The Minamata Convention on Mercury and its implications for management of dental caries in low- and middle-income countries

Evaluation of dental cements derived from mixtures of highly reactive ionomer glasses and bottle glass: Cement manipulation, mechanical, fluoride ion releasing, radiopaque and setting properties

OBJECTIVES

To evaluate the mechanical properties, fluoride release, radiopacity, and setting characteristics of dental cements derived from highly reactive ionomer glasses and bottle glass mixtures.

METHODS

Two highly reactive glass series, LG99 and LG117, were synthesized, milled, sieved, and characterized using XRD and laser particle size analysis. These glasses were mixed with predetermined ratios of ground bottle glass, poly(acrylic acid), and aqueous tartaric acid to form glass ionomer cements. The cements' working time (WT), setting time (ST), fluoride release, radiopacity, compressive strength (CS), and elastic modulus (EM) were evaluated. Mean differences in CS were analyzed using multivariate ANOVA with Tukey's post hoc test at p = 0.05.

RESULTS

The WT and ST for both groups ranged from 1.5 to 2.5 min. LG99 series cements showed significantly higher CS (∼65 MPa) and EM (∼2 GPa) than LG117 series (p < 0.05). Both series showed similar fluoride release profiles, peaking at 1.2 mmol/L at 28 days. Radiopacity for LG99 ranged from 0.97 to 1.34, while LG117 ranged from 0.60 to 0.95. Solid state 27Al magic-angle spinning-nuclear magnetic resonance (MAS NMR) confirmed the presence of Al(IV) and Al(VI), indicating setting completion by one day for both series. Bottle glass showed a chemical shift at 55.8 ppm, overlapping with LG99's Al(IV) signal. The 19F MAS NMR spectra revealed Al-F and F-Sr(n) species in all glasses, with LG117 forming CaF2 after one day in deionized water.

CONCLUSION

Mixtures of highly reactive ionomer glass and bottle glass produced cements with satisfactory properties for dental applications. Further research is needed to optimize their formulation and properties.

A comparative study on the mechanical and antibacterial properties of BPA-free dental resin composites

OBJECTIVE

The commonly used base monomer utilized in resinous commercial dental restorative products is bis-GMA which is derived from bisphenol-A (BPA) - a well-known compound which may disrupt endocrine functions. To address concerns about its leaching into the oral environment and to optimize the quality of dental composites, a BPA-free alternative base monomer, fluorinated urethane dimethacrylate (FUDMA), was designed by modifying a UDMA monomer system.

METHODS

Nine groups of composites were prepared by mixing the base monomers and TEGDMA in a ratio of 70/30 wt% to which were added silanized glass particles (mean diameter: 0.7 µm) in 3 different volume fractions (40, 45, and 50 vol%). Bis-GMA and UDMA base monomers were used as control groups in the same ratios. Various properties including degree of conversion (DC), flexural strength (FS) and flexural modulus (FM), water sorption (WS), solubility (SL), surface hardness and roughness, and initial adhesion property against S.mutans were investigated. One-way analysis of variance followed by Bonferroni test at α = 0.05 was used to analyze the results.

RESULTS

A significant difference in FS between FUDMA-based composite with 40 vol% filler (120.3 ± 10.4 MPa) and Bis-GMA-based composite with the same filler fraction (105.8 ± 10.0 MPa) was observed but there was no significant difference among other groups. The UDMA based group exhibited the highest WS (1.3 ± 0.3 %). Bis-GMA showed greater initial bacterial adhesion but was not statistically different from the other groups (p = 0.082).

SIGNIFICANCE

FUDMA-based resin composites exhibit comparable mechanical and bacterial adhesion properties compared with Bis-GMA and UDMA-based composites. The FUDMA composites show positive outcomes indicating they could be used as substitute composites to Bis-GMA-based composites.

