Pairs Of Teeth Research Articles

A New Sinamiin Fish (Actinopterygii) from the Early Cretaceous of Thailand: Implications on the Evolutionary History of the Amiid Lineage

The Sinamiidae are a family of halecomorph fishes (Holostei) stratigraphically limited to the Lower Cretaceous and confined to East Asia. The first species of sinamiids were discovered in China, and then new occurrences were recorded in Thailand and Japan. The three recognized genera, Sinamia, Siamamia and Ikechaoamia, are notably characterized by an unpaired parietal. Here, we describe a new genus and species of sinamiid based on material from the Aptian Khok Kruat Formation of Ban Krok Duean Ha, Nakhon Ratchasima, Thailand. The new taxon known from preserved specimens in 3D is characterized by four pairs of extrascapular and tall cylindrical teeth with a conical enamel stalk topped by an arrowhead-shaped acrodine cap, among other characters. A phylogenetic analysis of the halecomorph fishes shows that the new taxon is the sister of the other Thai species, Siamamia naga, and that the two are grouped with two Chinese genera in a strongly supported clade, the Sinamiinae. This subfamily is here grouped with the Amiinae that contained the extant Amia. This new discovery is a clue that Southeast Asia may have been a center of diversification for this fish clade, and the phylogenetic analysis reveals that amiines may have originated somewhere in Asia during the Cretaceous before they spread throughout the northern hemisphere.

Lithocarpusdahuensis (Fagaceae), a new species from Fujian Province based on morphology and genomic data.

Lithocarpusdahuensis, a new Fagaceae species from Fujian Province, China, is described and illustrated. The new species is morphologically similar to L.konishii, but its oblanceolate leaf blade has more pairs of acute teeth on the margin, denser lateral veins, smaller cupules enclosing up to 1/4-1/3 of the nut, and its nut is only half as long as those of L.konishii. The plastome of L.dahuensis was 161,303 bp in length and displayed the typical quadripartite structure. Phylogenetic analyses distinguished L.dahuensis from L.konishii with strong support based on whole plastome and nrITS, respectively.

Using the Caries Assessment Spectrum and Treatment Index to Determine the Caries Incidence in Primary and Permanent Molars Among School Children of Kolkata: A Cross-Sectional Study.

Caries in their early stages cannot be properly classified using the decayed, missing, and filled teeth (DMFT) index because it does not record precavitated lesions. Thus, the caries assessment spectrum and treatment (CAST) index is a good alternative as it is equipped to record the whole range of dental illnesses and count restored teeth as healthy ones. The participants in this cross-sectional study included 300 children who were seven-to-eight years of age. We used the CAST index to assess the extent of caries in the deciduous and permanent molars of these children. For this, all the permanent and baby teeth, the primary and secondary permanent molars, as well as the first and second deciduous molars were examined to determine the prevalence of each carious stage. The correlation of the distribution of the CAST codes between the first and second molars, the second and first molars, the right and left sides of the dental bend, and the opposing jaws was analyzed using Spearman's rank correlation coefficient, while the cut-off for statistical significance was a p-value of 0.05. The quantitative analysis was conducted using IBM SPSS Experiences Version 20 for Windows. By comparing CAST codes in the right and left molars, we were able to observe how the development of caries in paired teeth might affect one another. The rank correlation value was found to be less than 0.5 only in the primary second molars (55/65 and 85/75), which were found exclusively in the deciduous first molars. Moreover, the r values for the neighboring deciduous and permanent molars were found to be below 0.3, i.e., 65/64 (0.497), 74/75 (0.327), and 84/85 (0.411), which indicated a weak connection between them. When comparing the teeth in different jaws, we found reasonable correlations (r = 0.33-0.49), with only 64/74 outliers (0.501). We found that, in the examined population, there was a well-established correlation between the stages of caries development in the deciduous molars on the left side of the mouth.

