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Biomedical subjects

R G Oliver

Publications and source records attributed to R G Oliver.

At least 19 recordsLinked to original sources
PubMed1992

The bioprogressive technique in postgraduate teaching: 8 years of clinical experience.

The historical movement towards the adoption of the bioprogressive technique for postgraduate teaching on the Cardiff course is outlined. The department's experience in routinely teaching and using the appliance is described, with illustrations from a number of post-graduate cases. The advantages and disadvantages of a pre-adjusted sectional mechanics system are considered. The place of sectional mechanics in the future is discussed together with how such techniques may be included, with advantage, in any taught preadjusted appliance system.

Adolescent↗
PubMed1992

Different techniques of residual composite removal following debonding--time taken and surface enamel appearance.

Four different methods of in vitro residual composite removal following debonding performed by two different operators (an orthodontist and a hygienist) were assessed for enamel surface damage (using scanning electron microscopy) and the time involved. There was no difference in the quality of enamel surface appearance between the two operators, regardless of the method used for composite removal. There was a statistically significant difference (P less than 0.05) for the time taken for composite removal between the two operators using a tungsten carbide bur method only. It is suggested that an expanded duties auxiliary with the practical skills of the hygienist would be able to remove residual composite debris and produce a satisfactory polished enamel surface using tungsten carbide burs and aluminium oxide polishing discs, thus becoming a safe and cost-effective member of the orthodontic team.

Composite Resins↗
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↗
PubMed1992

Loss of the first permanent molar and caries experience of adjacent teeth.

The caries experience of the occlusal and distal surfaces of the second premolars and the occlusal and mesial surfaces of the second permanent molars was examined in four groups of subjects aged 19-20 years. Group 1 comprised subjects with first permanent molars present, Group 2 subjects with early loss of the first permanent molar (before the age of 11-12 years), Group 3 subjects with late loss of the first permanent molar (after 11-12 years but before 15-16 years) and Group 4 included a combination of Group 2 and Group 3. Loss of the first permanent molar was associated with increased caries or restorations in the occlusal surfaces of adjacent teeth, but reduced caries or restorations in the proximal surfaces of adjacent teeth. Early loss of the first molar was associated with significantly greater caries or restoration experience in proximal surfaces than late loss, but no difference was detected for occlusal surfaces.

Adolescent↗
PubMed1991

Effect of early programmes of high and low intensity exercise on physical performance after transmural acute myocardial infarction.

Does a programme of light exercise training after acute myocardial infarction produce the same improvement in treadmill performance as aerobic exercise training? Three hundred and eight men from a consecutive series of 479 men with transmural (Q wave) acute myocardial infarction, admitted to a single coronary care unit, were randomly allocated to eight weeks of group aerobic exercise training or group light exercise. Groups were well matched for all characteristics other than site of infarction, which did not significantly affect results. Mean (SD) physical working capacity (metabolic equivalents) determined by treadmill testing at the start of the study (in the third week after infarction) was 6.8 (2.2) v 6.7 (2.5) METs, at the end (in the eleventh week after infarction) 10.8 (2.3) v 9.9 (2.4) METs, and at 12 month review 10.8 (2.4) v 10.7 (1.9) METs for the exercise training group and the light exercise group respectively. The difference of 0.9 METs at the end of the study was the only significant difference between groups. There were no significant intergroup differences at any stage in resting and maximal heart rate, resting and maximal systolic blood pressure, or rate-pressure product. Apart from a small temporarily greater physical working capacity, the physical benefits of aerobic exercise training were equally well achieved by group light exercise.

Adult↗
PubMed1991

Cephalometric analysis comparing five different methods.

A commonly used cephalometric analysis was performed repeatedly on five lateral cephalometric radiographs using a variety of methods, and the angular values obtained compared. Two computerized methods, one utilizing direct digitization of the radiograph and the other digitizing an enhanced video image of the radiograph, were compared with each other and also against the traditional manual method of tracing. In addition, a single manual tracing of each of the radiographs was digitized using each computer method. It was found that direct digitization is less precise than both the traditional method and digitization of a tracing. The facility to enhance the radiographic image using video techniques did not produce any significant improvement in precision of the cephalometric variables studied.

Cephalometry↗
PubMed1991

A 'bonding' typodont.

A new technique is presented for the construction and use of a typodont suitable for teaching correct bracket positioning. The advantages of the method are illustrated.

