Premixed Mineral Trioxide Aggregate Setting Reaction in Primary Molar Pulpotomies

Purpose: To assess the setting of premixed mineral trioxide aggregate (NuSmile Neo-PUTTY) when used as a pulpotomy agent in primary molars, restored in a single visit, and to compare the effect of overlying materials, including zinc oxide eugenol (ZOE), resin-modified glass ionomer cement (RMGIC) and stainless steel crowns (SSC), on the microhardness of the NeoPUTTY. Methods: Forty-eight extracted primary molars were prepared with the standard pulpotomy technique. Approximately three mm of NeoPUTTY were placed on the pulpal floor of each tooth. The teeth were divided into four groups according to restorative material: ( 1) control group-none; (2) RMGIC; (3) ZOE; and (4) ZOE and SSC. Groups 2, 3 and 4 specimens were placed in artificially simulated oral cavity conditions. After 24 hours, all teeth were sectioned mesiodistally and polished. Microhardness was then measured in Knoop scales (HK) at one mm, two mm and three mm away from the NeoPUTTY-overlying material interface following the application of a 25-gf load force for 30 seconds at each site. One-way analysis of variance was used to compare the NeoPUTTY microhardness values between groups at each depth as well as between the three different depths within each group (P<0.05). Results: No statistically significant differences in mean HK values (57.9 to 62.3 range) were found between groups at each depth, or between depths within each group (Group 1, P=0.328; Group 2, P=0.74; Group 3, P=0.293; Group 4, P=0.788). Conclusion: The setting reaction of NeoPUTTY, as a function of microhardness, was not affected by the presence or type of overlying material used in a single-visit pulpotomy. This in vitro study found no evidence against the immediate restoration of primary molar pulpotomies done with NeoPUTTY.