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Biomedical subjects

T Berglundh

Publications and source records attributed to T Berglundh.

At least 37 records · Page 2Linked to original sources
PubMed2000

Anchorage of titanium implants with different surface characteristics: an experimental study in rabbits.

PURPOSE: To compare the anchorage of titanium implants with different surface roughness and topography and to examine histologically the peri-implant bone after implant removal. MATERIALS AND METHODS: Screw implants with five different surface topographies were examined: (1) turned ("machined"), (2) TiO2-blasted with particles of grain size 10 to 53 microns; (3) TiO2-blasted, grain size 63 to 90 microns; (4) TiO2-blasted, grain size 90 to 125 microns; (5) titanium plasma-sprayed (TPS). The surface topography was determined by the use of an optical instrument. Twelve rabbits, divided into two groups, had a total of 120 implants inserted in the tibiae. One implant from each of the five surface categories was placed within the left tibia of each rabbit. By a second operation, implants were installed in the right tibia, after 2 weeks in group A and after 3 weeks in group B. Fluorochrome labeling was performed after 1 and 3 weeks. Removal torque (RMT) tests of the implants were performed 4 weeks after the second surgery in group A and 9 weeks after the second surgery in group B. Thus, in group A, two healing groups were created, representing 4 and 6 weeks, respectively. The corresponding healing groups in group B were 9 and 12 weeks. The tibiae were removed, and each implant site was dissected, fixed, and embedded in light-curing resin. Ground sections were made, and the peri-implant bone was analyzed using fluorescence and light microscopy. RESULTS: The turned implants had the lowest Sa and Sy values, whereas the highest scores were recorded for the TPS implants. The corresponding Sa and Sy values for the TiO2-blasted implants were higher when a larger size of grain particles had been used for blasting. At all four observation intervals, the TPS implants had the highest and the turned implants the lowest RMT scores. The differences between the various TiO2-blasted implants were, in general, small, but the screws with the largest Sa value had higher RMT scores at 6, 9, and 12 weeks than implants with lower Sa values. The histologic analysis of the sections representing 6, 9, and 12 weeks revealed that fractures or ruptures were present in the marginal, cortical peri-implant bone. In such sections representing the TPS and TiO2-blasted implant categories, ruptures were frequently found in the zone between the old bone and the newly formed bone, as well as within the newly formed bone. CONCLUSIONS: The present study demonstrated that a clear relation exists between surface roughness, described in Sa values, and implant anchorage assessed by RMT measurements. The anchorage appeared to increase with the maturation of bone tissue during healing.

Animals↗
PubMed1999

Resolution of peri-implantitis following treatment. An experimental study in the dog.

The aim of the present experiment was i) to study the effect of anti-microbial therapy of experimentally induced peri-implantitis lesions and ii) to assess features of bone regrowth following treatment. Four beagle dogs were used. Three titanium fixtures (Brånemark System) were installed in each quadrant of the mandible (premolars previously extracted). Abutment connection was performed 5 months later and ligature induced breakdown was initiated. The ligatures were removed when approximately 50% of the initial bone support was lost. A 3-week antibiotic regimen (amoxicillin and metronidazole) was initiated 1 month later. Two days after the start of the antibiotic administration, the experimental implant sites were exposed to local therapy. The abutments were removed and the exposed fixture surfaces were treated with an abrasive (pumice) administered via a rotating brush (left side) or cleaned with cotton pellets soaked in saline (right side). Cover screws were attached to the fixtures and the implants were submerged. Fluorochromes were injected intravenously 2 weeks, 4 weeks and 12 weeks after surgery. The animals were killed 7 months after surgery and block biopsies of each implant site were dissected and prepared for histological analysis. The findings of the examinations disclosed that the inflammatory lesion was resolved and new bone formation had occurred in the previous defect following antimicrobial and local therapy. The amount of "re-osseointegration" that had taken place, however, was small. Indeed, at all experimental implant sites, a thin connective tissue capsule was found to separate the implant surface from the newly formed bone.

