In Situ Erosion Study to Investigate the Effectiveness of an Experimental Toothpaste

The aim of this study is to investigate the performance of an experimental dentifrice formulation in promoting enamel remineralization and inhibiting post-treatment enamel demineralization in an in situ erosion model, in comparison with a fluoride-free placebo and with a marketed competitor dentifrice product. The study will have 4 visits, 1 screening visit to assess participants eligibility and 3 treatment visits to assess product efficacy, where the treatment product will be dispensed and used under the supervision of a suitably trained study site personnel. Prior to each treatment visit, there will be a washout period of a minimum of 3 days. During this period participants will use their own dentifrice for at least one day, and a fluoride free dentifrice (provided) for two days prior to the next scheduled visit (including in the morning of the scheduled visit) to minimize any carry-over effects of the fluoride toothpaste.

• 0.254% w/w sodium fluoride and 5% KNO3 (Drug): Dentifrice containing 0.254% w/w sodium fluoride (1150 ppm fluoride) and 5% KNO3; plus 0.25% PVM/MA copolymer and 2.5% sodium lactate. Participants will brush it on the buccal surfaces of their natural teeth for 25 timed seconds and then swish the resulting toothpaste slurry around the mouth, without further brushing, for a timed period of 95 seconds. After expectorating the slurry, the participants will gently rinse their mouths with 15 millilitres \[mL\] of tap water for 10 seconds before expectorating again.
• 0.454% w/w stannous fluoride (Drug): Dentifrice containing 0.454% w/w stannous fluoride (1100 ppm fluoride). Participants will brush it on the buccal surfaces of their natural teeth for 25 timed seconds and then swish the resulting toothpaste slurry around the mouth, without further brushing, for a timed period of 95 seconds. After expectorating the slurry, the participants will gently rinse their mouths with 15 mL of tap water for 10 seconds before expectorating again.
• 5% KNO3 (Drug): Fluoride free placebo dentifrice containing 5% KNO3 (0 ppm fluoride), 0.25% PVM/MA copolymer and 2.5% lactate. Participants will brush it on the buccal surfaces of their natural teeth for 25 timed seconds and then swish the resulting toothpaste slurry around the mouth, without further brushing, for a timed period of 95 seconds. After expectorating the slurry, the participants will gently rinse their mouths with 15 mL of tap water for 10 seconds before expectorating again.

Primary outcomes

• % Surface Micro Hardness Recovery (SMHR; Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to a Fluoride Free Placebo Dentifrice to Enhance Remineralization of Enamel) [After 4 hrs following single exposure of treatment]: The %SMHR was calculated to assess the changes in mineralization status of enamel specimens. The mean indent length (micrometer) from five Knoop microindentations within each specimen was measured at baseline (B), after the first erosive challenge (E1), and after 2 and 4 hours intraoral phase (R). An increase in the indentation length compared to the baseline indicates softening of the enamel surface while decrease in the indentation length represents re-hardening of enamel surface. The %SMHR was calculated as : %SMHR = \[(E1-R)/(E1-B)\]*100. Greater values of %SMHR indicate that greater remineralization has occurred, thus higher values are more favorable.

