In vitro comparison of accuracy between conventional and digital impression using elastomeric materials and two intra-oral scanning devices.

AIM: The aim of this study was to compare the accuracy of full-arch conventional implant impressions using two different materials (A-silicone and polyether) to full-arch digital implant impressions produced from two intraoral scanning devices. MATERIALS AND METHODS: A master model was fabricated representing an edentulous mandible with four implants with internal connection placed at the sites of canines and first molars. The anterior implants were parallel to the residual ridge, while the two posterior implants had an angulation of 15° to the distal and 15° to the lingual respectively. The conventional technique was performed with open-tray of non-splinted impression copings. Two different impression materials were used, A-silicone and polyether at monophase medium body consistencies. The digital impressions were obtained with the use of two different intraoral scanners, after the connection of scan bodies. A total of 10 impressions were produced for each of the four experimental groups. The conventional models as well as the master model were digitized using a high-resolution laboratory scanner. The STL files of the models and of the intraoral impressions were imported in a powerful superimposition software, for the conduction of measurements in pairs of files. The software calculated the 3D deviations, as well as the linear and angular displacements among scan bodies at the digital files. For "trueness" measurements every STL file of each experimental group was superimposed to the digital master model, while for "precision" measurements all STL files of each experimental group were superimposed to each other. RESULTS AND CONCLUSIONS: The accuracy of full arch mandibular implant impressions was influenced both by the impression technique used (conventional vs. digital) and the impression material used (A-silicone vs. polyether) or the intraoral scanner used (Trios vs. Heron). In terms of "trueness," A-silicone showed the highest impression accuracy with the lowest deviation values, followed by polyether and Trios, but the differences between the three groups were in the majority not statistically significant. Heron showed statistically lower accuracy results in all measurements compared to the other groups. In terms of "precision", conventional impressions with the use of A-Silicone or polyether were statistically significantly superior to digital impressions with either scanner. A-Silicone and polyether showed no statistically significant difference between them.

A fully digital approach to replacing an obturator prosthesis using a 3D printed closed hollow bulb: Α dental technique.

The replacement of an obturator prosthesis using conventional methods has multiple issues. Standard tessellation language files generated from the superimposition of an accurate intraoral scanning of the maxillary defect and direct data acquisition of the existing hollow bulb obturator can facilitate the precise design of the prosthesis, requiring only minor adjustments. Rapid prototyping manufacturing techniques seem to ensure precise control of the integrity of the prosthetic component completion. The success of the technique is the simplicity and repeatability of designing and fabricating a retrievable and easily repairable obturator.

Flexural properties and fatigue limit of 3D-printed and milled resin-based materials.

