In vitro study of transmission of bacteria from contaminated metal models to stone models via impressions

Biological properties of experimental dental alginate modified for self-disinfection using green nanotechnology

OBJECTIVES

Disinfection of alginate impression materials is a mandatory step to prevent cross-infection in dental clinics. However, alginate disinfection methods are time-consuming and exert a negative impact on accuracy and mechanical properties. Thus, this study aimed to prepare disinfecting agents (CHX and AgNO3) and silver nanoparticles reduced by a natural plant extract to produce a self-disinfecting dental alginate.

METHODS

Conventional alginate impression material was used in this study. Silver nitrate (0.2% AgNO3 group) and chlorohexidine (0.2% CHX group) solutions were prepared using distilled water, and these solutions were later employed for alginate preparation. Moreover, a 90% aqueous plant extract was prepared from Boswellia sacra (BS) oleoresin and used to reduce silver nitrate to form silver nanoparticles that were incorporated in the dental alginate preparation (BS+AgNPs group). The plant extract was characterized by gas chromatography/mass spectrometry (GC/MS) analysis while green-synthesized silver nanoparticles (AgNPs) were characterized by UV-visible (UV-vis) spectroscopy and scanning electron microscopy (SEM). An agar disc diffusion assay was used to test the antimicrobial activity against Candida albicans, Streptococcus mutans, Escherichia coli, methicillin-resistant and susceptible Staphylococcus aureus strains, and Micrococcus luteus. Agar plates were incubated at 37 ± 1 °C for 24 h to allow microbial growth. Diameters of the circular inhibition zones formed around each specimen were measured digitally by using ImageJ software.

RESULTS

Chemical analysis of the plant extract revealed the presence of 41 volatile and semi-volatile active compounds. UV-Vis spectrophotometry, SEM, and EDX confirmed the formation of spherical silver nanoparticles using the BS extract. CHX, AgNO3, and the BS+AgNPs modified groups showed significantly larger inhibition zones than the control group against all tested strains. BS+AgNPs and CHX groups showed comparable efficacy against all tested strains except for Staphylococcus aureus, where the CHX-modified alginate had a significantly higher effect.

CONCLUSIONS AND CLINICAL RELEVANCE

CHX, silver nitrate, and biosynthesized silver nanoparticles could be promising inexpensive potential candidates for the preparation of a self-disinfecting alginate impression material without affecting its performance. Green synthesis of metal nanoparticles using Boswellia sacra extract could be a very safe, efficient, and nontoxic way with the additional advantage of a synergistic action between metal ions and the phytotherapeutic agents of the plant extract.

Evaluation of the Efficacy of Novel Self Disinfectant Solution in Irreversible Hydrocolloid Impression Material - An Experimental Study

Background

Irreversible hydrocolloid materials are widely used for both diagnostic and definitive impression procedures. Impressions can be disinfected by immersion or spraying in any compatible disinfectant. Disinfectants should not adversely affect the dimensional stability of the impression and physical properties of impression material and subsequent dental cast.

Objective

The study aims to evaluate the efficacy of a hypochlorous disinfectant solution mixed with irreversible hydrocolloid on setting time, antibacterial efficacy, and dimensional stability.

Methodology

Three groups were made with one control group and three alginate impression was made for each participants in the maxillary arch with 24-hours intervals between one another using the same brand of commercially available chromatic alginate. The working and setting time were noted. Bacterial swabs were collected using a dry sterile cotton swab in the mid palatal region. Dental casts were made using type III gypsum.

Result

The working and setting time had significant differences whereas the dimension among the cast has no significant difference. Microbial growth analysis had distinct differences among the groups.

Conclusion

The self disinfection method using a pioneer solution of hypochlorous HOCl (100 ppm) to mix the alginate impression material rather than the water with the same powder-liquid ratio prescribed by the manufacturer had the same dimensional stability with improved antimicrobial action.

Decontamination of lithium disilicate ceramics using various photosensitizers, herbal and chemical disinfectants, and the effect of surface conditioners on bond strength values

AIM

To assess and compare the antimicrobial efficacy of disinfectants on lithium disilicate ceramic (LDC) used in dental applications and shear bond strength (SBS) of LDC after using different conditioners hydrofluoric acid (HF), self-etching ceramic primers (SECP) and Neodymium-doped yttrium orthovanadate (Nd: YVO4).

