Effect of denture adhesives on masticatory performance: Multicenter randomized controlled trial.

PURPOSE: The purpose of this study is to investigate the effects of denture adhesives on masticatory performance via a 10-center, parallel, randomized, controlled trial of complete denture wearers in Japan. METHODS: The trial was conducted between September 2013 and October 2016. The inclusion criteria were complete edentulism, willingness to undergo new complete denture treatment, and willingness to return for recall treatment. The exclusion criteria were age 90 years or older, presence of severe systemic illness, inability to understand the questionnaires, wearing metal base complete dentures, denture adhesive user, wearing prosthetics for maxillofacial defects, wearing complete dentures with tissue conditioners, and severe xerostomia. Randomization of the powder-type denture adhesive (powder), cream-type denture adhesive (cream), and control (saline) groups was performed using a sealed envelope system. Masticatory performance was measured using color-changeable chewing gum. Intervention blinding was not feasible. RESULTS: Sixty-seven control, 69 powder, and 64 cream participants are analyzed using the intention-to-treat principle. The participants in all groups show significantly improved masticatory performance at post-intervention (paired t-test with Bonferroni correction P < 0.0001). However, no significant difference in masticatory performance is detected among the three groups (one-way analysis of variance). A significant negative correlation between pre- and post-changes in masticatory performance and intraoral condition scores is observed (Pearson's correlation coefficient, P < 0.0001). CONCLUSIONS: Although denture adhesives improved the masticatory performance of complete denture wearers, their clinical effects are comparable to those of saline solution. The use of denture adhesives is more effective in complete denture wearers with unsatisfactory intraoral conditions.

Short-term efficacy of exercise therapy for temporomandibular disorders: a case control study.

[Purpose] This study compared the short-term outcomes of manual therapy performed by a dentist and home exercises performed by patients as a single exercise therapy program for temporomandibular joint anterior disc displacement without reduction. [Participants and Methods] In this study we included seventeen patients with temporomandibular joint anterior disc displacement without reduction, moderate or greater temporomandibular joint functional impairment, and no treatment interventions. Patients receiving treatment underwent exercise therapy at the time of their first visit, whereas those in the non-treatment group received only an explanation of the condition. We evaluated the clinical symptoms (maximum painless opening distance, pain on motion and mastication, and degree of difficulty in daily life) at the first visit and at the two-week follow-up visit. [Results] For both groups, maximum painless opening distance and degree of difficulty in daily life improved significantly. For the treatment group, the pain on motion and mastication values significantly improved throughout the assessment period. [Conclusion] An exercise therapy program may be useful for the early treatment of temporomandibular joint anterior disc displacement without disc reduction.

Effects of denture adhesives on denture retention and occlusal forces in complete denture wearers: A multicenter, randomized controlled trial.

PURPOSE: This study aimed to determine the effects of denture adhesives on denture retention and occlusal force in complete denture wearers in a multicenter, randomized, parallel-group controlled trial. METHODS: Two hundred edentulous patients wearing complete dentures were allocated to three groups: powder-type denture adhesive, cream-type denture adhesive, and control (saline solution). Denture adhesives and saline solution were applied to the dentures for 4 days. The retentive force of the dentures and occlusal force were measured using a force transducer occlusal force meter at baseline and after 4 days of intervention. In addition to between-group comparisons, subgroup analyses of denture retention and occlusal force were performed based on the level of difficulty of the edentulism treatment. The levels were ranked as I (easy), II, III, and IV (difficult). RESULTS: Cream-type denture adhesives significantly improved the retentive force of the dentures (P<0.01) and occlusal force (P<0.05), with no significant differences between baseline and post-intervention forces in the powder-type denture adhesive and control groups. In within-group comparisons, cream-type denture adhesives improved both the retentive and occlusal forces at Level II (P<0.05), and powder-type denture adhesives improved the occlusal force at Level II (P<0.01). CONCLUSIONS: Application of cream-type denture adhesives effectively improves the denture retention and occlusal force in complete denture wearers with a moderate degree of difficulty during edentulism treatment.

