Influence of microabrasion on shear bond strength of composite resin to dentin

The purpose of this study was to determine the influence of microabrasion on shear bond strength of composite resin to dentin. Ninety noncarious recently extracted human molars were selected. The occlusal surface of teeth was ground, exposing flat dentin surface to accommodate bonded restorative material. The teeth were divided into nine groups of 10 teeth each. The dentin surfaces of the first group were conditioned with Total Etch for 10 seconds, then washed and dried to serve as control. Air abrasion conditioning of the remaining 8 groups was accomplished with "Micro Prep Director+" air abrasion device using 0.4mm nozzle tip perpendicular to sample surface and 1cm away from it. Surface abrasion was performed using a 27 micro m aluminum oxide particle stream at 60 psi for 10 seconds in two groups, and for 20 seconds in another two groups. Air pressure was then increased to 120 psi to abrade surfaces of another two groups for 10 seconds, and for 20 seconds in the remaining two groups. Additional conditioning with Total Etch was performed to the surfaces of the last four groups combined with air abrasion treatment. Three teeth from each of the nine groups were mounted in a profilometer and three Ra values were recorded for dentinal surface roughness before and after surface treatment. Remaining samples were prepared for bonded composite restorations, and shear bond strengths were determined using a testing machine. Results revealed significantly higher roughness of etched surface than air abraded dentin. Meanwhile acid etching created bond strengths to dentin that were almost twice as high as those achieved by air abrasion. It could be, thus, suggested that cavities prepared by air abrasion should also be acid etched to achieve adequate bonding with resinous materials

Exposure to mercury vapor and impact on health in the dental profession

In this study, detailed measurements of mercury vapor exposure in dental profession were carried out. The study was conducted on 33 dentists and dental nurses with a control group of 30 physicians and nurses work in the same hospital. The results showed that Hg-vapor concentration at any moment was dependant on the level of work-related activities. The urinary Hg concentration in the exposed group was 7.4 mug/L compared with 2.0 mug/L in the control group. There was a positive correlation between urinary Hg concentrations and Hg levels in air among the exposed group. By regression analysis, hours of practice/week and number of amalgam restoration/week were the most predicators of urinary Hg levels in dentistry. The results confirmed that a good ventilation system, the design of dental laboratories and the improvement of dental office hygiene were essential to keep the amount of inhaled or absorbed Hg-vapor below the threshold limits