Standard Tessellation Language File Research Articles

From CAD to G-code: Strategies to minimizing errors in 3D printing process

In this study, an analysis was conducted to quantify errors in the additive manufacturing process, with a focus on comparing data files. The primary objective was to minimise the reliance on physical testing of produced components by favouring verification within a virtual environment. The initial focus was on the conversion from the CAD (Computer-Aided Design) model to the STL (Standard Tessellation Language) file, where discrepancies between the two formats were identified. To achieve optimal meshing, it is crucial to configure conversion parameters effectively, avoiding both detail loss and the handling of excessively large files. Following this, a comparison between STL files and reconstructed G-code files was conducted, uncovering further approximations introduced by the most commonly used slicers. In conclusion, the analysis highlights that both the quality of the mesh and the slicing phase significantly impact the final component. Understanding these factors is essential for achieving an optimal print outcome.

Trueness of the apical and middle root portion segments of 3D-printed removable die and alveolar cast designs manufactured using stereolithographic 3D printing.

The present study evaluated the effects of the root portion design, segment (middle vs. apical), and part (die vs. cast) on the trueness of three-dimensional (3D)-printed removable die-cast complex. The trueness of apical and middle segments of the root portion of 45 3D-printed removable dies and casts with three different root portion designs (n = 15) was assessed using a metrology-grade computer program. The three removable dies and cast designs (root form [RF], conical [CON], and cylindric [CYL]) were created using professional computer-aided manufacturing computer programs (DentalCAD 3.1 Rijeka, and InLab CAD 22.0), and manufactured using stereolithographic 3D printer (Form3; FormLabs, Somerville, MA). Subsequently, the 3D-printed removable dies and casts were scanned by a single operator with an intraoral scanner (PrimeScan; Dentsply Sirona, Charlotte, NC), and their respective standard tessellation language files were aligned and compared to master reference files in a metrology-grade computer program (Geomagic Control X; 3D systems, Rock Hill, NC). The root mean square (RMS) values of the middle and apical segments for each removable die and cast were calculated and analyzed using a mixed model including a repeated measure 3-way analysis of variance (ANOVA) and post-hoc stepdown Bonferroni-corrected pairwise comparisons (α = 0.05). A statistically significant 3-way interaction between factors was detected, suggesting that the part (removable die or alveolar cast) and their design affected the RMS values of their apical and middle root portion segment. (p = 0.045). The post-hoc analysis identified significant differences between RMS values of the apical segments of the CON and CYL removable dies (p = 0.005). Significant differences were observed between the middle and apical segments of the CON (p < 0.001) and RF removable die designs (p = 0.004). No statistically significant differences were noticed between the RMS of the different alveolar cast designs (p > 0.05). Significant differences were detected between the apical and middle segments of the same alveolar cast design (p < 0.05). For the manufacturing trinomial and 3D printing strategy used in the present study, the interaction of the part, design, and segment affected the trueness of removable dies and alveolar casts. The trueness was higher on the middle segment on removable dies and alveolar casts in all designs used, except for CYL removable dies, where the trueness difference between segments was small. Higher trueness values may be achieved with designs with simple apical segment geometries.

Effect of preparation design and scan pattern on the accuracy of intraoral scans for complete arch laminate veneers under simulated intraoral variables

AbstractPurposeThe purpose of the study was to investigate the influence of different preparation designs and scan patterns on the accuracy of intraoral scans for complete‐arch maxillary laminate veneers.Materials and MethodsThree maxillary typodonts were used to obtain reference models with three different laminate veneer preparation designs: windows (W), beveled (B), and incisal overlap (IO). Reference scans were obtained with a desktop scanner. A total of 90 complete arch intraoral scans were made with an intraoral scanner (Medit i700) following three different scan patterns: straight motion (SM), zigzag motion (ZM), and combined motion (CM). Ten scans were made in each subgroup and exported as standard tessellation language (STL) files. Assessment of accuracy was conducted with a 3D software analysis program (Geomagic Control X). Each STL file was individually aligned with the reference scan using the best fit algorithm tool, and 3D differences were calculated using the root mean square (RMS) value. Two‐way analysis of variance (ANOVA) followed by post hoc comparison tests were applied to analyze precision and trueness data (α = 0.05).ResultsTwo‐way ANOVA and post hoc comparison tests revealed significant differences among different preparation designs and scan patterns (p &lt; 0.05). Regarding trueness, the IO when scanned with SM presented higher mean RMS than the other preparation designs (W and B) scanned with the same scanning pattern (p &lt; 0.05). Regarding precision, the groups of W and IO presented significantly higher mean RMS than the group of B when scanned with ZM (p &lt; 0.05).ConclusionsAccuracy of intraoral scans for complete‐arch laminate veneers was affected by different laminate veneer preparation designs and scan patterns.Clinical SignificanceModifying scan pattern according to preparation design helps to improve scan accuracy for complete‐arch laminate veneers.

