Polyvinyl Siloxane Impression Research Articles

Resin Composite Depth of Cure Through Transparent Matrix Materials Used for Injection Molding.

The purpose of this study was to compare the curing light transmittance and depth of cure (DOC) of resin composite through clear polyvinyl siloxane (PVS) impression materials and 3D printed clear matrix materials at various thicknesses. Cylindrical specimens (n=6) of three clear PVS materials (Affinity Crystal, Clear Bite Matrix, Exaclear) were fabricated in Teflon molds, and two 3D-printed clear matrix materials (Filtek matrix, IDB 2) were printed into specimens of five different thicknesses (2 mm, 4 mm, 6 mm, 8 mm, 10 mm). To measure light irradiance transmittance, specimens were placed on a radiometer (CheckUp), allowing the transmitted irradiance from a light-curing unit (Elipar DeepCure-S, 1450 mW/cm2) to be recorded. DOC of resin composite specimens was measured by placing flowable composite (PVS and IDB 2) or heated conventional composite (Filtek Matrix) into a split metal die with a 4 mm diameter opening. The composite was cured through the different matrix specimens using the Elipar DeepCure-S curing light for the manufacturer's recommended curing time (10 seconds) or double the curing time (20 seconds). The DOC of the composite specimens was measured according to ISO 4049 7.8, and the percentage of total cure (%TC) was calculated by dividing by the total cure (DOC with no matrix and 10-second cure). The correlation between irradiance transmittance and %TC was analyzed with Pearson's coefficient. For each matrix material, the %TC was compared to the total cure of the material using a Dunnett's test. The compressive modulus of each material was measured and compared with a one-way ANOVA. There was a statistically significant, strong positive correlation between irradiance transmittance and %TC for 10 seconds (r=0.90 p<0.001) and 20 seconds (r=0.89 p<0.001). There was not a statistically different DOC for the total cure with Affinity (2 mm), Clear Bite (2 mm), Exaclear (2, 4, 6 mm), IDB2 (2, 4, 6, 8 mm), and Filtek Matrix (2,4 mm) if a 20-second cure was used. Decreased light irradiance from curing through clear matrix materials decreases the DOC of resin composites. Doubling the curing time when curing through some matrix materials at certain thicknesses allowed a total cure.

Comparative analysis of the fit quality of monolithic zirconia veneers produced through traditional and digital workflows using silicone replica technique: an in vitro study

BackgroundThe success of a restoration largely depends on the quality of its fit. This study aimed to investigate the fit quality of monolithic zirconia veneers (MZVs) produced through traditional and digital workflows.MethodsA typodont maxillary right central incisor was prepared. The maxillary arch with the prepared tooth was scanned with Trios 3 Pod intra-oral scanner (IOS), which served as a pattern to create thirty 3D resin models through printing. Additionally, thirty conventional impressions of the maxillary with the prepared tooth were taken using polyvinyl siloxane (PVS) impression material. These impressions were cast using dental gypsum products to create thirty stone dies, which were then scanned externally. Sixty MZVs were milled from multi-layered zirconia disks. The marginal and internal gaps of restorations were assessed using the silicone replica technique.ResultsThe highest marginal accuracy for both the conventional and digital impression groups was observed in the cervical area, with values of 74.6 μm and 61.9 μm, respectively. The smallest internal gaps for both groups were also recorded in the cervical area, at 109.9 μm for the conventional group and 109.7 μm for the digital group. The digital group exhibited better marginal fit, particularly in the incisal and mesial areas (79.3 μm and 75.7 μm, respectively), compared to the conventional group (88.1 μm and 90.8 μm). No statistically significant differences in internal fit were observed.ConclusionMZVs fabricated using the digital workflow exhibited superior marginal fit compared to those fabricated using the conventional workflow, though both techniques yielded clinically acceptable results.

Evaluation of Internal Fit in Custom-Made Posts and Cores Fabricated with Fully Digital Versus Conventional Techniques.