Secondary outcomes

• % Relative Erosion Resistance (RER; Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to a Fluoride Free Placebo Dentifrice to Inhibit Demineralization of Enamel) [After 4 hrs following single exposure of treatment]: The %RER was calculated to assess the ability of treated enamel specimens to provide a combined benefit in terms of enhanced remineralization and acid resistance of the enamel. The mean indent length (micrometer) from five Knoop microindentations within each specimen was measured at baseline (B), after the first erosive challenge (E1), and after the second erosive challenge (E2) (E2 is measured for after both 2 and 4 hours of remineralization). An increase in the indentation length compared to the baseline indicates softening of the enamel surface while decrease in the indentation length represents re-hardening of enamel surface. The %RER was calculated as : %RER = \[(E1-E2)/ (E1-B)\]*100. Higher values of %RER indicate greater resistance to erosion, thus higher values are more favorable.
• Enamel Fluoride Uptake (EFU; Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to a Fluoride Free Placebo Dentifrice to Promote Fluoride Uptake in Enamel) [After 4 hrs following single exposure of treatment]: The EFU was measured to determine the amount of fluoride incorporation into the model erosive lesions. Each enamel specimen drilled to a depth of approximately 100 μm using a microdrill, through the entire lesion (four cores per specimen). The enamel powder pooled from four drilling samples was then, dissolved in a known volume of perchloric acid and immediately analyzed for fluoride content using a calibrated fluoride specific electrode. The amount of fluoride-uptake by enamel was calculated based on the amount of fluoride divided by the area of the enamel cores and expressed as microgram fluoride per square centimeter (μgF/cm\^2). Higher values of EFU indicate greater incorporation of fluoride into the enamel and are thus more favorable.
• % SMHR (Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to Comparator Containing 1100 Ppm Fluoride) [After 4 hrs following single exposure of treatment]: The %SMHR was calculated to assess the changes in mineralization status of enamel specimens. The mean indent length (micrometer) from five Knoop microindentations within each specimen was measured at baseline (B), after the first erosive challenge (E1), and after 2 and 4 hours intraoral phase (R). An increase in the indentation length compared to the baseline indicates softening of the enamel surface while decrease in the indentation length represents re-hardening of enamel surface. The %SMHR was calculated as: %SMHR = \[(E1-R)/(E1-B)\]*100. Greater values of %SMHR indicate that greater remineralization has occurred, thus higher values are more favorable.
• % RER (Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to Comparator Containing 1100 Ppm Fluoride) [After 4 hrs following single exposure of treatment]: The %RER was calculated to assess the ability of treated enamel specimens to provide a combined benefit in terms of enhanced remineralization and acid resistance of the enamel. The mean indent length (micrometer) from five Knoop microindentations within each specimen was measured at baseline (B), after the first erosive challenge (E1), and after the second erosive challenge (E2) (E2 is measured for after both 2 and 4 hours of remineralization). An increase in the indentation length compared to the baseline indicates softening of the enamel surface while decrease in the indentation length represents re-hardening of enamel surface. The %RER was calculated as : %RER = \[(E1-E2)/ (E1-B)\]*100. Higher values of %RER indicate greater resistance to erosion, thus higher values are more favorable.
• EFU (Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to Comparator Containing 1100 Ppm Fluoride) [After 4 hrs following single exposure of treatment]: The EFU was measured to determine the amount of fluoride incorporation into the model erosive lesions. Each enamel specimen drilled to a depth of approximately 100 μm using a microdrill, through the entire lesion (four cores per specimen). The enamel powder pooled from four drilling samples was then, dissolved in a known volume of perchloric acid and immediately analyzed for fluoride content using a calibrated fluoride specific electrode. The amount of fluoride-uptake by enamel was calculated based on the amount of fluoride divided by the area of the enamel cores and expressed as microgram fluoride per square centimeter (μgF/cm\^2). Higher values of EFU indicate greater incorporation of fluoride into the enamel and are thus more favorable.

Sex: All, ages: 18 Years to 65 Years, accepts healthy volunteers

Inclusion Criteria:

* Evidence of a personally signed and dated informed consent.
* Male and female participants who, at the time of screening, are between the ages of 18 and 65 years, inclusive.
* Participant who is willing and able to comply with scheduled visits, treatment plan, and other study procedures.
* 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 oral examination.
* Male participant able to father children and female participant of childbearing potential and at risk for pregnancy must agree to use a highly effective method of contraception throughout the study and for 5 days after the last dose of assigned treatment.
* Good oral health without lesions of the oral cavity that could interfere with the study evaluations.
* Maxillary dental arch suitable for the retention of the palatal appliance
* Unstimulated salivary flow rate of at least 0.2 mL/minute and a stimulated salivary flow rate of at least 0.8 mL/minute.
* Understands and is willing, able and likely to comply with all study procedures and restrictions.

