Postoperative Rehabilitation with a CAD/CAM-fabricated Occlusal Splint Following Plate Reconstruction after Hemimandibulectomy and Condylectomy: A Case Report.

Mandibular deviation (MD) is a common reconstruction sequela after segmental mandibulectomy. Although proper postoperative rehabilitation is critical for MD management and minimization, the information available is limited. This report describes postoperative rehabilitation with an occlusal splint fabricated using computer-aided design (CAD) and computer-aided manufacturing (CAM) (CAD/CAM-OS) and the results of a threedimensional occlusal analysis using an intraoral scanner after hemimandibulectomy and plate reconstruction. Despite the short follow-up, adherence to postoperative rehabilitation with CAD/CAM-OS for MD correction, even during radiotherapy, was demonstrated by the digital workflow and analysis results.

Radiographic alveolar bone assessment in correlation with primary implant stability: A systematic review and meta-analysis.

INTRODUCTION: The radiographic examination of alveolar bone using 3D radiographic examination is essential in dental implant treatment planning. Our study aimed to systematically review and quantitatively analyze the correlation between alveolar bone parameters, specifically bone density and cortical bone thickness, assessed using cone beam computed tomography (CBCT) and/or multidetector computed tomography (MDCT); and primary implant stability (PIS) determined using implant stability quotient (ISQ), Periotest® value (PTV), and insertion torque value (ITV). METHODS: This review was registered in the PROSPERO database (registration number CRD42022307245). An electronic literature search was conducted on the PubMed, SCOPUS, and Web of Science databases for papers published until February 2022. The Quality Assessment in Prognostic Studies (QUIPS) tool was used to assess risk of bias. Meta-analyses were conducted to calculate the estimated average correlation coefficient based on a multilevel random-effects model, followed by subgroup analysis. RESULTS: Twenty-six studies were included in this review, consisting of 17 prospective cohort studies, eight retrospective cohort studies, and one nonrandomized controlled trial. A total of 3109 implants placed in 1171 subjects were analyzed. Twenty-three studies were evaluated using meta-analysis. The alveolar bone condition was significantly correlated with ISQ (r = 0.60; p < .001), IT (r = 0.52; p < .001), and PTV (r = -0.42; p < .05). CONCLUSION: Alveolar bone condition is significantly associated with PIS. Low bone density and thin cortical bone can lead to low PIS; therefore, modification of treatment planning and surgical procedures might be needed to avoid poor osseointegration.

Development of triple-functionalized calcium phosphate nanoparticles as an advanced drug delivery system for bone tissue repair.

Introduction: During tissue repair or regeneration, several bioactive molecules are released and interact with each other and act as complex additives or inhibitors for tissue reconstruction. In this study, the bone-healing effects of the combination treatment with tumor necrosis factor-α (TNF-α) inhibition, vascular endothelial growth factor A (VEGF-A) and bone morphogenetic protein-7 (BMP-7) release by gene silencing, and gene transfection with calcium phosphate nanoparticles (CaP) in the rat femoral head was histologically, morphologically, and biochemically evaluated. Methods: A triple-functionalized paste of CaP carrying plasmid DNA encoding for BMP-7 and for VEGF), and siRNA against TNF-α was developed and denoted as CaP3mix. To compare the effects of 3mixCaP, CaP with plasmid DNA encoding BMP-7, VEGF, or siRNA encoding TNF-α was prepared and denoted as CaP/PEI/pBMP-7/SiO2, CaP/PEI/pVEGF/SiO2, or CaP/PEI/siRNA-TNF-α/SiO2, respectively. The bone healing in bone defects in the rat femoral head was investigated after 10 and 21 days of implantation. Results: The levels of bone formation-related markers OCN, Runx2, and SP7 increased at the protein and gene levels in 3mixCaP after 10 days, and 3mixCaP significantly accelerated bone healing compared with the other treatments after 21 days of implantation. Conclusion: The triple-functionalized CaP paste loading plasmid DNA encoding BMP-7 and VEGF and siRNA encoding TNF-α is a promising bioactive material for bone tissue repair.