This study aimed to assess and compare the internal fit of custom-made posts and cores fabricated using digital impressions (DI) and conventional vinyl polysiloxane (VPS) impressions in restorative dentistry. A typodont tooth model, simulating the anatomy of the root canal of a central incisor, was utilized for the study. Two groups were formed, Group A and Group B, and each group provided a total of 18 impressions of two types: DIs and VPS impressions. In Group A, posts and cores (PCs) were fabricated using Selective Laser Melting (SLM) from the DIs. Meanwhile, in Group B, conventionally cast (CC) PCs were created from the VPS impressions. Silicone replicas of the internal surfaces were produced, and measurements were made at seven different points for each group. A statistical analysis was performed to assess the differences in internal fit between the two impression techniques. The results revealed a statistically significant difference in mean internal fit between Group A (DI and SLM) and Group B (VPS and CC), with Group A exhibiting a mean internal fit of 182.6 µm and Group B showing a mean of 205.9 µm. While both groups demonstrated considerable variability in internal fit measurements, the digital impression technique showed promise for achieving superior internal fit, with a significantly greater fit for measuring points on sides and the most apical part of the post for Group A. Variations were observed across different measuring points, emphasizing the impact of impression technique on specific regions within the tooth. This study contributes to the growing body of knowledge in digital dentistry by highlighting the potential benefits of DIs in achieving a superior internal fit for custom-made PCs. Clinicians may consider the advantages of digital techniques to enhance the precision of their restorative procedures, although further research is warranted to evaluate the clinical impact of these findings.

Prospective clinical study of enamel wear caused by monolithic zirconia resin-bonded inlay-retained and wing-retained fixed partial dentures over 5 years

ObjectivesTo prospectively evaluate the wear of posterior zirconia resin-bonded fixed partial dentures (RBFPDs) with polished occlusal surfaces and their natural enamel antagonists compared to contralateral controls in an enamel-enamel contact over 5 years.Materials and methodsIn six patients with either an inlay- or wing-retained RBFPD made of monolithic 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), wear was evaluated indirectly using baseline and annual polyvinyl siloxane impressions. Resulting gypsum models were digitized and aligned by unchanged surface areas. Wear was analyzed by depth and area. For each parameter, descriptive statistics were used to express the degree of wear observed at yearly intervals for each group. A linear mixed regression analysis was performed to compare the enamel opposing 3Y-TZP group and the enamel-enamel controls at tooth level. All statistical tests were conducted at the 5% significance level.ResultsAfter 5 years, the mean enamel wear depth of teeth opposing 3Y-TZP was 77 μm, compared to 54 μm for control teeth. No wear was observed on the 3Y-TZP RBFPDs. Maximum enamel wear depth and wear area were 229 μm and 9 mm², respectively, for teeth opposing 3Y-TZP, and 135 μm and 5 mm² for control teeth. Significant differences in mean enamel wear depth emerged after 2 years of observation.ConclusionsPolished 3Y-TZP caused more enamel wear than natural antagonists over 5 years, but the wear remained within the range reported for other commonly used indirect restorative materials.Clinical relevanceThe clinical use of polished 3Y-TZP restorations appears to be justified in terms of natural antagonist wear behavior.

Changes in Occlusal Contacts upon the Cementation of Zirconia Crowns with Different Cement Spacers.

Background/Objectives: Occlusion plays a crucial role in the long-term success and functionality of dental restorations. The purpose of this study was to investigate the changes in occlusal contacts upon the cementation of zirconia crowns with different cement spacer settings in computer-aided design and computer-aided manufacturing (CAD-CAM) software (3Shape Dental System version 2.102.1.0). Methods: A master model of a prepared abutment for a crown on the right maxillary first molar was scanned, and 30 sets of sample casts and zirconia crowns were fabricated with varying cement spaces (70 μm and 120 μm). These casts were mounted in maximal intercuspation (MIP) on a semi-adjustable articulator. Pre-cementation adjustments were made to fit the crowns and maintain the existing occlusion. Occlusal records were taken before and after cementation using polyvinyl siloxane impression material. These records were analyzed using a DC light box and image analyzer to measure changes in contact area, intensity, and patterns. Paired sample t-tests were used to compare pre- and post-cementation occlusal contact areas of each sample (α = 0.05). Results: Significant differences in occlusal contact areas were found between pre- and post-cementation in both groups (p < 0.001). The mean post-cementation contact surface area for the 70 μm group was 6281 ± 3310 μm2, compared to 2339 ± 1206 μm2 before cementation. For the 120 μm group, the post-cementation area was 5545 ± 3491 μm2, compared to 2071 ± 909 μm2 before cementation. An increase in contact intensity was also observed after cementation. Conclusions: This study demonstrates that cementation increases occlusal contact surface area and intensity in both cement space groups.

