Cyclic Fatigue Properties of Titanium Alloys for Application in Dental Implants.

The present study investigated the cyclic fatigue properties of titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) as implant materials and compared their properties with those of commercially pure titanium. Ti-6Al-4V and Ti-6Al-7Nb cylinders with diameters of 3.0 mm were examined. The surfaces of the cylinders were roughened by sand blasting with alumina particles and acid etching. Static and cyclic tests were performed according to ISO 14801:2016. The yield force in the static test (YS) was measured in 5 specimens of each alloy using a universal testing machine. The yield force in a cyclic test (YC) was measured in 20 specimens of each alloy using the staircase method, which involved applying a cyclic load at a frequency of 10 Hz for 106 cycles. After the cyclic loading tests, cross-sections of the specimens were examined under an optical microscope. The YS values for Ti-6Al-4V and Ti-6Al-7Nb were 1463 N±93 N and 1405 N±79 N, respectively, and the YC values were 870 N±58 N and 853 N±202 N, respectively. Microscopic observation revealed cracks on the tensile side of some of the specimens, including run outs and failures. The results of this study suggest that the YC values for Ti-6Al-4V and Ti-6Al-7Nb were 40% less than those for YS. The yield force of Grade-4 Cp-Ti significantly decreased after cyclic loading. The YC values for Ti-6Al-4V and Ti-6Al-7Nb were approximately 900 N, which was markedly greater than that for commercially pure, Grade-4 titanium (700 N).

Relationship between two pressure-sensitive films for testing reduced occlusal force in diagnostic criteria for oral hypofunction.

OBJECTIVE: To measure the occlusal force in the same group of patients with the Dental Prescale 50H type R and the Dental Prescale II, examine the association between them, and determine the reference value for Dental Prescale II that corresponds to the 50H type R 200 N reference value used to make a diagnosis of oral hypofunction. BACKGROUND: Reduced occlusal force, a measure of frailty in older persons, was previously determined with Prescale 50H type R pressure-sensitive film, but it has been replaced by the Prescale II. MATERIALS AND METHODS: The study participants were 441 men and women aged ≥ 65 (mean, 71.8 ± 5.3) years. The occlusal force was measured with the two different types of pressure-sensitive film, and their association was examined. Receiver operating characteristic curves for the Prescale II measured values were created with the 200 N reference value used for the 50H type R film as the cut-off value. RESULTS: The analysis set included 391 participants for whom measurements were obtained using both the 50H type R and the Prescale II. Linear regression analysis produced regression equations, and a ROC curve analysis provided reference values of 500 N for the Prescale II (without pressure filter) and 350 N for the Prescale II (with pressure filter). CONCLUSION: In occlusal force tests for making a diagnosis of oral hypofunction, reference values for the Prescale II (without pressure filter) and for the Prescale II (with pressure filter) were determined. The findings suggested that the Prescale II can be used as a diagnostic examination for oral hypofunction.

Effect of Lip-seal Resistance Training on Lip-seal Strength in Young Adults.

Lip-seal strength is important for articulating bilabials, capturing food during eating, maintaining fluid within the oral cavity before swallowing, and achieving swallowing pressure. The objective of this study was to investigate the effect of lip-seal resistance training on lip-seal strength in young adults. The participants comprised 15 young healthy adults aged 26-34 years, all with complete dentition. Each was required to perform lip-seal resistance training 5 weekdays a week for 4 weeks with a commercially available instrument for that purpose. The instrument was placed on the midline, left corner, and right corner of the mouth, and pulled forward, leftward, and rightward, respectively. The participants were required to pull the training instrument forcefully while resisting by closing the lips together as strongly as possible until the instrument exited the lips. Lip-seal strength was measured at before and after training using a measurement device. Change in lip-seal strength between before and after training was analyzed using the Wilcoxon signed rank test. The mean lip-seal strength was 8.9±1.5 N before training and 10.4±1.8 N after. A significant difference was observed in lip-seal strength between before and after training (p=0.003), and the mean increase during the training period was 18.1±17.6%. The results showed that lip-seal resistance training for 4 weeks increased lip-seal strength in young adults. These findings suggest that training that involves pulling not only in a forward direction, but also in bilateral directions strongly stimulates the orbicularis oris muscle, resulting in an increase in lip-seal strength.

