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AIM: The present study examined the leaching and cytotoxicity of bismuth from ProRoot MTA and aimed to identify whether bismuth leaching was affected by the cement base and the immersion regime used. METHODOLOGY: The leaching profile of bismuth was examined from ProRoot MTA and compared with hydroxyapatite containing 20% bismuth oxide as well as hydroxyapatite and tricalcium silicate to investigate whether bismuth release changed depending on the cement base. Bismuth leaching was determined after 30 and 180 days of ageing immersed in Dulbecco's modified Eagle's medium (DMEM) using mass spectroscopy (ICP-MS). The media were either unchanged or regularly replenished. The pH, surface microstructure and phase changes of aged materials were assessed. Wistar rat femoral bone marrow stromal cells (BMSCs) and cutaneous fibroblasts were isolated, cultured and seeded for cell counting (trypan blue live/dead) after exposure to non-aged, 30- and 180-days-aged samples in regularly replenished DMEM. Aged DMEM in contact with materials was also used to culture BMSCs to investigate the effect of material leachates on the cells. Gene expression analysis was also carried out after direct exposure of cells to non-aged materials. Differences between groups were statistically tested at a significance level of 5%. RESULTS: All materials exhibited alterations after immersion in DMEM and this increased with longer exposure times. The bismuth leached from ProRoot MTA as detected by ICP-MS. Aged ProRoot MTA samples exhibited a black discolouration and surface calcium carbonate deposition. ProRoot MTA influenced cell counts after direct exposure and its 180-days leachates reduced BMSC viability. After direct BMSC contact with non-aged ProRoot MTA an upregulation of metallothionein (MT1 and MT2A) expression and down-regulation of collagen-1a (Col-1a) and bone sialoprotein (BSP) expression was identified. CONCLUSIONS: Bismuth leaching was observed throughout 180-days observation period from all materials containing bismuth oxide. This negatively influenced cell viability and gene expression associated with bismuth exposure. This is the first study to report that metallothionein gene expression was influenced by exposure to ProRoot MTA.

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The substitution of calcium with strontium in bioactive materials has been promising but there has been some concern over the material instability and possible toxicity. The aim of this research was the synthesis and characterization of calcium and strontium substituted bioactive materials and assessment of interactions with local tissues and peripheral elemental migration in an animal model. A bioactive glass, hydroxyapatite and hydraulic calcium silicate with 50% or 100% calcium substitution with strontium were developed and the set materials were characterized immediately after setting and after 30 and 180-days in solution. Following subcutaneous implantation, the local (tissue histology, elemental migration) and systemic effects (elemental deposition after organ digestion) were assessed. The strontium-replaced silicate cements resulted in the synthesis of partially substituted phases and strontium leaching at all-time points. The strontium silicate implanted in the animal model could not be retrieved in over half of the specimens showing the high rate of material digestion. Tissue histology showed that all materials caused inflammation after 30 days of implantation however this subsided and angiogenesis occurred after 180 days. Strontium was not detected in the local tissues or the peripheral organs while all calcium containing materials caused calcium deposition in the kidneys. The tricalcium silicate caused elemental migration of calcium and silicon in the local tissues shown by the elemental mapping but no deposition of calcium was identified in the peripheral organs verified by the assessment of the digested tissues. Strontium can substitute calcium in bioactive materials without adverse local or systemic effects.

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OBJECTIVE: About one-third of patients with depression fail to achieve remission despite treatment with multiple antidepressants. This study compared the efficacy and safety of switching patients with treatment-resistant depression from an ineffective antidepressant to flexibly dosed esketamine nasal spray plus a newly initiated antidepressant or to a newly initiated antidepressant (active comparator) plus placebo nasal spray. METHODS: This was a phase 3, double-blind, active-controlled, multicenter study conducted at 39 outpatient referral centers. The study enrolled adults with moderate to severe nonpsychotic depression and a history of nonresponse to at least two antidepressants in the current episode, with one antidepressant assessed prospectively. Confirmed nonresponders were randomly assigned to treatment with esketamine nasal spray (56 or 84 mg twice weekly) and an antidepressant or antidepressant and placebo nasal spray. The primary efficacy endpoint, change from baseline to day 28 in Montgomery-Åsberg Depression Rating Scale (MADRS) score, was assessed by a mixed-effects model using repeated measures. RESULTS: Of 435 patients screened, 227 underwent randomization and 197 completed the 28-day double-blind treatment phase. Change in MADRS score with esketamine plus antidepressant was significantly greater than with antidepressant plus placebo at day 28 (difference of least square means=-4.0, SE=1.69, 95% CI=-7.31, -0.64); likewise, clinically meaningful improvement was observed in the esketamine plus antidepressant arm at earlier time points. The five most common adverse events (dissociation, nausea, vertigo, dysgeusia, and dizziness) all were observed more frequently in the esketamine plus antidepressant arm than in the antidepressant plus placebo arm; 7% and 0.9% of patients in the respective treatment groups discontinued study drug because of an adverse event. Adverse events in the esketamine plus antidepressant arm generally appeared shortly after dosing and resolved by 1.5 hours after dosing. CONCLUSIONS: Current treatment options for treatment-resistant depression have considerable limitations in terms of efficacy and patient acceptability. Esketamine is expected to address an unmet medical need in this population through its novel mechanism of action and rapid onset of antidepressant efficacy. The study supports the efficacy and safety of esketamine nasal spray as a rapidly acting antidepressant for patients with treatment-resistant depression.

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