Correlation of impression removal force with elastomeric impression material rigidity and hardness

Accuracy of Selective Laser Melted Bar Retaining Mandibular Implant-Assisted Overdenture: An In Vitro Comparison of Different Impression Materials and Techniques

This study aimed to assess the accuracy of the marginal fit of 2 implant-supported overdenture bars fabricated with selective laser melting technology, using polyvinyl siloxane and vinyl siloxane ether impression materials and different impression techniques. Two implants with multi-unit abutments were inserted in a 3D-printed mandibular model and used as a reference model, then duplicated into a stone cast to fabricate custom trays for obtaining impressions with polyvinyl siloxane and vinyl siloxane ether impression materials, using both open and closed-tray techniques. This resulted in a total of 4 groups, each with 8 specimens. The impressions were poured and scanned, and 32 cobalt-chromium bars were fabricated using selective laser melting technology. Each bar was screwed onto one abutment of the reference model, and a standardized digital periapical radiograph of the opposite unscrewed side was taken; this process was repeated to the other abutment. The vertical misfit was measured at 3 predetermined positions on the unscrewed side, and 6 values per bar were recorded. The mean gap distance was measured, and the data were subjected to statistical analysis; the present study found that the open-tray technique with vinyl polyether siloxane impression material may offer improved accuracy for obtaining impressions for 2 implant-supported bars. The open-tray technique groups also showed better marginal fit than the closed-tray groups. However, further clinical research is required to confirm these findings.

Influence of intraoral conditions on the accuracy of digital and conventional implant impression techniques for two-implant-supported fixed dental prostheses

PURPOSE

To compare the trueness and precision of different impression techniques for two-implant-supported fixed dental prostheses between extraoral and intraoral conditions at different locations.

METHODS

Six volunteers participated in this study. A resin block with two parallel analogs was fabricated as an implant site simulator (ISS). The ISS was bonded to a molded ethylene vinyl acetate sheet to create a reference model. For each participant, four reference models were prepared based on the locations of the ISSs: maxillary posterior/anterior region (MaxP/MaxA) and mandibular posterior/anterior region (ManP/ManA). Five impressions were taken extraorally using the open-tray (conventional implant impression technique, CIT) and intraoral scanning (digital implant impression technique, DIT) techniques. The reference models were positioned in the participants' mouths, and impressions were obtained intraorally using the CIT and DIT. The interanalog distance (d) and angulation (θ) were measured to calculate trueness (Δd, Δθ) and precision (dP, θP). Two-way ANOVA and t tests were performed (α=0.05).

RESULTS

For the DIT, under intraoral conditions, the Δd and Δθ in MaxP and Δθ in ManP were significantly higher than those under extraoral conditions. For the CIT, under intraoral conditions, the Δd and Δθ in ManA and ManP and Δθ in MaxP were significantly lower than those under extraoral conditions. No significant differences in the dP and θP of either DIT or CIT were observed between the two conditions.

CONCLUSIONS

Intraoral conditions affected the trueness of DIT and CIT in different regions but had no influence on precision.

Optimal impression materials for implant-supported fixed complete dentures: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Although polyvinyl siloxane (PVS) materials and polyether (PE) materials have been the recommended materials for making impressions for implant-supported fixed complete dentures (IFCDs), a consensus regarding the optimal impression materials has yet to be established.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the effect of impression materials on the accuracy of conventional impressions for IFCDs and to provide guidance for selecting the optimal impression material.

MATERIAL AND METHODS

The PubMed, Web of Science, and Embase databases were searched and supplemented via hand searches. Studies comparing the accuracy of conventional impressions for IFCDs by using PVS and PE materials with either direct (open-tray) or indirect (closed-tray) techniques were included. Linear distance deviations and angular deviations between adjacent implants were evaluated. The mean difference (MD) with a 95% confidence interval (CI) was calculated for continuous data. A subgroup analysis was conducted to evaluate the impact of implant angulation (α=.05).

RESULTS

Among the 597 publications identified, 27 in vitro studies were included for qualitative analysis, and 12 were included for quantitative analysis. The general analysis revealed no significant differences in linear distance and angular deviations between the 2 impression materials with the direct or indirect technique. The subgroup analysis found that a statistically significant difference in linear distance deviations was found when implants were placed at an angle greater than 15 degrees, favoring PE materials when using the direct technique (P=.010, MD: 32.54 µm; 95% CI: 6.83 to 58.24) and indirect technique (P=.020, MD: 138.15 µm, 95% CI: 19.17 to 257.13). However, only 2 relevant studies assessed the indirect technique.

