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Biomedical subjects

P M Dummer

Publications and source records attributed to P M Dummer.

At least 91 records · Page 5Linked to original sources
PubMed1990

Two-part resin bonded cast metal bridges for use when abutment teeth have unequal effective root surface areas.

Resin bonded cast metal bridges have become a popular method of replacing missing teeth. Such bridges are usually constructed as single castings following modifications to the abutment teeth in order to ensure a distinct path of insertion and to secure maximum metal to tooth contact. Unfortunately, long term retention of resin bonded bridges cannot be guaranteed and many surveys have reported substantial failure rates, particularly in the posterior segments of the mouth. It is the authors contention that many of these failures occur because clinicians are neglecting one of the fundamental principles of fixed bridge prosthodontics, namely that abutment teeth should be matched for effective root surface area (bony support). This article describes how problems created by incompatible abutment teeth can be overcome successfully by the construction of resin bonded bridges in two parts which are cemented separately, but interlock to provide a movable joint. Such an arrangement allows independent movement of the abutment teeth whilst providing sufficient retention and support for the bridge. The two-part design can also overcome problems created by malaligned abutment teeth as well as allowing conventional full crown retainers to be combined with resin bonded retainers.

Adult↗
PubMed1990

Prevalence and distribution by tooth type and surface of developmental defects of dental enamel in a group of 15- to 16-year-old children in South Wales.

In 1984 the prevalence and distribution of developmental defects of dental enamel in 791 children aged 15-16 years was determined using the DDE index. The children were all residents of the county of South Glamorgan, Wales, which has a public water supply containing less than 0.1 mg fluoride/litre. The teeth were dried but not cleaned prior to examination and a dental operating light was used for illumination. Teeth with some type of defective enamel were seen in 50.1 per cent of children. White/single opacities were present in 28.3 per cent of children and white/diffuse, patchy opacities in 10.2 per cent of children. The enamel was abnormal in 5.71 per cent of all teeth with white/single opacities and white/diffuse, patchy opacities occurring in 1.81 per cent and 1.66 per cent of teeth respectively. There were no significant differences between boys and girls in terms of mouth or tooth prevalence of defects. Overall, 7.6 per cent of maxillary teeth were affected compared to 4.3 per cent of mandibular teeth. Most teeth were affected equally on right and left sides of the mouth except for maxillary lateral incisors and canines which had significantly more defects on the right (P less than 0.05 and P less than 0.005 respectively) and maxillary second molars, which had significantly more defects on the left (P less than 0.01). Maxillary central incisors (15.2 per cent) were affected by enamel defects most often followed by maxillary first molars (9.1 per cent) and maxillary lateral incisors and mandibular first molars (both 8.3 per cent).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Shaping of simulated root canals in resin blocks using files activated by a sonic handpiece.

A total of 180 simulated root canals in clear resin blocks with various lengths and degree of curvature were prepared by either Heliosonic, Rispisonic or Shaper files activated by a sonic handpiece. Each file type was used to prepare 60 canals employing an in/out, circumferential filing motion. The efficacy of the sonic handpiece and the three file designs were assessed by instrumentation time, deformation and fracture of instruments and loss of working distance. The shape of the prepared canals was assessed by direct observation and from composite photographic prints produced by super-imposing negatives of the canals obtained before and after preparation. Overall, canal shaping with the Rispisonic and Shaper files was rapid and efficient whilst that with the Heliosonic files was slower and ineffective. With each file type, prepared straight canals displayed a continuously tapering form that was narrowest at their end-point. The majority of curved canals prepared with Heliosonic files were hourglass in shape whilst the majority prepared with the Rispisonic and Shaper files were tapered. Zips and elbows were only created with Rispisonic and Shaper files in those canals with very short, acute curves. Under the conditions of this study the use of Rispisonic and Shaper files activated by a sonic handpiece proved a satisfactory method of shaping simulated root canals in resin blocks.

Dental Cavity Preparation↗
PubMed1989

A comparison of the ability of K-files and Hedstrom files to shape simulated root canals in resin blocks.

A total of 50 simulated root canals in clear resin blocks with various degrees and positions of curvature were prepared by either K-files or Hedstrom files. Each file type was used to prepare 25 canals employing an in/out circumferential filing motion. The efficacy of the files was assessed by instrumentation time, deformation and fracture of instruments, and loss of working distance. The shape of the prepared canals was assessed by direct observation and from composite photographic prints produced by superimposing negatives of the canals obtained before and after preparation. Overall, canal shaping with Hedstrom files was quicker and more effective. Both file types prepared straight canals in an appropriate manner but the majority of prepared curved canals were hourglass in shape. In general, K-files created zips which were wider and thus more pronounced than those produced by Hedstrom files. Wide 'danger zones' were also regularly created. The location of the aberrations depended largely on the original shape of the canal and in particular on the position of the beginning of the canal curve. Under the conditions of this study, the manipulation of K-files and Hedstrom files in a simple in/out circumferential filing motion proved an unsatisfactory method of shaping simulated curved root canals in resin blocks.