MATERIALS AND METHODS

One hundred and twenty LDC discs were fabricated by auto-polymerizing acrylic resin using the lost wax technique. S. aureus, S. mutans, and C. albican were inoculated on thirty discs (n=30 each). Each group was further divided into three subgroups based on different disinfecting agents used (n=30) Group 1: Garlic extract, Group 2: Rose Bengal (RB) activated by PDT, and Group 3: Sodium hypochlorite (NaOCl). An assessment of the survival rate of microorganisms was performed. The remaining thirty samples were surface treated using three different LDC surface conditioners (n=10) Group 1: HF + Silane (S), group 2: SECP, and Group 3: Nd: YVO4 laser+S. SBS and failure mode analysis were performed using a universal testing machine and stereomicroscope at 40x magnification, The statistical analysis was conducted using one-way ANOVA and Post Hoc Tukey test.

RESULTS

Garlic extract, RB, and 2% NaOCl sample displayed comparable outcomes of antimicrobial potency against C. albicans, S aureus, and S. mutans (p>0.05). Furthermore, SBS analysis showed HF+S, SECP, and Nd: YVO4+S exhibited comparable outcomes of bond strength (p>0.05).

CONCLUSION

Garlic extract and Rose bengal activated by PDT can be contemplated as alternatives to the chemical agent NaOCl used for LDC disinfection. Similarly, SECP and Nd: YVO4 possess the potential to be used for the surface conditioning of LDC to improve the bond integrity with resin cement.

Influence of contemporary ceramo-metallic crown decontamination on the surface roughness, color stability, and disinfection. An in vitro analysis

AIM

To assess the antimicrobial effects, surface roughness (Ra), and color change (ΔE) of Morinda Citrofolia, Sapindus Mukorossi, Indocyanine green photosensitizer, and 2% NaOCl on metal ceramic crown colonized with C. Albicans, S aureus, S. mutans, and E. coli.

MATERIAL AND METHODS

An aggregate of 40 (n = 10 each) Ni/Cr metal-ceramic crowns were fabricated and inoculated with the American Type Culture Collection (ATCC) of varied microbial colonies colonized by C. Albicans, S aureus, S. mutans, and E. coli. After inoculation, specimens were exposed to four different types of disinfection methods i.e. group 1: MC, group 2: SM, group 3:ICGP, and group 4 2% NaOCl respectively to evaluate antimicrobial efficacy, Ra, and color change. Later, the microbial assay was performed and expressed as CFU/ml (log 10). Ra was assessed using a surface analyzer and color change ΔE was evaluated using a spectrophotometer Statistical analysis was performed by using two-way ANOVA and Post HocTukey's test maintaining a significance level of p less than 0.05.

RESULTS

The highest antimicrobial efficacy for metallic-ceramic crown decontamination against all inspected microbial colonies was unveiled by group 1: MC, whereas the lowest disinfection efficacy was revealed by group 4 sterilized with 2% NaOCl (control). Metallic ceramic crown decontamination with MC and SM substantiated equivalent antimicrobial efficacy in plummeting CFU/mL (log10) of C.Albicans, S aureus, S.mutans, and E. coli (p>0.05). However, ICGP as a crown disinfectant validated antimicrobial efficacy significantly less compared to MC and SM (p<0.05). Ra was assessed post-disinfection with no changes observed (p>0.05) among all groups. Similarly, ΔE was significantly higher in crowns disinfected with ICGP (p<0.05) CONCLUSION: Metallic ceramic crown decontamination using herbal disinfectants Morinda Citrofolia and Sapindus Mukorossi exhibited favorable antimicrobial efficacies against microbial colonies of C. albicans, S aureus, S.mutans, and E. coli with no changes in surface roughness and color.

Disinfection of polyvinyl siloxane impression material using ozone gas, 0.1% riboflavin, glutaraldehyde, and microwave irradiation and their effect on physical properties

AIM

To assess the antimicrobial effect of ozone gas (OG) 0.1% riboflavin (RF), glutaraldehyde (GaH), and microwave irradiation (MI) on Polyvinyl siloxane impression material formerly colonized with E. coli, P. Aeruginosa, E. faecalis, and S.aureus and their effect on the physical properties MATERIAL AND METHODS: One hundred disk-shaped specimens (diameter 10 mm and thickness 3 mm) were developed by using polyvinylsiloxane impression material and inoculated by the American Type Culture Collection (ATCC) of E. coli, P. aeruginosa, E. faecalis, and S.aureus in an in-vitro setup. The samples were arbitrarily isolated into five groups and subjected for 3 min to the designated disinfection modality. Group 1 Control, group 2: GaH, group 3: 0.1% RF, group 4: MI, and group 5 OG. Following decontamination, the physical properties (contact angle, strain-in-compression, and tear strength) of impression materials were evaluated. Statistical analysis for CFU/mL (log10) for exposed E. coli, P. aeruginosa, E. faecalis, and S.aureus was performed by using analysis of variance (ANOVA) and Tukey's multiple comparison tests at a p-value of less than 0.05.