Assessment of clinical reproducibility for intraoral scanning on different anatomical regions for the complete maxillary edentulous arch with two intraoral scanners

ObjectivesThere are no in vivo studies comparing multiple intraoral scanners for the completely edentulous maxilla to PVS impressions. Investigations comparing intraoral scanners to polyvinyl siloxane impressions focus on comparing the overall scan and not individual anatomical regions. This study aims to evaluate two intraoral scanners and compare the results for different anatomical regions on the completely edentulous maxillary arch. Materials and methodsNineteen patients were recruited with a completely edentulous maxilla. A custom tray was constructed, and a sectional border moulded polyvinyl siloxane impression was made then scanned. An intraoral scan of the edentulous maxilla with a Trios 4 (3Shape, B/V) and Medit i700 (Medit corporation) was then captured. The scans were analysed for negative and positive surface deviations along with root mean square for distinct anatomical regions compared to the polyvinyl siloxane impression. A two-way ANOVA followed by Tukey HSD post hoc tests for each scanner was conducted for all anatomical regions to determine differences between the regions. ResultsThere was no significant difference between the two intraoral scanners included in this study for all anatomical regions or for the overall scan (0.435, 0.38), palatal vault (0.18, 0.181), ridge (0.218, 0.209), and post dam (0.233, 0.229) anatomical regions. Significantly higher deviation (p<0.05) was observed for the peripheral regions (0.607, 0.557) for each intraoral scanners Trio 4 and Medit i700. ConclusionDifferent intraoral scanners can capture all areas of a completely edentulous maxilla consistently, when compared to a polyvinyl siloxane impression, apart from the peripheries. Clinical significanceCare should be taken when scanning the peripheries. These regions are problematic to capture with an intraoral scanner. Border moulding should still be considered the optimal impression technique for the completely edentulous maxilla. The intraoral scanners investigated did not make a difference for the anatomical regions investigated.

Accuracy of intraoral versus desktop scanners used in digitizing polyvinyl siloxane impression for fabricating a CAD-CAM customized post and core.

This in vitro study aimed to compare the 3-dimensional (3D) accuracy of intraoral and desktop scanners when digitizing the post and core polyvinyl siloxane impressions. Ten extracted human teeth were prepared to build a post space in the root canal. Each tooth was scanned using a micro-computed tomography device (MCT), and the slice data were reconstructed as controls. A conventional quadrant polyvinyl siloxane impression was made and scanned thrice using an intraoral scanner (IOS) and a desktop blue-light scanner (IMS), with one of the scans randomly selected as the definitive cast. Precision was assessed by comparing the deviations among repeated scans. Trueness was evaluated by analyzing the deviations between the MCT and each definitive cast (MCT-IOS and MCT-IMS). The clinically acceptable root mean square (RMS) value was set to 50 µm. The mean RMS values of the repeated scans of IOS and IMS were 18.3 ± 3.9 µm and 13.9 ± 6.2 µm (P < 0.05), and the difference between them was 4.4 ± 5.9 µm. The mean RMS values of MCT-IOS and MCT-IMS were 28.3 ±3.0 µm and 31.3 ± 4.2 µm (P < 0.05), with a difference of 3.0 ± 2.9 µm. The RMS values were significantly lower than 50 µm (P < 0.05). The IOS showed slightly better trueness than the IMS but slightly lower precision. The precision and trueness of the two scanners for digitizing post and core impressions were acceptable for clinical application.

Effect of Implant Analog Design and Additively Manufactured Casts' Printing Layer Thickness on the Linear and Angular Accuracy of Analogs for Direct Digital Workflow: An In Vitro Study.

