Polyvinyl Siloxane Material Research Articles

In Vitro Comparative Analysis of Digital Versus Conventional Impressions in Fixed Prosthodontics

ABSTRACT Background: In the realm of fixed prosthodontics, the transition from conventional to digital impressions has been a subject of ongoing debate. This study aims to provide a comparative analysis of digital versus conventional impressions in terms of accuracy and efficiency. Materials and Methods: Twenty patients requiring fixed prosthodontic treatment were selected for this study. Each patient received both digital and conventional impressions. The digital impressions were obtained using an intraoral scanner, while conventional impressions were taken using polyvinyl siloxane material. The impressions were then used to fabricate fixed prostheses for each patient. Accuracy was assessed through measurement of marginal fit using a standardized technique, and efficiency was evaluated based on time taken for impression procedures. Results: The mean marginal discrepancy for digital impressions was found to be 38 micrometers (±5), whereas for conventional impressions, it was 45 micrometers (±7). Additionally, the average time taken for digital impressions was 12 minutes, compared to 20 minutes for conventional impressions. Conclusion: Digital impressions demonstrated superior accuracy and efficiency compared to conventional impressions in fixed prosthodontics.

Comparative evaluation of incorporation of ferrule in premolars endocrown designs to check any alterations in their fracture resistance: A pilot study.

Endocrown preparation of endodontically treated teeth as final restoration has been extensively studied for different teeth. Bindl et al. questioned the application of endocrowns for premolars due to the pulp chamber space's smaller dimensions, which diminish bonding surface area. The addition of ferrule into the endocrown preparations of premolars has not been extensively studied. Comparative evaluation of incorporation of the ferrule in premolars endocrown designs to check any alterations in their fracture resistance. The sample consisted of 40 maxillary first premolars without cracks or caries, extracted for orthodontic or periodontal purposes. The teeth were individually mounted with cold-cure acrylic resin. Group A: Composite endocrown without ferrule and Group B: Composite endocrown with ferrule. An endocrown former was prepared with elastomeric polyvinyl siloxane material (GC Exaclear). Endocrowns were then prepared with dual-cure core build-up composite-Core-x flow (Dentsply Maillefer, Switzerland) using the endocrown former so that morphologically, they all were almost identical. Endocrowns are cemented by dual-cure resin cement following manufacturer instructions. The fracture resistance of endocrowns with and without ferrule was evaluated and compared. The data were tabulated in Microsoft Excel and analyzed with SPSS version 24 software. The variables were presented with mean, standard deviation, and independent t-test. The P ≤ 0.05 is considered statistically significant. Group B (with ferrule) showed higher fracture resistance (622.06 N) than Group A (537.59 N) (without ferrule). Independent t-test showed that the difference was statistically significant (P = 0.008). Comparing the failure load findings, it could be concluded that ferrule-containing endocrown needed greater loads than ordinary endocrown restorations for failure.

Compressive modulus, translucency, and irradiance transmittance of clear PVS materials used for resin injection molding technique.

