Antigingivitis efficacy of a sodium bicarbonate toothpaste: Pooled analysis.

OBJECTIVE: The objective of this study was to investigate the antigingivitis and antiplaque treatment effect of a toothpaste containing 67% w/w sodium bicarbonate, at the individual tooth site, tooth region and whole mouth (overall) level, by way of a pooled analysis of data from similarly designed clinical trials. METHODS: Six randomized controlled GSKCH clinical trials, 12-24 weeks in duration, were selected based on pre-specified criteria which included access to patient level data, pre-treatment dental prophylaxis, >20 bleeding sites and mild-moderate gingivitis at screening and use of 67% sodium bicarbonate toothpaste and non-sodium bicarbonate (regular) toothpaste (negative control) for ≥4 weeks. Efficacy outcomes comprised plaque index (TPI), modified gingival index (MGI) and gingival bleeding (bleeding index (BI), number of bleeding sites (BS)). Treatment comparisons were made using ANCOVA for whole mouth (overall) scores and by tooth site region (facial overall, lingual overall; margin/body overall, facial margin/body, lingual margin/body; papillae/interproximal overall, facial papillae/interproximal, lingual papillae/interproximal). Pooled data for BI, MGI, and TPI at individual tooth sites was plotted as a mouthmap to summarize treatment response (change from baseline) by tooth site, at the 24-week timepoint. RESULTS: For all measures, whole mouth and for all tooth regions at all post-treatment timepoints, significant (p < 0.001) differences in favour of the 67% sodium bicarbonate toothpaste compared with control were observed. At the 24-week timepoint, facial regions demonstrated greater improvements than lingual regions, with the greatest between treatment improvement seen for the facial-papillae regions for bleeding (BS/BI), facial-margin regions for MGI and facial-body regions for TPI. All individual tooth sites demonstrated numerically greater reductions from baseline for the 67% sodium bicarbonate toothpaste than the control toothpaste following 24 weeks use, with the greatest improvements (change from baseline) seen for posterior and papillae tooth sites for bleeding, margin tooth sites for MGI and body tooth sites for TPI. CONCLUSION: This pooled analysis of patient level-data, limited to GSKCH long-term gingivitis clinical studies, demonstrates that twice daily use of a 67% sodium bicarbonate toothpaste effectively removes plaque from all tooth sites, and results in clinically significant improvements in measures of gingival health, overall and for all the tooth regions investigated, compared with a non-sodium bicarbonate (regular) toothpaste following 24 weeks twice daily use.

Randomised study of intra-oral kinetics of fluoride-containing toothpastes.

OBJECTIVES: This randomised, controlled, analyst blind, crossover study aimed to evaluate and compare salivary fluoride and calcium ion concentration over 60 min following brushing with an assigned treatment and following an orange juice (OJ) or deionised (DI) water rinse 60 min post-brushing. METHODS: Study treatments, both containing 1150 ppm fluoride as NaF and 5% w/w KNO3, were the Test (including 1.2 % w/w cocamidopropyl betaine) and Comparator (including tetrasodium pyrophosphate and sodium lauryl sulphate) toothpastes. Twenty nine participants were randomised to treatment. RESULTS: A sharp increase in salivary fluoride ion concentration immediately post-brushing with either toothpaste decreased over time. Fluoride concentration following Test toothpaste use was numerically higher than the Comparator at all timepoints, with a significant difference from 10 min post-brushing (p < .05). Following the 60 min rinse, there were no significant differences between the Test or Comparator + OJ groups in salivary fluoride concentration but the Test + DI water group was significantly lower than Test (p < .001) or Comparator (p < .001) + OJ groups. A reduction in salivary calcium ion concentration was seen immediately post-brushing and after the OJ rinse with both toothpastes. Significant differences were observed in favour of the Test toothpaste at all timepoints (p < .05) and for Test and Comparator + OJ group (p < .001) compared with Test + DI water rinse. Both treatments were generally well-tolerated. CONCLUSIONS: This study demonstrated that toothpaste formulations with identical declared fluoride concentrations and the same fluoride source give rise to differing intraoral fluoride concentrations over time, which are potentially related to different formulation excipient effects. CLINICAL SIGNIFICANCE: By understanding the interaction of toothpaste formulation excipients in the oral environment, formulations can be developed that maximise retention of fluoride in the oral environment.

Effect of phytate and zinc ions on fluoride toothpaste efficacy using an in situ caries model.

