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Biomedical subjects

M R Sims

Publications and source records attributed to M R Sims.

At least 55 records · Page 3Linked to original sources
PubMed1982

Root surface resorption, repair, and periodontal attachment following rapid maxillary expansion in man.

This study was designed to investigate human repair and reattachment of principal periodontal fibers in areas of resorption on anchor premolar root surfaces following rapid maxillary expansion. Maxillary first premolar teeth were obtained from patients requiring rapid maxillary expansion. Extraction of the teeth was scheduled after periods of retention varying between 14 and 53 weeks. The roots of the teeth were examined via light microscopy and scanning electron microscopy. Extensive root resorption characterized the buccal surfaces of anchor premolars. Repair of the resorptive defects was found to occur exclusively with cellular cementum. Anchor teeth retained for longer periods, up to the maximum of 53 weeks of retention in this study, generally demonstrated more advanced repair. Topographically, Sharpey fiber holes indicative of principal periodontal fiber insertion were found in repair cementum. However, these depressions were neither numerous nor consistent in their presence and location. In human teeth, periodontal attachment to resorbed and repairing surfaces was shown to be present. SEM studies of histologic sections revealed that periodontal fibers and fiber bundles inserted directly into the repair cellular cementum matrix, irrespective of the site of the lesion on the root.

Female↗
PubMed1982

Root resorption in bicuspid intrusion. A scanning electron microscope study.

Apical root surfaces covered by cellular cementum are rapidly subjected to resorption under orthodontic loads of varying magnitude and duration. Within the experimental parameters employed, the intrusive forces applied to the teeth produced a striking increase in root resorption compared with the control teeth. The amount of resorption increased markedly with the duration of the force, and to a lesser extent with the magnitude of the appliance activation. After 70 days, cellular cementum repair accompanied the continuing resorption. Little variation was detected in the susceptibility of different patients to root resorption in the experimental teeth. The same intrusive load applied for the same duration to similar teeth produced a corresponding degree of root resorption in various individuals. On the other hand, there were individual differences in the amount of resorption on untreated control teeth. There is a need to extent our understanding of the periodontal ligament and its associated tissues which provide the basis for our professional services. Clearly, root resorption and the capacity for repair are orthodontic facts of life. In the current climate of technological innovation great emphasis has been given to cephalometrics and appliance mechanics, which provide the orthodontist with the clinical stimulus of visual and tactile involvement. This paper is presented as a contribution to our knowledge of the unseen biological consequences which accompany that orthodontic treatment.

Adolescent↗
PubMed1981

Rapid maxillary expansion and external root resorption in man: a scanning electron microscope study.

The effects of rapid maxillary expansion on the external root structure of thirteen appliance-attached and five unattached maxillary first premolars from nine patients have been investigated with the scanning electron microscope (SEM). Topographic features of cementum and dentine resorption, as well as initial and subsequent remineralization changes, are described in detail. All anchor premolars exhibited root resorption, which was mostly confined to the buccal surface. Generally, the longer an anchor tooth remained in fixed retention, the more extensive the buccal root resorption. In contrast, the unattached maxillary first premolars and the opposing mandibular first premolars showed no evidence of resorption. Active resorption was the dominant process in anchor premolars extracted almost immediately after rapid expansion. Subsequently, repair became the predominant process, but continuing resorption was apparent even after 9 months of retention. Repair of root defects occurred by the deposition of cellular cementum which revealed little evidence of principal periodontal fiber reattachment within the advancing mineral front. The resorption pattern identified in the scanning electron microscope was not detected by in vivo radiographic examination. The significance of the findings is discussed.

Activator Appliances↗
PubMed1981

Upper molar root resorption because of distal movement. Report of a case.

A case of a patient whose upper first molars suffered severe root resorption as a result of distal tooth movement is presented. Complete destruction of one root was found to have occurred. The initial objective in treatment was to regain arch length and improve the molar relationships with headgear. Subsequently, full-bonded orthodontic therapy was initiated after extraction of all first molars, as loss of root length could be observed radiographically. Examination of the extracted upper first molar roots in a scanning electron microscope revealed extensive areas of superficial root surface resorption which were not detectable on radiographs of these teeth. Care should be taken to avoid impingement of roots on adjacent unerupted teeth, which may result in extensive root damage.