To evaluate the compressive modulus, translucency, and light curing irradiance transmittance of four clear polyvinyl siloxane (PVS) materials used for the injection molding technique at varying thicknesses, and to assess the correlation between color parameters and irradiance transmittance. Four clear PVS materials (Exaclear, Clear Bite Matrix, Affinity Crystal, and Memosil 2) were used in this study. Compressive modulus was measured by compressing cylindrical PVS specimens (n = 9; d = 10 mm; t = 6 mm) up to 30% strain using a universal testing machine. For the translucency analysis and irradiance transmittance, specimens (n = 5) were fabricated with five different thicknesses (d = 12 mm and t = 2, 4, 6, 8 and 10 mm). The L*, a, *b* values of specimens were obtained using a CIELab spectrophotometer (CMD-700, Konica Minolta) with calibrated white and black tiles; the translucency parameter was calculated. The same specimens were placed onto a spectrophotometer (MARC Light Collector) to measure irradiance transmitted through the specimens from a light curing unit (Valo Corded, Ultradent). Data were analyzed using analysis of variance (ANOVA) with Tukey post hoc test and the correlation between translucency and irradiance transmittance of materials for each thickness was evaluated using Pearson's correlation. Compressive modulus differences in PVS materials were significant (one-way ANOVA: df = 3, F = 76.27, p < 0.001); Affinity and Memosil 2 were highest with no significant difference between them (Tukey: t = -1.62; p = 0.382). Clear Bite was higher than Exaclear (Tukey: t = -3.70; p = 0.004). Exaclear was lowest. Translucency decreased with thickness (Two-way ANOVA: df = 3, F = 586.53, p < 0.001; thickness: df = 4, F = 1389.34, p < 0.001). Exaclear was most translucent at all thicknesses. L*, a*, b* values varied by material and thickness (L*: df = 3, F = 1213.32, p < 0.001; a*: df = 3, F = 10766.8, p < 0.001; b*: df = 3, F = 3260.42, p < 0.001). Memosil 2 had lowest b* values. Irradiance transmittance was affected by material and thickness (Two-way ANOVA: df = 4, F = 2388.86, p < 0.001). Exaclear had highest irradiance transmission, surpassing control at >6 mm. Violet/blue irradiance ratio decreased with thickness; Exaclear maintained a constant ratio, indicating preserved violet irradiance. There was a strong positive correlation between translucency and light irradiance (Pearson's r = 0.97, R2 = 0.86-0.96). Radiant exposure analysis suggests adjusting the curing time based on PVS thickness for optimal exposure (10 J/cm2) is achievable within 13-14 s for <2 mm and 21-30 s for 8-10 mm with Clear Bite, Affinity, and Memosil 2; whereas Exaclear requires less time. Compressive modulus in clear PVS materials varied by type; Affinity and Memosil 2 demonstrate higher modulus, offering more stability of the clear mold. Translucency and irradiance transmission through clear PVS materials decreased as their thickness increased, yet Exaclear exceled in maintaining high translucency and superior light transmission capabilities. Additionally, there is a strong positive linear correlation between translucency and light irradiance transmittance, offering a method to adjust curing times effectively based on material translucency. The light curing time to adequately polymerize composite through clear impression material may need to be increased, particularly with thicker matrices or less translucent materials.

The effect of flowable composite and glass ionomer liner on the marginal integrity of class II composite resin restorations

Aim of the study To evaluate the effect of flowable composite and glass ionomer liner on the marginal integrity of Class II composite resin restorations. Materials and methods A total of thirty non-carious human maxillary molar teeth were mounted in acrylic blocks. Simple Class II cavity with parallel walls was prepared. The cervical margin was established 1.5 mm above the cemento- enamel junction. The overall dimensions and depth of the cavities were standardized as follow: 4 mm length occlusocervically, 4 mm width buccolingulaly and 2 mm depth axially. Specimens were randomly divided into three equal groups (10 each). Group 1: The cavities were restored with Xtra Fil bulk fill composite without liner. Group 2: Xtra base flowable composite (1 mm thickness) was applied, followed by Xtra Fil bulk fill. Group 3: Ionoseal glass ionomer was applied as a base (1 mm thickness), followed by Xtra Fil bulk. Specimens were then subjected to 500 thermal cycles from 5 to 55oC with 30 s dwell time, and 15 s transfer time. Impressions of the teeth were made using a polyvinyl siloxane material, poured with epoxy resin. These replicas were left 24 h for complete setting. Then, Gold sputtered to be examined under scanning electron microscopy (SEM). Results were expressed as percentage of open margins for the total margin length for proximal and cervical margins and also the width of the gap were measured. The recorded data was collected, tabulated, and statistically analyzed using SPSS version 25. Results It was found that there was a significant difference in total gap length between group 1 and group 2 with P value = 0.000. Where group 1 has the biggest marginal gap length and the smallest marginal gap length belongs to Group 2. While there was no significant difference between group 1 and group 3 with P value 0.124. It was also found that there was no significant difference between groups in marginal gap widths. Conclusions The use of flowable composite and glass ionomer as liner could reduce microleakage of bulkfill composite restorations.

