Topical silver for treating infected wounds

BACKGROUND

Topical silver treatments and silver dressings are increasingly used for the local treatment of contaminated or infected wounds, however, there is a lack of clarity regarding the evidence for their effectiveness.

OBJECTIVES

To evaluate the effects on wound healing of topical silver and silver dressings in the treatment of contaminated and infected acute or chronic wounds.

SEARCH STRATEGY

We sought relevant trials from the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Wounds Group Specialised Register in March 2006 and in MEDLINE, EMBASE, CINAHL, and digital dissertations databases up to September 2006. In addition, we contacted companies, manufacturers and distributors for information to identify relevant trials.

SELECTION CRITERIA

Randomised controlled trials (RCTs) assessing the effectiveness of topical silver in the treatment of contaminated and infected acute or chronic wounds.

DATA COLLECTION AND ANALYSIS

Eligibility of trials, assessment of trial quality and data extraction were undertaken by two authors independently. Disagreements were referred to a third author.

MAIN RESULTS

Three RCTs were identified, comprising a total of 847 participants. One trial compared silver-containing foam (Contreet) with hydrocellular foam (Allevyn) in patients with leg ulcers. The second trial compared a silver-containing alginate (Silvercel) with an alginate alone (Algosteril). The third trial compared a silver-containing foam dressing (Contreet)) with best local practice in patients with chronic wounds.The data from these trials show that silver-containing foam dressings did not significantly increase complete ulcer healing as compared with standard foam dressings or best local practice after up to four weeks of follow-up, although a greater reduction of ulcer size was observed with the silver-containing foam. The use of antibiotics was assessed in two trials, but no significant differences were found. Data on pain, patient satisfaction, length of hospital stay, and costs were limited and showed no differences. Leakage occurred significantly less frequently in patients with leg ulcers and chronic wounds treated with a silver dressing than with a standard foam dressing or best local practice in one trial.

AUTHORS' CONCLUSIONS

Only three trials with a short follow-up duration were found. There is insufficient evidence to recommend the use of silver-containing dressings or topical agents for treatment of infected or contaminated chronic wounds.

Silver-Containing Dressings and the Need for Evidence

The field of wound care has been inundated with "active" dressings--those that deliver biologically active substances to the wound site--and much attention has been given to those containing silver. Silver is a broad-spectrum agent: it is bactericidal to a large number of Gram-positive and Gram-negative microorganisms, many aerobes and anaerobes, and several antibiotic-resistant strains. More than 10 dressings containing pure silver are currently available; all claim to enhance wound healing through the antimicrobial activity of silver. But research findings on silver's antimicrobial efficacy are often inconclusive or contradictory. How, therefore, can clinicians decide which dressing is most appropriate for each patient? A grading system for reviewing the literature is presented.

Effect of silver on burn wound infection control and healing: review of the literature

Silver compounds have been exploited for their medicinal properties for centuries. At present, silver is reemerging as a viable treatment option for infections encountered in burns, open wounds, and chronic ulcers. The gold standard in topical burn treatment is silver sulfadiazine (Ag-SD), a useful antibacterial agent for burn wound treatment. Recent findings, however, indicate that the compound delays the wound-healing process and that silver may have serious cytotoxic activity on various host cells. The present review aims at examining all available evidence about effects, often contradictory, of silver on wound infection control and on wound healing trying to determine the practical therapeutic balance between antimicrobial activity and cellular toxicity. The ultimate goal remains the choice of a product with a superior profile of infection control over host cell cytotoxicity.

Increased Bacterial Burden and Infection

PURPOSE

The purpose of this article is to provide practitioners with an overview of wound infection/inflammation and bacterial balance and to offer a guide to assessment and treatment of chronic wounds.

TARGET AUDIENCE

This continuing education activity is intended for physicians and nurses who assess and treat wound infections.

OBJECTIVES

After reading this article and taking this test, the participant should be able to: 1. Discuss factors associated with infection of the chronic wound, including the concept of bacterial balance and burden. 2. Identify signs of infection in the chronic wound and applicable diagnostic tests. 3. Describe appropriate treatment for the infected chronic wound.

