Thin-plate spline analysis of arch form in a Southern European population with an ideal natural occlusion.
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The purpose of the present study was to identify the mean configuration of the clinical arch form in a sample of Southern European subjects with ideal natural occlusion by means of Procrustes analysis, and to compare the identified configuration with 10 commercially produced arch forms by means of thin-plate spline (TPS) analysis. The sample comprised the study casts of 50 subjects (26 males and 24 females). The mean age of the sample was 26 years +/- 4 years. All subjects were young Caucasian adults of Southern European ancestry, and presented with an ideal natural occlusion. The three-dimensional (3D) co-ordinates of all dental points (facial axis points) were digitized using a 3D electromagnetic digitizer. The morphometric technique of TPS analysis with permutation tests was used to compare the configurations of landmarks in the various specimens. No sexual dimorphism was found for either upper or lower arch forms when the shape of the arches was assessed independently from size. The commercially available arch form that showed the least, though statistically significant, shape difference with respect to the average calculated configuration was the Brader arch form. (+info)
Regulation of mammalian tooth cusp patterning by ectodin.
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Mammalian tooth crowns have precise functional requirements but cannot be substantially remodeled after eruption. In developing teeth, epithelial signaling centers, the enamel knots, form at future cusp positions and are the first signs of cusp patterns that distinguish species. We report that ectodin, a secreted bone morphogenetic protein (BMP) inhibitor, is expressed as a "negative" image of mouse enamel knots. Furthermore, we show that ectodin-deficient mice have enlarged enamel knots, highly altered cusp patterns, and extra teeth. Unlike in normal teeth, excess BMP accelerates patterning in ectodin-deficient teeth. We propose that ectodin is critical for robust spatial delineation of enamel knots and cusps. (+info)
A radiographic study of the relationship between technical quality of coronoradicular posts and periapical status in a Jordanian population.
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A radiographic study was conducted to investigate the relationship between the technical quality of coronoradicular posts and periapical status. A total of 400 periapical radiographs, including 560 posts, of patients attending the Dental Department at Jordan University Hospital were scanned and studied. It was found that maxillary teeth were more frequently restored with posts (65.36%) than mandibular teeth (34.64%). Tapered posts accounted for 73.93% of the posts used. The ratio of the mean post length to crown length was 0.8, and that to root length was 0.45. The mean length of the remaining gutta percha apical to the end of the post was 6.22 mm. In addition, 25% of the posts deviated from the line of the root canal. Periapical radiolucency was evident in 53.93% of the assessed teeth. It is concluded that inadequate root canal treatment and coronoradicular posts are associated with increased prevalence of periapical radiolucency, and that general dental practitioners should be better trained in performing endodontic treatment and restoring endodontically treated teeth. (+info)
Influence of the remaining coronal structure on the resistance of teeth with intraradicular retainer.
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The aim of this study was to compare the resistance of endodontically treated teeth with intraradicular retainer different amounts of remaining coronal structure. Fifty freshly extracted maxillary canines were endodontically treated and randomly assigned to five groups (n=10), as follows: group 1 (control) = teeth with custom cast post and core; group 2 = teeth without remaining coronal structure; group 3, 4 and 5 = teeth with 1 mm, 2 mm and 3 mm of remaining coronal structure, respectively. All specimens in groups 2 to 5 were restored with prefabricated post and resin core. The teeth were embedded in acrylic resin and the fracture strength was measured on a universal testing machine at 45 degrees to the long axis of the tooth until failure. Data were analyzed statistically by one-way analysis of variance and Tukey's test. There was no significant differences (p>0.05) between the control group and group 2, and between groups 3, 4 and 5 (p>0.05). Control group and group 2 had significantly higher resistance strength than groups 3, 4 and 5 (p<0.00001). The findings of this study showed that teeth without remaining coronal structure had significantly higher fracture strength than those with remaining coronal structure (1 mm, 2 mm and 3 mm). When the dental crown was not completely removed, the amount of remaining coronal dentin did not significantly affect the fracture strength of endodontically treated teeth with intraradicular retainer. (+info)
Cessation of Fgf10 signaling, resulting in a defective dental epithelial stem cell compartment, leads to the transition from crown to root formation.