Exclusion Criteria:

* Participants who are investigational site staff members directly involved in the conduct of the study and their family members, site staff members otherwise supervised by the investigator, or participants who are GSK employees directly involved in the conduct of the study.
* Participation in other studies involving investigational drug(s) within 30 days prior to screening visit.
* Participation in other studies involving investigational oral care or cosmetic products within 30 days prior to screening visit.
* Acute or chronic medical or psychiatric condition that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study.
* Pregnant female participant (self - reported).
* Breastfeeding female participant.
* Known or suspected intolerance or hypersensitivity to the study materials (or closely related compounds) or any of their stated ingredients. Unwilling or unable to comply with the lifestyle guidelines described in this protocol.
* Medication that may interfere significantly with the saliva flow in the judgment of the investigator. Should new medications that may interfere with the saliva flow be added, a second salivary flow test will be performed.
* Participant with any condition that would impact on their safety or wellbeing or affect their ability to understand and follow study procedures and requirements.
* Any sign of grossly carious lesions (active), moderate or severe periodontal conditions, or severe tooth wear. Participant presenting at screening with minor caries may continue in the study if their carious lesions are repaired prior to the first treatment visit of the study.
* Wears oral appliance or orthodontia (besides participants wearing permanent lower retainers, which are eligible).
* Recent history (within the last year) of alcohol or other substance abuse. Participant who has previously been enrolled in this study.

Participant flow

Outcome results

• % Surface Micro Hardness Recovery (SMHR; Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to a Fluoride Free Placebo Dentifrice to Enhance Remineralization of Enamel) (Primary), Least squares mean, Percentage SMHR: Test Product 29.67 +/- 1.12; Placebo Product 21.98 +/- 1.12 (p <.0001)
• % Relative Erosion Resistance (RER; Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to a Fluoride Free Placebo Dentifrice to Inhibit Demineralization of Enamel) (Secondary), Least squares mean, Percentage RER: Test Product -23.65 +/- 1.96; Placebo Product -56.94 +/- 1.96 (p <.0001)
• Enamel Fluoride Uptake (EFU; Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to a Fluoride Free Placebo Dentifrice to Promote Fluoride Uptake in Enamel) (Secondary), Least squares mean, Microgram fluoride per square centimeter: Test Product 2.98 +/- 0.09; Placebo Product 1.17 +/- 0.09 (p <.0001)
• % SMHR (Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to Comparator Containing 1100 Ppm Fluoride) (Secondary), Least squares mean, Percentage SMHR: Test Product 29.67 +/- 1.12; Comparator Product 22.10 +/- 1.12 (p <.0001)
• % RER (Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to Comparator Containing 1100 Ppm Fluoride) (Secondary), Least squares mean, Percentage RER: Test Product -23.65 +/- 1.96; Comparator Product -34.63 +/- 1.96 (p <.0001)
• EFU (Comparison of 1150 Ppm Fluoride and 5% KNO3 Dentifrice Relative to Comparator Containing 1100 Ppm Fluoride) (Secondary), Least squares mean, Microgram fluoride per square centimeter: Test Product 2.98 +/- 0.09; Comparator Product 2.01 +/- 0.09 (p <.0001)

Adverse events

Time frame: 4 hours

Other adverse events by term

• Results publication: Creeth JE, Burnett GR, Souverain A, Gomez-Pereira P, Zero DT, Lippert F, Hara AT. In situ efficacy of an experimental toothpaste on enamel rehardening and prevention of demineralisation: a randomised, controlled trial. BMC Oral Health. 2020 Apr 17;20(1):118. doi: 10.1186/s12903-020-01081-y. PMID 32303206

• Study Protocol (PDF, 2017-11-07)
• Statistical Analysis Plan (PDF, 2018-02-27)

• GSK Clinical Trials, Study director, GlaxoSmithKline