Sexual transmission of GB virus C/hepatitis G virus

Tooth transposition is a positional interchange of two adjacent teeth. The most commonly transposed tooth is the permanent canine with either the first premolar or lateral incisor. The records of 54 subjects with transposed canines, both maxillary and mandibular, were collected. Pretreatment study models of these subjects were matched with a similar number of models from unaffected individuals. Bucco-lingual and mesio-distal tooth widths, arch depth and arch width were measured on each model. Thirty-four subjects (63 per cent) were female. Thirty-seven (68.5 per cent) of the cases involved the maxillary arch and thirty-three (89.2 per cent) of these upper arch transpositions were of the canine and first premolar. In cases involving the lower arch the canine was invariably transposed with the lateral incisor. Peg-shaped lateral incisors, supernumerary and/or congenitally absent teeth occurred in 19 subjects. There were some small, but significant differences in the dimensions of some teeth, however there were no statistically significant differences in arch depths, arch widths and most tooth dimensions in subjects with and without transposed canines. These factors do not appear to be related to the development of canine transposition.     

Dynamics of the drug scene in Switzerland 1977-1990

A mathematical model of anterior inter-arch relations was described in a previous article. This model is modified and manipulated and, using hypothetical dental measurements, results are generated and presented. The present work continues the two-dimensional examination of anterior dental relations in the first article, the emphasis remaining on incisor and canine overjet. Other authors have started by observing ideal occlusions, then have worked backwards to gain ratios of preferred maxillary to mandibular teeth widths; this restricts their studies to Class I occlusions with complete anterior dentitions and similar anterior form of both arches. This paper has no premise of normal or initial ratios. Incorporation of multiple factors allows forming and testing of hypotheses of anterior dental relations. Many factors influence anterior dental relations in varying degrees. Some dental measurement changes examined here are: the sum of teeth widths in each arch; spacing; crowding; angle of the arc of each arch and the antero-posterior buccal relation. Summary tables are presented to aid the prediction of the direction of inter-arch response to change in a dental measurement. Some inferences are discussed and are presented as a series of principles considered valid for this model. The principles may warrant testing with other arch form models.     

The impacted maxillary canine. Further observations on aetiology, radiographic localization, prevention/interception of impaction, and when to suspect impaction

Adjacent anomalous or missing maxillary lateral incisors have been implicated in the aetiology of palatally displaced canines by not providing proper guidance to the canine during its eruption. However, a recent review of the literature suggests that the aetiology of palatally displaced canines is genetic in origin. The aetiology of labially impacted canines differs, being due to inadequate arch space. Vertex occlusal radiographs have been recommended for localization but have limitations, and a case is illustrated where this radiograph is deceptive. The prevention/interception of a palatally displaced canine by the extraction of the deciduous canine is best carried out as early as the displacement is detected, mostly soon after 10 years of age. Usually, prevention/interception will avoid the surgical and orthodontic treatment needed to align a palatally impacted canine and may help prevent resorption of the adjacent incisor root. Suspicions that an impaction could occur or has occurred arise a) before the age of 10 years if there is a familial history and/or the maxillary lateral incisors are anomalous or missing; b) after the age of 10 years if there is asymmetry in palpation or a pronounced difference in eruption of canines between the left and right side; or the canines cannot be palpated and occlusal development is advanced; or, the lateral incisor is proclined and tipped distally; and, on a panoramic radiograph of the late mixed dentition if the incisal up of the canine overlaps the root of the lateral incisor.     