Topical antimicrobials in the control of wound bioburden

Bacterial colonization and infection are important factors in compromised wound healing, particularly in chronic wounds. Although "best practice" for controlling these factors currently is not defined, systemic antibiotics are generally accepted as the preferred choice for treating infection, provided ischemia does not reduce their bioavailability. However, widespread use of systemic and topical antibiotics is associated with the emergence of resistant bacterial strains such as methicillin-resistant Staphylococcus aureus. Colonization of wounds presents a double problem--potentially delayed healing and a potential source for cross-contamination. The judicious use of dressings, notably those containing certain antiseptic agents, can be a valuable option to control infection and promote healing. A review of the literature underscores the importance of considering the antiseptic route as part of a concerted approach to wound management and infection control.

Effect of a sustained silver-releasing dressing on ulcers with delayed healing: the CONTOP study

OBJECTIVE

To compare the effect of the sustained silver-releasing foam dressing Contreet Foam (ColoplastA/S) with local best practice (LBP) on delayed healing ulcers using a real-life setting.

METHOD

A total of 619 patients with ulcers of varying aetiologies were treated for four weeks with either the silver foam dressing or LBP.

RESULTS

Wound area was reduced by 50% with the silver foam and 34% with LBP Less slough and maceration, a faster reduction in exudate level and more positive wound progress was achieved with the silver foam. In addition, exudate handling, ease of use, odour and pain improved. Less time was spent on dressing changes, and mean wear time was longer for the silver foam (3.1 days) than for LBP (2.1 days). All differences were statistically significant (p < 0.05). The silver foam dressing outperformed all of the other dressing categories including moist wound healing products and other silver dressings.

CONCLUSION

This large-scale comparative real-life study shows that the silver foam dressing supports faster healing of delayed healing wounds.

The silver-releasing foam dressing, Contreet Foam, promotes faster healing of critically colonised venous leg ulcers: a randomised, controlled trial

The study compared the effect of a sustained silver-release foam dressing (Contreet Foam) with a foam dressing (Allevyn Hydrocellular) without added silver in critically colonised venous leg ulcers with delayed healing. The study was a multicentre, open, randomised, controlled study lasting for 4 weeks. Ulcer area and healing were assessed weekly. Odour, maceration, absorption capacity and leakage were evaluated at dressing changes. All adverse events were recorded. One hundred and twenty-nine patients were included (Contreet Foam: 65, Allevyn Hydrocellular: 64). The two groups were comparable in all respects. After 4 weeks, there was a significantly greater reduction in ulcer area in the Contreet Foam group (45%) than in the Allevyn Hydrocellular group (25%). After 1 and 4 weeks, odour was present in significantly less of the ulcers in the Contreet Foam group (17% and 19%, respectively) compared with the Allevyn Hydrocellular group (47% and 39%, respectively) and at the final visit there were significantly fewer leakages in the Contreet Foam group (19%) compared with the Allevyn Hydrocellular group (49%). Also, less maceration was observed after 1 and 4 weeks in the Contreet Foam group (34% and 37%, respectively) compared with the Allevyn Hydrocellular group (55% and 48%, respectively). The occurrence and cause of adverse events were equally distributed between the study groups. The present study provides evidence of the superior performance of the silver-releasing dressing, Contreet Foam, compared with a traditional moist foam wound healing dressing in the treatment of critically colonised, chronic venous leg ulcers. The results of this randomised, controlled study suggest an important role of sustained silver-releasing dressings in the treatment of critically colonised chronic wounds.

Silver as biocides in burn and wound dressings and bacterial resistance to silver compounds

Silver products have been used for thousands of years for their beneficial effects, often for hygiene and in more recent years as antimicrobials on wounds from burns, trauma, and diabetic ulcers. Silver sulfadiazine creams (Silvazine and Flamazine) are topical ointments that are marketed globally. In recent years, a range of wound dressings with slow-release Ag compounds have been introduced, including Acticoat, Actisorb Silver, Silverlon, and others. While these are generally accepted as useful for control of bacterial infections (and also against fungi and viruses), key issues remain, including importantly the relative efficacy of different silver products for wound and burn uses and the existence of microbes that are resistant to Ag+. These are beneficial products needing further study, although each has drawbacks. The genes (and proteins) involved in bacterial resistance to Ag have been defined and studied in recent years.

