Anti-biofilm activity of silver nanoparticle-containing glass ionomer cements.

OBJECTIVE: To develop a silver nanoparticle (AgNP) formulation for incorporation into glass ionomer cements (GICs) which minimises biofilm growth on restoration surfaces. METHODS: GICs, Fuji IX, Ketac Molar, and Riva Selfcure were modified with 6, 10 and 24 µg per GIC capsule of α-lipoic acid-capped AgNPs. Monoculture biofilms of Streptococcus mutans were cultured (72 h) on GIC specimens (n = 3) and biofilm accumulation was quantified using a viability stain with confocal laser scanning microscopy. Compression strength and flexural strength (CS & FS) were measured according to ISO 9917-1:2007 (n = 8, n = 25). GIC colour was measured at 0, 1, and 14 days following AgNP incorporation using a digital spectrophotometer. Silver release from AgNP-modified GIC specimens was monitored at 1, 3, 7 and 14 days using inductively coupled plasma-mass spectrometry. RESULTS: AgNP-modified Fuji IX demonstrated the greatest reduction in biofilm accumulation, with 10 µg Ag/capsule inhibiting biofilm formation by 99%. Ketac Molar and Riva Selfcure required 24 µg Ag/capsule to achieve 78% biofilm reduction. AgNP-modified GICs demonstrated significantly higher CS and FS than sintered silver-containing GICs, and possessed equivalent or higher strength values when compared to unmodified GICs. The colour shades of AgNP-modified GICs were more comparable to VITA shades of non-modified GICs than were sintered silver-containing GICs. The silver (≥99.6%) remained within the GIC for at least two weeks following incorporation. SIGNIFICANCE: AgNP-modified GICs exhibited significant antibiofilm activity and retained mechanical properties equivalent or superior to non-modified GICs. AgNP-modified GICs could reduce bacterial colonisation on and around restorations thereby reducing restoration failure caused by secondary caries.

The Dental Amalgam Phasedown in New Zealand: A 20-year Trend.

BACKGROUND AND OBJECTIVES: Information on the choice of material and performance of restorations placed in a dental practice annually is limited. The Minamata Convention on Mercury is likely to affect the use of amalgam worldwide. The objective of this research was to investigate the use of restorative materials at the University of Otago Faculty of Dentistry in New Zealand from 1998 to 2017. METHODS: Data from the Faculty of Dentistry's database from the years of interest were compiled. These data included information on the characteristics of restorations, including information on the material used and number of surfaces involved for each restoration. The tooth in which each restoration was placed was categorized by arch, tooth type, and deciduous or permanent dentition. RESULTS: Records identified 227,514 permanent restorations placed from January 1998 to December 2017, of which 91.7% were direct restorations. Among direct restorations, composite resin was the most commonly used material, followed by amalgam, glass ionomer, and compomer. The use of amalgam for direct restorations decreased from 52.3% of direct restorations in 1998 to 7.1% in 2017. A corresponding increase was observed in the use of tooth-colored direct restorations, particularly composites. Among indirect restorations, porcelain fused to metal, gold, and stainless steel (in pediatric applications) were the materials most frequently used. CONCLUSIONS: Despite having no official policy on reducing the use of dental amalgam, the Faculty of Dentistry is following the global trend in reducing its use, with composite resin now well established as the predominant restorative material used. If the current rate of decline persists unchecked, the Faculty of Dentistry could transition to being amalgam free by 2020, although it seems likely that the characteristics and principles of use of the material (and its removal) will be taught for some time to come. This knowledge is important to planning curriculum changes needed to prepare graduates for clinical practice.

Antimicrobial Activity of a Colloidal AgNP Suspension Demonstrated In Vitro against Monoculture Biofilms: Toward a Novel Tooth Disinfectant for Treating Dental Caries.

