Applications and performance of artificial intelligence models in removable prosthodontics: A literature review.

PURPOSE: In this narrative review, we present the current applications and performances of artificial intelligence (AI) models in different phases of the removable prosthodontic workflow and related research topics. STUDY SELECTION: A literature search was conducted using PubMed, Scopus, Web of Science, and Google Scholar databases between January 2010 and January 2023. Search terms related to AI were combined with terms related to removable prosthodontics. Articles reporting the structure and performance of the developed AI model were selected for this literature review. RESULTS: A total of 15 articles were relevant to the application of AI in removable prosthodontics, including maxillofacial prosthetics. These applications included the design of removable partial dentures, classification of partially edentulous arches, functional evaluation and outcome prediction in complete denture treatment, early prosthetic management of patients with cleft lip and palate, coloration of maxillofacial prostheses, and prediction of the material properties of denture teeth. Various AI models with reliable prediction accuracy have been developed using supervised learning. CONCLUSIONS: The current applications of AI in removable prosthodontics exhibit significant potential for improving the prosthodontic workflow, with high accuracy levels reported in most of the reviewed studies. However, the focus has been predominantly on the diagnostic phase, with few studies addressing treatment planning and implementation. Because the number of AI-related studies in removable prosthodontics is limited, more models targeting different prosthodontic disciplines are required.

Investigation of variation factors in EMG measurement of swallowing: instruction can improve EMG reproducibility.

Variability in swallowing electromyography (EMG) has been reported to occur due to individual differences, even in studies with appropriate control of factors affecting EMG such as food type, properties, and posture. The increased variability broadens the confidence intervals of measures obtained from EMG, such as time and amplitude, and makes it difficult to detect differences in muscle activity. This makes it impossible to detect slight changes in swallowing function at an early stage, which is required for clinical examination. In this study, we focused on the tipper type and dipper type of oral swallows, which differ in the timing of muscle activity. The frequency of occurrence of both types varies between participants, and both types could occur in the same participant. In this study, we measured swallowing EMG wherein participants were instructed to swallow with a tipper and a dipper. The results showed that there was a significant difference in the between-participant duration between these two types of swallows. Within-participant variability was significantly lower in the tipper-dipper instruction condition compared to the baseline condition, which assumed a mixture of tipper-dipper swallowing. These results demonstrate that instructions on swallowing method are effective in improving the reproducibility of EMG.

Evaluation of musculoskeletal workload of manual operating tasks using a hydraulic jack based on ergonomic postural analysis and electromyography: A case study of non-professional young male users.

BACKGROUND: Manual operations of the hydraulic jack device can become ergonomic stressors for the musculoskeletal system because of the required operational forces, muscle activities, or working postures. However, the usability of the hydraulic jack has not been fully explored for non-professional personnel. OBJECTIVES: To evaluate the musculoskeletal loads during manual operations of a hydraulic jack based on the ergonomic postural analysis and electromyographyMETHODS:Nine men operated the lever of a hydraulic jack with three positions: parallel to and near (P-N), parallel to and far from (P-F), and orthogonal to the jack lever (O). Postural loads were evaluated by Loading on the Upper Body Assessment (LUBA), an ergonomic observational method, and were classified into action categories. The surface electromyogram of eight muscles and the subjective sense of burden were also measured. RESULTS: The initial force for lever pushing reached 40-80 N and exceeded the recommended forces for the unusual postures. The overall assessment of LUBA showed that 31% of working postures observed in O position require immediate consideration and corrective action and the maximum holding time estimated was < 1 minute. The postural load increased due to the shoulder joint abduction in the P-F and O positions and due to the trunk rotation in O position. CONCLUSIONS: The results suggest that operating the hydraulic jack cause considerable postural loads and manual forces insufficient for several minutes of manual task. Therefore, improving working methods and tool designs are needed to improve usability and decrease the risk of musculoskeletal disorders during jack operations.

Contribution of Vibration, Tapping Sound, and Reaction Force to Hardness Perception During Indirect Tapping Using a White Cane.

