Double Tooth Research Articles

MANAGEMENT OF FUSED PRIMARY TEETH IN ESTHETIC ZONE A CASE REPORT

Tooth fusion arises through union of two normally separated tooth germs. Depending upon the stage of development of the teeth at the time of union, it may be either complete or incomplete and is more often seen in deciduous dentition. This article discusses esthetic oriented endodontic management of fused maxillary anterior in a 4-year-old child.

Tooth Profile Construction and Experimental Verification of Non-Circular Gear Based on Double Arc Active Design

The double arc pitch curve is a novel way for creating a non-circular gear tooth profile. Aiming at the problems of the rounding of non-integer teeth and the nonlinear equation system in the construction of double circular arc tooth profile, an active design method based on planetary gear transmission kinematics and gear-meshing theory is proposed. By studying the double arc pitch curve of the three engagement positions, combined with the uniform theory of the relative curvature of surfaces, the distribution characteristics of the solution of the nonlinear equation system are analyzed in depth, leading to the optimal solution of the characteristic parameter values of the pitch curve. Combined with UG modeling and ADAMS motion simulation, the gear engagement force and the angular velocity of the planetary gear around the center are compared and analyzed in the case of integer tooth ratio and non-integer tooth profile. The results show that the engagement force of the gear pair constructed by integer teeth is reduced by about 17%. The optimal combination of the numbers of teeth is determined by orthogonal experiments, on which trial production and hydraulic load tests are based. The results reveal that the torque of the product at a rated speed is about 2.6% higher than that of foreign prototypes, which verifies the effectiveness of the design method proposed in this paper.

Gemination of an Erupted Mandibular Third Molar: A Short Presentation of an Exceptionally Rare Clinical Occurrence.

Double teeth, like fusions and geminations, are rare disorders of tooth development. In this short case presentation, we describe the unique appearance of a fully erupted mandibular wisdom tooth in a 72-year-old patient whose tooth exhibited gemination. This was possible because tooth 46 had to be removed from the patient at the age of 20 and the missing molar was not replaced. This geminated tooth of 48 had been in function for almost 50 years and finally had to be removed due to a periodontal inflammation. To the best of our knowledge, this is the first case presented of this dental anomaly for a fully erupted lower wisdom tooth.

Using multi-flexible body dynamic analysis and the Taguchi method to decrease the variation of output angular velocity in a double circular-arc harmonic gear drive

The performance of a double circular-arc tooth harmonic gear drive, which offers advantages over traditional designs, such as lower stress during contact and increased fatigue life, was investigated in this research. The gear drive’s meshing was simulated using dynamic analysis software RecurDyn, and a significant variation in output angular velocity was observed. To address this issue, experiments were planned using the Taguchi method with the L9(34) orthogonal table. The data was analyzed using techniques such as average value calculation, signal-to-noise ratio calculation, variance analysis, and response chart analysis to identify the control factors with the greatest impact on output angular velocity variation. It was found that an improved design with lower output angular velocity variation could be obtained by adjusting these control factors to optimal levels. The findings suggest that the transmission quality of double circular-arc harmonic gear drives can be enhanced by combining multi-flexible body dynamic analysis with the Taguchi method.

Multiple Accessory Cusps Expression at Mandibular Third Molar: A Unique Variation of Dental Crown Morphology - A Case Report

Accessory cusps are occasional variations in tooth morphology that can be detected clinically. Third molars have a wide range of eruption patterns and shapes but are commonly impacted. Unlike root morphology, variations in the crown morphology of the third molar have rarely been reported. Variations in crown morphology are important because they can affect clinical outcomes. Here, we present a rare case of fully erupted mandibular third molar (MTM) with multiple accessory cusps. This case report describes a case of a 31-year-old female Kenyah with a unique crown morphology of her fully erupted, vital, and functional mandibular third molar (MTM) which has multiple accessory cusps seen on the buccal surface, giving the appearance of a double tooth. Her MTM presented with an incipient caries lesion, which was managed conservatively. Documenting variations in tooth morphology is crucial for individual identification. While most people opt to have their MTMs extracted, early management of well-erupted and functional teeth should be undertaken to prevent disease progression.

Failure analysis of composite pre-tightened teeth joints under bending and tension coupling load

With the application of composite pre-tightened tooth joint in engineering practice, relevant studies have found that in actual structures, the joints are subjected not only to axial tension but also to bending and tension coupling force. Therefore, to analyse the load mechanism and progressive failure process of the joint under bending-tension coupling, a experiment loading method for joint structure was first designed in this paper, and axial-tension and bending-tension coupling experiments of single and double teeth were carried out by this method. Then, a three-dimensional model of progressive failure based on the USDFLD subroutine and Tsai-Wu failure criterion is established based on the experiment condition, and finally, the progressive failure process of the joint in the case of bending-tension coupling is analysed by verifying the correctness of the finite element simulation. The study revealed that the top surface of the composite tooth is subjected to the combined effects of tension stress from the bending moment and tension stress from the axial force at the same time, so the joint damage starts at the top surface and the stress state at the top surface of the composite tooth needs to be considered.

Camouflage Correction of Skeletal Class III Severe Open Bite with Tooth Ankylosis Treated by Temporary Anchorage Devices: A Case Report

Tooth ankylosis is a disorder characterized by the fusion of tooth and alveolar bone. This case report describes the treatment of a severe open bite due to tooth ankylosis. A 14-year-old female patient with a chief complaint of masticatory dysfunction was diagnosed with skeletal Class III severe anterior open bite and tooth ankylosis. She visited our university hospital with a chief complaint of an anterior open bite. After the surgical luxation of the ankylosed maxillary right central incisor, the tooth was orthodontically retracted using a nickel-titanium wire. The right mandibular lateral incisor and canine were luxated and retracted using intermaxillary elastics from a temporary anchorage device (TAD), which was inserted in the opposite jaw. During the treatment, skeletal Class III malocclusion deteriorated due to anterior growth of the mandible. Therefore, TADs were inserted into the retromolar pad on both sides of the mandible and retracted into the mandibular dental arch. Although the mandibular right canine was luxated several times, it could not be brought to the occlusal line, and was thus extracted; the extraction space was replaced with a prosthesis. Consequently, a normal overjet and overbite with a straight profile were achieved. Extrusion of ankylosed teeth by intermaxillary elastics from a TAD is a valid treatment option for patients with severe open bites.

Contact stress analysis of external non-variable multi-modulus spur gear pairs

The conditions of correct gear engagement of a pair of involute gears and the principle of geometric relationship of involute tooth profile are derived to determine the pitch point of externally meshing non-variable multi-modulus spur gear pairs into the double tooth engagement region. The Hertzian contact stress model is used as the basis to derive the contact stress calculation equations for pitch point and other characteristic contact points, and the variation of the contact stress distribution on the contact line with the module ratio is analyzed. The results demonstrate that when the number of teeth of the gear pairs is determined, the larger the value of the module difference, the easier it is for the pitch point of the gear pairs to be in the double tooth meshing zone. Except for the double tooth meshing out point, the contact stress decreases with the increase of module ratio, and the maximum point of contact stress is at the upper boundary point of the single tooth meshing zone.

Considerations of the classification and treatment for fused teeth

Fused teeth were a phenomena of teeth anomalies in shape, which can affect the dental teeth both in primary and permanent dentition. Fused teeth do not only cause problems on crowding of dentition, abnormal occlusion and aesthetic, but also increase risks of dental caries, endodontics diseases, periapical diseases and periodontal diseases. Fusion of deciduous teeth may lead to abnormality of subsequent permanent teeth. Treatment of fused teeth may require multidisciplinary approach in endodontics, periodontics, oral and maxillofacial surgery, prosthodontics and orthodontics. The aim of the present article is to review the etiology, classification, clinical manifestations and treatment of fused teeth in order to provide dental clinicians with a reference of clinical management for fused teeth.

Coexistence of Fusion and Birooted Primary Canine in a Child

Bilateral birooted primary canine presentation is an exceptionally rare dental oddity, and its occurrence with primary double teeth is even rarer. In Indian literature, fused primary anteriors are the most common dental morphological anomalies, whereas only one case of bilateral birooted primary canines has been published. This article describes the case of a 3-year-old male with a chief complaint of pain and intraoral swelling associated with fused primary anterior teeth, wherein supernumerary roots in primary canines found bilaterally were an incidental radiographic finding. This case thus emphasizes the importance of a thorough and comprehensive intraoral and radiographic examination using numerous angulations for facilitating early diagnosis, favorable treatment outcome, and reduced need for complex orthodontic interceptions for similar dental anomalies.

Purification performance of modified polyacrylonitrile fiber-activated carbon fiber filter for heavy metal ions.

A heavy metal ion adsorbent (HFPANF) with high surface area was obtained from polyacrylonitrile fibers with fibrillation and alkali hydrolysis, and an activated carbon fiber filter was prepared by using HFPANF as the binder. The surface area of polyacrylonitrile was 48.64 m2/g due to fibrillation, which also led to the carboxyl content of the HFPANF up to 3.4mmol/g. Batch adsorption experiments on Cu2+ and Pb2+ showed that the adsorption capacities of HFPANF for Cu2+ and Pb2+ were 47.5mg/g and 54.3mg/g. The adsorption kinetics showed that the adsorption reached equilibrium at 90min and that the adsorption followed the pseudo-second order model. It indicates that the adsorption process is chemisorption. HFPANF formed a single tooth chelate with Cu and a double tooth chelate with Pb. HFPANF-ACF filter was prepared by wet molding technique. When the HFPANF content was 30%, the filter reached a compressive strength of 15.37MPa and its maximum flux was 180 L/h. 2.5mg/L of Cu and Pb were used for dynamic adsorption experiments and the heavy metal removal rate was still above 95% after filtering 600 L. The pressure drop of HFPANF-ACF filter was much smaller compared with that of GAC filter due to the combined effect of fibrillated nanofibers and ACF, which can improve the filtration efficiency of the filter.

The Palaeozoic genus Psephodus (Chondrichthyes, Cochliodontiformes) and the transition from teeth to tooth plates in holocephalians

Remains of the chondrichthyan Psephodus Morris and Roberts, 1862 consist mainly of isolated tooth plates. The genus has a range from the Late Devonian (Famennian) to the Late Mississippian (Serpukhovian). The most complete specimen is a partially articulated set of teeth and tooth plates of the type species, P. magnus , from the early Serpukhovian of East Kilbride, Lanarkshire, Scotland. A row of minute nodes is present along the basal margins of the Lophodus -like and Helodus -like teeth of the East Kilbride specimen. This distinguishes these teeth from typical Lophodus -like and Helodus -like teeth. As in Helodus simplex , some specimens of Psephodus display varying degrees of fusion of teeth from the same labiolingually oriented file into tooth plates. However, unlike Helodus simplex , some specimens of Psephodus display fusion of mesiodistally separated tooth plates, each representing a fused tooth file, into a larger tooth plate. Psephodus , which crosses the Devonian–Carboniferous boundary, may be ancestral to other Mississippian holocephalians, such as Cochliodus or Chondrenchelys , in which dentitions consist of a few tooth plates with only few, or no, separate teeth. An unpublished watercolour by Agassiz's artist Dinkel depicts five tooth plates, which can be designated as syntypes of P. magnus. A lectotype for Psephodus crenulatus is designated.

Mutations in LRP6 highlight the role of WNT signaling in oral exostoses and dental anomalies

ObjectiveThe objective of this study was to investigate molecular etiologies of oral exostoses and dental anomalies in 14 patients from eight families. MethodsOral and radiographic examinations were performed on every patient. Whole exome and Sanger sequencing were performed on DNA of the patients, the unaffected parents and unaffected siblings. LRP6 mutant proteins were modeled and analyzed. ResultsFive mutations in LRP6, including four missense (p.Glu72Lys, p.Lys82Asn, Tyr418His, and p.Ile773Val) and one nonsense mutation (p.Arg32Ter), were identified. These mutations have not been reported to be associated with dental anomalies or oral exostoses. Oral features included a variety of oral exostoses (7 of the 14 patients), root defects (6 of the 14 patients), and tooth agenesis (5 of the 14 patients). Less common dental anomalies included microdontia, tooth fusion, odontomas, and mesiodens. Analysis of the protein models of the five LRP6 mutations shed light on their likely impact on LRP6 protein structure and function. ConclusionFourteen patients with five LRP6 mutations, including two recurrent mutations and three novel ones, are reported. Our study shows for the first time that mutations in LRP6 are associated with mesiodens, fusion of teeth, odontomas, microdontia, long roots, molars with unseparated roots, and taurodontism.

Research on Meshing Characteristics of Trochoidal Roller Pinion Rack Transmission

As a precision transmission mechanism, the trochoidal roller pinion rack has been paid more and more attention in recent years, but its meshing characteristics have not been deeply explored. In order to investigate the meshing characteristics of the trochoidal roller pinion rack transmission, it is particularly important to research its line of action and meshing stiffness. The equation of the line of action of the trochoidal roller pinion rack is deduced by using its tooth profile formation principle. The motion simulation of the trochoidal roller pinion rack transmission is carried out to verify the correctness of the theoretical derivation of the equation of the line of action, and the influence of the basic parameters on the line of action is summarized. The meshing stiffness of the trochoidal roller pinion rack is calculated based on the energy method used for gear meshing stiffness, and the meshing stiffness is defined considering the time-varying characteristics of its pressure angle, and the influence of each basic parameter on the meshing stiffness is studied. The results shows that the meshing stiffness increases first and then decreases in the double tooth meshing area, while the meshing stiffness gradually decreases in the single tooth meshing area. The basic parameters including number of roller pins, the module, the rack tooth profile offset coefficient, the diameter coefficient of roller pin, and the addendum coefficient of rack have different effects on the line of action and meshing stiffness. The research conclusion can provide reference for the parameter design of the trochoidal roller pinion rack, and provide the meshing stiffness calculation method for the dynamic analysis of the transmission.

