Review of dental impression materials

Comparative Analysis of Three Different Impression Techniques for Impression Defects and Dimensional Accuracy Using a Digital Intraoral Scanner for Fixed Partial Dentures: An In Vivo Study

AIM

To evaluate the impression defects and compare the dimensional accuracy of three different impression techniques (single-step, two-step without spacer, two-step with spacer) for fixed partial dentures using a digital intraoral scanner in the anterior maxillary region.

MATERIALS AND METHODS

Thirty subjects, above the age of 18 years with maxillary central/lateral incisor requiring fixed prostheses were selected according to the inclusion and exclusion criteria. The impressions were rated and evaluated using Heine C2.3K Binocular loupes (Heine Ltd., Dover, NH, USA). An intraoral scanner and digital vernier calipers were used to study and compare the dimensional accuracy of all three impression techniques.  Results: Statistical analysis using the chi-square test revealed that the single-step double mix technique showed the least number of defects (40%), followed by the two-step without spacer (56.7%) and then the two-step with spacer (80%) impression techniques. Using Kruskal Wallis and Mann Whitney U test for dimensional accuracy, it was found that the two-step with spacer impression technique was closer to the control group (intraoral scanner) followed by the two-step without spacer and then the single-step double mix impression techniques.

CONCLUSION

All three impression techniques showed the presence of impression defects, mainly voids and bubbles. The single-step double mix and two-step without spacer techniques had more favourable outcomes compared to the two-step with spacer impression technique. The two-step with spacer impression technique was dimensionally more accurate compared to the two-step without spacer and single-step double mix techniques for fixed partial dentures.

Comparison of dimensional accuracy of elastomeric impression materials using 3D laser scanner

Background

The dimensional accuracy of elastomeric impression materials has been evaluated by different methods but their reliability is still questionable. The aim of this study was to evaluate the dimensional accuracy of elastomeric impression material using 3D laser scanner.

Method

In the present study, a metal die with its custom tray were designed. Using this die and tray, 10 impressions each were made from addition silicone (Aquasil LV; Dentsply), condensation silicone (Speedex coltene, Whaledent) and polyether (3M; ESPE). All the impressions were poured with Type IV die stone and total of 30 die replicas were obtained. These were scanned with a Picza 3D laser scanner (LPX 600, Roland,California) and the difference between the stone model was calculated by determining its volumetric changes using CAD-CAM pero version 2.0. One way analysis of variance (ANOVA) was used to compare the groups, whereas significance of mean difference between the groups was done by Tukey HSD.

Results

All the three groups showed mean decrease indicating a dimensional shrinkage from the master die. Mean percentage dimensional change in condensation silicone was maximum (-319.02 ±15.50) followed by polyether (-122.59 ± 0.64) and least in addition silicone (-23.83 ± 0.43). All the results were statistically significant (p<0.001).

Conclusion

Picza 3D laser scanner can precisely measure the volumetric changes in all the three elastomeric impression materials.

Comparative evaluation of wettability at various stages of working time for light body and medium body consistencies of three elastomeric impression materials

Aim:

The main purpose of this study was to compare the wettability of light and medium body consistencies of three different elastomeric impression materials during their working time.

Materials and Methods:

Vinylpolysiloxane, polyether, and vinylsiloxanether light body and medium body impression materials were used to fabricate the test samples. The contact angles of the impression materials were determined at 30^th s from the start of mixing until their entire range of working time using a goniometer. The mean contact angles at the early stage of working time and at the end of working time for two consistencies of each impression material were subjected for statistical analysis.

Results:

The result showed contact angle of all the impression materials toward the end of working time was less than the early stage with the statistical significance (P < 0.05). The contact angle of the light body impression material was less than the medium body impression materials with statistical significance (P < 0.05) except for vinylsiloxanether impression material.

Conclusion:

We have concluded from this study that vinylsiloxanether impression materials exhibited the least contact angle followed by polyether and the highest was recorded for vinylpolysiloxane impression material.

Comparative analysis of different impression techniques in relation to single tooth impression

It is of interest to compare the accuracy of three different impression techniques for a single tooth impression. We used 3 groups with 15 samples each in this study. Group 1: Putty and light body in a sectional stock tray; Group 2: Monophase and extra light body in a sectional stock tray; Group 3: Matrix impression technique. 15 impressions were taken of a prepared tooth on a typodont with each technique. The dimensions of the casts poured from these impression techniques were compared with the control typodont tooth. Data analysis shows that the matrix impression technique gave the best results in terms of dimensional study followed by monophase and extra light body impression technique and putty and light body impression technique gave the least accurate results. The results show that there is a statistically significant difference between the three impression techniques in terms of dimensional stability. Data analysis shows that the matrix impression technique gave the best results in terms of dimensional study followed by monophase and extra light body impression technique and putty and light body impression technique gave the least accurate results. The variations between the groups are within acceptable limits. Hence, it can be concluded that all the impression techniques will result in adequate dimensional stability and can be used in clinical scenarios.

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.

Protein and Polysaccharide-Based Fiber Materials Generated from Ionic Liquids: A Review

Natural biomacromolecules such as structural proteins and polysaccharides are composed of the basic building blocks of life: amino acids and carbohydrates. Understanding their molecular structure, self-assembly and interaction in solvents such as ionic liquids (ILs) is critical for unleashing a flora of new materials, revolutionizing the way we fabricate multi-structural and multi-functional systems with tunable physicochemical properties. Ionic liquids are superior to organic solvents because they do not produce unwanted by-products and are considered green substitutes because of their reusability. In addition, they will significantly improve the miscibility of biopolymers with other materials while maintaining the mechanical properties of the biopolymer in the final product. Understanding and controlling the physicochemical properties of biopolymers in ionic liquids matrices will be crucial for progress leading to the ability to fabricate robust multi-level structural 1D fiber materials. It will also help to predict the relationship between fiber conformation and protein secondary structures or carbohydrate crystallinity, thus creating potential applications for cell growth signaling, ionic conductivity, liquid diffusion and thermal conductivity, and several applications in biomedicine and environmental science. This will also enable the regeneration of biopolymer composite fiber materials with useful functionalities and customizable options critical for additive manufacturing. The specific capabilities of these fiber materials have been shown to vary based on their fabrication methods including electrospinning and post-treatments. This review serves to provide basic knowledge of these commonly utilized protein and polysaccharide biopolymers and their fiber fabrication methods from various ionic liquids, as well as the effect of post-treatments on these fiber materials and their applications in biomedical and pharmaceutical research, wound healing, environmental filters and sustainable and green chemistry research.

