A revision of the Dubois crocodylians, Gavialis bengawanicus and Crocodylus ossifragus, from the Pleistocene Homo erectus beds of Java

The paper presents an analytical investigation of the effect of the tooth wear on the dynamic transmission error of helical gear pairs with small number of pinion teeth. Firstly, the dynamic analysis is conducted to investigate only the effect of the time-varying mesh stiffness on the variation of dynamic transmission error along the line of action. Then, the tooth wear effect on the dynamics of helical gear with small number of pinion teeth is being researched. In the analysis, instantaneous dynamic contact analysis is used in wear depth calculations. A comparative study was performed to investigate the relation between total contact ratio, mesh stiffness and dynamic transmission error of helical gear pairs with small number of teeth.

ABSTRAC. The relationship between the numbers of premaxillary, maxillary and dentary teeth and head size is examined between the sexes in one species (Ctenotus essingtoni) and among single, unsexed adult specimens of 25 species of the Australian scincid lizard genus Ctenotus. The number of premaxillary teeth is constant in all cases except in males of C. essingtoni, where it increases slightly with size. The numbers of maxillary and dentary teeth increase with size in all cases. The slopes of the regressions of the number of maxillary teeth and the number of dentary teeth on size do not differ significantly between the sexes of C. essingtoni, but males have a higher intercept for maxillary teeth. The number of dentary teeth exceeds the number of maxillary teeth in all cases; within female C. essingtoni this difference increases with size. Comparisons are made with the limited data available from other lizard species. al of Herpetology, Vol. 25, No. 4, pp. 473-477, 199 right 19 1 Society for the Study of Amphibians and Reptiles

ObjectiveReconstruction plates are used to treat patients with a segmental mandibular defect after oral cancer surgery. Reconstruction plate failure analysis has rarely focused on occlusion, which conducts a mechanical force to the mandible and the plate. To determine the prognostic factors, we retrospectively evaluated patients who underwent reconstruction of a mandibular segmental defect with a reconstruction plate and assessed the number of residual paired teeth.Material and MethodsFrom among 390 patients with oral cancer who visited University of Tsukuba Hospital (Tsukuba, Japan) between 2007 and 2017, we selected and analyzed the data of 37 patients who underwent segmental resection of the mandible and reconstruction with reconstruction plates. Prognostic factors evaluated were patient age, sex, TNM classification, plate manufacturer, treatment with radiotherapy or chemotherapy, whether the patient had diabetes or smoked, and whether the patient had a small number of residual paired teeth, plate length, and use of a fibular‐free flap. Among these 37 patients, eight reconstruction plates had intraoral or extraoral exposure and were removed in 5 years.ResultsKaplan–Meier and log‐rank analyses revealed that the prognosis for the 5‐year plate exposure‐free rate was significantly poorer for patients with a small number of residual teeth than for patients with no teeth or those with a large number of residual teeth (.01). Univariate Cox regression analysis revealed that a small number of residual teeth was a significant prognostic factor in the loss of a reconstruction plate (hazard ratio: 5.63; 95% confidence interval [1.10, 25.85]; .04).ConclusionsA small number of residual teeth after the segmental resection of oral cancer is significantly involved in reconstruction plate survival and may be important in predicting reconstruction plate prognosis.

To produce evidence on an association between the number of teeth and selected cardiovascular risk factors among an elderly population. The study population comprised of 523 community-living elderly people who participated in the population-based Kuopio 75+ study. The data for each subject were collected using a structured clinical health examination, an interview and laboratory tests. Linear regression models were used to estimate adjusted mean values and confidence limits. Edentulous persons and persons with a small number of teeth had lower serum HDL cholesterol and higher triglyceride, leucocyte and blood glucose levels and a higher body mass index (BMI) compared with subjects to a large number of teeth. The study showed that, in the Finnish home-dwelling population aged 75 years or older, those with a large number of teeth were less likely to have cardiovascular risk factors such as a low serum HDL cholesterol level, a high triglyceride level and a high BMI than did subjects with a small number of teeth or who were edentulous.

Association of a lesser number of teeth with more risk of developing depressive symptoms among middle-aged and older adults in Japan: A 20-year population-based cohort study

A previously undescribed specimen reveals new information on the dentition of Sapeornis chaoyangensis

Maximum possible contact ratios which can be obtained by making use of x-zero gear pairs are determined for spur gear drives with small number of teeth. Rack cutter tip fillet radius and rack cutter geometry are taken into consideration in the analysis. Results for gear drives with various numbers of teeth and cut by rack cutters standardized by ISO and AGMA are given in forms of tables. Results are also compared with addendum modification coefficients recommended by ISO.

Tooth profile design for the manufacture of helical gear sets with small numbers of teeth

As the traditional calculation formula for contact strength of involute gear pair is not applicable for the calculation of those with small number of the teeth, some researches on the calculation of contact strength of involute gear pairs have been done. The calculation of the contact ratio of involute gear pair with a small number of teeth can confirm that its end face engagement must be of single-tooth mesh, while the research on the actual contacting lines in the meshing zone can find out the precalculated position, computational formula, and strength condition of the maximum contact stress according with the gear pairs with a small number of teeth.

