Gypsum casts as a potential source of microbial cross-contamination

A Comparative Evaluation of Three Methods of Disinfection of Gypsum Casts and the Changes in Surface Roughness and Dimensional Accuracy after Disinfection-An Ex Vivo Study

BACKGROUND

One of the major problems of everyday dental practice is cross-contamination. It can place office personnel, dentists, and patients at risk of acquiring serious illness. Disinfection helps in controlling this cross-contamination to an extent. The evaluation was done to find the efficient disinfection method on gypsum casts.

AIMS

The aim of this study is to evaluate and compare the efficacy of three methods of disinfection of gypsum casts, namely, chemical disinfection by immersion, spray method, and microwave method, and also to evaluate and compare changes in surface roughness and dimensional accuracy between the three methods after disinfection.

MATERIALS AND METHODS

Ex vivo and experimental study. Thirty participants were selected, and impressions of the maxillary arch were made using polyvinyl siloxane impression material. Ninety type IV die stone gypsum casts were poured. It was divided into three groups and was subjected to chemical disinfection by immersion and spray methods, and microwave method. The disinfected casts were evaluated for microbial growth, surface roughness, and dimensional accuracy. It was performed by using the one-way analysis of variance test and paired t-test followed by the Kruskal - Wallis test and Wilcoxon signed rank test (α = 0.05).

RESULTS

Microwave disinfection was more effective than both immersion and spray chemical disinfection methods (P < 0.010 and <0.001). The surface roughness of the microwave-irradiated casts had significantly increased after disinfection. However, there were no significant dimensional changes by any of the methods of disinfection.

CONCLUSION

Within the limitations of the study, the microwave method of disinfection is more effective in eradicating microorganisms when compared to chemical methods of disinfection by immersion and spray methods.

Antimicrobial Efficiency of Hypochlorous Acid and Its Effect on Some Properties of Alginate Impression Material

Dental clinicians and professionals need an affordable, nontoxic, and effective disinfectant against infectious microorganisms when dealing with the contaminated dental impressions. This study evaluated the efficiency of hypochlorous acid (HOCl) as an antimicrobial disinfectant by spraying technique for the alginate impression materials, compared with sodium hypochlorite, and its effect on dimensional stability and reproduction of details. HOCl with a concentration of 200 ppm for 5 and 10 min was compared with the control group (no treatment) as a negative control and with sodium hypochlorite (% 0.5) as a positive control. Candida albicans, Staphylococcus aureus, and Pseudomonas aeruginosa were selected to assess the antimicrobial activity with the colony forming unit test in addition to the dimensional stability and reproduction of details tests. The results revealed that HOCl had significant antimicrobial activity against all tested microorganisms and experimental time. Interestingly, HOCl showed no impact on the dimensional stability of alginate impression material. HOCl could be an effective antimicrobial agent for alginate impression material without interfering with their surface details and dimensional stability.

Chlorhexidine as a Disinfectant in the Prosthodontic Practice: A Comprehensive Review

INTRODUCTION

Controlling the cross-contamination between the dental clinic and laboratory is of utmost importance to maintain the health of dental healthcare personnel (DHCP) and patients. The aim of this paper was to review the current literature with regard to the use of chlorhexidine as a prosthetic disinfectant in prosthodontic practice.

MATERIALS AND METHODS

A scoping review of the literature was performed in Medline/PubMed, Ovid Embase, and the Cochrane Library. A search for all literature published from 1980 to 2021 was based on the following keywords: ['Chlorhexidine/gluconate' OR 'chlorhexidine', OR 'gluconate', OR 'denture disinfectants', OR 'antimicrobial', OR 'disinfectant', OR 'impression disinfectants, OR prosthesis' OR 'biofilm, microbiology'] OR [teeth]. We reviewed the disinfectant in terms of its mechanism of action, antimicrobial effectiveness, disinfection techniques, clinical applications, corrosiveness/damage to the structure of prostheses, and reasonable shelf life.

RESULTS

Chlorhexidine was tested under different concentrations ranging from 0.2 to 5%. It provided a significant reduction in biofilm viability but had a minimum effect on Candida albicans with a variable effect result that showed no significant differences in the dimensional changes by immersion of alginate dental impressions for no more than 10 minutes and no clinically significant dimensional differences on aluwax, polyether, condensation siloxane, and polyvinyl siloxane were noticed. Nonetheless, chlorhexidine altered the surface of the silicone and acrylic resins and affected the long-term hardness of the relining material.

CONCLUSION

Within the limitations of this review, the use of chlorhexidine disinfectant demonstrates a good measure in the reduction of contamination and cross-infection and has a minimal effect on the dimensional stability of most impression materials. Further studies with in-vitro testing are required to confirm these findings.

Infection Control in Dental Clinics: Prosthodontics Perspectives

AIM

The aim of this article is to discuss the infection control measures with focus on those related to prosthodontic work.

BACKGROUND

The risk of transmission of several infectious microorganisms during dental procedures and the increased awareness and knowledge of infectious diseases have led to an increased attention to the importance of infection control. Prosthodontists and dental personnel are exposed directly or indirectly to a significant risk of acquiring healthcare-associated infections.

REVIEW RESULTS

High standards of occupational safety and dental infection control must be applied by dental personnel for the safety of patients and dental healthcare workers. All reusable items (critical and semicritical instruments) that come in contact with the patient's saliva, blood, or mucous membranes must be heat-sterilized. Proper disinfectants should be used to disinfect nonsterilizable instruments (e.g., wax knifes, dental shade plastic mixing spatula, guides, fox bite plane, articulators, and facebows).

CONCLUSION

In prosthodontics, items potentially contaminated with patient's blood and saliva are transported between dental clinics and dental laboratories. Such fluids may contain microorganisms with high potential for transmission of several diseases. Therefore, sterilization and disinfection of all items used during prosthodontic work should be part of infection control protocol in dental care setting.

CLINICAL SIGNIFICANCE

In prosthodontic practice, a strict infection prevention plan should be implemented to minimalize the risk of infectious diseases transmission among prosthodontists, dental office, dental laboratory personnel, and patients.

