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Biomedical subjects

C B Preston

Publications and source records attributed to C B Preston.

At least 19 recordsLinked to original sources
PubMed1999

A longitudinal evaluation of extraction versus nonextraction treatment with special reference to the posttreatment irregularity of the lower incisors.

A tendency exists in contemporary orthodontics to pursue a completely non-extraction philosophy. Moreover, it has been shown that the extraction versus non-extraction debate is still with us. Controversy exists as to which treatment decision will eventually lead to orthodontic stability. It is thus imperative to conduct investigations on long-term changes of the dentition in both treatment regimens. The present study serves as an example of such a longitudinal study. A random sample, inclusive of both extraction and non-extraction treatments, was examined with respect to long-term stability and an assessment was made as to whether one treatment option favors success over the other. It was concluded that the correct initial treatment choice will not only lead to correction of the malocclusion, but will also ensure clinically acceptable stability with no significant differences between extraction and non-extraction treatments.

Bicuspid↗
PubMed1998

Adaptation of the bioprogressive philosophy to use brackets with .022" slots.

The Bioprogressive orthodontic treatment philosophy is traditionally associated with the use of brackets that have .018" slots. Proponents of the Bioprogressive philosophy suggest this slot configuration largely because they believe that lighter wires provide force levels that are within the biological limits of the periodontal support system. At the same time, the principles of orthodontic anchorage advocated by the Bioprogressive philosophy depend on careful torque control of both molar and anterior teeth. It is possible and sometimes advisable to use wires designed for use in brackets with .018" slots, in brackets with .022" slots. Under these circumstances, the thinner wires may not provide sufficient control over torque moments to develop the required degree of molar anchorage. This article suggests that with the use of certain wires, and with minor modifications to the shapes of arches, that the use of brackets with .022" slots need not conflict with many of the important principles of orthodontic treatment advocated in the Bioprogressive philosophy.

Chromium Alloys↗
PubMed1997

The relationship between ortho head posture and head posture measured during walking.

Murphy, Preston, and Evans recognized the dynamic nature of head posture and developed instrumentation capable of measuring and recording this posture in a continuous manner. The aim of the current project was to use the newly developed instrumentation to determine whether the difference is statistically significant between the mean natural head ortho posture, measured in a controlled manner, and the mean dynamic head posture obtained during 5 minutes of walking activity in an experimental situation. The mean ortho head posture and the mean walking head posture were measured in each of 30 men. The differences between these two sets of mean head postures were statistically significant (p < or = 0.05). In 23 persons, the mean walking head posture was tipped backward relative to the mean natural head ortho position.

Adult↗
PubMed1996

An evaluation of two methods used to determine the centre of gravity of a cadaver head in the sagittal plane.

A suitable method to locate the centre of gravity of the head is not available at present. Precise location of that centre will help in the understanding of aspects of cranial balance and what effect skeletal changes, following for example orthognathic surgery, may have on head posture. The objective of this research was to use a mechanical (empirical) method, based on accepted laws of physics, to determine the centres of gravity of cadaver heads in the sagittal plane and to compare these positions with those generated by a computer programme. The two methods located the centre of gravity in the same region but at a different position in each corresponding head. These differences were statistically significant (p < 0.01). It is likely that improved computer techniques together with modern three dimensional imaging methods will be able to locate the centre of gravity of a head in a living subject.

Cadaver↗
PubMed1993

A longitudinal evaluation of the anterior border of the dentition.

Posttreatment changes of orthodontically treated dentitions are inherent to every orthodontic practice. Various studies have documented the ideal posttreatment dental and cephalometric norms that could pertain to stable long-term occlusal results. Clinically, changes in these parameters are often observed as mandibular incisor crowding. The purpose of this study was to evaluate the longitudinal changes in certain variables representing the anterior border of the dentition. Eighty-eight white subjects were assessed regarding stability of the dentition after edgewise orthodontic treatment. (44% nonextraction, 56% extraction) The following variables in proximity of the anterior limit of the dentition (overbite, overjet, mandibular arch length, upper and lower incisor position, Little irregularity index) were assessed and correlated with each other. The data were subjected to descriptive statistics, the Friedman test for significant changes and pairwise comparisons, and the Spearman correlation test. Mandibular intercanine width was not significantly altered during treatment, but although not significantly, p > 0.05 did decrease beyond the original measurement during posttreatment evaluation (mean 7 years after treatment). The other variables influenced by the orthodontic manipulation were all within normal ranges and remained stable. The arch length decreased significantly (p < 0.05) during the entire evaluation period and was the only variable not stable. It was concluded that: (1) sound treatment leads to attainment of ideal occlusal parameters, (2) mandibular intercanine expansion could lead to failure of results, (3) arch length change plays a major role in causing irregularity of mandibular incisors after treatment, and (4) patient education regarding posttreatment orthodontic changes is imperative.

