Conical Teeth Research Articles

Using a planar rack cutter with variable modulus to generate a spherical gear pair

In this study, an imaginary planar rack cutter with variable modulus and discrete conical teeth was used to generate a spherical gear pair with double degree of freedom. First, a geometric method was used to design the mathematical model of the imaginary planar rack cutter with variable modulus and discrete conical teeth. Next, the relationship of coordinate systems between the generating and generated surfaces was established. Then, the family of the imaginary planar rack cutter surfaces was obtained by homogeneous coordinate transformation matrix. Further, two equations of meshing between the generating and generated surfaces were determined by the two-parameter envelope theory. The mathematical model of spherical gear pair with variable modulus and discrete ring-involute teeth can be created by using the two equations of meshing and the family of the imaginary planar rack cutter surfaces. The mathematical models of the spherical gear pair with double degree of freedom and tooth contact analysis method were used to investigate the assembly errors of the gear pair in four cases.

A new archosauriform reptile with distinctive teeth from the Middle Triassic (Ladinian) of Germany

ABSTRACT Skeletal remains of a small reptile with a distinctive dentition from the Lower Keuper (Erfurt Formation; Middle Triassic, Ladinian) of the Schumann quarry near Eschenau, in the municipality of Vellberg in Baden-Württemberg, Germany, represent a new taxon of non-archosaurian archosauriforms, Polymorphodon adorfi. It is diagnosed by various craniodental autapomorphies, including mesial and distal carinae of labiolingually flattened maxillary and dentary tooth crowns with large, somewhat hook-shaped denticles aligned at distinct angle to apicobasal axis of tooth crown; premaxilla with long, leaf-shaped posterodorsal process that is slightly longer than body of element; presence of prominent lateral fossa on premaxilla anteroventral to external narial fenestra; premaxilla with five gently recurved, conical teeth; medial surface of maxilla with distinct ledge above the interdental plates; and maxilla and dentary with distinctly heterodont dentition. Phylogenetic analysis recovered Polymorphodon adorfi in a position crownward of Erythrosuchus africanus but in an unresolved polytomy with derived non-archosaurian archosauriforms such as Proterochampsidae and Euparkeria capensis and with Archosauria. The maxillary and dentary teeth of Polymorphodon adorfi differ from those of other non-archosaurian archosauriforms and indicate a different, possibly omnivorous diet, suggesting that these reptiles were more diverse in terms of feeding habits than previously assumed.

Case of waardenburg syndrome type 1 in a family with dental abnormalities

Waardenburg syndrome type 1 (WS1; MIM #193500) is a rare autosomal-dominant auditory-pigmentary syndrome characterized by pigmentary abnormalities of the hair, skin, and eyes; congenital sensorineural hearing loss; and “dystopia canthorum.” The lateral displacement of the ocular inner canthi was caused by heterozygous mutation in the PAX3 gene on chromosome 2q36. This is the case report of a 7-year-old girl showing the characteristic features of WS1 with familial history. Four generations of the patient's family, comprising 32 members, were undertaken to determine the pattern of inheritance, expression of syndrome, and phenotypes. The clinical examination of the 32 family members (18 females, 14 males) showed that ten females (31.25%) and eight males (25%) were affected by WS1. The age of the patients ranged between 3 years and 76 years (mean 24.67 years). Out of 18 family members with WS1, ten members showed white forelock, six members showed dystopia canthorum, eight members had congenital sensorineural hearing loss, seven members had iris heterochromia, and three members had bilateral brilliant blue irises. Dental abnormalities were shown by nine family members including enamel hypoplasia, peg-shaped maxillary laterals, conical teeth, and class 3 malocclusion.

