Clinical evaluation of implant overdentures fabricated using 3D-printing technology versus conventional fabrication techniques: a randomized clinical trial.

AIM: To evaluate the oral health-related quality of life (OHRQoL) of patients rehabilitated with conventional or 3D-printed implant overdentures. MATERIALS AND METHODS: A randomized clinical trial (RCT) was designed. Twenty-eight completely edentulous participants were randomly allocated into two equal groups. All participants received two implants with ball attachments. Participants in the control group were rehabilitated with conventionally manufactured polymethyl methacrylate (PMMA) maxillary complete dentures (CDs) and mandibular implant overdentures, while those in the intervention group received digital light processing (DLP)-printed photopolymerizable PMMA maxillary CDs (NextDent) and mandibular implant overdentures. Follow-up appointments were scheduled at 3, 6, and 12 months where Oral Health Impact Profile 19 (OHIPEDENT19) data were used to assess the OHRQoL of the participants. Denture retention was measured using a digital force gauge device. RESULTS: The OHRQoL values were significantly higher (less improvement) in the conventional overdenture group at 6 months (P = 0.02) and 12 months (P = 0.04). A statistically significant difference was found between the mean retention values of the conventional and 3D-printed overdenture groups. For all the follow-up periods, the mean retention values were higher for the 3D-printed overdenture group (P = 0.001). CONCLUSION: 3D-printed overdentures may represent an alternative to conventionally fabricated ones. This study represents a stepping stone and proof of concept that support the potential future use of 3D-printed dentures.

3D printing in endodontics: report of three clinical cases with innovative approaches.

3D printing is a process whereby a given material is deposited in successive layers to create a 3D object. In dentistry, this technology involves three steps: digital data acquisition using a scanner and/or CBCT, data processing and design within a software application, and manufacturing through 3D printing. The aim of the present article is to discuss the clinical application of 3D printing in endodontics through the presentation of three specific and original endodontic clinical cases. Innovative approaches were utilized in these cases for the treatment of a calcified root canal, periapical surgery, and autotransplantation. The results of all three cases were promising regarding proper case selection and in the design process. 3D-printing technology may be helpful to reduce surgical time, operator bias, and the risk of procedural errors.

Digitally programmed (CAD) offset values for prototyped occlusal splints (CAM): assessment of appliance-fitting using surface-based superimposition and deviation analysis.

AIM: Limited data are available on the fitting properties of prototyped occlusal appliances. The aim of the present study was to assess the fitting of prototyped splints digitally designed with different offset values and generated with two different biocompatible resins. MATERIALS AND METHODS: Ten dental digital models were included, and occlusal splints were designed with different offset values (0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 mm). Each splint was 3D printed using two different biocompatible resins, and the gap between the splint and the teeth was recorded by placing impression material. A specific 3D technology was used to assess the gap volume between the splint and the teeth and to calculate the Euclidean distance between the surface points of two digital models, with and without the gap volume. RESULTS: The splints with a 0.20-mm offset value showed smaller gap volume and deviation analysis values compared with those with offset values of 0.15 and 0.25 mm (P < 0.05). These results were consistent with both types of biocompatible resins used. For each offset value tested, the gap volume and deviation value analysis did not significantly differ between the splints printed with the two different resins. CONCLUSION: According to the present findings, the 0.20-mm offset value would be the best choice when digitally designing occlusal appliances.

Additive manufacturing technologies for processing zirconia in dental applications.

OBJECTIVE: The objective of this narrative review was to summarize the current status and future perspectives of additive manufacturing (AM) technologies with a particular emphasis on manufacturing zirconia-based materials. AM technologies include vat photopolymerization, material jetting, material extrusion, selective laser sintering (SLS), and selective laser melting (SLM) technologies based on either powder bed fusion (PBF) technologies or direct energy deposition, or sheet lamination based on binder jetting technologies. MATERIALS AND METHODS: A comprehensive literature review was performed, specifically evaluating AM technologies assigned for processing zirconia. An electronic database search was performed using keywords and MeSH terms. The search was confined to full-text articles written in English and published in peer-reviewed journals between 1999 and 2018. RESULTS: A total of 62 articles were included in this review, of which 56 described the AM processes and 6 reported on AM applications in the field of dentistry. A broad diversity of literature exists regarding AM technologies for ceramic materials, which complicates the establishment of a classification system for the current AM technologies for zirconia. The variations in the composition of zirconia slurries or mixtures across different technologies often made it difficult to identify the proper nature of such information. Mechanical properties of printed zirconia materials utilizing different technologies were investigated through a wide range of tests. Overall, the review indicates that manufacturing zirconia using AM technologies could be achieved without issues, but mechanical properties appear to be poor compared with conventional manufacturing procedures. CONCLUSIONS: The results of this review indicate the necessity for further potential improvement in AM technologies for manufacturing zirconia reconstructions along with advances in material composition before zirconia could be considered as a material for standard care.

