Can an entry-level 3D printer create high-quality anatomical models? Accuracy assessment of mandibular models printed by a desktop 3D printer and a professional device

This study was performed to determine whether an in-house printed mandible model is sufficiently accurate for daily clinical practice. Ten example mandible models were produced with a desktop 3D printer (fused filament fabrication, FFF) and compared with 10 equivalent mandible models fabricated using a professional-grade 3D printer (selective laser sintering, SLS). To determine the precision of the printed models, each model was scanned with an optical scanner. Subsequently, every model was compared to its original standard tessellation language (STL) file and to its corresponding analogue. Mean ± standard deviation and median (interquartile range) differences were calculated. Overall these were −0.019 ± 0.219 mm and −0.007 (−0.129 to 0.107) mm for all 10 pairs. Furthermore, correlation of all printed models to their original STL files showed a high level of accuracy. Comparison of the SLS models with their STL files revealed a mean difference of −0.036 ± 0.114 mm and median difference of −0.028 (−0.093 to 0.030) mm. Comparison of the FFF models with their STL files yielded a mean difference of −0.055 ± 0.227 mm and median difference of −0.022 (−0.153 to 0.065) mm. The study findings confirm that in-house 3D printed mandible models are economically favourable as well as suitable substitutes for professional-grade models, in particular considering the geometric aspects.     

Patient-specific pre-contouring of osteosynthesis plates for mandibular reconstruction: Using a three-dimensional key printed solution

Purpose

In mandibular reconstructive surgery, the osteosynthesis plates require contouring according to the patients' individual anatomical situation. These plates are frequently contoured around a three-dimensional (3D) printed model. However, the translation to the actual patient can introduce inaccuracies and unwanted rotations in the condyles and mandibular ramus, due to malpositioning of the pre-contoured plate.

Accuracy of three-dimensional printed models derived from cone-beam computed tomography

ObjectivesTo determine the accuracy of three-dimensional (3D) printed models fabricated from cone-beam computed tomography (CBCT) scans of human mandibular dry skulls in comparison with models derived from intraoral scanner (IOS) data.Materials and MethodsSix human mandibular dry skulls were scanned by IOS and CBCT. Digital models (DMs) constructed from the IOS and CBCT data were fabricated physically using a 3D printer. The width and thickness of individual teeth and intercanine and molar widths were measured using a digital caliper. The accuracy of the DMs was compared between IOS and CBCT. Paired t-tests were used for intergroup comparisons.ResultsAll intraclass correlation coefficient values for the three measurements (mesial-distal, buccal-lingual, width) exceeded 0.9. For the mandibular teeth, there were significant discrepancies in model accuracy between the IOS (average discrepancies of 0.18 ± 0.08 mm and 0.16 ± 0.12 mm for width and thickness, respectively) and CBCT (0.28 ± 0.07 mm for width, 0.37 ± 0.2 mm for thickness; P < .01). Intercanine (P = .38) and molar widths (P = .41) showed no significant difference between groups.ConclusionsThere was a statistically significant difference in the accuracy of DMs obtained from CBCT and IOS; however, this did not seem to result in any important clinical difference. CBCT could be routinely used as an orthodontic diagnostic tool and for appliance construction.     

Head positioning in a cone beam computed tomography unit and the effect on accuracy of the three‐dimensional surface mode

Head position during cone beam computed tomography (CBCT) examination can easily deviate from the ideal, which may affect the accuracy of the segmented three‐dimensional (3D) model. The aim of this study was to determine the effect of head positioning on the accuracy of the 3D model. A human dry skull was positioned at predetermined orientations in a CBCT scanner and scanned in multiple orientations and voxel sizes. The resulting 3D surface models were superimposed over those derived from the reproducible centered positioned skull with 0° inclination. Color mapping and analysis of the differences expressed by the root mean square error (RMSE) were performed. The RMSE for each orientation using the 0.3 mm voxel ranged from 0.31 to 0.87 mm for the whole maxillofacial region, from 0.44 to 0.91 mm in the maxilla, and from 0.31 to 0.72 mm in the mandible. For the 0.4 mm voxel, the RMSE ranged from 0.47 to 0.86 mm for the whole maxillofacial region, from 0.60 to 0.96 mm in the maxilla, and from 0.56 to 0.86 mm in the mandible. The maxilla showed a slightly higher deviation than the mandible in both voxel groups. It can be concluded that the head position affects the accuracy of the segmented 3D model, but the inaccuracy does not exceed clinically relevant levels.     

