Randomized controlled trial investigating the effect of an acrylic-based resilient liner on perceived chewing ability in edentulous patients wearing mandibular complete dentures.

PURPOSE: The aim of this study was to investigate the effect of an acrylic-based resilient liner (ARL) on perceived chewing ability in patients using mandibular complete dentures compared with that of patients using mandibular complete dentures with a conventional acrylic resin (CAR). MATERIALS AND METHODS: This randomized controlled trial was conducted at two centers from April 2004 to July 2006. Seventy-four subjects were randomly allocated to either the ARL or CAR group using a random permuted block method after obtaining written informed consent. A valid questionnaire listing 35 foods was used to evaluate the subjects' perceived chewing ability of each item, assessed according to the following scale: 0=cannot eat, 1=can eat with difficulty, and 2=can eat easily. If subjects did not eat the food because they disliked it or had not eaten it since first wearing dentures, they filled in a triangle or square, respectively. These figures were treated as a 0 during analysis. RESULTS: No significant differences were observed between the ARL and CAR groups. The perceived chewing ability of subjects with new complete dentures was significantly higher than that of those with their old complete dentures. The duration of edentulism was positively associated with perceived chewing ability. CONCLUSIONS: An ARL applied to mandibular complete dentures has no significant impact on the perceived chewing ability of edentulous patients in comparison to a CAR.

The use of existing denture-satisfaction ratings for a diagnostic test to indicate prognosis with newly delivered complete dentures.

PURPOSE: The study investigated the relation between subjective satisfaction ratings of existing dentures and outcomes of newly delivered dentures, and the ability of the diagnostic test, using existing ratings, to indicate prognosis with newly delivered dentures. METHODS: Consecutive 165 edentulous patients were recruited from November 2001 to August 2006 at a university-affiliated hospital. Dentures were fabricated with an acrylic base with full-balanced occlusion using hard resin artificial teeth by multiple prosthodontists. At the baseline and 3-month after delivery, patients rate their overall, maxillary, and mandibular satisfaction for existing and replaced dentures on a 100-mm visual analogue scale (VAS). The association between baseline ratings and newly delivered dentures was analyzed by regression analysis. The test's performance was measured by constructing a two-by-two table; patients with the following cutoff values on the VAS (overall:

Investigation on how renewal of complete dentures impact on dietary and nutrient adequacy in edentulous patients.

PURPOSE: The aim of this study is to investigate changes of diet and nutrient adequacy between complete denture wearers with their existing dentures and those with new dentures. METHODS: After obtained their written informed consent 30 patients who visited Nihon University School of Dentistry at Matsudo Affiliated Hospital from March 2004 to November 2005 were asked to record their 3 consecutive day's meals and to take a picture of them. Furthermore, foods which they can eat with their dentures were examined the questionnaire developed by Hirai. Referring to the obtained records and pictures, one dietitian interviewed to confirm the exact intakes of meals. In addition, the masticatory ability was calculated using the questionnaire. The nutrient adequacy and masticatory score determined at the time of the first and second survey were examined by repeated-measures ANOVA. A p-value less than 0.05 was considered statistically significant. RESULT: The total intake of energy and nutrients was almost over 100% in both the groups. However, no statistically significant difference was obtained. The masticatory score with the existing and new denture were 66.1+/-18.5 and 58.3+/-19.9, respectively. The score increased significantly in the new denture group when compared with that of the existing denture group. CONCLUSION: The self-evaluation of the masticatory function improved after the switch from the old to new dentures.

Effects of resilient denture liner in mandibular complete denture on the satisfaction ratings of patients at the first appointment following denture delivery.

