Abrasive effects of diamond dentifrices on dentine and enamel

This study was to analyse the abrasive wear of differently composed diamond dentifrices loaded with 2.4 µm diamond particles on dentine and enamel surfaces in vitro. Bovine specimens were brushed with a diamond-loaded dentifrice (DD2; 2 g particles/kg), a diamond-loaded dentifrice (1.5 g/kg) containing 20% hydrated silica as extra abrasive (DD1.5+S), or a diamond-loaded dentifrice (3 g/kg) containing 20% hydrated silica abrasive (DD3+S). Values were compared to those obtained with Colgate Total (CT) and Elmex Sensitive plus (ES). Brushing was performed using a cross brushing machine (F = 2.5 N; 120 brushing strokes/min). Abrasive wear [µm] of specimens (n = 12) was measured profilometrically and adjusted to 10,000 brushing strokes (10 kBS). Data were compared between groups using one-way ANOVA and post-hoc pairwise tests with Tukey correction, alpha = 0.05. Diamond dentifrices and ES showed no difference on dentine specimens: DD2 7.7 ± 2.6 µm/10 kBS; DD1.5+S 10.1 ± 2.3 µm/ 10 kBS; DD3+S 10.1 ± 2.6 µm/10 kBS; ES 7.4 ± 1.1 µm/10 kBS, while CT­brushed specimens exhibited significantly higher dentinal abrasion compared to all other groups: CT 31.0 ± 7.7 µm/ 10 kBS. Diamond loading significantly influenced enamel wear (mean ± SD µm/10 kBS): DD2 1.8 ± 0.5 µm/10 kBS. Conversely, addition of the silica abrasive reduced these values: DD1.5+S 1.1 ± 0.3 µm/10 kBS; DD3+S 1.6 ± 0.3 µm/10 kBS. CT and ES revealed similarly low values: CT 0.3 ± 0.1 µm/10 kBS; ES 0.2 ± 0.1 µm/10 kBS. These data suggest that abrasion caused by diamond particles in experimental toothpastes is differentially affected by diamond particle load, additional abrasives, and the type of hard tissue.

Visualizing the dental biofilm matrix by means of fluorescence lectin-binding analysis.

The extracellular matrix is a poorly studied, yet important component of dental biofilms. Fluorescence lectin-binding analysis (FLBA) is a powerful tool to characterize glycoconjugates in the biofilm matrix. This study aimed to systematically investigate the ability of 75 fluorescently labeled lectins to visualize and quantify extracellular glycoconjugates in dental biofilms. Lectin binding was screened on pooled supragingival biofilm samples collected from 76 subjects using confocal microscopy. FLBA was then performed with 10 selected lectins on biofilms grown in situ for 48 h in the absence of sucrose. For five lectins that proved particularly suitable, stained biovolumes were quantified and correlated to the bacterial composition of the biofilms. Additionally, combinations of up to three differently labeled lectins were tested. Of the 10 lectins, five bound particularly well in 48-h-biofilms: Aleuria aurantia (AAL), Calystega sepiem (Calsepa), Lycopersicon esculentum (LEA), Morniga-G (MNA-G) and Helix pomatia (HPA). No significant correlation between the binding of specific lectins and bacterial composition was found. Fluorescently labeled lectins enable the visualization of glycoconjugates in the dental biofilm matrix. The characterization and quantification of glycoconjugates in dental biofilms require a combination of several lectins. For 48-h-biofilms grown in absence of sucrose, AAL, Calsepa, HPA, LEA, and MNA-G are recommendable.

Oral biofilm and caries-infiltrant interactions on enamel.

OBJECTIVES: This study aimed to analyze interactions between oral biofilms and a dental triethylene glycol dimethacrylate (TEGDMA)-based resin infiltration material on enamel. METHODS: Demineralized enamel specimens (14 days, acidic buffer, pH 5.0) were either infiltrated with a commercial TEGDMA resin and subjected to a three-species biofilm (Streptococcus mutans UAB 159, Streptococcus oralis OMZ 607 and Actinomyces oris OMZ 745) (group 1), applied to the biofilm (group 2), or merely resin infiltrated (group 3). A control group received no treatment (4). Biofilm formation and metabolic activity of biofilms were measured for group (1) and (2) after 24h CFU and a resazurin assay. Resin biodegradation was measured for group (1) and (3) by high performance liquid chromatography (HPLC) coupled with mass spectrometry after 6 and 24h incubation. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) images were taken to study the biofilm and material's autofluorescence in groups (1-4) after 24h. RESULTS: SEM and CLSM images showed reduced biofilm formation on resin-infiltrated specimens (group 1) compared to group 2, while no biofilm was detectable on groups 3 and 4. CFU data (log10 CFU per mL) of group 1 showed significantly reduced bacterial numbers (p<0.05) compared to group 2. However, HPLC analysis of TEGDMA leakage after 6h and 24h revealed no differences between group 1 and group 3. CONCLUSIONS: The results of the current study indicate that freshly resin-infiltrated enamel surfaces show a biofilm reducing effect, while monomer leakage was not affected by bacterial presence. CLINICAL SIGNIFICANCE: Resin infiltrated enamel surfaces are constantly exposed to the oral microflora. Yet, it is not known how biofilms interact with enamel-penetrated resins and if and to which extent accessory alignments in oral hygiene are needed.

