Karl-Anton Hiller

FDI World Dental Federation: clinical criteria for the evaluation of direct and indirect restorations—update and clinical examples

In 2007, new clinical criteria were approved by the FDI World Dental Federation and simultaneously published in three dental journals. The criteria were categorized into three groups: esthetic parameters (four criteria), functional parameters (six criteria) and biological parameters (six criteria). Each criterion can be expressed with five scores, three for acceptable and two for non-acceptable (one for reparable and one for replacement). The criteria have been used in several clinical studies since 2007, and the resulting experience in their application has led to a requirement to modify some of the criteria and scores. The two major alterations involve staining and approximal contacts. As staining of the margins and the surface has different causes, both phenomena do not appear simultaneously. Thus, staining has been differentiated into marginal staining and surface staining. The approximal contact now appears under the name “approximal anatomic form” as the approximal contour is a specific, often non-esthetic issue that cannot be integrated into the criterion “esthetic anatomical form”. In 2008, a web-based training and calibration tool called e-calib (www.e-calib.info) was made available. Clinical investigators and other research workers can train and calibrate themselves interactively by assessing clinical cases of posterior restorations which are presented as high-quality pictures. Currently, about 300 clinical cases are included in the database which is regularly updated. Training for eight of the 16 clinical criteria is available in the program: “Surface lustre”; “Staining (surface, margins)”; “Color match and translucency”; Esthetic anatomical form”; “Fracture of material and retention”; “Marginal adaptation”; “Recurrence of caries, erosion, abfraction”; and “Tooth integrity (enamel cracks, tooth fractures)”. Typical clinical cases are presented for each of these eight criteria and their corresponding five scores.

Permeability characteristics of bovine and human dentin under different pretreatment conditions.

In order to use bovine dentin instead of human dentin for in vitro adhesion and cytotoxicity tests the permeability characteristics of human and bovine dentin should be similar. In the present study hydraulic conductance (Lp) and diffusional water flux (J5) of human and bovine dentin slices were compared. The permeability experiments were performed in a split chamber using tritiated water in physiological saline. Lp and Js of bovine dentin were 0.7- to 2.4-fold and 1.1- to 3.5-fold that of human dentin (not statistically significant). For human and bovine dentin Lp and Js increased with etching and showed an inverse linear relationship (r > or = 0.7) with dentin thickness. The variability of bovine data was low (perfusion = 30%, diffusion = 22%) and about half that of the human data. In conclusion bovine dentin near the cementoenamel junction seems to be a suitable alternative for coronal human dentin for in vitro tests with respect to transdentinal permeability characteristics.

Incidence of Health Problems Associated with Tattooed Skin: A Nation-Wide Survey in German-Speaking Countries

Background: Millions of people are tattooed. However, the frequency of health problems is unknown. Methods: We performed an Internet survey in German-speaking countries. Results: The provenance of tattooed participants (n = 3,411) was evenly distributed in Germany. The participants had many (28%; >4) and large tattoos (36%; ≧900 cm2). After tattooing, the people described skin problems (67.5%) or systemic reactions (6.6%). Four weeks after tattooing, 9% still had health problems. Six percent reported persistent health problems due to the tattoo, of which females (7.3%) were more frequently concerned than males (4.2%). Colored tattoos provoked more short-term skin (p = 0.003) or systemic (p = 0.0001) reactions than black tattoos. Also the size of tattoos and the age at the time of tattooing play a significant role in many health problems. Conclusions: Our results show that millions of people in the Western world supposedly have transient or persisting health problems after tattooing. Owing to the large number and size of the tattoos, tattooists inject several grams of tattoo colorants into the skin, which partly spread in the human body and stay for a lifetime. The latter might cause additional health problems in the long term.

Differential gene expression involved in oxidative stress response caused by triethylene glycol dimethacrylate.