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.

Influence of disinfecting agents on the spatial dimensions of alginate mass impressions

Disinfection of dental impressions is a compulsory procedure performed in order to break the chain of infection. Disinfectants used for this purpose are divided into two large groups. These are ready-to-use disinfectants applied directly over the surface of the impression in the form of a spray and concentrates, which are used to prepare a solution in which the impressions are immersed for a specific period of time. This study aims to evaluate the influence of disinfectants on spatial dimensions of alginate mass impressions. Ninety cubic impressions were prepared using metal matrixes with external dimensions of 28 x 28 mm. Each impression was measured in two planes. The impressions were divided into three equinumerous sets of 30: Group I was disinfected with Zeta 7 Spray (n = 30), Group II was disinfected with Zeta 7 Solution (n = 30), and the control Group III (n = 30). The dimensions of the samples were measured in two planes after 24 (T1) and 120 (T2) hours. The obtained data was analysed statistically. The dimensions of the samples after 24 and 120 hours in the first group were significantly different from those of the control group and the differences were statistically significant (p <0.05). There was no statistically significant difference between the second and the control group after 24 and 120 hours. Ready-to-use disinfectants influence the dimensional stability of alginate-mass impressions. The time between taking the impression and preparation of the cast should be considered while choosing the disinfecting agent.

Effect of techniques, trays and materials on accuracy of impressions clinically made

Abstract Introduction Making accurate and dimensionally stable impressions to duplicate oral conditions and tooth morphology is an essential step of prosthetic dentistry for fabricating well-fitted indirect restorations and, consequently, ensure the longevity and success of the treatment. Several authors describe pros and cons of different impression techniques, although there is no unanimity among them about the best one. Objective This study evaluated casts’ accuracy made by different impression techniques, trays and materials. Material and method 10 patients were selected and 20 impressions from teeth #13 to #16 were performed using single-step (SS) and two-step techniques, made with metal stock and customized acrylic resin partial trays, vinyl polysiloxane and condensation silicone rubbers. Type IV gypsum was used to pour the casts. Three photographs of each patient (baseline), as their respective gypsum casts, were taken, measured in their interested buccal surface area. Comparisons of area values among experimental groups and baseline were performed. Data showed adherence to normal curve, being submitted to 3-way ANOVA/Bonferroni test (α=.05). Result Technique produced significant differences (P=0.02). SS technique was more accurate than BUR one (P=0.003; 95=1.22 to 5.98), but both resulted in similar casts to PVC, MOV and NR techniques, which were similar to each other (P>0.05). Conclusion SS technique showed the closest absolute values to baseline.

Alginate Materials and Dental Impression Technique: A Current State of the Art and Application to Dental Practice

Hydrocolloids were the first elastic materials to be used in the dental field. Elastic impression materials include reversible (agar-agar), irreversible (alginate) hydrocolloids and synthetic elastomers (polysulfides, polyethers, silicones). They reproduce an imprint faithfully, providing details of a high definition despite the presence of undercuts. With the removal of the impression, being particularly rich in water, the imprints can deform but later adapt to the original shape due to the elastic properties they possess. The advantages of using alginate include the low cost, a better tolerability on the part of the patient, the ease of manipulation, the short time needed for execution, the instrumentation and the very simple execution technique and possibility of detecting a detailed impression (even in the presence of undercuts) in a single step. A comprehensive review of the current literature was conducted according to the PRISMA guidelines by accessing the NCBI PubMed database. Authors conducted a search of articles in written in English published from 2008 to 2018. All the relevant studies were included in the search with respect to the characteristics and evolution of new marine derived materials. Much progress has been made in the search for new marine derived materials. Conventional impression materials are different, and especially with the advent of digital technology, they have been suffering from a decline in research attention over the last few years. However, this type of impression material, alginates (derived from marine algae), have the advantage of being among the most used in the dental medical field.

Ocular Impression-Taking-Which Material Is Best?

OBJECTIVES

To assess the efficacy and effect on clinical signs of a polyvinylsiloxane (Tresident; Shütz Dental Group GmbH, Germany) compared with an irreversible hydrocolloid (Orthoprint; Zhermack SpA, Badia Polesine, Italy) for ocular impression-taking.

METHODS

Twenty subjects were recruited (13 female and 7 male), with mean age 31.1±4.6 years (SD) (range 25.8-39.7). Subjects attended for 2 sessions, each of 1-hr duration, on 2 separate days. Each session was scheduled at the same time on each day. At each visit, the subject underwent an ocular impression procedure, using either Tresident or Orthoprint, in random order and to one eye only. Investigator 2 was blind to this assignment. Two experienced practitioners conducted the study, investigator 1 performed the ocular impression procedures and investigator 2 observed and assessed the clinical signs: logMAR visual acuity, ocular surface staining, tear break-up time (TBUT), and ocular hyperemia.

RESULTS

Visual acuity was unaffected by either material; TBUT was marginally disrupted by both materials, but was not clinically significant according to published criteria; ocular redness increased with both materials; and corneal staining was significantly greater after Orthoprint impression. Less redness and clinically insignificant staining after impression-taking, with fewer clinical complications, was found after use of Tresident.

CONCLUSIONS

Tresident offers a quicker, more effective, and clinically viable method of obtaining ocular impression topography compared with the traditional Orthoprint, and Orthoprint causes significantly more superficial punctuate staining of the corneal epithelium than Tresident.

Effect of Intermixing Brands on the Dimensional Accuracy of Master Cast using Putty-wash Impression Technique

AIM

The aim of this study was to evaluate the effect of intermixing brands of addition silicone impression materials on the dimensional accuracy of stone models using two-step putty-wash technique.

