Effect of using proper light-curing techniques on energy delivered to a Class 1 restoration.

OBJECTIVES: To determine the effect of proper light-curing instruction on the radiant exposure (energy density) delivered by dentists using six dental curing lights to a posterior Class 1 restoration. METHOD AND MATERIALS: Twenty-five dentists attending a professional meeting were instructed to position a patient simulator (MARC-PS, BlueLight), as they would for a patient, and then to expose the simulated Class 1 maxillary second molar preparation for a specified amount of time. At this point, the dentists were unaware of the purpose of the experiment. Each participant used three different curing lights, and the irradiance and radiant exposure (J/cm2) delivered to the preparation was recorded. Participants were then informed of the purpose of the exercise, and given specific light-curing instructions and training using the patient simulator, after which they re-exposed the same preparation using the same curing lights. Pre- and post-instruction radiant exposure values were compared using one-way ANOVA (α = .05), and for each light among all operators using a two-tailed, paired Student's t test. RESULTS: There was a wide variation in the radiant exposure delivered by the dentists and by the six curing lights, from 2.9 to 15.4 J/cm2. Before receiving additional light-curing instruction, 68% of dentists delivered less than 10 J/cm2. The radiant exposure delivered increased significantly (P < .001) by up to 30%, as a result of training using MARC-PS. CONCLUSION: The results indicate that some of the dentists participating in the present study delivered an inadequate amount of radiant exposure before instruction. More energy was delivered after a short training session using the MARC-PS. Reinforcing the proper photo-curing techniques may improve the outcome when placing resin-based restorations.

Effect of resin hydrophilicity on water-vapour permeability of dental adhesive films.

This study examined the water-vapour permeability of thin polymerized resin films fabricated from five co-monomer blends of increasing degrees of hydrophilicity, as measured by their Hoy's solubility parameters. Neat resin films were prepared from five experimental light-curable resins (n = 10). Each film was mounted in a Fisher permeability cup with 8 g of water placed inside the cup. The experiments were conducted in a modified twin-outlet desiccator connected to a vacuum pump in one outlet to permit a continuous airflow to encourage water evaporation. Weight losses by water evaporation were measured at 3, 6, 9, 24, 30, and 48 h by using an analytical balance. Additional resin films were examined by using transmission electron microscopy (TEM) after immersion in ammoniacal silver nitrate. A significant correlation was observed between the cumulative water loss at 48 h and the Hoy's total cohesive energy density (delta(t)). Transmission electron microscopy revealed silver-filled channels along film peripheries and silver grains of decreasing dimensions toward the film centres in co-monomer blends 3, 4, and 5 of increasing hydrophilicity. Hydrophilic dentin adhesives polymerized in thin films are prone to water loss by evaporation. This probably accounts for the water droplets seen on the surface of vital-bonded dentin after the application of simplified dentin adhesives.

Vasorelaxant effect of resin-based, single-bottle dentin bonding systems.

Single-bottle dentin bonding systems are currently in wide use. Because these materials are sometimes inadvertently placed on microscopic pulp exposures while at other times deliberately on frank exposures, their effects on pulpal soft tissues need to be evaluated. The present study assessed the vascular effects of 3M Single Bond (3MSB) and Prime & Bond NT (PBNT), using rat aortic ring preparations. It is hypothesized that these bonding agents induce relaxation of these preparations. Both 3MSB and PBNT caused endothelium-dependent and -independent relaxations in a concentration-dependent manner. The endothelium-dependent relaxation was associated with the release of nitric oxide. However, the responses to both agents did not involve the generation of prostanoids or KATP channel activation. At relatively low concentrations, the responses of endothelium-denuded tissues to 3MSB were greater than those to PBNT, indicating certain differences in the vascular action between these products. The data suggest that 3MSB and PBNT interfere with vascular function by causing vasorelaxation via mechanisms occurring in the smooth muscle and endothelium, including the release of nitric oxide. Among others, this effect may promote bleeding if these adhesives are placed on pulp exposures.