OBJECTIVES: To compare and explore the dose-response of phytate-containing 1150 ppm fluoride toothpastes on model caries lesions and to determine the impact of zinc ions. METHODS: This was a single-centre, randomised, blinded (examiner/laboratory analyst), six-treatment, four-period crossover, in situ study in adults with a removable bilateral maxillary partial denture. Study treatments were toothpastes containing: 0.425% phytate/F; 0.85% phytate/F; 0.85% phytate/Zn/F; F-only; Zn/F and a 0% F placebo. Where present, F was 1150 ppm as NaF; Zn was 0.3% as ZnCl2. Human enamel specimens containing early-stage, surface-softened (A-lesions) or more advanced, subsurface (B-lesions) caries lesions were placed into the buccal flanges of participants' modified partial denture (one of each lesion type per side). A-lesions were removed after 14 days of twice-daily treatment use; B-lesions were removed after a further 14 days. A-lesions were analysed for surface microhardness recovery. Both lesion types were analysed by transverse microradiography and for enamel fluoride uptake, with B-lesions additionally analysed by quantitative light-induced fluorescence. Comparison was carried out using an analysis of covariance model. RESULTS: Statistically significant differences between 1150 ppm F and the placebo toothpastes (p < 0.05) were shown for all measures, validating the model. No differences between fluoride toothpastes were observed for any measure with little evidence of a dose-response for phytate. Study treatments were generally well-tolerated. CONCLUSIONS: Results suggest phytate has little impact on fluoride's ability to promote early-stage lesion remineralisation or prevent more advanced lesion demineralisation in this in situ caries model. Similarly, results suggest zinc ions do not impair fluoride efficacy. CLINICAL SIGNIFICANCE: Toothpastes may contain therapeutic or cosmetic agents that could interfere with fluoride's caries prevention efficacy. The present in situ caries study has demonstrated that phytate, added to provide enhanced extrinsic stain removal/prevention, and zinc, added to inhibit malodour, do not impair fluoride efficacy.

Effects of a sodium fluoride- and phytate-containing dentifrice on remineralisation of enamel erosive lesions-an in situ randomised clinical study.

OBJECTIVE: The objective of this work was to evaluate effects of a dentifrice containing sodium fluoride (1150 ppm F) and the organic polyphosphate phytate (0.85% w/w of the hexa-sodium salt) on in situ remineralisation of early enamel erosive lesions and resistance to subsequent demineralisation. MATERIALS AND METHODS: Subjects (n = 62) wore palatal appliances holding eight bovine enamel specimens with pre-formed erosive lesions. They brushed their natural teeth with the phytate test dentifrice (TD); a positive control dentifrice (PC, 1150 ppm fluoride as NaF); a reference dentifrice (RD, disodium pyrophosphate + 1100 ppm fluoride as NaF) or a negative control dentifrice (NC, fluoride-free) in a randomised, double-blind, crossover design. Specimens were removed at 2, 4 and 8 h post-brushing and exposed to an ex vivo acid challenge. Surface microhardness (Knoop) was measured at each stage. The primary efficacy variable was relative erosion resistance (RER); other variables included the surface microhardness recovery (SMHR), acid resistance ratio (ARR) and enamel fluoride uptake (EFU). RESULTS: After 4 h, the results for RER, ARR and EFU were in the order PC > TD = RD > NC with PC > TD = RD = NC for SMHR. Results at 2 and 8 h were generally consistent with the 4 h data. Mineralisation progressed over time. Dentifrices were generally well-tolerated. CONCLUSIONS: In this in situ model, addition of phytate or pyrophosphate to a fluoride dentifrice inhibited the remineralising effect of fluoride. Both formulations still delivered fluoride to the enamel and inhibited demineralisation, albeit to a lesser extent than a polyphosphate-free dentifrice. CLINICAL RELEVANCE: Addition of phytate or pyrophosphate to a fluoride dentifrice may reduce its net anti-erosive properties.

An in-situ pilot study to investigate the native clinical resistance of enamel to erosion.

