Finer diameter needles require increased effort to deliver the irrigant and result in higher intra-barrel pressure. The syringe and needles used tolerated the pressure developed. Irrigant flow rate should be considered as a factor directly influencing flow beyond the needle. Wide variations of flow rate were observed among operators. Syringe irrigation appears difficult to standardize and control.

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Clones of Mentha spicata were cultivated in nutrient solution, to which lead and zinc were added in soluble form. The plants remained in a controlled environment for 2 weeks in this solution. The root lengths of the plants and the chlorophyll content of the upper and lower leaves were measured. The lead and zinc contents of the plant tissue were also determined. It was found that the increased concentration of metals resulted in a decrease in root growth and chlorophyll content. The relation that connects the concentration of the heavy metal to the decrease in root growth is logarithmic. It was also found that more lead than zinc entered the plant tissues, but unlike zinc did not reach the leaves.

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