Guided endodontics: a comparative in vitro study on the accuracy and effort of two different planning workflows.

AIM: To compare the accuracy and effort of digital workflow for guided endodontic access (GEA) procedures using two different software applications in 3D-printed teeth modeled to simulate pulp canal obliteration (PCO) in vitro. MATERIALS AND METHODS: 32 3D-printed incisors with simulated PCO were fabricated and mounted, four each on maxillary and mandibular study arches. Cone beam computed tomography (CBCT) and 3D surface scans were matched and used to virtually plan and prepare GEA by one operator using two different methods: 1) CoDiagnostiX (CDX; Dental Wings) with 3D-printed templates, and 2) Sicat Endo (SE; Sicat) with subtractive CAD/CAM-manufactured templates. Postoperative CBCT and virtual planning data were superimposed for analysis. Accuracy was assessed by measuring the discrepancies between planned and prepared cavities at the tip of the bur (three spatial dimensions, 3D vector, angle). Virtual planning effort was defined as the time and number of computer clicks. A 95% confidence interval (CI) was computed for each sample. RESULTS: SE successfully located root canals for GEA in 16/16 cases (100%) and CDX in 15/16 cases (94%). SE resulted in less mean deviation at the tip of the bur with regard to distance in the labial-oral direction (0.12 mm), 3D vector (0.35 mm), and angle (0.68 degrees) compared with CDX (0.54 mm, 0.74 mm, 1.57 degrees, respectively; P < 0.001). CDX required less mean planning time and effort for each four-tooth arch (10 min 50 s, 107 clicks) than SE (20 min 28 s, 341 clicks; P < 0.05). CONCLUSIONS: Both methods enabled rapid drill path planning, a predictable GEA procedure, and the reliable location of root canals in teeth with PCO without perforation.

CAD/CAM-fabricated removable partial dentures: a case report.

AIM: The objective of this case study is to present the manufacturing process and delivery of a removable partial denture (RPD) using computer-aided design/computer-aided manufacturing (CAD/CAM) technology. MATERIALS AND METHODS: A 46-year-old female patient presented at the Federal University of Rio Grande do Norte complaining of the lack of retention in her mandibular RPD. After the design and preparation of the abutment teeth, further appointments were made. In the first appointment, intraoral scanning (IOS) with a Trios scanner was performed, followed by virtual planning of the framework. The RPD was then printed, invested, cast by induction, and polished. In the second appointment, the RPD was delivered. CONCLUSION: The technique proved to be efficient in terms of clinical time and sufficient for patient comfort and satisfaction.

Metal additive manufacturing technologies: literature review of current status and prosthodontic applications.

OBJECTIVES: To review the current metal-based additive manufacturing (AM) technologies, namely powder bed fusion (PBF) technologies, and their current prosthodontic applications. The PBF technologies reviewed are selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM). MATERIALS AND METHODS: The literature on metal AM technologies was considered, and the AM procedures and their current applications in prosthodontics were collated and described. Published articles about AM metal in dental care were searched (MEDLINE, EMBASE, EBSCO, and Web of Science). All studies related to the description, analysis, and evaluation of prosthodontic applications using metal AM technologies. RESULTS AND CONCLUSIONS: AM technologies are reliable for many applications in dentistry, including metal frameworks for removable partial dentures (RPDs), overdentures, tooth- and implant-supported fixed dental prostheses (FDPs), and metal frameworks for splinting implant impression abutments. However, further studies are needed in future to evaluate the accuracy, reproducibility, and clinical outcome throughout function of AM technologies.

Accuracy assessment of 3D-printed tooth replicas.