Administration, Oral↗
PubMed1999

Some effects of periodontal therapy on local and systemic immunological parameters.

The aim of the present investigation was to study the effect of nonsurgical periodontal therapy on some local (gingival) and systemic host defense characteristics in subjects with advanced periodontal disease. 16 individuals with advanced periodontal disease were recruited. Following a clinical examination, the 3 deepest interproximal sites in the upper and lower premolar- or molar segments were selected for further analysis. Samples from the subgingival microbiota were obtained from the pocket of the selected sites and were prepared for a microbiological examination. The gingival tissue at one of the selected sites was also biopsied. Each excised soft tissue specimen was snap frozen and prepared for immunohistochemical analysis. A sample of peripheral blood was obtained from each individual and prepared for immunohistochemical analysis. Following the baseline examination, all 16 patients received periodontal therapy including oral hygiene instruction and scaling and root planing. Re-examinations regarding the clinical parameters were performed, the subgingival microbiota harvested from the sampling sites and one gingival biopsy was collected at 12 months and 24 months, respectively, among the selected sites. Samples of peripheral blood were obtained from the subjects at the 24-month re-examination. It was demonstrated that non-surgical periodontal therapy effectively reduced symptoms such as gingivitis and probing pocket depth in the subject sample and improved the overall probing attachment level. The treatment applied also markedly reduced (i) the total number of micro-organisms present in selected gingival pockets as well as (ii) the relative proportions of A. actinomycetemcomitans, P. gingivalis and P. intermedia of the subgingival microbiota. The improved clinical condition was, in addition, accompanied by a substantial reduction in the size of the inflammatory lesion (P-ICT) which in the soft tissue samples harvested at baseline was found to reside lateral to the pocket epithelium. Also qualitative alterations occurred in the lesions. Hence, following therapy (i) both the density of CD19 positive cells and the proportion of CD3 positive cells expressing TCR Vbeta genes were reduced in the P-ICT. while (ii) the overall relative number of CD3 positive cells remained unchanged. In conclusion, non-surgical periodontal therapy markedly changed the size and composition of the plaque associated lesion in the gingival tissue but apparently failed to affect the relative distribution of lymphocyte subsets in peripheral blood.

Adult↗
PubMed1999

Differences in the inflammatory response in young and old human subjects during the course of experimental gingivitis.

The aim of the present experiment was to study changes in (i) the composition of the inflammatory cell infiltrates and (ii) levels of alpha 2-macroglobulin, lactoferrin and IgG subclasses in gingival crevicular fluid in young and old individuals during 3 weeks of plaque formation. To establish healthy gingival conditions, all subjects received professional tooth cleaning during a 4 week pre-experimental period. The experimental sites included the mesio-palatal, palatal, and disto-palatal surfaces of all teeth present in the 15...25 tooth region. At baseline (day 0) assessments of plaque and gingivitis, microbial sampling and gingival fluid assessment were performed and one gingival biopsy harvested from each subject. Following the baseline examination, the participants abolished mechanical tooth cleaning measures in the palatal and approximal surfaces of 15...25. The clinical examination and the gingival fluid measurement were repeated on days 7, 14 and 21 of no oral hygiene. The microbiological sampling and the biopsy procedure were repeated on days 7 and 21. The gingival crevicular fluid samples harvested from the old individuals had higher levels of alpha 2-macroglobulin and IgG3 compared to young subjects. The immunohistochemical analyses of the biopsies demonstrated that the gingival lesion representing the old individuals harbored a higher proportion of B-cells and a lower density of PMN cells compared to the infiltrate in the young group of subjects. It is suggested that differences exist in the inflammatory response to de novo plaque formation in young and old individuals.

Adult↗
PubMed1999

Peri-implant tissues at submerged and non-submerged titanium implants.