OBJECTIVES: To investigate the differences in susceptibility of the surface of native and polished enamel to dietary erosion using an in-situ model. METHODS: Thirty healthy volunteers (n = 10 per group) wore mandibular appliances containing 2 native and 2 polished enamel samples for 30 min after which, the samples were exposed to either an ex-vivo or in-vivo immersion in orange juice for 5, 10 or 15 min and the cycle repeated twice with an hour's interval between them. Samples were scanned with a non-contacting laser profilometer and surface roughness was extracted from the data, together with step height and microhardness change on the polished enamel samples. RESULTS: All volunteers completed the study. For native enamel there were no statistical difference between baseline roughness values versus post erosion. Polished enamel significantly increased mean (SD) Sa roughness from baseline for each group resulting in roughness change of 0.04 (0.03), 0.06 (0.04), 0.04 (0.03), 0.06 (0.03), 0.08 (0.05) and 0.09 (0.05) µm respectively. With statistical differences between roughness change 45 min in-vivo versus 45 min ex-vivo (p < 0.05). Microhardness significantly decreased for each polished group, with statistical differences in hardness change between 30 min in-vivo versus 30 min ex-vivo (p < 0.05), 45 min in-vivo versus 30 min ex-vivo (p < 0.01), 45 min in-vivo versus 45 min ex-vivo (p < 0.01). CONCLUSIONS: The native resistance to erosion provided clinically is a combination of the ultrastructure of outer enamel, protection from the salivary pellicle and the overall effects of the oral environment. CLINICALTRIALS. GOV IDENTIFIER: NCT03178968. CLINICAL SIGNIFICANCE: This study demonstrates that outer enamel is innately more resistant to erosion which is clinically relevant as once there has been structural breakdown at this level the effects of erosive wear will be accelerated.

A randomised clinical evaluation of a fluoride mouthrinse and dentifrice in an in situ caries model.

OBJECTIVES: Fluoride mouthrinses provide advantages for fluoride delivery by maintaining elevated intra-oral fluoride concentrations following fluoride dentifrice use. This in situ caries study investigated potential anti-caries efficacy of a 220 ppm fluoride mouthrinse. METHODS: This was an analyst-blinded, four-treatment, randomised, crossover study using partially demineralised, gauze-wrapped, human enamel samples mounted in a mandibular partial denture. Participants brushed twice daily for 14 days with either a 1150 ppm fluoride or a fluoride-free placebo dentifrice and either rinsed once daily with the 220 ppm fluoride mouthrinse or not. Following each treatment period, percent surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU) were assessed. RESULTS: Fifty three participants completed the study. Compared with the placebo dentifrice/no rinse treatment, the fluoride-containing regimens demonstrated greater enamel remineralisation (%SMHR) and fluoridation (EFU): fluoride dentifrice/fluoride rinse (%SMHR difference: 21.55 [95% CI: 15.78,27.32]; EFU difference 8.35 [7.21,9.29]); fluoride dentifrice/no rinse: 19.48 [13.81,25.15]; 6.47 [5.35,7.60]; placebo dentifrice/fluoride rinse: 16.76 [11.06,22.45]; 5.87 [4.72,7.00] (all P < .0001). There were no significant differences in%SMHR between fluoride regimens. The fluoride dentifrice/fluoride rinse regimen was associated with higher EFU than the fluoride dentifrice/no rinse (1.88 [0.75,3.01], P = .0013) and placebo dentifrice/fluoride rinse regimens (2.48 [1.34,3.62], P < .0001). Treatments were generally well-tolerated. CONCLUSIONS: The in situ caries model demonstrated that the fluoride mouthrinse is effective in promoting enamel caries lesion remineralisation and fluoridation whether used following a fluoride or non-fluoride dentifrice. Additive (potential) anti-caries benefits of a fluoride rinse after a fluoride dentifrice were confined to enhancements in lesion fluoridation (EFU). CLINICAL SIGNIFICANCE: In conjunction with a fluoride dentifrice, fluoride mouthrinses enhance enamel fluoridation, which may be useful in caries prevention.

Randomized Clinical Dose-Response Study to Evaluate Plaque Removal by Three Experimental Sodium Bicarbonate Toothpastes Using a Single Brushing Model.