The effect on the performance of a dynamic navigation system of superimposing a standard tessellation language (STL) file obtained with an intraoral scan on a cone beam computer tomograph (CBCT). An experimental in vitro study

ObjectivesTo compare the accuracy and operative time of implant placement using a dynamic computer assisted implant surgery (dCAIS) system based on a cone beam computer tomography (CBCT) image, with and without superimposing a standard tessellation language (STL) file of an intraoral scan of the patient. MethodsTen identical resin models simulating an upper maxilla with posterior edentulism were assigned to two groups. In the CBCT+STL group, a CBCT file and an intraoral STL file were superimposed and used for registration; in the CBCT group, registration was performed using CBCT images. Six implants were placed in each model using the Navident® dynamic navigation system. Anatomy registration was performed by tracing fiducial points on the CBCT or STL image, depending on the group. Preoperative and postoperative CBCT images were overlaid to assess implant placement accuracy. ResultsSixty implants were analyzed (30 implants in each group). 3D platform deviation was significantly lower (mean difference (MD): 0.17 mm; 95 % confidence interval (CI): 0.01 to 0.23; P = 0.039) in the CBCT+STL group (mean: 0.71 mm; standard deviation (SD): 0.29) than in the CBCT group (mean: 0.88 mm; SD: 0.39). The remaining accuracy outcome variables (angular deviation MD: -0.01; platform lateral deviation MD: 0.08 mm; apex global MD: 0.01 mm; apex depth MD: 0.33 mm) and surgery time (MD: 3.383 min.) were similar in both groups (p > 0.05). ConclusionsThe introduction of an intraoral scan (STL) seems to reduce deviations slightly in dental implant placement with dCAIS systems. However, the clinical repercussion of this improvement is questionable. Clinical significanceSuperimposing an intraoral scan on the CBCT image does not seem to increase the accuracy of dCAIS systems but can be useful when radiographic artifacts are present.

Dynamic monitoring and esthetic evaluation of dimensional changes in the peri-implant soft tissue contour after the immediate implant placement and provisionalization with the modified socket-shield technique in the esthetic zone

Objective: To accurately measure the dynamic changes of peri-implant soft tissue within one year after the immediate implant placement and provisionalization with the modified socket-shield technique (MSST) in the esthetic zone, and to provide a basis for evaluating the effect of the modified socket-shield technique on the maintenance of peri-implant soft tissue. Methods: A total of 22 patients (22 implants) were prospectively included 1 year after completion of immediate implant placement and provisionalization (IIPP) within MSST in the esthetic zone from January 2022 to January 2024 at the Department of Oral Implantology in the Stomatological Hospital of Chongqing Medical University. The intraoral optical models of patients were obtained by an intraoral scanner system preoperatively and at 3, 6, and 12 months postoperatively, respectively. The standard tessellation language files of intraoral optical models at multiple time points were imported to Geomagic Studio 2013 to be superimposed and aligned for analyzing the peri-implant soft tissue contour on the labial side of the implant site at multiple levels. The amount of gingival margin recession, gingival papilla change, and thickness change of the labial side of the soft tissues at each postoperative point in time were measured at each postoperative time point, as well as evaluating the esthetic effect by the pink esthetic score (PES). Results: The patients were (40±13) years old (21-75 years), including 9 males and 13 females. No adverse events occurred in all the implants during the 12-month follow-up period. The recession level of the gingival margin of the implant site (GL) was 0.08 (0.07) mm, the recession level of the mesial papilla (ML) was 0.19 (0.25) mm, and the recession level of the distal papilla (DL) was 0.19 (0.10) mm. The average collapse thickness of the soft tissue contour on the labial side of the implant (ΔD) was (0.39±0.09) mm, mainly occurring within 2 mm of the root of the gingival margin. The height of the alveolar bone was reduced by (0.17±0.08) mm. The thickness of the labial alveolar bone at 1, 3, and 5 mm root side of the implant shoulder was reduced by (0.13±0.08), (0.12±0.10) and 0.04 (0.17) mm, respectively. The postoperative pink esthetic score was 13.00 (2.25) points at 12 months, which suggested that all implant sites achieved ideal esthetic results. Conclusions: The labial soft tissue contour at implant sites shows minimal change following immediate implant placement and provisionalization using the modified socket-shield technique for 1 year in the esthetic zone.