Finite Element Method for Prediction of Rock Breaking Performance of the Tipped Hob With Different Tooth Profiles

The raise boring machine, which plays a crucial role in wellbore construction, has been widely applied in subway tunnels and mine construction projects. High levels of quality and safety, make it recognized and promoted by an increasing number of users. The tipped hob as a rock-breaking cutter of the raise boring machine poses a direct influence on the efficiency of the well-bore construction. In this paper, the finite element software LS-DYNA is employed to establish the model of the crushed rock with the tipped hob, and the accuracy of the model is examined by experiments. On this basis, the variation laws and correlations of feed force, lateral force and positive force under different penetration depths are studied. The results show that as the penetration depth increases, the feed force, lateral force and positive force all grow exponentially. In the geological environment with high rock hardness, spherical tooth can effectively reduce cutter wear and conical tooth can achieve higher crushing ability. The research results provide a theoretical basis for the selection of a suitable tipped hob to improve rock breaking efficiency.

A helical gear with discrete ring-involute teeth

This study produces a skewed-imaginary planar rack cutter with discrete conical teeth that is used to create a helical gear with discrete ring-involute teeth. A mathematical equation for the skewed-imaginary rack cutter with discrete conical teeth is firstly solved. The coordinate system for the rack cutter and gear pair is then established and a family of the rack-cutter surfaces is obtained using homogeneous coordinate transformation. The relative velocity method is used to produce the equation for meshing between the rack cutter and the gear pair. Substituting the equation of meshing into the family of the rack-cutter surfaces gives the mathematical models for the gear pair with discrete ring-involute teeth. The transmission error for the gear pair is calculated using the assembly error and a tooth contact analysis. A computer-aided design software package is used to establish solid model for the gear pair. A software interference function is used to simulate the contact condition for the gear pair for various assembly errors. Finite element analysis software is then used to determine the contact stress for the gear pair. The transmission error and the contact stress for the gear pair are insensitive to any horizontal misalignment in the assembly errors.

Os odontoideum: diagnosis and role of imaging.

To elucidate the imaging manifestations of os odontoideum, establish the diagnosis and guide surgical therapy. Clinical and imaging data, including X-ray, CT and MR of 24 patients with os odontoideum, were retrieved and reviewed retrospectively. Os odontoideum with intact cortex was divided into round, conical and blunt tooth types. Four cases of orthotopic and 20 cases of dystopic os odontoideum were included. There was anterior displacement of the base of the dens in six cases, posterior displacement in nine cases and no displacement in nine cases. A widening of anterior atlanto-axial space was shown in 14 patients with varying degrees. Thickening of the soft tissue posterior to the dens was observed in 19 patients, spinal canal stenosis in 21 patients, cervical myelopathy in 10 patients and craniocervical junction malformation in 9 patients. Posterior C1-C2 pedicle screw fixation and fusion was performed in 12 patients and 4 patients underwent posterior occipito-cervical fixation and fusion. Radiographically, os odontoideum is defined as an independent ossicle of variable size with smooth circumferential cortical margins separated from the axis. Imaging can be used to assess atlanto-axial instability, associated normal or abnormal anatomical structures and guide surgical therapy.

Channa brunnea, a new species of snakehead (Teleostei: Channidae) from West Bengal, India

Channa brunnea, a new species of snakehead fish lacking pelvic fins, from West Bengal, India, is distinguished from its pelvic fin-less congeners by possessing an uniform dark brown body, ochre to bright-orange blotches on the caudal fin, fewer dorsal and anal-fin rays (35-37 vs. 47-51 and 24 vs. 28-32, respectively), fewer vertebrae (43 vs. 45-57), and fewer lateral-line scales (43-46 vs. 51-63). Though Channa brunnea superficially resembles C. bleheri, it can be distinguished from the latter by possessing dark-brown oblique markings on the upper half of the body; transverse scale rows (4½-5½ vs. 3½); pre-anal scales (22-26 vs. 17-20); 2 rows of teeth in the fifth ceratobranchial, the outer row with 16 large conical teeth (vs. 3 rows of teeth, the outer row with 13 large conical teeth); dentary with 20 large, stout, conical teeth in the inner row (vs. 32 medium-sized conical teeth); and a Kimura's two parameter (K2P) distance of 9.8-10.6%.