The present experiment was performed to study the peri-implant tissue response to non-submerged (1-stage) and initially submerged (2-stage) implant installation procedures. 6 beagle dogs were used. All mandibular premolars and the 1st, 2nd and 3rd maxillary premolars were extracted. After 3 months of healing, 3 fixtures of the Astra Tech System were installed and submerged in the right (or the left) edentulous, premolar region in each of the 6 dogs. Radiographs were obtained immediately after fixture installation. In the radiographs, the distance between the abutment-fixture junction and the most "coronal" bone in contact with the implant surface was determined. 3 months later, abutments were connected to the initially submerged fixtures and another 3 fixtures of the same system were installed in the contralateral, edentulous premolar region. Abutments were, however, immediately connected to the newly-installed fixtures (non-submerged side; test side). The mucosal flaps were replaced, adjusted and sutured in such a way that the coronal portion of the abutments remained exposed in the oral cavity. A new set of radiographs were obtained from all 6 implant sites in each animal. A period of plaque control was initiated. Clinical examinations were performed and radiographs obtained from all implant sites after another 3 months and at the termination of the experiment. 9 months after the 1st fixture installation procedure, the animals were sacrificed, the mandibles were removed, and each implant region dissected. The most mesially-located implant sites were processed for ground sectioning. The remaining biopsies were processed and embedded in EPON. The histometric analysis included assessment of the vertical dimension of the marginal soft and mineralized peri-implant tissues. The ground sections were used for measurements describing (i) "bone to implant contact" and (ii) "bone density". It was observed that the mucosa and bone tissue that formed at implants placed in a non-submerged or a submerged procedure had many features in common. Thus, figures describing (i) the height of the mucosa, (ii) the length of the junctional epithelium and the height and quality of the zone of "connective tissue integration", (iii) the % of bone to implant contact as well as (iv) the density of the peri-implant bone, were similar in the submerged and the non-submerged groups. It is therefore suggested that a non-submerged (1-stage) installation technique may provide conditions for tissue integration that are similar to those obtained using a submerged (2-stage) approach.

Alveolar Process↗
PubMed1999

Bone tissue reaction around implants placed in a compromised jaw.

The present experiment was carried out to examine bone tissue alterations that occurred around implants at which the marginal level of bone support at fixture installation was different at buccal and lingual surfaces. 8 beagle dogs were randomly divided into one test group and one control group. The mandibular premolars in the left side of the mandible (P1, P2, P3, P4) were extracted. In the 4 dogs of the test group, the buccal bone plate in the mandibular premolar region was removed to establish a bone defect that was about 25 mm long, about 5-6 mm high, and about 4 mm wide. In the 4 dogs of the control group, no bone resection was performed. 8 months after tooth extraction, 3 fixtures (Astra Tech AB, Mölndal, Sweden:TiO-blast: 8x3.5 mm) were installed in each dog. In the 4 dogs of the test group, the implants were positioned in the defect sites in such a way that (i) mechanical stability was achieved and (ii) their lingual surfaces were entirely invested in bone. At the buccal and approximal surfaces of the fixtures, however, the unthreaded portion (2 mm) and the 3 marginal threads remained exposed. In the control group, all implants were following installation entirely surrounded by bone tissue. After a healing period of 3 months, abutment connection was performed and a plaque control program initiated. 4 months later, the dogs were sacrificed. The mandibles were removed and placed in a fixative. Each implant region was dissected, the tissue samples were dehydrated, embedded, sectioned in a bucco-lingual plane and used for light microscopic examination. The findings demonstrated that osseointegration occurred at implants, placed in a chronic defect with large discrepancies between the buccal and lingual bone. During the process of healing and function, however, marked modeling and remodeling of the bone tissue took place. Thus, at the buccal surface, some bone regrowth and osseointegration occurred while at the lingual wall, there was a substantial resorption of the marginal bone and an enhanced number of bone multicellular units. Concomitant with the bone tissue alterations described, there was some recession of the peri-implant mucosa.

Animals↗
PubMed1999

Bone formation in furcation defects. An experimental study in the dog.