Evaluation of the accuracy of automated tooth segmentation of intraoral scans using artificial intelligence-based software packages

The accuracy of tooth segmentation in intraoral scans is crucial for performing virtual setups and appliance fabrication. Hence, the objective of this study was to estimate and compare the accuracy of automated tooth segmentation generated by the artificial intelligence of dentOne software (DIORCO Co, Ltd, Yongin, South Korea) and Medit Ortho Simulation software (Medit Corp, Seoul, South Korea). Twelve maxillary and mandibular pretreatment dental scan sets comprising 286 teeth were collected for this investigation from the archives of the Department of Orthodontics, Faculty of Dentistry, Alexandria University. The scans were imported as standard tessellation language files into both dentOne and Medit Ortho Simulation software. Automatic segmentation was run on each software. The number of successfully segmented teeth vs failed segmentations was recorded to determine the success rate of automated segmentation of each program. Evaluation of success and/or failure was based on the software's identification of the teeth and the quality of the segmentation. The mesiodistal tooth width measurements after segmentation using both tested software programs were compared with those measured on the unsegmented scan using Meshmixer software (Autodesk, San Rafael, Calif). The unsegmented scans served as the reference standard. A total of 288 teeth were examined. Successful identification rates were 99% and 98.3% for Medit and dentOne, respectively. Success rates of segmenting the lingual surfaces of incisors were significantly higher in Medit than in dentOne (93.7% vs 66.7%, respectively; P<0.001). DentOne overestimated the mesiodistal width of canines (0.11 mm, P= 0.032), premolars (0.22 mm, P< 0.001), and molars (0.14 mm, P= 0.043) compared with the reference standard, whereas Medit overestimated the mesiodistal width of premolars only (0.13 mm, P= 0.006). Bland-Altman plots showed that mesiodistal tooth width agreement limits exceeded 0.2 mm between each software and the reference standard. Both artificial intelligence-segmentation software demonstrated acceptable accuracy in tooth segmentation. There is a need for improvement in segmenting incisor lingual tooth surfaces in dentOne. Both software programs tended to overestimate the mesiodistal widths of segmented teeth, particularly the premolars. Artificial intelligence-segmentation needs to be manually adjusted by the operator to ensure accuracy. However, this still does not solve the problem of proximal surface reconstruction by the software.

Accuracy of digital and conventional implant-level impression techniques for maxillary full-arch screw-retained prosthesis: A crossover randomized trial.

