Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics

Abstract

Making use of 3D-printed teeth models in teaching students offers an innovative approach. Empowering a highly efficient digital science to improve teaching. This gives opportunity to learn and enable intuitive dentist and student-patient communication. Clear and engaged satisfactory experience for teacher, student and patient. Thanks to the perfect representation of teeth anatomy, making use of 3D models in the teaching of endodontics may well be recommended as holding substantial potential in improving overall quality of training at the preclinical stage, with a view to appreciably reducing overall risk of encountering complications during the actual clinical work. The mistakes made by the students, for example, at the access cavity for root canal treatment stage were assessed with the help of 3D models, as well as their overall, hands-on learning progress was evaluated. Also in the clinical process, before the procedure with the participation of a patient, a student or a specialist may perform a treatment procedure on a tooth printed in 3D, based on tomography, under the supervision of an experienced specialist. 3D printing digital solutions and the popularization of these solutions around the globe are helping dental clinics and hospitals to effectively and efficiently achieve digital transformation.

1. Introduction

In the following chapter, I want to present the possibilities of using 3D printers and 3D printing in the practical clinical teaching of endodontics. In this respect, the 3D printing of tooth models, needed for root canal therapy practice, and the virtual endoscopy technique are the most relevant for teaching [1, 2, 3, 4, 5].

The adoption and adaptation of the latest advances in digital technology, such as three-dimensional (3D) printed dental objects, have influenced the teaching and treatment of cases that cover virtually the entire field of dentistry [6].

This technology offers a unique setting for the development of clinical and educational treatment, as demonstrated by publications in the field. Using a conjunction of three classic technologies, already used in medicine, but combined all at once, results in modern performance in education and clinical treatment. This contributes to creating opportunities for the development of dental medicine, which is constantly improving in clinical, educational and, of course, research contexts. In order to benefit from their treatment, dentists in the current era can already interact with the available multidisciplinary knowledge and 3D printing to understand the essence of the new technology and meet the challenges of the digital medicine era. It, therefore, becomes legitimate to introduce this as a subject in the teaching process of students [4, 7].

All over the world, the digital solutions of 3D printing and their popularisation are helping teaching units and hospitals to achieve digital transformation in an effective and efficient way, of which this book and the chapter dedicated to education is a good example. Furthermore, in dentistry and facial areas close to the oral cavity, this technique is widely used in head and neck surgery (craniofacial and orthognathic implants), personalised oral soft tissue regeneration, orthopaedics (fracture printing in orthopaedic trauma surgery, 3D imaging), 3D printing and virtual 3D planning in endodontics, ophthalmology, template printing in mandibular (and surgical) reconstruction, prosthodontics (replication techniques for making e.g., digital dentures and overdentures, also on implants), periodontal regeneration and repair (periodontal implants), orthognathic surgery, 3D physical models of teeth, printing of bone implants and virtual endoscopy, as well as in autotransplantation [8, 9, 10, 11, 12, 13, 14, 15].

In the aforementioned areas, prior practice is recommended before starting treatment. The initial use of templates or 3D-printed models can facilitate treatment planning and reduce the risk of complications during clinical procedures performed as part of the teaching process [16].

3D printing consists of three stages, which ensure full integration of 3D digital dental solutions, namely, acquiring 3D data by means of cone-beam computed tomography (CBCT) (or other stationary and intraoral scanners, if necessary; in the study in which I participated, a 3D scanner ATOS Triple Scan III (GOM, Germany) was used), processing and designing the data using professional dental software, after transferring the obtained scans into an electronic version, for example, Model Creator (Exocad, Germany) or standard software provided by the manufacturer, and production of 3D dental objects from the obtained digital 3D dental models using, for example 3D resin printers, such as 3D Form 2 (Formlabs), employing materials with similar physical properties, for example hardness and brittleness, to the reproduced tissues (Figures 1–4) [1, 4, 16].

Figure 1.

3D printer kit (Formlabs), from left to right: Form cure, form wash and 3D printer.

Figure 2.

Already printed tooth on the platform.

Figure 3.

Printed molar tooth on the platform, before inserting into the washer. Tooth length is 18,08 mm.

Figure 4.

Already printed molar tooth, after using form washer, on the platform of form cure.

