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Purpose The purpose of this study was to comprehensively review the literature regarding the application of artificial intelligence (AI) in the dental field,focusing on the evaluation criteria and architecture types. Study selection Electronic databases (PubMed, Cochrane Library, Scopus) were searched. Full-text articles describing the clinical application of AI for the detection, diagnosis, and treatment of lesions and the AI method/architecture were included. Results The primary search presented 422 studies from 1996 to 2019, and 58 studies were finally selected. Regarding the year of publication, the oldest study, which was reported in 1996, focused on "oral and maxillofacial surgery." Machine-learning architectures were employed in the selected studies, while approximately half of them (29/58) employed neural networks. Regarding the evaluation criteria, eight studies compared the results obtained by AI with the diagnoses formulated by dentists, while several studies compared two or more architectures in terms of performance. The following parameters were employed for evaluating the AI performance: accuracy, sensitivity, specificity, mean absolute error, root mean squared error, and area under the receiver operating characteristic curve. Conclusions Application of AI in the dental field has progressed; however, the criteria for evaluating the efficacy of AI have not been clarified. It is necessary to obtain better quality data for machine learning to achieve the effective diagnosis of lesions and suitable treatment planning.

Purpose To investigate the difference in improvement of oral health-related quality of life (OHR-QoL) depending on the oral and denture conditions of a complete denture wearer when using a cream or powder type denture adhesive in a 10-center parallel randomized clinical trial.Methods Two hundred edentulous subjects who wore complete dentures were allocated to each of the three groups according to denture adhesive type: cream, powder, and control (saline solution). The materials were applied to the mucosal surface of the dentures for 4 days, and baseline data and data after the intervention were collected. OHR-QoL was assessed using the Japanese version of the modified Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT-J) scale for outcome. Multivariate analysis was used to investigate improvements in OHR-QoL according to participant characteristics among complete denture wearers using these materials.Results OHIP-EDENT-J scores were significantly decreased in all groups after the intervention (p < 0.05); however, there were no statistically significant differences among the groups. Multiple logistic regression analysis revealed a significant association between the vertical height of the maxillary and mandibular alveolar ridge and OHIP-EDENT-J scores in the cream-type denture adhesive group. In contrast, there were no significant association between participant characteristics and OHIP-EDENT-J scores in the powder-type adhesive and control groups.Conclusions The use of denture adhesives could improve OHR-QoL for complete denture wearers. The cream-type denture adhesives may be expected to improve OHR-QoL in patients with poor residual ridge conditions compared with patients with good residual ridge conditions.

The purpose of this study was to investigate the effect of denture adhesives on oral moisture in a 10-center parallel randomized clinical trial.Two hundred edentulous subjects wearing complete dentures were allocated into three groups: cream-type adhesive, powder-type adhesive and control groups. The adhesives (and saline solution in the control group) were applied to the mucosal surface of the dentures for 4 days, and baseline data and data after the intervention for eight meals over 4 days were obtained. For the main outcome, oral moisture was measured with a moisture checking device. Secondary outcomes were denture satisfaction, masticatory performance, denture retention, and occlusal force. In addition to between-group and within-group comparisons of oral moisture, investigations for secondary outcomes were undertaken in subgroups classified according to the degree of oral moisture at baseline (normal subgroup and dry mouth subgroup). Intention-to-treat analysis was also performed.Between-group and within-group comparisons of oral moisture showed no significant differences. The cream-type and powder-type denture adhesives were significantly effective in the dry mouth group for denture satisfaction ratings of ability to masticate, stability, retention, and comfort of mandibular dentures (p0.05). The masticatory performance and retentive force of the dry mouth denture adhesive using groups were significantly improved after intervention (p0.05).The oral moisture of complete denture wearers was not influenced by the use of denture adhesives. Our findings showed that denture adhesives improved subjective denture satisfaction, masticatory performance, and retention for complete denture patients with oral dryness.

Background Implant-assisted removable partial dentures (IARPDs) have recently become popular, but little information is available on the treatment outcomes based on the Kennedy classification and attachment types. Objective The objective of this review was to evaluate the treatment outcomes of IARPD delivered for distal extension edentulous areas based on the differences in the Kennedy classification and attachment type. Materials and methods English-language clinical studies on IARPD published between January 1980 and February 2020 were collected from MEDLINE (via PubMed), the Cochrane Library (via the Cochrane Central Register of Controlled Trials), Scopus online database, and manual searching. Two reviewers selected the articles based on pre-determined inclusion and exclusion criteria, followed by data extraction and analysis. Results Eighty-one studies were selected after evaluating the titles and abstracts of 2410 papers. Nineteen studies were finally included after the perusal of the full text. Fourteen studies focused on Class I, 4 studies investigated both Class I and II, and only 1 study was conducted on Kennedy’s class II. Eight types of attachments were reported. The ball attachment was the most frequently used attachment, which was employed in 8 of the included studies. The implant survival rate ranged from 91 to 100%. The reported marginal bone loss ranged from 0.3 mm to 2.30 mm. The patient satisfaction was higher with IARPD than with conventional RPDs or that before treatment. The results of prosthetic complications were heterogeneous and inconclusive. Conclusion IARPD exhibited favorable clinical outcomes when used as a replacement for distal extension edentulous areas. The comparison between the clinical outcomes of Kennedy’s class I and II was inconclusive owing to the lack of studies focusing on Kennedy Class II alone. The stud attachment was the most commonly used type in IARPDs. Overall, the different attachment systems did not influence the implant survival rate and patient satisfaction. Further high-quality studies are needed to investigate the attachment systems used in IARPD.

