Structure and function of proteins of the phosphotransferase system and of 6-phospho-beta-glycosidases in gram-positive bacteria.

New information about the proteins of the phosphotransferase system (PTS) and of phosphoglycosidases of homofermentative lactic acid bacteria and related species is presented. Tertiary structures were elucidated from soluble PTS components. They help to understand regulatory processes and PTS function in lactic acid bacteria. A tertiary structure of a membrane-bound enzyme II is still not available, but expression of Gram-positive genes encoding enzymes II can be achieved in Escherichia coli and enables the development of effective isolation procedures which are necessary for crystallization experiments. Considerable progress was made in analysing the functions of structural genes which are in close vicinity of the genes encoding the sugar-specific PTS components, such as the genes encoding the tagatose-6-P pathway and the 6-phospho-beta-glycosidases. These phosphoglycosidases belong to a subfamily of the beta-glycosidase family I among about 300 different glycosidases. The active site nucleophile was recently identified to be Glu 358 in Agrobacterium beta-glucosidase. This corresponds to Glu 375 in staphylococcal and lactococcal 6-phospho-beta-galactosidase. This enzyme is inactivated by mutating Glu 375 to Gln. Diffracting crystals of the lactococcal 6-P-beta-galactosidase allow the elucidation of its tertiary structure which helps to derive the structures for the entire glycosidase family 1. In addition, a fusion protein with 6-phospho-beta-galactosidase and staphylococcal protein A was constructed.

Purification and characterisation of the restriction endonuclease ItaI from Ilyobacter tartaricus recognizing 5'-GC decreases NGC-3'.

ItaI, an isoschizomer of the subclass IIW [Kessler and Manta, Gene 92 (1990) 1-248] restriction endonuclease (ENase), Fnu4HI [Leung et al., Nucleic Acids Res. 6 (1979) 17-25], has been isolated from Ilyobacter tartaricus. The ENase has the five-base palindromic recognition sequence, 5'GC decreases NGC-3'. It cleaves behind the second nucleotide and produces a one-nt 5' overhang.

[The incidence of caries in juvenile diabetics (author's transl)]. / Zum Kariesbefall jugendlicher Diabetiker.

The present state of knowledge regarding the aetiology of caries implicates the interrelationship between low-molecular carbohydrates and the bacterial flora as an essential factor in the potential development of caries. Persons with hereditary fructose intolerance and patients with diabetes mellitus are of special interest in studying these interrelations. The DMF/S index was calculated and a regression analysis carried out in 101 diabetic children and juveniles aged 4 to 18. The incidence of dentine caries was significantly lower in children with onset of diabetes preceding the appearance of the second dentition than in children with manifest diabetes of up to 3 years' duration. The DMF/S index was high in individual patients in spite of the prescribed dietary treatment.

A 3-year clinical study of a hybrid composite resin as fissure sealant and as restorative material for Class I restorations.

After 3 years, 78.0% of 64 reexamined fissure restorations (extended sealants) and small occlusal restorations were clinically acceptable or excellent, and 21.9% had to be repaired or replaced because they had fractured (6.3%) or were no longer clinically acceptable by some other criterion (15.6%). The conservative preventive resin restoration seems to be an effective treatment for small occlusal defects. Meticulous dental hygiene by the patient and regular examinations by the dentist are mandatory.

The relative caries-inhibiting efficacy of amine fluoride and sodium fluoride in compatible dentifrices--results of a consensus conference.

A conference concerning the caries-inhibiting efficacy of dentifrices that contain amine and sodium fluorides compared relevant clinical studies and found that both fluoride compounds contribute to the maintenance of dental health. Because of the differing test conditions, the study results cannot, however, be compared. Thus, there is no definite scientific proof of the superiority of one fluoride compound, and no such proof will exist until dentifrices containing amine fluoride and sodium fluoride are tested in a direct clinical comparison.

Five-year follow-up of internal bleaching.

A 5-year clinical follow-up study was conducted to determine the longevity of originally acceptable results for internal bleaching. The "walking internal bleaching" method is an acceptable technique of lightening discolored anterior teeth to provide an esthetically pleasing match with adjacent teeth. This follow-up study revealed a success rate of 79% for all indications after 5 years. If the indication is limited to one palatal endodontic opening, the total success rate can reach 91%. However, a 98% success rate is common when subjective evaluation of patients is considered. The results clearly indicated that internal bleaching provides long-term success for treatment of discolored nonvital anterior teeth over a period of years and does not have any detrimental effect on dental hard tissue. In ideal cases, if the procedure is performed precisely, the success rate can exceed 90% after five years.

[The stress transmission of prefabricated root canal posts]. / Kraftübertragung von vorgefertigten Wurzelkanalstiften.

Photoelastic stress analyses were done with nine prefabricated endodontic posts under axial and diagonal (26 degrees) burden with 5, 10, 15, 20, 25 kg. Stress presented itself in form of interference fringes, which became visible under polarized light. The tapered, grooved pins (Mooser and Unimetric) caused fringes along the shaft and apical as well. They worked at higher stress like a wedge. Cylindrical pins (Para Post Unity 5, Radix-anchor) showed relative strong fringes predominantly at the top. Cylindrically tapered pins (Tenax, CM, Pivomatic) and a conical pin with flat thread and grooves (Exatec-S) caused a more favourable stress distribution and the fringes at the top were clearly slighter.

Dental amalgam. I: Conventional and non-gamma-2 amalgams.