Effect of a new silver dressing on chronic venous leg ulcers with signs of critical colonisation

OBJECTIVE

To investigate the clinical performance and safety of a new silver-containing wound-contact layer, Physiotulle -Ag (Coloplast), in the treatment of chronic venous leg ulcers with delayed healing and signs of critical colonisation.

METHOD

This was an open prospective non-comparative multicentre clinical study. Patients were treated for four weeks with Physiotulle -Ag, which was covered by Alione Hydrocapillary Dressing (Coloplast).

RESULTS

Thirty patients were recruited into the study. One ulcer healed after three weeks of treatment. The mean relative ulcer area reduced by 55% after four weeks. Over the study period the mean amount of healthy granulation tissue increased from 26% to 62%, and the mean amount of fibrin decreased from 63% to 32%. The ratio of malodorous wounds was 50% at inclusion, 20% after one week and 3% after four weeks. The dressing was considered easy or very easy to apply in 100% and easy to remove in 89% of dressing evaluations. The dressing combination showed good exudate-management properties. Incidence and severity of maceration, erythema and eczema decreased during the study and no device-related adverse events were recorded.

CONCLUSION

Physiotulle -Ag is safe and easy to use in chronic venous leg ulcers in which healing is delayed and with signs of critical colonisation.

A discussion of silver as an antimicrobial agent: alleviating the confusion

Within the last 3 to 5 years, many silver-based antimicrobial dressings have become available and more are on the way. However, sometimes dressing manufacturers and authors make claims and send messages that conflict with data and conclusions in the literature, creating confusion for clinicians. A literature review of six relevant and frequently discussed topics was conducted. Pre-clinical and clinical study data suggest that: a) bacterial resistance to silver may occur, b) silver dissociation is affected by the test medium used, c) bactericidal activity differences may be a function of the bacterial strain used for testing, d) higher rather than lower levels of silver may be needed because Ag+ binds to proteins and nucleic acids, e) rapid delivery of silver (ie, rate of kill) may be a positive factor when considering prevention of silver resistance and biofilm formation, and f) based on the vast majority of in vivo studies available, silver does not adversely effect viable cells; thus, is not cytototoxic. Continued research into the implications of the data is warranted.

An in vitro model to measure the effect of a silver fluoride and potassium iodide treatment on the permeability of demineralized dentine to Streptococcus mutans

BACKGROUND

Diamine silver fluoride (Ag(NH3)2F), referred to as AgF, has been used to reduce the incidence of caries in primary dentitions but has been limited by the associated staining of both teeth and restorative materials. The application of potassium iodide (KI), following AgF prevents staining but its effects on the ability of AgF to reduce caries are not known. The aim of this study was to develop an in vitro model that would provide an indication of the permeability of demineralized dentine to Streptococcus mutans after treatment of the dentine with AgF followed by KI.

METHODS

Forty dentine discs were bonded to the base of forty 5mL polycarbonate screw top vials (that had had their bases removed), filled with nutrient medium, sterilized and placed into a continuous culture of S. mutans. Samples were divided into four groups as follows: 10 samples of demineralized dentine as a control, 10 samples of demineralized dentine treated with AgF/KI, 10 samples of demineralized dentine treated with KI and 10 samples of demineralized dentine treated with AgF. After two weeks the optical density of the growth medium chambers was measured to determine bacterial penetration and growth. Cultures were plated out to determine migration through the discs by S. mutans.

RESULTS

S. mutans migrated through all dentine discs. However, the samples treated with AgF and AgF/KI had significantly lower optical densities than the corresponding controls. The range of optical densities was least amongst demineralized samples treated with AgF/KI.

CONCLUSIONS

Under the conditions of this study, treatment of demineralized dentine discs with AgF followed by KI allowed the penetration of S. mutans. Based on optical density measurements, the treatment resulted in significantly fewer microorganisms being present subjacent to the discs treated with AgF and KI than the control discs at the end of the experimental period.