Effect of Adding Silica Nanoparticles on the Physicochemical Properties, Antimicrobial Action, and the Hardness of Dental Stone Type 4

This study was conducted to investigate the effect of adding silica nanoparticles on the physicochemical properties, antimicrobial action, and the hardness of dental stone type 4. Dental stone type 4 powder was physically mixed with nanoparticle powder at weight percentages (0, 0.5, 1, and 2 percent). The required amount of powder was added to water according to the manufacturer's instructions. The prepared set materials were subjected to the physicochemical studies; Fourier transmission infrared spectroscopy (FTIR) was taken up to investigate the functional groups and X-ray diffraction (XRD) was used to evaluate the crystallinity. Also, scanning electron microscopy (SEM) was used to examine the morphology of the prepared samples. Agar diffusion test was carried out for the prepared samples against the Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) to test the average growth inhibition zones. Finally, the Vickers surface hardness test was performed for each group using a hardness tester. The adding silica nanoparticles to dental stone type 4 increased the diameter of inhibition zones for the groups in both bacteria significantly (p < 0.05). The results showed that adding silica nanoparticles to dental stone type 4 increased the diameter of inhibition zones for the groups in both bacteria significantly (p < 0.0001). There was a significant difference between all groups and the 0% group in both bacteria (p < 0.0001). Besides, the adding of silica nanoparticles to dental stone type 4 increased the surface hardness significantly (p = 0.0057) without any effect on physicochemical properties. The 0% and the 0.5% groups had significant differences with the 2% group (p = 0.0046 and p = 0.0205 respectively). Then, at least 2% silica nanoparticles are needed for a significant increase. Clinical trials are needed to enlarge for dental stone type 4 containing silica nanoparticles in the future.

The accuracy of gypsum casts obtained from the disinfected extended-pour alginate impressions through prolonged storage times

Background

Manufacturers of the extended-pour alginates claimed their dimensional stability through prolonged storage. No data confirmed the ability of these materials to maintain their dimensions and the reproduced oral details following their chemical disinfection. Therefore, this study evaluated the dimensional stability and surface detail reproduction of gypsum casts obtained from disinfected extended-pour alginate impressions through different storage time intervals.

Methods

Two hundred and forty three hydrocolloid impressions were made from one conventional (Tropicalgin) and two extended-pour (Hydrogum 5 and Chromaprint premium) alginates. These impressions were subjected to none, spray and immersion disinfection before their storage in 100% humidity for 0, 72 and 120 h. The dimensional stability and the surface detail reproduction were indirectly evaluated under low angle illumination on the resulted gypsum casts. At α = 0.05, the parametric dimensional stability data were analyzed using One-Way ANOVA and Tukey’s comparisons, while the nonparametric detail reproduction data were analyzed using KrusKal Wallis and Mann–Whitney's tests.

Results

All gypsum casts exhibited a degree of expansion; however, the recorded expansion values did not differ between test categories (P > 0.05). Generally, casts obtained from spray-disinfected impressions showed lower detail accuracy (P < 0.05). Immersion-disinfected extended-pour alginates produced casts with better detail accuracy following 120 h of storage (P < 0.05).

Conclusion

All alginates materials offer comparable cast dimensions under different testing circumstances. Extended-pour alginates offer casts with superior surface details following their immersion disinfection and 120 h of storage. Spray-disinfection using 5.25% sodium hypochlorite affects the surface details of casts obtained from conventional and extended-pour alginates adversely.

Antimicrobial Efficacy of Irreversible Hydrocolloid Impression Impregnated with Silver Nanoparticles Compared to Surface Disinfected Impressions - An In vivo Study

BACKGROUND

Routine disinfection procedures have shown to cause incomplete disinfection and detrimental effects on dimensional properties of the impression. Hence, self-disinfecting impression materials impregnated with antimicrobial agents were developed.

PURPOSE

The purpose is to evaluate the antimicrobial efficacy of silver nanoparticles (AgNPs) impregnated in irreversible hydrocolloid (IH) impression material in in vivo conditions.

MATERIALS AND METHODS

This study comprised of four groups-IH impressions disinfected by immersion in 2% glutaraldehyde, IH impregnated with AgNPs of sizes 80-100 nm and 20-30 nm, nondisinfected impressions as control. Five impressions were made for each group and a total of 20 impression samples were made. The antimicrobial action of each sample was assessed by counting the number of colony forming units and by disc diffusion method.

RESULTS

The results were obtained and the data were statistically analyzed by Kruskal-Wallis test and tabulated. The results revealed that AgNPs of size 80-100 nm when impregnated in irreversible impression material showed effective antimicrobial action.

CONCLUSION

The anti-microbial action of 80-100 nm AgNP impregnated IH impressions is comparable to that of impressions disinfected by immersion in 2% glutaraldehyde for 10 min.

Evaluation of the quality of fixed prosthesis impressions in private laboratories in a sample from Yemen

Background

Fixed prosthodontics require an accurate impression for the teeth and the area to be restored for the laboratory to fabricate the desired restoration without mistakes. This study evaluated the quality of impressions received by private laboratories for the fabrication of fixed prosthesis by describing the frequency of clinically detectable errors and by analyzing association between the various factors involved.

Methods

165 impressions were collected from four dental laboratories. Jaw involved, type of tray, size of tray, number of prepared units, type of impression materials, techniques and viscosity in case of elastomeric impressions and type of prosthesis requested were recorded. Data referring to errors and visible defects including errors in finish line, in preparation area, in silicone impression technique and blood in impression were also documented. Factors affecting errors present were also assessed. Association between dentist gender and experience years and impression errors was assessed. Chi square and Fisher exact tests used to examine the association between categorical variables and outcomes.

Results

The total of error considering not immediately pouring as an error. Alginate was the most impression used. of impressions evaluated (50.9%), 97% were have at least one visible error; 92.1% had errors in finish line, 53.9% had errors in preparation area and (72.8%) of elastomeric impressions were have at least one error in technique. Blood in impression was detected in 52.1% of impressions. Significant association was found between material type and errors in finishing line and preparation area. Significant relationships were found between gender and errors in silicone impression technique (p < 0.05).

