Biomedical subjects

Thorkild Karring

Publications and source records attributed to Thorkild Karring.

27 records · Page 2Linked to original sources

PubMed2003

Deproteinized bovine bone (Bio-Oss) and bioactive glass (Biogran) arrest bone formation when used as an adjunct to guided tissue regeneration (GTR): an experimental study in the rat.

OBJECTIVES: Grafting of deproteinized bovine bone or bioactive glass has been suggested as an adjunct to guided tissue regeneration (GTR) for the treatment of periodontal and peri-implant bone defects but the influence of these materials on bone formation is not clarified. The aim of the study was to examine the long-term influence of deproteinized bovine bone (Bio-Oss) or bioactive glass (Biogran) on bone formation produced by GTR. MATERIAL AND METHODS: Eighteen rats were used. Following incisions along the inferior border of the mandible, muscle-periosteal flaps were raised to expose the mandibular ramus. Rigid, hemispherical, Teflon capsules (6 mm internal diameter and 1 mm peripheral collar) loosely packed with a standardized quantity of either deproteinized bovine bone (test group 1) or bioactive glass (test group 2), or empty capsules (control group) were then placed with their open part facing the lateral surface of the ramus (one capsule per animal). After 1 year, the capsules were removed by a reentry operation, and the animals were sacrificed. Histological specimens of the augmented sites were prepared, and the volumes of (1). newly formed bone, (2). graft particles, and (3). soft connective tissue in the space originally created by the capsule were estimated by a point-counting technique in three to four histological sections, taken by uniformly random sampling. RESULTS: Limited bone formation was observed in the two test groups. The major part of the space originally created by the capsules was occupied by graft particles embedded in connective tissue. The mean volume of newly formed bone occupied only 23% of the total space in the animals grafted with Bio-Oss and 12.6% in those grafted with Biogran. In the control animals, however, 88.2% (p<0.01) of the space was filled with newly formed bone. There were no signs of ongoing bone formation in any of the three experimental groups. CONCLUSION: It is concluded that grafting of Bio-Oss or Biogran as an adjunct to GTR arrests bone formation.

Animals↗

PubMed2003

Influence of demineralized bone matrix's embryonic origin on bone formation: an experimental study in rats.

BACKGROUND: There are results suggesting that differences regarding bone-inducing potential, in terms of amount and/or rate of bone formation, exist between demineralized bone matrices (DBMs) of different embryonic origins. PURPOSE: The aim of the present study was to examine whether the embryonic origin of DBM affects bone formation when used as an adjunct to guided tissue regeneration (GTR). MATERIALS AND METHODS: Endomembranous (EM) and endochondral (ECH) DBMs were produced from calvarial and long bones of rats, respectively. Prior to the study the osteoinductive properties of the DBMs were confirmed in six rats following intramuscular implantation. Following surgical exposure of the mandibular ramus, a rigid hemispheric Teflon capsule loosely packed with a standardized quantity of DBM was placed with its open part facing the lateral surface of the ramus in both sides of the jaw in 30 rats. In one side of the jaw, chosen at random, the capsule was filled with EM-DBM, whereas in the other side ECH-DBM was used. Groups of 10 animals were sacrificed after healing periods of 1, 2, and 4 months, and undecalcified sections of the capsules were produced and subjected to histologic analysis and computer-assisted planimetric measurements. RESULTS: During the experiment increasing amounts of newly formed bone were observed inside the capsules in both sides of the animals' jaws. Limited bone formation was observed in the 1- and 2-month specimens, but after 4 months of healing, the newly formed bone in the ECH-DBM grafted sides occupied 59.1% (range 45.6-74.7%) of the area created by the capsule versus 46.9% (range 23.0-64.0%) in the EM-DBM grafted sides (p =.01). CONCLUSION: It is concluded that the embryonic origin of DBM influences bone formation by GTR and that ECH-DBM is superior to EM-DBM.

Animals↗

PubMed2003

Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study.

Preservation of alveolar bone volume following tooth extraction facilitates subsequent placement of dental implants and leads to an improved esthetic and functional prosthodontic result. The aim of the present study was to assess bone formation in the alveolus and the contour changes of the alveolar process following tooth extraction. The tissue changes after removal of a premolar or molar in 46 patients were evaluated in a 12-month period by means of measurements on study casts, linear radiographic analyses, and subtraction radiography. The results demonstrated that major changes of an extraction site occurred during 1 year after tooth extraction.

Adult↗

PubMed2003

Clinical evaluation of an enamel matrix derivative in the treatment of mandibular degree II furcation involvement: a 36-month case series.