Chairside fabrication of provisional crowns on FDM 3D-printed PVA model

PurposeThe purpose of this study was to evaluate the dimensional accuracy of crowns fabricated using a polyvinyl alcohol (PVA) dental model.MethodsAn intraoral scanner (LAVA TDS) was used to scan a prepared molar abutment as a master model. The STL file obtained from the scanning process was transferred into the FDM 3D printer (Value 3D Magix MF-1000) and then models were fabricated with PVA filament. In order to compare with the conventional method, an impression of the master model was taken using silicone impression material to fabricate the conventional stone cast model (Conv). An indirect resin composite (Gradia) and self-cured acrylic resin (Curergrace) were used to fabricate crowns (n = 20) according to the manufacturer's instructions. Surface accuracy of the Conv and PVA models and internal accuracy of the crowns set on the models were measured using two methods; 3D digital analysis and silicon-fitting evaluation. Statistical analysis of the results was done using t-test and Willcoxon signed rank test with Bonferroni correction at 5% significance.ResultsDigital analysis showed the Root Mean Square (RMS) value of PVA model surface was higher than that of Conv, while there was no significant difference between the two crown materials. However, the silicon-fitting analysis showed marginal discrepancy of crowns fabricated on PVA model were within 100 µm.Conclusion3D printed PVA model can be used for chairside crown fabrication with an acceptable accuracy.     

Bracket transfer accuracy with two different three-dimensional printed transfer trays vs silicone transfer trays

ObjectivesTo compare the transfer accuracy of two different three-dimensional printed trays (Dreve FotoDent ITB [Dreve Dentamid, Unna, Germany] and NextDent Ortho ITB [NextDent, Soesterberg, the Netherlands]) to polyvinyl siloxane (PVS) trays for indirect bonding.Materials and MethodsA total of 10 dental models were constructed for each investigated material. Virtual bracket placement was performed on a scanned dental model using OnyxCeph (OnyxCeph 3D Lab, Chemnitz, Germany). Three-dimensional printed transfer trays using a digital light processing system three-dimensional printer and silicone transfer trays were produced. Bracket positions were scanned after the indirect bonding procedure. Linear and angular transfer errors were measured. Significant differences between mean transfer errors and frequency of clinically acceptable errors (<0.25 mm/1°) were analyzed using the Kruskal–Wallis and χ² tests, respectively.ResultsAll trays showed comparable accuracy of bracket placement. NextDent exhibited a significantly higher frequency of rotational error within the limit of 1° (P = .01) compared with the PVS tray. Although PVS showed significant differences between the tooth groups in all linear dimensions, Dreve exhibited a significant difference in the buccolingual direction only. All groups showed a similar distribution of directional bias.ConclusionsThree-dimensional printed trays achieved comparable results with the PVS trays in terms of bracket positioning accuracy. NextDent appears to be inferior compared with PVS regarding the frequency of clinically acceptable errors, whereas Dreve was found to be equal. The influence of tooth groups on the accuracy of bracket positioning may be reduced by using an appropriate three-dimensional printed transfer tray (Dreve).     

