Performance of three-lobe pressure-dam bearings

Endodontics has gained emphasis in the scientific community in recent years due to the increase in clinical and in animal models studies focused on endodontic medicine, which aims to evaluate the interrelationship between systemic and periapical tissues pathological conditions. These studies have shown that systemic changes can boost the pathogenesis of endodontic infection, favoring its development and progression. A contrary relationship is reported in numerous studies that affirm the potential of endodontic infection to trigger systemic damage and may lead to the worsening of pre-existing pathologies. Recently, the potential of filling materials to develop systemic changes such as neurological alterations had been evaluated, also showing that systemic diseases can negatively influence tissue responses to filling materials after endodontic treatment. Despite advances in endodontic medicine studies, there are still gaps in knowledge on the mechanisms of interactions between apical periodontitis (AP) and systemic diseases and much research to be done. In this sense, this critical narrative literature review aimed to show the evolution of studies in endodontic medicine to help the endodontist to know the role of systemic diseases in the pathogenesis of AP and the possible interference in the repair of periapical tissues after endodontic treatment, as well as to evidence the systemic complications that can be triggered or aggravated in the presence of endodontic infection.

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Evolution of endodontic medicine: a critical narrative review of the interrelationship between endodontics and systemic pathological conditions

The stability of ordinary journal bearings is found to increase by the use of multi-lobes. Studies have shown that performance can be further improved by incorporation of pressure dams into these bearings. This paper analyses the performance of a four-lobe pressure-dam bearing which is produced by incorporating two pressure dams on the upper two lobes and two relief-tracks on the lower two lobes of an ordinary four-lobe bearing. The results show that the performance of a four-lobe bearing with pressure dams is superior to that of an ordinary four-lobe bearing.

Static and Dynamic Characteristics of Four-Lobe Pressure-Dam Bearings

This paper analyzes the dynamic behavior of a new type of bearing, namely, four-lobe pressure-dam bearing. It is produced by incorporating two pressure dams in the upper two lobes and two relief tracks in the lower two lobes of an ordinary four-lobe bearing. The characteristic curves of this type of bearing show that it is much more stable as compared to an ordinary four-lobe bearing. A study of the performance characteristics of this type of bearing is also undertaken.

Stability Analysis of Four-Lobe Pressure-Dam Bearings

This paper presents an analytical study of dynamic characteristics of half-elliptical pressure dam bearings. One half (either upper or lower) of these bearings is elliptical, while the other half is circular. A step or pressure dam is cut in the upper half bearing surface. The lower half bearing surface is provided with a deep groove or relief-track. These bearings have been analyzed by the finite-element method. The results have been computed for dimensionless rotor flexibilities of 0.0, 0.5, 1.0, 2.0, and 4.0. Dynamic characteristics such as stiffness and damping coefficients, and stability threshold speed are presented in the form of graphs. It has been determined that half-elliptical pressure dam bearings are superior to circular pressure dam bearings in stability for bearings having same design parameters. Both these half-elliptical pressure dam bearings have almost identical dynamic characteristics. Rotor flexibility adversely affects the stability of these bearings and its effect is pronounced at h...

Dynamic Analysis of Finite Half-Elliptical Pressure Dam Bearings with Rotor Flexibility Effects

The stability of two-axial groove cylindrical journal bearing is improved by milling a step or pressure dam in the upper half surface and by cutting a deep groove or relief-track in the lower half surface. Dynamic analysis of elliptical bearings having similar construction of dam and relief-track, called elliptical pressure dam bearings, has revealed that these bearings are far more stable than ordinary cylindrical, cylindrical pressure dam, elliptical, three-lobe, etc., when supporting a rigid rotor. In this paper, the stability of finite elliptical pressure dam bearings supporting flexible rotors is discussed. The dimensionless rotor flexibilities selected are 0.5, 1.0, 2.0, and 4.0, which cover almost the entire range of practical interest. Effects of design parameters such as vertical preset, L/D ratio, Sommerfeld number, dam location and relief-track width ratio on the stability of these bearings, corresponding to various dimensionless rotor flexibilities are presented in the form of graphs. Also, th...

Stability of Finite Elliptical Pressure Dam Bearings with Rotor Flexibility Effects

BACKGROUND Diabetes mellitus (DM) may affect the healing and survival of root filled teeth with periapical lesions. AIM To systematically analyse the available clinical literature to evaluate the association between DM and the prevalence of radiolucent periapical lesions in root filled teeth. The review question was 'Is there a difference between the root canal treatment healing outcome (in terms of presence or absence of radiolucent periapical lesions) in diabetic and non-diabetic patients?'. DATA SOURCES A systematic review of cross-sectional studies and prospective clinical trials was conducted according to the PRISMA checklist. The review involved a search of the electronic databases of PubMed, Scopus and EBSCO host. STUDY ELIGIBILITY CRITERIA, PARTICIPANTS AND INTERVENTIONS The research protocol was previously registered in the International Prospective Register of Ongoing Systematic Reviews (CRD42019130954) and included defined inclusion/exclusion criteria. The included studies were related to the root canal treatment outcome in diabetic patients in terms of periapical radiolucent lesions associated with root filled teeth. STUDY APPRAISAL AND SYNTHESIS The selected studies were critically analysed by two evaluators using the Joanna Briggs Institute Critical Appraisal tool. The pooled odds ratio (OR) was recognized as the primary outcome variable and measure of the effect for the occurrence of periapical lesions associated with root filled teeth of control and diabetic patients. The random-effects Mantel-Haenszel method was used, at a 95% confidence interval, to calculate the pooled OR. A funnel plot was created to evaluate possible sources of heterogeneity. RESULTS Ten studies published between 1989 and March 2019 were selected after thorough analysis and exclusion according to the strict criteria. Seven cross-sectional studies, 1 longitudinal and 2 prospective clinical studies were included. The pooled OR was calculated by comparing 773 diabetic subjects and 1133 control subjects. The pooled OR for the observational studies and clinical studies were 1.42 and 6.36, respectively. This value signified a high prevalence of periapical lesions in root filled teeth in diabetic subjects. LIMITATIONS There are limited prospective clinical trials on this topic. The majority of the included studies are observational. CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS The data suggest a strong connection between the presence of periapical radiolucency on root filled teeth amongst diabetics as determined by the pooled OR.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/iej.13366

Diabetes mellitus and the healing of periapical lesions in root filled teeth: a systematic review and meta‐analysis

Stability of Finite Orthogonally-Displaced Pressure Dam Bearings

Achieving profound anesthesia in mandibular molars with irreversible pulpitis is a tedious task. This review aimed at evaluating the success of buccal/lingual infiltrations administered with a primary inferior alveolar nerve block (IANB) injection or as a supplemental injection after the failure of the primary injection in symptomatic and asymptomatic patients with irreversible pulpitis in human mandibular molars. The review question was "What will be the success of primary and supplemental infiltration injection in the endodontic treatment of patients with irreversible pulpitis in human mandibular molars?" We searched electronic databases, including Pubmed, Scopus, and Ebsco host and we did a comprehensive manual search. The review protocol was framed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) checklist. We included clinical studies that evaluated and compared the anesthetic outcomes of primary IANB with primary and/or supplementary infiltration injections. Standard evaluation of the included studies was performed and suitable data and inferences were assessed. Twenty-six studies were included, of which 13 were selected for the meta-analysis. In the forest plot representation of the studies evaluating infiltrations, the combined risk ratio (RR) was 1.88 (95% CI: 1.49, 2.37), in favor of the secondary infiltrations with a statistical heterogeneity of 77%. The forest plot analysis for studies comparing primary IANB + infiltration versus primary IANB alone showed a low heterogeneity (0%). The included studies had similar RRs and the combined RR was 1.84 (95% CI: 1.44, 2.34). These findings suggest that supplemental infiltrations given along with a primary IANB provide a better success rate. L'Abbe plots were generated to measure the statistical heterogeneity among the studies. Trial sequential analysis suggested that the number of patients included in the analysis was adequate. Based on the qualitative and quantitative analyses, we concluded that the infiltration technique, either as a primary injection or as a supplementary injection, given after the failure of primary IANB, increases the overall anesthetic efficacy.

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Anesthetic efficacy of primary and supplemental buccal/lingual infiltration in patients with irreversible pulpitis in human mandibular molars: a systematic review and meta-analysis.

Namrata Mehta

Papers

Stability of Finite Elliptical Pressure Dam Bearings with Rotor Flexibility Effects

Diabetes mellitus and the healing of periapical lesions in root filled teeth: a systematic review and meta‐analysis

Dynamic Analysis of Finite Half-Elliptical Pressure Dam Bearings with Rotor Flexibility Effects

Stability of Finite Orthogonally-Displaced Pressure Dam Bearings

Anesthetic efficacy of primary and supplemental buccal/lingual infiltration in patients with irreversible pulpitis in human mandibular molars: a systematic review and meta-analysis.