Canine sexual dimorphism in Egyptian Eocene anthropoid primates: Catopithecus and Proteopithecus. (1/398)

Two very small late Eocene anthropoid primates, Catopithecus browni and Proteopithecus sylviae, from Fayum, Egypt show evidence of substantial sexual dimorphism in canine teeth. The degree of dimorphism suggests that these early anthropoids lived in social groups with a polygynous mating system and intense male-male competition. Catopithecus and Proteopithecus are smaller in estimated body size than any living primates showing canine dimorphism. The origin of canine dimorphism and polygyny in anthropoids was not associated with the evolution of large body size.  (+info)

A modern human pattern of dental development in lower pleistocene hominids from Atapuerca-TD6 (Spain). (2/398)

The study of life history evolution in hominids is crucial for the discernment of when and why humans have acquired our unique maturational pattern. Because the development of dentition is critically integrated into the life cycle in mammals, the determination of the time and pattern of dental development represents an appropriate method to infer changes in life history variables that occurred during hominid evolution. Here we present evidence derived from Lower Pleistocene human fossil remains recovered from the TD6 level (Aurora stratum) of the Gran Dolina site in the Sierra de Atapuerca, northern Spain. These hominids present a pattern of development similar to that of Homo sapiens, although some aspects (e.g., delayed M3 calcification) are not as derived as that of European populations and people of European origin. This evidence, taken together with the present knowledge of cranial capacity of these and other late Early Pleistocene hominids, supports the view that as early as 0.8 Ma at least one Homo species shared with modern humans a prolonged pattern of maturation.  (+info)

Ectopic eruption of the maxillary canine quantified in three dimensions on cephalometric radiographs between the ages of 5 and 15 years. (3/398)

The eruption paths of 20 ectopic maxillary canine teeth (10 right, 10 left) were measured in three dimensions on annual lateral and depressed postero-anterior cephalometric radiographs of 15 patients between the ages of 5 and 15 years and compared with the eruption of normal canines. It was found that between the ages of 8 and 12 years ectopic canines on the left side moved more anteriorly than the normally erupting canines and the same was true of the right canines between the ages of 7 and 12 years. While the ectopic canines moved occlusally, their vertical movement was less than normal which accounts for the clinical finding that canines are impacted in the palate at a high level. The average palatally ectopic canine always moves palatally, and never shares in the buccal movement shown by normally erupting canines between the ages of 10 and 12 years. It was interesting to find that the differences between growth of normal and ectopic canines in the lateral plane of space are present as early as 5-6 years.  (+info)

Effects on tooth movement of force delivery from nickel-titanium archwires. (4/398)

The aim of this project was to determine the in vivo effects of tooth movement with nickel-titanium archwires on the periodontium during the early stages of orthodontic treatment. The extent of tooth movement, severity of gingival inflammation, pocket probing depth, gingival crevicular fluid (GCF) flow, and the amount of the chondroitin sulphate (CS) glycosaminoglycan (GAG) component of the GCF of one maxillary canine in each of 33 patients treated with a pre-adjusted appliance were measured before and at four stages during the first 22 weeks of treatment. The methods involved the use of a reflex metrograph to determine the type of tooth movement and electrophoresis to quantitate the CS in the GCF. It was found that GCF flow increased after 4 weeks of tooth movement whereas the increase in the amount of CS in the GCF, which is taken to be indicative of periodontal tissue turnover, occurred at the later stage of 10 weeks. Teeth which showed the greatest amount of tooth movement continued to express large amounts of CS in large volumes of GCF until 22 weeks, whilst the CS levels in those teeth moving to a smaller extent declined. These data suggest that nickel-titanium archwires may produce a super-elastic plateau effect in vivo on canine teeth, which are initially displaced from the arch such that large amounts of tooth movement occur in the first 22 weeks of treatment.  (+info)

A systematic review of the relationship between overjet size and traumatic dental injuries. (5/398)

