Introduction
An impression is a negative replica of the mouth’s soft and hard tissues which is typically taken for fabrication of indirect restorations [
1]. Although selection of an appropriate impression material is very challenging, yet it is very important for an accurate and well-fitting prosthesis. Duplication of the intraoral structures is done using different materials ranging from hydrocolloids to elastomeric impression materials [
2]. Elastomers are the most commonly used materials in everyday dental clinical practice for precise and accurate reproduction of oral cavity. Consequently, and until recently, we have been left with two good choices of elastomers, which are polyether (PE) and polyvinyl siloxane (PVS) [
3].
Polyvinyl siloxane (PVS) or addition silicone was first introduced in the 1970s. PVS is a variation of condensation silicones in which they are both polydimethylsiloxane polymer, but with different terminal groups and thus different setting reactions [
4]. PVS has inherently great dimensional stability, low polymerization shrinkage, high tear strength, and excellent elastic recovery [
5]. On the other hand, PVS are naturally hydrophobic and therefore their uses are limited to cases where a dry environment could be obtained [
6]. New modified hydrophilic polyvinyl siloxanes have been formulated afterwards, which can better flow, wet and record moist dental surfaces [
7].
In 1965, polyether impression materials were introduced into the market in the form of a base and a catalyst. The base is made of polyether macro monomer with terminal ethylene imine rings, fillers, and plasticizers, while, the catalyst consists of dichlorobenzene sulfonate, thickening agents and colorants [
8]. The polymer is formed during a cationic polymerization and opening of the imine rings, producing a cascade reaction that proceeds until polymerization stops. The backbone of the polymerized material is a copolymer of tetrahydrofuran and ethylene oxide with no reaction by-products resulting in a material with very good stability and accuracy [
9].
PEs have an excellent hydrophilicity, flow, and were considered a vast improvement over hydrocolloids and condensation silicones in properties as tensile strength, and dimensional changes [
10]. However, slow elastic recovery, stiffness and low tear strength are some of the drawbacks of the PE [
11]. In 2000, efforts to overcome the shortcomings have led to the launch of an improved-taste, more flexible polyether impression materials (Penta Soft), that combines all the positive characteristics of polyether together with ease of handling [
12].
Such improvement was achieved by decreasing the filler ratio to render a less rigid impression, and thus ease separation of impression from the mouth and the cast. Moreover, in 2005, a soft fast setting polyether impression material (6 min) was introduced through the addition of low-4 viscosity softeners to reduce the stiffness of the set PE [
13,
14].
Nowadays, many impression systems and techniques are becoming more popular including hybrid materials with altered properties and intraoral digital impressions [
15]. In numerous studies, it was reported that there is a comparable accuracy between digital scanners and conventional impressions in single crowns and short span bridges. However, they still show disadvantages compared to using conventional impression techniques with regard to longer spans or even full-arch rehabilitations [
16,
17]. Conventional impression methods provide as well simpler way for dental cast production and allow easier laboratory adjustments [
18]. Furthermore, the pervasive use of digital scanners is still limited due to high expenses and the need of special preparations that is sometimes challenging [
15,
16].
However, and especially with respect to the partially quicker digital impression making, it is desirable that the impression materials cure within a shorter time span. This would reduce both the chair side time of the patient and the valuable time of the operator as well. The vast majority of the available polyether and silicone materials polymerize within 5–7 min, which is considered relatively long for single or small fixed prosthetic appliances [
17]. To solve this issue, in 2020, a new PE material with a very fast working (0:45 s) and setting times (2:00 min) was very newly launched into the market. The objectives of the development of this material as claimed by the manufacturer is to combine the outstanding performance and accuracy of polyether with the fast-setting behavior of PVS [
17].
Surprisingly, up until now, there is only one study in literature where the authors assessed the dimensional accuracy of the newly introduced material [
17]. Moreover, there is no data available about the other physical and mechanical properties of the super quick set polyether although the manufacturer has claimed that they changed the composition to be able to decrease the setting time. Therefore, the aim of this in vitro study was to evaluate the dimensional accuracy, tear strength, and elastic recovery of the new super-fast setting impression material.
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.