Profiling of a shaped worm cutter for shaping gears with non-involute tooth profile

Of the mechanical transmissions used in mechanical engineering, the most common are gears with an involute profile of the teeth flanks. Gears made up of such wheels have a number of advantages, but they also have a number of significant disadvantages. Therefore jne of the current trends is the study of gears with a complex non-involute profile of the teeth flank which have advantages over involute gears in a number of applications, as well as the development of tools for their processing. There are two ways of gear teeth cutting: the copying method and the rolling-in method. The rolling-in method has advantages. The profile of the tool working by the rolling-in method does not depend on the number of teeth of the gear being cut, therefore, the same tool can be used to cut gears with any number of teeth. The accuracy of a gear made by the rolling-in method is significantly higher than the accuracy of a gear made by the copying method. This is primarily due to the continuity of the rolling-in process. When cutting teeth by the rolling method, the tooth surface is formed as a result of processing with a tool, the cutting edges of which are the tooth profile of the mating rack or the tooth profile of the mating gear, and during processing the tool and the workpiece form a mating gear pair. The most common gear cutting tool is the hob cutter. For the machining of gear wheels with a non-involute tooth profile widely used in industry equipment is used. One of the options for a rolling gear cutting tool for shaping gear wheels with a non-involute tooth profile can be a shaped worm cutter. The article describes the method of profiling of the cutting part of shaped hob cutter for machining of gear wheels with normal accuracy. To solve the problem the unified mathematical base – the apparatus of multiparameter mappings of space – the unified structure of mappings for gears and a compact set of unified operators, parameters and functional connections is used.

Serum Alkaline Phosphatase and Calcium in Relation to Periodontal Status among Perimenopausal and Postmenopausal Women

Background: Menopause is a physiological phenomenon that occurs in aging women. Periodontal disease is associated with menopausal status. Alkaline phosphatase (ALP) plays a role in general and periodontal bone turnover. Calcium is essential for the maintenance of bone and teeth, and serum ALP and calcium are specific bone markers related to the acceleration of bone mass loss in elderly women and periodontitis. Objectives: The aim of this study was to correlate the levels of serum ALP and calcium with periodontal status in perimenopausal and postmenopausal women with periodontitis. Methods: A total of 22 perimenopausal and 49 postmenopausal women underwent a full periodontal examination assessing the pocket depth, number of teeth lost, clinical attachment loss, plaque index, calculus index, and papillary bleeding index. Using these measurements, the subjects were divided according to periodontal severity. Serum ALP and calcium were measured using the Enzyme-Linked Immunosorbent Assay (ELISA) method. A correlation between serum ALP and calcium to periodontal status was investigated. Results: Serum ALP was significantly correlated with the severity of periodontitis, clinical attachment loss, and the number of teeth lost among perimenopausal and postmenopausal women (p < 0.05). Serum calcium levels were not correlated with periodontal status. Conclusion: Postmenopausal women tended to have more periodontal breakdown, and the level of serum ALP was increased in severe periodontitis.

Designing an outer toothed gear whose wheel teeth are outlined by the logarithmic spiral arcs

Toothed gears are the most common mechanical gears in machine building, which are characterized by high reliability and durability, a constant transfer number, and which can transmit high torque. During toothed gear operation, the surfaces of the teeth slide, which gives rise to friction forces and wears their working surfaces. To prevent this, the surfaces of the teeth need constant lubrication. This paper considers the design of a gear tooth engagement, which does not have friction between the surfaces of the teeth since they roll over each other without slipping. The profile of the tooth of such a gear is outlined by congruent arcs, symmetrical relative to the line that connects the center of rotation of the toothed wheel with the top of the tooth. These symmetrical curves at the top of the tooth intersect at the predefined angle. In the depressions of the wheel, adjacent teeth also intersect at the same angle. Such a condition can be ensured by a curve that at all its points crosses the radius-vector emanating from the coordinate origin, also at a stable angle equal to half of the given one. This curve is a logarithmic spiral. If the number of teeth of the drive and driven wheels is the same, then their teeth are congruent. Otherwise, the profiles of the teeth would differ but they could be outlined by congruent arcs of the same logarithmic spiral of the same length taken from different areas of the curve. The minimum possible angle at the top of the teeth is straight. At acute angle, the toothed gear operation is impossible. To build gear wheels with a right angle at the top of the tooth, it would suffice to set the number of teeth of the drive and driven wheels. The center-to-center distance is calculated using the derived formula. The transfer number of such a gear is variable but, with an increase in the number of teeth, the range of its change decreases. The algorithm of wheel construction is given.