Mechanical effects of different Swiss market-leading dentifrices on dentin.

In order to estimate the potential of dentifrices to harm exposed dentin, the mechanical properties of 15 dentifrices available in the Swiss market were investigated. A total of 120 bovine dentin samples were irradiated and analyzed for relative dentin abrasion (RDA). To investigate subsequent increases in surface roughness (Ra), dentin specimens (n = 180) were analyzed profilometrically at baseline and after brushing with test slurries. The cleaning efficacy (Ce) was determined using artificially stained tooth specimens (n = 180). The available fluoride content of the dentifrices was measured in respective slurries using an ion-selective electrode. The results of the mechanical analyses were categorized into four or five groups for each parameter. Four potential user groups were defined according to individual problem specifications and user demands. The results were compared to those of an earlier investigation of dentifrices published in 1998. The RDA results exceeded the values declared by the manufacturers and correlated significantly with the results of the Ra measurements. A significant positive correlation of RDA and Ce values was also shown. The measured fluoride content was often below the fluoride, declared by the manufactures. Only a few of the tested dentifrices qualified as suitable for all potential user groups. Major differences were observed between the mechanical properties found in the present study compared to those found in 1998. These changes in the properties of dentifrices during the past decade should be considered with respect to providing adequate recommendations for individual user demands.

Interproximal biofilm removal by intervallic use of a sonic toothbrush compared to an oral irrigation system.

BACKGROUND: The purpose of this in-vitro study was to investigate the potential of biofilm removal in interproximal tooth regions using intervallic cleaning with an oral irrigator or a sonic toothbrush. METHODS: Three-species biofilms (Streptococcus mutans (OMZ 918), Streptococcus oralis SK 248 (OMZ 60), Actinomyces naeslundii (OMZ 745)) were grown on hydroxyapatite discs for 3 days in culture media. Every 24 h, specimens were incubated for 15 min in resazurin solution (i.e., culture medium and 10 % v/v alamarBlue®) to measure the metabolic activity with a fluorescence spectrophotometer in relative fluorescence units (rfu) at baseline. Then, specimens were fixed in interproximal holding devices and underwent treatment with an oral irrigator (WF; Waterpik® Sensonic WP-100E), an active sonic toothbrush (WPa), or an inactive sonic toothbrush (WPi; Waterpik® Sensonic SR-3000E) for 10 s (n = 18/group). Untreated biofilms served as controls (CO). After treatment, bacterial activity was re-measured, and specimens were re-grown in fresh medium for 24 h until next cleaning procedure. Altogether, cleaning was repeated in intervals of three treatment days (d1, d2, d3). After d3, SEM images were taken (n = 8) and CFU was measured (n = 3). Metabolic activity was analyzed for each disc separately, rfu values were averaged for d1 to compare initial biofilm stability, and ratios of baseline and post-treatment values were compared. Results were analyzed using ANOVA with the post-hoc Scheffé test, or Kruskal-Wallis with post-hoc Mann-Whitney test. RESULTS: Median baseline rfu-values of d1 resulted in 7821.8 rfu (interquartile range = 5114.5). Highest reduction in metabolic activity was recorded significantly for the oral irrigator used for 10 s (residual activity per day d1: WF 17.9 %, WPa 58.8 %, WPi 82.5 %, CO 89.6 %; d2: WF 36.8 %, WPa 85.2 %, WPi 82.5 %, CO 90.0 %; d3: WF 17.2.%, WPa 79.6 %, WPi 96.3 %, CO 116.3 %). SEM images of untreated specimens (CO) and specimens treated with the sonic toothbrush (WPa and WPi) showed huge amounts of biofilm, while oral irrigator-treated specimens (WF) revealed barely any bacteria. CFU data confirmed the graduations between the groups. CONCLUSIONS: Cleaning of interproximal regions achieved better success with an oral irrigator as compared to the use of a sonic toothbrush. (350/350 words).

pH-dependent antibacterial effects on oral microorganisms through pure PLGA implants and composites with nanosized bioactive glass.

Biomaterials made of biodegradable poly(α-hydroxyesters) such as poly(lactide-co-glycolide) (PLGA) are known to decrease the pH in the vicinity of the implants. Bioactive glass (BG) is being investigated as a counteracting agent buffering the acidic degradation products. However, in dentistry the question arises whether an antibacterial effect is rather obtained from pure PLGA or from BG/PLGA composites, as BG has been proved to be antimicrobial. In the present study the antimicrobial properties of electrospun PLGA and BG45S5/PLGA fibres were investigated using human oral bacteria (specified with mass spectrometry) incubated for up to 24 h. BG45S5 nanoparticles were prepared by flame spray synthesis. The change in colony-forming units (CFU) of the bacteria was correlated with the pH of the medium during incubation. The morphology and structure of the scaffolds as well as the appearance of the bacteria were followed bymicroscopy. Additionally, we studied if the presence of BG45S5 had an influence on the degradation speed of the polymer. Finally, it turned out that the pH increase induced by the presence of BG45S5 in the scaffold did not last long enough to show a reduction in CFU. On the contrary, pure PLGA demonstrated antibacterial properties that should be taken into consideration when designing biomaterials for dental applications.