Irrigation Protocols Effect on Tensile Strength of Human Radicular Dentin

Objectives: To determinate the effect of two different irrigation protocols on tensile strength of human radicular dentin.
Methods: Experimental in vitro study. Protocol was approved by IRB. After a pilot study, sample size was calculated using a statistical formula. Forty-eight (48) human mandibular premolars extracted for orthodontic reasons were collected and stored in 0.9% saline solution for seven days. Crowns were sectioned at cement-enamel junctions and then randomly distributed into three groups of sixteen (16) teeth each: control group (no irrigation), experimental group 1 (irrigation with 12cc of 5.25% NaOCl at 40°C) and experimental group 2 (same as group 1, including Rc-prep™, Passive Ultrasonic Irrigation for 1 minute, drying, 17% EDTA irrigation during 1 minute and final wash with 96% ethyl alcohol). Root apical sections (3mm) were removed and then vertically sectioned in to two equal segments, in order to obtain an hour-glass-shape specimen (surface area of 2.23 mm²). They were observed using a stereomicroscope (STEMI 2000-C, Zeiss™, Jena, Germany) to identify presence of cracks that could affect the mechanical properties evaluated. Subsequently, specimens were placed in a customized steel device and a traction force was applied (0.5mm/min crosshead speed) using the Universal Testing Machine (Instron™ 3367, Instron Corp, Norwood, MA, USA). Statistical analysis was made using one way ANOVA, Duncan, Tukey, Sheffe and Bartlett tests.
Results: Tensile strength showed no statistical significant differences between the three groups evaluated (p=0.364). However, experimental group 2 reported the highest tensile strength mean (41.72MPa), followed by control group and experimental group 1 (33.59MPa and 32.63MPa respectively).
Conclusions: Irrigation protocols evaluated in this in vitro study do not affect the tensile strength of the human radicular dentin.