This study aimed to compare the accuracy of implant-level conventional and digital impressions for atrophied maxillary ridges. Twelve participants with atrophied edentulous maxillary ridges received six implants. Six months later and after soft tissue maturation around healing abutments, a control cast was constructed using the final passive restoration for each patient. Two types of implant-level impression techniques were carried out for each patient: (1) conventional (splinted open-tray) impression technique and (2) digital impression technique. For both techniques, scan bodies were labeled from the most distal implant on the left side (A, B, C, D, E, and F) and scanning was made. Accuracy of both techniques was measured using in vitro (two-dimensional and three-dimensional) and in vivo (clinical) methods. Two-dimensional methods include measurement of the difference in linear distances AB, AC AD, AE, and AF. Geomagic software was used to assess the three-dimensional deviation between the two impression techniques using the superimposition of standard tessellation language files. The incidence and percentage of nonpassive frameworks and framework misfits of final restorations for both types of impression techniques were assessed using the single screw test. For all distances, digital impressions recorded significantly higher deviation from control measurements than conventional impressions. The highest two-dimensional linear deviation was noted for AF distance and the lowest difference was noted for AB distance. For all scan bodies, digital impressions recorded significantly higher three-dimensional deviation than conventional impressions. The highest three-dimensional deviation was noted with scan bodies C and D. Digital impressions recorded a significantly higher incidence of nonpassive frameworks and framework misfits than conventional impressions. [Correction added on 11 June 2024, after first online publication: In the preceding sentence, "digital impressions" was changed to "conventional impressions" in this version.] CONCLUSION: Within the limitations of this study, it could be concluded that the conventional implant-level impression technique showed greater in vitro and in vivo accuracy than the digital impression technique when used for full-arch maxillary fixed restorations on inclined implants.

Comparing the accuracy of 3 different liquid crystal display printers for dental model printing

This study aimed to evaluate the accuracy in terms of trueness and precision of 3 different liquid crystal display (LCD) printers with different cost levels. Three LCD 3-dimensional (3D) printers were categorized into tiers 1-3 on the basis of cost level. The printers' accuracies were assessed in terms of trueness and precision. For this research, 10 standard tessellation language (STL) reference files were used. For trueness, each STL file was printed once with each 3D printer. For precision, 1 randomly chosen STL file was printed 10 times with each 3D printer. After that, a model scanner was used to scan the models, and STL comparisons were performed using reverse engineering software. For the measurements regarding trueness and precision, the Friedman test was used. There were significant differences among the 3 printers (P<0.05). The trueness and precision error were lower in models printed with a tier-1 printer than in the remaining 3D printers (P<0.05). The tier-2 and -3 printers presented very similar performance. LCD 3D printers can be accurately used in orthodontics for model printing depending on the specific orthodontic use. The cost of a printer is relevant to the results only for the higher expense of the 3D printer in this study.

Comparison between Conventional and Digital Impressions for Determining Axes and Distances of Three Implants in Straight and Curved Lines: An In Vitro Study.

Background: In this study, we aimed to compare the effects of conventional and digital impressions on several parameters (inter-implant distance, intra-implant distance, inter-implant axis, and intra-implant axis) of three implants in curved lines and straight lines by using a laboratory scanner (LBS) versus an intra-oral scanner (IOS). Methods: Two 3D models were fabricated using a printer, each model with three internal hex implants analogues at the positions of 15#,16#,17# (straight line) and 12#,13#,14# (curved line). Standard intra-oral scan bodies (ISBs) were used, and the two models were scanned using 7 Series dental wings (LBS, reference model), followed by ten scans with Primescan (digital method). Standard Tessellation Language (STL) files were created. Five polyether impressions were taken from each model (straight and curved), and gypsum type 4 models were poured; each model was scanned five times to create a total of 25 STL files for each group (conventional method). The comparison between all the STL files (conventional and digital) was made by superimposition of the STL files on the STL reference model laboratory file using a 3D analyzing software. A Kolmogorov-Smirnov test was performed, followed by Mann-Whitney tests and Wilcoxon signed-rank tests. (p < 0.05). Results: For the conventional method, the mean errors were significantly higher for the curved line model (12-14) compared to the straight line model (15-17) for most parameters (p < 0.05). For the digital method, the mean errors were significantly higher for the curved-line model (12-14) compared to the straight line model (15-17) in half of the parameters (p < 0.05). Within the curved line model (12-14) and the straight line model (15-17), the mean errors between the conventional method and the digital method were not significant for most variables. Conclusions: The difference between curved lines and straight lines has an impact on the mean error of the conventional method. Both methods are reliable for straight and curved lines in partially dentate situations.

The effect of ceramic bonder on shear bond strength at the metal-ceramic interface in casted and direct metal laser sintering cobalt-chromium alloy - An in vitro study.

