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Biomedical subjects

F Lutz

Publications and source records attributed to F Lutz.

At least 55 records · Page 3Linked to original sources
PubMed1997

The 'Lightspeed' preparation technique evaluated by Swiss clinicians after attending continuing education courses.

This survey evaluated acceptance of the Lightspeed canal preparation (LS) technique by Swiss practitioners. The technique was introduced to Switzerland in June 1994 and 10 other continuing education (CE) courses were held at the Zurich Dental School by July 1995. Acceptance was assessed by posting questionnaires to the CE course attendees. Of the 305 questionnaires posted, 177 (58%) were returned. Of the CE participants 80% had used the technique with 60% finding the method easier and 43% finding it quicker than their usual preparation techniques. Of the respondents 58% used the technique on all tooth types and 76% of the LS users had fractured an instrument at least once. Amongst others, fractures were caused by too much pressure (25%), incorrect insertion angles (17%) and by a complicated root morphology (15%). Fractures occurred high up on the instrument shaft (74%) and near the tip (7%). Working lengths were claimed by 62% to be easier to maintain by LS than their usual preparation techniques. Among the respondents 52% obturated LS prepared canals more easily and quickly compared with their usual preparation techniques. Only 10% of LS users would not recommend the technique, but those who would suggested that proper tuition was necessary to minimize the risk of instrument fracture. The LS technique was positively assessed by clinicians who attended the CE courses in Switzerland where endodontics is not accepted as a specialty.

Education, Dental, Continuing↗
PubMed1997

Caries and plaque inhibition in rats by five topically applied dentifrices.

The effectiveness of 5 different brands of dentifrices on caries and plaque were tested in rats in 2 experiments. 10 litters of rats each were infected with Streptococcus sobrinus OMZ-176 and Actinomyces viscosus Ny1. The rats were offered the diet 2000a containing either 40% of sucrose (study I) or 10% of sucrose (study II). The following products were tested topically: (1) H2O, (negative control); (2) chlorhexidine diacetate, (positive control); (3) Parodontax NF; (4) Meridol; (5) Colgate Total; (6) Mentadent C; (7) Dent Xpress. Comparisons with the water control in study I showed that plaque extent was decreased by chlorhexidine diacetate, Dent Xpress and by Mentadent C only. All fluoride-containing dentifrices tested reduced caries. In study II, comparisons with the water control showed that plaque extent was reduced by chlorhexidine diacetate, Parodontax, Meridol, Dent Xpress and by Mentadent C. All dentifrices reduced caries, however, the incidence was low. These 2 studies confirm that fluorides incorporated in dentifrices decrease dental caries in the rat. Differences in the effectiveness of caries inhibition between the 5 dentifrices could not be explained either by the form of fluoride utilized or by the antimicrobials added. Rather, the performance of a given dentifrice depended upon the concerted action of the particular ingredients. It appears that the effect of antiplaque agents should be evaluated in the rat model using a diet containing sucrose at a low level.

Actinomyces viscosus↗
PubMed1997

Dentin bonding: effect of tubule orientation on hybrid-layer formation.

In an attempt to compare the morphology of the resin-dentin interface in areas where the dentinal tubules run perpendicularly or at an angle to the cavity surface with that of areas where they run parallel to it, we studied a dentin adhesive system using transmission electron microscopy and fluorescence confocal laser scanning microscopy. The design of the study included the simulation of the normal hydrostatic pressure within the pulp and the dentinal tubules. Following acid etching of the dentinal surface with maleic acid/HEMA, the smear layer was removed, and a superficial zone was demineralized in such a way that the exposed collagenous dentin matrix retained its integrity. Confocal laser scanning microscopal investigations using primer labeled with rhodamine B showed that the penetration of the primer occurred not only vertically via surface porosities, but mainly laterally, via the dentinal tubules. The adhesive resin labeled with fluorescein completely infiltrated the demineralized layer, thereby forming a hybrid layer. The orientation of the dentinal tubules had a profound effect on the formation of the hybrid layer. In areas with perpendicular tubule orientation, the layer was 3.2 +/- 0.8 microns thick, showing solid 27.2 +/- 0.8 microns long resin tags in the dentinal tubules, and a network of tiny tags in their side-branches. In areas with parallel tubule orientation the layer was significantly thinner (1.3 +/- 0.6 microns) and resin tags were absent.

