Accuracy Of Different Impression Techniques Research Articles

Accuracy of different impression techniques for multiunit implant restoration: A qualitative in vitro study

Statement of problemDisplacement of impression copings and/or implant replicas during impression making and dimensional changes that occur during clinical and laboratory phases of making multiunit implant prostheses may affect the accuracy and fit of the prostheses. PurposeThe purpose of this qualitative study was to investigate and compare 3 different impression techniques for osseointegrated dental implant transfer procedures. Material and methodsThree impression transfer approaches were evaluated and compared: closed-tray impression technique (CTT), impression with plastic snap-fit impression copings; open-tray impression technique (OTT), impression with independent square copings; and OTT joining the impression copings with a photo-polymerized resin (PPT). A reference acrylic resin model with 4 implants was fabricated. Polyvinyl siloxane with a stock tray was used to make 45 impressions (n=15 for each impression technique), and 45 die definitive stone casts. A computer-aided design and computer-aided manufacturing (CAD-CAM) titanium framework was fabricated on the reference model. Three blinded operators evaluated the fit of the CAD-CAM titanium framework on each model to find clinically acceptable fit. The Kappa test was used for the agreement between the examiners (α=.05). ResultsAgreement was found among the 3 examiners on 44 of 45 specimens (Kappa value= 0.939; P<.001). In the CTT group, 14 casts were found to be acceptable. In the OTT group, nearly half of the specimens produced unacceptable fitting casts, whereas in the PPT group, 13 casts were found acceptable. ConclusionsCTT and PPT produced more accurate casts than the OTT technique, which yielded inferior results.

Accuracy of different impression techniques for multiple implants angulated to each other: An in vitro study

Aim and objective: To evaluate the accuracy of different impression techniques - namely the closed tray impression technique, the open tray non-splinted impression technique, the open tray splinted technique and an experimental technique for multiple implants placed at an angulation with each other. Materials and Methods: A master model was made of die stone which incorporated four implants having an internal hexagonal connection. The two terminal implants were placed at an angle of 20 degrees (lingually) whereas the two central implants were placed perpendicular to the cast. The samples were divided into four groups (Group I: Closed tray impression technique, Group II: Open tray impression technique non-splinted, Group III: Open tray impression technique splinted and Group IV: Experimental technique) based on the impression technique used. P-values were obtained using one-way analysis of variance (ANOVA) with Tukey’s correction for multiple group comparisons.Results: The P-value was greater than 0.05 (0.869) for Group III. Therefore, open tray splinted technique (Group III) was the most accurate impression technique when compared to the other techniques. On Inter - group comparisons it was noted that the values obtained by experimental technique were within close range of the values obtained by open tray splinted impression technique. Whereas, a comparison of Group I with Group III revealed 2 points of statistical significance (2 points of inaccuracy). Comparison of the Group II with Group III showed that all the points were statistically significant (all points were inaccurate). Conclusion: The open tray splinted impression technique provides best results for multiple implants placed at varying angulations. The experimental technique can be beneficial in areas of limited access, reduced mouth opening and exaggerated gag reflex.

Effect of modified tray design on accuracy of different impression techniques for parallel and divergent implants.

This study evaluated the effect of a modified tray design on the accuracy of implant impressions in comparison with the non-splinted and splinted impression techniques. Two titanium frameworks were produced to fit two parallel implants and two divergent implants with a 15o angle. According to the frameworks employed, two acrylic resin master models were fabricated. For each model, 10 impressions were taken with every technique. The maximum framework principal strain was calculated for every generated cast. For the parallel implant model, the strains of the non-splinted (118.4 με), splinted (89.0 με), and modified tray design impression (49.4 με) techniques were statistically similar (P = 0.16). For the divergent implant model, all the impression techniques showed a considerably higher strain than the parallel implant model. The splinted (287.0 με) and the modified (262.9 με) tray design impression techniques showed similar strains for the divergent implant model, which were significantly less than the strains for the non-splinted impression (518.0 με) technique (P < 0.05). Therefore, for two parallel implants, all the impression techniques exhibited similar accuracy. When angulation existed between the implants, the splinted and the modified tray design impression techniques were more accurate than the non-splinted impression technique.

An In Vitro Study to Evaluate the Accuracy of Different Impression Techniques of Implant Supported Prosthesis

Purpose: This study was designed to evaluate the dimensional accuracy of different impression techniques of implant-supported fixed dental prosthesis. Materials and Methods: Thirty impressions were made upon a specialized stainless-steel mold containing two parallel implant analogues. The impressions were divided into three groups according to implant impression technique used ten each; group (I) closed tray technique (C), group (II) open tray technique (O) and group (III) splinted open tray technique (OS). After taking impressions, they were poured with type IV dental stone and left for one day before analysis with a stereo microscope. Results: Regarding impression accuracy, there was no statistically significant difference between open tray and splinted open tray technique within the master mold while there was statistically significant difference between closed tray technique within the master mold. There was no statistically significant difference between open tray and splinted open tray technique while there was statistically significant difference between closed tray technique within the other two techniques. Conclusion: Closed tray technique showed more deviation in comparison to the master mold and the other two techniques that affect the final accuracy of multiple implant impression while no significant difference with the open tray technique of both types.

