Digital (R)Evolution: Open-Source Softwares for Orthodontics

applied sciences

Article Digital (R)Evolution: Open-Source Softwares for Orthodontics

Fabio Federici Canova 1,* , Giorgio Oliva 2, Matteo Beretta 1 and Domenico Dalessandri 2

1 Department of Medical and Surgical Specialties, Postgraduate Orthodontic School, Radiological Sciences and Public Health, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy; [email protected] 2 Department of Medical and Surgical Specialties, School of Dentistry, Radiological Sciences and Public Health, University of Brescia, Piazzale Spedali Civili 1, 25123 Brescia, Italy; [email protected] (G.O.); [email protected] (D.D.) * Correspondence: [email protected]

Abstract: Among the innovations that have changed modern orthodontics, the introduction of new digital technologies in daily clinical practice has had a major impact, in particular the use of 3D models of dental arches. The possibility for direct 3D capture of arches using intraoral scanners has brought many clinicians closer to the digital world. The digital revolution of orthodontic practice requires both hardware components and dedicated software for the analysis of STL models and all other ﬁles generated by the digital workﬂow. However, there are some negative aspects, including the need for the clinician and technicians to learn how to use new software. In this context, we can distinguish two main software types: dedicated software (i.e., developed by orthodontic companies) and open-source software. Dedicated software tend to have a much more user-friendly interface, and be easier to use and more intuitive, due to being designed and developed for a non-expert user, but very high rental or purchase costs are an issue. Therefore, younger clinicians with more extensive digital skills have begun to look with increasing interest at open-source software. The aim of the present study was to present and discuss some of the best-known open-source software for analysis of 3D models and the creation of orthodontic devices: Blue Sky Plan, MeshMixer, ViewBox, Citation: Federici Canova, F.; and Blender. Oliva, G.; Beretta, M.; Dalessandri, D. Digital (R)Evolution: Open-Source Keywords: digital orthodontic; open source software; Blue Sky Plan; Meshmixer; Blender; ViewBox Softwares for Orthodontics. Appl. Sci. 2021, 11, 6033. https://doi.org/ 10.3390/app11136033

Academic Editor: Dorina Lauritano 1. Introduction Among the innovations that have changed modern orthodontics, the introduction of Received: 10 June 2021 new digital technologies in daily clinical practice has had a major impact, in particular the Accepted: 25 June 2021 use of 3D models of dental arches. The possibility for direct 3D capture of arches using Published: 29 June 2021 intraoral scanners or the digitisation of plaster models has brought many clinicians closer to the digital world. The advantages of this revolution are many: the 3D models can be Publisher’s Note: MDPI stays neutral used for dental analysis as precisely as stone cast [1,2], and virtual models simplify storage with regard to jurisdictional claims in procedures by eliminating stone cast. published maps and institutional afﬁl- Digital 3D models are generally saved and displayed in the STL format (Standard iations. Triangle Language), which has now become the standard format for model evaluation. The STL format does not have color maps, so it is monochrome. If you want to include the color texture as well, the reference formats are obj (Object File Wavefront 3D) and ply (Polygon File Format). Copyright: © 2021 by the authors. The use of digital models has made it possible to modify the diagnostic approach, im- Licensee MDPI, Basel, Switzerland. proving and simplifying classic orthodontic analyses [3–6] and allowing virtual simulation This article is an open access article of the patient and dental movements [7,8]. In addition, the decreased invasiveness of the distributed under the terms and method and the possibility of overlapping the models allows greater control of therapeutic conditions of the Creative Commons progress [6,9,10]. The possibility of using 3D printing machines and very high precision Attribution (CC BY) license (https:// resins allows the creation of any orthodontic products [11]. There is also the possibility of creativecommons.org/licenses/by/ managing a full digital workﬂow: there are many devices that can be made without going 4.0/).

