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The term double tooth has often replaced the clinical diagnosis of gemination or fusion. If teeth have been extracted or exfoliated, the use of the neutral term ‘double tooth’ avoids the need to arbitrarily decide if it was gemination or fusion in origin. This case reports on a 16-year-old male who presented with an UL2 ‘double tooth’ and his combined restorative, surgical and orthodontic intervention to achieve his ideal result. CPD/Clinical Relevance: A multidisciplinary approach should be adopted when treating patients with a double tooth and an appropriate protocol as cited can be used.

Developmentally abnormal teeth presenting a complex root canal morphology requires special endodontic management. The present case report demonstrates successful endodontic management of a mandibular first premolar with an unusual concurrent occurrence of a double tooth and dens evaginatus with a C-shaped canal configuration in a 21-year-old patient that was diagnosed with pulpal necrosis with symptomatic apical periodontitis. In this case, the use of cone-beam computed tomography and the dental operating microscope contributed remarkably to the diagnosis and treatment of the complex root canal morphology of the anomalous tooth. Therefore, the use of recent advances in endodontics is strongly recommended in such cases to ensure predictable and successful results.

Dental anomalies such as fusion, germination, double teeth are frequently encountered during routine dental examination often leading to crowding or abnormal spacing in dental arches or increased susceptibility to dental caries and aesthetic problems in pediatric dental patients. Tooth fusion is illustrated when there is the union between dentin and / or enamel of two or more separate developing teeth. Since the fused tooth may pose a wide spectrum of dental problems hence managing such cases requires thorough knowledge and technical skills of dental practitioners. Most of the clinicians advocate minimal intervention technique and preventive approach along with a regular and a long term follow up for the management of fused teeth Keywords: Fusion, Gemination, Double tooth, Dental anomaly, Mandibular incisors, Dentition.

The presence of a double-tooth requires specific complex management due to the need for differential diagnosis and following treatment choices. The aim of this report was to present a rare case of a geminated mandibular lateral incisor, treated with an orthodontic approach. A Caucasian 10.9-year-old girl presented a lower right double-tooth incisor, with a class 1 molar and a class 2 cuspid tendency on both sides. The upper arch was constricted as shown by bilaterally tendencies to cross-bite, a slightly lower midline deviation was reported and a lack of space for all four permanent cuspids was confirmed also by the panoramic X-ray. In the lower arch, there was a severe crowding of about 14 mm and a buccally ectopic left canine. Overbite was normal and Overjet minimally increased. The double-tooth was identified like a geminated tooth, for the presence of one root and one pulp canal of increased size, as shown by the radiographic examinations. The anomalous tooth was managed with an orthodontic approach associated with a progressive stripping to reshape the crown. A two-phase treatment plan was performed, based on first maxillary expansion and lip bumper and then fixed appliances, in order to achieve a proper occlusion and a better aesthetic.

The computational model of spur gear meshing stiffness is established by using the hypothesis of cantilever beam of the gear. The meshing stiffness of spur gear is calculated by analytical method, and the distributional curve of meshing stiffness is obtained by comparison with FEM. Experimental verification of simulated results is performed by mechanical test-bed of closed flow. The experimental results show that the simulation results are in good agreement with the experimental results. Based on the FEM models of gear tooth with cracks of different lengths, the comparison between degradation trends in different meshing regions that shows that the degree of degradation in a single tooth meshing area is much higher than in a double teeth meshing region. In the FEM models of gear tooth with cracks of different lengths, the stiffness degradation rate of the double tooth indentation area increases first and then decreases, and the crack length is most obvious between 4 and 8 mm.

Objective: Dental anomalies occurring in deciduous teeth can affect the eruption of the permanent dentition and the occlusion stability. The occurrence of dental anomalies such as double teeth during the primary dentition in the daily practice might be frequent. The study aimed to qualitatively summarize the therapeutic management of double teeth in primary incisors.Material and Methods: A systematic review regarding the therapy of primary fused incisors in the mandible was performed and the obtained data were assessed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The following electronic databases were screened from 1st January, 1996 until 30th July, 2019: PubMed, Scopus, EBSCO and the archives of paediatric dental journals. The search terms were grouped in anatomic entity: (tooth OR teeth OR incisor), pathological condition: (fused OR fusion OR geminated OR double), intervention: (treatment OR intervention OR therapy OR prevention OR control OR management OR restoration), observed parameters: (primary dentition OR primary tooth OR primary teeth).Results: Ten articles met all inclusion criteria. The data disclosed the occurrence of double teeth in mandibular incisors. The main management of this clinical condition is either preventive or surgical involving the extraction of fused teeth, based on the deciduous nature of the teeth, the degree of caries and malocclusion development risk.Conclusion: An early diagnosis of dental anomalies is fundamental for the application of proper preventive strategies to avoid a potential malocclusion in permanent dentition and to maintain these teeth sound and caries-free until the eruption of the permanent dentition.

In the process of odontogenesis, a disturbance in the formation of the epithelium and mesenchyme can be observed and this can be manifested by atypical forms of dental development. Such biological phenomena with altered morphology are as follows: dens invaginatus (DI), dens evaginatus (DE), talon cusps, and double teeth (DT) or connate teeth (fusion and gemination). Patients with orthodontic anomalies who also exhibit teeth with morphogenetic disorders are presented in this article. Dens evaginatus and talon cusps pose orthodontic challenges in the treatment finishing phase. These reduce the possibility of achieving maximum intercuspidation between the lower and upper front teeth as well as poor incisor guidance. Other orthodontic challenges are as follows: the risk of occlusal trauma and periodontal loading of the antagonists and the possibility of accessory cusps to play the role of the inclined plane and lead to deviations in the closure of the lower jaw. The fused teeth can cause aesthetic and occlusal disturbances in the anterior segment. Furthermore, double teeth can lead to ectopic eruption or noneruption of adjacent teeth due to their increased crown size as is the case with one of the presented patients. This is because a double tooth occupies more space in the dental arch. If not diagnosed early, impaction of the adjacent tooth, violation of the occlusal ratios (Bolton/anterior), and exacerbation of the orthodontic deformity can be observed. The modern CBCT imaging is the best diagnostic method for identifying problems related to tooth positions or tooth germs.

