In vitro salivary pellicles from adults and children have different protective effects against erosion

Erosion behaviour of human, bovine and equine dental hard tissues

Dental hard tissues from different species are used in dental research, but little is known about their comparability. The aim of this study was to compare the erosive behaviour of dental hard tissues (enamel, dentin) obtained from human, bovine and equine teeth. In addition, the protective effect of the pellicle on each hard tissue under erosive conditions was determined. In situ pellicle formation was performed for 30 min on enamel and dentin samples from all species in four subjects. Calcium and phosphate release was assessed during 120 s of HCl incubation on both native and pellicle-covered enamel and dentin samples. SEM and TEM were used to examine surface changes in native enamel and dentin samples after acid incubation and the ultrastructure of the pellicle before and after erosive exposure. In general, bovine enamel and dentin showed the highest degree of erosion after acid exposure compared to human and equine samples. Erosion of human primary enamel tended to be higher than that of permanent teeth, whereas dentin showed the opposite behaviour. SEM showed that eroded equine dentin appeared more irregular than human or bovine dentin. TEM studies showed that primary enamel appeared to be most susceptible to erosion.

Association of salivary parameters and erosive tooth wear in preschool children

The aims of this study were to 1) assess the association between erosive tooth wear (ETW) according to the BEWE (Basic Erosive Wear Examination) scoring system and salivary parameters and 2) compare salivary parameters according to ETW severity in the subgroup of children with ETW. This cross-sectional study included 52 preschool children aged 5 years paired by sex. A calibrated examiner assessed ETW using BEWE criteria, and stimulated saliva was collected to determine salivary flow, osmolality, pH, and buffering capacity. The children were divided into two groups: without ETW (n=26; BEWE score 0) and with ETW (n=26; BEWE scores 1 and 2). Logistic regression analysis was used to determine the magnitude of the association between ETW and salivary parameters and estimates of odds ratios (OR). In the unadjusted analysis, the ETW group was more likely to have lower salivary flow (OR = 0.079; 95%CI = 0.013-0.469; p = 0.005) and lower osmolality (OR = 0.993; 95%CI = 0.985-1.000; p = 0.049). In the adjusted analysis, salivary flow remained significantly associated with ETW (OR = 0.087; 95%CI = 0.014-0.533; p = 0.008). Lower salivary osmolality values were observed in ETW, especially in preschool children with more severe ETW (BEWE score 2). Receiver operating characteristic (ROC) determined a salivary osmolality cutoff point of < 201 for the presence of ETW. In conclusion, salivary flow rate was significantly associated with ETW prevalence. Lower values of salivary osmolality were observed in preschool children with distinct erosive lesions with significant loss of tooth structure (BEWE 2).

Protease-inhibitors added to saliva in vitro influence the erosion protective effect of enamel pellicles

In contrast to pellicles formed in vivo, pellicles formed in vitro provide little to no erosion protection for enamel, possibly due to protein degradation from proteases during pellicle formation. With the objective to achieve a more similar effect as observed for in vivo pellicles, the effects of adding protease inhibitors (PI) to saliva in vitro, and/or exchanging saliva repeatedly during pellicle formation were investigated in a cyclic model of pellicle formation and erosion with human enamel specimens. We repeatedly assessed surface microhardness (SMH), measured initial and final surface reflection intensity (SRI), and determined calcium released during erosion. For all the parameters tested, we observed a clear positive effect on erosion protection when adding PI to saliva for pellicle formation: SMH remained harder, SRI remained higher, and less calcium was released. Additionally, exchanging saliva with fresh one during pellicle formation led to a protective effect, but not as strong as the addition of PI. We conclude that adding protease inhibitors to saliva in vitro for pellicle formation leads to an erosion protective effect, which was further increased by repeatedly exchanging the saliva. Whether the pellicle itself more closely resembles in vivo pellicles remains to be investigated.

Differences in susceptibility of deciduous and permanent teeth to erosion exist, albeit depending on protocol design and method of assessment

Controversial results showing that deciduous teeth are more susceptible to erosion than permanent teeth might be related to study designs. We investigated how different conditions (pH: 3.0, 4.0, 5.0; acid agitation: gentle or vigorous; acid exposure times: 1–5 min) affect the susceptibility of both teeth to erosion. Enamel specimens (90 deciduous, 90 permanent) were distributed into groups (n = 15 permanent, n = 15 deciduous) according to acid pH (pH 5, 4 or 3) and agitation (gentle or vigorous) during erosive challenge. Both milder (less incubation time, gentle agitation, and higher pH) and more severe (longer incubation times, vigorous shaking, and lower pH) conditions were used. Demineralization was measured by relative surface microhardness (rSMH) and calcium released to the acid. Demineralization increased gradually for both teeth with increasing incubation time, agitation (gentle or vigorous), and with decreasing acid pH. The differences between deciduous and permanent teeth depended on the protocol design and assessment method. Under milder conditions, demineralization was better detectable with rSMH. Under more severe conditions, differences were more perceptible with calcium analyses. Differences exist in the susceptibility to erosion between deciduous and permanent teeth, but they are only distinguishable when the appropriate assessment method is used for the specific erosive condition.