Evaluation of Dimensional Change in Different Elastomeric Impression Materials Used in Implants: An Original Research

ABSTRACT Aim: The study’s objective was to assess the dimensional accuracy of hybrid polyether and polyvinyl siloxane materials for implant impressions. Materials and Methods: Nine groups were created from 45 samples of various building materials and construction techniques from the study. Five samples were tested, and 45 impressions were recorded. Results: The hybrid non-splinted technique has improved implant site replication, accuracy, and low interimplant distance alterations. Conclusion: The finest possible reproduction of implant sites on the master cast was made feasible by the use of an open, non-splinted method and a hybrid polyvinyl siloxane–polyether impression material.

In Vitro Assessment of Dimensional Accuracy of Three Different Types of Interocclusal Recording Materials.

The aim of the current study was to evaluate the dimensional accuracy of three various interocclusal recording materials. A total of 90 disc-shaped samples were prepared using polyether paste, wax, and polyvinyl siloxane material with the support of stainless steel die. For the purposes of this investigation, three frequently utilized interocclusal recording materials were chosen, and 30 samples from each material were prepared. Group I: Bite registration using polyether paste; Group II: Bite registration using wax; Group III: Bite registration using polyvinyl siloxane material. No samples were exposed to direct sunlight during storage and were kept at room temperature. Using a 10x universal measuring microscope, each sample disc was examined for the presence of horizontal and vertical lines inscripted in the die. For each of the samples, readings were taken at different time periods of 24, 48, and 72 hours. After 24 hours, the less dimensional changes were found in polyether paste group (0.11 ± 0.07) followed by polyvinyl siloxane material group (0.19 ± 0.04) and wax group (0.25 ± 0.12). After 48 hours, the less dimensional changes were found in polyether paste group (0.34 ± 0.02) followed by polyvinyl siloxane material group (0.42 ± 0.01) and wax group (0.94 ± 0.12). After 72 hours, the least dimensional changes were found in polyether paste group (0.46 ± 0.14) followed by polyvinyl siloxane material group (0.92 ± 0.03) and wax group (1.14 ± 0.09). The present study concluded that both the material and time factors had an impact on dimensional stability. The most dimensionally stable group was the polyether paste group, which was followed by the polyvinyl siloxane and wax material groups. Interocclusal recording material records the occlusal connection between real or artificial teeth for occlusal rehabilitation planning and for creating removable and fixed dentures. The creation of a clinically acceptable prosthesis is dependent upon the accuracy of the patient's diagnostic or working casts and the interocclusal record. How to cite this article: Sonkesriya S, Subramanian D, Saha P, et al. In Vitro Assessment of Dimensional Accuracy of Three Different Types of Interocclusal Recording Materials. J Contemp Dent Pract 2023;24(12):936-939.

Comparison of retention of monolithic zirconia crowns with alumina airborne-particle abraded and nonabraded intaglio using three different cements: A clinical simulation

