Absorption Capacity of Wound Dressings: A Comparative Experimental Study.

In this study, absorption capacity of the most commonly used types of wound dressings was measured with an objective, quantifiable, and easily reproducible method. The use of objective measurements allowed us to perform an objective comparison of the capacity of the different types of dressings. An experimental study was performed, in which the absorptive capacity of polyurethane foams, alginate, hidrofiber, and hydrocolloid dressings was measured by using a methodology designed by the researchers. Polyurethane foams showed a higher absorption capacity than hidrofibers, alginates, and hydrocolloids when using a similar surface of dressing. A modification of dressing size after saturation was also observed, increasing its size in the case of foams and decreasing or maintaining it in the case of hidrofibers, alginates, and hydrocolloids. The results of this study show a better wound exudate management for polyurethane foams. However, when deciding which dressing to use for a specific wound, absorption capacity is not the only quality that should be taken into account, as other properties should also be considered.

How good are our impressions? An audit of alginate impression quality in the production of removable prostheses.

UNLABELLED: Impressions are taken regularly in practice giving vital information to the dental laboratory, but are there quality assurance systems in place to make sure that they are up to a sufficient standard? As dental professionals we have to appreciate that dental technicians can only work with the information given to them. This makes the skill of taking a good impression vital in order for us as clinicians to provide prostheses of good quality. This paper outlines an audit of alginate impressions and their quality in the making of removable prostheses. CLINICAL RELEVANCE: To record the quality of impression taking, and how one's own ability to critique an impression may differ from that of our colleagues.

The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing qualities of impressions that may lead to occlusal discrepancies with indirect restorations.

There are few published studies that directly assess the quality of impressions for crowns and bridges in the UK. This paper considers aspects of impression quality with particular attention to factors causing potential occlusal discrepancies in the final restoration. To this end three dental laboratories were visited over a 3-month period. All impressions for conventional crown and bridgework that arrived on the days of the visits were examined and assessed against criteria defined on a custom-designed assessment form. A total of 206 impression cases were considered in this study. Flexible impression trays were used for 65% of working impressions. Their use was more common for NHS work than for private work. 31.9% of all alginate impressions examined were not adequately fixed to the tray. Visible contamination of impressions was not uncommon.

Evaluation of alginate as a substitute for root-surrounding tissues in electronic root canal measurements.

Alginate as a substitute for root-surrounding tissue was investigated. The electronic working lengths of root canals under clinical conditions were compared with an in vitro simulation of the same teeth extracted and embedded in alginate. The working lengths in 26 teeth were determined on two occasions using an electronic apex locator, before extraction and after extraction with the same teeth embedded in an alginate mass. The apical 4 mm of the root canals were exposed following the measurements, and the distances between the apical constrictions and the tips of files repositioned in the canals were measured and recorded. The mean distance between the file tip and the constriction was +0.33 mm (±0.38) in vivo and +0.32 mm (±0.30) in vitro. The Wilcoxon signed-rank test indicated that these means were not significantly different. The apical constriction was assessed to be within the limits of 0.5 mm in 80.7% of in vivo cases and in 76.9% of extracted teeth. Statistical analysis demonstrated that there was no significant difference between the results recorded in vivo and in vitro regarding apical constriction localisation. Based on the results of this study, the alginate mass is a useful tool in evaluating the performance of electronic apex locators.

Product standardisation as a tool to control prescribing costs - a case study of alginate liquid preparations.

INTRODUCTION: Product standardisation involves promoting the prescribing of pre-selected products within a particular category across a healthcare region and is designed to improve patient safety by promoting continuity of medicine use across the primary/secondary care interface, in addition to cost containment without compromising clinical care (i.e. maintaining safety and efficacy). OBJECTIVES: To examine the impact of product standardisation on the prescribing of compound alginate preparations within primary care in Northern Ireland. METHODS: Data were obtained on alginate prescribing from the Northern Ireland Central Services Agency (Prescription Pricing Branch), covering a period of 43 months. Two standardisation promotion interventions were carried out at months 18 and 33. In addition to conventional statistical analyses, a simple interrupted time series analysis approach, using graphical interpretation, was used to facilitate interpretation of the data. RESULTS: There was a significant increase in the prescribed share of the preferred alginate product in each of the four health boards in Northern Ireland and a decrease in the cost per Defined Daily Dose for alginate liquid preparations overall. Compliance with the standardisation policy was, however, incomplete and was influenced to a marked degree by the activities of the pharmaceutical industry. The overall economic impact of the prescribing changes during the study was small (3.1%). CONCLUSION: The findings suggested that product standardisation significantly influenced the prescribing pattern for compound alginate liquid preparations within primary care across Northern Ireland.

