Effect of additive manufacturing process and storage condition on the dimensional accuracy and stability of 3D-printed dental casts.

STATEMENT OF PROBLEM: Additively manufactured dental casts are gaining popularity as the digital workflow is adopted in dentistry. However, studies on their dimensional accuracy and stability under different storage conditions in the dental laboratory are lacking. PURPOSE: The purpose of this in vitro study was to compare the effects of different additive manufacturing processes and storage conditions on the dimensional accuracy and stability of 3D-printed dental casts. MATERIAL AND METHODS: A completely dentate maxillary typodont model was digitized 10 times with a dental laboratory laser scanner, and the standard tessellation language (STL) files were used to manufacture 3D-printed diagnostic casts with the digital light projection (DLP) 3D printer (Asiga MAX) and material jetting (MJ) 3D printer (ProJet 3510 DPPro). Twenty DLP-printed and 20 MJ-printed diagnostic casts were digitized within 24 hours of production. Subsequently, all 3D-printed diagnostic casts were stored for 3 months, either in closed laboratory boxes or in dental laboratory open-face plastic containers with direct exposure to full-spectrum balanced light. After 3-month storage, all 40 3D-printed casts were digitized again. All scanned files were compared with the corresponding STL files in a surface-matching software program. The dimensional accuracy was measured and compared by the root mean square (RMS, in µm). Repeated measures analysis of variance (ANOVA) was used to compare RMS values among the variables, and the Tukey honestly significant difference (HSD) test was used for post hoc multiple comparisons (α=.05). RESULTS: The casts produced from the DLP 3D printer had a significantly higher mean ±standard deviation RMS of 153.7 ±25.4 µm than those produced with the MJ 3D printer with RMS of 134.1 ±16.0 µm (P<.001). The storage condition (box storage versus light exposure) did not affect the accuracy of the DLP-printed casts (P=.615) or the MJ-printed casts (P=.999). When comparing all 3D-printed casts after 3-month storage, group DLP-3M-Lit had the highest mean ±standard deviation RMS of 163.0 ±26.5 µm, and group MJ-3M-Box had the lowest RMS of 132.8 ±16.9 µm. The DLP-printed casts stored under light exposure were significantly less accurate than the MJ-printed casts stored in the box (P=.048). DLP-printed casts stored under light exposure showed significant surface color change under visual inspection. CONCLUSIONS: The MJ 3D printer produced more accurate 3D-printed dental casts than the DLP 3D printer. After 3-month storage, the DLP-printed casts stored under light exposure were the least accurate, and the MJ-printed casts stored without light exposure were the most accurate. The surface color change of DLP-printed casts stored under light exposure after 3-month storage was evident.

Evaluation of esthetic parameters related to a single implant restoration by laypeople and dentists.

STATEMENT OF PROBLEM: Currently available assessment tools for evaluating the esthetic outcome of implant restorations consist of objective indices created for dentists. The investigation of esthetic parameters according to the patient's perspective is lacking. PURPOSE: The purpose of this observational study was to evaluate and compare the importance of different soft-tissue and restoration-related esthetic parameters for patients and clinicians. MATERIAL AND METHODS: A photoediting software program (Photoshop CC; Adobe Corp) was used to produce 10 photographs with modified smiles from the original photograph by altering 1 parameter of the pink esthetic score and white esthetic score (PES/WES) at a time. A total of 120 participants were recruited in the study, including 40 laypeople, 40 prosthodontists, and 40 periodontists. A total of 440 visual analog scale (VAS) values were obtained for each group to record participants' subjective esthetic assessments of all photographs (10 modified and 1 original photograph). Repeated-measures ANOVA and post hoc mean comparison (t grouping) were used to identify whether the individual alteration on the PES and WES indices was significant for each group. RESULTS: For the laypeople, color (hue and value) appeared to be the most important parameter. After color, the order of importance was as follows: root convexity along with soft-tissue color and texture, level of facial mucosa, distal papilla, mesial papilla, translucency or characterization, surface texture, and tooth form. For the periodontists, color (hue and value) was also the most important parameter, but it was not separable from a cluster of other parameters: level of facial mucosa, root convexity along with soft-tissue color and texture, mesial papilla, and distal papilla. For the prosthodontists, color (hue and value) and level of facial mucosa were the most important parameters affecting esthetic assessment, followed by root convexity along with soft-tissue color and texture, mesial papilla, and distal papilla. CONCLUSIONS: All groups graded color (hue and value) as the most important parameter affecting the esthetic outcome and the original unaltered photograph as the most esthetically pleasing image. All participants (laypeople and dental specialists) appeared to be able to perceive the same 5 parameters including color (hue and value), level of facial mucosa, mesial papilla, distal papilla, and root convexity along with soft-tissue color and texture that are negatively affecting esthetic outcomes. Except for color (hue and value), restoration-related esthetic parameters had a lesser effect on the overall esthetic assessments for all groups.

