Polyvinyl Siloxane Impression Research Articles

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.

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.

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.

A Clinical Comparison of Dental impression accuracy between One-step and Two-step Dual phase impression technique by using Polyvinyl Siloxane Impression Material.

Objective:: The objective was to assess the number of visible defects within impression made by two different techniques. Methodology: This was comparative cross-sectional study was conducted between June 2019 to December 2019 at out patient department of Institue of dentistry, LUMHS Jamshoro. Two impressions were made from 53 crown preparation by using one step and two step dual phase impression techniques. Totaling to 106 impressions. Polyvinyl Siloxane impression material was used with each technique. Evaluation of impressions were made for tears, voids and bubbles and impression were compute as acceptable (A or B) and unacceptable (C or D). Result: There was no significant difference seen in proportion of overall evaluation of two impression technique, as compared by using “Chi-square test”. Conclusion: Insignificant difference was seen b/w one step and two step dual phase impression techniques. Keywords: One step impression technique, two step dual phase impression technique, dimensional accuracy.

A comparative in vitro analysis of various temporization materials with respect to pulp chamber temperature changes during polymerization.

(1) To compare the temperature rise in the pulp chamber with different resin materials used for making provisional fixed partial dentures in anterior and posterior region while using Polyvinylsiloxane impression materials as matrix. (2) To identify a superior provisionalization material based on the amount of heat dissipated suitable for anterior and posterior provisional fixed partial denture fabrication. Temporary crowns and bridges are integral to Fixed Prosthodontics. It has been observed that conventional fixed prosthesis temporisation materials release heat due to the exothermic polymerisation reaction. When such a provisional material is directly let to set on a vital tooth, the heat transfer causes irreversible changes in the pulp tissue depending of the degree of change. Hence, this study observes amount of heat generation in various materials during temporisation procedure, by simulating similar conditions. Two Models were fabricated, one simulating missing lateral incisor (Model A) and another simulating missing first molar (Model B). Intact maxillary central incisors and canine for Model A and intact mandibular Second Premolar and Second Molar were selected to act as abutments. These abutment teeth were fitted with the tip of a K-type Thermocouple inside their pulp chambers and these were connected to a digital thermometer. Five temporisation materials were chosen for fabrication of temporary crowns through Direct technique. (1) polymethy methacrylate (Self Cure acrylic), (2) bisacryl composite (Protemp 4), (3) visible light cure urethane dimethacrylate (Revotec LC), (4) barium glass and fumed silica infused methacrylate (Dentsply Integrity) and (5)nano-hybrid composite (VOCO Structur 3). Ten observations were made for each provisional material on each model. During each observation, temperature rise was recorded at 30s interval from the time of application, through the peak and till a decrease in temperature is observed. Polyvinyl siloxane was used as matrix for all except light cure resin, where polypropylene sheet was used. Anova test used for statistical. ANOVA test revealed that there was a significant difference in the temperature changes associated with the provisional restorative materials used. Among the five, polymethy methacrylate (self cure resin) showed the maximum rise in temperature, followed by bisacryl composite (Protemp 4), visible light cure urethane dimethacrylate (Revotec LC), barium glass and fumed silica infused methacrylate (Dentsply Integrity) and nano-hybrid composite (VOCO Structur 3). There was no comparable difference between Model A and B but an overall reduction of temperature rise was observed in model B. VOCO Structur 3 showed the least temperature rise in the pulp chamber, and overall temperature rise was less for model B which can be attributed to the residual dentin thickness.

Effectiveness of Microwave Sterilization on Surface Roughness of Polyvinyl Siloxane Impression Material

Effectiveness of Microwave Sterilization on Surface Roughness of Polyvinyl Siloxane Impression Material

Alignment Efficiency of Two Archwires in Adolescents with Moderate to Severe Crowding