AIM: The production of individual tooth replicas has two applications in dental practice: tooth autotransplantations and dental root analogue implants. These applications require a particularly high degree of precision. The purpose of this study was to establish and evaluate a method for fabricating individual 3D-printed tooth replicas. MATERIALS AND METHODS: 10 patients requiring extraction of a wisdom tooth and a preoperative cone beam computed tomography (CBCT) scan were included; exclusion criteria were intraoperative fragmentation or fracture of the tooth. 3D Slicer 4.6.2 was used for tooth segmentation and model generation based on CBCT data. The tooth replicas were manufactured by selective laser melting (SLM). The extracted teeth and 3D-printed replicas were scanned and tested for surface deviations in CloudCompare 2.8.1. RESULTS: The mean absolute surface deviation between the 3D-printed teeth and the corresponding extracted teeth ranged from 0.13 to 0.25 mm, with standard deviations of 0.10 to 0.21 mm; 95% of the measured surface points deviated less than 0.474 mm; the surface area was reduced by -6.0% and the volume by -3.4%. The root mean square was 0.238 mm and the mean maximum absolute surface deviation was 0.927 mm. The SLM technique showed a high precision with a mean absolute deviation of 0.045 mm and a standard deviation of 0.04 mm. CONCLUSION: 3D-printed tooth replicas with a very high accuracy could be produced based on CBCT data. The described method is suitable for manufacturing tooth replicas for use in tooth autotransplantations or for fabricating root analogue implants.

Investment casting with FFF (fused filament fabrication)-printed appliances: the intermediate step.

OBJECTIVE: Some modifications of orthodontic appliances such as the rapid maxillary expansion (RME) device with a Hyrax screw or Herbst are fabricated using traditional investment casting (lost-wax casting). This is precise but very labor-intensive. New technologies enable us today to use direct selective laser sintering (SLS) to produce freeform metallic structures. These machines are very expensive and only available in specialized laboratories. The aim of this investigation was to combine fused filament fabrication (FFF) 3D printing with wax-based filaments to produce orthodontic appliances via investment casting. METHOD AND MATERIALS: For demonstration purposes, a lingual arch, a palatal arch, and an RME appliance were digitally designed based on an intraoral scan. The *.stl files were sliced and printed with a dual-nozzle FFF printer. The object was printed with a wax-based filament especially suited for investment casting, and support structures were printed with water-soluble polyvinyl-alcohol (PVA) filament. The printed objects were cast in metal and finished. RESULTS: All appliances were successfully cast and polished. They were provisionally placed intraorally. The fit was clinically very good and comparable to traditionally crafted appliances. The printing and handling of the parts made of these special filaments is challenging. CONCLUSION: With this experiment, the successful production of investment casting using FFF printing was shown for the first time.

3D Evaluation of Accuracy of Tooth Preparation for Laminate Veneers Assisted by Rigid Constraint Guides Printed by Selective Laser Melting.

OBJECTIVE: To design and fabricate 3D-printed rigid constraint guides for the tooth preparation for laminate veneers and to evaluate the accuracy of guide-assisted preparation. METHODS: Twenty maxillary right central incisor resin artificial teeth were randomly divided into two equal groups and prepared for laminate veneers. Tooth preparations were performed, assisted by guides in the test group and by depth gauge burs in the control group, and both were finished by freehand operation. The typodonts were 3D scanned before preparation, after initial preparation and after final preparation. The tooth preparation depths at each step, including initial preparation depth, final preparation depth and loss of tooth tissue during polishing, were measured by 3D deviation analysis. Statistical analyses were conducted to investigate differences. RESULTS: The initial preparation depth was 0.488 mm (median, quartile 0.013 mm) in the test group and 0.521 mm (median, quartile 0.013 mm) in the control group. A statistically significant difference was found between them (P < 0.05). The final preparation depth in the test group (0.547 ± 0.029 mm) was significantly less than that in the control group (0.599 ± 0.051 mm) (P < 0.05), and closer to the predesigned value (0.5 mm). There was no statistically significant difference in the loss of tooth tissue during polishing between the test group (0.072 ± 0.023 mm) and the control group (0.089 ± 0.038 mm) (P > 0.05). CONCLUSION: In maxillary central incisors, the tooth preparation for laminate veneers could be conducted using 3D-printed rigid constraint guides, the accuracy of which is better than that of depth gauge burs.