Exploring threshold concepts, tacit knowledge, and strategies for competency in restorative dentistry and fixed prosthodontics: a mixed-methods study among undergraduate dental students

Abstract

Background

Acquiring competency in restorative dentistry (RD) and fixed prosthodontics (FP) is challenging for undergraduate dental students due to the presence of threshold concepts and tacit knowledge. The aim of this study was to identify the threshold concepts (knowledge barriers) and tacit knowledge (skill development barriers) necessary for achieving competencies in RD and FP using quantitative and qualitative approaches. The strategies for attaining these competencies were also proposed.

Methods

The present study adopted a critical-theorist mixed-method study design, using quantitative and qualitative approaches. The participants were third- to sixth-year dental students, and recent graduates. An online questionnaire was used to investigate the knowledge and skill required for achieving competency and barriers in RD and FP. Four focus group interviews were conducted to gather in-depth information. The data was analyzed using descriptive statistics and thematic analysis.

Results

A total of 275 dental students and recent graduates completed online questionnaires (56.8% response rate), and 28 of them participated in focus group interviews. The threshold concepts for RD comprised restorative techniques, covering cavity preparation design and restorative material selection. The tacit knowledge for RD was caries removal. Threshold concepts for FP focused on resin cement and treatment planning, including crown and bridge design and restorative material selection. The tacit knowledge for FP encompassed tooth or cavity preparation and material handling. Observing the actual work situations and the educators’ ability to articulate and clarify are crucial to overcome these barriers. Furthermore, working and practicing in real clinical situations was the most important factor for enhancing practical skill.

Conclusions

Developing competency in RD and FP requires integrating knowledge and skill. Barriers to competency development were identified based on threshold concepts and tacit knowledge. To enhance learning and competency development, focus should be placed on three components, including learners, teaching materials, and educators.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-025-06865-8.

Background

The undergraduate dental curriculum in Thailand spans six years, with the first three years dedicated to preclinical studies and the subsequent three years to clinical practice [1]. According to the Competency Standards for Thai General Dentists [2], operative dentistry and fixed prosthodontics (FP) competencies require a fundamental understanding of the etiology and risk factors of dental problems. These also encompasses comprehensive history taking, effective patient communication, treatment planning, dental material selection, and onwards referrals in complex cases. Operative dentistry is divided into two branches: restorative dentistry (RD) and endodontics. While endodontics focuses on skills related to root canal preparation and obturation, RD requires a distinct set of competencies involving the restoration of tooth structure and function. RD competency specifically includes using the appropriate instruments and performing restorative procedures, such as caries removal and fillings. In addition, FP competency requires treating patients with temporary and permanent fixed dental prostheses in non-complex cases, and effective communication with dental technicians [2]. RD in the undergraduate program is limited to direct restorations, while FP focuses on the indirect restoration without extensively altering the maxillo-mandibular relationship.

To acquire competency in RD and FP, dental students must overcome two learning barriers; threshold concepts and tacit knowledge, which impede cognitive knowledge and psychomotor skill development, respectively [3, 4]. Threshold concepts are transformative ideas in a discipline that fundamentally reshape students’ understand and engagement with subject matter [5–8]. These concepts are often troublesome, integrative, and irreversible, requiring students to navigate a liminal phase of fluctuating understanding before mastery. Their role is central to deep learning and professional development. In dental education, threshold concepts shift students from passive learners to active clinical decision-makers [4]. Challenging topics such as clinical reasoning, managing uncertainty, and spatial-temporal tasks, such as partial denture design and dynamic occlusion, often present as cognitive bottlenecks in this development process [1].