OBJECTIVES: This randomized, examiner-blind, crossover clinical study compared the plaque removal efficacy of three experimental toothpastes containing 20%, 35%, and 50% w/w sodium bicarbonate (NaHCO3) with commercial toothpastes containing 67% and 0% w/w NaHCO3 (positive and negative controls, respectively). METHODS: Fifty-six adults with a mean Turesky Modification of the Quigley-Hein Plaque Index (TPI) score of = 2.00 at screening and at the first treatment visit (pre-brushing) were randomized to a supervised single, timed (one minute) brushing with a 0%, 20%, 35%, 50%, or 67% w/w NaHCO3-containingtoothpaste. TPI was measured pre- and post-brushing. Participants completed five treatment visits, separated by a four- to six-day washout, and brushed once with each toothpaste. The primary efficacy analysis was change in whole mouth TPI score from pre- to post-brushing between the positive and negative control toothpastes (validation step). Secondary analyses were comparisons between each experimental toothpaste and the control toothpastes. Change in TPI score was analyzed using a mixed effect analysis of covariance. RESULTS: The difference in adjusted mean TPI change from pre- to post-brushing between the 67% and 0% w/w NaHCO3 toothpastes was -0.01 points (95% CI -0.06, 0.04), with no statistically significant difference between them (p = 0.6674). As such, study validity was not attained. Differences in adjusted mean change from pre- to post-brushing between each experimental toothpaste and the positive and negative controls ranged from 0.00 to -0.02 points. Twenty-two treatment-emergent, treatment-related adverse events, all oral, were reported by 17 participants (30.4%). These were spread uniformly across test toothpastes and controls. No serious adverse events were reported. CONCLUSIONS: There was no statistically significant difference in change in mean TPI score between toothpastes containing 67% w/w NaHCO3 and 0% w/w NaHCO3 following a single timed brushing. This unexpected observation may be attributed to lower than expected reduction in overall plaque and a possible Hawthorne effect. As study validation was not met, no further conclusions can be made. The study products were generally well tolerated.

Measurement of surface roughness changes of unpolished and polished enamel following erosion.

OBJECTIVES: To determine if Sa roughness data from measuring one central location of unpolished and polished enamel were representative of the overall surfaces before and after erosion. METHODS: Twenty human enamel sections (4x4 mm) were embedded in bis-acryl composite and randomised to either a native or polishing enamel preparation protocol. Enamel samples were subjected to an acid challenge (15 minutes 100 mL orange juice, pH 3.2, titratable acidity 41.3mmol OH/L, 62.5 rpm agitation, repeated for three cycles). Median (IQR) surface roughness [Sa] was measured at baseline and after erosion from both a centralised cluster and four peripheral clusters. Within each cluster, five smaller areas (0.04 mm2) provided the Sa roughness data. RESULTS: For both unpolished and polished enamel samples there were no significant differences between measuring one central cluster or four peripheral clusters, before and after erosion. For unpolished enamel the single central cluster had a median (IQR) Sa roughness of 1.45 (2.58) µm and the four peripheral clusters had a median (IQR) of 1.32 (4.86) µm before erosion; after erosion there were statistically significant reductions to 0.38 (0.35) µm and 0.34 (0.49) µm respectively (p<0.0001). Polished enamel had a median (IQR) Sa roughness 0.04 (0.17) µm for the single central cluster and 0.05 (0.15) µm for the four peripheral clusters which statistically significantly increased after erosion to 0.27 (0.08) µm for both (p<0.0001). CONCLUSION: Measuring one central cluster of unpolished and polished enamel was representative of the overall enamel surface roughness, before and after erosion.

Anticaries Potential of a Sodium Monofluorophosphate Dentifrice Containing Calcium Sodium Phosphosilicate: Exploratory in situ Randomized Trial.

Calcium sodium phosphosilicate (CSPS) is a bioactive glass material that alleviates dentin hypersensitivity and is postulated to confer remineralization of caries lesions. This single-centre, randomized, single (investigator)-blind, placebo-controlled, crossover, in situ study explored whether the addition of 5% CSPS to a nonaqueous fluoride (F) such as sodium monofluorophosphate (SMFP)-containing dentifrice affects its cariostatic ability. Seventy-seven subjects wore 4 gauze-covered enamel specimens with preformed lesions (2 surface-softened and 2 subsurface) placed buccally on their mandibular bilateral dentures for up to 4 weeks. Subjects brushed twice daily with 1 of the 5 study dentifrices: 927 ppm F/5% CSPS, 927 ppm F/0% CSPS, 250 ppm F/0% CSPS, 0 ppm F/5% CSPS, or 0 ppm F/0% CSPS. Specimens were retrieved after either 21 (surface-softened lesions; analyzed by Knoop surface microhardness [SMH]) or 28 days (subsurface lesions; analyzed by transverse microradiography). The enamel fluoride uptake was determined for all specimens using a microbiopsy technique. The concentrations of fluoride and calcium in gauze-retrieved plaque were also evaluated. Higher dentifrice fluoride concentrations led to greater remineralization and fluoridation of both lesion types and increased plaque fluoride concentrations. CSPS did not improve the cariostatic properties of SMFP; there were no statistically significant differences between 927 ppm F/5% CSPS and 927 ppm F/0% CSPS in percent SMH recovery (p = 0.6788), change in integrated mineral loss (p = 0.5908), or lesion depth (p = 0.6622). Likewise, 0 ppm F/5% CSPS did not provide any benefits in comparison to 0 ppm F/0% CSPS. In conclusion, CSPS does not negatively impact nor does it improve the ability of an SMFP dentifrice to affect remineralization of caries lesions.