MATERIALS AND METHODS

Two common brands of addition silicone impression material (Express and Aquasil) were used in this study. A total of 40 impressions of a stainless steel model simulating a three-unit bridge were made, 10 impressions for each group. Accuracy was assessed by measuring two dimensions (inter-abutment and intra-abutment) on stone models obtained from impressions of the stainless steel model. Each sample was measured thrice and the mean value was calculated. The data were analyzed using analysis of variance (ANOVA) and Scheffe's post hoc test.

RESULTS

The results indicated that each of the inter-abutment and intra-abutment dimensions of the stone models was significantly higher than those for the stainless steel model (p < 0.001). However, there was no statistically significant difference in each of the inter-abutment and intra-abutment dimensions of the stone models among the four tested groups (p < 0.05).

CONCLUSION

The results obtained were statistically analyzed and the values of the inter-abutment and intra-abutment dimensions were all within the clinically acceptable range.

CLINICAL SIGNIFICANCE

Intermixing brands of additional silicone impression materials evaluated in this study did not affect the dimensional accuracy of obtained stone casts. This will help to minimize the wastage of materials due to lack of either light or putty consistency of the same brand of additional silicone impression material.

Multibracket appliance: impression defaults and their reduction by blocking-out - a three-dimensional study

OBJECTIVES

This study examines accuracy of dental impressions and following plaster models taken during treatment with fixed appliances.

MATERIALS AND METHODS

A maxillary typodont was provided with brackets. Three examiners took impressions three times each of the variants: brackets only, archwire fixed by alastics, ligatures or Kobayashi-hooks, and brackets and archwire covered completely or just on the gingival side by protection or impression wax. Casts were scanned using Activity102(®). Virtual models were compared to the scan of the typodont using Comparison(®). Differences were measured and descriptively analyzed. Estimated means with 95% confidence intervals were computed. Significance was assessed using linear mixed models.

RESULTS

While pyramidal reference blocks had a mean difference of 0.019 mm (95% CI = 0.017-0.021 mm) to the master model, teeth without attachments showed 0.097 mm (95% CI = 0.082-0.111 mm), and teeth with brackets 0.169 mm (95% CI = 0.156-0.182 mm) (p < 0.001). Smallest mean was found when using protection wax only on the gingival bracket side (0.152 mm (95% CI = 0.113-0.192 mm)). Incisors deviated most (0.258 mm (95 % CI = 0.239-0.277 mm)).

CONCLUSIONS

Teeth with brackets make impressions more inaccurate because of undercuts. Removing the archwire before taking the impression or covering the brackets on the gingival side shows tendencies toward better precision.

CLINICAL RELEVANCE

Taking impressions during treatment with fixed appliances, some inaccuracy has to be taken into account.

Use of Clinical UV Chamber to Disinfect Dental Impressions: A Comparative Study

INTRODUCTION

Dental impressions are potential source of infection in a prosthodontic practice. Risk of transmission of infection through saliva, blood etc is considered as hazard for both dentist as well as dental auxiliary staff. A number of methods are currently employed for disinfecting the impressions which are technique sensitive and time consuming. This study focuses on disinfecting impression using dental UV chamber which is commonly employed for storing sterilized instruments.

AIM

The aim of this invitro study was to evaluate the use of clinical UV chamber to disinfect various impression materials at different time intervals and its comparison with 2% glutaraldehyde using standard immersion technique.

MATERIALS AND METHODS

Total sample size of 180 specimens was taken from three different impression materials. The impressions were made from 30 dentulous subjects. A total of ten impressions were made for each impression material i.e. alginate, addition silicone and polyether impression material. Six punch samples were taken from each impression. Out of 6 punch sample, one was kept as control, second was disinfected by immersing in freshly prepared 2% glutaraldehyde solution for 10 minutes and remaining four were exposed to UV rays for 3 minutes, 6 minutes, 10 minutes and 15 minutes using dental UV chamber. Amount of disinfection achieved was evaluated by counting the colonies over the culture plates with the help of digital colony.

RESULTS

The results showed that the mean CFUs for alginate were found to be i.e. 11797.40 ± 5989.73 (mean ± SD). The mean CFUs for addition silicone impression material was found 7095.40 with a standard deviation of 4268.83 and the mean CFUs for polyether impression material was found to be 2168.92 ± 1676 (mean ± SD).

CONCLUSION

For alginate and addition silicone impression material, disinfection was achieved on exposure to UV rays for a period of 10 minutes. However, for polyether impression material 3 minutes of exposure to UV rays was sufficient to cause complete disinfection.

Evaluation of defects in surface detail for monophase, 2-phase, and 3-phase impression techniques: an in vitro study

STATEMENT OF THE PROBLEM

Polyvinyl siloxane materials of various consistencies have been tested to reduce defects commonly associated with different definitive impression techniques.

PURPOSE

The purpose of this in vitro study was to compare the number of visible defects within the surface of a new 3-phase, 2-step impression injection technique with the number found in the monophase and in the conventional 2-phase, 1-step and 2-phase, 2-step impression techniques.

MATERIAL AND METHODS

Two complete crown abutment preparations were impressed 10 times for each of these 4 techniques, which gave 20 abutment impressions for each group. The 3-phase, 2-step impression--injection technique included extra-light--body impression material added for the impression and injected after reinsertion. After the removal of all of these impressions, an examiner counted the number of open voids and bubble-like enclosed voids visible to the naked eye at a working distance of approximately 150 mm. Only the defects in the area of the prepared abutments were included in the assessment.

RESULTS

The frequency of defects ranged from 100% of the impressions in the monophase group to 5% with the new 3-phase, 2-step impression injection technique. No statistical differences were seen between the two 2-phase (1-step and 2-step) impression techniques, although there were numerically fewer impressions with defects with 2 steps (45%) than with 1 step (55%). The 3-phase, 2-step impression injection technique had the greatest accuracy, with fewer specimens with defects (5%) than with either of the 2-phase techniques, although these differences did not reach statistical significance.

