Adsorption from black tea and red wine onto in vitro salivary pellicles studied by ellipsometry

In vivo modification of the enamel pellicle and saliva resveratrol levels after use of resveratrol-containing orodispersible capsules

OBJECTIVES

To evaluate in vivo 1) the bioavailability of trans-resveratrol when administered through sublingual capsules; 2) the effect of resveratrol on the protein composition of the acquired enamel pellicle (AEP).

DESIGN

Ten volunteers received a sublingual capsule containing 50 mg of trans-resveratrol. Unstimulated saliva was then collected after 0, 30, 60, and 120 min and AEP was collected after 120 min following administration of the capsule. In the next week, the volunteers received a placebo sublingual capsule, and saliva and AEP were collected again. Saliva samples were analyzed for free trans-resveratrol using high-performance liquid chromatopgraphy (HPLC), and AEP samples were subjected to proteomic analysis (nLC-ESI-MS/MS).

RESULTS

Trans-resveratrol was detected in saliva at all the time points evaluated, with the peak at 30 min. A total of 242 proteins were identified in both groups. Ninety-six proteins were increased and 23 proteins were decreased in the Resveratrol group. Among the up-regulated proteins, isoforms of cystatins, PRPs, Mucin-7, Histatin-1, Lactotrasnferrin and Lysozyme-C were increased and the isoforms of Protein S100, Neutrophil defensins, Albumin, PRPs, and, Statherin were decreased in Resveratrol group.

CONCLUSION

The sublingual capsule is effective at increasing the bioavailability of trans-resveratrol in saliva. Several proteins involved in important processes to maintain systemic and oral health homeostasis were identified. These proteins differently expressed due to the presence of trans-resveratrol deserve attention for future studies, since they have important functions, mainly related to antimicrobial action.

Astringency and its sub-qualities: a review of astringency mechanisms and methods for measuring saliva lubrication

Astringency is an important mouthfeel attribute that influences the sensory experiences of many food and beverage products. While salivary lubricity loss and increased oral friction were previously believed to be the only astringency mechanisms, recent research has demonstrated that nontactile oral receptors can trigger astringency by responding to astringents without mechanical stimulation. Various human factors have also been identified that affect individual responses to astringents. This article presents a critical review of the key research milestones contributing to the current understanding of astringency mechanisms and the instrumental approaches used to quantify perceived astringency intensity. Although various chemical assays or physical measures mimic in-mouth processes involved in astringent mouthfeel, this review highlights how one chemical or physical approach can only provide a single measure of astringency determined by a specific mechanism. Subsequently, using a single measurement to predict astringency perception is overly idealistic. Astringency has not been quantified beyond the loss of saliva lubrication; therefore, nontactile receptor-based responses must also be explored. An important question remains about whether astringency is a single perception or involves distinct sub-qualities such as pucker, drying, and roughness. Although these sub-quality lexicons have been frequently cited, most studies currently view astringency as a single perception rather than dividing it into sub-qualities and investigating the potentially independent mechanisms of each. Addressing these knowledge gaps should be an important priority for future research.

Plant extracts have dual mechanism on the protection against dentine erosion: action on the dentine substrate and modification of the salivary pellicle

To investigate the effect of some polyphenol-rich plant extracts on the protection of dentine against demineralization, both acting on the dentine and on the salivary pellicle. Dentine specimens (n = 180) were randomly distributed into 6 experimental groups (n = 30/group): Control (deionized water), Açaí extract, Blueberry extract, Green tea extract, Grape seed extract, and Sn²⁺/F^- (mouthrinse containing stannous and fluoride). Each group was further divided into two subgroups (n = 15), according to the site of action of the substance: on the dentine surface (D) or on the salivary pellicle (P). The specimens were submitted to 10 cycles: 30 min incubation in human saliva (P) or only in humid chamber (D), 2 min immersion in experimental substances, 60 min of incubation in saliva (P) or not (D), and 1 min erosive challenge. Dentine surface loss (DSL), amount of degraded collagen (dColl) and total calcium release were analyzed. Green tea, Grape seed and Sn²⁺/F^- showed significant protection, with least DSL and dColl. The Sn²⁺/F^- showed better protection on D than on P, whereas Green tea and Grape seed showed a dual mode of action, with good results on D, and even better on P. Sn²⁺/F^- showed the lowest values of calcium release, not differing only from Grape seed. Sn²⁺/F^- is more effective when acting directly on the dentine surface, while Green tea and Grape seed have a dual mode of action: with a positive effect on the dentine surface itself, but an improved efficacy in the presence of the salivary pellicle. We further elucidate the mechanism of action of different active ingredients on dentine erosion, where Sn²⁺/F^- acts better on the dentine surface, but plant extracts have a dual mode of action, acting on the dentine itself as well as on the salivary pellicle, improving the protection against acid demineralization.

Effect of At-Home Versus Over-the-Counter Bleaching Agents on Enamel Color, Roughness, and Color Stability

Background This study was designed to evaluate the efficacy of standard at-home bleaching agents in comparison to new over-the-counter (OTC) products on human enamel regarding color change, color stability, and surface roughness. Methodology A total of 80 extracted adult human maxillary central incisors were prepared and arbitrarily divided into the following four equal groups (N =20): group A: at-home opalescence boost containing 15% carbamide peroxide (CP); group B: crest whitening strips containing 6% hydrogen peroxide (HP); group C: light-emitted diode (LED) home tray with 20% CP + 4% HP; and group D: white and black toothpaste containing active charcoal components. Tooth color was measured using a spectrophotometer. Enamel surface roughness using a three-dimensional optical profilometer was measured before and after the bleaching procedure. To assess color stability, each bleached group was further subdivided into two equal subgroups (n = 10) according to the immersion media of either coffee or tea. Finally, the color was measured after 24 hours of immersion. Results All groups showed improvement in color from the baseline. The crest whitening strips group showed the lowest color improvement in comparison to all other groups. After staining, group C showed the lowest mean color change value ∆E2. No statistically significant difference was noted in surface roughness among all groups. Conclusions All OTC bleaching products as well as at-home bleaching improve teeth color and increase roughness on the enamel surface. Staining media has an adverse effect on the teeth after bleaching. The LED home tray showed a better whitening effect and color stability after bleaching.

Tooth color change promoted by different whitening toothpastes under alternate cycles of staining and brushing

OBJECTIVES

To compare the effect of whitening toothpastes with different mechanisms of action on discolored teeth subjected to additional staining/or not.

METHODS

One hundred twenty tooth specimens were stained for 14 days (staining broth under constant agitation and pH=7) and then allocated into the groups of toothpastes with different whitening ingredients (n=10): 1. Regular - Colgate Total 12 Clean Mint; 2. CLWI - Colgate Luminous White Instant (blue pigment); 3. CLWA - Colgate Luminous White Advanced Expert (hydrogen peroxide); 4. CLWAC - Colgate Luminous White Activated Charcoal (activated charcoal); 5. OB3D - Oral-B 3D WHITE Brilliant Fresh (abrasive); 6. TW - Teeth Whitening (charcoal powder). Specimens were submitted to two experimental models: A. Daily staining-toothbrush cycling: staining solution (5min), toothbrushing (45 strokes) and artificial saliva (3h), 2x/day, for 5days; B. Only toothbrushing (30.000 brushing strokes). Color change was determined with a spectrophotometer (CIEDE2000 and Whitening Index for Dentistry - WID) and statistically analyzed (α=0.05).

