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Biomedical subjects

B Melsen

Publications and source records attributed to B Melsen.

At least 55 records · Page 3Linked to original sources
PubMed1997

Different approaches to anchorage: a survey and an evaluation.

Orthodontic treatment outcome is often compromised by the loss of anchorage. The forces acting on the anchorage unit have, however received surprisingly little attention, and the loss of anchorage is most frequently expressed in the sagittal occlusal relationship. The present paper discusses the interaction between vertical and sagittal components of dentofacial development, and the importance of taking vertical forces into consideration is stressed. The biological background for anchorage is reviewed, i.e., the impact on the cellular reaction of the periodontal ligament around the teeth of the anchorage unit from the orthodontic force system and from occlusion. A new rigid appliance consisting of two occlusal splints connected with transpalatal arches is introduced. The advantage of using the patient's sense of occlusion as part of anchorage by means of this appliance is demonstrated in a number of case presentations.

Adult↗
PubMed1997

Masticatory muscle function after unilateral condylar fractures: a prospective and quantitative electromyographic study.

Electromyographic (EMG) recording of masticatory muscle activity was performed in 9 adult men with unilateral condylar fracture immediately after conservative treatment of the condylar fracture (T0) and 4 (T1) and 8 (T2) months after the trauma. From T0 to T2, maximal voluntary contraction of the anterior and posterior temporal muscles and of the masseter muscle opposite the fracture side (contralateral) increased significantly. Activity in the anterior temporal muscles also rose significantly during natural chewing, whereas the masseter muscles remained at the same level, but activity consistently tended to be strongest contralaterally to the condylar fracture. In addition, there was a tendency from T1 to T2 for natural chewing to take place predominantly on the contralateral side. The most obvious overall changes during the follow-up were shorter and stronger contractions in all muscles during chewing, on the side of the impaired joint. The increase of activity in the anterior temporal muscles during maximal bite and natural chewing, and the occurrence of stronger and shorter contractions during ipsilateral chewing, were interpreted as signs of improved function due to healing and relief of pain from the impaired joint. On the other hand, there was a specific rise of maximal activity only in the contralateral masseter, and during natural chewing, activity was constantly stronger in the same muscle in combination with the tendency of increasing predominance of contralateral strokes. These traits specifically related to the masseter muscles were considered an indication of a permanent functional distortion due to reflex suppression on the fracture side as an after-effect of the injury.

Adult↗
PubMed1997

Guided tissue regeneration using bioresorbable membranes: what is the limit in the treatment of combined periapical and marginal lesions?

The maintenance of single teeth may often be of crucial importance for the prognosis of the total dentition. In such cases, as when a single tooth supports a fixed partial denture, a special effort should be made to maintain that tooth. This study reports the treatment of six such terminal cases. The results of a combination of local and systemic antibiotics and the use of guided tissue regeneration with resorbable membranes and grafting material is demonstrated. After defect debridement and root planing, the defects were filled with Biostite (Coletica), and Paroguide (Coletica) membranes were placed. The results at reentry demonstrated the efficacy of these treatments, and all six treatments were considered successful. The influence of the individual components used in treatment is discussed.

Absorption↗
PubMed1997

Changes in the mechanical advantage of the masseter and temporal muscles following surgical correction of mandibular prognathism.

The purpose of this study was to determine if the mechanical advantage of the masseter and temporal muscles is altered and improved as expected in patients subjected to surgical correction of mandibular prognathism. It aimed also to detect any relationship between (1) the moment arms of the masseter and temporal muscles, the moment arm of the bite force, and any morphologic characteristics considered to be factors in determining the size of the moment arms; and (2) the changes in the moment arms and the changes that the combined orthodontic-surgical treatment could induce in the morphologic characteristics. Presurgical and postsurgical lateral cephalograms of 51 consecutive orthognathic surgery patients with severe mandibular prognathism were used. The radiographs were taken 1 week before surgery and approximately 1 year after surgery. The results indicated that the mechanical advantage of the masseter and temporal muscles had a tendency to increase following correction of the dysplasia. The changes in the moment arms of the masseter and the bite force seem to be dependent on the changes in some morphologic parameters such as the angle between the mandibular line and ramal line, the angle between the anterior cranial base and the mandibular line, and the angle between the anterior cranial base and the functional occlusal plane. The combination of changes in these angles together with the shortening of the mandibular length could also lead to a decrease of the advantage of both muscles.

Adolescent↗
PubMed1997

Adjunctive orthodontics as part of interdisciplinary treatment: a case report.

A patient who originally only required gnathologic and prosthetic treatment received orthodontic treatment, which led to a technically less complicated treatment. The removal of teeth with a dubious prognosis improved the long-term prognosis of the dentition. The space closure resolved the anterior protrusion and crowding and was mainly performed through anterior retraction reducing the dentoalveolar protrusion. The buccolingual root control made it possible to generate a better periodontal status in relation to the maxillary canines. A flat splint used as a retainer assisted the prosthodontist in establishing the structural position of the mandible and the intercuspation. The importance of a close interdisciplinary collaboration is stressed.