Three randomized clinical trials to assess the short-term efficacy of anhydrous 0.454% w/w stannous fluoride dentifrices for the relief of dentin hypersensitivity.

PURPOSE: To assess the short-term efficacy of dentifrices containing 0.454% weight/weight (w/w) stannous fluoride applied using a focused brushing methodology for the relief of dentin hypersensitivity (DH). METHODS: Three randomized, examiner blind, controlled, two treatment arm, parallel group studies were conducted utilizing a novel application method in which, prior to brushing the whole mouth, the stannous fluoride dentifrice was applied to two sensitive teeth by focused brushing. DH was assessed with an evaporative (air) stimulus (with the Schiff Sensitivity Scale and a Visual Analogue Scale [VAS, Studies 1 and 3 only]) and a tactile stimulus (using a Yeaple Probe). Clinical assessments were made at baseline, immediately after first use of study dentifrice and after 3 and 14 days of twice daily brushing. Study 1 compared a marketed 0.454% w/w stannous fluoride dentifrice indicated for short-term DH relief to a marketed standard fluoride dentifrice (negative control). Studies 2 and 3 compared a novel anhydrous 0.454% w/w stannous fluoride dentifrice to the same negative control. RESULTS: For Studies 1, 2 and 3, 118, 113 and 120 subjects respectively were randomized to treatment and included in the intent-to-treat populations. Study 1 showed significant DH improvements in all measures for the test dentifrice compared to the negative control at Day 14. Study 2 showed significant differences in favor of the test dentifrice for all measures at all time points (Immediate, Days 3 and 14). In Study 3, treatment with both test and control dentifrices resulted in significant improvements over baseline, but there were no significant between-treatment differences. While these studies provide evidence for relief of DH with 0.454% w/w stannous fluoride dentifrices after short-term use (14 days) using a novel focused brushing methodology, the evidence, especially at the earliest time points, is inconclusive and further testing is needed. Study dentifrices were well tolerated. ClinicalTrials.gov trial registration numbers: Study 1 NCT01494649; Study 2: NCT01592851; Study 3: NCT01724008; funded by GSK Consumer Healthcare.

Strontium effects on root dentin tubule occlusion and nanomechanical properties.

OBJECTIVES: Dentin hypersensitivity often is treated by promotion of dentin tubule occlusion. In this in vitro study we evaluated nanomechanical properties and degree of tubule occlusion conferred to sound and demineralized human root dentin following treatment with a 10% (w/w) strontium acetate solution and its relation to the treatment duration and delivery method. METHODS: 24 human cervical root dentin disks (8 groups of 3) were polished through 0.25 µm. 12 disks were subjected to an acid challenge (1% citric acid, pH 3.8) for 2 min. The specimens were incubated in artificial saliva, treated by soaking or brushing with deionized (DI) water or a solution of 10% strontium acetate for 2 min twice a day for 28 days. The occlusion percent and nanomechanical properties were determined at the baseline, 5, 14 and 28 days. Cross-sectioned specimens were prepared to evaluate the depth affected by strontium acetate / dentin interaction by SEM. Statistical analysis was performed using linear mixed effects models. RESULTS: A 10% strontium acetate treatment over 5-28 days significantly increased tubule occlusion for normal root dentin and to a lesser extent for demineralized dentin and increased the AFM based nanomechanical properties of demineralized dentin. Brushing was more effective than soaking in recovery of properties of demineralized dentin when treated with strontium. No difference in tubuleocclusion was found between the two delivery methods. SIGNIFICANCE: Strontium acetate itself proved to have the ability to occlude dentin tubules and result in small changes in the mechanical properties of dentin.

Confirmation of efficacy in providing relief from the pain of dentin hypersensitivity of an anhydrous dentifrice containing 0.454% with or without stannous fluoride in an 8-week randomized clinical trial.

