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

Modified Two-Step Impressions via the Incorporation of Venting Holes: A Technical Report

This study presents a methodology for obtaining a precise impression of the crown margin of prepared teeth by utilizing a two-step impression technique. The method begins with the fabrication of a custom tray made from heat-cured acrylic resin, followed by the acquisition of an initial impression using putty elastomeric material. Subsequently, the impression is relieved around the prepared teeth, and vent holes are strategically placed through both the impression and the tray. Finally, a light-body consistency impression material is applied. This streamlined technique enhances efficiency and minimizes the errors commonly encountered with traditional two-step impression methods.

Effect of different impression techniques on marginal fit of restoration - An In Vitro study

Introduction

Impression making is one such important clinical step, which is critical in the accurate fitting of resulting prostheses. Impression making itself depends on the type of material and the impression technique used to record the details. Various combinations of material and the technique have been described in the literature.

Aim

To evaluate the effect of three different impression techniques on the marginal fit of computer-aided designed/computer-aided manufactured (CAD/CAM) single unit composite fixed dental prostheses (FDP), different consistencies of addition silicone impression material and different tray design were utilized.

Method

Impression of prepared tooth on typodont was made using Matrix impression system, two-step putty wash technique, and individual tooth tray technique. Prosthesis was fabricated using CAD/CAM technology and marginal accuracy was evaluated using scanning electron microscopy (SEM).

Result

In the present study, the matrix impression system resulted in less microgap in both mid-buccal and mid-mesial region, whereas putty wash technique showed very high standard deviation in the interproximal region.

Conclusion

Matrix impression system had the best results at both mid-buccal and mid-mesial position with least marginal discrepancy.

Clinical Implication

The findings of this study could be used by clinicians to help them choose the viscosity of polyvinylsiloxane material and impression techniques for FDP that will result in high-accuracy impressions and well-fitting prostheses.

Is a Wiggling-Motion Modified Two-Step Impression Technique as Accurate as Conventional Techniques in Restorative Dentistry?

BACKGROUND

The purpose of this study was to evaluate dental impression accuracy of one-step and two-step techniques compared to a modified two-step technique.

METHODS

Four impression techniques were compared: (1) a one-step double mix (DM) technique, (2) a cut-out (CO) technique, in which space relief was created using a blade and a laboratory bur, (3) a membrane (ME) technique, in which space relief was created by placing a PVC membrane on top of the putty material during the primary impression, and (4) a wiggling motion (WI) technique, in which PVC membrane was placed and additional wiggling movements were performed during the first 20 s when the primary impression was seated upon the master model (MM). Impressions were poured with type IV stone. Casts were scanned with a laboratory scanner and measurements were made for each cast using three-dimensional analysis software.

RESULTS

All groups presented differences compared to MM group, in at least one intra-abutment distance. Groups DM and ME presented the most significant differences, in three and two distances, respectively, whereas CO and WI presented one significant different distance compared to MM. There were no differences between MM and the four techniques for inter-abutment distances.

CONCLUSIONS

WI yielded similar results with CO technique. Both performed better than the other groups.

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.

Clinical evaluation of one-step impression technique and definitive casts

Background/Aim: The purpose of this study was to evaluate the quality of impressions made with vinyl polysiloxane (VPS) material in clinical conditions by using the one-step impression technique, and the quality of casts generated from these impressions. The effect of operator, number and location of abutments, and presence of bleeding were also investigated. Material and Methods: A total of 150 fixed dental prosthesis (FDP) impressions were taken and considered acceptable by 3 experienced prosthodontists in a clinic in an institutional setting. The impressions were evaluated and rated by another experienced prosthodontist and respective casts were evaluated and rated by an experienced dental technician using a digital microscope with ×200 magnification. The defects observed were noted as bubbles, voids, tears, or other defects. A scale was structured for the impressions and casts with ratings of Alpha (excellent; no defects), Bravo (acceptable; small defects), Charlie (inadequate; defects that require remaking of impression), and Delta (unacceptable; substantial defects at preparation finish lines). The data were analyzed with the Chi-square test for inter-operator, number of abutments, and location of prepared tooth variables (a=0.05). Results: The scale ratings were 85 Alpha (57%), 52 Bravo (34%), 6 Charlie (4%), and 7 Delta (5%) for the impressions, and 81 Alpha (54%), 58 Bravo (39%), 4 Charlie (3%), and 7 Delta (5%) for the respective casts. Sixty-nine percent of the impressions and respective casts were rated with the same score. The scale rating results were not influenced by inter-operator variability or number of abutments. Location of the prepared tooth was significant for anterior/posterior (p=0.04), but was not significant for maxilla/ mandible (p>0.05). Bleeding at the preparation site had a significant effect on the acceptability of the impression (p=0.003). Conclusions: The acceptability of VPS impressions using onestep technique was independent of the operator, number of abutments, or whether the prepared tooth was in maxilla or mandible. Impressions of teeth in the anterior region were more acceptable than those located in the posterior. Bleeding negatively affected the acceptability of the impressions. Clinicians may use VPS impressions for the fabrication of FDPs using onestep dual-phase technique. However, clinicians should carefully evaluate their impressions when bleeding is present when using this technique.

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.

Three-dimensional Change of Elastomeric Impression Materials During the First 24 Hours: A Pilot Study

OBJECTIVES

To evaluate the three-dimensional (3D) changes of three elastomeric impression materials using a novel measurement method for the first 24 hours after preparation.

