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Biomedical subjects

N R Robertson

Publications and source records attributed to N R Robertson.

At least 19 recordsLinked to original sources
PubMed1992

Stresses induced by edgewise appliances in the periodontal ligament--a finite element study.

The quantification of stress in the periodontal ligament is an important concept, as stress in this tissue is transmitted to the alveolus, with subsequent bone remodelling and tooth movement. A number of clinical studies have suggested figures for such an optimal stress range. This study makes use of a finite element technique to determine the stress induced in the periodontal ligament in three dimensions when a maxillary canine tooth is subjected to an orthodontic force similar to that produced by an edgewise appliance. The maximum stress induced at the cervical margin of the periodontal ligament was 0.072 N/mm2, while the maximum stress induced at the level of the apical foramen was 0.0038 N/mm2. These results are discussed in the light of known clinical experience and compared with the stresses produced in the periodontal ligament by other orthodontic forces. The findings would suggest that even with 'perfect' edgewise mechanics it would be difficult to obtain canine movement by pure translation or 'bodily movement.'

Alveolar Process↗
PubMed1992

The Barry Project--a cephalometric assessment of treatment change in a consecutive sample of malocclusion.

This is the last of a three-part series examining the results of orthodontic treatment in a consecutive sample of malocclusion from a Welsh town. The cephalometric changes are compared for the different treatment regimes which were employed. Where the variables being examined were common to both radiographs and study cast records the treatment changes observed for the regimes were similar. Only limited 'skeletal' change, interpreted as a change in a few cephalometric measurements, was found to occur during treatment. Perhaps of most interest was the consistent reduction of 'A' point in the full fixed appliance group.

Cephalometry↗
PubMed1992

Bioprogressive brackets and pentamorphic arches.

The use of high torque values with no tip in preadjusted incisor brackets in the Bioprogressive system, in conjunction with narrow anterior rectangular archwires may produce crown spacing, root crowding and upright central incisors. The solution to these problems would seem either to reduce the time spent in rectangular wires or to change to a bracket with reduced torque, together with appropriate second order compensations in the archwire or the bracket.

Chromium Alloys↗
PubMed1987

The screening and categorization of patients: a case for natural selection?

A preliminary study was performed on the feasibility and validity of objective categorization of patients into basic 'treatment types'. The Reflex Metrograph was used for a three-dimensional cast analysis, and an H.P. 9874 A digitizer was used for a two-dimensional radiograph analysis. In both measurement techniques the method error was found to be acceptable. Using the Ricketts 10 Factor Analysis, it was found that by means of 'Clinical deviators' radiographs could be used to distinguish orthognathic cases from the other treatment groups. The three-dimensional study cast analysis showed promise, distinguishing a number of statistically significant factors within the lower arch and between simple and fixed appliance cases. A number of variables which might have been expected to be significant were confounded by their range of values within the groups. Further investigation is required with an improved technique of initial categorization of patients, perhaps by means of a panel of clinicians, and more sophisticated statistical techniques.

Cephalometry↗
PubMed1986

Diagnosis of cystic fibrosis in premature infants.

Meconium ileus and pancreatic changes, as described in cystic fibrosis, were found, at autopsy, in a series of six infants who received prolonged neonatal intensive care for prematurity. Cystic fibrosis had not been suspected clinically. These pathological findings are so frequent in sick premature infants, amounting to 12% of all neonatal autopsies conducted over a period of 2 yr in our unit, that we question their specificity for cystic fibrosis and suggest they may be a manifestation of disordered physiology in the severely ill neonate.

Autopsy↗
PubMed1984

Bilateral supplemental laterals: an unusual transplantation approach.

The case of a patient presenting with bilateral supplemental lateral incisors is reported. The upper lateral and supplemental on one side of the arch had a questionable prognosis due to extensive caries and at their removal the supplemental from the other side was successfully transplanted across the arch.

Child↗
PubMed1983

An examination of treatment changes in children treated with the function regulator of Fränkel.

Two groups of patients, one with a Class II, Division 1 malocclusion and the other with a Class III malocclusion, were treated with the Fränkel appliance. Lateral cephalometric radiographs were taken before and after correction of the arch relationship. An examination of the head films with the use of a digitizer and a computer suggests strongly that the principal changes produced by the appliance are dentoalveolar. The need for a randomized controlled clinical trial is emphasized.

Activator Appliances↗
PubMed1983

An 11-year follow-up of the effects of early bone grafting in infants born with complete clefts of the lip and palate.

This is a report at the age of 11 years of a clinical study of the effects of early bone grafting in infants born with complete clefts of the lip and palate. Matched pairs of similar cleft type were treated according to the same treatment protocol with the exception that only one of each pair received an autogenous rib bone graft at the age of 15 months. The overall impression left by this study is that early bone grafting is not beneficial to the patient.

Bone Transplantation↗
PubMed1983

Orthodontic treatment--time for a change?

There was a fall in the birthrate in England and Wales from 1964 until 1977 from 875,972 to 569,259 per annum. This short paper draws attention to the implications for the provision of orthodontic treatment and suggests that, since fewer patients are likely to present for treatment, an opportunity exists to improve the standard of care provided.

Child↗
PubMed1981

Telecentric photogrammetry: its development, testing, and application.

The development, testing, and application of a simple method of photogrammetry are outlined. Two phases of development are described, the first leading to the production of a frontal facial photograph with superimposed contour lines at 2 mm. intervals and the second leading to a frontal view together with right and left profile views of the patient. The choice of method used will naturally depend upon the purpose for which the clinician wishes to have a photogrammetric record of his patient. The root mean square error of the method is 0.33 mm.

Face↗