To evaluate how implant analog design and printing layer thickness affect the linear and angular accuracy of implant analogs in additively manufactured casts, comparing with conventional implant analogs in stone casts. A reference cobalt chromium mandibular model with a single implant was digitized with an industrial optical scanner and scan bodies compatible with a pressure/friction fit (S) or a screw-retained (N) implant analog for direct digital workflow. These scans were used to fabricate casts with 50 μm (S-50 and N-50) and 100 μm (S-100 and N-100) layer thickness (n&#61;10). Ten stone casts were made after single-step closed-tray polyvinylsiloxane impressions of the model (CNV). All casts were digitized with the same metal scan body and scanner used to digitize the master model, and these scans were superimposed over the scan of the master model to measure the linear (x, y, and z-axes) and angular (XY and YZ planes) deviations (Geomagic Control X). The precision of measured deviations was defined with the average deviation values. Generalized linear model analysis was used to compare the deviations within implant analogs for direct digital workflow, while 1-way analysis of variance and Dunnett's test were used to compare these analogs and conventional analogs (α &#61; .05) Results. The analog design affected the linear deviations (y-axis), while the interaction between the analog design and the layer thickness, and the analog design affected the angular deviations (XY plane, P ≤ .030). S analogs had lower linear and angular deviations than N analogs, and S-50 led to lower angular deviations than N-50 (P ≤ .030). CNV led to higher linear accuracy (y-axis) than N-50, N-100, and S-100 and led to lower angular deviations than all test groups (XY plane) (P ≤ .025). The analogs in S-50 casts had positional trueness similar to or higher than those in other test groups and their accuracy was mostly similar to those in CNV casts. Implant analogs for direct digital workflow deviated more towards lingual and gingival, and conventional analogs deviated more towards buccal, occlusal, and distal. All analogs had a tendency to tilt towards lingual and distal.

Characterization of spent nuclear fuel canister surface roughness using surface replicating molds

In this study we present a replication method to determine surface roughness and to identify surface features when a sample cannot be directly analyzed by conventional techniques. As a demonstration, this method was applied to an unused spent nuclear fuel dry storage canister to determine variation across different surface features. In this study, an initial material down-selection was performed to determine the best molding agent and determined that non-modified Polytek PlatSil23-75 provided the most accurate representation of the surface while providing good usability. Other materials that were considered include Polygel Brush-On 35 polyurethane rubber (with and without Pol-ease 2300 release agent), Polytek PlatSil73-25 silicone rubber (with and without PlatThix thickening agent and Pol-ease 2300 release agent), and Express STD vinylpolysiloxane impression putty. The ability of PlatSil73-25 to create an accurate surface replica was evaluated by creating surface molds of several locations on surface roughness standards representing ISO grade surfaces N3, N5, N7, and N8. Overall, the molds were able to accurately reproduce the expected roughness average (Ra) values, but systematically over-estimated the peak-valley maximum roughness (Rz) values. Using a 3D printed sample cell, several locations across the stainless steel spent nuclear fuel canister were sampled to determine the surface roughness. These measurements provided information regarding variability in normal surface roughness across the canister as well as a detailed evaluation on specific surface features (e.g., welds, grind marks, etc.). The results of these measurements can support development of dry storage canister ageing management programs, as surface roughness is an important factor for surface dust deposition and accumulation. This method can be applied more broadly to different surfaces beyond stainless steel to provide rapid, accurate surface replications for analytical evaluation by profilometry.

Accuracy of polyether and vinylpolysiloxane impressions when using different types of 3D-printed impression trays - an in vitro study.