RESULTS

For both models, ΔE00 and Δa did not differ significantly between the whitening toothpastes and the regular. All groups showed a decrease in tooth yellowness (-Δb) and an increase in WID. Group Teeth Whitening exhibited a decrease in luminosity (-ΔL). In model A, Groups did not differ significantly from the Regular in terms of ΔL (p=0.35) and Δb (p=0.74). Groups CLWI and OB3D exhibited a decrease in luminosity. Reduced redness (-Δa) occurred only in Group CLWI. In Model B, Groups OB3D (p=0.021) and CLWA (p=0.001) exhibited higher change in luminosity than in Group Teeth Whitening. All exhibited increased redness (+Δa) and lightness (+ΔL), except the Regular, CLWAC and Teeth Whitening. Group OB3D had a significantly higher change in Δb than the Regular (p=0.021).

CONCLUSIONS

Irrespective of the mechanism of action, all toothpastes reduced tooth yellowness and promoted similar overall color change. Exposure of the teeth to additional staining during the toothbrushing cycles did not influence the effect of the whitening toothpastes.

CLINICAL SIGNIFICANCE

Whitening toothpastes should be tested in conditions that more closely simulate their use in a clinical scenario, in which alternate cycles of staining and brushing occur on a daily basis. However, even in such conditions, they were unable to promote a color change that differed from that of a regular toothpaste.

Synergistic effect between plant extracts and fluoride to protect against enamel erosion: An in vitro study

Polyphenol-rich solutions, such as plant extracts and teas, can modify the salivary pellicle and improve the protection against dental erosion. In this study, we further explored how these polyphenol-rich plant extracts solutions behave in the presence of fluoride. We distributed enamel specimens into 9 groups (n = 15): Control_No_F- (Deionized water); Control_F- (500 ppm F-), Grape_Seed_No_F- (Grape seed extract), Grape_Seed_F- (Grape seed extract + 500 ppm F-), Grapefruit_Seed_No_F- (Grapefruit seed extract), Grapefruit_Seed_F- (Grapefruit seed extract + 500 ppm F-), Blueberry_No_F- (Blueberry extract), Blueberry_F- (Blueberry extract + 500 ppm F-), and Sn2+/F-_Rinse (commercial solution containing 800 ppm Sn2+ and 500 ppm F-). The specimens were submitted to 5 cycles (1 cycle per day), and each cycle consisted of: salivary pellicle formation (human saliva, 30 min, 37°C), modification of the pellicle (2 min, 25°C), pellicle formation (60 min, 37°C), and an erosive challenge (1 min, citric acid). Between cycles, the specimens were kept in a humid chamber. Relative surface hardness (rSH), relative surface reflection intensity (rSRI) and calcium released to the acid were analysed, using general linear models, and Kruskal-Wallis with post-hoc Dunn's tests. We observed that the presence of fluoride in synergy with the extract solutions provided better protection than the groups containing extract or fluoride only. For rSH, we observed a significant main effect of extracts (F(4,117) = 9.20; p<0.001) and fluoride (F(1,117) = 511.55; p<0.001), with a significant interaction (F(3,117) = 6.71; p<0.001). Grape_Seed_F- showed the best protection, better than fluoride, and Sn2+/F-_Rinse. Calcium results also showed greater protection for the groups containing fluoride, whereas for rSRI, despite a significant interaction between extract and fluoride (F(3,117) = 226.05; p<0.001), the differences between the groups were not as clearly observed. We conclude that polyphenols from plant extracts, when combined with fluoride, improve the protective effect of salivary pellicles against enamel erosion.

Pellicle modification with natural bioproducts: Influence on tooth color under erosive conditions

Salivary pellicle was modified with bioproducts and we assessed the change in tooth color and the protection of enamel to erosion. Human enamel specimens were assigned to one of three solutions: grape seed extract or black tea (bioproducts), or deionized water (negative control); after which one half the specimens underwent erosive challenges. The specimens underwent 15 cycles involving salivary pellicle formation (10 min, 37°C), incubation in solution (2 min, 25°C), subsequent pellicle formation (90 min, 37°C). Half of the specimens was kept in a humid chamber and the other half was submitted to erosion (2 min, 1% citric acid). After 15 such cycles, the pellicle was removed. Tooth color and the surface reflection intensity were assessed after every five cycles and after pellicle removal. For non-eroded specimens, the exposure to bioproducts promoted significantly greater color change than the deionized water, with increases in yellow appearance. After pellicle removal, the color was similar in all non-eroded specimens. The bioproducts increased the surface reflection intensity over cycles. For the erosion-exposed specimens, erosion itself resulted in color change. Black tea and deionized water resulted in increased yellow appearance. Exposure to the bioproducts resulted in higher relative surface reflection intensity values over time, but only grape seed extract resulted in higher relative surface reflection intensity value at the time of pellicle removal. The bioproducts caused transient staining effect, which was reduced after pellicle removal. For enamel submitted to erosion, grape seed extract resulted in less color change and better protection of enamel against erosion than black tea or water.

Influence of periodic polyphenol treatment on the anti-erosive potential of the acquired enamel pellicle-A qualitative exploratory study

OBJECTIVE

The aim of the present study was to investigate the impact of periodic polyphenol treatment on the ultrastructure and anti-erosive potential of an in-situ formed pellicle.

METHODS

Subjects wore intraoral appliances with buccally and palatally fixed bovine enamel specimens. During 6 h of intraoral pellicle formation, 100 ml black tea or tannic acid was applied ex-vivo every 25 min for 5 min. Untreated pellicles served as control. After the trial, specimens were immersed in 0.1% or 1% citric acid for 60 s and analysed for calcium release with atomic adsorption spectrometry and ultrastructure with transmission electron microscopy.

RESULTS

Specimens covered by pellicles treated with black tea or tannic acid released less calcium than untreated pellicles. Ultrastructural analyses reveal an increase in pellicle's thickness and density after treatment with polyphenols.

CONCLUSIONS

Periodic polyphenol treatment of the pellicle modify its ultrastructure and increase its anti-erosive potential.

CLINICAL SIGNIFICANCE

Consumption of polyphenolic beverages can enhance the anti-erosive potential of the enamel pellicle.

Ethanol- and Cigarette Smoke-Related Alternations in Oral Redox Homeostasis

Alcohol abuse as well as smoking cigarettes has been proven to negatively affect the oral environment. The aim of this work was to provide a systematic review of the literature on the influence of ethanol and cigarette smoking on oral redox homeostasis. A search was performed for scientific articles indexed in the PubMed, Medline and Web of Science databases. We identified 32,300 articles, of which 54 were used for the final review, including the results from 2000 to 2021. Among the publications used to write this article, n = 14 were related to the influence of alcohol consumption (clinical studies n = 6, experimental studies n = 8) and n = 40 were related to the influence of smoking (clinical studies n = 33, experimental studies n = 7) on oral redox homeostasis. The reviewed literature indicates that alcohol abusers and smokers are more likely to suffer from salivary gland dysfunction, as well as develop precancerous lesions due to DNA damage. Compared to alcohol abstainers and non-smokers, alcohol drinkers and smokers are also characterized by a deterioration in periodontal health measured by various indicators of periodontal status. In summary, alcohol abuse and smoking are associated with disrupted oral redox homeostasis, which may lead not only to tooth loss, but also contribute to various adverse effects related to mental health, digestive processes and chronic inflammation throughout the human body.