Conclusion

Within the limitations of this study, high frequency of detectable errors was found in fixed prosthesis impressions received by private dental laboratories. This high frequency is of serious concern, as this will result in poor fitted fixed prosthesis provided to patients.

SARS-CoV-2 and Oral Manifestation: An Observational, Human Study

The correlation between SARS-CoV-2 and oral manifestations is still controversial. The aim of this observational study was to determine the oral manifestation of the hospitalized patients for COVID-19. A total of 20 patients met the inclusion criteria and gave their signed informed consent. A questionnaire of 32 questions regarding the oral and systemic health condition was administrated to these patients during the convalescence. A descriptive statistic was performed. Data were analysed through the use of χ² test, to assess the statistical significance. A statistically significant increase of about 30% of reporting xerostomia during hospitalization was observed (p = 0.02). Meanwhile, a decrease of oral hygiene was observed during the hospitalization, even if a non-statistically significant difference was shown between the two study time points (before and after hospitalization). During the hospitalization period, 25% of patients reported impaired taste, 15% burning sensation, and 20% difficulty in swallowing. An interesting result was that among the systemic conditions, hypertension was observed in 39% of patients and mostly in female patients (62.5%). Further studies are necessary to better understand the symptoms of this new virus in order to faster detect its presence in humans. Probably, a multidisciplinary team following the COVID-19 patients could be of key importance in treating this disease.

Disinfection of dental impressions: knowledge and practice among dental technicians

Background: Dental impressions are a common source for transmission of infection between dental clinics and dental labs. Dental impressions can be cross-contaminated by patient's saliva and blood, which then cross-infect the dental casts poured from the impressions. Objective: To evaluate the current practices of disinfection of dental impressions and their protocols and to assess the knowledge of cross-infection control among dental technicians in Jordan. Method: Dental technicians (n=85) completed a self-administered questionnaire about their practices of disinfection for dental impressions. Results: The distribution of dental technicians was 63.8% fixed prosthodontics, 23.5% removable prosthodontics, 7.8% orthodontics, and 4.8% maxillofacial prosthodontics. The majority of the laboratories did not have instructions related to disinfection of impressions. About 50% of technicians were vaccinated against HBV. About 44.7%, and 42.9% of labs reported that they never disinfect alginate or silicon impressions, respectively. In addition, the majority of lab owners (53%) believed that the dentist should disinfect the impressions before shipping them to dental laboratories, while (45%) believed that disinfecting the impressions is the responsibility of the dental assistant. Moreover, about 38% of this study population reported not using gloves in their labs. In those labs were disinfection was used, 51% used spray disinfection whereas 32.6% used immersion disinfection. The cost of disinfectant was ranked as the most important factor (51.3% of the cases) for the dental technician to choose the disinfectant followed by its effectiveness. Conclusion: Dental technician practices in impression disinfection was not satisfactory, therefore, education programs about impression disinfection are needed.

Comparative Evaluation of the Effect of Chemical Disinfectants and Ultraviolet Disinfection on Dimensional Stability of the Polyvinyl Siloxane Impressions

Context

Infection control is an important concept in the present day practice of dentistry. Disinfection of dental impressions is part of the daily routine in a dental clinics. After disinfection, it is important that impressions remain dimensionally stable.

Aim

The purpose of this study was to compare the effect of chemical disinfectants and ultraviolet (UV) disinfection on the dimensional stability of the polyvinyl siloxane impressions.

Objectives

The objective of the study is (1) To evaluate the effect of chemical disinfectant (2% glutaraldehyde and 1% sodium hypochlorite) and UV disinfectant on the dimensional stability of polyvinyl siloxane impression material. (2) Comparative evaluation of the dimensional discrepancy between the cast poured from the polyvinyl impressions material, that is subjected to chemical disinfectant and UV disinfectant to that of cast poured from impressions that were nondisinfected.

Materials and Methods

A customized tray was fabricated to make impressions. Impressions were divided into four groups, 10 samples were disinfected with 2% glutaraldehyde for 20 min, 10 samples were disinfected with 1% sodium hypochlorite for 20 min, 10 samples were disinfected with UV light for 20 min, and 10 samples were not subjected to disinfection which served as control group. All the samples were poured after 30 min in die stone. Measurements were recorded using traveling microscope of 0.001 accuracy. Statistical analysis used in this study was the one-way ANOVA test.

Results

The result showed significant dimensional changes in samples disinfected with 2% glutaraldehyde and 1% sodium hypochlorite, whereas samples disinfected with UV disinfectant unit showed no significant dimensional changes when compared with control group samples. Within the chemical groups, impressions disinfected with 1% sodium hypochlorite showed more discrepancy in the dimensions when compared to the 2% glutaraldehyde disinfected group.

Conclusions

UV light disinfectant can be safely used to disinfect impressions as compared to chemical disinfectants in clinical prosthodontic procedures.

Influence of chloramine-T disinfection on elastomeric impression stability

Objective:

The aim of this study was to evaluate the stability of elastomer through detail reproduction and its dimensional stability (DS) after disinfection with 0.2% chloramine-T.

Materials and Methods:

The elastomeric impression dental materials used in this study were polydimethylsiloxane (Oranwash L), polyvinyl siloxane (Express), polysulfide (Permlastic), and polyether (Impregum Soft). The entire press procedure was performed on a matrix in accordance with the ISO 4823. Detail reproduction was analyzed using an optical microscope (Stereozoom Microscope) over the 20-μm line with 25 mm of length at a magnification of ×4. DS was measured using an optical microscope (Scanning Tunneling Microscope) by subtracting the distance between the lines X and X' over the 20-μm line on the matrix (DM) from the distance between the lines on the impression material (DI) divided by DM and multiplied by 100 establishing the equation: DS = ([DI – DM]/DM) ×100; then, 100% was added to the results of the equation. The detail reproduction values were subsequently subjected to descriptive analysis by percentage (%), and the DS values (%) were submitted to Kolmogorov–Smirnov test, two-way ANOVA (material × disinfectant), and Tukey's test (α = 0.05).