Importance of Prototype Use for Implant-Supported Complete Fixed Dental Prosthesis (ICFDP).

Restorative material options for implant-supported complete fixed dental prostheses (ICFDP) have progressed from traditional metal-acrylic or metal-ceramic combinations to today's monolithic zirconia or high-performance polymer designs. To avoid potential errors that may be introduced into the restorative process in the interim phase and to provide a more predictable clinical outcome of the definitive ICFDP, a clinical protocol utilizing a prototype prosthesis is described in this case report.

Fabrication of an interim complete removable dental prosthesis with an in-office digital light processing three-dimensional printer: A proof-of-concept technique.

This report describes a proof of concept for fabricating an interim complete removable dental prosthesis with a digital light processing 3-dimensional (3D) printer. Although an in-office 3D printer can reduce the overall production cost for an interim complete removable dental prosthesis, the process has not been validated with clinical studies. This report provided a preliminary proof of concept in developing a digital workflow for the in-office additively manufactured interim complete removable dental prosthesis.

Accuracy and reproducibility of virtual edentulous casts created by laboratory impression scan protocols.

STATEMENT OF PROBLEM: Although computer-aided design and computer-aided manufacturing (CAD-CAM) complete removable dental prostheses (CRDPs) have gained popularity, conventional impressions are still common for CAD-CAM CRDP treatment. These need to be digitized and converted into virtual edentulous casts with a laboratory impression scan protocol during prosthesis fabrication. How this can best be accomplished is unclear. PURPOSE: The purpose of this in vitro study was to compare the accuracy and reproducibility of virtual edentulous casts created by a dental laboratory laser scanner and a cone beam computed tomography (CBCT) scanner with a digitized master cast. MATERIAL AND METHODS: A master cast was digitized as the virtual reference cast. Ten polyvinyl siloxane impressions were made on the master cast and scanned with the dental laboratory laser scanner and CBCT scanner. The impressions were sprayed with antiglare spray and rescanned. Four groups of virtual study casts (N=40) were created from the impression scans. All virtual study casts and the reference cast were registered with surface-matching software, and the root mean square (RMS) values (representation of overall accuracy) and percentage of measurement data points within 1 standard deviation (SD) of mean RMS values (%, representation of overall reproducibility) among the 4 study groups were measured. Additionally, 95 numeric distance differences (representation of accuracy at each region) were measured in 5 distinct regions: the apex of the denture border, 6 mm from denture border, crest of the ridge, palate, and posterior palatal seal. The repeated-measures ANOVA and post hoc test (t grouping) were used to determine statistical differences (α=.05). RESULTS: The laboratory scanner group had a significantly larger RMS value (4.0 ±0.3 µm, P<.001) and smaller percentage of measurement data points within 1 SD of mean RMS value (77.5 ±1.0%, P<.001). The RMS values between the CBCT scanner (1.2 ±0.3 µm) and CBCT scanner-spray (1.1 ±0.2 µm) groups were not significantly different (P=.968), and the percentage of measurement data points within 1 SD of mean RMS values (90.1 ±1.1% versus 89.5 ±0.8%) were also not significantly different (P=.662). The numeric distance differences across 5 regions were affected by the scanning protocols (P<.001). The laboratory scanner and laboratory scanner-spray groups had significantly higher numeric distance differences at the apex of the denture border and crest of the ridge regions (P<.001). CONCLUSIONS: The CBCT scanner created more accurate and reproducible virtual edentulous casts, and the antiglare spray only significantly improved the accuracy and reproducibility of virtual edentulous casts created by the dental laboratory laser scanner. The accuracy of the virtual edentulous casts was different across 5 regions and was affected by the scanning protocols.