PURPOSE: The purpose of this study was to investigate whether edentulous patients with a permanent acrylic resilient liner denture (RLD) in mandibles exhibit significant improvements in their satisfaction ratings at the first appointment following the delivery of RLD dentures when compared to those with conventional heat-activated acrylic resin dentures (ARD) in mandibles. METHODS: Seventy-four subjects were randomly allocated into RLD and ARD groups by a random permuted block within the strata method after written informed consent. A parallel-randomized controlled clinical trial at two centers was conducted from April 2004 to July 2006. The outcomes were satisfaction ratings with a 100 mm visual analog scale (VAS) involving general satisfaction as well as satisfaction related to chewing, speaking, cleaning, stability, retention, comfort, and esthetics. The pain rating was also measured by the VAS. The outcomes were analyzed by Student t-test and Pearson's correlation coefficient. RESULTS: A significant difference between the RLD and ARD group in the maxillary denture was only obtained in the satisfaction rating of speaking. A significant difference between the RLD and ARD groups for the mandibular dentures was obtained in every satisfaction rating. The pain rating of the RLD group was significantly lower than that of the ARD group. The satisfaction ratings of mandibular denture functions significantly correlated with ratings of comfort and pain. CONCLUSION: Despite the limitation of a short-term observation, the mandibular satisfaction ratings were dramatically higher in RLD wearers than in ARD wearers.

Early tissue response to modified implant surfaces using back scattered imaging.

PURPOSE: It is now well known that implant surface properties affect osseointegration. Grit-blasting with abrasives and coating by plasma are methods to modify implant surfaces. This study aimed to compare the direction of new bone formation associated with three types of surfaces. MATERIALS AND METHODS: Titanium (Ti) alloy rods grit-blasted with alumina abrasive (Group 1, G1), with apatitic abrasive (Group 2, G2), and with apatitic abrasive and plasma-sprayed with hydroxyapatite (Group 3, G3) were implanted in surgically created defects in tibias of New Zealand white rabbits for 2 and 4 weeks. After sacrifice, the implants and surrounding bones were obtained and analyzed using back scattered imaging. RESULTS: Differences in patterns of bone formation among the groups were observed: originating from the cortical bone towards the implant surface (Type A), surrounding the implant (Type B) and originating from the medullary cavity (Type C). G1 and G3 showed Types A and B while G2 exhibited Types A, B and C. After 4 weeks, greater amount of new bone was observed in G2 group compared with those in G1 and G3 groups. CONCLUSIONS: This study demonstrated that patterns of bone formation are influenced by methods of surface modification.

[Comparative analysis of learning effect for students who experienced both lecture-based learning and problem-based learning in a complete denture course].

PURPOSE: The purpose of this study was to analyze the difference in educational effect on students who experienced both lecture-based learning (LBL) and problem-based learning (PBL) in a complete denture course. The analysis focused on differences between the two methods concerning self study, ability to understand clinical inference, and appraisal of class contents and tutors. METHODS: In the complete denture preclinical course, the class of 2003 received LBL in 3rd grade and PBL in 4th grade. PBL was planned to present five cases in five consecutive classes. Group discussion was carried out for each case, and a summary was required to be produced two times as a group, two times as an individual report and one time by group presentation. A questionnaire regarding the educational effect of LBL and PBL and assessment of tutors was administered. Factor analysis was carried out to classify the questionnaire items and each item was analyzed between LBL and PBL (Paired-t test). RESULTS: Factor analysis revealed that the questionnaire items could be classified into four components. Comparing lecture type and PBL: "study attitude" (4 out of 7 items), "clinical inference ability" (all items), "class contents" (5 out of 7 items) and "tutor appraisal" (2 out of 5 items) showed significant assessment with PBL. Eighteen of 27 items (66.6%) indicated the significant usefulness of PBL. CONCLUSION: PBL improves the educational effect of self study and clinical inference ability, in comparison with LBL. However, since students are passive about taking the same system class repeatedly, a strategy to improve their attitude needs to be considered.

Perception thresholds for electrical stimulation of the palatal mucosa.

PURPOSE: To define the normative ranges of the Current Perception Threshold (CPT) of the palatal mucosa and to correlate it with the subjects' attributes. MATERIALS AND METHODS: A group of 129 informed healthy subjects consented to participate in the study. A Neurometer NS3000 device was used to evaluate the CPTs of the nasopalatine nerve (NPN) and the greater palatine nerve (GPN) by using 2000-, 250-, and 5-Hz stimulations. After confirming the relationships with regard to gender, age, weight, height, alcohol consumption, duration of sleep, weight percentage of water content, smoking, and CPT, the normative ranges of the CPT measurements were obtained. RESULTS: Correlations were observed between age and CPTs obtained with the 2000- and 250-Hz stimulations of the GPN. The CPTs of the GPN were higher than those of the NPN. With the exception of the 5-Hz stimulation of the NPN, the CPTs in men were higher than those in women; however, the within- and between-site ratios exhibited no differences between the male and female subjects. No significant effects of smoking and alcohol consumption on CPT were observed. Range analysis revealed an increase in the CPTs as the frequency increased from 5 to 250 to 2,000 Hz. Within-site ratio analysis revealed increasing and spreading CPT ratios in the following order: 250/5 Hz, 2000/250 Hz, and 2,000/5 Hz. In the order of 5-, 250-, and 2000-Hz stimulations, decreasing ratios were observed for the between-site ratio analysis. CONCLUSION: This study provides useful diagnostic criteria for CPTs in the palatal mucosa.

