Addition Silicone Impressions in Fixed Prosthodontics: Clinical Standpoints

Addition silicones have revolutionized the field of fixed prosthodontics because of their dimensional stability, sufficient tear strength and excellent detail reproduction. This review study aims to provide a detailed description of the essential variables to be taken into account during the process of making addition silicone impressions in fixed prosthodontics. These variables include the selection of appropriate tray type, size, and fabrication; the use of tray adhesive; gingival displacement techniques; manipulation of the impression material; the choice of the impression material's viscosity; impression techniques; and the proper insertion, removal, disinfection, and pouring of the cast. Additionally, this review aims to help doctors produce high-quality impressions by empowering them to critically assess the impressions to spot mistakes and motivating them to redo impressions that have serious problems before submitting them to the laboratory.

Simultaneously Enhancing the Flame Retardancy, Water Resistance, and Mechanical Properties of Flame-Retardant Polypropylene via a Linear Vinyl Polysiloxane-Coated Ammonium Polyphosphate

It is challenging to improve the water resistance, flame retardancy, mechanical performance, and balance of halogen-free flame-retardant polypropylene (PP) composites. For this purpose, a linear vinyl polysiloxane (PD) was synthesized and then self-crosslinked under benzoyl peroxide to prepare surface-coated ammonium polyphosphate (APP@PD). Apparently, this linear vinyl polysiloxane self-crosslinking coating strategy was completely different from the commonly used sol-gel-coated APP with silane monomers. After coating, the water contact angles (WCA) of APP and APP@PD were 26.8° and 111.7°, respectively, showing high hydrophobicity. More importantly, PP/APP@PD/dipentaerythritol (DPER) showed a higher limiting oxygen index (LOI) and better UL-94 V-0 rate in comparison with PP/APP/DPER composites. After water immersion at 70 °C for 168 h, only PP/APP@PD/DPER kept the UL-94 V-0 rate and lowered the deterioration of the LOI, reflecting the better water-resistance property of APP@PD. Consistently, the cone calorimeter test results displayed a 26.2% and 16.7% reduction in peak heat release rate (PHRR) and total smoke production (TSP), respectively. Meanwhile, the time to peak smoke production rate (T_PSPR) increased by 90.2%. The interfacial free energy (IFE) between APP@PD and PP was calculated to evaluate the interfacial interaction between PP and APP@PD. A reduction of 84.2% in the IFE between APP@PD and PP is responsible for the improvement in compatibility and the increase in flame retardancy, water resistance, and mechanical properties of the composites.

Comparative surface detail reproduction for elastomeric impression materials: Study on reproducibility performance

For dental impression of a prepared tooth, the goal is a void-free negative representation from which an accurate cast of a tooth and its surrounding tissue can be reproduced. This in-vitro study assessed and compared the reproduction accuracies of surface detail obtained with three different dental elastomeric impression materials: vinyl polysiloxane (VPS), vinyl polyether silicone (VPES), and polyether (PE). A stainless-steel model with two abutments was used, with impressions taken 10 times for each material, for 20 abutment impressions per group, using a two-phase, one-step technique (heavy body/light body). The impressions were removed and assessed for numbers of enclosed voids and open voids visible on the surface. The defect frequency was 95% for impressions with the VPS and VPES materials, and 30% for the PE material. No significant differences were seen for number of impressions with defects for VPS versus VPES. Significant differences were seen for VPS and VPES versus the PE material (P <.05). No significant differences were seen for the defect type distributions across these three impression materials. The PE impression material showed better accuracy for reproduction of surface detail of these dental impressions compared to the VPS and VPES impression materials.

Influence of Vinyl Polysiloxane Impression Techniques on Marginal Fit of Metal Frameworks for Fixed Partial Dentures

Impression technique is one of the factors affecting restoration fit accuracy, which is a major aspect influencing its survival. The purpose of this study is to compare, in vivo, the effect of two commonly used Vinyl Polysiloxane (VPS) impression techniques on the metal framework fitting of fixed partial dentures. Ninety-two consecutive patients, diagnosed as partially edentulous, treated by fixed partial denture restorations, participated in the study. Group 1-impressions (n = 44) were subjected to the 1-step technique, while group 2 impressions (n = 48) were subjected the 2-step technique. Three accuracy assessment common methods: probe, tactile sense and radiographic test, were used to validate the clinical fit of the metal framework. Misfit was defined as even one test failure. Twenty-one (22.8%) out of 92 metal frameworks exhibited metal frameworks misfit, whereas the other 71 (77.2%) were found to be accurate. Group 1 presented significantly (p = 0.04) more metal frameworks misfit, 14/44 (31.8%) vs. 7/48 (14.6%). Restoration location (maxilla vs. mandible) had no statistically significant impact on the results (p = 0.461). The use of the VPS putty/wash 2-step impression technique is recommended to improve the clinical fit of fixed partial denture restorations.

Comparative Study of Dimensional Stability and Detail Reproduction of Reformulated and Nonreformulated Elastomeric Impression Materials

PURPOSE

To evaluate the dimensional stability and the detail reproduction of five current elastomeric impression materials in vitro.

MATERIALS AND METHODS

The materials examined were: 3 different polyether impression materials, a vinyl polysiloxane impression material, and a vinyl polyether silicone impression material. All impression materials were of a medium viscosity. One stainless steel die was fabricated according to the ANSI/ADA specification no.19 criteria. Twenty impressions of this die were made for each material. Dimensional accuracy and surface detail were evaluated 24 hours after making the impressions using a measuring microscope. The data were analyzed using Welch's analysis of variance, Games-Howell Post-Hoc, and the Pearson's chi-square tests (α = 0.05).