Tacit knowledge involves insights acquired through personal sensory experiences, such as touch, hearing, and smell [9]. This type of knowledge is context-specific and embedded in activity, often transmitted through imitation and mentoring [3]. In dentistry, challenges with tacit knowledge can be explained through psychomotor skill development, which includes cognitive, associative, and autonomous stages [10–12]. In the cognitive stage, students develop cognitive awareness of the desired outcome and performance. In the associative stage, continuous practice, repetition, trial and error helps students develop manual dexterity and connect movements with cognitive knowledge. In the final autonomous stage, students perform tasks with little or no cognitive effort, indicating that the psychomotor skill is internalized. Effective psychomotor learning is achieved when students can close the gap between the desired and actual performance, leading to permanent skill acquisition [12, 13].

The principles of competency provide a foundation for understanding how threshold concepts and tacit knowledge influence the development of RD and FP competencies. While earlier definitions emphasized performance-based outcomes [14], contemporary perspectives view competency as a holistic integration of knowledge, skills, attitudes required to perform specific task ethically and independently [15]. This framework is useful for identifying threshold concepts and tacit knowledge in RD and FP. Moreover, the integrative nature of competency has informed curriculum development across the South-East Asia countries, including in RD and FP, for nearly a decade [16].

The learning journey of undergraduate dental students begins at the novice level, where students initially lack knowledge and skills and still engage with basic science courses [17]. Then, they progress to the advanced beginner level, gradually developing essential knowledge and skills for dental practice through pre-clinical dental courses. Upon completing the undergraduate curriculum, students must demonstrate competency to be independent general practitioners. The aim of this study was to identify the threshold concepts (knowledge barriers) and tacit knowledge (skill development barriers) necessary for achieving competencies in RD and FP using quantitative and qualitative approaches. The strategies for attaining these competencies were also proposed.

Methods

Study design and participants

The RD and FP are generally viewed as scientific disciplines based on established principles and objective evidence, often referred to as representing an “absolute reality”. However, from an educational perspective, the teaching and learning of RD and FP are influenced by various factors such as learning styles, instructional approaches, and educational environments. These influences have gradually reshaped the disciplines, resulting in a “transformed reality”, wherein core principles coexist with context-specific concepts. This view aligns with the critical theory paradigm, which acknowledges the existence of reality while recognizing that it is continually shaped and transformed over time [18, 19].

Therefore, this study adopted a cross-sectional mixed-method study design within the critical theory paradigm, utilizing both quantitative and qualitative approaches. The study protocol was approved by the Human Research Ethics Committee of the Faculty of Dentistry (study code: HREC-DCU 2022-094). Conducted at the Faculty of Dentistry, Chulalongkorn University, the participants were third- to sixth-year dental students in the undergraduate program for the 2022 academic year, as well as recent dental school graduates who had completed their studies within the past two years.

In the undergraduate dental curriculum in Thai dental schools, lectures and laboratory practice related to RD and FP usually commence in the third and fourth years for pre-clinical students, with FP starting a semester later. Clinical practice for RD spans from the fourth to the sixth year for clinical students, while FP clinical practice extends from the fifth to the sixth year. Dental students enrolled in the RD laboratory course in the first semester of the third-year practice preparation skills for amalgam and composite restorations. In the second semester, they start to take FP lecture courses and practice single crown restorations.

Quantitative data was collected through an online survey, while qualitative data was obtained via focus group interviews conducted between December 2022 and February 2023. Because this study was designed based on the critical theory paradigm, which asserts that reality is shaped by external factors over time, it primarily embraced a qualitative approach. The quantitative (numerical) data was used only to support the qualitative (exploratory) part. No hypotheses were developed, nor scientific analyses (e.g. inferential statistics) were used to prove, reject, or generalize any emerging ideas or concepts. The study comprised three parts: literature and documentary analyses, an online questionnaire, and a focus group interview.

Literature and documentary analyses

For the literature and documentary analysis, information was collected from various sources. First, the course syllabi of the RD and FP lecture and laboratory courses provided overall contents/topics of both disciplines. Second, the minimum competency standards for Thai graduate dentists were analyzed, detailing the essential knowledge and skills that dental graduates must possess in relation to RD and FP. Third, RD and FP textbooks were used to provide detailed information that supports the course syllabi. Finally, RD and FP course evaluations across the 3rd and 6th year from the academic years 2020–2021 were collected to identify difficult contents or topics and learning barriers. The gathered information was used to develop a framework outlining the knowledge, skills, and barriers to achieve competency in RD and FP used to formulate questions for the survey questionnaire and focus group interviews (Supplementary File 1).

