Pellicle-covered Enamel Research Articles

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.

Quantification of the Adhesion Strength of Candida albicans to Tooth Enamel.

Caries is one of the most prevalent diseases worldwide, which is caused by the degradation of the tooth enamel surface. In earlier research the opportunistic pathogen Candida albicans has been associated with the formation of caries in children. Colonization of teeth by C. albicans starts with the initial adhesion of individual yeast cells to the tooth enamel surface. In this study, we visualized the initial colonization of C. albicans yeast cells on pellicle-covered enamel by scanning electron microscopy. To quantitatively unravel the initial adhesion strength, we applied fluidic force microscopy-based single-cell force spectroscopy to examine the key adhesion parameters adhesion force, rupture length and de-adhesion work. We analyzed single saliva-treated or untreated yeast cells on tooth enamel specimens with or without salivary pellicle. Under all tested conditions, adhesion forces in the lower nanonewton range were determined. Furthermore, we have found that all adhesion parameters were enhanced on the pellicle-covered compared to the uncovered enamel. Our data suggest that initial adhesion occurs through a strong interaction between yeast cell wall-associated adhesins and the salivary pellicle. Future SCFS studies may show whether specific management of the salivary pellicle reduces the adhesion of C. albicans on teeth and thus contributes to caries prophylaxis.

In Vitro Surface Investigation of Calcium Fluoride-like Precipitation on Human Enamel after Topical Treatment with the Organic Fluoride Nicomethanol Hydrofluoride.

The topical fluoride treatment of teeth can lead to a formation of CaF2-like material, which is considered to play a significant role in caries prevention. Different types of fluoride sources are applied. The aim of this study was to analyse the in vitro fluoridation effect of the lesser known organic fluoride compound nicomethanol hydrofluoride (NH) regarding fluoride accumulation and morphological changes on dental enamel surfaces. Materials and Methods: The fluoridation effect was investigated by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) after treatment with fluoride solutions at a concentration of 1350 ppm F - and a pH value of 5.5. NH was tested against inorganic sodium fluoride (NaF) as reference. Fluoridation was done on pellicle-free and pellicle-covered enamel. Results: Formation of globular CaF2-like material was observed for both fluoride types. However, NH led to considerably higher calcium fluoride accumulation on the enamel surface as shown by both EDX and SEM. The globule diameters varied between 0.2 and 0.8 µm. Cross-sectional analysis revealed that the globular precipitates lay directly on the enamel surface; only the very surface-near volume was affected. No statistically significant difference of the fluoridation effect was measured with vs without saliva pre-treatment. Conclusion: The experiments showed a 6 times greater F - surface uptake on dental enamel with NH compared to sodium fluoride, thus suggesting an important role of NH during remineralization phases, fostering equilibrium between de- and remineralization.

The effect of remineralizing agents on acidic erosion of pellicle-covered enamel

The effect of remineralizing agents on acidic erosion of pellicle-covered enamel

Effect of Conventional Mouthrinses on Initial Bioadhesion to Enamel and Dentin in situ

Aim: The study aimed to investigate the effect of a customary fluoride solution, containing sodium fluoride and amine fluoride, on initial biofilm formation on enamel and dentin in situ compared directly to chlorhexidine. Methods: Bovine enamel and dentin specimens were mounted on maxillary splints carried by 9 subjects. After 1 min of pellicle formation, rinses with tap water (control), chlorhexidine (meridol med CHX 0.2%, GABA) and a fluoride mouthrinse (elmex, GABA) were performed for 1 min. Subsequently, the slabs were carried for another 8 h. The adherent bacteria were determined by DAPI staining, live-dead staining and determination of colony-forming units after desorption; glucan formation was visualized with concanavalin A. Additionally, energy-dispersive X-ray spectroscopy (EDX) analysis of the in situ biofilm layers was conducted, and contact angle measurements were performed. Statistical evaluation was performed by means of the Kruskal-Wallis test followed by the Mann-Whitney U test (p < 0.05). Results: In the control group, significantly higher amounts of adherent bacteria were detected on dentin (4.8 × 10⁶ ± 5.4 × 10⁶ bacteria/cm²) than on enamel (1.2 × 10⁶ ± 1.5 × 10⁶ bacteria/cm², DAPI). Chlorhexidine significantly reduced the amount of adherent bacteria (dentin: 2.8 × 10⁵ ± 3.4 × 10⁵ bacteria/cm²; enamel: 4.2 × 10⁵ ± 8.7 × 10⁵ bacteria/cm²). Rinses with the fluoride solution also significantly reduced bacterial adherence to dentin (8.1 × 10⁵ ± 1.5 × 10⁶ bacteria/cm²). Fluoride could not be detected by EDX analysis of the biofilms. Fluoride mouthrinsing did not influence the wettability of the pellicle-covered enamel surface. Conclusion: In addition to the reduction of demineralization and antibacterial effects, fluorides inhibit initial biofilm formation on dental hard tissues considerably, especially on dentin.