RESULTS

Statistical differences were observed in the mean percent dimensional stability (F [4,47] = 39, p < 0.001) of the tested impression materials. The highest dimensional change was recorded for the vinyl polysiloxane impression material, with a mean percent value of -0.09 ± 0.02% (p < 0.001). The lowest dimensional change was recorded for the Monophase polyether material with a mean percent value of -0.03 ± 0.01% (p < 0.038). The best surface detail reproduction results were obtained using the Monophase polyether material (90% acceptable impressions), with no significant differences (χ² [4] = 3.86, p = 0.483) observed between the Monophase and the rest impression materials.

CONCLUSIONS

All materials exhibited acceptable dimensional stability, well below the ANSI/ADA specification no.19 standard of ≤0.5% dimensional change. All impression materials demonstrated acceptable surface detail reproduction with no significant differences between them.

Dimensional Stability of a Preliminary Vinyl Polysiloxane Impression Material

Oral rehabilitation success depends upon the accuracy and dimensional stability of the impressions. The purpose of this study is to evaluate the dimensional changes of a first impression type VPS (Vinyl Polysiloxane) (Imprint™ 4 Preliminary Penta™ Super Quick, 3M ESPE™, St Paul, MN, USA). 10 samples were obtained from this silicone with an automatic mixing machine (Pentamix 2, 3M ESPE™, Seefeld, Germany) according to International Organization for Standardization (ISO) 4823:2000 and stored in the IPQ (Portuguese Institute for Quality) for one week. The measurements were performed by laser interferometry, according to the Michelson technique. The dimensional stability was calculated according to the formula specified in ISO (International Organization for Standardization) 4823:2000. A statistical analysis via a one-way repeated measures ANOVA was performed. The material shrinkage was 0.29 ± 0.15% after setting, 0.32 ± 0.21% at 24 h and 0.30 ± 0.23% after 1 week. No significant shrinkage of the silicone under investigation was found over time. This material can be stored for a week without the risk of clinically significant dimensional changes.

Use of a bite registration vinyl polysiloxane material to identify denture flange overextension and/or excessive border thickness in removable prosthodontics

Vinyl polysiloxane (VPS) has multiple applications in prosthodontics. This article describes how a bite registration fast-set VPS material was used to identify length overextension and/or excessive border thickness of denture flanges. In addition, the advantages of VPS over conventional materials are presented.

Positive control for cytotoxicity evaluation of dental vinyl polysiloxane impression materials using sodium lauryl sulfate

OBJECTIVES

Vinyl polysiloxane (VPS) is elastomeric dental impression material which, despite having very few reports of adverse reactions, has shown high levels of cytotoxicity that is difficult to be interpreted without referencing to the positive control material. Therefore, in this study, positive control VPS was developed using sodium lauryl sulfate (SLS) for the reference of cytotoxicity test.

MATERIALS AND METHODS

The positive control VPS with SLS was formed with a different proportion of SLS (0, 1, 2, 4, 8 and 16 wt%) added to the base. The cytotoxicity test was then carried out using the extractions or dilutions of the extractions from each of the test samples using murine fibroblast cells (L929).

RESULTS

The final product of positive control VPS behaved similar to commercially available VPS; being initially liquid-like and then becoming rubber-like. Ion chromatography showed that the level of SLS released from the product increased as the proportion of added SLS increased, consequently resulting in an increased level of cytotoxicity. Also, the commercially available VPS was less cytotoxic than the positive control VPS with more or equal to 2 wt% of SLS. However, even the VPS with the highest SLS (16 wt%) did not cause oral mucosa irritation during the animal study.

CONCLUSIONS

The positive control VPS was successfully produced using SLS, which will be useful in terms of providing references during in vitro cytotoxicity testing.

In vivo Study of the Accuracy of Dual-arch Impressions

BACKGROUND

This study evaluated in vivo the accuracy of metal (Smart®) and plastic (Triple Tray®) dual-arch trays used with vinyl polysiloxane (Flexitime®), in the putty/wash viscosity, as well as polyether (Impregum Soft®) in the regular viscosity.

MATERIALS AND METHODS

In one patient, an implant-level transfer was screwed on an implant in the mandibular right first molar, serving as a pattern. Ten impressions were made with each tray and impression material. The impressions were poured with Type IV gypsum. The width and height of the pattern and casts were measured in a profile projector (Nikon). The results were submitted to Student's t-test for one sample (α = 0.05).

RESULTS

For the width distance, the plastic dual-arch trays with vinyl polysiloxane (4.513 mm) and with polyether (4.531 mm) were statistically wider than the pattern (4.489 mm). The metal dual-arch tray with vinyl polysiloxane (4.504 mm) and with polyether (4.500 mm) did not differ statistically from the pattern. For the height distance, only the metal dual-arch tray with polyether (2.253 mm) differed statistically from the pattern (2.310 mm).

CONCLUSION

The metal dual-arch tray with vinyl polysiloxane, in the putty/wash viscosities, reproduced casts with less distortion in comparison with the same technique with the plastic dual-arch tray. The plastic or metal dual-arch trays with polyether reproduced cast with greater distortion. How to cite the article: Santayana de Lima LM, Borges GA, Burnett LH Jr, Spohr AM. In vivo study of the accuracy of dual-arch impressions. J Int Oral Health 2014;6(3):50-5.