Intra- and inter-investigator reliabilities of oral moisture measured using an oral moisture-checking device.

BACKGROUND: Oral mucosal moisture determined using oral moisture-checking devices is used as a mouth dryness evaluation method. Such devices are capable of evaluating the state of mouth dryness in a simple manner and have applicability in a wide range of subjects; however, their intra- and inter-investigator reliabilities have not yet been clarified. OBJECTIVE: This study aims to investigate the intra- and inter-investigator reliabilities of measuring oral moisture using an oral moisture-checking device for a wide range of age groups. METHODS: Intra- and inter-investigator reliabilities were investigated in 28 young subjects and 19 older subjects aged ≥65 years. Three trained investigators independently measured oral mucosal moisture values using an oral moisture-checking device. Intra-investigator reliability was assessed using the coefficient of variation (CV) and intraclass correlation coefficient (ICC) (1.1), and inter-investigator reliability was assessed using ICC (2.1). RESULTS: Mean CV was 0.015 and 0.016, mean ICC (1.1) was 0.806 and 0.877, and ICC (2.1) was 0.873 and 0.829 in the young and older subjects, respectively. CONCLUSION: In young subjects, the mean values of ICC (1.1) and ICC (2.1) of the oral moisture-checking device were 0.806 and 0.873, respectively, whereas in older subjects, these values were 0.877 and 0.829, respectively. Thus, this confirms that the examination of oral mucosal moisture using the oral moisture-checking device has sufficient intra- and inter-investigator reliabilities for a wide range of age groups.

Retention force and allowable range of the angle of an implant-supported overdenture attachment system using healing screws and a silicone resilient denture liner.

STATEMENT OF PROBLEM: Changes in the intraoral condition immediately after implant placement and in patients using fixed prosthetic appliances with implant abutments cause problems that require the use of an easily adjustable implant-supported overdenture system. PURPOSE: The purpose of this in vitro study was to develop a simulated implant-supported overdenture attachment system by using healing screws for the patrix and a silicone resilient denture liner for the matrix and to investigate the initial retention force, time-course changes, and allowable range of the angle between attachments. MATERIAL AND METHODS: Tests on the retention force and allowable range of the angle were performed. Attachments using tissue-level healing screws (height: 2.0 and 3.0 mm) for the patrix and a silicone resilient denture liner for the matrix were prepared. In the retention force measurement test, the frequency of insertion and removal was set at 3 per day to simulate a 4-month relief period. The joined attachment model was pulled apart, and the maximum traction (N) required to remove it was defined as the retention force. The retention force was measured every 90 times (representing the number of insertions and removals per month). To test the allowable angle range, 2 patrices were used. The angle between the 2 patrices was set at 0, 10, 20, and 30 degrees, and the angular limit for joining with the matrix was measured. The initial retention force of the healing screw attachments was compared with that of a polymeric O-ring by using 1-way layout ANOVA followed by the Bonferroni test (α=.05). To analyze time-course changes in the 2 types of healing screw attachments, the retention force before insertion and removal was compared with that after repeated insertions and removals for each simulated period using 1-way layout ANOVA followed by the Dunnett test (α=.05). RESULTS: The initial retention force of the 2.0- and 3.0-mm healing screws was 2.4 ±0.1 and 2.6 ±0.2 N. After repeating insertions and removals to simulate use for 4 months, the retention force of the 2.0- and 3.0-mm healing screws was 1.8 ±0.2 and 2.2 ±0.1 N, respectively, both showing significant differences from the initial retention force (P<.05). The allowable angle range test revealed that insertion and removal of the healing screws was possible up to 30 degrees. CONCLUSIONS: Under the conditions of this in vitro study, repeated insertion and removal attenuated the retention force but was still equivalent to the retention force of the O-ring. The allowable range of the angle between patrices for insertion and removal was up to 30 degrees.

