Polyvinyl Siloxane Group Research Articles

Three-dimensional analysis of the accuracy of conventional and completely digital interocclusal registration methods

Statement of problemCompared with the frequent investigations into the accuracy of digital intraoral scans, studies analyzing digital determinations of jaw relationships based on intraoral scans are scarce. PurposeThe purpose of this in vitro study was to present an optical 3-dimensional method for analyzing deviations in static occlusion and to compare the accuracy of conventional and digital interocclusal registrations. Material and methodsA Frasaco jaw model was duplicated, articulated, and scanned with a high-precision industrial scanner, and the data were stored in a virtual standard tessellation language (STL) format, which served as the reference model. Fifteen paired mandibular and maxillary models were scanned with a digital intraoral scanner in the completely digital workflow (IOS group). Forty-five paired gypsum casts were poured from polyvinyl siloxane (PVS) impressions and associated with 2 different PVS registration materials. These casts were digitized with a laboratory scanner and grouped as follows (n=15/group): PVS group, conventional Futar D interocclusal record; sPVS group, conventional Futar Scan interocclusal record; and the AIR group, partially digital antagonist scan of the Futar Scan interocclusal record. The axes (X, Y, Z, and XYZ) of each paired model were aligned to those of the reference model by 3-dimensional superimposition, and deviations were calculated. To determine the ideal zero position, a best-fit over the mandibular teeth between the reference model and the actual model was estimated. Next, a second best-fit was determined between the maxillary models to determine the actual position of the mandibular model. The different registration methods were compared with the Mann–Whitney U test (α=.05). ResultsIn the IOS group, the interocclusal registration caused a mandibular deviation of 0.05 ±0.04 mm (mean ±standard deviation). This fit was better than those of conventional registrations with inserted interocclusal registration materials (PVS group and sPVS group), which caused mean z-axis deviations of 0.41 ±0.46 mm and 0.44 ±0.32 mm (P<.001), with the deviations leading to elevation of the mandibular model. The partially digital workflow with a scannable registration material (AIR group) showed significantly larger deviations in the x-axis (0.15 ±0.08 mm; P=.042) compared with the IOS group. No significant difference was observed in the total deviation between the IOS and the AIR groups. Both groups showed significantly smaller deviations than the conventional registration methods (P<.001 for the IOS group and P=.023 for the AIR group). ConclusionsIn comparison with maxillary and mandibular alignment using conventional interocclusal registration materials, digital interocclusal registrations showed greater accuracy in evaluating complete jaw models and can be recommended for clinical use. Additionally, the partially digital workflow with an antagonist scan of the interocclusal record provided acceptable results.

A Comparative Evaluation of Dimensional Accuracy and Surface Detail Reproduction for Polyvinyl Siloxane and Vinyl Siloxane Ether under Dry and Moist Conditions- An In-vitro Study

Introduction: The conventional impression procedure plays a major role in prosthodontics inspite of advancement in intra- oral scanning devices and 3D imaging procedures. Dimensional accuracy and surface detail reproduction are important for recording an impression. Aim: The study evaluated and compared the dimensional accuracy and surface detail reproduction of Polyvinyl Siloxane (PVS) and vinyl siloxane ether impression materials when used under dry and moist conditions. Materials and Methods: An in-vitro study was conducted in the Department of Prosthodontics, Rural Dental College, Pravara Institute of Medical Sciences, Loni, Ahmednagar, Maharashtra, India, for a period of two years from October 2018 to September 2020. A total of 60 impressions were made with PVS (Group A) and vinyl siloxane ether (Group B) under dry (A1, B1) and moist (A2, B2) conditions of stainless steel dies which had lines engraved on superior surface of the die. Using a Harloc’s Tool maker’s microscope, dimensional accuracy was measured by comparing the width of line Y in each impression. Surface detail reproduction was evaluated by American Dental Association (ADA) specification no. 19 where it stated continuous replication of at least any two lines out of the three lines inscribed on the die. Data analysis processing was performed in the SYSTAT version 12 (made by Crane’s software, Bangalore). Student’s unpaired t-test and Chi-square test were performed to determine statistical difference between PVS and vinyl siloxane ether where the level of significance was set at 5% and 1%. Results: The mean dimensional change and SD values for PVS under dry condition ranged from 21.93±2.46 to 22.40±2.89 (in mm). The mean dimensional change and SD values for PVS under moist condition ranged from 22.87±3.20 to 23.33±3.42. The mean dimensional change and SD values for vinyl siloxane ether under dry condition ranged from 21.93±3.61 to 24.73±5.20. The mean dimensional change and SD values for vinyl siloxane ether under moist condition ranged from 21.93±4.48 to 22.87±4.15. No statistical difference was found under dry and moist conditions within 2 hours and after 24 hours for both the materials. Conclusion: The study revealed no significant difference between dimensional accuracy and surface detail reproduction for PVS and vinyl siloxane ether. Both the materials can reproduce the details under dry and moist conditions satisfactorily and remained dimensionally stable till 24 hours after impression making.