Fusion and gemination are not entirely uncommon dental anomalies that may also be named ‘double teeth’. This is due to their unusual presentation in a twin-like fashion. Teeth with these irregularities may appear clinically similar, presenting as large and bulbous in shape with unusual anatomy and fissure patterns. The exact aetiology of these anomalies is uncertain, but many potential local or systemic disturbances during the morphodifferentiation stage of odontogenesis have been considered. Gemination occurs rarely in the permanent dentition and even less frequently in the posterior region of the oral cavity. This report presents a case of a geminated mandibular second molar and discusses the importance of early recognition and diagnosis of such teeth so that adequate preventative care and treatment can be provided.

A supernumerary tooth is an entity in addition to the normal series of teeth that, although rare, can be fused to a tooth, whether deciduous or permanent. Diagnosis and management in cases involving supernumerary teeth in the anterior region of the maxilla are often challenging. The clinical examination associated with the radiographic examination is decisive for the diagnosis and planning of cases. This article describes a case of unilateral fusion of a supernumerary tooth to a permanent upper lateral incisor, in which clinical and radiographic diagnosis was essential for a conservative approach. Descriptors: Diagnosis; Fused Teeth; Tooth, Supernumerary. References Rajab LD and Hamdan MA. Supernumerary teeth: review of the literature and a survey of 152 cases. Int J Paediatr Dent. 2002;12:244–54. Yang G. Supernumerary teeth and gemination. Br J Oral Maxillofac Surg. 2012;50:15–8. Zhu M, Liu C, Ren S, Lin Z, Miao L, Sun W. Fusion of a supernumerary tooth to right mandibular second molar: a case report and literature review. Int J Clin Exp Med. 2015;8(8):11890-95. Rudagi K, Rudagi BM, Metgud S, Wagle R. Endodontic management of mandibular second molar fused to a supernumerary tooth, using spiral computed tomography as a diagnostic aid: a case report. Case Rep Dent. 2012;2012:614129. Nandini DB, Deepak BS, Selvamani M, Puneeth HK. Diagnostic dilemma of a double tooth: a rare case report and review. Journal of Clinical and Diagnostic Research. 2014;8(1):271-72. Duncan WK, Helpin ML. Bilateral fusion and gemination: a literature analysis and case report. Oral Surg Oral Med Oral Pathol.1987;64(1):82-7. Gupta S, Singla S, Marwah N, Dutta S, Goel M. Synodontia between permanent maxillary lateral incisor and a supernumerary tooth: treatment J Oral Health Comm Dent. 2007;1:52-5. Mader CL (1979) Fusion of teeth. J Am Dent Assoc 98:62-4. Kumar V, Pandey V, Rohini G, Jyoti B. Fusion Between Maxillary Premolar and A Supernumerary Tooth: A Rare Case Presentation. J Clin Diagn Res. 2015;9(11): ZJ03-4. Maréchaux SC. The treatment of fusion of a maxillary central incisor and a supernumerary: report of a case. ASDC J Dent Child. 1984;51:196-99. De Siqueira VC, Braga TL, Martins MA, Raitz R, Martins MD. Dental fusion and dens evaginatus in the permanent dentition: literature review and clinical case report with conservative treatment. J Dent Child (Chic) 2004;71:69-72. Karacay S, Guven G, Koymen R. Management of a fused central incisor in association with a macrodont lateral incisor: a case report. Pediatr Dent. 2006;28:336-40. Cetinbas T, Halil S, Akcam MO, Sari S, Cetiner S. Hemisection of a fused tooth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;104:e120-24. Nunes E, deMoraes IG, de Novaes PM, de Sousa SM. Bilateral fusion of mandibular second molars with supernumerary teeth: case report. Brazilian Dent J. 2002;13:137-41.

Fusion can be described as the complete or partial union between the dentin and enamel of two or more developing teeth. This union could be seen in the primary or permanent dentition or between a permanent tooth and a supernumerary tooth. Various theories have been put forward to explain the aetiology of fusion including that of increased force generated during growth, use of thalidomide or viral infection during pregnancy and a genetic aetiology. Fusion may cause aesthetic problems, occlusal disturbances, increased tendency for dental caries and periodontal disease. Developmental anomalies such as fusion are not observed frequently in clinical practice. Morphologic alterations of teeth can be observed as an incidental finding during thorough clinical examination. This case report discusses 2 such cases of fusion along with review of literature. Keywords: Fusion, Developmental disturbance, Double tooth.

A new gear tooth modification model of planetary gear system was established by considering the characteristics of tooth longitudinal crowning modification and tooth profile modification. Using this model, the influences of modification parameters on the time-varying mesh stiffness, transmission error, contact spots and dynamic response of the planetary gear system were analyzed through numerical analysis. The results show that tooth profile modification can effectively restrain the mesh stiffness sudden variation in the single and double tooth alternation of both the internal and external mesh pairs, and significantly decrease the transmission error fluctuation. However, longitudinal crowning modification has no marked influence on mesh stiffness sudden variation or transmission error fluctuation. The tooth profile modification can significantly reduce the sudden variation of tooth surface load during gear mesh course. Longitudinal crowning modification can make the tooth surface load evenly distributed in tooth width direction. When the external meshing pairs are modified at the tooth profile individually, the magnitude values of main response resonance peaks of internal meshing pairs have a great reduction, but those values of external meshing pairs change slightly. In the case of tooth profile modification of the internal meshing pairs, the phenomenon is reversed. By contrast with tooth profile modification, longitudinal crowning modification has little influence on the resonance peaks of internal and external meshing pairs.

Introduction: A double tooth can be a consequence of fusion or gemination and is characterized by a size increasing of the tooth and a morphological modification. This anomaly concerns the anterior teeth and occurs in temporary and permanent dentition. Double teeth causes various problems (aesthetic, occlusal, endodontic, orthodontic, periodontal…). The management of clinical situations involving such abnormalities is often complex. Our aim is to present a reasoned analysis based on a systematic review of therapeutic attitudes used in different clinical situations when the abnormal tooth is located at the anterior maxillary region. Material and Methods: We carried out electronic research via Pubmed and Sciencedirect to collect case reports published during the 20 recent years (1999-2020). We included 46 articles corresponding to 57 relevant case report that we classified based on Aguilo and coll. Classification (1999). Results: Partial crown and root section is indicated for type I. Stipping is indicated for type II. The management of type III is compromised by the canal morphology. Extraoral and entraoral hemisection are only indicated for type IV. Coronoplasty is usually unavoidable. Endodontic, orthodontic, or periodontal treatment can be indicated depending on the situation. The extraction is considered as a last resort, the space is restored by autotransplantation of a supernumerary tooth, a prosthetic restoration, or an implant by the end of the craniofacial growth. Conclusion: The management of double teeth is a therapeutic challenge, every case is different, a multidisciplinary approach is recommended.