Rate of oral frailty and oral hypofunction in rural community-dwelling older Japanese individuals.

OBJECTIVE: To clarify the rate of oral frailty and oral hypofunction in rural community-dwelling older adults in Japan. BACKGROUND: Recently, the oral function of Japanese older adults has been evaluated multilaterally based on two concepts: oral frailty and oral hypofunction. Oral frailty is defined as a decrease in the oral function accompanied by a decrease in mental and physical functions. Oral hypofunction is a disease where the oral function is comprehensively decreased. However, their rates have not yet been elucidated. MATERIALS AND METHODS: Oral frailty and oral hypofunction were evaluated in 679 older adults from rural areas. To investigate the differences in occurrence rates due to the evaluation methods, one of the subordinate symptoms of oral hypofunction, the reduced occlusal force, was evaluated based on both the occlusal force (main method) and the number of teeth (alternative method). RESULTS: The rate of oral frailty was 22.3% in men and 22.7% in women. The rate of oral hypofunction was 39.0% in men and 46.9% in women. The overall rate of oral hypofunction was 43.6% when the reduced occlusal force of oral hypofunction was evaluated using the main method and 46.4% when evaluated using the alternative method. The proportion of participants with decreased occlusal force, the number of present teeth, oral diadochokinesis, tongue pressure and masticatory performance increased with age in both men and women. CONCLUSION: Among rural community-dwelling older adults, the rate of oral frailty was 22.5% and that of oral hypofunction was 43.6%.

Validity of a visual scoring method using gummy jelly for evaluating chewing efficiency in a large-scale epidemiological survey.

BACKGROUND: Several methods exist for objectively evaluating chewing efficiency by using gummy jelly. However, the validity of the subjective visual evaluation of chewing efficiency has not been assessed. OBJECTIVE: To verify with an epidemiological study, the validity of a visual scoring method using gummy jelly by testing the relationship between masticatory performance (MP) using a fully automatic measuring system and visual score (VS) using a visual scoring method. METHODS: Community-dwelling elderly individuals (n = 1234) ≥70 years old participated. One evaluator measured VS consecutively after participants chewed the gummy jelly (ie, actual-VS). The chewed jelly was photographed. Two evaluators used the photograph to measure the gummy jelly (ie, photo-VS). To test the validity of both methods, the correlation between actual-VS and MP and between photo-VS and MP were analysed. Inter-rater reliability between the evaluators of photo-VS was analysed. RESULTS: Significant correlations existed between actual-VS and MP and between photo-VS and MP (r = 0.86-0.87; P < 0.001). The intra-class correlation coefficient of the inter-rater reliability for photo-VS was very high (0.93; P < 0.001; 95% confidence interval: 0.877-0.953); however, the distribution of photo-VS deviated slightly from the actual-VS. A large coefficient of variation in the MP for low VSs suggested the influence of incomplete comminution, which was not reflected by the VS, and the accidental swallowing of small pieces during chewing. CONCLUSION: The VS deviated slightly from the MP calculated using a fully automated method; however, the VS can be utilised for epidemiological surveys with numerous participants.

Applying intraoral scanner to residual ridge in edentulous regions: in vitro evaluation of inter-operator validity to confirm trueness.

