3D Printing and Airway Stents

*Carlos Aravena and Thomas R. Gildea*

## **Abstract**

A central goal of an airway stent is to restore patency by preventing restenosis, holding the tracheobronchial wall, or occluding fistulas. Complications with stents, however, are frequent and can have grave repercussions. Stents are therefore viewed as a last resort in cases where other forms of treatment are ineffective. Furthermore, it is common for people with complex airways to have airway stents that do not fit them well, which can result in several complications. Three-dimensional printing technology was developed at the turn of the 20th century. It has been employed in a variety of applications and has transformed healthcare. This technology has mainly been employed in respiratory medicine to develop three-dimensional models of the airways and to make airway splints and prostheses to treat central airway diseases. In the past ten years, it has transformed and advanced personalized medicine, enabling the creation of patient-specific stents for people with complex airway diseases. Threedimensional printing might be used to create a patient-specific stent that would lessen risks, enhance the quality of life, and eliminate the need for additional procedures. This chapter discusses the most recent developments in three-dimensional printing technology, how they are being used to create airway prostheses to treat complex airway illnesses and the current body of research that supports their use.

**Keywords:** three-dimensional printing, 3D-printing, bronchoscopy, airway stents, patient-specific airway stent, computer-aided design, three-dimensional airway mold, 3D airway mold

## **1. Introduction**

A wide range of benign and malignant illnesses can impact the airway [1]. The diagnosis and treatment of these disorders rely significantly on bronchoscopy [2]. After non-invasive treatments are found to be ineffective, therapeutic bronchoscopy attempts to enhance the patient quality of life, reduce symptoms, and provide significant palliation [1, 3]. Flexible or rigid bronchoscopy (RB) is a procedure that can deliver a variety of therapeutic modalities, among them stent placement play an important role [1, 3–6]. Reestablishing patency, preventing restenosis, stabilizing the tracheobronchial wall, or occluding fistulas are the primary purposes of an airway prostheses [7, 8].

Stents could be made of metallic wire mesh, silicone, or a combination of these materials (hybrid), as well as various sizes and shapes [9]. It is typical to experience complications like migration, granulation, infection, and mucus clogging [7, 10–13]. Therefore, stents should only be temporary when no other methods can achieve appropriate and long-lasting patency [5, 14–16].

Because implantation may last long and result in a high rate of complications, using stents in benign obstructions require caution [14]. Due to the possibility of excessive complication rates uncovered metallic stents are not recommended for use in most benign airway diseases [14]. Silicone stents are the most popular choice for benign conditions [6, 14, 17]. The synthetic substance used to create silicone stents has a low tissue reactivity and is simple to remove [14, 16].

Unfortunately, there are not many sizes and forms of commercially available stents (CAS). Sometimes it's crucial to modify them to enhance fit and performance, particularly in patients with complicated airway anatomy [18]. This Customization usually involves cutting and stitching stents together in the operating room and requires an expert and highly trained doctor [18].

Because of the intricate features of the tracheobronchial anatomy, Threedimensional printing (3DP) technology is perfect for creating airway prostheses to treat difficult conditions. With the help of years of research and development, it is now possible to produce a patient-specific stent [19–22]. A patient-specific stent may help decrease risks, shorten healing time, and enhance patients' quality of life while alleviating symptoms and avoiding the need for additional bronchoscopies.

Recent research has examined the use of 3DP technology to produce silicone and hybrid airway prostheses and investigate biodegradable materials and drug-eluting stents (DES) [23].

This chapter discusses the most recent developments in three-dimensional printing technology, how they are being used to create airway prostheses to treat complex airway problems, and the body of research that supports their use.

## **2. Airway diseases and three-dimensional printing**

Anatomical modeling of various bodily components for preoperative planning purposes by surgeons was one of the earliest uses of rapid prototyping techniques in medicine [24, 25].

In respiratory medicine, 3DP technology has been used, particularly for conditions of the central airways. In 2013, Tam et al. printed inspiratory and expiratory threedimensional (3D) models of the tracheobronchial tree of a patient with airway disease due to relapsing polychondritis, and they explored the potential use for surgical or interventional planning and teaching [26].

In a case study published in 2013, Zopf and colleagues described how a bioresorbable airway splint was surgically inserted into a newborn's malacic left main bronchus [27].