Effect of customized abutment taper configuration on bone remodeling and peri-implant tissue around implant-supported single crown: A 3D nonlinear finite element study.

PURPOSE: The optimal configuration of a customized implant abutment plays a crucial role in promoting bone remodeling and maintaining the peri-implant gingival contour. However, the biomechanical effects of abutment configuration on bone remodeling and peri-implant tissue remain unclear. This study aimed to evaluate the influence of abutment taper configurations on bone remodeling and peri-implant tissue. MATERIALS AND METHODS: Five models with different abutment taper configurations (10°, 20°, 30°, 40°, and 50°) were analyzed using finite element analysis (FEA) to evaluate the biomechanical responses in peri-implant bone and the hydrostatic pressure in peri-implant tissue. RESULTS: The results demonstrated that the rate of increase in bone density was similar in all models. On the other hand, the hydrostatic pressure in peri-implant gingiva revealed significantly different results. Model 10° showed the highest maximum and volume-averaged hydrostatic pressures (69.31 and 4.5 mmHg), whereas Model 30° demonstrated the lowest values (57.83 and 3.88 mmHg) with the lowest excessive pressure area. The area of excessive hydrostatic pressure decreased in all models as the degree of abutment taper increased from 10° to 30°. In contrast, Models 40° and 50° exhibited greater hydrostatic pressure concentration at the cervical region. CONCLUSION: In conclusion, the abutment taper configuration had a slight effect on bone remodeling but exerted a significant effect on the peri-implant gingiva above the implant platform via hydrostatic pressure. Significant decreases in greatest and average hydrostatic pressures were observed in the peri-implant tissues of Model 30°. However, the results indicate that implant abutment tapering wider than 40° could result in a larger area of excessive hydrostatic pressure in peri-implant tissue, which could induce gingival recession.

Impact of implant location on load distribution of implant-assisted removable partial dentures: a review of in vitro model and finite-element analysis studies.

BACKGROUND: Appropriate load distribution among the supporting elements is essential for the long-term success of implant-assisted removable partial dentures; however, there is little information available on load distribution. PURPOSE: This study aimed to evaluate the effect of implant location on load distribution in implant-assisted removable partial dentures by reviewing in vitro models and finite-element analysis studies. MATERIALS AND METHODS: English-language studies which examined the load distribution of implant-assisted removable partial dentures and were published between January 2001 and October 2022 were extracted from PubMed, ScienceDirect, and Scopus online databases, and manual searching. Two reviewers selected the articles based on the predetermined inclusion and exclusion criteria, followed by data extraction and analysis. RESULTS: Forty-seven studies were selected after evaluating the titles and abstracts of 264 articles; two were identified manually. After screening the text, 12 studies were included: six in vitro model experiments and six finite-element analysis studies. All included studies used a mandibular free-end missing model (Kennedy Class I or II). The influence of implant location on load distribution to the abutment tooth, implant, and mucosa under the denture base was summarized in three cases: implant at the premolar, first molar, and second molar region. Due to differences in the measurement method of load distribution and loading condition to the denture, the results differed among the studies. CONCLUSIONS: The implant location in implant-assisted removable partial dentures can affect load distribution to the supporting elements, such as the abutment tooth, implant, and mucosa under the denture base.

Automated permanent tooth detection and numbering on panoramic radiograph using a deep learning approach.