BACKGROUND: The purpose of this study was to investigate the trueness of intraoral scanning of residual ridge in edentulous regions during in vitro evaluation of inter-operator validity. METHODS: Both edentulous maxillary and partially edentulous mandibular models were selected as a simulation model. As reference data, scanning of two models was performed using a dental laboratory scanner (D900, 3Shape A/S). Five dentists used an intraoral scanner (TRIOS 2, 3Shape A/S) five times to capture intraoral scanner data, and the "zig-zag" scanning technique was used. They did not have experience with using intraoral scanners in clinical treatment. The intraoral scanner data was overlapped with the reference data (Dental System, 3Shape A/S). Regarding differences that occurred between the reference and intraoral scanner data, the vertical maximum distance of the difference and the integral value obtained by integrating the total distance were analyzed. RESULTS: In terms of the maximum distances of the difference on the maxillary model, the means of five operators were as follows: premolar region, 0.30 mm; molar region, 0.18 mm; and midline region, 0.18 mm. The integral values were as follows: premolar region, 4.17 mm2; molar region, 6.82 mm2; and midline region, 4.70 mm2. Significant inter-operator differences were observed with regard to the integral values of the distance in the premolar and midline regions and with regard to the maximum distance in the premolar region, respectively. The maximum distances of the difference in the free end saddles on mandibular model were as follows: right side, 0.05 mm; and left side, 0.08 mm. The areas were as follows: right side, 0.78 mm2; and left side, 1.60 mm2. No significant inter-operator differences were observed in either region. CONCLUSIONS: The present study demonstrated satisfactory trueness of intraoral scanning of the residual ridge in edentulous regions during in vitro evaluation of inter-operator validity.

Morphological Investigation of Residual Ridge in Japanese Edentulous Elderly for Fabrication of Edentulous Stock Tray.

The objective of this study was to determine the size of the residual ridge in edentulous elderly Japanese persons for preparation of edentulous stock trays and clarify any correlations among the items measured. The participants comprised 74 patients requesting construction of a complete denture for the maxilla, mandible, or both. The length, width, and anterior and posterior height of the maxillary and mandibular residual ridge was measured on a prepared working model using a caliper. For each of the maxillary and mandibular edentulous residual ridges, correlations among measurement items were analyzed employing Pearson's correlation coefficient. In participants who were edentulous in both the maxilla and mandible, correlations between the maxillary and mandibular measurement items were analyzed employing Pearson's correlation coefficient. The results revealed that the mean maxillary length of the residual ridge was 55.21±4.07 mm, while mean mandibular length was 56.03±4.04 mm. The mean posterior width of the maxillary jaw was 48.79±4.14 mm, while that of the mandibular jaw was 57.33±3.24 mm. A strong correlation was found between the length and width of the residual ridge in both the maxilla and mandible, but no strong correlation was detected between the height in the anterior tooth region and any other item measured. These findings suggest that the size of any given item can be estimated by measuring either the length or width of the residual ridge when selecting a stock tray. We also propose that it is necessary to prepare stock trays with several different heights in the anterior tooth region, regardless of the length and width of the tray, or to adjust the length of the tray.

Relationship between masticatory function and frailty in community-dwelling Japanese elderly.

BACKGROUND: Frailty likely results in impaired functioning, and frail individuals requiring long-term care have recently attracted the attention of researchers. In the oral health field, the number of elderly individuals who require intervention for retaining occlusion has been increasing, as has the number of remaining teeth and required prosthetic treatment. Additionally, the number of elderly with reduced masticatory function has also been increasing, and frailty is a suspected factor. AIMS: The aim of this study is to clarify the relationship between frailty and masticatory function decline. DESIGN: A cross-sectional study. METHODS: A total of 747 participants (total mean age 73.6 ± 5.8 years old) underwent a comprehensive examination at the Tokyo Metropolitan Institute of Gerontology. Three masticatory functions were evaluated: maximum occlusal force, mixing ability, and self-reported chewing ability. Frailty was determined using all 25 questions of the Basic checklist developed by the Japanese Ministry of Health, Labour and Welfare, following the method reported by Satake et al. RESULTS: Binomial logistic analysis clarified the relationship between frailty and evaluation of each of the three masticatory functions. Significant correlations of pre-frailty or frailty with maximum occlusal force, mixing ability, and subjective chewing ability were observed. CONCLUSION: All three masticatory functions (maximum occlusal force, mixing ability, and self-reported chewing ability) were associated with pre-frailty or frailty in community-dwelling Japanese elderly.

A 2-year longitudinal study of the relationship between masticatory function and progression to frailty or pre-frailty among community-dwelling Japanese aged 65 and older.

