[Effect of printing orientation on physical and mechanical properties of 3D printing prosthodontic base resin materials].

OBJECTIVE: To analyze the influence of forming direction on the surface characteristics, elastic modulus, bending strength and fracture toughness of printed parts and the relationship between forming direction and force direction, and to provide scientific basis and guidance for the clinical application of oral denture base resin materials. METHODS: The 3D printing technology was used to print denture base resin samples. The shape and size of the samples referred to the current standard for testing conventional denture base materials. The samples used for physical performance testing were cylindrical (with a diameter of 15 mm and a thickness of 1 mm) and printed at different angles along the Z axis (0°, 45°, 90°). Scanning electron microscope was used to observe the microscopic topography of the different samples. The color stability of different samples was observed by color stabilizer. The surface roughness of the samples was analyzed by using surface roughness tester. The Vickers hardness was measured to analyze the hardness of the samples. The samples used for mechanical performance testing were rectangular (elastic modulus and bending strength: A length of 64 mm, a width of 10 mm, and a height of 3.3 mm; fracture toughness: A length of 39 mm, a width of 8 mm, and a height of 4 mm), divided into two groups: W group and H group. The W group was printed from the bottom up along the Z axis with the length × width as the bottom surface parallel to the X, Y axis plane, while the H group printed from the bottom up along the Z axis with the length × height as the bottom surface parallel to the X, Y axis plane. The forming angles of both groups were equally divided into 0°, 45°, and 90°. The elastic modulus, bending strength and fracture toughness of different samples were studied through universal mechanical testing machine. SPSS 22.0 software was used for statistical analysis. RESULTS: The microscopic topography and roughness of different samples were closely related to the printing direction, with significant differences between the 0°, 45°, and 90° specimens. The 0° specimens had the smoothest surface (roughness < 1 µm). The surface of the 45° specimen was the roughest (roughness>3 µm). The microhardness of the 0° sample was the best [(196.13±0.20) MPa], with a significant difference compared with the 90° sample [(186.62±4.81) MPa, P < 0.05]. The mechanical properties of different samples were also closely related to the printing direction. The elastic modulus, bending strength, and fracture toughness of the 45° samples in the W group were the highest compared with the other groups. The results of elastic modulus showed that in the H group, the 45° specimens had the highest elastic mo-dulus, which was significantly different from the 0° and 90° specimens (P < 0.05). The elastic modulus of 0° and 45° specimens in the W group were higher than those in 90° specimens (P < 0.05). The bending strength results showed that there was no significant difference between the specimens from dif-ferent angles in the H group. The bending strength of the 90° specimens in the W group was the smallest, and there was a significant difference between 90° and the 0° and 45° specimens (P < 0.05); And the bendind strength of the 0° and 45° specimens in the W group was significantly higher than that of the 0° and 45° specimens in the H group (P < 0.05). The fracture toughness results showed that the fracture toughness of the H group specimens was lower than 1.9 MPa m1/2, which was specified in the denture base standard. The 45° samples in the W group were the highest, with significant differences compared with the 0° and 90° samples (P < 0.05). And the 90° samples of the W group specimens were lower than 1.9 MPa m1/2. And the fracture toughness of the 45° specimen in the W group was significantly higher than that of all the specimens in the H group (P < 0.05). CONCLUSION: The 0° samples had relatively better physical properties. The 45° samples had the best mechanical properties. But the fracture toughness of specimens (H group and 90° samples of W group) did not yet meet clinical requirements. That indicated that the characteristics of the 3D printing denture base resin were affected by the printing direction. Only when the performance of the printed samples in all directions met the minimum requirements of the standard, they could be used in clinical practice.

EFFECT OF SURFACE ABRASION AND TEMPERATURE TREATMENT ON METASTABLE TETRAGONAL ZIRCONIUM DIOXIDE (EXPERIMENTAL STUDY).