CONCLUSIONS

When providing IFCDs, conventional impressions obtained by using PVS and PE materials were found to have similar accuracy in most scenarios. PE materials yielded better outcomes when implants were placed at an angle greater than 15 degrees.

Dental trauma splints for the mixed dentition - A finite element analysis of splint material, splint extension, missing teeth, and PDL representation

BACKGROUND/AIMS

Dental traumatic injuries are common in children during the mixed dentition stage. These injuries usually require splinting for stabilization, which is complicated by the various stages of the permanent tooth development and primary tooth exfoliation. The aim of this study was to evaluate the effect on mobility of splint materials and extensions for an avulsed central incisor, stabilized with and without the adjacent incisor under intrusive and extrusive loading with different periodontal ligament (PDL) conditions.

MATERIALS AND METHODS

Seventeen 3D model variations were created from a CBCT scan of a 7-year-old patient without erupted permanent upper lateral incisors. A 1000 N palatal load on the right central incisor simulated the avulsion injury and created an increased alveolus and bone deformation, resulting in an increased PDL thickness of 0.45 mm. Wire-resin composite splints with 0.9 mm cross-section (WCS) or 1.0 mm diameter nylon-resin composite splints (NCS) were created. The models simulated conditions with and without the adjacent upper central incisor. Two PDL conditions were investigated, simulating detached PDL or PDL with polyether impression material-like properties. Mobility was calculated under simulated biting loads in horizontal and vertical (intrusive and extrusive) directions.

RESULTS

The NCS allowed greater tooth mobility of the avulsed incisor than the WCS, irrespective of splint extension, PDL condition, or load application. During horizontal loading, polyether-like properties for the PDL allowed around 0.2 mm mobility of the avulsed tooth with the WCS, similar to the intact tooth, whereas a simulated detached PDL allowed 25% more mobility with a WCS than with a NCS.

CONCLUSIONS

Based on the FEA analysis, a 1.0 mm NCS may be suitable for splinting avulsion injuries during the mixed dentition stage compared to the considerably more rigid WCS. The NCS models provided flexibility for PDL healing while maintaining stability, even when missing adjacent teeth increased span widths. Extensions beyond directly adjacent teeth did not alter the mobility with the NCS but should still be considered an extra protection in case of bond failure or exfoliation.

Update on the Accuracy of Conventional and Digital Full-Arch Impressions of Partially Edentulous and Fully Dentate Jaws in Young and Elderly Subjects: A Clinical Trial

To update the available literature on the accuracy of conventional and digital full-arch impressions using the latest hardware and software, participants of different age groups and dental status were investigated. An established reference aid-based method was applied to analyze five intraoral scanners (IOS) CS 3800 (CS), iTero Element 5D (IT), Medit i700 (ME), Primescan (PS), and Trios 4 (TR), and one conventional polyether impression (CVI). Forty-five participants were classified into three groups: Age 27.3 ± 2.7 years fully dentate, 60.6 ± 8.1 years fully dentate, and 65.7 ± 6.2 years partially edentulous. The IOS datasets were investigated using three-dimensional software (GOM Inspect), and plaster casts of CVI were analyzed using a co-ordinate measurement machine. The deviations of the reference aid to impressions were determined. No significant differences in age between the three groups were observed by the IOS in terms of trueness (p < 0.05). These findings were confirmed for precision, except for TR. In contrast to CS (mean ± standard deviation 98.9 ± 62.1 µm) and IT (89.0 ± 91.0 µm), TR (58.3 ± 66.8 µm), ME (57.9 ± 66.7 µm), and PS (55.5 ± 48.7 µm) did not show significant differences than those of CVI (34.8 ± 29.6 µm) in overall view. Within the study, the latest IOSs still showed limitations in the accuracy of full-arch impressions. However, they seemed to be unaffected by age and fully dentate or partially edentulous dentitions with small gaps.

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

Aim:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

Evaluation of Elastomeric Impression Materials' Hydrophilicity: An in vitro Study

Introduction

Hydrophilicity of dental impression materials is crucial for obtaining an accurate impression and necessary for the production of a well-fitting cast restoration. The most common technique for evaluation of hydrophilicity is a contact angle measurement. The aim of the present in vitro study was to compare the water contact angles of four groups of elastomeric impression materials, before and during setting.

Material and methods

Flattened specimens (n=10) of tested impression materials were prepared by the use of a Teflon mold with specific dimensions. A 5μl droplet of deionized water fell on the specimen, and photos were taken using a Nikon D3200 DSLR camera and a 105 mm macro lens (Nikorr, Nikon) in specific time points.