BACKGROUND: An association has recently been reported between frailty and reduced masticatory function; however, the causal relationship remains unclear. OBJECTIVE: The aim of this study was to clarify the relationship between masticatory function and frailty progression. METHODS: Among 6699 individuals aged 65 and older (mean age 72.8 ± 5.2 years) who were invited to participate in comprehensive medical check-ups, 418 who underwent examinations at the Tokyo Metropolitan Institute of Gerontology in both 2013 and 2015 and who met inclusion criteria were included in this study. Frailty was determined with the Kihon Checklist developed by the Japanese Ministry of Health, Labour and Welfare. The following three masticatory functions were evaluated: occlusal force, mixing ability and subjective chewing ability. The following confounding factors were investigated: age, sex, grip strength, comfortable walking speed, Mini-Mental State Examination (MMSE) score, Self-Rating Depression Scale (SDS) score, skeletal mass index (SMI), number of medications taken and number of remaining teeth. Statistical analysis was performed with binomial logistic regression analysis. RESULTS: Logistic regression analysis revealed that comfortable walking speed, SDS score, MMSE score and masticatory function were significantly related to progression to frailty or pre-frailty. Of the three masticatory function items evaluated, mixing ability and subjective chewing ability were related to frailty progression. CONCLUSION: Our results confirm that masticatory function was associated with the progression to pre-frailty or frailty among community-dwelling individuals 65 years and older over the 2-year period of this longitudinal study. Of the masticatory function items evaluated, mixing ability and subjective chewing ability were associated with frailty progression.

Influence of the mechanical properties of resilient denture liners on the retention of overdenture attachments.

STATEMENT OF PROBLEM: Information is lacking about the selection criteria for silicone resilient denture liners applied as a matrix material for attachments on overdentures. PURPOSE: The purpose of this in vitro study was to investigate the mechanical properties of silicone resilient denture liners and their influence on the initial retention force of overdenture attachments and the reduction in retention force over time. MATERIAL AND METHODS: Nine types of silicone resilient denture liner were injected and fixed to the matrix section of an experimental denture base. They were then fitted to an epoxy resin model that simulated the residual ridge with a patrix ball attachment (n=10). The retention force of the denture was measured with a digital force gauge, and the maximum force of traction (N) was regarded as the initial retention force. The retention force reduction (N) after repeated insertion and removal (n=5) was calculated by subtracting the retention force after 3348 cycles (3-year simulated insertion and removal) from the initial retention force. The intaglio of the matrix was observed with a scanning electron microscope (SEM) before and after the 3348 cycles. Four mechanical properties (hardness, strain-in-compression, tensile strength, and arithmetic mean roughness) of the resilient denture liners were measured. One-way ANOVA of the initial retention force of each lining material was performed, followed by the Scheffe test (α=.05). Pearson correlation analysis was used (α=.05) to analyze correlations of the initial retention force with the retention force reduction after insertion and removal and the mechanical properties of each material. Multiple regression analysis with the stepwise method extracted the initial retention force and the retention force reduction as dependent variables, and the resilient denture liner mechanical properties as explanatory variables (α=.05). RESULTS: The initial retention force of the resilient denture liners was 1.3 to 5.4 N. Multiple comparisons showed significant differences in some groups (P<.05). The retention force reduction of the resilient denture liners was 0.2 to 1.9 N. Multiple regression analysis with the stepwise method extracted hardness and strain-in-compression as explanatory variables for the initial retention force and the retention force reduction. CONCLUSIONS: Within the limitations of this in vitro study, hardness was found to influence the initial retention force of the overdenture, and strain-in-compression influenced the retention force reduction in the 3-year simulation.

Maxillofacial prosthetic treatment factors affecting oral health-related quality of life after surgery for patients with oral cancer.

