Effect of the crown design and interface lute parameters on the stress-state of a machined crown-tooth system: A finite element analysis

The effect of preparation design and the physical properties of the interface lute on the restored machined ceramic crown-tooth complex are poorly understood. The aim of this work was to determine, by means of three-dimensional finite element analysis (3D FEA) the effect of the tooth preparation design and the elastic modulus of the cement on the stress state of the cemented machined ceramic crown-tooth complex. The three-dimensional structure of human premolar teeth, restored with adhesively cemented machined ceramic crowns, was digitized with a micro-CT scanner. An accurate, high resolution, digital replica model of a restored tooth was created. Two preparation designs, with different occlusal morphologies, were modeled with cements of 3 different elastic moduli. Interactive medical image processing software (mimics and professional CAD modeling software) was used to create sophisticated digital models that included the supporting structures; periodontal ligament and alveolar bone. The generated models were imported into an FEA software program (hypermesh version 10.0, Altair Engineering Inc.) with all degrees of freedom constrained at the outer surface of the supporting cortical bone of the crown-tooth complex. Five different elastic moduli values were given to the adhesive cement interface 1.8 GPa, 4 GPa, 8 GPa, 18.3 GPa and 40 GPa; the four lower values are representative of currently used cementing lutes and 40 GPa is set as an extreme high value. The stress distribution under simulated applied loads was determined. The preparation design demonstrated an effect on the stress state of the restored tooth system. The cement elastic modulus affected the stress state in the cement and dentin structures but not in the crown, the pulp, the periodontal ligament or the cancellous and cortical bone. The results of this study suggest that both the choice of the preparation design and the cement elastic modulus can affect the stress state within the restored crown-tooth complex.

Loss of Synaptic Connectivity, Particularly in Second Order Neurons Is a Key Feature of Diabetic Retinal Neuropathy in the Ins2Akita Mouse

Retinal neurodegeneration is a key component of diabetic retinopathy (DR), although the detailed neuronal damage remains ill-defined. Recent evidence suggests that in addition to amacrine and ganglion cell, diabetes may also impact on other retinal neurons. In this study, we examined retinal degenerative changes in Ins2^Akita diabetic mice. In scotopic electroretinograms (ERG), b-wave and oscillatory potentials were severely impaired in 9-month old Ins2^Akita mice. Despite no obvious pathology in fundoscopic examination, optical coherence tomography (OCT) revealed a progressive thinning of the retina from 3 months onwards. Cone but not rod photoreceptor loss was observed in 3-month-old diabetic mice. Severe impairment of synaptic connectivity at the outer plexiform layer (OPL) was detected in 9-month old Ins2Akita mice. Specifically, photoreceptor presynaptic ribbons were reduced by 25% and postsynaptic boutons by 70%, although the density of horizontal, rod- and cone-bipolar cells remained similar to non-diabetic controls. Significant reductions in GABAergic and glycinergic amacrine cells and Brn3a+ retinal ganglion cells were also observed in 9-month old Ins2^Akita mice. In conclusion, the Ins2^Akita mouse develops cone photoreceptor degeneration and the impairment of synaptic connectivity at the OPL, predominately resulting from the loss of postsynaptic terminal boutons. Our findings suggest that the Ins2^Akita mouse is a good model to study diabetic retinal neuropathy.

Polarization retention loss in PbTiO3 ferroelectric films due to leakage currents

The relationship between retention loss in single crystal PbTiO3 ferroelectric thin films and leakage currents is demonstrated by piezoresponse and conductive atomic force microscopy measurements. It was found that the polarization reversal in the absence of an electric field followed a stretched exponential behavior 1-exp[-(t/k)(d)] with exponent d>1, which is distinct from a dispersive random walk process with d <. The latter has been observed in polycrystalline films for which retention loss was associated with grain boundaries. The leakage current indicates power law scaling at short length scales, which strongly depends on the applied electric field. Additional information of the microstructure, which contributes to an explanation of the presence of leakage currents, is presented with high resolution transmission electron microscopy analysis.