Effects of cleaning sports mouthguards with ethylene-vinyl acetate on oral bacteria.

Background: Sports mouthguards, worn in the oral cavity to prevent sports injuries, are constantly exposed to various microorganisms that cause oral infections. Hence, the optimal cleaning methods for sports mouthguards have been thoroughly examined. In this study, we evaluated the efficiency of cleaning effects with a mouthguard cleaner (MC) on microbial biofilm formation in sports mouthguards in vitro and in vivo. Methods: We evaluated the cleaning effects of the discs produced by ethylene-vinyl acetate (EVA) on bacterial biofilms formed by the commensal bacterium Streptococcus oralis, the cariogenic bacterium Streptococcus mutans, and the opportunistic pathogen Staphylococcus aureus in vitro. EVA discs with biofilm were subjected to sterile distilled water (CTRL) and ultrasonic washing (UW), followed by treatment with MC and sodium hypochlorite (NaClO) as positive controls. Thereafter, the viable bacterial cell counts were determined. The bacteria adhering to the sheets before and after the treatment were observed under an electron microscope. The degree of cleanliness and measurement of viable microbial cell counts for total bacteria, Streptococci and Candida, opportunistic fungi, were evaluated on the used experimental sports mouthguards with and without UW and MC treatment in vivo. Results: The number of bacterial cells significantly decreased against all the tested biofilm bacteria upon treatment with MC, compared with CTRL and UW. Electron microscopy analysis revealed the biofilm formation by all bacteria on the EVA discs before cleaning. We observed fewer bacteria on the EVA discs treated with MC than those treated with CTRL and UW. Furthermore, the degree of cleanliness of the used experimental sports mouthguards cleaned using MC was significantly higher than that of the CTRL-treated mouthguards. Moreover, the viable microbial cell counts on the used experimental sports mouthguard were considerably lower than those on the CTRL ones. Conclusion: The cleaning effect of MC against oral bacteria was more effective than that of UW. MC treatment might have a potential future application as a cleaning method for sports mouthguards to protect athletes from oral infection.

Clinical efficacy of mandibular complete dentures with a resilient liner: study protocol for a multicenter randomized controlled trial.

BACKGROUND: During restoration of poorly fitting complete dentures (CDs) in edentulous patients, liners are used to reconstruct the concave surfaces of CDs with a new base material. These relining materials are classified into resilient liners (RLs) and non-resilient liners (NRLs), but the clinical effects of these liners and their selection criteria remain unclear. The purpose of this study is to evaluate the clinical efficacy of relining mandibular CDs using RL and NRL and to conduct a follow-up study. METHODS: The study is currently being conducted at eight centers, and a parallel-group randomized controlled trial (RCT) is underway. One hundred thirty-two edentulous patients with poorly fitting mandibular CDs will be assigned to two groups based on whether they will receive RL or NRL. Participants will have an RL or NRL applied for relining their CDs using an indirect method of dynamic impressions. Data will be recorded at 1 week and 3, 6, and 12 months after denture delivery. The primary outcome will be assessment of the patients' general satisfaction by using a 100-mm visual analog scale (VAS). Secondary outcomes will be measured as patient-reported outcomes, including food intake status and oral hygiene-related quality of life. Masticatory performance and the number of sore spots on the oral mucosa will also be recorded. Comparisons between the two groups and within-subject comparisons of pre- and post-intervention measurements will be conducted. DISCUSSION: For dentists and prosthetic researchers in Japan, this RCT will provide information on the clinical efficacy of RL materials in comparison to RNL in CD wearers. The new evidence regarding the use of RL materials in an aging population will also be useful to dentists in other countries in their routine clinical practice. TRIAL REGISTRATION: This clinical trial has been registered at the University Hospital Medical Information Network (UMIN) Center (UMIN000041950).

Effectiveness of silicone-based resilient denture liners on the patient-reported chewing ability: A randomized controlled trial.

