Olga Polydorou

Bio: Olga Polydorou is an academic researcher from University of Freiburg. The author has contributed to research in topics: UDMA & Dental composite. The author has an hindex of 18, co-authored 38 publications receiving 1135 citations. Previous affiliations of Olga Polydorou include University Medical Center Freiburg.

Long-term release of monomers from modern dental-composite materials

Abstract: The elution of monomers from composite materials influences the biocompatibility of dental restorations. The purpose of the present study was to investigate the elution of monomers [bisphenol A glycidyl methacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A (BPA)] from two light-cured materials (nanohybrid and ormocer) and from a chemically cured composite material, after different curing times (0, 20, 40 and 80 s) and different storage periods (24 h, 7 d, 28 d, and 1 yr after curing). Each specimen was stored in 1 ml of 75% ethanol. This medium was renewed after 24 h, 7 d, 28 d, and 1 yr. The ethanol samples were analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS). The amount of monomers released from the nanohybrid and the chemically cured composite was significantly higher than released from the ormocer. The curing time exerted a significant effect on the release of monomers. For the nanohybrid, less monomer was released after increasing the curing time. For the ormocer, 80 s of curing resulted in a higher degree of monomer release. The effect of storage differed between the monomers. Although the elution of TEGDMA was significantly decreased after storage for 28 d and 1 yr, a similar amount of BisGMA was released at each storage time-point analyzed, even after 1 yr. The present study showed that ormocer released a very small amount of monomers compared with the other materials.

Antibacterial effect of an ozone device and its comparison with two dentin-bonding systems

Abstract: Microorganisms remaining beneath restorations can cause secondary caries and pulp damage. Because of this, antimicrobial treatment could be useful. The aim of this study was to evaluate the antibacterial effect of the HealOzone device on Streptococcus mutans and to compare it with the already proven activity of two dentin-bonding systems. Thirty-five human molars were divided into 5 groups. Cavities were then cut into the teeth (n = 28 cavities per group). After sterilization, the teeth were left in broth cultures of 10(6) colony-forming units (CFU) ml(-1) of S. mutans at 36 degrees C for 48 h. The appropriate treatment followed (group A, control; group B, Clearfil SE Bond; group C, Clearfil Protect Bond; group D, 40 s of treatment with ozone; and group E, 80 s of treatment with ozone), and the cavities were then filled with composite resin. After 72 h, the restorations were removed, dentin chips were collected with an excavator, and the total number of microorganisms was determined. All treatments significantly reduced the number of S. mutans present compared with the control group. The antimicrobial effect of both bonding systems and treatment with 80 s of ozone was significantly higher than the 40 s ozone treatment. In conclusion, HealOzone and the bonding systems show striking antimicrobial effects against S. mutans.

The effect of different bleaching agents on the surface texture of restorative materials.

Abstract: Clinical Relevance In-office and home bleaching agents do not cause changes that would demand replacement of the restorations when the agents are applied on the polished surfaces of aesthetic denta...

Scientific Opinion on the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs: Executive summary

Abstract: This opinion describes the assessment of the risks to public health associated with bisphenol A (BPA) exposure. Exposure was assessed for various groups of the human population in three different ways: (1) external (by diet, drinking water, inhalation, and dermal contact to cosmetics and thermal paper); (2) internal exposure to total BPA (absorbed dose of BPA, sum of conjugated and unconjugated BPA); and (3) aggregated (from diet, dust, cosmetics and thermal paper), expressed as oral human equivalent dose (HED) referring to unconjugated BPA only. The estimated BPA dietary intake was highest in infants and toddlers (up to 0.875 µg/kg bw per day). Women of childbearing age had dietary exposures comparable to men of the same age (up to 0.388 µg/kg bw per day). The highest aggregated exposure of 1.449 µg/kg bw per day was estimated for adolescents. Biomonitoring data were in line with estimated internal exposure to total BPA from all sources. BPA toxicity was evaluated by a weight of evidence approach. “Likely” adverse effects in animals on kidney and mammary gland underwent benchmark dose (BMDL10) response modelling. A BMDL10 of 8 960 µg/kg bw per day was calculated for changes in the mean relative kidney weight in a two generation toxicity study in mice. No BMDL10 could be calculated for mammary gland effects. Using data on toxicokinetics, this BMDL10 was converted to an HED of 609 µg/kg bw per day. The CEF Panel applied a total uncertainty factor of 150 (for inter- and intra-species differences and uncertainty in mammary gland, reproductive, neurobehavioural, immune and metabolic system effects) to establish a temporary Tolerable Daily Intake (t-TDI) of 4 µg/kg bw per day. By comparing this t-TDI with the exposure estimates, the CEF Panel concluded that there is no health concern for any age group from dietary exposure and low health concern from aggregated exposure. The CEF Panel noted considerable uncertainty in the exposure estimates for non-dietary sources, whilst the uncertainty around dietary estimates was relatively low.

How much do resin-based dental materials release? A meta-analytical approach (vol 27 pg 723, 2011)

Abstract: OBJECTIVES Resin-based dental materials are not inert in the oral environment, and may release components, initially due to incomplete polymerization, and later due to degradation. Since there are concerns regarding potential toxicity, more precise knowledge of the actual quantity of released eluates is necessary. However, due to a great variety in analytical methodology employed in different studies and in the presentation of the results, it is still unclear to which quantities of components a patient may be exposed. The objective of this meta-analytical study was to review the literature on the short- and long-term release of components from resin-based dental materials, and to determine how much (order of magnitude) of those components may leach out in the oral cavity. METHODS Out of an initial set of 71 studies, 22 were included. In spite of the large statistical incertitude due to the great variety in methodology and lack of complete information (detection limits were seldom mentioned), a meta-analytical mean for the evaluated eluates was calculated. To relate the amount of potentially released material components with the size of restorations, the mean size of standard composite restorations was estimated using a 3D graphical program. RESULTS While the release of monomers was analyzed in many studies, that of additives, such as initiators, inhibitors and stabilizers, was seldom investigated. Significantly more components were found to be released in organic than in water-based media. Resin-based dental materials might account for the total burden of orally ingested bisphenol A, but they may release even higher amounts of monomers, such as HEMA, TEGDMA, BisGMA and UDMA. Compared to these monomers, similar or even higher amounts of additives may elute, even though composites generally only contain very small amounts of additives. A positive correlation was found between the total quantity of released eluates and the volume of extraction solution. SIGNIFICANCE There is a clear need for more accurate and standardized analytical research to determine the long-term release from resin-based materials. Several guidelines for standardization are proposed.