METHODS AND MATERIALS

Three impression materials consisting of a low-viscosity polyvinyl siloxane (PVS) (Aquasil LV, Dentsply Sirona, Charlotte, NC, USA) and two vinyl polyether silicone (VPES) materials consisting of a light body (EXA'lence LB, GC America, Alsip, IL, USA) and monophase (EXA'lence Monophase, GC America) materials were used in this study. All materials were prepared following manufacturer's recommendations with approximately 1-2 millimeters of material placed on the measurement pedestal of a calibrated noncontact, video imaging based, volumetric change measuring device (AcuVol ver 2.5.9, Bisco, Schaumburg, IL, USA). Data collection was initiated immediately, with measurements made every 30 seconds for 24 hours. Each material was evaluated 10 times (n=10). Evaluated parameters included were 24-hour mean shrinkage, mean shrinkage at time of recommended first pour, mean shrinkage between recommended first pour and 24 hours, mean maximum shrinkage, and the time of maximum shrinkage. Mean data, both within and between each group, was evaluated using Kruskal-Wallis/Dunn's tests at a 95% level of confidence (α=0.05).

RESULTS

All three materials were found to have significant differences (p<0.001) in volumetric shrinkage over 24 hours. Aquasil LV and EXA'lence LB polymerization shrinkage rates were statistically similar all through the 24-hour evaluation (p=0.92). All three materials demonstrated similar (p=0.19) shrinkage between 10 and 15 minutes after preparation, while between 5 and 16 hours both EXA'lence Monophase and low-viscosity materials demonstrated similar polymerization shrinkage values (p=0.22). EXA'lence Monophase demonstrated significantly greater 24-hour mean shrinkage (p<0.008) as well as shrinkage between recommended first pour time and 24 hours (p=0.003) than Aquasil LV and EXA'lence LB. EXA'lence Monophase demonstrated significantly greater (p=0.002) shrinkage at the recommended time of first pour as compared to Aquasil LV and EXA'lence LB that displayed similar shrinkage (p=0.89). Furthermore, all materials demonstrated increasing polymerization shrinkage values that reached a maximum between 16 for Aquasil LV and 20 hours for EXA'lence LB, after which some relaxation behavior was observed. However, EXA'lence Monophase did not display any relaxation behavior over the 24-hour evaluation.

CONCLUSIONS

Under the conditions of this study, volumetric polymerization shrinkage was observed for one polyvinyl siloxane (PVS) and two vinyl polyether silicone (VPES) materials for up to 24 hours. All impression materials exhibited fast early volumetric shrinkage that continued past the manufacturer's recommended removal time. Dimensional change behavior was not uniform within or between groups; resultant volume change between the manufacturer recommended pouring time and 24 hours might represent up to from 20% to 30% of the total material shrinkage. It may be prudent to pour elastomeric impressions at the earliest time possible following the manufacturer's recommendations.

A dental revolution: The association between occlusion and chewing behaviour

Dentistry is confronted with the functional and aesthetic consequences that result from an increased prevalence of misaligned and discrepant dental occlusal relations in modern industrialised societies. Previous studies have indicated that a reduction in jaw size in response to softer and more heavily processed foods during and following the Industrial Revolution (1,700 CE to present) was an important factor in increased levels of poor dental occlusion. The functional demands placed on the masticatory system play a crucial role in jaw ontogenetic development; however, the way in which chewing behaviours changed in response to the consumption of softer foods during this period remains poorly understood. Here we show that eating more heavily processed food has radically transformed occlusal power stroke kinematics. Results of virtual 3D analysis of the dental macrowear patterns of molars in 104 individuals dating to the Industrial Revolution (1,700-1,900 CE), and 130 of their medieval and early post-medieval antecedents (1,100-1,700 CE) revealed changes in masticatory behaviour that occurred during the early stages of the transition towards eating more heavily processed foods. The industrial-era groups examined chewed with a reduced transverse component of jaw movement. These results show a diminished sequence of occlusal contacts indicating that a dental revolution has taken place in modern times, involving a dramatic shift in the way in which teeth occlude and wear during mastication. Molar macrowear suggests a close connection between progressive changes in chewing since the industrialization of food production and an increase in the prevalence of poor dental occlusion in modern societies.

Correlation between 2D and 3D measurements of cement space in CAD-CAM crowns

STATEMENT OF PROBLEM

Although the 2D analysis of prosthesis cementation space has been popular, its correlation with volumetric comparison (3D data) of cement space is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the cement space in computer-aided design and computer-aided manufacturing (CAD-CAM) crowns of different materials and correlate 2D measurements of cement space with their corresponding 3D values (volume of cement space) by using microcomputed tomography (μCT) analysis of regions of interest.

MATERIAL AND METHODS

Ten molar crowns were milled in lithium disilicate (LD), resin nanoceramic (RN), and zirconia (Z) ceramics. Silicone replicas were produced and used as the analog cement layer and scanned with a desktop X-ray microfocus CT scanner. Twenty-eight slices were evaluated in 3 regions: marginal, axial, and occlusal (n=84 measurement points/specimen). After 3D reconstruction of the cement space, the volume was calculated. Data were statistically evaluated through 2-way ANOVA and Bonferroni test (α=.05). The Pearson correlation test was used to investigate the correlation between the 2D and 3D data.