The necessity of roughening the intaglio surface of zirconia crowns to achieve adequate retention is unclear. The purpose of this clinical simulation study was to evaluate the retention of airborne-particle-abraded and nonabraded monolithic zirconia crowns using 3 different cement types. Extracted human molars were used and prepared with a 10-degree taper. Impressions were made of the prepared teeth with a polyvinyl siloxane (PVS) material, and dies were made with Type 4 gypsum. Each die was scanned with a NobelProcera 1G Scanner, and the standard tessellation language (STL) files were transferred electronically to the Nobel Biocare production site, where a bar was added virtually on top of each crown and parameters were set for milling. Seventy-two Procera zirconia crowns were generated, of which half were airborne-particle abraded on the intaglio surface with 50-µm alumina particles at 400 to 500 kPa for 15 seconds. The other 36 received no intaglio treatment other than cleaning. Both groups of 36 crowns were divided into 3 subgroups of 12 specimens. The area of each preparation was calculated using a computer-aided design software program. The specimens were distributed to attain similar mean surface areas among the cementation groups. The crowns were cemented onto the specimen with a controlled force of 196N. The 3 cements used were self-adhesive, modified resin RelyX Unicem Aplicap, resin-modified glass ionomer RelyX Luting, and a composite resin, Panavia F2.0 with ED Primer A & B. All specimens were thermocycled (5 °C to 55 °C) for 5000 cycles and then removed axially with a universal testing machine (Instron Model 5585H) at a crosshead speed of 0.5mm/min. The removal force was recorded, and stress of dislodgement was calculated for each crown. A 2-way analysis of variance was used for statistical analyses. The type of failure was analyzed with the chi-squared test of association for independent samples (α=.05 for all tests). The mean dislodging force for crowns with airborne-particle abraded intaglio was 5.4MPa, which was statistically greater than the mean of 3.2MPa for nonabraded specimens (P<.001). No significant differences related to the dislodging stresses were detected among the 3 cements (P=.109). The mode of failure was similar whether abraded or not, with 50% of specimens retaining cement in the crown after separation. Alumina airborne-particle abrasion of the intaglio of zirconia to create surface roughness is beneficial in retaining the crowns, regardless of the cement type. The nonabraded crowns demonstrated significantly lower retentive stress with crown removal. The principal mode of failure was similar whether the zirconia intaglio was airborne-particle abraded or not. The most common mode of failure (>50% of specimens) was at least three-fourths of the cement remaining within the crown.

Effect of stabilization of patients on the accuracy and scanning time of maxillary dentate quadrants: A clinical study

As intraoral scanning has gained widespread acceptance as an alternative to conventional impression-making, numerous studies have evaluated the influence of operator-related factors and patient-related factors on scanning accuracy. While several authors have noted patient movements as a clinical limitation of scanning technologies, research providing empirical data or testing this hypothesis is lacking. The purpose of this clinical study was to assess the effect of using the Zero Motion Scanning Band, a silicone occlusal mouth prop, and an OptraGate lip retractor for stabilizing the head and jaw on the accuracy (trueness and precision) and scanning time of digital quadrant scans. A conventional impression was made of the maxillary right quadrant with polyvinyl siloxane material and then digitized using a calibrated extraoral scanner to create the reference file. Two different groups were created: no scanning aids (NSA) and with scanning aids (WSA). For the NSA group, scans were made without considering the participant's movements. For the WSA group, scans included the Zero Motion Scanning Band, a silicone occlusal mouth prop, and an OptraGate lip retractor. Sixty-four scans were captured with an intraoral scanner (TRIOS 3) for each group, and the scanning time was recorded. Using an inspection and metrology software program, scans of each group were superimposed on the reference file to determine 3-dimensional (3D) deviations. The Kolmogorov-Smirnov test evaluated the normality of the distribution of variables, and the Mann-Whitney U test was selected for data analysis of non-normally distributed variables, including 3D deviations and scanning time (α=.05). Significant differences for trueness and scanning time mean values were observed under different scanning conditions: with and without head and jaw positioning (P<.05). The modified scan protocol exhibited higher trueness, with smaller mean root mean square values of 38.4 ±2.7µm compared with 40.8 ±3.1µm in the nonmodified group. However, precision did not display a statistically significant difference with varying scanning conditions (P>.05). The use of the Zero Motion Scanning Band, a lip retractor, and a silicone occlusal mouth prop on the contralateral side of the scanned quadrant significantly improved the trueness and scanning time of the quadrant digital scan. Further evaluation of head and jaw stabilizing tools is recommended in more complex clinical scenarios, such as complete arch digital scans and scanning implant-supported restorations.

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).

