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Biomedical subjects

D Lundgren

Publications and source records attributed to D Lundgren.

At least 37 records · Page 2Linked to original sources
PubMed1995

The effect of mechanical intervention on jaw bone density.

The aim of this investigation was to test the hypothesis that jaw bone, subjected to mechanical intervention, will heal with increased density compared with conditions before the traumatic insult. The natural edentulous area between the incisor and the first molar on both sides of the maxillary jaw of 8 adult New Zealand white rabbits constituted the experimental model. On the test side, holes were drilled through the cortical plate and into the cancellous bone. No drilling was performed on the contralateral control side. One transversal ground section from each specimen, taken in the centre of and representing both the test and control site, was prepared to ensure that the same sagittal level of the jaw was represented. Morphometric measurements were performed and comprised assessments of the total cross-sectional area of 1) the edentulous part of the jaw, 2) the cortical bone plates and 3) the bone trabeculae and marrow spaces of the cancellous bone. The mechanical intervention resulted in a substantial alteration of the bone tissue morphology, the most conspicuous change being a markedly increased number of bone trabeculae per cancellous bone unit. Thus, the area occupied by bone trabeculae was about twice as large in the test sites compared with the control sites (+103%), whereas the area occupied by bone marrow cavities and cortical bone was significantly smaller. The clinical implications of the findings for potential treatment of fragile bone tissues and bone sites intended for implant insertion are discussed.

Alveolar Process↗
PubMed1995

Augmentation of intramembraneous bone beyond the skeletal envelope using an occlusive titanium barrier. An experimental study in the rabbit.

The aim of this investigation was to evaluate whether augmentation of intramembraneous bone beyond the skeletal envelope can be predictably achieved by placing a completely occlusive barrier on the skull bone of rabbits, hereby creating a secluded space with bone tissue being the only adjoining tissue. The experiment was carried out in 3 New Zealand white rabbits. In each animal, a midline incision was made down to the bone surface of the skull and a skin-periosteal flap was raised to expose the skull bone on both sides of the midline. Two prefabricated titanium domes with an inner diameter of 4.5 mm and an inner height of 3.0 mm were installed on each side. The domes were supplied with a horizontal, peripheral flange and a vertical edge, fitting tightly into a circular slit, prepared by a trephine into the skull bone. This arrangement ensured a stable anchorage of the dome and a reliable peripheral sealing of the space. The skin-periosteal flaps were relocated to cover the domes and sutured. After a healing period of 3 months, the animals were killed and the experimental areas excised and prepared for histological transversal ground sections with each dome in situ. The results demonstrated complete bone fill of all domes, with no signs of ingrowth of other types of tissues, indicating that the use of a barrier with total occlusiveness, sufficient stiffness and stability and reliable peripheral sealing will result in predictable bone augmentation of spaces also beyond the skeletal envelope.

Animals↗
PubMed1995

Continuous versus interrupted continuous orthodontic force related to early tooth movement and root resorption.

The aim of the present clinical investigation was to assess the effects of continuous and interrupted continuous forces of the same magnitude (50 cN = 50 g) on orthodontic tooth movement and related adverse tissue reactions, i.e., root resorption. Thirty-two maxillary first premolars in 16 patients, 8 boys and 8 girls (mean age 13.9 years), were moved buccally by means of a fixed orthodontic appliance with a sectional arch. The patients were divided into two groups of 8, for experimental periods of 4 and 7 weeks. The continuous force was checked and reactivated weekly to 50 cN. The interrupted continuous force applied to the contralateral premolars was left uncontrolled for 3 weeks, after which the arch was made passive for 1 week for tissue rest and recovery. Tooth movements were studied on dental casts using a coordinate measuring machine (Validator 100, TESA SA, Renens, Switzerland). Horizontal tooth movement with continuous force was more effective than with interrupted continuous force after 7 weeks. Histological sections of the experimental teeth, however, showed no difference in the amount or severity of root resorption between the two forces. Individual variations in both the magnitude of tooth movement and the amount and severity of root resorption for both of the two force systems were great.

Adolescent↗
PubMed1995

Repair of orthodontically induced root resorption in adolescents.

