Fracture resistance of over-flared root canals filled with MTA and resin-based material: an in vitro study

Aim: To measure the fracture resistance of over-flared roots filled with a variety of materials (gutta-percha-nano HA, resilon-epiphany, composite and mineral trioxide aggregate - MTA) using the Instron machine test and micro-computed tomography (Micro CT) Scan. In addition, scanning electron microscopy (SEM) images were used to illustrate the type of fracture patternsof the specimens. Methods: One hundred and twenty extracted human mandibular single rooted premolars were selected. A total of 105 out of the selected teeth were prepared to the working length and over-flared, leaving the apical 5 mm undisturbed. Fifteen samples had no treatment and were used as a positive control group (Group +ve). The 105 test teeth were further divided into 7 groups of 15 samples each. One of the 7 groups was designated as negative control (Group -ve) where teeth were over prepared and left without obturation.Remaining groups were filled with gutta-percha-nanoHA (Group1), gutta-percha-nano HA+composite (Group 2), gutta-percha-nano HA+MTA (Group 3), resilon-epiphany (Group 4),resilon-epiphany+composite (Group 5), and resilon-epiphany+MTA (Group 6). Fracture resistance of all samples was measured using the Instron testing machine. Three samples from each group had the depth of their fracture line measured by Micro CT Scan, and 2 samples from each group had their fracture pattern illustrated using SEM. Results: The highest fracture resistance was observed in Group +ve, followed by Groups 3, 6, 5, 2, 4, 1, and Group -ve, with values (in N) of: 1598 (641.0), 1190.5(424.2), 1164.7 (489.4), 821.2 (220.9), 683.4(179),658.4 (211.3), 658.4 (99.0), 158.3(49.3), respectively. Statistical analysis for root fracture resistance showed highly significant difference between all groups with p value < 001.Conclusions: Micro CT Scan and SEM analysis indicated the ability of MTA to withstand vertical force.

Sealing ability of gutta-percha/Nano HA versus Resilon/Epiphany after 20 months using an electrochemical model: an in vitro study

Aim: To evaluate the sealing ability of gutta-percha-nano-HA and Resilon-Epiphany by electrochemical method and micro-computed tomography (CT) scan at 48 h and 20 months using three different obturation techniques (cold lateral condensation technique, warm vertical condensation - System B, and warm vertical condensation with vibration - Down-Pak). Methods: 150 human mandibular single-rooted premolars were prepared and randomly allocated into 6 groups of 25 specimens each, and filled with either gutta-percha-nano HA or Resilon-Epiphany with the three different obturation techniques (cold lateral, warm vertical - System B, and warm vertical with vibration - Down-Pak). Electrochemical microleakage method was used to measure the microleakage after 48 h and after 20 months, and a micro-CT Scanner 1072 was used to evaluate the quality of obturation after 48 h. Results: Group 6 (Resilon-epiphany/Down-Pak technique) had the highest microleakage value, followed by Group 2 (Gutta-percha-nano HA/ System B technique), Group 4 (Resilon-Epiphany/Lateral condensation technique), Group 3 (Gutta-percha-nano HA/Down-Pak technique), Group 5 (Resilon-Epiphany/System B technique), and Group 1 (Gutta-percha-nano HA/Lateral condensation technique) with the values of 4.69 (6.06) KÙ, 3.88 (2.92) KÙ, 3.77 (3.75) KÙ, 3.38 (3.92) KÙ, 2.64 (2.90) KÙ, and 2.44 (4.34) KÙ, respectively. No significant difference in the quantity of leakage was observed for each root in each group between the two tested filling materials and their sealers (p=0.143). Micro CT scan investigations revealed more micro-voids in the Resilon-Epiphany Group obturated with Down- Pak technique. Conclusions: Nano-hydroxyapatite sealer with gutta-percha filling material provided a reasonable seal compared with Epiphany sealer and Resilon filling material.