Dental applications of 3D printing adopt one or more of the following common technics: Stereolithography (SLA), fused deposition modelling (FDM), MultiJet printing (MJP), PolyJet printing, ColorJet printing (CJP), digital light processing (DLP) and selective laser sintering (SLS) also known as selective laser melting (SLM). The most popular technique in teaching root canal treatment is the first mentioned that is SLA printing, for example using the dental model resin [10, 17].

2. 3D printing teaching discussion

Endodontics is such a field of science that is based on approximately 90% of manual skills. 3D printing technologies significantly improve and accelerate the acquisition of root canal treatment qualifications by students, while the use of 3D replicas of teeth obtained by means of 3D printing has contributed to the enhancement of qualification of teaching centres and the correctness of performed root canal treatments in undergraduate education. Printing 3D models is an innovative technique in the field of treatment and teaching (by reducing the likelihood of errors during treatments). 3D printing is the name used to describe the ‘manufacturing approach’ that creates a material by adding layer by layer. A student with little experience in root canal treatment will first have the opportunity to perform the procedure on a 3D replica of a real tooth. Thus, the aim of such a teaching process is to increase the effectiveness of correct root canal treatment in doctors during their speciality training in the area of restorative dentistry with endodontics [1, 4, 5, 17, 18, 19].

2.1 Teaching experience

On the basis of my experience and many years of teaching, I have identified the important elements needed in the development of teaching methodology in clinical classes. The most difficult part of the work for the student is to directly move from phantom classes to clinical classes, which significantly increases the demands placed on the student. A number of studies report that even the best-organised phantom classes are not able to translate the acquired skills, even if they are very good into the same tasks in clinical work. This is influenced by development of manual skills, which takes time. This phenomenon is related to ‘brain plasticity’, as well as the development of the right emotional attitude. From this one can conclude that the introduction of a didactic element of an intermediate nature, to play relatively smoothly a transitional role between phantom and clinical activities, is a very important element of the teaching process. It has turned out that 3D technology with 3D printing fits almost perfectly into these realities. This is possible because we use real-world models for pre-clinical and clinical learning [1, 2, 3, 4, 18].

Endodontics, or more precisely root canal treatment, cannot be taught strictly speaking; apart from the knowledge, which of course has to be learnt, manual skills need to be acquired. Clinical work involves performing tasks on obscure objects, which creates additional problems in gaining experience, which usually takes several years of continuous practice in this area of knowledge. In addition, the patient needs to be explained the course of treatment on the part of the tooth that cannot be seen and the need for necessary treatment. Many devices, instruments and materials are required for adequate endodontic treatment. Various types of diagnostic materials and devices have already been introduced over the years, including digital x-rays as well as digital cone tomography, intraoral cameras, fibre-optic endoscopes, 3D atlases (these are mainly physiology-based), operating microscopes and digital intraoral cameras. Fibre optic endoscopes (e.g., Ora scope) are particularly close to our field of application, as they are used in the tooth chamber to visualise the inside of the root canal (in order to obtain information for the doctor and patient and thus implement a favourable treatment plan). They can of course also be useful in the classroom to show a particular clinical issue on a monitor to a larger number of accompanying people, which without the use of a monitor would only be visible to the person performing the procedure. 3D printing and virtual endoscopy are better and more modern solutions. That is, what can be visualised better is of particular importance, so that the endodontist and the student are well-informed in the area of diagnostics, and modern technology has created new methods of image enhancement in the form of a model rather than the scans themselves. In this situation, in fact, any clinical problem can be visualised, printed and discussed in the wider community. In addition, the clinician relies on images, verbal information and numerical data, for example statistical or digital analyses (digital photography, digital x-rays and computerised visualisations), in communicating with the patient, in the process of assessing the patient and when selecting treatment options [2, 3, 4, 20].

2.2 Teaching objectives

Planning the technology acquisition strategy is the factor that determines the needs of an individual. Clinicians should focus on what is needed to provide the best solution for the patient and to establish clear needs. The adoption of new technologies, especially in teaching, must be based on clear objectives of the systems that are being implemented. Planning should be based on three areas: the main objective of the plan, the implementation plan and the measurement phase.