OBJECTIVE: This study aimed to assess the performance of the deep learning (DL) model for automated tooth numbering in panoramic radiographs. STUDY DESIGN: The dataset of 500 panoramic images was selected according to the inclusion criteria and divided into training and testing data with a ratio of 80%:20%. Annotation on the data set was categorized into 32 classes based on the dental nomenclature of the universal numbering system using the LabelImg software. The training and testing process was carried out using You Only Look Once (YOLO) v4, a deep convolution neural network model for multiobject detection. The performance of YOLO v4 was evaluated using a confusion matrix. Furthermore, the detection time of YOLO v4 was compared with a certified radiologist using the Mann-Whitney test. RESULTS: The accuracy, precision, recall, and F1 scores of YOLO v4 for tooth detection and numbering in the panoramic radiograph were 88.5%, 87.70%, 100%, and 93.44%, respectively. The mean numbering time using YOLO v4 was 20.58 ± 0.29 ms, significantly faster than humans (P < .0001). CONCLUSIONS: The DL approach using the YOLO v4 model can be used to assist dentists in daily practice by performing accurate and fast automated tooth detection and numbering on panoramic radiographs.

Effect of gingival height of a titanium base on the biomechanical behavior of 2-piece custom implant abutments: A 3-dimensional nonlinear finite element study.

STATEMENT OF PROBLEM: Titanium base (TiBase) abutments to restore an implant-supported single crown are available in different gingival heights, but information on the biomechanical effects of the gingival heights is lacking. PURPOSE: The purpose of this nonlinear finite element analysis study was to evaluate the effects of TiBase gingival heights on the biomechanical behavior of custom zirconia (CustomZir) abutments and TiBase, including von Mises stress and maximum and minimum principal stress. MATERIAL AND METHODS: TiBases with different gingival heights (0.5 mm, 1 mm, 1.5 mm, and 2 mm) with internal hexagon Morse taper connections were simulated in 3-dimensional models. The simulations (ANSYS Workbench 2020; ANSYS Inc) included the OsseoSpeed EV implant (Ø5.4 mm) (AstraTech; Dentsply Sirona), restoration, and surrounding bone in the mandibular first molar region. An occlusal force of 200 N was applied with a 2-mm horizontal offset toward the buccal side and a 30-degree inclination from the vertical axis. RESULTS: High-stress concentration was observed in the uppermost internal connection area on the buccal side and the antirotational part of the titanium abutment on the lingual side in all models. CustomZir abutments with a shorter gingival height exhibited larger concentrated areas of volume average stress von Mises stress and higher magnitude of maximum and minimum principal stress compared with a taller gingival height. CONCLUSIONS: A TiBase abutment with a taller gingival height reduced the fracture risk of a CustomZir abutment without increasing any mechanical risk.

Evaluation of the optimal hardness and thickness of music splints for wind instrument players.

STATEMENT OF PROBLEM: As players of single-reed wind instruments such as the clarinet and saxophone are likely to experience pain and trauma of the lower lip, a method to prevent these symptoms without disturbing the music quality and performance is required. PURPOSE: The purpose of this clinical study was to produce a custom music splint, an oral appliance for the players of single-reed wind instruments, by using sports mouthguard sheet materials and to determine its suppression effect on the pressure and pain of the lower lip and teeth and on fatigue and pain of the jaw. MATERIAL AND METHODS: The soft type and soft and hard 2-layer type of sheet materials for sports mouthguards were used to fabricate the music splints. Each type of material has 1-mm and 2-mm thicknesses; therefore, 4 kinds of music splint were produced. The participants, students who played wind instruments in university orchestras, were instructed to use each music splint when playing the instruments for 1 week (for at least 3 hours for each music splint) and to answer a questionnaire about the effect of each appliance. Eighteen participants answered the questionnaire. Based on the usual usage of oral appliances when playing instruments, the participants were classified into 2 groups; oral appliance typically used (group OA) (n=7) and oral appliance not used (group noOA) (n=11). To determine the effects of the 4 types of music splint, a multilevel linear regression analysis was applied to evaluate the nested structure of the data (α=.05). RESULTS: The use of the music splint significantly relieved pressure and pain on the lower lips. The soft type was more effective in group OA, and the thin type was more effective in group noOA. The thin- and soft-type music splints were associated with significantly better playing sensation and sound quality than other types of splint in both groups. CONCLUSIONS: The thin- and soft-type music splints can be effective and useful for suppressing oral symptoms when playing a single-reed wind instrument without disturbing the quality of the performance.