Salivary profile of children with erosive tooth wear: a transversal study

The aim of the present transversal study was to evaluate the clinical and biochemical salivary parameters of children with and without erosive tooth wear (ETW). The study population was children aged 4 to 9 years. A trained and calibrated examiner (kappa value for intraexaminer reliability = 0.89) classified the children into ETW (n = 24) and control groups (n = 24), and applied the O'Brien index. The salivary flow rate was initially evaluated by stimulated sialometry (paraffin chewing). Afterwards, the collected saliva was submitted to biochemical analyses of pH, uric acid, total buffering capacity, ferric-reducing antioxidant power, reduced glutathione, calcium, and phosphorus. Among the ETW children, 20 (83%) had dental lesions restricted to enamel, and 4 (17%) presented lesions affecting both enamel and dentin. A statistically significant difference between the groups was obtained only for the pH values (t-test; p = 0.004), with averages of 7.31 and 7.56 for the control and the ETW groups, respectively. Considering the parameters evaluated in general, it is suggested that the salivary profile of children with ETW does not differ considerably from that of children without ETW. However, the pH mean value seems to be slightly higher in ETW children, but is still within the normal physiological range.

Hypoallergenic infant formula lacks transforming growth factor beta activity and has a lower anti-inflammatory activity than regular infant formula

Hypoallergenic formulas are recommended for infants who are not breastfed and cannot tolerate cow milk formulas due to allergy. These formulas are hydrolyzed to break down larger protein chains into shorter, easy-to-digest, and potentially less allergenic proteins. Hydrolysis, however, possibly occurs at the expense of the transforming growth factor beta (TGF-β) and anti-inflammatory activity that is inherent in regular formula. Our objective was to determine the TGF-β and the anti-inflammatory activity of commercially available hypoallergenic and regular formulas. Human gingival fibroblasts were incubated with reconstituted formulas followed by detection of TGF-β target genes and activation of Smad2/3 signaling. Gingival fibroblasts and the oral squamous cell carcinoma cell line HSC-2 were also exposed to formulas before adding interleukin (IL)1β and tumor necrosis factor (TNF)α to provoke expression of pro-inflammatory cytokines. For murine bone marrow-derived macrophages, pro-inflammatory cytokine expression was stimulated with saliva. Changes in p65 nuclear translocation and phosphorylation of smad3 and p38 were analyzed by immunostaining. Our study demonstrated that regular formula, but not hypoallergenic formula, enhanced the expression of TGF-β target genes IL11, PRG4, and NOX4 in gingival fibroblasts. Hypoallergenic formulas also failed to initiate nuclear translocation of Smad2/3 and phosphorylation of Smad3. Moreover, regular formulas were more potent than hypoallergenic formulas in reducing the expression of pro-inflammatory cytokines in gingival fibroblasts, HSC-2 epithelial cells, and murine bone marrow macrophages. Hypoallergenic and regular formulas had a similar capacity to reduce p65 nuclear translocation and phosphorylation of p38 in fibroblasts. These findings suggest that hypoallergenic formulas lack in vitro TGF-β activity and have a lower anti-inflammatory activity compared with regular formulas.

Erosion-Protective Capacity of the Salivary Pellicle of Female and Male Subjects Is Not Different