PURPOSE: To compare the efficacy of an anhydrous dentifrice containing 0.454% w/w stannous fluoride and a negative control dentifrice containing 1,000 ppm fluoride, as sodium monofluorophosphate, at reducing dentin hypersensitivity over 8 weeks with twice-daily brushing. METHODS: This was a randomized, examiner-blind, parallel, two treatment group, stratified (by maximum baseline Schiff sensitivity score), 8-week clinical study carried out at a single site in 119 healthy subjects with at least two sensitive teeth, who met all study criteria at the screening and baseline visits. Clinical assessments of sensitivity to evaporative (air) [with Schiff sensitivity score and visual analogue scale (VAS)] and tactile (Yeaple probe) stimuli were employed to compare the efficacy of the test dentifrice containing 0.454% w/w stannous fluoride to the negative control dentifrice at reducing sensitivity after 4 and 8 weeks treatment. RESULTS: Of the 119 subjects randomized to study treatment, 113 completed the study. At 4 and 8 weeks, between treatment analyses found the test dentifrice to be significantly better than the negative control dentifrice in relieving dentin hypersensitivity for all measures (Schiff: P < 0.0001 at 4 and 8 weeks; VAS score: P = 0.0003 at 4 weeks, P < 0.0001 at 8 weeks; tactile threshold: P = 0.0138 at 4 weeks, P < 0.0001 at 8 weeks).

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.

A comparative in vitro study investigating the occlusion and mineralization properties of commercial toothpastes in a four-day dentin disc model.

OBJECTIVE: The objective of this study was to evaluate the relative level of dentin tubule occlusion and dentin mineralization conferred by a 5% w/w calcium sodium phosphosilicate (45S5)/1450 ppm fluoride toothpaste in comparison to a range of commercial toothpastes reported to occlude dentin tubules. METHODS: Two separate experiments were employed to (i) determine the level of dentin tubule occlusion, and (ii) explore the change in dentin mineralization conferred by a number of marketed toothpastes and controls, following twice-daily brushing in a longitudinal, acid challenge-based, dentin disc model. In Study I, 192 bovine dentin discs, polished and etched in citric acid to provide a smooth dentin surface with patent tubules, were divided into eight treatment groups and subjected to brushing with one of seven test toothpastes or deionized water over four days. Prior to and between treatments, the dentin samples were stored in saliva. The test products were fluoridated toothpastes containing: calcium sodium phosphosilicate (45S5); strontium acetate; arginine/calcium carbonate; amine fluoride; calcium sulphate/diphosphate; stannous fluoride; casein stabilized amorphous calcium phosphate toothpaste; and a non-occluding negative control, deionized water. At the end of each treatment day (1 though 4), one group of samples was removed for scanning electron microscopy (SEM) analysis and graded on a categorical visual scale to assess the level of dentin tubule occlusion. A subset of samples from Study I was also cross-sectioned and examined using SEM. For the exploratory mineralization study (Study II), 120 dentin specimens were prepared as previously described and divided into four treatment groups consisting of A, C, F, and a tooth sealant varnish (I), and subjected to the treatment regimen described in Study I. The dentin samples were assessed for changes in surface microhardness using an indenter fitted with a Knoop probe and the level of dentin occlusion. RESULTS: In Study I, the 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste (A), the stannous fluoride-containing toothpaste (F), and the strontium acetate-containing toothpaste (B) delivered the highest level of occlusion following four days of twice-daily brushing and a twice-daily acid challenge on days 3 and 4. Surface analysis of a subset of Study I samples, following four days of treatment, indicated that the 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste formed a distinct layer at the surface of dentin. For Study II, surface microhardness analysis revealed that the 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste (A) delivered significantly more surface hardening then the control or competitor toothpastes on days 2 and 4. CONCLUSION: Desensitizing toothpastes reported to operate by an occlusion mechanism have been observed to confer varying degrees of dentin tubule occlusion and dentin mineralization over four days in an acid challenge-based in vitro model. A 5% w/w calcium sodium phosphosilicate/1450 ppm fluoride-containing toothpaste was observed to impart a significant level of dentin tubule occlusion and surface hardening, and form durable occlusive deposits following four days of twice-daily brushing in vitro.

An in vitro investigation of two currently marketed dentin tubule occlusion dentifrices.