Results:

All elastomeric impression materials showed 100% of detail reproduction, regardless of the disinfection procedure. Polysulfide (not disinfected) and polysulfide and polydimethylsiloxane (after disinfection with 0.2% chloramine-T) showed the smaller mean values of DS.

Conclusion:

According to the stability properties analyzed, chloramine-T can be used for disinfection of elastomer molds.

Effect of ozonated water on the surface roughness of dental stone casts

Infection control of dental stone cast is an important issue. Ozone is effective for disinfection against microorganisms and inactivation of viruses. However, there is little information regarding the use of ozone. We prepared 4 types of gypsum specimens and 3 types of disinfectants (4-5 ppm Ozonated water [OZW], 2% glutaraldehyde [GL], and 1% sodium hypochlorite [SH]). Gypsum specimens were immersed in each disinfectant for 5 and 10 min, and surface roughness was then examined using laser scanning microscopy. Surface microstructure was investigated using scanning electron microscopy. Immersion of gypsum specimens in SH, GL, and OZW increased the surface roughness to a maximum of 1.04, 0.37, and 0.30 μm, respectively, based on the difference between the average values of surface roughness before and after the disinfection procedure. The effects of OZW and GL were comparable. OZW is useful as a candidate for relatively safe disinfection of material for dental stone casts.

Comparative Evaluation of Tensile Strength in Die Stone Incorporated with Sodium and Calcium Hypochlorite as Disinfectants: An in vitro Study

AIM

The aim of this study was to evaluate the tensile strength of die stone incorporated with sodium and calcium hypochlorite as disinfectants.

MATERIALS AND METHODS

Two commercially available type IV die stone (Kalrock: Kalabhai Karson Pvt., Ltd and Pearlstone: Asian Chemicals) and two commercially available disinfectant solutions (sodium hypochlorite and calcium hypochlorite: Beachem Laboratory Chemical Private Limited, Chennai and Leo Chem Private Limited, Bengaluru) were used in this study, and the tensile strength was measured using Lloyd's Universal Testing Machine.

RESULTS

The results show that incorporating the disinfecting solutions decreases the tensile strength of both products. The effect of decreasing tensile strength on type IV gypsum product is seen more in calcium hypochlorite when compared with sodium hypochlorite disinfecting solution, and the tensile strength of Kalrock specimens is higher than Pearlstone specimens after disinfecting with sodium hypochlorite and calcium hypochlorite solution. The statistical results also show significant results in all the groups when compared with the control group.

CONCLUSION

The incorporation of sodium and calcium hypochlorite disinfecting solutions is not an encouraging method for both die materials as it reduces the tensile strength of type IV gypsum product. Tensile strength of Kalstone® die material is superior than Pearlstone® die material after mixing with sodium hypochlorite and calcium hypochlorite.

CLINICAL SIGNIFICANCE

According to the recommendations of Americans with Disability Act (ADA) and the Centers for Disease Control and Prevention, disinfecting the whole cast without or minimal changes in physical and mechanical properties was the motto of the study. The tensile strength in type IV gypsum product plays a most important role in retrieval of cast from impression, especially in narrow tooth preparation. This study reveals that incorporating method of disinfecting solutions is not recommended as it reduces the tensile strength.

Evaluation of Antibacterial Effect and Dimensional Stability of Self-disinfecting Irreversible Hydrocolloid: An in vitro Study

AIM

This study evaluated the antibacterial activity and dimensional stability of irreversible hydrocolloids mixed with different concentrations of chlorhexidine gluconate instead of water.

MATERIALS AND METHODS

Experimental specimens (45 specimens) were prepared and allocated into three groups of 15 each. Group I: Impression material mixed with distilled water served as control. Groups II and III were prepared with 0.12 and 0.2% chlorhexidine gluconate solution, respectively. Specimens in each group were subjected to tests for dimensional stability. For antimicrobial activity, 30 specimens were prepared and allocated into three groups of 10 each named as group I (control), group II (0.12% chlorhexidine gluconate), and group III (0.2% chlorhexidine gluconate) similar to specimens for dimensional stability. Statistical analysis was performed using a one-way analysis of variance (ANOVA) and Tukey test.

RESULTS

Zones of inhibition were observed around test specimens, but not around control specimens; there was a significant intergroup difference in the diameters of the inhibition zones. In the test for dimensional stability, no significant differences were detected among groups, and the accuracy was clinically acceptable.

CONCLUSION

Irreversible hydrocolloid impression material mixed with chlorhexidine exhibits varying degrees of antibacterial activity without influencing the dimensional stability of set material.

CLINICAL SIGNIFICANCE

Many contagious diseases can be prevented by practical control of infection in the dental office. Chlorhexidine gluconate, as a mixing liquid, ensures disinfection of impression, and this method of disinfection is more convenient and avoids extra effort as in other disinfection techniques.

Experimental hydrophilic vinyl polysiloxane (VPS) impression materials incorporating a novel surfactant compared with commercial VPS

OBJECTIVES

To formulate experimental hydrophilic (Exp) VPS impression materials incorporating a novel surfactant (Rhodasurf CET-2), and to compare their contact angles (CAs) with commercial materials, before/after disinfection.

METHODS

CAs were measured immediately after setting and after disinfection (1% NaOCl; 30min and 24h), together with their change whilst a droplet remained on the materials surface (over 10, 20, 30 60 and 120s), on three commercial (Aquasil Ultra-Monophase [Aq M], Elite HD-Monophase [Elt M], Extrude Medium-bodied [Extr M]) and four experimental (Exp I-IV) materials, using the Drop Shape Analysis 100 technique. The results were compared statistically.

