3D printed teeth for bridge preparation training: development and assessment in dental education | BMC Medical Education

The 3D printed training teeth for bridge preparation training in H1 provided the most comprehensive simulation of an integrated clinical workflow within this study – including caries excavation, core build-up, prosthetic preparation, and the fabrication of provisional restorations – the subsequent training sessions focused more specifically on bridge preparation and the essential techniques for fully covering core build-ups with preparation margins placed in sound tooth structure. This led to a stepwise reduction in task complexity from H1 to H2 and further to H3. Therefore, limitations and methodological considerations must be addressed, along with a discussion of student feedback and an analysis of the educational implications.

Limitations and methodological considerations

Several methodological limitations should be acknowledged when interpreting the results of this study. First, the absence of randomization, crossover design, and examiner blinding may have introduced potential biases. Additionally, commercially available typodont teeth were used solely as a comparative reference rather than employing an objective benchmark, such as extracted human teeth. These constraints reflect the applied, curriculum-integrated context of the study and should be addressed in future controlled trials with more rigorous experimental designs.

Furthermore, the outcomes in this study were based exclusively on subjective assessments using VAS, capturing students’ perceptions rather than objective performance metrics. While VAS ratings offer valuable insights into student experience and engagement, they are inherently limited by individual variability and expectation. This is particularly relevant in the context of fourth-year dental students, whose clinical experience with real carious lesions and complex restorative procedures is limited. Their ability to assess realism in areas such as caries excavation or core build-up placement may therefore be constrained, and interpretations of realism should be viewed with caution.

The nature of item Q5.3 may also be seen as leading or suggestive, potentially biasing responses in favor of positive engagement with the new materials. Future questionnaire designs should ensure more neutral phrasing to avoid response bias.

Statistical analyses were primarily exploratory. Although post hoc corrections were applied to pairwise comparisons, no correction for multiple testing across all VAS items was implemented. While this approach allowed for a broad exploratory understanding, it increases the risk of Type I errors. Future studies may benefit from multivariate statistical models to address multiplicity, interaction effects, and longitudinal comparisons.

Finally, the progressive simplification of the training exercises from H1 to H3 – driven by external factors such as regulatory changes – reduced the complexity of tasks and limited comparability across sessions. While simplification improved student evaluations, it also confounded direct interpretation of training effectiveness over time. This highlights the need for consistent exercise structure and comparable workload across evaluation periods to ensure valid comparisons.

Student feedback

Many participants (n = 43) recommended increasing the hardness of the 3D printed teeth. Related aspects were a loss of definition at the preparation margin (n = 2) and an unrealistic surface structure (n = 2). These aspects may negatively impact the learning outcome. Inadequate hardness can lead to unrealistic tactile feedback, impairing the development of proper pressure control and hand skills. Moreover, indistinct margins hinder the ability to practice precise preparation techniques essential for clinical success. These factors may compromise the transfer of learned skills to real patient care, highlighting the need for improved material properties. The material used in the present study was Model V3 resin, which, after post-curing, exhibits a flexural modulus of 2.2 GPa, according to manufacturer specifications [13]. In comparison, the flexural modulus of root dentin has been reported as 17.5 ± 3.8 GPa [14], indicating that the mechanical stiffness of the 3D printed training teeth is considerably lower. Additionally, students noted the absence of an enamel layer in the printed teeth, highlighting the challenges in replicating enamel realistically using current 3D printing resins. An alternative material, the Rigid 10 K resin (Formlabs Inc.), may enhance the mechanical properties of the printed teeth due to its high stiffness and hard texture, which is reinforced with glass fibers. Formlabs Inc. reports in their technical data sheet a flexural modulus of 10 GPa for this resin following appropriate post-curing [15]. However, its greyish to beige coloration may detract from the esthetic quality of the training models. This represents a disadvantage, as students reported (n = 2) on bad visibility of the core build-up for the materials with comparatively better esthetics properties. Insufficient bonding of the components of the 3D printed teeth was reported (n = 5) and could be improved by enhanced post-curing or utilization of specific dental adhesion materials. Cresswell-Boyes et al. concluded that in their study with their specific setup, 3D printed teeth provided haptic feedback comparable to that of extracted human teeth and represented a valuable tool for preclinical dental education – when compared to commercially available typodont teeth, 3D printed teeth offered superior tactile realism, enhancing the simulation of clinical procedures [16]. Höhne et al. reported a 3D printed modular training model based on a patient’s cone beam computed tomography, incorporating enamel and dentin layers that provided both a realistic optical appearance and appropriate tactile feedback during preparation [17].