Influence of periodic milk or cream treatment on the anti-erosive potential of the acquired enamel pellicle

OBJECTIVE

The purpose of the present study was to assess the anti-erosive potential of the acquired enamel pellicle formed in situ under the influence of periodic milk or cream treatment.

METHODS

The pellicle was formed on bovine enamel specimens in the oral cavity at buccal and palatal sites of upper molars in 6 subjects, using removable acrylic splints. During 6-h of intraoral exposure, splints were removed from the oral cavity every 25 min, treated with milk or cream for 5 min, and subsequently re-inserted into the oral cavity. After 6 h, pellicle covered specimens were immersed in citric acid (0.1 or 1.0 %) for 1 min, and processed for measurement of surface microhardness, determination of calcium release by atomic absorption spectroscopy, scanning and transmission electron microscopy. Statistical analysis was performed with SAS.

RESULTS

Statistical analysis did not indicate major differences between erosive surface alterations on enamel specimens covered by pellicles treated with cream or milk, and those covered by control pellicles. In addition, TEM analysis did not reveal any differences concerning the ultrastructure of the different pellicle treatments during acid exposure. All pellicles were dissolved in part after exposure to 0.1 % citric acid and were nearly completely removed after treatment with 1.0% citric acid.

CONCLUSIONS

It is concluded that periodic treatment with milk or cream during pellicle formation in situ does not improve the protective potential of the acquired enamel pellicle against erosion.

CLINICAL SIGNIFICANCE

Modification of the pellicle by consumption of milk or cream prior to an acidic challenge cannot sufficiently protect enamel from erosion.

Vitamin E: A potential preventive approach against dental erosion-an in vitro short-term erosive study

OBJECTIVES

This study evaluated the in vitro effect of different components of palm oil on enamel in a short-term erosive challenge.

METHODS

The acquired enamel pellicle (AEP) was previously formed in situ for 2 h. Subsequently, the bovine enamel blocks were treated in vitro according to following solutions: G1-palm oil; G2-85% tocotrienol solution; G3-oily vitamin E; G4-oily vitamin A; G5-deionized water (negative control); G6-stannous-containing solution (Elmex® Erosion Protection Dental Rinse) (positive control). After application of the treatment solutions (500 µl, 30 s), the blocks were immersed in 0.5% citric acid (pH 2.4) during 30 s (initial erosion). The response variable was the percentage of surface hardness loss. Data were analyzed by one-way ANOVA and Fisher's Test (p < 0.05).

RESULTS

The positive control (G6), palm oil (G1) and oily vitamin E (G3) groups presented the lowest percentage of surface hardness loss, and were statistically different from the negative group (G5) (p < 0.05), and no differences were found between these three groups. The 85% tocotrienol solution (G2) and oily vitamin A groups (G4) were not different to the negative control group.

CONCLUSIONS

Stannous-containing positive control (Elmex® Erosion Protection), palm oil and oily Vitamin E were able to protect enamel against the erosive challenge performed in this in vitro study. In addition, vitamin E is probably the key ingredient of palm oil responsible for preventing enamel erosion.

CLINICAL SIGNIFICANCE

Vitamin E presented similar preventive effect to a commercial mouthwash stannous-containing solution (Elmex® Erosion Protection) against initial erosion and, it can be considered as a promising natural alternative for the formulations of solutions aiming to prevent erosive tooth wear.

Preventive Applications of Polyphenols in Dentistry-A Review

Polyphenols are natural substances that have been shown to provide various health benefits. Antioxidant, anti-inflammatory, and anti-carcinogenic effects have been described. At the same time, they inhibit the actions of bacteria, viruses, and fungi. Thus, studies have also examined their effects within the oral cavity. This review provides an overview on the different polyphenols, and their structure and interactions with the tooth surface and the pellicle. In particular, the effects of various tea polyphenols on bioadhesion and erosion have been reviewed. The current research confirms that polyphenols can reduce the growth of cariogenic bacteria. Furthermore, they can decrease the adherence of bacteria to the tooth surface and improve the erosion-protective properties of the acquired enamel pellicle. Tea polyphenols, especially, have the potential to contribute to an oral health-related diet. However, in vitro studies have mainly been conducted. In situ studies and clinical studies need to be extended and supplemented in order to significantly contribute to additive prevention measures in caries prophylaxis.

Proteomic profile of the acquired enamel pellicle of professional wine tasters with erosive tooth wear

The aim of this study was to compare the acquired enamel pellicle protein profile of professional wine tasters with mild and moderate erosive tooth wear. Twelve professional wine tasters participated (3 from a low tooth wear group; 9 from a high tooth wear group). Acquired enamel pellicle samples were collected and processed for proteomic analysis (nLC-ESI-MS/MS). The acquired enamel pellicle proteomic profile was different between the groups. The proteins found exclusively in the low tooth wear group were histatins 1 and 3 and mucins 7 and 21. When comparing the wear groups, proteins with higher levels in the low tooth wear group included neutrophil defensins (1 and 3), lysozyme C, lysozyme, myeloperoxidase, and squalene monooxygenase. In conclusion, the findings indicate that the proteins found at higher levels in the low tooth wear group and proteins exclusively found in the low tooth wear group might be protective and, therefore, could be good candidates for further studies regarding their potential to be added to dental products to protect professional wine tasters from extrinsic erosive tooth wear.

Reduction of extrinsic tooth stain by a toothpaste containing 10% high cleaning silica, 0.5% sodium phytate and 0.5% sodium pyrophosphate: an 8-week randomised clinical trial

Objective

To assess the effects for controlling extrinsic tooth stain of a whitening toothpaste containing 10% high cleaning silica, 0.5% sodium phytate and 0.5% sodium pyrophosphate, in comparison with a negative control toothpaste.

Methods

A total of 86 adults who met with the inclusion and exclusion criteria were invited to take part in the study. They were distributed into test and control groups randomly. At baseline, 4 weeks and 8 weeks, the same examiner provided the clinical examinations, including evaluations of oral soft and hard tissues and measurements of tooth stain of the anterior teeth using the Lobene Stain Index. Adverse events and any changes in general health conditions of the patients were monitored.

Results

When the study was completed, comparisons between patients in test and control groups yielded statistically significant differences in Lobene stain adjusted mean area score [0.83 (0.05) vs. 1.13 (0.05)], Lobene stain adjusted mean intensity score [0.99 (0.06) vs. 1.32 (0.06)] and Lobene stain adjusted mean composite score [1.45 (0.13) vs. 2.50 (0.13)] (All, P < 0.001). Patients in the test group exhibited reductions of 26.55%, 25% and 42%, respectively in Lobene stain area, intensity and composite scores, relative to patients in the control group. Comparisons within groups showed that all three Lobene scores at 8 weeks in both groups were lower than those at baseline (All, P < 0.001).