Characterizing mandibular growth using three-dimensional imaging techniques and anatomic landmarks

ObjectiveTo provide quantitative data on the multi-planar growth of the mandible, this study derived accurate linear and angular mandible measurements using landmarks on three dimensional (3D) mandible models. This novel method was used to quantify 3D mandibular growth and characterize the emergence of sexual dimorphism.DesignCross-sectional and longitudinal imaging data were obtained from a retrospective computed tomography (CT) database for 51 typically developing individuals between the ages of one and nineteen years. The software Analyze was used to generate 104 3DCT mandible models. Eleven landmarks placed on the models defined six linear measurements (lateral condyle, gonion, and endomolare width, ramus and mental depth, and mandible length) and three angular measurements (gonion, gnathion, and lingual). A fourth degree polynomial fit quantified growth trends, its derivative quantified growth rates, and a composite growth model determined growth types (neural/cranial and somatic/skeletal). Sex differences were assessed in four age cohorts, each spanning five years, to determine the ontogenetic pattern producing sexual dimorphism of the adult mandible.ResultsMandibular growth trends and growth rates were non-uniform. In general, structures in the horizontal plane displayed predominantly neural/cranial growth types, whereas structures in the vertical plane had somatic/skeletal growth types. Significant prepubertal sex differences in the inferior aspect of the mandible dissipated when growth in males began to outpace that of females at eight to ten years of age, but sexual dimorphism re-emerged during and after puberty.ConclusionsThis 3D analysis of mandibular growth provides preliminary normative developmental data for clinical assessment and craniofacial growth studies.     

3D printed versus conventionally cured provisional crown and bridge dental materials

Objectives

To optimize the 3D printing of a dental material for provisional crown and bridge restorations using a low-cost stereolithography 3D printer; and compare its mechanical properties against conventionally cured provisional dental materials.

Experimental and clinical assessment of three-dimensional cephalometry: A systematic review

ObjectivesThis study provides a systematic review of the current scientific literature on three-dimensional (3D) cephalometry. The null hypothesis was that 3D cephalometry is an accurate and reproducible diagnostic technique. To examine this hypothesis, the following three research questions were proposed: 1) What is the accuracy of 3D cephalometric measurements compared to in vitro measurements? 2) What is the intra- and inter-observer reliability of the selection of 3D cephalometric landmarks? 3) What is the reproducibility of the linear and angular measurements?MethodsA comprehensive database search was performed, using Medline, the Cochrane Central Register of Controlled Trials, Web of Science and Google Scholar. The titles and abstracts obtained from the search were screened and evaluated by two observers according to the inclusion and exclusion criteria.ResultsThe evaluation process yielded 21 articles. A high level of agreement (<1 mm) between the in vitro measurements and those obtained from 3D cephalometry was observed and some landmarks provided highly reproducible results. However, the linear (0.04–7.49 mm) and angular (0.99–9.30°) measurements differed greatly.ConclusionsThe null hypothesis was rejected. This study indicates critical points regarding 3D cephalometry and provides guidance for future research in this field.     

Magnetic resonance imaging for three-dimensional printing of the bony orbit: is clinical use imminent?

The aim of this study was to examine the accuracy of three dimensionally (3D) printed models of the bony orbit derived from magnetic resonance imaging (MRI) for the purpose of preoperative plate bending in the setting of orbital blowout fracture. Retrospective computed tomography (CT) and MRI data from patients with suspected orbital fractures were used. Virtual models were manually generated and analysed for spatial accuracy of the fracture margins. 3D-printed models were produced and orbital fan plates bent by a single operator. The plates were then digitized and analysed for spatial discrepancy using reverse engineering software. Seven orbital blowout fractures were evident in six orbits. Analysis of the virtual models revealed high congruence between blowout fracture margins on CT and MRI (n = 7, average deviation 0.85 mm). Three zygomaticomaxillary complex fractures were seen, for which MRI did not demonstrate the same accuracy. For plates bent to the 3D-printed models of blowout fractures (n = 6), no significant difference was found between those bent to CT versus those bent to MRI when compared for average surface and average border deviation (Wilcoxon signed rank test). Orbital blowout fractures can be defined on MRI with clinically acceptable accuracy. 3D printing of orbital biomodels from MRI for bending reconstructive plates is an acceptable and accurate technique.     