CONCLUSIONS

The 3-phase, 2-step impression injection technique provides improved defect-free reproduction of detail, showing fewer defects than other impression techniques.

Characterization of morphology and composition of inorganic fillers in dental alginates

Energy dispersive X-ray spectroscopy microanalysis (EDX), scanning electron microscopy (SEM), and Archimedes' Principle were used to determine the characteristics of inorganic filler particles in five dental alginates, including Cavex ColorChange (C), Hydrogum 5 (H5), Hydrogum (H), Orthoprint (O), and Jeltrate Plus (JP). The different alginate powders (0.5 mg) were fixed on plastic stubs (n = 5) and sputter coated with carbon for EDX analysis, then coated with gold, and observed using SEM. Volume fractions were determined by weighing a sample of each material in water before and after calcining at 450^°C for 3 h. The alginate materials were mainly composed of silicon (Si) by weight (C—81.59%, H—79.89%, O—78.87%, H5—77.95%, JP—66.88%, wt). The filler fractions in volume (vt) were as follows: H5—84.85%, JP—74.76%, H—70.03%, O—68.31%, and C—56.10%. The tested materials demonstrated important differences in the inorganic elemental composition, filler fraction, and particle morphology.

A Comparative Evaluation of Dimensional Accuracy and Surface Detail Reproduction of Four Hydrophilic Vinyl Polysiloxane Impression Materials Tested Under Dry, Moist, and Wet Conditions-An In Vitro Study

Vinyl polysiloxane (VPS) impression materials have application in a wide variety of situations in both fixed and removable prosthodontics. A major limitation of VPS impression materials is their hydrophobicity. There are two aspects of this problem, the wettability of the polymerized impression by dental gypsum materials and the ability of the unpolymerized material to wet intraoral tissues. To address this problem, manufacturers have added surfactants and labelled these new products as "hydrophilic vinyl polysiloxane." The purpose of this study was to evaluate and compare dimensional accuracy and surface detail reproduction of four hydrophilic VPS impression materials, when used under dry, moist, and wet conditions. A total of 180 samples were made of stainless steel die similar to as described in ADA sp. no. 19. The die was scored with three horizontal and two vertical lines. Impressions were made under dry, moist and wet conditions. Dimensional accuracy was measured by comparing the length of the middle horizontal line in each impression to the same line on the metal die, by using Universal Length Measuring machine. A 2-way ANOVA was performed on the percentage change data for measured lengths of the 4 impression materials under the 3 conditions to evaluate dimensional accuracy. Surface detail was evaluated in two ways: (1) by use of criteria similar to ADA sp. no. 19 for detail reproduction, and (2) by use of a method that categorized the impressions as satisfactory or unsatisfactory based on their surface characteristics: presence of pits, voids, or roughness. Pearson X2 (α = 0.05) was used to compare surface detail reproduction results. Conditions (dry, moist, and wet) did not cause significant adverse effects on the dimensional accuracy of all the four material. With both surface detail analyses, dry, moist, and wet conditions had a significant effect on the detail reproduction of all the four materials (P < 0.05). The study concluded that the dimensional accuracy of all the four impression materials tested was well within ADA standards. Best surface detail results were obtained only under dry conditions for all the four materials.

Dimensional stability of polyvinyl siloxane impression material reproducing the sulcular area

The dimensional stability of a thin intra sulcular impression material reproducing the preparation finish line was evaluated. Impressions were taken of a stainless-steel master model of a simulated abutment with a 'gingival sulcus' using Express regular, Express fast and Aquasil. The putty-wash two-step technique was applied with spacer thicknesses of 0.5, 1 and 1.5 mm. Mid mesiodistal and bucco-lingual measurements were taken directly from the sulcular impression material after 0.5, 2, 24, 48 and 72 h via a Toolmaker's microscope. The discrepancies between the measurements of the impression material and the master model were calculated. The discrepancies changed significantly over time (p<0.001). The use of a 0.5 mm spacer resulted in a negative deviation from the model (2-46 µm), minimally after 2 h. The use of 1 and 1.5 mm spacers showed a positive deviation from the model (21-52 µm) and both are equally recommended. Investment can be postponed until 72 h.

The effect of one-step vs. two-step impression techniques on long-term accuracy and dimensional stability when the finish line is within the gingival sulcular area

PURPOSE

To evaluate the effect of two putty-wash impression techniques on the long-term accuracy and dimensional stability of poly(vinyl siloxane) (PVS) in the gingival sulcus area.

MATERIALS AND METHODS

Impressions were taken from a master cast to simulate molar crown preparation. A space around the abutment served as the gingival sulcus. Fifteen impressions using the one- and two-step impression techniques were taken using Express Regular, Express Fast, and President impression materials with custom trays. Using a Toolmaker's microscope, the long (LD) and short distances (SD) of the abutment and the planar distance between two parallel lines (PL) at the circumference of the cast were taken at 0.5, 2, 24, 48, 72, 96, 120, and 144 hours after mixing. ANOVA was performed, with the discrepancy between the distances of the impressions and the master cast as the dependent variable.

RESULTS

The differences when different materials and impression techniques were used were significant (p < 0.001) for LD, SD, and PL, as was the interaction between the material, time, and technique (p < 0.001). SD discrepancies were higher than those of LD for all materials and times. The two-step impression technique was more accurate, with smaller discrepancies than the one-step impression technique. For all materials, the PL discrepancy was deemed acceptable (less than 0.5%) for all tested times. President had higher discrepancies than the other materials.

CONCLUSIONS

When using the two-step putty-wash impression technique, pouring of the impressions may be postponed up to 30 hours; however, when using the one-step impression technique, pouring should be performed within 2 hours.

