The influence of the modulus-density relationship and the material mapping method on the simulated mechanical response of the proximal femur in side-ways fall loading configuration.

Contributing to slow advance of finite element (FE) simulations for hip fracture risk prediction, into clinical practice, could be a lack of consensus in the biomechanics community on how to map properties to the models. Thus, the aim of the present study was first, to systematically quantify the influence of the modulus-density relationship (E-ρ) and the material mapping method (MMM) on the predicted mechanical response of the proximal femur in a side-ways fall (SWF) loading configuration and second, to perform a model-to-model comparison of the predicted mechanical response within the femoral neck for all the specimens tested in the present study, using three different modelling techniques that have yielded good validation outcome in terms of surface strain prediction and whole bone response according to the literature. We found the outcome to be highly dependent on both the E-ρ relationship and the MMM. In addition, we found that the three modelling techniques that have resulted in good validation outcome in the literature yielded different principal strain prediction both on the surface as well as internally in the femoral neck region of the specimens modelled in the present study. We conclude that there exists a need to carry out a more comprehensive validation study for the SWF loading mode to identify which combination of MMMs and E-ρ relationship leads to the best match for whole bone and local mechanical response. The MMMs tested in the present study have been made publicly available at https://simtk.org/home/mitk-gem.

Comparison of explicit finite element and mechanical simulation of the proximal femur during dynamic drop-tower testing.

Current screening techniques based on areal bone mineral density (aBMD) measurements are unable to identify the majority of people who sustain hip fractures. Biomechanical examination of such events may help determine what predisposes a hip to be susceptible to fracture. Recently, drop-tower simulations of in-vitro sideways falls have allowed the study of the mechanical response of the proximal human femur at realistic impact speeds. This technique has created an opportunity to validate explicit finite element (FE) models against dynamic test data. This study compared the outcomes of 15 human femoral specimens fractured using a drop tower with complementary specimen-specific explicit FE analysis. Correlation coefficient and root mean square error (RMSE) were found to be moderate for whole bone stiffness comparison (R(2)=0.3476 and 22.85% respectively). No correlation was found between experimentally and computationally predicted peak force, however, energy absorption comparison produced moderate correlation and RMSE (R(2)=0.4781 and 29.14% respectively). By comparing predicted strain maps to high speed video data we demonstrated the ability of the FE models to detect vulnerable portions of the bones. Based on our observations, we conclude that there exists a need to extend the current apparent level material models for bone to cover higher strain rates than previously tested experimentally.

Development of a balanced experimental-computational approach to understanding the mechanics of proximal femur fractures.

The majority of people who sustain hip fractures after a fall to the side would not have been identified using current screening techniques such as areal bone mineral density. Identifying them, however, is essential so that appropriate pharmacological or lifestyle interventions can be implemented. A protocol, demonstrated on a single specimen, is introduced, comprising the following components; in vitro biofidelic drop tower testing of a proximal femur; high-speed image analysis through digital image correlation; detailed accounting of the energy present during the drop tower test; organ level finite element simulations of the drop tower test; micro level finite element simulations of critical volumes of interest in the trabecular bone. Fracture in the femoral specimen initiated in the superior part of the neck. Measured fracture load was 3760N, compared to 4871N predicted based on the finite element analysis. Digital image correlation showed compressive surface strains as high as 7.1% prior to fracture. Voxel level results were consistent with high-speed video data and helped identify hidden local structural weaknesses. We found using a drop tower test protocol that a femoral neck fracture can be created with a fall velocity and energy representative of a sideways fall from standing. Additionally, we found that the nested explicit finite element method used allowed us to identify local structural weaknesses associated with femur fracture initiation.

Minimizing the risks of latex allergy: the effectiveness of written information.

BACKGROUND: Latex allergy has been identified as an occupational risk for the dental profession. This study assessed whether identified latex-allergic dental personnel changed their practices after receiving verbal and written information about the management of latex allergy. METHODS: A survey conducted at the 1998 Australian Dental Association Congress identified 157 dental personnel with clinical latex allergy, or at high risk from latex exposure. The workplace implications were then explained to them by a consultant allergist. Four weeks later, follow up written information on latex allergy was mailed out. The information sheet outlined possible symptoms and cross-reactions, implications for the workplace, hand care advice and management strategies to reduce latex exposure in the workplace. After six weeks, a questionnaire, designed to assess whether appropriate steps to reduce latex exposure had been taken, was mailed out. RESULTS: Seventy per cent of the questionnaires were returned. All respondents felt the information was easy to understand and informative. While 50 per cent of respondents indicated that they had changed to powder-free or non-latex gloves, only five respondents were fully compliant with all instructions. CONCLUSION: Compliance with instructions regarding minimizing exposure to latex in a group of latex-allergic dental personnel was poor.