Loss-of-Mains Protection System by Application of Phasor Measurement Unit Technology with Experimentally Assessed Threshold Settings

Loss-of-mains protection is an important component of the protection systems of embedded generation. The role of loss-of-mains is to disconnect the embedded generator from the utility grid in the event that connection to utility dispatched generation is lost. This is necessary for a number of reasons, including the safety of personnel during fault restoration and the protection of plant against out-of-synchronism reclosure to the mains supply. The incumbent methods of loss-of-mains protection were designed when the installed capacity of embedded generation was low, and known problems with nuisance tripping of the devices were considered acceptable because of the insignificant consequence to system operation. With the dramatic increase in the installed capacity of embedded generation over the last decade, the limitations of current islanding detection methods are no longer acceptable. This study describes a new method of loss-of-mains protection based on phasor measurement unit (PMU) technology, specifically using a low cost PMU device of the authors' design which has been developed for distribution network applications. The proposed method addresses the limitations of the incumbent methods, providing a solution that is free of nuisance tripping and has a zero non-detection zone. This system has been tested experimentally and is shown to be practical, feasible and effective. Threshold settings for the new method are recommended based on data acquired from both the Great Britain and Ireland power systems.

Electron-induced hydrogen loss in uracil in a water cluster environment

Low-energy electron-impact hydrogen loss due to dissociative electron attachment (DEA) to the uracil and thymine molecules in a water cluster environment is investigated theoretically. Only the A'-resonance contribution, describing the near-threshold behavior of DEA, is incorporated. Calculations are based on the nonlocal complex potential theory and the multiple scattering theory, and are performed for a model target with basic properties of uracil and thymine, surrounded by five water molecules. The DEA cross section is strongly enhanced when the attaching molecule is embedded in a water cluster. This growth is due to two effects: the increase of the resonance lifetime and the negative shift in the resonance position due to interaction of the intermediate negative ion with the surrounding water molecules. A similar effect was earlier found in DEA to chlorofluorocarbons. 

A new method for transmission loss allocation considering the circulating currents between generators

A new method is presented for transmission loss allocation based on the separation of transmission loss caused by load and the loss due to circulating currents between generators. The theoretical basis for and derivation of the loss formulae are presented using simple systems. The concept is then extended to a general power system using the Ybus model. Details of the application of the proposed method to a typical power system are presented along with results from the IEEE 30 bus test system. The results from both the small system and the standard IEEE test system demonstrate the validity of the proposed method.

Consistent effects of consumer species loss across different habitats

Our knowledge of the effects of consumer species loss on ecosystem functioning is limited by a paucity of manipulative field studies, particularly those that incorporate inter-trophic effects. Further, given the ongoing transformation of natural habitats by anthropogenic activities, studies should assess the relative importance of biodiversity for ecosystem processes across different environmental contexts by including multiple habitat types. We tested the context-dependency of the effects of consumer species loss by conducting a 15-month field experiment in two habitats (mussel beds and rock pools) on a temperate rocky shore, focussing on the responses of algal assemblages following the single and combined removals of key gastropod grazers (Patella vulgata, P. ulyssiponensis, Littorina littorea and Gibbula umbilicalis). In both habitats, the removal of limpets resulted in a larger increase in macroalgal richness than that of either L. littorea or G. umbilicalis. Further, by the end of the study, macroalgal cover and richness were greater following the removal of multiple grazer species compared to single species removals. Despite substantial differences in physical properties and the structure of benthic assemblages between mussel beds and rock pools, the effects of grazer loss on macroalgal cover, richness, evenness and assemblage structure were remarkably consistent across both habitats. There was, however, a transient habitat-dependent effect of grazer removal on macroalgal assemblage structure that emerged after three months, which was replaced by non-interactive effects of grazer removal and habitat after 15 months. This study shows that the effects of the loss of key consumers may transcend large abiotic and biotic differences between habitats in rocky intertidal systems. While it is clear that consumer diversity is a primary driver of ecosystem functioning, determining its relative importance across multiple contexts is necessary to understand the consequences of consumer species loss against a background of environmental change.

