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Biomedical subjects

P M Dummer

Publications and source records attributed to P M Dummer.

At least 73 records · Page 4Linked to original sources
PubMed1993

Comparison of two sonic handpieces during the preparation of simulated root canals.

The objective of this study was to assess and compare two sonic handpieces during the preparation of simulated root canals. A total of 60 simulated canals in clear resin blocks of various angles and positions of curvature were prepared using Shaper files activated either by an MM1500 Sonic Air or an MM1400 Mecasonic handpiece. Each handpiece was used to prepare 30 canals using an identical preparation procedure which involved a linear filing motion and an anticurvature technique in curved canals. The efficacy of the handpieces was determined for straight and curved canals separately and included an assessment of loss of canal length, weight loss from the blocks, smoothness of canal walls, transportation and overall shape of the prepared canals. Canals were prepared rapidly and effectively by both handpieces. Overall, the MM1500 handpiece was associated with significantly less distance loss (P < 0.05) and significantly more loss of weight (P < 0.01). Only four prepared canals (8%) had hour-glass shapes displaying zips and elbows, each handpiece created two. Only two canals (4%) had danger zones, both were created by the MM1400 handpiece. There was little difference between the handpieces in terms of the smoothness of canal walls, the direction and amount of transportation or the overall shape of canals. Under the conditions of this study, the new MM1400 Mecasonic handpiece performed as well as the established MM1500 Sonic Air.

Analysis of Variance↗
PubMed1992

Comparison of six files to prepare simulated root canals. 1.

A total of 300 simulated root canals of various angles and positions of curvature in clear resin blocks were prepared by hand using either K-files, K-Flex files, Flexofiles, Flex-R files, Hedstrom files or Unifiles. Each file type was used to prepare 50 canals employing a linear filing motion and an anticurvature stepback technique. Part 1 of this two-part report describes the efficacy of the files in terms of preparation time, instrument failure, loss of canal length and weight loss from the blocks. Two-way analysis of variance confirmed that there was significant variation for each parameter between instruments, between canal types, and with interaction between instruments and canal types. Overall, preparation with Hedstrom files was significantly quicker than with any other file, whilst preparation with K-files and K-Flex files took significantly longer. Fracture and deformation of instruments occurred substantially less often with Flex-R and Hedstrom files, but significantly more often with Unifiles. Loss of working distance occurred with all file types, but was significantly greater in canals prepared with K-files. Unifiles and Hedstrom files were responsible for significantly more weight loss than the other files, whilst K-files produced significantly less weight loss. Canals with rough undulating walls were created most often by Hedstrom files and Unifiles. Overall, under the conditions of this study, Flexofiles, Flex-R files and Hedstrom files appeared to be substantially more effective than K-files, K-Flex files and Unifiles.

Analysis of Variance↗
PubMed1992

Comparison of six files to prepare simulated root canals. 2.

A total of 300 simulated root canals of various angles and positions of curvature in clear resin blocks were prepared by hand using either K-files, K-Flex files, Flexofiles, Flex-R files, Hedstrom files or Unifiles. Each file type was used to prepare 50 canals employing a linear filing motion and an anticurvature stepback technique. Part 2 of this two-part report describes the efficacy of the files in terms of the prevalence of canal aberrations, the amount and direction of canal transportation and the overall postoperative canal shape. Hourglass shaped canals were found in 4.5% of curved canals, the majority of these being created by K-files and K-Flex files. Perforations were seen in 6.3% of curved canals, the majority being produced by Flex-R files and K-files. Excessive removal of material from along the inner aspect of the canal curve occurred in 10.4% of canals, by far the majority being created by Hedstrom files. Transportation of canals was a consistent finding with all instruments. Two-way analysis of variance revealed how significant differences in the absolute magnitude of transportation occurred between instruments, between canal types and by an interaction between instrument and canal type. In general, transportation was towards the outer aspect of the canal curve at the end-point of preparation and the zip and elbow, but towards the inner aspect at the beginning of the curve. Further towards the orifice, transportation reverted to the outer aspect of the canal curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

An in vitro study of the influence of X-ray beam angulation on the radiographic images of the amelocemental junction and simulated alveolar crest.

