Biomechanical Effect of Irrigants in Noninstrumented Dentin: Systematic Review and Meta-Analysis

One aspect of special concern in endodontics is the effect of irrigating solutions on the biomechanical properties of dentine. A systematic review of in vitro studies was conducted to analyze and systematize the effect of endodontic irrigating solutions on biomechanical properties in noninstrumented dentine, according to published in vitro studies. A literature review was conducted on different databases including papers from 2009 to 2019. Two researchers identified in vitro studies on permanent teeth root dentine that reported control group, featured nonmechanical preparation, and sample size ≥ 10. An instrument was designed for bias assessment in three categories (High-Uncertain-Low), applying 17 criteria. Using the PRISMA tool, an electronic search found 9,026 titles. From these, 28 were subjected to full-text analysis and 9 were chosen for qualitative analysis. It was identified that chelates decrease microhardness and stiffness. It was also inferred that the proteolytic effect of NaOCl reduces the elasticity modulus and flexural strength. The heterogeneity analysis, with a value I2:92% for microhardness and I2:81% for roughness, revealed high heterogeneity among the included studies. The random effect model identified with 95% confidence that NaOCl and EDTA significantly decrease microhardness: -3.00[-4.22, -1.78]; EDTA 17% at 15 min being on average the lowest value: -6.66[-8.32, -5.00]. For roughness, all the proposed solutions increased significantly: 2.37[1.67, 3.08]; the highest, 3.94[2.84, 5.04], was recorded by NaOCl2.5%-15 min. In contrast, CLX registered a high roughness value: 3.33[1.88, 4.77]. Dentinal microhardness reduction associated to chelates is a concentration and time- dependent variable. Collagen degradation by NaOCl is a time and concentration-dependent variable.