Title:
Influence of smear layer removal and application mode of MTA on the marginal adaptation in immature teeth: a SEM analysis.

Abstract:
This study was an ex vivo evaluation of the marginal adaptation of mineral trioxide aggregate as an apical barrier using teeth with an open apex and scanning electron microscopy.
Eighteen single-rooted human teeth were used. An artificial open apex was created using Gates Glidden drills #6-1 in a crown-down manner until the #1 bur passed through the foramen. A 1.36-mm divergent open apex was created at the foramen by retrograde apical transportation using a #40 Profile 0.6 taper instrument inserted to the length of the cutting blade. The teeth were divided into four groups (n = 4), and two teeth served as controls. The GI = mineral trioxide aggregate (MTA) was placed as a 5-mm-thick apical barrier without removal of the smear layer; GII = MTA was placed with indirect ultrasonic activation; GIII = apical plug was placed after removal of the smear layer without indirect ultrasonic activation; and GIV = MTA was placed with indirect ultrasonic activation, but the smear layer had been previously removed. The root apices were visualized with SEM (1000×), and 12 predetermined material/dentine interface points were measured (gaps). One-way anova and Bonferroni's post hoc tests were used to compare the linear measurements of the gaps between the groups.
GIV had the lowest gap when compared with other groups, and no statistical differences were found among GI, GII, and GIII.
The technique of MTA placement using passive ultrasonic vibration in association with smear layer removal improved the marginal adaptation of the material.