Accuracy of a new elastomeric impression material for complete-arch dental implant impressions

Accuracy of different digital acquisition methods in complete arch implant-supported prostheses: An in vitro study

STATEMENT OF PROBLEM

Digital methods such as intraoral scanners for recording the location of implants supporting complete arch prostheses have limitations. Photogrammetry devices should be able to digitize implant positions accurately, but standardized comparisons between different digital acquisition methods are lacking.

PURPOSE

The purpose of this in vitro study was to compare the repeatability of different digital acquisition methods for complete arch prostheses supported by 6 and 4 implants.

MATERIAL AND METHODS

A master cast was created with 6 and 4 dental implants with multiunit abutments to obtain the master digital casts. The evaluated devices were the industrial high-resolution 12-megapixel scanner (reference) Atos Compact Scan 12M (GOM), the laboratory scanners D2000 (3Shape A/S) and S900 Arti (Zirkonzahn), the photogrammetry devices iCam (iMetric4D) and PIC (PIC Dental), and the intraoral scanners TRIOS 3 (3Shape A/S) and iTero Element 5D (Align Technology). The resulting files were imported to a computer-aided design software program (exocad GmbH) to obtain the implant replicas as standard tessellation language (STL) files. These files were imported into a software program (Geomagic Control X) and superimposed per group through the best-fit algorithm to determine repeatability, defined as the closeness of agreement between each group's scanned results as root mean square (RMS) values. The normality of distribution was tested by the Shapiro-Wilk normality test, and the Kruskal-Wallis test with adjustment with the Bonferroni correction method was used accordingly (α=.05).

RESULTS

The repeatability means and 95% confidence intervals for the 4 implant scans were: 1.07 µm (0.86; 1.29) for GOM, 2.05 µm (1.89; 2.21) for D2000, 3.61 µm (3.23; 3.99) for S900, 7.01 µm (6.11; 7.91) for iCam, 5.18 µm (4.6; 5.76) for PIC, 20.52 µm (18.33; 22.72) for TRIOS3, and 20.5 µm (17.37; 23.63) for iTero. Statistically significant differences were found between devices, except for iCam versus PIC, GOM versus S900, iCam versus D2000, PIC versus D2000, and TRIOS3 versus iTero. The repeatability means and 95% confidence intervals for the 6 implant groups were: 1.36 µm (1.08; 1.65) for GOM, 3.17 µm (3.01; 3.33) for D2000, 2.15 µm (2.04; 2.25) for S900, 8.67 µm (8.06; 9.28) for iCam, 13.88 µm (12.62; 15.14) for PIC, 40.32 µm (36.29; 44.36) for TRIOS3, and 38.86 µm (34.01; 43.71) for iTero. Statistically significant differences were detected between devices, except for S900 versus GOM, PIC versus iCam, and iTero versus TRIOS 3.

CONCLUSIONS

The results suggest that photogrammetry could be a suitable alternative for recording implant locations of complete arch prostheses supported by 4 or 6 implants, with better repeatability than intraoral scanners. Increasing the number of implants decreased the repeatability of every device tested except the laboratory scanners.

Comparison of accuracy of hexed and nonhexed pickup impression copings in a multiple variable impression setup for recording multiple straight and angulated implant positions: An in vitro study

Aim

The aim of this study was to evaluate and compare the accuracy of hexed and nonhexed pickup impression copings with and without splinting using polyether (PE) and polyvinyl siloxane (PVS) impression materials in open-tray technique in recording multiple straight and angulated implant positions.

Settings and Design

An accurate impression results in an accurate definitive cast, thus minimizing the incidence of prosthesis misfit. The critical aspect is to record the three-dimensional location of the implant in bone rather than reproducing fine surface details. Precise fit of a fixed implant-supported prosthesis depends on the accuracy of the implant analog location within the definitive cast. Factors which affect impression accuracy include implant angulation, impression material, impression copings, technique, and splinting.

Materials and Methods

A sample size of 80 study models fabricated from the impression of different groups was included. A reference master model based on All-on-4 implant concept with two parallel (implants 1 and 2) and two angulated (implant 3 at 17° and implant 4 at 30°) was fabricated using implant angulation guide. All impressions were recorded using open-tray impression technique. The groups were divided into two main groups of 40 samples each. Group A used hexed open-tray impression copings and Group B used nonhexed open-tray impression copings. Both the groups involved impression recording using splinted (Subgroup I) and nonsplinted impression copings (Subgroup II). Further, impressions in each subgroup were made using PE (Subsubgroups a) and PVS (Subsubgroup b). A total of eight subsubgroups with ten samples each were included. Impressions were recorded for each group and poured into Type IV die stone for fabrication of study models. After 24 h, the study models and reference master model were fitted with implant abutments for measurement with coordinate measuring machine.

Statistical Analysis Used

The mean differences of the interimplant distance R1 (1-2), R2 (1-3), R3 (2-4), and R4 (3-4) between the reference model and sample models in different subsubgroups were calculated and three-way analysis of variance test was applied with Tukey's post hoc tests.

Results

No significant difference was found in mean coronal deviations for distance R1, R2, and R3 (P > 0.05) between different study groups. P = 0.02 for R4 (distance between 17° and 30° implants) between impression materials subsubgroups suggested that significantly less distortion was created in location of highly angulated implants (>30°) using PVS impression material. Splinting and type of coping did not have a significant influence on impression accuracy. Increasing angulation decreased the accuracy.

Conclusion

PVS was found equivalent in accuracy to rigid PE for recording parallel or angulated implants. Impressions of implants with higher angulations were recorded more accurately with PVS. The study found no difference in accuracy with or without splinting. Furthermore, nonhexed impression copings facilitate easier and accurate recording of multiple angulated implant location in bone.

