Effects of Calcium and Phosphate on Dissolution of Enamel, Dentin and Hydroxyapatite in Citric Acid.

The aim was to evaluate the effect of dissolved calcium and phosphate on dissolution rate of enamel, dentin and compressed hydroxyapatite (HA) in citric acid solution as a function of pH. At pH 2.5, dissolution rate of enamel increased significantly by 6% in 20 mmol/L added calcium but, otherwise, dissolution rates of neither enamel, dentin nor HA were significantly affected by 10 or 20 mmol/L calcium. However, enamel dissolution rate was reduced by > 50 mmol/L calcium. At pH 3.25 and 4.0, 10-20 mmol/L calcium inhibited dissolution of enamel by 29-100% and HA by 65-75% but did not affect dentin dissolution. Phosphate (10 or 20 mmol/L) did not inhibit dissolution of enamel, dentin or HA at any pH, but there were increases in dissolution rate of all three substrates at pH 2.5 and, in one test with dentine (at 20 mmol/L phosphate), at pH 3.25. The results suggest that calcium addition to soft drinks and other acidic products such as medications may reduce erosivity against enamel, provided that pH is not too low; that phosphate would not reduce erosivity against enamel; and that neither calcium nor phosphate at these concentrations would reduce erosivity against dentin.

Randomised controlled trial of a microneedle patch with a topical anaesthetic for relieving the pain of dental injections.

OBJECTIVES: To determine whether a microneedle patch combined with 5% topical lidocaine reduces dental injection pain more than a patch without microneedles combined with 5% topical lidocaine. METHODS: This proof of principle randomised, two-treatment, double-blind, crossover split-unit design study in 16 healthy participants investigated levels of perceived pain from 3 increasing pain provoking challenges, when topical 5% lidocaine dental gel was applied to the oral mucosa with a microneedle patch and a patch with no microneedles, prior to infiltration with local anaesthesia on 2 visits. Pain was assessed by visual analogue scale (VAS) and 4-point verbal rating scale (VRS). RESULTS: 15 participants completed the study. Mean pain scores, lower at buccal sites, increased in both groups across challenges 1-3: Test palatal 5.1, 11.9, 26.8; buccal 0.7, 2.8, 18.3; Control palatal 12.3, 18.7, 39.5; buccal 4.0, 6.9, 30.6. The microneedle patch plus lidocaine significantly lowered VAS pain scores at both sites for all challenges, the biggest mean difference seen palatally after challenge 3 (12.7, p < 0.001). VRS pain scores were also significantly reduced for test compared to control for all 3 challenges (p = 0.014). Buccal scores favoured the microneedle patch, significantly for pain challenge 3 (p = 0.025). No adverse events occurred. CONCLUSIONS: Prior oral application of a microneedle patch combined with 5% topical lidocaine gel reduced the pain experienced from dental infiltration. Microneedle patch use in the dental setting offers the prospect of improving degree and depth of anaesthesia from topically applied anaesthetic gel, without itself causing any pain. CLINICAL SIGNIFICANCE: Dental injections are associated with fear and anxiety. Application of a microneedle patch, combined with topical anaesthetic, to the oral mucosa prior to delivery of the injection reduces the pain from this dental procedure. This novel technique may allay patients' apprehension of local anaesthesia and improve quality of life outcomes.

The interactions between attrition, abrasion and erosion in tooth wear.

Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Knowledge of these tooth wear processes and their interactions is reviewed. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence is insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear, especially through formation of pellicle, but cannot prevent it.

A randomised crossover trial to compare the potential of stannous fluoride and essential oil mouth rinses to induce tooth and tongue staining.

This study compared the staining potential of two experimental amine fluoride/stannous fluoride mouth rinses (A and B), a phenolic/essential oil rinse (C) and a negative control, water, rinse (D). The study was a single centre, randomized, single-blind, four treatment crossover study design among healthy participants. Prior to each study period, participants received a dental prophylaxis. On the Monday of each period, subjects suspended oral hygiene, and under supervision, rinsed with the allocated mouth rinse immediately followed by a warm black tea solution at hourly intervals eight times a day for 4 days. On Friday, the area and intensity of staining on the teeth, the primary outcome measure and dorsum of tongue were assessed. This regimen was repeated for all the three subsequent treatment periods. Rinse B produced less stain than rinse A, but the difference was not significant (p = 0.20). Rinse B produced significantly more stain than rinse C (p < 0.05) and D (p < 0.001). For tongue staining, rinse B produced significantly more staining than D (p < 0.01) but not A or C. Overall, all test rinses produced more staining than placebo with an overall pattern for more staining with stannous formulations. Individuals using stannous or phenolic/essential oil mouth rinse formulations should be advised of the possible staining side effect and that this can be easily removed by a professional dental cleaning.

