An FTIR Study of the Setting Reaction of Various Endodontic Sealers

An ultrasonic-based experimental model to evaluate the setting time of endodontic sealers

AIM

To evaluate an ultrasonic-based experimental model (US), to assess the setting time of AH Plus^® , Bio-C Sealer^® and MTA Fillapex^® , and compare the results obtained with ANSI/ADA specifications (2012).

METHODS

To determine the setting time according to the ANSI/ADA specification, moulds measuring 10 mm (diameter) × 2 mm (thickness) were used, and for the US tests a transducer (1 MHz) and an oscilloscope were used. Fourier-transform infrared spectroscopy (FTIR) was used to evaluate the changes on chemical structure at the different setting times found by the US and ANSI/ADA methods. After checking the normal distribution, setting time data were analysed using unilateral analysis of variance with Tukey-HSD post-test to compare the methods.

RESULTS

AH Plus^® and Bio-C Sealer^® had longer mean setting time values for the US method than for the ANSI/ADA (p < .05), whilst for MTA Fillapex^® no significant difference was found between the methods (p < .05). FTIR spectra demonstrated that at the setting time determined by the US method, AH Plus^® and Bio-C Sealer^® were in a more advanced stage of polymerization than at the ANSI/ADA, whilst there was no significant difference for MTA Fillapex^® .

CONCLUSIONS

The use of US was effective for setting time determination and measured longer values than ANSI/ADA specification for AH Plus^® and Bio-C Sealer^® , identifying the entire (and not only superficial) setting of the endodontic sealers.

Post space preparation timing of root canals sealed with AH Plus sealer

OBJECTIVES

To determine the optimal timing for post space preparation of root canals sealed with epoxy resin-based AH Plus sealer in terms of its polymerization and influence on apical leakage.

MATERIALS AND METHODS

The epoxy polymerization of AH Plus (Dentsply DeTrey) as a function of time after mixing (8, 24, and 72 hours, and 1 week) was evaluated using Fourier transform infrared (FTIR) spectroscopy and microhardness measurements. The change in the glass transition temperature (Tg ) of the material with time was also investigated using differential scanning calorimetry (DSC). Fifty extracted human single-rooted premolars were filled with gutta-percha and AH Plus, and randomly separated into five groups (n = 10) based on post space preparation timing (immediately after root canal obturation and 8, 24, and 72 hours, and 1 week after root canal obturation). The extent of apical leakage (mm) of the five groups was compared using a dye leakage test. Each dataset was statistically analyzed by one-way analysis of variance and Tukey's post hoc test (α = 0.05).

RESULTS

Continuous epoxy polymerization of the material with time was observed. Although the Tg values of the material gradually increased with time, the specimens presented no clear Tg value at 1 week after mixing. When the post space was prepared 1 week after root canal obturation, the leakage was significantly higher than in the other groups (p < 0.05), among which there was no significant difference in leakage.

CONCLUSIONS

Poor apical seal was detected when post space preparation was delayed until 1 week after root canal obturation.

Effect of endodontic cement on bone mineral density using serial dual-energy x-ray absorptiometry

INTRODUCTION

Materials with new compositions were tested in order to develop dental materials with better properties. Calcium silicate-based cements, including white mineral trioxide aggregate (WMTA), may improve osteopromotion because of their composition. Nano-modified cements may help researchers produce ideal root-end filling materials. Serial dual-energy x-ray absorptiometry measurement was used to evaluate the effects of particle size and the addition of tricalcium aluminate (C3A) to a type of mineral trioxide aggregate-based cement on bone mineral density and the surrounding tissues in the mandible of rabbits.

METHODS

Forty mature male rabbits (N = 40) were anesthetized, and a bone defect measuring 7 × 1 × 1 mm was created on the semimandible. The rabbits were divided into 2 groups, which were subdivided into 5 subgroups with 4 animals each based on the defect filled by the following: Nano-WMTA (patent application #13/211.880), WMTA (as standard), WMTA without C3A, Nano-WMTA + 2% Nano-C3A (Fujindonjnan Industrial Co, Ltd, Fujindonjnan Xiamen, China), and a control group. Twenty and forty days postoperatively, the animals were sacrificed, and the semimandibles were removed for DXA measurement.

RESULTS

The Kruskal-Wallis test followed by the Mann-Whitney U test showed significant differences between the groups at a significance level of P < .05. P values calculated by the Kruskal-Wallis test were .002 for bone mineral density at both intervals and P20 day = .004 and P40 day = .005 for bone mineral content.

CONCLUSIONS

This study showed that bone regeneration was enhanced by reducing the particle size (nano-modified) and C3A mixture. This may relate to the existence of an external supply of minerals and a larger surface area of nano-modified material, which may lead to faster release rate of Ca(2+), inducing bone formation. Adding Nano-C3A to Nano-WMTA may improve bone regeneration properties.

A laboratory evaluation of the physical and mechanical properties of selected root canal sealers

AIM

To evaluate and compare the porosity, degree of conversion (DC) and hardness of two resin-based sealers; RealSeal and EndoRez, and a silicon-based sealer; GuttaFlow to that of a traditional zinc oxide-based sealer; TubliSeal.

METHODOLOGY

For porosity, four samples from each sealer were prepared and scanned using a SkyScan 1072 Micro-CT. Porosity was then calculated using specialized software. For DC, 10 samples from each sealer were prepared and placed onto a Fourier transform infrared spectroscopy spectrometer. Spectra readings were carried out before and after curing of the sealers, and the DC for each sealer was calculated. For hardness, 10 samples from each sealer were prepared and then tested using a Wallace hardness tester. SPSS software was used for statistical analysis of the data using one-way anova and independent t-tests.

RESULTS

TubliSeal had the highest percentage porosity (3.52%), whilst RealSeal had the lowest percentage porosity (0.41%). Statistically significant differences (P = 0.01) in porosity were present between all groups except between RealSeal and EndoRez groups. RealSeal exhibited a significantly higher DC% than EndoRez (P = 0.01), whereas EndoRez had the highest hardness number [28.54 Vickers hardness number (VHN)] whilst TubliSeal showed the lowest (13.57 VHN). Statistically significant differences in hardness were found between all groups (P = 0.01) except between RealSeal and EndoRez groups.

CONCLUSIONS

Resin-based sealers had less porosity, greater hardness and a high DC.