Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 9 Articles
The aim of this study was to make a comparison of the compressive properties of the goat temporomandibular joint (TMJ) disc to\nthe mandibular condylar cartilage (MCC) and to explore the transversely isotropic biphasic model. Samples taken mediolaterally\nfrom three regions of the TMJ disc and MCC were tested in unconfined compression at strain levels ranging from 10% to 50%\nand then assessed for biochemical content. The results indicated that the TMJ disc exhibits a significantly greater tangent modulus\nthan the MCC from 20% to 50% strain with values ranging from 729 �± 267 to 2413 �± 406 kPa and 363 �± 169 to 1677 �± 538 kPa,\nrespectively (P < .05). The collagen content of the TMJ disc was significantly greater than the MCC, while the opposite held for\nthe glycosaminoglycan (GAG) and DNA content. The results emphasize fundamental differences between the articulating tissues\nof the TMJ....
Objectives. The purpose of this analytical study was to examine and critique the engineering foundations of commonly accepted\nbiomechanical principles of mandible fracture repair. Materials and Methods. Basic principles of static equilibrium were applied\nto intact and plated mandibles, but instead of the traditional lever forces, the mandibles were subjected to more realistic occlusal\nforces. Results. These loading conditions produced stress distributions within the intact mandible that were very different and more\ncomplex than the customary lever-based gradient. The analyses also demonstrated the entirely different mechanical environments\nwithin intact and plated mandibles. Conclusions. Because the loading and geometry of the lever-idealized mandible is incomplete,\nthe associated widely accepted bone stress distribution (tension on top and compression on the bottom) should not be assumed.\nFurthermore, the stress gradients within the bone of an intact mandible should not be extrapolated to the mechanical environment\nwithin the plated regions of a fractured mandible....
Background: We aimed to assess the oral health status and risk factors for dental caries and periodontal disease\r\namong Sudanese adults resident in Khartoum State. To date, this information was not available to health policy\r\nplanners in Sudan.\r\nMethods: A descriptive population-based survey of Sudanese adults aged = 16 years was conducted. After\r\nstratified sampling, 1,888 adult patients from public dental hospitals and dental health centres scattered across\r\nKhartoum State, including different ethnic groups present in Sudan, were examined in 2009-10. Data were\r\ncollected using patient interviews and clinical examinations. Dental status was recorded using the DMFT index,\r\ncommunity periodontal index (CPI), and a validated tooth wear index.\r\nResults: Caries prevalence was high, with 87.7% of teeth examined having untreated decay. Periodontal disease\r\nincreased in extent and severity with age. For 25.8% of adults, tooth wear was mild; 8.7% had moderate and 1%\r\nsevere toothwear. Multivariate analysis revealed that decay was less prevalent in older age groups but more\r\nprevalent in southern tribes and frequent problem based attenders; western tribes and people with dry mouths\r\nwho presented with less than18 sound, untreated natural teeth (SUNT). Older age groups were more likely to\r\npresent with tooth wear; increasing age and gender were associated with having periodontal pocketing = 4 mm.\r\nConclusions: The prevalence of untreated caries and periodontal disease was high in this population. There\r\nappear to be some barriers to restorative dental care, with frequent use of dental extractions to treat caries and\r\nlimited use of restorative dentistry. Implementation of population-based strategies tailored to the circumstances of\r\nSudanese population is important to improve oral health status in Sudan....
Background: Artifacts caused by dental restorations, such as dental crowns, dental fillings and orthodontic appliances, are a\r\ncommon problem in MRI and CT scans of the head and neck. The aim of this in-vitro study was to identify and evaluate the\r\nartifacts produced by different dental restoration materials in CT and MRI images.\r\nMethods: Test samples of 44 materials (Metal and Non-Metal) commonly used in dental restorations were fabricated and\r\nembedded with reference specimens in gelatin moulds. MRI imaging of 1.5T and CT scan were performed on the samples\r\nand evaluated in two dimensions. Artifact size and distortions were measured using a digital image analysis software.\r\nResults: In MRI, 13 out of 44 materials produced artifacts, while in CT 41 out of 44 materials showed artifacts. Artifacts\r\nproduced in both MRI and CT images were categorized according to the size of the artifact.\r\nSignificance: Metal based restoration materials had strong influence on CT and less artifacts in MRI images. Rare earth\r\nelements such as Ytterbium trifluoride found in composites caused artifacts in both MRI and CT. Recognizing these findings\r\nwould help dental materials manufacturers and developers to produce materials which can cause less artifacts in MRI and\r\nCT images....