RESULTS

The volumes of the occlusal (LD 10 ±1 mm³; RN 9 ±1 mm³) and axial regions (LD 9 ±2 mm³; RN 8 ±1 mm³) were significantly higher than the volume of the marginal region for LD and RN specimens (LD 6 ±2 mm³; RN 4 ±1 mm³) (both P<.001). For the Z group, the axial region had the highest volume (19 ±2 mm³), followed by the volumes of the occlusal (15 ±1 mm³) and marginal regions (12 ±1 mm³). The Pearson correlation test determined a moderate positive correlation of the marginal area (r=0.606, P<.001) and of the axial region (r=0.588, P<.001). However, a moderate negative correlation was found between volume and thickness of the occlusal area (r=-0.437, P=.016).

CONCLUSIONS

Z showed more volume of cement space, as well as thicker cement space than LD and RN. The μCT analysis is an efficient method of analyzing cement thickness and volume in ceramic crowns at the selected regions of interest. A moderate positive correlation was found between the 2D and 3D analyses for the axial and marginal regions of ceramic crowns.

A Comparative Evaluation of Marginal Accuracy of Co-Cr Metal Copings Fabricated Using Traditional Casting Techniques and Metal Laser Sintering

Aims and objectives

The aim and objective of the study were to determine the amount of marginal discrepancy produced by cobalt-chromium (Co-Cr) copings fabricated using two different fabrication methods, i.e., traditional casting and direct metal laser-sintering (DMLS), and compare the values obtained between each fabrication technique and to evaluate if the fabrication technique can produce prosthesis that is within the standards of clinical acceptance of marginal discrepancy.

Materials and methods

Twenty metal copings each were fabricated by laser sintering and traditional casting method. The marginal gap at the buccal, lingual, mesial, and distal areas was measured using the silicone replica technique. The stereomicroscope and optical microscope were used to measure the marginal discrepancy between the working die and the copings. Statistical analysis was done using a t-test using Open-epi calculator software.

Results

The values indicate that the marginal gap was less for the copings fabricated using Co-Cr alloy crowns that were fabricated with direct metal laser-sintered technique than Co-Cr alloy crowns fabricated with conventional casting technique.

How to cite this article

Gautam N, Khajuria RR, Ahmed R, et al. A Comparative Evaluation of Marginal Accuracy of Co-Cr Metal Copings Fabricated Using Traditional Casting Techniques and Metal Laser Sintering. Int J Clin Pediatr Dent 2021;14(1):128-132.

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.

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.

A Comparative Study to Evaluate the Accuracy of Various Spacer Thickness for Polyvinyl Siloxane Putty-wash Impression Techniques: An In Vitro Study

INTRODUCTION

An accurate impression is one of the prime factors for success of any restoration, more so in field of fixed prosthodontics. The critical aspect is to reproduce fine surface details along with ease of use. Knowledge of impression materials and the techniques to which each is best suited is essential in achieving consistent results.

OBJECTIVE OF THE STUDY

The purpose of this study is to evaluate the accuracy of various putty-wash techniques in a laboratory model that simulated the clinical practice.

MATERIALS AND METHODS

A metal master model, containing three full crowns fixed partial denture (FPD) abutment preparations, was fabricated. A perforated custom tray was fabricated that can be placed in the same position on the master model for each impression. For each technique, 10 impressions of the master model were made and poured using a die stone. The measurements were made of the models using a measuroscope and the accuracy of the impressions was recorded.

RESULTS

The statistical comparison between groups I, II, III, and IV casts measurements by using the Mann-Whitney test showed highly significant statistical difference between the various groups from each other (p < 0.001).

CONCLUSION

The accuracy of the working casts obtained from group III impression (two-step using 1 mm coping) was the best, whereas it was least with group II impression (two-step using polyethylene spacer).

HOW TO CITE THIS ARTICLE

Gautam N, Ahmed R, Sharma S, et al. A Comparative Study to Evaluate the Accuracy of Various Spacer Thickness for Polyvinyl Siloxane Putty-wash Impression Techniques: An In Vitro Study. Int J Clin Pediatr Dent 2020;13(5):536-542.

Analysis of correlation between optical and microtomography measurements of cementation space in CAD-CAM ceramic crowns

STATEMENT OF PROBLEM

Identical computer-aided design (CAD) parameters may be used to mill a variety of ceramic materials for computer-aided design and computer-aided manufacture (CAD-CAM) crowns. Whether milled crown spacing matches the designed parameters when more than a single evaluation method is applied is unknown.

PURPOSE

The purpose of this in vitro study was to correlate the stereomicroscope and the microcomputer tomography (μCT) 2-dimensional analysis of the cementation space with the replica technique in assessing 3 different ceramic materials.

MATERIAL AND METHODS

The specimens were milled in lithium disilicate, resin nanoceramic, and zirconia (n=30). The cement space was measured at the marginal, axial, and occlusal regions. One hundred twenty measurements of each material were used to correlate the methodologies. Data were statistically evaluated with 2-way repeated measures ANOVA and the Tukey test (α=.05). The Pearson correlation coefficient was used for each region for both methodologies (μCT and optical microscopy) separately.

RESULTS

For the μCT analysis, no differences were observed (P>.05) among the materials, but the axial region showed a positive correlation with the marginal (r=0.957) and occlusal regions (r=0.349); the same was observed between the occlusal and marginal regions (r=0.338). However, for stereomicroscope evaluation, resin nanoceramic and zirconia present similar cementation space (P=960), both being different from lithium disilicate (P<.05). The marginal region presented a positive correlation with axial (r=0.149) and occlusal regions (r=0.344), but the axial region showed negative correlation with the occlusal surface (r=-0.205).

