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Biomedical subjects

E F Harris

Publications and source records attributed to E F Harris.

At least 73 records · Page 4Linked to original sources
PubMed1989

A cephalometric assessment of children with fetal alcohol syndrome.

Lateral cephalometric radiographs were quantitatively assessed in a series of 15 American black children with fetal alcohol syndrome (FAS). Although none was profoundly affected, FAS had been diagnosed in all the children at birth. Comparisons with age-, sex-, and race-matched controls disclosed a triad of facial profile differences: (1) frontal bossing, (2) palatal plane tipped up in the front with proclined upper incisors and a sharp nasolabial angle acquired from digit habits, and (3) above-average length of the mandibular corpus. Collectively these generate the perception of midface hypoplasia, although the midface actually is unremarkable in size and position. A high prevalence of chronic digit habits (8 of 15) is a secondary consideration in FAS, leading to localized skeletodental problems.

Black People↗
PubMed1989

Effects of orthodontic force on methionine enkephalin and substance P concentrations in human pulpal tissue.

Orthodontic treatment typically involves intermittent periods of patient discomfort caused by forces on the teeth and adjacent tissues. This sensation of discomfort presumably is caused by the action of neuropeptides in the peripheral and central nervous systems. The effects of orthodontic force on the concentrations of two endogenous neuropeptides, methionine enkephalin (ME) and substance P (SP), measured as immunoreactive-methionine enkephalin (ir-ME) and immunoreactive-substance P (ir-SP), in human tooth pulp were evaluated in 20 patients from whom premolars were extracted before orthodontic treatment. The teeth from nine controls were not subjected to a force, whereas the 11 experimental patients had force applied to their maxillary premolars either by a transpalatal spring ligature or, in one case, by a headgear. The ligature applied a force within the range of 120 to 245 gm; the headgear applied 600 gm. Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to purify the neuropeptides in the pulp homogenate, and radioimmunoassay (RIA) was used to quantify ir-ME and ir-SP in their appropriate HPLC fractions. (1) Females subjected to orthodontic force had significantly greater ir-ME concentrations than males. (2) The ir-SP concentration decreased significantly from the first to the third tooth extracted, then increased from the third to the fourth tooth. (3) Ir-SP and ir-ME concentrations are positively intercorrelated. The association was highest in the first tooth extracted from controls; surgical extraction decreased the correlation, although it continued to be positive. (4) The concentrations of ir-ME and ir-SP each correlated negatively with the magnitude of the orthodontic force and that correlation was enhanced when the value of the force was log-transformed.

Adolescent↗
PubMed1989

Odontometrics of the permanent teeth in cleft lip and palate: systemic size reduction and amplified asymmetry.

Mesiodistal diameters of the permanent teeth of 70 isolated cleft lip and palate cases were analyzed. Subjects with unilateral cleft lip and palate (CLP) exhibit significantly smaller crown sizes than controls. Size reduction averages 2.3 percent, which translates to a 5.2-mm mean difference summed across all 28 permanent teeth. Bilateral cases are twice as affected, with a 4.2 percent reduction (9.3 mm). The baseline level of left-right asymmetry is significantly amplified across the whole dentition, encompassing both early- and late-forming teeth and constituting a 30-percent increase in overall asymmetry. Also, there is a localized peak of disproportionately high asymmetry centered on the upper lateral incisor but extending to both the central incisor and canine. The consistency of these differences across all tooth types and among early- and late-forming teeth implies that isolated CLP is a sequelae of a systemic, generalized restriction of these individuals' growth potential.

Adolescent↗
PubMed1988

A principal components analysis of human odontometrics.

It has long been recognized that tooth crown diameters in hominoids are all positively intercorrelated one with another. This study reports on sex-specific correlation matrices derived from 2,650 individuals from the Solomon Islands, Melanesia. Mesiodistal and buccolingual diameters of all permanent teeth from one side are used, excluding third molars. Analysis discloses significant sex dimorphism in the strengths of the intercorrelations, with females being better integrated. Principal components analysis (PCA) provides an objective means of data reduction (shown here to be preferable to simple size summation methods) and decorrelation of the resulting linear combinations. Four components are extracted (with results being virtually identical in the two sexes) and arguments are put forth that varimax rotation to "a simpler solution" may be counterproductive. Before rotation, the four components are 1) overall size, 2) buccolingual widths contrasted with mesiodistal lengths, 3) anterior (I,C) contrasted with posterior (P,M) teeth, and 4) premolars contrasted with molars. Most of the explained (shared) variance (63%) extracted by PCA is in overall size of the dentition. There is a strong urge to view the results of these principal components analyses as reflective of biologically and genetically meaningful entities.