Conclusion

This study demonstrates that 8-week use of a toothpaste containing 10% high cleaning silica, 0.5% sodium phytate and 0.5% sodium pyrophosphate can effectively reduce extrinsic tooth stain.

Trial registration NCT04238429 (before enrollment of the first participant). Data register: March 4, 2018.

Optical detection of the potential for tooth discoloration from children's beverages by quantitative light-induced fluorescence technology

BACKGROUND

Some beverages are known to cause extrinsic staining on the tooth. This study investigated the degree of pigmentation caused by children's acidic beverages, and to confirm the possibility of the quantitative light-induced fluorescence (QLF) technology in assessing staining of the tooth.

METHODS

Bovine tooth specimens were subjected to an 8-day pH-cycling model, using six children's beverages (experimental groups) and a cola (control group), and a remineralizing solution. Before and after the pH-cycling, white-light and fluorescence images of the enamel surface were photographed with a QLF to evaluate color change (ΔE_after) and fluorescence loss (ΔF_after), respectively. Paired t-test was used to compare the tooth colors obtained before and after the pH-cycling. Spearman correlation analysis was performed to examine the correlation between the ΔE_after and ΔF_after values.

RESULTS

Median ΔE_after values of all the beverages ranged from 1.33 to 20.42, showing the greatest value in Koal-Koal Koala™ (KKK, p < 0.001). The ΔE_after was correlated with ΔF_after value negatively (ρ=-0.611, p < 0.001). The median ΔF_after varied by beverages (-38.86-0.00) and KKK caused the greatest value.

CONCLUSIONS

The cola and 6 children's beverages showed the possibility for discoloration on the tooth. The QLF technology may enable monitoring the discoloration induced on the tooth surface by acidic beverage.

The effect of red wine in modifying the salivary pellicle and modulating dental erosion kinetics

This study investigated the potential of red wine in modulating dental erosion kinetics in the presence or absence of salivary pellicle. Polished human enamel specimens were used in two conditions; presence or absence of acquired enamel pellicle; and subdivided according to exposure: red wine, orange juice, apple juice, or citric acid. The specimens were incubated in clarified whole human saliva (presence of acquired enamel pellicle) or in a humid chamber (absence of acquired enamel pellicle) for 2 h at 37°C, then in the test substances for 1 min, at 25°C, under shaking. This was repeated four times. Surface hardness was measured initially and after each cycle and surface reflection intensity was measured initially and after all cycles. In the presence of acquired enamel pellicle, red wine caused the least surface hardness loss, followed by orange juice, apple juice, and citric acid. Statistically significantly less surface reflection intensity loss was observed for red wine and orange juice than for apple juice and citric acid. In the absence of acquired enamel pellicle, red wine and orange juice caused less surface hardness loss than apple juice and citric acid. Orange juice showed the least surface reflection intensity loss, followed by red wine, citric acid, and apple juice. The polyphenol composition of these drinks can notably modulate the erosion kinetics.

Salivary pellicle modification with polyphenol-rich teas and natural extracts to improve protection against dental erosion

OBJECTIVE

To investigate the modification of the salivary pellicle with different polyphenol-rich teas and natural extracts for the protection against dental erosion.

METHODS

We performed two experiments: one with teas (Green tea, Black tea, Peppermint tea, Rosehip tea, negative control [NC]) and other with natural extracts (Grape seed, Grapefruit seed, Cranberry, Propolis, NC), where NC was deionized water. A total of 150 enamel specimens were used (n = 15/group). Both experiments followed the same design, consisting of 5 cycles of: salivary pellicle formation (30 min, 37 °C), modification with the solutions (30 min, 25 °C), further salivary pellicle formation (60 min, 37 °C) and erosive challenge (1 min, 1% citric acid, pH 3.6). Relative surface microhardness (rSMH), relative surface reflection intensity (rSRI) and amount of calcium release (CaR) were evaluated. Data were analysed with Kruskal-Wallis and Wilcoxon rank sum tests with Bonferroni correction (α = 0.05).

RESULTS

Regarding teas, Black and Green teas showed the best protection against dental erosion, presenting higher rSMH and lower CaR than NC. Peppermint tea was not different to NC and Rosehip tea caused erosion, showing the highest CaR and greatest loss of SMH and SRI. Regarding natural extracts, Grape seed and Grapefruit seed extracts presented the best protective effect, with significantly higher rSMH and lower CaR. Cranberry caused significantly more demineralization; and Propolis did not differ from NC.

CONCLUSION

Green tea, Black tea, Grape seed extract and Grapefruit seed extract were able to modify the salivary pellicle and improve its protective effect against enamel erosion, but Rosehip tea and Cranberry extract caused erosion.

CLINICAL RELEVANCE

Some some bio-products, such as teas and natural extracts, improve the protective effect of the salivary pellicle against enamel erosion. More studies should be performed in order to test the viability of their use as active ingredients for oral care products.

Pellicle Modification with Casein and Mucin Does Not Affect Surface Loss from Erosion and Abrasion

AIM

A combination of the proteins casein and mucin is known to modify the salivary pellicle and improve its protection of the underlying enamel from erosion. It is so far not known if this protection is confined solely to erosion, or if it also extends to abrasion, and this in vitro study aimed at investigating this question.

METHODS

A total of 72 human enamel specimens were prepared and randomly assigned to four groups: pellicle (P), casein/mucin (CM), pellicle + casein/mucin (PCM), and control (Ctrl). Each specimen underwent five cycles, each cycle consisting of a pellicle/treatment part, an erosion part (3 min in 1% citric acid, pH 3.6, 25°C, 70 rpm), and an abrasion part (50 toothbrush strokes within 25 s in toothpaste slurry with a 200-g load). The pellicle/treatment part consisted of 2 h of incubation in whole human saliva for group P, 2 h of incubation (25°C, 70 rpm) in a protein mixture of 1% casein and 0.27% mucin for group CM, and 2 h of incubation in saliva followed by 2 h of incubation in the protein mixture for group PCM. The fourth group (Ctrl) served as the control and was kept in a humid chamber without saliva or protein treatment. The enamel surfaces were scanned with an optical profilometer initially and after the final cycle, and surface loss was analyzed. Furthermore, the surface microhardness (SMH) was measured initially, after each pellicle/treatment part and each erosion cycle, and after the final abrasion cycle. The results were analyzed with Kruskal-Wallis and Wilcoxon tests with Bonferroni corrections.

RESULTS

The different treatments did not show differences in surface loss and therefore did not protect enamel from surface loss by abrasion. Nonetheless, we observed differences in the SMH values, namely the Ctrl group being significantly softer than the experimental groups.

CONCLUSION

The observed differences in SMH suggest that a different abrasion protocol could lead to differences in surface loss, and further investigation of whether and under which conditions pellicle modification leads to increased resistance to abrasion remains worthwhile.

The effect of polyphenol-containing solutions on in situ biofilm formation on enamel and dentin

OBJECTIVES

To investigate the effects of Chinese gallnut extracts and pure tannic acid on in situ biofilm formation on enamel and dentin samples over 24 h.