This study aimed to identify the physical factors contributing to the perception of the hardness of objects tapped using white canes, which are commonly used by the visually impaired for autonomous walking. First, physical factors such as vibration tapping sounds and reaction forces were measured during the indirect tapping of rubber sheets with different hardness using a white cane. Second, we determined the relationship between the subjective hardness perceived by the visually impaired individuals and the physical factors through multivariate analysis. In addition, we estimated the contribution of each factor. The result indicates that the white cane vibrated at similar frequencies during tapping even when the hardness of objects changed. In contrast, the tapping sound varied widely with the variation of the hardness of the rubber sheet. In addition, the peak values of the reaction forces significantly changed depending on the hardness. Based on the results of the multivariate analysis, the contributions of tapping sounds and reaction forces to hardness perception were remarkable. In contrast, the contributions of vibrations could not be found using our analytic method. These findings will help in the design and evaluation of support equipment for the visually impaired.

Training System for White Cane Technique Using Illusory Pulling Cues Induced by Asymmetric Vibrations.

A white cane is conventionally used by visually impaired persons to assist their mobility. To learn its proper operation, training by an orientation & mobility specialist is necessary. However, because the number of specialists is limited, visually impaired persons often do not receive sufficient training. To rectify this issue, a training environment in which the visually impaired can train independently is required. This paper proposes a training system that enables the visually impaired to learn white cane techniques using illusory pulling cues. Specifically, in the white cane touch technique, which is a basic white cane technique, a system that targets the swing width of the white cane is presented by illusory pulling cues. To verify the efficacy of the system, a prototype was implemented and evaluated via user tests. The results confirmed that the error of the swing width of the white cane decreased following use of the proposed system. The proposed system will contribute to the development of the mobility of the visually impaired by enabling them to train with the white cane independently and spontaneously, thereby reducing the workload of specialists.

Nutritional assessment in a maxillectomy patient from the preoperative period to definitive obturator insertion: A case report.

PATIENT: A 69-year-old Japanese male with squamous cell carcinoma of the right maxilla (T4M0N0) was referred to our department for a preoperative examination. An immediate surgical obturator was fabricated before surgery. He underwent surgical treatment, which included right subtotal maxillectomy and reconstruction with a split skin graft. One week postoperatively, the immediate surgical obturator was modified to expand the nasal cavity for obturator prosthesis. Oral intake was started 12 days postoperatively with an immediate surgical obturator in situ. The definitive obturator was fabricated after the wound surface had healed 8 months postoperatively. Assessment of the nutritional status included body mass index, serum albumin level, resting energy expenditure (REE) measured using indirect calorimetry, and predicted REE using the Harris-Benedict equation. These assessments were performed several times, from the time of admission until the definitive obturator was applied. DISCUSSION: Malnutrition occurs frequently in patients with head and neck cancer because this region is vital for swallowing and mastication. Maxillectomy patients require a maxillofacial prosthesis to improve their nutritional status from the preoperative period to recovery. This case report describes maxillofacial prosthetic treatment from the perspective of nutrition. The patient wore the immediate surgical obturator postoperatively, which was followed by marked weight loss after restoration, and then weight gain returned to the normal range when wearing the definitive obturator. CONCLUSION: Maxillofacial prosthetic treatments should make efforts to maintain nutritional status and achieve optimal function and quality of life in patients with head and neck cancers.

Assessing the Stiffness Perception of Acupressure Massage Beginning Learners: A Pilot Study.

Visually impaired licensed therapists must have the ability to perceive stiffness through their fingertips in the school for the blind. The teachers strive to provide careful introductory education based on a quantitative assessment of new students' basic stiffness perception. However, assessment materials to help teachers understand new students' stiffness perception are lacking. This study aimed to develop suitable fundamental assessment materials that visually impaired licensed teachers could use to quantitatively assess the difference in the stiffness perception ability of beginning learners in the early stages of learning. They were asked to discriminate the presented materials one at a time, which consisted of thermoplastic elastomers with different degrees of stiffness. We used these materials to compare the beginning learners' ability to perceive stiffness with that of teachers and found that teachers answered correctly at an overall significantly higher rate. Specifically, the teachers' correct response rate (78.8%) for the stiffness perception of all presented stimuli was approximately 15% higher than the beginning learners' correct response rate (64.2%). These results revealed areas of stiffness that are difficult for beginning learners to identify.

