Lipase-Mediated Dynamic Kinetic Resolution of 1-Phenylethanol Using Niobium Salts as Racemization Agents

In this work, a racemization method of (S)-1-phenylethanol by niobium salts was developed. Among the salts available, the niobium phosphate hydrate (NbOPO4.nH2O) reduced the enantiomeric excess (ee) of the chiral alcohol from 95 to 0% after 24 h at 60 ºC in toluene. This new racemization agent was combined with a lipase (CALB) in order to achieve a chemoenzymatic dynamic kinetic resolution (DKR). Experiments demonstrated that the DKR process is feasible and the corresponding (R)-1-phenylethyl acetate was obtained with 92% conversion and 85% ee.

Dentin Microhardness and Sealer Bond Strength to Root Dentin are Affected by Using Bioactive Glasses as Intracanal Medication

This study investigated the human dentin microhardness (MH) and the MTA Fillapex® (Fillapex) and AH Plus®(AH) bond strength (BS) to dentin after using calcium hydroxide (Ca(OH)2) and bioactive glasses (45S5 and an experimental niobium phosphate bioactive glass (NbG)) as intracanal medications. For the MH test dentin slices were filled with medications and were submitted to Knoop MH (KHN) test (at day-0 (baseline data/without medication) and at day-15 (after using medication)). For the BS test, after medications had remained for 15 days in the roots, dentin slices were obtained and filled with the sealers. Seven days later, sealer BS to dentin was measured by push-out test (MPa). Data were statistically analyzed. Failure mode was visually assessed. The use of NbG, 45S5 for 15 days, increased the dentin MH and reduced the BS between AH sealer and dentin, but did not interfere with the Fillapex BS.