*2.4.1 Polyamides*

Polyamides (nylon) are the condensation result of a diamine and a dibasic acid [55].

In 1950, they were introduced in dentistry, as an alternative to denture acrylic base, and are being characterized by different degrees of flexibility, depending on the type of polyamide. Their main indications include patients with tissue allergies, cases of retentive dental fields (which are normally problematic for the insertion and disinsertion of the removable partial denture), and repeated denture fracture, as they are unbreakable [56, 57]. A polyamide denture may be bounced off the floor without cracking its base.

The types of polyamides include superflexible polyamide (**Figure 11**), extremely elastic, and medium-low flexibility polyamide, a half-soft comfortable material.

**Figure 11.** *Metal-free superflexible polyamide removable partial dentures.*

#### **Figure 12.**

*Superflexible polyamide removable partial denture with metal clasps (right after injection and ready-to-go).*

The clasps may be manufactured of the same material as the denture base. In the case of medium-low flexibility polyamide, ready-made clasps may be used. Metal clasps are also an option. (**Figure 12**).