STATEMENT OF PROBLEM: After oral cancer surgery, tissue defects can cause deformity and limited mobility, complicating many essential functions. For patients with mandibular, tongue, and oral floor defects, evidence regarding the effects of maxillofacial prosthetics on their oral health-related quality of life (OHRQoL) is lacking. Therefore, maxillofacial prosthetic reconstruction has been implemented with no clear treatment goals. PURPOSE: The purpose of this clinical study was to identify factors affecting the improvement of OHRQoL by using maxillofacial prosthetic treatment after surgery to repair maxillary, mandibular, tongue, and oral floor defects. MATERIAL AND METHODS: All individuals who agreed to maxillofacial prosthetics after surgery for oral cancer were enrolled. Oral function and OHRQoL were evaluated before maxillofacial prosthesis placement and 1 month after final adjustments. The oral functions evaluated included masticatory function, swallowing function, and articulatory function. The Oral Health Impact Profile (OHIP-J54) was used to evaluate OHRQoL. Factors affecting changes in the OHIP-J54 score for participants' background and oral functions before and after treatment were analyzed through logistic regression analysis (stepwise method). RESULTS: Participants included 34 men and 16 women with an average age of 72.4 ±8.7 years. "Psychological discomfort" was correlated with the patient's sex and masticatory function. "Physical disability" was related to articulatory function. "Handicap" was related to the swallowing function. "Additional Japanese questions" were related to the patient's sex. CONCLUSIONS: Participants' sex and their oral functions, including masticatory, swallowing, and articulatory functions, were associated with improved OHRQoL because of maxillofacial prosthetics after surgery for oral cancer.

Oral hypofunction in the older population: Position paper of the Japanese Society of Gerodontology in 2016.

BACKGROUND: There is growing international interest in identifying the effects of ageing on oral health and on appropriate strategies for managing oral disorders. The Japanese Society of Gerodontology (JSG), as the official representative of researchers and clinicians interested in geriatric dentistry in Japan, makes several recommendations on the concept of "oral hypofunction." AIMS: This study proposes diagnostic criteria and management strategies to reduce the risk of oral hypofunction among older people. CONCEPTUAL FRAMEWORK: We define oral hypofunction as a presentation of 7 oral signs or symptoms: oral uncleanness; oral dryness; decline in occlusal force; decline in motor function of tongue and lips; decline in tongue pressure; decline in chewing function; and decline in swallowing function. The criteria of each symptom were determined based on the data of previous studies, and oral hypofunction was diagnosed if the criteria for 3 or more signs or symptoms were met. CONCLUSIONS: We recommend that more evidence should be gathered from clinical studies and trials to clarify our diagnostic criteria and management strategies.

Evaluation of Factors Associated with Tongue Coating Status in Elderly with Care Needs.

The tongue surface in older people requiring nursing care is often coated with a layer believed to comprise, keratinized products of degeneration, food residue, bacteria, and leukocytes attached to the tongue papillae. Which factors affect the status of this tongue coating remain to be elucidated, however. The purpose of this study was to evaluate factors related to tongue coating status in older people requiring nursing care. The study participants comprised 41 individuals admitted to special nursing homes for the elderly. After undergoing tooth brushing and tongue cleaning by the facility staff, the participants were required to refrain from oral cleaning until evaluation of tongue coating status, which was performed just after lunch. The moisture level of the tongue surface was measured and total number of oral microbes determined. Food type, care level, and sex were determined by a questionnaire given by the attending nurses. Correlations between the tongue coating status and various factors were analyzed using Spearman's rank correlation coefficient. The participants were divided into 2 groups according to the median value of the tongue coating status. Factors related to tongue coating were analyzed using binomial logistic regression analysis (α=0.05). Tongue coating status showed a significant correlation with the total number of oral microbes on the tongue surface (rS=0.449, p=0.003), type of food (rS=0.388, p=0.012), and care level (rS=-0.308, p=0.050). Logistic regression analysis revealed that the food type of the side dish significantly affected tongue coating status. These results showed a correlation between tongue coating status and type of food of the side dish in older people requiring nursing care.

Inhibition of denture plaque by TiO2 coating on denture base resins in the mouth.

