Development of a Chewing Robot With Built-in Humanoid Jaws to Simulate Mastication to Quantify Robotic Agents Release From Chewing Gums Compared to Human Participants.

Medicated chewing gum has been recognised as a new advanced drug delivery method, with a promising future. Its potential has not yet been fully exploited because currently there is no gold standard for testing the release of agents from chewing gum in vitro. This study presents a novel humanoid chewing robot capable of closely replicating the human chewing motion in a closed environment, incorporating artificial saliva and allowing measurement of xylitol release from the gum. The release of xylitol from commercially available chewing gum was quantified following both in vitro and in vivo mastication. The chewing robot demonstrated a similar release rate of xylitol as human participants. The greatest release of xylitol occurred during the first 5 minutes of chewing and after 20 minutes of chewing only a low amount of xylitol remained in the gum bolus, irrespective of the chewing method used. Saliva and artificial saliva solutions respectively were collected after 5, 10, 15 and 20 minutes of continuous chewing and the amount of xylitol released from the chewing gum determined. Bioengineering has been implemented as the key engineering strategy to create an artificial oral environment that closely mimics that found in vivo. These results demonstrate the chewing robot with built-in humanoid jaws could provide opportunities for pharmaceutical companies to investigate and refine drug release from gum, with reduced patient exposure and reduced costs using this novel methodology.

The ability of a potassium oxalate gel strip to occlude human dentine tubules; a Novel in vitro: In situ Study.

OBJECTIVES: To determine if an oxalate strip reduced fluid flow in dentine samples and whether this reduction was maintained following a 14 day intra-oral period. METHODS: Dentine tubule fluid flow was measured by a modified Pashley cell in 40 acid-etched dentine discs 1 mm thick, diameter >10 mm, with an acquired pellicle, pre-equilibrated with Hartmann's solution and conditioned by toothbrushing, pre and post treatment (10 min) with an oxalate (3.14 %) gel strip or no treatment. One control and one test sample were exposed in-situ for 14 days to the oral environment in 20 healthy adult volunteers, and fluid flow re-measured. The appliance containing the two samples was removed for brushing with water after mealtimes when the participant brushed their teeth and for a 2 min daily soak in chlorhexidine. RESULTS: Fluid flow rate was reduced significantly immediately following treatment with the oxalate strip compared to baseline flow rate by 58 %. Following 14 days in-situ oral environment phase, a significant further reduction in fluid flow compared to baseline was identified in both control and oxalate strip treated samples, both (p < 0.0001), but the reduction was greater in the test samples, 94 % vs 87 %, p < 0.01. CONCLUSIONS: This novel investigation is the first to show fluid flow measurement using the Pashley model in dentine samples that have been housed in the mouth for 14 days. Treatment with an oxalate strip designed for dentine hypersensitivity alleviation reduced dentine fluid flow more than control providing evidence that the oxalate treatment withstood the oral environment over a prolonged time. CLINICAL SIGNIFICANCE: This study demonstrated the efficacy and durability of the oxalate precipitate over a 14 day period in achieving and maintaining dentine tubule occlusion when participants had no dietary restrictions. This demonstrates the suitability of the oxalate strip for the treatment of patients suffering from dentine hypersensitivity pain.

An interproximal model to determine the erosion-protective effect of calcium silicate, sodium phosphate, fluoride formulations.

OBJECTIVES: Previous work has shown the effectiveness of a newly developed interproximal model to differentiate between the amount of remineralization caused by toothpastes used with or without a dual-phase gel treatment system containing calcium silicate, sodium phosphate salts and fluoride to repair acid-softened enamel. The aim of this study was to utilize the same interproximal model to identify how effective calcium silicate phosphate toothpastes are at reducing surface softening in the early stages of erosion. The model was also used to identify the effect of increasing the frequency of acid exposure on the reduction in surface hardness. METHODS: Human enamel specimens were prepared and mounted in an interproximal face-to-face arrangement and exposed to a cycling regime of whole human saliva, treatment, artificial saliva and 1% citric acid pH 3.75. Specimens were measured by surface microhardness at baseline and after three and seven days. The frequency of acid exposure was increased from 2 to 4 cycles a day for the second part of the study. RESULTS: The results showed that specimens treated with the calcium silicate phosphate toothpastes softened less than those treated with control fluoridated or non-fluoride toothpastes at each time point and following an increase in the frequency of acid exposure. SIGNIFICANCE: This work has demonstrated how an interproximal model can also be successfully used to determine differences in the erosion protection of various treatments as well as determining how they perform when the frequency of acid exposure is increased.

Establishing the Effect of Brushing and a Day's Diet on Tooth Tissue Loss in Vitro.

