Digital assessment of properties of the three different generations of dental elastomeric impression materials

Properties of a novel composite elastomeric polymer vinyl polyether siloxane in comparison to its parent materials: a systemic review and meta-analysis

BACKGROUND

The effectiveness of newly developed elastomeric polymer hybrid siloxane (PVES), which combines the properties of polyethylene (PE) and polyvinyl siloxane (PVS) elastomers, has been a subject of interest in recent studies. This study aimed to assess the physical properties of hybrid PVES materials by analyzing existing data from recent studies on this topic.

METHODS

A systematic literature search was conducted to retrieve peer-reviewed articles published up to February 5, 2023. The population, intervention, comparison, and pertinent outcomes were specified under the PICO framework. The primary data analysis was performed in Microsoft Excel, while statistical analysis used Meta-Essentials.

RESULTS

Of the 1152 articles assessed, 14 met the inclusion criteria. The meta-analysis of the selected studies indicated that polyether (PE) and polyvinyl siloxane (PVS) were highly correlated (two-tailed p-values of 0.000 and 0.001, respectively) with the improved tensile strength of vinyl polyether siloxane (PVES) with a significantly positive effect size. Similarly, the hydrophilic characteristics of PVES were significantly improved compared to those of PE and PVS. PE was a significant contributor to the hydrophilic characteristics of PVES, with a two-tailed p-value of 0.000. The effect size was highly positive for hydrophilicity but showed high heterogeneity. It was also observed that the dimensional accuracy of PVES was comparable to those of PE and PVS, with no statistically significant differences among the three materials.

CONCLUSIONS

PVES showed promising features, with improved tensile strength and hydrophilic characteristics compared to those of PE and PVS.

Accuracy of Selective Laser Melted Bar Retaining Mandibular Implant-Assisted Overdenture: An In Vitro Comparison of Different Impression Materials and Techniques

This study aimed to assess the accuracy of the marginal fit of 2 implant-supported overdenture bars fabricated with selective laser melting technology, using polyvinyl siloxane and vinyl siloxane ether impression materials and different impression techniques. Two implants with multi-unit abutments were inserted in a 3D-printed mandibular model and used as a reference model, then duplicated into a stone cast to fabricate custom trays for obtaining impressions with polyvinyl siloxane and vinyl siloxane ether impression materials, using both open and closed-tray techniques. This resulted in a total of 4 groups, each with 8 specimens. The impressions were poured and scanned, and 32 cobalt-chromium bars were fabricated using selective laser melting technology. Each bar was screwed onto one abutment of the reference model, and a standardized digital periapical radiograph of the opposite unscrewed side was taken; this process was repeated to the other abutment. The vertical misfit was measured at 3 predetermined positions on the unscrewed side, and 6 values per bar were recorded. The mean gap distance was measured, and the data were subjected to statistical analysis; the present study found that the open-tray technique with vinyl polyether siloxane impression material may offer improved accuracy for obtaining impressions for 2 implant-supported bars. The open-tray technique groups also showed better marginal fit than the closed-tray groups. However, further clinical research is required to confirm these findings.

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.

Effect of chemical disinfection on the dimensional stability of polyvinyl ether siloxane impression material: a systemic review and meta-analysis

BACKGROUND AND OBJECTIVES

Polyvinyl ether siloxane (PVES) possesses ideal characteristics for making precise and accurate dental impressions. PVES dimensional stability owes to its better polymeric properties derived from its parent materials poly ethers and polyvinyl siloxanes. As recommended use of chemical disinfecting agents is getting more popular, there is a growing concern associated with the effect of disinfectants on PVES dimensional stability. This study was aimed to understand the PVES behavior when subjected to chemical disinfectants.

MATERIALS AND METHODOLOGY

The data was collected from research studies retrieved from Google Scholar, Scopus, and PubMed using MeSH terms of keywords "vinyl polyether siloxane AND Disinfection" or (Vinyl polyether siloxane OR polyvinyl siloxane ether OR PVES) AND (disinfectant OR disinfection)" without any restriction to publication date. The PRISMA (Preferred Reporting Items for Systemic Review and Meta-Analysis) directions were observed during the data collection, screening of studies, and meta-analysis. The primary data were retrieved, and batch exported from databases using Harzing's Publish or Perish software; primary analysis was performed in Microsoft Excel, while statistical analysis for effect size, two-tailed p-values, and heterogeneity among studies was performed using Meta Essentials. The effect size was calculated using Hedge's g values at the 95% confidence level using the random-effects model. Heterogeneity among studies was measured using the Cochrane Q and I².

RESULTS AND CONCLUSION

Dental impressions made from the PVES elastomeric impression materials showed no significant changes in dimensional stability. Immersion in the chemical disinfectant for 10 min was associated with clinically irrelevant changes in the dimensions of the PVES impressions. Disinfection with sodium hypochlorite was associated with clinically significant changes in dimensions, with a two-tailed p-value of 0.049. Disinfection with 2-2.5% glutaraldehyde solution was not associated with any significant dimensional variability.