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Concept: Molar

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The aim of the study was to test the hypothesis that the gene defect causing congenital absence of maxillary lateral incisors also causes narrowing of the dentition. A total of 81 patients with one or two congenitally missing lateral incisors were retrieved; 52 (64.2 per cent) patients presented bilateral agenesis, whereas 29 (35.8 per cent) had unilateral agenesis. The control group consisted of 90 consecutively treated patients. The largest mesiodistal crown dimension for all teeth, except for the maxillary second and third molars, was measured on plaster casts using a digital caliper to the nearest 10th of a millimetre. Statistical testing was performed using the analysis of variance model (P < 0.05) to test for differences in the mesiodistal dimension between the sample and the control group. Significance has been assessed using a P-value threshold level of 5 per cent. Agenesis of maxillary lateral incisors was found to be a significant predictor of tooth size. Patients who were missing maxillary lateral incisors had smaller teeth compared to control subjects, except for the maxillary right and left first molars. This finding was true for both unilateral and bilateral lateral incisor agenesis. Interaction between maxillary lateral incisor agenesis and gender was not significant. Patients with congenitally missing lateral incisors have narrower teeth than patients without any dental anomalies, except for maxillary first molars. A higher prevalence of microdontic contralateral incisors was found in patients with unilateral agenesis with respect to the control group.

Concepts: Teeth, Analysis of variance, Molar, Incisor, Maxillary central incisor, Canine tooth, Maxillary lateral incisor, Mandibular lateral incisor

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Joubert syndrome (JBTS) and related disorders are defined by cerebellar malformation (molar tooth sign), together with neurological symptoms of variable expressivity. The ciliary basis of Joubert syndrome related disorders frequently extends the phenotype to tissues such as the eye, kidney, skeleton and craniofacial structures.

Concepts: Central nervous system, Brain, Neurology, Syndromes, Eye, Teeth, Molar

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Abstract Objective. To examine whether the rapid increase in the availability of cone-beam computed tomography (CBCT) has changed the number of inferior alveolar nerve (IAN) injuries related to the removal of mandibular third molars in Finland. The hypothesis was that the number of nerve injuries should diminish due to better imaging methods. Materials and methods. The number of CBCT devices, the annual number of CBCT examinations and the number of permanent IAN injuries occurring between 1997 and 2007 were analyzed. The data was collected from three national registers: the Radiation and Nuclear Safety Authority, the Social Insurance Institution and the Patient Insurance Centre. A detailed analysis was made from the cases of permanent IAN injuries. Results. The first CBCT device was registered in 2002 and the cumulative number of these devices in 2009 was 22. There was an increase from 555 to 3160 in the number of annual CBCT examinations during the period 2004-2009. The total number of permanent IAN injuries during the years 1997-2007 was 129 and remained stable throughout the period (regression analysis, p = 0.974, r (2) = 0.01). Conclusions. Contrary to this hypothesis, the availability of CBCT devices has had no significant influence on the number of IAN injuries related to mandibular third molar removals in Finland. More education should be given to optimize the use of CBCT to cover difficult cases that may give rise to complications.

Concepts: Regression analysis, Horse, Teeth, Molar, Examination, Nuclear safety, Mandibular canal, Mandibular third molar

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International Journal of Paediatric Dentistry 2013; 23: 145-152 Background.  Alternatives to vital pulpotomy treatment in primary teeth are being sought because of the high formaldehyde content of traditional formocresol (FC) pulpotomy medicaments. Aim.  The aim was to compare the clinical and radiographic success of vital pulpotomy treatment in primary molars using 3% sodium hypochlorite (NaOCl) versus a 1 : 5 dilution of Buckley’s FC. Design.  Pulpotomies were performed in primary molars of healthy children between 3 and 10 years old. Sixty-five primary teeth were randomized into two groups that were evaluated for treatment outcomes. Following treatment, the pulp chamber was filled with zinc oxide eugenol (ZnOE) and restored with a stainless steel crown cemented with glass ionomer cement. Clinical and radiographic outcomes were recorded at 6 and 12 months. Results.  The control (FC) and experimental (NaOCl) groups demonstrated 100% clinical success at 6 and 12 months. The NaOCl group had 86% (19/22) radiographic success at 6 months and 80% (12/15) at 12 months. The FC group had 84% (21/25) radiographic success at 6 months and 90% (9/10) at 12 months. No significant differences were found in the radiographic outcomes between the two groups at 6 and 12 months (Fisher’s exact test; P = 0.574 and P = 0.468, respectively). Conclusion.  NaOCl demonstrated clinical and radiographic success comparable to FC.