PURPOSE: The purpose of this study was to evaluate the flexural strength (FS), flexural modulus (FM), and fatigue limit (FL) of 3D-printed resin-based polymers and composites and compare them to 3D-printed composites. MATERIALS AND METHODS: A bar-shaped specimen (25 × 2 × 2 mm) was CAD designed according to ISO 4049:2019, and 60 duplicates of the 3D model were nested at a 45-degree angle with the printing platform and 3D-printed with three materials: denture teeth resin (Denture Teeth, Formlabs), temporary crown and bridge resin (Temporary CB, Formlabs), and composite (Flexcera Smile Ultra+, Desktop Health). The 3D model was also imported into a dental CAM software, duplicated 60 times, nested, and milled from a 3D-milled composite puck (Ivotion Denture Teeth, Ivoclar). All specimens were post-processed following the manufacturer's recommendation. The specimens were then subjected to a three-point bending test until failure using a Universal Testing Machine at a crosshead speed of 0.75 mm/min, and FS and FM were calculated. The remaining thirty specimens were tested for Fatigue Limit using the staircase approach starting at 50% FS maximum up to 1.2 M cycles at 10 Hz. The data were analyzed using one-way ANOVA and the Weibull distribution (α = 0.05). RESULTS: The results showed that Ivotion and Flexcera had higher FS (110.3 ± 7.1 MPa and 107.6 ± 6.4 MPa, respectively) and FM (3.3 ± 0.1 GPa and 3.0 ± 0.2 GPa, respectively) compared to the 3D-printed Denture Teeth (FS = 66.4 ± 18.5 MPa and FM = 1.8 ± 0.1 GPa) and Temporary CB (FS = 79.6 ± 12.1 MPa and FM = 2.7 ± 0.4 GPa). Weibull analysis showed that the Ivotion and Flexcera had a more uniform and narrower spatial distribution of defects (m: 27.98 and 29.19) than the printed materials, which had m values of 8.17 and 4.11 for Temporary CB and Denture Teeth, respectively. Although no differences were found in the static properties (FS and FM) between Ivotion and Flexcera, Ivotion presented a higher endurance limit than Flexcera (51.43 vs. 40.95 MPa). The Temporary CB presented 21.08 MPa and Denture Teeth presented 17.80 MPa of endurance limit. CONCLUSIONS: 3D-milled (Ivotion Denture Teeth) and 3D-printed (Flexcera Smile Ultra+) composites outperformed 3D-printed resins (Formlabs Denture Teeth and Temporary Crown & Bridge) in terms of flexural properties and fatigue resistance. 3D-milled (Ivotion) and 3D-printed (Flexcera) composites exhibited similar flexural properties, but 3D-milled composites showed a 25% higher fatigue endurance limit, suggesting improved clinical longevity.

Linear Accuracy of Intraoral Scanners for Full-Arch Impressions of Implant-Supported Prostheses: A Systematic Review and Meta-Analysis.

This article compares the accuracy of intraoral scanners (IOSs) used in the digital impression of full arches to fabricate implant-supported complete prostheses. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and was registered in the Open Science Framework (DOI 10.17605/OSF.IO/CPM9K). Six electronic databases, gray literature databases, and a manual search were performed in April 2022. Studies that evaluated the accuracy of intraoral scan impressions compared with conventional impressions in full-arch impressions were included for complete implant-supported prostheses. In addition, an adapted checklist for reporting in vitro studies was used to assess the risk of bias. Meta-analysis was conducted using a random-effects Hunter- Schmidt model. Nine studies were included in the analysis. IOS impressions present higher accuracy (137.86 µm) than conventional impressions (182.51 µm) (p<0.001). The heterogeneity of the study's methodology was I2»18.34. However, impression accuracy varies significantly with scan body type, IOS type, scanning strategy, and modification technique. For most IOS systems, the acceptable clinical threshold of linear accuracy of 200 µm can be achieved, except for the True Definition Scanner in one of the studies. Based on the results of the included studies, digital impressions using IOS present similar or better linear accuracy than conventional impression techniques.

Adherence of Candida albicans to Five Long-Term Silicone-Based Denture Lining Materials Bonded to CAD-CAM Denture Base.

PURPOSE: Knowledge about quantifying the number as well as the retention and adhesion of Candida albicans blastoconidia to silicone denture liners is limited. Thus, the aim of this in vitro study was to explore the adherence of C. albicans to the surface of five long-term silicone-based soft denture lining materials, using artificial saliva. MATERIALS AND METHODS: A total of 50 specimens (10 × 10 × 3 mm) of five long-term resilient liners (Molloplast-B; GC Reline Soft; Elite Soft Relining; Tokuyama Sofreliner S; Ufigel SC), bonded to a computer-aided design and computer-aided manufacturing denture base, were prepared. The specimens were inoculated and incubated in artificial saliva for 1 and 24 hours with a standardized (2.8 × 106 cfu/ml) C. albicans suspension. At the end of the incubation period, the specimens were stained with acridine orange and observed using fluorescence microscopy. RESULTS: After 1 hour and in 24 hours, Molloplast B demonstrated significantly earlier adherence of C. albicans cells compared to the other chairside materials (p < 0.001 and p < 0.001, respectively), where the mean number of cells also increased in the frontal parts. Regarding the rate of C. albicans proliferation from 1 to 24 hours within the materials, there was an increase in all materials (Molloplast B: p < 0.001; GC Reline Soft: p = 0.220; Elite Soft Relining: p = 0.032; Tokuyama Sofreliner S: p = 0.001; Ufigel Sc: p = 0.001). The Ufigel Sc showed a significant 2.5-fold increase at 24 hours. CONCLUSIONS: Long-term silicone denture liners accumulate a significant amount of C. albicans blastoconidia and their coverage by them increases progressively over time.