Relevance of rheological properties of sodium alginate in solution to calcium alginate gel properties.

The purpose of this study is to determine whether sodium alginate solutions' rheological parameters are meaningful relative to sodium alginate's use in the formulation of calcium alginate gels. Calcium alginate gels were prepared from six different grades of sodium alginate (FMC Biopolymer), one of which was available in ten batches. Cylindrical gel samples were prepared from each of the gels and subjected to compression to fracture on an Instron Universal Testing Machine, equipped with a 1-kN load cell, at a cross-head speed of 120 mm/min. Among the grades with similar % G, (grades 1, 3, and 4), there is a significant correlation between deformation work (L(E)) and apparent viscosity (η(app)). However, the results for the partial correlation analysis for all six grades of sodium alginate show that L(E) is significantly correlated with % G, but not with the rheological properties of the sodium alginate solutions. Studies of the ten batches of one grade of sodium alginate show that η(app) of their solutions did not correlate with L(E) while tan δ was significantly, but minimally, correlated to L(E). These results suggest that other factors--polydispersity and the randomness of guluronic acid sequencing--are likely to influence the mechanical properties of the resultant gels. In summary, the rheological properties of solutions for different grades of sodium alginate are not indicative of the resultant gel properties. Inter-batch differences in the rheological behavior for one specific grade of sodium alginate were insufficient to predict the corresponding calcium alginate gel's mechanical properties.

Dimensional stability of alginate impression material over a four hours time frame.

OBJECTIVE: To determine the dimensional stability of alginate impressions poured at varying time intervals in a tropical environment. MATERIALS AND METHODS: Alginate impressions of a master model of truncated metal cones were made and poured at varying time intervals of 5 minutes, 30 minutes, 1 hour, 2 hours and 4hours. The liner dimensional differences between the master cast and stone casts of alginate impressions poured at varying time intervals was determined. RESULTS: Although, there was observed increasing percentage differences with increasing length of time before pouring of the cast for all the inter-abutment distances measured, there was no statistical significant difference in dimension of the cast at ten minutes for all the distances measured except distance D with mean 50.23 and p value 0.010 while there were statistical significant changes observed at all the other time groups and distances. CONCLUSION: Alginate impressions should be cast within 10 minutes although, casts obtained from impressions stored by covering with wet gauze as is commonly done, for not more than 30 minutes will be clinically usable.

Prospective randomized controlled study of Hydrofiber dressing containing ionic silver or calcium alginate dressings in non-ischaemic diabetic foot ulcers.

AIMS: Diabetic foot ulcers (DFUs) are at risk of infection and impaired healing, placing patients at risk of lower extremity amputation. DFU care requires debridement and dressings. A prospective, multicentre study compared clinical efficacy and safety of AQUACEL Hydrofiber dressings containing ionic silver (AQAg) with those of Algosteril calcium alginate (CA) dressings in managing out-patients with Type 1 or 2 diabetes mellitus and non-ischaemic Wagner Grade 1 or 2 DFUs. METHODS: Patients stratified by antibiotic use on enrolment were randomly assigned to similar protocols including off-loading, AQAg (n = 67) or CA (n = 67) primary dressings and secondary foam dressings for 8 weeks or until healing. Clinical efficacy measures were healing outcomes and primarily healing speed. Adverse events were recorded. RESULTS: AQAg and CA groups were comparable at baseline. All ulcer healing outcomes improved in both groups. The mean time to healing was 53 days for AQAg ulcers and 58 days for CA ulcers (P = 0.34). AQAg-treated ulcers reduced in depth nearly twice as much as CA-treated ulcers (0.25 cm vs. 0.13 cm; P = 0.04). There was more overall ulcer improvement and less deterioration in AQAg subjects (P = 0.058), particularly in the subset initially using antibiotics (P = 0.02). Safety profiles of both groups were similar. CONCLUSION: When added to standard care with appropriate off-loading, AQAg silver dressings were associated with favourable clinical outcomes compared with CA dressings, specifically in ulcer depth reduction and in infected ulcers requiring antibiotic treatment. This study reports the first significant clinical effects of a primary wound dressing containing silver on DFU healing.