Female↗
PubMed1988

Nitinol arch wire in a simulated oral environment: changes in mechanical properties.

Changes in the mechanical properties of a nickel-titanium orthodontic alloy, nitinol (0.016-inch arch wires), were studied in a simulated oral environment across time, at various levels of acidity, and at different amounts of static deflection. Significant decreases in specific mechanical properties were observed in these incubated wires compared with a group kept dry and unstressed. Ultimate tensile strain, modulus of elasticity, and 0.2% yield strength each decreased. Acidity (pH 3 to 7) and amount of deflection (0 to 4 mm in a 10-mm span) did not affect the wire, but there was a significant, monotonic decrease in yield strength with time in the simulated oral environment. By 4 months this measure of susceptibility to permanent deformation increased by 15%. Consequently, long-term use (or reuse) of a nitinol wire may be associated with a modest, but statistically significant, degradation in performance, notably in the limit of the wire's elasticity.

Alloys↗
PubMed1988

The intrinsic stability of Class I molar relationship: a longitudinal study of untreated cases.

Attainment of a Class I molar relationship (Angle) is often a prime treatment objective. In addition to considerations of improved function and skeletodental harmonies, a Class I relationship often is deemed the "correct" and stable situation. This study assessed the relative stability of the sagittal molar relationship in orthodontically untreated persons with full dentitions who were followed longitudinally from young (approximately 20 years) to older (approximately 55 years) adulthood. The Class I relationship is indeed most stable; none of 69 cases (sides) starting in a Class I cusp-in-groove relationship moved from that condition. In contrast, Class II relationships naturally became significantly "more" Class II (that is, greater distoclusion), and Class III cases shifted significantly to greater mesioclusion.

Dental Occlusion↗
PubMed1987

Image enhancement of the mandibular condyle through digital subtraction.

The use of conventional radiography to visualize the mandibular condylar articulating surface is limited by the superimposition of surrounding bony elements, which can be termed structured noise. This study investigated the application of digital subtraction to reduce such noise. Two conventional radiographs were made of a temporomandibular joint: first a reference radiograph with the condyle seated in the glenoid fossa (simulating a patient with mouth closed), then a radiograph from the identical orientation but with the condyle translated slightly downward and forward (simulating mouth partially opened). The radiographs were digitized and, on a pixel-by-pixel basis, the intensity value of the second image was subtracted from the reference image to produce a third, subtracted image. The subtracted image provided a significantly improved visualization of the condyle's superior surface.

Humans↗
PubMed1987

Lower incisor space analysis: a contrast of methods.

Two current methods to assess spacing-crowding among lower anterior teeth are described and contrasted. These are the anterior space analysis of Merrifield and the irregularity index of Little. There is only a modest correlation between these methods (rs = +0.53) because they provide complementary information; space analysis is more attuned to tooth displacements while the irregularity index is susceptible to axiversions. Cases illustrating major divergences between the two methods are illustrated.

Adolescent↗
PubMed1987

The enkephalin response in human tooth pulp to orthodontic force.

Public perception is that dentistry and pain go hand in hand; thus, pain and pain control are important considerations to the profession. Recent studies have attempted to discover the precise metabolic events involved in neural transmission of nociceptive information. One focus has been the study of peptidergic pathways, which purportedly inhibit the firing of pain-conducting fibers. The research described in this article defined the existence of one enkephalin, methionine enkephalin (ME), in an extract of human tooth pulp tissue and the effect of orthodontic force on that ME concentration. One set of patients who had premolars extracted for orthodontic purposes served as controls. Another set, also diagnosed for premolar extractions, had a coil spring attached between the left and right maxillary premolars to supply an orthodontic force for a period of time prior to extraction. High-performance liquid chromatography, radioimmunoassay, radioreceptor assay, and mass spectrometry were used in a series of experiments to isolate, identify, and quantify ME in the pulp tissues. Principal results were as follows: for the first time ME was detected in human tooth pulp, orthodontic force caused a significant decrease in ME concentrations in the group of experimental teeth compared with controls, and ME levels of the first spring-attached tooth that was removed from each patient had a statistically significant inverse log-linear relationship to the amount of applied force. These data indicate that orthodontic force mobilizes at least one neuropeptidergic pathway in the human tooth pulp.