A novel silver nanoparticle (AgNP) formulation was developed as a targeted application for the disinfection of carious dentine. Silver nitrate (AgNO3) was chemically reduced using sodium borohydrate (NaBH4) in the presence of sodium dodecyl sulfate (SDS) to form micelle aggregate structures containing monodisperse 6.7- to 9.2-nm stabilized AgNPs. AgNPs were characterized by measurement of electrical conductivity and dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and inductively coupled plasma mass spectrometry. Antimicrobial activity of AgNPs was tested against planktonic cultures of representative gram-positive and gram-negative oral bacteria using well diffusion assays on tryptic soy broth media and monoculture biofilms grown with brain heart infusion ± sucrose anaerobically at 37°C on microtiter plates. Biofilm mass was measured by crystal violet assay. Effects were compared to silver diamine fluoride and chlorhexidine (negative controls) and 70% isopropanol (positive control) exposed cultures. In the presence of AgNPs, triplicate testing against Streptococcus gordonii DL1, C219, G102, and ATCC10558 strains; Streptococcus mutans UA159; Streptococcus mitis I18; and Enterococcus faecalis JH22 for planktonic bacteria, the minimum inhibitory concentrations were as low as 7.6 µg mL-1 and the minimum bacteriocidal concentrations as low as 19.2 µg mL-1 silver concentration. Microplate readings detecting crystal violet light absorption at 590 nm showed statistically significant differences between AgNP-exposed biofilms and where no antimicrobial agents were used. The presence of sucrose did not influence the sensitivity of any of the bacteria. By preventing in vitro biofilm formation for several Streptococcus spp. and E. faecalis, this AgNP formulation demonstrates potential for clinical application inhibiting biofilms.

Resin Infiltration of Caries in Primary Molars in a Community Setting: 24-Month Randomized Controlled Trial Findings.

This study aimed to assess whether resin infiltration of primary molar proximal lesions is more effective than noninvasive measures in radiographically controlling carious lesion progression into the dentin. A split-mouth randomized controlled trial included 90 children, each with 2 proximal lesions confined to the inner half of the enamel or ≤0.5 mm into the dentin. For each child, lesions were randomly allocated to test (infiltration: DMG Icon preproduct and fluoride varnish) or control (fluoride varnish) status. The primary outcome measure was 24-mo radiographic lesion progression. Placement of a restoration during the study period was counted as lesion progression. Proportions of teeth with progressed lesions were compared using the McNemar test. Children also reported on the treatment's acceptability to them. Children (46% female) ranged in age from 6 to 9 y. Their mean number of decayed, missing, and filled teeth (d3mft) was 2.8 (SD 2.6). At baseline, 58% and 42% of children were at moderate and low risk, respectively. Test and control lesions presented with similar radiographic lesions at baseline. At the 24-mo follow-up, 6 children had moved and 30 teeth had exfoliated. In the test and control groups, 15 of 66 lesions (22.7%) and 30 of 69 lesions (43.5%) had progressed, respectively (P < 0.05). The 2-y therapeutic effect (based on pairwise radiographic readings) of infiltration over fluoride varnish was 20.8% (95% confidence interval, 10.6%-30.2%). Nearly all children (96.7%) had enjoyed their visit to the clinic, and more than two-thirds (72.2%) were not worried about returning for treatment. Infiltration is more efficacious than fluoride varnish for controlling carious lesion progression in proximal lesions in primary molars, and most children find the treatment acceptable (Australian New Zealand Clinical Trials Registry ANZCTR.org.au ACTRN12611000827932). Knowledge Transfer Statement: These study findings can help clinicians decide which caries management approach they wish to use to prevent progression of proximal lesions in primary molars. With consideration of cost and patient preference, this information could lead to more appropriate therapeutic decisions.

A system of calibrating microtomography for use in caries research.

Desktop microcomputed tomography (micro-CT) offers a non-invasive 3-dimensional analysis of structures and their physical properties. To date, the use of micro-CT has mostly involved qualitative observations, with the extent of quantitative analysis relying on automated internal calibration by the micro-CT control software. However, the value of such calibration is limited by machine drift. For an accurate quantitative use of micro-CT, it is recognized that external means of calibration are needed. A novel system of calibration standards, also known as 'phantoms', is presented. A range of low mineral concentration phantoms involving triethylene glycol dimethacrylate/glycerolate dimethacrylate resin mixed with commercial pure hydroxyapatite (HAP), from 0.07 to 1.05 g/cm(3), was fabricated. Sintered HAP was impregnated with the same resin, producing phantoms with medium-level mineral concentrations up to 1.90 g/cm(3). These phantoms were easy to create, proved accurate and stable with repeated use, and were found to mimic the composite nature of dental enamel and dentine structures under investigation.

Effectiveness of sterilisation and disinfection procedures for dental amalgam carriers.

The potential for cross infection through dental amalgam carriers was investigated in 37 Dunedin dental practices and in the University of Otago School of Dentistry. Eighteen practitioners had autoclavable carriers, but only 2 autoclaved them at least daily. The School of Dentistry disinfected plastic carriers and autoclaved metal carriers. Microbiological examination, by culturing from the most commonly contaminated carrier site, showed that the School of Dentistry method for disinfection of plastic carriers was unreliable. Autoclaving was confirmed as the preferred method of sterilisation, but many existing carriers are not suited to this technique.