Triethylene glycol dimethacrylate (TEGDMA) is a comonomer that is released from dental resin-based materials into hydrophilic solvents. The compound reduces cell vitality, and causes genotoxicity in mammalian cells in vitro. Here, we used gene expression profiling, combined with pathway analysis tools, to identify the molecular events associated with TEGDMA cytotoxicity in human fibroblasts using Affymetrix HG-U133A 2.0 GeneChip arrays. Increased ROS production and a cell cycle delay caused by 3mm TEGDMA after a 6h exposure were related to a cell response at the transcriptional level. The predominant biological processes associated with the genes that were differentially expressed in untreated and treated cell cultures included oxidative stress, cellular growth, proliferation and morphology, cell death, gene expression as well as DNA replication and repair. The most significantly upregulated genes were GEM (17-fold), KLHL24, DDIT4, TGIF, DUSP5 and ATF3, which are all related to the regulation of the cell structure, stress response, and cell proliferation. TXNIP was the most downregulated transcript (five-fold), whose gene product regulates the cellular redox balance. The downregulation of NRG1, ASPM, FBXO5, and PLK2 is linked to the regulation of cell proliferation and cell structure. The underlying mechanisms of the up- and downregulation of genes seem to be activated by the production of ROS, and the related regulation of the cellular redox balance disturbed in the presence of TEGDMA appears to be of the utmost importance. The coordinated induction of genes coding for oxidative stress response and antioxidant proteins is a critical mechanism of protection against TEGDMA-induced cell damage.

TEGDMA-induced oxidative DNA damage and activation of ATM and MAP kinases

The development of strategies for the protection of oral tissues against the adverse effects of resin monomers is primarily based on the elucidation of underlying molecular mechanisms. The generation of reactive oxygen species beyond the capacity of a balanced redox regulation in cells is probably a cause of cell damage. This study was designed to investigate oxidative DNA damage, the activation of ATM, a reporter of DNA damage, and redox-sensitive signal transduction through mitogen-activated protein kinases (MAPKs) by the monomer triethylene glycol dimethacrylate (TEGDMA). TEGDMA concentrations as high as 3-5 mM decreased THP-1 cell viability after a 24h and 48h exposure, and levels of 8-oxoguanine (8-oxoG) increased about 3- to 5-fold. The cells were partially protected from toxicity in the presence of N-acetylcysteine (NAC). TEGDMA also induced a delay in the cell cycle. The number of THP-1 cells increased about 2-fold in G1 phase and 5-fold in G2 phase in cultures treated with 3-5 mM TEGDMA. ATM was activated in THP-1 cells by TEGDMA. Likewise, the amounts of phospho-p38 were increased about 3-fold by 3 mM TEGDMA compared to untreated controls after a 24h and 48h exposure period, and phospho-ERK1/2 was induced in a very similar way. The activation of both MAPKs was inhibited by NAC. Our findings suggest that the activation of various signal transduction pathways is related to oxidative stress caused by a resin monomer. Signaling through ATM indicates oxidative DNA damage and the activation of MAPK pathways indicates oxidative stress-induced regulation of cell survival and apoptosis.

The influence of glutathione on redox regulation by antioxidant proteins and apoptosis in macrophages exposed to 2-hydroxyethyl methacrylate (HEMA)