Adaptation of Relined Fiber Post Using Discontinuous Short Fiber-Reinforced Resin Composite to Restore Weakened Endodontically-Treated Premolars

Abstract Objective This study aimed to investigate the effect of relining prefabricated fiber-reinforced composite (FRC) posts using bulk-fill, flowable, discontinuous short fiber-reinforced composite (SFRC) on intracanal adaptation in weakened endodontically-treated premolar teeth. Materials and Methods Forty extracted human premolar teeth were selected and randomly allocated to five groups (n = 8) according to the canal preparation method and restorative technique after endodontic treatment: Group 1 (control): nonflared, closed apex root canals; group 2, 4: flared, open-apex root canals; group 3, 5: flared, closed apex root canals. Groups 1 to 3 were restored with standard RelyX fiber post size #1, while groups 4 and 5 were restored with customized RelyX fiber post size #1 and relined with bulk-fill flowable SFRC (everX Flow, GC, Tokyo, Japan). To evaluate intracanal adaptation, the empty root of each sample with the corresponding fiber post (standard or customized) inserted was measured twice using a micro-digital scale and the average value was calculated. The post was then removed, followed by the insertion of a light body polyvinyl siloxane (PVS) impression material into the canal, followed by reinsertion of the post and removal of excess material once the PVS was set. Finally, the sample weight was recorded, and the data were analyzed using one-way analysis of variance and the Bonferroni post hoc test (p-value = 0.05). Results A statistically significant difference (p &lt; 0.05) in PVS material weight was identified between the groups. Group 1 (control) had the lightest weight of PVS material, followed by groups restored with customized fiber posts (groups 4 and 5) and standard fiber posts (groups 2 and 3). Conclusion Anatomically-customized fiber posts with bulk-fill flowable SFRC provided better intracanal adaptation compared with standard fiber posts in teeth with compromised root canals.

Cord Placement Model: An Instructional Guide for Preclinical Dental Students to Practice the Skill of Retraction Cord Placement.

Gingival displacement is essential for ideal margin exposure and improved direct or indirect restorative outcome. Recent literature found many dentists prefer using retraction cord. Some contraindications of other displacement methods make retraction cord displacement preferred. It is necessary to teach dental students appropriate cord placement while minimizing gingival trauma. We developed a stone model using prepared typodont teeth and simulated gingiva that was made of polyvinylsiloxane material. Twenty-three faculty and 143 D2 students were briefed on the instructional guide. After faculty demonstration, D2 students practiced for 10-15 minutes under observation. The following year, former D2 (now D3) and D4 students were asked for feedback on the instructional experience. Fifty-six percent of faculty rated the model and instructional guide good to excellent, and 65% rated the student experience as good to excellent, with only one participant rating it poor. Seventy-eight percent of D3 students strongly agreed or agreed the exercise increased their understanding of the technique in placing cord on a patient. Furthermore, 94% of D4 students strongly agreed or agreed having this exercise in preclinical D2 year would have been helpful. Use of retraction cord to deflect gingiva is still preferred by most dentists. Completing the cord placement exercise on a model helps prepare students to perform the procedure on a patient before arriving at the clinic. Survey comments such as "useful exercise" support use of this instructional model. Overall, faculty and D3 and D4 students felt the exercise was beneficial to use in preclinical education.

Management of palatal defect post hemimaxillectomy: a case report

A 42-year-old woman was referred to the Department of Prosthodontics, Hasanuddin University Dental Hospital with speech, swallowing and chewing difficulties caused by a fractured and non-reusable acrylic obturator. The patient had been using the obturator since maxillary tumor resection in 2012, which resulted in a significant and deep defect in the right maxillary region. Intraoral examination revealed a defect in the midline of the palate that extended to the left alveolar bone, and 21, 22, 23, 24, 25, 26, 27, 16 were edentulous. The maxillary defect did not appear inflamed or infected, and the surrounding area appeared normal. The treatment plan was fabrication of a maxillofacial skeletal partial denture to rehabilitate the maxillary defect. Primary impressions were made with irreversible hydrocolloid ma-terial with a stock tray to obtain a study model. Custom tray was made for individual impressions with polyvinyl si-loxane material to obtain working models. A survey was conducted, and framework and bite rim were made. Maxil-lary denture was designed with Akers clasps at 35, 37, RPI at 45, full palatal palate as main connector. The denture framework was tried on, followed by determination of vertical dimensions. Denture alignment was done in the articu-lator using A3 color. The was prostheses were tried in and evaluated of retention, articulation, phonetics, and aes-thetics; then sent to dental laboratory for processing and the obturator was then inserted into the patient's mouth. Pati-ent follow-up was scheduled 24 hours and 1 week after insertion. It is concluded that the maxillofacial partial den-ture is a rehabilitation device that can result in decent retention and stabilization, especially in cases of acquired de-fects. The prosthesis can improve patient adaptation and ability with speech, mastication and swallowing functions.