PURPOSE: This randomized controlled trial (RCT) aimed to elucidate the effectiveness of silicone-based resilient denture liners on perceived chewing ability. METHODS: The RCT included completely edentulous patients on both the maxilla and mandible, who were willing to fabricate a new set of complete dentures. A random permuted block method (block size: 4) was used to assign groups to receive maxilla conventional complete denture and mandibular with either a conventional complete denture (CD) or complete demure relined with silicone-based resilient denture liner (RD). The patient-reported chewing ability of six foods, soybean curd, fish sausage, soybean sprout, cubic rice cracker, hard rice cracker, and dry squid, on a 100-mm visual analog scale was measured and reported at the final adjustment and three months after the final adjustment. Mann-Whitney U test was used to analyze the differences between the CD and RD (p < 0.05). RESULTS: Edentulous patients wearing mandibular complete denture with RD had a higher patient-reported chewing ability than those wearing a CD, but the fish sausage did not in the RD three months after the final adjustment. It also took three months for the patient-reported masticatory ability to improve for cubic rice crackers, hard rice crackers, and dry squid and to show a difference between the RD and CD groups. CONCLUSION: Although limited to some food types, mandibular complete dentures relined with silicone-based liners improved patient-reported chewing ability.

Effectiveness of silicone-based resilient denture liners on masticatory function: A randomised controlled trial.

OBJECTIVES: This randomised controlled trial aimed to compare the masticatory function between the silicone-based resilient denture liner and conventional denture among edentulous patients. METHODS: The trial included edentulous patients who were willing to have a new set of complete dentures. Participants were randomly assigned to receive mandibular complete dentures with either a 1) conventional denture base (CD group) or (2) silicone-based resilient denture liner (RD group). Masticatory performance (evaluated with gummy jelly) and the maximum occlusal force were measured at baseline, on final adjustment, and at 3 months after the final adjustment. The outcomes were analyzed using two-way mixed analysis of variance and a paired t-test. The statistical significance was set at p < 0.05. RESULTS: The masticatory performance was lower in the RD group than in the CD group; it increased significantly over time in the CD group, but not in the RD group. The maximum occlusal force in the RD group was significantly higher than that in the CD group; it increased significantly over time in the RD group, but not in the CD group. CONCLUSIONS: Silicone-based RD liners applied to mandibular complete dentures are effective in improving the maximum occlusal force but not the masticatory performance, as measured with gummy jelly. CLINICAL SIGNIFICANCE: Prior evidence has suggested that mandibular complete dentures with resilient denture liners improve masticatory function. However, the results of this study indicate that difficulties may remain with the mastication of foods with a certain texture (e.g., gummy jelly).

Multivariate analysis reveals oral health-related quality of life of complete denture wearers with denture adhesives: a multicenter randomized controlled trial.

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 effects of silicone-based resilient denture liners on pain: A randomized controlled trial.

PURPOSE: This randomized controlled trial aimed to study the effects of lining mandibular complete dentures with silicone-based resilient denture liners, especially with respect to sensation. METHODS: The trial included completely edentulous patients who were willing to fabricate new set of complete denture. A random permuted block method (block size: 4) was used to assign participants to one of the following groups: mandibular conventional denture (CD) group or mandibular denture with resilient denture liner (RD) group. The outcomes were evaluated using both, objective measures (current perception threshold (CPT) and pain threshold (PT)) for external stimuli measured using the Neurometer CPT® and subjective measures (physical pain and psychological discomfort measured using the Japanese version of Oral Health Impact Profile for Edentulous patients-OHIP-EDENT-J). The outcomes were measured twice, at immediately after completion of denture adjustments (first measurement), and 3 months after the completion of denture adjustments (second measurement). All outcomes were analyzed using the Student t-test. A p-value of <0.05 was considered statistically significant. RESULTS: CPT was significantly higher with RD than CD only at second measurement with frequency level of 2000 Hz and 5 Hz. The pain thresholds were significantly higher in the RD group than the CD group. The physical pain and psychological discomfort scores were significantly lower in the RD group than in the CD group. CONCLUSION: This study concludes that edentulous patients wearing mandibular complete dentures with silicone-based resilient denture liners dull perception mandibular ridge mucosa and felt less pain than those without the liners.