Metal allergy is one of the typical immune disorders encountered during the application of dental/medical materials and has a highly complex pathogenic mechanism. Semaphorin 3A (Sema3A), a member of the semaphorin family, is reported to be involved in various immune disorders. However, its role in metal allergy has not been clarified yet. Herein, we show that Sema3A promoted nickel (Ni) allergy by mediating tumor necrosis factor-alpha (TNF-α) production and mitogen-activated protein kinase (MAPK) activation in keratinocytes. Sema3A was upregulated in NiCl2-stimulated mouse keratinocytes and in Ni allergy-induced mouse ear tissue. TNF-α production and MAPK activation were altered when Sema3A was suppressed in keratinocytes. The specific deletion of Sema3A in keratinocytes alleviated Ni allergy and regulated the macrophage polarization towards an anti-inflammatory direction. Our results demonstrate that Sema3A promotes the development of metal allergy and should be explored as a potential target for the prevention and treatment of metal allergy.

The prefrontal cortex (PFC) plays an important role in several cognitive functions, such as planning, decision making, and social behavior. We previously reported that periodontal sensory input significantly increases PFC activity during the motor task of maintaining occlusal (biting) force. However, the relationships between periodontal sensation, PFC activity, and the performance of motor tasks have not been evaluated in detail. Therefore, using functional near-infrared spectroscopy, we investigated PFC activity by monitoring changes in cerebral blood flow (CBF) to specific areas of the PFC that corresponded to changes in occlusal force generated during four different biting tasks: (1) occlusion with the central incisor with an interocclusal distance of 5 mm (BI-5 mm); or (2) 10 mm (BI-10 mm); (3) occlusion with the first molars with an interocclusal distance of 5 mm (BM-5 mm), or (4) 10 mm (BM-10 mm). Occlusion of molars generated increased PFC regional CBF as the interocclusal distance decreased (BM-10 mm vs BM-5 mm). No significant differences in CBF during occlusion of incisors were found when comparing 5 mm and 10 mm intercostal distances (BI-5 mm vs BI-10 mm). The mean occlusal force generated by BM-5 mm occlusion was significantly lower than that generated by BM-10 mm occlusion. Taken together, our results suggest that the PFC decreases efferent signaling to motor units, to reduce occlusal force generated when periodontal sensation, which is greater when the interocclusal distance is reduced, is primarily responsible for maintaining occlusal force in the absence of sensations from the temporomandibular joint and muscle spindles.

Purpose To clarify the effect of geniohyoid (GH) muscle morphology and related function on masticatory ability using a decision-tree analysis. Materials and methods A total of 103 participants were enrolled. A cross-sectional area (CSA) of the GH muscle, neck circumference, body mass index, tongue pressure, jaw opening strength, and masticatory ability score were measured. The CSA of the GH muscle was selected as an independent variable for the first layer of the decision tree, with masticatory score as the dependent variable. Results and conclusion These data suggest that the CSA of the GH muscle may have a large impact on the masticatory ability score when evaluating masticatory ability.

Mastication plays a primary role in the process of eating. Hence, compromised masticatory ability may affect the nutrition and quality of life, which are particularly important concerns among older individuals. It remains unclear how is the masticatory ability assessed regarding the nutritional status. We examined the effect of various oral factors on three masticatory ability tests conducted among older individuals. A total of 100 older individuals were enrolled in this study. Body mass index (BMI) as an indicator of nutritional status, and age, sex, and the number of occlusal and molar occlusal supports as clinical attributes were recorded. Three masticatory ability tests (masticatory efficiency, masticatory score, and satisfaction with mastication) were conducted, and tongue pressure, cheek pressure, and occlusal force were assessed as oral functions. A significant but weak correlation was found between masticatory efficiency and the masticatory score, but not between masticatory efficiency and satisfaction score. Objective masticatory efficiency was strongly associated with objective oral factors, whereas subjective assessments of masticatory ability (masticatory score and satisfaction score) were not. Furthermore, BMI was significantly associated with subjective assessments of masticatory ability but not with objective masticatory efficiency. Both subjective and objective assessments of masticatory ability, along with considerations of nutritional formulations, are required for the maintenance and improvement of nutritional status in older individuals.

We previously studied the effect of peripheral sensory information from sensory periodontal ligament receptors on prefrontal cortex (PFC) activity. In the dental field, an alternative dental implant without periodontal sensation can be applied for missing teeth. In this study, we examine whether periodontal tactile input could increase cerebral blood flow (CBF) in the PFC against elderly patients with dental implants lacking periodontal tactile (implant group), elderly individuals with natural teeth (elderly group), and young individuals with natural teeth (young group). The experimental task of maintaining occlusal force as closed-loop stimulation was performed. Compared with the young group, the elderly group showed significantly lower CBF. Contrastingly, compared with the young group, the implant group showed significantly lower CBF. There were no significant differences between the elderly and implant groups. Regarding the mean occlusal force value, compared with the young group and the elderly group, the implant group had a numerically, but not significantly, larger occlusal force exceeding the directed range. In conclusion, the periodontal tactile input does not uniquely increase PFC activity. However, increased CBF in the PFC due to the periodontal tactile input in the posterior region requires existing attention behavior function in the PFC.