Evaluation of the Accuracy of Conventional and Digital Impression Techniques for Implant Restorations.

The increased use of CAD systems can generate doubt about the accuracy of digital impressions for angulated implants. The aim of this study was to evaluate the accuracy of different impression techniques, two conventional and one digital, for implants with and without angulation. We used a polyurethane cast that simulates the human maxilla according to ASTM F1839, and 6 tapered implants were installed with external hexagonal connections to simulate tooth positions 17, 15, 12, 23, 25, and 27. Implants 17 and 23 were placed with 15° of mesial angulation and distal angulation, respectively. Mini cone abutments were installed on these implants with a metal strap 1 mm in height. Conventional and digital impression procedures were performed on the maxillary master cast, and the implants were separated into 6 groups based on the technique used and measurement type: G1 - control, G2 - digital impression, G3 - conventional impression with an open tray, G4 - conventional impression with a closed tray, G5 - conventional impression with an open tray and a digital impression, and G6 - conventional impression with a closed tray and a digital impression. A statistical analysis was performed using two-way repeated measures ANOVA to compare the groups, and a Kruskal-Wallis test was conducted to analyze the accuracy of the techniques. No significant difference in the accuracy of the techniques was observed between the groups. Therefore, no differences were found among the conventional impression and the combination of conventional and digital impressions, and the angulation of the implants did not affect the accuracy of the techniques. All of the techniques exhibited trueness and had acceptable precision. The variation of the angle of the implants did not affect the accuracy of the techniques.

Dimensional accuracy of different impression techniques of partially edentulous mandibular arch

ABSTRACT Objective: The purpose of this in vitro study was to assess and compare the dimensional accuracy of three impression techniques: 1-step putty/light-body, 2-step putty/light-body, and the monophase technique. Methods: A partially edentulous standard stainless steel mandibular arch cast with reference points on the teeth was used to make the impressions. The anteroposterior and transverse distances were measured. All impressions were made with a polyvinyl siloxane using stock metallic (1- and 2-step putty/light-body techniques) or acrylic resin (monophase technique) trays. The monophase impressions were made using a light-body material and the 1- and 2-step putty/light-body impressions with putty and light-body materials. After impression procedures, the accuracy of each technique was assessed measuring the stone casts (n = 5) poured from the impressions using a microscope at 30x magnification and at 0.5 µm accuracy. The data were analyzed statistically using 2-way ANOVA and Tukey's test (p&lt;0.05). Results: Stone casts made by all techniques had significantly negative linear changes (shrinkage). The anteroposterior distances showed more dimensional changes than the transverse distances. The edentulous side showed more shrinkage than the anteroposterior side. Conclusion: No differences between the impression techniques were found, but significant dimensional changes were observed.

An in vitro study to evaluate the accuracy of different impression techniques of implant supported prosthesis

An in vitro study to evaluate the accuracy of different impression techniques of implant supported prosthesis

Three-dimensional accuracy of different impression techniques for dental implants.

Accurate impression making is an essential prerequisite for achieving a passive fit between the implant and the superstructure. The aim of this in vitro study was to compare the three-dimensional accuracy of open-tray and three closed-tray impression techniques. Three acrylic resin mandibular master models with four parallel implants were used: Biohorizons (BIO), Straumann tissue-level (STL), and Straumann bone-level (SBL). Forty-two putty/wash polyvinyl siloxane impressions of the models were made using open-tray and closed-tray techniques. Closed-tray impressions were made using snap-on (STL model), transfer coping (TC) (BIO model) and TC plus plastic cap (TC-Cap) (SBL model). The impressions were poured with type IV stone, and the positional accuracy of the implant analog heads in each dimension (x, y and z axes), and the linear displacement (ΔR) were evaluated using a coordinate measuring machine. Data were analyzed using ANOVA and post-hoc Tukey tests (α = 0.05). The ΔR values of the snap-on technique were significantly lower than those of TC and TC-Cap techniques (P < 0.001). No significant differences were found between closed and open impression techniques for STL in Δx, Δy, Δz and ΔR values (P = 0.444, P = 0.181, P = 0.835 and P = 0.911, respectively). Considering the limitations of this study, the snap-on implant-level impression technique resulted in more three-dimensional accuracy than TC and TC-Cap, but it was similar to the open-tray technique.

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™, 3M 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.