Appl. Sci. 2021, 11, 6033. https://doi.org/10.3390/app11136033 https://www.mdpi.com/journal/applsci Appl. Sci. 2021, 11, 6033 2 of 11

through the prototyping of a model, but rather by designing the entire device digitally with dedicated software [12–14]. Finally, the use of digital models also plays a fundamental role in scientiﬁc research [15–17], since stereolithography (STL) surfaces can be compared and analysed without loss of detail by different research groups in different places. This digital revolution has clearly affected the orthodontic world, but there are some negative aspects, including the need for the clinician to learn how to use new software. In this context, we can distinguish two main software types: dedicated software (i.e., developed by orthodontic companies) and open-source software. Dedicated software tends to have a much more user-friendly interface, and be easier to use and more intuitive, due to being designed and developed for a non-expert user, but very high rental or purchase costs are an issue. Therefore, younger clinicians with more extensive digital skills have begun to look with increasing interest at open-source software. These programs represent a very interesting resource: some software is totally free or marketed on a ‘pay-as-you-go’ basis. However, disadvantages include a fairly long learning curve. The aim of this study was to present and discuss some of the best-known open-source software for analysis of 3D models and the creation of orthodontic devices: Blue Sky Plan, MeshMixer, ViewBox, and Blender (Table1).

Table 1. Summarising table.

Blue Sky Bio Meshmixer Viewbox Blender download at www.blueskybio.com www.meshmixer.com www.dhal.com/viewbox.htm www.blender.org OS operating system macOS/Windows macOS/Windows Windows macOS/Windows free to use, only some blender is free, the add-on waiting time of 30 sec on free cost export on local system completely free blenderfordental version to use some tools are charged is charged surgical guide for palatal analyse 3D models, repair and edit 3d mesh, main use TADs, analyse models, repair and edit mesh edit mesh analyse models orthodontic set-up

2. Blue Sky Plan Blue Sky Plan (BSP) is an advanced treatment planning software distributed by BlueSkyBio (www.blueskybio.com, Blue Sky Bio, LLC—800 Liberty Drive, Libertyville, IL, USA, accessed on 22 May 2021), which was developed primarily for guided implant surgery. At the time of writing, the 4.8.2 release is available for 64-bit PC platforms, while it is still possible to use the software for the iOS platform, but it is no longer released for MacOS. It is a ‘pay-per-use’ software: it can be downloaded and used free of charge, without limitations and without license renewals. All software updates are free and available in many languages. Inside the software there are several modules, extremely useful for both orthodontic and prosthetic fields [18]. Most of the functions are free, and only the local saving of some STL files, such as surgical guides, is paid for at a reduced cost. Among the modules in the program, the most significant are the viewer module, the orthodontic module, and the guided surgery module.

2.1. Viewer Module Blue Sky Plan allows the user to import Digital Imaging and Communication in Medicine (DICOM) file sets for viewing in multi-window mode. The most common views are available (axial, coronal, implantology cuts) and easily switchable, with key combina- tions. Furthermore, 3D rendering is performed well since some presets are available, and this makes visualisation very efficient. Furthermore, automatic matching between the STL surface and the DICOM set allows to obtain a link between the volumes in a very short time. In the ‘model modification’ section, it is possible to edit the models of the patient’s arches, for example by orienting the models in the spatial plane, to create articulation pins Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 13

Furthermore, 3D rendering is performed well since some presets are available, and this makes visualisation very efficient. Furthermore, automatic matching between the STL sur- Appl. Sci. 2021, 11, 6033 3 of 11 face and the DICOM set allows to obtain a link between the volumes in a very short time. In the ‘model modification’ section, it is possible to edit the models of the patient’s arches, for example by orienting the models in the spatial plane, to create articulation pins that canthat be can printed, be printed, or even or even to match to match two twodifferent different STL STLsurfaces, surfaces, for example for example to evaluate to evaluate the modificationthe modiﬁcation of arch of arch shape shape (Fig (Figureure 1A,1B)A,B)..

(A) (B)

Figure 1. (A,B) STL and DICOM viewer.