This study performed barcoded multiplex pyrosequencing with a 454 FLX instrument to compare the microbiota of dental\nroot canal infections associated with acute (symptomatic) or chronic (asymptomatic) apical periodontitis. Analysis of\nsamples from 9 acute abscesses and 8 chronic infections yielded partial 16S rRNA gene sequences that were taxonomically\nclassified into 916 bacterial species-level operational taxonomic units (OTUs) (at 3% divergence) belonging to 67 genera and\n13 phyla. The most abundant phyla in acute infections were Firmicutes (52%), Fusobacteria (17%) and Bacteroidetes (13%),\nwhile in chronic infections the dominant were Firmicutes (59%), Bacteroidetes (14%) and Actinobacteria (10%). Members of\nFusobacteria were much more prevalent in acute (89%) than in chronic cases (50%). The most abundant/prevalent genera in\nacute infections were Fusobacterium and Parvimonas. Twenty genera were exclusively detected in acute infections and 18 in\nchronic infections. Only 18% (n = 165) of the OTUs at 3% divergence were shared by acute and chronic infections. Diversity\nand richness estimators revealed that acute infections were significantly more diverse than chronic infections. Although a\nhigh interindividual variation in bacterial communities was observed, many samples tended to group together according to\nthe type of infection (acute or chronic). This study is one of the most comprehensive in-deep comparisons of the microbiota\nassociated with acute and chronic dental root canal infections and highlights the role of diverse polymicrobial communities\nas the unit of pathogenicity in acute infections. The overall diversity of endodontic infections as revealed by the\npyrosequencing technique was much higher than previously reported for endodontic infections....
Background: Studies examining human and nonhuman primates have supported the hypothesis that the recent increase in\r\nthe occurrence of misalignment of teeth and/or incorrect relation of dental arches, named dental malocclusion, is mainly\r\nattributed to the availability of a more processed diet and the reduced need for powerful masticatory action. For the first\r\ntime on live human populations, genetic and tooth wear influences on occlusal variation were examined in a split\r\nindigenous population. The Arara-Iriri people are descendants of a single couple expelled from a larger village. In the\r\nresultant village, expansion occurred through the mating of close relatives, resulting in marked genetic cohesion with\r\nsubstantial genetic differences.\r\nMethodology/Principal Findings: Dental malocclusion, tooth wear and inbreeding coefficient were evaluated. The sample\r\nexamined was composed of 176 individuals from both villages. Prevalence Ratio and descriptive differences in the\r\noutcomes frequency for each developmental stage of the dentition were considered. Statistical differences between the\r\nvillages were examined using the chi-square test or Fisher�s exact statistic. Tooth wear and the inbreeding coefficient (F)\r\nbetween the villages was tested with Mann-Whitney statistics. All the statistics were performed using two-tailed distribution\r\nat p#0.05. The coefficient inbreeding (F) confirmed the frequent incestuous unions among the Arara-Iriri indigenous group.\r\nDespite the tooth wear similarities, we found a striking difference in occlusal patterns between the two Arara villages. In the\r\noriginal village, dental malocclusion was present in about one third of the population; whilst in the resultant village, the\r\noccurrence was almost doubled. Furthermore, the morphological characteristics of malocclusion were strongly different\r\nbetween the groups.\r\nConclusions/Significance: Our findings downplay the widespread influence of tooth wear, a direct evidence of what an\r\nindividual ate in the past, on occlusal variation of living human populations. They also suggest that genetics plays the most\r\nimportant role on dental malocclusion etiology....
Background: Patients scheduled for bariatric surgery (BS) are encouraged to chew slowly in order to optimise the digestion\r\nprocess. The influence of dental status on patientsââ?¬â?¢ ability to comply with advice on chewing behaviour is poorly\r\ndocumented. This study aims to compare modifications of chewing function before and after BS in three groups of obese\r\npatients differing in dental status.\r\nMethod and Findings: A cohort of 46 obese women provided three groups: FD group: fully dentate (7ââ?¬â??10 functional dental\r\nunits [FU]); PD group: partially dentate (4ââ?¬â??6 FU) without partial dentures; DW group: partial and complete denture wearers.\r\nChewing time (CT), number of chewing cycles (CC), and chewing frequency (CF) were measured before and after surgery\r\nduring mastication of standardised samples of raw carrot, peanuts, banana, apple and jelly. The median particle-size\r\ndistribution (D50) of the pre-swallowed bolus was also evaluated for peanut and carrot. Before surgery, the PD and DW\r\ngroups exhibited greater mean CCs and CTs than the FD group (SNK p,0.05) and produced a bolus with higher\r\ngranulometry (SNK, p,0.05) than the FD group. After surgery, CT and CC increased for all groups and for all foods, but not\r\nstatistically significant for jelly. The resulting changes in bolus granulometry observed depended on both food and dental\r\nstatus. The granulometry of carrot bolus remained as fine or as coarse in FD and DW groups respectively as it was before\r\nsurgery while it was significantly decreased in the PD group (Studentââ?¬â?¢s test, p,0.001).\r\nConclusions: After bariatric surgery, all the obese patients, regardless of dental status modified their chewing kinematics.\r\nThe effects of this chewing behaviour on bolus granulometry depended on dental status and type of food. Further studies\r\nare needed to understand better the impact of dental status on feeding behaviour and nutrition in patients with obesity....