Concept of a Novel Glass Ionomer Restorative Material with Improved Mechanical Properties

The objective of this study was to transfer the concept of ductile particle reinforcement to restorative dentistry and to introduce an innovative glass ionomer material that is based on the dispersion of PEG-PU micelles. It was hypothesized that reinforcing a conventional glass ionomer in this way increases the flexural strength and fracture toughness of the material. Flexural strength and fracture toughness tests were performed with the novel reinforced and a control glass ionomer material (DMG, Hamburg, Germany) to investigate the influence of the dispersed micelles on the mechanical performance. Transmission electron microscopy was used to identify the dispersed micelles. Fracture toughness and flexural strength were measured in a 3-point-bending setup using a universal testing machine. Before performing both tests, the specimens were stored in water at 37 °C for 23 h. The fracture toughness (MPa∙m0.5) of the novel glass ionomer material (median: 0.92, IQR: 0.89-0.94) was significantly higher than that of the control material (0.77, 0.75-0.86, p = 0.0078). Significant differences were also found in the flexural strength (MPa) between the reinforced (49.7, 45.2-57.8) and control material (41.8, 40.6-43.5, p = 0.0011). Reinforcing a conventional glass ionomer with PEG-PU micelles improved the mechanical properties and may expand clinical applicability of this material class in restorative dentistry.

Randomized clinical split-mouth study on a novel self-adhesive bulk-fill restorative vs. a conventional bulk-fill composite for restoration of class II cavities - results after three years

OBJECTIVES

This randomized prospective split-mouth study evaluated the clinical performance of a novel, tooth-colored, self-adhesive bulk-fill restorative (SABF, 3M) for restoration of class II cavities as compared to a conventional bulk-fill composite (Filtek One, 3M; FOBF) over 36 months. The null-hypothesis was that both materials perform equally regarding clinical success and performance according to the FDI clinical criteria and scoring system.

METHODS

30 patients received one SABF and one FOBF restoration each. For FOBF, Scotchbond Universal (3M) was used as adhesive (self-etch mode), whereas SABF was applied without adhesive. Two blinded examiners evaluated the restorations at baseline, 24 and 36 months using FDI criteria. Data were analyzed non-parametrically (χ²-tests; α=0.05).

RESULTS

29 patients were available for the 24- and 36-month examinations. Clinical success rate was 96.6% for both materials at 36-mo (one restoration failure due to secondary caries each). All other restorations revealed clinically acceptable FDI scores at all recalls. FOBF performed significantly better than SABF at all time points regarding surface lustre (p<0.001) and color match and translucency (p<0.001) and regarding marginal staining at 36-months (p=0.008). Marginal staining and marginal adaptation deteriorated significantly over time for both materials (both p<0.001).

CONCLUSIONS

The null-hypothesis could only partially be rejected. Both materials performed similarly regarding clinical success and performance within 36 months of clinical service, but SABF exhibited significantly inferior, but clinically fully acceptable esthetic properties as compared to FOBF. Both restorative materials showed clinically fully acceptable results over 36 months of clinical service and thus may be recommended for clinical use.

CLINICAL SIGNIFICANCE

The novel tooth-colored self-adhesive bulk-fill restorative exhibited clinically fully acceptable results over 36 months of clinical service, similarly to a conventional bulk-fill restorative used with a universal adhesive, but with slight shortcomings in esthetic properties. Therefore, both restorative materials may be recommended for clinical use.

Effect of finishing protocols and staining solutions on color stability of dental resin composites

Objective

The objective of this study was to evaluate the effect of finishing protocol and exposure to staining solutions on color stability of dental resin composites.

Materials and Methods

A nanofill and microhybrid composite, three finishing protocols (mylar, Soflex disc, and white polishing stone) and four staining solutions (tea, red wine, khat extract—two concentrations, control—distilled water) were evaluated. A digital spectrophotometer was used for color change (ΔE) measurements employing the CIE‐Lab‐color system. Paired/independent‐sample t test and two‐way analysis of variance (ANOVA) followed by Tukey's honestly significant difference posthoc test were used for inferential statistics at α = .05.