To investigate dimensional accuracy of polyether (PE) and vinylpolysiloxane (VPS) impressions taken with manually fabricated and 3D-printed trays. To evaluate impression accuracy, highly precise digital data of a metallic lower jaw model with prepared teeth (regions 34 and 36), an implant (region 47) and three precision balls placed occlusally along the dental arch served as reference. PE (Impregum, 3M Oral Care) and VPS (Aquasil, Dentsply Sirona) impressions (n = 10/group) were taken with trays fabricated using different materials and manufacturing techniques (FDM: filament deposition modeling, material: Arfona Tray, Arfona; printer: Pro2, Raise3D; DLP: digital light processing, material: V-Print Tray, VOCO, printer: Max, Asiga; MPR: manual processing with light-curing plates, material:LC Tray,Müller-Omicron) including an open implant impression. Scans of resulting stone models were compared with the reference situation. Global distance and angular deviations as well as local trueness and precision for abutment teeth and scan abutment were computed. Possible statistical effects were analyzed using ANOVA. Clinically acceptable global accuracy was found (all mean absolute distance changes < 100μm) and local accuracy for single abutments was excellent. All factors (abutment type, impression material, tray material) affected global accuracy (p < 0.05). In particular with PE impressions, MPR trays led to the best accuracies, both in horizontal and vertical direction. Within the limitations of this in vitro study, impression accuracy was high in use of both polyether and vinylpolysiloxane combined with different 3D-printed and customized trays making them recommendable for at least impressions for smaller fixed dental prostheses. Manually fabricated trays were overall still the best choice if utmost precision is required. Based on the results of this study, use of innovative CAD-CAM fabrication of individual impression trays fulfills the perquisites to be a viable option for impression making. In the sense of translational research, performance should be proved in a clinical setting.

In vitro Evaluation of Implant Impression Techniques and Elastomeric Materials: A Comparative Dimensional Accuracy Study

Context: Dimensional precision in implant impression. Aims: The purpose of this study was to comparatively evaluate the dimensional accuracy of two implant impression techniques with two different variants of vinyl polysiloxane impression material. Material and Methods: The edentulous mandible reference model was fabricated in clear resin. In the anterior region of the mandibular ridge, three dummy implants were placed in a spread-out configuration. Impressions were made using two elastomeric impression materials and two impression techniques using customised impression trays. Finished casts were then divided into four groups having four samples each. The mean centre-to-centre distances between adjacent analogues (in sample casts) and between adjacent implants (in the control cast) were measured with the help of a profile projector. Statistical Analysis Used: Data were analysed using Student’s t-test. Results: The open-tray technique showed more accurate results with a combination of medium body and light body, whereas in the closed tray technique, mono-phase vinyl polysiloxane appeared to be a better option. Amongst all, mono-phase with closed tray provided statistically significant results. P ˂ 0.05 in Group C and other group’s P ≥ 0.05. Conclusions: Within the limitations of this study, both implant impression techniques appeared to be equally accurate depending on clinical conditions, temperature and time of the procedure. However, mono-phase impression material with closed tray provided statistically significant results.

A method of impressing flabby ridge

Flabby ridge remained a challenge in dental clinical practice to obtain an accurate impression for edentulous patients. During the traditional impression making process, the excessive and displaceable soft tissue are usually compressed. In this article, we presented an impression method by using a modified special stock tray, impression compound and polyvinyl siloxane impression materials.•the suitable stock tray was modified with holes about 5 mm diameter in the corresponding area to the crest of the flabby ridge.•the primary impression was made by position the modified tray with the softened compound impression on the edentulous ridge, avoiding the area of the flabby ridge.•the final accurate impression was obtained by using the light body polyvinyl siloxane impression material.

In vitro evaluation of the impact of intraoral scanner, scanning aids, and the scanned arch on the scan accuracy of edentulous arches.