Screening for latex allergy with a questionnaire: comparison with latex skin testing in a group of dental professionals.

BACKGROUND: Latex allergy has emerged as an important cause of allergic reactions particularly in health workers. Due to the lack of a standardized extract for objective skin testing a screening questionnaire was developed. METHODS: At the 1995 Australian Dental Association Conference, all attendees were invited to complete a questionnaire and undergo skin testing to assess the level of latex allergy in this population and to assess the performance of the questionnaire as a screening test for latex allergy. RESULTS: The questionnaire had high specificity but poor sensitivity compared to skin testing with latex extract. CONCLUSION: This study compares at risk individuals identified by a screening questionnaire with those identified by objective skin testing. A questionnaire designed to screen for latex allergy was reliable for identifying those with low risk while overestimating those at risk of true latex allergy, demonstrating the need for objective testing with reliable allergens.

Opalescent dentine in two affected siblings.

This report describes the dental findings and management of siblings in a family in which three generations had been affected by osteogenesis imperfecta Type IV with opalescent dentine. Hereditary opalescent dentine, or opalescent teeth, is a pathologic dental condition characterised by a disturbance of dentine formation that occurs concurrently with osteogenesis imperfecta. Osteogenesis imperfecta is a genetically heterogenous group of systemic disorders of the connective tissue. The two siblings affected with opalescent dentine were treated under general anaesthesia, and included stainless steel crowns, extractions, and strip crowns on primary teeth. These reports highlight that appropriate treatment of the dentition of young patients with opalescent dentine should be carried out early in the primary dentition, and that this initial treatment can have long-term benefits in the mixed and permanent dentitions.

Prevalence of latex allergy in a dental school.

OBJECTIVE: To determine the prevalence of latex allergy in dental workers. DESIGN: Questionnaire survey of staff of a dental school. SETTING: The Westmead Dental School, a large dental facility in western Sydney. PARTICIPANTS: 230 staff members of the Westmead Dental School (consisting of general and specialist dentists, chairside assistants and registered nurses, laboratory technicians, dental therapists and hygienists) received questionnaires. MAIN OUTCOME MEASURES: The prevalence of latex allergy, defined by prompt onset of hand urticaria with or without generalised symptoms, and the prevalence of hand dermatitis and other glove-related symptoms. Also, the relationship between latex allergy and associated atopic status. RESULTS: 177 staff (77%) responded by the set collection date; 33% reported symptoms related to wearing gloves and 22% satisfied the criteria for glove dermatitis. Sixteen respondents (9%) reported characteristics suggestive of latex-glove allergy. CONCLUSIONS: Confirmation of the 9% prevalence of latex allergy among dental workers will require further studies incorporating an objective measure of IgE-mediated hypersensitivity.

Paediatric dentistry--what's new. A contemporary approach to the art and science of caries risk assessment.

Preventive dental care for children and adolescents has historically focused on fluoride therapy, oral hygiene and home care maintenance, simple dietary advice, and the placement of fissure sealants. Traditionally, dental caries has been regarded as a static phenomenon, eventuating in loss of tooth structure while the basis for treatment and management of this ubiquitous disease has essentially been mechanical. However, with current developments in new dental materials, techniques and preventive strategies, a more precise understanding and appreciation of the nature of the caries process is required. The development of dental caries is a common yet complex series of dynamic events under the influence of numerous inter-related biological, social, behavioural and psychological factors. It is now increasingly recognized that certain 'high risk' caries-susceptible individuals persist within our communities for whom preventive measures and restorative care alone are not enough to control the disease. This paper will discuss and outline current preventive concepts, individual risk factors, and dietary considerations which can be utilized in a contemporary approach to caries risk assessment.

A case of neurocristopathy that manifests facial clefting and maxillary duplication.

A case of a 6-year-old child with three facial clefts and maxillary duplication is presented. Computerized three-dimensional reconstruction from computerized tomography imaging was used in the diagnosis of this patient, and an explanation of the possible embryologic causes of this malformation is discussed.

The normal development of teeth.

Even though a dental assessment is not often a part of a child's regular medical check up, an understanding of the normal dental development and its variations is a valuable diagnostic tool. Dental health is a part of total health, and there is a need for increased communication between medical and dental practitioners to achieve this goal (Figure 32).

Oro-facial trauma in children.

Dentoalveolar trauma is unfortunately a regular part of medical practice. The prompt management of such injuries is vital in re-establishing a healthy dentition. As well, the promotion of preventive equipment is paramount: from seat belts and bike helmets to mouthguards. The purchase of over the counter one-size-fits-all mouthguards is not only a waste of money but dangerous. Well made mouthguards fitted by a dentist are a sensible investment to reduce the frequency and severity of costly dental injury and to preserve the attractive aesthetics of natural teeth (Figures 21 and 22). They must be worn in competition and at practice.