Digitally designed and additively manufactured tooth reduction guides for porcelain laminate veneer preparations: A clinical report.

Porcelain laminate veneers are a conservative treatment to enhance esthetics, tooth shape, color, and contours. Enamel preservation during tooth preparation is essential for the long-term success of these micromechanically retained partial coverage restorations. Different methods have been described to clinically assess tooth preparation relative to definitive restorative contours. This clinical report describes a digital workflow to fabricate 3-dimensionally (3D) printed tooth reduction guides based on digital esthetic planning. These 3D-printed reduction guides help clinicians visualize and gauge tooth preparations relative to the desired restorative contours, aid in enamel preservation, and overcome some of the limitations associated with conventionally fabricated tooth reduction guides.

Dental students' perspectives on three intraoral scanners and CAD/CAM systems before and after a pre-clinical elective course in digital dentistry.

Background: Intraoral scanners (IOS) are gaining interest in Dentistry for their ability to capture digital impressions of the oral cavity. These digital impressions facilitate the fabrication of indirect restorations using CAD/CAM technology. This study aimed to describe an elective course given to predoctoral dental students on the topic of Digital Dentistry and assess their learning outcomes and system preferences. Material and Methods: Three IOS were evaluated by eight students enrolled in a Digital Dentistry elective course. These systems included Emerald S (Planmeca), Cerec Omnicam (Denstply Sirona), and True Definition (3M/Midmark). After a literature review and a hands-on session were completed for each system, the students provided their perspectives on various factors such as ease of use, organization, and user-friendliness in a qualitative narrative of each system and quantitatively through a six-items survey. Results: Survey data suggests that the student cohort showed higher levels of previous familiarity, user preference, and clinical confidence in the Cerec and Planmeca systems as opposed to the True Definition system. Qualitatively, the students felt CEREC was the more educationally useful system to learn and presented with more ease of use, functionality, and efficacy than the other two systems. Conclusions: While each system proved to have its unique benefits and drawbacks, students' attitudes towards the Planmeca and Cerec systems were generally positive, while True Definition's evaluation was limited. Students appreciated their experiences throughout this elective, familiarizing themselves with various digital systems. Key words:Digital Dentistry, Intraoral Scanners, CAD/CAM, Dental Education, Learning Curve.

The effect of different pulp capping methods on the intrapulpal temperature when using light-cured procedures.

Background: To evaluate the intra-pulpal temperature during different direct pulp capping methods and light-cured procedures. Material and Methods: Class I preparations 5 mm long, 4 mm wide and 4 mm deep were performed in extracted third molars, leaving 0.5 mm of dentin at the pulpal floor with a 1 mm diameter of pulp exposure. Teeth were placed in a customized oral cavity chamber simulator in which the initial temperature was standardized at 36oC. The overall temperature variations (oC) in the pulp chamber during the light-activation processes were recorded live using an infrared camera (FLIR ONE PRO, FLIR Systems). The liners and bases evaluated were: Dycal (Dentisply), TheraCal LC (Bisco), Biodentin (Septodent), Vitrebond Plus (3M/ESPE), and Fuji IX GP (GC), followed by restoration with a bulk fill composite (EvoCeram Bulk Fill, Ivoclar Vivadent). All light-activation procedures were performed with the VALO Grand (Ultradent) light-curing unit. A power analysis was conducted to determine the sample size to provide a power of at least 0.8 with α=0.05. Statistical analyses were performed using ANOVA and Tukey's test for multiple comparisons. Results: The intrapulpal temperature increased above a 10oC to 20oC threshold difference for all liners and bases that were light cured. When added as second layers, neither of those could provide thermal insulation following additional light-activated procedures (p=0.25). The higher the number of procedures requiring light-activation, the longer the pulp temperature remained in those increased temperature thresholds. Conclusions: For direct pulp capping procedures, a reduced number light activation procedures should be indicated to reduce the time intra-pulpal temperature rises above a 10oC threshold. Key words:Liner, base, calcium hydroxide, glass ionomer, dental adhesive, bulkfill composite.

