Search PubMed⌕ Search

Biomedical subjects

J R Strub

Publications and source records attributed to J R Strub.

At least 55 records · Page 3Linked to original sources
PubMed1994

Influence of water storage and thermal cycling on the fracture strength of all-porcelain, resin-bonded fixed partial dentures.

The purpose of this in vitro study was to evaluate the influence of water storage and thermal cycling on the fracture strength of two designs of all-porcelain, resin-bonded fixed partial dentures made with the glass-infiltrated alumina ceramic In-Ceram. Forty frameworks of In-Ceram ceramic veneered with Vitadur-N porcelain were made to replace an upper central incisor bonded to extracted natural teeth. In 20 of the restorations the pontic was veneered only labially with Vitadur-N porcelain and no proximal box preparations were made (design A). The other 20 restorations had additional box preparations proximal to the pontic and the In-Ceram ceramic pontic framework was shifted to the labial aspect and veneered circumferentially with Vitadur-N porcelain (design B). Subgroups of 10 restorations were stored for 7 days in thymol solution or alternatively for 150 days in artificial saliva with thermal cycling for 18,750 cycles between 5 degrees and 55 degrees C. Restorations with design B had a statistically significantly higher fracture strength than restorations with design A. Storage in artificial saliva with thermal cycling significantly reduced the fracture strength of the resin-bonded In-Ceram fixed partial dentures. Therefore, the long-term clinical behavior of resin-bonded In-Ceram fixed partial dentures must be evaluated before general clinical use can be recommended.

Aluminum Oxide↗
PubMed1994

Titanium deposition in regional lymph nodes after insertion of titanium screw implants in maxillofacial region.

The deposition of titanium in regional lymph nodes was studied after insertion of endosseous, plasma-spray-coated titanium screw implants in a total of 19 beagle dogs. Five additional animals with no implants served as the control group. After killing the animals 9 months postoperatively, the regional lymph nodes were carefully excised, and samples were prepared for histologic examination. Other samples were used to identify foreign particles by energy-dispersive x-ray analysis and for measurement of the titanium concentration in the tissue by flameless atomic absorption spectroscopy. Very fine foreign-body particles could be seen in the histologic sections, and they were identified as titanium by energy-dispersive x-ray analysis. The atomic absorption analysis for titanium revealed a significantly higher concentration in the group with implants. The presence of very fine, poorly attached particles on the plasma-sprayed titanium surface suggests that these particles may be mechanically dislodged from the surface on insertion of the implants. This suggests that the fine particles may be transported by phagocytes to the regional lymph nodes, where they could be found without any signs of inflammation or foreign-body reaction.

Animals↗
PubMed1994

Bone augmentation using a synthetic bone graft in dogs.

The aim of this investigation was to evaluate clinically and histologically the use of a synthetic bone graft (Ionogran) alone and in combination with guided bone regeneration (GBR) for alveolar ridge augmentation. Five beagle dogs were used in this study. Prior to the augmentation procedure the maxillary and mandibular second, third and fourth premolars were extracted. Three months after the extractions, impressions from the area of the ridges were taken. Particles of Ionogran were then placed under mucoperiosteal flaps in each quadrant. On the experimental sites, an expanded polytetrafluoroethylene barrier was placed between the flap and the particles. Impressions were retaken at 1 and 3 months after surgery. Three months after surgery, the animals were sacrificed and specimens were prepared for histological evaluation. Computer-assisted volumetric analyses from the casts revealed an increase in ridge volume from baseline in both groups at 1 and 3 months. There was no difference in the height of the augmentation between the test and control sites. The histological results of this study indicate that this new synthetic bone graft appears to be a safe biocompatible grafting material. There were no apparent histological differences between the graft alone and graft/GBR sites. In both groups, however, graft particles were surrounded by dense fibrous connective tissue and bone formation was limited to the graft bone interface.

Aluminum Silicates↗
PubMed1993

Three-dimensional investigation of the accuracy of impression materials after disinfection.

