A modified shark-fin test simulating the single-step/double-mix technique: A comparison of three groups of elastomers.

The shark-fin test was modified to convey the clinical application of a single-step/double-mix technique assessing the behavior of two viscosities applied at one point in time. A medium and light body polyether (PE), a medium and light body polyvinylsiloxane (PVS), and a medium as well as heavy and light body vinyl polyether silicone (PVXE) impression material were analyzed solely, and in a layered mixture of 1:1 and 3:1 at working times of 50, 80, and 120 s. The fin heights were measured with a digital ruler. The wettability was measured 50 and 80 s after mixing by drop shape analysis. The results showed a synergistic effect of the medium and light body PE. This was not observed in PVXE and PVS. Interestingly, PVXE showed an antagonistic flow behavior in 3:1 mixture with medium body. PVXE was more hydrophilic than PE and PVS. Future rheological studies should clarify the detected flow effects.

Effect of Calcium Hydroxide as a Root Canal Dressing Material on Dentin Fracture Strength In Primary Teeth- In Vitro Study.

OBJECTIVES: The aim of the present study was to assess the effect of calcium hydroxide as a root canal dressing material on dentin microtensile fracture strength in human primary teeth in vitro. STUDY DESIGN: Thirty primary anterior teeth with root canals packed with calcium hydroxide were divided into groups of ten and immersed in saline at room temperature for 7, 30 and 90 days. Ten teeth with root canals filled with sterile saline were the control group. Microtensile fracture strength was measured in Mechanical tester Lloyd testing machine. RESULTS: There was a significant difference (P < 0.05) between the fracture strength of the calcium hydroxide-filled teeth after 90 days (19.1 MPa) compared with the control (35.8 MPa). Dentin microtensile fracture strength of the calcium hydroxide-filled teeth decreased at an average of 0.142 MPa per day. CONCLUSION: Calcium hydroxide placed in root canals for an extended time had a significantly negative effect on root strength. Long-term success of root canal treatment in primary anterior teeth is estimated as 65% with most of the failures result from trauma recurrence. CLINICAL RELEVANCE: Our results stress the need to evaluate the pros and cons of root canal treatment compared to extractions of non-vital primary incisors.