Clinical evaluation of three different materials used as pit and fissure sealant: 24-months results

To evaluate the retention and caries experience effects of three different materials used as fissure sealants after 24 months of clinical application: a resin-modified glass ionomer cement (A), a flowable resin composite (B) and a compomer (C). One hundred and seventeen (117) teeth were sealed with material A, 119 teeth with material B and 120 teeth with material C. Children were randomly assigned. Each one received only one of the materials studied. Plaque index, dmft score and socioeconomic level were scored at baseline. The clinical exams were conducted 6, 12 and 24 months after application of the sealant. Statistical analysis (Kruskal-Wallis) revealed that there were statistically significant differences between the retention rates of groups A and B and between groups B and C after 2 years, with material B showing better results. After 2 years, 3.1% of the teeth of group A, 4.3% of group B and 6.7% of group C were Carious+Filled. There was no evidence of association between caries presence after 2 years and plaque index, dmft score and socioeconomic level. These results suggest that flowable resin composite had a satisfactory retention after this period of evaluation and all three materials were effective on occlusal caries prevention.     

In vitro evaluation of microleakage of different materials used as pit-and-fissure sealants

The aim of this study was to evaluate in vitro the marginal microleakage of different materials used as pit-and-fissure sealants (Delton, Filtek Flow, Dyract Flow and Vitremer). Fifty-six extracted sound human third molars were randomly assigned to 4 groups (n=14). After sealant placement, the teeth were thermocycled (500 cycles; 5 degrees C, 37 degrees C and 55 degrees C), isolated, immersed in 2% buffered methylene blue dye for 4 h, included in acrylic resin and sectioned longitudinally in a buccolingual direction. The sections were analyzed for leakage using an stereomicroscope. A 4-criteria ranked scale was used to score dye penetration. All materials exhibited dye penetration to some extension and no statistically significant difference was observed among the groups (p>0.05). In conclusion, the findings of this study showed that a flowable composite resin, a flowable compomer and resin-modified glass ionomer placed on occlusal pits and fissures had similar marginal sealing as the unfilled self-cured resin-based sealant.     

Mechanisms of inhibition by fluoride of urease activities of cell suspensions and biofilms of Staphylococcus epidermidis, Streptococcus salivarius, Actinomyces naeslundii and of dental plaque

BACKGROUND/AIMS: Fluoride is known to be a potent inhibitor of bacterial ureases and can also act in the form of hydrofluoric acid as a transmembrane proton conductor to acidify the cytoplasm of intact cells with possible indirect, acid inhibition of urease. Our research objectives were to assess the inhibitory potencies of fluoride for three urease-positive bacteria commonly found in the mouth and to determine the relative importance of direct and indirect inhibition of ureases for overall inhibition of intact cells or biofilms. METHODS: The experimental design involved intact bacteria in suspensions, mono-organism biofilms, cell extracts, and dental plaque. Standard enzymatic assays for ammonia production from urea were used. RESULTS: We found that ureolysis by cells in suspensions or mono-organism biofilms of Staphylococcus epidermidis, Streptococcus salivarius or Actinomyces naeslundii was inhibited by fluoride at plaque levels of 0.1-0.5 mm in a pH-dependent manner. The results of experiments with the organic weak acids indomethacin and capric acid, which do not directly inhibit urease enzyme, indicated that weak-acid effects leading to cytoplasmic acidification are also involved in fluoride inhibition. However, direct fluoride inhibition of urease appeared to be the major mechanism for reduction in ureolytic activity in acid environments. Results of experiments with freshly harvested supragingival dental plaque indicated responses to fluoride similar to those of S. salivarius with pH-dependent fluoride inhibition and both direct and indirect inhibition of urease. CONCLUSION: Fluoride can act to diminish alkali production from urea by oral bacteria through direct and indirect mechanisms.     

A rare complication of idiopathic osteosclerosis

Idiopathic osteosclerosis (IO) is described as a localized no expansible radiopacity with unknown etiology. The IO is generally asymptomatic and could appear as round, elliptical or irregular in shape. The internal aspect is usually uniformly radiopaque. IO should be distinguished from condensing osteitis of dental origin, or other alveolar bone related radiopacities such as periapical cemental dysplasia. This condition may cause changes in tooth position or problems during orthodontic treatment. The purpose of the present study is to report a case of tooth resorption caused by ectopic eruption rote caused by IO. This condition represents a rare complication of IO.     

Region‐specific impairments in striatal synaptic transmission and impaired instrumental learning in a mouse model of Angelman syndrome

Angelman syndrome (AS) is a neurodevelopmental disorder characterized by mental retardation and impaired speech. Because patients with this disorder often exhibit motor tremor and stereotypical behaviors, which are associated with basal ganglia pathology, we hypothesized that AS is accompanied by abnormal functioning of the striatum, the input nucleus of the basal ganglia. Using mutant mice with maternal deficiency of AS E6‐AP ubiquitin protein ligase Ube3a (Ube3a^m?/p+), we assessed the effects of Ube3a deficiency on instrumental conditioning, a striatum‐dependent task. We used whole‐cell patch‐clamp recording to measure glutamatergic transmission in the dorsomedial striatum (DMS) and dorsolateral striatum (DLS). Ube3a^m?/p+ mice were severely impaired in initial acquisition of lever pressing. Whereas the lever pressing of wild‐type controls was reduced by outcome devaluation and instrumental contingency reversal, the performance of Ube3a^m?/p+ mice were more habitual, impervious to changes in outcome value and action–outcome contingency. In the DMS, but not the DLS, Ube3a^m?/p+ mice showed reduced amplitude and frequency of miniature excitatory postsynaptic currents. These results show for the first time a selective deficit in instrumental conditioning in the Ube3a deficient mouse model, and suggest a specific impairment in glutmatergic transmission in the associative corticostriatal circuit in AS.     

Concentration of Antibodies by Freezing Serum

Antibody content of sera was increased 16-fold by freezing at –11 C in tall narrow flasks. Fractional freezing of the serum caused the protein to sediment forming four layers. The highest antibody content was found in the lowest layer, approximately 1/5 of the total volume of serum. Paper electrophoresis showed an increase in total protein and gamma globulin of the lowest layer as compared to the control whole serum. Low antibody titer sera can thus be concentrated and made into useful diagnostic reagents with minimal equipment and work.