To assess the accuracy of complete maxillary and mandibular edentulous arch scans obtained using two different intraoral scanners (IOSs), with and without scanning aids, and to compare these results to those obtained using conventional impression methods. Two IOSs were used (TRIOS 4 [TRI] and Emerald S [EMR]) to scan maxillary and mandibular typodonts. The typodonts were scanned without scanning aids [TRI_WSA and EMR_WSA groups] (n = 10). The typodonts were then scanned under four scanning aid conditions (n = 10): composite markers [TRI_MRK and EMR_MRK groups], scanning spray [TRI_SPR and EMR_SPR groups], pressure indicating paste [TRI_PIP and EMR_PIP groups], and liquid-type scanning aid [TRI_LQD and EMR_LQD groups]. Conventional impressions of both arches were also made using irreversible hydrocolloids in stock trays [IHC] and using polyvinyl siloxane (PVS) impression material in custom trays (n = 10) which were digitized using a laboratory scanner. Using a metrology software program, all scans were compared to a reference scan in order to assess trueness and to each other to assess precision. Trueness and precision were expressed as the root mean square (RMS) of the absolute deviation values and the statistical analysis was modeled on a logarithmic scale using fixed-effects models to meet model assumptions (α = 0.05). The main effect of arch (p = 0.004), scanner (p < 0.001), scanning aid (p = 0.041), and the interaction between scanner and scanning aid (p = 0.027) had a significant effect on mean RMS values of trueness. The arch (p = 0.015) and scanner (p < 0.001) had a significant effect on the mean RMS values of precision. The maxillary arch had better accuracy compared to the mandible. The TRIOS 4 scanner had better accuracy than both the Emerald S scanner and conventional impressions. The Emerald S had better precision than conventional impressions. The scanning spray and liquid-type scanning aids produced the best trueness with the TRIOS 4 scanner, while the liquid-type scanning aid and composite markers produced the best trueness for the Emerald S scanner. The scanned arch and the type of scanner had a significant effect on the accuracy of digital scans of completely edentulous arches. The scanning aid had a significant effect on the trueness of digital scans of completely edentulous arches which varied depending on the scanner used.

Fracture resistance of endodontically treated root obturated with different root canal sealers( A comparative in vitro study)

Aim: The aim of this study is to evaluate and compare the fracture resistance of endodontically treated root obturated with four different root canal sealers.. Methods: Sixty extracted palatal root of upper molars were collected and sectioned to get a 11mm root length. All root canals were instrumented using edge endo X7 system rotary files and 35# size was the final size used to finish all the canals. After instrumentation the samples were divided into four groups of 15 samples in each according to the type of sealer used, a single cone obturation technique was used: Group 1: obturated with AH Plus sealer and gutta-percha. Group 2: obturated with Neosealer BC sealer and gutta-percha. Group 3: Obturated with MTA-Fillapex sealer and gutta-percha. Group 4: Obturated with OneFill BC sealer and gutta-percha. After incubation period of 7 days at 37°C and 100% humidity the samples covered with thin layer polyvinylsiloxane impression material to simulate a periodontal membrane and then molded in acrylic blocks so as to set the samples ready for fracture resistance test using universal testing machine at a cross head speed of 0.5mm/min., One-way ANOVA and Posthoc tests assessed the data statistically. Results: The results showed that fracture resistance was significantly higher in those canals that were filled with Neosealer BC sealer (69.90N) in comparison to the other different sealers used in the study (p≤0.05). Conclusion: Under the condition of this study, the following conclusions can be derived: The application of any root canal sealers resulted in an enhancement of the resistance to fractures in teeth that have undergone endodontic treatment. Neosealer Bioceramic sealer group showed the highest fracture resistance than other groups. Followed by Onefill bioceramic, MTA Fillapex and Ah plus.

Fracture Resistance of Posterior Milled Nanoceramic Crowns after Thermomechanical Aging.

Fracture resistance is an important parameter used to predict the performance of indirect dental restorations. The purpose of this in vitro study was to assess the fracture load of posterior milled nanoceramic crowns, in comparison with the lithium disilicate crowns, after fatigue loading, for two different restoration occlusal thicknesses. Forty test metal dies were fabricated by duplicating a master metal model consisting of an anatomic abutment preparation of the maxillary first premolar for a single crown. The dies were divided into two groups of 20 each for the fabrication of nanoceramic (Lava Ultimate) and lithium disilicate (IPS e.max CAD) single crowns. Each material group was further divided into two sub-groups of 10 dies each, based on crown occlusal thickness, of 0.5-mm and 0.75-mm (n = 10). Dental Type V stone dies poured from polyvinyl siloxane impressions of the test metal dies were laboratory scanned in order to design and mill 40 ceramic crowns. The crowns were cemented on to the test metal dies with a self-adhesive resin luting cement. All crowns were thermocycled (2500 cycles) and mechanically loaded (250,000 cycles) in a chewing simulator followed by static loading until failure, and the values noted. The data were statistically analyzed by 2-way ANOVA and Tukey HSD post-hoc multiple comparison tests (α = 0.05). The mean fracture loads ranged from 1022 to 1322 N for nanoceramic crowns and from 1145 to 1441 N for the lithium disilicate crowns. Two-way ANOVA revealed insignificant differences between the nanoceramic and lithium disilicate crowns (p > 0.05) in terms of fracture load. Significant differences were noted in the fracture resistance of crowns based on occlusal thickness (303 N; p = 0.013) regardless of the material used. Multiple comparisons by Tukey HSD post-hoc test showed insignificant differences between the four material-occlusal thickness groups (p > 0.05). The nanoceramic crowns were found to be comparable with lithium disilicate crowns in terms of fracture load. The mean fracture loads of all of the tested crowns were within the normal physiological masticatory load limits. Based on the fracture-resistance results, nanoceramic crowns seem to be suitable for clinical use for the tested occlusal thicknesses.

