Effect of Short-Duration, Localized Carbamide Peroxide Application to Remove Enamel Staining on Bond Strength of Resin Cement to Enamel.

UNLABELLED: Objective Peripheral enamel staining is often noticed after removal of long-term veneer or crown provisional restorations. Application of carbamide peroxide (CP) easily removes the stain, but the potential for immediate bonding with a resin-based cement is questionable. This project tested the short-term, shear bond strength of a commercial, photo-curable, resin cement to bovine enamel after application of a 10% concentration of CP placed for different exposure times. MATERIALS AND METHODS: Bovine enamel was flattened and polished. Surfaces had either no CP application (control), or 10% CP applied for 10, 20, or 30 seconds. Teeth were acid-etched, rinsed, dried, and controlled sized stubs of a commercial resin cement were photocured onto the treated surfaces. The shear bond strength of each specimen was determined using a universal testing machine, and results were compared using an analysis of variance at a preset alpha of 0.5 (n = 10/group). RESULTS: No significant differences (p = 0.819) in shear bond strength were found among any CP cleaning treatments or the experimental (nontreated) control. CONCLUSIONS: Short-term application of 10% carbamide peroxide prior to acid etching, to remove enamel stains in teeth prepared to receive ceramic veneers or crowns, does not reduce immediate shear bond strength of resin-based cement to enamel. CLINICAL SIGNIFICANCE: Clinicians can confidently apply 10% CP for short-term, localized stain removal on enamel and not be concerned about affecting subsequent bond strength of a resin-based cement to enamel. (J Esthet Restor Dent, 2016).

Changes in pediatric tracheostomy tubes exposed to home dishwashing.

OBJECTIVE: Determine the effects of household dishwashing on Tracheostomy Tube safety. INTRODUCTION: Tracheostomy tubes accumulate biofilms, which may limit their lifespan. Frequent cleaning of the tubes is a method for biofilm prevention. Cleaning practices vary widely. Some families prefer dishwashing of tubes, but its effects are currently unknown. We hypothesize that dishwashing has no significant effect on the physical properties of tracheostomy tubes and can be recommended as a safe way to clean tracheostomy tubes. METHODS: Twenty 4.0 Shiley™ pediatric tracheostomy tubes were randomly assigned into dishwashed (DW) and non-dishwashed (NDW) groups, 10/group. DW tubes were subjected to 12 wash cycles. Each tube's hardness along with the surface spectra were analyzed to assess for chemical composition changes. Three cannula samples from each group were also randomly assessed with scanning-electron microscopy and scored by blinded examiners to assess for changes in surface heterogeneity. RESULTS: Hardness testing revealed a statistically significant difference (p = 0.0009) between the NDW and the DW group indicating increased fragility in the dishwashed tubes. Spectral analysis revealed loss of plasticizers, indicating decreased flexibility. Blinded electron microscopy scoring revealed increased surface heterogeneity in the DW group (p = 0.00007). CONCLUSION: A significant decrease in tube hardness and increased surface heterogeneity were found with dishwashing. The spectral analysis demonstrated increasing fragility. We believe these effects could potentially lead to decreased mechanical safety. With increased surface heterogeneity there is a greater potential for biofilm formation. At this time, dishwashing cannot be recommended as a tracheostomy tube cleaning method.

Effects of subtoxic concentrations of benzoyl peroxide on cell lipid metabolism.

Benzoyl peroxide (BP), a tumor promoter, has been shown to cause free-radical-induced lipid peroxidation and membrane damage at toxic concentrations. However, its effects on lipid metabolism at concentrations that were not overtly toxic have not been investigated. The purpose of the current study was to examine the effects of BP and its final degradation product, benzoic acid (BA), on lipid metabolism. Two cell lines, hamster cheek pouch (HCP) and human monocytes (THP-1), were used to determine the effects of BP, BA, and BP combined with FeCl2 on cell lipid metabolism. Cells were exposed to BP and 14C acetate for 24 h, or cells with prelabeled lipids were harvested, and the lipids were extracted and separated with the use of thin-layer chromatography. Lipid metabolism of some neutral lipids such as triglycerides was altered for both cell types in response to BP. Also, cholesterol content was reduced in THP-1 cells and a phospholipid, phosphatidylethanolamine (PE), was reduced in HCP cells. The final degradation product of BP, BA, failed to elicit any response in lipid metabolism. Subtoxic concentrations of BP induced changes in neutral lipids such as triglycerides and cholesterol. The metabolism of major phospholipids except PE remained unchanged. The effects were related to BP and its degradation and varied with the cell type.

Effects of sub-toxic concentrations of camphorquinone on cell lipid metabolism.

The biological effects of camphorquinone (CQ), an initiator for light-polymerized resins, have been reported to relate to its ability to generate free radicals and cause radical-induced membrane damage via lipid peroxidation. However, the effects of CQ on lipids other than peroxidation may result in unfavorable tissue responses especially at concentrations that are not overtly toxic to cells. The purpose of the current study was to examine the effects of CQ on cell lipid metabolism at subtoxic concentrations, with or without visible light irradiation. HCP and THP-1 cells were exposed to CQ with or without light irradiation under clinically relevant conditions and lipid metabolism was analyzed using 14C-labeling and thin-layer chromatography. We found that CQ increased synthesis of neutral lipids, such as triglycerides, from 7 to nearly 15% of the total and diglycerides from 2% to about 3% of the total in HCP cells, while synthesis of phospholipids, such as sphingomyelin, was decreased by 1-1.5%. In THP-1 cells cholesterol synthesis increased more than 2-fold and cholesterol ester synthesis increased more than 5-fold. Light-activated CQ did not differ significantly in terms of its bioactivity compared to no-light conditions. We conclude that CQ significantly altered the metabolism of several important structural lipids in two cell types at sub-toxic concentrations that are clinically relevant. These changes in lipid metabolism may in turn affect membrane integrity and permeability and possibly lead to significant changes in cell responses.