The prevalence of vestigial teeth in two beaked whale species from the North Atlantic

Abstract Beaked whales, Family Ziphiidae, occur in deep offshore and oceanic seas, where they are very difficult to study, so that much of our knowledge about them is derived from stranded animals. Most beaked whales (e.g., genera Mesoplodon and Ziphius) have only one pair of mandibular teeth. A reduced dentition is widely regarded as an adaptation to suction feeding, primarily on squid. However, vestigial maxillary and mandibular teeth have been recorded in some species. Here, we describe new records of vestigial teeth in 12 Sowerby’s beaked whales, Mesoplodon bidens, and one Cuvier’s beaked whale, Ziphius cavirostris, from a total 14 animals of these species, which stranded in 2019–2021 in Scotland. In nine M. bidens some tooth crowns were erupted and mild occlusal wear was visible, whereas pathological teeth were seen in ten individuals. The occurrence of vestigial teeth in Sowerby’s beaked whale appears to be significantly under-recorded, suggesting that vestigial teeth form as part of the normal development of the dentition. The reasons for the under-recording of the occurrence and the possible functionality of vestigial teeth in ziphiids are discussed.

Dynamic analysis of gear pairs with the effects of stick-slip

The instantaneous dynamic contact state analysis is carried out to reveal the process of scuffing failure of the gear tooth pair. A stick-slip dynamic model of a two-gear set is proposed and the coupling effects of time-varying mesh stiffness, tooth separations, friction between the gear teeth surfaces, and potential stick-slip are considered. Dynamic analysis shows that stick contact is an important source of tooth scuffing failure. Additionally, stick contact dramatically increases the vibration amplitudes and causes chaos. Parametric studies show that heavy load and rough tooth surfaces increase the probability of sticking and increase the time of stick state over a single mesh period. This study provides a design guard for avoiding scuffing failure and improving the reliability of gear transmission.

Association between the number of bilateral free-end posterior tooth loss and mastication performance in RSGM USU patients

Mastication is the process of mechanically crushing food to form soft particles, facilitating theingestion process in providing nutrients to the body. One of the objectively assessed mastication functions is mastication performance. The number of tooth losses is one factor that affects mastication performance; the more tooth loss, the lower the mastication performance. Posterior teeth play an important role in mastication function, and loss of posterior teeth decreases mastication performance. The research aims to determine the association between the number of bilateral free-end posterior tooth loss and mastication performance. This type of research is descriptive-analytic with a cross-sectional design. The subjects in this research were 17 people. Data were collected by examining the oral cavity and color-changeable chewing gum to assess mastication performance using a colorimeter. Data were analyzed using the Mann-Whitney test. The results showed that all subjects with bilateral free-end posterior teeth loss in one and both arches had poor mastication performance. The statistical test results showed no association between the number of bilateral free-end posterior teeth loss and mastication performance in one and both arches with p = 1,000 (p 0.05). It can occur because this research does not pay attention to the number of occlusion pairs of posterior teeth and the results of the assessment of mastication performance are not quantitative. The number of bilateral free-end posterior tooth loss can be considered in assessing mastication performance as an educational basis for denture care. KEYWORDS: Posterior Bilateral Free End, Mastication Performance

Whole Field Analysis of Asymmetric Helical Gear Using Photo Stress Method and FEA Method

Objectives: To carry out dynamic state analysis of asymmetrical helical gears for contact stresses using photo stress technique and suitable finite element software. Methods: Currently the Hertz contact stress equation is used to calculate the contact stress which is based on certain speculations. The value of load transmitted by a gear may be known but whether it is taken by a single or more pairs of teeth are based on some assumptions and stresses thus calculated may not be true stresses. To get precise evaluation of stress field in gear tooth it is decided to carry out experimental work on asymmetric helical gear in actual working condition. The photo stress method not only provide magnitude of stress but also gives idea about stress distribution in gear. Finite element method is used for asymmetrical helical gear to validate experimental results. Findings: The stress values obtained by photostress method and FEA method has minimum error of 2.17% and maximum of 8.89% respectively. The error values are less than 10% and within the limit. We can observe close agreement between these two methods. Novelty: This study has provided a more accurate result than theoretical method of stress calculation. Photostress analysis method is one of the best test methods for evaluation of contact stress of asymmetric helical gear with different torque condition in actual working that is dynamic condition. Maximum error of 8.89% has been found with photostress method. Keywords: Asymmetric Gears; Contact Stress; Experimental Method; Reflection Polariscope; PhotoStress; Finite Element Analysis

