The two impression materials most commonly used in pediatric dentistry for space maintainers are alginate and compound.

Alginate is indicated primarily when removable appliances are being made. And as you know very well by now, removable space maintainers are rarely indicated and seldom used in pediatric dentistry.

We will focus on impression taking with compound. Compound is an excellent impression material, especially for fixed appliances. In particular, it is accurate and stable, and you will see how these qualities make it highly suitable for taking impressions for space maintainers as we proceed through the chapter.

Of course, alternative materials can be used. If you use other materials successfully and/or if your office routine is set up for other materials, by all means continue to use them. The most critical feature for an impression taking material for space maintainers is accuracy in obtaining the band registration around the tooth.

Although we like compound when taking impressions for space maintainers, we are fully aware that many clinicians prefer alginate because of their familiarity with this material. Consequently, the impression material of choice is left to the preference of the individual.

For purposes of this presentation, we will cover compound impression taking techniques for impression taking for both fixed bilateral and fixed unilateral appliances. We also emphasize these two techniques since they provide an opportunity to demonstrate two alternative impression taking procedures: taking impressions with and without impression trays. For bilateral impression taking, trays are always used. For unilateral impression taking, however, trays can be used or a "free-hand" (trayless) technique can be used.