The experimental gingivitis model has long been used to evaluate chemotherapeutic agents in mouthrinses. Only recently however has the model been modified to test undiluted dentifrices by using a toothshield both to apply dentifrice and to protect selected teeth from toothbrushing. This also enables participants to brush the rest of the mouth and avoid the unpleasantness of 3 weeks without oral hygiene. Because of its well-documented efficacy, chlorhexidine was used in a toothpaste formulation to investigate the validity of the partial-mouth, experimental gingivitis model for evaluating therapeutic dentifrices. Optimal gingival health was established in 88 adults, who then were randomly assigned to two equal groups. A toothshield was constructed for each subject to fit the teeth of one mandibular quadrant. During the trial chlorhexidine or placebo dentifrice was applied undiluted to the test teeth via the toothshield, which also prevented plaque removal during brushing of the remaining dentition. After 21 days, plaque and gingivitis had developed in both groups. However, the chlorhexidine group had significantly less plaque and gingivitis than the placebo group. No adverse soft tissue effects were observed. This study demonstrated that the partial-mouth, experimental gingivitis model allowed unhindered development of plaque and gingivitis that was comparable to whole-mouth studies in which oral hygiene was suspended for 3 weeks. By corroborating with chlorhexidine, it is concluded that this short-term clinical model is valid for evaluating the chemotherapeutic effects of dentifrices.

No abstract

The uptake, depth of penetration, and retention of aluminum (Al) in sound and acid-etched dental enamel were determined following in vitro applications of solutions containing 0.005 M or 0.037 M Al. Compared with controls, significant amounts of Al uptake (approximately 2000 to 6000 ppm) were detected in both sound and etched enamel, with significantly more Al deposited in the latter. Analysis of successive layers of treated enamel demonstrated that Al was located predominantly within the first 20 microns of surface enamel. Only slight reductions in Al retention occurred following one week of water-soaking or one minute of brushing with water or dentifrice, indicating that Al was firmly bound by enamel.

No abstract

The effects of sequentially applied solutions containing aluminum (Al) on enamel uptake and inhibition of acid dissolution were investigated. Following 10 consecutive 5-min treatments with seven Al solutions varying in concentration from 0.15 to 2.0 mmol/l, the subsequent acid dissolution of enamel was progressively reduced from 0 to over 70%. Teeth treated with 1.5 mmol/l Al from 1 to 30 consecutive 5-min periods demonstrated a stepwise increase in the reduction of enamel acid dissolution ranging from about 10 to 90%. Following the same treatment regimen, the amount of Al deposited in the enamel varied from 2,500 ppm after a single 5-min application to approximately 9,000 ppm after 20 or 30 consecutive treatments. These experiments showed that teeth repeatedly exposed to low concentrations of Al solutions (i.e. < 2 mmol/l) progressively accumulated significant amounts of Al in the surface enamel, which was associated with a concomitant decrease in the acid dissolution rate of enamel.