RESULTS

CAs of all experimental materials were within the range of those obtained for the commercial materials, with the exception of Exp-IV, which presented with the lowest CAs at the three time points. The control Exp-I was hydrophobic at all three time points (CAs ∼100+), as was Elite. Immediately after setting, Aq M had low CAs but these increased significantly after 30min of disinfection. After twenty four hours' disinfection CAs of all Exp/commercial VPS increased significantly compared to immediately after setting. The CAs of droplets left on the material (120s) decreased with time, even after disinfection, except for Exp-I.

SIGNIFICANCE

The novel surfactant Rhodasurf CET-2 in Exp-III and IV, is an effective surfactant, retaining a low CA after disinfection, compared with Igepal CO-530 in Aq M. Disinfecting VPS impression materials for more than 30min increases their surface CAs, and therefore prolonged disinfection periods should be avoided.

Comprehensive Review and Comparison of the Disinfection Techniques Currently Available in the Literature

The goal of disinfection in the dental office is to prevent the spread of infection from one patient to another and maintain the safety of the dental care providers. Prevention of cross infection has significant effect on infection control. The standard procedure of rinsing impressions under tap water immediately after removal from the mouth eliminates microorganisms along with saliva and blood. A broad search on published literature was done using the keywords impression materials, disinfection method, and sterilization of dental impression from 1980 to 2016 in Medline, Google Scholar, the internet, and textbooks. This article critically analyzes the various published methods of dental impression disinfection in dentistry.

Preliminary SEM Observations on the Surface of Elastomeric Impression Materials after Immersion or Ozone Disinfection

INTRODUCTION

Surface integrity of dental elastomeric impression materials that are subjected to disinfection is of major importance for the quality of the final prosthetic restorations.

AIM

The aim of this qualitative Scanning Electronic Microscopy (SEM) study was to reveal the effects of immersion or ozone disinfection on the surface of four dental elastomeric impression materials.

MATERIALS AND METHODS

Four dental elastomeric impression material brands were used (two vinyl polysiloxane silicones, one polyether, and one vinyl polyether silicone). Total of 32 specimens were fabricated, eight from each impression material. Specimens were immersion (0.525% sodium hypochlorite solution or 0.3% benzalkonium chloride solution) or ozone disinfected or served as controls and examined with SEM.

RESULTS

Surface degradation was observed on several speci-mens disinfected with 0.525% sodium hypochlorite solution. Similar wavy-wrinkling surface structures were observed in almost all specimens, when treated either with 0.3% benzalkonium chloride solution or ozone.

CONCLUSION

The SEM images obtained from this study revealed that both immersion disinfectants and ozone show similar impression material surface alterations. Ozone seems to be non-inferior as compared to immersion disinfectants, but superior as to environmental protection.

The Dental Solid Waste Management in Different Categories of Dental Laboratories in Abha City, Saudi Arabia

Aim:

To study the awareness, attitude, practice and facilities among the different categories of dental laboratories in Abha city.

Materials and Methods:

A total of 80 dental technicians were surveyed in the study. The dental laboratories included in the study were teaching institute (Group I), Government Hospital (Group II), Private Dental Clinic (Group III) and Independent laboratory (Group IV). The pre-tested anonymous questionnaire was used to understand knowledge, attitude, facilities, practice and orientation regarding biomedical waste management.

Results:

The knowledge of biomedical waste categories, colour coding and segregation was better among Group I (55-65%) and Group II (65-75%). The lowest standard of waste disposal was practiced at Group IV (15-20%) and Group III (25-35%). The availability of disposal facilities was poor at Group IV. The continuous education on biomedical waste management lacked in all the Groups.

Conclusion:

The significant improvement in disposal facilities was required at Group III and Group IV laboratories. All dental technicians were in need of regular training of biomedical waste management.

Clinical Significance:

The dental laboratories are an integral part of dental practice. The dental laboratories are actively involved in the generation, handling and disposal of biomedical waste. Hence, it is important to assess the biomedical waste management knowledge, attitude, facilities and practice among different categories of dental laboratories.

Modification of pH Conferring Virucidal Activity on Dental Alginates

To formulate an alginate dental impression material with virucidal properties, experimental alginate dental impression materials were developed and the formulations adjusted in order to study the effect on pH profiles during setting. Commercially available materials served as a comparison. Eight experimental materials were tested for antiviral activity against Herpes Simplex Virus type 1 (HSV-1). Changing the amount of magnesium oxide (MgO) used in the experimental formulations had a marked effect on pH. Increasing MgO concentration corresponded with increased pH values. All experimental materials brought about viral log reductions ranging between 0.5 and 4.0 over a period of 4 h. The material with the lowest pH was the most effective. The current work highlights the very important role of MgO in controlling pH profiles. This knowledge has been applied to the formulation of experimental alginates; where materials with pH values of approximately 4.2-4.4 are able to achieve a significant log reduction when assayed against HSV-1.

Evaluation of efficacy of microwave irradiation in disinfecting dental gypsum casts: an ex vivo study

The aim of this study is to assess the efficacy of microwave irradiation in disinfecting gypsum casts and also to compare its efficacy with validated method of chemical disinfection. The present study is an ex vivo study conducted on a sample of five irreversible hydrocolloid impressions in vitro and on ten patients gypsum casts in vivo following standard impression techniques to check the efficacy of microwave oven irradiation and compare its efficacy with standard chemical method of disinfection. Results were analysed using Mann-Whitney test and Wilcoxon signed rank test. Untreated gypsum casts showed cfu/ml counts with a median log value of 6, while microwave-irradiated ones had median cfu/ml counts of 0. Casts poured from chemically disinfected impressions demonstrated cfu/ml counts with a median log value of 5. Microwave irradiation was found to be effective in disinfecting gypsum casts when compared to chemical disinfectant in disinfecting dental impressions.

Plasma in dentistry

This review describes the contemporary aspects of plasma application in dentistry. Previous studies on plasma applications were classified into two categories, surface treatment and direct applications, and were reviewed, respectively according to the approach. The current review discussed modification of dental implant surface, enhancing of adhesive qualities, enhancing of polymerization, surface coating and plasma cleaning under the topics of surface treatment. Microbicidal activities, decontamination, root canal disinfection and tooth bleaching were reviewed as direct applications with other miscellaneous ones. Non-thermal atmospheric pressure plasma was of particular focus since it is gaining considerable attention due to the possibility for its use in living tissues. Future perspectives have also been discussed briefly. Although it is still not popular among dentists, plasma has shown promises in several areas of dentistry and is now opening a new era of plasma dentistry.