Contact analysis and strength calculations of involute spline couplings

A finite element method (FEM) is presented to conduct loaded tooth contact analysis and strength calculations of involute spline couplings. Special FEM software has been developed. Contact, bending and shear stresses of the spline couplings are analyzed by the developed software and they are compared with results obtained by an approximation method. It is found that “Edge loads” exist at tooth tip and root contacts and also exist at two sides of the face width when the pair of teeth has different face widths. Effects of tooth profile deviations and pitch errors on tooth contacts are also investigated by the developed software respectively. It is found that tooth contact and stresses are affected by the tooth profile deviations and pitch errors greatly. Finally, reliability of the presented method and software are discussed.

Validation of pairs of antagonist teeth for the evaluation of shortened dental arch in epidemiological studies.

The aim of this study was to evaluate the accuracy of pairs of antagonist teeth (epidemiological criterion) for defining pairs of teeth in occlusal contact (clinical criterion) and to estimate the agreement between the prevalence of "shortened dental arch" (SDA) and "functional dentition" (FD) when occlusal units (OUs) or posterior occluding pairs (POPs) are defined by the epidemiological or clinical criterion. Data were collected in an epidemiological oral health survey conducted in a municipality in Minas Gerais, Brazil. OUs and POPs were defined by the epidemiological criterion (dental crown status) or clinical criterion "gold standard" (carbon paper record of occlusal contacts during habitual maximum intercuspation). SDA corresponded to the presence of an intact anterior region and three to five OUs. FD was based on the concomitant presence of ≥ 1 tooth in each arch, 10 teeth in each arch, 12 anterior teeth, ≥ 3 premolar POPs, and ≥ 1 molar POP bilaterally. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of the epidemiological criterion were calculated. The study included 197 adults. Sensitivity, specificity, PPV, and NPV were 88.5, 87.9, 92.5, and 81.9%, respectively, and accuracy was 88.3%. The epidemiological criterion proved to be valid and could be used in epidemiological studies to calculate the prevalence of reduced dental configurations that consider POPs. The assessment of oral functionality is an aspect that should be included in the diagnosis of the clinical condition of patients, contributing to a more effective individual and collective oral health care plan.

Comparison of Effectiveness of Two Silver Compounds in Arresting Caries in Outreach Programs in Karnataka

Context: Silver compounds have been used clinically in dentistry and have effectively arrested dental caries. However, their potential use in community outreach programs has not been explored. Aims: This study aims to investigate the effectiveness of two silver compounds, silver diamine fluoride (SDF) and silver nitrate (SN), in arresting caries in deciduous teeth when used in outreach programs. Settings and Design: This is a randomized trial with a split mouth design done in three primary schools in Dharwad city. Subjects and Methods: This study was conducted among 174 teeth in 58 subjects between the ages of 4 years and 6 years. Pairs of carious teeth in each subject were randomized into two groups: Group A and Group B. Teeth in Group A were treated with 38% SDF and teeth in Group B were treated with 25% SN. These teeth were examined for the arrest of caries after treatment, at the end of 3 months and 6 months. Statistical Analysis: Descriptive statistics were used to analyze the demographic characteristics and percentages of arrested and active carious lesions. Chi-square test was done to compare the proportion of arrested teeth within and between the groups. Results: All the teeth showed arrest of caries immediately after treatment in both the groups which significantly reduced after 6 months. The result also showed that there was no significant difference in the reduction of arrested carious teeth between the two groups. Conclusions: Both SDF and SN can be used in outreach programs with comparable effectiveness in arresting dental caries.

Use of sun gear orbits to obtain the load sharing in planetary transmissions and its impact in the tooth load

The present work assesses the possibility of using the orbits described by the sun gear in order to analyse the load sharing ratio in planetary gear transmissions. Furthermore, the current work is extended to observe the impact of the floatability and different tangential pinhole position errors in the load borne in a single contact between a pair of teeth in comparison to the load per planet. Therefore, it highlights the inaccuracy of the load sharing ratio (LSR) as an indicator of the overload in one tooth of the planet. Moreover, the use of the orbits represented with respect to a rotating reference provides helpful information to determine the overloads and underloads in the planets due to the existence of a tangential error in sequentially phased transmissions. Therefore, this proposal provides a simpler solution to the measurement of the LSR in planetary transmissions with different numbers of planets than the use of strain gauges.