Acid Etching, Dental↗
PubMed1997

Closing of dentinal tubules by Gluma desensitizer.

Gluma Dentin Bond is an adhesive system, where the primer contains 5% glutaraldehyde and 35% hydroxyethyl methacrylate. Practitioners have reported a strong desensitizing effect of the Gluma system on dentin. This study, thus, sought to evaluate the effect of this system on dentin using various microscopic techniques. 12 non-restored human molars extracted for prosthodontic reasons were used. Prior to extraction the buccal cusps were removed such that a 2 mm x 2 mm wide dentin surface was exposed. The surfaces were treated in 6 ways: (1) application of Gluma 2 cleanser, Gluma 3 primer to which 0.1% w/v fluorescein was added, and Gluma 4 sealer; (2) as in (1) but treatment with H2O/0.1% w/v fluorescein instead of the Gluma 3; (3) as in (1) but without Gluma 2; (4) as in (1) but with application of 5% glutaraldehyde instead of Gluma 3; (5) as in (1) but without Gluma 4; (6) as in (1) but with application of 35% HEMA/0.1% w/v fluorescein instead of Gluma 3. Following extraction, 1 tooth per procedure was prepared for confocal laser scanning microscopy. The remaining teeth were fixed and prepared for SEM and TEM evaluation. In specimens of procedures (1) and (5), tubular occlusions could be seen to a depth of 200 microm. In specimens of procedure (4) tubular occlusions were found only to a depth of 50 microm. Such occlusions were not seen in control specimens (2), in specimens where the smear-layer had not been removed (3), or following application of HEMA alone (6). It is concluded that glutaraldehyde can intrinsically block dentinal tubules. The septa in the tubules may counteract the hydrodynamic mechanism for dentinal sensitivity.

Adhesives↗
PubMed1996

Plasmids containing cos ends inhibit the replication of phage phi CTX in Pseudomonas aeruginosa.

In bacteriophage phi CTX, the cohesive end sequences cos, the integrase gene int, the attachment site attP (the target site for int) and the gene ctx encoding a pore-forming cytotoxin CTX, are clustered. Phi CTX can infect some Pseudomonas aeruginosa strains with a subsequent induction of CTX expression. The 41 and 477 bp fragments containing cos ends of phi CTX DNA were cloned into the high copy number plasmid pHA10. After pretransformation with the cos ends containing plasmids, plaque formation of phi CTX and cytotoxin production in phi CTX-infected Pseudomonas aeruginosa cells decreased by 100- and 10-fold respectively. Twelve hours after phi CTX infection proteins binding with cooperativity to cos sequence containing cleavable ends and the 10 bp flanking sequences were detected by gel electrophoretic mobility retardation of [32P]cos DNA. The results suggest that the cos binding proteins of phi CTX are involved in phi CTX replication.

Base Sequence↗
PubMed1996

An in vivo comparison of gradient and absolute impedance electronic apex locators.

Two electronic apex locators based on the gradient (Apit) and absolute (Odontometer) impedance principles were evaluated. Distances of file tips to apical foramina were determined in vivo with the electronic apex locators and subsequently verified after extraction. Mean differences between file tips and apical foramina were +0.14 +/- 0.27 mm and -0.36 +/- 0.71 mm for the Apit and Odontometer, respectively. These differences were statistically significant (p < 0.001). the Apit's and Odontometer's results ranged from +0.85 to -0.65 mm and from +0.35 to 2.45 mm from the apical foramen, respectively. Ninety-three and 73% of the findings for the Apit and the Odontometer, respectively, were within the +/- 0.5 mm range, whereas 100% and 86%, respectively, were within the +/- 1.0 mm range. Thirty-three and 43% of the results for the Apit and the Odontometer, respectively, were 1.0 mm or less coronal to the apical foramen. The Apit tended to yield the more reliable results because of the narrower range.

Adult↗
PubMed1996

Mutational analysis of bacteriophage phi CTX cos site.

The DNA of phi CTX contains the gene ctx, located closely downstream of cos. This encodes for the pore-forming cytotoxin protein, CTX. phi CTX converts some Pseudomonas aeruginosa strains into CTX producers. After different periods of phi CTX infection, two distinct forms of phage DNA were isolated: circular DNA from bacterial cytosol and later linear DNA from phi CTX particles. When circular phi CTX DNA was transfected into the P. aeruginosa strains CF5 and E40, phi CTX was amplified and ctx expressed. phi CTX induced a protein fraction in CF5 cells that cleaved the 0.477 kb cos fragment at the cos site, indicating terminase activity. Deletion and point mutation variants of the cos DNA were prepared. Protein binding to DNA in vitro and competition experiments in vivo showed that portions of the cos site and its flanking sequences are differentially critical to the binding of phi CTX-induced proteins.

