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Biomedical subjects

F Lutz

Publications and source records attributed to F Lutz.

At least 19 recordsLinked to original sources
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↗
PubMed1995

[Prophylaxis pastes--the new abrasive Perlit compared to conventional polishing substances].

Perlit is a new dental abrasive, based on volcanic silica. It has a flat, irregular disc-shaped structure which fractures readily in use. Individual discs tend to become oriented parallel to the tooth surface during use while the rough edges also become rounded. A Perlit-based prophylactic paste thus produces polished surfaces although it also has excellent cleaning properties on both enamel and dentin when used with either rubber polishing cups or bristle brushes. The Perlit-based prophy paste, Cleanic, yielded the best results when compared to other prophy pastes during laboratory test scored with the Prophylaxis Paste Index (PPI: Cleaning efficacy: [Abrasivity x Surface roughness]). Consequently, Perlit-based prophy pastes can be used initially as cleaning pastes and the same portion will subsequently polish the dental surfaces as well. Thus Perlit nullifies the rule that an efficient cleaning paste will be abrasive and must produce a roughened dental surface.

Aluminum Oxide↗
PubMed1994

New adhesives in Class V restorations under combined load and simulated dentinal fluid.

OBJECTIVES: This study compared the efficacy of three dentinal adhesives using the "all etch" technique (All-Bond 2, Bisco; Scotchbond MP,3M Dental Products Co.; OptiBond, Kerr) with a dentinal adhesive which still uses phosphoric acid to condition enamel and a self-etching primer for dentin (A.R.T.-Bond, Coltene/Whaledent). METHODS: Eight V-shaped mixed Class V restorations were placed per group in extracted human premolars. The restorations were subjected to 1,200,000 mechanical occlusal cycles (max. force 49 N; frequency 1.7 Hz) and 3,000 simultaneous thermal cycles (5-50-5 degrees C). Dentinal fluid was simulated using 1:3 diluted horse serum and fed into the pulp chamber both during restoration and loading. Percentages of "continuous margin" were assessed on SEM replicas of enamel and dentinal margins at 200x magnification immediately before and after stressing, respectively. RESULTS: No significant differences were observed before stress between the materials either in enamel or in dentin. After stress, however, OptiBond and A.R.T.-Bond performed significantly better in dentin than the two other adhesives (Kruskal-Wallis, Mann-Whitney; p < 0.05). Although high initial values were observed, All-Bond 2 and Scotchbond MP were not stress-resistant under simulated physiological conditions. SIGNIFICANCE: The predicted clinical potential of All-Bond 2 and Scotchbond MP is inferior to that of OptiBond and A.R.T.-Bond.

Acid Etching, Dental↗