The Shortened Dental Arch Concept: Awareness, Knowledge, and Practice of Dentists in Dubai and the Northern Emirates, United Arab Emirates

This is a cross-sectional study utilizing an online questionnaire anonymously to investigate the awareness and views of dentists about SDA. The questionnaire was sent to all 901 dentists registered with the Emirates Medical Association (EMA). The questionnaire consists of 17 questions, which comprise demographics, awareness, and application in dental practice, preferred treatment modality, and risks and benefits associated with SDA. The data were analyzed using SPSS Statistics. The response rate reported was 40.3%. Two-thirds of the respondents (65.8%) were aware of the SDA concept; however, it was not usually applied in clinical practice (n = 196, 54.7%). Specialists were more aware of the concept (p ≤ 0.001) and applied it more frequently in their clinical practice (p=0.041) than general dental practitioners (GDPs). Respondents agreed that SDA was associated with the risks of teeth migration (n = 211, 59.9%), tooth wear (n = 196, 55.8%), and/or temporomandibular disorder (TMD) (n = 163, 45.3%). The implant was the treatment of choice for many of the participants (n = 169, 46.6%) to replace missing molars, followed by the acrylic removal partial denture (RPD) (n = 129, 35.5%). Most dentists who responded to this survey were aware of the SDA concept and had a positive attitude about it. However, they did not apply it frequently in their clinical practice.

Sex and age determination of human mandible using anthropological parameters and TCI and Kvaal methods: study of a Serbian medieval sample.

The aim of the study was to test the efficacy, reliability, and applicability of the Kvaal and Tooth Coronal Index (TCI) age determination techniques, and then to compare them with each other, as well as with the conventional anthropological age and sex determination techniques. The analyzed material originates from the medieval necropolis of the Vinča-Belo brdo site. During the research, 60 periapical (PA) and 30 orthopantomographic (OPT) images were analyzed. On each analyzed tooth, age assessment was performed using both TCI and Kvaal techniques. The obtained values of dental estimated age were compared with age estimated by anthropological analysis, and the deviations between the estimated and chronological age were analyzed in relation to the assessment technique, type of dental radiograph, tooth group, sex, and age. The mean error between TCI and the osteological method was 8.44 (SD = 7.56, Min = 0.169, Max = 36.4) and between Kvaal and the osteological method was 7.71 (SD = 5.57, Min = 0.133, Max = 26.7). The average value of age recorded by TCI method was 32.5years and by Kvaal method was 34.7years. There was no statistically significant difference based on the two radiographic methods, gender, individual teeth, or tooth group pairs. There was a statistically significant positive correlation between age and the error present. Gender determination based only on the mandible has a high correlation with the anthropological gender determination. The Kvaal method and the TCI method have proven their efficiency, reliability, and applicability. Significant correlation has been observed between dental and anthropological age and sex determination methods.

Comparison of conventional and split-cam strain wave gear through initial load and stress distribution

ABSTRACT This paper presents an analysis of stress developed in flex-gear (FG) cup with conventional strain wave generating (SWG) cam and split-cam SWG in strain wave gear/harmonic drive (HD), using initial load distribution by tooth pairs as a boundary condition in finite element method (FEM). The initial load distribution by tooth pairs is achieved with the assembly of ring gear (RG) and deformed FG before the application of any external load. A closed-form solution to the analytical method describes the exact initial load distribution by tooth pairs in the presence of secondary contacts. However, with spit-cam SWG the phenomenon of secondary contact is completely eradicated. Therefore, the load is distributed by contacting tooth pairs that lie only in the line of action and the tooth pair that lies along the major axis of split-cam SWG experiences maximum load compared to conventional SWG. The strain developed in FG cup based on the load distribution with both SWG cams obtained from FEM is verified with the experiment. The comparison shows a rise of 44 microns in circumferential strain around the major axis of deformed FG, when RG is assembled. This testifies the presence of initial load, which is distributed among all interfering tooth pairs before applying external load.