2.2. Orthodontic Orthodontic Module The orthodontic modulemodule allowsallows the the planning planning of of digital digital set-up set-up of theof the arches, arches, which which can canalso also be used be used for ‘in-ofﬁce’for ‘in-office’ production production of alignersof aligners (Figure (Figure2A,B). 2A, TheB). The orthodontic orthodontic module mod- uleallows allows the the user user to do to thedo the following: following: -- ImportImport an an STL STL file ﬁle and and segment segment the the dental dental elements. -- CarryCarry out out alignment alignment of of the arches. -- ImportImport th thee antagonist antagonist arch arch and view the contact points using colorimetric maps. -- PerformPerform inter inter-proximal-reduction-proximal-reduction (IPR). Appl. Sci. 2021, 11, x FOR PEER REVIEW-- ImportImport a a CBCT CBCT and and superimpose superimpose it it on on the the scanned scanned arch. arch. 4 of 13

-- CheckCheck all all alignment alignment steps steps and and save the STL file ﬁle for clear aligner therapy. The segmentation of teeth is an extremely fast and intuitive process, thanks also to the navigation menu that indicates the steps to be carried out: for each element, only the mesial and distal points must be marked, then the software will automatically calculate the segmentation curve using the contour gingival as a reference. However, the user is asked to correct the curve if there are smudges. Once the teeth have been segmented, it is possible to carry out the virtual set-up using a series of very interesting features: - The ability to view and control stripping. - Perform tooth movement functions both graphically with the handles, and with keyboard entry for greater precision. - The ability to view contacts with the antagonist arch. - The possibility to save and print the various movement steps in STL format for the production of transparent aligners. This feature must currently be paid for. (A) (B)

FigureFigure 2. ((AA,,BB)) In In the the orthodontic orthodontic module module there there are are the the teeth segmentation segmentation functions and the set set-up-up commands.

2.3. GuidedThe segmentation Surgery Module of teeth is an extremely fast and intuitive process, thanks also to the navigationThis is the menumain software that indicates module, the stepsand it to allows be carried the user out: to for design each element,implant onlysurgical the guidesmesial using and distal a few points simple must steps. be Although marked, the then module the software was created will automatically for implant-prosthetic calculate purposes,the segmentation in orthodontics curve using it can the be contoureffectively gingival used for as the a reference. design of However,templates thefor palatal user is asked to correct the curve if there are smudges. Once the teeth have been segmented, it is or vestibular temporary anchorage devices (TADs) for skeletal anchorage, thanks to the possible to carry out the virtual set-up using a series of very interesting features: fact that it is possible to absolutely customise the size of the implant to be inserted. It starts with- Thethe import ability toof viewtwo objects: and control a model stripping. scan in STL format, and DICOM files obtained from the CBCT exam. The software will then automatically match the two surfaces. Next, the TADs are inserted virtually, not using the available libraries, but by editing a new TAD that will be customised according to systematic choice. In this way, by modifying the apical diameter, cervical diameter, and collar height data, it is possible to use BSP with any implant company. The entire design of the surgical guide is very easy, intuitive, and free. Only the export of the guide in STL format is subject to a fee at a very low cost. Finally, through the functions of the GSR model, it is possible to generate a perforated model through the automatic Boolean subtraction of the STL volume of the TADs or the analog. In this way, BSP can be effectively used not only for printing the guide, but also for printing a perforated model to be used for the ‘one-step’ insertion of orthodontic devices (Figure 3A–C).

(A) Appl. Sci. 2021, 11, 6033 4 of 11

- Perform tooth movement functions both graphically with the handles, and with keyboard entry for greater precision. - The ability to view contacts with the antagonist arch. - The possibility to save and print the various movement steps in STL format for the Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 13 production of transparent aligners. This feature must currently be paid for.