Aim: (1) The aim of this study was to evaluate the effect of a ceramic bonder at the metal ceramic interface in sintered and casted cobalt–chromium (Co–Cr) alloy. (2) To compare the shear bond strength between the different manufacturing techniques: Casting and direct metal laser sintering (DMLS). Setting and Design: In vitro comparative study. Materials and Methods: For the casting group, 40 clear acrylic patterns with dimensions of 20 mm × 10 mm × 2.5 mm were designed in a software and casted with Co–Cr alloy. For DMLS samples, a standard tessellation language file with the abovementioned dimensions was created through a software to fabricate 40 samples. All the samples were equally distributed into the following four groups: Group A – Casted samples with the application of Cerambond (n = 20)Group B – Casted samples without application of Cerambond (n = 20)Group C – DMLS samples with application of Cerambond (n = 20)Group D – DMLS without application of Cerambond (n = 20). Ceramic buildup was done on all 80 samples, followed by firing up to a temperature of 920°C in a ceramic furnace. SBS was evaluated using a universal testing machine and failure modes were examined under the electron microscope. Statistical Analysis Used: ANOVA test and Tukey’s honestly significance difference post hoc test for multiple comparisons. Results: One-way analysis of variance test revealed that the shear load and bond strength values of all four groups were statistically different with P &lt; 0.001. Post hoc Tukey’s test showed statistically significant difference among the four groups. The mean shear strength of Group C was significantly greater when compared to other groups, respectively. Conclusions: Within the limitations of this study, the application of Cerambond to both casted and sintered samples showed significantly increased SBS values and it was also observed that sintered samples had higher strength than casted samples. Altogether, the results indicate that the use of Cerambond increased the shear strength between cobalt Cr alloy and ceramics, thereby prolonging the longevity of the restorations.

Impact of the superimposition reference area on intraoral scanning accuracy in a partially dentate maxilla

Statement of problemThe alignment of 3-dimensional (3D) files involves selecting a reference area before performing a local best fit alignment during the digital scan superimposition and is essential for comparing digital scans. Scan alignment relies on both reference area location and the alignment algorithm. However, a consensus on the impact of different reference areas on intraoral scanning accuracy is lacking. PurposeThe purpose of this in vitro study was to assess the impact of 3 superimposition reference areas on the accuracy of 3 intraoral scanners for a partially dentate maxilla. Material and methodsA Kennedy class II resin cast was scanned using 3 intraoral scanners (Primescan, TRIOS 3, and Emerald) outputting 30 digital scans (10 per scanner). Test scans from intraoral scanners were subsequently compared with a reference digital standard tessellation language file generated by a laboratory scanner with validated accuracy. The files were superimposed using best fit alignment for each intraoral scanner using 3 different superimposition reference areas (whole region of interest, palate, and all teeth). Accuracy was assessed by using a 3D analysis program (Geomagic Control X; 3D systems) for each scanner at 4 preselected areas. Test and reference scan differences were depicted on color maps and quantified via root mean square deviations. Differences were analyzed using regression analysis with the post hoc student t test and Bonferroni correction (α=.05). ResultsThe TRIOS 3 and Emerald produced positive deviations in the palatal color maps, whereas Primescan produced more uniform color maps, regardless of the superimposition strategy used. Primescan exhibited the best accuracy (trueness and precision) in both palatal and bounded edentulous areas, regardless of the superimposition reference area. The TRIOS 3 recorded the highest distal extension trueness (ranging from 42.9±7.7 µm to 65 ±19.5 µm), and Primescan achieved the highest precision (ranging from 28.5 ±9.8 µm to 48.9 ±16.9 µm), regardless of the superimposition area. Emerald demonstrated the highest teeth trueness (ranging from 31.6 ±6.8 µm to 69.6 ±11.5 µm), while Primescan produced the highest precision (ranging from 17.9 ±6.1 µm to 30.7 ±9.2 µm), regardless of the reference area used. ConclusionsThe chosen reference area for best fit alignment significantly influenced digital scan accuracy (P<.001). Primescan displayed the highest palatal and bounded edentulous area accuracy, with TRIOS 3 recording the highest distal extension trueness. Emerald recorded the highest teeth trueness and Primescan recorded the highest distal extension and tooth precision. All conclusions were independent of the superimposition strategy used.

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.