The aim of the present investigation was to study bone formation in an experimentally-produced furcation defect in the dog. 15 foxhound dogs (group A) and 4 large mongrel dogs (group B) were used. The 2nd and 4th mandibular premolars were extracted and the 3rd lower premolars (3P3) were assigned as experimental teeth. "Through and through" furcation defects, about 4 mm high and 3 mm wide, were first produced in the experimental teeth of the dogs in group A. Reconstructive surgery was subsequently performed in group A using a GTR technique. The dogs of group A were scheduled for biopsy 2 weeks (2 dogs), 1 month (2 dogs), 2 months (2 dogs), 4 months (3 dogs), 5 months (3 dogs) and 6 months (3 dogs) after GTR. The dogs in group B (4 animals) represented healthy, untreated pristine furcations and served as positive controls. Biopsies from the 3P3 regions were harvested, embedded in paraffin and prepared for histological analysis. Mesio-distal sections were cut with the microtome set at 7 microm. The sections were stained in hematoxylin and eosin, and Van Gieson. 3 sections, about 50 microm apart, and representing the central portion of the furcation site were selected for histological measurements. In group A, the proportions of various structures in the newly formed bone and marrow were assessed. In addition, the proportions of primary and secondary osteons, and the number of bone multicellular units (BMU)/mm2 mineralized bone tissue were determined. In the pristine furcations (group B), the histological analyses were performed in a corresponding area to that of the healing furcations. The results demonstrated that the process of bone formation in a large "suprabony" furcation defect can be divided into 3 different phases, namely, (i) the formation of a provisional connective tissue, (ii) the development of a primary bone spongiosa (including mainly woven bone), (iii) the replacement of the spongiosa by lamellar bone and bone marrow through processes of modeling and remodeling. The newly-formed trabeculae of woven bone were reinforced by the deposition of parallel-fibered bone and lamellar bone, a finding which substantiates the validity of the concept that woven bone possesses poor weight-bearing properties and, hence, needs to be re-inforced by a more mature type of bone. The modeling of the newly-formed bone resulted in the formation of (i) one large marrow space in the center of the furcation and, in addition, (ii) a smaller bone marrow space in the most coronal portion of the defect. At the end of the study (6 months), the bone marrow occupied a much larger space than in the bone tissue of pristine furcations. It was suggested that the process of modeling or remodeling of bone tissue in the furcation defect was not completed at the end of the study.

Animals↗
PubMed1999

The barrier between the keratinized mucosa and the dental implant. An experimental study in the dog.

The present study was performed in order to examine the composition of the connective tissue that forms an attachment to a dental implant. 6 beagle dogs were used. All mandibular premolars were extracted. After 3 months of healing, 6 fixtures--3 in each side of the mandible--(Astra Tech Implants, Dental System TiO blast; Astra Tech AB, Mölndal, Sweden) were installed. After another 3 months of healing, abutment (Uni-abutment 45; Astra Tech AB, Mölndal, Sweden) connection was performed and a plaque control program was initiated. The animals were sacrificed and perfused with a fixative through the carotid arteries. Each implant site, including the implant and the soft and hard peri-implant tissues, was dissected, decalcified in EDTA and further processed using a "fracture technique". The specimens were subsequently embedded in EPON, cut with the microtome set at 3 microm and the sections stained in PAS and toluidine blue. From the EPON-embedded blocks, ultra-thin sections were cut and electron micrographs were prepared. The detailed histologic and morphometrical examinations were restricted to a 200 microm wide zone of connective tissue interposed between the apical border of the junctional epithelium and the bone tissue. In the analysis, this zone was further subdivided into 2 different units; (i) one central, 40 microm wide unit (zone A) located immediately next to the implant surface, and (ii) one lateral, 160 microm wide unit (zone B) that was continuous with the central unit. The implant surface apical of the junctional epithelium and coronal of the bone crest appeared to be in direct contact with a connective tissue. Zone A of this connective tissue was characterized by its (i) absence of blood vessels and (ii) abundance of fibroblasts which were interposed between thin collagen fibers. The more lateral zone B contained comparatively fewer fibroblasts, but more collagen fibers and blood vessels. There are reasons to assume that the fibroblast rich barrier tissue next to the titanium surface plays a rôle in the maintenance of a proper seal between the oral environment and the peri-implant bone.