Students highlighted that the 3D printed teeth offered realistic practice opportunities (n = 18), along with anatomically accurate tooth shapes, positions, and defect representations (n = 13). The flexibility of the exercises (n = 12) and the simulation of patient-like clinical scenarios (n = 6) were also positively noted. These findings align with previous studies demonstrating that 3D printed models based on real patient data, as well as purpose-designed training models in pediatric dentistry, can significantly enhance the authenticity and educational value of hands-on training [18, 19]. The student feedback underscores the potential of 3D printing to bridge the gap between traditional typodont-based simulations and authentic clinical experiences. Unlike conventional mass-produced plastic teeth, which often lack anatomical variation and clinical complexity, 3D printed models offer a high degree of customization. In the context of the present study, this included the integration of features, such as carious lesions and core build-ups, that more accurately reflect real-world restorative challenges.

An improved retention of the 3D printed teeth was desired (n = 4) for both the KaVo and Frasaco models. The KaVo model utilizes a click mechanism for tooth retention, whereas the Frasaco model employs screws. Designing 3D printed teeth to fit the KaVo system proved challenging and labor-intensive, achieving only limited success. Conversely, the material properties of the 3D printed teeth in the Frasaco model complicated secure screwing, as the screws were prone to over-tightening, resulting in inadequate retention.

Students in H1 (n = 3) and H2(n = 3) reported difficulties in fabricating the provisional bridge restorations. These challenges were primarily due to unintended adhesion between the provisional material and the surface of the 3D printed teeth, even when Vaseline was used as a separating medium. This adhesion complicated removal and finishing of the provisional restorations. Students had prior experience fabricating provisional restorations on typodont teeth and understood the necessity of isolation using Vaseline. Lubrication with petroleum jelly or a suitable separating media represents a standard protocol in fabricating provisional restorations [20]. In the context of 3D printed materials, surface energy and texture may promote interaction with resin-based materials, even when lubricated. Surface treatments to optimize bond strength and manage adhesion behavior with 3D printed resins have been demonstrated in both fresh and aged materials [21, 22]. Therefore, implementing appropriate surface conditioning protocols is critical to balance the need for adequate provisional restoration retention with the requirement for reliable and clean removal.

In H1, students (n = 2) reported that the caries excavation appeared unrealistic. The carious lesion model used with Telio Onlay is well-established and familiar to the students; therefore, criticism of this exercise was not anticipated. Carnier et al. demonstrated that more realistic caries simulation can be achieved using 3D printed teeth with artificially designed carious lesions, enabling more authentic caries excavation experiences for students [23].

Improvements to the tooth morphology (n = 2), the inclusion of a pulp chamber (n = 1), and the incorporation of a deeper core build-up (n = 1) were recommended improvements by the students. While these modifications could be considered for future iterations of the hands-on training course, it is important to note that the increased complexity of the training materials would entail greater preparation efforts. Complex designs of 3D printed teeth – comprising multiple components and differentiated by color – have been reported in various educational contexts, including endodontic training, teeth with integrated adhesive bridge preparation guides, and modular models for restorative and prosthetic dentistry [11, 17, 24].

The realism of the pre-prosthetic exercise using 3D printed teeth was rated for caries excavation at ⌀30.58 (± 24.74) and for the placement of the core build-up at ⌀47.77 (± 26.22). The tactile sensation during preparation was rated comparably between the 3D printed teeth and typodont teeth. Despite frequent student feedback requesting greater hardness of the 3D printed teeth (n = 43) and the known material limitations compared to natural tooth structures, the comparable tactile ratings between groups indicate a perceived equivalence in this aspect. The learning process, learning success, and overall suitability were rated with no statistical difference for both 3D printed and typodont teeth. Notably, these ratings for the 3D printed teeth showed a partial but significant increase from H1 to H2 and H3. Students predominantly expressed a desire for additional practice exercises using 3D printed teeth (⌀64.80) and indicated moderate openness to complete the entire training program exclusively with 3D printed materials to prepare for patient treatment (⌀47.84).

Overall, students provided valuable insights into the strengths and limitations of the 3D printed training teeth. While aspects such as anatomical accuracy and training flexibility were positively received, material properties – including hardness, surface texture, and component retention – require further optimization to fully support realistic and effective simulation in dental education.

