The effect of retention grooves on gingival marginal leakage in class II posterior composite resin restorations

In this laboratory study, the effect of retention grooves in the proximal portion of class II cavities on the marginal microleakage using light-cured composite resin was examined. The retention grooves were placed at the axio-facial and axio-lingual line angles and in the gingival floor of the cavities. The teeth were restored with Herculite composite resin with etching and dentine bonding and polymerized in two different ways: (i) a single mass of restorative material was polymerized all at once; and (ii) incrementally placed amounts of restorative material were each polymerized separately until the cavity was completely filled. Marginal microleakage was evaluated by the degree of dye penetration at the gingival margin of the restorations after suitable thermocycling procedures. It was concluded that marginal microleakage was significantly reduced when the composite resin was placed and polymerized incrementally, and that no advantage was gained from retention grooves with this incremental technique. However, when polymerizing in one single mass of material, retention grooves were found to be necessary in order to reduce marginal microleakage at the gingival wall.     

Studies on host-virus interactions in the chick embryo-influenza virus system

The usefulness of the deembryonation technic has been analyzed as a tool in the study of various problems in the growth cycle of influenza virus in the entodermal cells of the allantoic of chick embryos. Various improvements in the deembryonation technic have been described. The method readily permits repeated sampling of the medium at various stages after infection (cumulative growth curves) or frequent exchanges of the medium (differential growth curve). However, the yield of infectious virus or of hemagglutinins is less than that observed in the intact chick embryo. The difference observed is greater than can be accounted for by the reduction in the available host cells and is assumed, therefore, to be due in part to interruption of blood and nutrient supply to the cells. This handicap can be overcome by the combined in ovo-deembryonation technic, in which deembryonation is performed at any desired time after infection of the intact chick embryo, and the medium is collected and analyzed after 1 to 3 hours of further incubation. The value of the technic is demonstrated by the fact that liberation of virus from infected cells can be detected earlier than in the intact egg. Furthermore, it continues at a nearly constant rate for many hours, thus proving to be erroneous previous inference which had been based upon in ovo experiments. The technic also permits readily the addition and subsequent removal of substances that might interfere with viral propagation. As an example a study was made of the effect of the receptor-destroying enzyme of V. cholerae (RDE) when added to the medium of eggs infected prior to deembryonation. By carefully grading the dose of virus and using an appropriate amount of RDE, one-step growth curves were obtained indicating that those cells not directly invaded by the seed virus were subsequently protected against infection by action of the enzyme. The smaller the amount of virus the less RDE was required in order to note a protective effect. With a decrease in the period of exposure to RDE regeneration of cell receptors became increasingly more apparent in that correspondingly greater amounts of virus were produced and liberated late in the incubation periods. These results confirmed and extended those reported by Stone. More extensive applications of these technics will be reported in subsequent papers of this series.     

The rate of OH− ion release from lining materials containing calcium hydroxide

summary Four light-cured calcium hydroxide and three chemically cured resin-based lining materials were compared for hydoxil ion (OH) release. Results indicated that the chemically cured calcium hydroxide cements were capable of OH− release for a longer period than the light-cured resin bases. Alkaliner (a chemically cured liner) produced and maintained the highest alkaline environment in the long-term, whereas calcium fluoride liner and Basic-L (both resin-based) showed the lowest values of OH− ion release.     

LOW-DOSE CYCLOSPORINE A IMPROVES SEVERE DISABLING PSORIASIS IN LATIN AMERICA

Background. Severe forms of psoriasis have been treated successfully with cyclosporine A (cyA) in Europe and North America. The aim of the present investigation was to record and evaluate this drug treatment in Latin American patients with severe psoriasis in a multicenter controlled dose-efficacy study. Patients and Methods. One hundred and fifty-two patients from 10 Latin American countries had on entry to the study a Psoriasis Area Severity Index (PASI) of 18 or more. Initial treatment was with cyA, 2.5 mg per kg per day for 6 weeks. At week 6, 27 patients with a baseline PASI score reduction of < 33% had the dose increased to 4 mg/kg/day. At week 12, 48 patients, who had not improved their baseline PASI scores by 66% or more, had their dose increased to 4 or 5 mg/kg/day, respectively. At the end of the study, 74 patients (56%) received cyA 2.5 mg/kg/day, 41 patients (31%) received 4 mg/kg/day, and 16 patients (12%) received 5 mg/kg/day. Results. Cyclosporine A treatment was considered successful in 84.7% of the patients, who reduced their initial PASI score by 66% or more at the end of treatment at week 18. Adverse effects were seen in 29 patients (19%). Hypertension occurred in 27% and an increase of serum creatinine level above 30% of the initial value in 40% of patients. Among other side effects were gastrointestinal complaints (5.1%), hirsutism (4.3%), muscle pain (2.2%), joint pain (2.2%), respiratory infections (2.2%), headache (1.4%), and hemorrhagic gingivitis (0.7%). Twenty-one patients (13.8%) were withdrawn from the study for various reasons: adverse events in five cases (3.3%), noncompliance in five cases (3.3%), lack of efficacy in three cases (2%) and nonrelated diseases in two cases (1.3%). There were also six patients of a group that finished earlier than planned. A follow-up at 8 weeks after treatment was performed in 106 patients; in this phase 60 patients (56.5%) continued with their previous successful PASI reduction. Relapses (i.e., PASI increasing by more than 50% over baseline) were seen in 22.6% of cases. Conclusions. Cyclosporine A is an effective and well-tolerated treatment for severe psoriasis. An initial dose of 2.5 mg/kg/day is recommended. Most of the patients have a good response to this dose.