The aim of this in vitro study was to determine the effect of X-ray beam angulation on the radiographic images and relative positions of the amelocemental junction and alveolar crest. Using an artificial model to represent the tooth/bone relationship, radiographs were taken of a total of 15 extracted premolar teeth which had been divided into three distinct groups on the basis of the contour (configuration) of their approximal amelocemental junction. Radiographs of the tooth/bone units were taken at baseline and with a range of horizontal and vertical X-ray beam angulations from 5 degrees to 20 degrees. Analysis of the radiographs revealed that when using the ideal horizontal angulation the radiographic image of the amelocemental junction was dependent upon its contour and was not always represented by its mid-point bucco-lingually. Changing the horizontal angulation of the X-ray beam altered substantially that part of the junction visible on the film regardless of contour. Variation in the vertical angulation of the X-ray beam had little influence on the distance between the radiographic images of the amelocemental junction and a point representative of the approximal crest of the alveolar bone. It is concluded that the contour of the approximal amelocemental junction has an influence on its radiographic appearance and that films taken with an inappropriate horizontal angulation never provide an image of its mid-point bucco-lingually.

Alveolar Process↗
PubMed1992

Radiographic evaluation of early periodontal bone loss in adolescents. An overview.

A number of studies have used radiographs to establish the prevalence of periodontal bone loss in adolescents, though widely differing findings have been reported. It is likely that such disparity of results can largely be attributed to the variety of criteria used to determine the presence of disease, some of which are highly subjective. In addition, a number of factors may affect the radiographic appearance of commonly chosen reference points. If epidemiological studies are to be interpreted correctly, it is important to examine these areas and, in particular, to determine the most objective means of recording disease in this age group. From a review of the literature, it would seem that assessments based on the radiographic distance between the amelo-cemental junction and the alveolar crest are the least subjective, yet whether this should be greater than 2 mm or 3 mm before bone loss is recorded, is still debated.

Adolescent↗
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

Comparison of undergraduate endodontic teaching programmes in the United Kingdom and in some dental schools in Europe and the United States.

The pattern of teaching root canal therapy within dental schools of the UK was determined and compared with that carried out within several dental schools in Europe and the USA. Although it appeared that 'teachers of endodontics' in the UK were advocating techniques adopted elsewhere, it was clear that, within the dental undergraduate curriculum as a whole, the teaching of root canal therapy was given a lower priority than that in some schools in Europe and the USA. Recommendations to remedy this unsatisfactory position are provided.

Education, Dental↗
PubMed1991

A method for the construction of simulated root canals in clear resin blocks.

A method for the construction of simulated root canals in clear resin blocks is described. The canals are inexpensive, simple to produce and are of high enough quality for use in both undergraduate and continuing education. With minor modifications, the canals can also be used for research, particularly during the assessment of instruments and preparation techniques.

Dental Pulp Cavity↗
PubMed1991

A longitudinal study of the condition of first permanent molars in a group of adolescents with special reference to elective orthodontic tooth extraction.

The aim of this study was to investigate changes in the condition of first permanent molars over the teenage years, with special reference to adolescents who lost premolar teeth for orthodontic purposes. A total of 453 South Wales schoolchildren (219 males and 234 females) were examined at the ages of 11-12 and 19-20 years. At 11-12 years, 89.6 per cent of the cohort had all four first permanent molars, while 3.3 per cent had already lost these teeth. Of those first permanent molars present, 61.7 per cent had some caries experience. At age 19-20, 80.6 per cent of subjects retained four first permanent molars while 4.4 per cent had none. Of the first permanent molars present, 80.6 per cent had been affected by caries. In 60 per cent of the 186 subjects (75 males and 111 females) who had lost premolar teeth in the course of orthodontic treatment, a sound premolar was extracted in preference to a first permanent molar which already had evidence of dental disease. At age 19-20 years, the majority of the first permanent molars were restored and otherwise sound, though a small number which had been restored at age 11-12 years had been lost due to caries.