Purpose To introduce a new clinical procedure for fabricating duplicates of complete dentures by bite pressure impression using digital technology, and to discuss its clinical significance. Methods The denture is placed on a rotary table and the 3-dimensional form of the denture is digitized using a general-purpose handheld optical scanner. The duplicate denture is made of polylactic acid by a 3-dimensional printer using the 3-dimensional data. Conclusion This procedure has the advantages of wasting less material, employing less human power, decreasing treatment time at the chair side, lowering the rates of contamination, and being readily fabricated at the time of the treatment visit.

A questionnaire survey was conducted to investigate eating behavior and the subjective symptoms of oral frailty, and to examine the relationship between them. A total of 744 subjects with ages over 65 years were included. The questionnaire comprised 18 question items indicating eating behavior and seven question items indicating oral frailty. All items were assessed according to 4 grades on a scale of 1 (not applicable) to 4 (applicable). The total score of oral frailty gradually increased with age. Regarding the scores for &ldquo, eating recognition&rdquo, and &ldquo, eating habits&rdquo, no changes were observed, however the scores for &ldquo, eating action&rdquo, demonstrated a decreasing tendency with age and the scores of &ge, 85 years age group was significantly lower than the 65&ndash, 69, 70&ndash, 74, and 75&ndash, 79 years age groups. As a result of multiple regression analysis, among the significant independent variable, the scores of &ldquo, I do not chew foods well&rdquo, under the category of &ldquo, showed the highest standard partial regression coefficients for dependent variable of symptoms of oral frailty. The significant association was found between the eating behavior and subjective symptoms of oral frailty, and this study suggests that the good chewing habit might be an important criterion for the prevention of oral frailty.

AIM To demonstrate the usefulness of a virtual reality device that authentically portrays the emotions of dementia patients and their families (VR Dementia Experience) for encouraging an understanding of and reducing and eliminating prejudice towards dementia patients among local residents. METHOD In Prefecture T, Town N, 85 residents of Neighborhood A were chosen as the intervention group, and 95 residents of Neighborhood B were chosen as the non-intervention group. The VR Dementia Experience was provided only to the residents of Neighborhood A. Residents of both neighborhoods completed a 35-item questionnaire regarding their degree of understanding and prejudice towards dementia patients before and after the intervention. RESULTS Seventy-seven residents of Neighborhood A and 82 residents of Neighborhood B were analyzed. Their gender, age, and pre-intervention test baseline values were equivalent in the degree of understanding and prejudice. Significant increases were observed in 9 of 35 items for Neighborhood A residents (7 understanding-related, 2 prejudice-related) and 2 items for Neighborhood B residents (1 understanding-related, 1 prejudice-related). To ascertain the usefulness of the VR Dementia Experience, we compared the number of items with a significant increase: 9/35 (25.7%) in Neighborhood A and 2/35 (5.7%) in Neighborhood B. An effect (≥ 20%) was observed among the residents of Neighborhood A. Furthermore, after exposure to the VR Dementia Experience, the connection between understanding, prejudice, and dementia was strengthened among the residents of Neighborhood A compared to the residents of Neighborhood B. CONCLUSION The VR Dementia Experience is a useful tool for encouraging an understanding of and reducing and eliminating prejudice towards dementia patients among local residents. However, to encourage the widespread usage of the technology, we should compare results with other public awareness campaigns as well as make improvements to the device and its VR content.

Background: No report has yet examined the impact of oral hypofunction on physical frailty in relation to intra‐relationships of physical frailty assessment items. The purpose of this study was to verify the potential of a clinical cascade between oral hypofunction and physical frailty, and especially to support the hypothesis that the influence of oral hypofunction on physical frailty is greater than the intra‐relationships among elements of physical frailty, and that sex differences significantly affect these relationships. Methods: The participants were 272 older adults (101 men and 171 women; mean age 75.1 ± 7.5 years). Maximum occlusal force (MOF) and oral dryness (OD), as indicators of oral hypofunction, and grip strength (GS) and walking speed (WS), as indicators of physical frailty, were measured. Mutual relationship of four variables was verified using covariance structure analysis. Results: In men, three paths from MOF to WS and GS and from WS to GS were confirmed, and those from MOF to WS and from WS to GS were found to be significant (p < 0.01). In women, three paths from MOF to WS and GS and from WS to GS were also confirmed, as with the men, and those from MOF to WS and from MOF to GS were found to be significant (p < 0.01). Model adaptability was shown to be good for both men and women. Conclusion: The results suggest our hypothesis was verified, and it is expected that the early detection of oral hypofunction, that is, MOF, may be important for assessing physical frailty, especially in women.

Purpose The present study aimed to examine three methods for imaging a complete denture form and to discuss the geometric assessment and availability of these methods. Methods Three methods were used: cone-beam computed tomography (CBCT), desktop dental scanning (DDS), and handheld optical scanning (HOS). Three sides of a cuboid resin block of a known size were measured on the captured images. Ten upper and lower complete dentures were digitized using each of the three methods. The denture forms in the standard triangulated language format were reconstructed using the computer aided design software with three resolutions: 0.1, 0.5 and 1.0. The two images were superimposed through a least-square algorithm, and the mean differences were examined among the three types of imaging methods and resolutions. Results The smallest mean differences and variations were obtained for CBCT and DDS, followed by HOS in the experiment using resin block. The lengths of longitudinal and horizontal sides were shortened in CBCT and DDS, whereas the height was shortened in HOS. The variations in each direction were very small by repetitive imaging within every imaging method. The difference between the CBCT and DDS was significantly smaller than that in the other two groups in experiment using actual dentures. The influence of resolution was comparatively low. Conclusions The results suggested that CBCT and DDS had a similar geometric assessment, but that of the HOS was lower.