The disadvantage of conventional amalgams lies in the fact that they form the so-called gamma-2 phase, which corrodes very easily. The gamma-2 phase can be reduced or suppressed by either adding powder with globules of a eutectic silver-copper alloy in portions of 9-33% to a common filing powder (dispersion type alloy) or by producing the powder from a homogeneous alloy of silver, copper and tin (one-component alloy). NG-2 amalgams show noticeably better physical properties than conventional amalgams. Nevertheless, they, too, corrode.

Dental amalgam. II: Exposure to mercury.

The intraoral mercury concentration as well as the concentration in the expiratory air and in the saliva of patients with amalgams is higher than that of patients with no amalgam fillings. Test persons with amalgam fillings do not show significantly higher mercury values than test persons without amalgam fillings. However, the urine of persons who are exposed to mercury at work contains more mercury than that of people who are not.

Dental amalgam. III: Toxicity.

Amalgam fillings contribute to the total exposure of the population to mercury in an analytically measurable way. As a matter of principle, it is therefore desirable to minimize the exposure to mercury. At the same time, this has to be balanced against necessities of dental surgery. Considering the inevitability of using amalgam in dental surgery, there is, at present, no reason to renounce this material from a toxicological point of view. There is no indication for mobilization tests and zinc therapy in combination with the mercury exposure from amalgam fillings.

Five-year survival rate of fissure sealings and fissure restorations.

Five hundred and thirty-four sealants and fissure restorations were checked up over a period of five years. The survival rate within five to six years amounted to 94.3% and 77.2% in relation to total and partial loss, respectively. It was significantly lower with molars than with premolars. No significant difference was found between sealants and fissure restorations nor with applications in the upper and lower jaws. Sealants and fissure restorations seem to be recommendable for the prevention as well as for conservative treatment of initial defects because more substance of the tooth is preserved than with conventional filling methods.

Fluorides.

Remineralization of early lesions and inhibition of demineralization are considered to be the prevailing mechanisms of action of fluorides. For this purpose a number of preparations are available today. Before applying them, one should be aware of their concentration, correct prescription, dosage, pharmacokinetics and potential side and after-effects.

Toothpastes.

It is well known that plaque is the main cause of caries and parodontopathies, which puts the role of toothpastes as an important means of prevention of odontopathies to the foreground. Toothpastes can be more or less oriented towards having a particular effect, such as cleaning, anticaries effect, antimicrobial effect or inhibition of the formation of tartar. Toothpastes contain substances which promote dental health, such as abrasives (silicium dioxide, brushite, calcite, calcite and aragonite, gibbsite etc.), active components (fluorides, triclosan, metal ions, sanguinarine and surface-active substances), substances which motivate the use of toothpaste (sweetening agents, aromatic oil, colours) and components which are necessary for technical reasons, such as moisturizing agents, binders and opacifiers.

[Abrasion of composites with poppy seed]. / Abrasion von Komposits nach Bearbeitung mit Mohnsamen.

Specimens of Lumifor, Brilliant Lux, Heliomolar, Estilux posterior, Visiomolar and Occlusion were abraded with poppy seed. Material loss was least pronounced for Occlusion and Visiomolar followed by Brilliant Lux, Estilux posterior, Lumifor and Heliomolar. Differences in surface roughness varied as a function of the investigation technique.

[Preparation of root canals with the Excalibur in comparison with manual instrumentation, Endocursor and Intra-Endokopf]. / Aufbereitung des Wurzelkanals mit dem Excalibur im Vergleich zu manueller Instrumentation, Endocursor und Intra-Endokopf.

64 curved root canals of acrylic models were instrumented from two experienced operators with Endocursor, Excalibur, Intra-Endokopf 3LDSY and by manual. A significant influence on the form of the root canal preparation had the factors instrument type, operator and the interferences between operator and instrument. The time of root canal preparation had a significant influence in the middle and coronal third of the root only. The best results are achieved by ideal combination of operator and instrument. With the Excalibur it is possible, to make a sparing and careful instrumentation. The excellent calibration guide is very helpful.

[Caries prevalence, periodontal status, traumatised anterior teeth and sealant in 11-14-year olds in Styria]. / Kariesprävalenz, Parodontalzustand, Frontzahntrauma und Versiegelungen bei 11- und 14jährigen der Steiermark.

The average caries prevalence for first year pupils in secondary schools (Hauptschulen and Gymnasien) was 3.2 DMFT and 5.8 DMFS. The corresponding values for fourth year pupils were 6.4 DMFT and 12.4 DMFS. The proportion of children with at least one extracted first molar was 9.2%. Significant differences were observed between the two schooltypes. The periodontal assessment showed pocket depth greater than 3 mm in at least one molar in 42% of the fourth year children. Only 3-4% of those examined had sealed fissures. Carles prevalence in Styrian children is considerably higher than reported for other countries. It therefore appears necessary to intensify dental health in this age group.

[Chemical degradation of 15 composites--an SEM study]. / Chemische Degradation von 15 Komposits--eine SEM-Studie.

SEM-micrographs of 15 untreated composites that were laid in 96% ethanol were investigated. The surface of untreated samples show different fissures and cracks. Under the influence of alcohol the fissures become wider, the bond between fillers and unfilled resin enlarges, and the filling particles become prominent or fall out. Fine-grained hybrid composites with an unfilled resin densely compacted with microfillers, are least prone to degradation.

[Age of onset of diabetes mellitus in relation to caries]. / La durée du diabète et la carie.

The DMF-Index of 101 children was established, regression analyses were made. It was found: -- that the D3-4MF/S was notably diminished in relation to patients with diabetes lasting a maximum of three years -- that the DMF/S of separately examined children was not reduced in spite of the diet. This may be interpreted as a sign of poor collaboration of the patient during therapy.