Erosion-inhibiting potential of a stannous chloride-containing fluoride solution under acid flow conditions in vitro

Objectives This study aimed to analyse the erosion-inhibiting potential of a single application of stannous chloride-containing fluoride solution on pellicle-covered enamel and dentine under constant acid flow conditions in vitro. Design Bovine enamel ( n = 60) and dentine ( n = 60) samples were exposed 1 h to the oral cavity of 4 healthy volunteers to allow for in situ pellicle formation. Pellicle-covered samples were randomly assigned to three groups (each n = 20 enamel and n = 20 dentine samples; 5 enamel and 5 dentine samples/volunteer) and treated once with a SnCl2/AmF/NaF (800 ppm Sn(II), 500 ppm F, pH 4.5) or a NaF solution (500 ppm F, pH 4.5) for 2 min or remained untreated (controls). Samples were eroded with hydrochloric acid (pH 2.6) in a small erosion chamber at 60 μl/min for 25 min. Calcium release into the acid was monitored in consecutive 30 s intervals for 5 min, then at 1 min intervals up to a total erosion time of 25 min using the Arsenazo III procedure. Data were statistically analysed by random-effects linear models ( p < 0.05). Results The stannous chloride-containing fluoride solution reduced calcium loss of enamel and dentine to up to 6 min and 3.5 min, respectively. Calcium loss (% of control) amounted from 24 ± 7 (30 s) up to 93 ± 14 (6 min) in enamel and from 38 ± 13 (30 s) to 87 ± 15 (3.5 min) in dentine. The sodium fluoride solution was unable to reduce enamel and dentine erosion at any time point. Conclusion A single application of a stannous chloride-containing fluoride solution reduced enamel and dentine erosion up to 6 min and 3.5 min of constant acid flow, respectively.

Protective Effect of Different Tetrafluorides on Erosion of Pellicle-Free and Pellicle-Covered Enamel and Dentine

The aim was to analyze the protective effects of titanium, zirconium and hafnium tetrafluorides on erosion of pellicle-free and pellicle-covered enamel and dentine in vitro. Eight groups of 20 specimens each of bovine enamel and bovine dentine were prepared. Half the specimens in each group were immersed in human saliva for 2 h for pellicle formation. Specimens were then left untreated (controls) or were treated for 120 s with TiF₄, ZrF₄ or HfF₄ solutions (0.4 or 1%) or 1.25% AmF/NaF gel. All specimens were eroded by exposure to hydrochloric acid, pH 2.6, for 25 min. Cumulative calcium release into the acid was monitored in consecutive 30-second intervals for 5 min, then at 2-min intervals up to a total erosion time of 25 min using the Arsenazo III procedure. Data were analyzed by ANOVA. 1% TiF₄ solution offered the best protective effect, especially in dentine (reduction of calcium loss about 50% at 25 min). 1% ZrF₄, 1% HfF₄ and 0.4% TiF₄ also reduced calcium loss, but to a lesser extent. Long-term effects were limited to dentine, while reduction of enamel erosion (about 25%) was restricted to 1-min erosion. The fluoride gel had a protective effect only in dentine. The efficacy of the tetrafluorides was influenced by the presence of the pellicle layer, in that the protection against dentine erosion by TiF₄ and ZrF₄ was greater on pellicle-covered specimens. Tetrafluoride solutions, especially 1% TiF₄, could decrease dental erosion, but were more effective on dentine than on enamel.