Over the years, I have relied on this scheme in the pattern of research I have done. The main objective of the plan is to convince us of the need to implement the technology, why it is needed and what the teaching benefits are? What goals must be achieved to have a problem-free implementation? All the information generated and processed in the practice and the way it is handled constitutes the strategic plan for the technology. Management of information received from the patient, students and other clinicians provides the basis for the transfer of materials before, during and after treatment. The implementation part involves planning and day-by-day practice until the implementation programme runs smoothly. Training and retraining of staff are essential in a fully functioning plan. The technology being implemented is advanced, so the fixed working hours of training and consultation with the available laboratory are essential. Courses and training are necessary to acquire basic skills. The implementation evaluation phase is important for verifying that the implementation plan is well-led and followed by improving performance, especially in terms of practical and manual skills. During the implementation of a technological system, a method of evaluating their progress towards the objectives implemented must be developed. Student and patient education is an important positive experience and part of any modern treatment, including endodontic treatment [1, 2].

In the first step, students were introduced to the analysis of 3D cone-beam tomography scans (Figures 5 and 6) to illustrate to students the results that would create in themselves the need to use this technology for their intended clinical purposes. To this end, a study (according to randomisation principles) was conducted to illustrate the quality of cavity preparation and the placement of fillings in extracted teeth in such a way that the student could learn about the quality and outcome of their work, with the realisation that this has clinical implications. That is, students were able to see the quality of their cavity preparation (e.g., the homogeneity of the prepared walls, as well as the seal of the placed fillings). Randomly allocated teeth were selected for the study and standardised cavity preparations were planned, followed by filling, using an adhesive technique with composite. The teeth prepared in this way were then scanned using CBCT and the scans were evaluated in IrfanView and Fiji Is Just ImageJ software. The teeth were then subjected to thermocycling and later subjected again to the same CBCT examination. The students were then able to evaluate the results of their work accurately on images not only from cone tomography scans but also after 3D visualisation (Figure 7). To make the work more tangible, of course, the examined teeth were also assessed under an optical microscope with a micrometre scale. The analysis results from the CBCT and virtual scan images were then compared with the images of the specimens themselves and similar results were obtained. This was proof that digitisation produces measurable comparable results and can be further implemented. The following pictures show the correctness of the preparation, that is the box-like shape of the cavity, as well as, in some situations, the loss of fillings, the protrusion beyond the standard curvature of the tooth crown, which was indicative of, for example, the care taken in finishing the filling or leaks in the adherence of the fillings. Only after these analyses did the students realise the need for quality in their work when they were able to make feedback visualisations of their work. They saw the possible consequences of developing pulpitis, for example in the case of a leakage, where it was not a phantom tooth but a real tooth with complications already present. The use of 3D model aids has significantly accelerated the progress of students’ work and changes in thinking but has also created the need to introduce 3D techniques into the format of didactic teaching [1, 2].

Figure 5.

Cone beam tomography (CBCT) image of molars during the assessment of cavity preparation and fillings.

Figure 6.

Cone beam tomography (CBCT) image of molars during the assessment of cavity preparation and fillings, tooth cross-section view.

Figure 7.

Virtual 3D image of teeth obtained from cone-beam tomography scans. Visible preparation of cavities and applied fillings.

Overall, when it comes to digitalisation, computers and software are invaluable in practice. Most clinicians are unable to consider practising with no digital solutions applied in their treatments. However, technology cannot replace the quality of care itself, especially in root canal treatment. This view may change with the implementation of 3D printing, as here the use of technology is an advancement in the acquisition of clinical skills, by working on real models of real clinical problems. This changes the student's thinking from a generic job, where a nameless phantom is treated, to the realisation that they are treating a specific tooth of a real person. In the study I proposed to the students, in my opinion, it should have been quite simple to open the chamber of the teeth, as this is the most visible part of the root canal treatment procedure. Obviously, this is the stage that determines proper access to the root canal and has an impact on the subsequent strength of the tooth crown as well as the ability to maintain patency of the root canal. We adopted a scale of 0–7 for the study (0—no mistakes, 1—one wall incorrectly prepared, and so on, 6—perforation and 7—damage eliminating the possibility of further work) (Figure 8). The entire study was performed according to randomisation rules. The principles of work and preparation were strictly defined in numerous lectures and training sessions in order to obviously standardise the study. The experience gained from this research work is described in this chapter [1, 2, 3, 4, 5].

Figure 8.

It shows graphical visualisation of results of preparation: incisors, premolars and molars teeth.

A total of 9 students with little root canal experience took part in the study. The 3D prepared teeth included the lower incisors (there were a total of 30 3D teeth, 10 per student), the upper premolars (also 30 3D teeth, 10 per student) and finally the lower molars (also 30 3D teeth, 10 per student) (Figure 9). At the beginning of the study, there were errors in all central incisor preparations (Figure 10), in about 67% of the premolars and in about 72% of the molars. However, after ten consecutive preparations, this result was, respectively, only 19% of errors for incisors, around 14% of errors for premolars and around 33% of errors for molars. All these results between the start and end points are statistically different. The 90 3D tooth models used in the study were produced from 3D scans of extracted teeth [1].