The aim of this study was to aggregate the risk of traumatic dental injury due to overjet using several published papers and performing a meta-analysis on the results. The 11 articles involved in this investigation were identified by a literature search of Medline (1966-1996) and Exerpta Medica (1985-1996) databases using predetermined keywords, and inclusion and exclusion criteria. In order to assess the quality of each paper, a methodological checklist for observational studies was developed resulting in a score between 0 and 100. The relative risk of overjet, compared with a reference, was expressed as an Odds Ratio (OR). For each study, the OR was computed using the data presented and, subsequently, these ORs were pooled across studies. The effect of confounders (i.e. age, gender), which could bias the relationship between overjet and dental injury was taken into account. Furthermore, the influence of quality of the study on the pooled OR was addressed. The average methodological score was 41. From the results, it can be concluded that children with an overjet larger than 3 mm are approximately twice as much at risk of injury to anterior teeth than children with an overjet smaller than 3 mm. The effect of overjet on the risk of dental injury is less for boys than for girls in the same overjet group. In addition, risk of injury of anterior teeth tends to increase with increasing overjet size. Furthermore, the pooled OR does not seem to be affected by the quality of the studies.  (+info)

The effect of tooth position on the image of unerupted canines on panoramic radiographs. (6/398)

The purpose of this study was to evaluate whether panoramic tomograms, which are routinely used in orthodontic practice, can provide adequate information to localize an impacted canine. The effect of changes in position and inclination of an impacted canine on orthopantomograms was investigated in an experimental set-up. An upper canine was removed from a human skull and replaced in a positioning system, enabling simulated positional variations in impactions. In comparison with the image of a contralateral well-aligned canine, the length of the impacted tooth always decreased or remained unchanged, whereas the tooth width increased or remained unchanged. The angulation of the image was unaffected by varying the position of the impacted canine, but altered when the inclination of the tooth in a sagittal or frontal direction was changed. If there was any transversal shift of the impacted canine on the orthopantomogram, it was always towards the mid-sagittal plane. The curvature of the tooth increased after dorsal inclination and decreased after ventral inclination (in comparison with the contralateral well-aligned canine).  (+info)

A medico-legal review of some current UK guidelines in orthodontics: a personal view. (7/398)

This article is a critical analysis from a medico-legal perspective of some current authoritative UK clinical guidelines in orthodontics. Two clinical guidelines have been produced by the Royal College of Surgeons of England and four by the British Orthodontic Society. Each guideline is published with the analysis immediately following it. Following recent UK case law (Bolitho v City & Hackney Health Authority, 1997) which allows the courts to choose between two bodies of responsible expert medical opinion where they feel one opinion is not 'logical', it is likely that the UK courts will increasingly turn to authoritative clinical guidelines to assist them in judging whether or not an appropriate standard of care has been achieved in medical negligence cases. It is thus important for clinicians to be aware of the recommendations of such guidelines, and if these are not followed the reasons should be discussed with the patient and recorded in the clinical case notes. This article attempts to highlight aspects of the guidelines that have medico-legal implications.  (+info)

Determination of the centre of resistance in an upper human canine and idealized tooth model. (8/398)

The purpose of this investigation was to analyse the influence of geometric and material parameters of a human canine on initial tooth mobility, and the stress and strain profiles in the periodontal ligament. While the material parameters of tooth and bony structures are known within an uncertain limit of approximately a factor of 10, values reported for the elasticity parameters of the periodontal ligament differ significantly. In the course of this study, bilinear behaviour was assumed for the mechanical property of the periodontium. The finite element model of an elliptical paraboloid was created as an approximation to the geometry of a human canine to reduce calculation time and to determine influences of the geometry on numerical results. The results were compared with those obtained for a realistic human canine model. The root length of both models was 19.5 mm. By calculating pure rotational and pure tipping movements, the centre of resistance (CR) was determined for both models. They were located on the long axis of the tooth approximately 7.2 mm below the alveolar crest for the idealized model and 8.2 mm for the canine model. Thus, the centre of resistance of a human canine seems to be located around two-fifths of the root length from the alveolar margin. Using these results, uncontrolled tipping (1 N of mesializing force and 5 Nmm of derotating momentum), as well as pure translation (additionally about 10 Nmm of uprighting momentum) were calculated. Comparing the idealized and the realistic models, the uncontrolled tipping was described by the parabolic-shaped model within an accuracy limit of 10 per cent as compared with the canine model, whereas the results for bodily movement differed significantly showing that it is very difficult to achieve a pure translation with the realistic canine model.  (+info)