The influence of the two new disinfection systems Hygojet/MD 520 and Impresept on the accuracy of eight impression materials was evaluated with a clinically relevant abutment arrangement. In addition, an "aseptic" irreversible hydrocolloid was tested under the same test conditions but without the disinfection procedure. The dimensional changes of all eight impression materials related to the disinfection procedures were small. Although statistically significant interactions of the impression materials and the disinfection systems were found, the influence of the two tested disinfection systems on the dimensional accuracy of the impressions does not seem to be clinically relevant. From the standpoint of impression accuracy, both tested disinfection systems and the tested "aseptic" irreversible hydrocolloid can be recommended for clinical and laboratory use.

Analysis of Variance↗
PubMed1993

Fracture strength of all-porcelain, resin-bonded bridges after testing in an artificial oral environment.

Twenty all-porcelain In-Ceram bridges were resin bonded to natural teeth on a study model. Ten of the test specimens were fixed on abutments placed directly in resin, and 10 were supported by an artificial periodontal membrane. Incisal forces of physiological magnitude and direction were applied in three bridges of both groups (test samples) in an artificial oral environment (1250,000 cycles). The fracture strength of the six test and 14 control specimens was tested in a universal testing instrument and the rupture strength measured. There was no significant difference between the fracture strength of the test and control samples. The artificial periodontal membrane around the abutment teeth did not reduce the fracture strength of the In-Ceram bridges.

Aluminum Oxide↗
PubMed1993

Extracellular matrix analysis of nifedipine-induced gingival overgrowth: immunohistochemical distribution of different collagen types as well as the glycoprotein fibronectin.

The purpose of this study was to demonstrate the localization of collagen types I, III, IV, V, VI and VII as well as the glycoprotein fibronectin in nifedipine-induced gingival overgrowth. The slices, after the use of indirect immunofluorescence (incubation with antibodies against these extracellular matrix components), showed a diffuse distribution with the anti-types I and III in the stroma and fluorescent staining of the basement membranes of the epithelium, blood vessels and nerves with collagen type IV antibodies. The increased number of vessels was localized near the surface of the lesion. Collagen type V - seen as a filamentous - and collagen type VI - as microfibrillar - components were also localized in the tissue, showing completely different patterns of distribution. Collagen type V appeared "crater"-like and type VI displayed a "honeycomb"-shaped structural model. The blood vessels were not stained but the area around their walls demonstrated an intense fluorescence with these antibodies. Collagen type VII showed a characteristic linear staining near to the epithelial basement membrane. In contrast to this, fibronectin localized with a varied intensity in the different areas of the tissues and presented a "cloud"-like structure. This shows differences between the matrix components in nifedipine-induced hyperplasia and confirms the heterogeneity of the matrix in health and in gingival alterations.

Adult↗
PubMed1993

Immunohistochemical distribution of extracellular matrix proteins as a diagnostic parameter in healthy and diseased gingiva.

This study showed histopathological findings of the extracellular matrix in healthy, inflamed, and hyperplastic human gingiva with immunohistochemical techniques. The distribution of collagen types V and VI, as well as of glycoprotein fibronectin, shows that they are extracellular matrix structural components which differentiate the tissue pathology. The orientation of the collagen fibers, the intensity of the fluorescent staining, the thickness of the fibrillar component, and the topographical localization of the connective tissue proteins are important parameters for tissue morphology. Therefore, bacterial deposits and the pharmacodynamic properties of drugs associated with gingival hyperplasia lead to an alteration of the matrix compared to the healthy tissues. This may be important in the tissue pathology in cases when the medical history of the patient is not known, as well as in forensic medicine.

Adult↗
PubMed1993

Treatment of ligature-induced peri-implantitis using guided tissue regeneration: a clinical and histologic study in the beagle dog.