Adolescent↗
PubMed1991

The development of instrumentation for the dynamic measurement of changing head posture.

Cranial posture and its possible relationship to the morphology of the skull has been studied in some detail, as have the relationships between cranial posture and such functions as respiration and jaw movements. To date, cranial posture has been assessed mainly with techniques that give static interpretations of the angular relationships between intracranial and extracranial reference lines. The present project was undertaken to develop a system of instruments capable of the continuous measurement and recording of cranial posture for extended periods of time. A number of aspects of this system were tested. The results indicate that the experimental array of instruments measures head posture accurately over a defined range of cranial movement. This new technique should make it possible to measure cranial posture in a more dynamic and physiologic manner.

Adult↗
PubMed1990

Provision of "comprehensive dental care" in various dental schools.

The purpose of this survey was to solicit information about comprehensive dental care (CDC) programmes in various dental schools. Seventy-four schools responded to a questionnaire which sought information about a range of topics pertaining to CDC. The 19 questions used were categorized under the following headings: implementation and success; physical nature of clinics; staffing; and, student involvement. The diverse nature of the responses is thought to be an expression of differing philosophies and of the presence of numerous constraints to the introduction of CDC. The various approaches to CDC make it very difficult to gauge the relative merits of the many systems reported. It appears from this study that departments will continue to play an important role in preparing students to participate in CDC programmes and that it would be safer to introduce students to CDC during the final year of study.

Comprehensive Dental Care↗
PubMed1986

Fluctuating dental asymmetry as a measure of odontogenic canalization in man.

Fluctuating odontometric asymmetry was evaluated in 202 Lengua Indians and in 125 contemporary caucasoids using Euclidean map analyses, rescaled asymmetry values, and Naperian logarithmic transformations. Both populations showed bimodal distributions of canalizing ability, with significantly more Lengua Indians being less well canalized. Student t-tests indicated that significant interpopulation differences in rescaled asymmetry values centered around maxillary mesiodistal dimensions. Analyses of variance failed to show significant levels of sexual dimorphism in the magnitude of asymmetry for both populations. It is concluded that even in a relatively stress-free population, there exist some individuals who are less well canalized than others. When a population is subjected to elevated levels of parasitic and nutritional stress, the number of less-well-canalized individuals increases significantly.

Dental Pulp Cavity↗
PubMed1986

On the non-existence of compensatory tooth size interaction in a contemporary human population.

Compensatory tooth size interactions between early and later developing teeth within the same tooth class were empirically evaluated in a sample of 125 study casts of Caucasoid children. Mean buccolingual and mesiodistal diameters for first and second molars, pre-molars, and incisors were calculated, and those first developing teeth that were either larger of smaller than the mean were identified. Pearsonian correlation coefficients and chi-square tests revealed highly significant positive correlations between smaller of larger early developing teeth and their later developing neighbors. This total lack of compensatory tooth size interaction was also confirmed when outsized teeth (larger of smaller than one standard deviation from the mean) were used. Similar results were obtained when tooth size was corrected for arcade length, hence allowing for the rejection of Sofaer's model of compensatory tooth size interaction.

Bicuspid↗
PubMed1985

Patterns of dental wear in the Lengua Indians of Paraguay.

Wear patterns were examined on dental casts of 202 living Lengua Indians from the Chaco area of Paraguay. Consideration was given to the development of the molar helicoidal plane, age-related changes in occlusal attrition, coalescence of dentine exposures, interproximal attrition, and erupted crown height. This study lends support to Osborn's theory of the helicoidal plane development by showing that attrition enhances rather than modifies posteruption molar occlusal planes. The rate of interproximal attrition was found to slow down with the eruption and functional initiation of the third molars. Sinuous and cavo-convex interproximal contact areas that are generated with age, however, appeared to be less abrasion resistant than straight surfaces, hence leading to an increase in interproximal attrition rates with advanced age. Maximum crown height reduction occurred between the ages of 20 and 40 years in central incisors, canines, and first molars. Kruskal-Wallis tests and log linera models failed to demonstrate significant sexually dimorphic or antimeric differences in wear patterns of Lengua teeth.

Adult↗