Effects of new wound dressings on healing of thermal burns of the skin in acute radiation disease

Effects of new wound dressing bacterial cellulose impregnated with SOD and poviargol (Procel-Super and Procel-PA) and Inerpan hydrogel dressing on the reparative processes in deep dermal burns (IIIa-IIIb degree) in rats exposed to total even irradiation in a dose of 4 Gy were studied. Inerpan and Procel-Super dressings proved to be the most effective under these conditions: they accelerated healing of burn wounds by 17.0 and 5.5%, respectively.

Therapeutic efficacy of three silver dressings in an infected animal model

The organic salt AgNO3 has been available as a topical armamentarium to the medical arena for centuries and for burns for the past 60 years. Thirty-five (1968) years later, Charles Fox introduced and popularized a new topical agent known as silver sulfadiazine. More recently, several new slow-release silver dressings came to the forefront. Acticoat (Smith & Nephew, Largo, FL) Silverlon (Argentum, Lakemont, GA) & Silvasorb (Medline Industries, Inc, Mundelein, IL). Because the standard of care is to change dressings daily, our study focused in on weekly dressing changes as a cost-containment issue. Sprague-Dawley rats received a standard contact burn (20% TBSA). On day 3, the wound was excised and infected with Pseudomonas aeruginosa and Staphylococcus aureus at 5.0 x 10 cfu/ml. The animals were divided into four groups (n = 5 each group): untreated control, Acticoat group, Silvasorb group, and Silverlon group. The dressings remained on the wounds for 10 days when the wounds were quantitatively assessed. Mean wound counts of the control ranged from 1.2 x 10(5) to 6.5 x 10(5) for P. aeruginosa and S. aureus, respectively. Acticoat dressing counts for both organisms were 0 and 1.8 x 10(3) (median alpha); Silvasorb was 0 and 6.3 x 10(3) and Silverlon was 1.5 x 10(4) x 7.4 x 10(4) (median), Acticoat and Silvasorb were both significantly lower (P < .05) than the control for P. aeruginosa, and Acticoat was significantly lower (P < .05) than the control for S. aureus. Although counts for Silvasorb (M) appear significantly lower than the controls for S. aureus, the numbers were not sufficient to be significant. However, Silverlon did achieve a slight significance. These preliminary data suggest that weekly dressing changes with these new silver dressings are feasible and economically and medically congruous.

Bacterial resistance to silver in wound care

Ionic silver exhibits antimicrobial activity against a broad range of micro-organisms. As a consequence, silver is included in many commercially available healthcare products. The use of silver is increasing rapidly in the field of wound care, and a wide variety of silver-containing dressings are now commonplace (e.g. Hydrofiber dressing, polyurethane foams and gauzes). However, concerns associated with the overuse of silver and the consequent emergence of bacterial resistance are being raised. The current understanding of the biochemical and molecular basis behind silver resistance has been documented since 1998. Despite the sporadic evidence of bacterial resistance to silver, there have been very few studies undertaken and documented to ascertain its prevalence. The risks of antibacterial resistance developing from the use of biocides may well have been overstated. It is proposed that hygiene should be emphasized and targeted towards those applications that have demonstrable benefits in wound care. It is the purpose of this review to assess the likelihood of widespread resistance to silver and the potential for silver to induce cross-resistance to antibiotics, in light of its increasing usage within the healthcare setting.

[Biomaterials and tissues material in the treatment of prosthetic grafts infections]

An article is presented the treatment of vascular prosthetic grafts infections. An the graft infection treated by the replacement of infected prosthesis with autogenic venous material or with venous and arterial allograft harvested from brain-dead organ donors together with multiple organ procurement is presented. Autogenous material has an ability a better healing in infected tissues and used with absorbable sutures may lead to complete recovery from vascular graft infection - a severe and often lethal complication. An article is presented the treatment of vascular prosthetic grafts infections with the use of more resistant prostheses of infection - silver coated prosthesis, prosthesis with antibiotic and polytetrafluoroethylene prostheses.