Content validity of the questionnaires was assessed by five experts in the restorative and prosthodontic fields. Face validity was conducted using 30 participants from the same sample group. The validity evaluation utilized an item-objective congruence method with a three-point ordinal scale, where each question was scored as follows: “−1” when the question clearly measures the objective, “0” when there is uncertainty, and “1” when the question does not measure the objective. Revisions were made to questions that received scores of “0” and “1” based on the feedback from the respondents.

Online questionnaire

An online questionnaire was distributed using a Google Form to 484 members of the target population, comprising 198 pre-clinical (3rd and 4th year) dental students, 193 clinical (5th and 6th year) dental students, and 93 recent dental school graduates. Two sets of questionnaires were developed for the preclinical students, and the clinical students plus recent graduates. Each questionnaire consisted of four sections with a four-level response scale in Sects. 2 and 3 (Supplementary File 2):

1. Demographic information.

2. Participants’ perception of the interconnection of fundamental knowledge and practical skill between RD and FP. The linkage was assessed using a four-point Likert scale: highly interconnected, moderately interconnected, not interconnected, and not interconnected at all.

3. Participants’ perception of the essential and challenging knowledge and skills required for learning and performing clinical practice related to RD and FP. For the pre-clinical students, this part solely focused on the difficult topics because they had been exposed to only didactic and laboratory courses.

4. Factors contributing to the enhancement of knowledge and skill development.

An open-ended question was also provided to allow for comments for additional focus group interview questions. Data were collected over a one-month period, with reminder messages sent during the second and third weeks via the Line group chat for each student cohort, including both current students and recent graduates. The survey questionnaire data was analyzed using descriptive statistics to calculate percentage distributions (%), means, and standard deviations, utilizing IBM SPSS statistical software version 29.0.

Focus-group interview

Based on a review of relevant literature and results from the quantitative questionnaire, semi-structured interview questions were developed and organized into four parts: opening questions, key questions, probing questions, and closing questions (Supplementary File 3). The literature addressed topics related to this study, including the nature of prosthodontics, relationship between RD and FP, competency, threshold concepts, and tacit knowledge. Quantitative results used to develop the interview questions included students’ self-perceived interconnection between RD and FP, the perceived difficulty and essentiality of related theoretical topics and practical skills, and factors supporting cognitive and psychomotor development in RD and FP.

Four focus group sessions were conducted using semi-structured interviews to collect qualitative data. The sessions were facilitated by three investigators (K.M, P.P., and S.P.) who were currently undergraduate dental students with no conflict of interest to the participants. The other two investigators (N.L. and S.C.) were lecturers who previously taught the participants. However, both lecturers did not get involved in the assessment or examination of student participants during the study period. The roles of all five investigators were explained to participants before the focus group session to declare reflexivity and transparency of the investigators.

The participants consisted of 7 preclinical students, 14 clinical dental students, and 7 recent graduates, selected through convenient and purposive sampling. They answered predefined questions about challenges in understanding and practicing skills in RD and FP, essential for competency development. Data collection continued until saturation was reached, the point at which no new insights were obtained. Audio recordings were transcribed, deconstructed, and coded for thematic analysis. This method was used to identify data patterns and explore the meanings within the qualitative data [20]. Three trained investigators (K.M, P.P., and S.P.) performed paper-based thematic analysis using an inductive approach, following established steps: data familiarization, generation of initial codes, grouping codes into preliminary themes, reviewing themes, defining final themes, and reporting the findings [21]. The identified themes were grouped and re-analyzed based on the principles of threshold concepts [5–7] and tacit knowledge [3, 9]. The three investigators independently analyzed the transcripts. Discrepancies were resolved through discussion with two experts in dental education (S.C.) and prosthodontics (N.L.) until reaching a consensus. The criteria for identifying threshold concepts and tacit knowledge were based on the existing literature [3, 7].

