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Biomedical subjects

L Pröbster

Publications and source records attributed to L Pröbster.

At least 19 recordsLinked to original sources
PubMed2000

Determination of the minimum number of marginal gap measurements required for practical in-vitro testing.

STATEMENT OF PROBLEM: Gap measurements along margins are frequently used to assess the quality of single crowns. However, the number of gap measurements required for clinically relevant results in laboratory studies is not known. PURPOSE: This study estimated the minimum number of gap measurements on margins of single crowns to produce relevant results for gap analysis. METHODS AND MATERIAL: Ten all-ceramic crowns were fabricated on a master steel die. Gaps along crown margins were investigated in a scanning electron microscope on the master steel die without cementation and on replica dies after conventional cementation. Measurements were made in 100 microm steps according to 3 gap definitions. The initial number of measurements per crown (n = 230) was reduced to smaller subsets using both systematic and random approaches to determine the impact on the quality of results. RESULTS: On the data of gap definition 1, reduction from 230 to about 50 measurements caused less than +/-5 microm variability for arithmetic means. Analysis of standard errors showed slowly increasing values smaller than 3 microm, both indicating no relevant impact on the quality of results. Smaller data sizes yielded accelerated increase of standard errors and divergent variabilities of mean. The minimum of 50 measurements did not depend on gap definition or on cementation condition. CONCLUSION: Fifty measurements are required for clinically relevant information about gap size regardless of whether the measurement sites are selected in a systematic or random manner, which is far more than what current in vitro studies use.

Aluminum Oxide↗
PubMed1998

[Using individually designed ceramic implants for secondary reconstruction of the bony orbit].

The use of autogenous transplants and the application of intraoperatively customised alloplastic materials show, in cases of secondary orbital reconstruction, a higher postoperative morbidity caused by additional approaches to the transplant donor site. On the other hand, thorough surgical exploration and fitting of the transplants or alloplastic materials greatly prolongs operating times. For these reason we designed ceramic implants (Bioverit) on the basis of stereolithography models and prefabricated them using a commercially available dental copy milling unit (Celay). In five cases up until now seven customised implants have been inserted for reconstruction of the lamina papyracea, zygomatic complex and infraorbital floor and rim. Encouraged by the good postoperative aesthetic and functional results, with significantly reduced operating times and morbidity in all cases, we will continue to take this technique into account for reconstruction after complex orbital fractures.

Adult↗
PubMed1998

Orbital reconstruction with individually copy-milled ceramic implants.

Diagnostic advances such as computed tomography and new surgical techniques have dramatically improved both the functional and aesthetic outcome of orbital reconstructions. Taking a further approach, we designed ceramic implants (Bioverit) on the basis of stereolithographic models. After copy milling a resin template with a commercially available dental unit (Celay), the prefabricated implants were inserted for reconstruction of the lamina papyracea (n = 1), zygomatic complex (n = 2), infraorbital floor (n = 5), and rim (n = 3). Intraoperatively, only slight modifications of the implants had to be performed. The results were encouraging, as all cases showed a good aesthetic and functional postoperative outcome. Preoperative evaluation of the osseous defect and prefabrication of the required implant reduced operating time and patient morbidity significantly.

Adult↗
PubMed1998

All-ceramic crowns on modified CeraOne abutments: a case report.

Single-tooth implants were used to replace congenitally absent maxillary lateral incisors in a 17-year-old patient. The inclination of the alveolar process caused a severe discrepancy between the axes of the planned implant and the crown. To avoid the need for a labial screw opening in the crown or labial overcontouring, a CeraOne abutment of the Brånemark system was modified by selective grinding in the dental laboratory. Individual all-ceramic crowns were fabricated with the Celay In-Ceram system.

Adolescent↗
PubMed1997

In vitro evaluation of a glass-ceramic restorative material.

The aim of the present study was to evaluate the clinically relevant properties of the recently introduced ceramic material IPS Empress, which is marketed for all-ceramic restorations. The following parameters were investigated: three- and four-point bending strength, bi-axial flexure strength, compressive and diametral tensile strength, compressive strength and marginal fit of full crowns. The results show that this material is a highly developed glass-ceramic with physical properties making this dental material well suitable for adhesively luted restorations.

Adhesives↗
PubMed1997

Marginal fit consistency of copy-milled all-ceramic crowns during fabrication by light and scanning electron microscopic analysis in vitro.

The aim of this study was to evaluate the marginal fit of copy-milled Celay In-Ceram crowns after different fabrication steps and to compare light-microscopic with scanning-electron-microscopic data. A master steel die of an upper middle incisor with a shoulder preparation and a rounded inner line angle was used. Impressions were taken to produce 10 working stone dies. One crown per working die was manufactured. The evaluation of the external marginal gap was performed on the master steel die by using a light microscope and a computerized video image analysis system after copy milling (A), glass infiltration (B), and veneering (C). Approximately 3900 readings were taken. In a final series the veneered crowns were measured by using a scanning electron microscope (Cs), yielding approximately 1000 readings. The results obtained were: A mean, 25.1 microm; s.d., 5.1 microm; range, 2.5-76.8 microm: B mean, 20.6 microm; s.d., 2.3 microm; range, 2.5-76.1 microm: C mean, 18.3 microm; s.d., 4.1 microm; range, 2.5-87.2 microm: Cs mean, 23.0 microm; s.d., 7.6 microm; range, 0.0-94.5 microm. The results were statistically evaluated using the t-test. The differences found between the series did not show practical relevance. Therefore, it is concluded that the manufacturing steps after copy milling have no obvious influence on the external marginal gap width. Scanning electron microscopic data seem to confirm the light-microscopic results. Hence, we expect that the Celay In-Ceram method yields a clinically acceptable marginal fit.