A guide to the properties and uses of silver dressings in wound care

Silver-release dressings are extensively used for wound management, particularly in the treatment of burns, chronic leg ulcers and wounds requiring an antibacterial. A variety of products is now available. The properties and uses of these dressings are discussed, followed by a review of advances over recent years

Effects of an activated charcoal silver dressing on chronic wounds with no clinical signs of infection

OBJECTIVE

This exploratory, clinical study aimed to explore the effect of an activated charcoal silver dressing (intervention) with cleansing and debridement (control) in reducing the level of bacteria in chronic wounds with no clinical signs of local infection.

METHOD

Patients were randomly assigned to the intervention or control group and monitored for two weeks. Samples for bacterial status and cultivation were obtained by surface smear (spatula) and percutaneous aspiration first at baseline and then after 15 days of treatment. Sixty-seven lesions were included in the intervention group and 58 in the control group.

RESULTS

At baseline, in the intervention group 71.6% of the wounds were contaminated, 7.5% had a high level of bacteria and 20.9% were infected. In the control group at baseline 65.5% of the wounds were contaminated, 6.9% colonised, 6.9% had a high level of bacteria and 20.7% were infected. There were no colonised wounds in the intervention group. After two weeks, combining totals of contaminated, colonised, a high level of bacteria and infection for each group, 85.1% (57/67) of the wounds in the intervention group had a positive bacterial level management (that is, a reduction in the number of bacteria in the wound) compared with 62.1% (36/58) in the control group (p=0.003).

CONCLUSION

Activated charcoal dressings that contain silver control infection and reduce healing times, eliminating bacterial barriers.

The use of combination treatments and dressings for a traumatic wound

With demographics, an ageing population and faster hospital discharges against us, district nurses are likely to be faced with more complicated wounds that require specialist attention. With national and local guidelines, the restriction of cost implications, patient compliance and 'best practice' to achieve, the nurse can find the task of choosing the correct course of treatment a daunting one. Nurses must not only consider the patient holistically, assess the wound and the predisposing factors that may be present, but also prescribe an effective treatment while being aware of what effects the treatment may have and be prepared to justify their actions when called to task. This article takes one case study detailing a traumatic wound and follows through the whole assessment and evaluation process to demonstrate how all of these demands were met. Dressings used in the case study are Promogran, Actisorb Silver 220 and Tielle Plus manufactured by Johnson & Johnson.

Silver dressings in clinical practice

Silver is among several topical antiseptics that are once again gaining popularity due, in part, to the rise of antibiotic-resistant genotypes. Because of differences in wounds and the variety of products--including various silver vehicles--available to treat them, all of the dressing characteristics appropriate for the specific wound being managed must be considered. This article addresses why silver is (and is not) a good choice for particular wounds and offers suggestions about what silver products best serve individual situations.

The truth about silver

Interest in silver as a topical agent in wound healing is undergoing a renaissance. Having basic information regarding silver's chemical properties and potential actions in the wound bed is important to its appropriate clinical use. Such information is also relevant to the interpretation of silver's in vitro antimicrobial (antiseptic) effects, which in turn relate to issues involved in the evaluation of the clinical effects of silver in vivo. Gaining an understanding of the basic science of silver products and the different challenges inherent to in vitro versus in vivo antimicrobial evaluations will allow clinicians to address several key questions inherent when considering the use of silver as a topical antimicrobial: 1) Are there different forms of silver? 2) How does the amount of silver released into the wound environment correlate with clinical benefit? 3) How does the rate of silver release correlate with clinical benefit?

Synthesis, X-ray crystal structure, anti-fungal and anti-cancer activity of [Ag2(NH3)2(salH)2] (salH2=salicylic acid)

[Ag(2)(NH(3))(2)(salH)(2)] (salH(2)=salicylic acid) was synthesised from salicylic acid and Ag(2)O in concentrated aqueous NH(3) and the dimeric Ag(I) complex was characterised using X-ray crystallography. The complex is centrosymmetric with each metal coordinated to a salicylate carboxylate oxygen and to an ammonia nitrogen atom in an almost linear fashion. The two [Ag(NH(3))(salH)] units in the complex are linked by an Ag-Ag bond. Whilst metal-free salH(2) did not prevent the growth of the fungal pathogen Candida albicans [Ag(2)(NH(3))(2)(salH)(2)], [Ag(2)(salH)(2)] and some simple Ag(I) salts greatly inhibited cell reproduction. SalH(2), [Ag(2)(NH(3))(2)(salH)(2)] [Ag(2)(salH)(2)] and AgClO(4) produced a dose-dependent cytotoxic response against the three human derived cancer cell lines, Cal-27, Hep-G2 and A-498, with the Ag(I)-containing reagents being the most effective.