There is no consensus in clinical orthodontics on which aligning arch wire should be used at the initial stage of treatment. This randomized clinical trial evaluated the efficiency of multistranded Nitinol (Supercable) aligning arch-wire versus a standard arch-wire (Nitinol) in the first stage of orthodontic treatment in adolescents with severe crowding. Forty patients ages 12 to 17 with an Irregularity Index as proposed by Little between 5 to 17 mm were selected. Vinyl polysiloxane impressions (VPS) were taken before treatment (T1) at 6 weeks (T2) and 12 weeks (T3). Roth prescription .022 x .028 Edgewise brackets were bonded using light cure adhesive to the six anterior teeth of each dental arch and bands were placed on all first molars. Subjects were paired by gender and Irregularity Index into two groups of 20 each and assigned either to the control group (Nitinol) or the experimental archwire (Supercable). The predictor variables in this study were the type of archwire, type of dental arch and the time intervals. The outcome variable was the Irregularity Index score. The Irregularity Index was measured using 3D digital study models (e-models) and GeoDigm software from the VPS impressions taken at T1, T2 and T3. The data was analyzed with both a Two and Three-way Analysis of Variance (p≤0.05) to identify differences in the alignment of the maxillary and mandibular teeth and to determine differences between the two archwires. The Two and Three way ANOVA showed that there was a statistically significant difference (p≤0.05) in the alignment capabilities between the maxilla and the mandible. However, there was no evidence of a statistically significant difference (p=0.301) between NiTi and Supercable archwires at any time interval.

Comparative analysis of dimensional changes in autoclavable polyvinyl siloxane (PVS) impressions under various Sterilization/Disinfection Protocols: A randomized controlled trial

BackgroundImpressions that maintain their dimensional stability after autoclaving effectively control cross-infection and contamination resulting from a patient's oral secretions. PurposeThe study aimed to assess the dimensional stability of autoclavable polyvinyl siloxanes after disinfection and sterilization. MethodsA stainless steel metal model containing three full veneer crown preparations was fabricated according to ANSI/ADA specification No. 19. Reference grooves were established on the occlusal and axial surfaces of the abutments for accurate measurements. Forty impressions were created from the master model using single-step impression technique monophase polyvinyl siloxane material (AFFINIS, Coltene/Whaledent, Altstatten, Switzerland). The impressions were categorized into four groups: Group A (control, ten untreated impressions), Group B (ten disinfected impressions with 5.25 % sodium hypochlorite [NaOCl]), Group C (ten disinfected impressions with 2 % glutaraldehyde), and Group D (ten autoclaved impressions at 134 °C for 18 min). Subsequently, stone casts were produced using type IV gypsum products (Gelstone R, BK Giulini Chemie, Ludwigshafen/Rh., Germany). The dimensional accuracy of the obtained casts was assessed by measuring the inter-abutment measurements (between the abutments) and the intra-abutment measurements (diameter and height of the abutments). These measurements were performed using a universal measuring microscope (Olympus stereomicroscope B061 Imaging Corp. Tokyo, Japan) with a precision of 0.001 mm. The dimensions of the stone casts from the study groups were then compared to those of the control group. Data analysis was performed using a one-way ANOVA with a significance level of α = 0.05. ResultsAFFINIS impressions subjected to chemical disinfection in 5.25 % NaOCl and 2 % glutaraldehyde with different immersion times showed slight expansion in the intra- and inter-abutment measurements. The impressions autoclaved at 134 °C for 18 min showed slight shrinkage in the intra- and inter-abutment measurements. The dimensional change was statistically non-significant, and the percent of dimensional changes within the experimental groups was within the clinically accepted limit (α < 0.5). ConclusionAFFINIS polyvinyl siloxanes retain dimensional stability suitable for clinical use when subjected to chemical disinfection and steam autoclaving.

Accuracy of merging scans of definitive fixed prosthodontic impressions to obtain single, accurate digitized master casts.

Many elastomeric impressions sent to commercial laboratory dental technicians may include marginal defects. To fabricate accurate restorations, digital technology may be used to merge digital files of defective impressions into a single standard tessellation language (STL) file free of errors. This would save clinicians and patients time and may improve clinical care. The purpose of this study was to compare the accuracy of digital master casts reconstructed from merged STL files of defective impressions with the file of the original defect-free preparations. Ivorine teeth on a dentoform were prepared to receive a posterior fixed dental prosthesis (FDP) with complete coverage preparations. An impression was made in a stock tray using polyvinyl siloxane (PVS) impression material and an extraoral scanner (E3, 3Shape, Denmark) was used to digitize the impression; this was the reference cast. Wax was used to create defects on the buccal and lingual margins of the preparations. Fifteen PVS impressions were made of the FDP preparations with defects in the mesial and distal margins; another set of 15 PVS impressions was made of FDP preparations with defects in the buccal and palatal margins for a total of 30 impressions. All impressions were digitized using the same extraoral scanner (E3, 3Shape, Denmark). Corresponding STL files were paired and merged, and a master cast was created by eliminating the defects using the scanned data. This master cast was compared to the reference cast using reverse engineering software (Geomagic, Morrisville, NC, USA). The results were expressed as average errors and standard deviations in the master casts relative to the reference cast. To account for the presence of positive and negative values in the data set, in terms of errors, the root mean square (RMS) value was calculated for each sample. The mean average error in the sample was -0.4 μm. The average upper limit of 95% confidence interval was +36.5 μm, while the average lower limit of 95% confidence interval was -37.3 μm. The mean RMS of the errors found was 18.9 μm. The results of this study indicated that merging digitized definitive impressions to correct marginal defects resulted in master casts with a high level of accuracy relative to the reference cast.

