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Biomedical subjects

M L Jones

Publications and source records attributed to M L Jones.

At least 145 records · Page 8Linked to original sources
PubMed1989

An assessment of the fit of a parabolic curve to pre- and post-treatment dental arches.

Study casts of the teeth are routinely used for diagnosis and to assess treatment change: the crowding of the teeth or shortage of space available within the dental arch is usually assessed visually. A full cast analysis program has been developed previously, making use of the three-dimensional Reflex Plotter linked to a computer. This study examines the validity of the fit of computer generated parabolic curves to dental arches, as performed in the measurement of crowding. Using a visual analogue method it was found that the parabola appeared to fit lower post-treatment dental arches best. However, reservations regarding the fit of symmetrical curves are expressed and other solutions suggested.

Dental Arch↗
PubMed1989

An initial assessment of the effect on orthodontic pliers of various sterilization/disinfection regimes.

Duplicates of six commonly used orthodontic instruments were allocated to four groups. One of the groups of instruments was stored as a control. The three other groups were exposed to different regimes of sterilization or cold disinfection over an extended period. Twenty characteristics of function, corrosion, and appearance were then judged by four observers twice using a visual analogue scale of 100 units. No statistical evidence was found of routine autoclaving causing more damage to pliers than cold disinfection; in fact, the data suggested the contrary. Chrome plated pliers appeared more resistant to damage and maintained their appearance better than stainless steel pliers.

Chromium Alloys↗
PubMed1988

A Reflex Plotter investigation into the dimensional stability of alginate impressions following disinfection by varying regimes employing 2.2 per cent glutaraldehyde.

Alginate impressions of an acrylic study cast pair were disinfected to a variety of regimes using 2.2 per cent glutaraldehyde. A number of linear measurements on the resultant plaster study casts were made using a Reflex Plotter to assess the effect on the dimensional stability of the casts. Significant differences were found for a number of the variables measured. Quantitatively these differences were small and of limited clinical significance; they may, however, be of greater significance where serial records are being collected for research.

Alginates↗
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

Orthodontic movement of a canine into an adjoining extraction site.

The orthodontic movement of a canine tooth into an adjoining extraction site using a removable appliance is calculated using the finite element method (FEM). The calculated movements are compared, using a reflex plotter, with actual clinical measurements made on several patients. In both cases, wide variations in tooth displacement and hence rotation are found. The most important variable indicated by FEM appears to be the angle at which the load acts on the tooth. The position and magnitude of load have only a minor influence.

Cuspid↗
PubMed1985

Initial tooth movement: force application and pain--a relationship?

Initial dental casts of 24 patients, who had previously completed a discomfort index card for the first 16 days following placement of a fixed appliance, were examined. A method is described whereby the anterior and overall crowding in the relevant dental arch was measured as a tooth/arch discrepancy index using the reflex metrograph. The crowding was measured in three dimensions as the discrepancy between the sum of the anatomic mesiodistal widths of the teeth and the actual mean arch shape canine to canine (3 to 3) and first molar to first molar (6 to 6) inclusive. An additional two-dimensional method using the best "goodness of fit" (least variance) of a parabolic arch shape for the mean arch length in the 6 to 6 crowding measurement is also described. The measurement accuracy of the reflex plotter was less than 0.12 mm. The method error for the crowding measurements expressed as root mean square (RMS) values was 0.97 mm for the anterior tooth/arch, 1.45 mm for the overall tooth/arch discrepancies, and 1.35 mm for the tooth/arch discrepancy based on the best fit of a parabolic curve. It is proposed that since the same bracket width and fully engaged arch wire type were used in every case, some relationship between the initial crowding that reflected the forces applied and the discomfort experienced by the patients might be expected. This was not found to be true. There was no correlation between the total discomfort experienced and the crowding measurements 3 to 3 or 6 to 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Disturbances of tryptophan metabolism in mice acutely deprived of tryptophan.

The effect of a dietary tryptophan deficiency on tissue serotonin (5-hydroxytryptamine) synthesis rates, systemic tryptophan metabolism and its response to steroid or cycloheximide treatment was investigated. Brain serotonin synthesis was depressed in tryptophan-deprived (TD) mice while duodenal serotonin synthesis was enhanced following a tryptophan load. Liver total protein content was initially depressed in TD mice but increased following a tryptophan load. Blood tryptophan and albumin were depressed in TD mice while the percentage of albumin-bound tryptophan significantly increased in TD mice. Serum-free fatty acids were not significantly altered. Furthermore, enzyme kinetics studies indicated that in TD mice, tryptophan-5-hydroxylase has a reduced Vmax, while the Km for both tryptophan and the pteridine cofactor was significantly lowered. The tryptophan hydroxylase response to tryptophan or hydrocortisone injection was accentuated in TD mice while the tryptophan-2,3-dioxygenase response to tryptophan or hydrocortisone injection was blunted in TD mice. Finally, injection of tryptophan and cycloheximide blocked the tryptophan-2,3-dioxygenase response while the tryptophan hydroxylase response was unaltered in both control and TD diet mice.

Animals↗
PubMed1985

A comparison of two- and three-dimensional incisor angles.

Two- and three-dimensional incisor angulations are compared in 40 patients using lateral radiographs and direct dental cast measurement using the Reflex Metrograph coupled to a computer. The two-dimensional upper and lower incisor angulations to the occlusal plane were also compared by the two methods. It was found that: The two-dimensional radiographic and three-dimensional dental cast inter-incisor angulation showed a significant difference at a probability level 0.01 greater than p greater than 0.001. The two-dimensional radiographic and two-dimensional dental cast upper left and right incisor angulations to the functional occlusal plane showed a significant difference at a probability level of 0.01 greater than p greater than 0.001. The significant differences can be attributed to the measurement of the incisor crown angulation in the dental cast measurement and the incisor tip and apex assessment in the radiographic technique. The system of dental cast measurement arguably provides a more realistic and reliable assessment of incisal angles than conventional radiographic measurement techniques.

Cephalometry↗
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↗
PubMed1984

Orthodontic treatment in Ehlers-Danlos syndrome.

The literature is briefly reviewed and the presentation and orthodontic treatment of a patient with Ehlers-Danlos syndrome is described. Surprisingly, in view of the nature of this collagen disorder, tooth movement appeared to progress normally; there was, however, a problem of mucosal ulceration which was alleviated through regular use of chlorhexidine mouthwash.

Adolescent↗