One of the significant drawbacks of using zirconium dioxide as a framework for prosthodontic structures is its propensity for breakage. Paradoxically, the higher the optical performance of zirconium dioxide, the more its mechanical durability tends to decrease and vice versa. A detailed analysis of the technological process has uncovered divergent opinions and significant disparities in recommendations concerning the fabrication of zirconium dioxide prosthodontic constructs. There are different recommendations regarding the need for abrasive blasting and regeneration firing. Consequently, conducting an in-depth experimental study on this matter and implementing the resulting findings will significantly contribute to addressing the challenges of prosthodontic rehabilitation for patients utilizing zirconium dioxide.

[Advances in the application of dynamic virtual patients in prosthodontics].

With the development and application of technologies such as facial scanning, intraoral scanning, virtual facebow and mandibular movement tracking in prosthodontics, dynamic virtual patients are gradually applied to preoperative analysis, esthetic diagnosis, treatment planning, and restorative implementation, becoming a research hotspot in recent years. This review focuses on data acquisition, construction of dynamic virtual patients and their application advantages, aiming to provide a reference for the clinical application of related digital technologies.

The chance and challenge of creating virtual patients in prosthodontics.

In the field of prosthodontics, the use of virtual patients for biomimetic restoration holds great promise for various applications. Virtual patients consist of digitized data that encompasses details on the morphology, structure, and spatial relationships within the maxillofacial and intraoral regions. Nonetheless, there are several challenges associated with acquiring digital data, achieving accurate alignment, and recording and transferring dynamic jaw movements. This paper aims to concentrate on the process of constructing virtual patients, highlight the key and challenging aspects of virtual patient construction, and advocate for the extensive adoption and utilization of virtual patient technology.

Translucency of recent zirconia materials and material-related variables affecting their translucency: a systematic review and meta-analysis.

BACKGROUND: Recent forms of translucent zirconia material have been developed, offering a wide range of options and varieties for enhancing aesthetics, making it a preferred choice in the field of prosthetic dentistry. However, there is insufficient understanding regarding the recent types of zirconia materials and their optical behavior. Understanding the variables that influence the translucency of zirconia and identifying strategies to enhance its esthetics are crucial. PURPOSE: The current systemic review highlights a comprehensive understanding of different zirconia generations in relation to their optical characteristics and evaluates material-related variables affecting their translucency. METHODS: The present review studied in-vitro studies that evaluated the optical characteristics of different yttria content of yttria stabilized materials. The topics explored were: (1) the different zirconia material generations and their optical behavior; (2) material-related factors that affect their translucency. The research was restricted to online publication in the English language from July 1, 2010, to July 31, 2023, using PubMed, Scopus, and Science Direct resources. The search key terms and their combinations were "zirconia," "translucent zirconia," "cubic zirconia," "highly translucent zirconia," "yttria partially stabilized zirconia," "monolithic zirconia," "translucency," "optical properties," and "light transmission." RESULTS: The data obtained from fifty-three studies addressed the optical characteristics of various zirconia generations. They reported that changing yttria content had a significant impact on translucency. Different kinds of zirconia ceramics of the same generation have varying translucencies. Achieving optimum aesthetics with monolithic zirconia is challenging due to factors related to material aspects such as the presence of additives, point defects, microstructure, thickness, phase distribution, and sintering conditions. CONCLUSIONS: Newly developed monolithic dental zirconia ceramics have improved aesthetics and translucency. However, additional research is necessary to evaluate their performance and long-term durability. TRIAL REGISTRATION: This systematic review was registered in PROSPERO, under number CRD42023474482.

Psychometric properties of the Arabic version of the perceived prosthodontic treatment need scale: Exploratory and confirmatory factor analyses.

