Addition Silicone Impression Material Research Articles

Impression Disinfection and Its Effect on Dimensional Accuracy and Surface Detail in the Times of COVID-19: An In Vitro Study.

Introduction The disinfection of impressions is crucial to eliminate the viral and other microbial loads to prevent the cross contamination of diseases. The aim of this study was to compare the effect of different virucidal disinfecting methods on the dimensional accuracy and surface detail reproduction (SDR) of impression materials. Methods A total of 160 samples were fabricated with different impression materials using zinc oxide eugenol (Group 1), alginate (Group 2), polyether (Group 3), and addition silicone (Group 4) impression materials, each containing 40 samples (n=40). These groups were further divided into Subgroups A, B, C, and D (n=10) based on the disinfecting method used. Disinfection was carried outusing 0.2% peracetic acid (A), a natural polymer of glucosamine (B), ultraviolet (UV) radiation (C), and ozonated water (D). The disinfected impressions were poured in type IV gypsum, and the obtained casts were checked for dimensional accuracy and surface detail reproduction (SDR). For dimensional accuracy, a one-way analysis of variance (ANOVA) test and, for surface detail reproduction, the chi-square test were used to compare the different subgroups of each impression material separately. Results Zinc oxide eugenol samples showed the lowest mean dimensional change when disinfected with 0.2% peracetic acid (1A=154.1 µm), and alginate showed the lowest mean dimensional change when disinfected using ozonated water (2D=134.9 µm). On the other hand, the lowest mean dimensional change observed in polyether and addition silicone samples was those which were disinfected using UV radiation (3C=100.9 µm and 4C=113.5 µm). Surface detail was reproduced adequately in most of the samples. Conclusion A 0.2% peracetic acid could be used to disinfect zinc oxide eugenol impressions, ozonated water for alginate impressions, and UV radiation for polyether and addition silicone impressions.

Orthodontic wires: newer approach for impression making and neutral zone in severely resorbed mandibular ridge: A case report

The management of the resorbed mandibular ridge is a difficult task. Rehabilitating a patient who is completely edentulous is a common dental procedure, but it can sometimes be challenging and difficult. Making an impression with the available stock trays, even after modification, is difficult in extremely resorbed ridges.Many materials have been used to record and transfer the neutral zone in complete dentures. So here we present a new technique of making an impression with properly adapted wire for recording the impression along with recording the neutral zone with a heavy body addition silicone impression material that rests on the wire loops projecting upward on the denture base to achieve maximum retention and stability and also for the preservation of residual alveolar ridge.

The Effect of Manipulation with Different Types of Gloves on Various Mechanical properties and Setting Time of Putty-Type Silicone Impression Materials

Aim: To evaluate the effects of handling with different type of gloves on the setting time, compressive and tensile strength of putty-type silicone impression materials. Methodology: The study was conducted at COMSATS Lahore and was approved by IRB FMH College of Medicine and Dentistry. In this in-vitro study three different type of gloves (Polythene, Latex and Vinyl) and two different brands each of addition silicone (Flexceed and Elite P&P) and condensation silicone (Zetaplus and Cavex) impression materials were used. These materials were divided into four different groups (A, B, C and D). Each group was subdivided into four sub-groups based on the gloves used for manipulation. Sixty samples(n=20) of two brands each of addition (Elite P&PA, Flexceed B) and condensation silicones (Zetaplus C and Cavex D) were prepared and analyzed to evaluate the setting time, compressive strength and tensile strength of addition and condensation impression materials. The samples were subdivided into groups A1, B1, C1, D1 (Control), A2, B2. C2, D2 (Polythene gloves), A3, B3, C3,D3 (Vinyl gloves) and A4, B4, C4, D4(Latex) respectively. Results: There was a significant effect(p<0.5) on the setting time of Elite P &P when mixed with latex gloves(A4) and Flexceed when mixed with polythene(B2) and latex gloves(B4) There was significant (p<0.5) effect on the setting time of Zetaplus when mixed with vinyl(C3) and latex gloves(C4). There was significant (p<0.5) effect on the setting time of Cavex when mixed with polythene(D2), vinyl(D3) and latex gloves(D4). There was a significant (p<0.5) effect on the tensile strength of both brand of addition and condensation silicone when mixed with polythene, vinyl and latex gloves as compared to control group. There was significant effect on the compressive strength of both brand of addition and condensation silicone except that polythene gloves don’t affect the compressive strength of one group of addition silicon B2(Flexceed) Practical implications: Dental silicone type of impression materials are widely used to fabricate different indirect restorations. Gloves are essential to control cross infection for the safety of the dentist and the patients and cannot be avoided for manipulation of these materials. Worldwide, dentists use different types of gloves to manipulate silicone impression materials. The composition and type of gloves affect the setting time and properties of addition and condensation silicones, and ultimately, it can affect and compromise the clinical outcome too. Conclusion: Latex and polythene gloves should be avoided for the manipulation of addition and condensation silicones putty impression materials due to considerable effect on the setting time. Vinyl gloves are a better choice as all others affected the mechanical properties. Keywords: Addition silicones, Condensation silicones, tensile strength, compressive strength, setting time