Double tooth is an anatomic variation referring either to a tooth stemmed from a fusion or a gemination. The root’s number will influence surgical treatment possibilities, conditioning a possible rootseparation, and the root canal anatomy will determine the necessity and difficulty of an endodontic treatment preceding any other tooth rehabilitation. This case report describes a fused permanent central incisor leading to an aesthetic and functional complaint. The Cone Beam Computed Tomography (CBCT) required for another symptomatic tooth was used to create a 3D model of the double tooth. This 3D planification allowed to establish the absence of an endodontic communication between the incisor’s two fused roots, which can be difficult to appreciate on the X-ray , as well as preparing the root separation surgery that was then realized. A few months later, the tooth became necrotic and another CBCT was prescribed. The endodontic treatment being necessary, a second 3D planification was conducted in order to analyze the anatomic modifications resulting from the root separation, to verify the absence of an endo-perio lesion and in fine compare two printed 3D models: one pre-op and one post-op. This approach is useful in the understanding of a complicated anatomy through three dimensional modeling and facilitates, La dent double est une variation anatomique pouvant désigner à la fois une dent issue d’une fusion ou d’une gémination. Le nombre de racines influera les possibilités thérapeutiques chirurgicales, conditionnant une possible hémisection, et l’anatomie canalaire déterminera de la nécessité et la difficulté d’un traitement endodontique préalable à toute autre réhabilitation de la dent. Nous rapportons ici le cas d'une incisive centrale supérieure permanente fusionnée à l’origine d’une gêne esthétique et fonctionnelle. L’imagerie tridimensionnelle à faisceau conique (Cone Beam Computed Tomography - CBCT) prescrite pour une autre dent symptomatique a servi à élaborer un modèle 3D de la dent double. Cette planification tridimensionnelle a permis d’établir l’absence de communication pulpaire entre les deux racines fusionnées de cette incisive, ce qui est difficile à déceler à partir de l’imagerie seule, ainsi que d’appréhender la chirurgie d’hémisection qui a ensuite été opérée. Dans un second temps, la dent s’étant nécrosée, un nouveau CBCT a été prescrit. Le traitement endodontique devant être conduit, une deuxième planification tridimensionnelle a été réalisée afin de visualiser les modifications anatomiques résultant de l’hémisection, vérifier l’absence de communication endo-parodontale pathologique et comparer les deux modèles 3D imprimés: pré-opératoire et post-opératoire. Cette approche est utile dans la compréhension d’une anatomie compliquée via la modélisation tridimensionnelle et facilite l’appréhension, l’établissement et la conduite du plan de traitement sur les aspects chirurgical et endodontique.

The aim of this study is to report aesthetic conservative treatment of double tooth anomaly. Case report: A 7.5-year-old patient presents an anomaly of the maxillary right upper central incisor with a bifid crown and an increased mesio-distal width and a central incisal notch, probably amenable to a gemination. Single tooth anesthesia and conservative enameloplasty procedure was performed, with universal adhesive and a single shade universal composite restorative material. Adhesive aesthetic restorations allow to resolve dental anomalies quickly, cheaply and asily for pediatric dentistry.

Gemination is a rare developmental abnormality. This abnormality occurs when one tooth bud attempts to split into two, resulting in a large bifid crown and usually a single root and root canal. The main reason of gemination is unknown. Gemination may be associated with any syndromes or it can be asyndromic. Gemination of premolar teeth is uncommon. The aim of this paper is to describe a rare case of gemination involving a mandibular first premolar, review similar case reports and discuss treatment and care modalities in literature. Our search revealed that only 13 cases of geminated premolar teeth (including supernumerary premolar teeth) were reported in the last 39 years. Proper clinical and radiographic examination, proper oral hygiene education and if needed symptomatic treatment planning is necessary to manage this rare developmental abnormality., Geminasyon nadir görülen gelişimsel bir anomalidir. Bir şekil anomalisi olan geminasyon, bir diş tomurcuğu iki bölünmeye çalışıldığında ortaya çıkar ve büyük bir bifid kron ve genellikle tek bir kök ve kök kanalı ile sonuçlanır. Geminasyonun temel nedeni bilinmemektedir. Geminasyon sendromlarla ilişkili olabilir ya da olmayabilir. Premolar dişlerin geminasyonu nadirdir. Bu yazının amacı; mandibuler birinci premolar dişte nadir görülen bir geminasyon olgusunu tanımlamak, literatürdeki benzer vaka raporlarını incelemek ve tanı seçenekleri ile tedavi yöntemleri hakkındaki güncel kaynakları değerlendirmektir. Araştırmamız, son 39 yılda premolar dişte geminasyon ile ilgili sadece 13 tane olgu sunumu olduğunu (süpernümere premolar dişler dahil) ortaya çıkardı. Bu nadir görülen dental anomaliye yaklaşımda doğru klinik ve radyografik muayene ile oral hijyen eğitimi ve semptomatik tedavi planlaması gereklidir.