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Mouse, rat and human molars begin to form root after the completion of crown formation. In these teeth, fibroblast growth factor (Fgf) 10 disappears in the transitional stage from crown formation to root. By contrast, rodent incisors and vole molars demonstrate continuous growth, owing to the formation and maintenance of a stem cell compartment by the constant expression of Fgf10. To clarify the relationship between root formation and disappearance of Fgf10, we carried out two experiments for the loss and gain of Fgf10 function. First, we examined postnatal growth in the incisors of Fgf10-deficient mice, which have the defect of a dental epithelial stem cell compartment referred to as ;apical bud', after implantation under the kidney capsule. The growth at the labial side in the mutant mice mimics the development of limited-growth teeth. 5'-Bromo-2'-deoxyuridine (BrdU) labeling and cytokeratin (CK) 14 and Notch2 immunostaining suggested that the inhibition of inner enamel epithelium growth and the more-active proliferation of the outer enamel epithelium and/or stellate reticulum result in Hertwig's epithelial root sheath formation. Second, we examined the effects of Fgf10 overexpression in the transitional stage of molar germs, which led to the formation of apical bud involving in the inhibition of HERS formation. Taken together, these results suggest that the disappearance of Fgf10 signaling leads to the transition from crown to root formation, owing to the loss of a dental epithelial stem cell compartment. (+info)
Root growth in the permanent teeth of 45,X/46,XX females.
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Studies on individuals with sex chromosome anomalies have provided proof of a direct differential promoting effect of the X and Y chromosome genes on tooth crown growth. 45,X/46,XX females are one subgroup of Turner patients who have both normal XX and one X sex chromosome cell lines. Their permanent tooth crown size is reduced, which is mainly due to thin enamel. 45,X females likewise show reduced crown size and enamel thickness, and their root size is reduced. By contrast, the lengths of the roots in 47,XYY males or males with an extra Y chromosome and 46,XY females or females with a male sex chromosome constitution are increased. The aim of the present study was to investigate permanent tooth root lengths in 45,X/46,XX females to obtain additional information on their dental growth. The study group consisted of 15 45,X/46,XX females, mean age 23.4 years; 10 female relatives, mean age 24.5 years; and 47 population control females, mean age 29.8 years, from the Kvantti research project. Root length measurements were made from panoramic radiographs on both sides of the jaw using a sliding digital calliper. The results showed that permanent tooth root lengths in 45,X/46,XX females were, in most cases, significantly shorter than those of the population controls or relatives. It is apparent that a reduced tooth crown size in 45,X/46,XX females is followed by reduced root growth. This begins 3 years after birth and continues to at least 14 years of age. It is suggested that the reduction in crown and root growth in 45,X/4,XX females is due to a deficiency in the amount of dental growth-promoting genes on the sex chromosomes. (+info)
Complicated crown fracture: a case report.
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This case report describes the treatment of a severe crown fracture of an immature mandibular permanent incisor in a 12 year-old boy referred to the Dental Traumatology Center of UNIGRANRIO University. After conventional endodontic procedures and dressing with calcium hydroxide, an apical plug was made with mineral trioxide aggregate in order to avoid an overflow of gutta-percha and endodontic sealer into the periapical tissues. Two years later, the tooth was clinically asymptomatic and radiographs showed total repair of the apical lesion. (+info)
Comparative assesment of gingival thickness using transgingival probing and ultrasonographic method.
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A decided attitude of expectation among many patients has given a new perspective to regenerative and plastic periodonta surgery. With authors emphasizing on the importance of gingival thickness, attempts are being made to obtain necessary information atraumatically and rapidly. Hence in the present study an attempt has been made to compare the two methods of assessing gingival thickness i.e transgingival probing and ultrasonographic method and also assess the gingival thickness in relation to central incisor lateral incisor and canine in Indian population. The gingival thickness was assessed in patients with healthy gingiva by both the methods. It was observed that transgingival probing method significantly over estimated the thickness of gingiva than the ultrasonographic method and the thickness of gingiva varies with morphology of the crown. It was concluded that compared to transgingival probing ultrasonographic method assesses gingiva thickness more accurately, rapidly and atraumatically. (+info)