Purpose There are two key considerations for successful esthetic dental treatments. This article systematically describes the two key considerations: the end points of esthetic dental treatments and assessments of esthetic outcomes, which are also important for acquiring clinical skill in esthetic dental treatments. Study selection The end point and assessment of esthetic dental treatment were discussed through literature reviews and clinical practices. Results Before designing a treatment plan, the end point of dental treatment should be established. The section entitled "End point of esthetic dental treatment" discusses treatments for maxillary anterior teeth and the restoration of facial profile with prostheses. The process of assessing treatment outcomes entitled "Assessments of esthetic dental treatment" discusses objective and subjective evaluation methods. Conclusions Practitioners should reach an agreement regarding desired end points with patients through medical interviews, and continuing improvements and developments of esthetic assessments are required to raise the therapeutic level of esthetic dental treatments.

Few studies have reported the application of digital technology to removable dentures, particularly for the process of impression and interocclusal recording for complete denture fabrication. This article describes a part-digitizing system of impression and interocclusal records for complete denture fabrication. The denture foundation area in an edentulous mouth, including the border areas and residual ridge, is outlined by tracing the surfaces with a 3-D pen-type digitizer. Specialized trays for final impressions and interocclusal records were generated using computer-aided design and manufactured using the digital data. Final impression and interocclusal records were carried out using these specialized trays. The computer-aided method using preliminary digital impressions and specialized trays would be feasible for clinical use for complete denture fabrication.

In this study, we evaluated the reliability and reproducibility of widely implemented salivary flow rate and oral dryness tests. In experiment 1, twenty young and healthy Japanese participants volunteered to participate. For each participant, the oral moisture (OM) level, unstimulated whole saliva volume (U-WSV), and stimulated whole saliva volume (S-WSV) were measured at the same time on two separate days. In experiment 2, twenty-seven patients who were over 65 years of age volunteered to participate. The OM level and U-WSV were measured at the same time on two separate days. In Experiment 1, the intra-class correlation coefficients (ICCs) corresponding to the S-WSV, U-WSV, and OM level were 0.23, 0.28, and 0.16, respectively, for the young participants. In Experiment 2, the ICCs corresponding to the U-WSV/spitting and OM level were 0.83 and 0.12, respectively, for the older participants. The results of Bland&ndash, Altman analysis confirmed the absence of systematic error, with the exception of the OM level results in Experiment 2, which indicated systematic bias. In conclusion, we believe that there is currently no consistent and reliable screening test for assessing salivary flow rate and oral dryness, although the spitting test was determined to be highly reliable.

Objective assessments of oral hygiene are important to prevent oral and systemic diseases. Two objective assessment tests are available to assess oral hygiene, (1) the adenosine triphosphate (ATP) + adenosine monophosphate (AMP) swab test, which incorporates a luciferase assay and (2) a bacteria count using the dielectrophoretic impedance measurement (DEPIM) method. In this study, we compared the two tests using a subjective visual assessment by professional clinicians and investigated the clinical significance of these tests. Twenty-seven young participants (mean age 26.3 &plusmn, 3.2 years) and twenty-seven older participants (mean age 75.1 &plusmn, 5.9 years) were recruited. Oral bacteria were sampled from three areas, including the tongue dorsum, the buccal mucosa, and the faucal mucosa, and saliva was obtained using a cotton swab. The amount of ATP + AMP and the number of bacteria were measured by each specific apparatus. Additionally, one examiner assessed the overall condition of oral hygiene using the visual analog scale (VAS). In the ATP + AMP swab test, the means were highest in saliva. For the bacteria count, the means were higher in the tongue dorsum and saliva and lower in the faucal and buccal mucosa. The results of the subjective assessment of oral hygiene indicated that the VAS-value was 3.78 &plusmn, 0.97 for the young group and 3.35 &plusmn, 0.81 for the older group. No significant difference was observed between the two groups. Additionally, no significant relationship between the values of the ATP + AMP swab test and the bacteria count was found for any of the four sample sites. In the older group, the subjective assessment of oral hygiene was significantly correlated with the values of the ATP + AMP swab test (multiple correlation coefficient = 0.723, p = 0.002). In conclusion, the values provided by the ATP + AMP swab test were not always correlated to the bacteria count. The results of this study suggest that the subjective assessment of oral hygiene was more highly correlated with the results of the ATP + AMP swab test, as compared to the bacterial count assay.

Polyetheretherketone (PEEK) is a semi-crystalline linear polycyclic thermoplastic that has been proposed as a substitute for metals in biomaterials. PEEK can also be applied to dental implant materials as a superstructure, implant abutment, or implant body. This article summarizes the current research on PEEK applications in dental implants, especially for the improvement of PEEK surface and body modifications. Although various benchmark reports on the reinforcement and surface modifications of PEEK are available, few clinical trials using PEEK for dental implant bodies have been published. Controlled clinical trials, especially for the use of PEEK in implant abutment and implant bodies, are necessary.