Description of new Pliocene to Early Pleistocene deer (Cervidae, Mammalia) remains from the Siwalik Hills in Pakistan with a discussion on paleobiogeography of cervids from the Indian subcontinent

The mole snake (Pseudaspis cana) is capable of inflicting unusual bites in defence and during male combat that present as two parallel lacerations. We investigated the dental morphology of the mole snake by making SEM images, and by CT-scanning and digitally reconstructing the skulls of 14 specimens comprising both sexes. The lengths, volumes, shapes and positions of maxillary and dentary teeth were compared within individuals, between individuals, and between sexes. CT reconstructions show the occurrence of large, flat triangular teeth at the posterior end of the maxilla that are angled to point towards the posterior of the skull. SEM imagery highlights the presence of sharp ridges (carinae) on the posterior edges of the posterior dentary and maxillary teeth. Males have greater dental specialization, maxillary tooth variation, enlargement of the posterior-most maxillary teeth, and dentary teeth with posterior carinae. We hypothesize that mole snake dental specializations are adaptations for their particular form of male combat and possibly for subduing prey in the confines of underground burrows. Our findings reveal a complex dental morphology in mole snakes and provide impetus for further studies on the functional morphology of snake teeth.

Two new species of lotic-breeding salamanders, Hynobius sematonotos and H. oyamai, are described from Chugoku district and northeastern Kyushu district, respectively, western Japan. They are members of the so-called H. naevius group and are phylogenetically close to H. naevius, H. katoi, and H. hirosei but divergent from them with large genetic distances. These new species have been treated as Chugoku and northeastern Kyushu lineages, respectively, of H. naevius to which they are morphologically very similar. However, these new species can be differentiated from H. naevius by several morphological traits. Hynobius sematonotos is characterized and discriminated from other species by combination of small body size, a shallow vomerine teeth series with small number of vomerine teeth, small number of upper and lower jaw teeth, relatively long head and snout, and large upper eyelid, relatively short axilla-groin, reddish purple ground color with grayish brown marking on the dorsum, and reddish to bluish gray ventral ground color with relatively large markings varying from pale-white to white. Hynobius oyamai is characterized and discriminated from other species by large body size, moderately deep vomerine teeth series with a medium number of vomerine teeth, large number of upper and lower jaw teeth, relatively wide internarial and long fifth toe, bluish purple ground color sometimes with pale white marking on dorsum. Hynobius sematonotos occurs in Honshu, disjunct from H. naevius and H. oyamai that occur allopatrically in Kyushu.

The aim of this study was to investigate the predictors of dental changes associated with long-term treatment with oral appliances (OAs) in patients with obstructive sleep apnea (OSA). This was a retrospective study to investigate Japanese patients with OSA receiving long-term treatment with OAs. Comparisons of cephalometric analysis were carried out between the initial and follow-up assessments of dental and skeletal changes. Based on dental changes, predictors that may cause side effects were investigated. A total of 64 patients (average age at start of treatment: 57.7 ± 14.2 years, 44 males) were included in this study. The average duration of treatment was 4.3 ± 2.1 years. Over the total treatment period, there was a significant reduction in overjet (OJ) (1.5 ± 1.3 mm) and overbite (0.90 ± 1.5 mm), and an increase in the lower incisor line to the mandibular plane (3.1 ± 5.4°). A larger reduction in OJ of ≥ 1 mm was associated with treatment duration, use frequency, and mandibular advancement of the OAs. In addition to these predictive factors, the number of teeth was correlated with the amount of OJ reduction. For long-term treatment with OAs, the risk of dental side effects should be considered, such as a reduction in OJ. A small number of maxillary teeth, as well as the factors associated with OAs, including treatment duration, use frequency, and mandibular advancement of the OAs, was correlated with an increased rate of OJ reduction. A commentary on this article appears in this issue on page 7.

Scanning electron microscopy was used to examine the morphology of the tooth crowns, and light microscopy was used to quantify the numbers and sizes of the teeth occurring on each of the major tooth-bearing bones of the ground skink, Scincella lateralis. In S. lateralis, monostichous, bicuspid teeth occur on the premaxilla, maxilla, and dentary but not on the pterygoid. No ontogenetic or sexual variation was observed in crown morphology. The sizes and numbers of teeth vary with respect to location, with dentary teeth much larger and more numerous than the teeth on the maxillary arcade. Body size was more frequently, positively correlated with tooth sizes and numbers than head width. In S. lateralis, a sexual dimorphism in the number of premaxillary teeth is present, and ontogenetic differences in tooth number and size also occur. This study represents the first complete description of

AimUsing a dated phylogenetic hypothesis with nearly complete species‐level sampling ofFicussubsect.Urostigmawith several samples per species, spatio‐temporal diversification patterns are clarified, and alternative hypotheses for repeated Palaeotropical intercontinental disjunctions (PIDs) are revisited.Location(Sub)tropics of Africa, Madagascar, Asia and Australia.MethodsEstimates of divergence times were obtained using a Bayesian relaxed clock analysis via the programbeastwith three calibration points. The output was used to analyse the historical biogeographical patterns via the programrasp(S‐DIVAoption). The results were compared with existing geological knowledge.ResultsThe subsection probably originated in Madagascar or Madagascar and India, and dispersed once (or twice) to Africa and once to Asia (1stPID). From Asia the taxa dispersed all over Southeast Asia and finally to the west Pacific. Wallace's Line was relatively recently crossed several times independently by widespread species. One dispersal event back from Asia to Africa is inferred (2ndPID).Main conclusionsThe combination of dates and area optimizations for the ancestral nodes ofFicussubsect.Urostigmaagree with the tectonic history of the various areas and divergence dates published forFicus. The firstPIDis explained by species rafting on India to Asia, after which the majority of species evolved in Asia‐Australia. The secondPIDprobably involved dispersal from India via south Asia and Arabia to Africa in the early Miocene before the world‐wide climate cooled down and areas became drier. Dispersal over Wallace's Line is by widespread species from which only a few local endemics in east Malesia‐Australia developed. The biogeographical history ofF. subsect.Urostigmasupports a complex picture of several crossings ofPIDs and it confirms that the route between Asia and Africa via south Asia and Arabia is often favoured. This route was available during a long period from Oligocene to mid‐Miocene and perhaps even up to 2 Ma.