Results

A total of 275 dental students and recent graduates completed online questionnaires (Table 1.), representing a 56.8% response rate. On average, the participants were 23.1 ± 3.1 years old, with an age range of 20–27 years. Based on the online questionnaire results, approximately 96% of the participants perceived the fundamental knowledge of RD and FP to be somewhat to moderately interconnected, while 80% reported a moderate to high interconnection in practical skills.

Table 1.

Characteristics of questionnaire participants (n=275) and their perceptions on interconnection between restorative dentistry (RD) and fixed prosthodontics (FP)

Characteristics	% Distribution (by column)
	Pre-clinical students (n=151; 54.9%)	Clinical students (n=82; 29.8%)	Recent graduates (n=42; 15.3%)
Age (years): mean ±SD	21.6 ±0.9	23.7 ±0.8	25.2 ±1.4
Sex: male	40.40	42.68	38.10
female	59.60	57.32	61.90
Interconnection between RD and FP	Total (n=275)
Knowledge: highly interconnected		6.55
moderately interconnected		42.91
somewhat interconnected		46.54
not interconnected at all		4.00
Skills: highly interconnected		22.91
moderately interconnected		56.36
somewhat interconnected		19.27
not interconnected at all		1.46

Quantitative findings from questionnaire

According to quantitative data analysis, the five most essential and challenging subjects related to RD and FP learning and skill development are shown in Figs. 1 and 2. The three most essential topics for learning RD and FP encompassed cavity preparation or fixed prosthesis design, fundamental knowledge of RD and FP, and occlusion (Fig. 1). In contrast, the three key topics essential for skill development consisted of making final impressions, tooth or cavity preparation, and prosthesis cementation. The most challenging learning topics were occlusion, dental materials, and fabricating fixed prostheses on existing removable dentures (Fig. 2). Furthermore, the most difficult skills involved tooth or cavity preparation, waxing for final prosthesis fabrication, and facebow transfer. To develop knowledge in RD and FP, observing the actual work situations and the educators’ ability to articulate and clarify were crucial (Fig. 3A). Meanwhile, working and practicing in real work situations was the most important factor for enhancing practical skill (Fig. 3).

Fig. 1.

Responses from questionnaire participants on the essential topics and skills related to restorative dentistry and fixed prosthodontics learning (n = 275) and practicing (n = 124). FP, fixed dental prosthodontics; RD, restorative dentistry

Fig. 2.

Response from questionnaire participants on the challenging topics and skills related to restorative dentistry and fixed prosthodontics learning (n = 275) and practicing (n = 124). FP, fixed dental prosthodontics; RD, restorative dentistry; RPD, removable partial dental prosthesis

Fig. 3.

Participants’ responses (%) on the six most common factors contributing to knowledge and skill development

Qualitative findings from focus group interviews

The results from focus-group interviews identified threshold concepts for RD as restorative techniques, covering cavity preparation design and restorative material selection (Table 2). The threshold concepts for FP comprised resin cement and treatment planning, which involves crown and bridge design and restorative material selection. The tacit knowledge for RD was caries removal, while for FP, it was tooth or cavity preparation and material handling (Table 3). The study did not focus on specific caries removal techniques but on the development of tacit knowledge related to clinical skills, regardless of whether the lesion was active or arrested dental caries. An overview of the results derived from the thematic analysis is presented as a thematic map in Fig. 4.

Table 2.