3D quantitative analysis and SEM qualitative analysis of natural antagonist enamel opposing CAD-CAM monolithic zirconia or lithium disilicate tooth-supported crowns versus enamel opposing natural enamel.

This study aimed to evaluate the maximum vertical wear, volume wear, and surface characteristic of antagonist enamel, opposing monolithic zirconia or lithium disilicate crowns. The study comprised 24 participants (n = 12), who were randomly allocated to receive either a 5 mol% Y-TZP or a lithium disilicate crown in positions which would oppose the natural first molar tooth. The contralateral first molar along with its antagonist was considered as the enamel opposing natural enamel control. Data collection was performed using an intraoral scanner and polyvinylsiloxane impression. The means of the maximum vertical loss and the volume loss at the occlusal contact areas of the crowns and the various natural antagonists were measured by 3D comparison software. A scanning electron microscope was subsequently used to assess the wear characteristics. The one-year results from 22 participants (n = 11) indicated no significant differences when comparing the zirconia crown's antagonist enamel (40.28 ± 9.11 µm, 0.04 ± 0.02 mm3) and the natural enamel wear (38.91 ± 7.09 µm, 0.04 ± 0.02 mm3) (P > .05). Also, there is no significant differences between lithium disilicate crown's antagonist enamel (47.81 ± 9.41 µm, 0.04 ± 0.02 mm3) and the natural enamel wear (39.11 ± 7.90 µm, 0.04 ± 0.02 mm3) (P > .05). While some studies suggested that monolithic zirconia caused less wear on opposing enamel than lithium disilicate, this study found similar wear levels to enamel for both materials compared to natural teeth.

A Comparative Evaluation of Three Methods of Disinfection of Gypsum Casts and the Changes in Surface Roughness and Dimensional Accuracy after Disinfection-An Ex Vivo Study.

One of the major problems of everyday dental practice is cross-contamination. It can place office personnel, dentists, and patients at risk of acquiring serious illness. Disinfection helps in controlling this cross-contamination to an extent. The evaluation was done to find the efficient disinfection method on gypsum casts. The aim of this study is to evaluate and compare the efficacy of three methods of disinfection of gypsum casts, namely, chemical disinfection by immersion, spray method, and microwave method, and also to evaluate and compare changes in surface roughness and dimensional accuracy between the three methods after disinfection. Ex vivo and experimental study. Thirty participants were selected, and impressions of the maxillary arch were made using polyvinyl siloxane impression material. Ninety type IV die stone gypsum casts were poured. It was divided into three groups and was subjected to chemical disinfection by immersion and spray methods, and microwave method. The disinfected casts were evaluated for microbial growth, surface roughness, and dimensional accuracy. It was performed by using the one-way analysis of variance test and paired t-test followed by the Kruskal - Wallis test and Wilcoxon signed rank test (α = 0.05). Microwave disinfection was more effective than both immersion and spray chemical disinfection methods (P < 0.010 and <0.001). The surface roughness of the microwave-irradiated casts had significantly increased after disinfection. However, there were no significant dimensional changes by any of the methods of disinfection. Within the limitations of the study, the microwave method of disinfection is more effective in eradicating microorganisms when compared to chemical methods of disinfection by immersion and spray methods.

Influence of the Crystallization Firing Process on Marginal and Internal Adaptation of Silicate-based Glass-ceramic Inlays Fabricated With a CAD/CAM Chairside System.