EFFECT OF DISINFECTANT SOLUTIONS ON THE WETTABILITY OF ADDITION SILICONE IMPRESSION MATERIALS AT TWO DIFFERENT EXPOSURE PERIODS- AN IN VITRO STUDY

Introduction: This study aims to evaluate the surface wettability of addition silicone impression materials, which were treated with two different disinfecting agents for two different time intervals. Methods: Twenty-five rectangle-shaped specimens from each of two different addition silicone impression materials (Express GT and Flexceed) were prepared. Five samples from each impression material were kept as the control without any disinfection. The rest of the specimens were divided into two groups according to the disinfecting agents, (2% Glutaraldehyde and 0.5% sodium hypochlorite) and disinfected for two time periods (10 minutes, and 60 minutes). Later, surface wettability was tested and recorded. Data were analyzed with analysis of variance (ANOVA). Results: The mean contact angle values of both impression materials at 10 minutes of disinfection were reduced when compared to the control group (without disinfection). As the disinfection time increases there was a tendency of decreasing the contact angle for Flexceed and Express GT impression material for glutaraldehyde disinfectant. But for Flexceed, the mean contact angle values increased after 60 minutes of disinfection with sodium hypochlorite.

A COMPARATIVE EVALUATION OF THE EFFECT OF CHEMICAL AND ULTRAVIOLET DISINFECTION ON DIMENSIONAL STABILITY OF POLYVINYL SILOXANE IMPRESSION MATERIAL: AN IN VITRO STUDY

Introduction: In recent advances, ultraviolet (U.V) radiation has proved to be efcacious in killing the microorganisms. Little is known about the effect of this radiation on dimensional stability of addition silicone impression materials, hence a study was conducted to evaluate and compare the effect of U.V disinfection with chemical agents on dimensional stability of polyvinyl siloxane impression material. A total of 60 Materials And Method: samples of PVS impression material were fabricated and divided into 4 groups based on different disinfecting agents i.e. 2% glutaraldehyde, 0.5% sodium hypochlorite and U.V radiation. The impression samples were infected with S.mutans strains , incubated, after which the samples were disinfected, colonies were counted and compared with the control and different disinfectant groups. Following this, the dimensional changes in the samples were evaluated using travelling microscope. Results : Highly signicant results were seen between the number of colonies obtained from control samples and the samples subjected to chemical and U.V disinfection. Whereas in terms of dimensional stability no statistically signicant difference was observed between 2% glutaraldehyde, U.V chamber and 0.5 % sodium hypochlorite. All the disinfect Conclusion: ants tested in this study they can be successfully used for disinfection purpose of Polyvinylsiloxane impression material as they were equally efcacious and did not cause any signicant change on the dimensional stability of PVS impression material.

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

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

Effect of disinfectants on the tear strength of addition silicone impression material - An in vitro study.

Addition silicone is a newer type of silicone impression material which has high dimensional stability, accuracy, and flexibility. They are mostly used for fixed restorations such as crowns and bridges. They have high tear strength; however, this strength may be altered upon disinfection. Disinfection of addition silicone prior use is important to reduce the microbial load. The aim of this study is to check whether there is any change in tear strength of addition silicone on disinfection with two commercially available disinfectants. Zhermack Elite HD + Putty material was tested in this study. Base and catalyst material was mixed and the material was cut into strips of dimension 70 mm × 10 mm × 2 mm. Five strips were immersed in sterillium and five strips were immersed in glutaraldehyde solution. These strips were then tested for their tear strength using Instron E3000 Universal Testing Machine. The values obtained were recorded in SPSS software version 22 (IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp.) for analysis and the P was obtained. The mean tear strength of Group 1, addition silicone immersed in sterillium disinfecting solution was found to be 7.148 ± 2.654 kN/m. The mean tear strength of Group 2, addition silicone immersed in glutaraldehyde disinfectant solution was found to be 7.326 ± 4.062 kN/m. An unpaired Student's t-test was done and P was found to be 0.235. The tear strength values between the groups was statistically not significant. Hence the tear strength of addition silicone was found to be greater in the glutaraldehyde disinfectant solution group.