Standards and guidelines for biopolymers in tissue-engineered medical products: ASTM alginate and chitosan standard guides. American Society for Testing and Materials.

The American Society for Testing and Materials (ASTM) is making a concerted effort to establish standards and guidelines for the entire field of tissue-engineered medical products (TEMPS). Safety, consistency, and functionality of biomaterials used as matrices, scaffolds, and immobilizing agents in TEMPS are a concern. Therefore, the ASTM has established a number of task groups to produce standards and guidelines for such biomaterials. Alginate is a naturally occurring biomaterial used for immobilizing living cells to form an artificial organ, such as encapsulated pancreatic islets. In order to aid in successful clinical applications and to help expedite regulatory approval, the alginate used must be fully documented. The ASTM alginate guide gives information on selection of testing methodologies and safety criteria. Critical parameters such as monomer content, molecular weight, and viscosity, in addition to more general parameters, such as dry matter content, heavy metal content, bioburden, and endotoxin content are described in the ASTM document. In a like manner, the characterization parameters for chitosan, a bioadhesive polycationic polysaccharide, are described in a separate guide. For chitosan, the degree of deacetylation is of critical importance. Control of protein content and, hence, potential for hypersensitivity, endotoxin content, and total bioburden are important in chitosan preparations for TEMPS. Together these two guides represent part of the effort on behalf of the ASTM and other interested parties to ensure quality and standardization in TEMPS.

[The disinfection of impressions to prevent hospital infections. Sodium hypochlorite as a disinfecting agent]. / Obezzarazhivanie ottiskov s tsel'iu profilaktiki vnutribol'nichnykh infektsii. Gipokhlorit natriia kak dezinfitsiruiushchee sredstvo.

Effect of sodium hypochlorite disinfection of impressions on the size and quality of plaster models is studied. Twenty-minute submerging of silicone impressions in 0.5% sodium hypochlorite solution did not change their size and did not deteriorate the quality of surface and hardness of plaster models. Stomalgin impressions cannot be disinfected by sodium hypochlorite solution because of expressed destructive effect of this disinfectant on the impressions.

A study to compare two film dressings used as secondary dressings.

Dressings manufactured from adhesive polymeric films have been used extensively in wound management for about 20 years. This report describes the results of a trial designed to compare the performance of two such dressings, used as secondary dressings, in a multi-centre randomised controlled community study involving 100 patients. Independent analysis of the study data revealed that, after adjusting for other effects, no genuine difference was demonstrated between the dressings in terms of their ability to resist wrinkling or prevent maceration (the primary outcome variable).

Characterization of the block structure and molecular weight of sodium alginates.

Sodium alginates are widely used within the pharmaceutical sciences, yet the molecular characteristics of these materials are frequently not stated. In this study, a range of characterization techniques is applied to five sodium alginate samples and the data compared, both between techniques and with the information obtained from the manufacturer. The mannuronic acid to guluronic acid (MG) ratio and the distribution of uronic acid residues of five sodium alginate samples have been measured using circular dichroism and NMR, with circular dichroism yielding MG ratios between 42.1 and 63.6%, depending on the grade of alginate used. The MG ratios obtained from NMR studies were in broad agreement with these values, and the technique also yielded information on the distribution of uronic acid residues within each batch; this was again found to vary considerably (NG > 1 values ranging from 6.9 to 17.5). It was noted that samples with similar MG ratios could have markedly different chain-distribution characteristics. The uronic acid ratio ranges obtained from the manufacturers were found to be in good agreement with those found experimentally. Intrinsic viscosity measurements were used to compare the molecular weights of the samples; values between approximately 12,000 and 180,000 were obtained for the different batches. The study has enabled comparison of different methods for characterization of sodium alginate samples, highlighting their relative merits and the possible protocols that might be adopted. A critical discussion is given of the individual and combined use of these techniques and the relevance of such studies to the rational design and quality control of alginate-based pharmaceutical systems.

Effects of long-term storage on properties of an alginate impression material.

STATEMENT OF PROBLEM: Storage stability is a critical characteristic for perishable dental materials. PURPOSE: The purpose of this shelf-life study was to document changes in the properties of an alginate impression material on exposure to various environmental conditions for more than 78 months. MATERIAL AND METHODS: Properties measured included recovery from deformation, strain in compression, compressive strength, tear strength, working time, and creep compliance. RESULTS: Results revealed increases in strength and working time and a decrease in recovery from deformation at 30 to 50 months: strength and recovery then remained constant past 6 years, whereas working time and creep compliance decreased. Only the most stressful environmental conditions (heat and humidity) caused spontaneous failure of the material to set. CONCLUSIONS: We concluded that, under most storage conditions, properties of the alginate material tested remain within ADA specification limits well past manufacturer's designated shelf life. ADA specifications should require manufacturers to verify that the shelf life of each perishable material is based on valid data. An accelerated aging test was developed to simulate real time property changes and to assist in evaluating similar materials.