EFFECT OF DIFFERENT BITE RECORDING MATERIALS ON MOUNTING ACCURACY OF WORKING CAST

Objective: To assess effect of different bite recording materials on accurate mounting of working casts. Materials and Methods: A 40 maxillary and mandibular stone casts were obtained from dentoform teeth using polyether impression material. Derived stone casts were divided according to bite registration material in to four groups (10 samples each); 1. wax group, 2. polyvinyl siloxane group, 3. polyether group and 4. Bis-crylic resin group. Ten bite records were obtained with poly vinyl siloxane recording material from hand articulated dentoform to serve as control group. The 40 produced mandibular stone casts were mounted on semi adjustable articulators using four bite registrations tested materials. Unilateral Polyvinyl siloxane bite registration were made for 40 mounted stone casts to evaluate bite registration accuracy. Then bite records were placed on a light box and a camera set at a fixed distance 8 inches was used to capture the light transmission that was projected through the bite material. The camera transferred the information to an image analysis program (ImageJ) which measure accuracy of registration materials. Results: Grey scale data showed parametric distribution while measurement error showed non-parametric distribution. The difference between tested groups and control group was compared using ANOVA test. The results revealed that, the different between test groups and control was insignificant (P-value = 0.104). Conclusions: All tested bite registration materials had comparable results, although Luxabite and polyether showed higher errors than polyvinyl siloxane and wax.

Marginal fit of zirconia copings fabricated after conventional impression making and digital scanning: An in vitro study

Statement of problemAlthough digital scanning has become popular, conventional impressions with polyvinyl siloxane (PVS) are still the gold standard for fabricating indirect restorations. Studies comparing the marginal fit obtained from both techniques are sparse. PurposeThe purpose of this in vitro study was to compare the marginal fit of zirconia copings fabricated by using a conventional impression and 2 digital scanning techniques. Material and methodsA typodont mandibular left second premolar was prepared for a complete crown. Ten impressions were made in each experimental group: PVS group, conventional impression with PVS; TRIOS 3 group, impression with intraoral scanner TRIOS 3; and CS 3600 group, impression with intraoral scanner CS 3600. Thirty zirconia copings were fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) technology, and the marginal discrepancy was measured in 4 locations per specimen by using a stereo microscope. Additionally, the marginal discrepancy of each coping obtained in the PVS group was measured on the stone die produced, creating the PVS A group. The mean value of discrepancy was calculated for each location and each group. Statistically significant differences among the impression techniques were tested with 1-way ANOVA, repeated measures ANOVA, and the t test (α=.05). ResultsThe mean ±standard deviation values of vertical marginal discrepancy were 106 ±87 μm for the PVS group, 34 ±49 μm for the PVS A group, 53 ±56 μm for the TRIOS 3 group, and 93 ±69 μm for the CS 3600 group. Statistically significant differences (P<.05) were found between the PVS group and TRIOS 3 group and between the CS 3600 group and TRIOS 3 group. ConclusionsDigital scanning with the TRIOS 3 showed lower values of marginal discrepancy than the digital scan with the CS 3600 and conventional impression making with an elastomer.

Accuracy of casts produced from conventional and digital workflows: A qualitative and quantitative analyses.