Evaluation of dentinal crack propagation, amount of gutta percha remaining and time required during removal of gutta percha using two different rotary instruments and hand instruments - An In vitro study.

One of the most important goal of non surgical endodontic retreatment is the successful removal of gutta percha and sealers from the root canal system. A variety of techniques have been recommended for retreatment procedures for the removal of gutta-percha and sealers with or without the help of adjunctive chemical solvents, by using stainless steel hand files or nickel-titanium rotary files, gate glidden burs, heated instruments, ultrasonic instruments, and lasers 1,3. The current advancements in the design of NiTi instruments have proved efficacious in the removal of filling materials from the root canal wall and various studies have also confirmed their cleaning ability and efficacy 4,5. Nevertheless, the use of rotary instrumentation can lead to the formation of dentinal cracks in the root canal dentin. Many researchers have reported the incidence of crack formation and propagation after the procedure with manual, rotary and reciprocating instruments. The behavior of rotary instruments in the generation of defects have been the point of greatest interest during many years 6. These dentinal cracks can be defined as defects with a complete crack line extending from inner root canal space up to the outer surface of the root when the tensile stress in the root canal wall exceeds the tensile stress of dentin 7. This study was conducted to investigate and to compare the amount of dentinal microcracks formation with various new instrumentation methods and conventional hand filing method. It also looks into amount of gutta-percha removed after retreatment from the canal and the time required for all the instrumentation technique. Sixty extracted human maxillary first molars with curved roots were mounted on addition silicone impression material incorporated in an aluminium hollow block, then instrumented using step-back preparation with 35 size K files. Obturation was done using gutta-percha with AH plus sealer. These were stored for 14 days and divided into three groups Mani GPR, Endostar Re Endo and H file and were subjected to retreatment procedures. Retreatment was considered complete when no filling material was observed on the canal wall and the canal was smooth and free of visible debris. The samples were examined under scanning electron microscope and the number of cracks were calculated. The percentage of root canal filling material and time taken was recorded. The data obtained were analyzed by using descriptive statistics, ANOVA (Analysis of Variance), chi-square test and Scheffe's post hoc test through SPSS for window (version 22.0). All the techniques showed similar amount of crack propagation, with no statistical difference between the group. Retreatment done using H Files required more time and removed less material. The coronal third showed less amount of gutta-percha remnants than the apical third in all groups. All the groups showed a similar amount of crack propagation. Less number of cracks were observed in the coronal one third and more amount of cracks were found at the apical third. Endostar RE Endo rotary instrument proved to be most effective and least time-consuming. Hedstrom Files required more time and removed less material.

Accuracy of Elastomeric Impression Made with Standard and Dual Arch Tray: An In-vitro Study

Introduction: The dual-arch impression techniques utilise special stock impression trays of various designs. These trays are made of plastic or metal with fabric or mesh material placed across the occlusal surfaces of the teeth connecting their buccal and lingual flanges. These special trays register the impression of the opposing segments of the dentition. The dual arch impression technique is used in dentistry effectively since many decades but there is very little evidence published regarding the effect of different tray design on the accuracy of impression. Aim: To evaluate the accuracy of inter-abutment distance in dies obtained from different dual-arch trays and with those obtained from stock metal trays. Materials and Methods: This in-vitro study was carried out in the Department of Prosthodontics, M.M. College Of Dental Sciences and Research, Mullana, Haryana, India between June 2016 to November 2017. A total of 70 elastomeric impression using heavy and light body addition silicone impression material were made, of the prepared typodont teeth of right mandibular first premolar and first molar for thee- unit fixed partial denture. impressions were grouped into four groups, based on the type of tray used i.e. Group A consisted of impressions obtained from plastic dual-arch trays (n=20), Group B- plastic reinforced with metal dual-arch trays (n=20), Group C- metal dual-arch trays (n=20) and Group D-full stock metal trays (n=10). Group A, B and C were further divided into Subgroup I (working side poured first) (n=10) and Subgroup II (non-working side poured first) (n=10) depending upon the sequence of pouring. The measurements were obtained using travelling microscope and statistical analysis was done using one-way Analysis of Variance (ANOVA) test which was then followed by a post-hoc test. Results: The inter-abutment distance showed a decreased value in all the groups when compared to the master model (p-value >0.05). Percentage decrease in inter-abutment distance was between 0.006% - 0.48%. The results indicated statistical insignificant difference when full arch metal stock tray impression is compared to all dual arch trays impression. There was insignificant difference between the inter-abutment distance obtained using dual arch trays which were poured with working or non working side first. Conclusion: The impressions obtained with both dual arch trays and stock tray, produced dies with distortion in a clinically relevant range. Thus, dual arch trays can be recommended for making impressions of short span fixed partial dentures, and can be considered to be an alternative to the conventional method.