Then, in 2015, George Z. Cheng et al. published the first case study of a 3D-modeled T-tube inserted into a patient's difficult upper airway. This prosthesis was made to allow for the three-dimensional reconstruction of the trachea from a computed tomography (CT) scan [28].

To treat a 56-year-old male patient with airway complications of granulomatosis with polyangiitis (GPA) who required numerous unsuccessful therapeutic bronchoscopies and multiple commercially and manually customized stents, Thomas R. Gildea created and implanted the first bronchial patient-specific airway stent (PSS) made of silicone under Food and Drug Administration clearance for compassionate use in 2016. He did this using CT imaging and 3DP technology [20, 22]. In 2017, Gildea and

*3D Printing and Airway Stents DOI: http://dx.doi.org/10.5772/intechopen.110414*

colleagues described the one-year experience of this patient and another with complex airway disease attributable to GPA. Both patients improved their average time between treatments and stent life following implantation after inserting PSS made utilizing 3DP technology [20, 22].

Guibert et al. presented a case of a patient with an airway problem following lung transplantation in 2016; the right airway had dehiscence, a stenotic bronchus intermedius, and complex morphology. After a 3D airway was built from a CT scan, and the difficulties were virtually removed, a planned 3D mold was made and used to create a unique stent. It was successfully implanted with RB [29].

Similar efforts have been made in treating tracheobronchomalacia in adult patients using 3DP technology [29]. Shan and colleagues recently published their experiences with hybrid stents that were assisted with 3DP technology to treat malignant airway obstruction and aerodigestive fistula [30, 31].

## **3. Airway stents and 3D printing procedures**

To make airway stents, many 3D techniques and materials have been employed. In order to create a 3D reconstruction of the trachea using a CT scan, Cheng and colleagues employed 3D slicer, a free, open-source, and multi-platform software application that is frequently used for medical, biomedical, and related imaging research. The virtual T-tube was created using Solidworks® (computer-aided design (CAD) software) then a 3D model was imported, matching his patient's virtual difficult upper airway. The silicone customized T-tube was created and put through the tracheostomy stoma under bronchoscopy supervision [19, 28].

Gildea and colleagues used specialized software created for orthopedic surgery to transfer the digital imaging from a CT scan (COS Inc., Cleveland, OH, USA). The airway is turned into a virtual 3D prototype. The ideal stent dimensions, including the area, diameter, angulation, branching, length, and wall thickness, were defined using this virtual model of each patient's anatomy. The doctor creates a virtual depiction based on clinical requirements by placing spheres in the 3D airway and adjusting their forms and sizes using the software tools. Using 3DP technology, a mold of the prescribed stent is created, and medical-grade silicone is then injected into this mold to create the stent (**Figure 1**). External studs are inserted after the stent has been finished, cleaned, and polished to produce a flat surface. The stent is sterilized using steam sterilization. The stent is then implanted utilizing RB and conventional procedures and instruments [20, 32].

Guibert employed a similar process, creating a virtual 3D mold (VGStudio MAX software). To create an Ertacetal POM mold, the 3DP (RolandDG MDX 40A) was fed with the 3D data. This mold was used to create a personalized silicone stent. The stent is placed during a therapeutic RB procedure [29, 33].

Using CAD software, Shan and associates could recreate 3D representations of the airway using information from a 64-slice multidetector spiral CT scan (Vitaworks, Shanghai, China). After different colors were given to the airway and tumor, the image was transformed into a 3D stereolithographic (STL) file. An airway mold composed of photosensitive polymers was produced using the 3D reconstruction data and a 3DP (RS600, Union Tech, Shanghai, China). The dimensions of the 3D-printed airway mold's area of interest were measured. The temperature-memory nickel-titanium alloy-covered self-expandable Y-shaped metallic airway stents (Micro-Tech, Nanjing, China) were then created utilizing the 3D printed airway model as a template.

#### **Figure 1.**

*Patient specific silicone stent (PSS) created with 3D printing technology. After a 3D virtual mold of the airway is created. The physician uses a software placing a series of spheres in the target airway to adjust the dimensions and make a virtual representation of the PSS. (A) Stent design with spheres. (B) Stent design. (C) Silicone stent. Picture authorized by Visionair, Cleveland, OH, USA.*

Flexible bronchoscopy was used to evaluate the patient and install the guidewires before inserting the stents. A stent delivery system was advanced posteriorly out from the endotracheal tube, and the stent was deployed with fluoroscopy [30, 31].