METHODS

Bovine enamel and dentin samples were buccally fixed on maxillary splints. Six volunteers wore the splints for 24 h, and rinsed their mouths with tap water (control), 1% tannic acid- and 1% Chinese gallnut extracts-containing solution twice a day, 3 min after the splints were placed in the mouth and before night sleep. Live/dead staining was used for fluorescence microscopic (FM) visualization and quantification of bacteria viability of biofilms formed on enamel and dentin samples. Biofilm coverage was evaluated and recorded by FM and scanning electron microscopy (SEM). In addition, biofilms were analyzed by transmission electron microscopy (TEM). The Kruskal-Wallis test was used to analyze biofilm data.

RESULTS

Rinsing with tannic acid- and Chinese gallnut extracts-containing solutions significantly reduced in situ biofilm coverage on enamel and dentin samples (P < 0.05). The bacterial viability of biofilms formed on enamel samples was significantly reduced compared to the control (P < 0.05). TEM analysis revealed an increase in pellicle's electron density and thickness and only few or no bacteria adherent to the pellicle in the experimental samples.

CONCLUSIONS

Rinsing with tannic acid- and Chinese gallnut extracts-containing solutions can effectively inhibit in situ biofilm formation, modify the ultrastructure of biofilms on enamel and dentin surfaces and significantly reduce the bacterial viability of biofilm on enamel surfaces.

CLINICAL SIGNIFICANCE

Tannic acid- and Chinese gallnut extracts-containing solutions might be used for dental biofilm management.

Effect of fragaria vesca, hamamelis and tormentil on the initial bacterial colonization in situ

OBJECTIVE

The presentin situ study aims to examine the influence of the polyphenolic tea drugs fragaria vesca, hamamelis and tormentil on the initial oral bioadhesion.

DESIGN

Initial biofilm formation was performed on bovine enamel slabs which were carried intraorally by 12 subjects. After 1 min of intraoral pellicle formation, the subjects rinsed with fragaria vesca, tormentil (0.8 mg/8 mL) and hamamelis (0.2 mg/8 mL) for 10 min. Tap water served as negative control, 0.2 % CHX as positive control. The investigations took place on different days (wash-out: 2 days). Afterwards, fluorescence microscopy has been performed per test solution (n = 5) and per subject (n = 12) to visualize bacterial adhesion and glucan formation (8 h oral exposition) with DAPI, ConA and BacLight. Additionally, TEM was used to visualize the pellicle ultrastructure and expectorate samples. Statistical evaluation was carried out using the Kruskal-Wallis- (p < 0.5), Mann-Whitney U test (p < 0.5) and Bonferroni-Holm-correction (p < 0.1).

RESULTS

Rinsing with the polyphenolic tea extracts reduced significantly initial bacterial colonization (DAPI) compared to the negative control. There was no significant difference betweenfragaria vesca, hamamelis and tormentil. All solutions showed a reducing effect on the glucan formation. No significant difference was observed between fragaria vesca and CHX. Considerable alterations of the pellicle's ultrastructure manifested by an increase in thickness and electron density resulted from rinsing with the three polyphenolic aqueous extracts.

CONCLUSIONS

Fragaria vesca, hamamelis and tormentil significantly reduce initial bioadhesion and glucan formation in situ and are therefore recommended as adjuvant antibacterial oral therapeutics.

Effect of phytosphingosine on staining resistance and microhardness of tooth enamel

OBJECTIVE

To evaluate the protective effect of phytosphingosine (PHS) against staining on dental enamel.

MATERIALS AND METHODS

Ninety-six specimens of bovine teeth (6 mm × 6 mm × 2 mm) were cut, and initial color (Easyshade, VITA), microhardness (HMV-2, Shimadzu) and fluorescence (Matlabs software, Matworks) measurements were performed. Specimens were separated into four groups according to the treatments: Distilled water (control); Human saliva (HS); PHS; PHS + HS. Specimens (n = 6) were submitted to staining procedures: Distilled water (immersion for 30 days-control); Coffee (15 minutes, twice a day/for 15 days); Black tea (as described for Coffee) and cigarette smoke (20 cigarettes/sample). Final measurements were performed, and data were analyzed (Color-CIEDE2000, fluorescence-2-way ANOVA, Tukey, and microhardness-Kruskal-Wallis Dunn, P < .05).

RESULTS

Coffee caused the highest color change (ΔE₀₀ ), followed by black tea, regardless of the treatment employed. Distilled water and cigarette smoke produced similar color changes (P > .05) for the groups control (water = 1.0 + - 0.5/ cigarette = 2.3 0.3) and PHS (water = 0.8 0.4/ cigarette = 2.3 0.4). PHS + HS demonstrated intermediate means than PHS and HS when stained with coffee and tea. After treatments, the least fluorescence alterations occurred for the groups treated with distilled water and cigarette, regardless of the treatment, with no difference (P > .05) between them. There was a significant difference (P < .05) on microhardness between all the groups, as PHS + HS > PHS > HS > Distilled water.

CONCLUSIONS

It was concluded that PHS treatment did not protect the staining of the enamel by coffee and tea, but increased the microhardness, both in the presence and absence of a salivary pellicle.

PRACTICAL IMPLICATIONS

Phytoshingosine is a novel agent and considered a promising component for anti-biofilm and anti-erosion properties by the formation of a diffusion barrier on the dental enamel. In line, PHS might be considered for anti-staining purposes.

Short-term effects of stain-causing beverages on tooth bleaching: A randomized controlled clinical trial

OBJECTIVES

To evaluate the short-term effects of stain-causing beverages on the effectiveness of in-office tooth bleaching.

METHODS

Participants were recruited and randomly divided into 3 groups based on beverages used for rinsing during and after the bleaching procedure: group N (tap water, control group), group C (coffee), and group T (tea). Participants were instructed to rinse with the respective solutions for 30 s, 4 times daily for 4 weeks. All participants received two in-office bleaching treatment sessions with 40 % hydrogen peroxide (Opalescence BOOST PF 40 %, Ultradent); the sessions were separated by a 1-week interval. Tooth colour was assessed using a spectrophotometer (Easyshade, Vita ZahnFabrik) before the bleaching procedure (T0), immediately after the first session of bleaching (T1), immediately after the second session of bleaching (T2), as well as one week (T3) and three weeks after (T4) the end of bleaching. Tooth sensitivity (TS) was ranked using a numerical rating scale (NRS) and a visual analogue scale (VAS) at different time points.

RESULTS

No significant difference in the whiteness index (W), △E, △a* and △b* values among the 3 groups was observed at any time interval (P for all > 0.05). At T4, the △L* value in group C was significantly lower than that in groups T and N (P = 0.022 and P = 0.001, respectively), though no significant difference in △L* values was observed among the 3 groups at T1 (P = 0.402), T2 (P = 0.643) and T3 (P = 0.177). Additionally, no significant difference was found in the TS values among the 3 groups at any of the evaluation time points (P for all > 0.05).

CONCLUSIONS

Exposure to coffee or tea during the bleaching treatment period did not affect the effectiveness of the treatment. However, exposure to coffee after the bleaching treatment did affect the effectiveness of the treatment. Exposure to stain-causing beverages did not affect the bleaching-induced TS (ClinicalTrials.gov Identifier: NCT03933527).

CLINICAL SIGNIFICANCE

The consumption of coffee or tea during tooth bleaching may not interfere with the colour change produced by the treatment. However, clinicians should advise their patients to refrain from, at least to some extent, consuming coffee after the bleaching procedure to maintain the effectiveness of the treatment.

