Biomedical subjects

G Schmalz

Publications and source records attributed to G Schmalz.

At least 73 records · Page 4Linked to original sources

PubMed1998

Characterization of immunocompetent cells in the diseased canine periodontium.

The beagle dog with naturally occurring periodontal disease is one of the most widely used animal models in periodontal research for histological studies on disease pathogenesis and on the effect of potential therapeutic regimens. However, previous studies were restricted to morphological assessment of immunocompetent cells because of the lack of available cell-specific markers. In this study we systematically characterized the specificity and immunoreactivity of a panel of anti-human antibodies for identification (ABC method) of immunocompetent cells in formalin-fixed, EDTA-decalcified, paraffin-embedded inflamed periodontal tissues obtained from six beagle dogs. Canine lymph nodes and a panel of different human tissues served as positive controls. Polyclonal anti-CD3 immunolabeled canine T-lymphocytes specifically. Anti-CD79alpha (clone HM57) reacted with B-lymphocytes and plasma cells, and CD79alpha (clone JCP117) showed no staining in canine tissues. Neutrophils, monocytes, small macrophages, and keratinocytes reacted with an anti-myeloid/histiocyte antibody (clone MAC387). Anti-CD68 (clones PG-M1 and EBM11) immunolabeled large macrophages and plasma cells. Clone EBM11 also stained osteoclasts and cementoclasts. With the exception of JCB117, all antibodies revealed similarly favorable immunolabeling of canine and human immunocompetent cells. Long-term EDTA decalcification appeared to weaken immunostaining of plasma cells with HM57. MAC387 and CD68 can be used to distinguish macrophages in different differentiation stages in canine periodontal tissues. (J Histochem Cytochem 46:1443-1454, 1998)

Animals↗

PubMed1997

Glutaraldehyde-containing dentin bonding agents are mutagens in mammalian cells in vitro.

The mutagenic potential of glutaraldehyde-containing dentin bonding agents was shown in previous studies using a bacterial gene mutation assay, the Ames test. However, current strategies of genotoxicity testing and regulatory requirements for the biological evaluation of medical devices recommend a battery of tests that indicate induced mutations in prokaryotic and eukaryotic cells. Accordingly, the mutagenicity of three glutaraldehyde-containing bonding agents (Syntac adhesive, Prisma Universal Bond 3 adhesive, and Gluma 3) was investigated using a quantitative mammalian cell gene mutation assay (V79/HPRT test) in the present investigation. The materials were extracted in dimethyl sulfoxide (0.1 g/2 mL) for 24 h and original extracts were then serially diluted in cell culture medium before exposure to V79 cells. Cytotoxic and mutagenic effects were observed with identical concentrations of extracts of the different test materials. There was a moderate decrease of the number of surviving cells immediately after the end of exposure. Mutagenicity at the hprt locus in V79 cells was found with all materials tested, and the increases in the absolute numbers of mutants were dose dependent. The mutant frequencies were about 15- (Syntac adhesive and Gluma 3) to 20-fold (Prisma UB3 adhesive) higher than solvent control values. Since other substances than glutaraldehyde may be responsible for the mutagenic effects in mammalian cells in this study, work is currently in progress to identify the individual mutagenic compounds of dentin adhesives and related composite materials.

Animals↗

PubMed1997

Clinical evaluation of heat-pressed glass-ceramic inlays in vivo: 2-year results.

In the present study, the 2-year clinical and scanning electron microscope (SEM) results for heat-pressed ceramic inlays are reported. In a selected patient population, 51 cavities were restored with all-ceramic inlays. All margins were located within the enamel. The inlays were luted to the cavities with a high-viscosity, dual-cure luting composite. After 2 days, 1 year, and 2 years, the restorations were evaluated clinically, using the modified USPHS criteria. Quantitative margin analysis was performed in the SEM on the replicas fabricated at the recall times. The data were tested for significant differences, using the chi-square test for the clinical evaluation and the Mann-Whitney U-test for the margin analysis. After 2 years, the clinical evaluation of the margin adaptation revealed Bravo ratings for 14 restorations (27.5%); 37 restorations (72.5%) were rated Alfa. Compared to the baseline data, this difference was statistically significant (p < or = 0.5). SEM analysis revealed that the ceramic-composite interface exhibited significantly (p < or = 0.01) more gap formation than the enamel-composite interface at all times of evaluation. Wear of the luting composite could be determined along 50% of the restoration interface during the first year, 53% during the second year. The inlay restorations controlled in this study perform well after a period of 2 years.