Impact of tooth replacement on the nutritional status of partially dentate elders

OBJECTIVES: The aim of this study was to compare the impact of two different tooth replacement strategies on the nutritional status of partially dentate older patients. Nutritional status was measured using the full version of the Mini Nutritional Assessment (MNA) and the short form of the Mini Nutritional Assessment (MNA-SF).

MATERIALS AND METHODS: A randomised controlled clinical trial was conducted (Trial Registration no. ISRCTN26302774). Partially dentate patients aged 65 years and older were recruited and randomly allocated to the two different treatment groups: the removable partial dentures (RPD) group and the shortened dental arch (SDA) group. Nutritional status was measured using the MNA and MNA-SF administered at baseline and 1, 6 and 12 months after treatment intervention by a research nurse blinded to the treatment group allocation of all participants.

RESULTS: Data collected using the full version of the MNA showed significant improvements in mean MNA scores over the length of the study (p < 0.05). For the entire patient group, there was a mean increase of 0.15 points at 6 months and a further increase of 0.19 points at 12 months. These increases were similar within the treatment groups (p > 0.05). For MNA-SF, the analysis showed that there were no significant differences recorded over the data collection points after treatment intervention (p < 0.05).

CONCLUSION: Tooth replacement using conventional and functionally orientated treatment for the partially dentate elderly showed significant improvements in MNA score 12 months after intervention.

CLINICAL RELEVANCE: Prosthodontic rehabilitation may play an important role in the nutritional status of partially dentate elders.

Comparison of functionally orientated tooth replacement and removable partial dentures on the nutritional status of partially dentate older patients: a randomised controlled clinical trial

OBJECTIVES: The aims of this study were to conduct a randomised controlled clinical trial (RCT) of partially dentate older adults comparing functionally orientated treatment based on the SDA concept with conventional treatment using RPDs to replace missing natural teeth. The two treatment strategies were evaluated according to their impact on nutritional status measured using haematological biomarkers.

METHODS: A randomised controlled clinical trial (RCT) was conducted of partially dentate patients aged 65 years and older (Trial Registration no. ISRCTN26302774). Each patient provided haematological samples which were screened for biochemical markers of nutritional status. Each sample was tested in Cork University Hospital for serum Albumin, serum Cholesterol, Ferritin, Folate, Vitamin B12 and 25-hydroxycholecalciferol (Vitamin D).

RESULTS: A mixed model analysis of covariance (ANCOVA) indicated that for Vitamin B12 (p=0.9392), serum Folate (p=0.5827), Ferritin (p=0.6964), Albumin (p=0.8179), Serum Total Cholesterol (p=0.3670) and Vitamin D (p=0.7666) there were no statistically significant differences recorded between the two treatment groups. According to the mixed model analysis of covariance (ANCOVA) for Vitamin D there was a significant difference between levels recorded at post-operative time points after treatment intervention (p=0.0470). There was an increase of 7% in 25-hydroxycholecalciferol levels recorded at 6 months compared to baseline (p=0.0172). There was no further change in recorded levels at 12 months (p=0.6482) and these increases were similar within the two treatment groups (p>0.05).

CONCLUSIONS: The only measure which illustrated consistent significant improvements in nutritional status for either group were Vitamin D levels. However no significant difference was recorded between the two treatment groups.

CLINICAL SIGNIFICANCE: Functionally orientated prosthodontic rehabilitation for partially dentate older patients was no worse than conventional removable partial dentures in terms of impact on nutritional status.

