Abstract

Objectives: To describe the particle size of ProRoot MTA, Portland cement and bismuth oxide samples by using laser particle diffraction and scanning electron microscopic image analysis on the same samples in comparison and generate understanding of most commonly expected size ranges. Motivation of the study is to ascertain a size range of selected powders most suitable for root canal treatment. This is the first study of its kind in Scandinavia comparing local available powders for use in important and critical medical application.

Methods: Samples of white ProRoot MTA, Aalborg White Portland Cement and Bismuth oxide were examined twice using a laser diffraction technique and scanning electron microscopy, respectively, followed by SEM image analysis. A HELOS laser diffraction particle size analyzer was used. Each powder sample was dissolved in isopropanol briefly with ultrasound to make wet dispersions. Distribution of particle size was measured on volume basis. All particles with a diameter less than 1μm were excluded from size analysis, as the HELOS laser diffraction technique did not measure particles below this size. For image analysis, the specimens were prepared on glass mounted on metal stubs and sputter coating with carbon in some cases and studied in a CamScan scanning electron microscope. ProRoot MTA was further examined by backscatter SEM and x-ray analysis. Representative images from each powder sample were analyzed using a digital image analysis program. The particle diameter size was calculated after measurement on minimum and maximum particle diameter with a digital ruler.

Results: Statistical analysis shows that Portland cement contains larger amounts of large particles than ProRoot-MTA and Bismuth oxide. Similarly, the ProRoot-MTA contains a larger amount of smaller particles than Portland cement or Bismuth oxide. This difference is by 22%, 10% and 6% in Portland cement, Bismuth oxide and ProRoot-MTA respectively (laser diffraction method). Similar trend is observed in Image analysis. According to the laser diffraction method, 48% of the ProRoot-MTA, 25% of Portland and 19% of Bismuth oxide particles were under 5 μm. Both methods produced data concerning particle size relatively quickly.

Conclusion: The distribution of larger particle size is higher in Portland cement as compared to ProRoot MTA and Bismuth oxide. The distribution of smaller particle size is higher in ProRoot MTA in comparison to both Portland cement and Bismuth Oxide. This gives an idea as to what particle size is expected in different batch of materials, how they can be sorted out to know their exact size and how this can serve as measure of suitability for further cavity filling application (root canal treatment).