Comparative Evaluation of the Dimensional Accuracy of Different Putty-Wash Techniques Using Additional Silicon Impression Material In Vitro Study

Purpose: The aim of the present study was to evaluate and compare the dimensional accuracy of stone models made by addition silicone impression material using three putty- wash impression techniques: one step putty wash (dual viscosity), two step and modified two step putty wash technique. Material and Methods: A stainless steel master model was constructed simulating a three-unit fixed prosthesis. Fifteen impressions were make of this master model with each impression technique. The first technique, one step dual viscosity was made with putty in the tray and light body on brass dies and impression was make. The second technique, two step putty/wash, the first step using putty on the tray with acrylic spacer on the dies and impression was make then followed by loading wash material on the dies and reseating the first impression in the second step. The third technique, modified two step made using putty/light body as in the first technique then a hole was made at the edge of two abutments in the polymerized impression, then light body was loaded into the tray and over the model and the tray is reseated. Total of forty five impressions were obtained and casts poured using type IV stone. The accuracy of these casts measured using a travelling microscope. Three dimensions diameter, height, and interabutment distances measurements were obtained and statistical analysis was done using paired T-test, One way ANOVA, and Least Significant Difference (LSD) tests. Result: Showed that a significantly larger dimensions of the resultant stone casts of all techniques in comparison to the master model (P

Appraisal of Dimensional Accuracy in Five Brands of Extended Pour Irreversible Hydrocolloid Materials for FDP Impression

Aim. The purpose of this study was to assess and compare the dimensional accuracies of five brands ofextended pour irreversible hydrocolloid materials for fixed dental prosthesis impression.Materials and methods. Impressions of a master stainless steel model were made with five extended pourirreversible hydrocolloids and one addition silicone impression material. A total of ninety impressions(n=90) were made, with fifteen for each group of impression material. The stone dies retrieved fromthese impressions were analysed with Baty-Vision Systems - Venture 3D CNC machine, for dimensionalaccuracies. Comparison of continuous data between two groups was done with the Wilcoxon rank-sum test(Mann Whitney U test) and for more than two groups with the Kruskal Wallis test (? = .05)Results. All six impression materials showed some amount of error. On comparison of the median totalabsolute deviation of the various dimension of stone dies, the accuracies of impression materials in decreasingorder appeared to be Neocolloid >> Affinis >> Coltoprint >> Zelgan >> 3M ESPE >> Plastalgin. On thecontrary, a comparison of the impression materials, in terms of several dimensions of stone dies differingsignificantly from the stainless-steel model, the sequence in terms of accuracy was, Coltoprint > Affinis >3MESPE > Neocolloid > Plastalgin > Zelgan.Conclusions. Based on the dimensional accuracies of the stone dies retrieved from the impressions,Neocolloid was found to be the best impression material with the least possible deviation, followed byColtoprint and Affinis.

Accuracy of Digital Impression Taking Using Intraoral Scanner versus the Conventional Technique.