Denture relining using digital replication method: A dental technique.

The aim of this report was to digitize traditional denture relining using a digital duplication method, in addition to assessing the wear resistance of three-dimensional (3D) printed denture teeth. A complete denture was relined using light body impression. The denture with impression was scanned yielding a standard tessellation language file that was designed to print the denture base and teeth. The printed teeth were fitted into the sockets of the printed denture base and then bonded using auto-polymerized acrylic resins, followed by finishing and polishing. Dentures were inserted and fit and occlusion were adjusted as needed, and the patient was scheduled for follow-up appointments at one week, three months, and six months. At each follow-up visit, dentures were scanned using a 3Shape E3 desktop scanner and scans were superimposed. The occlusal wear was assessed in reference to the first scan after the denture insertion visit. The accuracy of the intaglio surface of dentures was within clinically acceptable limits. The clinical evaluation of inserted dentures in terms of retention, occlusion, esthetic, and patient satisfaction was encouraging. Using digital duplication, conventional dentures could be relined. The advantages of digital records include eliminating polymerization dimensional changes, and reducing cost and clinical time by minimizing the number of visits, which is particularly helpful with geriatric patients.

Effect of Duplication Techniques on the Fitting Accuracy of CAD-CAM Milled, 3D-Printed, and Injection-Molded Mandibular Complete Denture Bases.

Digital technology has been introduced in prosthodontics, and it has been widely used in denture duplication instead of a conventional denture duplication technique. However, research comparing different denture duplication techniques and how they affect the fitting accuracy of the denture base is scarce. The aim was to assess the impact of duplication techniques on the accuracy of the fitting surface of computer-aided design and manufacturing (CAD-CAM) milled, 3D-printed, and injection-molded complete denture bases (CDBs). This study involved fabricating a mandibular complete denture base with three marked dimples as reference marks (A, B, and C at the incisive papilla, right molar, and left molar areas) using a conventional compression molded technique. This denture was then scanned to generate a standard tessellation language (STL) file; after that, it was duplicated using three different techniques (milling, 3D printing, and injection molding) and five denture base resin materials-two milled CAD-CAM materials (AvaDent and IvoBase), two 3D-printed materials (NextDent and HARZ Labs), and one injection-molded material (iFlextm). Based on the denture base type, the study divided them into five groups (each with n = 10). An evaluation of duplication accuracy was conducted on the fitting surface of each complete denture base (CDB) using two assessment methods. The first method was a two-dimensional evaluation, which entailed linear measurements of the distances (A-B, A-C, and B-C) between reference points on both the scanned reference mandibular denture and the duplicated dentures. Additionally, a three-dimensional superimposition technique was employed, involving the overlay of the STL files of the dentures onto the reference denture's STL file. The collected data underwent statistical analysis using a one-way analysis of variance and Tukey's pairwise post hoc tests. Both evaluation techniques showed significant differences in fitting surface accuracy between the tested CDBs (p ˂ 0.001), as indicated by one-way ANOVA. In addition, the milled CDBs (AvaDent and IvoBase) had significantly higher fitting surface accuracy than the other groups (p ˂ 0.001) and were followed by 3D-printed CDBs (NextDent and HARZ Labs), while the injection-molded (iFlextm) CDBs had the lowest accuracy (p ˂ 0.001). The duplication technique of complete dentures using a CAD-CAM milling system produced superior fitting surface accuracy compared to the 3D-printing and injection-molded techniques.

In vitro comparative study between complete arch conventional implant impressions and digital implant scans with scannable pick-up impression copings

