Academic literature on the topic 'Maxillary first molar'

Primeiros molares superiores (1oMS) podem apresentar na sua raiz mésio-vestibular um segundo conduto (MV2) que é geralmente de pequena dimensão e grande variação anatômica. Os MV2 são de difícil visualização em radiografias convencionas (bidimensionais) o que pode ser causa importante de insucessos de tratamentos endodônticos. Este problema pode ser solucionado pelo uso de um método imaginológico mais sensível como a tomografia computadorizada por feixe cônico (TCFC). Com o objetivo de determinar, pela primeira vez na literatura, a prevalência e a morfologia do conduto MV2 numa população brasileira foram avaliadas 414 TCFC, de pequeno FOV (5 ou 8) e alta resolução tomadas para fins de diagnósticos num intervalo de 2 meses. Destas foram selecionadas as TCFCs de 186 mulheres e 101 homens, com idades entre 9 e 93 anos (média de 49,43 ± 16,76), que apresentavam ao menos um 1oMS, totalizando 362 dentes. Para avaliar a reprodutibilidade na detecção do conduto MV2 nas TCFC todas as imagens foram avaliadas por três examinadores diferentes e os dados foram comparados pelo teste Kappa. Obteve-se como resultado alta reprodutibilidade interobservadores (Kappa entre 0,79 e 0,88; p<0,0001). Assim sendo, os dados obtidos de apenas 1 dos examinadores foram avaliados estatisticamente por testes ANOVA, ou Kruskal Wallis e de Correlação de Pearson (p<=0,05). O conduto MV2 foi detectado em 68,23% dos 1osMS avaliados. A raiz mésiovestibular destes dentes apresentou predominantemente o Tipo II (38,12%) da classificação de Vertucci (1984). A presença do conduto MV2 foi significativamente maior em pacientes com idades menores (média de 45.04; p<0,01) que daqueles que não apresentaram o MV2 (média de 53.46). Não houve correlação entre a presença de conduto MV2 tanto com relação ao gênero (p=0,14), nem ao lado do 1oMS (p=0.53), quanto ao tamanho do FOV (p=0.09) da TCFC. Houve correlação negativa significativa (p=0.008) entre a classificação de Vertucci do MV2 e o tamanho do FOV da TCFC, ou seja, TCFC de FOV menor (FOV 5) encontraram MV2 com tipos maiores da classificação de Vertucci. Setenta e cinco pacientes apresentavam os 2 1osMS nas TCFCs, destes 58 pacientes (77,33%) apresentaram ou presença ou ausência do conduto MV2 simultaneamente em ambos lados. As idades dos pacientes que apresentaram o conduto MV2 nos dentes de ambos os lados (44; 58,66%) foram significativamente menores que daqueles que não apresentaram o conduto MV2 em nenhum dos lados (14; 18,66%) e também em somente um dos lados (17; 22,66%) (p<0,05). Concluiu-se que há alta prevalência do conduto MV2 na população examinada que ocorrem predominantemente em indivíduos jovens. Mais ainda, a detecção do MV2 independe do tamanho do FOV, porém TCFCs de FOV menor são mais sensíveis na análise de detalhes anatômicos destes condutos.<br>Upper first molars (UFM) may have on their mesiobuccal root a second canal (MB2), which is usually small and with large anatomical variation. The MB2s are difficult to detect in conventional radiographs (two-dimensional) and can be a major cause of failure of endodontic treatments. This problem could be circumvented by using a more sensitive imaginologic method as cone beam computed tomography (CBCT). In order to determine for the first time in the literature the prevalence and morphology of MB2 canal in a Brazilian population 414 CBCTs of small FOV (5 or 8) and high resolution taken for diagnostic purposes in a 2-month interval were evaluated. Of these, CBCTs of 186 women and 101 men, aged 9 to 93 years old (mean age 49.43 ± 16.76) who had at least one UFM were selected, totaling 362 teeth. To assess the reproducibility of the MB2 canal detection in CBTCs three different investigators evaluated all images and the data were compared with the Kappa\'s test. A high interobserver reproducibility (Kappa between 0.79 and 0.88; p <0.0001) was observed. Then, the data obtained from only one of the examiners were analyzed by ANOVA or Kruskal Wallis and Pearson\'s correlation (p <= 0.05). The MB2 canal was detected in 68.23% of the UFM examined. The mesiobuccal root of these teeth predominantely presented the Type II (38.12%) according to Vertucci\'s classification (1984). The presence of MB2 was similar in both genders female and male (p=0,14) and significantly higher in patients with younger ages (mean 45.04 years old, P <0.01) than in those who did not present the MB2 (average 53.46 years old). There was no correlation between the presences of MB2 canal in relation to the side of the UFM (p = 0:53), as well as to the size of the FOV (p = 0:09). There was a significant negative correlation (p = 0.008) between the Vertucci\'s classification of MB2 and the size of FOV (i.e. the smaller FOV detected MB2 with higher Vertucci\'s types). Seventy-five patients had 2 UFM in the CBTCs, from these 58 patients (77.33%) showed the presence or absence or MB2 canal simultaneously on both sides. The ages of the patients with MB2 in teeth on both sides (44; 58.66%) were significantly smaller than those of patients who did not presente the MB2 on either side (14; 18.66%) or in only side (17; 22.66%) (p <0.05). It was concluded that there is high prevalence of MB2 in the examined population, which occurred predominantly in young individuals. Moreover, the detection of MB2 does not dependent on the size of FOV but CBTCs of smaller FOV are more sensitive in the analysis of anatomical details of these canals.