CONCLUSIONS

The measurements of the scanned replicas were accurate when thinner sections were under measurement. Although the same space parameters were set in the CAD software program, definitive internal dimensions varied among the milled crowns.

Effect of Core Materials on the Dimensional Accuracy of Casts Made of Two Different Silicone Impression Materials: An Experimental Study

Background and Aim:

Dimensional accuracy of impressions is crucial to the quality of fixed restorations. This accuracy can be highly affected by the type of core and impression materials. This study aimed to assess the effect of different core materials on dimensional accuracy of two silicone impression materials.

Materials and Methods:

In this in vitro study, three master core models were fabricated of amalgam, composite resin, and nickel–chromium. Of each model, 30 impressions were taken; 15 with additional and 15 with condensational silicone impression material. The accuracy of impressions of the three core materials was assessed by measuring two linear dimensions and one vertical dimension on the stone casts.

Statistical Analysis:

Data were analyzed with two-way analysis of variance and Scheffe post hoc test (α = 0.05).

Results:

Accuracy of the three measured dimensions was significantly affected by both the impression and core materials (P < 0.05). Additional silicone was significantly more accurate in linear dimensions, and impressions of the amalgam core were significantly more accurate than other cores in linear dimensions.

Conclusion:

Additional silicone impression material had more detail reproduction, and the impressions of amalgam core were more accurate than the composite and nickel–chromium core materials.

Dimensional Stability and Acuracy of Silicone - Based Impression Materials Using Different Impression Techniques - A Literature Review

A quality-made dental impression is a prerequisite for successful fixed-prosthodontic fabrication and is directly dependent on the dimensional stability, accuracy and flexibility of the elastomeric impression materials, as well as on the appropriately used impression techniques. The purpose of this paper is to provide a literature review of relevant scientific papers which discuss the use of various silicone impression materials, different impression techniques and to evaluate their impact on the dimensional stability and accuracy of the obtained impressions. Scientific papers and studies were selected according to the materials used, the sample size, impression technique, storage time, type of measurements and use of spacer for the period between 2002 and 2016. In the reviewed literature several factors that influence the dimensional stability and accuracy of silicone impression molds, including the choice of the type of viscosity, impression material thickness, impression technique, retention of the impression material on the tray, storage time before the casting, number of castings, hydrophilicity of the material, release of byproducts, contraction after polymerization, thermal contraction and incomplete elastic recovery were presented. The literature review confirmed the lack of standardization of methodologies applied in the research and their great diversity. All findings point to the superiority of the addition silicone compared to the condensation silicone.

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.

Comparison of double-phase impression technique in 1 step and 2 steps by evaluating dimensional stability and accuracy of condensation silicones

The diverse viscosities of silicone impression materials are suited for their use in various impression techniques, intended to improve the precision of the cast impression in the form of a plaster model. The purpose of this research is to determine the dimensional stability and accuracy of the double-phase impression technique in 1 step and 2 steps by using a condensation silicone impression material. This research was carried out by using a precise stainless-steel master model and an individual aluminum tray. Comparing the abutments of the master model and the abutments of the double-phase impression technique in 2 steps, showed that they are wider on average 81 µm, while the abutments from the double-phase impression technique in 1 step are on average 281 µm wider in diameter. After analyzing the results obtained in relation to the diameter of the abutments, it can be concluded that the double-phase impression technique in 2 steps is dimensionally more stable and accurate compared to the double-phase impression technique in 1 step. This study shows that dimensional stability and accuracy of impression materials also depend on the selection of appropriate impression technique and proper performance in order to obtain a high quality dental impression that will be the basis for an accurate fixed-prosthodontic fabrication. Keywords: silicone impression material, impression technique, fixed partial dentures, dimensional stability and accuracy

Comparative evaluation of dimensional stability of impression materials from developing countries and developed countries after disinfection with different immersion disinfectant systems and ultraviolet chamber

Objectives

It was to analyse and compare the effect of different disinfectant systems on the dimensional stability of commonly used irreversible hydrocolloid and addition silicone impression materials from developing countries as compared to materials from developed countries.

Material and methods

Disinfectant systems used were glutaraldehyde, sodium hypochlorite and ultraviolet chamber. The stability after disinfection of commonly used alginate and addition silicone of native origin (Algin-Gum & Ad-Sil) was compared with similar impression materials from developed countries (Vignette and Aquasil) and results compared. A CAD/CAM manufactured stainless steel die simulating maxilla with four metal studs at canine and molar region was used. Impressions were made and disinfected after rinsing and drying and casts poured. The cross arch distance, interabutment distance and the occluso-gingival length of the studs was measured under traveling microscope and observations were recorded and compared. ANOVA test and Bonferroni test was applied.

Results

An increase in the interabutment and cross arch distance and decrease in occluso-gingival height was seen in the casts obtained. Glutaraldehyde immersion showed variation in the interabutment and cross arch distance for all materials studied. Ultraviolet chamber and sodium hypochlorite produced best results. Dimensional stability of impression materials like Vignette, Algin-Gum & Aquasil was found to within clinically acceptable limits after disinfection while maximum deviation was seen with Algin-Gum.