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used in dental treatment. Clinicians can use chairside CAD/CAM technology, which has the advantage of being able to fabricate inlays on the same day. We aimed to evaluate the effects of crystallization firing processes, fabrication methods (one-step and two-step), and materials on marginal and internal adaptations of silicate-based glass-ceramic all-ceramic inlays fabricated with CAD/CAM chairside systems. Ten artificial mandibular left first molars were prepared with standardized ceramic class II mesial-occlusal (MO) inlay cavities. Optical impressions were obtained using CEREC Omnicam Ban. IPS e-max CAD (IE), (Ivoclar Vivadent, Schaan, Liechtenstein), Initial LiSi Block (LS) (Hongo, Bunkyoku, Tokyo, Japan), VITA Suprinity (SP), (Vita Zahnfabrick, Bad Säckingen, Germany), and Celtra Duo (CD) (Ivoclar Vivadent, Schaan, Liechtenstein) (n=10) were milled using CEREC MC XL (Bensheim, Germany). IE and SP were crystallization-fired using CEREC Speed Fire. The silicone replica technique was used for the measurement of internal (axial and pulpal walls) and marginal (cervical and occlusal edge) adaptations. The adaptations were measured using a thin layer of light-body polyvinyl siloxane impression material placed between the master tooth inlay preparation and restoration. Marginal and internal adaptations of IE, LS, SP, and CD were measured using a stereomicroscope (500×). For IE and SP, marginal and internal adaptations were measured before and after the crystallization firing process. Data analyses were conducted using one-way ANOVA and the Tukey test. For IE and SP, marginal and internal adaptations before and after the crystallization firing process were analyzed using the t-test. The significance level was set at α=0.05. One-way ANOVA revealed statistically significant differences in occlusal and cervical edge marginal adaptations among the material groups (p<0.001). The Tukey HSD test revealed a significant difference in marginal occlusal and cervical edge adaptations between LS and CD groups and IE and SP groups (p≤0.05). For IE and SP inlays, the t-test revealed a significant difference between occlusal and cervical edge adaptations before the crystallization firing process and those after the crystallization firing process, with the latter group showing a more significant discrepancy in adaptation than the former group (p≤0.05). Fabrication methods (one- and two-step) affected the marginal adaptation compatibility but not internal compatibility of MO inlays. The crystallization firing process affected the marginal adaptation of inlays using lithium silicate or lithium disilicate glass-ceramics. However, adaptation to the cavity was considered clinically acceptable for all materials.

Trueness and precision of complete arch dentate digital models produced by intraoral and desktop scanners: An ex-vivo study

ObjectivesThe study aimed to compare the trueness and precision of five intraoral scanners (Emerald S, iTero Element 5D, Medit i700, Primescan, and Trios 4) and two indirect digitization techniques for both teeth and soft tissues on fresh mandibular and maxillary cadaver jaws. MethodsThe maxilla and mandible of a fully dentate cadaver were scanned by the ATOS industrial scanner to create a master model. Then, the specimens were scanned eight times by each intraoral scanner (IOS). In addition, 8 polyvinylsiloxane (PVS) impressions were made and digitized with a Medit T710 desktop scanner. Stone models were then poured and again scanned with the desktop scanner. All IOS, PVS, and stone models were compared to the master model to calculate the mean absolute surface deviation for mandibular teeth, maxillary teeth, and palate. ResultsFor mandibular teeth, the PVS trueness was only significantly better than the Medit i700 (p < 0.001) and Primescan (p < 0.05). In maxillary teeth, the PVS trueness was significantly better than all IOSs (p < 0.05–0.001); the stone trueness was significantly better than Emerald S (p < 0.01), Medit i700 (p < 0.001) and Primescan (p < 0.01). In the palate, PVS and stone trueness were significantly lower than the iTero Element 5D (p < 0.01) and Trios 4 (p < p < 0.01). Stone trueness was significantly lower than the Medit i700 (p < 0.05). The precision in the palate was significantly lower for PVS and stone than for Emerald S (p < 0.01, p < 0.05), iTero Element 5D (p < 0.01, p < 0.01), Primescan (p < 0.001, p < 0.001), and Trios 4 (p < 0.001, p < 0.01). Significant differences in trueness between the IOSs were observed only in the mandibular teeth. The Medit i700 performed worse than Emerald S (p < 0.01) and iTero Element 5D (p < 0.01). For mandibular teeth, the Medit i700 was significantly more precise than Primescan (p < 0.01) and the Emerald S (p < 0.05). The Trios 4 was significantly less precise than Emerald S (p < 0.05). The precision of Medit i700 was significantly worse than iTero Element 5D (p < 0.01) for maxillary teeth, as well as the Primescan (p < 0.01) and Trios 4 (p < 0.05) for the palate. ConclusionsIn general, indirectly digitized models from PVS impressions had higher trueness than IOS for maxillary teeth; precision between the two methods was similar. IOS was more accurate for palatal tissues. The differences in trueness and precision for mandibular teeth between the various techniques were negligible. Clinical significanceAll investigated IOSs and indirect digitization could be used for complete arch scanning in mandibular and maxillary dentate arches. However, direct optical digitization is preferable for the palate due to the low accuracy of physical impression techniques for soft tissues.