Establishment of the integrated safety domain for spur gear pair and its safety characteristics in the domain

In order to reveal the evolutionary mechanism of the safety characteristics for the gear transmission system, the integrated safety domain is established and the safety characteristics of the spur gear pair in it are researched according to our previous research results. An integrated safety domain including 8 safety grades of the spur gear pair considered its multi-state meshing characteristics is established. Single and double drive-side meshing, tooth disengagement, single and double back-side contacting and the tooth surface contact fatigue, tooth surface plastic deformation and tooth root bending fatigue under drive-side meshing and back-side contacting are included in the established integrated safety domain. The calculated multi-initial values bifurcation diagrams, the calculated safety characteristic transition curves and the constructed bifurcation & safety dendrogram are used in combination to investigate the transition process of the system motion and its safety characteristics. Phase portraits, Poincaré maps and safe basins are used in combination to investigate the transition mechanism of the system motion and its safety characteristics. The influences of load on the system safety characteristics in three different safety domains are analyzed comparatively when the multi-state meshing characteristic of spur gear pair is considered. The influences of the meshing frequency and the fluctuation amplitude of meshing stiffness on the safety characteristics of the system in the established integrated safety domain are investigated. The transition mechanism of the system safety characteristics and the range of three sensitive parameters are obtained. The identification method of the safety characteristic considering the integrated safety domains and the fractal degree of the safety basin is introduced. The study is helpful in the selection of system parameters for mitigation and design against fatigue or improving safety. It is also helpful for grading safety early warning of the gear transmission system and the corresponding safety protection measures or adjusting system parameters can be taken according to actual engineering requirements.

Dental pathologies in lamniform and carcharhiniform sharks with comments on the classification and homology of double tooth pathologies in vertebrates.

Double tooth pathologies are important indicators of trauma, disease, diet, and feeding biomechanics, and are widely documented in mammals. However, diagnosis of double tooth pathologies in extinct non-mammalian vertebrates is complicated by several compounding factors including: a lack of shared terminology reflecting shared etiology, inconsistencies in definitions and key features within and outside of mammals (e.g., gemination, fusion, twinning, concrescence); differences in tooth morphology, heterodonty, regeneration, and implantation between mammals and non-mammalian vertebrates; and the unmet need for diagnostic criteria that can be applied to isolated teeth, which are common in the fossil record. Here we report on double tooth pathologies in the lamniform and carcharhiniform Cenozoic sharks Otodus megalodon (NCSM 33639) and Carcharhinus leucas (NCSM 33640, 33641). All three teeth bear a singular bifid crown with mirrored halves and abnormal internal microstructure—a single, bifurcating pulp cavity in C. leucas and a more than tripling of vessels in O. megalodon (from two to seven main ascending canals). We identify these abnormalities as likely examples of gemination due to their symmetry, which rules out fusion of tooth buds in one tooth file in different developmental stages in polyphyodont taxa; however, we note that incomplete forms of mesiodistal tooth fusion can be morphologically indistinguishable from gemination, and thus fusion cannot be rejected. We further compile and recategorize, when possible, the diversity of tooth pathologies in sharks. The identification of double tooth pathologies in O. megalodon and C. leucas has paleobiological implications. Such pathologies in sharks are largely hypothesized to stem from trauma to developing tooth buds. Carcharhinus leucas is known to feed on prey documented to cause feeding-related oral traumas (e.g., rays, sawfish, spiny fish, and sea urchins). However, O. megalodon, is considered to have largely fed on marine mammals, and perhaps turtles and/or fish, raising the possibility that the dietary diversity of this species is, as of yet, underappreciated. The genetic underpinnings of tooth morphogenesis and regeneration is highly conserved throughout vertebrate evolution, suggesting a homologous framework can be established. However, more research is needed to link developmental, paleobiological, and/or paleoenvironmental factors to gemination/fusion in polyphyodont taxa. We argue that the definitions and diagnostic criteria for dental pathologies in vertebrates require standardization in order to advance macroevolutionary studies of feeding trauma in deep time.