## **4. Biodegradable stents**

Research is being done on biodegradable stents (BDS) that might temporarily sustain patency in an airway [34]. They may be helpful when temporal stenting is desired in individuals with benign airway disorders [9]. The prosthetic material must be biocompatible, release harmless residues as it degrades, be strong enough to maintain the integrity of the airway, and be durable enough to allow the airway to reconstruct [34, 35]. Research has been done on several synthetic degradable polymers, including polyesters containing lactic acid, glycolic acid, dioxanone, caprolactone, polytrimethylene carbonates, polyanhydrides containing sebacic acid, and polyarylates generated from tyrosine [34, 36–38]. Studies in animal models showed that, depending on the polymer employed, stents had a high safety profile, were biocompatible, and degraded quickly over time [38–40].

According to studies conducted on patients, the BDS is safe and reduce symptoms. However, several patients might develop cough, mucosal hyperplasia, granulation tissue, biofilm, expectoration of stent parts after insertion, and other complications resulting from a lack of radiation force or re-stenosis [41–43].

Related to 3DP and BDS, research has been done on materials that can be directly printed to create an airway stent. In 2015, Nidah M. Hussain from the University of South Carolina used 3DP technology to design and print a bioresorbable tracheobronchial stent to investigate potential improvements on existing stents. He concluded that thermoplastic polyurethane is potentially viable as a biologically degradable silicone substitute and polycaprolactone is compatible with fused deposition modeling printing [44].

*3D Printing and Airway Stents DOI: http://dx.doi.org/10.5772/intechopen.110414*

With the use of elastomeric polyurethane (EPU), Catherine Wood and colleagues created a platform for designing and manufacturing 3DP flexible airway EPU stents. They concluded that the 3D-printed EPU stent performs similarly to silicone stents after conducting comparison testing [45].

In an in-vivo examination of healthy rabbits, Paunovic et al. reported employing a digital light 3DP customized bioresorbable stent. The stents were made of biocompatible dual polymer that remained in situ for seven weeks [46].

Because of the potential for quick and direct manufacture, customization, biocompatibility, and degradability, these 3DP materials seem promising. However, more investigation should be done to enhance degradation time, radial force and reduce problems, particularly re-stenting before it is used in patients.

## **5. Drug eluting stents**

DES have been widely used in cardiology to decrease coronary stent complications such as re-stenosis or stent thrombosis [47].

The use of stents in central airway obstruction has been related to numerous complications and looking to reduce adverse events (AEs) rate or to treat airway obstruction airway-DES research has been ongoing since the last decade [48].

In 2011, Zhu and colleagues randomized different types of stents in 20 rabbits, the bioabsorbable stents with mitomycin C had the best performance, with less mucus plugging and airway obstruction [48]. Other drugs have shown to decrease the granulation tissue or scar formation in animal models, such as airway DES with paclitaxel, sirolimus, methylprednisolone, or cisplatin [49–54].

The potential use of DES in airway diseases is not limited to preventing mucus plugging or granulation tissue formation. It could prevent stent-related infection, treat long-term malignant central airway, or manage benign central airway stenosis. Several chemotherapeutic, anti-proliferative, or antifibrotic agents have been proposed [55].

3DP technology can be used to create a personalized drug-eluting stent. According to the patient's need, it could have different polymers and drugs or a combination to produce a sustained drug release effect and prevent or treat different conditions [56].

## **6. 3D printing and clinical research**

The number of studies on 3DP and airway stents has grown since 2015. Ten publications using 3DP and PSS in humans were identified (**Table 1**) [22, 28–33, 57–59]. Most studies have focused on benign airway conditions such as tracheobronchomalacia, post-radiotherapy airway complications, post-surgical airway complications, post-transplant airway illnesses, and GPA airways. Silicone was the most used stent material in benign airway disorders [22, 29, 32, 33, 57, 60, 61]. Malignant central airway obstruction and malignant aerodigestive fistula have been the subjects of more recent research. Except for one study, they utilized covered metal stents [30, 30, 58].

To produce the PSS, nine studies reported printing a 3D airway mold (there is no description in one study). Additionally, Y tracheobronchial or bronchial stents were the majority. In six studies, Y-bronchial stents or a bronchial branch to the right upper lobe were made using a 3D mold.