Inhibition of hydroxyapatite dissolution by whole casein: the effects of pH, protein concentration, calcium, and ionic strength.

Formulating drinks with reduced erosive potential is one approach for reducing dental erosion. In this study, whole casein was added to citric acid solutions representative of soft drinks, and the hydroxyapatite dissolution rate was assessed. Adding 0.02% (w/v) casein to acid solutions significantly reduced the hydroxyapatite dissolution rate by 51 +/- 4% at pH values of 2.80, 3.00, 3.20, 3.40, and 3.60, although the baseline dissolution rates of course varied as a function of pH. The protein concentration [0.002, 0.02, and 0.2% (w/v) casein] had no significant effect on dissolution inhibition. Adding both casein and calcium to citric acid resulted in a further reduction in the dissolution rate at low and intermediate calcium concentrations (5 and 10 mM) but not at higher calcium concentrations (20 and 50 mM). Ionic strength had no significant impact on the efficacy of casein. Casein also significantly reduced the hydroxyapatite dissolution rate when the hydroxyapatite was coated with a salivary pellicle. The reduction in dissolution rate is ascribed to firmly adsorbed casein on the hydroxyapatite surface, which stabilizes the crystal surface and inhibits ion detachment.

Meta-analyses of studies of 0.2% delmopinol mouth rinse as an adjunct to gingival health and plaque control measures.

BACKGROUND: Delmopinol is a third-generation anti-plaque agent used as a mouthwash to reduce plaque and alleviate gingivitis. OBJECTIVE: To create an overview of the anti-plaque efficacy of 0.2% delmopinol as an adjunct to normal oral hygiene measures by meta-analysis of completed clinical trials. MATERIALS AND METHODS: Eight double-blind, parallel-group studies were identified. Study durations ranged from 8 to 24 weeks. Five studies (n=913) involved supervised rinsing; three studies (n=467) involved unsupervised rinsing. These sets of trials were analysed separately and in combination. Efficacy outcomes comprised modified plaque index, modified gingival index (MGI) and gingival bleeding on probing (BOP). RESULTS: Delmopinol 0.2% was superior to placebo for the reduction of plaque scores in both sets of studies. Effects on MGI and BOP were also better with delmopinol 0.2% than with placebo. In most instances, 95% confidence intervals were wholly in favour of delmopinol. Pooled analysis of all eight studies confirmed statistically significant effects of delmopinol 0.2% compared with placebo (p<0.00001). Delmopinol met the efficacy criteria of the American Dental Association in studies of extended duration. CONCLUSION: Delmopinol 0.2% mouthwash is effective as an adjunct measure for reducing plaque burden and indices of gingivitis, whether or not it is used under supervision.

Tooth brushing, tooth wear and dentine hypersensitivity--are they associated?

Evidence suggests that patients suffer the painful symptoms of dentine hypersensitivity when dentine is exposed and the dentinal tubule system is opened to the oral cavity to allow stimuli to trigger a neural response in the pulp via a hydrodynamic mechanism. The processes needed to localise lesions of dentine hypersensitivity include loss of enamel and/or gingival recession. Whilst tooth brushing with or without toothpaste appears to cause minimal wear to enamel (in the absence of acids), circumstantial evidence implicates tooth brushing with gingival recession and exposure of dentine. Other tooth wear processes, notably attrition and acid erosion, cause loss of enamel and can expose dentine. Therefore, sensitivity may result. How lesions of dentine hypersensitivity are initiated is a matter of conjecture and based on extrapolating data from studies, mainly in vitro, to effect in vivo. Again, this circumstantial type of evidence suggests that abrasion by some toothpastes and erosion by dietary acid could open the tubule system. Little is known about the actual effect of de-sensitising toothpastes on lesions of dentine hypersensitivity even though they are formulated to either occlude dentinal tubules or block the neural response in the pulp. Clinical studies have produced contradictory findings for the efficacy of products and there have been extremely few evidence-based reviews. In conclusion, available evidence supports a probable link of tooth brushing, with or without toothpaste and an acidic diet, to both tooth wear and dentine hypersensitivity, and also suggests that dentine hypersensitivity is a tooth wear phenomenon. Although there is a need for more direct clinical and scientific evidence for these associations, it is recommended that they be taken into consideration when planning management strategies for the dentine hypersensitivity sufferer.

Tooth bleaching by different concentrations of carbamide peroxide and hydrogen peroxide whitening strips: an in vitro study.