Clinical evaluation of marginal fit of uncemented CAD-CAM monolithic zirconia three-unit restorations in anterior areas, using scannable and conventional polyvinyl siloxane impression materials

BackgroundThe accuracy of impression techniques determines the marginal fit of fixed prostheses. Marginal accuracy plays a main role in the success and failure of treatments. This in-vivo study evaluated the marginal fit of anterior three-unit monolithic zirconia fixed partial dentures (FPDs) using conventional and scannable polyvinyl siloxane impression materials.MethodsTen patients were selected to replace the lateral teeth with a three-unit monolithic zirconia bridge. For each patient, in the first group, an impression was made with a two-step putty-wash technique using scannable polyvinyl siloxane material (BONASCAN; DMP, Greece). In the identical session, as the second group, an impression of conventional putty-wash polyvinyl siloxane was taken (BONASIL A+ Putty; DMP, Greece). The marginal discrepancy was measured through the replicas, which were cut perpendicularly within the buccolingual and mesiodistal directions. An Independent t-test was employed for data analyses (P < 0.05).ResultsThe marginal discrepancy in a conventional method for central abutment in mid-buccal, mid-lingual, mid-mesial, and mid-distal was higher than in the scannable method but it was not significant (P > 0.05). Also, the marginal discrepancy for canine abutment in the conventional method was higher than in the scannable method, but it was not significant, either (P > 0.05).ConclusionsFPDs fabricated from both scannable and conventional impression materials were not superior to each other in marginal fit for both central and canine abutments by evaluation using the replica technique.

Marginal integrity of composite resin restoration in class I cavities prepared by hydro-abrasion

Aim To evaluate and compare the marginal integrity of composite resin restorations made by two different preparation techniques: conventional drill and hydro-abrasion. Materials and methods Forty extracted human premolars with simple occlusal caries were used. The teeth were fixed with sticky wax to the base of plastic cylinder. The cylinder was filled with self-curing acrylic resin so that only root was embedded within the self-curing acrylic resin. The teeth were randomly divided into two main groups (n = 20) according to the preparation technique. Group I: class I cavity preparation was done by the conventional drill method using a #245 Carbide bur and contra angle high-speed hand piece with water coolant. Cavity design was restricted to remove caries with no undercuts, and no beveling. Group II: class I cavity preparation was done by Aquacut Quattro air hydro-abrasion unit which uses a gamma irradiated aluminum oxide particle as abrasives (29 μm), cutting fluid and a hand piece of 0.6 mm diameter tip. The preparation in both groups was restored by the same composite resin (Grandio) and adhesive systems (Futurabond U) following the manufacturer's instructions. All specimens were thermocycled. Impressions for each tooth was made using a polyvinyl Siloxane material. The impressions were then poured with epoxy resin. These replicas were examined under scanning electron microscope. Scanning electron microscope photographs of tested samples were used for the gap evaluation. Results It was found that, group I recorded higher mean value of marginal gap length (157.57 ± 35.15 μm) than group II that recorded (69.55 ± 20.02 μm). Also, group I recorded higher mean value of marginal gap length ratio (10.72 ± 2.47) than group II that recorded (7.44 ± 2.69). Conclusion Conventional drilling technique was faster than the hydro-abrasion technique for cavity preparation. Hydro-abrasion technique showed more marginal adaptation than conventional drilling technique.