Adult↗

PubMed1997

Postoperative exposure of bioresorbable GTR membranes: effect on healing results.

The goal of this investigation was to evaluate the effect of postoperative exposure of two different bioresorbable membranes on the guided tissue regeneration (GTR) healing results compared to nonexposed sites. In each of 25 patients one pair of contralateral intrabony lesions was treated either with polylactic acid (PLA) or polyglactin 910 (PG-910) membranes. Postoperative exposure occurred in 9 PLA and 13 PG-910 sites. Standardized clinical [papillary bleeding index (PBI), gingival recession (REC), probing pocket depth (PPD), probing attachment level (PAL)] and radiographic examinations (digital subtraction radiography) were performed immediately before (baseline) and 6 and 12 months postoperatively (p.o.). Subgingival bacterial samples from surgical sites were evaluated by culture at baseline, 6 weeks, and 6 and 12 months p.o. Six months after surgery the changes (delta) of REC were significantly (P < or = 0.05) greater in exposed than in nonexposed sites, independently of the membrane material (median): exposed sites, delta REC = -1 mm; nonexposed sites, delta REC = 0.0 mm. However, 12 months p.o. no significant differences were found due to a decrease in the initial recessions in exposed sites. Although a higher percentage of exposed than nonexposed sites harbored periodontal pathogens 6 weeks p.o. at the gingiva-faced membrane surface, membrane exposure did not have a significant negative effect on delta PPD, delta PAL, or radiographic bone density changes 6 and 12 months p.o. Both membranes showed significant gains in PAL and bone density in both exposed and nonexposed sites. In conclusion, this study demonstrates that with consistent infection control the postoperative exposure of PLA and PG-910 membranes has no significant negative effect on the regeneration outcome, although higher initial gingival recessions must be expected than in the nonexposed sites. However, in exposed sites plaque and infection control were clearly impeded by the rough, exposed membrane surfaces and by the initially negative gingival morphology.

Adult↗

PubMed1997

Concepts in biocompatibility testing of dental restorative materials.

Due to the diversity of adverse biological effects which might be caused by dental restorative materials, biocompatibility assessment cannot rely on a single test but has to be based on a planned and structured approach (concept). First, the possible harm evoked by the material, the known data, and suitable biological and other test methods available must be taken into consideration. Modern regulatory concepts require for this purpose the services of experts to propose the appropriate set of required tests for a given material. The use of standards is generally emphasized because of better comparability of the data. Other tests may be chosen if more appropriate. Modern scientific concepts of biocompatibility testing are based on the need for rapid and cost-effective test methods, avoiding animal tests whenever possible. While formerly in vitro experiments did not take into account the special clinical situation in which the material would be used, modern concepts try to simulate important parameters of the in vivo situation as closely as possible. This may be achieved, for example, by including suitable barriers between the material and the target cells, by constructing appropriate target cells, and by choosing clinically relevant markers for measuring the biological effects caused by the material. There are indications so far that through this approach the number of animal tests can be reduced. The use of these methods may also lead to a better understanding of the mechanisms behind the biological reactions (mechanistic approach) in describing the biocompatibility of dental restorative materials.

Animals↗

PubMed1997

Clinical and quantitative marginal analysis of feldspathic ceramic inlays at 4 years.

The aim of this clinical study was to evaluate feldspathic ceramic inlays both by clinical criteria and quantitative margin analysis in continuation of an earlier, identically conducted 2-year study. Fifty feldspathic ceramic inlays were adhesively luted in Class II preparations with all margins located in enamel. The inlays were evaluated clinically according to modified USPHS criteria after 3 and 4 years. Quantitative margin analysis was performed with a scanning electron microscope (SEM). Clinically, the inlays showed no recurrent caries and no changes in colour, but superficial marginal discolouration (6%) was apparent after 4 years. Margins were perceptible clinically in 64% of the cases after 4 years. Quantitative margin analysis showed significantly more marginal gaps at the composite/ceramic interface than at the enamel/composite interface, There was neither a significant decrease in perfect margins nor a significant increase in marginal gaps and marginal imperfections at both interfaces between the third and fourth year. Clinically, the inlays performed very well up to 4 years. Clinical evaluation using an explorer only detected substance loss in the cementation gap. The SEM evaluation showed significantly higher changes in marginal qualities during the first 2-year interval of clinical service compared to the second 2-year interval following an exponential mathematical regularity. Quantitative margin analysis should be included in clinical long-term trials to detect early marginal deficiencies at the luting interfaces.