A dosimetric analysis of behavioral effects of acute toluene exposure in rats and humans

Contradictory findings from studies on pretreatment malalignment as a risk factor for relapse of maxillary incisor alignment may be due to inappropriate sample selection and measurement technique. In an attempt to clarify the issue, 745 sets of study models made before (T1) and after (T2) orthodontic treatment and at long-term out of retention (T3) were screened. On the basis of the configuration of the maxillary anterior teeth on the T3 study models, three groups were established: one with significant spacing (group 1, n = 30); one with significant irregularity (group 2, n = 49); and one with perfect alignment (group 3, n = 28). The occlusal surfaces of the 321 maxillary study models at T1, T2, and T3 were photocopied and the tooth anatomic contact points digitized. An algorithm was used to fit the dental arch to the digitized points. Amount of incisor rotation and anatomic contact point displacement of the maxillary anterior teeth relative to the dental arch were computer generated. Interdental spaces in the maxillary anterior segment, as well as overjet and overbite, were measured manually. Nonstructural data were collected from the charts. Logistic regression analyses revealed that irregularity was associated with greater anatomic contact displacement and with greater incisor rotation both at T1 and T2 (P < 0.01). Similar analyses also revealed that spacing was associated with greater interdental spaces at T1 and T2 (P < 0.01). Correlation analyses revealed that the pattern of pretreatment rotational displacement has a strong tendency to repeat itself after retention (P < 0.001), as opposed to the pattern of contact point displacement and interdental spacing.     

Hemispheric control of motor function: a whole brain echo planar fMRI study

A sample of 130 patients with vertical maxillary hyperplasia; mandibular hypoplasia with a high mandibular plane angle; narrow, tapered maxillary dental arch form; and anterior vertical open bite were collected from three different institutions to evaluate the stability of transverse maxillary arch dimensions after correction of the open bite. Surgical treatment consisted of Le Fort I or bimaxillary osteotomies. Intermolar, interpremolar, and anterior arch widths were measured three-dimensionally on dental casts using a Reflex microscope, and transverse stability after orthodontic or surgical maxillary expansion was analyzed. Orthodontic expansion followed by a one-piece Le Fort I intrusion osteotomy was performed in 77 patients, and surgical maxillary expansion by a multisegment Le Fort I intrusion osteotomy was performed in 53 patients. The increase of transverse arch width and the relapse after orthodontic or surgical expansion were not significantly different. The transverse arch width in these two groups did not relapse in 20% of the patients after a mean follow-up of 69 months. An additional bilateral sagittal split osteotomy had no detectable effect on stability. Patients who underwent a multisegment Le Fort I osteotomy stabilized with rigid internal fixation showed better transverse stability than those with intraosseous wire fixation and maxillomandibular fixation. Maxillary intermolar and interpremolar arch width relapses were not correlated with tongue interposition or loss of interdigitation. The relapse of these arch widths showed significant correlations with clockwise rotation of the mandible but not with changes of overbite or overjet.     

A modified, lingually supported cantilevered Herbst appliance

This new, fixed-functional appliance/Herbst/Bioprogressive system is designed for patient comfort and mandatory compliance. It also combines the positive clinical effects of four fixed-functional systems. It allows rapid palatal expansion of the upper arch, alveolar uprighting of the lower arch, upper and lower incisor alignment, and sagittal correction of Class II malocclusions to occur simultaneously with one appliance fixed in both arches. It is indicated for use in growing patients with skeletal Class II malocclusions. The ideal timing for treatment is the late mixed dentition. Being able to remove the appliance after one year with the upper second bicuspids erupting slightly Class III so the clinician can immediately begin fixed finishing mechanics would be ideal. This new Herbst design will reduce the frequency of orthognathic surgery and upper bicuspid extraction to camouflage Class II malocclusions. At the same time, it gives total control to the clinician in treating some more difficult, non-compliant patients. Fixed-functional appliances, which improve treatment efficiency and treatment results and provide for patient comfort, while at the same time give the treating clinician almost total control of the three planes of facial growth will open new doors for orthodontic treatment and research in the next century.     