Attachment Sites, Microbiological↗
PubMed1996

Serum antibody concentrations of cytotoxin, exotoxin, A, lipopolysaccharide, protease, and elastase and survival of patients with Pseudomonas aeruginosa bacteremia.

The relationship between survival and serum concentrations of antibody to cytotoxin, exotoxin A, lipopolysaccharide (LPS; IgM and IgG), protease, and elastase (determined by enzyme-linked immunosorbent assay) was studied in a group of 41 patients with Pseudomonas aeruginosa bacteremia. The lowest mean concentrations of antibody to cytotoxin (P < .05) and of IgG to LPS (P < .01) were noted in the patients who died within 48 hours of onset. The mean level of antibody to cytotoxin in patients who died 9-45 days or 5-22 months following onset was similar to that in controls, while in patients who survived > or = 24 months the level was higher than in controls (P < .01). The mean level of IgG to LPS was highest in patients who survived > or = 24 months. The mean concentrations of antibody to the other antigens (except IgM to LPS) were higher in patients than in controls (P < .01). No significant change occurred in any mean antibody concentrations over time. Administration of antipseudomonal antibodies, especially to cytotoxin and LPS, should be considered in the early stages of therapy for patients with P. aeruginosa bacteremia.

ADP Ribose Transferases↗
PubMed1995

Site-specific integration of the phage phi CTX genome into the Pseudomonas aeruginosa chromosome: characterization of the functional integrase gene located close to and upstream of attP.

The site-specific integration of the phage phi CTX genome, which carries the gene for a pore-forming cytotoxin, into the Pseudomonas aeruginosa chromosome was analysed. The 1,167 bp integrase gene, int, located immediately upstream of the attachment site, attP, was characterized using plasmid constructs, harbouring the integration functions, and serving as an integration probe in both P. aeruginosa and Escherichia coli. The attP plasmids p1000/p400 in the presence of the int plasmid pIBH and attP-int plasmids pINT/pINTS can be stably integrated into the P. aeruginosa chromosome. Successful recombination between the attP plasmid p1000 and the attB plasmid p5.1, in the presence of the int plasmid pIBH in E. coli HB101 showed that the int gene is active in trans in E. coli. The int gene product was detected as a 43 kDa protein in E. coli maxicells harbouring pINT. Proposed integration arm regions downstream of attP are not necessary for the integration process. pINT and phage phi CTX could be integrated together into P. aeruginosa chromosomal DNA, yielding double integrates.

Attachment Sites, Microbiological↗
PubMed1995

Pseudomonas aeruginosa cytotoxin: the Asp197-Gly-Asp-Tyr-His-Tyr-His-Tyr202 containing loop is critical for plasma membrane binding.

The cytotoxin from Pseudomonas aeruginosa is a pore-forming toxin that binds specifically to water channel-related molecules of the erythrocyte membrane. Here, we have defined a domain, Asp197-Gly-Asp-Tyr-His-Tyr202 of the cytotoxin, to be essential for receptor binding. Cytotoxin point mutants from the recombinant gene carrying substitutions in the domain were characterized in terms of inhibiting the binding of radioiodinated natural cytotoxin to rat erythrocyte and producing cytotoxic effects in human granulocytes. A synthetic peptide representing residues 191-211 of the cytotoxin acted as a competitive inhibitor at a concentration of 10(-5) M. In contrast, two other cytotoxin-specific peptides were inactive. Structure prediction of the binding sequence shows a loop structure with similarities to the sequence around His332 in Aeromonas aerolysin essential to receptor binding.

Amino Acid Sequence↗
PubMed1995

Time required to remove totally bonded tooth-colored posterior restorations and related tooth substance loss.