Results

The CAD/CAM material showed the highest contact angle measurements. The light body polyvinylsiloxane (PVS) material 1, polyether and vinylsiloxanether material showed comparable contact angle measurements especially at the initial time point. A statistically significant reduction of contact angles was reported during setup time for all PVS, PE and vinylsiloxanether materials, while the most expressed reduction of contact angle measurements, and thus the most significant increase of hydrophilicity were reported for light wash PVS material 2.

Conclusions

The CAD/CAM impression material showed the most hydrophobic behavior. PVS materials showed excellent hydrophilicity. Polyether and polyvinyloxanether impression materials presented lower contact angle measurements, and thus superior hydrophilicity, compared with other tested materials initially and during setting. All tested impression materials presented a stepwise development of hydrophilicity during the setting stage.

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.

Dental Impression Materials and Techniques

Dental impression making is the process of creating a negative form of the teeth and oral tissues, into which gypsum or other die materials can be processed to create working analogues. Contemporary dentistry generates new information every year and digital dentistry is becoming established and influential. Although dentists should stay abreast of new technologies, some of the conventional materials and time-tested techniques remain widely used. It is important to review the impression-making process to ensure that practitioners have up-to-date information about how to safely and effectively capture the exact form of the oral tissues to provide optimal patient management.

A modified shark-fin test simulating the single-step/double-mix technique: A comparison of three groups of elastomers

The shark-fin test was modified to convey the clinical application of a single-step/double-mix technique assessing the behavior of two viscosities applied at one point in time. A medium and light body polyether (PE), a medium and light body polyvinylsiloxane (PVS), and a medium as well as heavy and light body vinyl polyether silicone (PVXE) impression material were analyzed solely, and in a layered mixture of 1:1 and 3:1 at working times of 50, 80, and 120 s. The fin heights were measured with a digital ruler. The wettability was measured 50 and 80 s after mixing by drop shape analysis. The results showed a synergistic effect of the medium and light body PE. This was not observed in PVXE and PVS. Interestingly, PVXE showed an antagonistic flow behavior in 3:1 mixture with medium body. PVXE was more hydrophilic than PE and PVS. Future rheological studies should clarify the detected flow effects.

Ultrasonic monitoring of the setting of silicone elastomeric impression materials

This study used an ultrasonic measurement device to monitor the setting behavior of silicone elastomeric impression materials, and the influence of temperature on setting behavior was determined. The ultrasonic device consisted of a pulser-receiver, transducers, and an oscilloscope. The two-way transit time through the mixing material was divided by two to account for the down-and-back travel path; then it was multiplied by the sonic velocity. Analysis of variance and the Tukey honest significant difference test were used. In the early stages of the setting process, most of the ultrasonic energy was absorbed by the elastomers and the second echoes were relatively weak. As the elastomers hardened, the sonic velocities increased until they plateaued. The changes in sonic velocities varied among the elastomers tested, and were affected by temperature conditions. The ultrasonic method used in this study has considerable potential for determining the setting processes of elastomeric impression materials.

Influence of different fillers on the properties of an experimental vinyl polysiloxane

The aim of the study was to evaluate the effect of the incorporation of different fillers on an experimental vinyl polysiloxane (VPS) at two different concentrations, 20% and 40%. Different fillers were added to an experimental VPS. The study was developed in two stages: (i) incorporation of fillers in different concentrations: (a) 20 wt% fillers, and (b) 40 wt%. The fillers were added to experimental VPS and mixed with a speed mixer; (ii) characterization of experimental VPS; after the base paste and catalyst paste were mixed, the experimental VPS was used to make specimens specifically for each test, which were stored at 23°C for 24 hours. The tests were designed according to the specific standardization for the analysis of tensile strength, detail reproduction, Shore A hardness, and elastic recovery. For analysis of filler size pattern, scanning electron microscopy at 1500× magnification was used. The aerosil OX-50 40% (AE), and pure aluminum hydroxide 40% (PAH) groups presented the highest tensile strength and Shore A hardness values. However, those were the only groups that did not present continuous detail reproduction of an intersection of 20 μm line. The elastic recovery was not statistically significant. The undesirable characteristics of VPS (lowest Shore A hardness and tensile strength) were observed when it was added to the composition of acrylic polymer (AP) and fiberglass (FG) in both concentrations, 20% and 40%. In groups AE and PAH, agglomerates of nanofillers were shown in SEM micrography, while the other groups presented different shapes and fillers sizes.

Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison

Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas.