A comparison of three finite element models of an edentulous mandible provided with implants

The stress distribution in an edentulous mandible provided with two implants in the interforaminal region was calculated by means of three different finite element models. The implants were connected with a bar or remained solitary. The first model was a three-dimensional representation of the entire mandible, the second model of the interforaminal region of this same mandible, whilst the third model was a two-dimensional representation of the interforaminal region. The differences in stress distribution around the connected implants and the solitary implants between these three models were analysed.
It can be concluded that for a parameter study the stress distribution around the dental implants following from a three-dimensional finite element model of only the interforaminal region of an edentulous mandible can be used. For such studies therefore, benefit can be gained from the advantages of reduced modelling and calculation time.     

The Diagnostic Value of Rectal Examination

The rectal examination is a much advocated procedure for assessingabdominal and urinary symptoms. A Medline literature searchyielded only a few studies, not one of them in a general practicesetting. The sensitivity of the rectal examination to rectalcarcinoma and appendicitis is low, while it is high for prostatecarcinoma. When reviewing the likelihood ratios of normal andabnormal findings of rectal examinations it was concluded thatit may be a useful procedure in the case of abnormal findingsin patients presenting rectal problems and in assessing menwith prostate problems, although it does not seem useful indiagnosing appendicitis. However, since the diagnostic valuesin general practice and in referred populations may be difterent,there is a need for further prospective studies in settingsof general medical practice.     

General practitioners' satisfaction with and attitudes to out-of-hours services

Background  

In recent years, Dutch general practitioner (GP) out-of-hours service has been reorganised into large-scale GP cooperatives. Until now little is known about GPs' experiences with working at these cooperatives for out-of-hours care. The purpose of this study is to gain insight into GPs' satisfaction with working at GP cooperatives for out-of-hours care in separated and integrated cooperatives.     

The influence of a flexible coating on the bone stress around dental implants

summary The influence of a three-layered flexible coating of Polyactive® on bone stress distribution was investigated by three-dimensional finite element models of mandibular bone, in which a titanium implant (coated or uncoated) was located. Poly-active® is a system of poly(ethylene oxide) poly(butylene terephthalate) segmented co-polymers with bone-bonding capacity. In the case of sagittal and transversal loading, the use of a Polyactive® coating reduced both the minimum principal stress in the bone and the compressive radial stress at the bone-implant interface. However, it raised the maximum principal and the tensile radial stress. In the case of vertical loading, the application of a flexible coating reduced the compressive radial stress at the bone-implant interface around the neck of the implant by a factor of 6.6 and the tensile radial stress by a factor of 3.6. Variations in composition and thickness of the coating did not affect the results significantly.     

Location of implants in the interforaminal region of the mandible and the consequences for the design of the superstructure

The location and the number of implants to support an overdenture is of major importance for the superstructure design. Sometimes, jaw bone anatomy or posteriorly placed implants enforce the use of an angular bar to achieve a position above the alveolar ridge. Loads on such a bar may introduce a moment on the implants which can result in high bone stresses and eventually the loss of the implants.
This study on stress distribution in the bone around the implants in an edentulous mandible was performed using a three-dimensional finite element model. One model with two implants placed just anteriorly of the mental foramen and connected with an anteriorly placed bar, following the curvature of the alveolar ridge, was compared with two other designs. First with a similar model but now without a bar and secondly with a model with four implants connected with straight bars.
It is concluded that loading a bar, which is placed anteriorly of the interconnecting line between two implants, causes extremely large compressive and tensile stress concentrations in the bone around the implants. Therefore, in those cases, it is advised not to connect the implants or, in case a bar-clip attachment is preferred, to place additional implants in the frontal region.     

Loading conditions of endosseous implants in an edentulous human mandible: a three-dimensional, finite-element study

The design of dental superstructures influences the loading on dental implants and the deformation of the anterior interforaminal bone in an edentulous mandible. This deformation causes stress in the bone around the implants and may lead to bone resorption and loss of the implant. The stress distribution around dental implants in an edentulous mandible was calculated by means of a three-dimensional, finite-element model of the anterior part of the jaw. This model was built from data obtained from slices of a single human mandible and was provided with four endosseous implants in the interforaminal region. The implants were either connected with a bar or remained solitary. The solitary implants or the bars were loaded either uniformly or non-uniformly. In case of a non-uniform distribution, either the central bar or the central implants were loaded or the lateral bars or the lateral implants were loaded. The most extreme stresses in the bone were always located around the neck of the implant. In the case of the uniform distribution of the loading there were more or less equal extreme principal stresses around the central and lateral implants. If the load was not uniformly distributed on the superstructure then the implant that was nearest to the place of loading showed the highest stress concentration; with connected implants there was a reduction in the magnitude of the extreme principal stresses compared to solitary implants.     

Effectiveness and cost-effectiveness of a multidisciplinary intervention programme to prevent new falls and functional decline among elderly persons at risk: design of a replicated randomised controlled trial [ISRCTN64716113]

Background  

Falls are common among community-dwelling elderly people and can have a considerable impact on quality of life and healthcare costs. People who have sustained a fall are at greater risk of falling again.     

Bedwetting and behavioural and/or emotional problems

Objective: To assess the link between enuresis nocturna and the severity of behavioural and/or emotional problems in Dutch children and the course of these problems. Setting: West-Mine Region in the Netherlands. Subjects and methods: Prospective cohort study involving 66 of the 80 bedwetting children from all 1652 children born in 1983 in this region. After 1 y, contact was still possible with 64 of the enuretics. We used the Dutch version of the Child Behaviour Checklist (CBCL) and a questionnaire about bedwetting. Results: The mean T-score for Total Problems (CBCL score) in 1992 (M1; mean age 8. 6) was 52. 1, and 1 y later was 49. 2 (M2). There was no significant difference in the CBCL scores for Ml, M2 and a matching group from the Dutch CBCL norm population, either in the group who remained wet or in the group who became dry. There were no differences between the sexes. There was no link between the severity of behavioural and emotional problems and the frequency of bedwetting. However, more children with bedwetting than expected were in the clinical range. Conclusion: There was no difference in behavioural and/or emotional problems between the first and the second measurement and the matching group from the CBCL norm group. There were no differences in behavioural and/or emotional problems between primary and secondary bedwetters, nor were there any consequences related to the frequency of bedwetting.