Faunal change over 3 decades to reveal Rotundocollarette capoori n.gen., n.sp., a unique anisakid from Johnius dussumieri from the Central west coast of India at Goa.

A unique anisakid roundworm, Rotundocollarette capoori n. gen., n.sp. infesting Johnius dussumieri from the Central West coast of India at Goa has been described. The worms are typically characterized by a cephalic collarette, a muscular collarette in post-caudal zone, intestinal caecum and a ventricular appendix. 3 pores, a part of cephalic infrastructure-a dorsal oral aperture, a dorso-laterally placed genital pore, and a sub-ventral excretory pore, at the junction of the bases of the 2 ventro-lateral lips, were typically unique as revealed by SEM studies. A pair of large squarish teeth flanked each of these three pores in the cephalic region, with 3-5 denticles in the median group, at the junction of the two arms of V-shaped structure, that joined 26-29 denticles on each arm of this V-shaped formation, running parallel and crossed past dentigerous ridges on each lip. In addition, a set of 49-50 medially organized denticles occupying the dorsal arm of V-shaped formation, in the medial space, were a conspicuous configuration, besides 70min triangular denticles at the junction of sub-ventral lips. A spined mucron at the tip of tail. The key provided by Moravec and Justine (Parasite 27:58, 2020. 10.1051/parasite/2020053) to segregate Porrocaecum-like nematode genera (Porrocaecum, Pseudoterranova, Pulchrascaris, Euterranova, and Neoterranova) has been revised to include the newly proposed genus, Rotundocollarette capoori n.gen., n.sp. The significance of the emerging nematode as an environmental bioindicator has been specified.

Occurrence of Ancylostoma Caninum from a Gray Fox Urocyon Cinereoargenteus in Southeastern Mexico.

SummaryThe hookworm Ancylostoma caninum is a common nematode of wild and domestic canids worldwide. In Mexico, there are few records of helminths in wild canids, especially in the southeastern region. The aim of the present study was to examine the helminths from a gray fox Urocyon cinereoargenteus in southeastern Mexico. A road-killed female gray fox found in Merida, Yucatan, Mexico, was examined for helminths. Only nematodes were found in the intestine of the gray fox and identified using morphological studies and molecular analysis of 28S rRNA gene fragments. The characteristics exhibited by the nematode specimens were in accordance with descriptions of A. caninum: e. g. oral opening with a pair of prominent chitinous plates bearing three pairs of ventral teeth, lateral rays with a common trunk, dorsal ray divided into two branches with each branch terminating in three digitations. BLAST analysis of the 28S sequence showed similarity and coverage values of 99.8 % and 100 %, respectively, with a sequence of A. caninum from the domestic dog Canis familiaris in Australia. The genetic distance between the Australian specimen and the Yucatan specimen of A. caninum was 0.1 %, that is, they were only different in a single nucleotide. The gray fox examined in this study was found close to a rural community where A. caninum has been recorded from domestic dogs, which could be the source of infection. Our study increases the distribution of this nematode parasitizing the gray fox in Mexico and provides the first nucleotide sequence of A. caninum from the gray fox.

Functional dentition and associated factors

Studying the different indicators of functional dentition classification can contribute to the understanding of the associated factors, and thus help in the definition of strategies associated with oral health care. This approach has been little explored in the literature, especially when considering the older age group. Aim: The aim of this study is to evaluate the factors associated with three distinct functional dentition classification. Methods: Crosssectional exploratory study using secondary data from the Frailty in Older Brazilians (FIBRA) Project of 876 older adults living in Campinas, Brazil. The indicators of dental function assessed was number of natural teeth present, occluding pairs of teeth and the Eichner index, which were verified by trained dentists, following the World Health Organization criteria for epidemiological studies in oral health. The explanatory variable assessed was the selfperception of oral health-related quality of life measured by the Geriatric Oral Health Assessment Index (GOHAI) and its dimensions. It was also collected sociodemographic information such as age, gender, race/ethnicity, schooling, family income, smoking behavior and frailty status. The association was verified through Poisson regressions for number of teeth and pairs of teeth in occlusion and multinomial regression for the Eichner index, adjusted by sociodemographic and health variables. Results: Lower prevalence of participants with less than 21 teeth who negatively perceived GOHAI´s pain and discomfort dimension and higher prevalence of having less teeth among the ones that negatively perceived GOHAI´s physical and functional dimensions. No association was found between the perception of quality of life and occlusion pairs of teeth and the Eichner Index. Conclusion: Two out of three indicators assessed were associated with quality of life. Therefore, it is important to select sensitive indicators to be able to identify and better comprehend this relationship.