Effect of denture adhesives on oral moisture: A multicenter randomized controlled trial.

PURPOSE: The purpose of this study was to investigate the effect of denture adhesives on oral moisture in a 10-center parallel randomized clinical trial. METHODS: 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. RESULTS: 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 (p<0.05). The masticatory performance and retentive force of the dry mouth denture adhesive using groups were significantly improved after intervention (p<0.05). CONCLUSIONS: 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.

Receptivity of the mandible versus the maxilla to external stimuli in patients with complete dentures.

PURPOSE: This study aimed to investigate whether the mandible is more receptive to external stimuli than the maxilla in patients with complete dentures by comparing regional current perception thresholds (CPTs) and pain threshold (PTs). METHODS: A single operator obtained measurements from maxillae at the incisor foramen and the left side of the greater palatine foramen region and the mandible at the left side of the mental foramen region, using the Neurometer CPT/C device, CPT and PT values from the oral mucosa of 20 edentulous individuals wearing complete dentures were analyzed. Participant characteristics such as mucosal thickness, occlusal force, age, and sex. Mucosal thickness over target regions and occlusal force were measured by the same operator using Krupp SDM and Occlusal Force-Meter GM10s devices. Differences in CPT and PT among the three measurement regions were tested with an analysis of covariance, and post hoc t-tests with the Bonferroni correction. RESULTS: There were no significant differences between the mental foramen, incisor papilla, and greater palatine regions CPT values. PTs obtained at all current frequencies (2000Hz, 250Hz, and 5Hz) were lowest in the mental foramen region and highest in the greater palatine region. Covariates including sex, mucosal thickness, and occlusal force had no significant influence on CPT or PT values at all frequencies. CONCLUSIONS: The mandible exhibits higher receptivity to external pain stimuli than the maxilla.

Verification of the reliability of current perception threshold and pain threshold testing by application of an electrical current stimulus to mandibular mucosa in young adults.

BACKGROUND: There is little evidence regarding the reliability of CPT and PT measurements to gauge mandibular perception. Thus, this study aimed to evaluate the test-retest reliability of CPT and PT values obtained from the mandibular oral mucosa and to test the bilateral differences in CPT and PT values obtained from the mental foramen region and buccal shelf region by a single operator. METHODS: CPT and PT values were obtained from the mental foramen and buccal shelf regions of 20 volunteers (10 males and 10 females; average age: 26.4 ± 2.6 years) by using the Neurometer CPT/C® device to deliver electrical stimulation. RESULTS: Relative and absolute reliabilities were confirmed over two measurements of CPT and PT over a 7- to 10-day measurement interval. Intra-class correlation coefficients (ICCs) for CPT and PT table obtained from the mental foramen region were >0.8, while most ICC for the buccal shelf region were <0.8. Standard error of measurement, minimal detectable change and Bland-Altman analyses showed that the CPT and PT measurements had no systematic error and could serve as useful methods. At all frequencies, the bilateral difference in CPT and PT values at the mental foramen and buccal shelf region was not significant. CONCLUSION: CPT and PT measurements using a custom-made device that applied an electrical current to the mental foramen region have appropriate reliability to assess intra-oral sensitivity to electrical stimulation in young adults.

Measurement reliability of current perception threshold and pain threshold in parallel with blood sampling.