Results

Soflex finish was associated with least staining and comparable color stability for the two materials in tea and red wine. In Khat 2, microhybrid composite had statistically significant better color stability than nanofill for Soflex finish (14 days t = 3.270, p = .011). For microhybrid composite, mylar resulted in highest mean ΔE, whereas Soflex recorded the least in all staining solutions. For nanofill composite, white stone resulted in highest mean ΔE, whereas Soflex demonstrated the least mean ΔE in all staining solutions, except red wine where mylar demonstrated the least mean ΔE. For mylar finish, nanofill demonstrated statistically significant better color stability than microhybrid in both red wine (14 days t = 4.902, p = .001) and Khat 1 (14 days t = 3.252, p = .012). For stone finish, microhybrid demonstrated statistically significant better color stability than nanofill in all staining solutions (14 days t ≥ 4.785, p ≤ .001). Two‐way ANOVA showed a statistically significant difference in mean ΔE between and within specimens (F = 42.658, p < .001). All staining solutions caused clinically unacceptable discoloration for mylar and white stone finish. For Soflex finish, red wine produced clinically unacceptable color difference beyond 48 h.

Conclusion

There was a difference in color stability of resin composites depending on filler type, further influenced by finishing protocol. Soflex disc finish results in better color stability than mylar and white stone in both microhybrid and nanofill composites.

Clinical significance

Esthetic dental restorations such as resin composites are routine in contemporary restorative practice. Color stability of composites may be influenced by surface finish, dependent on the filler type, and consumption of chromogenic substances such as khat. To prolong their service, selection of suitable finishing protocols is an important consideration.

[Global oral health in the international health policy spotlight-challenges and new opportunities for sustainable improvement]

Orale Erkrankungen sind ein signifikantes globales Gesundheitsproblem über alle Länder und Bevölkerungsgruppen hinweg. Mit fast 3,5 Mrd. Erkrankungsfällen (2017) sind so viele Menschen betroffen wie von keiner anderen Krankheitsgruppe. Die Haupterkrankungen sind unbehandelte Karies der bleibenden oder der Milchzähne, fortgeschrittene Parodontopathien, Zahnlosigkeit sowie Karzinome der Mundhöhle und Lippen. Bei weitgehend unverändert hoher globaler Prävalenz erhöhen durch Bevölkerungswachstum bedingte stark steigende Fallzahlen den Druck auf schwache oder überlastete Gesundheitssysteme, insbesondere in Ländern der unteren und mittleren Einkommensgruppen.

Dennoch wird der Mundgesundheit in vielen Ländern nur unzureichende Priorität eingeräumt und sie erhält als wichtiges Thema im gesundheitspolitischen Diskurs der deutschen und globalen Akteure nach wie vor wenig Aufmerksamkeit. Eine der fundamentalen Herausforderungen ist dabei die Gewährleistung eines allgemeinen und fairen Zugangs zu adäquater universeller Basisgesundheitsversorgung für alle Menschen ohne Verursachung von finanziellen Härten (Universal Health Coverage).

Dieser Beitrag gibt einen einführenden Überblick über die globalen Trends der weltweiten Krankheitslast der oralen Haupterkrankungen, die von starken Ungleichheiten geprägt sind. Verbesserungsansätze aus der bevölkerungsweiten Risikoreduktion und Prävention, der Versorgungsplanung sowie gesundheitspolitische Lösungen werden kurz vorgestellt. Dabei werden die im internationalen Diskurs wichtigen Themen angesprochen und die im Rahmen einer Lancet-Artikelserie zur globalen Mundgesundheit aus dem Jahr 2019 entwickelten Reformbereiche besprochen. Schließlich werden neue Initiativen diskutiert sowie Empfehlungen für die deutsche und internationale gesundheitliche Entwicklungspolitik gegeben, die in den kommenden Jahren die Situation der globalen Mundgesundheit entscheidend verbessern könnten.