A digital workflow for pair matching of maxillary anterior teeth using a 3D segmentation technique for esthetic implant restorations

We investigated a state-of-the-art algorithm for 3D reconstruction with a pair-matching technique, which enabled the fabrication of individualized implant restorations in the esthetic zone. This method compared 3D mirror images of crowns and emergence profiles between symmetric tooth pairs in the anterior maxilla using digital slicewise DICOM segmentation and the superimposition of STL data. With the outline extraction of each segment provided by 100 patients, the Hausdorff distance (HD) between two point sets was calculated to identify the similarity of the sets. By using HD thresholds as a pair matching criterion, the true positive rates of crowns were 100, 98, and 98%, while the false negative rates were 0, 2, and 2% for central incisors, lateral incisors, and canines, respectively, indicating high pair matching accuracy (> 99%) and sensitivity (> 98%). The true positive rates of emergence profiles were 99, 100, and 98%, while the false negative rates were 1, 0, and 2% for central incisors, lateral incisors, and canines, respectively, indicating high pair matching accuracy (> 99%) and sensitivity (> 98%). Therefore, digitally flipped contours of crown and emergence profiles can be successfully transferred for implant reconstruction in the maxillary anterior region to optimize esthetics and function.

A general mathematical modeling and finite element analysis of a strain wave gear possessing a double-circular-arc-with-a-common-tangent profile

In this study, the characteristics of a strain wave gear (SWG) with a double-circular-arc with a common tangent (DCACT) profile were simulated using two-dimensional (2D) and three-dimensional (3D) finite element analysis (FEA). First, theoretically generated tooth profiles for the flexible spline (FS) and circular spline (CS) of an SWG were developed according to the theory of gearing. An automated mesh-generating computer program was developed in Visual C++ to establish 2D and 3D finite element models of the SWG based on its derived geometry. An FEA was then performed to explore the meshing characteristics, including the stress distribution, torsional angle, torsional stiffness, and number of engaged teeth, of the SWG. Continuous meshing of multiple tooth pairs between the FS and CS from the 2D FEA verified the conjugation of tooth profiles. The coning effect on the FS during assembly of the SWG was also predicted and discussed from the 3D FEA results. The 3D FEA produced more accurate and practical results than the 2D FEA did. Additionally, 3D FEAs of a modified (with longitudinal crowning) and unmodified (without longitudinal crowning) FS were performed and compared. Finally, a 3D FEA of a modified FS was successfully conducted to predict cyclic contact stress, root stress, and transmission error.

Four new species and new records of Micropeneta Pic, 1921 (Coleoptera: Tenebrionidae: Gnathidiini) from the Oriental and Papuan Regions, including a checklist and an identification key.

The genus Micropeneta Pic, 1921 (Tenebrionidae: Gnathidiini) was known so far by seven species in the Oriental Region. Newly collected material is presented herein including four species new to science: M. alabaca sp. n., M. kinabaluca sp. n., both from Borneo, M. laotica sp. n. from Laos, and M. papuana sp. n. from West Papua. The material shows that the genus is also distributed in Indochina and on New Guinea. The species of Micropeneta are characterised by the male head with a pair of distinct glabrous cephalic horns or shorter processes; some species possess additionally the anterior margin of the male pronotum with a pair of teeth or flat swellings, or the anterior part of pronotum with a broad impression. A checklist for all species and an identification key (suitable for males only) is added.