Participants’ statements indicating threshold concepts for restorative dentistry and fixed dental prosthodontics

Restorative dentistry
Restorative techniques	“In a real clinical situation, teeth are not in an ideal condition. Therefore, the decision to choose the appropriate material for dental fillings and the techniques required not only depending on knowledge from lectures but also on experience, which undergraduate students still lack and rely solely on educators.” – 5th year student (5B)
	“There are many instruments for tooth filling, each designed for specific uses and steps. It can be confusing for beginners to comprehend the correct procedures and instructions in clinical practice.” – 4th year student (4E)
	“There is no dedicated lecture for checking the occlusion in the operative lectures, we learn about normal occlusion in the occlusion course and in other lessons, but there is no clear instruction for achieving the desired occlusion for direct restoration.” – 5th year student (5D)
Fixed dental prosthodontics
Treatment planning	“For undergraduates, a fixed prosthesis is typically seen as just a crown. However, when we are required to work with partial coverage fixed prostheses, such as onlays and inlays, we often struggle with understanding what is right or wrong regarding the design, preparation ideas, and mechanics.” – 6th year student (6B)
	“When facing two different treatment options, we understand deeply that there is only one best choice. However, making this decision relies not only on knowledge from lectures but also on the patient’s socioeconomic status, which influences the design and material used. Inexperienced dental students like us struggle to determine which option would be the best.” – 5th year student (5 A)
	“In my case, the patient had a root canal-treated tooth with a loss of coronal structure. In my opinion, the remaining tooth structure was not adequate, so the placement of a post and core was required. However, with the educator’s recommendation, the final design is just an onlay without a post.” – 5th year student (5G)
Resin cement	“Whenever I had to use resin cement, I have to review the lecture over and over again. It is challenging to have a clear picture of the molecular interaction between active components and tooth structure in mind.” – 6th year student (6 A)
	“Resin cement is very overwhelming because there are various brands to choose from, and each brand has different active components, mechanisms of action, as well as instructions and indications for use.” – recent graduate dentist (F)

Table 3.

Participants’ statements indicating Tacit knowledge for restorative dentistry and fixed dental prosthodontics

Restorative dentistry
Caries removal	“In the caries removal step, I knew that caries still remained, but I didn’t go for the rest of it because of the fear of pulpal exposure and lack of confidence in tooth preparation.” – 5th year student (5D)
	“When it comes to tooth preparation, I’m very afraid of caries removal, especially near the gum line. In the lab, I also don’t want to make mistakes because I’m afraid of having to buy new artificial teeth. With patients, I’m even more cautious because I fear damaging their gums. However, the skills gained from the lab are helpful because I know how much pressure to apply when doing tooth preparation in clinical practice. Working with real patients’ teeth in the lab closely resembles working on real patients, although it is more challenging because real patients have cheeks and tongues.” – 5th year student (5E)
Fixed dental prosthodontics
Tooth preparation	“Tooth preparation can be time-consuming and very stressful for a beginner like me because I cannot control my hand movements precisely, and it takes time to do proper work.” – 4th year student (4D)
	“At first, I didn’t really understand what the final result would look like, so I overprepared the proximal part. However, as I observed my friend’s work and instructor’s demonstration, I finally grasped the end goal of the preparation.” – 4th year student (4F)
	“Having a picture of a prepared tooth for crown restoration in a tooth with severe loss of structure is harder than in a full-structure tooth” – 5th year student (5 A)
	“When I was an undergraduate student, my post and core case almost resulted in perforation due to severe loss of tooth structure. Aligning dental burs with the tooth axis was challenging.” – Recent graduates (B)
Material handling	“Taking final impressions with light body silicone is very delicate, even in laboratory practice. In clinical practice, I find it even more challenging as there are additional factors to consider, such as patient manipulation and moisture control.” – 5th year student (5G)
	“I struggle with obtaining impressions of abutment teeth. I have tried several times but still cannot get it right, and I do not know why my impressions kept failing. It is only with the help of my advisor that my impressions are usable.” – 6th year student (6G)

Fig. 4.