Alveolar Process↗
PubMed1999

Root resorption and signs of repair in Papillon-Lefèvre syndrome. A case study.

The aim of this investigation was to describe some tooth-related histological features of prepubertal periodontitis. Teeth extracted during treatment of two Papillon-Lefevre syndrome patients were processed by means of the sawing and grinding technique. Light microscopy examination revealed little or no cementum in the coronal parts of the roots. Resorptions of various depths (0.02 to 1.5 mm) and to various extents (affecting up to 1/3 of the root surface) were observed in the 5 investigated teeth. Some resorptive defects on 1 of the examined incisors showed signs of spontaneous repair. Extrinsic fibers were inserted into the new cellular intrinsic fiber cementum which had formed directly on the bottom of the defect. Intact acellular extrinsic fiber cementum was found where fibers were still attached. Here, the characteristic of pristine cementum, a hyaline layer of peripheral dentin, could be identified. If resorption was not present, the cementum did not show any signs of hypoplasia. Thus, histological features of prepubertal periodontitis in the current material were (i) areas of extensive resorption, (ii) signs of spontaneous repair, and (iii) healthy cementum.

Child↗
PubMed1998

Soft tissue response to plaque formation at different implant systems. A comparative study in the dog.

The aim of the present experiment was to study the location and composition of plaque associated lesions in the mucosa adjacent to implant systems that differed with respect to both geometry and dimension. At day 0 extraction of the mandibular premolars were performed. After a healing period of 3 months, fixtures of the Astra Tech Implants, Dental System, the Brånemark System and the ITI Dental Implant System were installed. In each mandibular quadrant 1 fixture of each implant system was installed in a randomized order. A period of plaque control was initiated. Following another 3 months of healing, abutment connection was performed in the 2-stage systems (the Astra Tech Implants, Dental System and the Brånemark System). After 1 month, the plaque control measures were abandoned and plaque formation was allowed for 5 months. The animals were killed and biopsies representing each implant region obtained. The tissue samples were prepared for light microscopy and exposed to histometric and morphometric measurements. The present study demonstrated that plaque formation resulted in the establishment of an ICT lateral to a pocket epithelium. The lesion was found to be similar regarding extension and composition in the peri-implant mucosa of the 3 implant systems tested. The vertical extension of the ICT was in all systems within 91-99% of the vertical dimension of the junctional epithelium. The marginal bone level, measured from the abutment/fixture (PS) border, did not differ between the three systems.

Animals↗
PubMed1998

Local and systemic TCR V gene expression in advanced periodontal disease.

The aim of the present investigation was to study the expression of specific alpha/beta T cell receptor (TCR) gene products in relation to some microbiological and immunological features of advanced destructive periodontitis. 21 individuals with advanced periodontal disease (diseased group) and 16 age- and sex-matched healthy subjects (healthy group) were recruited. Following a clinical examination of the diseased group, the 3 deepest interproximal sites in the upper and lower premolar- or molar segments (i.e., 12 sites in each individual) were selected for further analysis. Samples from the subgingival microbiota were obtained from the pocket of the selected sites and were prepared for a microbiological examination. The gingival tissue at one of the selected sites was also biopsied. Each excised soft tissue specimen was divided into 2 equal portions. One portion of the biopsy was prepared for histometric and morphometric analyses. The 2nd portion was snap frozen and prepared for immunohistochemical analysis. A sample of peripheral blood was obtained from each individual of the diseased and the healthy group and prepared for immunohistochemical analysis. The selected sites of the diseased group harbored varying numbers of microorganisms which have been associated with periodontal disease. The excised gingival tissue contained inflammatory lesions with substantial numbers of lymphocytes and plasma cells including T- and B-cells and a TCR V alpha/beta gene repertoire dominated by Vbeta 17. The TCR profile of the lesion, however, differed markedly from that of the circulating blood of the diseased subjects. While only minor differences were observed between the blood samples of the diseased and the healthy subjects regarding the TCR genes, CD5, HLA-DR and CD5+CD19 positive cells occurred in higher proportions in the blood samples of the subjects susceptible to periodontal disease than in healthy controls. It may be suggested that (i) TCR V alpha/Vbeta expression in peripheral blood samples of subjects with periodontal disease does not differ from that of healthy individuals, and (ii) the periodontitis lesion expresses a unique TCR repertoire in which the Vbeta 17 gene dominates.