Background Behaviors relating to food intake, i.e., speed of chewing, number of chews, and bite size, are important for decreasing energy intake, which might reduce excess body weight and thus metabolic risk. This study aimed at investigating the influence of mouthful volume on the number of chews and food bolus properties in addition to clarifying appropriate eating behaviors related to mouthful volume. Methods Fifteen young Japanese women volunteered to participate. The subjects were asked to spit the food bolus in a glass dish just before swallowing when eating 3 different foods: boiled rice, fish sausage, and peanuts. The 3 physical properties of solidity, adhesiveness, and cohesiveness were measured in the bolus, and the number of chews was noted. Results The number of chews significantly increased with increasing mouthful volume with all 3 foods; conversely, the number of chews per unit of food weight (g) decreased significantly with boiled rice and fish sausage. Trends were observed for solidity and cohesiveness, which varied with increasing mouthful volumes. Conclusions Decreased mouthful volume resulted in a greater number of chews per weight of food and more appropriate bolus properties; therefore, a change in mouthful volume could be a useful behavior modification for regulation of energy intake.

Purpose This in vitro study investigated the effect of attachment installation conditions on the load transfer and denture movements of implant overdentures, and aims to clarify the differences among the three types of attachments, namely ball, Locator, and magnet attachments. Materials and Methods Three types of attachments, namely ball, Locator, and magnetic attachments were used. An acrylic resin mandibular edentulous model with two implants placed in the bilateral canine regions and removable overdenture were prepared. The two implants and bilateral molar ridges were connected to three-axis load-cell transducers, and a universal testing machine was used to apply a 50 N vertical force to each site of the occlusal table in the first molar region. The denture movement was measured using a G2 motion sensor. Three installation conditions, namely, the application of 0, 50, and 100 N loads were used to install each attachment on the denture base. The load transfer and denture movement were then evaluated. Results The resultant force decreased with increasing installation load for all attachments. In particular, the resultant force on implants on the loading side of the Locator attachment significantly decreased when the installation load was increased from 0 to 50 N, and that for magnetic attachment significantly decreased when the installation load was increased from 50 to 100 N. For the residual ridges on the loading side, the direction of the forces for all attachments changed to downward with increasing installation load. Furthermore, the yaw Euler angle increased with increasing installation load for the magnetic attachment. Conclusions Subject to the limitations of this study, the use of any installation load greater than 0 N is recommended for the installation of ball and Locator attachments on a denture base. Regarding magnetic attachments, our results also recommend installation on a denture base using any installation load greater than 0 N, and suggest that the resultant force acting on the implant can be decreased by increasing the installation load; however, a large installation load of 100 N should be avoided when installing the attachment on the denture base to avoid increasing the denture movement.

The Japan Prosthodontic Society developed a multi-axis assessment protocol to evaluate the complex variations in patients who need prosthodontic care, and to classify the level of treatment difficulty. A previous report found the protocol to be sufficiently reliable. The purpose of this multi-center cohort study was to evaluate the validity of this multi-axis assessment protocol.The treatment difficulty was evaluated using the multi-axis assessment protocol before starting prosthodontic treatment. The time required for active prosthodontic treatment, medical resources such as treatment cost, and changes in the oral health-related QOL before and after treatment, were evaluated after treatment completion. The construct validity of this protocol was assessed by the correlation between the dentist's pre-operative subjective assessment of the treatment difficulty, and the level of difficulty determined by this protocol. The predictive validity was assessed estimating the correlations between a "comprehensive level of treatment difficulty" based on the four axes of this protocol and total treatment cost, total treatment time, and changes in the oral health-related QOL before and after treatment.The construct validity of this protocol was well documented except for psychological assessment. Regarding the predictive validity, the comprehensive level of treatment difficulty assessed before treatment was significantly correlated with the three surrogate endpoints known to be related to the treatment difficulty (total treatment cost, treatment time, and improvement in the oral health-related QOL). To further clarify the validity of the protocol according to patients' oral condition, a subgroup analysis by defects was performed. Analyses revealed that treatment difficulty assessment before treatment was significantly related to one or two surrogate endpoints in the fully edentulous patients and the partially edentulous patients. No significant relationship was observed in the patients with mixture of full/partial edentulism and the patients with teeth problems, possibly due to the small sample size in these groups.This study revealed that the multi-axis assessment protocol was sufficiently valid to predict the level of treatment difficulty in prosthodontic care in patients with fully edentulous defects and with partially edentulous defects.

The prefrontal cortex (PFC) plays a role in complex cognitive behavioural planning, decision-making, and social behaviours. However, the effects of sensory integration during motor tasks on PFC activation have not been studied to date. Therefore, we investigated the effect of peripheral sensory information and external information on PFC activation using functional near-infrared spectroscopy (fNIRS). Cerebral blood flow (CBF) was increased around bilateral Brodmann areas 46 and 10 during visual and auditory information integration during an occlusal force (biting) task. After local anesthesia, CBF values were significantly decreased, but occlusal force was similar. In conclusion, the effects of peripheral sensory information from the periodontal ligament and external information have minimal impacts on occlusal force maintenance but are important for PFC activation.

Clasp retainers made of metal alloys may be esthetically unappealing or cause allergic reactions. To investigate alternative materials, we used the nonfiller polyetheretherketone (PEEK) to fabricate the clasp retainer of a removable partial denture for the mandibular bilateral distal free-end abutment of an 84-year-old female. Two years later, few color and texture changes of PEEK were found macroscopically. The rest part and the clasp arm fitted well without any deformation. There were no particular occlusal or periodontal problems. Subjective satisfaction was expressed by both the practitioner and the patient.