Conclusion

Evaluated materials can be safely disinfected with sodium hypochlorite and ultraviolet chamber. Addition silicone of native origin is at par with impression materials from developed countries but same cannot be said about alginate.

Accuracy of Multiple Pour Cast from Various Elastomer Impression Methods

The accurate duplicate cast obtained from a single impression reduces the profession clinical time, patient inconvenience, and extra material cost. The stainless steel working cast model assembly consisting of two abutments and one pontic area was fabricated. Two sets of six each custom aluminum trays were fabricated, with five mm spacer and two mm spacer. The impression methods evaluated during the study were additional silicone putty reline (two steps), heavy-light body (one step), monophase (one step), and polyether (one step). Type IV gypsum casts were poured at the interval of one hour, 12 hours, 24 hours, and 48 hours. The resultant cast was measured with traveling microscope for the comparative dimensional accuracy. The data obtained were subjected to Analysis of Variance test at significance level <0.05. The die obtained from two-step putty reline impression techniques had the percentage of variation for the height −0.36 to −0.97%, while diameter was increased by 0.40–0.90%. The values for one-step heavy-light body impression dies, additional silicone monophase impressions, and polyether were −0.73 to −1.21%, −1.34%, and −1.46% for the height and 0.50–0.80%, 1.20%, and −1.30% for the width, respectively.

Accuracy of Gypsum Casts after Different Impression Techniques and Double Pouring

This study evaluated the accuracy of gypsum casts after different impression techniques and double pouring. Ten patients were selected and for each one it was obtained 5 partial putty/wash impressions with vinyl polysiloxane (VPS) material from teeth #13 to #16 with partial metal stock trays. The following techniques were performed: (1) one-step; two-step relief with: (2) PVC film; (3) slow-speed tungsten carbide bur and scalpel blade, (4) small movements of the tray and (5) without relief—negative control. The impressions were disinfected with 0.5% sodium hypochlorite for 10 minutes and stored during 110 and 230 minutes for the first and second pouring, respectively, with type IV gypsum. Three intra-oral lateral photographs of each patient were taken using a tripod and a customized radiographic positioner. The images were imported into ImageJ software and the total area of the buccal surface from teeth #13 to #16 was measured. A 4.0% coefficient of variance was criterion for using these measurements as Baseline values. The casts were photographed and analyzed using the same standardization for the clinical images. The area (mm²) obtained from the difference between the measurements of each gypsum cast and the Baseline value of the respective patient were calculated and analyzed by repeated-measures two way-ANOVA and Mauchly’s Sphericity test (α = 0.05). No significant effect was observed for Impression technique (P = 0.23), Second pouring (P = 0.99) and their interaction (P = 0.25). The impression techniques and double pouring did not influence the accuracy of the gypsum casts.

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.

Dimensional Accuracy of Hydrophilic and Hydrophobic VPS Impression Materials Using Different Impression Techniques - An Invitro Study

INTRODUCTION

The dimensional stability of the impression material could have an influence on the accuracy of the final restoration. Vinyl Polysiloxane Impression materials (VPS) are most frequently used as the impression material in fixed prosthodontics. As VPS is hydrophobic when it is poured with gypsum products, manufacturers added intrinsic surfactants and marketed as hydrophilic VPS. These hydrophilic VPS have shown increased wettability with gypsum slurries. VPS are available in different viscosities ranging from very low to very high for usage under different impression techniques.

AIM

To compare the dimensional accuracy of hydrophilic VPS and hydrophobic VPS using monophase, one step and two step putty wash impression techniques.

MATERIALS AND METHODS

To test the dimensional accuracy of the impression materials a stainless steel die was fabricated as prescribed by ADA specification no. 19 for elastomeric impression materials. A total of 60 impressions were made. The materials were divided into two groups, Group1 hydrophilic VPS (Aquasil) and Group 2 hydrophobic VPS (Variotime). These were further divided into three subgroups A, B, C for monophase, one-step and two-step putty wash technique with 10 samples in each subgroup. The dimensional accuracy of the impressions was evaluated after 24 hours using vertical profile projector with lens magnification range of 20X-125X illumination. The study was analyzed through one-way ANOVA, post-hoc Tukey HSD test and unpaired t-test for mean comparison between groups.

RESULTS

Results showed that the three different impression techniques (monophase, 1-step, 2-step putty wash techniques) did cause significant change in dimensional accuracy between hydrophilic VPS and hydrophobic VPS impression materials. One-way ANOVA disclosed, mean dimensional change and SD for hydrophilic VPS varied between 0.56% and 0.16%, which were low, suggesting hydrophilic VPS was satisfactory with all three impression techniques. However, mean dimensional change and SD for hydrophobic VPS were much higher with monophase, mere increase for 1-step and 2-step, than the standard steel die (p<0.05). Unpaired t-test displayed that hydrophilic VPS judged satisfactory compared to hydrophobic VPS among 1-step and 2-step impression technique.

CONCLUSION

Within the limitations of this study, it can be concluded that hydrophilic Vinyl polysiloxane was more dimensionally accurate than hydrophobic Vinyl polysiloxane using monophase, one step and two step putty wash impression techniques under moist conditions.

The dimensional accuracy of polyvinyl siloxane impression materials using two different impression techniques: An in vitro study

Aim of the Study:

To evaluate and compare the linear dimensional changes of the three representative polyvinyl siloxane (PVS) impression materials and to compare the accuracy of single mix with double mix impression technique.