2.3. Guided Surgery Module This is the main software module, and it allows the user to design implant surgical guides using a few simple steps. Although the module was created for implant-prosthetic purposes, in orthodontics it can be effectively used for the design of templates for palatal or vestibular temporary anchorage devices (TADs) for skeletal anchorage, thanks to the fact that it is possible to absolutely customise the size of the implant to be inserted. It starts with the import of two objects: a model scan in STL format, and DICOM ﬁles obtained from the CBCT exam. The software will then automatically match the two surfaces. Next, the TADs are inserted virtually, not using the available libraries, but by editing a new TAD that will be customised according to systematic choice. In this way, by modifying the apical diameter, cervical diameter, and collar height data, it is possible to use BSP with any implant company. (A) The entire design of the(B)surgical guide is very easy, intuitive, and free. Only the export of the guide in STL format is subject to a fee at a very low cost. Finally, through Figure 2. (A,B) In the orthodontic module there are the teeth segmentation functions and the set-up commands. the functions of the GSR model, it is possible to generate a perforated model through the automatic Boolean subtraction of the STL volume of the TADs or the analog. In this way, 2.3. Guided Surgery Module Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 13 BSP can be effectively used not only for printing the guide, but also for printing a perforated This is the main software module, and it allows the user to design implant surgical model to be used for the ‘one-step’ insertion of orthodontic devices (Figure3A–C). guides using a few simple steps. Although the module was created for implant-prosthetic purposes, in orthodontics it can be effectively used for the design of templates for palatal or vestibular temporary anchorage devices (TADs) for skeletal anchorage, thanks to the fact that it is possible to absolutely customise the size of the implant to be inserted. It starts with the import of two objects: a model scan in STL format, and DICOM files obtained from the CBCT exam. The software will then automatically match the two surfaces. Next, the TADs are inserted virtually, not using the available libraries, but by editing a new TAD that will be customised according to systematic choice. In this way, by modifying the apical diameter, cervical diameter, and collar height data, it is possible to use BSP with any implant company. The entire design of the surgical guide is very easy, intuitive, and free. Only the export of the guide in STL format is subject to a fee at a very low cost. Finally, through the functions of the GSR model, it is possible to generate a perforated model through the automatic Boolean subtraction of the STL volume of the TADs or the analog. In this way,(B) BSP can be effectively used not only for printing the guide, but also for printing a perforated model to be used for the ‘one-step’ insertion of orthodontic devices (Figure 3A–C).

(A) (C)

Figure 3. (A–C). Surgical moduleFigure for 3. TADs (A–C guided). Surgical insertion. module for TADs guided insertion.

3. Meshmixer Autodesk MeshMixer (Autodesk, Inc., Mill Valley, CA, USA) is an open-source software to create and edit 3D objects with a simple and intuitive interface. It is one of the many useful programs produced by Autodesk, a leading software house in the 3D design sector. At the time of writing, it is available as version 3.5, downloadable from the website www.meshmixer.com (accessed on 22 May 2021), and is available for both Windows PC and MacOS, completely free of charge and with a detailed user manual. The name is self- explanatory: the program allows the mixing of several meshes together in order to obtain new objects with a characteristic design. It also allows the user to ‘sculpt’ our 3D object using a series of tools such as volume brushes, surface brushes, symmetry tools and others. Since the application is free and non-commercial, its interface is perfectly designed to be easy to use. For those who want to use MeshMixer more seriously, many tutorials are available on the official website and on YouTube. In the orthodontic field, MeshMixer has multiple applications due to its versatility and the absence of registrations and costs [19–21]. MeshMixer allows the user to: - Repair holey meshes by closing holes in the STL file. - Edit STL models when there are surface aberrations linked to the incorrect reconstruction of portions of the tooth (for example in the case of metal or ceramic teeth that reflect the scanner light in a non-perfect way, and consequently the reconstruction software can interpolate an incorrect surface). - Convert models from open shell to closed surface format. - Mount the two arches in the virtual articulator in order to simulate and evaluate the patient’s occlusion, as part of a virtual mock-up. Appl. Sci. 2021, 11, 6033 5 of 11

3. Meshmixer Autodesk MeshMixer (Autodesk, Inc., Mill Valley, CA, USA) is an open-source software to create and edit 3D objects with a simple and intuitive interface. It is one of the many useful programs produced by Autodesk, a leading software house in the 3D design sector. At the time of writing, it is available as version 3.5, downloadable from the website www.meshmixer.com (accessed on 22 May 2021), and is available for both Windows PC and MacOS, completely free of charge and with a detailed user manual. The name is self-explanatory: the program allows the mixing of several meshes together in order to obtain new objects with a characteristic design. It also allows the user to ‘sculpt’ our 3D object using a series of tools such as volume brushes, surface brushes, symmetry tools and others. Since the application is free and non-commercial, its interface is perfectly designed to be easy to use. For those who want to use MeshMixer more seriously, many tutorials are available on the official website and on YouTube. In the orthodontic field, MeshMixer has multiple applications due to its versatility and the absence of registrations and costs [19–21]. MeshMixer allows the user to: - Repair holey meshes by closing holes in the STL file. - Edit STL models when there are surface aberrations linked to the incorrect reconstruction of portions of the tooth (for example in the case of metal or ceramic teeth that reflect the scanner light in a non-perfect way, and consequently the reconstruction