Effect of dental headlights spectrum on the polymerization and working time of light-cured resin composites.

Background: The use of dental headlights is a common practice to better illuminate the operatory field and achieve excellence in restorative dentistry. However, visible light-cured dental materials can have reduced working time under headlight illumination. The aim of this study was to evaluate the influence of the spectral irradiance power of two dental headlights on the degree of polymerization and working time of light-curable dental composites. Material and Methods: Two headlights, StarLight Nano 3 (StarMed) (SN) and Zeon Endevour XL (Orascoptic) (ZE) were characterized using a spectrophotometer coupled to an integrating sphere (MARC® Light Collector, BlueLight Analytics). The degree of conversion of the two composites, Filtek Supreme (3M) and Tetric Prime (Ivoclar Vivadent), was evaluated using an FTIR spectroscope (NicoletTM iS20, Thermo Fisher). Results: Both headlights emitted a significant amount of blue light. The Zeon headlamp without filter emitted a broader spectrum with lower blue intensity and higher CRI than the White LED of the Nano 3. The Zeon headlamp with the blue blocking filter emitted a broader spectrum than the Orange LED of the Nano 3. There were no differences in the degree of conversion and working time of the Filtek Supreme and Tetric Prime composites when illuminated by the different headlamps. Both Zeon and the White LED of the Nano 3 were capable to cure the composites within only 5-10 minutes of irradiation. There were no changes in the degree of conversion of the composites when the Orange LED of the Nano 3 or the blue blocking filter of the Zeon were used. Conclusions: Both headlights reduced the working time of light-cured materials. The use of orange filters prevented the composite polymerization and maintained the working time. Key words:Surgical Headlight, degree of conversion, working time, light-curing.

Effect of Staining Solutions on Color Stability, Gloss and Surface Roughness of Removable Partial Dental Prosthetic Polymers.

PURPOSE: To assess the effect of commonly used solutions on color stability, gloss, and surface roughness of removable partial dental prostheses polymers. MATERIALS AND METHODS: Discs (n = 112) were made of a poly(etheretherketone) (PEEK) polymer, a polyamide, an acetal resin and a heat-cured poly(methylmethacrylate) PMMA acrylic resin polished according to manufacturers' instructions. Seven specimens of each material were immersed in coffee, red wine, coca cola and distilled water for 30 days at 37ο C. Changes of color (ΔΕ*) and color coordinates L*α*b* after immersion were calculated with a colorimeter. Changes in the values of gloss and surface roughness parameters (Sa, Sz, Str, Sdr, Sci, Svi) were also measured. Two-way ANOVA and pairwise comparisons were used to evaluate the effect of material and staining solution on parameter value alterations (α = 0.05). RESULTS: The two-way ANOVA revealed that the interaction between material and staining solution significantly affected color changes after immersion [F(9,96) = 44.67, p < 0.001]. PEEK presented the lowest color change (ΔΕ* = 3.83 ± 2) while polyamide had the highest color change overall (ΔΕ* = 14.59 ± 8.65) (p < 0.001). Coffee caused the highest color (ΔΕ* = 13.08 ± 6.98) and gloss changes (ΔG = -6.36 ± 19.2 GU) among different solutions (p < 0.001). PEEK showed the highest alteration of gloss (ΔG = -11.31 ± 15.49 GU), with significant difference with the other three materials (p < 0.001). Insignificant interaction of material and immersing solution was found for surface roughness parameters (p > 0.05). CONCLUSIONS: Among the materials tested, PEEK seemed to be the most stable material when subjected to common, everyday staining solutions. Therefore, PEEK could be a viable solution for an RPDP framework fabrication, expanding the material list of prosthetic options. Further research and clinical trials are required to confirm the above statement.