Adult↗
PubMed1996

Limited chondro-osteogenesis by recombinant human transforming growth factor-beta 1 in calvarial defects of adult baboons (Papio ursinus).

The therapeutic utility of a single application of recombinant human transforming growth factor-beta (hTGF-beta) has not been previously tested in large osseous wounds in primates. Sixteen calvarial defects, 25 mm in diameter, were prepared in four adult male baboons (Papio ursinus). In each animal, three defects were treated with increasing doses of hTGF-beta 1 in conjunction with baboon insoluble collagenous bone matrix as carrier (5, 30, and 100 micrograms of hTGF-beta 1/g of matrix). The fourth defect was implanted with collagenous matrix without hTGF-beta 1 as control. Serial undecalcified sections were prepared from the specimens harvested on day 30. Islands of cartilage and endochondral osteogenesis were found in hTGF-beta 1-treated defects, irrespective of the doses used. Histomorphometry of the defect site showed no significant differences between control and hTGF-beta 1-treated specimens with regard to bone and osteoid volumes. However, analysis of the regenerated tissue in proximity to the defect margins only showed that, on average, greater amounts of bone formed in specimens that were treated with 5 and 30 micrograms of hTGF-beta 1 when compared with controls. This suggests a possible effect on osteoblastic cells originating from the periosteal and endosteal spaces of the severed calvaria. Overall, however, this difference has no therapeutic implications for the healing of large cranial wounds in primates. The present findings indicate that a single application of hTGF-beta 1, in conjunction with collagenous matrix, results in limited chondro-osteogenesis in defects of membranous bone of adult baboons.

Analysis of Variance↗
PubMed1996

Human recombinant transforming growth factor-beta 1 in healing of calvarial bone defects.

Bone healing plays an important role in orthognathic and craniofacial surgery. Bone tissue repair and regeneration are regulated by an array of growth and morphogenetic factors. Osteogenesis proceeds through a cascade of molecular and cellular events sequentially coordinated by members of both the bone morphogenetic protein and transforming growth factor-beta (TGF-beta) families. The efficacy of a single application of 2, 5, or 10 micrograms of recombinant human (rh) TGF-beta 1 to promote bone regeneration in 5-mm experimental calvarial defects of adult male rats was assessed histologically and histomorphometrically. The histomorphometric results of the experimental site were compared with those of the contralateral control side. Dosegroup comparisons were also performed. None of the control and experimental bone defects demonstrated complete bone closure. Limited bone regeneration was found close to the margins of the defects. A statistically significant difference in volume fraction composition (bone, osteoid, and soft tissue) was found between the 5- and 10-microgram rhTGF-beta 1-implanted and control defects. No difference was found in the 2-microgram rhTGF-beta 1-implanted group. The percentage of bone closure was statistically significantly higher in the 5-microgram rhTGF-beta 1-implanted group than in the control group. The present findings indicate that a single application of different doses of rhTGF-beta 1 does not promote clinically relevant osteogenesis in membranous calvarial bone defects in adult rats.

Animals↗
PubMed1995

A methodical study of shape changes in human oral cells perturbed by a simulated orthodontic strain in vitro.

Cells are known to alter their shape as a response to physical and chemical changes. Mechanical loads applied to teeth produced cellular perturbations resulting in orthodontic movement. An in vitro model was developed to simulate the in vivo strain of orthodontic movement. Calibrated forces were applied to human periodontal ligament cells and buccal mucosal fibroblasts (controls). A biaxial strain-producing device was used to stretch vital cells growth on flexible polytetrafluorethylene membranes. In addition, a new cell adhesive, Cell Tak, was employed to examine the effect of an adhesive substrate on the cellular response to two known loads. The shape changes of unstrained (control) and strained cells were evaluated by time-lapse telemicroscopy, and plots of time-dependent alterations in area and shape were recorded. The fusiform cells became more rounded over a given time of up to 1400 s. The responses appeared to be independent of cell type, the strain employed, and the presence of cell adhesive. Scanning electron microscopy demonstrated, irrespective of cell type, that the surface of stressed cells produced a striking number of microvilli as compared with the relatively smooth-surfaced controls.

Adult↗
PubMed1995

Influence of indomethacin on bone turnover related to orthodontic tooth movement in miniature pigs.

The purpose was to evaluate the influence of a prostaglandin inhibitor, indomethacin, on the tissue reaction related to orthodontic tooth movement. Sixteen miniature pigs were chosen for the study, eight of which received indomethacin perorally every day of the 39-day observation period. Sentalloy expansion springs (GAC, Central Islip, N.Y.) delivering 100 cN were inserted on a segmented arch between the central lower incisors. Intravital labeling with tetracycline was used for the evaluation of the rate of bone formation. After the pigs were killed, the bone turnover was evaluated on undecalcified methacrylate embedded sections and on microradiographs. The histomorphometric analysis of bone turnover revealed that the relative extent of resorption surfaces was decreased significantly in the indomethacin treated animals. Formation surfaces were also decreased although not significantly. The bone turnover, but not the mineralization rate, was influenced. The results corroborate the recommendation that prostaglandin inhibitors should be avoided during orthodontic treatments.

Administration, Oral↗
PubMed1995

The effect of bite-blocks with and without repelling magnets studied histomorphometrically in the rhesus monkey (Macaca mulatta).

The effect of bite-blocks with and without repelling magnets as proposed for the treatment of open bite was analyzed. Twelve male juvenile monkeys were divided into three groups of four. Group A was used as control, group B was given bite-blocks containing samarium cobalt disks, and group C received identical bite-blocks without active magnets. The monkeys were observed for 24 weeks before death. Histomorphometric evaluation was then performed on the molar roots, their periodontal tissues, the zygomaticotemporal suture, and the pterygomaxillary suture. The root surfaces of the molars in both the bite-block group and the magnetic group were characterized by pronounced resorption that sometimes was active and occasionally undergoing repair with bony tissue. The sutures also clearly reflected the effect of both appliances used, although more markedly in the cases of bite-blocks containing active magnets. The surface density expressing the sutural area, was increased significantly, possibly as an adaptation to the altered functional demand. The cellular activity of the sutural surfaces also was increased markedly in both appliance groups, reflecting an ongoing adaptation. A steady state had not been reached. The study demonstrated a widespread effect of the force developed by bite-blocks with and without magnets. The final quantity and the reversibility of the effect is not known, however. More long-term studies should be undertaken to obtain this information.

Adaptation, Physiological↗
PubMed1995

Case report: treatment of dental asymmetry.

The treatment of dental asymmetries often comprises several treatment alternatives. This case report describes the treatment alternatives for an asymmetry generated secondary to surgical removal of an odontoma that included the germ of the lower left lateral incisor. The opening of the space was chosen based on the patient's wish. The asymmetrical biomechanical force system used for the correction of the midline is presented as free-body diagram.

Adult↗
PubMed1995

Condylar condition and mandibular growth during early functional treatment of children with juvenile chronic arthritis.

TMJ involvement in children with Juvenile Chronic Arthritis (JCA) will frequently cause disturbance of the growth of the mandible. Orthodontic treatment of these patients often includes orthognathic surgery, and are complicated to handle with respect to the damaged joint and impaired function. The aim of this presentation is to suggest an early treatment with a functional splint appliance, a distraction splint, with the purpose of increasing function of the joint and ensuring continuous growth of the mandible.

Arthritis, Juvenile↗
PubMed1995

Financial consequences of reducing treatment availability in a publicly-funded orthodontic service. A decision analysis problem.

When a third party is responsible for funding a component of the health service, cost/benefit assessments become important. Such assessments become urgent when the budget is reduced. In this paper decision analysis has been applied to evaluate potential savings by reducing the proportion of children offered free orthodontic treatment through the National Health Service in Denmark. Data for the development of the decision tree was acquired using the Delphi technique. The results suggest that a reduction in the proportion of children offered early treatment might ultimately lead to an increased consumption of resources. Further investigation of the issue is needed before definitive recommendations can be made.

Budgets↗
PubMed1995

Guided bone regeneration in calvarial bone defects using polytetrafluoroethylene membranes.

Guided bone regeneration is defined as controlled stimulation of new bone formation in a bony defect, either by osteogenesis, osteoinduction, or osteoconduction, re-establishing both structural and functional characteristics. Bony defects may be found as a result of congenital anomalies, trauma, neoplasms, or infectious conditions. Such conditions are often associated with severe functional and esthetic problems. Corrective treatment is often complicated by limitations in tissue adaptations. The aim of the investigation was to compare histologically the amount of bone formed in an experimentally created parietal bone defect protected with one or two polytetrafluoroethylene membranes with a contralateral control defect. A bony defect was created bilaterally in the parietal bone lateral to the sagittal suture in 29 6-month-old male Wistar rats. The animals were divided into two groups: (1) In the double membrane group (n = 9), the left experimental bone defect was protected by an outer polytetrafluoroethylene membrane under the periosteum and parietal muscles and an inner membrane between the dura mater and the parietal bone. (2) In the single membrane group (n = 20), only the outer membrane was placed. The right defect was not covered with any membrane and served as control. The animals were killed after 30 days. None of the control defects demonstrated complete or partial bone regeneration. In the single membrane group, the experimental site did not regenerate in 15 animals, partially in four, and completely in one. In the double membrane group, six of the experimental defects had complete closure with bone, two had partial closure, and one no closure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