Appl. Sci. 2021, 11, x FOR PEER REVIEW software can interpolate an incorrect surface). 6 of 13 - Convert models from open shell to closed surface format. - Mount the two arches in the virtual articulator in order to simulate and evaluate the patient’s occlusion, as part of a virtual mock-up. -- SimulateSimulate the the surgical surgical set set-up,-up, moving moving an an arch arch with with respect respect to the to the antagonist antagonist in an in ex- an tremelyextremely simple simple way. way. -- DesignDesign orthodontic orthodontic bands bands that that can can then then be printed be printed with with the laser the- laser-meltingmelting technique tech- [22].nique [22]. -- DesignDesign any any other other prosthetic prosthetic or or orthodontic orthodontic structure structure (lingual (lingual retainers, retainers, retaining retaining devices,devices, palatal palatal bars, bars, etc etc.),.), which which can can be be saved saved in in STL STL format format and and printed printed in in the the most appropriateappropriate material. material. -- CreateCreate a a virtual virtual mock mock-up-up of of the patient using the libraries with ideal tooth shapes mademade available available for for free. free. Drawing, Drawing, saving saving the the project, project, and and exporting exporting the the STL STL file ﬁle are totatotallylly free. free. EvenEven with thesethese advantages,advantages, and and despite despite the the relative relative ease ease of use of foruse afor user a accustomeduser accus- tomedto CAD/CAM to CAD/CAM design, design, MeshMixer MeshMixer may not may be not easy be to easy use to for use an orthodontistfor an orthodontist or dental or dentaltechnician technician with low-level with low computer-level computer skills (Figure skills. 4(Figure). 4)

Figure 4. MeshmixeMeshmixerr can be used to repair meshes or create custom bands.

4. Viewbox ViewBox is a software developed by DHAL (dHAL Software, Kifissia, Greece), available in the 4.1.0.12 release for the Windows platform only at the time of writing, and downloadable from the website www.dhal.com/viewbox.htm (accessed on 22 May 2021). In the free version, all the native tools of the program are useable, but there is a waiting time of 30 s to use some tools. Therefore, the free version can be effectively used without any limitations for model analysis (Figure 5). Appl. Sci. 2021, 11, 6033 6 of 11

4. Viewbox ViewBox is a software developed by DHAL (dHAL Software, Kiﬁssia, Greece), available in the 4.1.0.12 release for the Windows platform only at the time of writing, and downloadable from the website www.dhal.com/viewbox.htm (accessed on 22 May 2021). In the free version, all the native tools of the program are useable, but there is a waiting Appl.Appl. Sci. Sci. 20 202121, 11, 11, x, xFOR FOR PEER PEER REVIEW REVIEWtime of 30 s to use some tools. Therefore, the free version can be effectively used7 7of of without13 13

any limitations for model analysis (Figure5).

FigureFigure 5. 5.Models Models opened in in Viewbox. Viewbox. Figure 5. Models opened in Viewbox. InIn the the latest latest version of of the the software, software, many many specific speciﬁc functions functions are included are for included 3D mod- for 3D els. ToIn thethese latest are version associated of the all software, analyses usedmany for specific 2D images functions such are as includedteleradiographies for 3D mod- or models.els. To Tothese these are areassociated associated all ana alllyses analyses used usedfor 2D for images 2D images such as such teleradiographies as teleradiographies or orsimple photographs. photographs. The The software software allows allows the user the to userrepair, to modify, repair, or modify, improve or the improve mesh the simpleof the model,photographs. and prepare The software the model allows for printing the user (Figure to repair, 6). modify, or improve the mesh meshof the of model, the model, and prepare and prepare the model the modelfor printing for printing (Figure 6). (Figure 6).