Sterilization effect of atmospheric pressure non-thermal air plasma on dental instruments

PURPOSE

Autoclaves and UV sterilizers have been commonly used to prevent cross-infections between dental patients and dental instruments or materials contaminated by saliva and blood. To develop a dental sterilizer which can sterilize most materials, such as metals, rubbers, and plastics, the sterilization effect of an atmospheric pressure non-thermal air plasma device was evaluated.

MATERIALS AND METHODS

After inoculating E. coli and B. subtilis the diamond burs and polyvinyl siloxane materials were sterilized by exposing them to the plasma for different lengths of time (30, 60, 90, 120, 180 and, 240 seconds). The diamond burs and polyvinyl siloxane materials were immersed in PBS solutions, cultured on agar plates and quantified by counting the colony forming units. The data were analyzed using one-way ANOVA and significance was assessed by the LSD post hoc test (α=0.05).

RESULTS

The device was effective in killing E. coli contained in the plasma device compared with the UV sterilizer. The atmospheric pressure non-thermal air plasma device contributed greatly to the sterilization of diamond burs and polyvinyl siloxane materials inoculated with E. coli and B. subtilis. Diamond burs and polyvinyl siloxane materials inoculated with E. coli was effective after 60 and 90 seconds. The diamond burs and polyvinyl siloxane materials inoculated with B. subtilis was effective after 120 and 180 seconds.

CONCLUSION

The atmospheric pressure non-thermal air plasma device was effective in killing both E. coli and B. subtilis, and was more effective in killing E. coli than the UV sterilizer.

Effect of microwave disinfection on compressive and tensile strengths of dental stones

BACKGROUND AND AIMS

Although microwave irradiation has been used for disinfection of dental stone casts, there are concerns regarding mechanical damage to casts during the process. The aim of this study was to evaluate the effect of microwave irradiation on the compressive strength (CS) and diametral tensile strength (DTS) of stone casts.

MATERIALS AND METHODS

In this in vitro study, 80 cylindrical type III and IV stone models (20 × 40 mm) were prepared and divided into 8 groups of 10. The DTS and CS of the specimens were measured by a mechanical testing machine at a crosshead speed of 0.5 cm/min after 7 times of frequent wetting, irradiating at an energy level of 600 W for 3 minutes and cooling. Data were analyzed by Student's t-test.

RESULTS

Microwave irradiation significantly increased DTS of type III and IV to 5.23 ± 0.64 and 8.17 ± 0.94, respectively (P < 0.01).

CONCLUSION

According to the results, microwave disinfection increases DTS of type III and IV stone casts without any effects on their CS.

Promising role of calcium hypochlorite as a disinfectant: an in vitro evaluation regarding its effect on type V dental stone

AIM

The current study has been chosen to evaluate the efficacy of calcium hypochlorite as a disinfecting additive for the gypsum products and its effect on compressive and tensile strength of the set material. It is hypothesized that, the addition of calcium hypochlorite to type V dental stone in sufficient quantity to disinfect the material would have no deleterious effect on compressive or tensile strength.

MATERIALS AND METHODS

Total of 160 samples made up of type V dental stone were divided broadly into two groups of 80 samples each for the sake of compressive and tensile strength testing in dry and wet conditions: Out of each group, 10 samples without addition of any disinfectant (0% calcium hypochlorite) was compared with other group of 30 samples after adding disinfectant, i.e. each subgroup containing 10 samples each (0.5, 1.0 and 1.5% calcium hypochlorite).

CONCLUSION

Within limitations of this in vitro study it is assumed to prepare type V dental stone that contains a disinfectant, has adequate compressive strength and tensile strength, and can significantly act against a resistant species like Bacillus subtilis.

CLINICAL SIGNIFICANCE

When calcium hypochlorite was added to dental stone, extra mixing water was required to produce a material of nearly same pouring consistency. The samples, which were put to microbiological tests, showed effective action of disinfectant on Bacillus subtilis. No deleterious effect on compressive or tensile strength could be found after putting the selected samples with calcium hypochlorite.

The effect of repeated immersion of gypsum cast in sodium hypochlorite and glutaraldehyde on its physical properties: An in vitro study

Background:

One method used to disinfect a dental cast is immersion in a disinfecting solution. Repeated immersion of a cast in disinfectant may affect its physical properties.

Purpose:

The purpose of this study was to evaluate the changes in dimensional accuracy and hardness of the dental casts as a result of repeated disinfection in 0.525% sodium hypochlorite and 2% glutaraldehyde solutions.

Materials and Methods:

Sixty specimens were made of type III dental stone. Twenty specimens were immersed in slurry, a supernatant solution of calcium sulfate in distilled water (control casts), 20 specimens in 0.525% sodium hypochlorite, and 20 specimens in 2% glutaraldehyde solutions for 30 min and air dried for 24 h. This process was repeated for 7 times for testing. Linear dimensional change and hardness were determined according to American National Standards Institute/American Dental Association (ANSI/ADA) standards. The data were analyzed using two-way analysis of variance.

Results:

For specimens prepared with type III stones, treatment was by immersion in slurry (group I – control casts), and by immersion in 0.525% sodium hypochlorite (group II – test group 1) and in 2% glutaraldehyde solution (group III – test group 2). The specimens treated with sodium hypochlorite and glutaraldehyde showed more linear dimensional change compared to the specimens treated in slurry. However, the difference between test casts and control casts was significant. But the difference between the two test groups was not significant. Both the test groups showed decrease in hardness of the specimens compared to that specimens in control group. But the difference between two test groups was not significant in hardness. However,the values remained close to ANSI/ADA standards.

