Zirconia-veneered polyetherketoneketone frameworks of implant-supported complete arch fixed dental prostheses: A report on 5 patients.

Metal frameworks have been used for implant-supported complete arch fixed dental prostheses (ISCFDPs) for maxillary or mandibular edentulous arches with a crown height space of more than 15 mm. However, technical difficulties in the casting, weight, and lack of passivity of the metal have led dentists and dental laboratory technicians to choose materials with different biomechanical properties, including polyetheretherketone (PEEK) and polyetherketoneketone (PEKK). This clinical report describes the design of ISCFDPs using PEKK frameworks, the number of cantilevers, the condition of the opposing dentition, and the incidence of complications, including zirconia crown or PEKK framework fracture, as well as the clinical outcomes of 5 patients observed prospectively over 8 to 65 months. No mechanical complications of PEKK-made ISCFDPs opposing removable prostheses occurred, regardless of the presence of cantilevers. The ISCFDPs that opposed natural dentition or a combination of the natural dentition and fixed prostheses showed different clinical outcomes depending on the length of cantilevers and the number and location of pontics.

Accuracy evaluation of 3D printed interim prosthesis fabrication using a CBCT scanning based digital model.

OBJECTIVES: This study aimed to evaluate the marginal and internal gaps in 3D-printed interim crowns made from digital models of cone-beam computed tomography (CBCT) conversion data. MATERIALS AND METHODS: Sixteen polyvinylsiloxane impressions were taken from patients for single crown restorations and were scanned using CBCT. The scanning data were converted to positive Standard Triangulation Language (STL) files using custom-developed software. The fabricated stone models were scanned with an intraoral optical scanner (IOS) to compare the surface accuracy with the STL data obtained by CBCT. The converted STL files were utilized to fabricate interim crowns with a photopolymer using a digital light-processing 3D printer. The replica method was used to analyze the accuracy. The marginal and internal gaps in the replica specimen of each interim crown were measured with a digital microscope. The Friedman test and Mann-Whitney U test (Wilcoxon-signed rank test) were conducted to compare the measurements of the marginal and internal gaps with a 95% level of confidence. RESULTS: The root-mean-square values of the CBCT and IOS ranged from 41.00 to 126.60 µm, and the mean was 60.12 µm. The mean values of the marginal, internal, and total gaps were 132.96 (±139.23) µm, 137.86 (±103.09) µm, and 135.68 (±120.30) µm, respectively. There were no statistically significant differences in the marginal or internal gaps between the mesiodistal and buccolingual surfaces, but the marginal area (132.96 µm) and occlusal area (255.88 µm) had significant mean differences. CONCLUSION: The marginal gap of the fabricated interim crowns based on CBCT STL data was within the acceptable range of clinical success. Through ongoing developments of high-resolution CBCT and the digital model conversion technique, CBCT might be an alternative method to acquire digital models for interim crown fabrication.

Accuracy of Customized Prefabricated Screw-Type Immediate Provisional Restorations after Single-Implant Placement.

Limited evidence is available comparing the differences between pre-operative and post-operative 3D implant positions from the viewpoint of prosthetics. We aimed to investigate the differences between preplanned positions of virtual provisional restorations and their actual positions following fully guided single-implant placement. Ten maxillary typodonts with missing right central incisors were imaged using cone-beam computed tomography, and digital impressions were obtained using an intraoral scanner. These data were imported into implant-planning software, following which the provisional restorations were designed. After data superimposition, an appropriate implant position was determined, and a computer-assisted implant surgical guide was designed for each typodont. Orders generated from the implant-planning software were imported into relevant computer-aided design software to design the custom abutments. The abutments, provisional restorations, and surgical guides were fabricated, and each restoration was cemented to the corresponding abutments, generating a screw-type immediate provisional restoration. The implants were placed using the surgical guides, and the screw-type provisional restorations were engaged to the implants. The typodonts were then rescanned using the intraoral scanner. The restorations designed at the treatment planning stage were compared with those in the post-operative scan using metrology software. The angular deviation around the central axis of the implant was measured, and the differences in the crown position were converted to root mean square (RMS) values. The post-operative provisional restorations exhibited an absolute angular deviation of 6.94 ± 5.78° and an RMS value of 85.8 ± 20.2 µm when compared with their positions in the pre-operative stage. Within the limitations of the present in vitro study, the results highlight the potential application of customized prefabricated immediate provisional restorations after single-implant placement.

Load-Bearing Capacity of Posterior CAD/CAM Implant-Supported Fixed Partial Dentures Fabricated with Different Esthetic Materials.

PURPOSE: To compare the load-bearing capacity after long-term use (5-year simulation) of posterior three-unit implant-supported fixed partial dentures (FPDs) fabricated with different esthetic materials. MATERIALS AND METHODS: A total of 20 specimens fabricated from one design file using CAD/CAM were divided into four groups: polyetherketoneketone (PEKK) veneered with composite resin (CR); PEKK veneered with lithium disilicate (LD); zirconia veneered with fluorapatite (FA); and monolithic zirconia. Samples were placed into a chewing simulator with simultaneous thermocycling. The fracture load after aging was measured using the universal testing machine with load on the central fossa of the pontic. RESULTS: FPDs fabricated with PEKK + LD had significantly higher fracture load (1,526.56 [SD 95.54] N) compared to PEKK + CR (1,069.54 [SD 67.94] N) (P < .05). FPDs fabricated with zirconia materials had significantly higher fracture load compared to PEKK materials (P < .05). There was no significant difference between monolithic zirconia and zirconia + FA (P > .05). CONCLUSION: FPDs fabricated with PEKK + LD were superior to PEKK + CR. These materials can be promising alternatives for use as implant-supported FPD materials in the high-stress-bearing posterior region. Zirconia + FA can be an alternative to monolithic zirconia in cases that require more esthetics.

Evaluation of the accuracy and precision of four intraoral scanners with 70% reduced inlay and four-unit bridge models of international standard.

The aims of this study were to evaluate the feasibility of 70% reduced inlay and 4-unit bridge models of International Standard (ISO 12836) assessing the accuracy of laboratory scanners to measure the accuracy of intraoral scanner. Four intraoral scanners (CS3500, Trios, Omnicam, and Bluecam) and one laboratory scanner (Ceramill MAP400) were used in this study. The height, depth, length, and angle of the models were measured from thirty scanned stereolithography (STL) images. There were no statistically significant mean deviations in distance accuracy and precision values of scanned images, except the angulation values of the inlay and 4-unit bridge models. The relative errors of inlay model and 4-unit bridge models quantifying the accuracy and precision of obtained mean deviations were less than 0.023 and 0.021, respectively. Thus, inlay and 4-unit bridge models suggested by this study is expected to be feasible tools for testing intraoral scanners.