BackgroundThe diagnostic assessment of the level of difficulty in treating patients who need prosthodontic care is useful to establish a medico-economically efficient system with primary care dentists and prosthodontic specialists.Materials and methodsA multi-axis assessment protocol was established using the newly established treatment difficulty indices. The protocol contains Axis I: oral physiological conditions (e.g., teeth damage and/or missing teeth); Axis II: general health and sociological conditions (e.g., medical disorders); Axis III: oral health-related quality of life (OHRQOL; e.g., oral health impact profile: OHIP); and Axis IV: psychological health (e.g., mood, anxiety, somatoform disorders). A preliminary study on the test–retest consistency of the protocol was conducted to check the levels of reliability of the indices prior to a large-scale, multi-center cohort study on the validity of the protocol.ResultsThe test–retest consistency in terms of the oral physiological condition (Axis I) after data reduction was 0.63 for patients with teeth problems, 0.95 for partially edentulous patients, and 0.62 for edentulous patients. The reliability for general health and sociological conditions (Axis II), OHRQOL (Axis III), and psychological health (Axis IV) were 0.88, 0.74, and 0.61, respectively. These values reflect either “sufficient agreement” or “excellent agreement” in accordance with the criteria established by Landis and Koch (1977) [1].ConclusionThis protocol is the first multi-axis assessment scheme introduced for prosthodontic treatment with sufficient reliability. This new system is therefore expected to have a significant impact on future dental diagnostic nomenclature systems.

Two-implant overdentures have become the accepted treatment for restoring mandibular edentulism. The dimensions of regular implants sometimes limit their use, such as in the case of narrow ridges. Mini-implants with reduced diameters (less than 3.0 mm) enable insertion into narrow ridges. A magnet-retained two-mini-implant overdenture system was developed and is described in this paper. Additionally, we describe a clinical mandibular procedure using the system and evaluate its biomechanical performance.

The 'main occluding area', the location where food crushing occurs during the first stroke of mastication, is reported to be an important concept; however, it is currently limited to findings in individuals with normal dentition. The purpose of this study was to assess the changes in the location, area and bite force of the main occluding area before and after implant treatments. We enrolled 50 partially edentulous and 22 normally dentate subjects. To identify the location of the main occluding area, each subject was instructed to freely bite once on a dental stopping using the partially edentulous side or the normally dentate area. The location, occluding contact area and bite force of the main occluding area before and after the implant treatments were analysed. The main occluding area was located at a reproducible location in the partially edentulous and normally dentate subjects. This location was principally the first molar region, and for the partially edentulous patients with missing teeth in the molar regions, it moved from the premolar region to the first molar region after treatment. The occluding contact area and bite force for the main occluding area increased (P < 0·05) after the implant treatment in the partially edentulous patients with missing teeth in the molar regions. These results suggest that the main occluding area can be restored to the first molar region after implant treatment and may be an important factor in the assessment of prosthodontic treatment.

Purpose Assessment of swallowing dysfunction, particularly the risk of aspiration, is extremely important to clinicians because it provides crucial information for preventing morbidity and mortality from dysphagia. The purpose of this study was to describe a magneto-impedance sensor-aided screening system (MISS) for assessing swallowing function and clarify its effectiveness with the repetitive saliva-swallowing test (RSST). Methods An MI sensor attached to the skin over the sternum detected the distance from a magnet attached to the skin over the thyroid cartilage during swallowing as the change of magnetic fields. The MISS was validated by videofluoroscopic and videoendoscopic observations. Further, the swallowing behavior of 93 individuals was assessed by using the MISS and then analyzed with the RSST. Swallowing behavior can be recorded and investigated objectively by signal inspection in the MISS compared with the conventional methods. The MISS is a simple and straightforward method for recording and safe because of dry swallow. The MISS system was validated by using simultaneous recordings with videofluoroscopic or videoendoscopic examinations, and compared with the conventional RSST method. Conclusions The MISS combined with the RSST is an effective screening test for swallowing function.

Purpose The purpose of this retrospective study was to assess the implant survival rate and the risk factors associated with implant failure in patients who had undergone immediate implant restoration. Materials and methods We performed a retrospective review and an outcome assessment of all patients who received immediate implant restoration between 2000 and 2010 in our department at Tokushima University Hospital. The patients were divided into groups on the basis of the predictor variables: age, gender, implant location, and number of implants per jaw. The cumulative implant survival rate in the paired groups was determined by using Kaplan–Meier analysis and the log-rank test. Cox proportional hazards model was subsequently used to identify exposures associated with implant failure. Results Using the Kaplan–Meier method, the survival rates at 1, 3, and 9 years were calculated to be 98.8%, 98.0%, and 94.7%, respectively. No statistically significant association was observed between the implant survival rates and the predictor variables: gender, age, location, and number of implants. Conclusions Immediate implant restoration is a reliable prosthetic procedure with an acceptable survival rate compared to the conventional implant procedure.