Conclusion:

The results demonstrated that repeated immersion of type III dental stone specimens in slurry with distilled water, 0.525% sodium hypochlorite and 2% glutaraldehyde, along with drying in air, caused a significant increase in linear dimension and a significant decrease in hardness.

Drug and dental impression materials

Guidelines to prevent cross contamination with infectious agents have been instituted for dental clinical and laboratory procedures. However, compliance by dental offices and clinics in disinfecting impression material has not been universal. Techniques for disinfecting impression materials are spraying or immersing impression materials. These techniques can reduce the surface detail and dimensional accuracy of impressions; most disinfectants are irritants. This study reviewed whether antimicrobial activity can be achieved by mixing certain drugs with the impression material and their effects on the disinfection are achieved through such additions.

Effect of the disinfection technique on the linear dimensional stability of dental impression materials

The purpose of this study was to evaluate the dimensional stability of heavy and light bodied condensation silicones after immersion in disinfectant solution for 10 or 20 minutes. The impression materials were Optosil Comfort and Xantopren VL Plus and the disinfectant solutions were 1% sodium hypochlorite and 2% glutaraldehyde. Impressions were made on a perforated stainless steel tray, according to the American Dental Association specification No. 19, adding up to a total of 50 samples. The double mixing method (one time, two viscosities) was used. Impressions were removed from the roulette block after 7 minutes to ensure complete curing and then immersed in the solutions. Impressions not submitted to treatment composed the control group. After these steps, the impressions were removed from the solution, rinsed in running water and air-dried. Three-dimensional measurements were calculated using an optic microscope graduated at 0.001 mm. The two-way ANOVA indicated no differences (p>0.05) for any combination between variables. The results showed that the solution studied can be safely used to disinfect condensation silicone in clinical prosthodontic procedures.

Effect of alginate chemical disinfection on bacterial count over gypsum cast

PURPOSE

To evaluate the efficacy of sodium hypochlorite (1 : 10) and iodophor disinfectants on alginate impressions along with their effect on the survived bacterium count on the gypsum cast.

MATERIALS AND METHODS

Four alginate impression on each dentate patients were made, of which Group I were not washed or disinfected, Group II impressions were merely washed with water, Group III were disinfected by spraying with sodium hypochlorite (1 : 10), Group IV were disinfected with iodophor (1 : 213). Gypsum cast (type III) were made from all the impression. Impressions and gypsum cast were swabbed in mid palatal region for bacterial culture. Bacterial colony counting done after 3 days of incubation at 37℃ in blood agar media. The data obtained was analyzed by one way ANOVA test at a significant difference level of 0.05.

RESULTS

Group I and Group II showed significantly more bacteria compared to Group III and Group IV. Bacterial colonies on the alginate impression and gypsum cast in group disinfected with Sodium hypochlorite (1 : 10) were 0.18, 0.82 respectively compared to group treated with iodophor (1 : 213). There was an increase in bacterial count on dental cast compared to source alginate impressions.

CONCLUSION

Sodium hypochlorite (1 : 10) was found to be better disinfectant for alginate impression. There was an indication of increase in number of bacteria from alginate impression to making of dental cast. Additional gypsum cast disinfectant procedures need to be encouraged to completely eliminate cross infection to dental laboratory.

A study on the effect on surface detail reproduction of alginate impressions disinfected with sodium hypochlorite and ultraviolet light - An In Vitro study

OBJECTIVES OF THE STUDY

To evaluate the surface detail reproduction of dental casts with impressions made using commercially available alginate impression materials after disinfecting with chemical disinfectant sodium hypochlorite and physical means of disinfection using ultraviolet radiation.

MATERIALS AND METHODS

A stainless steel die was used to make impression according to ADA/ANSI specification No. 18 having 25, 50 and 75 µm lines. Totally 70 impressions were made and divided in to 7 groups. The impressions in the first group were only rinsed with 250 ml of water. The 2nd, 3rd and 4th groups were disinfected by immersing in sodium hypochlorite for 1, 5 and 10 minutes, respectively. Fifth, 6th and 7th group samples were disinfected by placing them in ultraviolet chamber for 6, 12 and 18 minutes, respectively. All the impressions were poured immediately using type III gypsum. The casts were recovered and subjected for evaluation of the 75 µm lines using stereomicroscope.

RESULTS

There was no statistically significant change in the surface detail reproduction when disinfected with sodium hypochlorite or ultraviolet radiation.

CONCLUSION

Alginate impressions subjected to immersion disinfection using sodium hypochlorite for 1, 5 and 10 minutes and subjected to ultraviolet disinfection for 6, 12 and 18 minutes exhibited no statistically significant differences for surface detail reproduction compared to control groups.

The effects of disinfectants on dimensional accuracy and surface quality of impression materials and gypsum casts

BACKGROUND

The study aimed to evaluating the effect of disinfecting impression materials on the dimensional accuracy and surface quality of the resulting casts.

METHODS

Impressions of a steel die constructed according to ANSI/ADA specification No.18 were made with each of alginate, addition cured silicone, condensation cured silicone and zinc oxide eugenol paste, and disinfected consequently by each of 0.2% chlorhexidine gluconate, 1% sodium hypochlorite, 2% gluteraldehyde for 5 minutes, and 0.5% sodium hypochlorite for 10 minutes. Dimensions of the disinfected impressions and their resultant casts were measured using a computerized digital caliper, and the dimensional changes were calculated. Reproduction of detail and surface quality of the resultant casts were assessed by grading casts surfaces according to a specific scoring system.

RESULTS

The 0.5% sodium hypochlorite was found to produce the least dimensional changes in all the impression materials. Corsodyl produced the maximum changes in both alginate and zinc-oxide eugenol while addition-cured silicon was most affected by Gluteraldehyde and condensation-cured silicon was most affected by Hexana. The dimensional changes, however, were minimal and clinically insignificant. Addition-cured silicon showed the best surface quality and dimensional stability followed by condensation-cured silicon. Alginate and zinc-oxide eugenol had poorer surface quality and were affected to a higher extent by the disinfection procedures.