Influence of delayed pouring on irreversible hydrocolloid properties

The aim of this study was to evaluate the physical properties of irreversible hydrocolloid materials poured immediately and after different storage periods. Four alginates were tested: Color Change (Cavex); Hydrogum (Zhermack); Hydrogum 5 (Zhermack); and Hydro Print Premium (Coltene). Their physical properties, including the recovery from deformation (n = 3), compressive strength (n = 3), and detail reproduction and gypsum compatibility (n = 3), were analyzed according to ANSI/ADA specification no. 18. Specimens were stored at 23ºC and humidity and were then poured with gypsum immediately and after 1, 2, 3, 4, and 5 days. The data were analyzed by two-way analysis of variance (ANOVA) and Tukey's test at p < 0.05. All of the alginate impression materials tested exhibited detail reproduction and gypsum compatibility at all times. Hydro Print Premium and Hydrogum 5 showed recovery from deformation, as established by ANSI/ADA specification no. 18, after 5 days of storage. As the storage time increased, the compressive strength values also increased. Considering the properties of compounds' recovery from deformation, compressive strength, and detail reproduction and gypsum compatibility, irreversible hydrocolloids should be poured immediately.

Comparison of the surface roughness of gypsum models constructed using various impression materials and gypsum products

Background/purpose

This study compared the surface roughness of gypsum models constructed using various impression materials, gypsum products, and storage times before repouring.

Materials and methods

Three alginate impression materials, four commercial silicone impression materials, and three types of gypsum product (MG crystal rock, Super hard stone, and MS plaster) were used. Impression materials were mixed and poured into five plastic rings (20 mm in diameter and 2 mm high) for each group, and the surfaces of the set gypsum product models of 63 groups, which were poured immediately, and 1 hour and 24 hours later, were assessed using a surface roughness tester. One-way ANOVA and Bonferroni's comparison tests were used for the statistical analyses.

Results

The surface roughness: (1) was greater for most specimens constructed from alginate impression material (2.72 ± 0.45–7.42 ± 0.66 μm) than from silicone impression materials (1.86 ± 0.19–2.75 ± 0.44 μm); (2) differed with the type of gypsum product when using alginate impression materials (surface roughness of Super hard stone > MG crystal rock > MS plaster), but differed little for silicone impression materials; and (3) differed very little with the storage time before repouring.

Conclusion

The surface roughness of stone models was mainly determined by the type of alginate impression material, and was less affected by the type of silicone rubber impression material or gypsum product, or the storage time before repouring.

Effects of the space for wash materials on sulcus depth reproduction with addition-curing silicone using two-step putty-wash technique

Aim of this study was to investigate effects of space thickness and consistency of wash materials on sulcus depth reproduction with silicone impressions, low (L), medium (M), and very high consistency (VH), using two-step putty-wash technique. Impressions were taken from truncated cones with 50-, 100-, or 200-μm-wide sulci, using the combinations L+VH or M+VH and different space thickness for wash materials: 2 mm (ST2), 1 mm (ST1), and approximately 25 μm (ST0.025). Sulcus depth reproduction tended to increase with increasing sulcus width. Sulcus reproduction of ST0.025 was deeper than those of the other groups. At 100- and 200-μm sulcus widths, sulcus reproductions of ST1 and ST2 with L+HV were deeper than with M+HV. Regardless of consistency, the thin spacer produced deep reproduction. Adequate 0.5 mm sulcus reproductions were obtained with 100 and 200 μm wide sulci and 1- and 2-mm spacer widths, combined with low consistency impression material.

Surface detail reproduction and dimensional accuracy of stone models: influence of disinfectant solutions and alginate impression materials

This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds disinfected with 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to models produced using molds which were not disinfected, with 3 alginate materials (Cavex ColorChange, Hydrogum 5 and Jeltrate Plus). The molds were prepared over matrix containing 20-, 50-, and 75-µm lines, performed under pressure with perforated metal tray. The molds were removed following gelation and either disinfected (using one of the solutions by spraying followed by storage in closed jars for 15 min) or not disinfected. The samples were divided into 12 groups (n=5). Molds were filled with dental gypsum Durone IV and 1 h after the start of the stone mixing the models were separated from the tray. Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-µm line with 25 mm in length, in accordance with the ISO 1563 standard. The dimensional accuracy results (%) were subjected to ANOVA. The 50 µm-line was completely reproduced by all alginate impression materials regardless of the disinfection procedure. There was no statistically significant difference in the mean values of dimensional accuracy in combinations between disinfectant procedure and alginate impression material (p=0.2130) or for independent factors. The disinfectant solutions and alginate materials used in this study are no factors of choice regarding the surface detail reproduction and dimensional accuracy of stone models.

Accuracy of Single-Step versus 2-Step Double-Mix Impression Technique

Objective. To investigate the accuracy of dies obtained from single-step and 2-step double-mix impressions. Material and Methods. Impressions (n = 10) of a stainless steel die simulating a complete crown preparation were performed using a polyether (Impregum Soft Heavy and Light body) and a vinyl polysiloxane (Perfectim Blue Velvet and Flexi-Velvet) in two consistencies, in one or two (without relief) steps. Accuracy of the stone dies was accessed at a measuring microscope, using a metallic crown with perfect fit to the reference crown preparation. Data were submitted to 2-way ANOVA and Tukey test (α = 0.05). Results. The single-step technique resulted in slightly larger dies, while the 2-step technique without relief produced significantly smaller dies, when compared to the original stainless steel die. Stone dies obtained from 2-step polyether impressions were significantly smaller when compared to dies obtained from 2-step vinyl polysiloxane impressions (Impregum 2-step: -290.94 ± 71.64 μm; Perfectim 2-step: -201.86 ± 28.58 μm). No significant differences were observed in dies obtained from either polyether or vinyl polysiloxane with the single-step technique (Impregum single-step: 63.52 ± 16.60 μm; Perfectim single-step: 79.40 ± 14.11 μm). Conclusion. Higher discrepancies were detected for the 2-step impression technique without relief for the investigated materials.

Linear dimensional accuracy of a polyvinyl siloxane of varying viscosities using different impression techniques

AIM

The present study is an in vitro study to evaluate the linear dimensional accuracy of commercially available polyvinyl siloxanes of varying viscosities using different impression techniques.