Füzyon ve geminasyon, özellikle süpernumere diş veya hipodontiyle birlikte görüldüğü durumlarda klinik olarak ayırıcı tanı koymak zor olmaktadır. Bu nedenle çoğu araştırmacı bu dişler için “çift diş” terimini kullanmayı tercih etmektedir. Eğer bu dişler komşu iki diş germinin birleşmesi sonucu oluşuyorsa füzyon; tek diş germinin bölünme girişimi sonucu oluşuyorsa geminasyon olarak tanımlanmaktadır. Bu olgu sunumunda daimi üst sol santral dişi etkileyen çift diş olgusunun tedavisi anlatılmaktadır. Yapılan klinik ve radyografik muayeneler sonucunda, bu dişin üst sol santral kesici ile süpernumere dişin füzyonundan oluştuğu belirlenmiştir. Çift diş, komşu santral dişin kron boyutunda olacak şekilde ikiye ayrılarak süpernumere diş, ilgili kökle birlikte çekilmiştir. Bir yıllık takip sonunda sol santral kesici dişin vitalitesinin devam ettiği belirlenmiştir. Bu olgu, çift dişin ayrılmasında doğru teşhisin önemli olduğunu ve konik ışınlı bilgisayarlı tomografi (KIBT) tabanlı verilerin komplike olan tedavi planlanmasında oldukça yararlı olduğunu göstermektedir., It is difficult to clinically make differential diagnosis between fusion and gemination, especially when these anomalies take place together with hypodontia or supernumerary tooth. The term “double tooth” is therefore preferred by many authors. These teeth may occur due to the fusion of adjacent tooth germs, hence the term fusion. Alternatively, this anomaly may be the result of attempted division of a single tooth germ, hence the term gemination. This case report describes the management of double tooth affecting the permanent maxillary left central incisor. As a result of clinical and radiographic examinations, it was determined that this tooth consisted of fusion of central left maxillary incisor and supernumerary tooth. The double tooth was separated for having crown size of adjacent central incisor and supernumerary tooth with related root was extracted. After 1- year follow up, the maxillary left central incisor still remains vital. This case shows that a precise diagnosis is important in sectioning a double tooth, and that cone-beam computed tomography (CBCT)- based data are very useful in planning complex treatment.

Fusion is known as a developmental anomaly described by the union of two neighbouring teeth. The worldwide prevalence of bilaterally fused teeth in the primary dentition is about 0.02% which is considered very rare. Only few cases of bilateral fusion have been reported in Indian population. This paper presents a rare case of three-year-old boy with bilateral fusion of primary mandibular lateral incisors and canine teeth. Treatment consisted of pit and fissure sealants and topical fluoride application. To conclude, fused primary teeth are considered as harmless asymptomatic abnormality.

Gear tooth spalling is one of the most common defects in gear transmission. The loss of surface materials due to tooth spall reduces the Time-Varying Mesh Stiffness (TVMS) of the gear pair, and thus modifies the vibration response of the gear transmission. The evaluation of the TVMS of the gear tooth pair under gear tooth spalling conditions plays an important role in gear dynamic simulation and the corresponding fault feature analysis. Common approaches assume that the tooth spall has a flat bottom with a constant tooth spall depth. This assumption implies an abrupt change in dent depth and cliff-like material loss. However, in practice, the flake of the surface material usually results in a gradually changing dent depth with a curve-shaped bottom. Thus, the modelling of tooth spalls with a flat bottom may result in mesh stiffness differences. To address this shortcoming, this paper proposes a curved-bottom shaped tooth spall to model the tooth spalling geometric features as observed in practice. The proposed method is constructed based on an ellipsoid geometry which is capable of varying radii in three dimensions to best fit the shape of the tooth spall. The foundation stiffness within the double tooth contact area in the proposed method is corrected and the non-linearity of Hertzian contact stiffness is considered. The effectiveness of the proposed method on modelling single and multiple tooth spalls with different shapes and severity conditions is then validated.

Accurate estimation of tooth-root stress has been of great interest to researchers and engineers to prevent catastrophic damage of gear transmission system. However, analytical models in AGMA standard are not precise and FEM are mostly focused on the analysis of spur gear pairs. As a result, very little research has been conducted to investigate the time-varying tooth-root stress of helical gears. In this study, effects of helix angle, mechanical errors, and coefficient of friction on the time-varying tooth-root stress of helical gears has been rigorously investigated based on our previous proposed method. 10% tensile stress and compressive stress could be reduced with the increase of helical angle. Coefficient of friction has significant effects on the tensile stress of gear pairs. The peak value of time-varying tooth-root stress shifts from HPSTC to LPSTC due to its influence. The increase of parallel misalignment could reduce up to 18% tensile stress during approach process in double tooth contact condition.

Fusion is an anomaly manifested in both deciduous and permanent dentitions. Triple tooth refers to the union of three separate tooth entities. It can involve the normal dentition or supernumerary teeth. Triplication is rarely encountered in deciduous and permanent dentition with an incidence of 0.02%. The case presented herein describes a rare case of triplication in permanent maxillary incisors and supernumerary teeth in a 15-year-old female.

Gemination aka twinning and fusion, are rare occurrences in posterior mandibular teeth, often requiring endodontic and surgical treatment for functional, orthodontic or cosmetic reasons. The diagnosis and design of a precise treatment plan in cases involving double teeth are in most cases challenging. The purpose of this case report is to describe a successful multidisciplinary treatment protocol for a double tooth. Upon completion of the endodontic, restorative and orthodontic treatments, the clinical and radiographic three-year follow-up revealed that the rest of the transected premolar showed evidence of healing of the supporting tissues and satisfactory cosmetic result.