The Influence of Cone Beam Computed Tomography-Derived 3D-Printed Models on Endodontic Microsurgical Treatment Planning and Confidence of the Operator

IntroductionCurrently, there are no studies evaluating the impact of 3-dimensional (3D) printed models on endodontic surgical treatment planning. The aims of this study were: 1) to determine if 3D models could influence treatment planning; and 2) to assess the effect of 3D supported planning on operator confidence.MaterialsEndodontic practitioners (n = 25) were asked to analyze a preselected cone beam computed tomography (CBCT) scan of an endodontic surgical case and answer a questionnaire that elucidated their surgical approach. After 30 days, the same participants were asked to analyze the same CBCT scan. Additionally, participants were asked to study and to perform a mock osteotomy on a 3D printed model. The participants responded to the same questionnaire along with a new set of questions. Responses were statistically analyzed using chi square test followed by either logistic or ordered regression analysis. Adjustment for multiple comparison analysis was done using a Bonferroni correction. Statistical significance was set at ≤0.005.ResultsThe availability of both the 3D printed model and the CBCT scan resulted in statistically significant differences in the participants' responses to their ability to detect bone landmarks, predict the location of osteotomy, and to determine the following: size of osteotomy, angle of instrumentation, involvement of critical structures in flap reflection and involvement of vital structures during curettage. In addition, the participants’ confidence in performing surgery was found to be significantly higher.ConclusionsThe availability of 3D printed models did not alter the participants’ surgical approach but it significantly improved their confidence for endodontic microsurgery.     

The 3D-printed miniplate-jig system: a new,rapid, precise,and user-friendly approach to miniplate fixation of free-tissue mandibular reconstructions

Patient-specific, additively manufactured (printed) titanium reconstruction plates have been widely used to improve accuracy and efficiency of fibular flap reconstruction of the mandible. Miniplates possess some potential advantages over single-piece reconstruction plates, however multiple-miniplate fixation can be more technically demanding and may lengthen the duration of surgery. Furthermore, incremental angulation errors in screw placement for each miniplate could compromise overall dimensional accuracy of the neomandibular reconstruction. This preliminary article reports the first clinical use of a new patient-specific, printed titanium miniplate-jig system in a patient undergoing hemimandibulectomy for osteoradionecrosis of the mandible with fibular flap reconstruction. Our initial experience with the new device and technique demonstrates a quick, user friendly, and precise method for the placement and fixation of multiple miniplates in fibular-flap reconstruction of the mandible.     

Comparison of additive manufactured models of the mandible in accuracy and quality using six different 3D printing systems

The aim of this study was to analyze and compare the accuracy and quality of six 3D printing systems available on the market.Data acquisition was performed with 12 scans of human mandibles using an industrial 3D scanner and saved in STL format. These STL files were printed using six different printing systems. Previously defined distances were measured with a sliding caliper on the 72 printed mandibles. The printed models were then scanned once again. Measurements of volumes and surfaces for the STL files and the printed models were compared. Accuracy and quality were evaluated using industrial software. An analysis of the punctual aberration between the template and the printed model, based on a heat map, was also carried out. Secondary factors, such as costs, production times and expendable materials, were also examined.All printing systems performed well in terms of accuracy and quality for clinical usage. The Formiga P110 and the Form 2 showed the best results for volume, with average aberrations of 0.13 ± 0.23 cm³ and 0.12 ± 0.17 cm³, respectively. Similar results were achieved for the heat map aberration, with values of 0.008 ± 0.11 mm (Formiga P110) and 0.004 ± 0.16 mm (Form 2). Both printers showed no significant difference from the optimal neutral line (Formiga P110, p = 0.15; Form 2, p = 0.60). The cheapest models were produced by the Ultimaker 2+, with an average of 5€ per model, making such desktop printers affordable for rapid prototyping. Meanwhile, advanced printing systems with sterilizable and biocompatible printing materials, such as the Formiga P110 and the Form 2, fulfill the high expectations for maxillofacial surgery.     