目的：インプラントオーバーデンチャーはMcgill consensusにおいて，無歯顎補綴治療における第一選択だと報告されている．今回は，下顎インプラントオーバーデンチャーに用いられるアタッチメントの選択基準を明らかにする一助とするため，よく用いられるボールアタッチメント，バーアタッチメント，磁性アタッチメントの臨床成績について文献考察を行った．研究の選択：文献検索に使用したデータベースはPubMed，医学中央雑誌を利用し，下顎インプラントオーバーデンチャーの術後の臨床成績について記述した文献のみを対象とした．その中より，選択基準ならびに除外基準によって27文献が採択された．それらを抄読後，1. 歯周組織評価，2. 力学的評価，3. メンテナンス，4. 患者満足度に焦点を当てて考察を行った．結果：ボールアタッチメントが全般的に良好な臨床結果を示した．一方で，バーアタッチメントはボールアタッチメントとほぼ同程度の結果であり，マグネットアタッチメントはそれらにやや劣るもののアタッチメントが未使用の義歯に比べ，良好な臨床結果を示した．結論：アタッチメントを用いた下顎インプラントオーバーデンチャーは無歯顎補綴治療において有効な選択肢であることが示唆された．さらに，それらのアタッチメントの選択基準を明確にしたガイドラインを作成する為にも，アタッチメントとオーバーデンチャーの最良の連結方法，手順を実験的および臨床結果の蓄積を通して明らかにしていく必要があると考えられる．

Data recording on a dental prosthesis for personal identification is proposed. Data recording was performed on a dental Au–Ag–Pd alloy with a complex surface shape by femtosecond laser processing with a surface detection function based on confocal optical detection. The processed morphology of a flat dental alloy sample was investigated over wide ranges of focus positions and laser fluences of the irradiating pulses. From the experimental results, appropriate recording conditions are discussed from the viewpoint of data recording. This is the first demonstration of two-dimensional data recording on such an object with a complex curved shape (an alloy crown).

Purpose: The purpose of this study was to consider the possibility of undergraduate dental education improvement by comparing the dental courses in a Japanese dental school with a UK dental school using the speciality of removable prosthodontics.Methods: Two dental schools, the University of Tokushima in Japan and the University of Birmingham in the United Kingdom, were compared. We compared both dental schools on the curriculum, lectures in removable prosthodontics, phantom head practice in removable prosthodontics, and clinical practice.Results: There are large differences in undergraduate dental education courses between the two dental schools, especially in clinical practice. Clinical practice exposure in the University of Birmingham is more than three times as long as the University of Tokushima. The number of patients available for treatment in Birmingham is much more than Tokushima and the minimum requirements in removable prosthodontics in Birmingham is more than eight times as many as Tokushima.Conclusion: Large differences in the undergraduate dental education courses between the two dental schools, including the number of patients for students, may be caused by the dental policy, the economy, religion and customs. It is important to execute education methods such as virtual reality simulation, Problem-Based Learning (PBL), Web-based courseware and Video-based self learning because of the lack of available patients in Japan.

Purpose: The purpose of this study was to investigate denture plaque microflora of geriatric inpatients and maxillary defect patients from the standpoint of infection control in the elderly.Methods: Denture plaque was collected from 80 elderly subjects who were categorized into 3 groups: group A, 21 healthy complete denture wearers; group B, 49 complete denture wearers residing at a geriatric hospital; and group C, 10 complete denture wearers with maxillary defects. The microflora was investigated by counting the total number of microorganisms, including streptococci, staphylococci, and Candida spp.Results: The colony-forming unit (CFUs) count and incidence, particularly those of Candida spp., were significantly higher in group B (P

Purpose The aim of this study was to compare 3-dimensional surfaces of study and working casts for edentulous jaws and to evaluate the accuracy of preliminary impressions with a view to the future application of digital dentistry for edentulous jaws. Methods Forty edentulous volunteers were serially recruited. Nine dentists took preliminary and final impressions in a routine clinical work-up. The study and working casts were digitized using a dental 3-dimensional scanner. The two surface images were superimposed through a least-square algorithm using imaging software and compared qualitatively. Furthermore, the surface of each jaw was divided into 6 sections, and the difference between the 2 images was quantitatively evaluated. Results Overall inspection showed that the difference around residual ridges was small and that around borders were large. The mean differences in the upper and lower jaws were 0.26mm and 0.45mm, respectively. The maximum values of the differences showed that the upward change mainly occurred in the anterior residual ridge, and the downward change mainly in the posterior border seal, and the labial and buccal vestibules, whereas every border of final impression was shortened in the lower jaw. The accuracy in all areas except the border, which forms the foundation, was estimated to be less than 0.25mm. Conclusion Using digital technology, we here showed the overall and sectional accuracy of the preliminary impression for edentulous jaws. In our clinic, preliminary impressions have been made using an alginate material while ensuring that the requisite impression area was covered.

In this article, intrinsic problems lying in Prosthodontics research and educational field were pointed out and Prosthodontics as it ought to be as a nature science was discussed. Prospect of prosthetic dentistry/Prosthodontics as a clinical science was categorized the following four and discussed: 1) systematizing of conventional Prosthodontics, such as crown, bridge, partial and complete denture, 2) contribution to oral rehabilitation of mastication, swallowing, and speech for elderly and inpatient elderly, 3) innovation of prosthetic dentistry using more comfortable and aesthetic prosthesis, such as Implant and Adhesive Dentistry, and 4) translational research. Finally, essential prerequisites to achieve bright future of Prosthodontics were proposed.

The placement of individual identification on a prosthesis is very important for forensic dentistry and traceability. This article describes the unique naming/labeling of dentures with information for individual identification using a method in which information is invisible under natural light but visible under ultraviolet light-emitting diode/black light exposure. The use of laser beam machining with this method will enable the recording of a large amount of information.