Amaç: Bu olgu sunumunun amacı; tesadüfen karşılaşılan, daimî dentisyondaki ikiz diş vakalarının klinik ve radyografik bulgularını sunmaktır. Olgu Tanımlanması: Dişlerdeki şekil anomalilerinden olan füzyon ve geminasyonu klinik muayene sırasında birbirinden ayırt etmek için ağız içindeki diş sayısına bakılmaktadır. Diş sayısında herhangi bir nedenle diş kaybı olmadan eksiklik varsa füzyon olarak tanımlanmaktadır; geminasyonda ise diş sayısı değişmeden sadece büyük diş görülmektedir. Gazi Üniversitesi Diş Hekimliği Fakültesi Ağız, Diş ve Çene Radyolojisi Anabilim Dalı’na birçok dental neden ile başvuran ve şikâyet nedenine göre radyografi istenen 8 hastanın (4 kadın, 4 erkek) intraoral ve radyografik muayenesinde ikiz dişlere rastlandı. Vakalarımızda geminasyon- füzyon ayrımı klinik ve radyografik inceleme ve diş sayısı ile tespit edildi. Bulgular: İkiz diş görülen 8 hastanın yaş ortalamaları 26.75 idi. İkiz dişlerin 3 tanesi geminasyon 5 tanesi ise füzyondu. İkiz dişlerin 4 tanesi kadınlarda (3’ü sağda (% 75) diğer 1‘i solda (% 25)), 4 tanesi erkeklerde (3’ü sağda (% 75), 1’i solda (% 25 )) görülmekteydi Sonuç: Füzyon veya geminasyon tanısının konulması zor olsa da daimî dişlerde karşılaşma oranının yüksek olduğu göz ardı edilmemelidir. Patolojik bir bulgu vermedikçe klinik muayene sırasında gözden kaçma ihtimali yüksektir. Bu yüzden ikiz dişlerin daimî dentisyonda görülme prevalansı ile ilgili daha fazla araştırma yapılması gerektiği düşüncesindeyiz., Background: The aim of this case report was to present clinical and radiographic findings of incidentally found twin teeth in permanent dentition. Case Descriptions: The number of teeth in the oral cavity is examined clinically in order to differentiate fusion and gemination which are tooth shape alterations. Fusion results in an reduced number of teeth in the arch while a large tooth is seen without any reduction of teeth number diagnosis is gemination. Intraoral and radiographic examination of 8 patients who attended to Gazi University Faculty of Dentistry, Department of Oral and Maxillofacial Radiology with many dental causes, twin teeth were observed. Diagnosis of fusion and gemination were done by clinic and radiographic examination and determining the number of teeth in the arch. Results: The mean age of patients with twin teeth was 26.75. Three of the twin teeth were geminations and 5 of them were fusions. Four of the twin teeth were seen in women (3 of them was at right (75 %), 1 of them were at left side (25 %)), 4 of the twin teeth were seen in men (3 of them were at right (75 %), 1 of them were at left side (25 %)). Conclusion: Although it is difficult to differentiate twin teeth as fusion or gemination, it is a fact that there is a high rate of twin teeth in permanent dentition. Unless there is a pathological finding, it is likely to be overlooked during clinical examination. Therefore, in our opinion more research studies are needed on the prevalence of twin teeth in permanent dentition.

Gear meshing surfaces are readily exposed to wear due to inadequate lubrication and long-time operation. Accumulative wear causes variations of gear tooth profile, resulting in variations of gear tooth's mesh stiffness and gear system's dynamic characteristics. This study presents an evaluation of influences of tooth surface wear (TSW) on stiffness of the gear mesh considering wear evolution process. Specifically, a wear prediction model for external spur gear (ESG) was established according to the Archard's wear equation. Considering the worn tooth profile, a modified analytical time-varying mesh stiffness (TVMS) model was derived by the potential energy method. The modified TVMS model was then applied for an ESG pair and the numerical results demonstrate that TSW may lead to significant reductions of mesh stiffness during the double tooth contact period. Furthermore, effects of TSW on TVMS were quantified and the results indicate that the mean decrease of mesh stiffness is almost proportional to the maximum tooth wear in the initial wear evolution process.

Aiming at the problem of the low electromagnetic torque performance of the traditional Variable Flux Memory Machine (VFMM), a novel double-tooth Variable Flux Memory Machine is proposed in this paper. Firstly, the topology and operation principle of the novel double-tooth VFMM are introduced. By using the 2-D finite element analysis method, the open circuit characteristics of the novel double-tooth VFMM and the traditional single-tooth VFMM with low coercive force (LCF) in different magnetization states are compared and analysed, and the electromagnetic torque in the flux-enhanced state is compared and studied. In addition, the efficiency maps of double-tooth VFMM are investigated. Compared with the traditional single-tooth VFMM, the flux adjustment ability of the double-tooth VFMM is more than doubled, and the electromagnetic torque under the same current is increased by 21.8%. The results show that the double-tooth VFMM has better flux adjustment ability and larger electromagnetic torque.

Developmental anomalies of teeth are of clinical interest because of the problems associated with them. This report describes a unique case of unilateral fusion of primary mandibular lateral incisor and canine and discusses the possible future treatment options anticipated for management of fused deciduous teeth. Clinically, this case provides an insight into management options for fused deciduous teeth for general dental practitioners.

Based on the analysis of arc tooth cylindrical gear forming principle and on the basis of existing processing methods, also combined with the principle of ordinary milling knife plate rotating, This paper puts forward an improved double-edged milling method of the Circular-Arc-Tooth-Trace cylindrical gear, which includes two aspects: one is the double edged sword substance milling gear, double-point tool forming tooth at a time, with the module gear form point contact transmission vice; the second is to use double tooth gear milling tool, cutting tool a tooth, the gear machining and broadsword dish of double edge milling gear transmission line contact vice. It concluded that the improved processing technology is more advanced, the method of production is more efficient.

Twinning is referred to the development of two separate teeth that arose from the complete separation of one tooth bud. To the best of our knowledge very few cases of twinning in primary or permanent dentition have been previously reported. Here, we report an additional case of twinning involving primary maxillary left lateral incisor and a literature review of clinical and radiographic findings of previous reported cases of gemination and twinning is also discussed. A six-year-old male patient reported to the dental clinic with the complaint of decay in the left front teeth region of the upper jaw. On clinical examination, dentinal caries was observed on the labial surface of primary maxillary left lateral incisor. The tooth showed a deep groove present in relation to the labial surface and incisal edge and continued cervically as a shallow groove. The patient had normal compliment of teeth for his age. The intra-oral periapical radiograph of the maxillary anterior region revealed large crown and a radiolucent notch was observed in relation to the incisal edge of the maxillary left primary lateral incisor. Relatively one pulp chamber and two root canals were observed in relation to the primary maxillary left lateral incisor, which was suggestive of a case of twinning involving primary maxillary left lateral incisor. This present case is the first case report of twining seen in primary dentition.

Developmental anomalies in the hard tissue are seen frequently in dental practice. Gemination and fusion are the most commonly encountered anomalies, and distinction between the two is always challenging. Gemination, also called double tooth, is an anomaly exhibiting two joined crowns and usually a single root. It represents an incomplete attempt of a single tooth germ to split. It is considered multifactorial in etiology, with genetic and environmental causes. This paper discusses a rare example of bilateral gemination (prevalence 0.04%) of maxillary central incisors with completely separated roots. Multidisciplinary care ensured a successful esthetic and functional outcome.