Randomized controlled clinical trial for verifying the effect of silicone-based resilient denture liner on the masticatory function of complete denture wearers.

PURPOSE: The purpose of this study was to investigate whether application of permanent silicone-based resilient denture liner (SR) to mandibular complete dentures significantly improves patients' masticatory ability compared to conventional heat-activated acrylic resin (AR). MATERIALS AND METHODS: Twenty-eight edentulous patients were randomly placed into 1 of 2 crossover groups (AR-SR/SR-AR) by using a random permuted block within strata method. The AR-SR group received AR denture treatments followed by SR denture treatments. The SR-AR group received treatments in the reverse sequence. The outcomes were classified by matiscatory performance, mandibular movement, electromyographic activity, and maximum occlusal force. RESULTS: No significant differences were observed in any of the baseline characteristic measurements between groups. SR denture wearers exhibited significantly higher masticatory performance than AR denture wearers. SR denture wearers exhibited a longer early-stage occluding period than AR denture wearers. There were no differences in electromyographic activity between the AR and SR groups. There were no significant differences in maximum occlusal force between the AR and SR groups. CONCLUSION: This study showed that the application of SR to mandibular complete dentures resulted in significant improvements to the patients' masticatory ability compared to AR.

[Reliability of the measurement of current perception thresholds in the palatal mucosa].

PURPOSE: The purpose of this study was to investigate the possibility of applying measurement of the Current Perception Threshold (CPT) to the oral mucosa. METHODS: Forty healthy volunteers (20 males and 20 females; mean age, 29.5 +/- 5.1 years) were recruited for the study. CPT measurements were performed over the nasopalatine nerve area and greater palatine nerve area with 5,250 and 2000 Hz electrical stimulation using the Neurometer NS3000. The CPTs were measured on three separate days, and each measurement was carried out once a day by a single operator. RESULTS: Each of the electrical stimulations of 5,250 and 2000 Hz had a specific CPT. There were no significant differences in the CPT values measured over the three days. The CPTs were lower in the females than in the males. There were no significant differences in the CPTs in the greater palatine nerve area between the right and the left side. No order effect was observed on the CPTs in the greater palatine nerve area of either side in the first and second measurements. The intraclass correlation coefficient of the CPT measurements was as high as 0.80. CONCLUSION: It was concluded based on the high reliability of the measurements obtained, that CPT measurement can be applied to the oral mucosa.

Prospective clinical trial comparing lingualized occlusion to bilateral balanced occlusion in complete dentures: a pilot study.

PURPOSE: The aim of this prospective comparative trial was to evaluate whether patients treated with complete dentures with lingualized occlusion (LO) exhibited more positive results than patients treated with complete dentures with bilaterally balanced occlusion (BBO). MATERIALS AND METHODS: Twenty-eight completely edentulous patients, ranging in age from 60 to 82 years (mean age 70.9), consented in writing to be participants in this trial. The first 14 patients enrolled in the study protocol were treated with complete dentures with LO, and the next 14 patients were treated with complete dentures with BBO. Baseline characteristics were measured prior to the trial. Main outcome variables involved subjective outcomes of general satisfaction, ability to masticate, and stability and retention of the prostheses; these were quantified with a 100-mm visual analog scale. Objective outcomes were masticatory performance and the number of adjustments. Statistical assessments of the 2 groups were compared using multiple linear regression analysis. The baseline characteristics were analyzed by Student t test and chi-square test. RESULTS: There were no significant differences between the groups at baseline. The height of the alveolar ridge exhibited significant correlations with masticatory performance (P = .02). The occlusal scheme exhibited a significant correlation with only the patient's retention satisfaction rating (P = .03). CONCLUSION: Despite limitations of this study attributed to the small sample size and lack of randomization, this pilot study found that edentulous patients fitted with complete dentures with LO experienced and expressed greater satisfaction with their denture retention. In addition, it was observed that a higher alveolar ridge resulted in greater masticatory performance.