Methodology:

A study mold was prepared according to revised American Dental Association specification number 19 for nonaqueous elastic dental impression materials. Three PVS impression materials selected were Elite-HD, Imprint^™ II Garant, Aquasil Ultra Heavy. Two impression techniques used were single mix and double mix impression technique. A total of 60 specimens were made and after 24 h the specimens were measured using profile projector.

Statistical Analysis:

The data were analyzed using one-way analyses of variance analysis and significant differences were separated using Student's Newman–Keul's test.

Results:

When all the three study group impression materials were compared for double mix technique, the statistically significant difference was found only between Imprint^™ II Garantand Elite-HD (P < 0.05). Similarly, using single mix technique, statistically significant difference were found between Elite-HD and Imprint^™ II Garant (P < 0.05) and also between Aquasil Ultra Heavy and Elite-HD (P < 0.05). When the linear dimensional accuracy of all three impression material in double mix impression technique and single mix impression technique were compared with the control group, Imprint^™ II Garant showed the values more nearing to the values of master die, followed by Aquasil Ultra Heavy and Elite-HD respectively.

Conclusion:

Among the impression materials Imprint^™ II Garant showed least dimensional change. Among the impression techniques, double mix impression technique showed the better results.

Dimensional accuracy of stone casts made from silicone-based impression materials and three impression techniques

The aim of this study was to measure and compare the dimensional accuracy of stone casts of a partially edentulous mandibular arch made by two condensation silicones, two addition silicones and three impression techniques (1-step putty/light-body, 2-step putty/light-body and monophase technique). A partially edentulous standard stainless steel mandibular arch cast was obtained with reference points on the permanent mandibular right and left canines, and permanent mandibular right and left second molars. The anteroposterior distances (between the mandibular left canine and second molar and between the mandibular right canine and second molar) and transverse distances (between the mandibular left and right canines and between the mandibular left and right second molars) of stainless steel cast were measured by a microscope at 30× magnification and 0.5 µm accuracy. All impressions were made with condensation or addition silicones. The 1- and 2-step putty/light-body impressions were accomplished with putty and light-body materials and the monophase impressions with light-body material only. After the impression procedures, accuracy of each material and technique was assessed measuring the stone casts poured (n=5) from the impressions, by the same microscope. The differences between the values of stone cast and stainless steel cast were calculated, presented as percentages and analyzed statistically by two-way ANOVA and the means compared by Tukey's test (α=0.05). All distances measured on stone casts showed altered dimensions with significantly negative linear changes (shrinkage) as compared to those of the stainless steel cast. The stone casts made from the addition silicones were dimensionally more accurate. No differences were found among the impression techniques.

Dimensional Accuracy of Two-Step Impressions Measured on Scanned Casts in CAD

PURPOSE

The purpose of the study was to find out how light-body impression material thickness influences the horizontal dimensional accuracy of casts examined on a scanned model.

MATERIALS AND METHODS

Customized manikin mandibles were used for impression taking with a dual-phase impression method. These mandibles were prepared in a way that allowed the control of light-bodied impression material thickness. First premolars were prepared for a full crown by supragingival chamfer on both sides in all mandibles. For the measurements, buccal and lingual reference points were made at the preparation margin. Impressions were taken at nine thickness levels and a control level (TTotal = 10; 0-1.2 mm), and the reference points' average distance was compared across thickness levels on both the left and right side. We carried out three measures for each specimen and used three specimens per thickness level. Total sample size was N = 180, creating a sizable database to understand the influence.

RESULTS

The results indicated that light-body impression material thickness had no influence on the horizontal dimension of a die measured on scanned dies in these specific circumstances.

CONCLUSIONS

The thickness of light-body impression material in the dual-phase impression taking technique did not have a significant influence on the horizontal accuracy of scanned dies, which makes the technique safe and reliable for single crown restorations without having to take extra precautions for the thickness of light-body impression material.

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.

A Comparison of Dimensional Accuracy of Addition Silicone of Different Consistencies with Two Different Spacer Designs - In-vitro Study

INTRODUCTION

Dimensional accuracy of impression materials is crucial for the production of working casts in Fixed Prosthodontics. The accurate replication of tooth preparations and their arch position requires impression materials that exhibit limited distortion.

METHODS

This study was conducted to comparatively evaluate the dimensional accuracy of additional silicones by comparing two different techniques and spacer designs, by measuring the linear changes in interpreparation distance. The impressions were made from a stainless steel master die simulating a three unit bridge. A total 80 die stone (type IV, Ultrarock) models were obtained from the impressions made using two different parameters. The two different parameters are Multimix and Monophasic technique and different spacer designs.

RESULT

The interpreparation distance of the abutments in the casts was measured using a travelling microscope. Each sample was measured thrice and the mean value was calculated. The results obtained were statistically analysed and the values fall within the clinically acceptable range.

CONCLUSION

The most accurate combination is multimix technique with spacer design which uses less bulk of impression material.