Expression of integrins in marmoset (Callithrix jacchus) ovary during folliculogenesis

The model of 25 children with mild Class II, Division 1 malocclusions who had their upper buccal segments moved distally with an en masse appliance were measured at the beginning of treatment and at the completion of buccal segment retraction. A reflex microscope, interfaced to a personal computer, was adapted for this purpose. A custom-made jig and linear stepping motor permitted the recording of both buccal and incisal measurements of the teeth in occlusion, as well as individual arch parameters. Software was designed to record and calculate the required measurements. The method error associated with this approach ranged from 0.01 to 0.5 mm. Results indicated that mean distal movement of the buccal segments approximated 6 mm, equivalent to a full cusp of buccal segment retraction. A small spontaneous reduction in overjet was seen. The upper arch showed spontaneous alignment and increases in width, length, and perimeter. In the lower jaw, transverse expansion was accompanied by a small increase in arch perimeter. Arch length, however, was slightly reduced. It was concluded that the system was an acceptable method of recording occlusal changes during orthodontic treatment, supplementing routine cephalometry. Furthermore, a full unit of buccal segment retraction could be expected, by using a removable appliance/headgear technique.     

A longitudinal study of arch size and form in untreated adults

Adulthood-the lengthy phase following attainment of biologic maturity-often is perceived as a period of "no change" or one of slow deterioration. Recent skeletodental studies discount this stereotype. Changes in arch size and shape were studied here in a longitudinal series of 60 adults with intact dentitions. Full-mouth study models were taken at about 20 years of age and again at about 55 years. Some variables-particularly those between arches (incisor overbite and overjet, molar relationship) and mandibular intercanine width-remained age-invariant. In contrast, all other measures of arch width and length changed significantly (P < 0.01): Arch widths increased over time, especially in the distal segments, whereas arch lengths decreased. These changes significantly altered arch shape toward shorter-broader arches. The data suggest that changes during adulthood occur most rapidly during the second and third decades of life, but do not stop thereafter. Possible mechanisms driving these changes in tooth position are discussed.     

Risk factors associated with incisor injury in elementary school children

This study examined risk factors associated with incisor injury in 3396 third and fourth grade school children in Alachua County, Florida. One of six orthodontists completed a standardized examination form for each child to assess severity of incisor injury, gender, age, race, skeletal relationships, morphologic malocclusion, incisor exposure, interlabial gap, TMJ sounds, chin trauma, and history of lower facial trauma. One in five (19.2%) exhibited some degree of incisor injury. This was limited to a single tooth in 73.1% of those with injury, while enamel injury predominated (89.4%). The majority of the injuries (75.4%) were localized in the maxillary arch, with central incisors the most frequently traumatized. Chi-square tests of association indicated that gender, race, school, orthodontist, history of lower facial trauma, chin trauma, profile, and maxillary and mandibular horizontal positions were associated with incisor injury (P < 0.05). Wilcoxon rank sum tests identified differences in age, overjet, time of screening, and interlabial gap between those with and without injury (P < 0.05). Results of logistic regression analyses indicated risk of incisor injury was greater for children who had a prognathic maxilla, a history of trauma, were older, were male, and had greater overjet and mandibular anterior spacing.     

Approximating Wetted Perimeter in Power-Law Cross Section

The wetted perimeter is an open-channel parameter that influences surface drag and also influences infiltration in furrows and unlined canals. Various approximations to the wetted perimeter are examined for channel cross sections in which the top width is a power law of depth. Exact solutions are available only for select values of the exponent. Interpolation between exact values, partial sums of series approximations, and numerical integration are compared. A simple nonlinear interpolation scheme or a three-term summation yields results accurate to within 1% of the range of typical channel geometries. Common numerical approximations are shown to yield errors in excess of a range of from 3 to 10%.     

Extraoral tooth eruption and transposition of teeth following trauma

A six-year-old boy presented with extraoral eruption of a mandibular permanent canine and a loosely attached lateral incisor in the labial vestibule, 3 months following trauma to the chin. The trauma not only caused displacement of the permanent tooth buds, but also resulted in transposition of the lateral incisor and canine with subsequent ectopic eruption. The case is presented to demonstrate one of the infrequent complications of trauma involving the unerupted tooth buds of permanent teeth and its unusual clinical presentation.     