METHODS

Different impression techniques used were: (a) putty wash, with a two-step technique with polyethylene spacer, using a stock tray; (b) putty wash, with a one-step technique, using a stock tray; (c) single-mix technique, utilizing medium viscosity in a custom tray; and (d) multiple-mix technique, utilizing a heavy- and low-viscosity combination in a custom tray. For each technique, 10 impressions were made of a metallic maxillary dentulous master model.

RESULTS

The result of this study dictates that a heavy- and low-viscosity combination, double-mix technique in a custom tray produced an accurate result in all dimensions, followed by the single-mix technique, utilizing medium viscosity in a custom tray, and the putty wash two-step technique with polyethylene spacer, using a stock tray. Group 2 putty wash, one-step, simultaneous technique produced the least accurate result in all dimensions.

CONCLUSION

The putty wash two-step techniques were found to be as accurate as the multiple-mix technique, utilizing a heavy- and low-viscosity combination in a custom tray, and the single-mix technique, utilizing medium viscosity in a custom tray. Making custom trays is time consuming and costly.

A new paradigm for operative dentistry

It is over 100 years since G V black gathered together most of the knowledge then current on the caries process and set clear parameters for the discipline of operative dentistry. His four-volume treatise set standards that were relevant for the times and, in fact, were so well described that they remained dominant in this discipline until quite recently. However, over the last 50 years there has been great progress in scientific method and in knowledge of the common diseases of the oral environment, including the caries process, so maybe it is time for change. The term “paradigm” describes a philosophy of science, a generally accepted model of how ideas relate to one another, forming a conceptual framework within which scientific research is carried out. Black defined the paradigm within which further research was to be conducted during the following years and the profession accepted his lead. However, it is not expected that the parameters of a profession should remain unchanged over a substantial period so it is suggested that the dental profession should, at this time, recognize a new paradigm. Improvements in scientific method have led to a better understanding of the oral environment, resulting in extensive changes for this profession. It is suggested that the standards set by Black should be now consigned to history and an entirely new paradigm adopted. First, the profession must recognize that dental caries is a bacterial disease and its primary efforts should be directed towards identification and elimination of the disease prior to initiating repair of the damage that it has caused. Preservation of natural tooth structure is then the next responsibility. There should be maximum use made of preventive strategies, including remineralization, followed by minimal intervention cavity designs and the use of bioactive restorative materials to restore the lesions. The profession should be prepared to move on.

Effect of storage period on the accuracy of elastomeric impressions

Aims:

To investigate the effect of the storage period on the accuracy of recently developed elastomeric materials.

Methods:

Simultaneous impressions of a steel die were taken using a polyether (I: Impregum Soft Heavy and Light body, 3M ESPE) and vinyl polysiloxane (P: Perfectim Blue Velvet and Flexi-Velvet, J.Morita). The trays were loaded with the heavy-bodied impression materials while the light-bodied impression materials were simultaneously spread on the steel die. The impressions were poured after 2 hours, 24 hours, and 7 days. Impressions were stored at approximately 55% relative humidity and room temperature. Ten replicas were produced for each experimental condition (n=60). Accuracy of the stone dies was assessed with a depth-measuring microscope. The difference in height between the surface of the stone die and a standard metallic ring was recorded in micrometers at four demarcated points, by two independent examiners. Dxata were submitted to two-way ANOVA and Tukey test (α = 0.05).

Results:

Significant differences were found among the groups. Smaller discrepancies were observed when pouring was performed up to 24 hours (I-2h= 65.0 ± 15.68 μm; I-24h= 81.6 ± 11.13 μm) for the polyether, and up to 7 days for the vinyl polysiloxane (P-2h= 79.1 ± 13.82 μm; P-24h= 96.8 ± 6.02 μm; P-7d= 81.4 ± 4.3 μm). Significant dimensional discrepancies, however, were observed when polyether was stored for 7 days (I-7d= 295.3 ± 17.4 μm).

Conclusion:

Storage may significantly affect the dimensional accuracy of impressions and, thus, a maximum period and storage condition should be specified for the recently developed materials.

The dynamic interaction of water with four dental impression materials during cure

PURPOSE

The purpose of this work was to investigate the interaction of water with four different dental impression materials: Aquasil (Ultra XLV Type 3), Take 1 (Wash Regular Set), Genie (Light Body, Standard Set), and Impregum Garant (Soft Light Bodied Consistency).

MATERIALS AND METHODS

Apparent contact angles of de-ionized water made against thin horizontal sample films of the different materials under different conditions were measured from analysis of profile images of symmetrical sessile drops of water placed on the sample films using a Model FTA200 dynamic drop shape analysis system, which included a JAI M30 high speed CCD camera combined with a zoom microscope. Data were taken for specimens of dry ages (times following mixing) from a minimum of 20 seconds up to 1220 seconds. Imaging was started before the initial water/impression material contact, and lasted for at least 420 seconds in each case. The interval at the beginning of each run was 0.033 second, and then increased by a factor of 1.012 to the end. During the initial 3 seconds following the drop deposition, the drop's shape oscillated due to inertial effects, so apparent contact angle data during this period were neglected in all cases. All measurements were made at room temperature. The drops were enclosed in a humidified chamber that suppressed evaporation. All data were repeated at least five times, and results were analyzed where appropriate using one-way ANOVA. Microscopic images of the water/impression material interactions for fresh (uncured) materials were acquired to reveal the destructive interactions that resulted from such contact. Finally, surface tension measurements were made of water that had been contacted with material of varying dry age using the pendant drop method capability of the drop shape analysis system. These helped to assess the origin of hydrophilicity development for the different materials.