Dental Cavity Preparation↗
PubMed1989

Shaping of simulated root canals in resin blocks using the step-back technique with K-files manipulated in a simple in/out filling motion.

A total of 60 simulated root canals in clear resin blocks of various lengths and degree of curvature were prepared by hand with K-files using a step-back enlargement technique. The instruments were manipulated exclusively with a simple in/out filing or rasping motion with no attempt at rotation or twisting. The preparation technique was assessed by instrumentation time, deformation and fracture of instruments, and loss of working distance. The shape of the prepared canals was assessed by direct inspection and from composite photographic prints produced by superimposing negatives of the canals obtained before and after preparation. In general, the preparations were time-consuming and tedious to complete. Deformation and separation of instruments occurred mainly in those canals with short, severe curves. Loss of working distance was a universal finding and was associated to a degree with the straightening of curved canals inherent in their preparation. Prepared straight canals displayed a continuously tapering form being narrowest at their end-point. On the other hand, prepared curved canals were invariably hourglass in shape. Under the conditions of this study the manipulation of K-files in a simple in/out filing motion proved an unsatisfactory method of preparing simulated curved root canals in resin blocks.

Dental Pulp Cavity↗
PubMed1988

The relationship of anterior overjet to plaque and gingivitis in children.

The aim of the present investigation was to evaluate the relationship of overjet to periodontal status. Detailed examinations of occlusal and periodontal characteristics were completed on 914 12-year-old children. Plaque indices, bleeding indices, and anterior overjet were recorded for each incisor tooth. There was a significant association between mean plaque scores and the extremes of overjet measurement, suggesting that tooth cleaning is more difficult in these cases. Also, it was apparent that for right-handed children, the plaque and gingivitis scores were lower on the left side of the mouth.

Child↗
PubMed1987

A study of the association of fraenal attachment, lip coverage, and vestibular depth with plaque and gingivitis.

The effects of fraenal attachment, upper lip coverage, and mandibular vestibular depth on plaque and bleeding indices in the maxillary and mandibular anterior segments were studied in a group of 1015 school children aged 11.5 to 12.5 years. The position of the mandibular labial fraenum was relatively unimportant to plaque and mandibular gingivitis, but anterior fraenal attachment in the maxilla appeared to affect the retention of plaque and the degree of gingivitis. Maxillary and mandibular plaque and bleeding scores increased with decreasing upper lip coverage at rest. In the mandibular anterior segment, plaque and bleeding indices decreased with increasing vestibular depth. Further analysis demonstrated that fraenal attachment and vestibular depth and fraenal attachment and lip coverage were significantly associated. However, two-way analysis of variance indicated that the influence of fraenal attachment, vestibular depth, and lip coverage on plaque and gingivitis was independent. The influences of these soft tissue variables on plaque accumulation and gingivitis were of small clinical significance and not in themselves a justification for mucogingival surgery.

Child↗
PubMed1986

Distribution of developmental defects of tooth enamel by tooth-type in 11-12-year-old children in South Wales.

The distribution of enamel developmental defects in 759 11-12-yr-old children from South Wales is described. Overall, 8% of maxillary teeth were affected compared to 3.6% of mandibular teeth. Most teeth were affected equally on right and left sides of the mouth except for maxillary lateral incisors, which had significantly more defects on the right (P less than 0.05) and maxillary first molars, which had significantly more defects on the left (P less than 0.025). Maxillary central incisors (18.7%) were affected by enamel defects most often followed by maxillary first molars (8.1%) and maxillary lateral incisors (7.2%). The ranking order of the teeth varied when the prevalence of the different types of defects was assessed. White demarcated opacities were seen most often in maxillary central incisors (10.8%), yellow demarcated opacities in maxillary first molars (1.8%), diffuse opacities in maxillary central incisors (6.6%) and hypoplasias in mandibular first premolars (1.5%). Defects of all types occurred most frequently on the buccal surfaces of the teeth. In premolar and molar teeth more defects occurred on the occlusal surface than on the lingual.

Child↗
PubMed1986

Dental and social effects of malocclusion and effectiveness of orthodontic treatment: a strategy for investigation.

Study of the effectiveness of orthodontic treatment is complicated by a variety of factors, including the need for longitudinal, multidisciplinary appraisal and difficulties of randomisation, control and sample composition. This report outlines a recent initiative adopting a longitudinal, observational approach with a cohort of approximately 1000 12-yr-olds, selected by disproportionate stratified sampling in order that occlusal features of low prevalence, but high orthodontic interest, would be well represented. In the event, 4810 subjects were listed and after certain exclusions, 3420 children were screened. Using preselected screening criteria, 663 with specific occlusal features were selected and an additional 355 children with nonspecific features were randomly allocated on a pro-rata basis. This gave a final study population of 1018. Baseline dental data included the recording of caries, periodontal status and mandibular function. Study models were obtained and analysed using a new standardised technique for recording the alignment of individual teeth. Photographs of the face and dentition were collected and a rating system developed to score dental and facial attractiveness. Social-psychological data were recorded via self-rating questionnaires, interviews, parental questionnaires, teacher questionnaires and peer ratings.

Child↗