Enhanced enamel benefits from a novel toothpaste and dual phase gel containing calcium silicate and sodium phosphate salts

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ABSTRACT

Objective

To investigate the enamel health benefits of a novel toothpaste and a dual phase gel containing calcium silicate, sodium phosphate and fluoride.

Methods

Enamel demineralisation was assessed using two pH cycling protocols with either lactic acid or citric acid as the acid challenge. Remineralisation of lactic acid softened and citric acid softened enamel was assessed using a number of protocols. All demineralisation and remineralisation evaluation was by surface microhardness measurements.

Results

The novel calcium silicate/phosphate fluoride toothpaste inhibited enamel demineralisation to a significantly (p < 0.05) greater extent than control formulations, including a fluoride control. The novel calcium silicate/phosphate fluoride toothpaste also showed significant (p < 0.05) remineralisation of lactic acid and citric acid softened enamel compared to fluoride and non-fluoride controls. The addition of the novel calcium silicate/phosphate fluoride dual phase gel provided enhanced remineralisation of citric acid softened enamel compared to fluoride and non-fluoride controls.

Conclusions

These studies show that formulations containing calcium silicate, sodium phosphate salts and fluoride provide enhanced enamel demineralisation and remineralisation in vitro benefits.

Clinical significance

The novel oral care formulations containing calcium silicate, sodium phosphate salts and fluoride is a new approach to the protection of enamel from acid attacks and the repair of demineralised enamel, leading to increased dental hard tissue benefits.

Introduction

Enamel mineral loss can lead to a range of common oral health problems. For example, the action of acid on enamel can give rise to enamel demineralisation and is present in both caries and erosion processes. In the caries process, acids are produced through plaque bacterial metabolism of fermentable sugars such as sucrose, which results in the progressive loss of mineral ions underneath a relatively intact surface layer and eventually leads to cavitation and tooth loss1. In contrast, in the erosion process the source of acids is not of bacterial origin and mineral loss occurs at the surface with direct contact of intrinsic acids such as hydrochloric acid from gastroesophageal reflux disease, or extrinsic acids such as fruit juice and soft drinks.

Fluoride is well established as a therapeutic agent providing protection from acid challenges as well as repair of demineralised enamel2., 3., 4.. Fluoride can be delivered by the regular brushing with a fluoride containing toothpaste to give a lower incidence of dental caries5. Fluoride has also been shown to reduce enamel mineral loss following acid erosion challenges via in vitro and in situ studies6.

Continued efforts to improve the efficacy and enamel health benefits of fluoride toothpastes have generally focussed on enhancing fluoride delivery or adding other beneficial agents. One approach is the delivery of calcium containing materials to the oral cavity, which has the potential to elevate calcium levels in plaque and saliva. This has the potential effect of limiting the impact of acid challenges by reducing enamel demineralisation whilst promoting enamel remineralisation7. For example, a fluoridated calcium glycerophosphate toothpaste showed enhanced enamel protection from an acid challenge in vitro compared to a fluoride control8, the addition of micron sized calcium carbonate and calcium glycerophosphate to a fluoridated calcium carbonate based toothpaste showed significantly greater remineralisation than a fluoride and non-fluoride controls9, and a fluoridated silica-based toothpaste containing hydroxyapatite significantly reduced enamel demineralisation from citric acid challenges compared to controls10., 11.. A recent review of mineralisation agents described a number of formulations that contained different calcium sources, including those listed above and for example, containing amorphous calcium phosphate, tricalcium phosphate, calcium sodium phosphosilicate and dicalcium phosphate dihydrate6.

A new calcium silicate and sodium phosphate salts (monosodium phosphate and trisodium phosphate) toothpaste containing 1450 ppm fluoride (added as sodium mono-fluorophosphate) has been developed to provide enhanced enamel health benefits. Furthermore, a new dual phase gel has also been developed to provide additional enamel remineralisation benefits. The new dual phase gel contains part A: a fluoridated phase containing calcium silicate and sodium phosphate salts and part B: a phase containing sodium fluoride. This dual phase gel is proposed as an adjunct to daily use of the toothpaste. The toothpaste has been shown to deposit calcium silicate onto the enamel surface and form hydroxyapatite. It is hypothesised that this new toothpaste formulation can reduce enamel demineralisation by acid and promote remineralisation of acid softened enamel and that the new dual phase gel can aid in the enamel remineralisation process. The objective of the current study is to investigate the efficacy of these new toothpaste and dual phase gel formulations. The null hypothesis to be tested is that a calcium silicate/phosphate fluoride toothpaste will not provide any significant in vitro enamel demineralisation and remineralisation benefits versus control formulations and that a calcium silicate/phosphate fluoride dual-phase gel will not provide additional in vitro enamel remineralisation versus a control.

Section snippets

Materials and Methods

A number of different in vitro methods and models were used to investigate the enamel health benefits of the calcium silicate/phosphate fluoride toothpaste. Inhibition of demineralisation and promotion of remineralisation were evaluated using lactic acid and citric acid protocols to represent early caries and erosive conditions respectively. The novel calcium silicate/phosphate fluoride formulations were also evaluated in remineralisation protocols.

Demineralisation pH Cycling: Experiment 1

The results of the lactic acid demineralisation experiment are shown in Figure 1. It is shown that the calcium silicate/phosphate fluoride toothpaste prevented demineralisation. Statistical analysis (JMP v.9.0, SAS) for this treatment showed that there was no statistically significant difference (p > 0.05, Student’s tTest) between the post pH cycling and baseline HK values. However, there were significant differences (p < 0.05, Student’s tTest) in HK values between post pH cycling and baseline for

Discussion

The null hypotheses can be rejected because the calcium silicate/phosphate fluoride toothpaste was shown under several different protocols to provide enamel demineralisation and remineralisation benefits versus control formulations and the calcium silicate/phosphate fluoride dual-phase gel was shown to provide additional in vitro enamel remineralisation versus fluoride and non-fluoride control toothpastes.

In vitro pH cycling models have been used extensively to study enamel demineralisation and

Conclusions

A novel calcium silicate/phosphate fluoride toothpaste significantly protects enamel from in vitro demineralisation caused by lactic or citric acid, compared to control toothpaste. In a remineralisation study incorporating lactic acid surface softened enamel specimens the novel toothpaste significantly promoted remineralisation compared to a sodium fluoride control. The novel calcium silicate/phosphate fluoride toothpaste was also significant in remineralising enamel specimens softened with

Conflict of interest statement

Kate Hornby, Stephen Ricketts, Carole Philpotts and Andrew Joiner are all employees of Unilever Plc. Bruce Schemehorn and Richard Willson received funding support from Unilever Oral Care for the reported work.

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