The aim of this investigation was to study the reparative potential of orthodontically induced root resorption. Sixty-four maxillary right and left first premolars in 32 patients (15 boys and 17 girls, mean age 13.7 years) were moved buccally with fixed orthodontic appliances and a continuous force of 50 cN (approximately 50 g), activated weekly for 6 weeks. The patients were divided into 4 groups of 8. Retention periods varied from 1 week to 8 weeks. Histological preparations showed that root resorption affected all the test teeth. The percentage of resorptive areas that had begun to repair ranged from 28% after 1 week of retention to 75% after 8 weeks. The healing cementum was almost exclusively of the cellular type. Partial repair, with the resorption cavity walls only partially covered with cementum, was the most frequent type of repair during the first 4 weeks of retention (17% to 31%). Functional repair, with the total surface of the resorption cavity walls covered with varying thicknesses of cementum, dominated after 5, 6, 7 and 8 weeks of retention (33% to 40%). There were no large differences in the healing potential in the cervical, middle, and apical thirds of the root. After 8 weeks, three out of four resorptive areas showed some degree of repair. Individual variations in healing potential were large.

Adolescent↗
PubMed1995

The influence of the design of two different bioresorbable barriers on the results of guided tissue regeneration therapy. An intra-individual comparative study in the monkey.

The aim of the present study was to compare two bioresorbable barriers to evaluate whether differences in design influence the result of guided tissue regeneration (GTR) therapy. Twenty-four (24) plaque exposed, recession type defects in 4 monkeys were treated. Contralateral defects were randomized for test or control treatment. During a healing period of 6 weeks, gingival recession resulting in device exposure occurred at 3 test and 10 control sites. One control barrier was exfoliated. Histologically, 9 of the 12 test barriers were completely integrated with the surrounding tissues. At 3 test sites, epithelium had migrated apically outside the barrier to a level not exceeding one-third of the height of the device. Seven of the 11 control barriers were enclosed by dentogingival epithelium. The adjacent connective tissue exhibited local inflammatory cell infiltrates (ICT). At the remaining 4 control sites, the epithelial downgrowth as well as the adjacent ICT areas were limited to the coronal 1/3 of the device. New attachment; i.e., new cementum with inserting collagen fibers, averaged 2.2 mm and 0.8 mm at the test and control sites respectively (P < 0.01). Based on the results of the present study, it was concluded that a bioresorbable GTR device, designed to prevent epithelial downgrowth along the barrier surface, has a higher potential to promote new attachment formation than a device which does not have this property.

Animals↗
PubMed1995

Membrane-guided bone regeneration. Segmental radius defects studied in the rabbit.

We tested the principle of guided tissue regeneration (GTR) for healing segmental long-bone defects. 7 mm (3 animals) or 10 mm (5 animals) long segmental defects were created in the diaphyses of both radii in 8 rabbits. The defect on one side was covered with a barrier membrane of expanded polytetrafluoroethylene membrane shaped as a tube, while the contralateral side with no membrane served as the control. Healing was followed with radiographs obtained repeatedly during a 13- (n 3) or 27- (n 5) week period. Thereafter, the animals were killed and ground sections of the defect sites were prepared for histologic examination. Radiographically, the control sites showed some early subperiosteal callus formation and nonunion of the defects after 6 weeks. The bone ends were rounded off and sealed with cortical bone. No major changes were noted after 6 weeks. At the test sites, subperiosteal bone formation at the bone ends was first observed radiographically at 2 weeks. At 9 weeks, a thin cortical bone bridged the defect along the inner surface of the membrane. Histologically, an interrupted line of thin, cortical bone was observed along the inner surface of the barrier membrane. Fatty bone marrow occupied the central and largest volume of the defect. We conclude that it seems possible to use the principle of GTR to accomplish bone union of segmental long-bone defects.

Animals↗
PubMed1994

The use of a new bioresorbable barrier for guided bone regeneration in connection with implant installation. Case reports.