Adolescent↗
PubMed1990

Factors influencing the initiation of carious lesions in specific tooth surfaces over a 4-year period in children between the ages of 11-12 years and 15-16 years.

An analysis of factors influencing the initiation of carious lesions on specific tooth surfaces over a 4-year period in children between the ages of 11-12 years and 15-16 years is presented. Approximately 1000 children, resident in the County of South Glamorgan, Wales, were assessed for caries status and oral cleanliness in 1980 when aged 11-12 years and again in 1984 when aged 15-16 years. On both occasions, the children completed detailed questionnaires on dental health-related topics. Surfaces which were sound when the children were 11-12 years were identified and subsequently awarded a score of zero if they remained sound at 15-16 years or a score of one if they had developed carious lesions or had been filled. For each child, a mean mouth caries initiation score was computed for specific groups of surfaces, namely pit and fissure surfaces in posterior teeth, approximal surfaces in posterior teeth, buccal and lingual smooth surfaces of all teeth and approximal surfaces of anterior teeth. One-way analysis of variance and multiple regression techniques revealed that a number of factors had a significant influence on the initiation of caries. The factors and their level of significance varied between the surfaces. However, relatively little (less than 6 per cent) of the total variance in caries initiation score could be explained by the identified factors. Overall, more lesions developed in pit and fissure surfaces in posterior teeth than in the other surfaces included in the analyses.

Adolescent↗
PubMed1990

Factors influencing the caries experience of a group of children at the ages of 11-12 and 15-16 years: results from an ongoing epidemiological survey.

An analysis of factors influencing the caries experience of adolescents in South Wales is presented. Approximately 1000 children were assessed for caries status and oral cleanliness in 1980 when aged 11-12 years and again in 1984 when aged 15-16 years. In addition, on both occasions, the children completed detailed questionnaires on dental health-related topics. When aged 11-12 years, the observed mean DMFT, DMFS and DFS scores of the children were 4.0, 6.7 and 5.5 respectively. The corresponding scores at age 15-16 years were 6.5, 11.8 and 10.2. A preliminary analysis using conventional multiple regression techniques revealed that a number of factors had a significant influence on the caries experience of the children. The significance of the factors depended on the sex of the population subgroup, the age of the children and the particular caries index studied. However, at both ages the factors of most significance were the number of erupted teeth, total mean plaque score and the reported amount of money spent on sweets per week. A further evaluation using analysis of covariance with the number of erupted teeth and surfaces as the covariates confirmed the significant influence of the total mean plaque score and amount of money spent on sweets. In addition, both analyses indicated that toothbrushing frequency and social class had a significant influence on the caries experience of boys.

Analysis of Variance↗
PubMed1990

The production of secondary caries-like lesions on cavity walls and the assessment of microleakage using an in vitro microbial caries system.

The aim of this study was to assess microleakage along restored cavity walls using a new in vitro microbial technique. Extracted human teeth containing cavities restored with a microfine posterior composite were incubated in broth inoculated with a single strain of Streptococcus mutans for 10 days, using a sequential batch culture technique. Each margin of the cavities was finished in one of three ways: butt joint and etching; butt joint and no etching, or; bevel joint and etching. The assessment of microleakage was achieved by examining sections of the teeth histologically using polarized light for the presence or absence of caries-like cavity wall lesions. Outer (surface) lesions were also examined and displayed the characteristic zones of early natural caries lesions. The cavity wall lesions were observed as a translucent zone in 31% of butt and unetched margins, 16% of butt and etched margins, and 5% of bevelled and etched margins.

Acid Etching, Dental↗
PubMed1990

Traumatic injury to maxillary incisor teeth in a group of South Wales school children.