Effect of Different Retightening Procedures on Screw Stability in External-Hex and Internal Trichannel Connections: An In Vitro Study.

PURPOSE: To evaluate the effect of different abutment screw retightening procedures on the screw stability between the abutment and implant. MATERIALS AND METHODS: External hexagon connection (EHC) and internal trichannel connection (ITC) implants were employed in this study. Each abutment screw was used for the following specific applications (n = 5 for each group): group 0 = abutment was tightened and retightened with a 10-minute interval; group 1 = abutment was tightened and retightened with a 10-minute interval, then loaded for 500,000 cycles; group 2 = abutment was loaded for 83,000 cycles during tightening and retightening, then loaded for 500,000 cycles; group 3 = abutment was loaded for 167,000 cycles during tightening and retightening, then loaded for 500,000 cycles; and group 4 = abutment was loaded for 250,000 cycles during tightening and retightening, then loaded for 500,000 cycles. Both tightening and retightening torques were set at 35 Ncm, and dynamic oblique loading between 0 N and 200 N was applied on the abutment in all groups. The settling values of the abutments after retightening and the abutment removal torque values (RTVs) after testing were measured. RESULTS: No significant differences in settling values were found between EHC and ITC. There were significant differences in the RTVs of EHC implants, but ITC implants showed no difference in RTV with different prosthetic retightening applications. CONCLUSION: The retightening application affected the joint stability of EHC implants but did not affect the settlement and joint stability of ITC implants. Int J Prosthodont 2023;36:181-188. doi: 10.11607/ijp.6863.

Effect of implant placement depth on bone remodeling on implant-supported single zirconia abutment crown: A 3D finite element study.

PURPOSE: This study aimed to evaluate the influence of subcrestal implant placement depth on bone remodeling using time-dependent finite element analysis (FEA) with a bone-remodeling algorithm over 12 months. METHODS: Seven models of different subcrestal implant placement depths (0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm) were analyzed using FEA to evaluate the biomechanical responses in the bone and implant, including von Mises equivalent stress, strain energy density (SED), and overloading elements. SED was used as a mechanical stimulus to simulate cortical and cancellous bone remodeling over the first 12 months after final prosthesis delivery. RESULTS: The highest increase in cortical bone density was observed at Depth 1.5, whereas the lowest increase was observed at Depth 3.0. In contrast, the highest increase in bone density was observed at Depth 3.0 in the cancellous bone, whereas the lowest increase was observed at Depth 0. The highest peak von Mises stress in the cortical bone occurred at Depth 2.5 (107.24 MPa), while that in the cancellous bone was at Depth 2.5 (34.55 MPa). Notably, the maximum von Mises stress values in the cancellous bone exceeded the natural limit of the bony material, as indicated by the overloading elements observed at the depths of 2.0, 2.5, and 3.0 mm. CONCLUSIONS: Greater bone density apposition is observed with deeper implant placement. An implant depth of more than 1.5 mm exhibited a higher maximum von Mises stress and greater overloading elements.

In vivo measurement of three-dimensional load exerted on dental implants: a literature review.

BACKGROUND: For biomechanical consideration of dental implants, an understanding of the three-dimensional (3D) load exerted on the implant is essential, but little information is available on the in vivo load, including the measuring devices. PURPOSE: This review aimed to evaluate studies that used specific load-measuring devices that could be mounted on an implant to measure the functional load in vivo. MATERIALS AND METHODS: An electronic search utilizing the internet research databases PubMed, Google Scholar, and Scopus was performed. The articles were chosen by two authors based on the inclusion and exclusion criteria. RESULTS: In all, 132 studies were selected from the database search, and 16 were selected from a manual search. Twenty-three studies were finally included in this review after a complete full-text evaluation. Eleven studies were related to the force measurements using the strain gauges, and 12 were related to the piezoelectric force transducer. The principles of the two types of devices were completely different, but the devices produced comparable outcomes. The dynamics of the load magnitude and direction on the implant during function were clarified, although the number of participants in each study was small. CONCLUSIONS: The load exerted on the implant during function was precisely measured in vivo using specific measuring devices, such as strain gauges or piezoelectric force transducers. The in vivo load data enable us to determine the actual biomechanical status in more detail, which might be useful for optimization of the implant prosthetic design and development of related materials. Due to the limited data and difficulty of in vivo measurements, the development of a new, simpler force measurement device and method might be necessary.