BACKGROUND: It is crucial to take into account the concerns of dental patients about their prosthodontic needs when planning the course of treatment. However, there is a dearth of research that examines these needs among adult dental patients. OBJECTIVES: This study aims to translate and validate the perceived prosthodontic treatment need scale (PPTN) in Arabic. METHODS: The 17-item PPTN scale was translated from English into Arabic and completed by 206 patients seeking prosthodontic treatment in a dental hospital in Saudi Arabia. Data collection was carried out in September and October 2023. Exploratory factor analysis (EFA) was used to ascertain the underlying factor structure; a unidimensional scale was hypothesised and tested using confirmatory factor analysis (CFA), including several multiple model fit indices. The assessment of reliability was conducted using Cronbach's alpha. The convergent and discriminant validity of the final scale were examined. RESULTS: EFA produced an 11-item scale distributed into three factors that explain 65.43% of the total variance with eigenvalues > 1. All items showed acceptable reliability, ranging from 0.65 to 0.84. The first factor pertained to social issues, while the second item was concerning dental appearance. Lastly, the third factor included functional difficulties associated with tooth loss or dental problems. The results of the CFA demonstrate a satisfactory level of model fit, with the standardised factor loadings ranging from 0.51 to 0.89. Convergent and discriminant validity of the model factors were established. CONCLUSION: The translated questionnaire was deemed legitimate and would be useful in comprehending patients' perceived treatment requirements, hence contributing to the advancement of prosthodontic research and practical implementation.

Recent advances in additive manufacturing of patient-specific devices for dental and maxillofacial rehabilitation.

OBJECTIVES: Customization and the production of patient-specific devices, tailoring the unique anatomy of each patient's jaw and facial structures, are the new frontiers in dentistry and maxillofacial surgery. As a technological advancement, additive manufacturing has been applied to produce customized objects based on 3D computerized models. Therefore, this paper presents advances in additive manufacturing strategies for patient-specific devices in diverse dental specialties. METHODS: This paper overviews current 3D printing techniques to fabricate dental and maxillofacial devices. Then, the most recent literature (2018-2023) available in scientific databases reporting advances in 3D-printed patient-specific devices for dental and maxillofacial applications is critically discussed, focusing on the major outcomes, material-related details, and potential clinical advantages. RESULTS: The recent application of 3D-printed customized devices in oral prosthodontics, implantology and maxillofacial surgery, periodontics, orthodontics, and endodontics are presented. Moreover, the potential application of 4D printing as an advanced manufacturing technology and the challenges and future perspectives for additive manufacturing in the dental and maxillofacial area are reported. SIGNIFICANCE: Additive manufacturing techniques have been designed to benefit several areas of dentistry, and the technologies, materials, and devices continue to be optimized. Image-based and accurately printed patient-specific devices to replace, repair, and regenerate dental and maxillofacial structures hold significant potential to maximize the standard of care in dentistry.

ChatGPT performance in prosthodontics: Assessment of accuracy and repeatability in answer generation.

STATEMENT OF PROBLEM: The artificial intelligence (AI) software program ChatGPT is based on large language models (LLMs) and is widely accessible. However, in prosthodontics, little is known about its performance in generating answers. PURPOSE: The purpose of this study was to determine the performance of ChatGPT in generating answers about removable dental prostheses (RDPs) and tooth-supported fixed dental prostheses (FDPs). MATERIAL AND METHODS: Thirty short questions were designed about RDPs and tooth-supported FDP, and 30 answers were generated for each of the questions using ChatGPT-4 in October 2023. The 900 generated answers were independently graded by experts using a 3-point Likert scale. The relative frequency and absolute percentage of answers were described. Accuracy was assessed using the Wald binomial method, while repeatability was evaluated using percentage agreement, Brennan and Prediger coefficient, Conger generalized Cohen kappa, Fleiss kappa, Gwet AC, and Krippendorff alpha methods. Confidence intervals were set at 95%. Statistical analysis was performed using the STATA software program. RESULTS: The performance of ChatGPT in generating answers related to RDP and tooth-supported FDP was limited. The answers showed a reliability of 25.6%, with a confidence range between 22.9% and 28.6%. The repeatability ranged from substantial to moderate. CONCLUSIONS: The results show that currently ChatGPT has limited ability to generate answers related to RDPs and tooth-supported FDPs. Therefore, ChatGPT cannot replace a dentist, and, if professionals were to use it, they should be aware of its limitations.

Setting the boundaries and scope of practice for the two sister specialities of dentistry: Operative dentistry-endodontics and prosthodontics.

