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.

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 electromyography

METHODS:

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.

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.

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.

Basic Study of the Influence of the Manner of Grasping, Number of Contacts, and Auditory Information on Recognition of Hardness of Objects by Visually Impaired Persons Using White Canes

White canes are widely used as tools to assist visually impaired persons to walk. The white cane is used to acquire environmental information as a clue for walking. It is important to know what information can be acquired by using the cane, how accurate the acquired information is, and how we can improve the information and accuracy. Clarification of these questions would contribute to development of white canes that enable better acquisition of environmental information. It would also assist in the design of buildings with appropriate guidance for visually impaired persons on the basis of information acquired through the canes. In this study, in order to acquire basic knowledge about hardness recognition, experiments were performed using four conditions: 1) Tapping or pushing the object with the index finger tip and white cane tip, 2) use or non-use of the auditory sense to study its usefulness, 3) different ways of grasping the cane, and 4) different number of checks. Nine visually impaired persons who usually walked alone using white canes participated in the experiments. They estimated the hardness of a rubber sheet under various combinations of the operation conditions and hearing conditions. Results showed that the number of checks had little effect on the user’s estimation of the hardness of the sheet. For the recognition of the contact target hardness using the white cane, it was effective to simultaneously use information from different modalities, namely tactile and auditory information. We also observed that, when pushing the cane with the index fingers, the users could feel the objects as if they had directly touched them with the fingers.

Evaluation of swallowing ability using swallowing sounds in maxillectomy patients

Maxillectomy for oral tumours often results in debilitating oral hypofunction, which markedly decreases quality of life. Dysphagia, in particular, is one of the most serious problems following maxillectomy. This study used swallowing sounds as a simple evaluation method to evaluate swallowing ability in maxillectomy patients with and without their obturator prosthesis placed. Twenty-seven maxillectomy patients (15 men, 12 women; mean age 66.0 ± 12.1 years) and 30 healthy controls (14 men, 16 women; mean age 44.9 ± 21.3 years) were recruited for this study. Participants were asked to swallow 4 mL of water, and swallowing sounds were recorded using a throat microphone. Duration of the acoustic signal and duration of peak intensity (DPI) were measured. Duration of peak intensity was significantly longer in maxillectomy patients without their obturator than with it (P < .05) and was significantly longer in maxillectomy patients without their obturator than in healthy controls (P < .025 after Bonferroni correction). With the obturator placed, DPI was significantly longer in maxillectomy patients who had undergone soft palate resection than in those who had not (P < .05). These results suggest swallowing ability in maxillectomy patients could be improved by wearing an obturator prosthesis, particularly during the oral stage. However, it is difficult to improve the oral stage of swallowing in patients who have undergone soft palate resection even with obturator placement.

Evaluation of Swallowing Sound Using a Throat Microphone with an AE Sensor in Patients Wearing Palatal Augmentation Prosthesis

An increase in the population of dysphagia patients due to an aging population has led to increased attention on examination methods based on swallowing sound as simple methods of screening aspiration. However, an issue with the conventional method of cervical auscultation is that its accuracy varies based on the examiner. Previous studies examined the use of throat microphones and acceleration sensors to examine the acoustic characteristics of swallowing sound. Nevertheless, extant studies to date did not reach a level of clinical application. This study focused on using a throat microphone that is conventionally used to measure swallowing sound and an AE sensor to measurement a high-frequency range equal to and exceeding 20 kHz (upper limit 2 MHz). The study involved measuring the sounds of swallowing water of healthy subjects and patients wearing palatal augmentation prosthesis who had done surgical operation to treat head and neck cancer with the objective of using swallowing sound for screening aspiration. Acoustic characteristics of measured swallowing sound were analyzed using probability distributions using Quantile-Quantile (Q-Q) plots and spectral analysis based on wavelet transform. The findings indicated that with respect to patients with PAP, the duration time of the swallowing sound and the Q-Q plot departure rate were both significantly higher when compared with those in healthy subjects. The analysis based on wavelet transform indicated that the AE sensor allowed measurements of waveforms at a higher frequency range when compared to those in the case of the throat microphone. Additionally, an increased frequency of higher-frequency signals was associated with patients with PAP when compared to healthy subjects. The results revealed that it is possible to measure waveforms in the high-frequency range by using the AE sensor. The findings suggested the validity of analysis of the swallowing sound based on probability distributions using the Q-Q plot to evaluate the swallowing sound.

