I am delighted to announce the exciting news that we have received just under 900 abstracts for presentation in the scientific program of the VIth World Congress on Pain in Adelaide, April l-6, 1990. This 1s about a 50% increase in the number of abstracts submitted for the 1987 Congress in Hamburg and it represents by far the greatest number of scientific papers ever offered for the an IASP Congress. This surely reflects the healthy state of IASP and is also a very encouraging indlcator of the high level of activity in basic and clinical research in the field of pain throughout the world. Based upon our previous experience with the ratio of congress delegates to scientific abstracts, the Adelaide Congresses promises to be the largest world congress on pain we have so far held.

International association for the study of pain

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.

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

Clinical Trials: Design, Conduct, and Analysis , by Dr Curtis Meinert, is a good reference for many practitioners of clinical trials The book deals with single-center and multiple-center randomized prospective clinical trials, and uses several examples (14) of current and important clinical trials, such as the University Group Diabetes Program, the Persantine Aspirin Reinfarction Study, and the Hypertension Prevention Trial In addition to the necessary discussions on such key ingredients as study design, sample size and power, randomization forms design, and data collection, the text has several sections that deal with important and necessary issues rarely addressed: committee structures, publication policies, operation manuals, sample consent forms, and budget preparation recommendations This book has many tables and figures representing the actual data from previous clinical trials, which helps maintain interest for the clinician investigator, and includes an appendix that provides sketches of several major trials used throughout the text In addition, the

Clinical Trials: Design, Conduct, and Analysis

Monomer conversion, microhardness, internal marginal adaptation, and shrinkage stress of bulk-fill resin composites

Mechanical properties, shrinkage stress, cuspal strain and fracture resistance of molars restored with bulk-fill composites and incremental filling technique.

Clinical Relevance Degree of conversion (DC) affects various physical properties and biocompatibility of a composite restoration. Adequate DC is especially important for bulk-fill materials, which are designed for placement in thick layers.

Raman spectroscopic assessment of degree of conversion of bulk-fill resin composites--changes at 24 hours post cure.

Effect of temperature on post-cure polymerization of bulk-fill composites.

Clinical Relevance With regard to enamel and dentin microhardness and chemical composition, bleaching lights can be safely used. The adverse effects of peroxide concentration and gel acidity could be reversed after a two-week amorphous calcium phosphate and artificial saliva treatment.

Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching.

Resin composites containing reinforcing inert glass fillers combined with bioactive glass (BG) can aid in the prevention of secondary caries, which is a major cause of failure of contemporary composite restorations. A series of previous studies on experimental resin composites filled with BG 45S5 has demonstrated that methacrylate resin polymerization can be impaired by the addition of unsilanized BG, leading to lower degrees of conversion (DC). In order to distinguish whether the polymerization inhibition is caused by a direct (temperature-independent) effect of BG or an indirect (temperature-dependent) effect of restricted mobility of reactive species, this study used Raman spectroscopy to evaluate the DC values of experimental composites post-cured at 37 °C and 150 °C. The potential of BG to adversely affect DC was highly dependent on the resin system. The highest DC reduction was observed in the resin system based on ethoxylated bisphenol A dimethacrylate (Bis-EMA), followed by bisphenol A glycidyl methacrylate (Bis-GMA). In contrast, the DC for urethane dimethacrylate (UDMA) was not compromised by BG. Increasing the mobility of reactive species by heating at 150 °C showed limited potential for increasing the DC in the Bis-EMA and Bis-GMA resin systems, indicating a direct inhibitory effect of BG on polymerization.

/pdf/degree-of-conversion-of-experimental-resin-composites-3k62y6bz3c.pdf

Degree of conversion of experimental resin composites containing bioactive glass 45S5: the effect of post-cure heating.

To evaluate the effect of bioactive glass 45S5 (BG) in experimental composites on flexural strength (FS), flexural modulus (FM), modulus of resilience (MR), and material reliability after artificial aging in water for 1, 7, and 30 days, and an additional accelerated aging for 3 days in a 75 vol% ethanol-water solution. Five experimental light-curable composites were prepared with 0–40 wt% of BG and a total filler load of 70 wt%. The resinous matrix was Bis-GMA/TEGDMA in 60:40 by weight. Mechanical properties were evaluated using a three-point bending test (ISO/DIN 4049:1998) with n = 20. Weibull statistics were used to assess material reliability. Additionally, the degree of conversion (DC) was assessed 24 h post-cure using FT-Raman spectroscopy. FS and FM decreased linearly as the amount of BG was increased. The ISO 4049 requirement for a minimum FS of 80 MPa was fulfilled in experimental composites with up to 20 wt% of BG. Degradation of FS and FM with artificial aging was more extensive in materials with higher BG amounts. MR decreased as a function of BG amount and artificial aging. Material reliability (Weibull modulus) was stable through aging for composites with up to 10 wt% of BG. DC was negatively influenced by the BG amount and ranged from 64 to 81%. Increasing the amount of unsilanized BG fillers from 0 to 40 wt% resulted in a progressive decline in mechanical properties and a more extensive degradation during artificial aging. Bioactive fillers diminished the mechanical properties in a dose-dependent manner.

Matej Par

Papers

Raman spectroscopic assessment of degree of conversion of bulk-fill resin composites--changes at 24 hours post cure.

Effect of temperature on post-cure polymerization of bulk-fill composites.

Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching.

Degree of conversion of experimental resin composites containing bioactive glass 45S5: the effect of post-cure heating.

Mechanical properties of experimental composites containing bioactive glass after artificial aging in water and ethanol.