To develop an in vitro model to mimic the effects of meals equivalent to a day's diet on tooth tissue loss (TTL). To identify how diet effects tooth wear and to test the efficacy of dental products designed to reduce tooth wear in a more realistic environment. A typical Friday diet was devised comprising: Breakfast then brushing, lunch, dinner then brushing. Groups of enamel samples were exposed to one meal, or all three in series, a control group was exposed to water and brushed. The daily cycle was repeated to represent two days' consumption; TTL was quantified by non-contact profilometry. This pilot study highlighted adaptions that could be made to the model such as human enamel and saliva to further replicate natural eating habits. The sum of the TTL measured after Breakfast, lunch and dinner (bovine enamel specimens exposed to single meals) was less than that exhibited by the group of samples exposed to the series of meals but this difference was not significant (p = 0.09).In the absence and presence of brushing, TTL caused by breakfast and dinner was similar, but significantly greater than that caused by lunch (p < 0.05). While brushing increased TTL, this increase was not significant. It is possible to model a daily diet in vitro, and the data obtained confirms that the combination of food and drink affects the degree of TTL. This supports the further development of an in vitro model that includes alternative foodstuffs. This would aid understanding of the effects different diets have on TTL and could test new products designed to prevent TTL.

A randomised clinical trial investigating calcium sodium phosphosilicate as a dentine mineralising agent in the oral environment.

OBJECTIVE: The ability of a dentifrice containing the bioactive material calcium sodium phosphosilicate (CSPS) to remineralise the surface of dentine and physically occlude patent tubules was investigated in a 20 day in situ randomised clinical study. METHODS: Changes in surface microhardness and surface topography of dentine specimens treated for 5, 10, 15 and 20 days, twice daily with either a dentifrice containing 5% CSPS or a fluoride-only containing placebo dentifrice were compared. The substantivity of any mineral deposits formed on the surface of dentine were investigated by the application of an intra-oral dietary acid challenge twice daily during the final 10 days of treatment. RESULTS: After 5 and 10 days of treatment, the dentine samples in both treatment groups demonstrated an increase in surface microhardness. After 10 days of treatment the increase in surface hardness was directionally greater for the specimens treated with 5% CSPS dentifrice. Introducing an intra-oral acid exposure resulted in a reduction in surface microhardness which was significantly greater for the specimens treated with the placebo dentifrice compared to the dentifrice containing 5% CSPS, at day 20. Occlusion of the patent tubules was evident at each time-point and was significantly greater for the 5% CSPS containing dentifrice on days 5 and 10. On day 15 both dentifrices demonstrated the same degree of occlusion. CONCLUSION: This in situ study demonstrated that dentifrice containing 5% CSPS may have potential to mineralise and occlude the dentine in the oral environment. CLINICAL SIGNIFICANCE: This work provides evidence of potential agents that can be used to reduce the pain of dentine hypersensitivity when formulated into dentifrice and applied as part of a normal oral hygiene routine.

Introduction of an interproximal mineralisation model to measure remineralisation caused by novel formulations containing calcium silicate, sodium phosphate salts and fluoride.

OBJECTIVES: To introduce a new interproximal mineralisation model and to investigate the effectiveness of novel toothpaste and dual phase gel formulations to remineralise acid softened enamel in a simulated interproximal environment. METHODS: Specimens were positioned opposite each other with an approximately 100 µm space between enamel surfaces to simulate an interproximal environment. Target specimens were demineralised in 1% (w/v) citric acid, pH3.75. Specimens were daily immersed in artificial saliva (AS) for 1h, treated with formulations, re-immersed in AS for 6h, re-treated and re-immersed in AS for a further 1h. Study 1 evaluated prototype calcium silicate/phosphate fluoride toothpaste formulations. Study 2 evaluated novel calcium silicate/phosphate fluoride toothpaste and dual phase gel formulations. Both studies contained fluoridated and non-fluoridated controls. The surface microhardness of each target enamel block was measured following demineralisation and following days three, seven and fourteen for study one and after days one, three and seven for study two. RESULTS: This new mineralisation model was able to show increased remineralisation from calcium silicate/phosphate fluoride prototype formulations over fluoridated formulations alone, after three and seven days of treatment. Using this new model, the combined application of novel calcium silicate/phosphate fluoride toothpaste and novel calcium silicate/phosphate fluoride dual phase gel showed the greatest amount of remineralisation, which was significantly greater than sodium fluoride and non-fluoride controls. CONCLUSIONS: Employing a new interproximal mineralisation model successfully determined the remineralisation potential of novel calcium silicate/phosphate fluoride oral healthcare formulations. CLINICAL SIGNIFICANCE: Modifying a mineralisation model to include specimens positioned in an interproximal environment allows us to better understand the remineralisation potential of oral healthcare products. It is important to minimise mineral loss at interproximal sites as the enamel within these areas is thinner than the rest of the crown.