OBJECTIVES: The study was conducted to measure the time required to remove large totally bonded tooth-colored posterior restorations and related tooth substance loss. This information was collected to determine if there were differences between bonded restorations and conventional restorations. METHODS: Molars were restored with the following materials: amalgam, composite, glass ionomer cement or glass ceramic cusp coverages. After submitting them to an in vitro aging process, they were attached to a lower jaw model in a phantom head. Six dentists removed the test restorations under standardized, quasi-clinical conditions. RESULTS: While the amalgam was completely removed, some glass ionomer cement vestiges were found. In the glass-ceramic group, the margins were covered with remnants of the composite luting agent in several places. The most restorative material was left in the composite group. The loss of tooth structure after removal of amalgam, glass ionomer cement, composite and glass ceramic was 17.6 mm3, 19.6 mm3, 39.9 mm3 and 41.8 mm3, respectively. When comparing the removal time, the glass ionomer group scored best with an average of 11.9 min followed by the amalgam group with an average of 15.2 min, followed by 24.9 min for the composite group and 30.4 min for the glass ceramic group. SIGNIFICANCE: The removal of totally bonded posterior restorations made of composite and ceramic is more technically demanding and more time-consuming than the removal of glass ionomer and amalgam restorations.

Acrylic Resins↗
PubMed1995

[Materials and technics in root canal treatments in Switzerland--a determination of their status].

No data is available on either the materials nor techniques used by Swiss clinicians when doing root canal therapy (RCT). Consequently, in January 1993 questionnaires were posted to all dentists registered with the Swiss Dental Association, excluding those known not to practice RCT. Sixteen questions were answered detailing the disinfecting and obturating materials used, which types of files, preparation and obturation techniques were used and which radiographs were taken during RCT. Demographic details were also answered. Of the 3353 questionnaires posted, 2091 (62.4%) were completed and returned. Major results showed that 50.6% of the responding clinicians used AH26 to obturate canals, 45% Endomethasone and 36.6% N2. Canals were disinfected using Ledermix (81.2%), Asphaline (67.6%), Ca(OH)2 (60.2%). Clinicians used H2O2 and NaOCl equally frequently (75%). Hedstroem files, reamers and flexofiles were used by 52%, 29% and 26% of the clinicians, respectively. Canals were obturated by single-cone technique (68%), lateral condensation (34%), or by using only a paste or sealer (23%). 86.4% take a diagnostic radiograph, 69.2% determine working length from radiographs, and 91.5% take a final radiograph as well. Too many Swiss clinicians still use formaldehyde-containing products in root canal therapy coupled with a "single cone" or a "no cone" obturation technique.

Humans↗
PubMed1995

[The subjective evaluation of oral health in 40- to 69-year-old subjects. A representative survey of 600 persons in German- and French-speaking Switzerland].

Individual oral hygiene, professional dental care and subjective satisfaction with the oral health were investigated in 600 persons representative for the German- and French-speaking population of Switzerland. They cleaned their teeth on average 2.4 x per day, 85% had a "family dentist" whom they had last visited 14.6 months ago and who works to their full satisfaction. On average, every 13.5 month they underwent professional cleaning of their teeth which was performed in 55% by their dentist and in 45% by a dental hygienist. They were well satisfied with the condition of their teeth and gums and even better so with their reconstructions. In 1984 a gap of consumption of toothbrushes and toothpastes had been apparent in over 50-year-old people. Today this is just visible in the over 60 year old. 40 to 60 year old people care for their oral hygiene and regularly go to professional control and cleaning appointments. Only over 60 year old people are consuming slightly less dental services and buying less toothbrushes and toothpastes. Turning points are loss of teeth, retirement, isolation and sharp cuts in income.

Adult↗
PubMed1995

[The computer-generated occlusion of Cerec-2 inlays and onlays].

The Cerec-2 unit offers three different options to generate the occlusion: anatomically extrapolated ("Extrapolation"), correlated to a wax-up or functionally generated path ("Correlation") and bucco-orally flat ("Linear") as known from Cerec-1. These three computer-generated occlusions were evaluated by measuring the vertical discrepancy and the specific time needed for manufacturing (design, machining, contouring and adjusting the occlusal relation) of inlays and overlays. The occlusion of inlays generated with "Extrapolation" (0.42 +/- 0.16 mm) and "Correlation" (0.80 +/- 0.17 mm) showed significantly (p < 0.001) less vertical discrepancy than "Linear" (2.46 +/- 0.50 mm). The specific production time of inlays differed significantly (p < 0.001) between "Extrapolation" (16.05 +/- 0.80 min), "Linear" (19.25 +/- 1.14 min) and "Correlation" (27.33 +/- 0.75 min). The vertical discrepancies of overlays generated with "Correlation" (1.26 +/- 0.43 mm) were significantly (p < 0.001) lower than with "Extrapolation" (2.46 +/- 0.50 mm) and "Linear" (2.75 +/- 0.57). The specific overlay production time was significantly (p < 0.001) longer with "Correlation" (39.44 +/- 1.36) than with "Linear" (23.9 +/- 1.26 min) and "Extrapolation" (23.71 +/- 1.01 min). Related to the technical status of 10/1994 and as a result of the present evaluation, "Extrapolation" was chosen to be the most practical of the computer-generated occlusions evaluated in the present study.