Improved biocompatibility but limited graft survival after purification of alginate for microencapsulation of pancreatic islets.

Graft failure of alginate-polylysine microencapsulated islets is often interpreted as the consequence of a non-specific foreign body reaction against the microcapsules, initiated by impurities present in crude alginate. The aim of the present study was to investigate if purification of the alginate improves the biocompatibility of alginate-polylysine microcapsules. Alginate was purified by filtration, extraction and precipitation. Microcapsules prepared from crude or purified alginate were implanted in the peritoneal cavity of normoglycaemic AO-rats and retrieved at 1, 2, 3, 6, 9, and 12 months after implantation. With crude alginate, all capsules were overgrown within 1 month after implantation. With purified alginate, however, the portion of capsules overgrown was usually less than 10%, even at 12 months after implantation. All recipients of islet allografts in capsules prepared of purified alginate became normoglycaemic within 5 days after implantation, but hyperglycaemia reoccurred after 6 to 20 weeks. With intravenous and oral glucose tolerance test, all recipients had impaired glucose tolerance and insulin responses were virtually absent. After graft failure, capsules were retrieved (80-100%) by peritoneal lavage. Histologically, the percentage of overgrown capsules was usually less than 10% and maximally 31%. This small portion cannot explain the occurrence of graft failure. The immunoprotective properties of the capsules were confirmed by similar if not identical survival times of encapsulated islet allo- and isografts. Our results show that purification of the alginate improves the biocompatibility of alginate-polylysine microcapsules. Nevertheless, graft survival was still limited, most probably as a consequence of a lack of blood supply to the encapsulated islets.

Method for the quantification of alginate in microcapsules.

Alginate is a key reagent in the preparation of microcapsules for cell transplantation. To address the question of the intracapsular alginate concentration, a sensitive assay has been developed to quantify the alginate content of microcapsules. The method is based on the metachromatic change induced by alginate binding to the dye, 1,9-dimethyl methylene blue (DMMB). The assay has a high sensitivity and precision. It covers a wide concentration range enabling the measurement of alginate in dilute supernatants as well as in microcapsules. For the latter, the membrane is initially dissolved by incubating the microcapsules in an alkaline medium. The effect of potentially interfering substances (poly-L-lysine (PLL), citrate, chloride, sodium) and of pH has been studied. Poly-L-lysine interfered with the assay at pH 6.5 but not at pH 13. Interference by sodium augmented with increasing sodium concentration and reached a plateau at 200 mM. This problem was overcome by routinely adjusting all samples to 500 mM sodium. The other substances tested had a negligible effect on the assay. The reliable measurement of alginate with this new assay will allow the optimization of the intracapsular alginate concentration.

An investigation into the compatibility of some irreversible hydrocolloid impression materials and dental gypsum products. Part I. Capacity to record grooves on the international standard die.

Some alginate impression materials produce rough, chalky, soft surfaces on gypsum casts. This is recognized by various standards, which include tests for an alginate's compatibility with gypsum, and its capacity to record details and impart these to a gypsum cast. These qualities were looked at in this study. The method used closely followed that laid down by International Standard ISO 1563-1978(E) for alginate impression materials. Ten alginates and seven gypsum products were tested. Using the criteria specified by this Standard, it was found that none of the materials tested was able to record the finest (0.020 mm) line on the test block. However, two elastomeric impression materials tested in the same manner also failed to reproduce this line, as did all the gypsum products when tested directly against the block. These findings cast some doubt on the efficacy of utilising such a fine line in the classification of these materials. Only thirty-four of the seventy possible combinations were able to reproduce the 0.050 mm line. Eight combinations reproduced the 0.075 mm line as the finest line, and the remainder (thirty-eight) failed to record any of the lines. Some of the alginate materials were treated with fixing solutions of varying concentrations of potassium sulphate and alum. The results obtained varied, sometimes producing marked improvement, sometimes deterioration in the surface quality of the subsequent gypsum casts, despite the fact that none of the manufacturers of the alginates recommended the use of fixing solutions.