Development of the New Type Conical Teeth of PDC Drill Bit

The work elements of PDC drill bits are cylindrical polycrystalline diamond composite sheet and the cutting teeth of such shape can only cut the rock with the caster angle rake. In the process of drilling hard rocks, due to the large shear resistance and discontinuous cutting and rock breaking process, the rotation torque and torque ripple of drill bits are relatively large, resulting in low rock breaking efficiency and serious impact damage of composite sheet (Wilmot, 1998). In order to improve the ability of PDC drill bits to drill hard rock, a kind of cone PDC tooth is designed, which can plough and cut rocks with top rake, with low rock breaking resistance. It can reduce the rotation torque and torque ripple of drill bits, and improve the rock breaking efficiency and impact resistance of PDC drill bits.

Bryconops rheorubrum (Characiformes: Iguanodectidae), new species from the Rio Xingu Rapids, Brazil

A new species of Bryconops is described from the rio Xingu Basin, Brazil, that differs from all congeners by the following combination of characters: predorsal scales 8–9, perforated scales in the lateral line 43–45, and pigmentation pattern composed of wide silvery midlateral band on body, hyaline dorsal and anal fins (in alcohol), and dark blotch on distal half of dorsal caudal-fin lobe. The new species shares with members of the subgenus Bryconops maxillary relatively short, edentulous or with one conical tooth, and gill rakers without ossified denticles. The middle and lower Xingu support a remarkable diversity of Bryconops composed of at least nine species-level taxa; comments on their local distributions and habitats are provided, as well as a key to their identification.

Medium Sized Stocky Titanosaur from South Asia

Recently, four coexisted titanosaurs from latest Maastrichtian Vitakri Lameta Formation of Indo-Pakistan are recognized as Isisaurus and Pakisaurus of large-sized slender pakisaurids, Saraikimasoom and Gspsaurus of the smallest and medium sized transversely stocky gspsaurids. Gspsaurus pakistani based on associated skull (with conical teeth tapering gradually from base to tip), vertebral and appendicular elements found from Alam 19 locality of Vitakri area, Barkhan district, Balochistan, Pakistan, South Asia. Gspsaurus bears sufficient skeletal elements and can be used for evolutionary studies.

A new genus and species of clingfish from the Rangitāhua Kermadec Islands of New Zealand (Teleostei, Gobiesocidae).

Flexorincus, new genus and species, is described from 15 specimens (14.0–27.2 mm SL) collected from shallow (0–9 meters) intertidal and sub-tidal waters of the Rangitāhua Kermadec Islands, New Zealand. The new taxon is distinguished from all other members of the Gobiesocidae by a combination of characters, including a heterodont dentition comprising both conical and distinct incisiviform teeth that are laterally compressed with a strongly recurved cusp, an oval-shaped opening between premaxillae, a double adhesive disc with a well-developed articulation between basipterygia and ventral postcleithra, and many reductions in the cephalic lateral line canal system. The new taxon is tentatively placed within the subfamily Diplocrepinae but shares a number of characteristics of the oral jaws and the adhesive disc skeleton with certain members of the Aspasminae and Diademichthyinae.

Finite element analysis of conical teeth for hydraulic pipe tongs

During well operation, corrosive gas such as H2S in the well will cause serious corrosion damage to the column. In order to minimize the impact of corrosion, the oilfield gradually replaced the standard steel casing by a corrosion-resistant alloy (CRA) casing. Conventional tongs was widely used on casing for mark-up and break-out operation. But Zhou et al [1] thought that the tong teeth destroys the galvanized layer of CRA on the casing surface, where the corrosion easily happens. Therefore, a design scheme of the conical teeth for hydraulic pipe tongs was proposed, and the mechanical properties of the conical teeth were simulated by finite element software to analyze the degree of damage to the casing.

A new ichthyodectiform fish, Amakusaichthys goshouraensis gen. et sp. nov. from the Upper Cretaceous (Santonian) Himenoura Group in Goshoura, Amakusa, Kumamoto, Japan

ABSTRACTA new ichthyodectiform fish, Amakusaichthys goshouraensis gen. et sp. nov. is described based on several specimens from the Late Cretaceous (Santonian) Hinoshima Formation of the Himenoura Group at Goshoura, Amakusa, Kumamoto in Kyushu, Japan. Amakusaichthys is hypothesized to form a clade with the genus Heckelichthys from the North Atlantic and western Tethyan regions. This new species is highly distinct from other ichthyodectiforms in having the long snout and small mouth with fine conical teeth, which indicates this group had greater diversity than it had been thought.