The influence of fillers and protease inhibitors in experimental resins in the protein profile of the acquired pellicle formed in situ on enamel-resin specimens

OBJECTIVE

This study evaluated the influence of the addition of fillers and/or protease inhibitors [(epigallocatechin gallate - EGCG) or (chlorhexidine - CHX)] in experimental resins in the protein profile of the acquired pellicle (AP) formed in situ on enamel-resin specimens.

DESIGN

324 samples of bovine enamel were prepared (6 × 6 × 2 mm). The center of each sample was added with one of the following experimental resins (Bis-GMA+TEGDMA): no filler, no inhibitor (NF-NI); filler no inhibitor (F-NI); no filler plus CHX (NF-CHX); filler plus CHX (F-CHX); no filler plus EGCG (NF-EGCG); filler plus EGCG (F-EGCG). Nine subjects used a removable jaw appliance (BISPM - Bauru in situ pellicle model) with 2 slabs from each group. The AP was formed for 120 min, in 9 days and collected with electrode filter paper soaked in 3% citric acid. The pellicles collected were processed for analysis by LC-ESI-MS/MS.

RESULTS

A total of 140 proteins were found in the AP collected from all the substrates. Among them, 16 proteins were found in common in all the groups: 2 isoforms of Basic salivary proline-rich protein, Cystatin-S, Cystatin-AS, Cystatin-SN, Histatin-1, Ig alpha-1 chain C region, Lysozyme C, Mucin-7, Proline-rich protein 4, Protein S100-A9, Salivary acidic proline-rich phosphoprotein ½ and Statherin. Proteins with other functions, such as metabolism and transport, were also identified.

CONCLUSION

The composition of the experimental resins influenced the protein profile of the AP. This opens a new avenue for the development of new materials able to guide for AP engineering, thus conferring protection to the adjacent teeth.

Preparation and Characterization of Natural Bleaching Gels Used in Cosmetic Dentistry

The novelty of this study consists of the formulation and characterization of three experimental bleaching gels with hydroxylapatite oxides and fluorine (G28®, G29®, G30®) based on natural fruit extracts compared to the commercial Opalescence 15% (GC, Ultradent, South Jordan, UT, USA). Studies have been conducted on the effect that the experimental bleaching gels have on the color and morphology of different restorative materials (Nanofill®-Schulzer, P.L. Superior Dental Materials GmbH, Hamburg, Germany, and experimental nanocomposites (P11®, P31®, P61®)), immersed in coffee and artificial saliva (for 10 days and 30 days). The study also includes a cytotoxicity test on the gels and nanocomposites after bleaching, with ISO 109993-5 protocols on human dental follicle stem cells. UV-VIS spectroscopy, computerized measurement, and fluorescence spectrometry were used in order to observe the color changes, while the microstructure of the surface was investigated by Scanning Electron Microscopy (SEM). All of the samples immersed in coffee showed the highest color shift in comparison to the baseline. The color difference ΔE values obtained using the two methods (UV-Vis, computerized based on digital images) both after coloring and bleaching, respectively, were different for all four types of nanocomposites stored in the coffee, while no difference was observed in those stored in artificial saliva. The studied experimental gels and nanocomposites had a low cytotoxic effect on cell cultures after bleaching.

Whitening Efficacy of Chewing Gum Containing Sodium Metaphosphate on Coffee Stain: Placebo-controlled, Double-blind In Situ Examination

This study aimed to evaluate the ability of chewing gum containing sodium metaphosphate (SMP) to remove coffee stains from enamel in situ. This was a double-blind (subjects, evaluators), parallel-group, crossover, randomized clinical trial with 30 healthy adult volunteers. Each participant held an appliance with a hydroxyapatite (HA) pellet on the lower lingual side of his or her mouth for two hours to allow pellicle formation. The appliances were subsequently immersed in coffee solution at 37°C for 48 hours. The color of the HA pellet before and after coffee immersion was measured using a spectrophotometer. The participant set the appliance and chewed two pieces of test gum, which contained 7.5 mg of SMP per piece, or control gum without SMP. Each cycle included five minutes of exposure to chewing gum, after which the appliances were placed in 100% relative humidity at room temperature for a 30-minute incubation. This cycle was repeated five times for each gum type. The color of the HA pellet was measured after each chewing cycle using the spectrophotometer. In addition, ΔE* values, which indicate the change in pellet color after each chewing cycle compared with after coffee immersion, were calculated. Data were analyzed using the paired t-test with Bonferroni adjustment to compare ΔE* values of control and test gum after each chewing cycle. The ΔE* values of test gum were significantly higher than those of control gum after all chewing cycles, excluding the first cycle (p<0.05). This finding indicates that test gum containing SMP was more effective at removing coffee stains from the HA pellet than control gum. We conclude that chewing gum containing SMP can effectively remove coffee stains from HA pellets. Thus, SMP is a promising agent to be further explored in tooth-cleaning studies.

Impact of oral astringent stimuli on surface charge and morphology of the protein-rich pellicle at the tooth-saliva interphase

The proteinaceous pellicle layer, which develops upon contact with saliva on the surface of teeth, is important for the formation of oral biofilms and for the protection of teeth from abrasion and chemically induced erosion. Astringent food ingredients comprising polyphenols, cationic macromolecules, and multivalent metal salts are known to interact with the pellicle. However, astringent-induced changes in the physicochemical properties of the tooth-saliva interphase are not yet completely understood. Here we provide comprehensive insights into interfacial charging, ultrastructure, thickness, and surface roughness of the pellicles formed on the model substrates silicon oxide (SiO₂), Teflon^® AF, and hydroxyapatite, as well as on bovine enamel before and after incubation with the astringents epigallocatechin gallate, tannic acid, iron(III) salt, lysozyme, and chitosan. Quartz crystal microbalance with dissipation monitoring demonstrated viscous behavior of untreated pellicles formed in vitro on the different materials. Electrokinetic (streaming current) measurements revealed that cationic astringents reverse the charge of native pellicles, whereas polyphenols did not change the charge under physiological pH condition. In addition, transmission electron microscopy and atomic force microscopy showed a concentration-dependent increase in average film thickness and pellicle surface roughness as induced by astringents. These multifaceted alterations of the salivary pellicle may come along with an increase in roughness perceived on the teeth, which is part of the complex sensations of oral astringency.

The relevance of alcohol to dental practice

Alcohol is a very widely used drug which can cause dental disease and influence dental treatment. It is therefore important that dental professionals take an alcohol history from all patients and are aware of how to give alcohol reduction advice. This article discusses the impact of alcohol on oral health, including oral cancer, trauma, halitosis, tooth wear, periodontal disease and caries, with reference to the available literature. It also outlines current alcohol risk level advice and guidance regarding giving alcohol reduction advice in a dental setting.

Oral astringent stimuli alter the enamel pellicle's ultrastructure as revealed by electron microscopy

OBJECTIVES

This electron microscopic study aimed at investigating effects of oral astringent stimuli on the enamel pellicle's morphology.