RESULTS

The most effective antimicrobial efficacy for impression disinfection against all scrutinized microbial colonies were displayed by group 5 OG and the lowest disinfection effectiveness was unveiled by the control group with no treatment. The intragroup comparison revealed that impression disinfection with GaH, MI, and ozone corroborated analogous antimicrobial efficacy(p > 0.05). The disinfecting capacity of the impression material with 0.1% RF was significantly less than MI, GaH, and OG (p < 0.05).

CONCLUSION

Disinfection of polyvinyl siloxane impression material with ozone gas, microwave irradiation, and glutaraldehyde demonstrated reasonable antimicrobial efficiencies against E. coli, P. aeruginosa, E. faecalis, and S.aureus with no detrimental effects on the physical properties of impression material. More studies are advocated to extrapolate the findings of the present study.

Effect of heat sterilization and chemical method of sterilization on the polyvinyl siloxane impression material. A comparative study

Background:

Dental impression is a crucial part of the process of constructing a well-fitting prosthesis. In the clinical scenario, impressions can act as a vehicle for the transfer of bacteria and fungi. Therefore, an attempt was made to evaluate the dimensional accuracy of the newly introduced polyvinyl siloxane (PVS) impression material upon autoclaving and comparing it to the traditional means of chemical disinfection.

Materials and Methods:

A cross-sectional comparative in vitro study was conducted. Three groups were made for testing different sterilization methods. The sample size for the study was kept as 30 observations in each of the three groups. Test samples were prepared by making an impression of the die using the putty-wash technique. Statistical analysis was done by applying unpaired t-test, paired t-test, one-way analysis of variance (ANOVA) and post hoc Tukey's honestly significant difference (HSD).

Results:

Initial mean of samples of group I were compared to A (actual measurement of metal ruled block = 24.960), a dimensional change of 1.6% was found. Similarly, in group II, a change of 1.59% was found and in group III the change was 1.7%. There was mean shrinkage of 24.557 mm in group I, 24.586 mm in group II, and 24.535 mm in group III and these changes were found statistically significant.

Conclusion:

Dimensional changes in the impression material after disinfection with 2% glutaraldehyde were considered high compared to autoclaving and, hence, it may not be advisable to disinfect this material with 2% glutaraldehyde.

Evaluation of efficacy of Aloe Vera as a Disinfectant by Immersion and Spray methods on Irreversible Hydrocolloid Impression Material and its Effect on the Dimensional Stability of Resultant Gypsum Cast - An in Vitro Study

The need to use a natural alternative for disinfecting dental impression materials, which should be biocompatible and effective, led us to evaluate the efficacy of Aloe vera as a disinfectant by immersion and spray method on alginate impression material and its effect on the dimensional stability of the resultant gypsum cast.

The efficacy of the disinfection procedures against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans was evaluated by determining the number of colony-forming units (CFU) recovered after disinfection of alginate discs inoculated with 1x106 CFU for defined intervals with aloe vera solution (99.96%). Dimensional stability was determined from the mean percentage deviation of three measurements that were taken between the fixed points on the casts using a traveling microscope and compared with corresponding measurements from the master model and controls. Statistical analysis of data was determined by analysis of variance.

We found out that there is a mean percentage reduction in colony count of S. aureus, P. aeruginosa, and C. albicans after 3 minutes of immersion in aloe vera and after 3 minutes spray disinfection. Complete elimination of all the microorganism cells after 7 min immersion and spray disinfection. There was a statistically significant difference in the increase of the mean anteroposterior (AP) and cross arch (CA) dimension after 3 and 7 minutes immersion in aloe vera.

Spraying with aloe vera for 7 minutes was proved to be the most effective disinfection procedure without altering dimensional stability.

Development of an Impression Material with Antimicrobial Properties for Dental Application

PURPOSE

To evaluate the antimicrobial activity and physico-mechanical properties of an irreversible hydrocolloid in which nanostructured silver vanadate decorated with silver nanoparticles (AgVO₃ ) was added at various concentrations (0% - control, 2.5%, 5%, and 10% by weight).

