Acidic and alkaline chemicals' influence on a tricalcium silicate-based dental biomaterial.

Bioactive hydraulic tricalcium silicate materials are commonly used in several dental procedures. Mineral Trioxide Aggregate (MTA) is one such material, which is used in a variety of clinical applications, the most recent of which is root canal sealing material, during which, the MTA potentially comes in contact with remnants of the chemical agents used for disinfecting root canals. The effects of commonly used root canal irrigating solutions on MTA have not been investigated in depth, thus far. The aim of this study was to determine the effect of five common chemical agents used in root canal preparation (sodium hypochlorite/NaOCl, ethylene diaminetetraacetic acid/EDTA, mixture of sodium hypochlorite and etidronic acid/NaOCl + EA, mixture of EDTA and Chlorhexidine/QMix, or saline) on a commercial tricalcium silicate (MTA Plus). Samples were analyzed using scanning electron microscopy with energy dispersive spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy and Inductively coupled plasma techniques to see effects of phases formed and calcium ion release. Specimens immersed in NaOCl and NaOCl + EA had strong peaks for calcium hydroxide, but materials exposed to EDTA and QMix had lesser XRD peaks for calcium hydroxide. The calcium hydroxide peak in the XRD indicates hydration of tricalcium silicate and formation of amorphous calcium silicate hydrate. Calcium released from samples immersed in EDTA and NaOCl was less than in NaOCl + EA and QMix solutions. Fewer calcium phosphate crystals and less calcium hydroxide were observed with the samples in NaOCl, EDTA and QMix, which could have an important impact as it negatively influences the bioactivity. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 377-387, 2019.

In vitro investigations into the etiology of mineral trioxide tooth staining.

AIM: To investigate the role of bismuth oxide, a constituent of contemporary mineral trioxide aggregate (MTA) materials, and its response to various solutions that may contribute to the potential discoloration that occurs following MTA applications within the scope of endodontics. SETTING AND DESIGN: Laboratory assessment of chemical reactions with white ProRoot(®) MTA and white Portland cement (WPC). MATERIALS AND METHODS: Set specimens and freshly mixed specimens of white ProRoot(®) MTA and white ProRoot(®) MTA powder, along with specimens of WPC were exposed to distilled water, phosphate buffered saline (PBS), 10% formalin, hydroxyethylmethacrylate (HEMA), sodium hypochlorite, sodium hydroxide (NaOH) base, and hydrochloric acid (HCl) acid. Specimens were visually inspected periodically for color changes. RESULTS: All forms of ProRoot MTA showed discoloration when exposed to 10% formalin within 30 min, as opposed to WPC, and were completely blackened at 4 days. Bismuth oxide alone and with calcium oxide also turned black within 30 min after exposure to 10% formalin. No discoloration was seen when exposed to the other solutions. CONCLUSIONS: Exposing MTA in various forms to a variety of liquids has determined that bismuth oxidein combination with other chemical moieties is the prime cause of staining observed by clinicians.

Emergency department resource use by supervised residents vs attending physicians alone.

IMPORTANCE: Few studies have evaluated the common assumption that graduate medical education is associated with increased resource use. OBJECTIVE: To compare resources used in supervised vs attending-only visits in a nationally representative sample of patient visits to US emergency departments (EDs). DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional study of the National Hospital Ambulatory Medical Care Survey (2010), a probability sample of US EDs and ED visits. EXPOSURES: Supervised visits, defined as visits involving both resident and attending physicians. Three ED teaching types were defined by the proportion of sampled visits that were supervised visits: nonteaching ED, minor teaching ED (half or fewer supervised visits), and major teaching ED (more than half supervised visits). MAIN OUTCOMES AND MEASURES: Association of supervised visits with hospital admission, advanced imaging (computed tomography, ultrasound, or magnetic resonance imaging), any blood test, and ED length of stay, adjusted for visit acuity, demographic characteristics, payer type, and geographic region. RESULTS: Of 29,182 ED visits to the 336 nonpediatric EDs in the sample, 3374 visits were supervised visits. Compared with the 25,808 attending-only visits, supervised visits were significantly associated with more frequent hospital admission (21% vs 14%; adjusted odds ratio [aOR], 1.42; 95% CI, 1.09-1.85), advanced imaging (28% vs 21%; aOR, 1.27; 95% CI, 1.06-1.51), and a longer median ED stay (226 vs 153 minutes; adjusted geometric mean ratio, 1.32; 95% CI, 1.19-1.45), but not with blood testing (53% vs 45%; aOR, 1.18; 95% CI, 0.96-1.46). Of visits to the sample of 121 minor teaching EDs, a weighted estimate of 9% were supervised visits, compared with 82% of visits to the 34 major teaching EDs. Supervised visits in major teaching EDs compared with attending-only visits were not associated with hospital admission (aOR, 1.15; 95% CI, 0.83-1.58), advanced imaging (aOR, 1.21; 95% CI, 0.96-1.53), or any blood test (aOR, 1.02; 95% CI, 0.79-1.33), but had longer ED stays (adjusted geometric mean ratio, 1.32; 95% CI, 1.14-1.53). CONCLUSIONS AND RELEVANCE: In a sample of US EDs, supervised visits were associated with a greater likelihood of hospital admission and use of advanced imaging and with longer ED stays. Whether these associations are different in EDs in which more than half of visits are seen by residents requires further investigation.

The impact of the demand for clinical productivity on student teaching in academic emergency departments.

OBJECTIVE: Because many emergency medicine (EM) attending physicians believe the time demands of clinical productivity limit their ability to effectively teach medical students in the emergency department (ED), the purpose of this study was to determine if there is an inverse relationship between clinical productivity and teaching evaluations. METHODS: The authors conducted a prospective, observational, double-blind study. They asked senior medical students enrolled in their EM clerkship to evaluate each EM attending physician who precepted them at three academic EDs. After each shift, students anonymously evaluated 10 characteristics of clinical teaching by their supervising attending physician. Each attending physician's clinical productivity was measured by calculating their total relative value units per hour (RVUs/hr) during the nine-month study interval. The authors compared the total RVUs/hr for each attending physician to the medians of their teaching evaluation scores at each ED using a Spearman rank correlation test. RESULTS: Seventy of 92 students returned surveys, evaluating 580 shifts taught by 53 EM attending physicians. Each attending physician received an average of 11 evaluations (median score, 5 of 6) and generated a mean of 5.68 RVUs/hr during the study period. The correlation between evaluation median scores and RVUs/hr was -0.08 (p = 0.44). CONCLUSIONS: The authors found no statistically significant relationship between clinical productivity and teaching evaluations. While many EM attending physicians perceive patient care responsibilities to be too time consuming to allow them to be good teachers, the authors found that a subset of our more productive attending physicians are also highly rated teachers. Determining what characteristics distinguish faculty who are both clinically productive and highly rated teachers should help drive objectives for faculty development programs.