Aluminum Silicates↗

PubMed1997

SEM analysis of marginal expansion and gap formation in Class II composite restorations.

OBJECTIVES: Morphological changes in terms of marginal expansion have been observed at the dentin-composite interface of resin composite restorations with the scanning electron microscope (SEM), which could not be described with the criteria conventionally used for quantitative marginal analysis. The purpose of the present study was to elucidate the influence of marginal expansion upon marginal integrity and clarify the cause of these morphological changes. METHODS: A total of 22 extracted human molars were restored with Class II resin composite restorations, with and without the use of a dentin bonding agent. The cervical restoration margin was located below the cemento-enamel-junction (CEJ). The marginal adaptation at the dentin- and enamel-composite interfaces was evaluated and measured on replicas using quantitative SEM analysis after different storage periods. The chemical composition of the marginal expansion was determined qualitatively by EDX (Energy Dispersive X-Ray) analysis using original tooth samples. The results obtained from quantitative SEM analysis were statistically analyzed by applying the Mann-Whitney U-test and the error rates method. RESULTS: Significantly less marginal expansion occurred at the enamel interface than at the dentin-composite interface (p < or = 0.01). Within the dentin, less marginal expansion was observed with the use of a dentin bonding agent than without a dentin bonding agent (p < or = 0.05). At 1 y, a significant (p < or = 0.05) decrease in marginal expansion was observed in both groups. EDX analysis revealed that the chemical composition of the marginal expansion is comparable to the resin composite, since peaks for silicon, barium and ytterbium could be found at these sites. SIGNIFICANCE: In Class II resin composite restorations below the CEJ, partial disruption of the adhesive bond may occur initially when curing the restoration. Water sorption causes gap reduction by hygroscopic expansion, seen in the SEM as a volume increase. Thus, the observed morphological changes can be regarded as an early sign of insufficient adhesion between composite and dentin at sites where disruption of the bond occurred initially, whether or not a dentin bonding agent was used.

Acrylates↗

PubMed1997

Periodontal regeneration of intrabony defects with resorbable and non-resorbable membranes: 30-month results.

The aim of this prospective split-mouth-study was to compare the healing results in intrabony defects 12 and 30 months after placement of resorbable (polyglactin-910) and non-resorbable (e-PTFE) GTR-membranes. 11 healthy patients with 30 defects participated. 10 patients with 10 pairs of contralateral lesions, which were treated with both membrane types, were included in the split-mouth-design. Furthermore, in an additional group-design all 30 (16 polyglactin-910 and 14 e-PTFE) treated sites were evaluated. Clinical examinations (PBI, REC, PPD, PAL) and radiographic examinations were carried out under standardized conditions immediately before as well as 12 and 30 months after surgery. Additionally, for the assessment of the effectiveness of the 2 membranes by comparing the regeneration results of different defects, the vertical relative attachment gain (V-rAG) was calculated as a % of the PAL gain related to the maximum possible attachment gain (expressed by the baseline depth of the osseous defect intraoperatively measured). Digital subtraction radiography (DSR) was carried out for the quantitative assessment of bone density changes due to GTR. In the split-mouth-design, both types of membranes provided significant V-rAGs (median) after 12 months (polyglactin: 81.7%; e-PTFE: 100.0%) and after 30 months (polyglactin: 69.1%; e-PTFE: 83.8%) compared to baseline. In 90.0% of the polyglactin and e-PTFE sites, a probing attachment gain of at least 2 mm was maintained over the 30-month period. However, in 2 polyglactin treated sites, and 5 e-PTFE treated sites, a new attachment loss was found between 12 and 30 months. DSR showed bone density gain 12 and 30 months postsurgically. No statistically significant differences could be observed between the 2 membrane materials with regard to clinical and radiographic findings. This was confirmed when considering the total number of defects (group-design). In conclusion, based on this 30-month-study resorbable polyglactin membranes may be regarded as a useful alternative to the well established e-PTFE membranes for the treatment of intrabony defects.