Digital Evaluation of Trueness and Precision of Modern Impression Materials in Implant- Retained Mandibular Overdentures.

The purpose of this in vitro study was to evaluate the dimensional accuracy, trueness, and precision of vinyl siloxane ether (VSXE) and polyvinylsiloxane (PVS) impression materials using different impression techniques. A three-dimensional (3D) printed mandibular model with implants and metal rods served as the reference model. Impressions were taken in custom trays, resulting in four groups: PVS-closed-tray, VSXE-closed-tray, PVS-open-tray, and VSXE-open-tray. The reference model and impressions were scanned and analyzed using 3D analysis software to assess the trueness and precision within each group. There was significant difference in trueness between the groups, with PVS closed tray showing a higher deviation than VSXE-closed-tray and PVS-open-tray. VSXE-open-tray had the lowest deviation, which was statistically significant. In terms of precision, PVS-closed-tray showed the highest deviation, while no significant differences were found among the other groups. VSXE impression material with an open tray technique consistently demonstrated the highest levels of accuracy and precision. Conversely, PVS impression material with a closed tray technique yielded less favorable results. Better understanding of trueness and precision of new impression materials with new impression techniques will increase their clinical effectiveness.

Food impaction on three-dimensional printed models with periodontal ligament simulation.

This study aims to evaluate food impaction on three-dimensional (3D) printed models with periodontal ligament simulation. Based on a commercial typodont pair, 3D maxillary and mandibular models were created with no teeth and with tooth sockets that were 1 mm wider than the original ones from 24 to 27 or 34 to 37 for periodontal ligament simulation with vinyl polysiloxane impression material. In total, 35 pairs of 7 combinations, including maxillary/mandibular typodonts in occlusion with maxillary/mandibular 3D models with/without a distal gap of canines on 3D models (tooth 23 or 33) were mounted on hinge articulators and divided into seven groups (n = 5). Each sample experienced the same manual chewing simulation on a customized device. The proximal surfaces were photographed to measure the percentage of food impaction area using ImageJ software. Group with fixed maxillary and mandibular teeth showed more food impaction than other groups with significant differences in the average of maxilla and the average of all proximal areas. The flexibility of the periodontal ligament and the degree of freedom of the teeth in their sockets may contribute to the extent of food impaction in proximal spaces.

A Newly Formulated Vinyl Polysiloxane Impression Material with Improved Mechanical Properties.