Chromatography, High Pressure Liquid↗
PubMed1982

Evaluation of the anti-herpesvirus drug combinations: virazole plus arabinofuranosylhypoxanthine and virazole plus arabinofuranosyladenine.

Combinations of Virazole plus arabinofuranosylhypoxanthine (ara-Hx) and Virazole plus arabinofuranosyladenine (ara-A) were investigated in KB or BHK cells infected with types 1 or 2 herpes viruses. Combinations of Virazole and ara-Hx exhibited significant synergy as evaluated graphically (isobolograms) or by fractional inhibitory concentration (FIC) indices. Optimal ratios for the combination were 1:1 to 1:10 for Virazole to ara-Hx. At these ratios, FIC indices in the range of 0.5-0.2 were commonly observed. Combinations of Virazole and ara-A were antagonistic when observed in the presence of pentostatin, an adenosine deaminase inhibitor. In the absence of pentostatin, the minimum inhibitory concentration (MIC) of ara-A and degree of synergy with Virazole were variable.

Animals↗
PubMed1982

Lip morphology and area changes associated with surgical correction of mandibular prognathism.

Changes in lip morphology and area, measured in two dimensions from standardized lateral head films, were assessed in a series of twenty adults at three times: pre-surgically, 8--14 months post-surgically, and a long-term follow-up at 5--7 years. All individuals received the same, single surgical procedure (Obwegeser sagittal split for correcting mandibular prognathism. Upper and lower lip changes were quantified as millimetres displacement of the lip centroid vertically and horizontally, plus changes in cross-sectional area. Direction and amount of change, its dependency on the amount and kind of surgically induced symphyseal changes, and the intercorrelations among lips and among lip and symphysis variables were statistically evaluated, both univariately and multivariately. Three measures are made of symphysis change: horizontal and vertical repositioning and amount and direction of rotation. Horizontal repositioning primarily affected the lengthening and areal increase of the upper lip. Vertical repositioning had its major influence in the height and cross-sectional area of the lower lip: a superior shift of the mandible made the lower lip shorter, more protrusive and smaller in area; an inferior shift produced an increase in lower lip height with increased area. The third variable, symphyseal rotation, had its greatest influence on the labial-lingual shift of the upper lip's centroid. The long-term follow-up showed little change from the 1 year post-operative conditions; equilibrium of the soft tissue components was then achieved fairly soon after surgery.

Adult↗
PubMed1980

Sex differences in lingual marginal ridging on the human maxillary central incisor.

Although incisor dimensions are on average larger in males, at least one incisor trait, lingual marginal ridging, is significantly more common in females. This is documented for the upper central incisor in a collation of 38 samples of living populations representing six racial groups. Caucasian, Asian, Polynesian, Melanesian, and American Indian females each possess significantly higher frequencies than their male counterparts. American Blacks do not show a sex difference. Sex differences in the duration and rate of incisor crown development do not explain this dimorphism. Possible underlying genetic causes are reviewed, and the hypothesis is proposed that relevant portions of both X chromosomes in females are contributing to greater trait expression.

Asian People↗
PubMed1980

Tooth size of Ticuna Indians, Colombia, with phenetic comparisons to other Amerindians.

This study reports an odontometric analyses of unadmixed, adult Ticuna Indians, Colombia, South America. This group is characterized by crown diameters intermediate in size relative to the known Amerindian range and, in turn, to the range in modern man. Sex dimorphism is absent in Ticuna tooth size; there is a strong retention of the MI > M2 size sequence. The Ticuna are compared multivariately to other Indian groups reported in the literature, using the size and shape coefficients of L.S. Penrose. Tooth size clusters the groups into small, medium, and large-toothed classes, but does not yield a pattern attributable to known genetic or historical affinities. Shape coefficients distinguish Indians from non-Indians (Caucasian, Negroid, and Australian samples), primarily on the basis of 11-12 proportionalities. Neither size nor shape discriminates between North and South American groups.

Adolescent↗