**Table 1.**

*Clinical studies description of PSS assisted by 3DP technology.*

## *3D Printing and Airway Stents DOI: http://dx.doi.org/10.5772/intechopen.110414*

**293**

Improvement in symptoms was observed in all studies (**Table 1**). Guibert et al. used 3DP silicone PSS in 10 patients, the majority had post-transplant airway complications and reported high rates of congruence between the stent and the airway, 80% improvement in dyspnea (>1 New York Health Association score point gain), quality of life (>10% increase in VQ11 Chronic Obstructive Pulmonary Disease-specific quality of life score), and pulmonary function test (>10% Forced Expiratory Volume in 1 second (FEV1) or Peak Expiratory Flow (PEF) increase) [33].

A retrospective analysis of patients who got 3DP silicone PSS at the Cleveland Clinic was reported by Aravena et al. Interventional pulmonologists completed a survey and two physicians rated stent-related AEs using the Common Terminology Criteria for Adverse Events scoring system. Four patients received a total of 13 PSS. No difference was noted in the loading, positioning, or removal of the PSS in comparison to the CAS (p > 0.05). Following the placement of the PSS, bronchoscopists saw a substantial clinical improvement (p = 0.03). The PSS's average lifespan was considerably longer than the CAS's (300.2 days vs. 124.0 days, p = 0.001) by a large margin. With PSS, the median time between bronchoscopies was significantly longer than with CAS (65.6 days vs. 36.6 days, p = 0.004) [57, 61].

In a study by Shan et al., 12 individuals with malignant airway obstruction caused by lung or esophageal cancer had 13 covered metal PSS implants. Hugh-Jones dyspnea scale and Karnofsky performance status (KPS) improvements were reported (P = 0.003 and P = 0.006, respectively) [30].

Regarding the AEs that were portrayed in the different trials. At three months, Guibert and colleagues reported a 40% complication rate, one patient with a mucus plug, two stent migrations, and one untreatable cough. Three of them needed to have their stents removed. One patient experienced distal stenosis at a lobar level that needed balloon dilatation, and another mucus plug incident occurred at the end of the four-month follow-up period. There were no lifethreatening problems found [33]. Aravena and associates found that silicone PSS had less severe migration than CAS (p = 0.0225). The statistical differences between the two groups did not exist for any other AEs [57, 61]. Shan et al. demonstrated a 50% (6/12) complication rate with coated metal PSS after 5.6 months of follow-up. Only two patients had significant granulation tissue development, four patients had mucus blocking, and no patients needed their stents removed or had migration [30].

## **7. Discussion**

Using any stent is always a last resort in cases of complex benign or malignant airway diseases. There are several problems associated with stents. Migration, stent obstruction by either granulation tissue or mucus, and infection are the three most frequent adverse outcomes of silicone stenting. These disorders can also be interrelated [5, 6, 14–18]. Even with non-malignant diseases, many patients still benefit from long-term palliation despite the risk.

The technical success of the PSS congruence to the complicated airway is high. It can result in a decline in AEs because fit issues could be responsible for many stent-related consequences. The migration rate is greater for either too loose or too tight stents. Excessive pressure from a stent on the airway might cause tissue necrosis and perforation. An improperly fitted stent may promote granulation at the ends or result in poor secretion clearance. Additionally, the material used may have clinical

#### *3D Printing and Airway Stents DOI: http://dx.doi.org/10.5772/intechopen.110414*

implications. Even in silicone stents, there are prostheses with a different durometer and elastic modulus that can have a distinct impact on wall stress.

The benefits could be substantial. Through all the research mentioned, symptoms have consistently improved. In one study, the lung function test and quality of life improved [31]. The PSS and CAS were only contrasted in one research. This showed a longer stent life and longer intervals between treatments, which may be associated with an improvement in the quality of life for patients with complicated benign airway diseases who often need several consecutive bronchoscopies to try to achieve palliation [57, 61].

Improving performance status scale is an important additional finding related to malignant disorders [30, 31, 58]. It could be linked to decreased adverse events (AEs), better congruence, and airway obstruction relief, which would aid with symptoms and possibly enhance clinical performance, allowing for the potential of receiving oncologic therapy.

Additionally, the 3DP PSS is at least as secure as the CAS. The rate of complications is comparable, and no problems that threaten life have been reported. The development of 3DP PSS with Y-bronchial and Y-tracheobronchial stent shapes, which are compatible with and suit the intricate airways of those patients, likely contributed to a reduction in migration rate compared to CAS (**Table 1**) [57, 61].

