Evaluation of the Fluoride Dose Response of a Modified In Situ Caries Model

The purpose of this study is to evaluate the fluoride dose response of different dentifrice fluoride concentrations - 0, 250, 500 and 1100 ppm fluoride of our existing in situ model involving the use of human enamel specimens placed in the buccal flange area of the subjects partial denture with the modified model involving placement of bovine enamel specimens in a denture tooth location.

This will be a double blind, single center, 4-way crossover design study involving 34 adult subjects, between the ages of 18 and 85 years. Two to three days before the start of each treatment period the subjects will have their teeth cleaned to remove all accessible plaque and calculus and will be provided with a non-fluoride dentifrice to use until their next visit. At the beginning of each testing period, two gauze-covered 4 × 4 mm partially demineralized human enamel specimens will be placed in the buccal flange area of the subject's mandibular partial denture. In addition, two gauze-covered 4 mm round partially demineralized bovine enamel specimens will be placed in the buccal surface of two posterior denture teeth of the same side of the partial denture. Once specimens are placed, subjects will wear their partial dentures twenty-four hours a day and use their assigned toothpaste twice daily, as instructed, until their next visit. Specimens will be removed after two weeks and the subjects will undergo a four to five day washout period followed by another cleaning and two to three day lead in period. This process will be repeated until all subjects have used all four test products. Changes in the mineral content of the enamel specimens will be assessed using the SMH and TMR. Enamel fluoride uptake (EFU) will be determined using the microdrill enamel biopsy technique. In addition the net acid resistance (NAR) and the comparative acid resistance (CAR) of the remineralized enamel specimens will be determined.

Eligibility Criteria:
Inclusion Criteria:

1. provide voluntary, written informed consent;
2. be between 18 and 85 years old;
3. understand and be willing, able and likely to comply with all study procedures and restrictions;
4. be wearing a removable mandibular partial denture with sufficient room in one posterior buccal flange area to accommodate two enamel specimens (required dimensions 12 × 7 mm) and room on the same side to accommodate two 4 mm round specimens in the buccal surface of two posterior denture teeth;
5. be willing and capable of wearing their removable partial denture 24 hours a day for four (4), two-week treatment periods;
6. be willing to allow study personnel to drill specimen sites (as described #4) in their mandibular partial denture;
7. be in good medical and dental health with no active caries or periodontal disease; NOTE; subjects presenting at screening with caries may continue in the study if their carious lesions are restored prior to beginning treatment 1.
8. have a salivary flow rate in the range of normal values (unstimulated whole saliva flow rate ≥ 0.2 mL/min; gum base stimulated whole saliva flow rate ≥ 0.8 mL/min).

Exclusion Criteria:

1. currently be pregnant, intending to become pregnant during the study period or breast feeding;
2. currently have any medical condition that could be expected to interfere with the subject's safety during the study period;
3. currently be taking antibiotics or have taken antibiotics in the two weeks prior to the beginning treatment 1;
4. have participated in another clinical study or receipt of an investigational drug within 30 days of beginning treatment 1; or
5. be taking fluoride supplements, required to use a fluoride mouthrinse or have received a professional fluoride treatment in the two weeks preceding specimen placement;
6. be taking or have ever taken bisphosphonate drugs (e.g., Fosamax, Actonel and Boniva) for the treatment of osteoporosis;