Polyetheretherketone (PEEK) Post and Core Restorations: A 3D Accuracy Analysis between Heat-Pressed and CAD-CAM Fabrication Methods.

PURPOSE: The purpose of this study was to evaluate the accuracy of polyetheretherketone (PEEK) based post and core restorations using heat-pressed and computer-aided design and computer-aided manufacturing (CAD-CAM) methods. MATERIALS AND METHODS: Post and core patterns (n = 10) were fabricated using an acrylic pattern resin and each pattern was scanned to generate a resin pattern standard tessellation file (STL-R) to be used as the standard control group for the 3D profilometric analysis. The STL-R files were loaded into a computer-aided manufacturing (CAM) machine and a milling disk made of a modified PEEK-based polymer with 20% ceramic fillers was milled into post and core restorations. Each original post and core resin pattern was sprued, invested and pressed using pellets made of the same PEEK material and a PEEK pressing unit. The resulting post and core restorations from the CAD-CAM and heat-pressed methods were scanned to generate STL-M (milled) and STL-P (heat-pressed) files, respectively. STL-M and STL-P files were digitally aligned and compared to STL-R files using a 3D analysis software. The 3D spatial distribution deviation was exported, and the statistical analysis was performed using the 95% CI deviation distribution from the Gaussian function subtraction. The statistical outcome for each group was merged and a 3D color-coded map was created showing the average deviation (α = 0.05). RESULTS: The heat-pressed post and core restoration showed 79 ±6% of the areas within ±50 µm while the CAD-CAM post-and-core restoration showed 66 ±9%. The CAD-CAM post and core restorations show 6 ±5% of the areas above the ideal for marginal adaptation limit threshold of 200 µm, while only 0.7 ±0.7% was found for the heat-pressed. CONCLUSIONS: The heat-pressed method to manufacture PEEK-based post and core restorations showed higher accuracy than the CAD-CAM method.

Complete denture digital workflow: Combining basic principles with a CAD-CAM approach.

This report describes a digital workflow for the fabrication of a complete maxillary denture opposing an implant-retained overdenture. This procedure provides a predictable and accurate 3-visit technique to digitally scan and articulate edentulous ridges, avoiding the discomfort associated with analog impression making. Wax rims were applied to intraorally relined plastic edentulous stock trays. The occlusal relationship was registered at the appropriate vertical dimension of occlusion by using these tray and rim assemblies. The digital laboratory scanning of the relined tray and rim assemblies resulted in accurate virtual articulation of the digital edentulous intraoral scans. The removable restorations were digitally designed, milled, and delivered, and the clinical and laboratory steps are described.

How witnessing rudeness can disrupt psycho-motor performance of dental students.

Rude and disrespectful behaviors are ubiquitous and pervasive in the workplace. The purpose of this study was to examine the effects of witnessed rudeness on dental student psychomotor performance. Using an experimental, between-subjects design, 71 2nd (Sophomore) year dental students witnessed either an experimental (rude) or control (neutral) condition in which a confederate lab manager interacted in a rude or neutral manner with a prospective lab assistant candidate. Students then performed a mock prosthodontics psychomotor examination as part of the fixed prosthodontics preclinical course. Results indicated that those students who arrived at the experimental session cognitively depleted (+1 SD above the mean) and were exposed to the rude condition were significantly more likely to make critical errors when performing a posterior bridge preparation, compared to those students in the control group. There were no significant differences between the rude and control conditions for participants who were not cognitively depleted (-1 SD below the mean). Overall, the findings indicate that for those dental students suffering from cognitive depletion, merely witnessing rudeness can have adverse impacts on psychomotor performance and potentially, eventual patient care.