Dental academia in Pakistan has recently achieved an important milestone. The name of Operative Dentistry speciality has been changed to Operative Dentistry & Endodontics (ODE). It was a much-needed change that was first felt about two decades ago. However, with the correction of name, there are certain challenges that this speciality has to manage now. These include improving the curriculum, setting up standards, and lastly, setting up its boundaries and scope of practice as some of its scope overlaps with a sister speciality called Prosthodontics. This overlapping of the boundaries of dental disciplines is a problem that is unique to Pakistan, India, and some East Asian countries where Operative Dentistry or Conservative Dentistry is combined with Endodontics. This paper aims to discuss the objective delineation of dental procedures and suggest a model of peaceful co-existence of sister dental specialities.

Identifying barriers and strategies for achieving competency in removable prosthodontics in undergraduate dental students: a mixed-method study.

BACKGROUND: Developing competency in removable prosthodontics (RP) is challenging for undergraduate dental students because it involves threshold concepts and tacit knowledge. Understanding this process can enhance learning and professional development in RP. The objective of this study was to identify the barriers hindering knowledge (threshold concept) and skill (tacit knowledge) development, and to propose strategies for achieving RP competency. METHODS: Adopting critical theory, quantitative and qualitative approaches were implemented. The participants were third- to sixth-year dental students and recent dental school graduates. An online questionnaire was used to investigate the knowledge and skills required for achieving RP competency and barriers to RP competency development. Four focus groups were conducted to gather in-depth information. The data was analyzed using descriptive statistics and thematic analysis. RESULTS: A total of 322 respondents completed the questionnaire (67% response rate), and 26 of them participated in focus group interviews. The four threshold concepts to achieve RP competency were the basic principles of RP, removable partial denture design, occlusion, and dental materials. The two main tacit knowledges were impression making and material handling skills. The curriculum should integrate strategies to assist dental students in overcoming intrinsic barriers such as self-experience, revision, and spatial-temporal relationship, along with extrinsic factors such as clinical correlations of content, discussions, and immediate feedback. CONCLUSIONS: Threshold concepts and tacit knowledge in RP for undergraduate dental students have been proposed The strategies to overcome barriers comprise intrinsic and extrinsic factors that include the adoption of experiential learning. This study suggests effective teaching methods and learning strategies to maximize student learning and RP competency development when designing the undergraduate RP curriculum in dental education.

Prosthodontic rehabilitation of patients with a unilateral subtotal maxillectomy using a customised subperiosteal zygomatic implant: a post-COVID-19 mucormycosis.

Restoring the maxillary resection defect involving the alveolar process, the hard and soft palate and the paranasal sinuses in terms of phonetics, mastication and deglutition is more challenging, especially with young patients with aesthetic concerns.This case report describes the prosthodontic rehabilitation of a young patient with a unilateral subtotal maxillectomy due to post-COVID-19 mucormycosis. A patient-specific subperiosteal implant was planned to rehabilitate the patient's bony defect. Using postsurgical CT, a customised subperiosteal titanium framework was fabricated by the direct metal laser sintering method using grade IV titanium alloy. The fabricated framework was implanted over the patient's zygomatic anatomic contour. Three months later, the patient-specific implant was unveiled to the oral cavity, an open-tray impression was made and the fixed implant prosthesis was fabricated.This case report opens a new realm of rehabilitation for severely compromised maxillary bony defects and impaired oral functioning with no other viable conventional reconstruction options.

Perio-prosthodontic pontic site management, part II: Pontic site reconstruction strategies to enhance the esthetic and biological outcomes.