Thematic map illustrating threshold concepts, tacit knowledge, and strategies for achieving competencies in restorative dentistry (RD) and fixed prosthodontics (FP)

Discussion

The present study identified threshold concepts and tacit knowledge that act as barriers to understand and develop skills in RD and FP. Our findings highlighted the interconnection between RD and FP, as they share similar threshold concepts and tacit knowledge. The threshold concepts encompass tooth or cavity preparation design, and restorative material selection. Caries removal and tooth preparation are tacit knowledge in RD and FP, respectively.

The threshold concepts in RD and FP, including tooth preparation design and restorative material selection, pose challenges due to complexity of real clinical situations compared with ideal laboratory conditions. The undergraduate FP curriculum mainly focuses on full coverage crowns, while clinical practice often requires alternative restorative designs, such as partial coverage crowns and onlays. Decisions on FP design and material selection are influenced by various factors, such as clinical experience and preference of the educators, and patient’s financial constraints. Dental students typically practice on ideal tooth anatomy in the laboratories but lack experience in adapting to specific tooth defects and determining the need for post placement. The variety of instruments and techniques for individual case further challenges the decision-making process for beginners.

A key difference between RD and FP is the inclusion of resin cement as a threshold concept in FP. This complexity arises from the variety of material brands, consistencies, handling steps, and surface treatment associated with different restorative materials, unlike the more consistent adhesive bonding used for dental fillings. In clinical practice, dental students need to perform complex, irreversible procedures under educator supervision [22], highlighting the importance of integrating knowledge, skills, and professional character in real practices. Consequently, students at the advanced beginner stage may struggle with resin cement principles and applications due to limited clinical experience.

Our findings highlighted challenges in tasks requiring precise psychomotor ability, visualization, and material handling. Tooth preparation emerged as tacit knowledge for both RD and FP because it requires a combination of visualizing the result and controlling hand movements during the preparation process. This is because both cognitive awareness (mental imaginary) and motor movement (dexterity and precision) are required during the associative stage of psychomotor development [10, 12]. A clear understanding of tooth preparation procedures and a mental image of the desired outcome facilitates students shaping and contouring the prepared tooth. Students lacking this visualization may find it difficult to achieve the desired results.

However, good visualization skills alone are insufficient for achieving correct tooth preparation. Dental students with good visualization might remain struggle with hand movement control and aligning dental burs, as cognitive awareness occurs in the frontal lobe of the brain while motor movements are controlled by the basal ganglia [3]. These functions develop separately but can be integrated through practice with immediate feedback. Therefore, knowing tooth preparation techniques and visualizing outcomes does not guarantee effective performance. This explains why students consider tooth preparation as a major tacit knowledge due to their lack of clinical experience. Similarly, caries removal is challenging because the caries texture in a patient’s vital tooth often differs from laboratory practice. This difficulty arises from the need for fine motor control, limited clinical experience, and the challenges of replicating real clinical situations.

To overcome the threshold concept and tacit knowledge in RD and FP, focus should be on three components: learners, teaching materials, and educators. Students need a solid knowledge foundation to learn new concepts and develop psychomotor skills. Strong prior knowledge facilitates learning through zone of proximal development [23], where prior knowledge and guiding materials act as learning scaffolds for understanding new concepts, and develop cognitive awareness required for psychomotor development [10]. Core knowledge for RD and FP includes dental anatomy, occlusion, and dental materials, which assist students understand normal oral structures and conditions before engaging in operative or prosthodontic reconstruction. Moreover, learning materials should be designed for clarity, utilizing visual media, and connecting clinical cases with lectures and demonstrations to support learning through zone of proximal development.

Clinical educators play a crucial role by sharing their experiences, providing immediate feedback, and facilitating discussions and demonstrations. They should encourage students to identify mistakes, exchange knowledge, and receive guidance for improvement. Advice and feedback are essential for students to gain confidence, correct misconceptions, and manage tacit knowledge [3]. Advanced beginner students require extensive clinical practice with educator guidance and feedback to develop cognitive awareness and motor skill, strengthening neural linkages between the frontal lobe and basal ganglion during the associative stage. The present study revealed that clinical observation and educator explanations are essential for effective learning. Consistent with a previous report [24], maximizing dental student learning requires educational strategies that provide support and guidance, as well as encourage learning-by-doing in real professional contexts.