Digital versus conventional full-arch impressions in linear and 3D accuracy: a systematic review and meta-analysis of in vivo studies

OBJECTIVES

The purpose of this systematic review was to compare the accuracy of digital and conventional full-arch impressions in vivo.

MATERIALS AND METHODS

This systematic review was conducted according to the PRISMA and registered at the PROSPERO (CRD42021232736). Electronic and hand searches were performed to identify in vivo studies comparing the linear or 3D accuracy of digital and conventional impressions. The risk of bias (ROB) of included studies was assessed by QUADAS-2, and the overall quality of evidence was assessed by GRADE.

RESULTS

Twenty-two studies met the inclusion criteria, and 13 studies were included in the meta-analysis. There was no significant difference between digital and conventional impressions in the linear measurements of tooth width, anterior Bolton ratio, overall Bolton ratio, intercanine distance (ICD), and intermolar distance (IMD). The repeated measurement mean errors (RMEs) were less than 0.1 mm, the intra-examiner intraclass correlation coefficient (ICC) values were more than 0.9, and the inter-examiner ICC values were more than 0.87 for both impression techniques. The 3D deviation between digital and alginate impressions was 0.09 mm. The 3D precision of both impression techniques was less than 0.1 mm.

CONCLUSIONS

The trueness of digital and alginate full-arch impressions was similar, and both impression techniques showed high precision. More research was needed to compare digital impressions and other conventional impression materials.

CLINICAL RELEVANCE

For patients with completely natural dentition, the digital impressions obtained directly from intraoral scanning can be considered a viable alternative to alginate impressions.

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.

Dimensional accuracy of vinyl polyether and polyvinyl siloxane impression materials in direct implant impression technique for multiple dental implants

Purpose:

The present study compared the dimensional accuracy of vinyl polyether silicone (VPES) and polyvinyl siloxane (PVS) impression materials used for non-splinted (NS) and splinted (S) direct open-tray impression techniques for multiple implants inserted in simulated edentulous mandibles.

Materials and methods:

A mandibular stainless steel model with eight internal connections for implant analogs was fabricated to simulate a clinical scenario. The acrylic resin splinted and non-splinted direct impressions were obtained for both VPES and PVS materials. Seventy-two cast samples were divided into four groups based on the impression techniques and materials used. The dimensional accuracies of the casts were measured in three different axes using a computerized coordinate measuring machine (CMM), and were statistically compared.

Results:

The differences in the distortion values between the VPES and PVS impression materials were not statistically significant. Similarly, the differences between the splinted and non-splinted groups among the VPES and PVS materials were not statistically significant.

Conclusion:

The casts fabricated from VPS or PVS impression materials provide similar dimensional accuracy regardless of the implant splinting method.

Accuracy of guided surgery using the silicon impression and digital impression method for the mandibular free end: a comparative study

Background

Implant treatment using guided surgery is becoming widespread in clinical dental practice. Furthermore, the development of digital technology has enabled the use of intraoral scanners (IOSs) to fabricate surgical guide plates. The objective of this study was to compare the accuracy of guided surgery using the silicone impression method with a three-dimensional (3D) scanner and the digital impression method with IOS for one side of the mandibular free end. In addition, we compared the accuracy of tooth-supported vs tooth/mucosa-supported surgical guide plates.

Results

The accuracy of the tooth-supported surgical guide plate using the new IOS method instead of the method of obtaining impressions with conventional silicone resulted in better measurements of 3D deviation at the crest, 3D deviation at the apex, and angular deviation. In terms of the accuracy of the tooth/mucosa-supported surgical guide plate, there were no significant differences in all measurements. The surgical guide plate using an IOS and the tooth/mucosa-supported surgical guide plate may enable more accurate guided surgery.

Conclusion

Tooth/mucosa-supported guided surgery involving preparation with an IOS may result in more accurate implant surgery.

Effect of contemporary retraction agents and cleaning with hydrogen peroxide on the polymerization of elastomeric impression materials

The aim of the study is to investigate the polymerization inhibition of elastomeric impression materials vinylpoly siloxane (VPS) and polyether (PE) when used in combination with retraction materials with and without subsequent cleaning with hydrogen peroxide (H₂O₂). Methods: Seven stainless steel specimens were fabricated. Four hundred and twenty impressions were made with three different elastomeric materials (140 each) as follows: group 1: VPS-Panasil; group 2: VPS-Express; group 3: PE-Monophase. Each material group was further subdivided into seven subgroups, based on use of no retraction material (control), three different retraction materials [Retraction capsule (RC3M), Dryz, Expasyl], and two cleaning techniques (water and H₂O₂). All subgroups included 20 impressions, which were made by a single operator using an automix gun. Evaluations were made using a visual scale by three calibrated examiners blindly and independently. Subjective categorization of the impressions were made as inhibited and uninhibited. Data were analyzed using Fisher's exact test and significance was set at p < 0.05. Results: Inhibited impressions were lower than uninhibited impressions among VPS materials (Panasil and Express); Panasil and Express showed comparable (p > 0.05) impression retardation. PE showed significantly higher inhibition compared to VPS materials (p < 0.05). Expasyl showed significantly higher polymerization inhibition than other retraction materials (p < 0.05). The use of H₂O₂ for cleaning showed significant reduction in polymerization inhibition than cleaning with water for Expasyl (p < 0.05). Conclusion: Overall contemporary retraction materials showed low potential for polymerization inhibition of elastomeric impression materials. Expasyl should be cleaned with H₂O₂ prior to impression making. However, Dryz and RC3M can show accurate impressions with water cleaning alone.