PURPOSEComparing the accuracy of casts produced from digital workflow to that of casts produced from conventional techniques.MATERIALS AND METHODSWhole arch alginate (ALG) and polyvinyl siloxane (PVS) impressions were taken with stock trays and custom trays, respectively. The ALG impressions were poured with type III dental stone, while the PVS impressions were poured with type IV dental stone. For the digital workflow, IOS impressions were taken and physical casts were produced by 3D printing. In addition, 3D printed casts were produced from images obtained from a laboratory scanner (LS). For each technique, a total of 10 casts were produced. The accuracies of the whole arch and separated teeth were virtually quantified.RESULTSWhole arch cast accuracy was more superior for PVS followed by LS, ALG, and IOS. The PVS and ALG groups were inferior in the areas more susceptible to impression material distortion, such as fossae and undercut regions. The LS casts appeared to have generalized errors of minor magnitude influencing primarily the posterior teeth. The IOS casts were considerably more affected at the posterior region. On the contrary, the IOS and LS casts were more superior for single tooth accuracy followed by PVS and ALG.CONCLUSIONFor whole arch accuracy, casts produced from IOS were inferior to those produced from PVS and ALG. The inferior outcome of IOS appears to be related to the span of scanning. For single tooth accuracy, IOS showed superior accuracy compared to conventional impressions.

Comparison of Some Mechanical and Physical Properties of three Types of Impression Materials with Different Dental Implant Angulations

Choosing an appropriate impression material is a challenge for many dentists, yet an essential component to provide an excellent clinical outcome and improve productivity and profit. The purpose of present study was to compare wettability, tear strength and dimensional accuracy of three elastomeric impression materials, with the same consistencies (light-body). Three commercially available light body consistency and regular set 3M ESPE Express polyvinylsiloxane (PVS), 3M ESPE Permadyne polyether (PE), and Identium (ID), impression materials were comparedTear strength test, contact angle test and linear dimensional accuracy were evaluated for three elastic impression material. Among the three experimental groups PE impression material exhibited the higher mean values of tear strength, followed by ID group then PVS which showed the lowest mean value. For wettability test, Polyether group exhibited the lowest mean values of contact angle, followed by mean values of contact angle of ID group, while the PVS group showed the highest contact angle. There was a significant difference in the linear distance measurements between the two parallel impression coping/analogue assembly of the working models obtained by using (Identium, 3M ESPE ExpressPVS , 3M ESPE Permadyne polyether) the polyether impression materials provide higher tear strengths and lower wettability than elastomer impression materials and Identium material have acceptable tear strengths and wettability. All three experimental impression materials were distorted in both conditions (angled and parallel implant situations)

A Comparison of implant impression precision: Different materials and techniques.

BackgroundPrecision of implant impressions is a prerequisite for long-term success of implant supported prostheses. Impression materials and impression techniques are two important factors that impression precision relies on.Material and MethodsA model of edentulous maxilla containing four implants inserted by All-on-4 guide was constructed. Seventy two impressions using polyether (PE), polyvinyl siloxane (PVS), and vinyl siloxanether (VSE) materials with direct and indirect techniques were made (n=12). Coordinates of implants in casts were measured using coordinate measuring machine (CMM). Data were analyzed with ANOVA; t-test and Tukey test were used for post hoc.ResultsWith two-way ANOVA, mean values of linear displacements of implants were significantly different among materials and techniques. One-way ANOVA and Tukey showed significant difference between PE and VSE (P=0.019), PE and PVS (P=0.002) in direct technique, and between PVS and PE (P<0.001), PVS and VSE (P<0.001) in indirect technique. One-way ANOVA and t-test showed significant difference between the two techniques in PVS groups (P<0.001) and in PE groups (P=0.02). Two-way ANOVA showed mean values of rotational displacement of implants were significantly different among materials. One-way ANOVA and Tukey test showed significant difference between PVS and PE (P=0.001) and between PVS and VSE (P=0.012) in indirect groups.ConclusionsOn the basis of the results, when deciding on the material to make an impression of implants, PE is recommended for direct technique while PE and VSE are recommended for indirect technique. Recommended technique for VSE is either direct or indirect; and for PE and PVS is direct. Key words:Polyvinyl siloxane, polyether, vinyl siloxanether, direct technique, indirect technique, All-on-4, coordinate measuring machine.