On interaction between fatigue of reconstruction plate and time-dependent bone remodeling.

BACKGROUND AND OBJECTIVE: The fibula free flap (FFF) has been extensively used to repair large segmental bone defects in the maxillofacial region. The reconstruction plate plays a key role in maintaining stability and load-sharing while the fibula unites with adjacent bone in the course of healing and remodeling. However, not all fibula flaps would fully unite, and fatigue of prosthetic devices has been recognized as one major concern for long-term load-bearing applications. This study aims to develop a numerical approach for predicting the fatigue life of the reconstruction plate by taking into account the effect of ongoing bone remodeling. METHODS: The patient-specific mandible reconstruction with a prosthetic system is studied in this work. The 3D finite element model with heterogeneous material properties obtained from clinical computerized tomography (CT) data is developed for bone, and eXtended Finite Element Method (XFEM) is adopted for the fatigue analysis of the plate. During the remodeling process, the changing apparent density and Young's modulus of bone are simulated in a step-wise fashion on the basis of Wolff's law, which is correlated with the specific clinical follow-up. The maximum biting forces were considered as the driving force on the bone remodeling, which are measured clinically at different time points (4, 16 and 28 months) after reconstruction surgery. RESULTS: Under various occlusal loadings, the interaction between fatigue crack growth and bone remodeling is investigated to gain new insights for the future design of prosthetic devices. The simulation results reveal that appropriate remodeling of grafted bone could extend the fatigue life of fixation plates in a positive way. On the other hand, the rising occlusal load associated with healing and remodeling could lead to fatigue fracture of fixation plate and potentially cause severe bone resorption. CONCLUSION: This study proposes an effective approach for more realistically predicting fatigue life of prosthetic devices subject to a tissue remodeling condition in-silico. It is anticipated to provide a guideline for deriving an optimal design of patient-specific prosthetic devices to better ensure longevity.

Comparison of the accuracy of resin-composite crowns fabricated by three-dimensional printing and milling methods.

This study aimed to compare the dimensional accuracies of three-dimensional (3D)-printed and milled resin-composite crowns, and to determine acceptable abutment-tooth shapes for printing. Four first-molar abutment models were prepared: the master model form and three models with sharp occluso-axial line angles. Crowns were designed on each abutment using computer-aided design software. The drill-offset value was set at 0.0 or 0.5 mm to evaluate the effect on the dimensional accuracy of milling. A digital light processing-based 3D printer was used to fabricate 3D-printed crowns. Milled crowns were fabricated by wet-milling. The trueness was evaluated by superimposing the design data. Regardless of the abutment form, 3D-printed crowns showed higher accuracy with fewer marginal discrepancies than milled crowns. Milled crowns showed significant dimensional deviations, especially at cusps. Moreover, offset correction resulted in grooves on the internal surface of milled crowns with negative deviations, which were especially evident in crowns for the sharp models.

Morphological comparison of masseter muscle fibres in the mandibular rest and open positions using diffusion tensor imaging.