Adult↗
PubMed1998

GTR treatment of degree III furcation defects with 2 different resorbable barriers. An experimental study in dogs.

The aim of the present study was to describe the periodontal tissue that formed after GTR when different resorbable barriers were applied to degree III furcation defects. The study was performed in 5 foxhound dogs. The 2nd and 4th premolars in both sides of the mandible were extracted. Degree III furcation defects were produced in the 3rd mandibular premolars. 5 weeks later, GTR therapy using a barrier composed by a polylactide-glycolide copolymer was performed on one quadrant (group A). In the contralateral quadrant, a barrier made of polylactide and citric acid ester (group B) was used. The dogs were sacrificed 6 months after reconstructive therapy. Tissue blocks containing the experimental teeth were excised, demineralised in EDTA and embedded in paraffin. Serial sections were cut in the mesio-distal plane and parallel with the long axis of the roots. The microtome was set at 7 microm. The sections were stained in hematoxyline and eosin. From each biopsy, 3 sections representing the central part of the furcation were selected for light microscopic examination. In the healed furcation sites, descriptive histological analysis and histomorphometric measurements of the newly formed tissues were performed. In both groups the root surface of the healed furcation defects was covered by a cellular, extrinsic-intrinsic fibers type cementum. The composition of the newly formed periodontal ligament was similar in both groups. The proportions of bone, bone marrow and periodontal ligament, however, were substantially larger in group A than in group B. In Group B, an area in the previous furcation defect was consistently occupied by a granuloma. It is suggested that the presence of the granuloma in the healed furcation defect prevented bone regrowth.

Animals↗
PubMed1998

The use of metronidazole and amoxicillin in the treatment of advanced periodontal disease. A prospective, controlled clinical trial.

The present clinical trial was performed to study the effect of systemic administration of metronidazole and amoxicillin as an adjunct to mechanical therapy in patients with advanced periodontal disease. 16 individuals, 10 female and 6 male, aged 35-58 years, with advanced periodontal disease were recruited. A baseline examination included assessment of clinical, radiographical, microbiological and histopathological characteristics of periodontal disease. The 16 patients were randomly distributed into 2 different samples of 8 subjects each. One sample of subjects received during the first 2 weeks of active periodontal therapy, antibiotics administered via the systemic route (metronidazole and amoxicillin). During the corresponding period, the 2nd sample of subjects received a placebo drug (placebo sample). In each of the 16 patients, 2 quadrants (1 in the maxilla and 1 in the mandible) were exposed to non-surgical subgingival scaling and root planing. The contralateral quadrants were left without subgingival instrumentation. Thus, 4 different treatment groups were formed; group 1: antibiotic therapy but no scaling, group 2: antibiotic therapy plus scaling, group 3: placebo therapy but no scaling, group 4: placebo therapy plus scaling. Re-examinations regarding the clinical parameters were performed, samples of the subgingival microbiota harvested and 1 soft tissue biopsy from 1 scaled and 1 non-scaled quadrant obtained 2 months and 12 months after the completion of active therapy. The teeth included in groups 1 and 3 were following the 12-month examination exposed to non-surgical periodontal therapy, and subsequently exited from the study. Groups 2 and 4 were also re-examined 24 months after baseline. The findings demonstrated that in patients with advanced periodontal disease, systemic administration of metronidazole plus amoxicillin resulted in (i) an improvement of the periodontal conditions, (ii) elimination/suppression of putative periodontal pathogens such as A. actinomycetemcomitans, P. gingivalis, P. intermedia and (iii) reduction of the size of the inflammatory lesion. The antibiotic regimen alone, however, was less effective than mechanical therapy with respect to reduction of BoP - positive sites, probing pocket depth reduction, probing attachment gain. The combined mechanical and systemic antibiotic therapy (group 2) was more effective than mechanical therapy alone in terms of improvement of clinical and microbiological features of periodontal disease.