Effects of Asymmetric Vibration Frequency on Pulling Illusions.

It is known that humans experience a haptic illusion, such as the sensation of being pulled in a particular direction, when asymmetric vibrations are presented. A pulling illusion has been used to provide a force feedback for a virtual reality (VR) system and a pedestrian navigation system, and the asymmetric vibrations can be implemented in any small non-grounded device. However, the design methodology of asymmetric vibration stimuli to induce the pulling illusion has not been fully demonstrated. Although the frequency of the asymmetric vibration is important, findings on the frequency have not been reported. In this study, we clarified the influences of the effects on the pulling illusion based on the investigation of asymmetric vibration frequency differences. Two psychophysical experiments that related to the frequency of asymmetric vibration were performed. Experiment I showed that the illusion occurs for specific vibration waveforms at 40 Hz and 75 Hz. As a result of Experiment II, the threshold was the lowest when the frequency was 40 Hz, and highest when the frequency was 110 Hz. This result supports the previous hypothesis that the Meissner corpuscles and the Ruffini endings contribute to the illusion, while the Pacinian corpuscles do not.

Effects of age and gender on swallowing activity assessed by electromyography and laryngeal elevation.

BACKGROUND: Quantitative assessment of swallowing function is necessary to prevent swallowing impairment due to ageing. Though surface electromyography (EMG) has been widely used to measure swallowing activity, the relationship between EMG results and swallowing function is unclear. OBJECTIVE: This study examined the relationship between the temporal characteristics of muscle activity and laryngeal elevation (LE) during swallowing. METHODS: This study analysed 60 healthy volunteers in two age groups (young, between 20 and 38 years; old, between 65 and 75 years), each containing the same number of male and female participants. Surface EMG signals were recorded from the suprahyoid and infrahyoid muscle groups (SH-EMG and IH-EMG, respectively). LE was measured using an array of pressure sensors. The participants swallowed 3 mL of water under three swallowing speed conditions: fast, normal and slow swallowing. The EMG duration, EMG time intervals before and after the onset of LE (pre-LE and post-LE intervals, respectively), and the LE velocity were analysed. RESULTS: Both EMG duration and the post-LE interval of IH-EMG were significantly longer in the older group. As for the gender effect, the pre-LE interval of SH-EMG was significantly longer and the LE velocity was significantly higher in men than in women. Furthermore, there was a negative correlation between pre-LE interval and LE velocity in the fast swallowing condition. CONCLUSION: Though ageing slightly prolonged the muscle activity time, gender influenced swallowing activity in a more complex manner. Therefore, it is important to take gender into account when examining swallowing function with increasing age.

A pseudo-mastication sound presentation device to improve the texture of nursing care foods.

The texture of foods is affected by concurrent auditory sensations. To improve the texture of nursing care foods, we developed a pseudo-mastication sound presentation device based on electromyogram (EMG) signals from the muscles of mastication. EMG signals have enabled us to promptly present care recipients with pseudo-mastication sounds. However, actual mastication sounds vary in intensity and duration more than EMG signals. Here, we investigated changes in EMG signals and actual mastication sounds during the mastication of two food types (rice crackers and Japanese pickles) to improve our device. We found that the intensity and duration of mastication sounds decreased as the number of mastication strokes increased. Furthermore, the intensity and duration of mastication sounds and the latency between the onset of EMG signals and the onset of mastication sounds also varied by food type. For EMG signals, only the intensity varied by food type. Based on our findings, we modified our pseudo-mastication sound presentation device to enable control of the intensity and duration of pseudo-mastication sounds based on the number of mastication strokes and food type. Reproducing more natural pseudo-mastication sounds can improve care recipients' motivation for ingesting nursing care foods, thus preventing malnutrition and frailty.