Anomaly and correlation of killing in the therapeutic properties of silver (I) chelation with glutamic and tartaric acids

OBJECTIVES

To investigate whether silver chelates or silver ions are more effective as therapeutic agents, and to examine their mode of action so that safer and stable compounds that have a broad spectrum of therapeutic activities can be developed.

METHODS

Efficacy was investigated against Pseudomonas aeruginosa (ATCC 15442) by determining MIC via a broth macrodilution procedure using NCCLS methods for antibiotic susceptibility testing.

RESULTS

It was found that the responsible agent for silver therapeutic properties is the silver chelates rather than silver ions, contradicting previous findings, and the efficacy profiles mimic that of free silver ions present in solution.

CONCLUSIONS

Silver therapeutic activities seem to be more effective as complexes-an intracellular package-rather than free silver ions, demonstrating that the effect of silver is linked to cells' DNA unwinding, and not respiratory or membrane functionality as was traditionally recognized.

[How I treat... the critical bacterial colonization of a leg ulcer. The Yin and the Yang features of silver-based dressings]

The critical bacterial colonizaion of leg ulcers can impair their healing rate, aggravate the patient discomfort and increase the medical and nursing costs. In recent times, the dressings designed for leg ulcers have followed a pace of conceptual revolution. Some of them are now offered containing an antiseptic of the silver salt family. The silver concentraton delivered into the wound bed is important to consider when assessing treatment efficacy. The diversity of the silver-based dressings currently on the European market is as large as their differences in activity. Only a minority of these dressings adequately control the wound biocenosis. Their cost which is high for the patient, must be compared to that of nursing care that may become less important. The expected beneficit is a reduction in healing time.

[Argyria--an almost-forgotten dyschromia]

A 79-year-old woman presented with a long history of grey-blue discoloration of the light-exposed areas. Her face, forearms, and the backs of both hands were affected. The proximal parts of her fingernails were impressively discolored, but her toenails were not affected. The patient reported that she had received oral therapy with the silver-containing drug Gastrarctin in 1959. The diagnosis of argyria was confirmed by documenting high tissue levels of silver in light-exposed skin. Argyria has become uncommon as medications containing silver are no longer employed and occupational protection for those with exposure to silver salts has become more refined.

Clinical performance of a new silver dressing, Contreet Foam, for chronic exuding venous leg ulcers

OBJECTIVE

This study aimed to evaluate the safety and performance of a new sustained silver-releasing dressing, Contreet Foam (Coloplast A/S), in the treatment of moderately to highly exuding chronic venous leg ulcers in which healing is delayed due to the presence of bacteria.

METHOD

The clinical performance of Contreet Foam was studied for four weeks in 25 patients with moderately to highly exuding delayed-healing venous leg ulcers. Healing was assessed on a weekly basis with reference to the wound-bed tissue composition, degree of odour and pain, dressing performance and the dressing's effect on the peri-ulcer area. Blood samples were analysed for silver content.

RESULTS

Twenty-three out of 25 patients completed the study. One ulcer healed and no wound infections occurred during the study period. A mean 56% reduction in ulcer area (from 15.6 to 6.9 cm2) was recorded during the four weeks, and there was a mean 25% reduction in granulation tissue from dull to healthy after one week. Wound odour reduced significantly after one week. Mean dressing wear time was 3.1 days, and there were only minimal incidences of leakage. Serum silver levels did not exceed reference values.

CONCLUSION

Contreet Foam was found to be safe and performed well when used in the treatment of delayed-healing chronic venous leg ulcers, combining effective antibacterial properties with excellent exudate management.

DECLARATION OF INTEREST

This study was supported by Coloplast A/S, Humlebaek, Denmark.