This study aimed to analyse if the erosion-protective potential of the salivary pellicle is different between female and male subjects. Bovine enamel and dentin specimens (each n = 3) were exposed to the oral cavity of healthy female or male volunteers (each n = 25, females: 25.8 ± 3.5 years, males: 26.7 ± 4.0 years) for 120 min to form a salivary pellicle. Subsequently, each 2 enamel and 2 dentin specimens were eroded with hydrochloric acid (pH 2.6, 60 s). Specimens of the control group (each n = 30) were eroded without presenting a salivary pellicle. Calcium release into the acid was determined photometrically. Additionally, total protein content in the pellicle (each n = 1 enamel and dentin specimen/volunteer) and different salivary parameters (flow rate, pH, buffer capacity, protein, albumin, calcium, phosphate, fluoride) were assessed. Statistical analyses were performed by one-way ANOVA, t tests, multiple linear regressions and Pearson correlations (p < 0.05). The erosion-protective capacity was not significantly different among female (calcium release [% of control]: enamel: 82.6 ± 28.1, dentin: 80.7 ± 24.0) and male (enamel: 76.0 ± 27.5, dentin: 87.1 ± 34.9) subjects. The protein content of the pellicle was not different between female and male subjects. The protein content and pH of unstimulated saliva were significantly reduced in female compared to male volunteers. Calcium release was neither correlated with the protein content of the salivary pellicle nor with salivary parameters. Under the conditions of the present study, the erosion-protective capacity of the salivary pellicle of female and male subjects is not different.

The use of fluoride for the prevention of dental erosion and erosive tooth wear in children and adolescents

BACKGROUND

Erosive tooth wear (ETW) has gained increasing clinical relevance. It is estimated that worldwide 30-50% of deciduous and 20-45% of permanent teeth are affected. One of the most important nutritional factors causing ETW is the overconsumption of soft drinks, but also patient-related factors like reflux or eating disorders can lead to erosive lesions. Whether acids lead to erosive demineralisation depends on their degree of saturation with respect to tooth mineral at their actual pH.

REVIEW

Fluoride compounds like sodium or amine fluoride seem to be of limited efficacy against erosion, the main reason for this is the missing biofilm in the erosive process as well as the lower pH of the acids compared to bacterial acids. This means that to achieve some kind of preventive effect it would be necessary to use products with higher fluoride concentration, which is not an appropriate option for small children, and/or to increase the frequency of application. In addition, the fluoride compound plays a role as promising effects were found when fluoride is combined with titanium or stannous ions. TiF₄ can cause acid-resistant surface coatings and when Sn²⁺/F^- formulations are applied, Sn is not only found on the surface but is also incorporated into enamel and dentine. Both effects make the tooth surface more resistant against acid demineralisation. Different fluoride-containing vehicles have been tested to prevent erosion/ETW, such as toothpastes, rinses, gels and varnishes. Toothpastes offer some degree of protection, especially Sn²⁺-containing formulations, but effects of the active ingredients are sometimes counteracted by the presence of abrasives.

CONCLUSION

Detecting associated factors and influencing them is the main instrument in arresting erosive tooth wear. Additionally, patients at risk for dental erosion should always use an additional fluoride source preferably containing Sn²⁺.

Reduced statherin in acquired enamel pellicle on eroded teeth compared to healthy teeth in the same subjects: An in-vivo study

The aim of this in-vivo study was to compare total protein and four key salivary proteins present in the acquired enamel pellicle (AEP) on eroded and non-eroded surfaces in participants with erosive tooth wear. Participants with erosive tooth wear of dietary non-intrinsic origin, present on the occlusal surfaces of the lower first molars and an unaffected posterior occlusal surface in the same quadrant were recruited from restorative dental clinics at King's College London Dental Institute (n = 29, REC ref 14/EM/1171). Following removal of the salivary film, AEP samples were collected from the eroded occlusal surfaces (EP, n = 29) and the non-eroded occlusal surfaces (NP, n = 29) using 0.5% sodium dodecyl sulfate (SDS) soaked filter papers. Total protein concentration was analysed using bicinchoninic acid assay (BCA). Protein fractions were separated using SDS-PAGE and immunoblotted against: mucin5b, albumin, carbonic anhydrase VI (CA VI) and statherin antibodies. Amounts were quantified using ImageLab software against purified protein standards of known concentration. ANOVA followed by paired t-test and Wilcoxon's matched-pair signed-rank test were used to test statistical significance. The difference was considered to be significant at a P value < 0.05. The total protein on eroded surfaces was significantly lower compared to the total protein on non-eroded surfaces [0.41mg/mL (0.04) and 0.61 mg/mL (0.11)] respectively (p< 0.05). The median (min, max) amount of statherin was also significantly lower on eroded occlusal surfaces [84.1 (20.0, 221.8) ng] compared to AEP from non-eroded teeth in the same subjects [97.1(30.0, 755.6) ng] (p = 0.002). No statistical differences were observed for mucin 5b, albumin or CA VI. The total protein and statherin in the in-vivo AEP were different between eroded and non-eroded tooth surfaces of the same patient.