Adult↗

PubMed1997

Resin-modified glass ionomer cements: fluoride release and influence on Streptococcus mutans growth.

The aims of the present study were to measure the fluoride release of 1 glass ionomer cement, 1 cermet, 3 resin-modified glass ionomer cements and 1 compomer, and to determine the influence of each material on bacterial growth. Test specimens were eluted in saline for 180 days. Every 2 days, the specimens were transferred into fresh saline and the fluoride content of the solution was measured. Furthermore, 48-h, 14-d, 90-d, and 180-d eluates were inoculated with Streptococcus mutans and bacterial growth was recorded nephelometrically. Fluoride release dropped significantly over time for each material with values between 6.2 (Ketac-Silver) and 29.3 (Photac-Fil) ppm after 48 h to values between 0.6 (Ketac-Silver) and 1.7 (Ketac-Fil, Vitremer) ppm after 180 days. Each material reduced bacterial growth at each time of examination, but the effect decreased significantly over time with a maximum growth of 71.7% (Ketac-Fil) to 85.6% (Ketac-Silver) after 48 h and 94.7 (Vitremer) to 99.0% (Ketac-Silver) after 180 days (growth control = 100%). Both Ketac-Silver and Dyract showed a significantly lower inhibiting effect on bacterial growth than the other materials. The tested materials showed a good correlation between fluoride release and influence on bacterial growth. However, both effects dropped dramatically over the 180-days period.

Cariostatic Agents↗

PubMed1997

Epithelium-fibroblast co-culture for assessing mucosal irritancy of metals used in dentistry.

No valid animal or in vitro model exists to assess the potential mucosal irritancy of dental materials. However, recently, a commercially available model system based on a recombined co-culture of human fibroblasts and human epithelial cells has been introduced for evaluating the time-dependent irritancy of cosmetic products. Cell viability and prostaglandin E2 (PGE2) release from the cells were used as markers for the irritative potential of test materials. The objective of the present study was to evaluate the suitability of this model for monitoring the irritative potential of metals and cast alloys used in dentistry. The human fibroblast-keratinocyte co-cultures were exposed to test specimens fabricated from copper, zinc, palladium, nickel, tin, cobalt, indium, a high noble cast alloy, and from a dental ceramic. Cell survival rates decreased after exposure to copper (14-25%), cobalt (60%), zinc (63%), indium (85%), nickel (87%), and the non-oxidized and oxidized high noble cast alloy (87%/90%) compared to untreated control cultures. Dental ceramic, palladium and tin did not influence cell viability. In parallel, the PGE2 release was continuously monitored up to 24 h using a competitive displacement enzyme immunoassay. PGE2 release increased most highly in the cultures exposed to copper (6-25 fold), cobalt (7 fold), indium (4 fold), and zinc (2 fold) compared to untreated control cultures. The PGE2 determination proved to be a non-destructive method for continuous monitoring of cell reactions in the same culture. The model used seems promising for evaluating the time-dependent mucosal irritancy of dental cast alloys.

Biomarkers↗

PubMed1997

Environmental issues in dentistry--mercury. FDI Commission.

One of the consequences of placing amalgam restorations is that mercury is required for the trituration process. In turn, this raises the issue of the possible environmental impact of mercury. This report considers ways in which any impact can be modified and reduced by careful attention to mercury usage and hygiene in the dental practice, the use of filters and separators in waste water pipes and the appropriate disposal of waste contaminated with amalgam. The total amount of mercury discharged into the environment varies considerably in different parts of the world due to both natural and human activities. The extent to which dentistry adds to this total also varies according to local circumstances and requirements. Recommendations are given for further development of ways to reduce mercury discharge and for further research into the environmental impact of the metal.

Dental Amalgam↗

PubMed1996

Mutagenic activity of various dentine bonding agents.