Statement of problemIntraoral digital scan techniques have been widely used and sufficient evidence supports this technique in partially edentulous patients. However, the evidence supporting the use of intraoral scanners (IOSs) for edentulous patients is limited. PurposeThe purpose of this in vitro study was to measure and compare the accuracy of complete arch conventional pick-up implant impressions with open and closed trays, complete arch digital implant scans with IOSs, and 3-dimensional (3D) printed casts from complete arch digital implant scans. Material and methodsSix implants were placed in a mandibular model. Scannable pick-up impression copings were inserted in the implants, scanned with a reference scanner, and exported in standard tessellation language (STL) format (Group Control). Splinted open-tray pick-up impressions (Group OT, n=5) and closed-tray pick-up impressions (Group CT, n=5) were made, and stone casts were fabricated. Digital scans (Group DS, n=5) were made with an IOS, and the STL files were exported to fabricate 3D printed casts (Group STL, n=5). Scannable pick-up impression copings were inserted in the dental implant analogs in Groups OT, CT, and STL and scanned with the reference scanner. Using a 3D inspection software program, the recording techniques were compared with the control. Root mean square (RMS) values were calculated from the control, and superimposed digitized casts from different recording techniques. Analysis of variance was used to determine differences in RMS values, and theTukey post hoc test was used to determine difference between different groups. ResultsGroup CT had the lowest mean dimensional difference when superimposed with Group Control, followed by Groups DS, OT, and STL. Significant differences were found in RMS values between Control and digitized casts fabricated with different techniques (P<.05). The post hoc Tukey test revealed that Group DS (P<.05) was significantly different from the other groups, while no significant difference was found among Groups CT, OT, and STL (P>.05). ConclusionsBased on the findings of the present study, 3D printed casts from digital scans have the same accuracy as stone casts from conventional impressions in complete arch implant cases. Intraoral scans had the highest accuracy. Complete arch pick-up impression techniques using dual-functioning scannable pick-up impression copings are as accurate as splinted complete arch pick-up impressions.

Design and Additive Manufacturing of a Prototype Using Fused Deposition Modeling Technique

A screw jack is a tool for lifting heavy loads with little effort. In this paper, the design, model and fabrication of a Screw jack using 3D Printing Technology is discussed. Digital fabrication, or 3D printing or additive manufacturing, creates physical objects from a geometrical representation by successive addition of materials. In agriculture, health care, motor vehicles, locomotives and aviation, 3D Printing is increasingly being applied for mass customization or production for all types of open-source design. Design is an important industrial activity which influences the quality of the product. The parts of a screw jack are modelled by using the modelling software Creo Parametric. The CAD model of the screw jack is then converted into. STL (Standard Tessellation Language) format in which the 3D Printer receives the printing input. The STL files are then imported to modelling software to analyze mesh and rectify errors. The rectified STL files of parts of the screw jack are imported to Makerbot software, and parts are made ready for 3D Printing using Makerbot FDM (Fused Deposition Modelling) 3D Printer. The parts printed in an FDM 3D printer are assembled based on the tolerances obtained, and the final prototype is fabricated.

An evaluation of the sources and extent of error in the position of implants placed using 3D-printed stereolithographic surgical guides.

Introduction/Background. Errors can be introduced in implant placement when using stereolithographically manufactured fully limiting surgical guides due to various factors, such as discrepancies in designing and manufacturing of surgical guides (intrinsic error), built-in variations in design of mechanical components of guide systems and implant dimensions (inherent error) or due to placement error by the operator (operator error). Aim. The aim of this study was to evaluate influence of various factors on implant position when using these guides. Materials and Methods. Prosthetically-driven implant positions were planned with pre-operative cone beam computed tomography (CBCT) data and digital scans using a computer aided designing (CAD) software. Static guided implant surgery was performed under local anaesthesia using fully limiting mucosa-supported surgical guide. Pre-operative and post-operative CBCTs were superimposed using surgical sleeve as a reference to evaluate the placement error by operator (N=12). To evaluate intrinsic error, standard tessellation language (STL) files of the virtual design of the surgical guides and the STL file obtained after scanning the 3D printed stereolithographic surgical guides were superimposed. Inherent error was calculated using a geometric model. Results. Intrinsic error was observed to be a major contributing factor in angular deviation of implant, linear deviation observed at implant shoulder as well as at implant apex. Operator error was observed to be a major contributing factor for mean vertical deviation observed at apex of implant. Conclusion. This study showed that accuracy of implant placement was largely influenced by discrepancies introduced during designing and manufacturing of stereolithographic surgical guides as compared to other sources.

An evaluation of the sources and extent of error in the position of implants placed using 3D-printed stereolithographic surgical guides.

