Effect of variations from the recommended powder/liquid ratio on some properties of resin-modified cements

Effect of Biosilicate® Addition on Physical-Mechanical and Biological Properties of Dental Glass Ionomer Cements

This study investigated the influence of incorporating Biosilicate^® on the physico-mechanical and biological properties of glass ionomer cement (GIC). This bioactive glass ceramic (23.75% Na₂O, 23.75% CaO, 48.5% SiO₂, and 4% P₂O₅) was incorporated by weight (5%, 10%, or 15%) into commercially available GICs (Maxxion R and Fuji IX GP). Surface characterization was made by SEM (n = 3), EDS (n = 3), and FTIR (n = 1). The setting and working (S/W time) times (n = 3) and compressive strength (CS) were analyzed (n = 10) according to ISO 9917-1:2007. The ion release (n = 6) was determined and quantified by ICP OES and by UV-Vis for Ca, Na, Al, Si, P, and F. To verify cell cytotoxicity, stem cells from the apical papilla (SCAP) were exposed to eluates (n = 3, at a ratio of 1.8 cm²/mL) and analyzed 24 h post-exposure. Antimicrobial activity against Streptococcus mutans (ATCC 25175, NCTC 10449) was analyzed by direct contact for 2 h (n = 5). The data were submitted for normality and lognormality testing. One-way ANOVA and Tukey's test were applied for the working and setting time, compressive strength, and ion release data. Data from cytotoxicity and antimicrobial activity were submitted for Kruskal-Wallis' testing and Dunn's post hoc test (α = 0.05). Among all experimental groups, only those with 5% (wt) of Biosilicate^® showed better surface quality. Only M5% showed a comparable W/S time to the original material (p = 0.7254 and p = 0.5912). CS was maintained for all Maxxion R groups (p > 0.0001) and declined for Fuji IX experimental groups (p < 0.0001). The Na, Si, P, and F ions released were significantly increased for all Maxxion R and Fuji IX groups (p < 0.0001). Cytotoxicity was increased only for Maxxion R with 5% and 10% of Biosilicate^®. A higher inhibition of S. mutans growth was observed for Maxxion R with 5% of Biosilicate^® (less than 100 CFU/mL), followed by Maxxion R with 10% of Biosilicate^® (p = 0.0053) and Maxxion R without the glass ceramic (p = 0.0093). Maxxion R and Fuji IX presented different behaviors regarding Biosilicate^® incorporation. The impacts on physico-mechanical and biological properties were different depending on the GIC, but therapeutic ion release was increased for both materials.

Evaluation of the Flexural Strength, Water Sorption, and Solubility of a Glass Ionomer Dental Cement Modified Using Phytomedicine

Objectives: Various medicinal plant parts and extracts have been proven to be sources of biologically active compounds, many of which have been incorporated in the production of new pharmaceutical compounds. Thus, the aim of this study was to increase the antimicrobial properties of a glass ionomer cement (GIC) through its modification with a mixture of plant extracts, which were evaluated along with a 0.5% chlorohexidine-modified GIC (CHX-GIC) with regard to the water sorption, solubility, and flexural strength. Methods: Salvadora persica, Olea europaea, and Ficus carcia leaves were prepared for extraction with ethyll alcohol using a Soxhlet extractor for 12 h. The plant extract mixture (PE) was added in three different concentrations to the water used for preparation of a conventional freeze-dried GIC (groups 1:1, 2:1, and 1:2). Specimens were then mixed according to the manufacturer’s instructions and tested against the unmodified GIC (control) and a GIC modified with 0.5% chlorhexidine. Water sorption and solubility were evaluated after 7 days of immersion in distilled water. Flexural strength was evaluated in a three-point bending test after 24 h using a universal material testing machine at a crosshead speed of 1 mm/min. One-way analysis of variance (ANOVA) was used for comparison between the groups. Tukey’s post hoc test was used for pairwise comparison when the ANOVA test was significant. Results: There were no statistically significant differences between the control (M = 20.5%), CHX-GIC (M = 19.6%), 1:1 (M = 20.0%), 1:2 (M = 19.5%), and 2:1 (19.7%) groups with regard to the percentage of water sorption, while for water solubility the 2:1 (M = −0.39%) plant-modified group was significantly different from all of the other groups. Flexural strength test results showed that the 2:1 group (M = 26.1 MPa) recorded significantly higher mean values compared to all other tested groups. Conclusion and clinical relevance: The plant extracts did not negatively affect the water sorption and solubility of the GIC, while the flexural strength was improved by the addition of the plant extract at higher concentrations.