Three-dimensional CAD system is designed by using PRO-E tools. In particular, gear model has been widely used. The usual design philosophy is to perform parametric modeling based on different gears, find the relationship between different parameters, make use of restrictive relationship between different parameters, and complete its modeling process. In this paper, on the basis of this concept, the amount of modification is adaptively determined according to the actual conditions of the operational test situation in actual working conditions, and model modification lengths are optimized in which the amount of model modifications can all be allocated in the active or passive wheel sprocket teeth, and can also be modified both in active and passive wheel. Model modifications are done only in double tooth meshing zone and the gradually open lines in single tooth meshing zone are not modified to ultimately achieve the purpose of gear model optimizing.

Double tooth is a dental anomaly consequent to fusion of two or more teeth or gemination of a single tooth. This report describes a unique case of double tooth in relation to a mandibular lateral incisor exhibiting the presence of four root canals. The role of conventional radiography and advanced three-dimensional imaging techniques in the better assessment of complex root canal systems and their aid in endodontic management has also been highlighted.

Double teeth present challenges for their clinical management. Recent advances in imaging, particularly cone-beam computed tomography (CBCT), have aided clinicians in accurate diagnosis and management. Data from CBCT imaging can be used for three-dimensional reconstruction to further aid pre-surgical planning. A 14-year-old Caucasian male presented with an aesthetically unacceptable double tooth in the 22 region. Clinical and radiographic examination and assessment included CBCT imaging and three-dimensional reconstruction. Based on this information, together with a comprehensive assessment of the patient’s motivation, a treatment plan consisting of extra-alveolar sectioning, re-implantation, endodontic therapy and composite resin restoration was carried out. The patient failed to return for follow-up at 6 months post-treatment. However, he did return at 12 months, where clinical and radiographic examination was undertaken. At this point the tooth was clinically sound and bony infill was seen radiographically. The information gained from the pre-surgical imaging with CBCT was useful in planning treatment in this case. However, this had to be combined with a careful assessment of the patient’s motivation to ensure that the course of treatment embarked upon was likely to be successful whilst addressing the patient’s concerns.

Dental anomalies of number and forms may occur in the primary and permanent dentition. Various terms have been used to describe dental twinning anomalies: Germination, fusion, concrescence, double teeth, conjoined teeth, twinned teeth, geminifusion, and vicinifusion. Fused tooth is a developmental anomaly that is seen more frequently in the primary than the permanent dentition. Double tooth involving deciduous anterior teeth is found mostly in the mandible.Very few cases of nonsyndromic double primary molar have been reported in the literature. The succeeding permanent tooth is often found missing congenitally in the same region. This article reports a very rare unilateral occurrence of an anomalous, primary mandibular first macromolar formed by fusion with a dysmorphic premolar like supernumerary tooth in deciduous dentition period. Instead of agenesis of succedaneous tooth, the double tooth has been succeeded by normally developing mandibular first premolar in the same region.

Supplemental teeth refer to extra teeth that resemble the normal tooth series. Bilateral supplemental central incisors in a healthy individual are rare and bilateral supplemental incisors with double-tooth like appearance are exceptionally rare and has not been previously reported in the dental literature. This clinical report describes an 8-year old healthy Indian boy referred for the management of delayed eruption of his permanent maxillary incisor teeth. Following clinical and radiographic examination the two supplemental incisors closer to the midline were extracted under local analgesia and both of them exhibited double-tooth like appearance. The present case refutes the conventional wisdom that “supplemental teeth are usually smaller than the normal tooth type they resemble and occur distal to the normal tooth series”, illustrates that the unusual can occur and that the clinician should be aware of such variations.

To assess management of non-syndromic double tooth affecting permanent maxillary central incisors, we performed a systematic review and also present 2 case reports. We searched MEDLINE via PubMed and the reference lists of included reports. Eligible studies were any type of clinical studies describing the management of non-syndromic double tooth affecting the crown of a permanent maxillary central incisor. We included 68 studies corresponding to 72 relevant case reports. Therapeutic options in descending order of priority were restorative dentistry (35%), hemisection (33%), abstention (17%) or extraction (15%). Orthodontic management resulted in 57% of cases. We report an 11-year-old boy with bilateral fusion of the two maxillary central incisors and a 9-year-old boy with a double left central incisor and a supernumerary lateral right incisor. A multidisciplinary approach is key to management of permanent maxillary central incisors affected by coronary anomalies.

Introduction: Schizodontia (germination) and fusion are tooth anomalies hard to distinguish, therefore referred to as ‘double tooth’. The condition may raise from division of a single tooth germ or from fusion with a supernumerary tooth. The field theory explains association of tooth position and it’s susceptibility to anomalies of form and number. Case description: A 25 year old female patient came to our observation with three third molars (18, 38, 48) which showed two to three additional cusps. Patient had difficulties with oral hygiene maintenance which caused pericoronitis. Lateral incisors and canines had marked tuberculum dentale. Upper first and second molars both expressed Carbelli’s cusp, grade 6 and 5 respectively according to ASUDAS. Lower first and second molars had 6 and 5 cusps, respectively. Orthopantomogram showed teeth 38 and 48 had accessory cusps under the buccal mucosa and 48 had enlarged distal root. Family anamnesis revealed father had supernumerary tooth in upper frontal region and cousin had supernumerary permanent lower lateral incisors. Discussion: Findings on 18, 38 and 48 indicate schizodontia while alternative could be fusion with supernumerary tooth. According to the field theory, third molars as last teeth in the molar field, are the most susceptible to aberrations. This may be related to genetic and epigenetic factors and duration of the development. Conclusion: Processes that occurred during tooth formation resulted in complex tooth morphology which may be a family trait in this case

International Journal of Paediatric Dentistry 2012; 22: 419–426 Background. Abnormally, large teeth are often referred to as ‘double teeth’. These can pose numerous challenges for the clinician. There is no published protocol on the management of double teeth. Aim. To review the published literature and also patients managed at the Eastman Dental Hospital (EDH) and to develop a clinical protocol for the management of double teeth in children and adolescents. Design. Literature was searched (Medline and Embase) and data collated. Patient notes of cases managed at the EDH were reviewed. Results. Eighty-one teeth from 53 papers and 22 patients were included in the review. Success criteria were only reported in 32 papers and were variable. Twenty-three papers had no follow-up period. The main factor in determining the management of a double tooth was root and root canal system morphology. The treatment of choice in teeth with separate roots was hemisection and in those with a single root was crown modification or extraction. Conclusion. It was not possible to determine the best management strategies because of the variable reporting in the literature. The authors have proposed a protocol for management and a data collection sheet for essential information needed when reporting on double teeth cases.