[Combined use of an antihypoxic agent and a B-cell stimulator]

Evaluation of the effect of poviargol on the B cells of mice showed that the drug activity is retained for 21 h upon single injection. An analysis of the refractory period between the B-cell stimulant introduction and the administration of various antihypoxants showed that the most effective treatment is provided by poviargol injection 14 days before and antihypoxant (IEM-1875 preparation) 30 min before the hypoxia model induction. This regime, ensuring the best protection of experimental animals from hypoxia, can be of great importance and value in the prophylaxis of hypoxia in various pathological conditions.

Silver. I: Its antibacterial properties and mechanism of action

Silver products have two key advantages: they are broad-spectrum antibiotics and are not yet associated with drug resistance. This article, the first in a two-part series, describes the main mechanism of action of this metallic element.

Tobacco smoking, nicotine, and nicotine and non-nicotine replacement therapies

Tobacco smoking is associated with an increased risk for the development of coronary and pulmonary vascular diseases and smoking cessation will greatly reduce this risk. Nicotine replacement and nonnicotine modalities have been used alone and in combination to help in smoking cessation. These treatment modalities appear to be safe in patients with known stable coronary artery disease.

Study on acid resistance of human dental enamel and dentin irradiated by semiconductor laser with Ag(NH3)2F solution

OBJECTIVE

The purpose of this study was to investigate the acquired acid resistance of human dental enamel and dentin treated by 38% diamine silver fluoride [Ag(NH3)2F] solution and semiconductor (diode) laser irradiation in vitro.

BACKGROUND DATA

There have been no reports on the acid-resistant effect by combined use of fluoride and semiconductor laser.

METHODS

Sixty crowns of extracted human molars were divided into two groups for enamel and dentin samples, and each group was subdivided into three subgroups of 10 each. Each subgroup of enamel and dentin samples served as a control; one was treated with Ag(NH3)2F and the other was treated with Ag(NH3)2F and semiconductor laser irradiation at 2 W for 30 sec. Then all samples were immersed in 5 ml of 0.1 M lactic acid (pH 4.8) at 37 degrees C for 24 h. The concentration of calcium ion (Ca2+) dissolved in the solution was measured by atomic absorption spectrophotometry, and the samples were observed by stereoscopy and scanning electron microscopy (SEM).

RESULTS

In both enamel and dentin samples, dissolved Ca2+ concentration in Ag(NH3)2F- or Ag(NH3)2F- and laser-treated group was significantly decreased compared with that in the control (p < 0.01). SEM findings showed that numerous cubic particles ranging from 0.1 to 0.5 mcirom were observed only in the combined treated groups of both enamel and dentin samples.

CONCLUSIONS

A significantly decreased solubility of human enamel and dentin was acquired after treatment by Ag(NH3)2F and semiconductor laser irradiation, which suggested that this combined use has the capability of a more efficient acid-resistant effect on human dental hard tissues.

Healing of porcine donor sites covered with silver-coated dressings

OBJECTIVE

To compare rates of healing of donor sites in pigs between those dressed with silver-coated dressings and those dressed with petrolatum-impregnated absorbent gauze.

DESIGN

Open study with each animal acting as its own control.

SETTING

University research facility, Canada.

ANIMALS

6 young specific-pathogen-free domestic pigs.

INTERVENTIONS

A total of 72 wounds about 1 cm x 2 cm x 0.4 mm were made in rows of eight on each pig with a dermatome. They were divided into three groups of 24, and dressed with petrolatum gauze, or silver-coated dressings moistened with sterile water either once only or daily for 10 days. All dressings were secured in place with an elastic bandage.

MAIN OUTCOME MEASURES

Erythema, infection, epidermal migration, and healing.

RESULTS

Wounds dressed with moistened silver-coated dressings re-epithelialised significantly more quickly. This resulted in complete re-epithelialisation within 70% of the time taken by those wounds dressed with petrolatum gauze.

CONCLUSION

Silver-coated dressings provide a moist environment for the healing wound combined with an effective antimicrobial agent, and this significantly accelerates healing compared with wounds dressed with traditional petrolatum gauze dressings.