Introduction/Background. Errors can be introduced in implant placement when using stereolithographically manufactured fully limiting surgical guides due to various factors, such as discrepancies in designing and manufacturing of surgical guides (intrinsic error), built-in variations in design of mechanical components of guide systems and implant dimensions (inherent error) or due to placement error by the operator (operator error). Aim. The aim of this study was to evaluate influence of various factors on implant position when using these guides. Materials and Methods. Prosthetically-driven implant positions were planned with pre-operative cone beam computed tomography (CBCT) data and digital scans using a computer aided designing (CAD) software. Static guided implant surgery was performed under local anaesthesia using fully limiting mucosa-supported surgical guide. Pre-operative and post-operative CBCTs were superimposed using surgical sleeve as a reference to evaluate the placement error by operator (N=12). To evaluate intrinsic error, standard tessellation language (STL) files of the virtual design of the surgical guides and the STL file obtained after scanning the 3D printed stereolithographic surgical guides were superimposed. Inherent error was calculated using a geometric model. Results. Intrinsic error was observed to be a major contributing factor in angular deviation of implant, linear deviation observed at implant shoulder as well as at implant apex. Operator error was observed to be a major contributing factor for mean vertical deviation observed at apex of implant. Conclusion. This study showed that accuracy of implant placement was largely influenced by discrepancies introduced during designing and manufacturing of stereolithographic surgical guides as compared to other sources.

Influence of different palatal morphologies on the accuracy of intraoral scanning of the edentulous maxilla: A three-dimensional analysis.

This study investigated the influence of different palatal morphologies on the accuracy of intraoral scanning (TRIOS 4) of edentulous maxillae. Six typodonts were fabricated for different palatal morphologies with flat (F), medium (M), and deep (D) palates, with palatal wrinkles (W), or smooth palates (S), resulting in six groups: WF, WM, WD and SF, SM, SD. Ten scans were performed for each group; standard tessellation language files obtained were imported into a software to measure trueness and precision in micrometer. Trueness was calculated as the mean of the standard deviation values obtained by superimposing each scan onto the reference scan. Precision was achieved by overlapping each scan with that with the best trueness in the group. Descriptive and post-hoc analyses were conducted. The mean values for trueness were as follows: WM=48.7±4.7, WD=161.7±18.4, WF=85.9±16, SM=48.1±2.4, SD=349.9±8.8, and SF=349.1±25.5. The precision values were as follows: WM=46.7±7.3, WD=46.9±9, WF=48.9±6.7, SM=46±2.7, SD=105.9±17.4, SF=72.6±10.8. Significant differences were observed for trueness between SM and SD (P < 0.001), SM and SF (P < 0.001), and WF and SF (P = 0.003); whereas for precision, significant differences were reported between WD and SD (P = 0.015). Regarding trueness and precision, no difference was found between WM and SM (P = 1.0). Medium palatal depth showed the best accuracy. The mean accuracy values were within the clinical acceptability thresholds for all palatal morphologies. The presence of rugae improved the precision of deeper palates and the trueness of flat palates. No differences were observed in the medium palates with or without rugae.

Fabrication of sports mouthguards using a semi-digital workflow with 4D-printing technology.

Purpose This technical procedure report explains the fabrication protocol for a newly developed 4D-printed sports mouthguard (MG) based on 4D-printing technology.Methods An intraoral scanner was used to scan a maxillary arch model. A two-layer sports MG was designed based on the scanned model using computer-aided design software and output in a standard tessellation language file format. Two types of filament materials were used for the MG material: a thermoplastic shape memory polyurethane elastomer with a unique glass transition temperature for the external layer and a thermoplastic elastomer for the internal layer. Both MGs were printed using a fused deposition modeling 3D printer and assembled using adhesives after trimming the support material. To confirm the shape-memory performance of the fabricated 4D-printed MG, a deviation analysis was performed by superimposing the internal surface data of the fabricated MG and the MG whose shape was recovered. The distance between the data obtained by deviation analysis was calculated, and the root mean square error value (mm) was determined.Conclusions The 4D-printing technology simplifies the complex processes required with conventional methods. It also overcomes the issues of conventional and 3D-printed MGs, such as the reduced fitting accuracy caused by deformation, because this technology employs shape memory materials.