Background: Dental caries is the result of a complex interplay among environmental, behavioral, and genetic\r\nfactors, with distinct patterns of decay likely due to specific etiologies. Therefore, global measures of decay, such as\r\nthe DMFS index, may not be optimal for identifying risk factors that manifest as specific decay patterns, especially\r\nif the risk factors such as genetic susceptibility loci have small individual effects. We used two methods to extract\r\npatterns of decay from surface-level caries data in order to generate novel phenotypes with which to explore the\r\ngenetic regulation of caries.\r\nMethods: The 128 tooth surfaces of the permanent dentition were scored as carious or not by intra-oral\r\nexamination for 1,068 participants aged 18 to 75 years from 664 biological families. Principal components analysis\r\n(PCA) and factor analysis (FA), two methods of identifying underlying patterns without a priori surface\r\nclassifications, were applied to our data.\r\nResults: The three strongest caries patterns identified by PCA recaptured variation represented by DMFS index\r\n(correlation, r = 0.97), pit and fissure surface caries (r = 0.95), and smooth surface caries (r = 0.89). However,\r\ntogether, these three patterns explained only 37% of the variability in the data, indicating that a priori caries\r\nmeasures are insufficient for fully quantifying caries variation. In comparison, the first pattern identified by FA was\r\nstrongly correlated with pit and fissure surface caries (r = 0.81), but other identified patterns, including a second\r\npattern representing caries of the maxillary incisors, were not representative of any previously defined caries\r\nindices. Some patterns identified by PCA and FA were heritable (h2 = 30-65%, p = 0.043-0.006), whereas other\r\npatterns were not, indicating both genetic and non-genetic etiologies of individual decay patterns.\r\nConclusions: This study demonstrates the use of decay patterns as novel phenotypes to assist in understanding\r\nthe multifactorial nature of dental caries....
Multiple Osteochondromas (MO; previously known as multiple hereditary exostosis) is an autosomal dominant genetic\ncondition that is characterized by the formation of cartilaginous bone tumours (osteochondromas) at multiple sites in the\nskeleton, secondary bursa formation and impingement of nerves, tendons and vessels, bone curving, and short stature. MO\nis also known to be associated with arthritis, general pain, scarring and occasional malignant transformation of\nosteochondroma into secondary peripheral chondrosarcoma. MO patients present additional complains but the relevance\nof those in relation to the syndromal background needs validation. Mutations in two enzymes that are required during\nheparan sulphate synthesis (EXT1 or EXT2) are known to cause MO. Previously, we have used zebrafish which harbour\nmutations in ext2 as a model for MO and shown that ext22/2 fish have skeletal defects that resemble those seen in\nosteochondromas. Here we analyse dental defects present in ext22/2 fish. Histological analysis reveals that ext22/2 fish have\nvery severe defects associated with the formation and the morphology of teeth. At 5 days post fertilization 100% of ext22/2\nfish have a single tooth at the end of the 5th pharyngeal arch, whereas wild-type fish develop three teeth, located in the\nmiddle of the pharyngeal arch. ext22/2 teeth have abnormal morphology (they were shorter and thicker than in the WT)\nand patchy ossification at the tooth base. Deformities such as split crowns and enamel lesions were found in 20% of ext2+/2\nadults. The tooth morphology in ext22/2 was partially rescued by FGF8 administered locally (bead implants). Our findings\nfrom zebrafish model were validated in a dental survey that was conducted with assistance of the MHE Research\nFoundation. The presence of the malformed and/or displaced teeth with abnormal enamel was declared by half of the\nrespondents indicating that MO might indeed be also associated with dental problems....
Loading....