Comprehensive Analysis of Repair/Reinforcement Materials for Polymethyl Methacrylate Denture Bases: Mechanical and Dimensional Stability Characteristics

Fracture of complete denture is a common problem as acrylic resins hold inherent limitations. This necessitates affirmation of a selection criterion by evaluating the critical requirements of repair materials. The study intended to evaluate mechanical properties and dimensional stability of common denture base repair and reinforcement materials under standard experimental protocol. Seven types of denture reinforcement materials were chosen. Forty cuboidal samples were made in accordance with ISO 178 for three point bending test and divided to eight groups of five samples each. One group acted as control and samples of seven groups were sectioned and repaired with chosen materials. Five mechanical properties—fracture load, deflection, flexural strength, fracture toughness and elastic modulus were evaluated for all groups. Forty mandibular complete denture specimens were utilized for evaluating fracture load and deflection under loading. Dimensional stability after repair with seven different repair materials was analyzed in two planes (Linear and curvilinear) utilizing separate set of denture samples. Heat cure polymethyl methacrylate with polyethylene fiber was affirmed as material of choice based on this study as it accomplishes the most critical norms of requirement.     

Mechanical testing of thin-walled zirconia abutments

Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bicomponent aesthetic abutments has been suggested.

Objective:

Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments.

Material and Methods:

Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25º angle inclination (n=10 each group). Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20ºC±5ºC. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope.

Results:

Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean F^max was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253) and dynamic testing (p=0.135). A significant difference in the bending moment required for fracture was detected between the groups (p=0.01). Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region.

Conclusion:

Angled or straight thin-walled zirconia abutments presented similar F^max under fatigue testing despite the different bending moments required for fracture. The main implication is that although zirconia angled or straight abutments presented similar mechanical behavior, the failure mode tended to be more catastrophic in straight (fracture at the cervical region) compared to angled abutments.     

Facteurs associés au burnout en anesthésie–réanimation. Enquête 2009 de la Société française d’anesthésie et de réanimation

Objective

To assess factors related to burnout in anesthesia and intensive care.

Design

National prospective observational study.

Materials and methods

Questionnaire posted on the French Society of anesthesia website from 3rd June 2009 to 27th August 2009: Maslach Burnout Inventory (MBI), Fast Alcohol Consumption Evaluation (FACE) and The Harvard National Depression Screening Day Scale (HANDS) scales and questions to assess health, work and personal life.

Results

One thousand six hundred and three questionnaires returned: 1091 anesthetists (67.6%), 241 intensivists (14.9%), 204 nurses (12.6%), emergency physicians (2.8%), supervisor nurses (0.9%). Seven hundred and sixty three in a university hospital (47.3%), 259 in a regional hospital (16.1%), 405 in a private structure (25.1%), 71 in a non-lucrative private structure (4.4%), 75 in a military hospital (4.6%). Rest of safety: 69.2% of institutions. Depression: 38.7%. Drug or chemicals addicted: 10.6%. Alcohol addicts: 10.6%. Among them, 62.3% of individuals were in burnout. Burnout was linked to fragmented sleep (P < 0.00001), interpersonal conflicts (P < 0.00001), perception of rest of safety (P < 0.02), mental history (P < 0.00001), suicidal ideations (P < 0.00001), depression (P = 0.00001), alcohol (P < 0.002), drug consumption (P < 0.00002), and accidents after a nightshift (P < 0.05). Subjects in burnout intended more frequently to leave the profession (P < 0.00001). Leaving in couple had a protective effect (P < 0.005). The logistic regression model retained seven covariates independently associated with burnout: quality of work, of personal life, of fatigue, depression, conflicts with colleagues and patients, regretting the choice of specialty.

Conclusion

This study of the largest cohort of anesthesia personnel performed in France detects a high proportion of burnout. It highlights links with tensors that may constitute possibilities of prevention of the burnout syndrome.     

Low-Frequency Fatigue in Individuals With Spinal Cord Injury

Abstract

Background/Objective: This study examined magnitude and recovery of low-frequency fatigue (LFF) in the quadriceps after electrically stimulated contractions in spinal cord-injured (SCI) and able-bodied subjects.

Subjects: Nine SCI (ASIA A-C, levels C5-T9, injured 13.6 ± 12.2 years) and 9 sedentary able-bodied subjects completed this study.

Methods: Fatigue was evoked in 1 thigh, and the nonfatigued leg served as a control. The fatigue test for able-bodied subjects lasted 15 minutes. For SCI, stimulation was adjusted so that the relative drop in force was matched to the able-bodied group. Force was assessed at 20 (P20) and 100 Hz (PI 00), and the ratio of P20/P100 was used to evaluate LFF in thighs immediately after, at 10, 20, and 60 minutes, and at 2, 4, 6, and 24 hours after a fatigue test.