RESULTS

For short curing times (dry ages), water showed a destructive effect on the integrity of all of the impression materials, as evidenced by the formation of a crater beneath the water drop and a scum of material at its surface. These effects diminished with dry age until a critical curing time was reached, beyond which such destructive interactions were no longer detectable. These critical curing times were determined to be 80, 140, 110, and 185 seconds for Aquasil, Take 1, Genie, and Impregum, respectively. The initial contact angle following the respective critical curing time was lowest for Impregum, at 66 degrees ; while values for Aquasil, Genie, and Take 1 were 93 degrees , 104 degrees , and 110 degrees , respectively. Beyond the critical curing times for the different materials, different degrees of hydrophilicity were observed. Aquasil showed the lowest final contact angle (<10 degrees ), with Impregum, Take 1, and Genie showing 31 degrees , 34 degrees , and 40 degrees , respectively. Measurements of the surface tension of water after contact with the different materials suggested that for Aquasil, hydrophilicity appears to be developed through the leaching of surfactant from the material, whereas for Impregum, Take 1, and Genie, hydrophilicity is developed at least in part through a change in surface structure in contact with water. Impregum and Aquasil materials of dry ages well beyond the critical curing time exhibited a stick-slip behavior in their interline movement or contact angle evolution. This was believed to be due to the slowness in the leaching of surfactant (in the case of Aquasil) or the re-orientation of unleachable surface groups (in the case of the other materials) in comparison to the inherent kinetics of water drop spreading.

CONCLUSIONS

All materials investigated in the fresh, uncured state showed qualitative decomposition when put in contact with water through the formation of a crater beneath the water drop and a scum of material at its surface. These effects diminished with curing time until beyond a critical value, no such effects were evident. The initial hydrophilicity of the materials as determined by the contact angles obtained at their respective critical dry ages was greatest for Impregum. Beyond the critical curing time, different degrees of hydrophilicity were observed, with Aquasil showing the lowest final contact angle.

Dimensional accuracy of resultant casts made by a monophase, one-step and two-step, and a novel two-step putty/light-body impression technique: an in vitro study

STATEMENT OF PROBLEM

Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy.

PURPOSE

The purpose of this in vitro study was to compare the dimensional accuracy of a monophase, 1- and 2-step putty/light-body, and a novel 2-step injection impression technique.

MATERIAL AND METHODS

A stainless steel model with 2 abutment preparations was fabricated, and impressions were made 15 times with each technique. All impressions were made with an addition-reaction silicone impression material (Aquasil) and a stock perforated metal tray. The monophase impressions were made with regular body material. The 1-step putty/light-body impressions were made with simultaneous use of putty and light-body materials. The 2-step putty/light-body impressions were made with 2-mm-thick resin-prefabricated copings. The 2-step injection impressions were made with simultaneous use of putty and light-body materials. In this injection technique, after removing the preliminary impression, a hole was made through the polymerized material at each abutment edge, to coincide with holes present in the stock trays. Extra-light-body material was then added to the preliminary impression and further injected through the hole after reinsertion of the preliminary impression on the stainless steel model. The accuracy of the 4 different impression techniques was assessed by measuring 3 dimensions (intra- and interabutment) (5-mum accuracy) on stone casts poured from the impressions of the stainless steel model. The data were analyzed by 1-way ANOVA and Student-Newman-Keuls test (alpha=.05).

RESULTS

The stone dies obtained with all the techniques had significantly larger dimensions as compared to those of the stainless steel model (P<.01). The order for highest to lowest deviation from the stainless steel model was: monophase, 1-step putty/light body, 2-step putty/light body, and 2-step injection. Significant differences among all of the groups for both absolute dimensions of the stone dies, and their percent deviations from the stainless steel model (P<.01), were noted.

CONCLUSIONS

The 2-step putty/light-body and 2-step injection techniques were the most dimensionally accurate impression methods in terms of resultant casts.

Investigating solid waste production and associated management practices in private dental units

In the municipality of Thessaloniki in 2006 mercury-bearing dental wastes were not managed properly by 80% of dentists and metal-bearing waste was handled in accordance with internationally established best management practices by less than 50% of dentists. Those results were documented through a biennial field-based research study that took place in private dental units within the Thessaloniki Urban Area. For quantifying the waste produced, structured questionnaires were used and interviews with dentists were performed. In the present work, results of this survey are presented; critical parameters and factors affecting the quantity and quality of the dental waste stream are reported together with the analysis and classification of dominant conditions and needs of the dental sector in the waste management field.

An Experimental Study on Particular Physical Properties of Several Interocclusal Recording Media. Part III: Resistance to Compression After Setting

PURPOSE

The purpose of this study was to evaluate the resistance to compression after setting of several elastomeric interocclusal recording materials.

MATERIALS AND METHODS

Testing of the resistance to compression after setting was performed following a modification of the method described in specification No. 19 (4.3.6) of the A.D.A., for the elastomeric impression materials-1 cylindrical stainless steel mold with an internal diameter of 20 mm and a height of 20 mm was constructed. Mixing of the interocclusal registration media was conducted according to manufacturers' instructions, and the materials were injected into the mold. Two subsequent loads, one of 100 g/cm2 and a second of 1000 g/cm2 were exerted on each sample. The deformation of each was calculated using a vertical traveling micrometer microscope with an accuracy of +/- 0.001 mm.

RESULTS

One-way ANOVA revealed significant differences among the materials (F=331.58, p <0.0005). Tukey's HSD (p <0.05) test was used to determine the significant differences between the materials.

CONCLUSIONS

Polyvinylsiloxane Blu Mousse displayed the greatest resistance to compression, as compared to other elastomeric interocclusal recording materials tested.

An Experimental Study on Particular Physical Properties of Several Interocclusal Recording Media. Part II: Linear Dimensional Change and Accompanying Weight Change

PURPOSE

The purpose of this study was to evaluate the linear dimensional change and accompanying weight change of several elastomeric interocclusal recording media.

MATERIALS AND METHODS

Ten 50 mm long, 8 mm wide, 3 mm deep Teflon molds and a stainless steel die were constructed for the purposes of this study. The die was made in order to produce standardized reference lines, which were used for the measurement of the linear change. After homogeneous mixing, each material was carried from the mixing pad or directly from the mixing tip to the Teflon mold. The mold was inverted onto the stainless steel die. The materials were allowed to set for the manufacturers' suggested setting time plus an additional 3 minutes to ensure polymerization of the material. An electronic scale (Galaxy 110, Ohaus, Pine Brook, NJ) was used for the measurement of the weight change of the specimens and a traveling micrometer microscope (Griffin Ltd., London, England) was used to measure the linear changes at 5 time intervals: 0, 1 hour, 24, 48, and 72 hours.