Acrylic Resins↗
PubMed1990

Telephone directory listings of presumptive Chinese surnames: an appropriate sampling frame for a dispersed population with characteristic surnames.

Choosing an appropriate sampling frame for an epidemiologic study depends on the characteristics of the population under investigation and the sources available for identification of potential subjects. Not all countries maintain (or permit sampling from) population registers. In studies of dispersed populations, electoral rolls may lead to sampling bias, and random-digit dialing is inefficient. A dispersed population characterized by distinctive surnames might be appropriately identified and sampled through telephone directory listings, however. The method proved feasible and efficient for a prevalence study of health-related characteristics of Chinese residents in Melbourne, Australia, yielding a sample demographically comparable to the corresponding census population.

Adult↗
PubMed1989

Distortion of edgewise orthodontic brackets associated with different methods of debonding.

The effects of three different methods of bracket removal on the dimensions of the arch wire slot of edgewise brackets were examined. Gross distortion (visible to the naked eye) and microscopic distortion were found for all three methods. Gross bracket distortion was found infrequently with one method. At a microscopic level, all methods produced approximately equal levels of distortion, principally an increase in vertical slot dimensions. The implications of these findings for recycling brackets are discussed.

Dental Bonding↗
PubMed1989

A clinical study of amount of adhesive remaining on enamel after debonding, comparing etch times of 15 and 60 seconds.

This study is a follow-up of a previously reported trial that examined bond failures with either a 15- or 60-second enamel etch time. For the current study the same subjects were followed through to debonding at the end of active treatment. Two different methods of bond removal were used and an assessment of the amount of adhesive remaining was made by means of an Adhesive Remnant Index (ARI). ARI was not affected by etch time, age, sex, quadrant, or length of time on test; however, there was a statistically significant association with the position of the tooth in the arch, bracket type, debonding method, and operator. There would appear to be no clinical disadvantage with an enamel etch time of 15 seconds.

Acid Etching, Dental↗
PubMed1989

Scanning electron microscope appearance of the enamel/composite/bracket areas using different methods of surface enamel treatment, composite mix and bracket loading.

Minimal plaque retention on and around orthodontic brackets is of paramount importance if iatrogenic tooth damage is to be avoided. This study made use of the scanning electron microscope to examine how variations in composite mix and finishing affected the smoothness and adaptation at the bracket, composite, and enamel interfaces. The study indicated that the optimum choice for good composite/enamel adaptation with a smooth composite surface and good composite/bracket adaptation involves the use of an intermediate unfilled resin layer, a paste/liquid mix of composite placed on a bracket which is optimally loaded, and no excess composite removed with an instrument.

Acid Etching, Dental↗
PubMed1989

Morphology of the maxillary lateral incisor in cases of unilateral impaction of the maxillary canine.

Two groups of subjects who demonstrated unilateral maxillary canine impaction were examined, a Caucasian group and an Oriental group. It was found that there are significant differences between the groups for sex of patients seeking treatment, site of impaction (buccal/palatal), and arch form. The Oriental group was significantly more crowded in the canine area than the Caucasian group. In almost all cases the dimensions of the lateral incisor on the side of impaction were smaller than the non-impacted side, although five subjects from the Caucasian female sub-group did not conform to this pattern, and for the Oriental male sub-group the mesiodistal crown width was larger on the impacted side.

Adolescent↗
PubMed1988

A clinical trial comparing the failure rates of directly bonded brackets using etch times of 15 or 60 seconds.

A clinical trial was conducted to compare bond failure when 15-second or 60-second acid etch times were used for the direct bonding of metal edgewise brackets. Bonds totaling 1174 were studied over a period of 6 to 13 months. Analysis of failure rate, bond survival time, and cement remaining after failure showed no statistical difference between the 15-second and 60-second etch groups. There were statistical differences in bond failures relating to the position of the tooth in the arch (p less than 0.001) and to the type of bracket (p less than 0.001).

Acid Etching, Dental↗
PubMed1988

The effect of different methods of bracket removal on the amount of residual adhesive.

The amount of residual adhesive following three different methods of bracket removal was examined. The effects of tooth position, bracket base type, and composite mix were also examined. It was found that there was a nonsignificant trend for more composite to remain on upper anterior teeth and a highly statistically significant difference between a paste/paste and paste/liquid composite mix. Bracket base type showed no significant difference. One method of bracket removal resulted in significantly less composite remaining than the other two methods.

Acrylic Resins↗