OBJECTIVE: Ridge deformities are present in most patients after tooth extraction; these defects make the management of future implant and pontic sites challenging to deal with. The restorative team should be able to diagnose and treat these deformities to allow for successful outcomes. Many approaches have been described to reconstruct pontic sites, each with specific indications. This article describes the different approaches to reconstructing pontic sites and their indications to allow for a proper esthetic and biological environment for future restorations. CLINICAL CONSIDERATIONS: Depending on the severity of the defect, location, and the esthetic necessity, pontic site enhancement can be done through different approaches, some requiring soft tissue grafting, hard tissue grafting, or both. Understanding the indications of the treatment options is essential to allow the clinician to make the right therapeutic decision and achieve the best possible perio-prosthodontic outcomes. CONCLUSIONS: An adequate balance between the soft tissue and prosthetics is essential to achieve successful results on implant-supported or tooth-supported fixed dental prostheses (FDPs). Selecting the right approach to treat ridge deformities is necessary to increase treatment success, reduce over-treatment, and create a biologically sound environment for restorations. CLINICAL SIGNIFICANCE: Pontic site enhancement through reconstructive surgery will allow for esthetically pleasing and biologically stable results, allowing restorations to emulate natural structures lost after tooth extraction.

Bibliographic analysis and evaluation of the mesh keywords in the journal of prosthodontics: Implant, esthetic, and reconstructive dentistry.

BACKGROUND: Various studies have been conducted to analyze data via bibliometric analysis in different dentistry, including prosthetic dentistry. However, these studies evaluated the most cited published articles in dentistry. OBJECTIVE: To analyze and evaluate the characteristic development of several mesh keywords in the Journal of Prosthodontics - Implant, Esthetic, and Reconstructive Dentistry between 1992 and 2022. METHODS: The Scopus databases was searched to retrieve the data related to 8 categories, including published articles, most cited documents, authors and organizations, and maximum articles cited during the evaluation period. The data retrieved were exported to a Microsoft Excel sheet and were analyzed using the bibliometrix package. The data were first analyzed for ten years and then for 30 years. The highest of 10 were reported for each category, and co-authorship, reoccurrence, and linked data were also reported. RESULTS: 2603 published documents were recorded from the Scopus databases. Articles comprised 87.9% of the total published work, followed by review articles at 5.46%. The most productive decade was between 2013 and 2022. 3793 terms were used during the evaluation period, with the maximum number in 2003-2012 (2481). A total of 5392 keywords were used during 1992-2022, with the highest number (3232) from 2013 to 2022. A total of 6108 authors were acknowledged, with the maximum number (3964) from 2013 to 2022 and the fewest (767) from 1992 to 2002. Authors from different countries increased from 17 countries in 1992-2002 to 52 countries in 2013-2022 (total = 63 countries). Similarly, the number of organizations increased from 312 organizations in 1992-2002 to 1315 organizations in 2013-2022 (total = 1976 organizations). CONCLUSION: The current bibliometric analysis delivered a comprehensive overview about more spread research topics and its impactful role in contemporary dentistry, especially prosthetic dentistry.

Self-assessment skills of undergraduate dental students in the preclinical course of complete removable prosthodontics at Tehran University of Medical Sciences.

INTRODUCTION: This study evaluated the self-assessment skills of third-year dental students regarding their performance in complete removable prosthodontics (CRP) preclinical course. METHODS AND MATERIALS: This cross-sectional study was conducted on all third-year dental students attending the International Dental College of Tehran University of Medical Sciences. The students were requested to self-assess their performance in primary impression making, custom tray fabrication, border moulding, final impression making, master cast fabrication, record-base fabrication and tooth arrangement in CRP preclinical course. The performance of dental students in each step was scored by themselves and their mentors. Data were analysed by the Mann-Whitney U, Pearson's correlation and t-tests (α = 0.05). RESULTS: Totally 25 male (55.6%) and 20 female (44.4%) dental students were evaluated. Significant differences were noted between male and female dental students in self-assessment scores regarding adequate extension of the custom tray (p = .027), the correct position of tray handle (p = .020), visibility of vestibular width and depth on the cast (p = .011), the coincidence of upper and lower midlines (p = .005) and correct orientation of maxillary and mandibular planes in the articulator (p = .036). The mean self-assessment score of female students was significantly higher than that of male students (p = .01). The scores given by the mentors were not significantly different for male and female students (p = .975). The difference between the self-assessment score of students and the mentor score was not significant (p = .067) either in males or in females (p > .05). CONCLUSION: Undergraduate dental students favourably self-assessed their performance in all steps of the preclinical course of CRP, comparable with their mentor assessment.