The potential mutagenicity of bonding agents of the new generation was characterised by employing an in vitro gene mutation assay. Eight different components of three dentine bonding systems (Scotchbond Multi Purpose, Prisma Universal Bond 3 and C&B Metabond) were tested in the Ames test using four different Salmonella strains (TA97a, TA98, TA100 and TA102). The materials were eluted in dimethyl sulphoxide and physiological saline; aliquots of the serially diluted eluates were then used in the standard plate incorporation assay. No mutagenic effects were found with Scotchbond Multi Purpose primer and adhesive, Prisma Universal Bond 3 primer, and C&B Metabond base, powder and activator. However, the glutaraldehyde-containing Prisma Universal Bond 3 adhesive elicited a strong mutagenic effect in S. typhimurium strain TA102. Mutation rates caused by dimethyl sulphoxide eluates as well as physiological saline eluates were about five times higher than solvent control values. A mutagenic effect was also observed with C&B Metabond catalyst, especially in strain TA97a when the material was eluted in physiological saline. Both mutagenic responses were not influenced by a metabolically active microsomal fraction from rat liver. We consider the results observed in the Ames test as a first indication of possible mutagenic activity in higher organisms. Therefore, the materials are currently under further investigation using a quantitative in vitro mammalian cell mutation assay.

Animals↗

PubMed1996

A commercially available cell culture device modified for dentin barrier tests.

The suitability of a dentin barrier test based on a commercially available cell culture chamber was evaluated by testing the cytotoxicity of dental cements. The two chambers of the culture device as produced are separated by a membrane. This was replaced by a bovine dentin disk (500 micrometers thick). Mouse fibroblasts were grown on the "pulpal" side of the dentin for 24 h; test materials were then placed into the "cavity" side of the upper chamber. The number of viable cells was determined after 24 h. After exposure to zinc phosphate cement at a powder/liquid ratio of 2:1, approximately 100% of cells survived. A ratio of 1:1 yielded 81% survival. Only 24% and 28% of the cells survived after exposure to Ketac Fil and Ketac Silver, respectively. The light-curing glass ionomer cement (vitrebond) and zinc oxide-eugenol killed all cells. These results agree with those obtained from a previous study, wherein the dentin barrier test device was constructed in our laboratory.

Animals↗

PubMed1996

Evaluation of a dentin barrier test by cyctotoxicity testing of various dental cements.

In this study, cell reaction after exposure to several dental cements was determined using a dentin barrier test device. The reaction of mouse fibroblasts grown on the "pulpal" side of a bovine dentin disk was determined after exposure to dental cements applied on the "cavity" side of the disk. For pretreatment, dentin disks (500-micrometer-thick) were etched on one side and either sterilized by autoclaving or disinfected with ethanol. It was found for both pretreatment groups that zinc phosphate cement was less toxic than the conventional glass ionomer cements. A light-cured glass ionomer cement and zinc oxide-eugenol were the most toxic materials tested. Disinfecting the dentin slices instead of autoclaving reduced the toxicity of the phosphate cement and the glass ionomer cements tendentiously. Because the strong cytotoxic reaction evoked by zinc oxide-eugenol and by the glass ionomer cements is in contrast to in vivo findings, further improvements of the dentin barrier test device will be necessary.

Animals↗

PubMed1996

Toxicity parameters for cytotoxicity testing of dental materials in two different mammalian cell lines.

The present study compares three specific toxicity parameters for cytotoxicity testing of chemically different dental materials. Two glass ionomer cements, a zinc phosphate cement, and a composite material were used to evaluate the sensitivity of three assays: two viability assays, the MTT assay and the quantifiable neutral red assay, and a proliferation assay based on the determination of the total protein content of a cell culture. The colorimetric assays were carried out using transformed mouse fibroblasts (L-929 cells) and fibroblasts derived from biopsies of normal human gingiva. In most cases, all colorimetric assays detected much weaker cytotoxic responses, if any, in gingival fibroblasts than in L-929 cells. The viability assays indicated cytotoxicity of the extracts to two glass ionomer cements in L-929 cells when the materials were set at 0% relatively humidity for 24 h. The severe cytotoxicity of the zinc-phosphate cement in both viability assays was less influenced by the setting conditions. The cytotoxicity of the composite material was most pronounced in the neutral red assay. In general, both the MTT assay and the neutral red assay were more sensitive than the colorimetric proliferation assay. These assays can be performed very effectively; only few cells are needed for rapid, reliable and inexpensive screening purposes of a large number of samples in a short time. Automated processing with a microplate reader after non-radioactive labeling of the cells and subsequent automated analyses of original data, with no need for sophisticated and expensive equipment, are additional advantages of the systems.