Clinical feasibility of deep learning-based automatic head CBCT image segmentation and landmark detection in computer-aided surgical simulation for orthognathic surgery

The purpose of this ambispective study was to investigate whether deep learning-based automatic segmentation and landmark detection, the SkullEngine, could be used for orthognathic surgical planning. Sixty-one sets of cone beam computed tomography (CBCT) images were automatically inferred for midface, mandible, upper and lower teeth, and 68 landmarks. The experimental group included automatic segmentation and landmarks, while the control group included manual ones that were previously used to plan orthognathic surgery. The qualitative analysis of segmentation showed that all of the automatic results could be used for computer-aided surgical simulation. Among these, 98.4% of midface, 70.5% of mandible, 98.4% of upper teeth, and 93.4% of lower teeth could be directly used without manual revision. The Dice similarity coefficient was 96% and the average symmetric surface distance was 0.1 mm for all four structures. With SkullEngine, it took 4 minutes to complete the automatic segmentation and an additional 10 minutes for a manual touchup. The results also showed the overall mean difference between the two groups was 2.3 mm for the midface and 2.4 mm for the mandible. In summary, the authors believe that automatic segmentation using SkullEngine is ready for daily practice. However, the accuracy of automatic landmark digitization needs to be improved.     

Accuracy of three-dimensional dental resin models created by fused deposition modeling,stereolithography, and Polyjet prototype technologies: A comparative study

Objectives: The aim of this study was to assess the dimensional accuracy of fused deposition modeling (FDM)–, Polyjet-, and stereolithography (SLA)–produced models by comparing them to traditional plaster casts.Materials andMethods: A total of 12 maxillary and mandibular posttreatment orthodontic plaster casts were selected from the archives of the Orthodontic Department at the Indiana University School of Dentistry. Plaster models were scanned, saved as stereolithography files, and printed as physical models using three different three-dimensional (3D) printers: Makerbot Replicator (FDM), 3D Systems SLA 6000 (SLA), and Objet Eden500V (Polyjet). A digital caliper was used to obtain measurements on the original plaster models as well as on the printed resin models.Results: Comparison between the 3D printed models and the plaster casts showed no statistically significant differences in most of the parameters. However, FDM was significantly higher on average than were plaster casts in maxillary left mixed plane (MxL-MP) and mandibular intermolar width (Md-IMW). Polyjet was significantly higher on average than were plaster casts in maxillary intercanine width (Mx-ICW), mandibular intercanine width (Md-ICW), and mandibular left mixed plane (MdL-MP). Polyjet was significantly lower on average than were plaster casts in maxillary right vertical plane (MxR-vertical), maxillary left vertical plane (MxL-vertical), mandibular right anteroposterior plane (MdR-AP), mandibular right vertical plane (MdR-vertical), and mandibular left vertical plane (MdL-vertical). SLA was significantly higher on average than were plaster casts in MxL-MP, Md-ICW, and overbite. SLA was significantly lower on average than were plaster casts in MdR-vertical and MdL-vertical.Conclusions: Dental models reconstructed by FDM technology had the fewest dimensional measurement differences compared to plaster models.     

Stability of bioabsorbable fixation systems according to different locations of mandibular fracture: A three-dimensional analysis

This study aimed to elucidate whether the stability of an unsintered hydroxyapatite particles/poly-_l-lactide (uHA/PLLA) system is comparable with that of titanium, according to different load-bearing areas of the mandible. The study included patients who underwent open reduction and internal fixation of the mandibular body, angle, or subcondylar fracture. The stability of uHA/PLLA systems was compared between the immediate and 6-month postoperative time points using three-dimensional cone-beam CT image analysis. The positional changes of each landmark were measured in three-dimensional (3D) coordinate systems using simulation software. Among 36 patients, there were more displacements of the landmarks between the immediate and 6-month postoperative time points after subcondylar fracture reduction than after body or angle fracture reductions. Strong upward displacements of the landmarks after subcondylar fracture reduction were found in the lateral pole [mean (SD) = 1.75 (3.16), p-value = 0.003] and medial pole [mean (SD) = 1.64 (2.50), p-value = 0.024], but not in the center. Subgroup analyses revealed similar unstable results in males on the condylar landmarks after subcondylar fracture reduction. There were tendencies for lateral displacement of the coronoid process in the body fracture group [mean (SD) = 0.8 (0.83)] and angle fracture group [mean (SD) = 0.75 (0.58)] postoperatively (p-value = 0.01). This study concluded that bioresorbable osteosynthesis can be recommended for body or angle fractures, while the indication for subcondylar fractures is less clear.     