Adult↗
PubMed1998

The mucosal attachment at different abutments. An experimental study in dogs.

The present experiment was performed to examine if the material used in the abutment part of an implant system influenced the quality of the mucosal barrier that formed following implant installation. 5 beagle dogs were included in the study. The mandibular premolars and the 1st, 2nd and 3rd maxillary premolars were extracted. Three fixtures of the Brånemark System were installed in each mandibular quadrant (a total of 6 fixtures per animal). Abutment connection was performed after 3 months of healing. In each dog the following types of abutments were used: 2 "control abutments" (c.p. titanium), 2 "ceramic abutments" (highly sintered Al2O3), 1 "gold abutment", and 1 "short titanium abutment". This "short titanium abutment" was provided with an outer structure made of dental porcelain fused to gold. Following abutment connection a plaque control program was initiated and maintained for 6 months. The animals were sacrificed and perfused with a fixative. The mandibles were removed and each implant region was dissected, demineralized in EDTA and embedded in EPON. Semithin sections representing the mesial, distal, buccal and lingual aspects of the peri-implant tissues were produced and subjected to histological examination. The findings from the analysis demonstrated that the material used in the abutment portion of the implant influenced the location and the quality of the attachment that occurred between the periimplant mucosa and the implant. Abutments made of c.p. titanium or ceramic allowed the formation of a mucosal attachment which included one epithelial and one connective tissue portion that were about 2 mm and 1-1.5 mm high, respectively. At sites where abutments made of gold alloy or dental porcelain were used, no proper attachment formed at the abutment level, but the soft tissue margin receded and bone resorption occurred. The abutment fixture junction was hereby occasionally exposed and the mucosal barrier became established to the fixture portion of the implant. It was suggested that the observed differences were the result of varying adhesive properties of the materials studied or by variations in their resistance to corrosion.

Aluminum Oxide↗
PubMed1997

Healing around implants placed in bone defects treated with Bio-Oss. An experimental study in the dog.

The aim of the present experiment was to (i) study the healing after 3 and 7 months of bone defects filled with cancellous bovine bone mineral and (ii) compare the healing around implants placed in normal bone and in defects filled with bovine bone mineral. 5 beagle dogs, about 1-year-old, were used. At baseline, extractions of all mandibular left and right premolars were performed. Bone defects were prepared in the left mandibular quadrant. The defect was immediately filled with natural bovine cancellous bone mineral particles (Bio-Oss, Geistlich Sons Ltd. Wolhusen, Switzerland). No resective surgery was performed in the right jaw quadrant. In both quadrants the flaps were adjusted to allow full coverage of the edentulous ridge and sutured. 3 months later, 2 dogs (group I) were euthanized and biopsies from the premolar regions obtained and prepared for histologic analysis. The 3 remaining dogs (group II) were at this time interval (3 months) subjected to implant installation in the premolar region of both the right and left mandibular jaw quadrants. 2 fixtures of the ITI Dental Implant System (Straumann, Waldenburg, Switzerland; solid-screw; 8 x 3.3 mm) were installed in each side. The fixtures in the test side were placed within the previously grafted defect area, while the fixtures in the control side were placed in normally healed extraction sites. A 4 month period of plaque control was initiated. At the end of this period, a clinical examination including assessment of plaque and soft tissue inflammation was performed and radiographs obtained from the implant sites. Biopsies were harvested and 4 tissue samples were yielded per dog, each including the implant and the surrounding soft and hard peri-implant tissues. The biopsies were processed for ground sectioning or "fracture technique" and the sections produced were subjected to histological examination. The volume of the hard tissue that was occupied by clearly identified Bio-Oss particles was reduced between the 3- and 7-month intervals. This indicates that with time, Bio-Oss becomes integrated and subsequently replaced by newly formed bone. In other words, this xenograft fulfils the criteria of an osteoconductive material. It was also observed that 4 months after implant installation, the titanium/hard tissue interface at test and control sites exhibited, from both a quantitative and qualitative aspect, a similar degree of "osseointegration".