Objectives: Intraoral scanners have shown promising results when used as an adjunct or alternative to conventional impression techniques. This study compared the accuracy of digital impression taking using an intraoral scanner versus the conventional technique. Materials and Methods: In this in-vitro experimental study, a typodont molar tooth was prepared as the standard model and scanned by TRIOS intraoral scanner. Ten digital impressions were fabricated as such and intraoral scans were sent to the manufacturers. In the conventional method, using addition silicone impression material, a stone die was fabricated. Using a computer-aided design/computer-aided manufacturing scanner, the die was scanned, and the data were transferred to the software. After the fabrication of frameworks, the replica technique was used. The replicas’ thickness (indicative of the gap between the framework and the model and the accuracy of impression taking) was 12 points. The data were analyzed using student's t-test. Results: The mean thickness of replicas (gap between the internal surface of frameworks and the standard model) at the three points in the buccal, lingual, mesial, and distal sections in the digital impression technique was lower than that in the conventional technique (P<0.0001). In other words, the accuracy of impressions taken by the digital method was significantly higher than those taken by the conventional method. Conclusion: Intraoral digital scanner had significantly higher accuracy than the conventional method in all points. Thus, the digital method can be reliably used as an adjunct or alternative to the conventional method to increase the accuracy of impression taking.

The effect of using sectional stock tray on the accuracy of gypsum cast

Patients with restricted mouth opening are a common occurrence in prosthodontic practice. Sectional impression technique was simplified manipulation and decreased patient's trauma. The aim of study is to compare between the impression done by using sectional and full arch stock trays, and to evaluate volumetric changes in the abutments of partially edentulous arch and the linear dimensional changes between the abutments of stone casts at different intervals of time. The measurements were done by using 3D (IOTA 1203, DEA) machine on (80) die stone casts prepared after taking an impression (two-step technique) of hand mix Dorisil and Supersil addition silicone impression materials using a special mold and test apparatus. There was low significance in the volumetric differences among casts produced from sectional stock trays in relation to that produced from full arch stock trays. Little linear dimensional changes between abutments of casts prepared from sectional stock tray of an average 0.031mm were found. According to these results, sectional trays can be used instead of full arch trays in clinical cases of restricted mouth opening.

An In-Vitro Evaluation of the influence of repeat pours of addition silicone impressions on the dimensional accuracy of resultant casts: an original research study

Background and Aim: For miscellaneous purposes, the prosthodontists and dental laboratory technicians usually attempt repeated pouring of the impression in order to avoid expenses and curb upon the chair-side time. There are numerous factors which can affect dimensions of subsequent casts on repeated pouring. These include the process of polymerization, temperature and the material used to fabricate the replica of working cast. The sole aim of this study was to evaluate if repeated pouring of addition silicone impression would influence the dimensional accuracy of resultant casts. Materials &amp; Methods: Addition silicone impression material along with tray adhesive were used to evaluate the influence of repeat pours on the dimensional accuracy of resultant casts at various time intervals i.e. at 15 minutes, 75 minutes, 24 hours and 7 days. Vision measurement machine was used for measurement of dimensions. A metal control model of 8*6*2 cm was made with abutments. Various dimensional markings and measurements (for inter-abutment distance &amp; intra-abutment distance) were completed. All 80 resultant casts were along with the master model was dimensionally evaluated with “Vision Measurement Machine”. Statistical Analysis and Results: Statistical analysis was completed by SPSS (statistical package for social sciences) version 21.0 and Epi-info version 3.0. The result of this study showed that working dies obtained from Addition silicone at various time intervals i.e. 15 minutes, 75 minutes, 24 hours and 7 days exhibited insignificant dimension changes clinically. The p-value was taken significant when less than 0.05 (p&lt;0.05) and Confidence interval of 95% was taken. Post-Hoc Bonferroni test showed no significant difference for the inter-interval comparison of mean inter-abutment distance (Line 2-3). Conclusion: Within the limitations of the study authors concluded that the addition silicone impression material could be preferred material in the field of prosthodontics for repeated pouring up-to 7 days due to its favorable qualities like dimensional accuracy and stability, elastic recovery from undercuts, low creep and moderate to high tear resistance.

To evaluate the effect of storage temperature on the linear dimensional accuracy of delayed and repeat pours of two addition silicone impression materials