Evaluation of dimensional stability, compressive resistance, and detail reproduction of thermoplastic resin (BDIMPRESS), elastomeric and composite bite registration material: An in vitro study.

The fabrication of an accurate prosthesis depends mainly on precise recording of the maxillo-mandibular relationship of the patient and transferring it to the articulator. BDIMPRESS is a new thermoplastic material that has been proposed as a potential material to be used as an inter-occlusal registration, but there has been no literature evidence regarding its application as a bite registration. The main purpose of this study is to evaluate and compare the dimensional stability, detail reproduction, and compressive resistance of new interocclusal recording material with other two commonly used materials. In Vitro Comparative study. The study was conducted according to ADA Specification standards of testing for dimensional stability, detail reproduction and compressive resistance. Specimens were prepared for three different materials (Thermoplastic resin, Polyvinyl siloxane, and Bis- acrylic) with 12 samples each. One way ANOVA was done for statistical analysis. Polyvinyl siloxane material was dimensionally stable (mean at 1 hr: 24.928 mm; 24 hrs: 24.919 mm & 48 hrs: 24.912 mm) followed by Bis- acrylic material (mean at 1 hr: 24.851 mm; 24 hrs: 24.825 mm & 48 hrs: 24.815 mm). On one way ANOVA, strong significance was observed between groups (P = 0.00). Thermoplastic resin showed higher amount of detail reproduction with 10 (out of 12 samples) samples showing satisfactory results. While bis- acrylic material showed the least compressive resistance (Strain %: 0.484%; Displacement- 0.0990mm). One-way ANOVA showed presence of significance between the groups (P = 0.024). Polyvinyl siloxane showed superior dimensional stability, thermoplastic resin showed better detail reproduction and bis- acrylic showed high resistance to compression over other materials.

Effect of different impression techniques on marginal fit of restoration - An In Vitro study.

Impression making is one such important clinical step, which is critical in the accurate fitting of resulting prostheses. Impression making itself depends on the type of material and the impression technique used to record the details. Various combinations of material and the technique have been described in the literature. To evaluate the effect of three different impression techniques on the marginal fit of computer-aided designed/computer-aided manufactured (CAD/CAM) single unit composite fixed dental prostheses (FDP), different consistencies of addition silicone impression material and different tray design were utilized. Impression of prepared tooth on typodont was made using Matrix impression system, two-step putty wash technique, and individual tooth tray technique. Prosthesis was fabricated using CAD/CAM technology and marginal accuracy was evaluated using scanning electron microscopy (SEM). In the present study, the matrix impression system resulted in less microgap in both mid-buccal and mid-mesial region, whereas putty wash technique showed very high standard deviation in the interproximal region. Matrix impression system had the best results at both mid-buccal and mid-mesial position with least marginal discrepancy. The findings of this study could be used by clinicians to help them choose the viscosity of polyvinylsiloxane material and impression techniques for FDP that will result in high-accuracy impressions and well-fitting prostheses.

Fabrication of a CAD-CAM combination matrix for trial restorations: A dental technique

The trial restoration increases outcome predictability in restorative treatments, enhances communication among specialists and patients, and guides tooth preparations. It should reproduce the planned design precisely because many decisions will be made based on the transferred design. Traditionally, a diagnostic waxing design is transferred to the mouth with a flexible silicone matrix. However, a rigid matrix would ensure an accurate transfer of the planned design by avoiding the deformation of the silicone index. A step-by-step technique for fabricating a computer-aided design and computer-aided manufactured (CAD-CAM) rigid matrix relined with polyvinyl siloxane material to fabricate a trial restoration is presented. The technique ensures accurate detail reproduction and dimensional stability, avoiding deformation and ensuring a predictable transfer of the planned design.

