Effect of cariogenic biofilm challenge on the surface hardness of direct restorative materials in situ

Objectives

The presence of cariogenic biofilm could result in surface degradation of composite and ionomeric restorative materials. Thus, this study evaluated in situ the alterations in the surface microhardness of these materials under biofilm accumulation and cariogenic challenge.

Methods

In a split-mouth, double-blind, cross-over study, 10 volunteers wore palatal intra-oral devices containing bovine enamel slabs restored with composite resin (CR – Z250) or resin-modified glass ionomer (RMGI – Vitremer). Two phases of 14 days were carried out, one for each restorative material. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1100 μg F/g as NaF. A 20% sucrose solution was applied extra-orally 10×/day on each restored dental slab. Knoop microhardness was used to calculate the percentage of surface hardness loss (%SHL).

Results

All materials showed a decrease in surface hardness after the in situ period. The restorative materials presented the following average for %SHL: RMGI without biofilm accumulation = 8.9 and with biofilm accumulation = 25.6, CR without biofilm accumulation = 14.7 and with biofilm accumulation = 17.0.

Conclusion

Biofilm accumulation and the presence of cariogenic challenge promoted faster degradation of ionomeric materials, but this was not observed for composite resin.

Clinical significance

The oral environment affects the surface hardness of aesthetic restorative materials. Biofilm accumulation and cariogenic challenge promote surface degradation for ionomeric materials, but not for composite resin.     

New thiazolyl-pyrazoline derivatives bearing nitrogen mustard as potential antimicrobial and antiprotozoal agents

A new series of N-substituted pyrazoline derivatives 6a–g , 7a–g , 8a–g , and 9a–g was synthetized by reaction of hydrazine derivatives and chalcone–thiazole hybrids bearing nitrogen mustard 5a–g . The chalcones 5a–g were obtained by Claisen–Schmidt condensation of thiazole-2-nitrogen mustard 3 and selected acetophenones 4a–g . These new compounds 6/7/8/9a–g were screened for their antifungal activity against Cryptococcus neoformans, with IC₅₀ values of 3.9–7.8 µg/ml for the N-3,5-dichlorophenyl pyrazolines 9e – g . Interestingly, those compounds show low cytotoxic effects toward erythrocytes (RBC). In addition, N-acetyl ( 6a,b ) and N-formyl pyrazolines ( 7a , 7b , 7c , and 7g ) showed inhibitory activity against methicillin-susceptible Staphylococcus aureus, methicillin-resistant S. aureus, and vancomycin-intermediate S. aureus, with the most important minimum inhibitory concentration values ranging from 31.25 to 125 µg/ml. Regarding the antiprotozoal activity, thiazolyl-pyrazolines 9g , 8f , and 7c display high activity against Plasmodium falciparum, Leishmania (V) panamensis, and Trypanosoma cruzi, with EC₅₀ values of 11.80, 6.46, and 4.98 μM, respectively, and with 7c being approximately 2.6-fold more potent than benznidazole with a selectivity index of 1.61 on U-937 human cells, showing promising potential as a novel antitrypanosomal agent.     

Patient and Provider-Identified Factors Contributing to Surgical Readmission After Colorectal Surgery

Purpose: Nearly one in seven surgical patients is readmitted to the hospital within 30 days of discharge. Few studies have identified patient-centric factors that raise the risk of both preventable and nonpreventable postoperative readmissions. Materials and Methods: Over 6 months in 2012, 48 colorectal surgical patients were identified on re-admission within 30 days of discharge. We prospectively obtained information on the patient's and primary surgeon's views on factors that contributed to readmission, and compiled data to produce an external list of contributing factors. A standard cost analysis was performed. Results: 48 colorectal surgery patients participated, and 47 were included in this patient-centric evaluation of factors leading to readmission. The three primary readmission diagnoses included dehydration, fever, and ileus or small bowel obstruction. Of all readmissions, 23% were considered to be preventable. 38% of patients had scheduled follow-up appointments that were documented in the medical record at the time of discharge. Providers identified several factors contributing to readmission including difficulty understanding discharge plan, medication management and premature discharge. Per patient, the cost of preventable readmission was $15,366 (±20%; $12,293–$18,439). Total preventable cost was $169,025 (±20%; $135,220–$202,829). Conclusions: The ability to obtain an outpatient postoperative appointment and the understanding of their own postoperative care were the most commonly identified barriers. Interventions to help reduce unnecessary readmissions include a standard discharge process and coordinator, and routine (<7 days) postdischarge outpatient appointments. Successful reduction of preventable readmissions would result in approximately $3.6 million in cost savings per 1,000 colorectal readmissions.     

Gangliosides, Ab1 and Ab2 antibodies II. Light versus heavy chain: An idiotype-anti-idiotype case study

The antibody heavy chain is generally more important than the light chain for the interaction with the antigen, although many reports demonstrate the influence of the light chain in the antibody binding properties. The heavy chains of anti-N-glycolyl-ganglioside P3 mAb and anti-idiotypic 1E10 mAb display complementary charged residues in their H-CDRs, particularly in H-CDR3. A basic residue in P3 mAb H-CDR1 was shown to be crucial for the interaction with the antigen and 1E10 mAb. The immunogenetic features of three other P3 mAb anti-idiotypic mAbs are now analyzed. One of them bears the same heavy chain as 1E10 mAb and a different light chain, but differs in its binding to P3 mAb mutants where H-CDR basic residues were replaced and in the binding to 1E10-specific phagotopes. Chimeric hybrid antibodies with P3 and 1E10 mAb heavy chains and unrelated light chains were obtained to further determine the importance of heavy chains in P3 and 1E10 mAb binding properties. One of the P3 heavy chain hybrid antibodies retained the specificity of P3 mAb with slight affinity differences. The heavy chains appear to play the main role in these mAb interactions, with the light chains modulating the affinity to their ligands.     

In vitro Candida colonization on acrylic resins and denture liners: influence of surface free energy, roughness, saliva, and adhering bacteria

This study aimed to determine the influence of surface roughness (Ra), surface free energy (SFE), saliva, and bacteria on Candida adhesion to denture materials. The Ra and SFE of 2 acrylic resin specimens and 2 denture liner specimens were measured and assayed in a flow chamber for bacteria culture perfusion plus Candida albicans or C glabrata cultures. Adhesion was determined by counting under light microscopy. Candida adhesion showed significant differences depending on the factors involved. The overall colonization was significantly decreased by saliva and influenced by bacteria. Candida adhesion was strongly affected by Ra, saliva, and bacteria, but not by SFE.     

Micafungin activity against Candida bloodstream isolates: effect of growth medium and susceptibility testing method

An excellent correlation between micafungin MICs were demonstrated against Candida bloodstream isolates (n = 200) by the Sensititre YeastOne and National Committee for Clinical Laboratory Standards M27-A2 methods. Use of antibiotic medium 3 (2%) dextrose improved micafungin activity and was not associated with paradoxical growth as noted with 3 Candida isolates tested using RPMI (2%) dextrose.