Background: Addition silicone elastomers are the most commonly used impression materials for making final impression for fixed partial dentures, implants, and removable partial dentures. The dimensional stability and accuracy of addition silicone impression material is influenced by the storage time, temperature, and repeat pour. Aim and Objectives: The aims and objectives of this study were to evaluate the accuracy of two different types of addition silicone elastomeric impression materials, stored at different temperatures; to evaluate the accuracy of two different types of addition silicone elastomeric impression materials after delayed and repeated pour; and to compare the linear dimensions of two different types of addition silicone elastomeric impression materials with a control die. Materials and Methods: A machined standard steel master die and a metal custom impression tray were made for making a final impression of machined standard steel master die. The final impression was made by using two different brands of addition silicone impression materials (Aquasil™ Ultra Impression material, Dentsply/Caulk, Milford, DE, USA, and 3M™ ESPE™). Double-step putty light-body impression technique was used for making the final impression. In this manner, a total of eighty impressions were made, and they were divided into two groups namely Group I and Group II. To study the effect of delayed pours and storage temperature, the two groups were further divided into four subgroups, with ten impressions each. All the ten impressions of each subgroup were stored in an acrylizer at 40°C, −10°C for 24 h, −2°C for 48 h, and 0°C for 1 week inside a refrigerator in sealed plastic bags before being poured with type IV dental stone. To study the effect of repeat pours on the accuracy of stone casts, all the ten impressions of each subgroup were immediately re-poured with type IV die stone after the removal of the first set of casts. Thus, again a fresh set of eighty casts were obtained having forty casts to each group. Results: When the impressions were stored in the acrylizer at 40°C, −10°C for 24 h, −2°C for 48 h, and 0°C for 1 week, the addition silicone impression materials did not show any significant change when compared to the control samples. Conclusion: Both the types of addition silicone elastomeric impression materials maintained their accuracy after delayed pours and repeat pours. Storing impressions under different conditions caused no adverse effect upon the accuracy of both types of addition silicone elastomeric impression materials. There was no significant change in the dimensions of stone casts obtained from both impression materials as compared to the dimensions of the master die. Even though if the addition silicone impression material is delayed, i.e. poured up to 1 week, repeat poured, and exposed from − 10°C to 40°C, the linear dimensional accuracy will not be adversely affected.

Comparison of three dimensional accuracy of two implant level impression techniques; using three different elastomeric impression materials-an in vitro study

Aim: To compare 3-Dimensional accuracy of open and closed impression technique using three elastomeric impression materials to transfer the intraoral position of implant fixture to the working cast. Objective: To compare 3-Dimensional accuracy of open and closed tray impression technique by using addition silicone, condensation silicone and polyether impression materials for making implant level impressions. Materials and Methods: Experiments was conducted to find the three dimensional accuracy of casts made with three impression materials for implant impressions by open and closed tray impression techniques. Five implant analogs were placed on a maxillary acrylic model; impression posts were screwed to implant analogs. 30 stock trays and 30 open window custom trays were prepared. These 30 stock trays and 30 open window custom trays were again divided into three subgroups by using three impression materials. Then the impressions were poured using die stone according to manufacturer’s instructions. Specific dimensions of resultant cast was measured. The dimensional changes were measured using White light laser scanner and data analysis was done by XOV Rapidform Software. Comparison between materials was done by ANOVA test followed by Tukey’smultiple comparison test. Comparison between two techniques was done by unpaired‘t’ test. Results: The data was subjected to statistical analysis which was done by ANOVA test followed by Tukey’s multiple comparison test and Comparison between two techniques was done by unpaired‘t’ test. Statistical analysis shows significantly less difference in open tray technique when compared to closed tray impression technique. Conclusion: Within the limitation of this study;1. Open tray impression technique is more accurate than the closed tray impression technique for making implant impression; 2. Polyether and Addition silicone elastomeric impression materials were there commended materials for implant impressions. Keywords:

Dimensional accuracy of master casts made by one-step versus two-step putty wash addition silicone impression techniques: An in vitro study

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. The purpose of this study was to compare the dimensional accuracy of one-step putty wash and two-step putty wash impression techniques using commercially available addition silicone impression material. The accuracy was assessed by measuring intraabutment and interabutment dimensions on stone dies poured from impressions of the master model, by using Toolmaker’s microscope. Keywords: Addition silicone impression material, Toolmaker’s microscope, Polyvinyl siloxane, Universal testing machine (UTM).