Animals↗
PubMed1997

Healing at implants with and without primary bone contact. An experimental study in dogs.

The aim of the present investigation in the dog was to study: (i) if it was possible by the use of EREt to predictably expand the compromised alveolar ridge; (ii) if proper osseointegration also occurred at sites where the implant following installation was devoid of direct bone contact. 5 beagle dogs, about 1-year old, were included in the study. During a preparatory period, the mandibular premolars were extracted and the ridge in the edentulous regions markedly reduced. After 3 months of healing, ridge expansion surgery was performed. A partial thickness flap was raised on the buccal and lingual surfaces for the soft tissue preparation. The buccal part of the ridge was mobilised and the bone plate with its periosteum displaced in the buccal direction. In each quadrant, 2 fixture sites were prepared in the mandibular bone apical of the displaced bone plate. 2 unthreaded titanium plasma sprayed fixtures were installed in such a way that the coronal border of the fixture was flush with the level of the lingual and buccal bone plate. The "internal" distance between the mobile buccal and the non-mobile lingual bone plates was identical to the diameter of the fixtures, i.e., 3.3 mm, while the distance between the mesial and distal borders of the 2 implants and the mesial or distal bone was > 5 mm. In each quadrant, 1 additional fixture was installed in the non- reduced mesial part of the alveolar ridge (control site). 3 months after fixture installation, abutment connection was performed. Following abutment connection, a plaque control program was initiated and maintained for 4 months, at which time, the dogs were re-examined and biopsies obtained for histological examination. It was observed that bone regeneration and osseointegration may occur to titanium fixtures placed in surgically-created bone defects. The amount of bone that was in intimate contact with the fixture surface was similar in test and control sites. In addition, the periimplant mucosa at test and control implants had similar dimensions and composition in terms of junctional epithelium and connective tissue.

Alveolar Ridge Augmentation↗
PubMed1997

On the dynamics of periodontal tissue formation in degree III furcation defects. An experimental study in dogs.

The aim of the experiment was to describe the formation of periodontal tissues in degree III furcation defects following GTR therapy. The study was performed in 8 foxhound dogs. The 2nd and 4th premolars in both sides of the mandible were extracted. Furcation defects were produced in the 3rd mandibular premolars. 3 weeks later, reconstructive surgery was performed. The dogs were scheduled for sacrifice 2, 4, 8, and 20 weeks after GTR therapy. Tissue blocks containing the experimental teeth were excised, demineralized in EDTA and embedded in paraffin. Serial sections were cut in the mesio-distal plane and parallel with the long axis of the roots. The microtome was set at 7 microns. The sections were stained in hematoxyline and eosin. From each biopsy, 3 sections representing the central part of the furcation, were selected for light microscopic examination. In the healed furcation sites, descriptive histological analysis of the newly-formed tissues was performed and the relative proportions of the hard and soft tissues were determined. It was demonstrated that at 2 weeks, the furcation defect contained granulation tissue and cell-rich connective tissue, while at 4 weeks the furcation was mainly occupied by connective tissue. At 8 weeks, woven bone occupied the central portion of the furcation, whereas connective tissue and cementum were observed in the lateral portions. The furcation area at 20 weeks was comprised of newly-formed cementum, periodontal ligament and bone. The onset of cementum formation had started as early as 2 weeks after GTR therapy. The cementum formation apparently occurred in 3 phases: organisation of collagen fibers adjacent and perpendicular to the root surface (phase 1), assembly of the collagen fibers and deposition of matrix (phase 2), and addition of cells and collagen fibers organised parallel to the root surface (phase 3). Bone formation took place through a process that included (1) organisation of a fibrous connective tissue, (2) differentiation of this tissue into woven bone and, (3) maturation of the woven bone into lamellar bone and bone marrow.

Alveolar Process↗