Effect of apical constriction diameter, irrigant flow rate, and needle tip design on apical pressure / 대한치과재료학회지

The purpose of this study was to evaluate the effects of apical constriction (AC) diameter, irrigant flow rate, and needle tip design on apical pressure (AP) during the root canal irrigation. Five extracted human mandibular premolars were instrumented up to #35 (0.06 taper) using nickel-titanium rotary instruments. AC was determined at 1 mm from the apical foramen. Three needles with different tip designs (notched, side-vented, and flat) were placed 3 mm from AC. APs were measured with varying flow rates of 0.05, 0.1, 0.2, and 0.3 mL/s. The AC diameter of the teeth was enlarged to #40 and #45 (0.06 taper) successively, and the aforementioned measurement procedure was repeated (n=5). When the other conditions were controlled, AP increased with decreasing AC diameter or increasing irrigant flow rate, and the AP of flat needle was the highest, followed by notched, and side-vented needle (p0.35 mm, open-end (notched or flat) needles can be used to improve irrigant replacement in the apical portion using a flow rate of 0.05 mL/s.

Effect of needle tip design and position, and irrigant flow rate on apical pressure / 대한치과재료학회지

The purpose of this study was to evaluate the effect of needle tip design and position, and irrigant flow rate on apical pressure (AP) during root canal irrigation. Five human mandibular premolars were instrumented up to #35 (0.06 taper) using nickel-titanium rotary instruments. Three different needles according to change of needle tip design (notched, side-vented, and flat) were positioned at the point of 1, 3, and 5 mm from the apical constriction (needle tip position). For each needle tip design and position, APs were measured with varying flow rates of 0.05, 0.1, 0.2, and 0.3 ml/s. When the other conditions were controlled, AP increased with decreasing needle tip position or increasing irrigant flow rate (p < 0.05). The AP of flat needle was the highest, followed by notched, side-vented needle for the same needle tip position and irrigant flow rate. The APs at needle tip position of 1 mm or with more than 0.1 ml/s flow rate were higher than central venous pressure (5.88 mmHg) for all conditions. Flat needle was not recommended for clinical use due to sharp increase of AP with changing needle tip position and irrigant flow rate. For safe and effective root canal irrigation, irrigant should be applied with the needle tip position of 3 mm and flow rate of less than 0.05 ml/s.