This will be a single centre, single blind, randomized, three treatment, three period crossover design, modified, in situ, study in healthy participants. In this in situ model the tubule occlusion properties of dentifrices will be evaluated by comparing an experimental dentifrice formulation to a regular fluoride dentifrice and a negative control (mineral water) over a ten day period.

This modified in situ model study will evaluate the mode-of-action of an experimental dentifrice containing stannous fluoride to occlude tubules compared to a regular fluoride dentifrice and a negative control (mineral water). The study treatments will be administered for a total of 10 days, with participants wearing two appliances in their mouth that will hold samples of dentine. The dentine samples will be examined after 1, 4, 8 and 10 days of treatment using scanning electron microscopy (SEM) and the resulting images graded for the amount of occlusion. In addition, the robustness of any occlusion generated by the treatments will be tested by exposing the dentine samples to an acid challenge (orange juice) after 9 and 10 days treatment.

Inclusion Criteria:

• Demonstrates understanding of the study procedures, restrictions and willingness to participate as evidenced by voluntary written informed consent and has received a signed and dated copy of the informed consent form.
• Aged between 18 and 80 years
• Understands and is willing, able and likely to comply with all study procedures and restrictions.
• Good general and mental health with, in the opinion of the investigator or medically qualified designee: No clinically significant and relevant abnormalities in medical history or upon oral examination, absence of any condition that would impact on the participant's safety or well being or affect the individual's ability to understand and follow procedures and requirements.
• Be able to accommodate the lower bi-lateral buccal intra-oral appliances each fitted with four dentine samples

Exclusion Criteria:

• Women who are known to be pregnant or who are intending to become pregnant over the duration of the study.
• Women who are breast-feeding
• Current or recurrent disease/dental pathology that in the opinion of the investigator could affect the study outcomes.

Current susceptibility to acid regurgitation, any orthodontic appliances, restorations, bridgework or dentures that in the opinion of the investigator would interfere with the study outcomes, recurrent or regular aphthous ulcers, severe gingivitis, carious lesions and periodontal disease,signs of severe dental erosion, any condition or medication which in the opinion of the investigator is currently causing xerostomia, and individuals who require antibiotic prophylaxis for dental procedures

• Known or suspected intolerance or hypersensitivity to the study materials (or closely related compounds) or any of their stated ingredients
• Participation in another study (clinical or cosmetic studies) or receipt of an investigational drug within 15 days of the screening visit, previous participation in this study.
• Recent history (within the last year) of alcohol or other substance abuse
• An employee of the sponsor or the study site or members of their immediate family. The site for this protocol is the Clinical Trials Unit in the Bristol Dental School and Hospital. Employees of the Bristol Dental School and Hospital not associated with the Clinical Trials Unit are eligible to participate
• Any participant who, in the judgement of the investigator, should not participate in the study

All randomized participants were included for baseline evaluation

Baseline to Day 10