The irritation and pain associated with oral blood sampling necessary to monitor glycemic control can alter oral sensation, but no studies have measured the reliability of oral sensation testing when performed concurrently with blood sampling. The primary and secondary aims of this study were to verify the measurement reliability of current perception threshold (CPT) and pain threshold (PT) tests performed before and after blood sampling and to investigate the differences in CPTs/PTs obtained from the oral cavity, hand, and foot, respectively. CPT/PT measurements were obtained from the oral mucosa and the tips of fingers and toes of 18 volunteers (10 males and 8 females, average age = 26.3 years) using electrical stimulation at frequencies of 5, 250, and 2,000 Hz. Participants also provided blood samples by pricking their own index fingers with a small needle. All subjects completed the following 3 conditions at once-weekly intervals as follows: (a) sensory measurements followed by blood sampling (SB block); (b) blood sampling followed by sensory measurements (BS block); (c) sensory measurements without blood sampling (CO control block). Cronbach's α coefficients were over 0.78 for the SB, BS, and CO blocks, and are considered to be acceptable for assuring measurement reliability. The oral cavity had significantly lower CPT/PTs than both hands and feet, such that the threshold increased in the order oral cavity < hand < foot. CPT and PT measurements performed concurrently with blood sampling are both reliable and region specific, and for which the oral cavity is the most sensitive testing region.

A double blind randomized clinical trial comparing lingualized and fully bilateral balanced posterior occlusion for conventional complete dentures.

PURPOSE: A lingualized occlusion (LO) for complete dentures reduces lateral inferences and occlusal force contacts and direction; thus, LO is theorized to be more suitable for patients with compromised ridges than fully bilateral balanced articulation (FBBA). However, no studies have yet provided evidence to support LO in edentate patients with compromised alveolar ridges. The purpose of this study was to compare LO and FBBA in edentulous individuals with compromised ridges. METHODS: Sixty edentulous individuals were randomly allocated into groups and received dentures with either LO or FBBA. Following delivery, several denture-related satisfaction variables were measured using 100mm visual analogue scales; oral health-related quality of life (OHRQoL) was also assessed using the Oral Health Impact Profile (OHIP). Sub-group analyses of the effect of moderate and severe mandibular bone loss were also carried out. RESULTS: No significant differences were detected between LO and FBBA with the primary outcome. At 6 months, participants with severely atrophied mandibles and FBBA rated their satisfaction with retention of mandibular dentures significantly lower than those with LO (median LO: 86, FBBA: 58.5, p=0.03). They also had significantly lower OHRQoL for the domain of Pain (median LO: 4, FBBA: 5, p=0.02). General satisfaction and total OHIP scores significantly improved between baseline and 6 months only for the LO subjects with severely atrophied mandibles (satisfaction: p=0.003, OHIP total score: p=0.0007). CONCLUSIONS: The results indicate that the LO occlusal scheme with hard resin artificial teeth is more efficient for patients with severely resorbed mandibular ridges.

Study protocol for a multi-center, randomized controlled trial to develop Japanese denture adhesive guidelines for patients with complete dentures: the Denture Adhesive Guideline trial: study protocol for a randomized controlled trial.

BACKGROUND: Denture adhesives, characterized as medical products in 1935 by the American Dental Association, have been considered useful adjuncts for improving denture retention and stability. However, many dentists in Japan are hesitant to acknowledge denture adhesives in daily practice because of the stereotype that dentures should be inherently stable, without the aid of adhesives. The aim of this study is to verify the efficacy of denture adhesives to establish guidelines for Japanese users. The null hypothesis is that the application of denture adhesives, including the cream and powder types, or a control (isotonic sodium chloride solution) would not produce different outcomes nor would they differentially improve the set outcomes between baseline and day 4 post-application. METHODS: This ten-center, randomized controlled trial with parallel groups is ongoing. Three hundred edentulous patients with complete dentures will be allocated to three groups (cream-type adhesive, powder-type adhesive, and control groups). The participants will wear their dentures with the denture adhesive for 4 days, including during eight meals (three breakfasts, two lunches, and three dinners). The baseline measurements and final measurements for the denture adhesives will be performed on the first day and after breakfast on the fourth day. The primary outcome is a general satisfaction rating for the denture. The secondary outcomes are denture satisfaction ratings for various denture functions, occlusal bite force, resistance to dislodgement, masticatory performance, perceived chewing ability, and oral health-related quality of life. Between-subjects comparisons among the three groups and within-subjects comparisons of the pre- and post-intervention measurements will be performed. Furthermore, a multiple regression analysis will be performed. The main analyses will be based on the intention-to-treat principle. A sample size of 100 subjects per group, including an assumed dropout rate of 10 %, will be required to achieve 80 % power with a 5 % alpha level. DISCUSSION: This randomized clinical trial will provide information about denture adhesives to complete denture wearers, prosthodontic educators, and dentists in Japan. We believe this new evidence on denture adhesive use from Japan will aid dentists in their daily practice even in other countries. TRIAL REGISTRATION: ClinicalTrials.gov NCT01712802 . Registered on 17 October 2012.