A Full Digital Workflow for the Duplication of an Existing Implant Retained Overdenture Prosthesis: A Novel Approach.

The purpose of this clinical case report is to describe a fully digital workflow for the duplication of an existing implant retained overdenture, highlighting the benefits of digitally fabricated dentures. The patient presented with an existing mandibular implant retained overdenture on Locator attachments that needed to be replaced. The existing overdenture was duplicated/scanned with the use of an intraoral scanner and was 3D printed using acrylic resin. This resin duplicate was sectioned in the midline and served as a unilateral record base to digitally record maxillo-mandibular relationship. The occlusal relationship was scanned unilaterally with the record base (sectioned duplicate) in place, and the procedure was repeated for the opposite side. All scans (edentulous, bite registrations and preliminary scan) were superimposed and the software managed to position and stich everything together. A try-in copy denture (ProArtCAD Try in, Ivoclar Vivadent AG, Schaan, Liechtenstein) was milled in order to imitate the conventional wax teeth try-in. A definitive milled overdenture was fabricated and delivered. A reinforcing polyetheretherketone mesh was fabricated, utilizing computer assisted design/computer assisted manufacturing technology and was incorporated into the pre-designed customized space into the polymethylmethacrylate base, using indirect light-polymerized nano-filled composite resin (crea.lign; bredent GmbH & Co. KG). Occlusion was verified and the patient was instructed oral hygiene, home maintenance and was informed for the required recall visits.

The Use of Modified Polyetheretherketone Post and Core for an Esthetic Lithium Disilicate Anterior Ceramic Restoration: A Clinical Report.

This clinical report presents the use of a modified polyetheretherketone (PEEK) post and core in order to support a lithium disilicate ceramic crown for a maxillary lateral incisor. When considering post-and-core restorations, material flexibility is essential to prevent root fractures. The low elastic modulus of PEEK (4 GPa) could result in lower root fracture rates, preserving tooth structure and favoring tooth re-restoration if the post fractures. PEEK is biocompatible, presents adequate bond strength with dentin when bonded with a resin cement, and can be used under ceramic restorations because of its white, esthetic color. PEEK posts and cores could also cost less when fabricated using common laboratory procedures. Polyetheretherketone (PEEK) posts and cores could be a viable alternative to rigid cast or zirconia posts, or even to fiber-reinforced composite posts, especially when combined with lithium disilicate crowns.

An 8-Year Clinical Outcome of Posterior Inlay Retained Resin Bonded Fixed Dental Prosthesis Utilizing High Performance Polymer Materials: A Clinical Report.

This clinical report presents the use of a modified polyetheretherketone (PEEK) Inlay Retained Resin Bonded Fixed Dental Prosthesis (IRRBFDP) framework, veneered with indirect high impact composite for the bilateral restoration of mandibular first molar teeth, as the most conservative treatment option for a medically compromised patient. When used as a framework, PEEK's elastic modulus (approximately 4 GPa), could result in the reduction of stresses transferred to the abutment teeth and the cementation interface accordingly, therefore it could result in lower de-bonding rates and higher success rates. Furthermore, the high bond strength with the veneering composite material and the luting cements permit its use for resin-bonded restorations. Preparation guidelines, indications and advantages for the fabrication of IRRBFDPs are described in this clinical report. No technical complications such as de-bonding of the framework, connector or retainer fracture of the adhesive frameworks or loss of retention were observed during the course of 8 years. Prosthetic replacement of single missing posterior mandibular teeth utilizing IRRBFDPs with high performance polymer materials could potentially offer long-term high survival rate outcomes. Further clinical evidence is required in order to justify the above statement.

PEEK Maxillary Obturator Prosthesis Fabrication Using Intraoral Scanning, 3D Printing, and CAD/CAM.