[Behavioral study of denture acceptance. Part 1 qualitative investigation of linguistic data and validity of coding process].

PURPOSE: The purpose of this study was to extract questionnaire items based on qualitative data from edentulous patients obtained by individual interview. METHODS: Forty-three patients (20 complete denture, 20 partial denture and three non-denture wearers) who had visited the dental hospital affiliated to Nihon University School of Dentistry at Matsudo voluntarily agreed to be interviewed about their denture use with ten questions structured by Triandis theory in an open-rended manner. Responses to interview were recorded by voice recorder and qualitatively analyzed into linguistic and coded items, i.e. fragmentation and editing of recorded data followed by linguistic coding. The coded items were then classified into one of the 4 domains of Triandis theory: intentions of their denture acceptance (I), social factor (SF), affect (A) and perceived consequences (PC). RESULTS: The analysis of qualitative data, description, fragmentation and editing, accumulated 722 linguistic items. These were summarized into 72 codes, and classified into twelve I, nine SF, nine A and 42 PC. CONCLUSIONS: The 72 coded items, which summarized the edentulous qualitative data including the 4 domains of Traindis theory, are considered useful as questionnaire items of behavioral investigation. Further large-scale studies using this questionnaire will be needed to clarify the reasons for denture acceptance.

Pain patterns and mandibular dysfunction following experimental trapezius muscle pain.

AIMS: To clarify the effects of experimental trapezius muscle pain on the spread of pain and on jaw motor function. METHODS: In 12 male subjects aged 25 to 35 years, experimental pain was induced in the superior border of the trapezius muscle by injecting 0.5 mL of hypertonic (6%) saline. The control infusion consisted of a 0.5-mL isotonic (0.9%) saline solution. Pain intensity was evaluated on a visual analog scale (VAS). An experimental (EX) and a control (CT) injection were administered to the subjects in a randomized sequence. RESULTS: Pain intensity as scored on the VAS increased immediately after the EX injection and decreased gradually after reaching a peak of 68.0 +/- 16.1 mm at 60 seconds after injection. The VAS scores in the EX condition were significantly higher than after the CT condition from 30 to 330 seconds after injection (P < .05, analysis of variance [ANOVA]). Mean (+/- SD) maximal unassisted mouth opening before injection in the EX condition was 54 +/- 5.7 mm and decreased immediately after the injection, reaching a low of 47.8 +/- 5.1 mm. A gradual recovery to normal was then observed. This reduction of mouth opening in the EX condition was significant compared with the CT condition from immediately after the injection to 60 seconds after the injection (P < .05, ANOVA). According to the subjects, pain spread most often to the infra-auricular zone (n = 6), and the posterolateral part of the neck (n = 10). CONCLUSION: The present results suggest that experimental trapezius muscle pain can spread over a wide area and is also accompanied by a temporary reduction of mouth opening.

Effect of bench cooling on the dimensional accuracy of heat-cured acrylic denture base material.

OBJECTIVES: In order to obtain an insight on the internal stress caused by both polymerization and thermal shrinkage during the fabrication process of heat-cured denture resin, the effect of bench cooling on the dimensional accuracy of a heat-cured denture base resin was examined. METHODS: A dimensional change of a dumbbell-shaped specimen during the fabrication process was measured directly by using the strain gauge method. After polymerization, the specimens were treated in one of the following two processing methods: (1) rapid cooling: the specimen was removed from a stone mold within a container of boiling water at 100 degrees C and then left to cool in a thermo-stabilized room of 20+/-1 degrees C; (2) bench cooling: the flask was left to cool in a thermo-stabilized room of 20+/-1 degrees C for 140min, after which, the specimen was removed from the stone mold. The strain from deflasking was derived from the difference in the strain, before and after the removal of the specimen from the stone mold. The strain differential, before and after cooling, was determined as the total strain. RESULTS: The bench cooling for the heat-cured denture base resin reduced the strain caused by thermal shrinkage during the fabrication process. The observed reduction in the strain was 26% for the C(L) (direction of center's length), 11% for the E(L) (direction of left-edge's length), and 12% for the E(W) (direction of left-edge's width), when compared with the results obtained from the rapid-cooling method. CONCLUSIONS: The flask should be slowly cooled to room temperature, since the internal stress developed by thermal shrinkage will be relaxed during the cooling process.