OBJECTIVE: The objective of this study was to evaluate the relative level of dentin tubule occlusion afforded by two dentifrices specifically developed to occlude dentin tubules, following finger-applied dab-on application and by repeated brushing, in a longitudinal acid-challenge-based dentin disk model. The impact of a dietary acid alone (grapefruit juice) on the level of dentin tubule occlusion conferred by each product following dab-on application was also explored in a separate short-term stand-alone exploratory dentin disk-based in vitro study. METHODS: For the longitudinal study, 120 bovine dentin discs, polished and etched in citric acid for two minutes to provide a smooth dentin surface with patent tubules, were divided into three treatment groups and subjected to a finger application of the dentifrice only, or a combination of finger application and brushing. Prior to and between treatments, the dentin samples were stored in saliva (for > 60 minutes). The test products were an 8% w/w strontium acetate dentifrice (currently marketed as Sensodyne Rapid Relief), an arginine-based dentifrice (marketed as Colgate Sensitive Pro-Relief), and deionized water. For the exploratory acid resistance study, 24 dentin samples were divided into two treatment groups. Treatment consisted of a single dab-on application with the test dentifrices to the hydrated surface of dentin, followed by exposure to either a 30-second or 10-minute grapefruit juice acid challenge. For both models, at the end of each treatment period, the samples were removed for scanning electron microscopy analysis and graded on a categorical visual scale. All data were analyzed statistically by unpaired t-test comparison. RESULTS: In the longitudinal (four-day) model, the strontium acetate-based dentifrice occluded dentin tubules significantly better than the currently marketed arginine-based dentifrice post-dab-on treatment and grapefruit juice challenge (p < 0.0001). At all other time points, the strontium acetate dentifrice demonstrated significantly better occlusion than the arginine-based dentifrice (p < or = 0.0001). In the exploratory acid resistance model, the level of occlusion observed for the strontium acetate dentifrice was statistically significantly greater when compared to the arginine dentifrice following 10-second and 10-minute (p < 0.0001) exposures to grapefruit juice. CONCLUSION: A strontium acetate dentifrice is observed to deliver statistically significantly greater levels of dentin tubule occlusion when compared to the arginine dentifrice following dab-on and brushing application under dietary acid-challenge conditions in this in vitro model. This study suggests that the arginine-containing dentifrice may be more susceptible to acid-mediated dissolution than the strontium-based dentifrice under the conditions employed in this in vitro model.

Development of an acid challenge-based in vitro dentin disc occlusion model.

OBJECTIVE: The objective of this study was to evaluate the utility of a novel acid challenge-based dentin disc occlusion model, and to compare the occluding effect and acid resistance exhibited by currently marketed occlusion dentifrices in vitro. METHODS: Ninety-six bovine dentin discs were polished and etched in citric acid (6% w/w) for two minutes to provide a smooth dentin surface with patent tubules. The discs were divided into three treatment groups. Each treatment group was brushed (Oral-B Vitality Precision Clean/EB 17 FlexiSoft head) twice a day, for up to four days, with either a strontium acetate dentifrice (Sensodyne Rapid Relief), an arginine-based dentifrice (Colgate Sensitive Pro-Relief), or water. Prior to and between treatments, the dentin samples were stored in human saliva. On days 3 and 4, following dentifrice treatment and incubation in saliva (60 minutes), the samples were subjected to a grapefruit juice challenge. Eight samples from each treatment group were removed from the study on each day and analyzed by scanning electron microscopy (SEM). The SEM images were graded according to a categorical occlusion scale, and the data were analyzed by ANOVA. RESULTS: The strontium acetate dentifrice occluded dentin tubules significantly better than the negative control (water) on days 1 through 4 (day 4 p < or = 0.0001). The marketed occlusion-based dentifrices demonstrated various degrees of dentin tubule occlusion over the four days. The strontium acetate dentifrice demonstrated significantly better occlusion than a currently marketed arginine-based occlusion dentifrice on day 1 (p = 0.0337), day 2 (p = 0.0021 ), and day 4 (p < or = 0.0001). CONCLUSION: An in vitro model has been developed that can differentiate the dentin tubular occlusive effects of currently marketed occlusion dentifrices. Surface analysis reveals that the occluding deposits vary according to product, and that some are more susceptible to acid mediated dissolution.

Initial stages of enamel erosion: An in situ atomic force microscopy study.