This study evaluated the treatment of ligature-induced peri-implantitis using guided tissue regeneration (GTR) around submerged and nonsubmerged implants in beagle dogs. Two titanium implants were placed bilaterally in the premolar regions of the mandible in each of 10 beagle dogs. Cotton floss ligatures were placed around the implant necks and no oral hygiene procedures were performed for 5 months. Periodontal surgery was performed, and in five dogs (submerged group) the abutments were removed and an e-PTFE barrier was placed to cover the test implants and their adjacent osseous defects, while the control implants received no barriers. In the other five dogs (nonsubmerged group), flap surgery was performed without removing the abutments. In the test sites, an e-PTFE barrier was placed around the abutment and adjacent defects, while on the control sites no barrier was placed. Nondecalcified specimens were prepared using standard histologic methods and analyzed. No differences were found between any of the clinical parameters in both the control and experimental sites from the submerged and nonsubmerged groups. Histologic and histomorphometric analyses also revealed no significant differences between groups with regard to new bone formation. In the experimental (GTR) groups, however, the amount of regenerated connective tissue was significantly greater than on the control groups. Under the conditions of this study, the treatment of peri-implantitis using GTR did not enhance clinical parameters or bone formation around "diseased" implants.

Alveolar Bone Loss↗
PubMed1992

[Severe atrophy of the alveolar ridge in edentulous patients. Combined treatment using bone grafts and screw implants].

In cases of advanced alveolar ridge atrophy, when the bone available for endosseous implants is not sufficient, endosseous implants are combined with augmentation of the alveolar ridge by means of autologous bone transplants. Depending on the type of atrophy found, the authors use three different surgical procedures: onlay technique, sandwich technique and alveolar extension technique. In all cases functional loading of the implants was performed by way of an entirely implant-supported bridgework. Results to date indicate that initial postoperative resorption is followed by a virtual standstill once the implants have been loaded.

Alveolar Process↗
PubMed1991

[Tensile strength of the bond to In-ceram after varying modes of surface conditioning].

The tensile bond strengths of six different resin-bonding-systems to the aluminium oxide ceramic In-Ceram were tested. The samples were stored in artificial saliva (37 degrees C) up to 150 days and thermocycled (5 degrees-55 degrees C, 18,750 cycles). After sandblasting or silicoating of In-Ceram the tensile bond strength of the modified Bis-GMA resin Panavia-Ex showed no significant changes within this observation period. Using the conventional Bis-GMA resin Microfill-pontic, silicoating In-Ceram with the Rocatec-system resulted in a better bond strength than the use of a silane. The used etching procedure with boiling 70% sulphuric acid was proven to be unsuitable for a long-term stable bond.

Acid Etching, Dental↗
PubMed1991

[Texture formation of the dental ceramic core material In-Ceram and thermal expansion of its individual components].

Electron microscopic investigations of the core material In-Ceram show how its texture is formed. While these are processed the Al2O3 crystallites turn idiomorphic. Etching the material with sulphuric acid selectively dissolves the glassy phase and reveals the crystallites. The chemical composition of the two components of the core material is determined by microprobe analysis. While the crystallites are pure Al2O3, the glass consists of La2O3, SiO2, Al2O3 and CaO. Measurements of the thermal expansions of the glass and the Al2O3 frame show the value for the glass to be 5.1% lower than that of the Al2O3 frame. This results in internal pressure and contributes to the high strength of the material.

Aluminum Oxide↗
PubMed1990

[Resin bonding bridges--state of the art].

Adhesive fixed partial denture (FPD) technology has gradually become viable in recent years, suitable for use in general dental practice. The most important prerequisites for success are patient selection and meticulous production techniques. Indications and limits of this technique are evaluated on the basis of the current state of the art. Initial preprosthetic treatment and clinical procedures are described. Research that has been done so far appears to demonstrate that adhesive FPDs are compatible with healthy periodontal tissues, even though some over-contouring of the adhesive tabs on the abutment teeth seems to be unavoidable. First clinical long-term studies have shown, however, that the failure rate of adhesive FPDs is higher than with conventional crown and bridge techniques. Porcelain-fused-to-metal FPDs on pure titanium frames and full ceramic FPDs are new developments in adhesive FPD technology which are not yet fit for use in dental practice.

Acid Etching, Dental↗