Animals↗

PubMed1996

Quantitative digital subtraction radiography for assessment of bone density changes following periodontal guided tissue regeneration.

OBJECTIVES: The quantitative assessment of alveolar bone density changes in periodontal defects following guided tissue regeneration (GTR). METHODS: Twelve patients with 30 intrabony lesions and 16 furcation defects took part. Standardized radiographic and clinical examinations were carried out immediately before and then 5 and 13 months after surgery. Intra-oral radiographs were evaluated by means of digital subtraction radiography (DSR). Within the subtraction images, a window ('experimental region') was defined covering the visible density changes in the defect area. Background noise was measured by using a similarly sized window ('control region') located in an area not affected by GTR. Bone density changes were quantitatively evaluated by calculation of the mean, standard deviation and maximum and minimum values of the grey-level histogram within these windows. RESULTS: DSR revealed significant bone density gain after GTR in intrabony and furcation defects. While a continuous increase was observed over the 13 month period in intrabony defects, changes in furcation defects occurred mostly in the 5-13 month period. Clinically, a distinct vertical and horizontal attachment gain was found. The correlation coefficients between changes in radiographic density and clinical parameters were low, indicating a difference in the information obtained by the two diagnostic methods. CONCLUSION: Quantitative DSR is a valuable, non-invasive, objective method to obtain information on density changes in intrabony and furcation defects treated by GTR. However, a full assessment of soft and hard tissue changes requires both clinical evaluation and DSR.

Alveolar Bone Loss↗

PubMed1995

Resin-modified glass ionomers for luting posterior ceramic restorations.

OBJECTIVES: Until recently, esthetic inlay restorations in posterior teeth have been limited to cavities surrounded by enamel. Dentin adhesive systems in combination with luting composites and light-cured resin-modified glass ionomer cements offer a possibility for bonding ceramic inlays to cavities when the cervical margin is in dentin. This study was designed to compare in vitro marginal integrity of ceramic inlays bonded to dentin to restorations placed in cavities with margins located entirely in the enamel. METHODS: In the present in vitro study, the sealing abilities of a dentin bonding agent/luting composite combination (Syntac/Dual Cement, Vivadent) and resin-modified glass ionomers (Photac Fil, Photac Bond, ESPE; Dyract, De Trey Dentsply; Fuji II LC, GC Dental Industrial Corp.; and Vitremer, 3M Dental Products) used as luting agents in cavities extending beyond the cemento-enamel junction, were compared to the sealing abilities of a conventional luting composite (Vita Cerec Duo Cement, Vita) in cavities within sound enamel. SEM analysis and dye penetration were performed to evaluate marginal integrity at the cervical cavity margins. RESULTS: The dentin bonding agent/luting composite combination (Syntac/Dual Cement) rendered a marginal seal within the dentin similar to the quality obtained with the conventional luting procedures within sound enamel. When three out of the five resin-modified glass ionomers were used as luting agents (Dyract, Fuji II LC and Vitremer), the results were comparable to those reported for the dentin bonding agents and the conventional method. SIGNIFICANCE: Light-cured resin-modified glass ionomer cements may be considered as an alternative to dentin bonding agents when the cavity margins of ceramic inlay restorations are within the dentin. However, further studies, e.g., wear resistance, must be performed.

Bicuspid↗

PubMed1995

Effect of dimension of luting space and luting composite on marginal adaptation of a class II ceramic inlay.

This study evaluated the in vitro marginal quality at the interproximal cervical margin of class II Cerec restorations. Marginal quality was evaluated separately by (1) SEM analysis before and after simultaneous thermocycling and mechanical loading for the integrity of the restoration surface and (2) dye penetration after thermocycling and mechanical loading to evaluate the strength of the bond within the depth of the cavity. The results reveal that marginal integrity is influenced by the width of the luting space and the luting composite. With a luting space of 100 microns, marginal quality with as little as 3% to 14% loss of adhesion can be obtained. Luting spaces greater than 100 microns can partially be compensated by the luting composite. For Cerec inlays, highly filled luting composites with a high viscosity are recommended.

Adhesiveness↗