This report presents 4 cases with 6 implant exposures after the installation of Brånemark System implants which called for treatment applying the guided bone regeneration technique. A bioresorbable barrier (GUIDOR Matrix Barrier) was used to cover the defects, 4 defects with and 2 without the support of autologous bone chips. Complete bone filling was found in 4 (2 without and 2 with bone chips) and partial filling in 2 (with bone chips) of the treated defects, as registered at the abutment connection 6-7 months after surgery. Besides its ability to serve as a barrier for guided bone regeneration, it was found that the matrix barrier had the following properties; biocompatibility observed as uneventful tissue healing, malleability facilitating the clinical handling and ability to be resorbed within 6 to 7 months, as evaluated by clinical inspection. The observations of the present case reports indicate that the tested barrier may be used for guided bone regeneration in connection with implant installation. It is advisable, however, to use a supporting material to prevent barrier collapse, although bone regeneration can be achieved in certain situations without such material if the defect morphology is favourable.

Aged↗
PubMed1994

Periodontal tissue response to a new bioresorbable guided tissue regeneration device: a longitudinal study in monkeys.

This study evaluated periodontal tissue response to a new bioresorbable guided tissue regeneration barrier material following guided tissue regeneration treatment of dehiscence-type defects at 45 teeth in 15 monkeys. The results were clinically and histologically evaluated 6 weeks and 3,6, 12, and 24 months posttreatment. Healing was uneventful and without inflammation or other adverse tissue reactions. Following 6 weeks of healing, the matrix barrier was completely integrated with the surrounding tissues, preventing epithelial downgrowth along the device. There were no inflammatory cell infiltrates adjacent to the material. New attachment (ie, new cementum with inserting collagen fibers) and new supporting bone were found after 6 weeks of healing. The matrix barrier maintained its functional stability for a minimum of 6 weeks. The subsequent slow resorption process of the material occurred without detrimental effects on the surrounding tissues, demonstrating the biocompatibility of the material. The material was completely resorbed after 6 to 12 months. At the final stages of the resorption process, macrophages and multinuclear cells were present within the tissue that replaced the material. The design and the resorption pattern of the matrix barrier are discussed in relation to the regenerative wound healing process.

Animals↗
PubMed1994

A radiological inventory of possible sites for cylinder implants in edentulous regions of the jaws. An epidemiological study.

Implant treatment is nowadays requested as an alternative mode of treatment for both total and partial edentulousness. The purpose of the study was to assess the maximum number of possible implant sites in a group of adults. The study material comprised 579 persons divided into the age-groups 20, 30, 40, 50, 60 and 70 years. Based on radiological examination, the subjects were grouped according to Eichner's index. They comprised both dentate and edentulous individuals. Templates, marked with cylinder implants of different dimensions, were placed over edentulous regions. The possible number of cylinder-shaped endosseous implants that could be placed anterior to the second molar was assessed in relation to bone availability and anatomical structures. Gaps treated with fixed bridges were not registered. Altogether 1,048 presumptive fixture sites were marked, of which 78% in the age-groups 60 and 70 years. Eichner groups C 1-3, which comprised the edentulous persons, constituted 12% of the subjects and accounted for 57% of the possible number of implants. All edentulous mandibles and 70% of the edentulous maxillae were judged suitable for placement of implants. On average 5.5 and 5.8 sites were marked per edentulous maxilla and mandible, respectively. Groups B1-4 comprised 21% of the subjects and accounted for 37% of the implants. It is discussed that implant treatment in totally edentulous jaws will increase in relative terms in Sweden as in other Scandinavian countries, i.e. the percentage of edentulous jaws treated with implants will increase. In absolute terms, however, the treatment will probably decrease owing to a marked decrease in the number of edentulous individuals. The future need for implant treatment in the residual dentition will probably increase but it is difficult to predict by how much.

Adult↗
PubMed1992

Influence of occlusion on posterior cantilevers.

The incorporation of posterior two-unit cantilevers in fixed prosthodontics is generally discouraged because of the assumption that large posterior chewing and biting forces might jeopardize the prosthesis and the abutment teeth. This investigation was performed to study (1) the distribution of chewing and closing forces in dentitions with cross-arch bilateral posterior two-unit cantilever fixed partial dentures and (2) the influence of different occlusal arrangements on the magnitude of these forces along the cantilever segments. Six patients were included in the study. Axially directed closing and chewing forces were measured with miniature transducers bilaterally mounted in pontic units anteriorly and in each of the four cantilever units. In ideal occlusion, occlusal forces decreased considerably along the cantilever segments in the distal direction. Infraoccluding the distal cantilever unit by 80 microns had little influence on the magnitude of the initially small local force in this region, whereas an 80 microns high primary occlusal contact considerably increased the local force over the distal cantilever unit. The clinical implications of the results are discussed.

Acrylic Resins↗
PubMed1992

Healing-in of root analogue titanium implants placed in extraction sockets. An experimental study in the beagle dog.

The aim of these animal experiments was to characterize and evaluate the healing-in of root analogue titanium implants fitting with high precision to the alveolar wall. Four beagle dogs were used in the study. The roots of the 3rd and 4th mandibular premolars in both quadrants of 3 dogs and in 1 quadrant of 1 dog (dog 4) were extracted after hemisection. Each root was machine-copied to 1 titanium analogue. In dog 4, however, 2 titanium analogues were fabricated from each of the 4 extracted roots. This enabled insertion of analogues also into the contralateral sockets obtained by extraction of the corresponding roots immediately before implant installation, which was undertaken 2 weeks after the first extractions. Thus, in all, 32 analogues were implanted in their respective (or contralateral) sockets following ridge incision and elevation of mucoperiosteal flaps. The analogues were carefully covered by the repositioned flaps. In dog 4, 2 analogues from the immediate sockets and 2 from the 2-week sockets were surgically exposed and supplied with titanium crowns after a healing period of 2 months. The healing after implantation was evaluated by clinical, radiographic and histological measures after 2, 12 or 36 months. Two analogues (6%) were lost due to early (during the 1st week) exposure to the oral cavity. Another 2 analogues (6%) were, although not exposed, encapsulated by soft tissue and were easily removed with a surgical forceps. Twenty-eight analogues (88%) were healed-in by contact between bone and implant (osseointegration).(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Process↗
PubMed1992

Periodontal conditions around tipped and upright molars in adults. An intra-individual retrospective study.

In 69 individuals from a randomized epidemiological material comprising 450 adults, an intra-individual comparison of the periodontal condition of 73 mesially tipped molars (30 degrees or more to a line perpendicular to the occlusal plane) and contralateral upright molars was made. The alveolar bone level mesially and distally of each tooth was registered in periapical radiographs. The occurrence of plaque, gingivitis and probeable pocket depths of 4 mm or more mesially and distally of each tooth was registered. No significant differences between tipped and upright molars could be found, regardless of the variable tested. The clinical implications of the findings are discussed from an orthodontic as well as a periodontal and prosthetic point of view.

Adult↗
PubMed1992

Frequency distribution of individuals aged 20-70 years according to severity of periodontal disease experience in 1973 and 1983.

The aim of this study was to compare changes in periodontal status of a Swedish population over a 10-year period expressed as frequency distributions of individuals according to severity of periodontal disease experience. The study involved 600 randomly selected individuals evenly distributed into age groups 20, 30, 40, 50, 60 and 70 years, examined in 1973 and another randomly selected group of 597 individuals similarly age distributed and examined in 1983. Based on clinical data and full mouth intraoral radiographs all individuals were classified into 5 groups according to severity of periodontal disease experience. In 1983, 23% of the individuals were classified as having healthy periodontal tissues, group 1, compared to 8% in 1973. The changes were most pronounced in the age groups 20 and 30 years, among whom 58% and 35%, respectively, were registered as having healthy periodontium in 1983. The prevalence of individuals with gingivitis without signs of lowered periodontal bone level, group 2, was 22% in 1983 compared to 41% in 1973. In all, 49% of the dentate population in 1973 and 45% in 1983 showed no marginal alveolar bone loss. Moderate periodontal bone loss, group 3, was found in 41% of the population in 1983 compared to 47% in 1973. Among 30-, 40-, and 50-year-olds, there were more, and among 60- and 70-year-olds, fewer individuals in this group in 1983 compared to 1973. 96% of the dentate population were classified as belonging to groups 1, 2 or 3 in 1973 compared to 86% in 1983.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Long-term prognosis of extensive polyunit cantilevered fixed partial dentures.

The aim of this retrospective study was to elucidate the long-term prognoses of extensive fixed partial dentures including unilateral or bilateral polyunit cantilevers in patients with healthy but reduced periodontal support. Following periodontal therapy 36 cross-arch fixed partial dentures with two or more cantilever units unilaterally or bilaterally were fitted in 34 patients. In the prosthodontic design, special attention was given to the retention to long parallel preparations, to the dimensions of the framework, and to the occlusal design. After completion of therapy, the patients were enrolled in a regular maintenance care program and followed up for a period of 5 to 12 years. During this follow-up period one abutment tooth was fractured in one patient. One fixed partial denture with extremely reduced periodontal support was lost as a result of complete periodontal breakdown from occlusal trauma. For 33 fixed partial dentures, neither periodontal nor technical complications occurred.

Dental Abutments↗
PubMed1991

Experience of long-term intraperitoneal insulin treatment using a new percutaneous access device.

A pilot study was conducted to determine the efficacy of a new percutaneous device, designed to help to deliver insulin from an external, multiprogrammable pump to the abdominal cavity in patients with Type 1 (insulin-dependent) diabetes. Six patients received intraperitoneal insulin therapy for 15-24 months, a total experience of 9.4 patient-years. Glycosylated haemoglobin stabilized at 7.6 +/- 0.7% with no change in insulin dose. Four patients had to submit to reimplantation after 30 to 60 weeks. One patient met with inconvenient location of the device and three had blockage of the system. In four patients treatment had to be interrupted due to blockage of the intraperitoneal catheter by omental-tissue encapsulation. In two of those patients this blockage was combined with deeper infections. In another patient treatment had to be interrupted due to chronic, local, subcutaneous infection.

Adult↗
PubMed1991

Prosthetic reconstruction of dentitions seriously compromised by periodontal disease.

Dentitions seriously compromised by periodontal disease are often in need not only of cause-related periodontal therapy of high quality but also of relevant prosthetic rehabilitation. Contrary to traditional claims, clinical investigations published during the last 2 decades demonstrate that, if adequately treated and controlled, such dentitions can carry fixed, cross-arch bridges on an extremely reduced amount of periodontium, with a good long-range prognosis. It has also been shown that a markedly reduced but healthy and favourably distributed periodontium supporting such constructions can withstand occlusal forces of considerable magnitude. Another controversial topic, related to fixed bridges, involves indications and contra-indications for cantilever segments. Some clinical investigations demonstrate a markedly increased risk of failure if the fixed bridge is provided with cantilever units, while other controlled studies with defined specifications on the design of the constructions exhibit a high success rate after 8 years or more also for bridgework where 2 or 3 cantilever units are included. The force pattern along cantilever segments of both tooth-supported and implant-supported bridges has been extensively studied. The results show that the force distribution depends not only on the occlusal contact pattern and the dimensioning of the cantilever beam, but also on the type of prosthetic construction in the opposite jaw occluding with the cantilever segment. The free-standing, implant-supported bridge has recently become an important treatment modality for rehabilitation of the partially edentulous jaw, and follow-up studies demonstrate a high success rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Denture Design↗
PubMed1990

Occlusal interferences and cantilever joint stress in implant-supported prostheses occluding with complete dentures.

Naturally occurring closing and chewing forces were measured in dentitions with mandibular fixture-supported bilateral distal two-unit cantilever fixed prostheses occluding with complete dentures, and the vertical bending stress in the cantilever joint of the preferred chewing side was assessed. Occlusal forces were measured using eight miniature strain gauge transducers bilaterally and symmetrically mounted in complete dentures. Occlusal forces over the entire prosthesis were registered in basic (habitual) occlusion and with a 100-microns-high premature occlusal contact on the second cantilever unit. Closing and chewing forces increased distally. The premature occlusal contact did not significantly influence the total forces over the entire dentition but increased the local forces over the second cantilever unit. The group mean maximal vertical bending stress for closing forces reached the fatigue limit for unhardened type III dental gold alloy in basic occlusion. Although the interfered occlusion resulted in a significant redistribution of forces and significantly altered the stress contributions from each cantilever unit, maximal vertical bending stress in the cantilever joint was not significantly influenced. During chewing, the fatigue limit was not reached in basic or in interfered occlusion.

Adult↗