Comparison of the retentive and photoelastic properties of two prefabricated endodontic post systems

Abstract

This in vitro study compared the retention and photoelastic stress patterns from two loading conditions, vertical (133.2 N, 30 pounds) and oblique at a 26 degrees angle (133.2 N, 30 pounds) for two prefabricated post systems. The post studied were: (1) Flexi-Post (a split-shank threaded post) and (2) C-Post (a carbon fibre bound in an epoxy resin, passive double taper tier post). Two groups with 10 specimens per group were subjected to retentive forces with a universal testing machine (MTS 810 Material Testing Machine). In addition, two photoelastic test blocks were prepared with simulated root canals for each post studied. After cementation the photoelastic blocks were photographed before vertical and oblique loading and after loading. One-way analysis of variance (ANOVA) for retention data revealed a highly significant difference (P<0.0001) between groups. The Flexi-Post had a statistically higher mean retention force of 1180.6 N (265.9 pounds), while the C-Post had a mean of 171.8 N (38.7 pounds). Photoelastic analysis indicated minimal stresses for both the Flexi-Post and C-Post in the unloaded state. The C-Post showed asymmetrical apically stress patterns, while loaded in both states. The multi-tiered system of the Flexi-Post clearly distributes stress symmetrically, while the C-Post distributes stresses asymmetrically. The symmetric, even stresses and statistically higher retentive strength for Flexi-Post are more favourable than the asymmetric, uneven stresses and relatively low retentive strength for the C-Post.

Investigation of distortions around the cervical area of teeth restored with two kinds of crown materials

“…This means that even when the same load is applied to both types of crowns, both the magnitude and distribution of stress within the root dentin may also differ according to material type. To date, the stress distributions of endodontically treated teeth have been analyzed with a variety of methods: finite element analysis 4,[9][10][11] , photoelastic stress analysis [12][13][14] , and loading tests 2,[15][16][17] . With finite element analysis, finite element modeling is a complex and difficult task.…”

Comparative Overall Health Status Assessment of Subjects with Allergic Contact Dermatitis to Formaldehyde and Glutaraldehyde

“…Surveys concerning the sensitizing effects of formaldehyde and glutaraldehyde in dental practice are relatively nonnumerous and multidirectional (4,7,13,20). Summarized data from a four-year study, concerning the incidence of occupational allergic contact dermatitis in dental nurses, showed that it was established in 66.7% of the investigated subjects, the most frequent sensitizing agent being glutaraldehyde, followed by formaldehyde and glyoxal (16).…”

Photoelastic stress analysis of different post and core restoration methods

“…8, were compared. Table 1 , the strain gage method [8][9][10] , the finite element method 11,29) , and the photoelastic method 13,14) have been used as stress analysis techniques for abutment construction. With the loading test, it is effective in measuring fracture loads and resistance through the destruction of test specimens and then observation of failure modes from the facture fragments.…”

“…On stress measurement and analysis, a wide range of methods are available, namely the strain gage method [8][9][10] , the loading test 2) , the finite element method 11,12) , and the photoelastic method [13][14][15] . In particular, the photoelastic method was established by Sir David Brewster, a British physicist, and B. Zak 15) applied this method in dental research for the first time in 1935 to investigate stress distributions in teeth and alveolar bones.…”

“…To date, many studies have investigated the stress distributions of restored teeth with post and core using the photoelastic method 16) . However, most of them have employed cast metal post and core in their investigations, whilst only a few carried out their investigations using composite resin cores with different prefabricated posts 14) . The purpose of this study was to evaluate the stress distributions of three different post and core systems (composite resin post and core, composite resin core with glass fiber post, and cast metal post and core) and determine which post and core system contributes optimally to preventing stress concentration and root fracture.…”