An in vitro assessment of the physical properties of manually- mixed and encapsulated glass-ionomer cements

Objectives

The last decade has seen a variety of modifications of glass-ionomer cements (GICs), such as inclusion of bioactive glass particles and dispensing systems. Hence, the aim was to systematically evaluate effect of mixing modes and presence of reactive glass additives on the physical properties of several GICs.

Materials and methods

The physical properties of eight commercial restorative GICs; Fuji IX GP Extra (C&H), Ketac^TM Fill Plus Applicap (C&H), Fuji II LC (C&H), Glass Carbomer Cement and Equia® Forte Fil, capsulated versus manually mixed were assessed. 256 cylindrical specimens were prepared for compressive strength and microhardness, whilst 128 disc-shaped specimens were prepared for biaxial flexural strength tests. Fluid uptake and fluoride release were assessed. Data were analysed using one-way ANOVA and Games-Howell post-hoc tests (alpha = 0.05).

Results

Both encapsulated GIC/RMGICs exhibited significantly improved mechanical properties in comparison to manually mixed equivalents, which in turn showed higher fluid uptake and early fluoride release (p < 0.05). The glass carbomer cement exhibited improved mechanical properties post ageing and evidence of mineral deposits were apparent in the microstructure.

Conclusions

The mixing mode and inclusion of reactive glass additives in cements had a statistically significant effect on physical properties of the selected GICs-RMGICs.

The effects of erroneous mixing of zinc carboxylate cements

The mechanical properties of luting agents are determined by the mixing ratio of powder and liquid. The purpose of this in vitro study was to evaluate the therapeutic range of zinc carboxylate cements by investigating the mechanical properties of such cements when formulated using erroneous powder/liquid ratios. Using the recommended powder/liquid ratio as a standard, four different mixing ratios (25% and 50% more or less powder) were used to prepare each carboxylate cement (Aqualox, Carboco, Durelon). A veneering composite (Sinfony) was used as control. Vickers hardness and three-body abrasion were evaluated. In each carboxylate cement, both a 25% and 50% increase in liquid content resulted in significantly lower Vickers hardness, whereas a higher powder content altered the saturation concentration but did not result in increased hardness; this effect was particularly obvious in Carboco. Durelon showed a linear relationship between wear and powder/liquid ratio, whereas Carboco and Aqualox displayed a more exponential increase in wear in mixings with an increased liquid content. The mechanical properties of carboxylate cements were altered in mixtures with an increased liquid content, but not in those with a high powder content. Mixing ratio errors greater than 25% may significantly affect the clinical performance of carboxylate cements.

Streptococcal adhesion to various luting systems and the role of mixing errors

OBJECTIVE

This study aims at ranking various luting systems according to their susceptibility to adhering Streptococcus mutans and at evaluating the influence of incongruent mixing ratios on adhesion quantities.

MATERIAL AND METHODS

Circular specimens measuring 8 mm in diameter were made of nine widely used dental cements -- three of them mixed in different ratios -- and then incubated with S. mutans. Adhering streptococci were quantified using a biofluorometric assay in combination with an automated plate reader for cell quantification. Surface roughness (R(a)) was determined by perthometer measurements.

RESULTS

Meron plus revealed the highest R(a) (0.90 microm) and glass the lowest R(a) (<0.01 microm). In regular cement mixtures, the highest mean fluorescence intensities indicated the presence of many viable bacteria [Meron Plus (35,533 relative fluorescence units (rfu)), Maxcem (13,374 rfu), and Panavia F 2.0 (11,701 rfu)]. Moderate fluorescence intensities were found in Harvard (4,171 rfu), Ketac cem (3,766 rfu), Durelon (3,276 rfu), Calibra (3,259), Rely X Unicem (4,358 rfu), and Bifix SE (3,102 rfu). A medium correlation between R(a) and S. mutans adhesion was found. Changes in regular cement proportions (powder/liquid and base/catalyst, respectively) had a significant influence on relative fluorescence intensities, which linearly increased with a higher proportion of liquid in Harvard and with a higher proportion of catalyst in Calibra and Maxcem.

CONCLUSIONS

Various luting systems revealed considerable differences in their potential to adhere S. mutans. Variations from recommended cement proportions led to significant changes in the amount of adhering streptococci.