Effect of solvent type and content on monomer conversion of a model resin system as a thin film.

OBJECTIVE: The purpose of this study was to examine the effect of solvent concentration on the degree of conversion of a model photo-activated resin formulation when placed as a thin film in ambient air. METHODS: A photo-activated co-monomer mixture (ethoxylated bis-GMA/TEGDMA) (Bisco Inc.) was diluted into six concentrations (from 1.0 to 13.0M) with either acetone or ethanol. A controlled volume of diluted, uncured resin was placed on the horizontal surface of an attenuated reflectance unit and the infrared (IR) spectrum obtained. A light emitting diode light-curing source (Bluephase, Ivoclar/Vivadent) then immediately irradiated the specimen for 10s (n=5). Five minutes after exposure, IR spectra of the cured material were obtained, and monomer conversions were calculated using standard methods that monitored changes in aliphatic-to-aromatic CC absorbance ratios in the uncured and cured states. RESULTS: In the acetone/model resin system, maximum conversion occurred with 2.5-5.0M solvent. In the ethanol/model resin system, conversion peaked at 2.5M solvent. Above 5.0M solvent, conversion values declined rapidly for both solvents. A 13.0-M solution resulted in near 0% conversion for both solvents. At 2.5 and 5.0M acetone, conversions exceeded those of equivalent concentrations of the ethanol-based system. CONCLUSIONS: For both an acetone- and ethanol-solvated model resin system, conversion did not immediately decrease with addition of solvent, but instead increased over that of the model resin alone. At higher solvent content (greater than 2.5M ethanol and 5.0M acetone), conversion rapidly declined, with ethanol causing less conversion at equal-molar solvent concentrations.

Injury reports in a dental school: a two-year overview.

As teaching institutions, it is vital for dental schools to collect data on accidental injuries to identify potential problems, improve the quality of care of patients, and educate future practitioners about risk management. Our data reveal important trends concerning such injuries. These data were compiled over a two-year period (2001-03) from accident reports at one dental school. We categorized the accidents as follows: source (instrument causing the injury), recipient of injury, time of day, location within the dental school where the injury occurred, and body part injured. The population examined in this study consisted of predoctoral and postdoctoral dental students, staff, faculty, and patients of the dental school. The majority of injuries occurred in the predoctoral clinic toward the middle to the end of the scheduled clinic periods. The instrument most likely involved was a needle, and the body part most commonly injured was a finger. The collection and analysis of injury data may be used to identify trends that will aid in the prediction and prevention of these injuries and, at a national level, serve as a benchmark that other dental schools can employ to assess their relative frequency of injury.