Dimensional Stability and Retention Strength of Impressions to Custom Impression Trays Fabricated Using Conventional Method and Additive Technology - An In-vitro Study.

3D printing technology is replacing manual fabrication in all fields. 3D-printed impression trays should be assessed as they could replace conventional impression trays in the future. In-vitro comparison and evaluation of the dimensional stability and retention strength of impressions to custom impression trays fabricated using conventional method and additive technology. A maxillary edentulous auto-polymerizing acrylic resin model served as the master model. Two moulds were prepared from the master model in order to obtain 12 casts. One cast was scanned for 3D printing digital light processing (DLP) and fused deposition modelling (FDM) 24 impression trays using polylactic acid (PLA). Twelve casts were used to fabricate light cure impression trays. Polyvinyl-siloxane impressions were made on the master model using 36 impression trays and 18 trays each were used to assess dimensional stability and retention strength. In dimensional stability analysis, one sample t-test revealed a statistically significant difference between each group and the master model followed by a one-way ANOVA. There were significant differences, but the difference was less with FDM trays (P < 0.05). In retention strength analysis, one-way Analysis of variance (ANOVA) revealed statistically significant difference between each group and post-hoc test revealed specific difference, the highest with FDM trays (P < 0.05). Dimensional changes were observed at 30 minutes and 72 hours. Lesser dimensional changes were observed when impressions were made using FDM trays followed by DLP and light cure trays. The mean retention strength seen in descending order was FDM, followed by DLP and light cure trays. The best retention strength was noticed when impressions were made using FDM trays.

Comparison of the elastic recovery and strain-in-compression of commercial and novel vinyl polysiloxane impression materials incorporating a novel crosslinking agent and a surfactant.

This study aims to formulate experimental vinylpolysiloxane (VPS) impression materials and compare their elastic recovery and strain-in-compressions with three commercial VPS materials (Aquasil, Elite, and Extrude). Five experimental materials (Exp), two hydrophobic (Exp-I and II) and three hydrophilic (Exp-III, IV and V) were developed. Exp 1 contained vinyl-terminated poly-dimethyl siloxane and a conventional cross-linking agent (poly methylhydrosiloxane), while Exp- II contained a novel cross-linking agent that is tetra-functional dimethyl-silyl-ortho-silicate (TFDMSOS). Exp III-V (hydrophilic materials) were formulated by incorporating different concentrations of non-ionic surfactant (Rhodasurf CET-2) into Exp II formulation. Measurement of elastic recovery and strain-in-compression for commercial and experimental materials were performed according to ISO4823 standard using the calibrated mechanical testing machine (Tinius Olsen). One-way analysis of variance (one-way ANOVA) and Tukey's post-hoc (HSD) test were used for statistical analysis and a p-value of ≤ 0.05 was considered significant. Exp-I has statistically similar values to commercial VPS. The Exp-II showed the highest elastic recovery, while % elastic recovery was reduced with the addition of the non-ionic surfactant (Rhodasurf CET-2). The % reduction was directly related to the concentration of Rhodasurf CET-2. In addition, Exp II had significantly higher strain-in-compression values compared to Exp-I and commercial materials. These values were further increased with the addition of a non-ionic surfactant (Rhodasurf CET-2) was added (Exp-III, IV and V).

Comparison of the accuracy between full-arch digital scans and scannable impression materials: an in vitro study.

In some clinical cases, full-arch impression could be difficult to take correctly with the digital way. Patients with high flow salivary rate or with difficulties in mouth opening can still benefit from a conventional impression with elastomer materials that can be directly or indirectly digitized. The aim of this study was to compare the accuracy and precision of two different intraoral scanners (IOSs) and an impression material with scannable properties, by means of three-dimensional analysis of a complete dental arch. An anatomical model of complete upper arch, modified with a Scan body placed in the retroincisive area, was used. It was firstly scanned by a desktop scanner to create a digital reference model. Then, 3 groups were created, each constituted by 5 samples. In the first group, 5 impressions were taken from the same master model with the scannable PVS material (Hydrorise Implant), 5 scans were taken using Trios4 (3Shape) and other 5 scans with iTero Element 5D (iTero). STL files obtained from IOSs, and scanned impressions were three-dimensionally superimposed on the STL file of the reference model using the Scan body geometry. The ANOVA Test (P<0.005) did not show any statistically significant difference between the accuracy and precision values of the groups. Each group shows clinically acceptable deviations from the reference model. Scannable polyvinylsiloxane impression materials are equally accurate and precise as the two IOSs tested in full-arch dentate impressions.