Evaluation of the Bond Strength of Universal Tray Adhesives on Silicone Impression Materials Using an Acrylic Tray

To evaluate the bond strength of two commercially available universal tray adhesives on polyvinylsiloxane addition silicone and condensation silicone impression materials to an autopolymerizing polymethyl methacrylate acrylic tray material. Sixty flat square specimens were fabricated from autopolymerizing polymethyl methacrylate tray material to which an eye hook was incorporated to serve as the point of attachment to a universal testing machine. A polyvinyl chloride (PVC) pipe of 15 mm diameter and 25 mm long was used to house the impression material, and a metal rod was inserted into two centered holes to provide retention that serves as the second point of attachment to the universal testing machine. The specimens were divided into 4 groups of 15 specimens each. The first and second groups of specimens were applied with Coltene and Zhermack universal tray adhesives and tested with addition silicone impression material. The third and fourth groups were coated with the above-mentioned adhesives, respectively, and tested with condensation silicone. Each specimen was then attached to the universal testing machine. The maximum force at which separation failure occurred was divided by the area of adhesion and recorded as the adhesive strength in MPa. A significant difference was observed between mean MPa values of Zhermack and Colten universal tray adhesives, where the F value of 1314.116 was found to be significant at 0.000 levels indicating that the Zhermack adhesive had higher MPa than Coltene adhesive. Impression material again indicated significant difference (F = 132.514; p = 0.000), where addition silicone had higher MPa value than condensation silicone. Also, the interaction between adhesive and impression material was found to be significant (F = 10.794; p = 0.002). The adhesive bond strength of Zhermack universal tray adhesive was higher compared to that of Coltene universal tray adhesive irrespective of the elastomeric impression material. It was also found that bond strength of Zhermack universal tray adhesive with addition silicone impression material was the highest and Coltene universal tray adhesive with condensation silicone impression material was the least of all the four groups. Tray adhesives need to be applied to the tray to obtain an accurate and consistent impression. If there is a separation of impression materials from the tray, it may results in a distorted impression leading to poor final restorations.

Compatibility of types III/IV Gypsum with addition silicone impression material

Background: Addition silicone is an elastomeric impression material used to obtain an accurate impression. Compatibility between impression material and gypsum will affect the surface quality of the resulting models. Types III and IV gypsum are very commonly used in dentistry to pour impressions and produce working models; despite this, there has been no further research regarding the differences between the two types in terms of compatibility with addition silicone impression materials. Objectives: To compare the compatibility of types III and IV gypsum with addition silicone impression materials. Methods: Gypsum compatibility was assessed on the basis of its ability to reproduce lines of certain widths. Thirty samples were produced by impressing a stainless steel ruled block (in accordance with ANSI/ADA Specification No. 19) with addition silicone (independent variable) and then pouring in type III or IV gypsum (dependent variable). The samples were divided into two groups: in Group A, addition silicone was poured with type III gypsum; in Group B, addition silicone was poured with type IV gypsum. The lines from the stainless steel ruled block that formed in the gypsum samples were observed with a microscope at 10x magnification. Each line was then assessed with a score from 1 to 4, according to Morrow’s standardization, where a score of 1 indicates that the line was reproduced clearly and sharply over its entire 25 mm length, and a score of 4 indicates that the line is reproduced incompletely with roughness and/or blemishes. The data were analyzed using the Mann–Whitney U test. Results: Group B (addition silicone poured with type IV gypsum) produced more results rated as 1 (60% of the group’s samples) than Group A (only 46.67% of the group’s samples). Conclusion: On the basis of the number of scores rated as 1, type IV gypsum was more compatible than type III gypsum with addition silicone.

Effect of Time and Method of Drying on Bond Strength of Tray Adhesives with Vinyl Polysiloxanes

To establish an effective combination of drying time and drying method of the tray adhesive so that maximum bond strength can be achieved between impression tray and impression material. Cylindrical specimens of auto-polymerizing resin and addition silicone impression material were made. A total of 150 specimens were tested. They were divided into two groups Dentsply and GC. Each group was further divided into five subgroups: • Drying with compressed air for half the time as recommended by the manufacturer • Drying with air blower for half the time as recommended by the manufacturer • Open air drying as recommended by the manufacturer • Open air drying for 15 minutes • Open air drying for 1 hour The samples were tested for tensile bond strength using the universal testing machine. The results were subjected to statistical analysis. Open air drying as recommended by the manufacturer was better than drying with a blower or compressed air. There was no significant difference between open-air drying for 5 minutes and open-air drying for 15 minutes or 1 hour. Open air drying as recommended by the manufacturer, i.e. 5min, showed good bond strength and drying for more than 5mins does not significantly increase bond strength. Tray adhesive should not be dried with compressed air or air blower. Tray adhesive should be applied and kept to dry according to the manufacturer's recommended time.