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Τετάρτη 23 Νοεμβρίου 2022

Implant deformation and implant–abutment fracture resistance after standardized artificial aging: An in vitro study

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Abstract

Background and purpose

Zirconia abutments have been widely adopted in clinical implant practice. The unique mechanical properties of zirconia may significantly affect the long-term prognosis of implant treatments. The purpose of this study was to investigate the influence of abutment material on implant deformation and fracture resistance of internal conical connection implant–abutment complexes of two diameters after standardized artificial aging.

Materials and methods

Thirty original abutments (one-piece titanium, one-piece zirconia, zirconia with alloy base) with two diameters (regular, narrow) were connected to internal conical connection implants and subjected to a standardized artificial aging process consisting of thermal cycling and mechanical cyclic loading. Microcomputed tomography (μCT) scans of implant bodies were performed before and after aging. 3-dimensional images of implant bodies were generated from the μCT scans and aligned for before and after aging to calculate the volumetric deformation amount. Finally, fracture resistance was measured using a mechanical static loading test for the surviving aged and 30 brand-new specimens.

Results

All specimens survived artificial aging. No significant difference in implant deformation was found in the regular groups (p = 0.095). In narrow groups, the one-piece zirconia group showed significantly less deformation (p < 0.0001). For fracture resistance, no significant decrease was observed after aging in any group (p > 0.05). One-piece zirconia abutments showed significantly lower strength than the other two materials for both diameters (p < 0.0001).

Conclusions

In the regular diameter system, abutment material had no significant influence on the tested mechanical property degradation after simulated long-term oral use. The mechanical performance of narrow diameter one-piece zirconia abutments differed from the other two materials. For optimal performance, one-piece zirconia abutments should be adopted only in anterior regions.
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Characterization of FA1654: a putative DPS protein in Filifactor alocis

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Abstract

The survival/adaptation of Fillifactor alocis, a fastidious gram positive asaccharolytic anaerobe, to the inflammatory environment of the periodontal pocket requires an ability to overcome oxidative stress. Moreover, its pathogenic characteristics are highlighted by its capacity to survive in the oxidative-stress microenvironment of the periodontal pocket and a likely ability to modulate the microbial community dynamics. There is still a significant gap in our understanding of its mechanism of oxidative stress resistance and its impact on the virulence and pathogenicity of the microbial biofilm. Coinfection of epithelial cells with F.alocis and P.gingivalis, resulted in the upregulation of several genes including HMPREF0389_01654(FA1654). Bioinformatics analysis indicates that FA1654 has a "di-iron binding domain", and could function as a DNA Starvation and Stationary Phase Protection (DPS) protein. We have further characterized the FA1654 protein to deter mine its role in oxidative stress resistance in F.alocis. In the presence of hydrogen peroxide induced oxidative stress there was a ∼1.3 fold upregulation of the FA1654 gene in F.alocis. Incubation of the purified FA1654 protein with DNA in the presence of hydrogen peroxide and iron resulted in the protection of the DNA from Fenton-mediated degradation. Circular Dichroism (CD) and Differential Scanning Flourimetry (DSF) studies have documented the intrinsic ability of rFA1654 protein to bind iron, however the rFA1654 protein is missing the intrinsic ability to reduce hydrogen peroxide. Collectively, the data may suggest that FA1654 in F.alocis is involved in oxidative stress resistance via an ability to protect against Fenton-mediated oxidative stress-induced damage.

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Use of the Toxicity Index in Evaluating Adverse Events in Anal Cancer Trials: Analysis of RTOG 9811 and RTOG 0529

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imageNovel toxicity metrics that account for all adverse event (AE) grades and the frequency of may enhance toxicity reporting in clinical trials. The Toxicity Index (TI) accounts for all AE grades and frequencies for categories of interest. We evaluate the feasibility of using the TI methodology in 2 prospective anal cancer trials and to evaluate whether more conformal radiation (using Intensity Modulated Radiation Therapy) results in improved toxicity as measured by the TI. Patients enrolled on NRG/RTOG 0529 or nonconformal RT enrolled on the 5-Fluorouracil/Mitomycin arm of NRG/RTOG 9811 were compared using the TI. Patients treated on NRG/RTOG 0529 had lower median TI compared with patients treated with nonconformal RT on NRG/RTOG 9811 for combined GI/GU/Heme/Derm events (3.935 vs 3.996, P=0.014). The TI methodology is a feasible method to assess all AEs of interest and may be useful as a composite metric for future efforts aimed at treatment de-escalation or escalation
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Identifying vulnerable populations with symptomatic cholelithiasis at risk for increased health care utilization

