A bio-molecular film ex-vivo model to evaluate the influence of canal dimensions and irrigation variables on the efficacy of irrigation

Aim To devise an ex vivo model to test the efficacy of irrigation (static/dynamic) in removing a bio-molecular film from root canal walls. Methodology Forty human teeth with single straight canals were randomly allocated to two groups for static (n = 20) or dynamic (n = 20) irrigation. The root canals were prepared to different apical sizes (20, 40) and tapers (0.04, 0.08). The teeth were split longitudinally into two, stained collagen was applied to the canal surfaces and the tooth reassembled in a silicone matrix for dynamic or static irrigation. Digital images of the canal surface were taken before and after irrigation with 9, 18, 27 and 36 mL solution. The percentage of canal surface covered with stained collagen was quantified (ipWin4((R))). The data were analysed using paired t-tests and linear regression models. Results All the five explanatory variables: 'volume of irrigant used', 'mode of irrigation', 'orientation of open port of needle', 'corono-apical level of canal' and 'root canal dimension' had a significant (P < 0.001) influence on outcome of irrigation. The corono-apical level of canal was the most dominating factor. After irrigation, the apical third had 19.9% and 33.8% less area covered with the bio-molecular film than the middle and coronal thirds respectively. Conclusion The stained collagen bio-molecular film could not be removed completely by either static or dynamic irrigation. Factors influencing removal, in rank order of decreasing priority, were: corono-apical level, apical size and taper of canal preparation, and dynamic/static irrigation.