Classification of mandibular defects

A classification of mandibular defects based on functional as well as aesthetic factors is presented. By taking into account the difficulties in restoring form and function and not simply relying on traditional anatomic landmarks, it is hoped that this method will allow different types of reconstructions to be fairly evaluated. It also should help surgeons to tailor individual reconstructive techniques to specific clinical situations. Major difficulties in mandibular reconstruction arise when a condyle requires replacement, when there is a mucosal and/or skin component to the defect, and when the area to be reconstructed involves the anterior arch. The classification is based on three upper-case and three lower-case characters: H, C, L and o, m, s. H defects are lateral defects of any length, including the condyle but not significantly crossing the midline; L defects are the same only without the condyle; C defects consist of the entire central segment containing the four incisors and the two canines. Combinations of these letters are possible (an angle-to-angle defect, for example, is represented as LCL). Thus H and L defects may reach or even extend slightly beyond the midline but are not referred to as LC or HC unless they contain the entire central segment. The letters o (neither a skin nor a mucosal component), s (skin), m (mucosa), and sm (skin plus mucosa) are added to denote the epithelial requirement.     

Continued risk behaviour among HIV positive drug injectors in London: implications for intervention

The increment depth discrimination function was originally described by Ogle [(1953) Journal of the Optical Society of America, 43, 906-913] as a single exponential function. In contrast, recent studies have suggested that a two-component function better describes increment depth discrimination. To determine the relative effects of stereoscopic and non-stereoscopic width cues on the form of the function, we measured increment depth discrimination under conditions where both stereoscopic and dichoptic width cues were available. We found that increment depth discrimination data were well described by two-segment functions if both stereoscopic and dichoptic width cues were available. However, when dichoptic width cues were eliminated, by randomizing the pedestal disparity (crossed or uncrossed disparity) between trials, the increment depth discrimination function was better described by a single exponential function. This result has important implications for models of stereoscopic depth processing because it shows that stereoscopic depth discrimination thresholds progressively increase as a function of distance from the horopter.     

Abnormalities of the maxillary incisors in children with cleft lip and palate

Dental anomalies of the maxillary anterior teeth were studied in seventy-seven children affected by unilateral and bilateral clefts of the lip and alveolar process, with or without involvement of the palate. As for the permanent lateral incisor in the cleft area, our results show that its congenital absence is the most frequent abnormality followed by anomalies in size and shape and supernumerary teeth. Enamel hypoplasia was found to affect the permanent central incisor on the cleft side more frequently. Early recognition of tooth abnormalities during the primary dentition phase for an interceptive treatment of potentially severe problems was emphasized.     

Space analysis: a comparison between sonic digitization (DigiGraph Workstation) and the digital caliper

The introduction of the DigiGraph Workstation permits the use of sonic digitization to measure lateral cephalometric values, mesiodistal tooth size and arch perimeter discrepancy as a one-stop diagnostic record taking set-up. This study compared the reproducibility of mesiodistal total tooth widths and arch perimeter values, on plaster casts, given by the DigiGraph Workstation and by digital calipers. Forty-seven sets of plaster casts of Southern Chinese children (mean age 12.5 years) comprised the sample. Arch perimeter was measured using calipers in six segments from the distal of the first permanent molar to its antimere in each arch. The total mesiodistal widths of all teeth, excluding second and third molars, were also measured. The difference between the available arch perimeter and the total tooth widths was taken as the arch perimeter discrepancy. Sonic digitization of the study casts was completed according to instructions of the DigiGraph software. Paired t-tests and F-tests were used to compare the two methods. Compared with manual measurement, there was an over-estimation of the total tooth widths by 1 mm in the mandible and 0.5 mm in the maxilla, and an arch perimeter discrepancy of 1.6 mm in the mandible and 0.4 mm in the maxilla when using the sonic method. The sonic digitization was not as reproducible as the digital caliper and its clinical usefulness in evaluating the space problem of an individual malocclusion should be interpreted with caution.     