Concepts: Horse, Chlorine, Teeth, Molar, Fisher's exact test, Exact test, Canine tooth, Zinc oxide eugenol

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Abstract Objective: To compare the root development and the growth rate of the mandibular third molar (M3 inf) in individuals where the M3 inf erupted vs individuals exhibiting M3 inf impaction. Materials and Methods: Serial standardized intraoral radiographs (Eggen technique) were taken annually of the mandibular third molar region from 132 subjects (71 male and 61 female) from 15 to 20 years of age. Based on the films, 264 lower third molars were classified into an eruption and an impaction group. Root development was recorded according to a quantitative method described by Haavikko (1970), and the eruption status was analyzed using logistic regression. Results: In total, 155 (59%) of the M3 inf erupted, and 109 (41%) were impacted at age 20. In 44 (33%) patients both M3 inf were impacted, in 21 (16%) patients one tooth was erupted and the contralateral tooth impacted, and in 67 (51%) patients both M3 inf were erupted. The more mature a tooth was at age 15, the higher was the probability of eruption (odds ratio: 3.89, P < .001). The growth rate of the root development stage was statistically significantly associated with the probability of eruption (odds ratio: 10.50, P  =  .041). Conclusions: Delayed mandibular third molar root development is associated with impaction. Radiographs taken at age 15 may predict the risk of impaction and thereby guide decision making for the orthodontist or the oral and maxillofacial surgeon.

Concepts: Logit, Decision theory, Teeth, Molar, Oral and maxillofacial surgery, Wisdom tooth, Mandibular third molar

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Pitheciines (Pithecia, Chiropotes, and Cacajao) are a specialized clade of Neotropical seed predators that exhibit postcanine teeth with low and rounded cusps and highly crenulated occlusal surface enamel. Data on feeding ecology show that Pithecia consumes proportionally more leaves than other pitheciine species, and comparative studies demonstrate its greater molar relief and relative shearing potential. However, data on pitheciine food mechanics show that Pithecia masticates seeds with greater crushing resistance than those preferred by Chiropotes. This variation predicts an opposing morphology characterized by low and more rounded occlusal surfaces in Pithecia. We build on previous research using new methods for molar surface shape quantification by examining pitheciine second molar shearing crest length, occlusal relief, surface complexity, and surface curvature relative to nonseed specializing platyrrhines and within the context of the observed interspecific variation in pitheciine feeding ecology. Consistent with the previous analyses, our findings demonstrate that pitheciine molars exhibit low shearing, relief, and curvature compared with nonseed predators, independent of phylogeny. Pitheciines also exhibit highly “complex” occlusal topography that promotes the efficient breakdown of tough seed tissues. Overall, Pithecia, Chiropotes, and Cacajao share a similar topographic pattern, suggesting adaptation to foods with similar structural and/or mechanical properties. However, Cacajao differs in surface complexity, which reflects some variation in its feeding ecology. Contrary to the predictions, Pithecia and Chiropotes do not differ in any of the topographic variables examined. The range of demands imposed on the postcanine teeth of Pithecia might therefore select for an average topography, one that converges on that of Chiropotes. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.

Concepts: Teeth, Molar, Pitheciidae, Pitheciinae, Saki monkey

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To estimate the prevalence of preoperative periodontal defects and analyze 12-month spontaneous healing on the distal aspect of the mandibular second molar (M2) after impacted mandibular third molar (M3) extraction.