A Comparative Evaluation of the Linear Dimensional Accuracy of Four Impression Techniques using Polyether Impression Material

There is much discussion in the dental literature regarding the superiority of one impression technique over the other using addition silicone impression material. However, there is inadequate information available on the accuracy of different impression techniques using polyether. The purpose of this study was to assess the linear dimensional accuracy of four impression techniques using polyether on a laboratory model that simulates clinical practice. The impression material used was Impregum Soft™, 3 M ESPE and the four impression techniques used were (1) Monophase impression technique using medium body impression material. (2) One step double mix impression technique using heavy body and light body impression materials simultaneously. (3) Two step double mix impression technique using a cellophane spacer (heavy body material used as a preliminary impression to create a wash space with a cellophane spacer, followed by the use of light body material). (4) Matrix impression using a matrix of polyether occlusal registration material. The matrix is loaded with heavy body material followed by a pick-up impression in medium body material. For each technique, thirty impressions were made of a stainless steel master model that contained three complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring eight dimensions (mesiodistal, faciolingual and inter-abutment) on stone dies poured from impressions of the master model. A two-tailed t test was carried out to test the significance in difference of the distances between the master model and the stone models. One way analysis of variance (ANOVA) was used for multiple group comparison followed by the Bonferroni's test for pair wise comparison. The accuracy was tested at α = 0.05. In general, polyether impression material produced stone dies that were smaller except for the dies produced from the one step double mix impression technique. The ANOVA revealed a highly significant difference for each dimension measured (except for the inter-abutment distance between the first and the second die) between any two groups of stone models obtained from the four impression techniques. Pair wise comparison for each measurement did not reveal any significant difference (except for the faciolingual distance of the third die) between the casts produced using the two step double mix impression technique and the matrix impression system. The two step double mix impression technique produced stone dies that showed the least dimensional variation. During fabrication of a cast restoration, laboratory procedures should not only compensate for the cement thickness, but also for the increase or decrease in die dimensions.

Effect of the impression margin thickness on the linear accuracy of impression and stone dies: an in vitro study

The space available for impression material in gingival sulcus immediately after the removal of retraction cord has been found to be 0.3-0.4 mm. However after 40 s only 0.2 mm of the retracted space is available. This is of concern when impression of multiple abutments is to be made. Hence a study was planned to determine the minimum width of the retracted sulcus necessary to obtain a good impression. Five metal dies were machined to accurately fit a stainless steel block with a square cavity in the center with spaces, 1 mm deep and of varying widths (0.11-0.3 mm) away from the block. Polyvinyl siloxane impressions were made and poured using a high strength stone. Using traveling microscope, length and widths of abutment, impression and die were measured and compared for linear accuracy and completeness of impression. Results showed 1.5-3 times greater mean distortion and larger coefficient of variance in the 0.11 mm group than in the wider sulcular groups. ANOVA test for distortion also showed statistically significant differences (P < 0.05). 75 % of impressions in 0.11 mm group were defective compared to less than 25 % of impressions in other width groups. It is not always possible to predictably obtain accurate impressions in sulcus width of 0.11 mm or lesser. Dimensionally accurate and defect free impressions were obtained in sulcus width of 0.15 mm and wider. Hence clinicians must choose retraction methods to obtain a width greater than 0.35 mm. Further immediate loading of the impression material after cord removal may improve accuracy.

Comparison of the accuracy for three dental impression techniques and index: an in vitro study

OBJECTIVES

This in vitro study compared the dimensional accuracy of stone index (I) and three impression techniques: tapered impression copings (T), squared impression copings (S) and modified squared impression copings (MS) for implant-supported prostheses.

METHODS

A master cast, with four parallel implant abutment analogs and a passive framework, were fabricated. Vinyl polysiloxane impression material was used for all impressions with two metal stock trays (open and closed tray). Four groups (I, T, S and MS) were tested (n=5). A metallic framework was seated on each of the casts, one abutment screw was tightened, and the gap between the analog of implant and the framework was measured with a stereomicroscope. The groups' measurements (80 gap values) were analyzed using software (LeicaQWin - Leica Imaging Systems Ltd.) that received the images of a video camera coupled to a Leica stereomicroscope at 100× magnification. The results were statistically analyzed with Kruskal-Wallis One Way ANOVA on Ranks test followed by Dunn's Method, 0.05.

RESULTS

The mean values of abutment/framework interface gaps were: Master Cast=32 μm (SD 2); Group I=45 μm (SD 3); Group T=78 μm (SD 25); Group S=134 μm (SD 30); Group MS=143 μm (SD 27). No significant difference was detected among Index and Master Cast (P=.05).

CONCLUSION

Under the limitations of this study, it could be suggested that a more accurate working cast is possible using tapered impression copings techniques and stone index.

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.

An evaluation of dimensional accuracy of one-step and two-step impression technique using addition silicone impression material: an in vitro study

The study is aimed to evaluate the dimensional accuracy, the effect of undercut of two different configurations and the elastic recovery of addition silicone impression material assessed indirectly, by measuring the dimensions on stone models recorded from the impression of the master model, using one-step and two-step impression technique, for addition silicone impression materials. Measurements are taken to evaluate horizontal or linear and vertical dimensional changes, of the abutment V and abutment C from the stainless steel model. Heavy body/light body material is used for making one-step impression technique in a custom tray. Putty/light body is used for taking two-step technique in a stock metal tray. Improved die stone is used for pouring the impression. The different 11 locations on the dies produced by two different techniques are measured microscopically on image analyzer and compared with those of stainless steel model. Anova test was applied to test the differences of mean values of inter and intra abutment measurements, to calculate p value. Unpaired t test was applied to calculate t value. Results showed less deviation of stone models produced by one-step technique from stainless steel model, whereas the deviation of stone models produced by two-step is comparatively more. (p < 0.01). This difference of deviation is significantly less in one-step as compared to two-step technique. One-step is sufficiently dimensionally accurate than two-step technique in conjunction with addition silicone impression material. They have the best elastic recovery from the two undercut configurations.