Gemination and fusion are morphological dental anomalies, characterized by the formation of a clinically wide tooth. Gemination occurs when one tooth bud tries to divide, while fusion occurs if two buds unite. The terms double teeth, double formation, conjoined teeth, geminifusion, vicinifusion and dental twinning are often used to describe fusion and gemination. Double teeth are associated with clinical problems such as poor esthetics, spacing problems and caries susceptibility. Management of such cases requires a comprehensive knowledge of the clinical entity as well as the problems associated with it. This report presents a case of primary double tooth in a 6-year-old boy involving maxillary left central incisor. The anomalous tooth was carious and pulpally involved. This was treated conservatively by endodontic treatment and esthetic rehabilitation was done with direct composite restoration using a silicone buildup guide. The treated tooth was followed up until exfoliation.

A gear’s finite-element model has been set up according to the parameter functions of the involute and tooth root curve, single and double tooth meshing region have been obtained according to the results of contact analysis. A tooth root’s bending stress has been calculated when meshing in the ultimate position in single tooth meshing region, and this stress has been contrasted with the results of a classical method as the maximum of a circle. The results of theoretical method were far away from that of finite-element calculation before being modified and were a little larger than the later after being modified. Reasons leading to this difference have been analyzed.

BACKGROUND: The diagnosis and management strategies of double teeth have largely relied on clinical examination and conventional radiographic findings. Cone-Beam Computed Tomography (Cone-beam CT) was developed in the late 1990’s and, therefore, is a relatively recent addition to the imaging armamentarium for use in Maxillofacial Radiology. There have been no publications in the dental literature demonstrating the use of Cone-beam CT or 3D stereolithography in the diagnosis and surgical planning of the management of double teeth. CASE REPORT: An 11 year old girl presented with a double left lateral maxillary incisor. Conventional plain film radiography failed to provide the requisite information for pre-operative planning. Cone-beam Computed Tomography (Cone-beam CT) allowed determination of location of fusion, three-dimensional (3D) visualisation of pulpal anatomy and the construction of a 3D stereolithographic model for surgical planning. The double tooth was surgically divided in situ under local analgesia. The redundant distal unit was extracted and the residual mesial unit built up in composite resin following physiological mesial drift of displaced maxillary left canine. No endodontic therapy was required. FOLLOW-UP: At a 10-month follow-up visit, clinical and radiographic vitality and success was noted. CONCLUSION: The great amount of radiological information which Cone-beam CT can offer not only improves pre-operative and surgical planning, but the 3D models provided can be used to further educate and inform patients and guardians in the management of double teeth.

Plastic gears made of Nylon 6 are especially susceptible to failure due to extreme heat accumulation in the single tooth mesh area, which results in damage that consequently shortens gear teeth life and causes transmission errors. In this experimental study, the teeth width of plastic spur gears made of Nylon 6 were modified and investigated. The values of load sharing, F/b, in single and double tooth meshing areas were leveled by widening the single tooth zone along the meshing area, and the performances of both modified and unmodified gears were studied experimentally under three different loadings. It was observed that modified Nylon 6 gears exhibit lower tooth temperatures, which results in a decrease in wear rate as compared to unmodified gears. Consequently, teeth width modification helps to increase Nylon 6 gear performance.

Talon cusp is a rare developmental anomaly in deciduous and permanent dentition. This paper reports a case of talon cusp affecting the deciduous maxillary left incisor from a Portuguese child who died more than 680 years ago. Metric analysis suggests that the affected tooth is a double tooth. The possible co-existence of these two anomalies in the deciduous dentition, although clinically rare, represents the second archaeological case reported.

La fusión dental es la unión de dos gérmenes dentales normalmente separados, mientras que la geminación se define como el intento de división de un único germen dental. La fusión y geminación de molares es poco frecuente en la dentición permanente. Describimos un caso clínico de un tercer molar inferior derecho fusionado a un cuarto molar supernumerario en un paciente varón de 36 años que ha presentado repetidos episodios de pericoronaritis. Tras el estudio radiológico se realiza la exodoncia del cordal semiincluido bajo anestesia local. Llevamos a cabo una revisión bibliográfica al respecto.Dental fusion is the union of two tooth buds that normally are separated, while gemination is defined as an attempt by a single tooth bud to divide. The fusion and gemination of molars is uncommon in permanent teeth. We report a clinical case of a right lower third molar fused to a supernumerary fourth molar in a 36-year-old male patient with repeated episodes of inflammation. After the radiologic study, the semi-impacted third molar was extracted under local anesthesia. The literature was reviewed.

Variation in size, form and morphology of the teeth result in anomalies such as macrodontia, microdontia,hyperdontia, hypodontia, double tooth, taurodontism and dens in dente. While traits that may occur more commonly in certain ethnic groups may be considered to be specific to that population. The characteristics of these anomalies and traits are presented along with the prevalence figures for their occurrence in primary dentition of southern Chinese.

Fusion is a rare occurrence in molar teeth. The purpose of this rare case presentation is to describe the nonsurgical endodontic treatment of maxillary molar. A 28-year-old patient was referred for endodontic treatment of her chronic apical abscess of right maxillary second molar. In the clinical examination, a sinus tract adjacent to involved tooth and a small crown of supernumerary tooth fused to the buccal surface of the molar at gingival margin was observed. Endodontic treatment was decided for the involved molar for functional reason. Recall examination, a year after completion of endodontic and restorative treatments, showed the tooth was clinically asymptomatic and there was no radiographic lucency around the apical region.

