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).
CONCLUSIONS: 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.

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.
在口腔修复领域，构建虚拟患者进行数字化仿生修复展现出广阔的应用前景。虚拟患者由包含口颌面部信息的数字化素材构成，能准确地反映出口颌面结构的形态和空间关系。然而，在数字化素材的获取、精确配准过程和动态颌位关系的记录与转移中，均存在诸多挑战。本文将围绕虚拟患者的构建流程，阐述目前构建虚拟患者的关键点和难点，推动虚拟患者技术在口腔修复领域的普及和推广。.

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.
随着面部扫描、口内扫描、虚拟面弓、下颌运动轨迹记录等技术在口腔修复领域的发展及应用，动态虚拟患者技术逐渐被应用于口腔修复的术前分析、美学诊断、治疗设计及修复体制作，并成为近年的研究热点。本文从口腔动静态数据获取、动态口腔虚拟患者的构建、动态口腔虚拟患者的应用优势等方面对动态虚拟患者技术在口腔修复领域中的应用和研究展开综述，以期为相关数字化技术的临床应用提供参考。.

OBJECTIVE: This review aims to summarize the available technologies, material categories, and prosthodontic applications of additive manufacturing (AM) dental ceramics, evaluate the achievable accuracy and mechanical properties in comparison with current mainstream computer-aided design/computer-aided manufacturing (CAD/CAM) subtractive manufacturing (SM) methods, and discuss future prospects and directions.
METHODS: This paper is based on the latest reviews, state-of-the-art research, and existing ISO standards on AM technologies and prosthodontic applications of dental ceramics. PubMed, Web of Science, and ScienceDirect were amongst the sources searched for narrative reviews.
RESULTS: Relatively few AM technologies are available and their applications are limited to crowns and fixed partial dentures. Although the accuracy and strength of AM dental ceramics are comparable to those of SM, they have the limitations of relatively inferior curved surface accuracy and low strength reliability. Furthermore, functionally graded additive manufacturing (FGAM), a potential direction for AM, enables the realization of biomimetic structures, such as natural teeth; however, specific studies are currently lacking.
CONCLUSIONS: AM dental ceramics are not sufficiently developed for large-scale clinical applications. However, with additional research, it may be possible for AM to replace SM as the mainstream manufacturing technology for ceramic restorations.

OBJECTIVE: This study aimed to develop and evaluate a simple, non-destructive method for assessing the misfit and passivity of implant-retained prostheses frameworks.
METHODS: To simulate the rehabilitation of a mandible posterior partially edentulous area using 3-unit screw-retained frameworks supported by two implants were fabricated and divided into the following five groups (n = 10 in each group): OP = one-piece framework cast in Co-Cr with the conventional method (control-group); Co-Cr frameworks sectioned and welded by laser (=LAS) or tungsten inert gas (=TIG); Co-Cr CAD-CAM = milled Co-Cr framework; Zir CAD-CAM = milled zirconia framework. The horizontal |X| and vertical |Y| misfits were measured using confocal laser scanning microscopy with one or both screws tightened. Data were analyzed by a two-way ANOVA with repeated measures and Bonferroni correction (α = 0.05).
RESULTS: The greatest |X| misfit was observed in the OP group with both screws tightened (290 µm) and one screw tightened (388 and 340 µm). The conventional casting groups sectioned and welded by laser or TIG had lower mean values (235.35 µm, both screws tightened; and 275 µm, one screw tightened) than the OP framework. However, these values still exceeded those of the milled Co-Cr and zirconia frameworks (190 and 216 µm with both screws tightened). Across all reading conditions, every framework subjected to testing consistently maintained vertical |Y| misfit levels below the threshold of 53 µm; however, the milled frameworks exhibited higher vertical misfits than the frameworks obtained by the conventional cast method.
CONCLUSIONS: The frameworks, whether cast and sectioned with laser welding or milled from Co-Cr, exhibit improved marginal misfit and enhanced passive fit when compared to other fabrication methods. Additionally, the use of confocal laser scanning microscopy is highly effective for passivity and misfit analysis.