Figure 9.

Example printout, 3D group of premolars.

Figure 10.

Example of perforation of incisor tooth, number 20.

The students gained once again a very large and interesting experience during their own assessment of their own specimens after performing only the root canal treatment procedure. The specimens were then visualised using a special scanner so that the preparation could be viewed in depth. In addition, during the practical classes, students were able to use the training microscope (only when assessing their own prepared earlier teeth as a feedback instrument) to evaluate their own work. They themselves witnessed their own growing experience with each model they prepared and concluded that the effectiveness of this method led to safer treatment for the patient. For example, all students preparing incisors only started to eliminate crown damage and perforations one by one by the fourth model, and by the seventh model, all three students were free of these two most serious complications. In molars, for example, one student in three, in this group, only avoided perforation and chamber damage in the fifth model. In general, it could be assumed that all nine students showed significant improvement in preparation from the seventh model. It can, therefore, be assumed that practical coursework tends to make sense with ten preparation attempts. I would also like to mention that the students were assessed after the first preparation of the 3D model, just in case, to make sure they knew what a correct preparation was and to avoid copying mistakes. They also had in front of them constantly visible patterns of the correct preparation [1].

In our study with students, 3D models are produced based on real patient teeth. This provides the students with an almost realistic simulation of preparation in a real clinical situation.

I have noticed that even though it is possible to explain to students the whole procedure step by step, as well as to describe the complications that can occur after what we call an abnormality in the preparation, it is still only when they practise using real models from specific people that they realise the risks and responsibilities that accompany their work. Perforated tooth models are a fairly common complication, although the long axis of the tooth is visible. I would like to mention that in the clinical setting, except for examples of advanced periodontitis, the entire area of the long axis of the tooth and the curvatures of the root are not visible because, as we know, they are hidden in the alveolar bone. I would like to point out that the masses to be printed were very close to the hardness of the bone, so the preparation in the 3D model of the tooth was overall quite close to real conditions [1].

2.3 Historical background

In 1983, Charles Hull was the first to introduce a 3D printer. He applied the method of stereolithography in this technology. In order to characterise the 3D printing process, three basic steps can be identified: scanning of a selected tooth (e.g., using cone-beam tomography (CBCT)), digital reconstruction of the scanned image (e.g., using available dedicated software) and then 3D printing of a model of the tooth (e.g., using dedicated printers) [20].

The requirements for precision printing have enabled the use of 3D printing in medicine, since 1990, which, in the first instance, found its way into prosthetics. With regard to history, dental education was based on extracted teeth, resin blocks or commercially available resin teeth for pre-clinical training and the possibilities that the anatomy rooms had, according to accepted criteria [20].

2.4 Scope of knowledge

In the literature, there are isolated publications on the use of 3D printers in dentistry and in the education of students. Carrying out a study to improve the quality of didactic education will be another attempt to improve the skills in the field [4, 5, 18, 21].

The development of this technology makes it possible to improve treatment and teaching techniques by reducing the risk of errors during procedures primarily in clinical teaching, based predominantly on educational models and clinical simulations. From a didactic point of view in the teaching process, demonstrating the effectiveness of this teaching method is of particular importance. A student with little experience in root canal treatment will be given the opportunity to perform the procedure first on a 3D replica of a tooth that is in the root canal treatment plan in his or her class. This will enable them to avoid mistakes resulting from little clinical experience. The same is true for doctors—in difficult clinical cases.