CONCLUSIONS

The results were comparable with the standard specifications for dimensional stability. Recommendations were made for the use of 10 minutes immersion in 0.5% sodium hypochlorite as the most appropriate disinfection protocol to the investigated impression materials.

KEYWORDS

Disinfectants; Gypsum casts; Impressions; Alginate; Addition-cured silicone; Sodium hypochlorite.

Effect of incorporation of disinfectant solutions on setting time, linear dimensional stability, and detail reproduction in dental stone casts

PURPOSE

The aim of this paper was to analyze the influence of incorporation of disinfectants during the cast die stone-setting time. Setting time, linear dimensional stability, and reproduction details on casts were measured.

MATERIALS AND METHODS

Die stone type IV specimens with disinfection solutions (sodium hypochlorite 1%, glutaraldehyde 2%, chlorhexidine 2%) were incorporated in two concentrations (50%, 100%). The detail reproduction, dimensional stability, and setting time were tested in accordance with ADA recommendations.

RESULTS

Disinfecting solutions promoted an increase in setting time compared to control; sodium hypochlorite was responsible for the highest setting time. The addition of undiluted sodium hypochlorite 1.0% led to contraction during setting, but the groups with 50% diluted sodium hypochlorite 1.0% and undiluted chlorhexidine 2.0% resulted in intermediate values compared to the other groups, thus matching the control. The others did not demonstrate any effect on expansion. For detail reproduction, it was observed that the control group presented results similar to the others, except those where sodium hypochlorite was added.

CONCLUSIONS

The addition of sodium hypochlorite in both dilutions significantly altered, negatively, all the evaluated properties. But the addition of glutaraldehyde and chlorhexidine did not promote any significant alterations in the evaluated properties.

Impression materials: a comparative review of impression materials most commonly used in restorative dentistry

Impression materials are used to record intraoral structures for the fabrication of definitive restorations. Accurate impressions are necessary for construction of any dental prosthesis. The relationship between static and mobile oral structures must be reproduced accurately for an optimum cast. The more common types of impressions are used for fabricating diagnostic and master casts. Accurate impressions depend on identifying the applications that do or do not fit each material's characteristics. Materials used without adequate knowledge of their characteristics can impair a successful outcome. Often, the choice of impression materials depends on the subjective choice of the operator based on personal preferences and past experience with particular materials.

Effect of Disinfection on the Dimensional Stability of Polyether Impression Materials

PURPOSE

Difficulties in sterilizing impressions have led to chemical disinfection solutions as an alternative; however, some impression materials are more sensitive to humidity. For example, polyether impression materials are more hydrophilic. This study investigated the effect of three disinfecting methods on the dimensional stability of three polyether impression materials.

MATERIALS AND METHODS

Three polyether impression materials (P2, Impregum Penta Soft, and Impregum Penta) were submitted to the following treatments: spray disinfectant (Mikrozid Liquid), immersion in 2% glutaraldehyde solution (Super-On), immersion in 0.525% sodium hypochlorite solution for 10 minutes, and a control group (not disinfected). Each group included five samples. After treatment, dimensional change was evaluated according to ISO 4823. The data were analyzed by 2-way analysis of variance at alpha= 0.05.

RESULTS

The mean percentages of linear dimensional change of materials P2, Penta Soft, and Penta were -0.040%, 0.098%, and 0.100%, respectively. The dimensional change associated with different disinfectant agents mikrozid liquid, 2% glutaraldehyde, room air (control), and 0.525% sodium hypochlorite was 0.013%, 0.024%, 0.077%, and 0.096%, respectively. The interaction between the impression materials and the disinfectant treatment was not significant. The disinfectant agents can be classified in two groups as low- and high-effected. The control group did not significantly differ from either group.

CONCLUSION

From the standpoint of dimensional change, the disinfectants tested for 10 minutes caused no significant linear dimensional change in the polyether impression materials, compared with the control group.

Occupational hazards in orthodontics: A review of risks and associated pathology

The purpose of this article was to review the occupational hazards related to the practice of orthodontics. A systematic approach was used to include all risks involved in an orthodontic practice. The classification of hazards was based on major sources of risks by system or tissue and by orthodontic office area (dental chair, laboratory, sterilization area, x-ray developing area). Potentially hazardous factors relate to the general practice setting; to specific materials and tools that expose the operator to vision and hearing risks; to chemical substances with known allergenic, toxic, or irritating actions; to increased microbial counts and silica particles of the aerosols produced during debonding; to ergonomic considerations that might have an impact on the provider's muscoleskeletal system; and to psychological stress with proven undesirable sequelae. The identification and elimination of these risk factors should be incorporated into a standard practice management program as an integral part of orthodontic education. Professional organizations can also assist in informing practitioners of potential hazards and methods to deal with them.

Effect of immersion disinfection with Perform-ID on alginate, an alginate alternative, an addition-cured silicone and resultant type III gypsum casts

OBJECTIVE

This study investigated the effect of a commonly used immersion disinfectant upon three different impression materials and any subsequent effects on the abrasion resistance, hardness and surface detail reproduction of gypsum casts.

DESIGN

A laboratory study.

MATERIALS AND METHODS

Under standardised conditions a total of 120 impressions were made of a ruled test block using irreversible hydrocolloid (Alginoplast), an 'alginate alternative' addition-cure silicone (Position Penta) and a conventional addition-cure silicone (President). The impressions were examined for surface detail reproduction prior to and after disinfection with Perform-ID. The type III casts were evaluated for surface detail reproduction, surface hardness and abrasion resistance.

RESULTS

(1) None of the disinfected alginate specimens could reproduce the 50 microm line. (2) Casts produced from the disinfected alginate were significantly less hard than from disinfected Position Penta and President (P <0.001). (3) Disinfection significantly affected the abrasion resistance of casts made from Position Penta (P = 0.029). (4) Disinfection did not significantly affect President or its subsequent casts (P >0.05).

CONCLUSION

If disinfecting with Perform-ID, the impression should be made with a conventional addition-cured silicone if good surface detail reproduction of the impression material and a hard and abrasion resistant type III gypsum cast are required.