Artificial intelligence represented by deep learning has attracted attention in the field of dental implant restoration. It is widely used in surgical image analysis, implant plan design, prosthesis shape design, and prognosis judgment. This article mainly describes the research progress of deep learning in the whole process of dental implant prosthodontics. It analyzes the limitations of current research, and looks forward to the future development direction.

OBJECTIVE: 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.

BACKGROUND: The traditional Chinese dentistry classroom teaching model focuses on the instruction of knowledge details, but less on the frameworks and learners\' motivation. Here, we introduced a combination of mind mapping and PBL instruction (MBL)into the prosthodontics course for Chinese dental students. This study aimed to evaluate the effectiveness and efficiency of MBL in prosthodontics and make observations from the students\' perspectives, based on their response with the learning process.
METHODS: We prospectively enrolled 56 fourth-year undergraduates of stomatology, and these participants were randomly allocated into either the combined mind map teaching group (MBL) or the problem-based learning group (PBL) to attend the prosthodontics course. An anonymous questionnaire was also administered to both groups to evaluate the students\' perceptions and experiences, using closed and open-ended items. Data were analyzed using descriptive statistics and thematic analysis.
RESULTS: The students\' responses to closed items indicate their experience in PBL and MBL to be positive, including increased motivation, improved memory of knowledge, enhanced discipline connection and raised teamwork, with fairly higher ratings for the MBL group. However, the tutor-guided competence scores including the memory and framework part, were significantly higher for MBL group than PBL group (two-way ANOVA, p < 0.01, p < 0.001, respectively). Meanwhile, the self-perceived competence scores including the motivation, framework and teamwork part, were significantly higher for MBL group than PBL group (two-way ANOVA, p < 0.01, p < 0.001, p < 0.05, respectively).
CONCLUSIONS: Our findings suggest that MBL teaching approach can help in integration of knowledge structure and enhance clinical reasoning. MBL is an effective and well-organized method in prosthodontics course for dental students.

OBJECTIVE: The surge in digitalization and artificial intelligence has led to the wide application of robots in various fields, but their application in dentistry started relatively late. This scoping review aimed to comprehensively explore and map the current status of the clinical application of robots in dentistry.
METHODS: An iterative approach was used to gather as much evidence as possible from four online databases, including PubMed, the China National Knowledge Infrastructure, the Japan Science and Technology Information Aggregator, Electronic, and the Institute of Electrical and Electronics Engineers, from January 1980 to December 2022.
RESULTS: A total of 113 eligible articles were selected from the search results, and it was found that most of the robots were developed and applied in the United States (n = 56; 50%). Robots were clinically applied in oral and maxillofacial surgery, oral implantology, prosthodontics, orthodontics, endodontics, and oral medicine. The development of robots in oral and maxillofacial surgery and oral implantology is relatively fast and comprehensive. About 51% (n = 58) of the systems had reached clinical application, while 49% (n = 55) were at the pre-clinical stage. Most of these are hard robots (90%; n = 103), and their invention and development were mainly focused on university research groups with long research periods and diverse components.
CONCLUSIONS: There are still limitations and gaps between research and application in dental robots. While robotics is threatening to replace clinical decision-making, combining it with dentistry to gain maximum benefit remains a challenge for the future.

Symmetric extraction of premolars is a frequently used orthodontic treatment for dental crowding and protrusion. However, when a patient has incisors with ankylosis, the establishment of a treatment protocol often plagues orthodontists. An adolescent patient with a history of incisor trauma sought treatment for dental protrusion and crowding. Upon percussion of his infrapositioned maxillary central incisors, characteristic dull metallic sounds were noted, and a lack of normal mobility of these teeth under the application of external forces was detected. Follow-up radiographs after the trauma showed replacement root resorption of the maxillary central incisors. Based on clinical and radiological findings, ankylosis of the maxillary central incisors was tentatively diagnosed. A combination of orthodontic and prosthodontic treatment options involving extraction of the maxillary central incisors and mandibular first premolars was chosen to resolve the functional and esthetic problems. After treatment, well-aligned dentition, improved smile esthetics, and a more harmonious facial profile were achieved, and these outcomes remained stable during the follow-up period. This case report illustrates a viable treatment strategy for tackling predicaments caused by ankylosed incisors, which is unusual in the literature.