Purpose : This in vitro study investigated the influence of implant splinting on stress distribution in two experimental implant-bone models.Materials and Methods : Two experimental implant-bone models simulated the original Branemark model with four implants between the mental foramina and one additional implant placed on each side posterior to the mental foramen. The stress distribution on each implant in the models was examined by applying a static load to the superstructure. Three types of superstructures were studied to determine the effect of additional implants in the posterior region : 1) a metal superstructure supported by all six implants (Full dental arch ; Metal FDA) ; 2) the same type of superstructure made of resin instead of metal (Resin FDA) ; and 3) the metal superstructure supported by four anterior implants, with the conical abutments removed from the two posterior implants (Short dental arch ; Metal SDA).Results : Regardless of the type of superstructure tested, high stress was observed around each loaded implant. The highest stress was concentrated on the distal implants of the FDA compared to the stress on the anterior implants.Conclusion : The elevated stress concentration around the implants found in the present in vitro study is considered to be one of the reasons for the high failure rate of additional posterior mandibular implants.

目的: 客観的な咀嚼機能評価法を確立することは, 補綴処置の効果を評価するだけでなく, 診断や治療法の選択においても重要なことである. 今回, 着色ゼリーを用いた簡便な咀嚼機能評価法 (以下CG比色法) を考案し, 篩分法と比較しながら, その有効性について検討することを目的とした. また, 目視による比色判定の可能性を含め, 本評価法の進展性についても考察した.方法: 咀嚼機能に異常がない被験者13名に, 着色ゼリーを咀嚼させ, 口腔内残留色素の吸光度を測定した. 同時に, 節分法 (Manly法) による咀嚼機能評価も行い, 両者を比較検討することにより本評価法の有効性を評価した. また, 色素水溶液の色見本を参考に, 被験色素水溶液の吸光度を検者に推定させ, 目視による比色判定を試みた.結果: 咀嚼回数の増加とともに節分法の咀嚼値, CG比色法の吸光度も増加した. また, 筋分法は咀嚼回数が増えるに従い, 咀嚼値の増加率が減少するのに対し, CG比色法では吸光度の増加率は一定であった. また, 篩分法の咀嚼値はCG比色法の吸光度の対数に比例した. 目視による比色判定については, 色素水溶液の吸光度が0.5以下であれば, 実際の吸光度との間の誤差が比較的小さく, そのばらつきも小さかった.結論: CG比色法の吸光度と篩分法の咀嚼値とは対数関係にあり, 咀嚼回数が20回以下であれば, 本評価法は節分法と同等の有効性があることがわかった. また, 視感比色による咀嚼能率評価の可能性が得られた.

目的: 歯科用磁性アタッチメントのキーパーと根面板とをレーザー溶接し, その吸引力と腐蝕性を従来の鋳接法と比較検討することである.方法: 市販の歯科用磁性アタッチメントのキーパーと歯科用金銀パラジウム合金を本実験に用いた. 鋳接法とレーザー溶接法を用いて試料を製作した. 自家製の測定装置を用いて, 磁石構造体とキーパーの吸引力を測定し, 製作方法により吸引力に差が生じるかを検討した. また, 0.9% NaCl溶液5mlに37℃ で21日間浸漬し腐食試験を行い, その表面性状を観察した.結果: 磁石構造体とキーパー間の吸引力については, 製作方法による差は生じなかった. キーパーの腐食試験では, 鋳接法により製作したすべての試料で錆を生じた. レーザー溶接法で製作した一部の試料では錆を生じたが, まったく錆を生じなかった試料もみられ, その試料の表面には腐食生成物は認められなかった.結論: 磁性アタッチメント用キーパーをレーザー溶接する方法が, 磁性アタッチメントの吸引力と腐食に及ぼす影響を鋳接法と比較検討した結果, 吸引力に対する影響は認められなかった. また, レーザー溶接したキーパーには腐食が全く生じなかったものが認められた. よって, ンーザー溶接によりキーパーと歯科用合金の境界を完全に溶接しシールドすれば, 腐食を生じる可能性が低くなり, キーパー付根面板の製作過程へのレーザー溶接の導入は有用であることが示唆された.

Magnetic overdenture attachments can provide useful denture retention. A technique is proposed that involves installing the magnetic keeper in the overdenture abutment coping using laser welding. Compared with the conventional cast-to technique, the new technique provides a suitable contour to the abutment coping with the magnetic keeper and ensures proper mounting in the abutment coping, installing the magnetic keeper easily and effectively.

目的: チタンとハイドロキシアパタイト (以後, Ti, HAと略す) の異なる表面性状をもつインプラントについて伝導特性の相違を比較し, オッセオインテグレーションの評価を推定することを目的とした.方法: ウサギ脛骨に2種類の表面性状のインプラントを埋入した. 10週後に, インパルス打診試験を行い, インパルスハンマーと骨髄内に固定した小型圧力センサーにより, その振動特性と骨髄圧を測定し, インプラント材質間の差異を比較した. また, 組織学的にインプラント周囲骨の状態を検索し, 圧伝導特性との関係を検討した.結果: 観測されたインパルス継続時間では, HAで163±23μsec, Tiで165±20μsecと有意な差はなかった. 一方, 最大骨髄圧値は, HAで90.3±30.6mmHg, Tiで117.4±54.8mmHgと有意にTiのほうが大きく, また, 偏差もHAに比べTiのほうが大きかった. インパルス継続時間と最大骨髄圧値の間にはTiで負の相関関係が認められたが, HAでは相関が認められなかった. インプラント周囲骨の組織学的検索においては, インプラント間での差異は確認できなかった.結論: 骨髄圧値の測定から, TiとHAにおける圧伝導性の相違が認められた. 両者の周囲骨の組織像に差は認められず, インプラントの材質による影響が大きいことが示唆された. 評価法を構築していくうえで, 材質の特性の差異を考慮する必要性が示唆された.