This report presents a digital technique for the fabrication of a two-piece hollow bulb maxillary obturator prosthesis. The procedure described resulted in an accurate prosthesis while avoiding the discomfort associated with analog impressions. The manipulation of a routine postoperative CT scan in conjunction with a 3D printer allowed for the fabrication of a 3D-printed anatomical cast, from which the two-piece hollow bulb obturator was fabricated. The obturator prosthesis framework was digitally designed and milled from a modified PEEK material, resulting in a lightweight prosthesis with excellent biocompatibility. The clinical and laboratory steps involved are described.

Color changes of polyetheretherketone (PEEK) and polyoxymethelene (POM) denture resins on single and combined staining/cleansing action by CIELab and CIEDE2000 formulas.

PURPOSE: The purpose of study was to investigate the long-term effect of staining and/or cleansing solutions on the color stability of two non-metal removable partial denture materials. METHODS: One hundred disks (25×3mm) of polyoxymethylene (POM) and polyetheretherketone (PEEK) were immersed in water, wine, coffee, cleanser and combo bath, simulating normal daily use. Color parameters in the CIELAB system was measured every 30 cycles up to 240 using a contact colorimeter and color differences estimated using ΔEab and ΔE00 formulas. Two-way repeated measures ANOVAs and regression analyses were performed at α=0.05. RESULTS: Regression analysis indicated a strong R2 between color changes and number of cycles, for both materials. Tests of within-subjects effects for the ΔEab revealed significant differences among cycles and between the materials in the wine and coffee baths (p<0.001). Significant materialXcycles interactions were also recorded with all staining baths. ΔE00 values were lower than ΔEab up to 63.6%. Tests within and between-subjects effects for the ΔE00 gave similar but not the same with ΔEab results. CONCLUSIONS: ΔE00 found to correlate well with ΔEab. Long term exposure of both materials showed a progressive discoloration in all except control baths. POM discolored more than PEEK in coffee, and combo baths but not in cleanser. Discoloration was smaller in combo bath (where a cleanser was also used) indicating the effectiveness of a cleanser to prevent long term discoloration of both materials.

The influence of impression coping splinting on the accuracy of the open-tray technique.

The objective of this study was to examine the effect of splinting of the impression copings on the accuracy of the cast when the open-tray technique is used. An epoxy master cast with 3 implants was fabricated. The first 2 implants were parallel to each other and perpendicular to the horizontal plane (implants A and B), and the third implant (implant C) had a 25-degree inclination. A passively fitting metal framework that was fabricated over this master cast was used to measure accuracy of fit. Ten casts were fabricated from this epoxy resin master cast with the use of polyether material and the open-tray technique. For the first 5 casts, the impression copings were splinted with dental floss and autopolymerizing acrylic resin; in the next 5 casts, the impression copings were not splinted. The metal framework in the master cast was fixed in the new specimens, and the microgap between this prosthesis and the implant analogs was evaluated. The specimens were observed under an optical microscope, and microgap measurements were made on photographs taken at a standardized magnification of 40×. The inclined implant C had the smallest mean microgap among the 3 implants, but the differences were not statistically significant. Microgaps for all 3 implants were smaller when they were splinted, but the difference from the mean of the nonsplinted counterpart was statistically significant only for the inclined implant. The results suggest that there is no clinical advantage in splinting the impression copings for parallel implants. On the other hand, when the implants are not parallel, splinting of the impression copings can result in greater accuracy of the fabricated cast.

Fabrication of a 3D-printed interim obturator prosthesis: A contemporary approach.

This report describes the combination of analog and digital techniques for the fabrication of a 2-piece hollow bulb maxillary obturator. The procedure described provides an accurate representation of the surgical defect while avoiding the discomfort associated with analog impressions. The manipulation of a routine postoperative computed tomography (CT) scanner in conjunction with a 3D printer allowed for the fabrication of a 3D-printed anatomic cast from which the 2-piece hollow bulb obturator was fabricated. The clinical and laboratory steps involved are described in this article.