OBJECTIVE: To investigate the tooth whitening effects of various concentrations of carbamide peroxide (CP) gels and 6% hydrogen peroxide (HP) whitening strips used on an intrinsic, in vitro stain model in a simulated home-applied bleaching protocol. METHOD: Extracted third molars were sectioned and stained to Vita shade C4 using a standardized tea solution. Stained specimens were then bleached with 10, 15, 20, 22, and 30% CP gels applied in custom-made trays for 8-hour sessions for 14 days. A 6% HP whitening strip product was also tested in a regimen of twice-daily 30-minute treatments for 14 days. Shades were assessed at baseline and at 2, 5, 7, 10, and 14 days of treatment using a shade guide (SG) and a shade vision system (SVS), recorded as shade guide unit (SGU) changes from baseline, and CIE L*a*b* recordings using a chromometer. RESULTS: By day 14, all CP treatments resulted in at least 12 SGU improvements by SG and SVS methods: the HP treatment mean was just less than 12 SGU. With the chromometer, the CP improvements ranged from approximately 19 to 28 units and 16 units for the HP whitening strips. Observationally, by SG and SVS, CP treatments achieved the maximum improvement (12-13 SGU) at different time points: day 5 for 30% CP, day 10 for 22% CP, and day 14 for the other three treatments. SG and SVS data were virtually binary, switching from 0 to scores of 9 or above as bleaching progressed. The differences between the six treatments in the mean day to achieve a positive SG or SVS score (9 or more units) approached significance. For each of the SG, SVS, and L*a*b* scores, the dose-response correlation with CP concentration was significant at one or more assessment times. SG and SVS showed extremely strong agreement in detecting change and substantial agreement with L*a*b*. CONCLUSION: This in vitro study supports the limited data available from the very few available randomized controlled clinical trials indicating that CP and HP home-use bleaching systems can achieve considerable tooth whitening outcomes, albeit at different rates, which appear to be concentration dependent. CLINICAL SIGNIFICANCE: There is a clear significant relationship for both concentration and duration of exposure for CP bleaching agents. The final shade change is independent of the concentration of bleaching agent, with time as the dominant variable. Higher concentrations of CP that have not been investigated previously may be a treatment option for esthetic improvement of shade where time is at a premium, but caution must be exercised in view of the possible increased incidence of sensitivity.

An investigation of some food-approved polymers as agents to inhibit hydroxyapatite dissolution.

Dental erosion involves dissolution of the hydroxyapatite fraction of enamel and dentine, so agents that reduce the dissolution rate of hydroxyapatite could find application in food products aimed at reducing erosion. This study was performed to test some common food ingredients and additives for their effect on the dissolution rate of hydroxyapatite in a citric acid solution representative of soft drinks. Pyrophosphate, tripolyphosphate and a linear chain polyphosphate (average 25 phosphate units) significantly reduced the hydroxyapatite dissolution rate by 35, 46 and 64%, respectively. Xanthan gum and carboxymethylcellulose significantly reduced the hydroxyapatite dissolution rate by 29 and 16%, respectively. The protective effect may be ascribed to the binding of condensed phosphate or to the formation of an adsorbed layer of gum at the hydroxyapatite surface. Several other common food additives had no statistically significant effect on the hydroxyapatite dissolution rate. Polyphosphate exhibited a considerable persistence of action, causing a reduction in the dissolution rate for 3 h after treatment. Tripolyphosphate was slightly persistent, and pyrophosphate and xanthan gum did not exhibit a substantial persistence of action. A solution containing polyphosphate and xanthan gum reduced the hydroxyapatite dissolution rate by 70% and exhibited a similar persistence of action to the solution containing only polyphosphate. These compounds are suggested to have potential as erosion-reducing agents in soft drinks.

Comparison of three in-office bleaching systems based on 35% hydrogen peroxide with different light activators.

PURPOSE: To compare in vitro the bleaching effects obtained with and without the use of the various lights on power bleaching systems. METHODS: 19 groups of five tooth specimens were prepared and allocated randomly to treatments. Only specimens with shade C4 were accepted for the study. Three commercial bleaching products all based on 35% hydrogen peroxide were used with and without four different light sources. Shade assessments were made using a Shade Guide (SG), Shade Vision System (SVS) and chromometer. RESULTS: For SG, all but the light only treatment resulted in measurable improvement in shade ranging from 4.6 to 14.6 shade guide units. Similar findings were apparent with SVS and chromometer. No change was seen in the light only treatments by SVS or SG with very small changes by chromometer. In mean terms with all three gels, least change was noted when there was no light used. For SG, SVS and chromometer data analysis over all treatment groups, excluding light only treatments, revealed highly significant differences. Within bleach product treatment differences were only significant with one gel both with and without light activation. Differences between gels with the same light and no light revealed some significant differences in SG and chromometer data but not SVS. In mean terms the order of efficacy of gels with each light and no light was the same for the majority of data sets.

Tooth brushing, tooth wear and dentine hypersensitivity--are they associated?