METHODS

Pellicles were formed in situ within 30min on bovine enamel slabs, fixed to individuals' upper jaw splints. The pellicle-coated specimens were immersed in vitro in seven diverse astringent solutions and subsequently analyzed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, as well as transmission electron microscopy (TEM). Four biocompatible astringents, namely the polyphenol epigallocatechin gallate, the metal salt iron(III) sulfate, the basic protein lysozyme, and the aminopolysaccharide chitosan, were additionally applied in situ. After rinsing the oral cavity with these compounds, the pellicle's ultrastructure was imaged by SEM and TEM, respectively. Untreated pellicle samples served as controls.

RESULTS

Exposure to polyphenols and lysozyme induced particularly thicker and electron-denser pellicles in comparison to the control pellicle with similar characteristics in vitro and in situ. In contrast, acidic chitosan and metal salt solutions, respectively, revealed minor pellicle alterations. The incorporation of Fe and Al into the pellicles treated with the corresponding inorganic salts was verified by EDX analysis.

CONCLUSIONS

Astringent-induced pellicle modifications were for the first time visualized by TEM. The ultrastructural alterations of the dental pellicle may partly explain the tooth-roughening effect caused by oral astringent stimuli.

CLINICAL SIGNIFICANCE

Astringents might modify the pellicle's protective properties against dental erosion, attrition, as well as bacterial adhesion, and by this means may influence tooth health. The findings may thus be particularly relevant for preventive dentistry.

Effect of gels containing chlorhexidine or epigallocatechin-3-gallate on the protein composition of the acquired enamel pellicle

OBJECTIVE

This study evaluated changes in protein profile of the acquired enamel pellicle (AEP) formed in vivo, after application of gels containing chlorhexidine or EGCG and further challenge with citric acid.

DESIGN

AEP was formed in 9 volunteers for 2h and then treated with one of the following gels: placebo, 400μM EGCG or 0.012% chlorhexidine. A thin layer of gel was applied and after 1min the excess was removed. One hour after gel application, the AEP was collected from the buccal surface (upper and lower jaw) of one of the sides with filter paper dipped in 3% citric acid. On the other side, erosive challenge was performed through gentle application of 1% citric acid (pH 2.5) for 20s (using a pipette) followed by washing with deionized water. The AEP was collected as mentioned before. Proteomic analysis was performed through liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The MS/MS spectra obtained were compared with human protein databases (SWISS-PROT). Label-free quantitation was done using the PLGS software.

RESULTS

In total, 223 proteins were identified. After treatment with EGCG and CHX gels, proteins with potential functions to protect against caries and erosion such as PRPs, calcium-bind proteins and Statherin were increased. When EGCG and CHX-treated AEPs were challenged with citric acid, there was increase in cystatins and Profilin-1.

CONCLUSION

CHX- and EGCG-treated AEPs, submitted to challenge with citric acid or not, had remarkable changes in their proteomic profiles.

Effect of Tannic Acid on the Protective Properties of the in situ Formed Pellicle

OBJECTIVES

In the present in situ/ex vivo study the impact of tannic acid on the erosion-protective properties of the enamel pellicle was tested. Additionally, the antiadherent and antibacterial effects of tannic acid were evaluated.

METHODS

The pellicle was formed in situ on bovine enamel samples fixed on individual splints worn by 6 subjects. Following 1 min of pellicle formation the volunteers rinsed for 10 min with tannic acid. After further oral exposure for 19 min, 109 min, and 8 h overnight, respectively, slabs were incubated in HCl ex vivo (pH 2.0, 2.3, 3.0) over 120 s. Subsequently, kinetics of calcium and phosphate release were measured photometrically. Samples after a 1-min fluoride mouth rinse as well as enamel samples with and without a 30-min in situ pellicle served as controls. Antiadherent effects were evaluated after a 1-min rinse with tannic acid and oral exposure of the slabs overnight. DAPI (4',6-diamidino-2-phenylindole) combined with concanavalin A staining and live/dead staining was used for fluorescence microscopic visualization and quantification of adherent bacteria and glucans. Modification of the pellicle's ultrastructure by tannic acid was evaluated by transmission electron microscopy (TEM).

RESULTS

Tannic acid significantly improved the erosion-protective properties of the pellicle in a pH-dependent manner. Bacterial adherence and glucan formation on enamel were significantly reduced after rinses with tannic acid as investigated by fluorescence microscopy. TEM imaging indicated that rinsing with tannic acid yielded a sustainable modification of the pellicle; it was distinctly more electron dense.

CONCLUSION

Tannic acid offers an effective and sustainable approach for the prevention of caries and erosion.

Effect of Inula viscosa on the pellicle's protective properties and initial bioadhesion in-situ

OBJECTIVES

The present in situ study investigated the effect of Inula viscosa tea on the pellicle's acid protective properties and on initial oral biofilm formation.

DESIGN

Biofilm formation was performed on bovine enamel slabs on individual maxillary splints. Following 1min of pellicle formation, eight subjects rinsed for 10min with Inula viscosa tea and the splints remained for 8h intraorally. Samples carried after 1-min rinsing with CHX (0.2%) or without rinse served as controls. BacLight™ staining, 4',6-diamidino-2-phenylindole (DAPI)-staining and fluorescence in situ hybridization (FISH) were used for fluorescence microscopic detection of adherent bacteria. For investigation of acid protective properties, three subjects rinsed for 10min with Inula viscosa tea after 1min pellicle formation and kept the splints intraorally for further 19min. Physiological 30-min pellicles and native enamel samples served as controls. After HCl incubation of the samples ex-vivo over 120s (pH 2.0, 2.3, 3.0) calcium- and phosphate release were quantified photometrically. Potential influences on the pellicle's ultrastructure by Inula viscosa tea were evaluated by transmission electron microscopy (TEM).

RESULTS

Application of Inula viscosa tea yielded a significant reduction of adherent bacteria on all enamel samples as detected by fluorescence microscopy. For calcium- and phosphate release no significant effect was recorded. TEM investigation indicated a modification of the pellicle's ultrastructure, but no enhanced protection against erosive noxae.

CONCLUSION

Rinsing with Inula viscosa tea influences the bacterial colonization on enamel in situ over 8h but has no impact on acid protective properties of the pellicle.

Discoloration of PMMA, composite, and PEEK

INTRODUCTION

To assess the discoloration and stain removal potential of different cleaning methods relevant to individual/professional prophylaxis and laboratory cleaning on polyetheretherketone (PEEK), poly(methyl methacrylate) (PMMA)-based, and composite (COMP) materials after storage in different media for 7 days.

METHODS

One thousand three hundred twenty specimens of PEEK, PMMA, and COMP (N = 440 of each group) were prepared and stored in four different media for 7 days to cause stain. Samples were divided into three cleaning groups (n = 10): (i) individual prophylaxis, (ii) laboratory protocols, and (iii) professional prophylaxis. Color was determined by a portable spectrophotometer and calculated between different time points (∆E). The data was statistically evaluated using univariate analyses, Kruskal-Wallis H and Mann-Whitney U tests (p < 0.05).

RESULTS

The significantly (p < 0.001) lowest discoloration was found when specimens were stored in distilled water and chlorhexidine (CHX), followed by red wine. Curry solution caused the highest discoloration. PEEK showed the significantly (p < 0.001) lowest color changes, while COMP showed the highest changes. Ultrasonic bath and Air Flow Plus (AFP) were the significantly (p < 0.001) most effective methods to remove staining. The least cleaning effect was found using a soft toothbrush (ST), a medium-hard toothbrush (MT), and SunSparkle (SS) cleaning system.