Effect of a dietary supplement on peri-implant bone strength in a rat model of osteoporosis.

PURPOSE: Osteoporosis contributes to impaired bone regeneration and remodeling through an imbalance of osteoblastic and osteoclastic activity, and can delay peri-implant bone formation after dental implant surgery, resulting in a prolonged treatment period. It poses several difficulties for individuals with large edentulous areas, and decreases their quality of life. Consequently, prompt postoperative placement of the final prosthesis is very important clinically. Peri-implant bone formation may be enhanced by systemic approaches, such as the use of osteoporosis supplements, to promote bone metabolism. We aimed to confirm whether intake of synthetic bone mineral (SBM), a supplement developed for osteoporosis, could effectively accelerate peri-implant bone formation in a rat model of osteoporosis. METHODS: Thirty-six 7-week-old ovariectomized female Wistar rats were randomly assigned to receive a standardized diet with or without SBM (Diet with SBM group and Diet without SBM group, respectively; n=18 for both). The rats underwent implant surgery at 9 weeks of age under general anesthesia. The main outcome measures, bone mineral density (BMD) and pull-out strength of the implant from the femur, were compared at 2 and 4 weeks after implantation using the Mann-Whitney U test. RESULTS: Pull-out strength and BMD in the Diet with SBM group were significantly greater than those in the Diet without SBM group at 2 and 4 weeks after implantation. CONCLUSIONS: This study demonstrated that SBM could be effective in accelerating peri-implant bone formation in osteoporosis.

The influence of patient characteristics on acrylic-based resilient denture liners embedded in maxillary complete dentures.

PURPOSE: A major complication associated with the use of resilient denture liners (RDLs) is a change in hardness over time. In vivo studies on the deterioration of RDLs over time are needed. We aimed to investigate the influence of patient characteristics on the hardness of acrylic-based RDLs (ARDLs) embedded in complete maxillary dentures. We hypothesized that 1 month after application of the ARDLs, the hardness would be influenced by age, saliva condition, occlusal force, smoking, drinking, denture wearing during sleeping, denture cleanser usage, and denture type. METHODS: Thirty complete maxillary denture wearers were recruited after obtaining informed consent. One investigator measured the Shore D hardness of the commercially available ARDLs, Soften (SFT), FD Soft (FDS), and Bio Liner (BIO) using a Vesmeter(®). The salivary flow rates and pH values and the occlusal force were measured for all patients before initiation of the study. T-tests and Pearson's correlation coefficients were used for the statistical analyses. A p-value of <0.05 was considered statistically significant. RESULTS: Smoking, wearing dentures while sleeping, use of denture cleansers, and denture type were associated with an increase in the hardness of the RDLs. The resting saliva pH only influenced the hardness of the SFT ARDLs. CONCLUSIONS: Smoking, denture wearing while sleeping, denture cleanser usage, denture type, and resting saliva pH are important predictors of the deterioration of ARDLs over time.

Improved Bone Micro Architecture Healing Time after Implant Surgery in an Ovariectomized Rat.