碩士<br>長庚大學<br>顱顏口腔醫學研究所<br>92<br>Abstract The purpose of this study was to evaluate the space changes after premature loss of the maxillary first deciduous molar during the eruption of first permanent molar and use established model to investigate the long-term space changes after unilateral premature loss of the maxillary first deciduous molar. Nineteen children with unilateral premature loss of the maxillary first deciduous molar were selected from the children’s dental clinic for this study. The age ranged from 4.1 to 7.1 years with an average of 5.9 years. Maxillary study casts were made from alginate impression for each initial examination and follow-up examination six months later. Six measurements including D＋E space, arch width, arch length, arch perimeter, intercanine width and intercanine depth were tested for comparisons between the initial examination and the follow-up examination six months later. The D＋E space of intact deciduous molars served as a control. The results showed that the D＋E space on the extraction was significantly shorter in the group with the follow-up examination six months later as compared to that group with the initial examination (p<0.01). The arch length was significantly shorter in the group with the follow-up examination six months later as compared to that group with the initial examination the follow-up examination six months later (p<0.01). The intercanine width after the follow-up examination six months later was significantly wider than the initial examination (p<0.01). However, the absence of significant differences was found on arch width, arch perimeter and intercanine depth between the initial examination and the follow-up examination six months later (p>0.05). It is concluded that early space changes after premature loss of the maxillary first deciduous molar during the eruption of first permanent molar are mostly distal shift of the primary cuspid and maxillary permanent anterior incisors.

碩士<br>國立臺北科技大學<br>製造科技研究所<br>97<br>The aims of this study are to establish a three-dimensional model for porcelain fused to metal (PFM) of the maxillary first molar based on Digital Imaging and Communications in Medicine (DICOM) data from computed tomography (CT) scanning, and to analyze the stress distribution and displacement of the maxillary first molar by using the finite element method. According to the concept of reverse engineering, the CT DICOM data were input into Mimics software to build a preliminary 3D model. After loading the preliminary model into the Freeform software, an enhanced model identified by the finite element analysis (FEA) software was created, which consisted of porcelain crown, metal crown, dentin, pulp, periodontal membrane, cortical bone and cancellous bone. Finally, by using the software－COSMOS/Works, we simulated the chew of teeth and analyzed the stress distribution and displacement of the maxillary first molar with PFM in different materials (i.e., Au-Pd allay, PFM,Ni-Cr alloy and Ti-alloy) under perpendicularity loading and oblique loading, respectively. We successfully combine the CT scanning images and Mimics and FreeForm software to construct a three-dimensional finite element model for PFM of the maxillary first molar. The model with high degree of similarity in geometry and mechanics can be applied to the natural examples and suggested to provide useful information for further biomechanical researches as well.

