Håkon Valen Rukke

• Researcher at Nordic Institute of Dental Materials

This study assessed the antibacterial characteristics of the dentin/material interface and dentin surfaces exposed to experimental hydraulic calcium silicate cement (HCSC) with or without bioactive glass (BG) replacement (20% or 40%) or mixed with a silver nanoparticle (SNP) solution (1 or 2 mg/mL), and Biodentine, TotalFill BC RRM putty and Interm...

Hovedbudskap For single kroner produsert av laboratorier både i Norge og i utlandet avdekket denne studien store mangler i funksjonelle egenskaper, så vel som kjemisk sammensetning, og hvorvidt samsvarserklæringen var fullstendig eller i det hele tatt inkludert. Det er tannlegenes ansvar å velge egnet legering, og å kontrollere i samsvarserklæringe...

The main objective of this systematic review was to assess cancer risk, and mortality after cancer diagnosis, for exclusive users of Swedish snus, compared with non‐users of tobacco. We followed international standards for systematic reviews and graded our confidence in the risk estimates using the GRADE approach. Our search gave 2450 articles, of...

For individuals with very high to extremely high caries activity and poor control of daily oral hygiene, a simple treatment for arresting their caries activity is necessary. Silver Diamine Fluoride (SDF) has become increasingly common for this purpose due to its efficacy and ease of application. To avoid or reduce tooth discoloration after SDF trea...

In response to the World Health Organization's (WHO) call to develop alternative antibacterial methods, we investigate endogenous compounds and biopolymers. Lumichrome (LC) is an endogenous, lipophilic degradation product of riboflavin (vitamin B2) that can act as a photosensitizer for antimicrobial applications. LC is also a photocrosslinker of co...

Objective: Use of snus, a moist, smokeless tobacco product, may lead to local changes in the oral mucous membrane in the area where the snus is placed. It can also cause irreversible gingival retraction. This cross-sectional study aimed to investigate the relationship between use of snus, oral mucosal lesions (snus induced lesions) and gingival re...

Aim: The aim of this in vitro study was to compare nine different bonding agents of so-called universal type with one well-recognized, 3-step etch-and-rinse bonding agent, as control, in a composite-to-composite shear bond strength (SBS) test. Materials and methods: Cylindrical composite substrates were made according to manufacturers' specifica...

Background and aims: Smokeless tobacco is a heterogeneous product-group with diverse composition and prevalence globally. Tobacco use during pregnancy is concerning due to risk of adverse pregnancy-outcomes and effects on child health. Nicotine may mediate several of these effects. This systematic review measured health outcomes from Swedish smoke...

Objectives To investigate the effect of inclusion of silver nano-particles (SNP) or bioactive glass (BG) on the surface characteristics and bacterial adhesion of prototype tricalcium silicate (TCS)–based cements alongside two commercial cements, under different aging periods and exposure conditions. Materials and methods A basic formulation of rad...

The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emergin...

Tobacco smoking and use of snus (smokeless tobacco) are associated with adverse effects on pregnancy and neonatal outcomes. Nicotine is considered a key toxicant involved in effects caused by both smoking and snus, while pyrolysis products including polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke represents the constituents most unequall...

Nanotopography influences on bacterial adhesion were investigated with surfaces with controlled interspatial nanopillars distances. Surfaces were coated with proteins (fibrinogen, collagen, serum and saliva) prior to E. coli adhesion under flow conditions. PiFM provided chemical mapping and showed that proteins adsorbed both between and onto the na...

Objective: Assess the biological and physicochemical properties of AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS) leachates with and without chlorhexidine (CHX). Methods: The sealers were studied in no contact and 1-minute contact with CHX. For biological properties (antibacterial activity and cytotoxicity), leachates were formed in saline of...

Aim: Assess whether sodium hypochlorite (NaOCl) or chlorhexidine (CHX) and two irrigation protocols may alter the antibacterial properties of dentine and three endodontic sealers using a novel ex vivo tooth model. Methodology: Prior to antibacterial testing, the tooth model was validated by means of scanning electron microscopy (SEM) to evaluate...