The impact of tooth loss on cognitive function

Objective To investigate if there is epidemiological evidence of an association between edentulism and cognitive decline beside that currently available from limited sample-sized case series and cross-sectional studies considering limited co-variables. Materials and methods Data from two USA national health surveys [NHIS 2014–2017 and NHANES 2005–2018] were analyzed using multinomial logistic regression to study the impact of type of edentulism and number of remaining teeth on memory and concentration problems. Age, gender, socioeconomic status, education level, cardiovascular health index, body mass index, exercise, alcohol, smoking habits, and anxiety and depression were used as covariates. Results The combined population sample was 102,291 individuals. Age, socioeconomic status, educational level, anxiety and depression levels, and edentulism showed the highest odds ratios for cognitive decline. Number of teeth present in the mouth was found to be a predictor of cognitive status. This association showed a gradient effect, so that the lower the number of teeth, the greater the risk of exhibiting cognitive decline. Conclusions Edentulism was found among the higher ORs for cognitive impairment. Clinical relevance Maintenance of functional teeth through the promotion of oral health may contribute to the preservation of memory/concentration and other essential cognitive functions. Thus, increasing and efficiently coordinating efforts aimed at preventing of tooth loss in the adult population could substantially contribute to reduce the incidence of cognitive impairment.

Justification of the rotary working bodies of the cultivator for processing between the rows of plantations of lavender oilseed on the basis of agricultural biomechanics

The article presents the methods and results of modeling in agricultural biomechanics, which made it possible to substantiate models of cultivator working bodies adapted to the soil environment based on rotary discs with teeth. The biological prototype of this design is the burrowing limb of a rhinoceros beetle. It is proposed to solve the problems of improving the shape of rotary discs with teeth on the basis of the use of a mechanical-bionic approach, which allows to analytically describe the dependencies for determining the minimum number of steps of cutting notches between the teeth and the number of teeth on the disc, as well as the rational value of their length. The use of a new type of working bodies - a toothed flat disc, designed in a bionic manner, will increase the efficiency of weed control during inter-row tillage, and also reduce traction resistance.

Genome-wide association study of periodontal pocketing in Finnish adults

Background A genome‐wide association study is an analytical approach that investigates whether genetic variants across the whole genome contribute to disease progression. The aim of this study was to investigate genome-wide associations of periodontal condition measured as deepened periodontal pockets (≥ 4 mm) in Finnish adults. Methods This study was based on the data of the national Health 2000 Survey (BRIF8901) in Finland and the Northern Finland Birth Cohort 1966 Study totalling 3,245 individuals. The genotype data were analyzed using the SNPTEST v.2.4.1. The number of teeth with deepened periodontal pockets (≥ 4 mm deep) was employed as a continuous response variable in additive regression analyses performed separately for the two studies and the results were combined in a meta-analysis applying a fixed effects model. Results Genome-wide significant associations with the number of teeth with ≥ 4 mm deep pockets were not found at the p-level of < 5 × 10−8, while in total 17 loci reached the p-level of 5 × 10−6. Of the top hits, SNP rs4444613 in chromosome 20 showed the strongest association (p = 1.35 × 10−7). Conclusion No statistically significant genome-wide associations with deepened periodontal pockets were found in this study.