Cetopsis varii, a new species of whale catfish (Siluriformes: Cetopsidae) from the Meta Basin, Colombia.

Cetopsis varii sp. nov. Cetopsidae (Cetopsinae) is described from the Río Meta basin in eastern Colombia, at middle portions of the Río Orinoco basin. The new species differs from congeners by a combination of features: the absence of a humeral spot, presence of eye, conical teeth on vomer and dentary and rounded posterior nares, along with details of body, dorsal and caudal-fin pigmentation. The osteology of the new species is investigated through high-resolution X-ray computed tomography and cleared and stained specimens. Data thus obtained are used to code the new species for character states utilized in a previous phylogenetic analysis of Cetopsidae. Analysis of the expanded matrix shows that C. varii is the sister group to C. orinoco.

New fossils of the giant pholidosaurid genus Sarcosuchus from the Early Cretaceous of Tunisia

The Lower Cretaceous vertebrate assemblages from southeastern Tunisia contain one of the most diverse, unique and significant vertebrate faunas of this period in North Africa. The fossil record of crocodyliforms from these assemblages is becoming better understood with the increasing number of palaeontological discoveries that have been made over the past few years. However, very little data is available on the North Gondwanan pholidosaurid crocodyliform Sarcosuchus due to the paucity of material likely because of selective taphonomic factors. Here, I describe and figure new fossils of the pholidosaurid genus Sarcosuchus from Aptian-Albian deposits of the Tataouine Basin in southeastern Tunisia. These fossils include well-preserved dorsal osteoderms, which were found in anatomical connection, several isolated teeth and fragmentary remains mostly pertaining to the appendicular and axial skeletons. Anatomical studies and comparisons with other specimens have been performed, supporting the attribution of the material to the genus Sarcosuchus. I show that no attempt at a specific level can be made on the basis of the present fossils. The large size of the osteoderms and the stout conical teeth indicate that many Sarcosuchus individuals reached enormous body sizes.Sarcosuchus would have prospered in a flood dominated river-delta system that characterized the Tethyan margin of Gondwana by the end of the Lower Cretaceous. The abundant remains of diverse fish taxa including actinopterygians, sarcopterygians and chondrichthyans are indicative of a productive ecosystem, and further suggest that the diet of the Tunisian taxon included large bodied fish. This discovery provides a substantial addition to the extremely poor record of the North African crocodylomorphs with new insights into their palaeobiogeographic distribution, palaeoecology and extinction.

Oligodontia Management in Patients with Ectodermal Dysplasia Syndrome

Background and aim: A relatively common sex- linked dermatitis characterized by a congenital dysplasia of one or more ectodermal structures is Ectodermal dysplasia (ED). Common signs include fragile skin and nails, defective teeth and salivary glands, frontal bossing with prominent supra orbital ridges, nasal bridge depression and protuberant lips. There are often a few conical teeth existing (hypodontia or Oligodontia) that results in generalized spacing. Deciduous and/or the permanent dentition may fail to form (anodontia), and, consequently, hypoplasia of jaws may happen in both cases. This article reports a case of ED and shows how to handle it. Case report: A 5 years old girl with HED visited SBMU, school of dentistry. Clinical examination showed hypotrichosis following the missing of eyelashes and eyebrows, dry skin, saddle nose and pigmentation on the legs which are characteristics of ED. Partial denture for lower jaw and composite restoration for upper jaw was used as the treatment plan. Conclusion: Preventive treatments are very crucial to save present teeth in ED patients. One treatment option is to use removable dentures as a cost-benefit and desired intermediate treatment to restore both function and esthetics and improve patient’s psychological status in Oligodontia cases.