TIME DEPENDENT EVALUATION OF EFFICACY ON INHIBITION OF BACTERIAL AND FUNGAL GROWTH OF THREE DISINFECTANTS BY IMMERSION AND SPRAYING METHOD ON POLYVINYL SILOXANE IMPRESSION MATERIAL - AN IN-VITRO STUDY

Aim:To determine the efficacy of three disinfectants-2% Glutaraldehyde,0.2% Peracetic acid,70%Isopropyl alcohol with time(3 minutes and 7 minutes) on Staphylococcus Sp. and Candida Sp. on polyvinyl siloxane impression material. Settings and Design:This was an in vitro comparative study. Materials and Methods:A standard inoculum of 0.5 McFarlandwas applied on the prepared polyvinyl siloxane disc surface.Discs were disinfected by immersion and spraying method for 3 minutes and 7 minutes.After that discs were collected in nutrient broth,vortexed and a small volume of the broth was centrifuged.It was thentransferred to test tube containing neutralizing agents of the corresponding disinfectants.0.1 ml from the test tube was transferred to culture plate and incubated to study thesurvivality of Staphylococcus Sp. and Candida Sp. Statistical Analysis Used:One way ANOVAtest was performed to check the mean reduction of microorganism in each group after disinfection by immersion and spraying.Inter group comparison of disinfection efficacy within certain time(3 minutes or 7 minutes) span was done by Tukeys post hoc test. Results:Percentage(%) of mean reduction of staphylococcus and candidas growth obtained from this studywere 99.99% by immersion and spraying method within 3 minutes and 7 minutes. Significance:Both immersion and spraying methods had similar reduction efficacy(99.99%) when compared with control.

Treatment of Worn Tusks Using Metal Crowns in Two Young Captive Walruses (Odobenus Rosmarus).

Two young walruses, recently transferred to the Vancouver Aquarium, presented with severe abrasion to their tusks. The walruses were sedated, and clinical examination and radiographs of the tusks showed that the pulp chambers were not exposed. The tips of the tusks were then prepared to receive metal crowns. Vinyl polysiloxane impressions were obtained and sent to the laboratory for chrome-nickel crown fabrication. A week later, the crowns were cemented onto the tusks and remained in place on follow-up examinations.

Use of polyvinyl siloxane impressions to monitor sub-5-μm erosive tooth wear on unpolished enamel

Statement of problemWhether polyvinyl siloxane impressions are capable of reproducing 5-μm changes on natural freeform enamel and potentially enabling clinical measurements of early surface changes consistent with wear of teeth or materials is unclear. PurposeThe purpose of this in vitro study was to investigate and compare polyvinyl siloxane replicas with direct measurements of sub-5-μm lesions on unpolished human enamel lesions by using profilometry, superimposition, and a surface subtraction software program. Material and methodsTwenty ethically approved unpolished human enamel specimens were randomized to a previously reported cyclic erosion (n=10) and erosion and abrasion (n=10) model to create discrete sub-5-μm lesions on the surface. Low viscosity polyvinyl siloxane impressions were made of each specimen before and after each cycle and scanned by using noncontacting laser profilometry and viewed with a digital microscopy and compared with direct scanning of the enamel surface. The digital maps were then interrogated with surface- registration and subtraction workflows to extrapolate enamel loss from the unpolished surfaces by using step-height and digital surface microscopy to measure roughness. ResultsDirect measurement revealed chemical loss of enamel at 3.4 ±0.43 μm, and the polyvinyl siloxane replicas were 3.20 ±0.42 μm, respectively. For chemical and mechanical loss direct measurement was 6.12 ±1.05 μm and 5.79 ±1.06 μm for the polyvinyl siloxane replica (P=.211). The overall accuracy between direct and polyvinyl siloxane replica measurements was 0.13 +0.57 and −0.31 μm for erosion and 0.12 +0.99 and −0.75 μm for erosion and abrasion. Surface roughness and visualization with digital microscopy provided confirmatory data. ConclusionsPolyvinyl siloxane replica impressions from unpolished human enamel were accurate and precise at the sub-5-μm level.