Figure 6. Mesh repair and scan edge optimisation. Figure 6. Mesh repair and scan edge optimisation. FigureViewBox 6. Meshis able repair to import and scanand analy edges optimisation.e 3D models from different formats (STL, OBJ, PLY).V iewBoxThe main is advantageable to import of ViewBox and analy is these 3D possibility models tofrom store different all patient formats data in(STL, a single OBJ, PLY).database, The mainwhether advantage photos, of X -ViewBoxrays, or scans. is the possibilityIn the daily to routine, store all this patient allows data for in greatera single database,ordering ofwhether patient photos, data archiving X-rays, andor scans. greater In ease the ofdaily information routine, thisbackup. allows The for software greater ordering of patient data archiving and greater ease of information backup. The software Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 13

Appl. Sci. 2021, 11, 6033 7 of 11

Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 13 is characterised by an impressive versatility regarding the range of analyses possible (Fig- ure 7). ViewBox is able to import and analyse 3D models from different formats (STL, OBJ, isPLY). characterised The main by advantage an impressive of ViewBox versatility is the regarding possibility the to range store allof analyses patient data possible in asingle (Fig- uredatabase, 7). whether photos, X-rays, or scans. In the daily routine, this allows for greater ordering of patient data archiving and greater ease of information backup. The software is characterised by an impressive versatility regarding the range of analyses possible (Figure7).

Figure 7. Examples of linear and angular measurements. FFigureigure 7. 7. ExamplesExamples of of linear linear and and angular angular measurements. measurements. Generating a customised analysis is very simple, and numerous tutorials can be found Gene onGenerating therating software a customised customised website. analysis analysis Measurements is is very very simple, simple, can and be and numerous linear numerous and tutorials angular, tutorials can be andcan found be involve pointsfoundon the selected on software the softwaremanually website. website. by Measurements the Measurementsoperator can or bepoints can linear be built linear and by angular, and software. angular, and involveIn and addition involve points to per- formingpointsselected selectedsimple manually andmanually byrapid the byanalyses, operator the operator or ViewBox points or points built allows by built software. the by development software. In addition In addition of to summary performing to per- reports of forminganalyses.simple andsimple It rapidis possibleand analyses,rapid to analyses, set ViewBox reference ViewBox allows values allows the in developmentthe order development to more of easily summaryof summary analyse reports reports the ofresults ofanalyses. analyses. It It is is possible possible to to set set reference reference valuesvalues inin orderorder toto more easily analyse the the results results obtained. In addition to classic metric analyses, it is possible to make superimpositions of obtained.obtained. In In addition addition to to classic classic metric metric analyses, analyses, it it is is possible possible to to make make superimposit superimpositionsions of of modelsmodelsmodels in in inorder order order to to to analyseanalyse analyse thethe dental dental movements movementsmovements occurring occurring occurring during during during therapy. therapy. therapy. Unlike Unlike Unlike most most most software,software,software, tooth tooth tooth displacements displacements displacements can can be bebe visualised visualisedvisualised tooth tooth-by-tooth tooth-by--bytooth-tooth by by carefully carefullyby carefully observing observing observing the the the individualindividualindividual position position position variationsvariations variations (Figure (Figure 88). ).8).

(A) (B) Figure 8. ((A,)B ) Example of a colormap created by superimposing two(B models.) FigureFigure 8. ( 8.A,(BA), BExample) Example of of a acolormap colormap created by by superimposing superimposing two two models. models. In addition to creating individual patient reports, it is possible to export directly to spreadsheets analyses carried out on different patients or on different models of the same In Inaddition addition to to creating creating individual patient patient reports, reports, it isit possibleis possible to export to export directly directly to to patient.spreadsheets All ana analyseslyses and carried patient out data on are different saved patients in an archive or on file different that can models be easily of the copied same spreadsheets analyses carried out on different patients or on different models of the same andpatient. saved All on analyses an external and disk patient to protect data are against saved indata an loss. archive ﬁle that can be easily copied patient. All analyses and patient data are saved in an archive file that can be easily copied and saved on an external disk to protect against data loss. and saved on an external disk to protect against data loss.