MATERIALS AND METHODS

The agar diffusion method (n = 10) was used to evaluate the inhibitory effect on the following species: Streptococcus mutans, Staphyloccocus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. The gelation time, flow capacity and plastic deformation were verified (n = 10). The data were analyzed using the Kruskal-Wallis test followed by the Dunn post-test, or via one-way ANOVA with multiple comparisons with a Bonferroni adjustment depending on the distribution (α = 0.05).

RESULTS

All percentages of the nanomaterial were able to promote the antimicrobial activity of a hydrocolloid, with the formation of an inhibition zone (p < 0.05). In general, there was a dose-dependent effect on antimicrobial activity: higher concentrations of the nanomaterial promoted greater action except in the cases of P. aeruginosa (p < 0.001; F = 51.74) and S. aureus (p < 0.001), where the highest inhibition was for the 2.5% group. No difference was found in the gelation time when the control was compared with the groups with AgVO₃ (p > 0.05). The difference was between the 5% and 10% groups (p = 0.007), and the latter promoted an increase in time. The flow capacity of the hydrocolloid with 5% of AgVO₃ was significantly lower when compared with the control (p = 0.034). The AgVO₃ influenced the plastic deformation (p < 0.001) in such a way that concentrations of 5% (p = 0.010) and 10% (p < 0.001) promoted an increase in this property when compared with the control.

CONCLUSIONS

AgVO₃ can be incorporated into an irreversible hydrocolloid as an antimicrobial agent without promoting adverse effects on physical-mechanical properties when used in concentrations of 2.5%.

A self-disinfecting irreversible hydrocolloid impression material mixed with povidone iodine powder

Objectives:

The aim was to evaluate the effect of adding povidone (PVP) iodine powder with different concentrations to irreversible hydrocolloid on both microbiological and dimensional stability.

Materials and Methods:

Regular set of (alginate) irreversible hydrocolloid was selected as control group. PVP-iodine powder was mixed with the alginate powder at concentrations of 1, 5, 10, 15, and 20% by weight (test groups). All specimens were tested for their antimicrobial effect against Streptococcus mutans and Staphylococcus aureus as well as dimensional stability.

Results:

The results of test groups showed that concentrations 1, 5, and 10, weight % had little effect against S. mutans and S. aureus microorganisms. While concentrations 15 and 20 weight % had demonstrated greater effect on microbial growth. The mean of dimensional stability in mm of modified alginate with PVP-iodine at 15 and 20 weight % was –0.119 ± 0.255 and –0.035 ± 0.074, respectively. While the mean dimensional stability in mm of unmodified alginate was –0.112 ± 0.176. The results of dimensional stability showed that 15 and 20 concentrations of test groups adversely affect the dimensional stability. The adverse effect was noticed to be significant in concentration 20%, where as it was nonsignificant in 15% concentration.

Conclusion:

Modified alginate impression material with 15 weight % PVP-iodine powered give the material, a self-disinfected properties with less deteriorating effect on dimensional stability.

Microbial contamination of laboratory constructed removable orthodontic appliances

OBJECTIVES

This study aims to determine whether laboratory constructed removable orthodontic appliances are free from microbial contamination prior to clinical use and to evaluate the dental hospital cross-infection procedures to ensure that patient-derived contamination does not enter the construction process, thereby propagating a cycle of cross-contamination.

MATERIALS AND METHODS

The construction process of removable orthodontic appliances from three individuals was evaluated at every stage, from impression to final delivery of the appliance using molecular microbiological techniques. The bacterial profiles at each stage of appliance construction were obtained using denaturing gradient gel electrophoresis, along with the bacterial profiles of the three participants' saliva. This enabled the bacterial profiles found at each stage of construction to be compared directly with the saliva of the person for whom the appliance was being constructed. Bacteria were identified at each stage using 16S rDNA PCR amplification and sequence phylogeny.

RESULTS

There was no evidence of bacterial cross-contamination from patients to the laboratory. The current process of disinfection of impression appears to be adequate. Contamination was found on the final removable appliances (0.97 × 10(2)-1.52 × 10(3) cfu ml(-1)), and this contamination occurred from within the laboratory itself.

CONCLUSIONS

Every effort is made to reduce potential cross-infection to patients and dental professionals. Newly constructed removable appliances were shown not to be free from contamination with bacteria prior to clinical use, but this contamination is environmental. Further studies would be required to determine the level of risk this poses to patients.