The aim of the present study was to evaluate the clinical outcome following application of an enamel matrix derivative in degree II mandibular furcation involvements. Ten patients with chronic periodontitis, presenting a total of eight buccal and eight lingual degree II furcation involvements, were included in the study. The following clinical parameters were evaluated prior to treatment and after 6, 12, and 36 months: probing attachment level in horizontal direction in the buccal and/or lingual furcation area (PAL-H) and probing attachment level in vertical direction (PAL-V) at the center of the buccal/lingual furcation area. The postoperative healing phase was uneventful in all cases, and no complications were observed throughout the entire study period. At 6 months, the mean PAL-H of the buccal defects was reduced from 4.0 +/- 1.3 mm to 2.6 +/- 1.4 mm, and the mean PAL-V was reduced from 5.2 +/- 2.0 mm to 4.0 +/- 1.6 mm. At the lingual defects, the mean PAL-H was reduced from 3.6 +/- 1.3 mm to 3.1 +/- 1.1 mm, and the mean PAL-V was reduced from 5.6 +/- 2.0 mm to 4.3 +/- 1.8 mm. At 12 and 36 months, clinical parameters remained similar, without any further clinical improvement. These results suggest that the treatment of degree II mandibular furcation involvements with enamel matrix derivative might lead to clinical improvement. However, controlled clinical trials and histologic studies are needed to examine the clinical significance of these results and the characteristics of healing following application of enamel matrix derivative.

Adult↗

PubMed2002

Augmentation of the mandible with GTR and onlay cortical bone grafting. An experimental study in the rat.

The aim of the present study was to evaluate the effect of augmenting the mandible with onlay mandibular bone grafts that were covered with e-PTFE membranes according to the principle of guided tissue regeneration (GTR). The experiment was carried out in 30 rats. The inferior border of the mandible and parts of the mandibular body were exposed on both sides. On one side, an autogenous bone graft that was harvested from the angle of the mandible was placed on the inferior border of the mandible and was fixed with a titanium microimplant. Subsequently, the graft was covered with an e-PTFE membrane. The contralateral side, serving as control, was treated the same way except for the placement of the membrane. Groups of six animals were sacrificed 15, 30, 60, 120 and 180 days following surgery, and specimens that were prepared from the experimental and control sites were analyzed histologically. The bone graft underneath the membrane initially presented superficial resorption but, subsequently, the space that was created by the membrane gradually became filled with bone. After 180 days, the area underneath the membrane was completely filled with bone and it was impossible to distinguish between the bone graft and the newly formed bone. Generally, the bone grafts at the control sides were characterized by a gradual resorption during the entire experimental period. At 180 days after transplantation, only a few grafts at the control sites had retained their height, and there was frequently a lack of continuity between the bone graft and the underlying mandibular bone. It can be concluded that onlay mandibular bone grafts combined with GTR may improve the predictability of mandibular augmentation, in comparison to bone grafting alone.

Alveolar Ridge Augmentation↗

PubMed2002

Alveolar ridge augmentation by combining autogenous mandibular bone grafts and non-resorbable membranes.

The aim of the present study was to evaluate the effect of using mandibular cortical bone grafts covered with e-PTFE membranes for maxillary alveolar ridge augmentation, in comparison with the use of mandibular cortical grafts alone. The experiment was carried out in 20 rats. At one side of the maxillary jaw, the edentulous alveolar ridge between the incisor and the first molar was augmented by means of an autogenous mandibular bone graft, which was fixed with a titanium microimplant and covered with a Teflon membrane. The contralateral side, serving as control, was treated the same way, except for the placement of a membrane. Histological analysis at 15, 30, 60 and 90 days after surgery demonstrated that, in situations where the membrane was not exposed to the oral cavity during healing, the mandibular bone grafts presented no resorption and were in continuity with the maxillary bone at the recipient site. In situations where the membrane had become exposed, however, the bone grafts presented extensive resorption and lack of continuity with the bone at the recipient site. These latter findings were similar to those made at the non-membrane-treated side. The results indicate that the volume of autogenous bone graft used for alveolar ridge augmentation can be retained by covering the graft with a membrane, provided that the membrane is properly adapted and is kept covered with mucosa during healing.

Alveolar Ridge Augmentation↗

PubMed2002

Augmentation of the rat jaw with autogeneic cortico-cancellous bone grafts and guided tissue regeneration.