A previous study demonstrated tacit knowledge and threshold concepts in removable dental prosthodontics [1]. Our findings revealed that fixed and removable prosthodontics share similarities and differences in barriers to knowledge and skill development. Both fields identify fundamental knowledge and prosthesis design as threshold concepts, requiring integration of basic knowledge with various clinical contexts. Tacit knowledge in both areas includes material handling, especially in impression making, which includes patient management and factors such as moisture control and gingival retraction, differing from laboratory practice. Visualization of desired outcomes is essential in both fixed and removable prosthodontics. RD and FP require visualizing preparation techniques, including bur position, dentist position, final tooth preparation, and final prosthesis design. In contrast, removable prosthodontics involve imaging mandibular movement and the dynamic movement of dentures. FP requires more fine motor skills for controlling dental burs, greater chair-side management, and involves irreversible tooth alterations. Therefore, students need to develop more extensive procedural and psychomotor skills to achieve satisfactory outcomes in FP.

Laboratory practice with dental models assists FP by encouraging visualization, but may not be sufficient for removable work, which involves muscle control and patient-specific movement [1]. Removable prosthodontics requires patient management skills, such as recording the vertical dimension and centric relation, while fixed prosthodontics focuses on fine motor skills due to the limited nature of undergraduate FP case that do not alter these relations [2].

The present findings indicate that RD and FP are interconnected and complementary, as students reported a perceived moderate to high level of interconnection between the two disciplines. Further studies on developing psychomotor skills for undergraduate dental students will enhance operative and prosthodontic education, and curriculum design. It is important to note that the work in other dental disciplines may vary significantly, leading to different learning barriers and requirements for knowledge and skill development. Extending these findings to other disciplines require additional research to address unique learning styles, skills development, and barriers.

Some limitations in this study included a relatively low response rate for the questionnaire, which may introduce non-response bias, particularly among recent graduates working in public sectors with limited FP cases. However, in this critical-theory-based study, the questionnaire primarily served to generate questions for focus group interviews, with quantitative data supporting the main qualitative findings. Additionally, this study was conducted at a single dental school, where the sequences of learning topics, teaching methods, environment, and facilities are specific to that setting. Qualitative research inherently involves personal interpretation and judgment, which can introduce biases [25]. To mitigate this, reflexivity was applied to objectively explain the experiences, beliefs, and assumptions of the investigators [26]. Further studies using both quantitative and qualitative approaches are recommended to enhance generalizability and provide deeper insight, as threshold concepts and tacit knowledge commonly emerge during the development of RD and FP competencies across diverse contexts.

Conclusions

Developing competency in RD and FP requires the integration of knowledge and skill, with the two branches being interconnected. Barriers to developing RD and FP competencies were proposed using threshold concepts and tacit knowledge as a foundation. To enhance learning and competency development in undergraduate dental students for RD and FP, attention should be focused on three components: learners, teaching materials, and educators.

Authors’ contributions

KM, PP, and SP play major role in data collection, data interpretation, preparation of the figure presentation of the published work, and writing the original draft and editing the manuscript. SC and NL play major role in conceptualization, study design, provision of study resources, data validation, writing the original draft, and editing the manuscript. SC is an expert in dental education, and NL is a prosthodontist in the dental faculty.

Data availability

The data generated during the current study is available upon request to the corresponding authors.

Declarations

Ethics approval and consent to participate

The study had been performed in accordance with the Declaration of Helsinki and was approved by the Human Research Ethics Committee of the Faculty of Dentistry, Chulalongkorn University (code no. HREC-DCU 2022-094). All participants agreed and signed informed consent prior to study participation.

Consent for publication

No publication consent required.

Competing interests

The authors declare no competing interests.