A novel homozygous mutation in PVRL4 causes ectodermal dysplasia‐syndactyly syndrome 1

Ectodermal dysplasias (EDs) are a group of hereditary disorders defined by alterations in two or more ectodermal structures. One recently described rare entity is the autosomal recessive inherited ectodermal dysplasia-syndactyly syndrome 1 (EDSS1). Homozygous and compound heterozygous missense and nonsense mutations in the poliovirus receptor related-4 (PVRL4) gene, encoding cell adhesion molecule nectin-4, have been identified as causal for EDSS1. We here report a consanguineous family with a 2-year-old girl featuring EDSS1, including slowly progressive alopecia on the head, pili torti-like twisted hairs in trichoscopy, widely spaced, peg-shaped and conical teeth, proximal syndactyly with fusion of the 2nd to 4th toes, and generalized dry skin. There was no palmoplantar hyperkeratosis and sweating appeared normal to slightly enhanced, especially on the head. Using exome sequencing, we identified the novel homozygous nonsense mutation c.229C>T (p.Gln77Ter) in PVRL4.

Orthodontic Management Of An Erupted Mesiodens: A Case Report

Introduction: Hyperdontia is the condition of having supernumerary tooth, or teeth, which appear in addition to the regular number of teeth. It is a developmental anomaly and has been argued to arise from multiple aetiologies. It may remain embedded in the alveolar bone or can erupt into the oral cavity. Mesiodens is a supernumerary tooth located in the anterior maxilla, placed palatally or in between the maxillary central incisors. It may be single or paired, erupted or impacted and at times even inverted. Aesthetic or functional problems are two main issues associated with mesiodens.This case report demonstrates the orthodontic management of a case of a nonsyndromic male patient with conical type supernumerary tooth at the maxillary anterior region with a Class I malocclusion complicated by palatally erupted upper right lateral tooth with Bolton discrepancy. Good aesthetic and functional result achieved at the end of treatment.

A new Cretaceous dercetid fish (Neoteleostei: Aulopiformes) from the Turonian of Colombia

The extinct neoteleost family Dercetidae includes elongate, long-jawed marine fishes that are known from the Late Cretaceous to Paleocene in deposits from the Levant, Europe, North Africa, England, Mexico and Brazil. The fossil record of the family in South America is very sparse and previously was restricted to outcrops in Brazil. Herein we describe a new dercetid fish from the Turonian of Colombia, †Candelarhynchus padillai gen. et sp. nov. A single articulated specimen is preserved in part and counterpart; the posterior part of the fish is missing. The specimen differs from other dercetid species by the following unique combination of morphological features: lack of scutes on the flanks of the body, presence of a single pair of transverse processes associated with the abdominal vertebrae, roofed posttemporal fossa, single row of small conical teeth on the dentary and maxilla, toothless premaxilla ornamented with pronounced longitudinal striations and protruding forward far beyond the anterior end of the dentary, and relatively large pectoral fins positioned high on the body. When included in a phylogenetic analysis of †Enchodontoidei, †C. padillai gen. et sp. nov. falls within a monophyletic family Dercetidae and is placed as sister taxon to the Late Cretaceous dercetid †Hastichthys from Israel, indicating faunal connections between the Eastern and Western Tethys. The new taxon provides novel insights into the distribution of dercetid fishes in the Western Tethys region during the early Late Cretaceous.http://zoobank.org/urn:lsid:zoobank.org:pub:29F97139-98BD-48E5-AAC0-091980F866E2

Taxonomic Revision of the GenusAphyodite, with Description of Two New Species (Teleostei: Characidae)

The genus Aphyodite has a complex taxonomic history. It was described as monotypic, and the only diagnosis provided was “an Aphyocharax with a scaled caudal fin”. After the description, the genus was revised twice, but some morphological inconsistences remained, pending a proper morphological analysis. Currently, Aphyodite is a member of Aphyoditeinae and can be distinguished from all the other representatives of this subfamily by having the first infraorbital with a conspicuous sensory canal not reaching the anterior edge of the bone. During the revision of the genus, two new species were found: Aphyodite apiaka, new species, from the Rio Madeira basin, that can be diagnosed from its congeners by the length of the first infraorbital sensorial canal, which is longer than half length of bone; and Aphyodite tupebas, new species, from the Rio Solimões basin, that can be diagnosed from its congeners by the possession of only conical teeth in the premaxilla.