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imageBACKGROUND Gallstones are a common problem in the United States with many patients suffering from symptomatic cholelithiasis (SC). Patients with SC may first present to the emergency department ED) and are often discharged for elective follow-up; however, it is unknown what system and patient factors are associated with increased risk for ED revisits. This study aimed to assess longitudinal ED utilization and cholecystectomy for patients with SC and identify patient, geographic, and hospital characteristics associated with ED revisits, specifically race/ethnicity and insurance status. METHODS Patients discharged from the ED with SC between July 1, 2016, and December 31, 2017, were identified from California administrative databases and followed for 1 year. Emergency department revisits and cholecystectomy after discharge were examined using logistic regression, clustering standard errors by hospital. Models adjusted for patient, geographic, and hospital variables using census and hospital administrative data. RESULTS Cohort included 34,427 patients who presented to the ED with SC and were discharged. There were 18.8% of the patients that had one or more biliary-related ED revisits within 1 year. In fully adjusted models, non-Hispanic Black patients had higher odds for any ED revisit (adjusted odds ratio 1.23; 95% confidence interval, 1.09–1.39) and for two more ED revisits (adjusted odds ratio 1.48; 95% confidence interval, 1.20–1.82). Insurance type was also associated with ED revisits. CONCLUSION Non-Hispanic Black patients experienced higher utilization of health care resources for SC after adjusting for other patient, geographic and hospital variables. Strategies to mitigate these disparities may include the development of standardized protocols regarding the follow-up and education for SC. Implementation of such strategies can ensure equitable treatment for all patients. LEVEL OF EVIDENCE Prognostic and Epidemiological; Level III.
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Surgical stabilization of rib fractures versus nonoperative treatment in patients with multiple rib fractures following cardiopulmonary resuscitation: An international, retrospective matched case-control study

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imageBACKGROUND The presence of six or more rib fractures or a displaced rib fracture due to cardiopulmonary resuscitation (CPR) has been associated with longer hospital and intensive care unit (ICU) length of stay (LOS). Evidence on the effect of surgical stabilization of rib fractures (SSRF) following CPR is limited. This study aimed to evaluate outcomes after SSRF versus nonoperative management in patients with multiple rib fractures after CPR. METHODS An international, retrospective study was performed in patients who underwent SSRF or nonoperative management for multiple rib fractures following CPR between January 1, 2012, and July 31, 2020. Patients who underwent SSRF were matched to nonoperative controls by cardiac arrest location and cause, rib fracture pattern, and age. The primary outcome was ICU LOS. RESULTS Thirty-nine operatively treated patient were matched to 66 nonoperatively managed controls with comparable CPR-related characteristics. Patients who underwent SSRF more often had displaced rib fractures (n = 28 [72%] vs. n = 31 [47%]; p = 0.015) and a higher median number of displaced ribs (2 [P25–P75, 0–3] vs. 0 [P25–P75, 0–3]; p = 0.014). Surgical stabilization of rib fractures was performed at a median of 5 days (P25–P75, 3–8 days) after CPR. In the nonoperative group, a rib fixation specialist was consulted in 14 patients (21%). The ICU LOS was longer in the SSRF group (13 days [P25–P75, 9–23 days] vs. 9 days [P25–P75, 5–15 days]; p = 0.004). Mechanical ventilator-free days, hospital LOS, thoracic complications, and mortality were similar. CONCLUSION Despite matching, those who underwent SSRF over nonoperative management for multiple rib fractures following CPR had more severe consequential chest wall injury and a longer ICU LOS. A benefit of SSRF on in-hospital outcomes could not be demonstrated. A low consultation rate for rib fixation in the nonoperative group indicates that the consideration to perform SSRF in this population might be associated with other nonradiographic or injury-related variables. LEVEL OF EVIDENCE Therapeutic/Care Management; Level III.
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