Morphological and anatomical aberrations present a great challenge to the endodontic treatment. In such cases, knowledge of anatomical variations and developmental disturbances of teeth is essential for successful root canal treatment. The purpose of this article is to differentiate the diagnostic dilemma between gemination and fusion and to step by step outline the endodontic management of such types of anatomical aberrations. A 21-year-old female was referred to a practicing endodontist for the root canal treatment of maxillary left premolar. The patient’s chief complaint was a throbbing pain with sensitivity to cold and hot associated with the offending tooth since 1 month. Clinical examination revealed three intact crowns with tooth coloured restorations on each of them performed by a general dentist [Table/Fig-1]. [Table/Fig-1]: Clinical examination revealed three intact crowns with tooth colored restorations on each of them All the crowns were termed as mesial, distal and palatal. Her systemic health was good and medical history was non-contributory. Distal and palatal crowns demonstrated atypical morphology, palatal the most atypical whereas the mesial crown was characteristically & anatomically similar to the maxillary first premolar. Radiographically, it appeared to be a single root at the cemento-enamel junction [Table/Fig-2]. No periapical pathology was evident which led to the diagnosis of irreversible pulpitis with acute apical periodontitis. [Table/Fig-2]: Preoperative radiograph shows the presence of separate roots at cement-enamel junction After an informed consent access openings were made into each crown using Endo access bur (Dentsply Tulsa, UK) to allow access into the pulp chamber and preparation of the chamber walls, in one operation. Working length was established [Table/Fig-3] using an apex locator (Root ZX mini, J. Morita, USA) which was confirmed using a radiovisiography (Kodak RVG 5100, Care stream dentals LLC, North America). [Table/Fig-3]: Working length was established All the canals were prepared with Hyflex CM rotary files (Coltene Whaledent, Switzerland) in a crown down manner. Sodium hypochlorite was used as an irrigant. Obturation was performed with warm vertical condensation using System B and Obtura II (Sybron Endo, CA, USA) for backfilling. A radiograph was taken immediately to verify the obturation [Table/Fig-4]. After a week the patient reported with complete resolution of the symptoms. Gemination is a developmental anomaly of tooth shape that develops when a single tooth bud attempts to form two teeth. It leads to the formation of two or more identical crowns with a single root and root canal radio graphically [1,2]. Fusion is often correlated and confused with gemination. In our case we distinguished between the two on the basis of the following features: [Table/Fig-4]: Postobturation radiograph Morphology- Gemination results in mirror images of coronal portion of the tooth whereas fusion gives a crooked appearance to the oral cavity. Anatomy- Radio graphically fused teeth has a separate pulp chamber and root canal while gemination has a single pulp chamber. Count of teeth- Mader in 1979 emphasized on the count of teeth in the arch as a differentiating feature between gemination and fusion. He stated that fusion is counted as one tooth in the arch and in gemination the number is increased. This was called as two-tooth rule. He explained that if the resulting dental anomaly is counted as two teeth with the normal count present in the arch, it is fusion. Whereas the resulting dental anomaly is counted as two with the extra count present in the arch, it is termed as gemination or a fusion between normal and supernumerary teeth [3]. Morphological and anatomical variations are not uncommon finding; however, their simultaneous presentation is. This case presents the occurrence of fusion in a supernumerary tooth, which is a very rare finding. Yang et al., reported a geminated supernumerary tooth with two crowns and one root in the maxillary premolar region [3,4]. Fusion between supernumerary teeth and permanent teeth occurs less frequently than fusion between other types of teeth. Yuzuwa et al., reported incidence of 0.1% fusion with a supernumerary tooth [5]. Diagnostic tools such as radiographic examinations and an operating microscope played an important role in the diagnosis of this case. Endodontic treatment is usually difficult owing to complex anatomy, tooth position in the arch and difficulty in isolation. Strict adherence to biomechanical principles of root canal preparation provided successful treatment. Multidisciplinary treatment modalities have been suggested for fused teeth. The endodontic treatment depends on the thorough knowledge of the morphological variations of root canal anatomy [5]. Diagnostic tools such as cone-beam computed tomography and better visualization by using an operating microscope are all important aids in detecting communication. The occurrence of fusion between normal and supernumerary tooth is very rare but the clinician should be conscious of specific treatment needs, canal variations and importance of radiographic diagnosis. Clinicians should also consider the status of pulp of the supernumerary tooth and the tooth to which it is fused. Proper diagnosis and treatment planning of the fused teeth can ensure predictable and successful results.

A great number of abnormalities in form and number of teeth is congenital. These abnormalities are manifested in a decreased or increased number of teeth or just in changes of tooth form. The term of double teeth is a dental anomaly which a single-tooth germ tries to produces two teeth. A 16-year-old boy presented to our clinic to solve a dental anomaly of his teeth. His medical history was non-contributory. In the clinical and radiographic evaluation, it was determined that the double tooth had twinned crown and one single root. Fixed orthodontic treatment was planned for the patient. Regular dental controls might improve our ability to detect these anomalies and plan for the treatment at the appropriate time.

This report describes a 37-year-old man with 3 erupted supernumerary teeth in the maxilla and 6 impacted supernumerary teeth in the mandible, 2 of which were fused (a double tooth and a triple tooth).

Based on the analysis of arc tooth cylindrical gear forming principle and on the basis of existing processing methods, also combined with the principle of ordinary milling knife plate rotating, This paper puts forward an improved double-edged milling method of the Arc tooth cylindrical gear, which include two aspects: one is the double edged sword substance milling gear, double-point tool forming tooth at a time, with the module gear form point contact transmission vice; The second is to use double tooth gear milling tool, cutting tool a tooth, the gear machining and broadsword dish of double edge milling gear transmission line contact vice. It concluded that the improved processing technology is more advanced, the method of production is more efficient.

Objectives: The purpose of the present study was to evaluate mandibular talon cusps distribution from the compre - hensive literature search and proposal of new classification Material and Methods: The study was a review of articles published in the English language from January 1960 to December 2013. The PubMed/MEDLINE/Google Scholor databases were searched electronically using "talon cusp", "dens evaginatus", "anterior teeth", mandible, "primary dentition" and "permanent dentition" as search terms in various combinations. The citation lists from the included references were subsequently examined, and a hand search was also performed in an attempt to identify additional reports. The distribution, characteristics, common tooth type, associated dental anomaly and proposal of new classification have been included in final data analysis. Descriptive statistics were carried out using Chi square test (SPSS, version 17). Results: Overall 37 citations were retrieved from the literature where one was prevalence studies and rest were case reports among those two were duplication. Total 35 articles with 43 patients were reported on mandibular talon cusps. Males were predominantly affected than females ( p