Modular training model for education of students in restorative and prosthodontic dentistry.

INTRODUCTION: At the moment, no commercial model solution is available for the individualisation of the dentition depending on the clinical case scenario. Furthermore, the realistic training of most restorative and prosthodontic procedures on a single dental study model is not possible. The aim of this study was the creation of a new training model to fill this gap. MATERIALS AND METHODS: Complete upper and lower jaw models were created based on existing scans and radiological data from a patient. All components for 100 complete models and 1128 teeth for the training were produced with a SLA-printer. Overall, 94 voluntary students attending the first and second preclinical course in prosthodontics tested the functionality of the model with three different tooth types against a standard dental study model and real teeth. After the training, the model was rated in a questionnaire. RESULTS: The production of the models and teeth was feasible. The overall rating of the different teeth was worse for type I (Ø 3.6 ± 1.1), significantly better for type II (Ø 2.5 ± 1.0) and type III (Ø 2.4 ± 1.0) than a standard typodont tooth (Ø 2.7 ± 1.1). The new model was rated significantly better overall (Ø 2.6 ± 1.0) than the standard training model (Ø 3.0 ± 1.1). CONCLUSIONS: The aim of this study was fulfilled. A superior training model was created with equivalent and better tooth types. The new teeth were outstanding in terms of cost-efficiency, appearance and feeling during preparation.

[Effect of 4 kinds of prosthodontic materials on masticatory and gingival function].

PURPOSE: To investigate the effect of 4 kinds of prosthodontic materials on masticatory and gingival function. METHODS: A total of 167 patients with dental defects who underwent prosthodontic treatment from October 2019 to January 2022 were collected. They were randomly divided into 4 groups with 41 cases in the pure titanium group, 40 cases in the cobalt-chromium alloy group, 43 cases in the nickel-chromium alloy group and 43 cases in the zirconium dioxide group. The curative effect and satisfaction degree after 6 months of treatment in 4 groups were recorded and compared. The masticatory function (chewing efficiency, bite force), gingival function[plaque index(PLI), gingival index(GI) and sulcus bleeding index(SBI)], gingival crevicular fluid inflammation-related indicators[tumor necrosis factor alpha(TNF-α), interleukin-6(IL-6), aspartate aminotransferase(AST) and alkaline phosphatase (alkaline phosphatase, ALP)] before and after treatment were measured and compared in 4 groups. Statistical analysis was performed with SPSS 20.0 software package. RESULTS: There was no significant difference in curative effect in 4 groups(P＞0.05). Before and after treatment, there was no significant difference in mastication efficiency and bite force in 4 groups(P＞0.05). Before treatment, there was no significant difference in PLI, GI, SBI, gingival crevicular fluid weight, TNF-α, IL-6, AST and ALP in gingival crevicular fluid in 4 groups(P＞0.05). Compared with before treatment, PLI, GI and SBI in 4 groups were decreased after treatment (P＜0.05), and the decrease was in the order of cobalt-chromium alloy group≈nickel-chromium alloy group＜pure titanium group＜zirconia dioxide group. Before treatment, there was no significant difference in the weight of gingival crevicular fluid, TNF-α, IL-6, AST and ALP in gingival crevicular fluid in 4 groups(P＞0.05). The crevicular fluid weight, TNF-α, IL-6, AST and ALP in gingival crevicular fluid were significantly increased(P＜0.05), and the increase was in the order of zirconia group＜pure titanium group＜cobalt-chromium alloy group≈nickel-chromium alloy group. There was no significant difference in restoration integrity and color satisfaction in 4 groups(P＞0.05), but there was significant difference in marginal fitness and sensitivity satisfaction in 4 groups(P＜0.05). CONCLUSIONS: Pure titanium, cobalt-chromium alloy, nickel-chromium alloy and zirconium dioxide can be used for the treatment of dentition defects, and they all can obtain satisfactory chewing function. In addition, zirconium dioxide restoration has the effect of improving gingival function and inflammation-related indicators of gingival crevicular fluid with a broader application prospect.