Time-resolved in situ atomic force microscopy has been employed to examine erosion progression in untreated and fluoride-treated enamel specimens during exposure to citric acid. Contact with the acidic reaction solution initiated the emergence and growth of dissolution pits in both the native and the fluoride-treated enamel. In native enamel, pits are first observed after 90 min exposure to the reaction solution, compared to 250 min in the case of the fluoride-treated enamel. These findings indicate that, within the constraints of this study, a single application of fluoride solution (1000 mg/L, 2 min) confers protection to the enamel surface against acid-mediated erosion. This paper also highlights the potential role intrinsic defects may have on the susceptibility of enamel to erosion and, in part, may explain why some people are more susceptible to acid erosion.

Advances in methodologies to characterize dentine and dentine hypersensitivity treatments in vitro.

The aim of this paper is to highlight recent advances in the development of analytical and in vitro methodologies to assess the potential efficacy of dentine hypersensitivity treatments. The paper will cover the utility of X-ray computed nanotomography, secondary ion mass spectrometry, dynamic laser scanning confocal microscopy, and x-ray microtomography in the context of characterizing dentine, understanding the permeability and mass transport properties of dentine, and exploring the mechanism of action for purported hypersensitivity treatments. It will be shown that X-ray tomography, secondary ion mass spectrometry, and dynamic fluid flow confocal microscopy provide unsurpassed information pertaining to the ultra-structural and mass transport properties of dentine, properties that underpin the hydrodynamic theory and the therapeutic route for desensitizing treatments. The paper concludes that advances in analytical instrumentation and in vitro methodologies have improved our understanding of the ultra-structural and chemical properties of dentine, mass transport within dentine, and the quality and predictive value of in vitro models. Such understandings aid the development of efficacious dentifrice formulations to treat dentine hypersensitivity.

Diffusive transport within dentinal tubules: an X-ray microtomographic study.

The hydrodynamic theory of dentine hypersensitivity proposes that external stimuli cause dentinal fluid movement within dentinal tubules thereby triggering mechanosensitive nerves and eliciting a pain response. The aim of this study was to employ X-ray microtomography (XMT) to monitor diffusion of caesium acetate through dentine to investigate the extent to which transport occurs within the primary tubules compared to that through branched microtubules believed to run perpendicular to the direction of the primary dentinal tubules. 2.0-mm thick coronal dentine disks masked to leave half of the upper surface exposed were imaged by XMT, initially in water, which was then replaced with an aqueous solution of 0.50 mol l(-1) caesium acetate. Further XMT images were acquired after 1 and 6 days immersion. The XMT images were used to measure the change in the X-ray linear attenuation coefficient resulting from caesium acetate ingress into dentine. There was clearly considerable ingress of caesium acetate into the dentine lying below the exposed surface, but considerably less beneath the sealed surface, suggesting that diffusive transport occurs predominantly in the direction of the primary dentinal tubules, with no significant lateral transport. Primary tubules are clearly the dominant transmission route for triggering the mechanosensitive nerves present at the dentine-pulp interface, and for delivery of nerve desensitising agents.

High-resolution non-destructive 3D interrogation of dentin using X-ray nanotomography.

OBJECTIVES: Dentin, a calcareous material sandwiched between the pulp and the enamel in the tooth structure contains highly orientated tubules. As a result of enamel erosion, gum recession, physical trauma or caries the dentin tubules can become patent to the oral cavity. It has been demonstrated in vivo that dentinal fluid flows out of the tubule lumen into the oral cavity and it has been postulated that alterations in fluid flow form the basis of dentin hypersensitivity. In order to better understand the mode of action of desensitising occlusion-based agents the ability to interrogate dentin non-destructively is paramount. Destructive analysis of the tooth structure may yield subtle artifacts leading to erroneous conclusions or inhibit the accurate assessment of the relationship between an occluding agent and the internal dentin morphology. This paper describes the use of a novel and accessible, non-invasive, high-focused X-ray computer tomographic technique for analysis of the dentin substructure. METHODS: Dentin slices, ca. 300microm3 in size, were taken from the coronal section of unerupted human third molars and etched in citric acid to reveal the open tubule structure. Samples were analyzed, in their dry state, using the Skyscan 2011 nanoCT system. RESULTS: Numerous, homogeneously dispersed elliptical features, distinguished by their contrast and hence low-mineral density, were observed. These features are observed to be approximately 2-5microm in diameter at a density equivalent to 10(6)cm(-2). 2D CT re-slices demonstrate that these circular features form highly orientated cylindrical manifestations extending throughout the sample. SIGNIFICANCE: Ultra-high-resolution X-ray computed tomography has been shown to be a powerful new technique for interrogating the submicron tubular structure of dentin non-destructively.