Accuracy of different putty-wash impression techniques with various spacer thickness

One of the most important steps is accurate impression making for fabrication of fixed partial denture.

The two different putty-wash techniques that are commonly used are: (1) Putty-wash one-step technique, (2) putty-wash two-step technique.

A uniform wash space is needed for an accurate impression. Nissan et al recommended the use of two-step technique for accurate impression making as there is uniform wash space for the light body material to polymerize.

The aim of the present study was to compare the accuracy of stone casts obtained from different putty-wash impression techniques using various spacer thickness.

The critical factor that influences the accuracy of putty-wash impression techniques is the controlled wash bulk which is absent in one-step putty-wash impression technique and with polyethylene spacer was used.

How to cite this article: Chugh A, Arora A, Singh VP. Accuracy of Different Putty-Wash Impression Techniques with Various Spacer Thickness. Int J Clin Pediatr Dent 2012;5(1):33-38.

Effect of different impression techniques on the dimensional accuracy of impressions using various elastomeric impression materials: an in vitro study

Production of exemplary crowns and fixed partial dentures depends upon the usage of impression material and its technique of usage that accurately reproduces prepared teeth and their relationship to the adjacent oral structure.

AIM

To evaluate the linear dimensional accuracy of the elastomeric impressions using various impression techniques using different combinations of viscosities of impression materials.

MATERIALS AND METHODS

Crown preparation was done in a dentulous acrylic resin denture base model with six natural teeth embedded into it was made to represent the dentulous maxillary arch. A total of 55 impressions were obtained and poured in die stone using various impression techniques with different combinations of viscosities of impression materials.

RESULTS

Among the six techniques used, the heavy body light body two-step technique using custom tray showed the least distortion which was closely followed by the putty wash two-step technique with 2 mm spacer using stock tray.

CONCLUSION

The study revealed that the heavy body light body two-step technique with custom tray provided the best results.

CLINICAL SIGNIFICANCE

Dimensional accuracy of impressions is very much required for precisely fitting of prosthesis. This study may be helpful to select the technique and materials as per clinical requirement of accuracy of impressions.

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.

Comparative analysis of dimensional precision of different silicone impression materials

OBJECTIVES

To investigate the accuracy of four commercial types of additional silicone impression materials (AFFINIS®, Virtual®, Relay 2002 CD® and Silagum®).

MATERIALS AND METHODS

The accuracy of impression material was measured indirectly by measuring three dimensions on stone cast poured from impressions of a stainless steel master model. The three dimensions on stone cast were measured at 1 hour, 2 days, 1 and 2 weeks after making the impression. Two impression techniques were used in the current study. The two-step impression technique was used for AFFINIS® and Virtual®, while single-step technique was used for Relay 2002 CD® and Silagum® materials. Twenty impressions were made of the master cast at four different periods for each of the tested four materials with a total of 320 impressions. Two vertical dimensions and one horizontal dimension were measured on master cast using optical microscope. Statistical analysis was run to compare the mean measurements for tested casts from each impression and time interval with the master cast.

RESULTS

No statistical significant differences were found (p > 0.05) in the accuracy of tested materials. There was no significant difference of master cast and impression cast means over time. Additionally, impression technique could be correlated with accuracy.

CONCLUSION

The tested additional silicones showed accuracy over time and they could be delayed up to 4 weeks duration without any significant changes in its dimensional stability. Silagum® impression material was the most accurate followed by Relay 2002 CD®, Virtual® and AFFINIS®.

CLINICAL SIGNIFICANCE

Silagum® impression material is most accurate followed by Relay 2002 CD®, Virtual® and AFFINIS®.

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.

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.

A clinical evaluation of fixed partial denture impressions

STATEMENT OF PROBLEM

Providing the dental laboratory with an accurate replication of the hard and soft tissue of a patient is important. Therefore, it is essential to examine whether clinicians critically evaluate impressions routinely before sending them to the laboratory.

PURPOSE

This study evaluated the quality of impressions sent to commercial laboratories for the fabrication of fixed partial dentures (FPD) by describing the frequency of clinically detectable errors and by analyzing correlations between the various factors involved.

MATERIAL AND METHODS

A total of 193 FPD impressions were evaluated, immediately after arrival at 11 dental laboratories, by 3 calibrated examiners. The impression technique and material used, tray type, and number of prepared units were recorded for each impression. Data relating to errors and faults, including defects in material polymerization, retention to tray, tissue contact by tray, crucial areas beyond tray borders, heavy-bodied material exposure through the wash material (for double-step impressions), inadequate union of materials, retraction cords embedded in impressions, and air bubbles, voids, or tears along the margin were also documented. The data were analyzed with the Pearson chi-square test (alpha = .05).

RESULTS

Of the impressions, 89.1% had 1 or more observable errors. Significant correlations were found between material type and voids or tears at the finish line (Rv = 0.17, P < .025) and between material type and polymerization problems (Rv = 0.223, P < .004).

CONCLUSIONS

Within the limitations of this study, impressions made with polyethers had the most detectable errors, followed by condensation-type silicones. The high frequency of detectable errors found in impressions sent for FPD fabrication is of concern.