Results: The magnitude of LFF (up to 1 hour after fatigue) was not different between able-bodied and patients with SCI. However, recovery of LFF over 24 hours was greater in able-bodied compared with patients with SCI in both the experimental (P < 0.001) and control legs (P < 0.001). The able-bodied group showed a gradual recovery of LFF over time in the experimental leg, whereas the SCI group did not.

Conclusions: These results show that individuals with SCI are more susceptible to LFF than able-bodied subjects. In SCI, simply assessing LFF produced considerable LFF and accounted for a substantial portion of the response. We propose that muscle injury is causing the dramatic LFF in SCI, and future studies are needed to test whether “fatigue” in SCI is actually confounded by the effects of muscle injury.     

Treatment of sleep disorders may improve fatigue in multiple sclerosis

Objective

In a previous polysomnographic cross-sectional study we found a significant relationship between sleep disorders and multiple sclerosis (MS) related fatigue. The purpose of this open follow-up observation was to compare the impact of treatment of sleep disorders on MS related fatigue measured with the Modified Fatigue Impact Scale (MFIS).

Methods

Non-randomized follow-up observation: treated versus untreated patients, subgroups according to compliance with sleep medical treatment recommendations (univariate, multivariate analysis, multiple logistic regression). 66 MS patients were followed after polysomnography, 49 patients with relevant sleep disorders and 17 without.

Results

Mean MFIS scores decreased from 41.2 to 26.2 (p = 0.025) in patients with good compliance (GC; n = 18), from 42.4 to 32.1 (p = 0.12) in patients with moderate compliance (MC; n = 12), and from 41.6 to 35.5 (p = 0.17) in non-compliant patients (NC; n = 17). Mean MFIS values increased in patients without sleep disorders from 22.9 to 25.4 (NSD; n = 12, p = 0.56). In multiple logistic regression, treatment of sleep disorders predicted decrease of MFIS-values (GC versus NSD odds ratio 13.4; p = 0.015; 95% confidence interval (CI) 1.7–107.2, MC versus NSD odds ratio 13.8; p = 0.028; 95% CI 1.3–143.3).

Conclusions

Sleep medical treatment may improve MS related fatigue when patients adhere to treatment recommendations.     

Effect of fibre post length and adhesive strategy on fracture resistance of endodontically treated teeth after fatigue loading

Objectives

To evaluate the effect of the length of fibre-posts¹ and type of adhesive cement² on the fracture resistance of endodontically treated teeth, after fatigue loading.

Methods

Eighty extracted upper pre-molars were sectioned at the CEJ and endodontically treated. After 24 h of water storage at 37 °C, RelyX Posts (3M-ESPE) were cemented with Panavia F 2.0 (Kuraray) or RelyX Unicem (3M-ESPE). A standardized composite core was built. Specimens were divided into four groups depending on the post–core ratio: (A) 2/1 (control); (B) 3/2; (C) 1/1 (small diameter); (D) 1/1(large diameter) and submitted to 1,200,000 cycles using a chewing simulator (Willytech). Immediately afterwards, all specimens that survived fatigue loading were fractured using a universal loading device (Micro-tester, Instron). Data were analysed with ANOVA.

Results

Four percent of the specimens failed during fatigue loading. The length of the post into the root affected the fracture resistance. The statistical outcome varied according to the inclusion of specimens failed during fatigue loading. However, the control group always had the lowest fracture resistance. The type of adhesive cement did not affect the fracture resistance. A prevalence of not-repairable failures was observed in specimens restored with the longest posts, whilst shorter posts led to more repairable failures.

Conclusions

Shortening the post length and the ensuing preservation of more tooth structure, offer the potential for reparability through an in-built fail safe mechanism and may thus reduce the occurrence of catastrophic failures.     

The effects of aromatherapy with lavender essential oil on fatigue levels in haemodialysis patients: A randomized clinical trial

ObjectiveThis study was intended to examine the efficacy of lavender essential oil for the alleviation of fatigue in haemodialysis patients.Methods and materialsThis randomized clinical trial was conducted on 59 haemodialysis patients in two groups. The routine care group received the routine care, but the experimental group inhaled lavender essence 5% for 10 min, three times a week for 4 consecutive weeks. The Fatigue Severity Scale was used to assess fatigue before the intervention and after the last intervention in the second and fourth weeks.ResultsNo statistically significant differences were observed between the two groups in terms of the fatigue scores before, and after the last intervention in the second and fourth weeks.ConclusionOur result does not support other studies suggesting that lavender essential oil is effective on fatigue in haemodialysis patients. This conflicting result can mostly be ascribed to a variety of factors such as duration of aromatherapy and differences in concentrations of lavender essential oil.