes up calcium. The dissociation of the hydroxyapatite was monitored by electrical conductivity and pH of the aqueous phase. It is suggested that this mechanism may be of some significance in vivo.