Corrosion Generation and Cleaning Effect on Surgical Instruments with Attached Radiofrequency Identification Tags in Long-Term Usage.

Background: Faulty cleaning of surgical instruments may lead to corrosion damage and a higher risk of surgical site infection. We have developed a method in which each instrument has an attached radiofrequency identification (RFID) tag for individual management. However, because of the structure of the instruments, a risk of corrosion from poor cleaning exists; therefore, observation during long-term usage is necessary. Methods: The cleaning effect at the jig of the RFID tag was verified by the amount of residual protein left by various cleaning methods. In our investigation of long-term usage, we examined 94 surgical instruments with RFID tags used in the operating room for 50 months employing a microscope to identify any corrosion at the jig. Results: The method using a washer disinfector (WD) was found to be highly effective. From observation after long-term usage, friction by the RFID tag occurred in about 70% of the jigs. However, no pitting or general corrosion was seen. Conclusions: When WD is used properly, there is only a minor risk of residual protein, and corrosion does not occur even with long-term use. By using surgical instruments with RFID tags, it is possible to determine the number of uses and the history at the individual level. This facilitates operation of safe surgical instruments by limiting the number of times a particular instrument is used.

Buckling Force Variability of Semmes⁻Weinstein Monofilaments in Successive Use Determined by Manual and Automated Operation.

(1) Objective: This study was conducted with the objective of characterizing the variability of a force on a simulated skin surface using the Semmes⁻Weinstein monofilament test (SWMT). (2) Research Design and Methods: Two distinct experiments were performed to determine the effects of human hand motion variability on the monofilament buckling force, and to determine the monofilament's mechanical properties using a positioning stage. (3) Results: In manual operation (by human hand motion), the buckling force over the ten compressions decreased by over 10%, and the human hand motion variations during the SWMT may have impacted the buckling force. When the SWMT was performed under manual control, the buckling force was closely correlated with the number of compressions. In automated operation (by positioning stage), the buckling force was affected not only by the number of compressions but also by both the velocity and the contact angle between the monofilament and the skin surface. (4) Conclusions: The buckling force decreased in ten successive compressions, independent of the hand motion. Hence, medical staff need to consider not only the operator's hand motion but also the effect of repeated trials.

Texture-dependent effects of pseudo-chewing sound on perceived food texture and evoked feelings in response to nursing care foods.

Because chewing sounds influence perceived food textures, unpleasant textures of texture-modified diets might be improved by chewing sound modulation. Additionally, since inhomogeneous food properties increase perceived sensory intensity, the effects of chewing sound modulation might depend on inhomogeneity. This study examined the influences of texture inhomogeneity on the effects of chewing sound modulation. Three kinds of nursing care foods in two food process types (minced-/puréed-like foods for inhomogeneous/homogeneous texture respectively) were used as sample foods. A pseudo-chewing sound presentation system, using electromyogram signals, was used to modulate chewing sounds. Thirty healthy elderly participants participated in the experiment. In two conditions with and without the pseudo-chewing sound, participants rated the taste, texture, and evoked feelings in response to sample foods. The results showed that inhomogeneity strongly influenced the perception of food texture. Regarding the effects of the pseudo-chewing sound, taste was less influenced, the perceived food texture tended to change in the minced-like foods, and evoked feelings changed in both food process types. Though there were some food-dependent differences in the effects of the pseudo-chewing sound, the presentation of the pseudo-chewing sounds was more effective in foods with an inhomogeneous texture. In addition, it was shown that the pseudo-chewing sound might have positively influenced feelings.

The effect of a crunchy pseudo-chewing sound on perceived texture of softened foods.