Aluminum Oxide↗
PubMed1996

Four year clinical study of glass-infiltrated, sintered alumina crowns.

The clinical outcome of 95 consecutively placed In-Ceram complete coverage crowns, 68 posterior and 28 anterior, all luted with conventional cements, was studied. In the 56 month observation period no total failure requiring replacement of a restoration occurred. The veneer of a molar single crown fractured, while its ceramic core remained intact. With four crowns, marginal caries was observed after 2-4.5 years. It was concluded from this clinical study that In-Ceram complete coverage all-ceramic crowns are indicated for anterior and posterior teeth.

Adult↗
PubMed1996

Three-point bending strength of ceramics fused to cast titanium.

Titanium requires special ceramic systems for veneering. This study compared the three-point bending strength of three commercially available titanium ceramic systems with a NiCr-alloy with conventional ceramics. Three-point bend specimens 25 x 5 x 0.5 mm were cast from polyethylene patterns. After alpha-case removal, they were veneered with 8 x 5 x 1 mm of ceramics at the center of the bar. Specimens were tested in a universal testing machine without ageing, after thermocycling, and after 90 d storage in an electrolyte solution. Titanium-ceramic systems were found to have a significantly lower bond strength in comparison to the NiCr-ceramic system. One of the titanium ceramic systems had a significantly lower bond strength in comparison to the other systems investigated. It could be concluded that bonding between titanium and ceramics is obtainable; however, the achievable bonds strengths did not match the NiCr-ceramic control.

Analysis of Variance↗
PubMed1995

Blood group phenotype determines lectin-mediated adhesion of Pseudomonas aeruginosa to human outer ear canal epithelium.

Pseudomonas aeruginosa is the most frequent bacterial pathogen causing acute diffuse otitis externa. In a recent prospective phase II study we demonstrated that lectin-mediated bacterial adhesion can be blocked by receptor-analogue carbohydrates in patients suffering from Pseudomonas aeruginosa-induced acute otitis externa. In this investigation, human ABO blood group antigens were analysed on outer ear canal epithelial cells with standard routine histological procedures by monoclonal antibodies for the blood groups A and B, and with Ulex europaeus I lectin for the blood group O, respectively. In all cases (n = 20) the blood groups could be shown immunohistologically. P. aeruginosa-specific adhesion and inhibition assays were performed in the presence of N-acetylgalactosamine (GalNAc), N-acetylglucosamine (GlcNAc), D-mannose and A-like substance. Outer ear canal tissue sections were incubated with P. aeruginosa (strain PA 60), presenting lectin-specificity for GalNAc. Sections from patients presenting with blood group A were closely settled with bacteria in the presence of non-specific GlcNAc, D-mannose and PBS however, GalNAc and A-like substance inhibited the microbial adhesion. Amongst others, P. aeruginosa present adhesion molecules (lectins) with specificity for GalNAc. Thus, the correlation between blood group A phenotype and P. aeruginosa-induced acute diffuse otitis externa was investigated. Statistical evaluation proved a highly significant association. These data support the hypothesis that P. aeruginosa lectins with GalNAc specificity apparently adhere to GalNAc moieties, representing the terminal blood group A-determinant and further indicate that patients presenting with blood group A may have a genetic disposition for this form of otitis externa.

ABO Blood-Group System↗
PubMed1994

[Orthodontics and implantology. Their course and results after joint planning].

The therapeutical repertoire for treating patients with missing teeth was significantly expanded by the development of modern implant methods. We have performed a retrospective analysis covering all children who between 1977 and 1993 had been considered for implants as a method for gap management. All patients were pretreated up to early adolescence using standard orthodontic procedures. Unfortunately, it turned out that an originally planned implant was not suitable in approximately 2/3 of the patients because of inadequate alveolar conditions. These patients were subsequently treated by conventional orthodontic gap closure or adhesive prosthetics.

Adolescent↗
PubMed1992

Slip-casting alumina ceramics for crown and bridge restorations.

The In-Ceram technique uses alumina ceramics and glass in a two-step firing procedure to create a high-strength core material for single-tooth restorations as well as small fixed partial dentures. Fine-grain alumina particles are sintered to form a porous substructure, which is infiltrated with molten glass. The combination of these two processes gives the material its outstanding properties. The sintering process is almost without shrinkage, providing an excellent fit, while the glass infiltration leaves practically no porosities, resulting in high strength.

Aluminum Oxide↗
PubMed1991

Custom-made resin-bonded attachments supporting a removable partial denture using the spark erosion technique: a case report.

A removable partial denture supported by resin-bonded precision attachments was constructed for a patient with intraoral symptoms of a cleidocranial dysostosis. Because of the anatomic situation, the youth, and the preprosthetic orthodontic treatment of the patient, a conventional prosthetic solution seemed inappropriate. Custom-made attachments were constructed with the spark erosion technique. They were fixed to the abutment teeth with resin-bonded retainers. The combination of the resin-bonding technique with the modern technology of spark erosion thus allowed a conservative approach to the oral rehabilitation of a young patient.

Adolescent↗
PubMed1991

[Surface morphology of alloys treated with the Rocatec system].

The new Rocatec-System is propagated for improving the resin metal bond. With a tribotechnical blasting procedure a silicate layer is applied to the alloy surface. The resin is bonded to this layer with a silane coupling agent. This study investigates the alloy surface morphology alterations caused by the blasting procedures. The volume loss increases with blasting time, high gold alloys showing higher volume loss. Thin edges are deformed due to the high blasting pressure.

Composite Resins↗