We here report on photoactive organic-inorganic hybrid thin films prepared by the molecular layer deposition (MLD) method. The new series of hybrid films deposited using 2,6-naphthalenedicarboxylic acid (2,6-NDC) and either hafnium chloride (HfCl4), yttrium tetramethylheptanedionate (Y(thd)3) or titanium chloride (TiCl4) were compared with the know...

Objectives To assess long-term survival of pulpotomized primary molars and factors related to the survival of the teeth. Materials and methods This retrospective longitudinal study was based on electronic dental health records of children who attended public health service. Eligible children were <12 years and had a pulpotomy procedure code in the...

Background Stainless-steel crowns (SSCs) are recommended for restorative treatment of young teeth severely affected by caries, fractures or dental developmental disorders (DDDs). However, despite recommendations and clinical evidence, SSCs are not widely used by general dentists, who favour extraction and more conventional restorations. The present...

Objective The project aims to evaluate whether inhalation of particles released upon grinding of dental composites may pose a health hazard to dentists. The main objective of the study was to characterize the dust from polymer-based dental composites ground with different grain sized burs and investigate particle uptake and the potential cytotoxic...

Objectives Assess the antibacterial, physical and chemical properties of AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS) in contact with 2% chlorhexidine digluconate (CHX) used as final irrigant prior to root canal obturation. Methods The antimicrobial properties were investigated by direct contact tests for planktonic and biofilm growth of E. fa...

Bacterial fimbriae are an important virulence factor mediating adhesion to both biotic and abiotic surfaces and facilitating biofilm formation. The expression of type 1 fimbriae of Escherichia coli is a key virulence factor for urinary tract infections and catheter-associated urinary tract infections, which represent the most common nosocomial infe...

Objective Charcoal-containing dentifrices are gaining popularity, but scientific information on their effect on oral health is scarce. This study investigated properties of dentifrices that may affect dentine abrasivity, as well as their ability to adsorb fluoride, their pH and the presence of harmful substances. Materials and methods The dentifri...

Objective This study investigated the effect of surface nano-patterning on adhesion of an oral early commensal colonizer, Streptococcus mitis and the opportunistic pathogen Staphylococcus aureus and human fibroblasts (HDFa) in a laminar flow cell. Methods Nanostructured surfaces were made by functionalizing glass substrates with 40 nm SiO2 nanopar...

The aims of the study were to investigate functional and esthetic properties, the composition of the alloy, and the content of hazardous elements of single dental crowns with metal skeleton and fired porcelain. Epoxy models made from full mouth impressions taken of a patient with a crown preparation of the right maxillary first permanent molar were...

Background: A wide range in the prevalence of molar-incisor-hypomineralization (MIH) has been reported. Population-based studies are recommended. However, such studies are expensive and time-consuming. Objectives: To estimate the magnitude of MIH condition among 8-year-olds based on routine oral health examinations and to associate first permanent...

Aim: This survey assessed Finnish dentists' treatment decisions and choices of restorative materials in selected paediatric dental patient cases, with special emphasis on stainless steel crowns (SSCs). Methods: A questionnaire with patient descriptions and tooth photographs was e-mailed to members of Finnish Dental Society (n=3,747). The respond...

Thin films of metal–organic frameworks (MOFs) are promising for a wide range of applications including membranes for separations and sensor materials in microelectronics. Growth of such thin films using atomic/molecular layer deposition (ALD/MLD) has recently been demonstrated; however, the range of examples is still narrow. Here, we expand the rep...

Introduction: Coronal leakage and reinfection after root canal therapy is an important reason for endodontic failure. Zinc oxide-eugenol (ZOE) -based materials are often used as a coronal seal to prevent secondary infection. The antibacterial effect of ZOE cement is mainly due to leaching of eugenol from the material, but the effect is reported to...

Background: Leakage of unpolymerized methacrylate monomers after placement of methacrylate-containing polymeric dental materials leads to human exposure. Based on studies using murine macrophages and LPS from Escherichia coli (E. coli), dental monomers like 2-hydroxyethyl methacrylate (HEMA) are known to inhibit lipopolysaccharide (LPS) induced cy...

Surface modifications in the nanoscale regime have shown promising potential in the combat against bacterial adhesion and colonization of surfaces. However, detailed knowledge of how the bacteria-substrate interactions occur is still limited. Herein we have used a gradient in nanostructure density on a surface, realized by immobilizing 40 nm sized...