STATEMENT OF PROBLEM: Information is lacking about antiadhesion effect of titanium dioxide (TiO2) coating on denture base resins in the mouth. PURPOSE: The purpose of this clinical study was to investigate the antiadhesion effect of TiO2 coating on denture base resins. MATERIAL AND METHODS: Ten healthy dentate participants (mean 27 ±2 years of age) participated in this study. Disks and palatal appliances were made with denture base resin. They were divided into 2 groups: a TiO2-coated group and an uncoated group. A primer and a top coat containing TiO2 were applied to the surfaces of the resin by means of an air spray. In the denture plaque staining test, resin disks were fixed to the retainer, placed in each participant's mouth for 3 days, and stained with a dental plaque-disclosing solution. The staining rate was calculated. The resin disks and palatal appliances were used to measure the total number of microbes. The resin specimens were placed in each participant's mouth for either 3 or 7 days and swabbed to count the total number of microbes. The chewing gum adherence test was performed both subjectively and objectively. Subjectively, each participant wearing a palatal appliance rated adherence using a visual analog scale. The objective test was performed with a chewing gum adhesion test. The staining rate, the total number of microbes, and the visual analog scale values were statistically analyzed using the Wilcoxon signed rank test, and the adhesive force was statistically analyzed using a Student t test. RESULTS: In the denture plaque staining test, the measurement of microbes, and the resin chewing gum adherence test results, significant differences were observed between the TiO2-coated groups and the uncoated groups. CONCLUSIONS: TiO2 coating of the denture base acrylic resin inhibited the adhesion of microbes, denture plaque, and highly adhesive food.

Time-dependent effects of tongue cleaning with mouthwash or mouth moisturising gel on the number of microbes on the tongue surface of elders with care needs.

OBJECTIVE: The purpose of this study was to investigate time-dependent change in the number of microbes on the tongue surface after tongue cleaning using a mouthwash or mouth moisturising gel for elders fed with a feeding tube and with care needs. MATERIALS AND METHODS: Twelve elders fed through a feeding tube and with care needs participated in this prospective crossover study. There were four kinds of tongue cleaning modes as follows: (i) tongue cleaning with a mouthwash; (ii) tongue cleaning with a mouth moisturising gel; (iii) tongue cleaning with water; (iv) no tongue cleaning as a negative control. The total number of microbes on the tongue surface was measured using a rapid oral bacteria detection device at baseline, immediately after cleaning, and at 1, 3 and 5 hours after cleaning to evaluate the time-dependent change for each tongue cleaning mode. RESULTS: There were no significant differences regarding microbial count on every measurement in negative control and tongue cleaning with water. There were significant decreases immediately after cleaning, and at 1, 3 and 5 hours after cleaning compared to baseline when the tongue was cleaned with a mouthwash. There was a significant decrease between baseline and immediately after cleaning when the tongue was cleaned with a mouth moisturising gel. CONCLUSION: Tongue cleaning with mouth moisturising gel decreased the number of microbes on the tongue surface immediately after cleaning, and tongue cleaning with mouthwash decreased it for 5 hours.

Biocompatibility of a titanium dioxide-coating method for denture base acrylic resin.

OBJECTIVES: Ease of denture cleaning is of paramount importance in geriatric patients and those with limited dexterity. We have previously investigated methods of coating dentures with titanium dioxide (TiO2 ) and reported the effects (self-cleaning and antibacterial) of such treatments in in vitro studies. This study was to verify the biocompatibility of a TiO2 -coated acrylic resin produced by the new coating method with spray-coating technique. METHODS: Specimens were prepared from denture base acrylic resin and polished up to grit #1000. The TiO2 -coating agent was sprayed onto the specimens using an airbrush gun. Specimens were then divided into 'polymethyl methacrylate (PMMA)', 'primer-coated PMMA' and 'TiO2 -coated PMMA' groups to be evaluated for biological safety using a hamster oral mucosa irritation test, a guinea pig skin sensitisation test and a rabbit intracutaneous test. The biological reaction was scored. RESULTS: Reaction scores were considerably <1.0, the acceptable limit set by the ISO, in all three tests. Indeed, in most samples, there was no deleterious effect at all. CONCLUSION: These results tested on animals demonstrate that denture base resin coated with TiO2 by this method does not cause irritation or sensitisation of the oral mucosa, skin or intracutaneous tissue and is therefore good biocompatibility for use in close proximity to oral mucosa and skin.