Development of a three-dimensional treatment planning system based on computed tomographic data

Current surgical treatment planning systems predict three-dimensional (3D) corrections from two-dimensional (2D) data and are inadequate for complex movements. In this paper, we present a 3D planning system based on computed tomographic (CT) data. A three-dimensional CT scan of the craniofacial skeleton forms the database. Software developed in the Harvard Surgical Planning Laboratory was modified for the craniofacial skeleton. Reproducible skeletal landmarks are identified for superimposition. A 'cutting tool' is used to segment the mandible and segments are moved to their predicted positions. A 'collision tool', alerts the operator of skeletal interferences. An analysis of selected scans is used to demonstrate the system. Three-dimensional visualization of the facial skeleton, selection of landmarks, measurement of angles and distances, simulation of osteotomies, repositioning of bones, detection of collisions and super-imposition of scans were accomplished. In an illustrative case of Hemifacial Microsomia, predicted and actual 3D corrective movements of the entire mandible were documented. Analysis of scans indicated that 3D planning can prevent insufficient jaw lengthening or other surgical inaccuracies which occur with standard 2D methods. Software demonstrated here will allow the surgeon to accurately plan treatment and evaluate craniomaxillofacial surgery outcomes. Future applications may include surgical navigation.     

A new method for automatic tracking of facial landmarks in 3D motion captured images (4D)

The aim of this study was to validate the automatic tracking of facial landmarks in 3D image sequences. 32 subjects (16 males and 16 females) aged 18–35 years were recruited. 23 anthropometric landmarks were marked on the face of each subject with non-permanent ink using a 0.5 mm pen. The subjects were asked to perform three facial animations (maximal smile, lip purse and cheek puff) from rest position. Each animation was captured by the 3D imaging system. A single operator manually digitised the landmarks on the 3D facial models and their locations were compared with those of the automatically tracked ones. To investigate the accuracy of manual digitisation, the operator re-digitised the same set of 3D images of 10 subjects (5 male and 5 female) at 1 month interval. The discrepancies in x, y and z coordinates between the 3D position of the manual digitised landmarks and that of the automatic tracked facial landmarks were within 0.17 mm. The mean distance between the manually digitised and the automatically tracked landmarks using the tracking software was within 0.55 mm. The automatic tracking of facial landmarks demonstrated satisfactory accuracy which would facilitate the analysis of the dynamic motion during facial animations.     

Dental image replacement on cone beam computed tomography with three-dimensional optical scanning of a dental cast,occlusal bite,or bite tray impression

The goal of the present study was to compare the accuracy of dental image replacement on a cone beam computed tomography (CBCT) image using digital image data from three-dimensional (3D) optical scanning of a dental cast, occlusal bite, and bite tray impression. A Bracket Typodont dental model was used. CBCT of the dental model was performed and the data were converted to stereolithography (STL) format. Three experimental materials, a dental cast, occlusal bite, and bite tray impression, were optically scanned in 3D. STL files converted from the CBCT of the Typodont model and the 3D optical-scanned STL files of the study materials were image-registered. The error range of each methodology was measured and compared with a 3D optical scan of the Typodont. For the three materials, the smallest error observed was 0.099 ± 0.114 mm (mean error ± standard deviation) for registering the 3D optical scan image of the dental cast onto the CBCT dental image. Although producing a dental cast can be laborious, the study results indicate that it is the preferred method. In addition, an occlusal bite is recommended when bite impression materials are used.