Compare force strengths when using wet and dry cotton pellets with different set times for MTA.
N=32 freshly extracted maxillary and mandibular molars divided into 4 equal groups – wet cotton pellet 24 hours, wet cotton pellet 72 hours , dry cotton pellet 24 hours, dry cotton pellet 72 hours
Teeth sectioned to leave the furcation only and Mounted in acrylic. ISO size 014 perf made. Plexiglass fitted over specimen to act as a guide plate for an Instron force probe for “pushout” test. Saline soaked Gelfoam placed on coronal side to simulate clinical conditions. Placed MTA mixed with 2% xylocaine with 1:100k epi into perforation. MTA condensed with a wet cotton pellet. Wet or dry cotton pellet left for either 24 or 72h. Instron force probe placed vertical force until 0.2mm displacement of MTA. Max force recorded. Specimens left in humidity for 14 days. Re-performed pushout test to evaluate if readhesion occurred between dentin wall & MTA.
Force strength comparisons:
72h wet > 24 wet
72h dry > 24 dry
24h wet in 2 wks > 24h wet
24h dry in 2 wks > 24h dry
72h wet > 72h wet in 2 weeks
72h dry > 72h dry in 2 weeks
Recommendations for procedure to placeme MTA : place matrix (e.g., GelFoam) moistened with an anesthetic. Place MTA and then a Cotton pellet (wet or dry) then the temporary restoration. Wait 72 hours. Place permanent restoration.