碩士<br>國立陽明大學<br>牙醫學系<br>105<br>Statement of problem Traditionally, if we want to restore the tooth with sub-gingival defect, there are some problems need to face, like remove too much sound tooth structure, hard to take impression, remove excessive cement difficulty. Recently, deep margin elevation technique become the solution for those problems. However, no sufficient evidences and long time clinical follow up to support the prognosis of deep margin elevation. Only some in vitro studies focus on margin integrity of interface between different materials, we could not understand the stress distribution of those interfaces. Purpose Using the finite element method to observe the stress distribution between interfaces of human upper first molar with deep margin elevation technique from different depth of distal sub-gingival defect and restored by ceramic onlay, and compared to a model only restored by onlay without deep margin elevation technique. Material and methods Combined micro computed tomography and three dimensional computer-aided design software to build up a human upper first molar model, then make four different models: sub-gingival 1mm, 2mm and 3mm distal defect, then build up to supra-gingival 1mm, each of those three models contains 5 parts: onlay, cement layer, composite resin, enamel and dentin. And one model which with distal sub-gingival defect restored by onlay directly, contains four parts: onlay, cement layer, enamel and dentin. Loading force with 800N and 300N to simulate the biting force of clenching and chewing, then observing the stress distribution of the interface between composite resin and dentin. Result Comparing sub-gingival 2mm models, with or without deep margin elevation technique. The model with deep margin elevation reduces the von mise’s stress and maximum shear stress of the interface between composite resin and dentin. Moreover, both two stress increased over distal side of the interface, especially in the model with sub-gingival 3mm defect while clenching, the maximum shear stress is equal to the bonding strength of modern bonding systems. Conclusion Within the limitation of finite element analysis, the following conclusion can be drawn: (1) when the defect within 2mm, using deep margin elevation technique can reduce the stress concentration between composite resin and dentin, (2) if the defect approach to 3mm, deep margin elevation technique is not recommended, (3) deep margin elevation technique is also not recommended for those patients with clenching.

Purpose: To retrospectively assess the incidence and predictive factors for self-correction of ectopic eruption of maxillary permanent first molars (EE) and the prevailing attitudes amongst surveyed specialists regarding intervention in cases of EE. Methods: Charts of patients diagnosed with EE were assessed for predictive clinical and radiographic factors. An online survey was sent to pediatric dentists and orthodontists. Results: The rate of self-correction was 71%. One third of self-corrections occurred after age 9. Increased amount of impaction (r(43)=0.59, p<.001) and degree of resorption (r(57)=0.41, p=.001) were positively correlated with irreversibility. Orthodontists estimated the spontaneous self-correction rate to be lower (t(1178)=19.2, p<.001) than pediatric dentists. Conclusions: One third of self-corrections occurred after 9 years of age and delaying treatment of EE may be a viable option when uncertain of the outcome. Reliable predictive factors of irreversibility of EE were identified. Differences exist between pediatric dentists and orthodontists regarding management of EE.

