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.

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.

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.

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.

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.

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.

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.

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.

Managing Gag Reflex during Removable Partial Denture Treatment: A Review and a Clinical Report.

A gag reflex is a common occurrence during dental procedures. A hypersensitive gag reflex is less frequently encountered and may prevent the dental provider from successfully completing critical clinical stages, resulting in poor treatment outcomes. Once patients suffer an unpleasant gag reflex experience in a dental office, they may become phobic, delaying or postponing their dental treatment. The purpose of this article is to review available treatment options and present a report of a partially edentulous patient with an exaggerated gag reflex, focusing on clinical management using a simple yet effective table salt technique and proper prosthesis design.

Evaluation of a Realistic Cleansing Protocol for Preventing Discoloration of Denture Resins.

PURPOSE: To evaluate the efficacy of a realistic staining/cleansing protocol for long-term prevention of discoloration of denture base resins. MATERIALS AND METHODS: Sixty discs (20 × 2.5 mm) of auto- and heat-polymerizing denture acrylic resins were fabricated following manufacturer's instructions, polished on one side and stored in water (37°C) for 24 hours before they were assigned randomly into 6 groups (3 for each material, n = 10) to receive 220 cycles of three immersion protocols. Group A was immersed in the following baths: (1) filtered coffee at 45°C for 2 minutes, (2) tap water at 24°C for 20 seconds, (3) as bath 1, (4) as bath 2, (5) Corega Extradent cleansing solution at 45°C for 3 minutes, and (6) water at 24°C for 20 seconds. Group B was immersed in the four first baths of group A (without cleansing action) and group C in bath 1 for the cumulative action of 20 cycles (80 minutes in 45°C coffee) and bath 2 for 40 seconds. A noncontact optical interferometric profilometer was used for qualitative evaluation of the specimens and a contact colorimeter to estimate color change values (ΔΕ*ab) at baseline and every 20 cycles in the baths for a total of 220 cycles. Data were statistically analyzed using a 2-way-repeated measures ANOVA with Bonferoni multiple comparisons and trend analysis at α = 0.05 level of significance. RESULTS: Data indicated changes in color from 1.7 to 14.2 ΔΕ*ab units. The highest values were related to the number of cycles and group B immersion protocol. Significant differences were found among immersion protocols (p < 0.001) and immersion cycles (p < 0.001) with a significant interaction between protocols and cycles (p < 0.001) but not between denture resins (p = 0.991). CONCLUSION: The evaluated protocol A was found effective in preventing color changes in both denture resins even after a long period of action. Protocol C had a much lower staining effect on both resins than protocol B and behaved similarly to protocol A until 140 to 160 cycles. Therefore, it is probably not appropriate for use in short-term color stability experiments.

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.

The all-on-4 modified polyetheretherketone treatment approach: A clinical report.

A modified polyetheretherketone (PEEK) implant framework material in combination with prefabricated high-impact poly(methyl methacrylate) (PMMA) veneers was used as an alternative material for the fabrication of a complete maxillary arch implant-supported fixed restoration. The elastic performance of the PEEK framework (elastic modulus of 4 GPa) combined with PMMA veneers may reduce the occlusal forces, protecting the implant-supported restoration and the opposing dentition, especially in all-on-4 treatments, where lack of proprioception and wide interimplant distance are present. Long-term clinical evidence is required before recommending the application as an alternative restorative material for such a prosthesis.

Polyetheretherketone Overlay Prosthesis over High Noble Ball Attachments to Overcome Base Metal Sensitivity: A Clinical Report.

A modified polyetheretherketone (PEEK) framework material in combination with heat-polymerized denture base acrylic resin was used for the fabrication of an overlay prosthesis for a patient sensitive to base metals. High noble metal was used for the fabrication of the post/coping/ball attachment assemblies to promote retention and stability. These protruding attachments into the acrylic resin could result in stress concentration; therefore, a framework is often used to strengthen the prosthesis. PEEK frameworks could be a treatment alternative to high noble or Ti frameworks since they combine good mechanical properties with biocompatibility, reduced cost, and common laboratory procedures.

Using modified polyetheretherketone (PEEK) as an alternative material for endocrown restorations: A short-term clinical report.

A modified polyetheretherketone (PEEK) framework material veneered with indirect light-polymerized composite resin was used as an alternative material for the fabrication of an endocrown restoration for an extensively damaged molar. The elastic modulus of the polyetheretherketone framework (4 GPa) veneered with indirect composite resin could dampen the occlusal forces protecting tooth structures better than ceramic materials. This is important in the restoration of extensively damaged molars with weak roots. Long-term clinical evidence is required before recommending the application as a substitute material.

Modified PEEK as an alternative crown framework material for weak abutment teeth: a case report.

This case report describes the fabrication of 3 single crowns for a patient with weakened abutment teeth. The patient exhibited nocturnal bruxism and clenching but refused to use an occlusal appliance. The abutment teeth were endodontically treated and presented with loss of tooth structure and thin axial walls. The patient was seeking a metal-free restoration, and all-ceramic restorations were contraindicated because of the potential for abrasion of the opposing teeth and direct force transmission to the weak abutment teeth. The restoration of choice was a modified polyetheretherketone (PEEK) framework material veneered with an indirect light-cured composite resin. This approach offered characteristics such as biocompatibility, protection of opposing teeth, a cushioning effect, abrasion resistance almost equal to that of dentin, ease of intraoral repair in case of chipping, and a high level of comfort. The use of PEEK frameworks veneered with indirect light-cured composite resin could be a viable alternative for the treatment of weakened abutment teeth in patients with parafunctional habits.

Modified PEEK Resin Bonded Fixed Dental Prosthesis for a Young Cleft Lip and Palate Patient.

OBJECTIVE: This clinical report presents the use of a modified poly ether-ether ketone material as an alternative material for the fabrication of resin-bonded fixed dental prosthesis (RBFDP) framework. This new material can be used for patients allergic to metals, maintaining the same high esthetic demand of ceramics, presenting light weightness and a flexibility similar to bone as a distinct advantage over ceramic materials. CONCLUSIONS: The use of a BioHPP RBFDP framework could be considered as an alternative restoration for the replacement of missing lateral incisors in young patients with cleft palate defects. CLINICAL SIGNIFICANCE: This modified PEEK material known as BioHPP, is a biocompatible, non allergic, rigid material with good mechanical properties, wear resistance, chemical stability, high polishing and low absorption properties. BioHPP frameworks can be manufactured either via CAD/CAM or via the conventional lost wax technique. The low modulus of elasticity, combined with the use of indirect composite resin as a veneering material, provide a distinct advantage over ceramics or metal ceramics on dampening the occlusal forces, reducing the risk of debonding. (J Esthet Restor Dent 28:201-207, 2016).

Modified PEEK resin-bonded fixed dental prosthesis as an interim restoration after implant placement.

A polyetheretherketone (PEEK) (BioHPP) framework veneered with composite resin was used as an alternative material for the fabrication of an interim 3-pontic resin-bonded fixed dental prosthesis (RBFDP) after implant placement. The low modulus of elasticity (4 GPa) of PEEK combined with the use of indirect light-polymerized resin as a veneering material used for a RBFDP provided an advantage over metal ceramics or ceramics in dampening the occlusal forces and reducing debonding rates. Further long-term clinical evidence is required before recommending the application as a substitute material.