CONCLUSIONS

PEEK seems more stable against discolorations than other denture resin materials. Regarding the cleaning potential, individual prophylaxis can be conducted with toothbrushes. For professional prophylaxis, air-abrasion devices using gentle powders are effective. Laboratory protocols should include gentle cleaning methods like ultrasonic bath.

CLINICAL RELEVANCE

Clinicians and dental technicians should inform their patients about the discoloration potential of certain foods/beverages and recommend the most efficient cleaning, but preventive methods.

Application of Plant Extracts for the Prevention of Dental Erosion: An in situ/in vitro Study

OBJECTIVES

Antiadherent and antibacterial effects of certain plant extracts have been proven to be beneficial in preventive dentistry. In the present in situ/in vitro crossover study, the impact of plant extracts rich in polyphenols on the erosion-protective properties of the in situ pellicle was evaluated.

METHODS

Individual splints were prepared for 12 subjects for intraoral exposure of bovine enamel specimens. Following formation of a 1-min pellicle, watery plant extracts (leaves of the wild form of Ribes nigrum, the wild form of Origanum as well as a combination of both) were administered for 10 min in situ. Alternatively, a mouth rinse with fluorides (Elmex Kariesschutz) was performed for 1 min. After further oral exposure for 19/28 min, respectively, slabs were removed and incubated with HCl in vitro over 120 s (pH 2, 2.3, 3). The resulting calcium and phosphate release was quantified photometrically. Slabs with and without a 30-min in situ pellicle served as controls. The modification of pellicle ultrastructure was evaluated by transmission electron microscopy (TEM).

RESULTS

Plant extracts modulated the erosion-protective properties of the native in situ pellicle in all test groups in a pH-dependent manner. The combination of R. nigrum leaves and Origanum enhanced the protective properties of the pellicle at all pH values; the administration of this preparation was comparable, yet superior, to the effect of the fluoridated mouth rinse. TEM images indicated that rinsing with R. nigrum leaves/Origanum yielded a distinctly thicker and more electron-dense pellicle.

CONCLUSION

The combination of certain plant extracts offers a novel approach to the complementary prevention of dental erosion.

Strategies for a direct characterization of phosphoproteins on hydroxyapatite surfaces

We show in this work how systems formed by phosphoproteins on calcium phosphate surfaces can be directly characterized, in real time, in liquid medium, without the need for elution or labeling. Specifically, we show how this is possible by applying three different techniques: ellipsometry, quartz crystal microbalance with dissipation, and atomic force microscopy-based friction force spectroscopy. We apply these techniques to study two different model systems, i.e. those formed upon the adsorption of two model phosphoproteins (κ- and β-casein) on hydroxyapatite (HA) surfaces. Information on the kinetics of adsorption, surface excess, viscoelasticity, water content, thickness of the layers, and protein-surface interaction is provided. Results indicate that both phosphoproteins form homogeneous elastic highly hydrated monolayers on the HA surfaces, the strength of β-casein layers being higher by approximately a factor of 4. Based on the experimental results, models for the conformation of κ- and β-casein molecules adsorbed on HA surfaces are proposed.

Effect of nano-carbonate apatite to prevent re-stain after dental bleaching in vitro

OBJECTIVES

This study examined the effect of nano-carbonate apatite (n-CAP) to prevent re-staining and the change of enamel surface after dental bleaching in vitro.

METHODS

Twenty-four bovine specimens were bleached for 2 weeks with 10% carbamide peroxide (CP). After bleaching, the specimens were divided into the following four groups: distilled and deionized water (DDW, negative control), 10% n-CAP, NaF (positive control) and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP, positive control). Each group was subjected to pH cycling for 7 days. The specimens were treated for 4 min 3 times per day and re-staining was induced naturally by artificial saliva in the remineralization process. After pH cycling, the changes in colour were evaluated with spectrophotometry and scanning electron microscopy (SEM). The difference in colour between before and after pH cycling was evaluated using an ANOVA and Tukey test.

RESULTS

After pH cycling, the colour difference of n-CAP group was significantly lower than that of the DDW and CPP-ACP groups (p<0.05). SEM showed that n-CAP particles were deposited regularly on the damaged surface compared to the other groups.

CONCLUSION

10% n-CAP could significantly maintain the initial colour and protect the damaged enamel structure after bleaching.

Analysis of the erosive effect of different dietary substances and medications

Excessive consumption of acidic drinks and foods contributes to tooth erosion. The aims of the present in vitro study were twofold: (1) to assess the erosive potential of different dietary substances and medications; (2) to determine the chemical properties with an impact on the erosive potential. We selected sixty agents: soft drinks, an energy drink, sports drinks, alcoholic drinks, juice, fruit, mineral water, yogurt, tea, coffee, salad dressing and medications. The erosive potential of the tested agents was quantified as the changes in surface hardness (ΔSH) of enamel specimens within the first 2 min (ΔSH2-0 = SH2 min - SHbaseline) and the second 2 min exposure (ΔSH4-2 = SH4 min - SH2 min). To characterise these agents, various chemical properties, e.g. pH, concentrations of Ca, Pi and F, titratable acidity to pH 7·0 and buffering capacity at the original pH value (β), as well as degree of saturation (pK - pI) with respect to hydroxyapatite (HAP) and fluorapatite (FAP), were determined. Erosive challenge caused a statistically significant reduction in SH for all agents except for coffee, some medications and alcoholic drinks, and non-flavoured mineral waters, teas and yogurts (P < 0·01). By multiple linear regression analysis, 52 % of the variation in ΔSH after 2 min and 61 % after 4 min immersion were explained by pH, β and concentrations of F and Ca (P < 0·05). pH was the variable with the highest impact in multiple regression and bivariate correlation analyses. Furthermore, a high bivariate correlation was also obtained between (pK - pI)HAP, (pK - pI)FAP and ΔSH.

Nanoscale Characterisation of Salivary Pellicle

Salivary pellicle is an organic biofilm formed by the physisorption of proteins and carbohydrates onto the surface of dental enamel exposed to the oral environment. The pellicle has several key roles in oral physiology including lubrication and reduction of friction between teeth during mastication, as well as chemical protection of the enamel against acidic solutions. However, pellicle proteins are known to react with dietary compounds to cause extrinsic staining on the tooth surface.

In this study, nanoindentation and AFM have been used in vitro to examine the acquired salivary pellicle formed in vivo on dental enamel. The mechanical properties, growth, structure and morphology of pellicle grown in vivo on human enamel surfaces have been analysed. In addition, the effects of dietary agents such as polyphenols on the pellicle's morphology and properties have been studied.

It was found that initial adsorption of proteins on the enamel surface occurred within 30 seconds of exposure to the oral cavity, with full growth achieved within 2 hours. Differences in the properties of the pellicles such as surface adhesion, and time dependent effects due to polyphenol interaction were measured using nanoindentation. It was seen that the polyphenol interaction has a significant effect on these properties. These results suggest that the stained pellicle is mechanically stiffer, but also less viscous and more fluid like. This could explain why traditional tooth brushing techniques do not efficiently remove this layer.