CLINICAL SIGNIFICANCE

Dental professionals have a duty of care to minimise or eradicate potential risks of cross-infection to patients and other members of the team. To date, much less attention has been paid to contamination from the orthodontic laboratory, so contamination and infection risks are unknown.

Viability changes: Microbiological analysis of dental casts

Background

This study evaluated the survival of the most prevalent oral bacteria and fungi (Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, and Candida albicans) in dental casts, and compared changes in the amounts of these microorganisms at different time intervals to determine how long dental casts may pose threat to the health of dental personnel and patients.

Material/Methods

When manufacturing the casts, regular water was replaced with sterile distilled water, where suspensions of the studied bacteria or the fungus at certain concentrations were prepared. When the dental casts were fully set (solidified), plaster shavings were examined immediately after the contact of the studied microorganism with the plaster, as well as after 1, 2, 24, 48, 72, 96, and 120 hours. Following that, we measured how the amount of the studied bacteria and fungi in 1 gram of the plaster changed within the studied period of time.

Results

Klebsiella pneumoniae survived in plaster for up to 4 days, and the reduction in the number of these bacteria became statistically significant after 1 day (p<0.05). Staphylococcus aureus remained viable in plaster for up to 4 days, and the number of these bacteria dropped after 1 day (p<0.05). Escherichia coli disappeared after 2 days, and a reduction was already observed after 2 hours (p<0.05). Candida albicans in plaster models died within 2 days, and a reduction in their number was observed after 1 day (p<0.05).

Conclusions

The microorganisms did not multiply in the gypsum casts and their number significantly dropped instead of increasing.

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.

In vitro evaluation of dimensional stability of alginate impressions after disinfection by spray and immersion methods

Background and aims

The most common method for alginate impression disinfection is spraying it with disinfecting agents, but some studies have shown that these impressions can be immersed, too. The aim of this study was to evaluate the dimensional stability of alginate impressions following disinfecting by spray and immersion methods.

Materials and methods

Four common disinfecting agents (Sodium Hypochlorite, Micro 10, Glutaraldehyde and De-conex) were selected and the impressions (n=108) were divided into four groups (n=24) and eight subgroups (n=12) for disinfecting by any of the four above-mentioned agents by spray or immersion methods. The control group (n=12) was not disinfected. Then the impressions were poured by type III Dental Stone Plaster in a standard method. The results were ana-lyzed by descriptive methods (mean and standard deviation), t-test, two-way analysis of variance (ANOVA) and Duncan test, using SPSS 14.0 software for windows.

Results

The mean changes of length and height were significant between the various groups and disinfecting methods. Regarding the length, the greatest and the least amounts were related to Deconex and Micro 10 in the immersion method, respectively. Regarding height, the greatest and the least amounts were related to Glutaraldehyde and Deconex in the im-mersion method, respectively.

Conclusion

Disinfecting alginate impressions by Sodium Hypochlorite, Deconex and Glutaraldehyde by immersion method is not recommended and it is better to disinfect alginate impressions by spraying of Micro 10, Sodium Hypochlorite, Glutaraldehyde and immersion in Micro 10.

Accuracy and stability of impression materials subjected to chemical disinfection - a literature review

Disinfection of impressions by immersion or spraying with disinfecting solutions is considered nowadays mandatory for effective infection control. The purpose of this review was to examine existing evidence on the effects that chemical disinfection may have on critical qualities of impressions, namely dimensional accuracy and stability over time. A PubMed search was conducted to include original laboratory research articles written in English, published between 1980 and 2005 in peer-reviewed journals and investigating the effect of chemical disinfection, by immersion or spraying, on the dimensional changes that the impression materials experience after setting. Studies were also sought manually, by tracing the references cited in the retrieved articles. The reports on dimensional changes of disinfected impression materials, although rather numerous, are difficult to compare and analyze because of variations of the experimental design. The investigations broadly agree that the disinfection process does not generally affect the dimensional integrity of the impressions, in spite of the statistically significant differences occasionally found. However, the immersion in the disinfecting solution encourages water absorption phenomena in the case of the so-called hydrophilic impression materials, especially after the long-term immersion. Chemical interactions between impressions and disinfectants may occur, but they do not appear to influence the dimensional behaviour of the former. The overall effect of the disinfection is influenced not only by the changes experienced by the impression per se, but also by the alterations of the acrylic tray containing the impression and of the gypsum product poured in it.