Resin monomers like 2-hydroxyethyl methacrylate (HEMA) disturb cell functions including responses of the innate immune system, mineralization and differentiation, or induce cell death via apoptosis. These phenomena are associated with oxidative stress and a reduction in the concentration of the antioxidant glutathione (GSH), resulting in imbalanced redox homeostasis. Thus far, the precise mechanism of how resin monomers interfere with cellular redox regulation is unknown. The present study provides insight into the induction of apoptosis and the differential expression of antioxidant enzymes depending on the availability of GSH. Buthionine sulfoximine (BSO) was used to inhibit GSH synthesis, while 2-oxothiazolidine-4-carboxylate (OTC), and N-acetylcysteine (NAC) as prodrugs supported GSH synthesis in RAW264.7 mouse macrophages exposed to HEMA (0-8 mm) for 24 h. The level of GSH was significantly decreased after cells were preincubated with BSO, and the formation of reactive oxygen species (ROS) increased in cultures subsequently exposed to HEMA. Apoptosis was drastically increased by BSO in HEMA-exposed cell cultures as well, but OTC and NAC retracted HEMA-induced cell death. These results show that dental monomer-induced apoptosis is causally related to the availability of GSH. The hydrogen peroxide decomposing enzymes glutathione peroxidase (GPx1/2) and catalase were differentially regulated in HEMA-exposed cultures. Expression of GPx1/2 was inhibited by HEMA and further reduced in the presence of BSO. SOD1 (superoxide dismutase) expression was inhibited in the presence of HEMA, and was decreased to an even greater extent by BSO, possibly due to H(2)O(2)-feedback inhibition. The expression of catalase was considerably up-regulated in HEMA-exposed cultures, implying that H(2)O(2) is the type of ROS that is significantly increased in monomer-exposed cells. OTC and NAC counteracted the effect of HEMA on GPx1/2, SOD1, and catalase expression. HO-1 (heme oxygenase) expression was strongly enhanced by HEMA, suggesting the need for further antioxidants like bilirubin to support enzyme activities that directly regulate H(2)O(2) equilibrium. Expression of the oxidoreductase thioredoxin (TRX1), the second major thiol-dependent antioxidant system in eukaryotic cells, was slightly reduced, while the oxygen-sensing protein HIF-1α was downregulated in HEMA-exposed cell cultures. These results indicate that cells and tissues actively respond to monomer-induced oxidative stress by the differential expression of enzymatic antioxidants.

Helicobacter pylori in human oral cavity and stomach

The oral cavity has been suspected as an extra-gastroduodenal reservoir for Helicobacter pylori infection and transmission, but conflicting evidence exists regarding the occurrence of H. pylori in the mouth, independently of stomach colonization. Ninety-four gastric biopsy patients were analysed for the concurrent presence of H. pylori in the mouth and stomach. Samples were collected from different areas within the mouth and H. pylori DNA was amplified by the polymerase chain reaction (PCR) and verified by sequencing. Helicobacter pylori-specific serology was performed, and stomach colonization was determined by culture. In addition, relevant dental and periodontal parameters, as well as general health parameters, were recorded. Helicobacter pylori was found in the stomach of 29 patients and in the oral cavity of 16 patients. In only six patients was the bacterium detected simultaneously in the stomach and mouth. Notably, the 10 patients in whom the bacterium was found solely in the mouth did not have serum antibodies to H. pylori. The occurrence of H. pylori in the mouth was found to be correlated neither to any general or oral health parameters, nor to any particular site of collection. This study shows that H. pylori can occur in the oral cavity independently of stomach colonization.

Influences of protein films on antibacterial or bacteria-repellent surface coatings in a model system using silicon wafers.

Immobilization of defined chemical functionalities to biomaterial surfaces is employed to optimize them not only for tissue compatibility but also for prevention of bacterial infection. Grafting surfaces with chains of poly(ethylene glycol) (PEG) results in bacterial repellence whereas modification with cationic groups conveys them with bactericidal properties. Since biomaterials in situ will become exposed to a protein-rich environment, it is necessary to investigate the influence of prior protein adsorption on the antibacterial activity of this type of chemical surface modification. In the present study, we immobilized short-chain PEG and two pyridinium group-containing methacrylate monomers, 12-methacryloyloxydodecylpyridinium bromide (MDPB) and 6-methacryloyloxyhexylpyridinium chloride (MHPC), to silicon wafer model surfaces to investigate the influence of prior protein adsorption on the bactericidal activity of the surface coating towards subsequently attached bacteria. Adsorbed amounts of human serum albumin and salivary proteins were found to be two times higher on cationic compared to PEG-modified surfaces. An analogous tendency was found for attachment of Streptococcus gordonii and Streptococcus mutans to the same surfaces without prior protein exposure. However, most bacteria attached to cationic surfaces were found to be dead. Prior exposure of cationic surfaces to protein solutions drastically altered bacterial attachment dependent on the type of protein solution and bacterial species employed. Significantly, the original bactericidal activity of pyridinium-coated surfaces was found greatly reduced upon adsorption of a protein film. As a conclusion we propose that future approaches should combine the protein- and bacteria-repellent properties of PEG-coatings with the bactericidal function of charged cationic groups.