Elderly individuals whose ability to chew and swallow has declined are often restricted to unpleasant diets of very soft food, leading to a poor appetite. To address this problem, we aimed to investigate the influence of altered auditory input of chewing sounds on the perception of food texture. The modified chewing sound was reported to influence the perception of food texture in normal foods. We investigated whether the perceived sensations of nursing care foods could be altered by providing altered auditory feedback of chewing sounds, even if the actual food texture is dull. Chewing sounds were generated using electromyogram (EMG) of the masseter. When the frequency properties of the EMG signal are modified and it is heard as a sound, it resembles a "crunchy" sound, much like that emitted by chewing, for example, root vegetables (EMG chewing sound). Thirty healthy adults took part in the experiment. In two conditions (with/without the EMG chewing sound), participants rated the taste, texture and evoked feelings of five kinds of nursing care foods using two questionnaires. When the "crunchy" EMG chewing sound was present, participants were more likely to evaluate food as having the property of stiffness. Moreover, foods were perceived as rougher and to have a greater number of ingredients in the condition with the EMG chewing sound, and satisfaction and pleasantness were also greater. In conclusion, the "crunchy" pseudo-chewing sound could influence the perception of food texture, even if the actual "crunchy" oral sensation is lacking. Considering the effect of altered auditory feedback while chewing, we can suppose that such a tool would be a useful technique to help people on texture-modified diets to enjoy their food.

Application of metal hydride paper to simple pressure generator for use in soft actuator systems.

Metal hydride (MH) actuators have a simple structure and a number of features that make them attractive for use in rehabilitation engineering and assistive technology. The MH actuator provides a high power-to-weight ratio, high-strain actuation, human-compatible softness, and noiseless operation, while being environmentally benign. On the other hand, there remain technical challenges to be overcome to improve the MH actuator regarding its speed of operation and energy efficiency, given the low heat conductivity of the MH powder that is used as the pressure generator for soft actuation. To overcome the issues of low heat conductivity and the handling of MH powder, we developed an MH paper, which is a special paper incorporating MH powder and carbon fiber, for use as a new pressure-generating element for a soft MH actuator system. In addition, the basic properties and structure of the proposed MH paper were investigated through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and several thermodynamic experiments. The results of these experiments showed that the hydrogen absorption and desorption rates of the MH paper were significantly higher than those of the MH powder around room temperature.

Evaluation of the variation in sensory test results using Semmes-Weinstein monofilaments.

The purpose of this study is to examine the variability in sensory test of tactile results using Semmes-Weinstein monofilament (SWM). At present, several methods for measuring the tactile sensitivity are clinically used in diabetic peripheral neuropathy screening. One of these methods is a touch test that uses a device with nylon SWMs, i.e., SWMs embedded in a plastic handle. A small pushing force is applied at the handle to bow the filaments. Because of its ease and simplicity, the SWM test is conducted at the patient's bedside in a hospital. However, previous studies have reported some problems with this test. Studies have shown variations in the measured data, and it is uncertain whether these variations are caused by mechanical properties of the nylon fiber or by the motion of the operator's hands. We carried out two experiments to examine the effect of (1) the variability caused by the human operator conducting the SWM test on the test results and (2) the number of compressions of the SWM on the test results. In experiment 1, we measured the velocity of the operator's hand motion and the buckling force of the SWMs. The results showed variability in the hand motion of the operator conducting the SWM tests. In experiment 2, we measured the buckling force of the SWMs under a controlled velocity. We compared the buckling force of the SWMs through a number of trials. These results showed that the buckling force gradually decreases as the number of test cycles increase. In conclusion, we find that the accuracy of the SWM tests is a factor of the number of test cycles. Additionally, manual training for standardizing skills of medical staff members needs to be developed. Furthermore, the characteristics of the SWMs deteriorated over time. In future work, we aimto find a solution to minimize the variability in the SWM test results and develop a new testing system that uses tactile sensibility for diabetic peripheral neuropathy screening.

Measuring gait pattern in elderly individuals by using a plantar pressure measurement device.