Cost-effectiveness of tooth replacement strategies for partially dentate elderly: a randomized controlled clinical trial

OBJECTIVE: To conduct a cost-effectiveness analysis comparing two different tooth replacement strategies for partially dentate older patients, namely partial removable dental prostheses (RDP) and functionally orientated treatment based on the shortened dental arch concept (SDA).

METHODS: Ninety-two partially dentate older patients completed a randomized controlled clinical trial. Patients were randomly allocated to two treatment groups: the RDP group and the SDA group. Treatment effect was measured using impact on oral health-related quality of life (OHrQOL), and the costs involved in providing and maintaining care were recorded for all patients. Patients were followed for 12 months after treatment intervention. All treatment was provided by a single operator.

RESULTS: The total cost of achieving the minimally important clinical difference (MID) in OHrQOL for an average patient in the RDP group was €464.64. For the SDA group, the cost of achieving the MID for an average patient was €252.00. The cost-effectiveness ratio was therefore 1:1.84 in favour of SDA treatment.

CONCLUSION: With an increasingly ageing population, many patients will continue to benefit from removable prostheses to replace their missing natural teeth. From a purely economic standpoint, the results from this analysis suggest that the treatment of partially dentate older adults should be focused on functionally orientated treatment because it is simply more cost-effective.

Presentation of lacrimo-auriculodento- digital (LADD) syndrome in a young female patient

BACKGROUND: Lacrimo-auriculo-dento-digital (LADD) syndrome (OMIM #149730) is an autosomal-dominant congenital disorder that can be caused by heterozygous mutations in the tyrosine kinase domains of the genes encoding fibroblast growth factor receptors 2 (FGFR2) and 3 (FGFR3), and has been found in association with a mutation in the FGF10 gene, which encodes an Fgfr ligand. Clinical signs vary, but the condition is characterised by involvement of the lacrimal and salivary systems, cup-shaped ears, hearing loss and dental abnormalities. Additional features may include involvement of the hands and feet with other body systems particularly the kidneys.

CASE REPORT: Previous literature on the subject has been reviewed and this case is the first presentation of LADD syndrome in the Republic of Ireland, as a sporadic case in a 12-year-old girl who exhibited a range of dental and digital anomalies.

TREATMENT: Her general medical practitioner managed her medical care whilst her oral care necessitated a multidisciplinary approach involving restorative and orthodontic elements.

FOLLOW-UP: The initial restorative phase of treatment has successfully improved the appearance of the patient's anterior teeth using direct resin composite build-ups.

Caries incidence following tooth replacement for partially dentate elders

Objective: To compare caries incidence following two different tooth replacement strategies for partially dentate older patients; namely functionally orientated treatment according to the principles of the Shortened Dental Arch (SDA) and conventional treatment using Removable Partial Dentures (RPDs). Method:A randomised controlled clinical trial (RCT) was conducted of partially dentate patients aged 65 years and older. Patients were randomly allocated to two different treatment groups: the RPD group and the SDA group. Each member of the RPD group was restored to complete arches with cobalt-chromium RPDs used to replace missing teeth. Patients in the SDA group were restored to a shortened arch of 10 occluding pairs of natural and replacement teeth using adhesive bridgework. All of the operative treatment was completed by a single operator. Caries incidence was measured over a 2-year period following treatment intervention and recorded using the International Caries and Detection System (ICDAS). Result:In total, 89 patients completed the RCT (45 SDAs and 44 RPDs). Patients in the RPD group recorded a significantly higher incidence of new carious lesions (p<0.001) and recurrent carious lesions (p<0.001) compared to the SDA group. A mixed model of covariance (ANCOVA) revealed that treatment group (p<0.001) and co-morbidity (p<0.001) were significant predictors of caries incidence. Conclusion:Two years after provision of prosthodontic treatment there was a significantly higher incidence of new and recurrent caries lesions in subjects provided with RPDs compared with SDA treatment. This will have a significant impact on the ongoing maintenance costs for these two treatment groups.