O conhecimento da morfologia dos canais radiculares e suas frequentes variações é um requisito fundamental para o tratamento endodôntico. É geralmente admitido que a principal causa de falha do tratamento endodôntico é a incapacidade de reconhecer e consequentemente tratar adequadamente todos os canais radiculares do dente. A raiz mesiovestibular do primeiro molar maxilar tem gerado mais pesquisa e investigação do que qualquer outra raiz. Entretanto, há uma falta de uniformidade na literatura relativamente à abordagem do segundo canal mesiovestibular que está presente em 73% dos casos. A falta de tratamento do segundo canal mesiovestibular reduz o prognóstico para o tratamento endodôntico a longo prazo. Assim é frequentemente esquecido durante os procedimentos de rotina pelo facto de ser difícil localizá-lo sem ajuda. Esta dissertação tem como objetivo principal efetuar uma revisão da literatura científica existente sobre os dispositivos de localização do segundo canal mesiovestibular, começando pela radiologia convencional e em seguida pela imagem tridimensional, que parece ser uma ferramenta confiável para explorar a anatomia dos canais radiculares, assim como os métodos e técnicas clinicas que facilitam a sua localização durante a prática. Desde modo, pode concluir-se que existem vários métodos de localização do segundo canal mesiovestibular que o Médico Dentista deve conhecer para executar o tratamento endodôntico do primeiro molar maxilar nas melhores condições possíveis, a fim de evitar a re-contaminação bacteriana e assim o fracasso do tratamento.<br>Knowledge of root canal morphology and its frequent variations is a fundamental requirement for endodontic treatment. It is generally accepted that the main cause of failure of endodontic treatment is the inability to recognize and consequently adequately treat all root canals of the tooth. The mesiobuccal root of the first maxillary molar has generated more research and investigation than any other root. However, there is a lack of uniformity in the literature regarding the approach to the second mesiobuccal canal, wich is presente in 73% of cases. The lack of treatment of the second mesiobuccal canal reduces the prognosis for longterm endodontic treatment. It is often forgotten during routine procedures because it is difficult to locate it without help. The main objective of this dissertation is to review the existing scientific literature on the localization devices of the second mesiobuccal canal, starting with conventional radiology and then with three-dimensional imaging, which seems to be a reliable tool for exploring the anatomy of root canals, as well as the clinical methods and techniques that facilitate their location during practice. Therefore, it can be concluded that there are several methods of locating the second mesiobuccal canal that the dental surgeon should know to execute the endodontic treatment of the first maxillary molar in the best possible conditions, in order to avoid bacterial re-contamination and thus treatment failure.

碩士<br>國立臺灣大學<br>臨床牙醫學研究所<br>104<br>Objectives The aim of this study was to use cone-beam computed tomography (CBCT) to analyze the morphology and similarity / symmetry of root canal systems in the maxillary first and second molars in Taiwanese. Materials and methods A total of 519 patients in the dental department of NTUH from January 2014 to December 2014 were enrolled. Overall, CBCT images of 1741 maxillary molars were blindly examined by two endodontists to analyze the correlation of root canal systems between the first molars and second molars as well as the bilateral first or second molars. Results The most common type in Taiwanese maxillary first molars is 3R4C (3 roots/4 canals), whereas in maxillary second molars is 3R3C.The symmetry of root canal system in bilateral maxillary first and second molars were found in 87.36% and 79.85%,respectively. The similarities of root canal system in adjacent maxillary first and second molars were 53.07% in right side and 52.58% in left side. The concurrence of MB2 canal in bilateral maxillary first molars is 77.8%, whereas is 35.97% in maxillary second molars. In the 110 patients MB2 canal in bilateral maxillary second molars, the chances of bilateral MB2 canals in their maxillary first molar is almost 100%. Conclusions Maxillary first molars have higher prevalence of 3R4C root canal system than maxillary second molars. The symmetry and similarity were higher in bilateral maxillary homonym molars than in adjacent maxillary molars. These information and assessing CBCT images in advance provide a totally understandings of the whole root canal system, and improve the endodontic treatment outcome efficiently.

Methods: Two hundred CBCT images with bilateral permanent maxillary first molar were carefully examined by two dentists. Information obtained was on the number and morphology of roots per tooth, the number of canals per root, the root canal configuration in each root using Vertucci’s classification, the relationship between MB2, tooth position and different age groups, and the frequency of C-shaped root canals were determined. Results: The prevalence of three separate roots was 91%. The frequency of three roots where two of them were fused was 8%. Two fused roots were observed in 0.5% of teeth and three fused roots were seen in 0.5% teeth. Regarding the mesiobuccal roots (MBR), the most frequent was Vertucci type IV root canal configuration (42.75%), then type I ( 39.5%),Type II (15%), type III (1.25%); type V (0.75%), and type VI (0, 75%). The occurrence of bilateral MB2 was 65, 75% while the unilateral occurrence of MB2 was 34, 24%.There was no significant difference between 5 age groups (p=0.759, and tooth position p=9977 in regard of presence of MB2. (Distobuccal roots (DBR) displayed a type I configuration in 99.5% of teeth, with only 0.5% of teeth displaying a type IV canal configuration. All palatal roots (PR) had type I canal configuration. No C shaped canals were observed in the sample of 400 permanent maxillary first molars teeth. Conclusion: Cone-beam computed tomography provides valuable information about the anatomy of root and canal morphology which may facilitate root canal therapy.<br>MT2017