Evidence suggests that patients suffer the painful symptoms of dentine hypersensitivity when dentine is exposed and the dentinal tubule system is opened to the oral cavity to allow stimuli to trigger a neural response in the pulp via a hydrodynamic mechanism. The processes needed to localise lesions of dentine hypersensitivity include loss of enamel and/or gingival recession. Whilst tooth brushing with or without toothpaste appears to cause minimal wear to enamel (in the absence of acids), circumstantial evidence implicates tooth brushing with gingival recession and exposure of dentine. Other tooth wear processes notably attrition and acid erosion cause loss of enamel and can expose dentine. Therefore sensitivity may result. How lesions of dentine hypersensitivity are initiated is a matter of conjecture and based on extrapolating data from studies, mainly in vitro, to affect in vivo. Again this circumstantial type of evidence suggests that abrasion by some toothpastes and erosion by dietary acid could open the tubule system. Little is known about the actual effect of desensitising toothpastes on lesions of dentine hypersensitivity even though they are formulated to either occlude dentinal tubules or block the neural response in the pulp. Clinical studies have produced contradictory findings for the efficacy of products and there have been extremely few evidence based reviews. In conclusion, available evidence supports a probable link of tooth brushing, with or without toothpaste and an acidic diet to both tooth wear and dentine hypersensitivity, and suggests also that dentine hypersensitivity is a tooth wear phenomenon. Although there is a need for more direct clinical and scientific evidence for these associations, it is recommended that they be taken into consideration when planning management strategies for the dentine hypersensitivity sufferer.

Correlation and examiner agreement between a new method of plaque scoring and a popular established plaque index, modelled in vitro.

BACKGROUND, AIMS: Scoring of supragingival plaque is common to epidemiological studies, oral hygiene assessments and clinical trials of oral hygiene products. These clinical practices utilize indices such as the Turesky et al. (1970, Journal of Periodontology 41, pp. 41-43) modification [Turesky Plaque Index (TPI)] of the Quigley & Hein (1962, Journal of the American Dental Association 65, pp. 26-29) plaque index for evaluating plaque extension. Whilst this index is in common use by clinicians, there is potential for ambiguity in the interpretation of scores by different examiners. The aims of this study were to compare examiner agreement between a new method of plaque scoring (NMPS) and TPI, and to determine if there was a correlation between the two indices. METHODS: Simulated plaque was scored from eight study casts, each consisting of 14 teeth. The two indices were both scored twice from the study casts by eight examiners experienced in plaque scoring. The first readings obtained were analysed for a correlation between the indices and between-examiner variability. Within-examiner variability was assessed using both first and second readings of each index. RESULTS: A positive correlation was found between the two indices (r = 0.717). The NMPS was found to have better inter- and intra-examiner agreement than TPI. CONCLUSION: The NMPS was found to have less variability within and between examiners than TPI: evaluation of NMPS in a clinical setting would now appear warranted.

Radiological examination of dental castings -- a review of the method and comparisons of the equipment.

The mechanical stability of crowns or bridges as well as frameworks for removable partial dentures depends on factors like thickness and metal structure. The biological compatibility can be influenced by porosities and soldered joints. Radiological testing is a non-destructive method to check defects in dental castings. As dental precious metal alloys have high X-ray absorption, testing of high gold alloys should be performed with a suitable X-ray machine at a tube voltage of 120 kV since the X-ray penetration of dental X-ray units using a tube voltage of 70 to 80 kV is not high enough for these alloys. As the absorption of Co-Cr alloys and of titanium is much lower, these materials can be tested with a dental X-ray apparatus. The radiographs show location and size of metal defects. They enable an examination of metal thickness and content of porosities. Metal defects reducing the biological compatibility or cast stability can be detected prior to clinical fitting.

The effect of unstimulated and stimulated whole saliva on extrinsic staining in vitro--a developmental method.

OBJECTIVES: To detect any differences in the propensity of unstimulated and stimulated, individual whole saliva to cause in vitro staining by chlorhexidine and tea. METHODS: Unstimulated and stimulated human saliva was collected on a daily basis and used to coat optically clear acrylic specimens. Specimens were subjected to an established chlorhexidine/tea staining model in vitro shown to correlate well with in vivo staining, and cycles repeated until an optical density of <2 was reached. RESULTS: Stain development increased incrementally with increasing cycles. Overall differences in chlorhexidine/tea staining were noted both between subjects and between unstimulated and stimulated saliva used. Mean staining for the subject group, at each cycle was always higher with unstimulated saliva compared to stimulated saliva and differences reached statistical significance at cycles 2-5. CONCLUSIONS: In vitro stain formation using unstimulated saliva from different individuals occurred at a faster rate and to a greater extent than when stimulated saliva from the same subjects was used, presumably reflecting differences in composition. Understanding the nature of these differences could provide fundamental information on the very poorly understood process of tooth staining.