The present animal study investigated whether oral intake of synthetic bone mineral (SBM) improves peri-implant bone formation and bone micro architecture (BMA). SBM was used as an intervention experimental diet and AIN-93M was used as a control. The SBM was prepared by mixing dicalcium phosphate dihydrate (CaHPO4·2H2O) and magnesium and zinc chlorides (MgCl2 and ZnCl2, respectively), and hydrolyzed in double-distilled water containing dissolved potassium carbonate and sodium fluoride. All rats were randomly allocated into one of two groups: a control group was fed without SBM (n = 18) or an experimental group was fed with SBM (n = 18), at seven weeks old. At 9 weeks old, all rats underwent implant surgery on their femurs under general anesthesia. The implant was inserted into the insertion socket prepared at rats' femur to a depth of 2.5 mm by using a drill at 500 rpm. Nine rats in each group were randomly selected and euthanized at 2 weeks after implantation. The remaining nine rats in each group continued their diets, and were euthanized in the same manner at 4 weeks after implantation. The femur, including the implant, was removed from the body and implant was pulled out by an Instron universal testing machine. After the implant removal, BMA was evaluated by bone surface ratio (BS/BV), bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular number (TbN), trabecular star volume (Vtr), and micro-CT images. BS/BV, BV/TV, TbTh and Vtr were significantly greater in the rats were fed with SBM than those were fed without SBM at 2 and 4 weeks after implantation (P < 0.05). The present results revealed that SBM improves the peri-implant formation and BMA, prominent with trabecular bone structure. The effect of SBM to improve secondary stability of the implant, and shortening the treatment period should be investigated in the future study.

Characteristics of the pain tolerance threshold induced by electrical stimulation of the alveolar ridge.

The purpose of this study was to determine the characteristics of the pain tolerance threshold (PTT) induced by electrical stimulation of the alveolar ridge. A total of 100 healthy volunteers studying or working at Nihon University School of Dentistry at Matsudo and patients from Nihon University School of Dentistry at Matsudo Affiliated Hospital, including 51 men (58.7 ± 17.6 years old) and 49 women (60.7 ± 17.1 years old), participated in this study. The volunteers were enrolled after obtaining written informed consent. PTT measurements were obtained using a Neurometer CPT/C® device to deliver electrical stimulation around the left greater palatine foramen at frequencies of 5 and 250 Hz. When the stimulus could no longer be tolerated, the participant released a button to automatically discontinue the stimulus. After the distribution of the PTT values was analyzed, the influence of gender, age, and Eichner index on PTT was analyzed. The Eichner index values were divided into three categories: group A (four supporting zones), group B (less than four supporting zones but with anterior tooth contact), and group C (no occlusal contact). The PTT values did not show a normal distribution. There were no significant differences in PTT between men and women. PTT was significantly associated with age (P = 0.017) at 5 Hz in men. There were no significant differences in PTT among the Eichner index groups. The characteristics of the PTT of the alveolar ridge are as follows: (1) age and PTT at 5 Hz are significantly associated with men but not with women, and (2) the Eichner index has no influence on the PTT.

Effect of an acrylic resin-based resilient liner applied to mandibular complete dentures on satisfaction ratings among edentulous patients.

PURPOSE: The aim of this study was to investigate whether an acrylic resin-based resilient liner (ARL) could improve the satisfaction ratings of complete denture wearers. The null hypothesis was that no difference exists between the satisfaction ratings of conventional acrylic resin denture (CARD) wearers and those of ARL denture (ARLD) wearers. MATERIALS AND METHODS: From April 2004 to July 2006, a randomized controlled trial was conducted at two centers, including 74 edentulous patients. Of these, 37 patients were each randomly allocated to the ARLD and CARD groups. All of the patients rated their satisfaction with dentures, including general satisfaction and satisfaction with chewing ability, speaking, cleaning, stability, retention, comfort, and esthetics. These satisfaction ratings were measured by a 100-mm visual analog scale. Perceived chewing ability of different foods, divided into five grades, was measured using a questionnaire. The mastication index (MI) was calculated for each grade. RESULTS: General satisfaction, satisfaction with chewing, and satisfaction with speaking were significantly higher in the ARLD than in the CARD group (P = .049, .025, and .049, respectively). The chewing satisfaction with maxillary dentures in the ARLD group was significantly higher than that of the CARD group (P = .02). No significant difference existed between the MI of the ARLD (69.2 ± 17.0) and CARD groups (66.7 ± 18.7). CONCLUSIONS: Within its limitations, this study showed that the ARL improves a complete denture wearer's satisfaction ratings.