MTA Mineral Trioxide Aggregate Mix

After mixing MTA

Curing MTA

Wet-curing, where water is gently and progressively added to the cement is analogous to a step described in the instructions for use where a wet cotton placed above the MTA, which serves to wet-cure the MTA. The concern of the cotton pellet is, if it is too dry, water will be drawn out of the cement, and if it is too wet, it will also weaken the cement. Furthermore, its use provides a vulnerability as the tooth has the placement of the permanent restoration delayed, and furthermore, the cotton pellet use compromises the seal.³⁸

An alternative is membrane curing, where a material is placed above the MTA that will not significantly affect the water content of the MTA. This could be through the placement of a GIC or RMGIC liner on the MTA that will protect the MTA, and enable immediate permanent restoration or obturation of the tooth.

In the industrial model, air time can feature fast drying due to heat and wind which is exacerbated by the large surface area exposed to air. In a tooth environment, much of the surface area of the setting cement would be beside dentine, a water containing structure and therefore moisture loss would be of a lesser concern. Wind is of no concern in the tooth model.

Research with White ProRoot MTA, which has an initial set time of 45 minutes, has illustrated that glass ionomer placement at 45 minutes on top of the MTA has no significant difference in bond strength than glass ionomer placement at 72 hours.²²

^{22. Yesilyurt
C, Yildirim T, Tasdemir T, Kusgoz A. Shear bond strength of
conventional glass ionomer cements bound to mineral trioxide aggregate. J
Endod 2009;35:1381-1383.}
^{38. Vail
MM, Steffel CL. Preference of temporary restorations and spacers: a
survey of Diplomates of the American Board of Endodontists. J Endod
2006;32:513-515.}

Cleaning MTA from an MTA Carrier

To remove MTA that has set within a MAP carrier (Dentsply) I've established the following methods:

1. If all else fails, dentists can use a size 20 K file (which is like a very long narrow screw) and progressively poke, twist and scatch out the MTA. It takes 15 minutes at most, and this was with MTA that was given 2 weeks to set within the carrier. I emphasise a stainless steel K file rather than a hedstrom file as the K file is shaped like a screw to screw out the MTA, as opposed to the hedstrom file which has a Christmas tree cross section which cannot twist out or drill out the MTA. The problem with a NiTi file is that it tends to bend more rather than the stainless steel file. The method of cleaning out the MTA from the MTA carrier resembles doing cleaning a pulp chamber. They can use larger files if they want. It’s best to use sterile files of course. Dentists can opt to use files that would otherwise be thrown out, but definitely, autoclave them to prevent any concerns should a sharps injury occur.

2. If they want to multitask while removing the MTA, they can place the tip within vinegar while they are doing something else, and when there’s a spare moment between patients, use the 20 K file as it will soften the MTA. It won’t, unfortunately, dissolve the MTA no matter how long they leave it for.

3. If the place the carrier within vinegar 1hour after use, they may be able to press out the MTA out of the carrier. In otherwords, the vinegar softens the MTA, but, in any case, there’s a good chance using the K file to scratch out the MTA is the way to go.

4. I’m currently testing if there are any solutions that will clean out the MTA and will certainly update this if I find a solution that rapidly dissolves the MTA while not damaging the MTA carrier.