Comparison of Adhesive Resistance to Chewing Gum among Denture Base Acrylic Resin, Cobalt-Chromium Alloy, and Zirconia.

The purpose of this study was to compare the adhesiveness of chewing gum to acrylic resin, cobalt-chromium alloy, and zirconia. Test specimens were fabricated using acrylic resin (resin), cobalt-chromium alloy (Co-Cr), and Ceria stabilized tetragonal zirconia polycrystal-based nanostructured zirconia/alumina composite (zirconia). Specimens of each material were attached to the upper and lower terminals of a digital force gauge. The operator masticated chewing gum, wiped off any saliva, and placed the gum on the lower specimen. The gum was compressed to a thickness of 1 mm between the upper and lower specimens. Thereafter, traction was applied to the upper specimen at a cross-head speed of 100 mm/min under 3 different conditions (dry, wet with distilled water, and wet with artificial saliva) to determine the maximum adhesive strength of the chewing gum. The statistical analysis was performed using the Bonferroni test after a one-way analysis of variance (α=0.05). Under dry conditions, adhesive force was 14.8±6.8 N for resin, 14.0±4.8 N for Co-Cr, and 4.3±2.3 N for zirconia. Significant differences were noted between resin and zirconia, and between Co-Cr and zirconia. When distilled water was applied to the specimen surface, the adhesive strength was 16.8±1.7 N for resin, 8.3±2.1 N for Co-Cr, and 2.7±0.8 N for zirconia. Significant differences were noted between resin and Co-Cr, resin and zirconia, and Co-Cr and zirconia. When artificial saliva was applied to the specimen surface, the adhesive force was 18.5±2.8 N for resin, 5.3±0.8 N for Co-Cr, and 3.0±1.7 N for zirconia. Significant differences were noted between resin and Co-Cr, and resin and zirconia. Chewing gum adhered less strongly to zirconia than to acrylic resin or cobalt-chromium alloy.

Influence of early clinical exposure for undergraduate students on self-perception of different aspects of geriatric dental care: Pilot study between two colleges from Japan and India.

OBJECTIVE: The objective of this study is to identify the influence of early clinical exposure for undergraduate students on self-perception of different aspects of geriatric dental care. MATERIALS AND METHODS: We have selected two different colleges from Japan and India, namely, Tokyo Dental College (TDC), Tokyo, and Government Dental College (GDC), Nagpur, respectively. The GDC students exposed to patients in a 3(rd) year and TDC in the 5(th) year of course. Survey of 74 undergraduate students GDC and 95 of TDC was conducted. The questionnaire was developed based on to the 50 points undergraduate curriculum by European College of Gerodontology. The questionnaire categorized into four parts; Part I (15 questions) on aging and medicine, Part II (15 questions) on communication skills, Part III (15 questions) on diagnosis/treatment, and Part IV (5 questions) on need of more training in Gerodontology. Their own-perception on self-knowledge and competency was scored on 4 level scale as 3, 2, 1, and 0 for response yes, rather yes, rather no, and no, respectively. Average scores were calculated and presented. RESULTS: The differences of the opinions as per students' perception level were found to be slightly more affirmative in GDC students (1.9 for the 4(th) year and 2 for the 5(th) year) than TDC students (1.1 for 5(th) grade and 1.5 for 6(th) grade). Both clinical and didactic hours should be increased in curriculum according to the TDC (89%) and GDC (79%) students. Separate gerodontology subject is suggested from TDC (76%) to GDC (81%) students. CONCLUSION: Average scores about own-perception of knowledge and competency about aging, medicine, and communication skills were almost same in both GDC and TDC students. With early clinical exposure, GDC students appear have better self-perception regarding the different aspects of the geriatric dental care including subject knowledge, communications, diagnosis, and treatment planning than TDC students with late clinical exposure.