RESULTS

Analysis of variance for a significance level of 5% revealed that there was a statistically significant effect of the "material" factor on the weight changes (F= 2,229.98, p < 0.0005). There was also a statistically significant effect of the "time" factor on the weight changes (F= 2,332.04, p < 0.0005). Descriptive statistics and Tukey's Honest Significant Difference Test revealed that the elastomeric material with the greatest weight changes is polyether (Ramitec). Analysis of variance for a significance level of 5% revealed that there is a statistically significant effect of the "material" factor on the linear changes (F= 215.54, p < 0.0005). There is also a statistically significant effect of the "time" factor on the linear changes (F= 1,996.01, p < 0.0005). Descriptive statistics and Tukey's Honest Significant Difference test revealed that the elastomeric material with the smallest linear changes is polyether (Ramitec).

CONCLUSIONS

Of all materials tested, Ramitec (polyether) presented the smallest linear change at all time intervals. Addition reaction silicones presented statistically significant differences in recordings of linear changes among them only at the 1st and the 24th hour. Linear changes did not seem to be associated with weight changes.

Accuracy of three polyvinyl siloxane putty-wash impression techniques

STATEMENT OF PROBLEM

There is much discussion in the dental literature concerning the effect of the impression technique on the accuracy of cast restorations.

PURPOSE

This study assessed the accuracy of 3 putty-wash impression techniques using the same impression material (polyvinyl siloxane) in a laboratory model.

MATERIAL AND METHODS

The 3 putty-wash impression techniques used were (1) 1-step (putty and wash impression materials used simultaneously); (2) 2-step with 2-mm relief (putty first as a preliminary impression to create 2-mm wash space with prefabricated copings. In the second step, the wash stage was carried out); and (3) 2-step technique with a polyethylene spacer (plastic spacer used with the putty impression first and then the wash stage). For each technique, 15 impressions were made of a stainless steel master model that contained 3 complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring 6 dimensions (intraabutment and interabutment) on stone dies poured from impressions of the master model.

RESULTS

One-way analysis of variance showed statistically significant differences among the 3 putty-wash impression techniques, for all intraabutment and interabutment measurements (P <.001). Overall discrepancies of the 2-step technique with 2-mm relief putty-wash impression technique were significantly smaller than that in the 1-step and polyethylene putty-wash impression techniques.

CONCLUSION

The polyvinyl siloxane 2-step, 2-mm, relief putty-wash impression technique was the most accurate for fabricating stone dies.

The effects of different storage conditions on polyether and polyvinylsiloxane impressions

While being shipped to a laboratory, impressions can be exposed to excessive temperatures. This study compared the effects of different time and temperature storage conditions, including temperature extremes of 66 C and -10 C, on the accuracy of addition silicone and polyether impressions. The greatest distortion generally occurred as a result of the 66 C temperature extreme. The authors recommend that impressions be poured in stone according to manufacturers' specifications before being shipped to a dental laboratory.

Comparison of the dimensional accuracy of one- and two-step techniques with the use of putty/wash addition silicone impression materials

This study compared the putty/wash one-step and two-step techniques for making addition silicone impressions. For each technique 15 impressions were made of a stainless steel base to which three tapered posts were attached. Stone models were made of all impressions. The results indicated that the interabutment distances increased slightly compared with the stainless steel model for both techniques, but the differences between techniques were not considered to be clinically important. The intraabutment measurements for the abutment without undercut increased, whereas abutments with undercuts decreased. These variations from the stainless steel model were also clinically insignificant.

Effects of the setting stage on the accuracy of double-mix impressions made with addition-curing silicone

This study investigated the accuracy of double-mix impressions relative to the time of placing the tray impression material on preparations covered with medium-viscosity silicone. The curing kinetics of the addition-curing silicone impression materials and the accuracy of impressions were investigated. The observed kinetics showed the possibility of the appearance of elastic characteristics of the syringed material before the tray impression was placed. The accuracy of the impressions was not statistically different unless the setting reactions had progressed so that the consistencies of both the syringed and the tray impression were high. These results indicated that the double-mix impression was accurate independent of the curing kinetics of the syringed material alone.

Viscosity of monophase addition silicones as a function of shear rate

The viscosity of monophase addition silicone impression materials was measured as a function of shear rate. The setting of mixed catalyst and base was prevented by addition of a small amount of phenyl propiolic acid. All products showed a 6- to 10-fold decrease in viscosity with an increasing shear rate (shear thinning). The addition of phenyl propiolic acid had little or no effect on the viscosity of three materials. However, when added to the catalyst or base only of two products, it increased their viscosity and exaggerated the shear thinning effect.

Accuracy of one-step versus two-step putty wash addition silicone impression technique

This study compared the accuracy of one-step putty wash with two-step putty wash impression techniques. Five addition silicone impression materials-Mirror 3 (MR), Mirror 3 Extrude (ME), Express (E), Permagum (P), and Absolute(A)--were tested. A stainless steel model containing two full-crown abutment preparations was used as the positive control. Five replications for one-step and two-step putty wash impressions of the master model were made for each test material. Accuracy of the materials was assessed by measuring six dimensions on stone dies poured from impressions of the master model. Accuracy of addition silicone impression material is affected more by material than technique. Accuracy of the putty wash one-step impression technique was not different from the putty wash two-step impression technique except at one of the six dimensions where one-step was more accurate than two-step. Mirror 3 putty wash two-step impression presented less distortion than Mirror 3 Extrude putty wash one-step or two-step impression.

Properties of a new polyether urethane dimethacrylate photoinitiated elastomeric impression material

The photoinitiated impression material is supplied premixed as a light-bodied material in a light-tight plastic syringe and as a heavy-bodied material in a tube. The impression material has excellent physical, mechanical, and clinical qualities with noteworthy long working times, short setting times, dimensional stability, accuracy, high tear strength, good wettability, biocompatibility, and ease of cold disinfection without loss of quality. The impression material is also compatible with gypsum and silver or copper metallizing baths. Accurate casts can be obtained by means of either a double-impression technique or a double-mix technique.