Metabolite quantification by NMR and LC-MS/MS reveals differences between unstimulated, stimulated, and pure parotid saliva

Saliva is a readily available biofluid that is sensitive to metabolic changes and can be collected through rapid and non-invasive collection procedures, and it shows great promise for clinical metabolomic studies. This work studied the metabolite composition of, and the differences between, saliva samples collected by unstimulated spitting/drooling, paraffin chewing-stimulated spitting, and parotid gland suction using targeted nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for metabolite quantification. As applied here, these two analytical techniques provide complementary metabolite information and together extend the metabolome coverage with robust NMR quantification of soluble metabolites and sensitive targeted LC-MS/MS analysis of bioactive lipids in specific metabolic pathways. The NMR analysis was performed on ultrafiltrated (3kDa cutoff) saliva samples and resulted in a total of 45 quantified metabolites. The LC-MS/MS analysis was performed on both filtered and unfiltered samples and resulted in the quantification of two endocannabinoids (AEA and PEA) and 22 oxylipins, which at present is the most comprehensive targeted analysis of bioactive lipids in human saliva. Important differences in the metabolite composition were observed between the three saliva sample collection methods, which should be taken into consideration when designing metabolomic studies of saliva. Furthermore, the combined use of the two metabolomics platforms (NMR and LC-MS/MS) proved to be viable for research and clinical studies of the salivary metabolome.

Carbohydrate-electrolyte drinks exhibit risks for human enamel surface loss

Objectives

The aim of this investigation was to give insights into the impact of carbohydrate-electrolyte drinks on the likely capacity of enamel surface dissolution and the influence of human saliva exposure as a biological protective factor.

Materials and Methods

The pH, titratable acidity (TA) to pH 7.0, and buffer capacity (β) of common beverages ingested by patients under physical activity were analyzed. Then, we randomly distributed 50 specimens of human enamel into 5 groups. Processed and natural coconut water served as controls for testing three carbohydrate-electrolyte drinks. In all specimens, we measured surface microhardness (Knoop hardness numbers) and enamel loss (profilometry, µm) for baseline and after simulated intake cycling exposure model. We also prepared areas of specimens to be exposed to human saliva overnight prior to the simulated intake cycling exposure. The cycles were performed by alternated immersions in beverages and artificial saliva. ANOVA two-way and Tukey HDS tests were used.

Results

The range of pH, TA, and β were 2.85 - 4.81, 8.33 - 46.66 mM/L and 3.48 - 10.25 mM/L × pH, respectively. The highest capacity of enamel surface dissolution was found for commercially available sports drinks for all variables. Single time human saliva exposure failed to significantly promote protective effect for the acidic attack of beverages.

Conclusions

In this study, carbohydrate-electrolyte drinks usually consumed during endurance training may have a greater capacity of dissolution of enamel surface depending on their physicochemical proprieties associated with pH and titratable acidity.

Does erosion progress differently on teeth already presenting clinical signs of erosive tooth wear than on sound teeth? An in vitro pilot trial

Background

Erosive tooth wear (ETW) is clinically characterized by a loss of tooth surface, and different enamel depths may have different susceptibility to demineralization. Therefore, the aim of this in vitro pilot study was to assess if the progression of erosive demineralization is faster on teeth already presenting signs of ETW when compared to originally sound teeth.

Methods

We selected 23 central incisors: 14 were clinically sound (Sound) and 9 presented clinical signs of early erosive tooth wear (ETW-teeth). The teeth were embedded in resin, leaving an uncovered window of native enamel (6.69 ± 2.30 mm²) on the incisal half of the labial surface. We measured enamel surface reflection intensity (SRI) initially and after each consecutive erosive challenge (1 % citric acid, total of 4, 8, 12, 16, 20 and 24 min). Calcium released to the citric acid was measured with an atomic absorption spectrometer.

Results

We observed higher initial SRI values in ETW-teeth than in Sound teeth (p = 0.007). During in vitro erosive demineralization, we observed that erosion on originally Sound teeth progressed significantly slower (p = 0.033) than on ETW-teeth: SRI decreased by 75 % (from 100 to 25 %) on Sound teeth, and by 89 % (from 100 to 11 %) on ETW-teeth. Calcium release increased during erosion, but presented no significant differences (p = 0.643) between originally Sound (0.031 μmol/mm²) and ETW-teeth (0.032 μmol/mm²). There was satisfactory correlation between calcium release and rSRI values (r_s = −0.66).

Conclusion

The optical reflectometer distinguished originally sound teeth from those with signs of ETW, and the results suggest that acid demineralization progresses differently on teeth already presenting clinical signs of ETW than on sound teeth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-016-0231-y) contains supplementary material, which is available to authorized users.