This study examines, from photographic records, the prevalence of accidental damage to maxillary incisor teeth in a group of 968 11/12-year-old South Wales school-children; 15.3% showed evidence of trauma ranging from enamel fractures or discolouration to actual loss of a tooth. Boys (19.4%) showed a higher prevalence of trauma than girls (11%). Maxillary central incisors were the most at risk from trauma, with coronal fractures being the most commonly sustained injury. Those subjects who showed evidence of trauma had an statistically (p less than 0.001) but not clinically significantly greater overjet than did those who had none. The percentage of subjects suffering trauma increased significantly with increasing overjet, but lip incompetence did not affect the prevalence of accidental damage. Though statistically unsupported due to the small numbers involved in this cohort, it appeared that the rougher nature of boys activities and their more active participation in sports were of greater importance than the magnitude of their overjet in determining whether their teeth were at risk from trauma. In contrast, it was the magnitude of the overjet which was the dominant factor in girls. Despite the wide availability of relatively simple means of restoration and, in the majority of cases, regular dental examinations, only 14.8% of traumatised teeth had received treatment at this age.

Child↗
PubMed1990

The effect of toothbrushing frequency, toothbrushing hand, sex and social class on the incidence of plaque, gingivitis and pocketing in adolescents: a longitudinal cohort study.

Reported toothbrushing frequency and the effect of toothbrushing frequency, toothbrushing hand, sex and social class on the incidence of plaque and periodontal disease in a group of 720 adolescents examined at age 11-12 years and again at 15-16 years is presented. At 11-12 years, the mean toothbrushing frequency was 11.5 times per week. By age 15-16 years, it had risen to 13.3 times per week. Children from social class I were less likely to brush once per day or less and more likely to brush twice daily than those from social class V. At both examinations, consistently low negative correlations were seen between reported toothbrushing frequency and the mean scores for buccal and lingual plaque, buccal, mesial and total bleeding. Few significant differences were seen between left- and right-handed toothbrushers at age 11-12 years. These were almost entirely due to differences between the boys. By age 15-16 years, no significant differences existed between the two groups. At both examinations, the boys had higher plaque, bleeding and pocketing scores than did the girls. At 15-16 years of age, all social classes exhibited lower mean total pocketing scores than at age 11-12 years. At 11-12 years of age, the social class differences were mainly contributed by the girls, while at re-examination plaque and bleeding scores for both sexes showed an overall trend to increase from social class I through to social class V. At 11-12 years of age, the boys showed a trend for pocketing to increase from social class I through to social class V. This was absent at 15-16 years of age. The girls showed no such trend at 11-12, but it had emerged by age 15-16. The results again demonstrate the influence of social class and sex rather than toothbrushing frequency and handedness on oral hygiene and gingival health. However, in view of the high number of statistical tests employed, some caution must be exercised in the interpretation of differences significant at the 5 per cent level.

Adolescent↗
PubMed1990

Root canal retained restorations: 1. General considerations and custom-made cast posts and cores.

The first article in this series reviews general considerations relating to the use of root canal retained restorations. The authors discuss factors affecting retention, the arguments for cast versus wrought posts, reinforcement of the tooth, and treatment planning. Clinical procedures for constructing custom-made cast posts and cores, using direct and indirect techniques, are also described. The three subsequent articles will deal with threaded and unthreaded prefabricated post-and-core systems, and root-face attachments for the retention of complete and partial overdentures.

Humans↗
PubMed1990

Root canal retained restorations: 3. Root-face attachments.

It has been common practice for many years to use retained roots to provide support and stability for partial or full dentures. The retention of such overdentures is greatly enhanced if the remaining roots are modified and restored with posts and root-face attachments. The final article in this series on root canal retained restorations classifies and describes some of the root-face attachments currently available, and also describes a number of prefabricated post systems with integral overdenture attachments. Guidelines for clinical and laboratory procedures are given.

Denture Design↗