Appl. Sci. 2021, 11, x FOR PEER REVIEW 9 of 13 Appl. Sci. 2021, 11, 6033 8 of 11

5. Blender and the Blenderfordental Add-On 5. BlenderBlender and (Blender the Blenderfordental Foundation, Amsterdam, Add-On The Netherlands) is one of the most widelyBlender used (Blenderprograms Foundation, for processing Amsterdam, and editing The 3D Netherlands) images [19] is one[23]. of It the is mostavailable widely at www.blender.orgused programs for (accessed processing on and 22 editingMay 2021) 3D imagesfor Windows, [19,23]. iOS It is, and available Linux at platforms. www.blender. The softwareorg (accessed is completely on 22 May free 2021) and for open Windows, source, iOS,but compared and Linux to platforms. previous Theprograms, software it is muchcompletely more complex free and to open use source, in its original but compared version. toIt previouswas developed programs, for pure it is 3D much drawing more andcomplex requires to use CAD/CAM in its original modelling version. skills It was that developed are not common for pure among 3D drawing orthodontists. and requires To overcomeCAD/CAM this modelling complexity, skills Blenderfordental that are not common (www.blenderfordental.com among orthodontists. To, accessed overcome on this 22 Maycomplexity, 2021) has Blenderfordental developed add- (onswww.blenderfordental.com that transform Blender into, accessed a platform on 22 that May is very 2021) easy has todeveloped use and more add-ons complete. that transform The Blenderfordental Blender into a platformbasic module that is(model very easy designer) to use is and the more first modulecomplete. to Theobtain Blenderfordental if you want to basic use the module software, (model and designer) it has been is the specially ﬁrst module designed to obtain for theif you dental want world. to use With the software,this module and it itis has possible been speciallyto carry out designed many useful for the operations dental world. for bothWith thethis analysis module it of is cases possible and to th carrye modification out many useful of models, operations and for for preparationboth the analysis for 3D of printingcases and (Figure the modiﬁcation 9). of models, and for preparation for 3D printing (Figure9).

Figure 9. ReadyReady-to-print-to-print molds with plain bases or tweed bases. The models can be emptied or connected by by means of a vertical articulator.

ModelsModels can can be be loaded loaded and and oriented oriented in in almo almostst any any format format currently currently used used for for 3D 3D files. ﬁles. InIn the model designer,designer, orientationorientation is is performed performed by by the the operator operator selecting selecting four four points, points, or byor byadding adding the the articulator articulator module, module, it it is is possible possible to to obtain obtain a a moremore complexcomplex modelmodel alignment thanksthanks to to the the use use of of patient phot photosos and extraoral references. Once Once oriented oriented correctly, correctly, the modelmodel can can be be cleaned of of imperfections thanks thanks to to the the vast library of brushes present in blender,blender, similar similar to to those offered offered by MeshMixer, or by using the hotkeys provided by Blenderfordental.Blenderfordental. It It is is the thereforerefore simple simple to to inspect inspect the the mesh, mesh, close close any any holes holes present present on onit, eliminateit, eliminate scan scan defects, defects, and andcreate create clear clear and andsharp sharp edges. edges. It is also It is possible also possible to create to createbases forbases the fordigital the digitalplinth of plinth 3D models, of 3D models, and to prepare and to preparethe model the for model printing. for printing.Once the bases Once havethe bases been havecreated, been the created, software the allows software the allows user to the perform user to many perform operations many operations on the mod- on els,the models, including including linear, angular linear, angular and arch and measurements, arch measurements, creating creating removable removable dental dental elements,elements, separating separating individual individual teeth, teeth, analysing analysing occlusal occlusal contacts, contacts, analysing analysing lateral lateral and pro- and truprotrusivesive movements, movements, and andsimulating simulating the advancement the advancement of the of mandibular the mandibular arch archwith with a vir- a tualvirtual articulator articulator (Figures (Figures 10– 1013).–13 ). The software can be further integrated with the purchase of other useful modules, for example to reconstruct occlusal tables, to create templates for mock-up or design of occlusal splints, or removing the brakes. There are advanced functions for inter-model study: different models can be aligned with each other, the relative movements that have occurred can be analysed, and variation in arch shape can be evaluated. It is also possible to create guides for implant insertion with functions similar to those already described for BSP. To prepare models for printing, the software allows you to empty them while maintaining the desired thickness, to examine the direction of the normals, and to inspect the mesh for any distortions and sharp corners and for export. Finally, using only the Appl. Sci. 2021, 11, 6033 9 of 11

Appl. Sci. 2021, 11, x FOR PEER REVIEW 10 of 13 basic module, it is possible to add articular pins to models that allow bringing the printed Appl. Sci. 2021, 11, x FOR PEER REVIEWmodels back into the correct and desired occlusion. 10 of 13 Appl. Sci. 2021, 11, x FOR PEER REVIEW 10 of 13

FigureFigure 10. Occlusal contacts contacts analy analysedsed by by the the software. software. Figure 10. Occlusal contacts analysed by the software. Figure 10. Occlusal contacts analysed by the software.