Ceramics↗
PubMed1995

[Mercury emission measurements in a crematorium. The dentistry aspects].

The amount of mercury released during cremation was calculated in a major Swiss city at two crematoria. A total of 60 mercury "output" calculations were carried out by the Swiss Material Testing Institute (Empa). The amount of mercury initially present ("input") in the dentitions of 54 deceased persons was assessed from their post-mortem dental radiographs and by clinical examination. The correlation between the "input" and the "output" was 0.93, irrespective of the age at death. However, the "input" was calculated to be 1.8 times higher than the "output" for the deceased people with amalgam restorations. In the blind study, the difference was 1.3 times. The main source of mercury was undoubtedly the amalgam restorations. The amount of mercury recorded during the cremation of 88% of the deceased people without amalgam restorations was under the accepted level of 200 micrograms/m3. However, in 3 cases, the amount of mercury was slightly more than 200 micrograms/m3. In contrast, the amount of mercury recorded during the cremation of only 18% of the deceased people with amalgam restorations was less than the accepted level of 200 micrograms/m3. The amount of mercury contamination during cremation as a result of amalgam fillings is so low that no additional preventive measures are required at the crematoria.

Adult↗
PubMed1995

[The curing of composites under Cerec inlays].

96 Cerec CAD/CIM inlays (Vita Cerec Mk II, shades A2C and B3C) were seated into one reusable mod-cavity in a human molar. Light- (Brilliant Lux Incisal, Coltène) and dual- (Vita Duo Cement) curing composite resin respectively were used and the proximal areas were irradiated using a curing light (Coltolux II) with 4 different procedures: A) 210 s; B) 120 s (including 30 s Luciwedge, LW); C) 120 s (no LW) and D) 60 s. Vickers hardness (VHN) of the cured resin was measured at the pulpo-axial walls of the removed inlays. Polymerization-% of the resin was calculated relative to VHN of control samples, whose polymerization was scored as 100%. Two way Anova and Scheffé test were used for statistical comparison of the data. The results for the light-/dual-curing groups for shade A2C were: A) 97/89%, B) 89/90%, C) 91/88% D) 79/69%. Results for shade B3C were: A) 97/87%, B) 86/87%, C) 89/88% and D) 71/69%. No significant differences (p > 0.05) were found between light- and dual-curing. With procedures A, B and C light- and dual-curing resulted in adequate polymerization rates (PR > 85%) whereas D (PR < 80%) was significantly (p < 0.001) lower than A, B and C. Dual-curing resin had no advantages vs. light-curing with respect to polymerization rate when seating Cerec CAD/CIM inlays. The overall handling of the light-curing composite resin was judged to be easier than that of the dual cure material.

Analysis of Variance↗
PubMed1995

[Root canal treatment in Switzerland. The quantitative aspects--a determination of its status].

No recent data is available on the number of patients treated for root canal therapy in Switzerland. The aim of this study was to determine, by means of questionnaires, how many and which teeth were root canal treated in Switzerland by private practitioners. One questionnaire concerned the frequency of certain endodontic treatments performed during 10 consecutive working days. 30.1% of the posted questionnaires were correctly completed, returned and evaluated. Per dental practitioner, a total of 4.4 root canal treatments were begun during the 10 consecutive working days. A further 2.2 antiseptic dressings per practitioner were changed during the 10 days. Each dentist completed a root canal therapy on 5.3 teeth, 0.7 re-treatments and 0.1 pulpotomies during the 10 consecutive working days. 40% of all root canal treated teeth were molars which is rather high when compared to data available from other countries. Extrapolating the results to the entire Swiss population, 12.1 patients have a root canal therapy or a re-treatment per year. A similar result (12.9 patients) was recorded for the USA in 1979.

Humans↗