BACKGROUND: Hip fracture in the elderly is a serious problem, and solutions to prevent falls are needed. OBJECTIVE: This study focused on elucidating data critical to fall prevention by evaluating ambulatory function, and we achieved this by developing a plantar pressure measurement device to determine gait function. METHODS: Our device enables measurement of gait function in the unrestrained state by transmitting wireless data. In this study, we applied the device to field experiments involving 98 subjects (39 healthy individuals, 44 elderly non-fallers, and 15 elderly fallers). Gait features were determined by measuring the pressure values and foot contact patterns used as gait function parameters in previous studies. RESULTS: In particular, decreased peak pressure values were noted at heel strike and toe off during walking in elderly fallers compared with elderly non-fallers. In addition, compared with healthy subjects, elderly fallers also showed extension of the double support phase, and differences in individual gait pattern features were observed between the groups. CONCLUSIONS: Experiments confirmed that our device can be used to obtain the gait features of a diverse group of elderly individuals. Moreover, our device enables objective and quantitative evaluation of gait function and thus may be useful for evaluating gait function in the elderly.

A pilot study of a plantar sensory evaluation system for early screening of diabetic neuropathy in a weight-bearing position.

The purpose of this study is to develop smart equipment to quantify plantar tactile sensibility for the early diagnosis and tracking of peripheral neuropathy caused by diabetes mellitus. In this paper, we offer a new testing system that is composed of a plantar tactile stimulation platform with a small moving contactor to stretch the skin tangentially, a response switch for each tactile stimulus, a motor control box, and a personal computer (PC) for psychophysical data processing. This quantitative sensory testing system has detailed measurements available and is easy to use compared with the conventional testing devices, such as von Frey monofilaments, pin-prick testing devices, and current perception threshold testers. When using our testing system in a weight-bearing position, we observed that the plantar tactile thresholds for the tangential stretching stimulus on the plantar surface of the foot ranged from approximately 10 um to 30 um for healthy subjects. However, the threshold for a subject with diabetes was nearly three times higher than that for healthy subjects. The significant difference between these values suggests that the plantar sensory evaluation system using the lateral skin stretch stimulation can be used for early diagnosis, for the accurate staging of diabetic neuropathy, and for evaluating its progression noninvasively in a clinic and at home.

A system utilizing metal hydride actuators to achieve passive motion of toe joints for prevention of pressure ulcers: a pilot study.

This paper describes the influence of human toe movement on blood flow and the design of a toe joint passive motion system for preventing pressure ulcers. First, we measured lower extremity blood flow in the foot during active and passive motion of the toe to facilitate the design of new rehabilitation equipment. Also, the flexion and extension angles and the force of the toe joints were measured to determine appropriate specifications for the system. Increases in blood flow were observed at the external malleolus during movement. Flexion and extension angles and the force of the toe joints were found to differ significantly among participants. It is shown that a toe joint passive motion system can be effective in preventing pressure ulcers. On the basis of these results, a device using alloys of metal hydride (MH) as an actuator that is suitable for the system to initiate toe motion, was developed.

The effect of an auxiliary stimulation on motor function restoration by FES.

Functional Electrical Stimulation (FES) is a technology to generate neural activity in an artificial way to activate muscles. However, as reported by some researchers, the human responses to FES are likely to be affected by several factors, such as spasticity, muscle fatigue, nerve habituation and so forth. Consequently, the function restoration by FES is neither durable, nor stable. In order to realize long-term and stable FES assistance, this study investigated whether and why an Auxiliary Stimulation (AS) to the Gastrocnemius, with current frequency ranged from 2000 to 6000 Hz, could alleviate the symptom of spasticity and muscle fatigue caused by the stimulation to the Tibialis Anterior. We have developed a portable auxiliary stimulator, and performed experiments to verify its effectiveness. The results showed that our approach enabled comparatively stable and durable function restoration assistance. Moreover, for understanding underlying neuromuscular processes elicited by the AS and its qualitative nature, this study also measured the Hoffmann-reflex (H-reflex) in soleus muscle before and after the AS, to interpret the effect of the Auxiliary Stimulation.