2.5 Teaching pathway and controlled learning process

A trainee doctor with little experience in root canal treatment will have the opportunity to perform a complex procedure on a 3D replica of the tooth first before treating the patient's tooth in question. This will enable them to avoid mistakes resulting from little experience in different clinical situations. Take, for example, a situation where there are obliterations of the root canal, in which the still unobstructed canal lumen is present in the more apical parts, gradually narrowing the root as a result of, for example dentin deposition due to age, the presence of caries, orthodontic treatment, systemic diseases or the occurrence of trauma. If inflammation, such as pulpitis or periodontitis, is detected on clinical or radiographic examination, intervention is indicated. The risk of a complication when treating a root canal with obliteration can account for up to 75% of perforation incidents when attempting to localise and negotiate calcified canals. Students, as shown in the study, have difficulty even opening the chamber of a tooth that is not obliterated. In the classic procedure, the risk of perforation is reduced by methods that provide straightforward access to the canal orifice and the use of specialised instrumentation, such as the surgical microscope and ultrasonics. A trainee with little experience may choose unfavourable paths of access cavity preparation and under realistic conditions irreversibly damage the tooth. It is based on the fact that, when planning the opening of the tooth chamber or the angle of insertion of instruments for root canal negotiation or removal of obstruction during work, we may decide that a different insertion path may have been more advantageous, which then exposes the tooth to the loss of additional dental hard tissue [18].

The use of cone beam tomography in today's dentistry is widespread and frequent. Because of this, many patients now have a CBCT examination for various reasons (which, together with the favourable radiation dose, facilitates this examination), which is the basis for printing 3D models. The lack of 3D models may cause clinical errors, due, for example, to insufficient data on the treated tooth space, which, as I have already described, may contribute to further complications, for example strip perforation or unnecessary loss of hard tooth tissue.

Student training consists of learning how to operate the printer, resin selection, tooth preparation technique, virtual assembly of data obtained from cone beam tomography (simple single tooth models) to produce a virtual 3D tooth model, and the printing process. The plan of the digital model is already important, as already at this stage students draw a number of conclusions about the issues related to their planned treatment. In a didactic setting, the teaching assistant often helps with clinical work, but nevertheless cannot do the work for the student the whole time. In the end, the students have to perform the set procedure themselves. Due to the mere lack of manual dexterity, every clinical procedure is an emotional burden and is fraught with the risk of complications due to the lack of an imagined treatment endpoint. One of the first principles of medicine refers to the statement: ‘before you start the treatment, imagine what the end will look like’. Only virtual planning and working on real models of the scanned tooth can help build up an idea of the intended positive expected treatment results and identify the cause in the case of unintended complications [18, 21, 22].

During the course of their studies, when operating a 3D printer, students will learn about various parameters, including XY resolution, which is the most common specification used to describe the quality or detail of a print and is analogous to size in pixels, it is the smallest movement the printer's laser can make in a horizontal layer. However, XY resolution does not take into account many variables that affect the quality of a component. In fact, professional 3D printers have more than 100 different settings that affect XY resolution. Layer thickness or Z-height usually describes the surface finish of the component, meaning that a lower layer height improves the surface finish. In addition, the thickness of the layer is influenced by the type of resin and the printer settings [18, 32].

In accordance with the growing interest in 3D printing technology during my consultations within the dental community (when presenting research at symposia and conferences), as a specialist in restorative dentistry with endodontics, when presenting the study described in this manuscript, I have received numerous communications regarding the provision of training in 3D printing of teeth in the context of considering the implementation of such courses. This demonstrates a particular interest in this technology. All those interviewed agreed on the potential of this technology in all its applications, particularly in decision support for complex root canal treatment cases.

3D printed tooth models and electronic images, used as a graphical guide to visualise the problem in question, can help operators plan and manage complex non-surgical and surgical endodontic treatment and develop skills, thus becoming an invaluable educational resource. Learning from one's mistakes without compromising the patient's health is a leading element of this technique. Three-dimensional (3D) volumetric images provide a three-dimensional view of the anatomy, facilitating treatment planning and teaching; when designing a 3D model, students must also model the area of their preparation, which forces them to familiarise themselves with the treatment.

2.6 Non-surgical endodontic treatment

Therefore, a study on non-surgical treatment using 3D printing of teeth, comparing a group of people who will be opening teeth for root canal treatment, having first opened 3D replicas of these teeth, with a group of people who will be opening teeth for root canal treatment without first being able to explore the anatomy of the teeth, could be used in endodontics as a means of teaching students. This contributes to the understanding of tooth morphology, for example the simulation of tooth chamber opening and root canal preparation [1].

In the studies I participated in, the study design was as follows. The extracted teeth (incisors, premolars and molars) were scanned using cone beam computed tomography (CBCT), and the resulting data was then analysed with the 3D model visualisation software, EXOCAD and Model Creator.

The 3D teeth were made from Dental Model compound and printed using a Form 2 3D printer (Form 2, CadXpert), using computer-based stereolithography (SLA) technology. The device is medically approved, with a special focus on dentistry, due to its high-resolution printing capabilities.