Concepts: Teeth, Molar, Wisdom tooth, Mandibular third molar

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SUMMARYTo quantitatively evaluate on lateral cephalograms horizontal, vertical, and angular changes in the position of the maxillary first molar based on the presence and absence of erupted maxillary second molars when it is distalized with the XBow appliance.In this retrospective study, a total of 102 consecutively treated cases were assessed. Lateral cephalograms were obtained at the start and after completion of active treatment with the XBow appliance. In one group of patients, distal movement of the maxillary first molars was performed before the eruption of maxillary second molars; in the other group of patients, both first and second maxillary molars were simultaneously moved distally. All cephalograms were superimposed on palatal plane using the method of best-fit. In order to compare the mean horizontal, vertical, and angular changes in molar position between the treatment groups and gender, a multivariate analysis of covariance (MANCOVA) was performed with the pre-treatment class II severity used as a covariate. Regression analysis was also performed to further explore any possible relationships between the predictor variables and the quantity and quality of distalization.A MANCOVA revealed that the eruption stage of the maxillary second molar did not have a significant effect on the change in position of the maxillary first molar after treatment with a XBow appliance.When distalizing maxillary first molars with a XBow appliance, there is no difference in the amount of distalization in patients with erupted and unerupted maxillary second molars.

Concepts: Teeth, Posterior superior alveolar artery, Molar

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It has been suggested that third molars increase mandibular fragility because they do not contribute to its strength. For ethical reasons, a human study design that would permit the elucidation of this interference is not possible. This study evaluated the impact of the presence of erupted third molars on the mandibular angle of resistance when submitted to trauma. A three-dimensional (3D) mandibular model was obtained through finite element methodology using computed tomography (CT) with the geometry and mechanical properties to reproduce a normal mandibular structure. Human mandibles with no, one or two erupted third molars were evaluated. Whenever the third molar was present there was a greater concentration of tensions around the cervical part of its alveolus. Approximated Von Mises equivalent stress of the third molar region was 107.035MPa in the mandible with teeth and 64.6948MPa in the mandible without teeth. In the condylar region it was 151.65MPa when the third molar was present and 184.496MPa when it was absent. The digital models created proved that the mandibular angle becomes more fragile in the presence of third molars. When they are absent the energy concentrates on the lateral e posterior aspect of the condylar neck.

Concepts: Concentration, Mandible, Model, Teeth, Molar, Temporomandibular joint, The Fragile, Ludwig von Mises

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PURPOSE: To assess the relationship between the presence or absence of visible third molars and outcomes for periodontal inflammatory disease. METHODS: Obstetric subjects, at enrollment in an institutional review board-approved, multisite study, Maternal Oral Therapy to Reduce Obstetric Risk (N = 1,798), were divided into 2 groups, those with no visible third molars (n = 692) and those with at least 1 visible third molar (n = 1,106), the predictor variables for this study. The principal outcome variables were the patient-level periodontal status of the first/second molars: mean periodontal probing depths, mean attachment levels, and mean extent scores. Periodontal disease severity also was assessed by criteria from the Oral Conditions and Pregnancy trial and the Centers for Disease Control and Prevention/American Academy of Periodontology. Outcomes according to the presence or absence of third molars were compared with χ(2) statistics and multivariable analyses. Significance was set at P < .05. RESULTS: Significantly more subjects had at least 1 third molar (62%) as compared with subjects with no visible third molar (38%) (P < .01). Ethnic characteristics of the 2 groups were similar. Overall, more subjects were white (61%), with most identifying their ethnicity as Latino. African-American subjects were well represented (37%). Subjects with a visible third molar were more likely to be significantly older, to be receiving medical assistance, and to have used tobacco before pregnancy. If subjects had at least 1 visible third molar, the mean first/second molar probing depths, attachment levels, and scores for bleeding on probing were significantly greater even after adjustment for covariates. On the basis of either Oral Conditions and Pregnancy criteria or Centers for Disease Control and Prevention/American Academy of Periodontology criteria, subjects were significantly more likely to have moderate or severe periodontal disease if a third molar was detected. CONCLUSION: If at least 1 visible third molar was detected in subjects in the Maternal Oral Therapy to Reduce Obstetric Risk study at enrollment as compared with no detected third molars, periodontal outcomes were significantly worse.

Concepts: Medicine, Periodontology, Gingiva, Ethnic group, Teeth, Molar, Periodontitis, Periodontal disease