Figure 11. Virtual articulator. FigureFigureFigure 11. 11.11. Virtual Virtual articulator. articulator. articulator.

Figure 12. Templates prepared for inserting bands. FigureFigure 12. 12. TemplatesTemplates Templates prepared preparedprepared for for for inserting inserting inserting bands. bands. Appl. Sci. 2021, 11, 6033 10 of 11

Appl. Sci. 2021, 11, x FOR PEER REVIEW 11 of 13

FigureFigure 13. 13.Examples Examples ofof linearlinear and angular angular measurements. measurements.

6. ConclusionsThe software can be further integrated with the purchase of other useful modules, for example to reconstruct occlusal tables, to create templates for mock-up or design of occlusalThe digital splints, revolution or removing of orthodontic the brakes. There practice are requires advanced both functions hardware for componentsinter-model and dedicatedstudy: different software models for the can analysis be aligned of STL with models each other, and alltheother relative files movements generated that by thehave digital workflow.occurred can Some be analysed, are closed-source and variation software, in arch shape developed can be evaluated. by the scanner It is also manufacturers possible themselves,to create guides while for others implant are insertion open-source with functions software. similar to those already described for BSP.To To use prepare open-source models softwarefor printing, effectively, the software it is allows important you to to empty be able them to while switch main- from one programtaining tothe another, desired thickness, and to use to several examine programs the direction at the of the same normals, time, sinceand to each inspect has the specific characteristicsmesh for any anddistortions functions and thatsharp must corners be integrated. and for export. Finally, using only the basic module,While it low is possible operating to add costs articular are the pins main to models advantage, that allow open-source bringing the software printed is mod- generally associatedels back into with the a correct longer and learning desired curve, occlusion. since programs are not dedicated to particular instruments. However, free online tutorials are available that allow the user to quickly 6. Conclusions learn the functions and commands of programs, and thereby automate many processes and saveThe time. digital The revolution communities of orthodontic and forums practice that arerequires created both around hardware open-source components software and dedicated software for the analysis of STL models and all other files generated by the also help in its development and dissemination. digital workflow. Some are closed-source software, developed by the scanner manufac- New open-source programs will lead to new perspectives in the dental industry. turers themselves, while others are open-source software. Indeed,To if use the open costs-source for accessing software moderneffectively, digital it is important technologies to be able remain to switch high, from even one though theyprogram are likely to another, to decrease and to in use the several coming programs years, the at the use same of open-source time, since each software has specific can help to bringcharacteristics new generations and functions of dentists that must closer be tointegrated. the digital world. While low operating costs are the main advantage, open-source software is generally Authorassociated Contributions: with a longerConceptualization, learning curve, F.F.C. since and programs G.O.; methodology, are not dedicated M.B.; software,to particular F.F.C. and G.O.;instruments. validation, However, D.D. and free M.B.; online formal tutorials analysis, areD.D.; available investigation, that allow F.F.C.; the user data to curation, quickly G.O.; writing—originallearn the functions draft and preparation, commands F.F.C. of programs, and G.O.; and writing—review thereby automate and editing, many processes M.B. and D.D.; supervision,and save time. D.D.; The project communities administration, and forums M.B. that All authorsare created have around read and open agreed-source to software the published versionalso help of the in manuscript.its development and dissemination. Funding:NewThis open research-source received programs no externalwill lead funding. to new perspectives in the dental industry. In- deed, if the costs for accessing modern digital technologies remain high, even though they Institutionalare likely to Review decrease Board in the Statement: coming Notyears, applicable. the use of open-source software can help to Informedbring new Consent generations Statement: of dentistsNot applicable. closer to the digital world. Conflicts of Interest: The authors declare no conflict of interest. Appl. Sci. 2021, 11, 6033 11 of 11

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