CLINICAL OUTCOME OF PERI-IMPLANT SOFT AND HARD TISSUES AFTER IMMEDIATE IMPLANT PLACEMENT: A SYSTEMATIC REVIEW AND META-ANALYSIS

Background: One of the most important challenges in dental implant placement is supporting and preserving soft tissue and bone structures. Numerous studies on fixation of soft and hard tissues at the single or double teeth site have reported immediate placement using a flapless protocol, while many studies have reported fewer results in molar extraction solutions. The current study aims to determine the clinical outcome of peri-implant soft and hard tissues following immediate implant placement. Materials & Methods: This study was conducted in the Department of Orthodontics, College of Stomatology, Xi’an Jiaotong University, Xi’an, China, from January 2021 to September 2021. In this systematic review, the search strategy was to screen electronically all relevant, authentic articles on databases of Embase, LIVIVO, EBSCO, Web of Science, LILACS, Scopus, and PubMed, published from 2011 to September 2021. Risk ratio (RR) was determined for implant failure, and mean differences (MD) were determined for soft tissue, horizontal and vertical buccal bone resorption by 95% CI, Inverse-variance, and fixed effect model or Mantel-Haenszel method between the intervention (bone substitute material) and control (no bone substitute material) groups through Stata/MP v.16. Results: Risk ratio of implant failure was similar in intervention and control group 0.02 (RR=0.02; 95%CI=-0.04 to 0.08; p=0.49). Mean differences were statistically greater in intervention than control group for soft tissue 1.65 mm (95%CI=1.05 to 2.25; p=0.00), horizontal bone resorption -0.47 mm (95%CI=-0.77 to -0.17 mm; p=0.00) and vertical buccal bone resorption -0.14 mm (95%CI=-0.24 to -0.03 mm; p=0.01). Conclusion: Our findings revealed no significant difference in implant failure between an intervention (bone substitute material) and control (no bone substitute material) groups. Mean differences were statistically greater in the intervention than the control group for soft tissue, horizontal bone resorption, and vertical buccal bone resorption. Using bone substitute material can improve long-term peri-implant soft tissue, horizontal and vertical buccal bone resorption. It is recommended to use bone-substitute material with a thin buccal plate.

Concrescent Teeth: Extraction Implications - A Case Report

Background: Concrescent teeth belong to the group of double teeth with disturbed anatomy of shape and structure. The concrescence consists of the aggregation of root cementum of adjacent teeth. This anomaly usually concerns the upper teeth in the lateral part of the jaw. Concrescent teeth can be treated conservatively, endodontically, orthodontically and surgically. Objective: The aim of this article is to present the case of the concrescence of upper teeth, a second molar tooth with an impacted third molar, and to draw the attention of clinicians to this rare anomaly that may cause medical and legal problems. Case presentation: This article presents the case of a 53-year-old woman who reported to the dentist’s office to extract tooth 17 due to chronic periodontitis and an impacted and abnormally placed tooth 18. Result: During the extraction, concrescence of the teeth was noted. The teeth were removed, and the alveoli were surgically treated. The postoperative period was uncomplicated. Conclusion: In this paper, the authors draw the attention of clinicians to the fact that the occurrence of concrescent teeth in clinical practice is rare and that it is difficult to diagnose this anomaly on the basis of routine radiological diagnostics based on 2D images. They also point to the necessity of a thorough physical examination and a thorough assessment of teeth before extraction, the extension of imaging diagnostics by conical CT scan in justified cases, and informing the patient about possible complications. In order to avoid serious complications, the extraction of the concrescent teeth should be performed by an experienced specialist in dental or maxillofacial surgery.

Dentigerous Cyst with Double Teeth in a Dog

Dentigerous Cyst with Double Teeth in a Dog

Computerized design, simulation of meshing and stress analysis of non-generated double circular-arc helical gear drives with different combinations of transverse pressure angle

The computerized design of non-generated double circular-arc helical gear drives with different combinations of transverse pressure angle based on the active design of the meshing line function is presented. The application of different transverse pressure angles for the double circular-arc tooth profiles is discussed and the parametric equations for the driving and driven gear tooth surfaces are derived. The meshing performance and mechanical behavior are studied in terms of the achieved contact patterns and the evolution of the contact and bending stresses for nine cases of design. The results show that one of the cases of design of double circular-arc helical gear drives considering a combination of transverse pressure angles of 25 and 15 degrees for the convex and concave circular-arc profiles of the pinion shows better mechanical performance with respect to the other combinations of different transverse pressure angles. The proposed geometry of non-generated gears is appropriate for manufacturing by injection molding or additive manufacturing for plastic, ceramic, metal as well as nanocomposite gears.