Background: Current knowledge on treatment strategies and choice of restorative materials when treating deep caries or severe dental developmental defects (DDDs) in young individuals is scarce. Therefore, the aim was to investigate Norwegian dentists´ treatment decisions and reasons for treatment choice when treating deep caries in primary teeth a...

Dental health care professionals have the opportunity to play a key role in tobacco prevention and cessation among adolescents. Snus use has increased in Norway, especially in the age group 16–24, whereas there has been a decline in smoking. This study investigated attitudes and activities related to snus prevention among dental health care profess...

The lifespan of a resin‐based restoration is limited, with the main reason for failure being secondary caries. Biofilm formation at the tooth–material interface is a necessary etiological agent for caries development. Dental materials with antimicrobial properties may reduce formation of biofilm and thus increase the longevity of restorations. This...

Objectives: Cellular responses including cell death are induced by in vitro exposure to the un-polymerized dental monomer 2-hydroxyethyl methacrylate (HEMA). Activation of the Nrf2/ARE signaling pathway has been suggested to mediate the cellular responses. Activation of this pathway may occur either indirectly through generation of increased oxida...

Bacteria within the oral cavity live primarily as complex, polymicrobial biofilms. Dental biofilms are necessary etiological factors for dental caries and periodontal diseases but have also been implicated in diseases outside the oral cavity. Biofilm is the preferred lifestyle for bacteria, and biofilms are found on almost any surface in nature. Ba...

Background: Caries decline in the western world is accompanied by strong polarization among children; 8% of Finnish 5-year-olds having 76% of untreated caries. This high caries risk group needs preventive and restorative strategies. Aim: To explore survival of extensive restorations in primary molars. Design: This study was based on health rec...

There is considerable research activity to discover new compounds and to explore new technologies and methods to kill and/ or prevent the formation of dental biofilms. Antimicrobials and other treatments are used in dentistry to eliminate bacteria and bacterial biofilms. Antimicrobial compounds are incorporated into dental materials to inhibit biof...

Introduction: The aim of this study was to investigate the antibacterial activity of 4 endodontic sealers against bacteria planktonic grown or in biofilms commonly detected from persistent and secondary endodontic infections. Methods: The antibacterial activity of the sealers AH Plus, TotalFill BC sealer, RoekoSeal, and Guttaflow 2 was investiga...

Use of physical protective equipment at dental clinics Members of the dental team are exposed daily to biological, chemical and physical agents. These vary for example, from microorganisms to noise, and are present in forms as diverse as aerosols and gasses. National and international directives, legislation and guidelines for infection control, an...

Natural deep eutectic solvents (NADES) are a third class of liquids, separate from water and lipids. Some NADES, especially those containing organic acids, have been suggested to possess antimicrobial properties. Such properties may be advantageous when NADES are used as solvents in e.g. antimicrobial photodynamic therapy. However, to control the t...

Objectives: This study aimed to investigate dentists' exposure to curing light and to obtain information about the dentists' knowledge on practical use and technical features of their curing lights as well as their safety awareness. Methods: A pre-coded questionnaire was sent electronically to all dentists (n=1313) in the Public Dental Service (...

The root canal filling concludes the classical triad in endodontic treatment: biomechanical instrumentation, disinfection and obturation. The purpose of the root canal filling is to prevent penetration of bacteria into the root canal and to prevent access of nutrients and growth of residual bacteria. The function of the root canal filling is to sea...

Objectives: This study aimed to investigate dentists' treatment choices concerning "repair or replacement" of defective restorations. Methods: A pre-coded questionnaire was sent electronically to all dentists (n=1313) in the Public-Dental-Service (PDS) in Norway. Part one: The dentists were asked about age and gender, whether they performed dire...

Interference with bacterial quorum sensing communication provides an anti-virulence strategy to control pathogenic bacteria. Here, using the Enteropathogenic E. coli (EPEC) O103:H2, we showed for the first time that thiophenone TF101 reduced expression of lsrB; the gene encoding the AI-2 receptor. Combined results of transcriptional and phenotypic...

