The combined effects of salivas and occlusal indicators on occlusal contact forces

Background Some occlusal detection products are designed for use on dry teeth, but this is not always achieved. Others are suited for dry and wet applications. Objective The objective of this study is to assess the combined effects, on occlusal contact forces, of two previously studied affecting variables—occlusal detection products and saliva. Methods We used a full‐arch dentiform with three occlusal detection products (an articulating film, an articulation paper and T‐Scan) in combination with human (HS) and an artificial saliva. The maxillary arch assembly, weighing ~54 N (the maximum bite force), was lowered onto (occlusion) and lifted off (disclusion) of the mandibular arch through 10 cycles by a mechanical testing machine. The forces and moments acting on the mandibular arch were continuously recorded by a load cell that supported it. Results The maximum values of Flateral (the in‐occlusal plane component of the occlusal contact force) were analysed by occlusion/disclusion separately using one‐way ANOVA, with factor for group type to identify the significant effect of salivas on products, effect of products, effect of salivas with products, effect of human saliva. A difference in occlusion and/or in disclusion was considered different. Statistical differences (P < 0.0001) in Flateral were found in: dry product vs product + HS, dry product vs product + artificial saliva (with articulating film and T‐Scan) and HS vs product + HS (with articulation paper and T‐Scan). Conclusion All products were affected by the salivas, except articulation paper by artificial saliva

Periodic forcing in viscous fingering of a nematic liquid crystal

We study viscous fingering of an air-nematic interface in a radial Hele-Shaw cell when periodically switching on and off an electric field, which reorients the nematic and thus changes its viscosity, as well as the surface tension and its anisotropy (mainly enforced by a single groove in the cell). We observe undulations at the sides of the fingers which correlate with the switching frequency and with tip oscillations which give maximal velocity to smallest curvatures. These lateral undulations appear to be decoupled from spontaneous (noise-induced) side branching. We conclude that the lateral undulations are generated by successive relaxations between two limiting finger widths. The change between these two selected pattern scales is mainly due to the change in the anisotropy. This scenario is confirmed by numerical simulations in the channel geometry, using a phase-field model for anisotropic viscous fingering.Comment: completely rewritten version, more clear exposition of results (14 pages in Revtex + 7 eps figures

The roles of wedging and friction in the mechanics of dental occlusal contacts

Objective: The primary aim of this project is to elucidate the basic mechanical engineering principles that govern and explain unexpected and counter-intuitive occlusal contact force measurements. Methods: Forces were measured on matched pairs of first molar denture, ceramic and stainless steel crowns during occlusion and disclusion, with human saliva and dry (control). The weighted maxillary assembly, guided by a precision slide, was lowered onto, and raised from, the mandibular crown. The forces experienced by the mandibular tooth were continuously measured by the load cell that supported it. Statistical analyses included LOESS smoothing splines and generalized additive models. Principles of basic statics and classic friction were applied to explain and validate the results. Results: It was determined that within the span of a single chomp, the in-occlusal plane force component (Flateral) on the tooth is highly variable in direction and/or magnitude. The most salient observations were that Flateral was higher in disclusion than in occlusion, and the largest Flateral did not necessarily occur when the bite force was maximum. Furthermore, saliva significantly affected the results. Conclusions: The results demonstrated that contacting teeth experience complex transient mechanical environments that can be readily explained with elementary engineering principles involving wedging and friction at the occlusal contacts

Systematic review of psychological approaches to the management of neuropsychiatric symptoms of dementia

Objective: The authors systematically reviewed the literature on psychological approaches to treating the neuropsychiatric symptoms of dementia.Method: Reports of studies that examined effects of any therapy derived from a psychological approach that satisfied prespecified criteria were reviewed. Data were extracted, the quality of each study was rated, and an overall rating was given to each study by using the Oxford Centre for Evidence-Based Medicine criteria.Results: A total of 1,632 studies were identified, and 162 satisfied the inclusion criteria for the review. Specific types of psychoeducation for caregivers about managing neuropsychiatric symptoms were effective treatments whose benefits lasted for months, but other caregiver interventions were not. Behavioral management techniques that are centered on individual patients' behavior or on caregiver behavior had similar benefits, as did cognitive stimulation. Music therapy and Snoezelen, and possibly sensory stimulation, were useful during the treatment session but had no longer-term effects; interventions that changed the visual environment looked promising, but more research is needed.Conclusions: Only behavior management therapies, specific types of caregiver and residential care staff education, and possibly cognitive stimulation appear to have lasting effectiveness for the management of dementia-associated neuropsychiatric symptoms. Lack of evidence regarding other therapies is not evidence of lack of efficacy. Conclusions are limited because of the paucity of high-quality research ( only nine level-1 studies were identified). More high-quality investigation is needed

On the Construction and the Structure of Off-Shell Supermultiplet Quotients

Recent efforts to classify representations of supersymmetry with no central charge have focused on supermultiplets that are aptly depicted by Adinkras, wherein every supersymmetry generator transforms each component field into precisely one other component field or its derivative. Herein, we study gauge-quotients of direct sums of Adinkras by a supersymmetric image of another Adinkra and thus solve a puzzle from Ref.[2]: The so-defined supermultiplets do not produce Adinkras but more general types of supermultiplets, each depicted as a connected network of Adinkras. Iterating this gauge-quotient construction then yields an indefinite sequence of ever larger supermultiplets, reminiscent of Weyl's construction that is known to produce all finite-dimensional unitary representations in Lie algebras.Comment: 20 pages, revised to clarify the problem addressed and solve

The effects of salivas on occlusal forces

Contacting surfaces of opposing teeth produce friction that, when altered, changes the contact force direction and/or magnitude. As friction can be influenced by several factors, including lubrication and the contacting materials, the aim of this study was to measure the occlusal load alterations experienced by teeth with the introduction of different salivas and dental restorative materials. Pairs of molar teeth were set into occlusion with a weighted maxillary tooth mounted onto a vertical sliding assembly and the mandibular tooth supported by a load cell. The load components on the mandibular tooth were measured with three opposing pairs of dental restorative materials (plastic denture, all-ceramic and stainless steel), four (human and three artificial) salivas and 16 occlusal configurations. All lateral force component measurements were significantly different (P < 0·0001) from the dry (control) surface regardless of the crown material or occlusal configuration, while the effects of the artificial salivas compared to each other and to human saliva depended on the crown material