Variation of the ultrasonic response of a dental implant embedded in tricalcium silicate-based cement under cyclic loading.

The use of tricalcium silicate-based cement (TSBC) as bone substitute material for implant stabilization is promising. However, its mechanical behavior under fatigue loading in presence of a dental implant was not reported so far because of the difficulty of measuring TSBC properties around a dental implant in a nondestructive manner. The aim of this study is to investigate the evolution of the 10 MHz ultrasonic response of a dental implant embedded in TSBC versus fatigue time. Seven implants were embedded in TSBC following the same experimental protocol used in clinical situations. One implant was left without any mechanical solicitation after its insertion in TSBC. The ultrasonic response of all implants was measured during 24 h using a dedicated device deriving from previous studies. An indicator I based on the temporal variation of the signal amplitude was derived and its variation as a function of fatigue time was determined. The results show no significant variation of I as a function of time without mechanical solicitation, while the indicator significantly increases (p<10(-5), F=199.1) at an average rate of 2.2 h(-1) as a function of fatigue time. The increase of the indicator may be due to the degradation of the Biodentine-implant interface, which induces an increase of the impedance gap at the implant surface. The results are promising because they show the potentiality of ultrasonic methods to (i) investigate the material properties around a dental implant and (ii) optimize the conception of bone substitute materials in the context of dental implant surgery.

Closing the ring to bring up the light: synthesis of a hexacyclic acridinium cyanine dye.

The synthesis of a geometrically constrained and near-planar hexacyclic acridinium cyanine dye 9 is reported. When compared to its unlocked and non-fluorescent monomethine cyanine dye analogue 3, this photostable dye emits in the green area of the spectrum with a remarkable quantum yield close to unity in organic solvents and above 0.5 in water. A detailed steady-state and time-resolved spectroscopic study revealed that dye 9 forms emissive aggregates in water, which are responsible for a red-shifted and broadened emission band and longer emission lifetime, τ≈33 compared to 6.5-7.0 ns for the monomeric dye. Dye 9 also binds strongly to DNA (both duplex and quadruplex) in its monomeric form and is very efficiently taken up by cells, in which it accumulates primarily into the nucleus.