Influence of abutment tooth geometry on the accuracy of conventional and digital methods of obtaining dental impressions

Statement of problemDirect (intraoral) and indirect (desktop) digital scanning can record abutment tooth preparations despite their geometry. However, little peer-reviewed information is available regarding the influence of abutment tooth geometry on the accuracy of digital methods of obtaining dental impressions. PurposeThe purpose of this in vitro study was to evaluate the influence of abutment tooth geometry on the accuracy of conventional and digital methods of obtaining dental impressions in terms of trueness and precision. Material and methodsCrown preparations with known total occlusal convergence (TOC) angles (−8, −6, −4, 0, 4, 8, 12, 16, and 22 degrees) were digitally created from a maxillary left central incisor and printed in acrylic resin. Each of these 9 reference models was scanned with a highly accurate reference scanner and saved in standard tessellation language (STL) format. Then, 5 conventional polyvinyl siloxane (PVS) impressions were made from each reference model, which was poured with Type IV dental stone scanned using both the reference scanner (group PVS) and the desktop scanner and exported as STL files. Additionally, direct digital impressions (intraoral group) of the reference models were made, and the STL files were exported. The STL files from the impressions obtained were compared with the original geometry of the reference model (trueness) and within each test group (precision). Data were analyzed using 2-way ANOVA with the post hoc least significant difference test (α=.05). ResultsOverall trueness values were 19.1 μm (intraoral scanner group), 23.5 μm (desktop group), and 26.2 μm (PVS group), whereas overall precision values were 11.9 μm (intraoral), 18.0 μm (PVS), and 20.7 μm (desktop). Simple main effects analysis showed that impressions made with the intraoral scanner were significantly more accurate than those of the PVS and desktop groups when the TOC angle was less than 8 degrees (P<.05). Also, a statistically significant interaction was found between the effects of the type of impression and the TOC angle on the precision of single-tooth dental impressions (F=2.43, P=.002). Visual analysis revealed that the intraoral scanner group showed a homogeneous deviation pattern across all TOC angles tested, whereas scans from the PVS and desktop scanner groups showed marked local deviations when undercuts (negative angles) were present. ConclusionsConventional dental impressions alone or those further digitized with an extraoral digital scanner cannot reliably reproduce abutment tooth preparations when the TOC angle is close to 0 degrees. In contrast, digital impressions made with intraoral scanning can accurately record abutment tooth preparations independently of their geometry.

Clinical marginal fit of zirconia crowns and patients’ preferences for impression techniques using intraoral digital scanner versus polyvinyl siloxane material

Statement of problemThe use of digital intraoral scanners is increasing; however, evidence of its precision in making crown impressions clinically remains scarce. Patients should also feel more comfortable with digital impressions, but only a few studies evaluating this subject have been performed. PurposeThe purpose of this clinical study was to evaluate the marginal fit of monolithic zirconia crowns and patients’ preferences for digital impressions versus polyvinyl siloxane (PVS) impressions. Material and methodsSixteen participants with indications for single molar crowns were included. After crown preparation, digital impressions by intraoral scanner and PVS impressions were made. The participants were asked to complete a 6-item questionnaire with a visual analog scale related to perceptions of each of the following topics: time involved, taste/smell, occlusal registration, size of impression tray/scanner, gag reflex, and overall preference. Computer-aided design and computer-aided manufacturing monolithic zirconia crowns were fabricated from both impressions. The crowns were evaluated intraorally, and a blinded examiner measured the marginal discrepancy of silicone replicas under a stereomicroscope. Intraexaminer reliability was evaluated by calculating the intraclass correlation coefficient. Data for patients’ preferences and marginal discrepancies were analyzed using the paired t test (α=.05). ResultsVisual analog scale scores for digital impressions were statistically significantly higher than those for PVS impressions in every topic (P<.05), except for occlusal registration. The results showed excellent reliability of the examiner with an intraclass correlation coefficient of .996. No significant difference was found in marginal discrepancies between the PVS group and the digital group on all sides (P>.05). ConclusionsNo differences were found in the clinical marginal fit of zirconia crowns fabricated from either digital impressions compared with PVS impressions. Furthermore, patients’ satisfaction with digital impressions was significantly higher than with conventional impressions.