Polyetherketoneketone (PEKK), a framework material for complete fixed and removable dental prostheses: A clinical report.

This clinical report demonstrates the use of polyetherketoneketone (PEKK) as a framework material with individually luted heat-pressed lithium disilicate glass-ceramic crowns for an implant-supported complete fixed dental prosthesis (ICFDP) and a conventional complete removable dental prosthesis (CRDP). This prosthesis design provides a non-computer-aided design and computer-aided manufacturing (CAD-CAM) option for the fabrication of ICFDPs and CRDPs with individualized ceramic crowns for optimal esthetics. The performance of PEKK as a framework material needs to be assessed in clinical trials.

Integrating a facial scan, virtual smile design, and 3D virtual patient for treatment with CAD-CAM ceramic veneers: A clinical report.

This clinical report describes a digital workflow using the virtual smile design approach augmented with a static 3-dimensional (3D) virtual patient with photorealistic appearance to restore maxillary central incisors by using computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic lithium disilicate ceramic veneers.

Integrating hinge axis approximation and the virtual facial simulation of prosthetic outcomes for treatment with CAD-CAM immediate dentures: A clinical report of a patient with microstomia.

This clinical report describes a digital workflow using extraoral digital photographs and volumetric datasets from cone beam computed tomography (CBCT) imaging to create a 3-dimensional (3D), virtual patient with photorealistic appearance. In a patient with microstomia, hinge axis approximation, diagnostic casts simulating postextraction alveolar ridge profile, and facial simulation of prosthetic treatment outcome were completed in a 3D, virtual environment. The approach facilitated the diagnosis, communication, and patient acceptance of the treatment of maxillary and mandibular computer-aided design and computer-aided manufacturing (CAD-CAM) of immediate dentures at increased occlusal vertical dimension.

Use of CBCT Imaging, Open-Source Modeling Software, and Desktop Stereolithography 3D Printing to Duplicate a Removable Dental Prosthesis-A Proof of Concept.

This article describes an alternative computer-aided design/computer-aided manufacturing (CAD/CAM) technique that uses cone-beam computed tomography (CBCT) imaging, open-source 3-dimensional (3D) modeling software, and a desktop stereolithography (SLA) 3D printer to duplicate an existing complete removable dental prosthesis (CRDP). Intended to offer a proof of concept, this proposed technique provides dental clinicians who have access to a CBCT imaging unit and a desktop SLA 3D printer an option to manufacture a duplicated prosthesis in-office. The 3D model of the CRDP can be preserved indefinitely, and the CAD/CAM process makes it possible to manufacture the CRDP multiple times with ease, when necessary. Different materials can be selected for the SLA 3D printer, and the duplicated prosthesis could be used for a variety of clinical and laboratory indications, such as a custom tray, a trial prosthesis, a reference record for a definitive prosthesis in laboratory procedures, or a radiographic template. Clinicians should select and use 3D software, printers, and materials with proper biocompatibility and classification and clearance from respective medical device regulatory bodies (such as US Food & Drug Administration) in different intended applications.

Satisfaction of Dental Students, Faculty, and Patients with Tooth Shade-Matching Using a Spectrophotometer.