Educational implications

The use of 3D printing in dental education has generally been well received by students and provides educators with increased flexibility and variety in their teaching methods [12]. The novelty of this study is the context of bridge preparation with an integrated workflow encompassing caries excavation, core build-ups and fabrication of temporary restorations.

Karagkounaki et al. reported in their review on previous studies in dental education focusing on a single aspect of training as well as modular training models [12]. Other studies reported more pronounced benefits of 3D printed training materials. However, it must be emphasized that the concept applied in the present study was novel and more complex in its design. It could be argued that the complexity of the required skills and workflows may have exceeded the learners’ current routines. In previous preclinical practices students focused on individual steps without an integrated workflow. This interpretation aligns with the cognitive load theory in the context of medical education [25]. The transition from preclinical to clinical practice poses a significant challenge for students, necessitating tailored curriculum adjustments [4]. In clinical practice, integrated workflows encompassing pre-prosthetic and prosthetic procedures are standard and essential for patient care. This learning gap was the focus of this study, as previous course supervision revealed that students encountered difficulties when transitioning to these clinical workflows.

The 3D printed teeth from H1 provided the most comprehensive and realistic representation of an integrated workflow. Especially regarding the newly implemented changes the licensing regulations for dental education in Germany resulting in time constraints and the need for adaptive and wide-ranging training, these comprehensive and realistic training opportunities subsequently become more relevant. In fact, long-term educational outcomes and potential enhancements in patient treatment during clinical training constitute more meaningful endpoints than immediate student evaluations following the exercise. It is important to acknowledge that the complexity of the simulated treatment scenarios may have led to cognitive overload among students, particularly in H1. This form of simulation – featuring an integrated clinical workflow combining multiple procedural steps – was a novel concept in the context of their training. Previously, students had primarily practiced individual, isolated skills in structured exercises. The unfamiliarity with managing a realistic, patient-like workflow in a single session likely contributed to initial challenges and lower evaluations. Nevertheless, these integrated simulations are critical for developing clinical competence and bridging the gap between pre-clinical and clinical training. The adaptability of 3D printed exercises enables educators to tailor training scenarios to specific learning objectives or curriculum milestones. This flexibility supports competency-based education by allowing for the creation of progressive, patient-relevant cases that evolve with students’ skill levels. As dental education continues to emphasize clinical preparedness and critical thinking, 3D printed models offer a promising avenue for developing both procedural accuracy and decision-making in a safe, simulated environment. Standardized printed models can ensure uniformity in training conditions across cohorts and institutions, improving comparability and enabling objective benchmarking of performance.

Lee et al. introduced a simulated training approach using 3D printed, patient-specific models to support the transition from preclinical to clinical education, with the aim of better preparing students for their initial clinical experiences [26]. They emphasized the value of simulation as a transitional educational tool, particularly in the context of restorative procedures involving irreversible tooth preparations. The present study builds on this concept by employing 3D printed teeth for bridge preparation within an integrated workflow. This allows students to engage in realistic, patient-like, and logically structured practice sessions without performing invasive procedures or risking patient harm.

The total cost of resin was relatively low at €37.84. In contrast, expenses for typodont teeth used in bridge preparation training for 116 students amounted to €696. However, these typodont teeth do not support integrated workflows or allow for individual features such as core build-ups or customized tooth anatomies. The cost advantage of 3D printed teeth thus presents a significant benefit in dental education, offering a scalable and feasible solution. The 3D printed teeth developed in this study are feasible, allow for further customization, and could be produced in larger quantities. Richter et al. highlighted for their study with 3D printed dental models in undergraduate conservative training for caries excavation exceptional cost-efficiencies [27]. Nevertheless, primary costs associated with 3D printed teeth lie in the time and labor required for design, printing, post-curing, and assembly. Di Lorenzo et al. reported in their study with 3D printed teeth for endodontic training also on these associated indirect costs to the overall cost-efficient 3D printed training utilities [11]. Hands-on courses are accompanied by time-consuming and intense support and supervision by trained staff [28]. This, however, reflects authentic circumstances typical of educational environments.

Overall, the 3D printed teeth represented a valuable tool for students when training bridge preparations with defect-oriented preparation techniques, especially as typodont teeth offer only limited scope for customization, integrated workflows and complex preparation techniques. The null- hypothesis can thus be rejected.