Pairwise alignment of the amino acid sequence of lsrB from Salmonella enterica subsp.serovar enterica typhimurium and E. coli O103:H2 str.12009. The yellow marks represent the amino acids in which AI-2 bind to in the binding pocket of the LsrB receptor. (TIF)

The effect of epinephrine and norepinephrine on planktonic growth. No significant effect on planktonic growth was observed in response to epinephrine or norepinephrine. (TIF)

Natural deep eutectic solvents (NADES) is a newly discovered group of eutectics which has shown promise as a solvent in antimicrobial photodynamic therapy (aPDT). The purpose of this study was to investigate preparations of an anionic porphyrin, meso-tetra-(4-carboxyphenyl)-porphine (TCPP), solubilised in NADES, with regard to their physicochemical...

In Streptococcus mutans, an oral colonizer associated with dental caries, development of competence for natural genetic transformation is triggered by either of two types of peptide pheromones, competence-stimulating peptides (CSPs) (18 amino acids [aa]) or SigX-inducing peptides (XIPs) (7 aa). Competence induced by CSP is a late response to the ph...

Aim . The aim of this study was to investigate the antibacterial and antibiofilm properties of low viscosity chitosan on S. epidermidis growth and biofilm formation. Methods and Results . The antibacterial and antibiofilm properties were investigated, during both planktonic growth and biofilm formation. This was performed using different concentrat...

Streptococcus mitis is a colonizer of the oral cavity and the nasopharynx, and is closely related to Streptococcus pneumoniae. Both species occur in encapsulated and unencapsulated forms, but in S. mitis the role of the capsule in host interactions is mostly unknown. Therefore, the aim of this study was to examine how capsule expression in S. mitis...

Streptococcus pneumoniae infections characteristically cause a high degree of inflammation. The S. pneumoniae polysaccharide capsule prevents opsonophagocytosis and is essential for virulence. The capsule might also be expected to reduce the host’s inflammatory response by inhibiting bacterial interactions with pro-inflammatory signalling proteins...

Introduction: CSP and the recently identified XIP pheromones trigger competence for natural transformation in Streptococcus mutans. XIP has optimal activity in chemically defined medium (CDM), in contrast to CSP that is more effective in complex medium and has limited activity in CDM. Objectives: Our aim was to explore the mechanism of ineffective...

Objective: The aims of the study were to investigate the possible presence of a small hydrophobic peptide (SHP) pheromone system in Streptococcus mitis type strain NCTC 12261, and to investigate transcriptome changes in response to the novel pheromone. Methods: Genome analysis of the sequenced S. mitis strain NCTC 12261 was conducted in two-steps...

Background Carriage of and infection with Streptococcus pneumoniae is known to predominantly induce T helper 17 (Th17) responses in humans, but the types of Th cells showing reactivity towards commensal streptococci with low pathogenic potential, such as the oral commensals S. mitis and S. salivarius, remain uncharacterized. Methods Memory CD4+ T...

The polysaccharide capsule surrounding Streptococcus pneumoniae is essential for virulence. Recently, Streptococcus mitis, a human commensal and a close relative of S. pneumoniae, was also shown to have a capsule. In this study, the S. mitis type strain switched capsule by acquisition of the serotype 4 capsule locus of S. pneumoniae TIGR4, followin...

Objective:In Streptococcus mutans, an oral colonizer associated with dental caries, the competence system is unique among streptococci, as it can be triggered by both CSP and XIP pheromones. CSP is sensed by a histidine kinase of the ComDE two-component system, whereas XIP is sensed inside the cells following internalization by the Opp permease. CS...

The competence-stimulating peptide (CSP) and the sigX-inducing peptide (XIP) are known to induce Streptococcus mutans competence for genetic transformation. For both pheromones, direct identification of the native peptides has not been accomplished. The fact that extracellular XIP activity was recently observed in a chemically defined medium devoid...

The polysaccharide capsule of Streptococcus pneumoniae is a hallmark for virulence in humans. In its close relative Streptococcus mitis, a common human commensal, analysis of the sequenced genomes of six strains revealed the presence of a putative capsule locus in four of them. We constructed an isogenic S. mitis mutant from the type strain that la...

Objectives: To investigate whether the commensal Streptococcus mitis has a functional capsule locus, which is the hallmark of virulence in the closely related pneumococcus, and which characterizes phenotypic differences between S. mitis wild type and its isogenic capsule locus deletion mutant. Material and methods: Genome analyses using compa...