The Effect of Time and Storage Environment on the Dimensional Stability of Thermoplastic Resin Post Patterns: An In Vitro Study

Background Statement

To avoid cross‐contamination, it is essential to disinfect post patterns before fabricating the cast‐metal post. It is of great importance to study the effect of various disinfectants and storage media, as well as time, on the dimensional stability of thermoplastic resin post patterns.

Methods

In this in vitro experimental study, 24 thermoplastic resin patterns were prepared using an extracted single‐rooted mandibular premolar and stored in one of three solutions: water, 0.5% sodium hypochlorite (3

NaOCl), or Ventisept ( n  = 8 per group). Measurements of apical diameter (AD), coronal diameter (CD), and crown–apical length (CAL) were recorded at baseline and after 1, 2, 4, 8, 24, and 48 h using a digital micrometer. A two‐way repeated‐measures analysis of variance (ANOVA) was performed to evaluate the effect of storage medium, time, and their interaction, followed by Bonferroni‐adjusted pairwise comparisons using SPSS version 27. A  p ‐value < 0.05 was considered statistically significant in all tests.

Results

After 48 h, resin patterns stored in each environment significantly expanded compared to their baseline measurements (all p   < 0.001) in AD, CD, and CAL dimensions (0.17, 0.25, and 0.06 mm in NaOCl; 0.07, 0.07, and 0.06 mm in water; 0.04, 0.06, and 0.05 mm in Ventisept). Statistically significant differences among storage environments were observed for AD, CD, and CAL. NaOCl showed greater dimensional changes than water and Ventisept for AD and CD (both p   < 0.001). Ventisept showed lower dimensional changes than water for AD ( p = 0.021) and then both water ( p = 0.025) and NaOCl ( p = 0.008) for CAL. These expansions occurred rapidly in the first few hours, and the rate of dimensional change decreased at later time points.

Conclusion

Under the conditions tested, storage environment and duration influenced the dimensional stability of thermoplastic resin post patterns. Ventisept was associated with smaller dimensional changes, whereas NaOCl produced greater expansion, particularly in the apical and coronal dimensions. These findings suggest that the choice of storage/disinfection medium and the duration of storage should be considered when thermoplastic resin post patterns are maintained before subsequent laboratory procedures.