A comparison of different methods and materials for establishing maximal intercuspal position: A clinical study

Statement of problemWhich method or material used to record the intercuspal position yields the best accuracy of location of the maxillary and mandibular casts is unclear. PurposeThe purpose of this clinical study was to determine the most reliable method of recording a patient’s maximal intercuspal position by comparing 2 common methods with 2 popular registration materials. Material and methodsComplete arch impressions were made of both jaws with a polyvinyl siloxane impression material in a metal stock tray followed by 4 interocclusal registrations for each of the 17 participants. Two registration techniques were used. More than 1 record was obtained in the first technique, as the participant had to close through a wax sheet or a polyvinyl siloxane material. In the second technique, a polyvinyl siloxane material was injected from the buccal aspect between occluded tooth surfaces. Casts were made from Type 4 stone and vertical measurements of the casts were carried out by using digital vernier calipers, accurate to 100 μm. Hand articulation of the casts was used as the control. Consistency of measurement was assessed by the intraclass correlation coefficient, and comparisons were made by using repeated-measures regression analysis. ResultsStatistical analysis showed significant discrepancies when the participant closed through both wax and polyvinyl siloxane material (P<.001). No statistically significant differences to the control group were present when polyvinyl siloxane was injected laterally after closure. ConclusionsHand articulation was the most accurate method of reproducing the maximal intercuspal position in a completely dentate individual with horizontal and vertical occlusal stability and was therefore considered the control. Recording the position after the participant had closed by using a polyvinyl siloxane material was the most accurate.

Effects chemical disinfectants on surface roughness of conventional impression materials used for dental prosthetic procedures.

To compare the effects of disinfectants on surface roughness of the conventional impression materials following chemical disinfection procedures. Equal numbers (65 for each impression material) of disc-shaped (15 × 3 mm) samples (Total n = 195) were fabricated from polyvinyl siloxane (Zhermack Elite), polyether (3M Impregum Penta Soft), and vinyl siloxane ether (Kettenbach Identium Lightbody) impression materials. Each impression material group was divided into five subgroups including one control group (n = 13). Impression material samples were immersed in CaviCide for 3 min, Zeta 7 solution for 10 min, and 5.25% sodium hypochlorite solution for 3 and 10 min. Surface roughness (Ra) was measured using a profilometer (Mitutoyo-SJ 410, Mitutoyo Corp.). The study data were analyzed statistically. A statistically significant difference was found among impression materials and disinfectants in terms of surface roughness (P < 0.05). Polyvinyl siloxane material showed a lower Ra value compared to Polyether and VSE materials; while polyether material showed a significantly lower Ra value compared to VSE material. Ra values of the control group were significantly lower than the disinfectant group immersed in 5.25% NaOCl solution for 10 min. Among all impression materials, polyvinyl siloxane showed the least surface roughness following disinfection procedures. Impression disinfectants that are specially designed for disinfecting dental impressions resulted in less surface roughness in all impression materials. With this study, it was aimed to obtain a smooth and clear model for the production of correct and compatible prostheses in the laboratory while at the same time purifying the impressions from microorganisms.

Dimensional Changes in Extraction Sockets: A Pilot Study Evaluating Differences between Digital and Conventional Impressions

Traditionally, soft tissue records are obtained by dental impression using impression materials; however, accurately recording the soft tissue immediately after tooth extraction is difficult. We measured the tissue changes after tooth extraction and compared two impression modalities (digital versus conventional) by measuring the changes at the soft tissue level. In this case, 15 patients with 17 single extraction sites were enrolled. Conventional impression (CI) using vinyl polysiloxane material and digital impression (DI) using an intraoral scanner were prepared immediately after extraction (T0) and at 2 months post-extraction (T1). Standard tessellation language files were generated for superimposition of the tissue surface. The tissue changes and discrepancies were measured on the superimposed surfaces. The differences in the changes and the discrepancy between the tissue surface impression at each time point were compared. At all measuring levels, the total tissue change was significantly different between groups DI and CI (p &lt; 0.05). DI exhibited a more pronounced tissue surface at both time points, and the total discrepancy was statistically significantly greater at T0 than at T1 (p &lt; 0.05). The values from DI and CI demonstrated small but significantly different for the same study material. The interpretation of such differences may depend on the clinical situation or scientific value.