To evaluate the mechanical properties of a newly formulated vinyl polysiloxane (VPS) impression material. Experimental, Capture (S&C Polymer), Express, Imprint 3 and Imprint 4 (3M ESPE), Start VPS (Danville), Honigum (DMG), Virtual (Ivoclar Vivadent), Elite HD+ (Zhermack) were evaluated for tear strength, tensile strength, and elongation at break. Un-nicked specimens with a 90° angle on one side (type C) for tear strength were prepared and tested according to ASTM-D624. Dumbbell-shaped specimens (type 1) for tensile strength and elongation at break were prepared and tested according to ISO 37. All tests were carried out at 500 mm/min on a Shimadzu (AGS-X-10 KN-table top) tester. A one-way analysis of variance (ANOVA) was used to analyze the data. Experimental material showed significantly higher or higher tear strength and elongation at break compared to other impression materials for both light body (LB) and heavy body (HB). For tensile strength, Experimental is similar to most impression materials; however, significantly lower than Imprint 3 and Start VPS for LB. This parameter for HB is higher or significantly higher than other impression materials except Start VPS. Tear strength and tensile strength were not correlated for LB but have a weak or moderate correlation for HB. Elongation at break is inversely proportional to tensile strength moderately for LB; however, there is no or very weak relation for HB. Experimental VPS impression material demonstrated a significantly higher tear strength and adequate tensile strength with higher elongation compared to other commercially available VPS impression materials. Adequate mechanical properties can provide accurate impressions for successful clinical fabrication of restorations. Experimental VPS impression material is suitable for use in dental impressions for fabrication of restorations.

Trueness of maxillomandibular relationship in 3D-printed and conventional casts

ObjectivesTo compare the trueness of maxillomandibular relationship between articulated 3D-printed and conventional diagnostic casts in maximum intercuspation (MIP). MethodsReference casts were articulated in MIP, and scanned using a Coordinate Measurement Machine (CMM, n = 1). Digital scans were made from the reference casts by using an intraoral scanner (IOS, n = 10) (Trios 4; 3Shape A/S). IOS scans were processed to create 3D-printed casts by using MAX UV385 (Asiga) and NextDent 5100 (3DSystems) 3D-printers. The conventional workflow implemented vinylpolysiloxane (VPS) impressions and Type IV stone. Stone and 3D-printed casts were articulated and digitized with a laboratory scanner (E4; 3Shape A/S). The 3D-printed casts were scanned on two occasions: with and without positioning pins. Inter-arch distances and 3D-contact area were measured and compared. Statistical tests used were Shapiro-Wilk, Levene's, Welch's t-test, and 2-way ANOVA (α=0.05). ResultsIOS group showed similar or better maxillomandibular relationship trueness than stone casts and 3D-printed casts (p < 0.05). 3D-contact area analysis showed similar deviations between 3D-printed and stone casts (p > 0.05). The choice of 3D-printer and presence of positioning pins on the casts significantly influenced maxillomandibular relationship trueness (p < 0.05). ConclusionsArticulated 3D-printed and stone casts exhibited similar maxillomandibular relationship trueness. Clinical SignificanceAlthough 3D-printing methods can introduce a considerable amount of deviations, the maxillomandibular relationship trueness of articulated 3D-printed and stone casts in MIP can be considered similar.

Dimensional Stability of Additively Manufactured Dentate Maxillary Diagnostic Casts in Biobased Model Resin.

This study aimed to evaluate the dimensional stability of maxillary diagnostic casts fabricated from a biobased model resin, which consists of 50% renewable raw materials for sustainable production, a model resin, and stone, over one month. A master maxillary stone cast was digitized with a laboratory scanner to generate a reference file. This master cast was also scanned with an intraoral scanner to additively manufacture casts with a biobased model resin (BAM) and a model resin (AM). Polyvinylsiloxane impressions of the master cast were also made and poured in type III stone (CV) (n = 8). The same laboratory scanner was used to digitize each model one day (T0), 1 week (T1), 2 weeks (T2), 3 weeks (T3), and 4 weeks (T4) after fabrication. Deviations from the reference file were calculated with an analysis software and analyzed with generalized linear model analysis (α = 0.05). The interaction between the material and the time point affected measured deviations (p < 0.001). Regardless of the time point, CV had the lowest and AM had the highest deviations (p < 0.001). BAM mostly had lower deviations at T0 and mostly had higher deviations at T4 (p ≤ 0.011). AM had the highest deviations at T4 and then at T3, whereas it had the lowest deviations at T0 (p ≤ 0.002). The measured deviations of CV increased after each time point (p < 0.001). BAM casts had deviations within the previously reported clinically acceptable thresholds over one month and had acceptable dimensional stability. Therefore, tested biobased resin may be a viable alternative for the sustainable manufacturing of maxillary diagnostic casts that are to be used clinically.