The aim of the present study was to evaluate the effect of augmenting the maxillary alveolar ridge and the lateral aspect of the mandible with onlay autogeneic cortico-cancellous bone grafts that were covered with e-PTFE membranes. The experiment was carried out in 51 rats. In 15 rats, the edentulous maxillary jaw between the incisor and the first molar was augmented by means of an autogeneic ischiac bone graft that was fixed with a gold-coated microimplant. In one side, the graft was covered with an e-PTFE membrane, while the other side, which served as control, was treated without a membrane. In the other 36 rats, the lateral aspect of the mandible was augmented in both sides by means of an autogeneic ischiac bone graft that was fixed with a gold-coated or a titanium microimplant. In one side, the augmented area was covered with an e-PTFE membrane, while the contralateral side was treated without a membrane. Histological analysis at 60, 120 and 180 days after augmentation of the maxilla showed that, in the case of the test sites (where most of the membranes were either exposed or lost), the bone grafts presented extensive resorption and there was a lack of bone continuity between the graft and the recipient site. Similar findings were made at the non-membrane-treated control sides. In the case of augmentation of the mandible with membranes, the bone grafts were not resorbed, but were integrated into newly formed bone at the recipient site. In the control sides, the grafts presented varying degrees of resorption and integration into the recipient bone. It is concluded that, in comparison to bone grafting alone, onlay ischiac bone grafting combined with guided tissue regeneration eliminates the risk of bone graft resorption and ensures integration of the graft into newly formed bone at the recipient site, provided that closure of the operated area can be maintained during healing.

Alveolar Ridge Augmentation↗

PubMed2002

Alveolar ridge augmentation using a resorbable copolymer membrane and autogenous bone grafts. An experimental study in the rat.

The aim of the present study was to compare the result of maxillary alveolar ridge augmentation by the combined use of mandibular bone grafts and resorbable membranes (Resolut), with that achieved by the use of the same type of bone graft combined with the placement of e-PTFE membranes (Gore-Tex). The experiment was carried out in 30 rats. In one side of the maxillary jaw, the edentulous alveolar ridge between the incisor and the first molar was augmented by means of an autogenous mandibular bone graft that was fixed with a titanium microimplant and covered with a resorbable membrane. The contralateral side, serving as control, was treated in the same way, with the difference that an e-PTFE membrane was placed over the bone graft. Histological analysis at 15, 30, 60, 120 and 180 days after surgery demonstrated that, in both test and control sites where the membrane was properly adapted and not exposed, the bone grafts presented no resorption and were integrated into the maxillary bone at the recipient site. In cases where the membrane was exposed, however, the bone grafts presented extensive resorption and lack of continuity between the graft and the recipient bed. At 60-180 days after surgery, the exposure of both types of membrane had frequently led to complete resorption of the grafts, encapsulation of the titanium microimplant by fibrous connective tissue, or exfoliation of the microimplant. It is concluded that alveolar ridge augmentation can be predictably accomplished by combining mandibular bone grafting with the placement of resorbable or non-resorbable membranes according to the GTR principle, provided that the membrane is properly adapted over the graft and complete closure of the treated area is maintained during healing.

Absorbable Implants↗

PubMed2002

Bone and suture regeneration in calvarial defects by e-PTFE-membranes and demineralized bone matrix and the impact on calvarial growth: an experimental study in the rat.

The aim of this study was to evaluate the effect of: guided tissue regeneration (GTR) alone, implantation of demineralized bone matrix (DBM) alone, and of the combined treatment on the healing of craniectomy defects involving the sagittal cranial suture, and to examine subsequent calvarial growth. Sixty four-week-old rats were used in the study. These animals were randomly assigned to five groups (A-E) of 12 animals. In four groups (A-D), a calvarial defect (5.0 mm) involving the sagittal suture was produced in each animal. Group A: The defect was left untreated. Group B: DBM was implanted into the defect. Group C: The cerebral and the galeal aspect of the defect was covered with an e-PTFE membrane. Group D: The defect was treated with the double membrane technique combined with implantation of DBM. Group E: The animals were sham-operated, no defect was created. In all groups, two gutta-percha points were placed to indicate the lateral borders of the parietal bones. Histological analysis 4 months following surgery showed that the untreated cranial defects (A) had healed with fibrous connective tissue in the midportion of the defect. The DBM grafted defects (B) healed either completely with bone containing DBM particles or partially with bone and connective tissue. The defects (D) treated with DBM combined with GTR healed completely with bone, while the defects (C) treated with membranes alone healed with bone but a suture-like tissue similar to the normal sagittal suture of the sham-operated controls (E) was always present in the midportion of the defect. Cephalometric radiography demonstrated that the membrane-treated (C) and the sham-operated animals (E) exhibited similar coronal growth of the cranial vault following treatment. Craniometric measurements on chemically defleshed specimens showed that sham-operated and membrane-treated animals presented significantly more biparietal width than the animals treated with DBM alone or DBM combined with GTR (P < 0.05). The results demonstrated that predictable osseous healing including the formation of a sagittal suture can be accomplished in craniectomy defects by GTR, and undisturbed cranial growth reestablished. The treatment of the defects with DBM alone or DBM combined with GTR resulted in craniosynostosis and reduced cranial growth.

Analysis of Variance↗