Child↗
PubMed1977

Oxytalan fibre organization in marsupial mandibular periodontal tissues.

The arrangement and distribution of oxytalan fibres in Australian marsupials has not previously been reported. Periodontal tissues of wombat, wallaby, possum, and marsupial mouse were examined to ascertain oxytalan fibre organization. Despite adaptation of the marsupial masticatory apparatus to different diets the oxytalan fibre organization in the periodontal ligament shows a basic pattern which corresponds with that reported in other animals. The oxytalan system forms a continuous meshwork of fine, branching fibres which completely invests each tooth root and connects adjacent teeth. Thick ribbon-like apico-occlusally orientated oxytalan fibres, thought to form by the coalescence of thinner fibres, are restricted to the periodontal ligament. The oxytalan fibres are embedded in cementum and attached to blood vessels in the pariodontal ligament. Oxytalan fibres do not insert into alveolar bone. Histological evidence indicates functional remodelling of the oxytalan fibre system in continuously erupting teeth.

Animals↗
PubMed1977

Tensile properties of orthodontic wire.

1. Wires with a range of tensile properties are available for construction of a Stage 1 arch wire in the Begg orthodontic appliance. 2. Over a period of 3 days, a detectable amount of stress relaxation occurs in some orthodontic wires loaded initially to 20 kg.

Dental Stress Analysis↗
PubMed1977

The oxytalan fiber system in the mandibular periodontal ligament of the lathyritic mouse.

Experimental lathyrism was produced in young albino mice with a diet containing 50% sweet pea seed (Lathyrus odoratus). After 7 days on the lathyritic diet, sections of themandibular molar and incisor periodontal ligaments, when oxidized and treated with aldehyde fuchsin, demonstrated enhanced staining of the oxytalan fibers and numerous vessels. At this time aldehyde fuchsin or orcein also revealed marked pathological changes in the periodntal ligament of all molars. When athyrism was prolonged for 12 weeks, both the molar and incisor oxytalan systems were still readily identifiable although the molar periodontal ligament continued to be serverely affected by lathyrism. The oxytalan fibers retained their characteristic tooth-vascular association in all of the lathyritic mice. Oxytalan fibers of the lathyritic and control animals showed similar reactions to enzyme digestion with beta-glucuronidase, elastase, and pepsin. However, gingival elastic fibers reacted in a different way from oxytalan fibers with beta-glucuronidase and elastase treatment. These findings indicate that in the lathyritic mouse the oxytalan fiber system of functioning teeth possesses a high degree of permanence and is metabolically distinct from collagen and elastic fibers.

Animals↗
PubMed1976

Reconstitution of the human oxytalan system during orthodontic tooth movement.

Orthodontic tooth movement in man has revealed that the oxytalan fiber system possesses a high order of maintenance. Oxytalan fibers did not merely increase in number during orthodontic movement. On the contrary, the oxytalan fiber system underwent reconstruction and adaptation to extensive metabolic and anatomic changes within the periodontium. With the use of light orthodontic forces, the oxytalan fiber system was constantly remodeled on both the tension and compression sides and maintained a characteristic cementum-vascular relationship even when teeth were moved a significant distance through the alveolar bone. In contrast, heavier forces caused localized destruction of the oxytalan system in regions of excessive pressure and tension. Reconstitution of the oxytalan system provided evidence against the concept that oxytalan fibers are stretched by orthodontic movement and subsequently contribute to relapse by elastic rebound. In man the oxytalan fiber system of the periodontal ligament is arranged as a three-dimensional fiber meshwork and exhibits a complex geometry like other fiber systems in the connective tissues. Knowledge of the interaction between elastic and collagen fibrillar assemblies has been used to derive some speculative concepts of oxytalan-collagen interaction. These concepts have been put forward with the intention of stimulating further interest in the oxytalan fiber meshwork. The present investigation emphasizes that the use of the light microscope to examine and record static images of complex biologic changes can provide new knowledge of the structure and function of human connective tissues.

Adolescent↗