The erosion-inhibiting effect of TiF4, SnF2, and NaF solutions on pellicle-covered enamel in vitro

Objective. The aim of this study was to compare the protective effect of TiF4, SnF2, and NaF treatment on the development of erosion-like lesions in pellicle-covered human enamel. Material and Methods. Twelve human molars were each divided into 5 specimens, 4 of which were immersed in saliva for 2 h. Three pellicle-covered specimens from each tooth were treated with a TiF4, SnF2, or NaF solution (all 0.5 M F) for 2 min. Control specimens, one with and one without pellicle, were included. Immersion in acid (0.01 M HCl) was carried out stepwise (2+2+2+2 min). The etching depths (in µm) were measured using white light interferometry. Results. Compared with the control with pellicle, TiF4 reduced enamel loss by 100% after 2 min and by 24% after 8 min of acid exposure. The corresponding values for SnF2 were 45% and 14%. NaF provided no significant protection of the surface. The pellicle-covered specimens showed reduced lesion depths after 6 and 8 min compared to the controls without pellicle. Conclusions. TiF4 gave the best protection against acid attack. SnF2 provided significant protection only after 2 min of acid exposure, while NaF had no significant protective effect.

An in vitro Study on the Effect of TiF4 Treatment against Erosion by Hydrochloric Acid on Pellicle-Covered Enamel

The aim of this in vitro study was to examine the effect of fluoride treatment on pellicle-covered enamel exposed to an acidic challenge simulating gastric reflux. Sixteen bovine and 16 human teeth were sectioned into four pieces, divided into four groups: (1) control, (2) 2-hour pellicle, (3) TiF₄, and (4) 2-hour pellicle + TiF₄, and subsequently subjected to 3 ml 0.01 M HCl stepwise for 4 + 4 + 4 min. The acid was analysed for calcium by atomic absorption spectroscopy. TiF₄ reduced Ca release from enamel by 76, 57 and 56% following the 4 + 4 + 4-min acid exposures, respectively, in bovine and 44, 54 and 54% in human enamel. These results suggest that treatment of enamel with a TiF₄ solution, with or without pellicle removal, may provide protection for the enamel against acid attack.

The effects of pellicle formation on streptococcal adhesion to human enamel and artificial substrata with various surface free-energies.

The influence of a pellicle on streptococcal adhesion was studied. A "ripened" two-hour salivary pellicle and an "early" five-minute salivary pellicle were formed on human enamel and artificial solid substrata with varying surface free-energies. Three strains of oral streptococci, also with widely different surface free-energies, were used for adhesion studies. Pellicle formation and streptococcal adhesion took place at a constant shear rate of 21 s-1. Adhesion of S. mitis BMS to bare and pellicle-covered enamel was low and not significantly affected by the presence of a pellicle (0.7 x 10(6) and 0.6 x 10(6) cells.cm-2, resp.), whereas the numbers of S. sanguis 12 and S. mutans NS adhering to bare enamel (4.2 x 10(6) cells.cm-2 and 13.8 x 10(6) cells, cm-2, resp) were significantly reduced by the presence of a pellicle. This reduction was almost complete after only five minutes of salivary protein adsorption (1.9 x 10(-6) and 1.1 x 10(6) cells.cm-2 for S. sanguis and S. mutans, resp.) but further reduced for S. sanguis adhering to a ripened pellicle (0.7 x 10(6) cells.cm-2). The numbers of streptococci adhering at equilibrium to bare enamel could be fitted to a thermodynamically based model, which was previously described for bacterial adhesion to homogenous artificial substrata. Streptococcal adhesion to artificial substrata exposed to saliva was low, and the differences among uncoated materials were markedly reduced even after only five minutes' exposure to saliva.