BACKGROUND: The masseter muscle has a complicated multipennate internal structure and exhibits functional differentiation when performing various stomatognathic functions. It is important to understand the internal structural changes of the muscle during functioning to elucidate characteristic muscle disorders such as local myalgia. Diffusion tensor imaging (DTI) may be useful for investigating the internal structural features of muscle. OBJECTIVES: To evaluate the features of masseter muscle fibres in human participants using DTI fibre tractography, and to elucidate the structural differences in the masseter muscle between the mandibular rest and open positions. METHODS: Five healthy men (age 31 ± 7 years) underwent DTI and T1-weighted MRI of the right masseter muscle in the mandibular rest and open positions. MR images were used as a reference for muscle layer segmentation (superficial, intermediate, and deep). DTI fibre tractography of the masseter muscle was performed and the orientation of the DTI fibres was analysed in each layer using coordinates based on the Frankfurt horizontal plane. RESULTS: The DTI fibre orientation of the deep layer significantly changed between the mandibular rest and open positions in the frontal plane (p < 0.05, Wilcoxon rank sum test). However, no significant change was found in the superficial and intermediate layers. CONCLUSION: DTI fibre tractography confirmed regional differences in the orientation change of the masseter muscle fibres between different mandibular positions. The results may support the existence of functional partitioning inside the masseter muscle and suggest that DTI may be useful for the evaluation of muscle fibres in multipennate muscles.

Medical-Dental Collaboration and Interprofessional Training for Maxillofacial Diseases at Tohoku University Hospital.

The Tohoku University Hospital has been a clinical and research facility for all the related departments of Tohoku University. Medical-dental and interprofessional collaboration has resulted in special treatment teams, made up of members of departments such as the center for head and neck cancer, the center for dysphagia, and the cleft lip and palate center. Those treatment teams held conferences, case study meetings, reading sessions, and in-hospital seminars. The purpose of this study was to evaluate the outcomes of various medical-dental and the interprofessional collaboration at Tohoku University Hospital and training program to equip hospital dentists in higher medical institutions. The attainment targets are the acquisition of basic medical skills and knowledge under the guidance of supervising doctors. As a result, the hospital dentists could acquire their own specialized knowledge and skills certificated by each academic society. The smooth team treatment has been achieved, and the number of cases discussed by cancer boards and center for dysphagia has increased year by year due to the efficiency of their clinical pathways. On the dental care side as well, the wearing rates of maxillofacial prosthetic devices such as maxillofacial prostheses and palatal augmentation prostheses (PAP) have improved, which have contributed to improving patient's stomatognathic function. Tohoku University Hospital has been practicing collaboration between medical and dental professionals and it has produced mutual benefits. Our interprofessional training system based on the medical-dental collaboration could develop professionals who have acquired cross-disciplinary knowledge and skills from experienced doctors.

Effectiveness of an actuator-driven pulsed water jet for removal of softened carious dentin.

The aim of this study was to assess the utility of an actuator-driven pulsed water jet (ADPJ) as a hardness-dependent carious dentin removal device by using different outputs. Thirty-six plane surface dental caries samples were treated with the ADPJ at 150, 200, and 250 voltage (12 teeth each). The Knoop hardness number (KHN) and Ca/P mass ratio were measured at 70 µm from the deepest point of the removing groove. Furthermore, three other teeth samples were manually treated with the ADPJ at the three above mentioned voltages (one tooth each) for 1 min. The KHN and Ca/P mass ratio were measured at 70 µm from the surface of the residual dentin part. In both the KHN and Ca/P mass ratio, higher residual dentin depended on the applied voltage of ADPJ. The ADPJ enabled the removal of softened carious dentin in an applied voltage-dependent manner.

Application of Diffusion Tensor Imaging Fiber Tractography for Human Masseter Muscle.

Diffusion tensor imaging (DTI) has been used to indicate the direction of nerve and muscle fibers by using the characteristics that water molecules preferentially diffuse along the fibrous structure. However, DTI fiber tractography for multipennate muscles, such as the masseter muscle, is challenging due to a lack of data regarding the imaging parameters. This study aimed to determine the optimal DTI parameters for masseter muscle fiber tractography. A 27-year-old healthy man voluntarily underwent DTI and T1-weighted magnetic resonance imaging of the right masseter muscle. Four imaging parameter settings were created by combining the following parameters that particularly affect the signal-to-noise ratio: b-value, number of excitations (NEX), and number of motion probing gradient (MPG) directions. DTI fiber tractography was performed using specific software for each parameter setting. The length and orientation of the muscle fibers in each layer were calculated. As a result, the masseter muscle fibers of each layer were identified on DTI. Although the detected fiber length was affected significantly by the imaging parameters, the fiber orientation was insignificantly affected. The appropriate combination of the b-value, NEX, and the number of MPG directions for masseter muscle fiber tractography could be determined based on previously reported anatomical data of the masseter muscle fibers. DTI may enable the non-invasive evaluation of masseter muscle fiber length and orientation. Elucidation of the details of masseter muscle fiber orientation is useful in evaluating stomatognathic biomechanics and muscle disorders.