Oral Status and Dementia Onset: Mediation of Nutritional and Social Factors

Some modifiable risk factors for dementia are closely related to oral health. Although eating and speaking abilities are fundamental oral functions, limited studies have focused on the effect of malnutrition and lack of social interaction between oral health and dementia. We investigated the mediating effects of nutritional and social factors on the association between the number of teeth and the incidence of dementia. This 6-y cohort study used data from the Japan Gerontological Evaluation Study targeting older adults aged 65 y and above. The number of teeth (exposure) and covariates in 2010 (baseline survey), mediators (weight loss, vegetable and fruit intake, homeboundness, social network) in 2013, and the onset of dementia (outcome) between 2013 and 2016 were obtained. The Karlson–Holm–Breen mediation method was applied. A total of 35,744 participants were included (54.0% women). The mean age at baseline was 73.1 ± 5.5 y for men and 73.2 ± 5.5 y for women. A total of 1,776 participants (5.0%) had dementia during the follow-up period. There was a significant total effect of the number of teeth on the onset of dementia (hazard ratio, 1.14; 95% CI, 1.01–1.28). Controlling for nutritional and social mediators, the effect of the number of teeth was reduced to 1.10 (95% CI, 0.98–1.25), leaving an indirect effect of 1.03 (95% CI, 1.02–1.04). In the sex-stratified analysis, the proportion mediated by weight loss was 6.35% for men and 4.07% for women. The proportions mediated by vegetable and fruit intake and homeboundness were 4.44% and 4.83% for men and 8.45% and 0.93% for women, respectively. Furthermore, the proportion mediated by social networks was 13.79% for men and 4.00% for women. Tooth loss was associated with the onset of dementia. Nutritional and social factors partially mediated this association.

Morphological reassessment of the movable calcar of delphacid planthoppers (Hemiptera: Fulgoromorpha: Delphacidae)

This study presents the morphology of calcar in adult Delphacidae based on representatives of the genera Ugyops Guérin-Meneville, 1834, Notuchus Fennah, 1969 (Ugyopini), Asiraca Latreille, 1798 (Asiracini), Kelisia Fieber, 1866, (Kelisini), Stenocranus Fieber, 1866 (Stenocranini), Chloriona Fieber, 1866, Megadelphax Wagner, 1963, Muellerianella Wagner, 1963, Javesella Fennah, 1963, Conomelus Fieber, 1866, Euconomelus Haupt, 1929, Hyledelphax Vilbaste, 1968, Stiroma Fieber, 1866, Struebingianella Wagner, 1963 and Xanthodelphax Wagner, 1963 (Delphacini). We used SEM electron microscopy, to define seven types of calcar structure (Types 1, 2, 5, 6, 7, 8, and 9) based on combinations of characters including shape, number of teeth and differentiation of sensory structures in species from fifteen genera. Additionally, two other types (Types 3 and 4) were determined based on the calcar descriptions from previous studies. Similarities and differences in calcar structure and function were discussed and emerging relationships between planthopper species and their particular habitats were indicated.

Severity of Dementia Is Associated with Increased Periodontal Inflamed Surface Area: Home Visit Survey of People with Cognitive Decline Living in the Community

No studies have measured the periodontal inflamed surface area in people with dementia, although periodontal disease is a major health issue in this group. This study aimed to determine the relationship between dementia severity and periodontal inflamed surface area. An interdisciplinary team, including a dentist and psychiatrist, conducted an in-home survey of older people living in the community. This cross-sectional study was designed as part of a larger cohort study. The interdisciplinary team visited 198 individuals with cognitive decline. We surveyed the clinical dementia rating, periodontal inflamed surface area, number of teeth, and other health issues. We used multiple linear regression analysis to assess the 75 people who were able to take part in all the visits. Number of teeth (Beta = 0.479, p < 0.001), clinical dementia rating (Beta = 0.258, p = 0.013), and age (Beta = 0.250, p = 0.017) were independently associated with periodontal inflamed surface area after adjusting for biological sex, depression, diabetes, collagen disease, visual disorder, and osteoporosis medication. To make communities more dementia-friendly, we must protect older people with dementia from developing poor oral health, which may require home visits for dental assessment.