Retentive characteristics of a vinylpolysiloxane overdenture attachment system.

Numerous different attachments are used to retain overdentures on implants. The purpose of this study was to evaluate a new chairside attachment system based on polyvinylsiloxane (PVS). A total of 250 specimens were fabricated (n = 10) to measure the retention force (RF) in dependence of the following parameters: fatigue (after 100, 200, 500, 1,000, and 5,000cycles of dislodging), thermal undulation (10,000cycles between 5 and 55°C), implant angulation (0°, 5°, and 10°), and disinfection (three different agents). Three different PVS materials (shore hardness (SH), SH25, SH50, and SH65) were evaluated; locator attachments (LR blue) served as controls. Data were imported into a statistical program and analyzed at a 5% level of significance. Initial RFs were dependent on the shore hardness (p ≤ 0.001, ANOVA). No changes in RFs were observed for PVS groups after repeated dislodging and thermal undulation. Locator attachments revealed a significant decrease in retention force of up to 58% (p ≤ 0.001, Fig.3). No significant changes in RFs were induced by implant angulation. Retention force was decreased in some PVS groups after storage in disinfection solution. Polyvinylsiloxane attachments provide an alternative to locator attachments, exhibiting better stability of the retention force. The presented directly fabricated chairside attachment system represents RFs superior to existing attachment systems after artificial aging.

Evaluation of Accuracy of Complete-Arch Multiple-Unit Abutment-Level Dental Implant Impressions Using Different Impression and Splinting Materials

This in vitro study evaluated the accuracy of multiple-unit dental implant casts obtained from splinted or nonsplinted direct impression techniques using various splinting materials by comparing the casts to the reference models. The effect of two different impression materials on the accuracy of the implant casts was also evaluated for abutment-level impressions. A reference model with six internal-connection implant replicas placed in the completely edentulous mandibular arch and connected to multi-base abutments was fabricated from heat-curing acrylic resin. Forty impressions of the reference model were made, 20 each with polyether (PE) and polyvinylsiloxane (PVS) impression materials using the open tray technique. The PE and PVS groups were further subdivided into four subgroups of five each on the bases of splinting type: no splinting, bite registration PE, bite registration addition silicone, or autopolymerizing acrylic resin. The positional accuracy of the implant replica heads was measured on the poured casts using a coordinate measuring machine to assess linear differences in interimplant distances in all three axes. The collected data (linear and three-dimensional [3D] displacement values) were compared with the measurements calculated on the reference resin model and analyzed with nonparametric tests (Kruskal-Wallis and Mann-Whitney). No significant differences were found between the various splinting groups for both PE and PVS impression materials in terms of linear and 3D distortions. However, small but significant differences were found between the two impression materials (PVS, 91 μm; PE, 103 μm) in terms of 3D discrepancies, irrespective of the splinting technique employed. Casts obtained from both impression materials exhibited differences from the reference model. The impression material influenced impression inaccuracy more than the splinting material for multiple-unit abutment-level impressions.

Silver-plated dies. Part I: Platability of impression materials

The purpose of this study were to determine the acceptability of silver-plated dies made from representative brands of impression material from each of the four groups of elastomers and to determine the time required for initial plating of dies. Permlastic and Impregum , each previously shown to produce consistent silver-plated dies, were used for comparison. Representatives from the condensation-reaction and addition-reaction ( polyvinylsiloxanes ) silicones groups were tested until satisfactory materials were selected. Citricon and Xantopren - Optosil were tested in the former group and President and Reprosil in the latter. Conclusions include the following: All materials were flash-plated in 10 minutes or less. Acceptable silver-plated dies were obtained from Permlastic and Impregum . Acceptable silver-plated dies were obtained from condensation-reaction silicones with Xantopren - Optosil . From the polyvinylsiloxane group, Reprosil plated more consistently than President. Both produce acceptable dies. The technique modification studied was not effective for Citricon and President. The surface quality of silver-plated dies and the consistency of plating varies with materials. Individual impression materials should be tested prior to their routine clinical use with silver-plating procedures.