Bone remodeling following mandibular reconstruction using fibula free flap.

To investigate bone remodelling responses to mandibulectomy, a joint external and internal remodelling algorithm is developed here by incorporating patient-specific longitudinal data. The primary aim of this study is to simulate bone remodelling activity in the conjunction region with a fibula free flap (FFF) reconstruction by correlating with a 28-month clinical follow-up. The secondary goal of this study is to compare the long-term outcomes of different designs of fixation plate with specific screw positioning. The results indicated that the overall bone density decreased over time, except for the Docking Site (namely DS1, a region of interest in mandibular symphysis with the conjunction of the bone union), in which the decrease of bone density ceased later and was followed by bone apposition. A negligible influence on bone remodeling outcome was found for different screw positioning. This study is believed to be the first of its kind for computationally simulating the bone turn-over process after FFF maxillofacial reconstruction by correlating with patient-specific follow-up.

Resin Cement-Zirconia Bond Strengthening by Exposure to Low-Temperature Atmospheric Pressure Multi-Gas Plasma.

The purpose of this study was to investigate the effect of gas species used for low-temperature atmospheric pressure plasma surface treatment, using various gas species and different treatment times, on zirconia surface state and the bond strength between zirconia and dental resin cement. Three groups of zirconia specimens with different surface treatments were prepared as follows: untreated group, alumina sandblasting treatment group, and plasma treatment group. Nitrogen (N2), carbon dioxide (CO2), oxygen (O2), argon (Ar), and air were employed for plasma irradiation. The bond strength between each zirconia specimen and resin cement was compared using a tension test. The effect of the gas species for plasma irradiation on the zirconia surface was investigated using a contact angle meter, an optical interferometer, an X-ray diffractometer, and X-ray photoelectric spectroscopy. Plasma irradiation increased the wettability and decreased the carbon contamination on the zirconia surface, whereas it did not affect the surface topography and crystalline phase. The bond strength varied depending on the gas species and irradiation time. Plasma treatment with N2 gas significantly increased bond strength compared to the untreated group and showed a high bond strength equivalent to that of the sandblasting treatment group. The removal of carbon contamination from the zirconia surface and an increase in the percentage of Zr-O2 on the zirconia surface by plasma irradiation might increase bond strength.

Current applications and development of artificial intelligence for digital dental radiography.

In the last few years, artificial intelligence (AI) research has been rapidly developing and emerging in the field of dental and maxillofacial radiology. Dental radiography, which is commonly used in daily practices, provides an incredibly rich resource for AI development and attracted many researchers to develop its application for various purposes. This study reviewed the applicability of AI for dental radiography from the current studies. Online searches on PubMed and IEEE Xplore databases, up to December 2020, and subsequent manual searches were performed. Then, we categorized the application of AI according to similarity of the following purposes: diagnosis of dental caries, periapical pathologies, and periodontal bone loss; cyst and tumor classification; cephalometric analysis; screening of osteoporosis; tooth recognition and forensic odontology; dental implant system recognition; and image quality enhancement. Current development of AI methodology in each aforementioned application were subsequently discussed. Although most of the reviewed studies demonstrated a great potential of AI application for dental radiography, further development is still needed before implementation in clinical routine due to several challenges and limitations, such as lack of datasets size justification and unstandardized reporting format. Considering the current limitations and challenges, future AI research in dental radiography should follow standardized reporting formats in order to align the research designs and enhance the impact of AI development globally.