Hydraulically Efficient Power-Law Channels

A power-law channel is a generalized form of a channel and includes parabolic and triangular cross sections. For an exponent m<0.5 in the power law, the relative wetted perimeter has been estimated from a series expansion truncated to four terms. For values of the exponent m ≥ 0.5 the relative wetted perimeter has been estimated using an appropriate non-linear interpolation expression. A table to estimate relative wetted perimeter based on these expressions is presented for design purposes. With these expressions for relative wetted perimeter, and using the Lagrange method of undetermined multipliers, for any given maximum side slope, the area and/or wetted perimeter is minimized subject to the equality constraint of a uniform flow (Mannings) equation. Using this technique, for any given side slope, the exponent of the power-law channel can be determined and hydraulically efficient power-law channels can be designed. Optimized power-law channels are compared with trapezoidal and parabolic channels. The existing parabolic design of the Pehur High Level Canal, Pakistan is compared with an optimum power-law channel.     

Effects of unilateral upper incisor extraction on facial growth of young rats

The effects of unilateral extraction of the upper incisor (one tooth) on facial growth of young rats were studied. The remaining upper incisor showed deviation towards the opposite side, and there was regular dental wear of all the incisors. The effects were evident only in the mid-facial area. Cephalometric measurements showed significant shortening with deviation of the incisor bone on the extraction side. There was no significant disturbance of the growth of the rest of the maxilla and mandible. These results indicate that upper incisor extractions have a localized influence, leading to impairment of incisor bone growth.     

Responsiveness of experimental surgical-wound infections to topical chemotherapy

The anterior dentition of three species of African colobines (Colobus polykomos, C. badius, and C. verus) was investigated metrically and the results analyzed for three characters: (1)intraspecific tooth size relations, (2)sexual dimorphism, and (3)interspecific relations. Based on incisor size sequences C. polykomos and C. badius appear to be more closely related to each other than either is to C. verus. However, incorporating the results of a previous study on postcanine dentition the three species appear to be equally closely related. The magnitude of sexual dimorphism in canine size decreases from C. badius to C. verus to C. polykomos. Interspecific differences in the degree of canine size dimorphism may be attributed to differential intensities of male intrasexual selection; however, the interspecific differences in canine size dimorphism do not correspond to the interspecific differences in body size dimorphism.     

Accommodation and presbyopia in the human eye. Changes in the anterior segment and crystalline lens with focus

PURPOSE: To characterize changes in the sagittal dimensions of the human crystalline lens and anterior segment as a function of accommodation, to determine the potential age dependence of these changes, and to evaluate these changes in relation to the development of presbyopia. METHODS: Scheimpflug slit-lamp photography, as well as a variety of standard ophthalmologic methods, was used to collect information about lens and anterior segment sagital dimensions in a population of 82 adults with refractive error < or = magnitude of 2.0 diopters and at least 0.25 diopter of accommodation for subjects 18 to 70 years of age. Data were analyzed statistically for dependence on accommodation, age, and age dependence of accommodative rate. RESULTS: The rate of change per diopter of accommodation for each measured variable within the lens is independent of age for the entire adult age range. With increasing accommodation, the lens becomes thicker and the anterior chamber shallower along the polar axis. This increase in sagittal lens thickness is entirely because of an increase in the thickness of the lens nucleus. Because the anterior and posterior halves of the nucleus increase in thickness at approximately the same rate with accommodation, the increase in lens thickness results from equal changes in the lengths of the anterior and posterior portions. CONCLUSIONS: Because changes along the sagittal axis of the anterior segment with accommodation are independent of age, any explanation of presbyopia that relies on simple changes in the rates of lens thickening and anterior chamber shallowing with age does not hold. In light of other age-related changes in the anterior segment and lens (e.g., increased sharpness of lens curvature, increased lens sagittal thickness, decreased anterior chamber depth), it appears that compensatory mechanisms to preserve far vision with age also preserve the rate of change per diopter of sagittal spacings.