90 teeth were prepared. Thirty identical teeth, molars, premolars and incisors, were printed as replicas of the treated natural teeth, one from each tooth group, made on the basis of the corresponding natural tooth. They were divided into nine groups, randomly allocating 10 teeth of the same shape to each group. Within each group, the teeth were numbered in sequence. Dental students with little experience in root canal treatment were assigned to do the work, one to each group.

Differences between the start and end points of the tooth chamber opening procedure for root canal treatment according to the adopted criteria were studied for 90 teeth.

Dental students with little experience in root canal treatment were assigned to perform the preparation. Next, the correctness of performing these procedures was assessed by two independent researchers, according to the adopted criteria. The correct procedure of opening the tooth cavity and making the correct access to the root canal entrance was evaluated. Teeth were scanned using the cone beam computed tomography (CBCT) technique and the data was analysed in the three-dimensional visualization software.

The correctness of the execution of these procedures was then assessed by two independent investigators (experts and the students themselves under the microscope), according to the adopted criteria: 0—no errors, 1–4—wall correction, 5—chamber floor correction and 6—perforation (mesial and distal wall in incisors and lateral walls in molars). (The study was approved by the bioethics committee, no. 122.6120.235.2016) [1].

2.6.1 Results obtained

The data obtained were analysed using Statistica 12.0 software. The Kruskal-Wallis test and the multiple comparisons test were performed for the entire group, and significant statistical differences were found P = 0.0001. The results are also shown in Chart 1. Premolar teeth were the most favourably prepared, followed by the incisors and molars [1].

2.6.2 Presentation of the results

The study showed that each subsequent tooth cavity preparation procedure was more successful. This is best seen in the comparison between the first and last replicas. In the process, students gained experience.

Printing single objects in three dimensions, using special printers and software, is a very innovative and promising technology for pre-clinical teaching and treatment. The use of a 3D printer is justified in the teaching process [1].

2.7 Surgical endodontic treatment

In the surgical planning of endodontic treatment, we use 3D printing, with additive manufacturing and rapid prototyping techniques, which are used with satisfactory accuracy, mainly in diagnosis and surgical planning, and then in the direct production of implantable devices. The main limitation is the time and money spent on generating 3D objects, and the fact that the type, material and layer thickness of the printer affect the accuracy of the printed models [15, 28].

3. Virtual endoscopy

An interesting method based on the 3D printing process is a virtual simulation (Figure 11). It is used in medicine, and also in dentistry, to teach dental students, including surgical techniques. On this basis, 3D prints of the areas of interest can be made, although digital 3D visualisation alone may already be enough. This means that we are referring to the clinical use of virtual endoscopy. Significant software developments in image processing, resulting in breakthroughs in image editing, as well as the development of the CT and MR scanners themselves, have made it possible to create virtual models. As a result, we now have a method for obtaining volumetric reconstructions, as well as virtual endoscopy, which is based on these reconstructions. This technique allows for the spatial presentation of the anatomical and morphological structures of the human being (Figure 12). Images obtained with this virtual technique are produced as a result of a CT or MR examination, without the need for classic clinical examinations such as endoscopy. This offers the possibility of non-invasive diagnosis and visualisation of small tissue structures (Figures 13 and 14). I have demonstrated the use of virtual endoscopy in a selection of images. I underwent a CT scan used in medicine. Based on the data acquired, soft and hard tissues, including teeth, were reconstructed (Figure 15). On the basis of the 3D images obtained, successive tissue layers can be inspected, for example by removing superficial structures to visualise the deeper ones. The following pictures show further examples (Figures 16–20). Particularly important are the images of the tooth after root canal treatment with the visualisation of the root canal filling and the canal lumen of the following tooth during root canal treatment, after preparation using a rotary system. In the visualisations, the texture of the scanned image is slightly overscaled, so a 3D programme is required to be able to accurately sharpen the object we want to print. This is why specialist knowledge and experience in the field, as well as training and courses, are needed. In practice, on the basis of the images reconstructed for the virtual endoscopy technique, once the images have been converted to the format used by the 3D printer, the given images can be printed. Virtual endoscopy is also a basis to learn, how to create a virtual 3D model for pre-bioprinting process based on computer numerical control machining processes. In this area, computed tomography is used and magnetic resonance imaging is used too. When a virtual model with endoscopy imaging of tomographic reconstruction is done, it is possible to print layer-by-layer, for example tissue-like structures, 3D models, using a special material known as bio-links [4, 22, 23, 24, 25, 26, 27, 28, 29, 31].