The PSS may be loaded and inserted using traditional techniques, just like conventional stents [57, 61]. This is crucial since deploying some complex stent designs, such as the dynamic Y-stent, requires specialized equipment.

The research in 3DP PSS do not have a sufficient sample size to generalize the application of patient-specific stenting. Many studies are retrospective cohorts or cases, which are both highly biased. But the early experience has demonstrated that PSS are highly successful and safe in the palliative treatment of extraordinarily complicated airway diseases, above all currently available best practices, despite the small sample size.

## **8. Future directions**

3DP technology is developing fast and will be an important tool for personalized medicine in patients with complex airway diseases. Research is still being done to make more advancements. New materials that might be directly printed and biodegradable may be preferred when temporal stents are needed [46]. Additionally, 3DP drug-eluting stents might be a feasible therapeutic strategy for avoiding excessive granulation tissue, precluding infections, and managing malignant or benign obstruction of the airway [23, 62].

We envision the future of 3DP of completely compatible or engineered biological tissue prosthesis that promotes improvement of the damaged tissue and replace part of the impaired airway.

## **9. Conclusion**

Over the past few decades, 3DP technology has made significant progress. This technology has been applied to healthcare for preoperative planning, education, medical equipment, prostheses, implants, and medical models. Respiratory medicine is at the forefront of a revolution in personalized treatment by making individualized airway stents tailored to the unique requirements of patients with complicated malignant or benign airway disease. These patient-specific airway stents developed utilizing 3DP technology can potentially reduce the number of treatments needed and adverse events (AEs) and improve symptoms and quality of life.

To ascertain the real impact this technology will have on this group of patients, new research with markedly better methodology will be necessary yet challenging.

## **Conflict of interest**

CA has no conflicts of interest to declare. Visionair is the manufacturer of one of the Stents created with 3DP technology presented in this review. TRG is the inventor and may be entitled to royalty payments from the company in accordance with Cleveland Clinic policy.

## **Author details**

Carlos Aravena1 \* and Thomas R. Gildea2

1 Faculty of Medicine, Department of Respiratory Diseases, Pontificia Universidad Católica de Chile, Santiago, Chile

2 Department of Pulmonary, Allergy, and Critical Care Medicine, Respiratory Institute, Cleveland Clinic, Cleveland, OH, USA

\*Address all correspondence to: caravenal@med.puc.cl

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[62] Xu J. Development of 3D-Printed, Drug-Eluting Airway Stents for the Personalised and Local Treatment of Central Airway Pathologies Statement of Originality. Camperdown, Australia: The University of Sydney; 2021

## **Chapter 13**

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

*Przemysław Kustra*

## **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.

**Keywords:** digital stomatology, digital oral medicine, three-dimensional printing, virtual endoscopy, three-dimensional teaching

## **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 [1–5].

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 [8–15].

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].

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

*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

#### **Figure 1.**

**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.*

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 *Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

**Figure 5.** *Cone beam tomography (CBCT) image of molars during the assessment of cavity preparation and fillings.*

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, 17–19].

#### **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

*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

**Figure 6.**

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

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

**Figure 7.** *Virtual 3D image of teeth obtained from cone-beam tomography scans. Visible preparation of cavities and applied fillings.*

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].

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

**Figure 8.** *It shows graphical visualisation of results of preparation: incisors, premolars and molars teeth.*

*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

#### **Figure 9.** *Example printout, 3D group of premolars.*

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 [1–5].

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].

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,

**Figure 10.** *Example of perforation of incisor tooth, number 20.*

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

*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

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 nonsurgical 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,

## *Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

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

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

*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

**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.*

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, 22–29, 31].

## **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

*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*

**Figure 20.** *3D virtual endoscopy, root canal, molar and view inside the orifice of the tooth.*

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

**Figure 21.** *3D virtual reconstruction of the spatial arrangement of the pulp tissues.*

(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, 30–34].

## **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.

## **Acknowledgements**

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**


*Making Use of Three-Dimensional Models of Teeth in Practical Teaching of Endodontics DOI: http://dx.doi.org/10.5772/intechopen.109167*


## **Author details**

Przemysław Kustra Jagiellonian Univercity Medicall College, Institute of Dentistry, Kraków, Poland

\*Address all correspondence to: przemyslaw.kustra@uj.edu.pl

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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## **Chapter 14**