Pilot Study on an Acoustic Measurements System of the Swallowing Function Using an Acoustic-Emissions Microphone

The goal of this study is to evaluate the swallowing functions of people with dysphagia using an acoustic microphone sensor. As a basic investigation towards this end, we measured the swallowing sounds using an acoustic emissions microphone sensor (AE sensor), then analyzed the frequency range of the measured signals, and we examined the method for obtaining the necessary information to evaluate the swallowing functions. For the measurement, two types of sensors, i.e., a condenser throat microphone and an AE sensor, were employed to measure the swallowing sounds. The acoustic signals obtained were subjected to spectral analysis using the wavelet transformation, and a comparison was performed between the measurable ranges of the acoustic signals obtained by the AE and the acoustic sensors. The results from the wavelet transformation of the acoustic signals obtained by the AE sensor indicated that acoustic signals generated during swallowing contained frequency information of 3 kHz and higher, which were not measurable with the acoustic sensor used in the experiment. In addition, we proposed a method of evaluating swallowing sounds using a novel approach based on the probability distribution. From the analysis results, it was found that the distance between the theoretical values and the measured values has a high correlation with the sample viscosity. Furthermore, it was found that the data measured with the AE sensor more sensitively reflected the difference in the sample viscosity. We were thus able to demonstrate the possibility of evaluating the swallowing function via the proposed method.

Experimental Study on Physical Burden of Transfer Assistance for Excretion – Comparison Between Transfer-Type Wheelchair and Ordinary Wheelchair –

Assisting the elderly to or from a toilet for excretion is a heavy burden, and staff at nursing homes and families at home have problems such as backache and tiredness. There are several previous studies on standing up from a chair, bed, or toilet seat but almost no studies on the series of actions required for excretion (i.e., from a bed to a transfer apparatus and from the transfer apparatus to the toilet seat). The difference in the physical burden (muscular strength) for helpers when using the Norisukesan II, a transfer-type wheelchair developed in collaboration with the authors, and an ordinary wheelchair when transferring a patient to or from a toilet for excretion was studied by biometrics with surface electromyogram (EMG) patterns. We chose a total of 11 healthy adult examinees, 10 males and one female, with an average age of 47.7±9.7. Muscle activity was measured at eight positions: right and left biceps brachii muscles, right and left quadriceps femoris muscles, upper right and left trapezius muscles, and right and left waist muscles. The results showed that if the transfer-type wheelchair was used, the muscle activity of the helpers’ biceps brachii muscles decreased by 70%, that of the quadriceps femoris muscles decreased by 60%, that of the trapezius muscles decreased by 70%, and that of the waist muscles decreased by 40%, when compared to using the ordinary wheelchair. It was therefore quantitatively clarified that assisting patients with the transfer-type wheelchair could reduce the assisting burden significantly, as the helpers did not have to tightly hold or turn the patients.

A Pilot Study of a Tactile Measurement System Using Lateral Skin Stretch on Foot Plantar Surface

The purpose of this study is to develop smart equipment to quantify plantar tactile sensibility for early diagnosis and tracking of peripheral neuropathy caused by diabetes mellitus. In this paper, we present new testing equipment composed of a plantar tactile stimulation platform with a moving contactor to stretch the skin tangentially, a response switch for each tactile stimulus, a motor control box, and a personal computer for psychophysical data processing. This testing equipment offers more precise measurements and is easy to use compared to conventional testing tools such as von Frey monofilaments, pin-prick testing devices, and current perception threshold testers. Using our testing equipment, we showed that the plantar tactile threshold for the tangential stretching stimulus on the first metatarsal head of the feet ranges from approximately 10 to 60 μm for subjects without diabetic foot problems. Meanwhile, the plantar tactile threshold of some subjects suspected of having diminished protective sensation by the Semmens-Weinstein monofilament testing is approximately 100 μm or more. These preliminary results suggest that our testing equipment based on the plantar sensation elicited by lateral stretching of skin has the potential for quantitative diagnosis in subjects suspected of suffering from neuropathy, and for monitoring changes over time to sustain quality of life.

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.

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.