Figure 11.

3D reconstruction (of my head), frontal view and deeper structures of the skull visible under the skin surface.

Figure 12.

3D reconstruction (of my head), side view and deeper cranial structures visible below the skin surface.

Figure 13.

3D reconstruction (of my head), lateral view and visible soft tissues including blood vessels and under the surface of the skin.

Figure 14.

3D reconstruction (of my head), oblique view and visible hard tissues including structures inside the skull.

Figure 15.

3D reconstruction of a tooth after root canal treatment with filled root canals.

Figure 16.

3D virtual reconstruction of the inner part of the tooth root canal after preparation with the Flex Master rotation system.

Figure 17.

3D virtual reconstruction of the outer part of the root canal, the tooth apex after preparation with the rotary system and Flex Master.

Figure 18.

3D virtual reconstruction of a molar tooth.

Figure 19.

3D virtual endoscopy, root canal and molar tooth.

Figure 20.

3D virtual endoscopy, root canal, molar and view inside the orifice of the tooth.

4. Bioprinting

The 3D bioprinting needs three steps, as 3D printing,. Pre-bioprinting, bioprinting and post-bioprinting. Bio inks are used in bioprinting step using: a liquid mixture of cells, matrix and nutrients. Post-bioprinting is just a final process to create a stable structure from the biological material. 3D bioprinting is also used adapted stereolithography process, and also digital light processing is used too. Future directions of this study cover two main technologies: Bioprinting techniques and biomaterials.

Finally, it can be mentioned that students in the teaching process can already learn to use 3D printing to treat pulp tissue, in the sense of endodontic treatment, by using a bioprinted tissue scaffold. Bioprinting is a very innovative and promising technology for treatment and teaching. The technique has applications in all scientific fields and is also being implemented as a teaching component. Oral soft tissue engineering involves the reconstruction or reestablishment of oral and maxillofacial function and aesthetics. As an emerging technology of the early 21st century, three-dimensional (3D) bioprinting offers great potential for application in scaffold development and tissue and organ engineering. Although oral soft tissues include the dental pulp, periodontium, gingiva, oral mucosa and salivary glands, as well as the associated skin in the maxillofacial area, vascular, muscular and neural tissue, the current use of 3D bioprinting in oral soft tissue reconstruction is mainly limited to dental pulp regeneration (Figure 21). A variety of bio-inks is used to introduce dental pulp cells into the dentin matrix to restore the dental pulp tissue. 3D bioprinting has only been described in a few in vitro studies on periodontal ligament reconstruction and salivary gland culture; 3D bioprinting used to regenerate gingival/oral mucosa tissue has not been demonstrated yet. In the 3D printing process, machines such as a robotic bioprinter are already used, and even compact microfluidic bioprinting platforms are in use. Also, it is important to make more easier and intuitive software for less advanced practitioners [14, 30, 31, 32, 33, 34].

Figure 21.

3D virtual reconstruction of the spatial arrangement of the pulp tissues.

5. Summary/conclusions

Enhancement of a highly efficient 3D digital solutions improves the overall clinical experience when printing 3D models. A set of available clinical tools helps teachers to assess and pre-design the scanned elements. Electronic 3D models help the dentist to have better, more intuitive communication with the student and the patient, which gives a clear message and the possibility to involve the student and the patient themselves in a satisfying experience. In the scan-to-print process, dental models can be edited and printed, enabling direct visualisation of the treatment plan (e.g., in the case of prosthetics, the restoration production cycle is shortened). Students could, by gaining experience, skilfully change the treatment plan. This was possible after using virtual endoscopy and 3D printing. I encourage you to broaden your knowledge in developing scientific topics such as biomaterials, biomedical engineering, additive manufacturing and tissue engineering, and to obtain insights into the future of biofabrication.

Acknowledgments

I would like to thank all of the students who participated in the study and colleagues from work.

Conflict of interest

‘The authors declare no conflict of interest.’

Acronyms and abbreviations

SLA

Stereolithography

FDM

fused deposition modelling

MJP

MultiJet printing

PJP

PolyJet printing

CJP

ColorJet printing

DLP

digital light processing

SLS

selective laser sintering

SLM

selective laser melting

CBCT

Cone beam computed tomography

CT

computed tomography

MR

magnetic resnonance