Influence of Root Canal Disinfectants on Growth Factor Release from Dentin

INTRODUCTION During dentinogenesis, growth factors become entrapped in the dentin matrix that can later be released by demineralization. Their effect on pulpal stem cell migration, proliferation, and differentiation could be beneficial for regenerative endodontic therapies. However, precondition for success, as for conventional root canal treatment, will be sufficient disinfection of the root canal system. Various irrigation solutions and intracanal dressings are available for clinical use. The aim of this study was 2-fold: to identify a demineralizing solution suitable for growth factor release directly from dentin and to evaluate whether commonly used disinfectants for endodontic treatment will compromise this effect. METHODS Dentin disks were prepared from extracted human teeth and treated with EDTA or citric acid at different concentrations or pH for different exposure periods. The amount of transforming growth factor-β1 (TGF-β1), fibroblast growth factor 2, and vascular endothelial growth factor were quantified via enzyme-linked immunosorbent assay and visualized by gold labeling. Subsequently, different irrigation solutions (5.25% sodium hypochloride, 0.12% chlorhexidine digluconate) and intracanal dressings (corticoid-antibiotic paste, calcium hydroxide: water-based and oil-based, triple antibiotic paste, chlorhexidine gel) were tested, and the release of TGF-β1 was measured after a subsequent conditioning step with EDTA. RESULTS Conditioning with 10% EDTA at pH 7 rendered the highest amounts of TGF-β1 among all test solutions. Fibroblast growth factor 2 and vascular endothelial growth factor were detected after EDTA conditioning at minute concentrations. Irrigation with chlorhexidine before EDTA conditioning increased TGF-β1 release; sodium hypochloride had the opposite effect. All tested intracanal dressings interfered with TGF-β1 release except water-based calcium hydroxide. CONCLUSIONS Growth factors can be released directly from dentin via EDTA conditioning. The use of disinfecting solutions or medicaments can amplify or attenuate this effect.

Effect of Dentin on the Antibacterial Activity of Dentin Bonding Agents

Dentin bonding agents with antibacterial effects may inhibit secondary caries formation and pulp inflammation by eliminating residual bacteria in and on dentin. Therefore, the antibacterial effects of Prime & Bond NT (PB), Prime & Bond NT without fluoride (PBNF), Gluma Comfort Bond (GL), ABF, Xeno CF II (XE), 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEG-DMA), and 0.2% chlorhexidine were tested against Streptococcus mutans, S. sobrinus, and Lactobacillus acidophilus using the agar-diffusion method with and without bovine-dentin disks (200 microm and 500 microm thickness) placed between the bacteria and the test substances. Without dentin, ABF Primer showed growth inhibition for all bacterial strains. XE inhibited S. mutans and S. sobrinus, and PB S. sobrinus. ABF Bonding inhibited L. acidophilus. PBNF, HEMA, and TEGDMA did not have any antibacterial effects. Dentin disks of 500 microm thickness reduced the inhibitory effect of chlorhexidine to 23% to 54% compared with direct application. ABF Primer (nonpolymerized) produced inhibition zones against all tester strains regardless of dentin disks interposed or not. XE (against S. mutans and S. sobrinus) and PB (against S. sobrinus) did not produce any inhibition zones on 200 microm thick dentin. After polymerization, the ABF system did not inhibit bacterial growth on 200 microm thick dentin disks. A dentin barrier reduces significantly the antibacterial activity of chlorhexidine and dentin bonding agents.