The aims of this study were to evaluate dental students' clinical shade-matching outcomes (from subjective use of shade guide) with an objective electronic shade-matching tool (spectrophotometer); to assess patients', students', and supervising faculty members' satisfaction with the clinical shade-matching outcomes; and to assess clinicians' support for use of the spectrophotometer to improve esthetic outcomes. A total of 103 volunteer groups, each consisting of patient, dental student, and supervising faculty member at the University of Louisville, were recruited to participate in the study in 2015. Using the spectrophotometer, clinical shade-matching outcome (ΔEclinical) and laboratory shade-matching outcome (ΔElaboratory) were calculated. Two five-point survey items were used to assess the groups' satisfaction with the clinical shade-matching outcome and support for an objective electronic shade-matching tool in the student clinic. The results showed that both ΔEclinical (6.5±2.4) and ΔElaboratory (4.3±2.0) were outside the clinical acceptability threshold ΔE values of 2.7, when visual shade-matching method (subjective usage of shade guide) was used to fabricate definitive restorations. Characteristics of the patients, dental students, supervising faculty members, and restorations had minimal to no effect on the ΔEclinical The patients, dental students, and supervising faculty members generally had positive opinions about the clinical shade-matching outcome, despite the increased ΔEclinical observed. Overall, clinical shade-matching outcomes in this school need further improvement, but the patients' positive opinions may indicate the need to revisit the acceptability threshold ΔE value of 2.7 in the academic setting.

Managing complications resulting from limited prosthetic space with a monolithic, multichromatic CAD-CAM implant-retained overdenture: A dental technique.

This article proposes a 2-visit clinical protocol to manage prosthodontic complications resulting from limited prosthetic space, using a monolithic, multichromatic computer-aided design and computer-aided manufacturing (CAD-CAM) acrylic resin implant overdenture. The advantages and limitations of using this approach are outlined and discussed.

Creation of a 3-dimensional virtual dental patient for computer-guided surgery and CAD-CAM interim complete removable and fixed dental prostheses: A clinical report.

This clinical report proposes a digital workflow using 2-dimensional (2D) digital photographs, a 3D extraoral facial scan, and cone beam computed tomography (CBCT) volumetric data to create a 3D virtual patient with craniofacial hard tissue, remaining dentition (including surrounding intraoral soft tissue), and the realistic appearance of facial soft tissue at an exaggerated smile under static conditions. The 3D virtual patient was used to assist the virtual diagnostic tooth arrangement process, providing patient with a pleasing preoperative virtual smile design that harmonized with facial features. The 3D virtual patient was also used to gain patient's pretreatment approval (as a communication tool), design a prosthetically driven surgical plan for computer-guided implant surgery, and fabricate the computer-aided design and computer-aided manufacturing (CAD-CAM) interim prostheses.

Cone beam computed tomography imaging as a primary diagnostic tool for computer-guided surgery and CAD-CAM interim removable and fixed dental prostheses.

This article describes a digital workflow using cone beam computed tomography imaging as the primary diagnostic tool in the virtual planning of the computer-guided surgery and fabrication of a maxillary interim complete removable dental prosthesis and mandibular interim implant-supported complete fixed dental prosthesis with computer-aided design and computer-aided manufacturing technology. Diagnostic impressions (conventional or digital) and casts are unnecessary in this proposed digital workflow, providing clinicians with an alternative treatment in the indicated clinical scenario.

Digital approach to planning computer-guided surgery and immediate provisionalization in a partially edentulous patient.

This report describes a digital approach for computer-guided surgery and immediate provisionalization in a partially edentulous patient. With diagnostic data obtained from cone-beam computed tomography and intraoral digital diagnostic scans, a digital pathway of virtual diagnostic waxing, a virtual prosthetically driven surgical plan, a computer-aided design and computer-aided manufacturing (CAD/CAM) surgical template, and implant-supported screw-retained interim restorations were realized with various open-architecture CAD/CAM systems. The optional CAD/CAM diagnostic casts with planned implant placement were also additively manufactured to facilitate preoperative inspection of the surgical template and customization of the CAD/CAM-fabricated interim restorations.

A cost-effective treatment for severe generalized erosion and loss of vertical dimension of occlusion: laboratory-fabricated composite resin restorations.

This case report describes preventive and restorative treatment planning for a 56-year-old female patient with severe, chronic, poorly controlled gastroesophageal reflux disease and resulting loss of vertical dimension of occlusion. First, the demineralization process was controlled through collaboration with the patient's physician, and measures were taken to restore adequate stimulated salivary flow. Then, for financial reasons, indirect laboratory-fabricated composite resin restorations were adhesively bonded to replace lost tooth structure and reestablish the patient's collapsed vertical dimension. Indirect-laboratory fabricated restorations can be a cost-effective alternative to direct composite resin or all-ceramic restorations for the treatment of chronic severe erosion, but there are no long-term clinical reports in the current literature to support or contraindicate the use of indirect composites for this type of clinical application. Therefore, careful, long-term follow-up evaluations are planned for this patient.

Comparison of Virtual Dental Implant Planning Using the Full Cross-Sectional and Transaxial Capabilities of Cone Beam Computed Tomography vs Reformatted Panoramic Imaging and 3D Modeling.

PURPOSE: To compare the choice and placement of virtual dental implants in the posterior edentulous bounded regions using the full cross-sectional and transaxial capabilities of cone beam computed tomography (CBCT) vs reformatted panoramic images and three-dimensional (3D) virtual models. MATERIALS AND METHODS: Fifty-two cases with posterior bounded edentulous regions (61 dental implant sites) were identified from a retrospective audit of 4,014 radiographic volumes. Two image sets were created from selected CBCT data: (1) a combination of reformatted panoramic imaging and a 3D model (PIref/3D), and (2) the full 3D power in CBCT image volume analyses (XS). One virtual implant was placed by consensus of three prosthodontists in each image set: PIref/3D and XS. The choice of implant length and the perceived need for ridge augmentation were recorded for implant placement in both test situations. All the virtual implant placements from both PIref/3D and XS image sets were inspected retrospectively using virtual 3D models, and the number of exposed threads on both the buccal and lingual/palatal aspects of the virtual dental implant was evaluated. The chi-square and paired t tests were used with the level of significance set at α = .05. RESULTS: Shorter implants were chosen more often using XS than PIref/3D (P = .001). Fewer threads were exposed when placed with XS than with PIref/3D (P = .001). The use of XS reduced the perceived need for ridge augmentation compared with PIref/3D (P = .001). CONCLUSION: The use of the full 3D power of CBCT (including cross-sectional images in all three orthagonal planes and transaxially) provides supplemental information that significantly changes the choice of virtual implant length and vertical position of the implant, and reduces the frequency of perceived need for ridge augmentation before implant placement.

Maxillary and mandibular immediately loaded implant-supported interim complete fixed dental prostheses on immediately placed dental implants with a digital approach: A clinical report.

This clinical report describes the treatment of maxillary and mandibular immediate implant placement and immediately loaded implant-supported interim complete fixed dental prostheses with a contemporary digital approach. The virtual diagnostic tooth arrangement eliminated the need for a customized radiographic template, and the diagnostic data collection required for computer-guided surgery (digital diagnostic impressions, digital photographs, and a cone beam-computed tomography [CBCT] scan) was completed in a single visit with improved workflow efficiency. Computer-aided design and computer-aided manufacturing (CAD/CAM)-fabricated surgical templates and interim prosthesis templates were made in a dental laboratory to facilitate computer-guided surgery and the immediate loading process.

Use of intraoral digital scanning for a CAD/CAM-fabricated milled bar and superstructure framework for an implant-supported, removable complete dental prosthesis.

This report describes a clinical technique for fabricating a maxillary implant-supported, removable complete dental prosthesis by using an intraoral digital scanner to register implant positions and soft tissue morphology. The presented technique uses computer-aided design/computer-aided manufacturing (CAD/CAM) technology with a subtractive manufacturing process to fabricate a milled bar (infrastructure framework) and an additive process to fabricate a friction fit, superstructure framework. This digital restorative pathway may decrease patient discomfort and reduce the labor associated with fabricating implant-supported, removable complete dental prostheses.