Comparison of metal concentrations in rat tibia tissues with various metallic implants.

To compare metal concentrations in tibia tissues with various metallic implants, SUS316L stainless steel, Co-Cr-Mo casting alloy, and Ti-6Al-4V and V-free Ti-15Zr-4Nb-4Ta alloys were implanted into the rat tibia for up to 48 weeks. After the implant was removed from the tibia by decalcification, the tibia tissues near the implant were lyophilized. Then the concentrations of metals in the tibia tissues by microwave acid digestion were determined by inductively coupled plasma-mass spectrometry. Fe concentrations were determined by graphite-furnace atomic absorption spectrometry. The Fe concentration in the tibia tissues with the SUS316L implant was relatively high, and it rapidly increased up to 12 weeks and then decreased thereafter. On the other hand, the Co concentration in the tibia tissues with the Co-Cr-Mo implant was lower, and it increased up to 24 weeks and slightly decreased at 48 weeks. The Ni concentration in the tibia tissues with the SUS316L implant increased up to 6 weeks and then gradually decreased thereafter. The Cr concentration tended to be higher than the Co concentration. This Cr concentration linearly increased up to 12 weeks and then decreased toward 48 weeks in the tibia tissues with the SUS316L or Co-Cr-Mo implant. Minute quantities of Ti, Al and V in the tibia tissues with the Ti-6Al-4V implant were found. The Ti concentration in the tibia tissues with the Ti-15Zr-4Nb-4Ta implant was lower than that in the tibia tissues with the Ti-6Al-4V implant. The Zr, Nb and Ta concentrations were also very low. The Ti-15Zr-4Nb-4Ta alloy with its low metal release in vivo is considered advantageous for long-term implants.

Effects of relief space and escape holes on pressure characteristics of maxillary edentulous impressions.

STATEMENT OF PROBLEM: The selective pressure technique has been recommended for making impressions of maxillary edentulous residual ridges. Although various methods for making impressions have been reported, a definitive procedure has not been clearly elucidated. PURPOSE: This in vitro study evaluated changes in impression pressure produced by different types of relief space and escape holes in the impression tray for making an impression of a simulated maxillary edentulous arch. MATERIAL AND METHODS: Silicone impression material (Exadenture) and a maxillary edentulous acrylic cast were used. A miniature pressure sensor was embedded at the mid-palatal suture (point-P) and at the left first molar area on the edentulous ridge (point-R). Three types of tray relief were used: no spacer (NS), a 0.36-mm-thick sheet of wax (SS), or a 1.40-mm-thick base plate wax (BS). Four types of escape holes were made: no hole (NH), or escape holes of 0.5, 1.0, or 2.0 mm in diameter (05H, 10H, and 20H, respectively) in the area opposing point-P. Twelve trays were formed using these relief space and escape hole combinations. The cast and tray were attached to a rheometer for applying a continuous isotonic force of 5.0 kgf and compressive speed of 120 mm/min. Impressions were made and measurement of pressure (kPa) began immediately prior to compression and continued until the materials had polymerized for 2 minutes, with a sampling time of 5 Hz. Measurements were performed 5 times for each tray. The data were analyzed using 3-way analysis of variance and the Bonferroni test (alpha=.05). RESULTS: At initial pressure, the data obtained at point-P showed significantly higher values for NSNH, NS05H, SSNH, and SS05H (range: 22.29 +/- 1.58 kPa to 29.96 +/- 1.41 kPa) than those at point-R (range: 18.61 +/- 1.12 kPa to 22.71 +/- 2.11 kPa). At end pressure, the data obtained from NSNH at point P showed a significantly higher value (25.36 +/- 1.69 kPa) than that of point-R (15.36 +/- 0.99 kPa) (P<.001), whereas data from NS10H and NS20H at point-P showed a significantly lower value (6.32 +/- 0.84 kPa and 4.50 +/- 0.42 kPa) than at point-R (15.50 +/- 0.49 kPa and 14.98 +/- 0.88 kPa) (P<.001). The data obtained from SS05H, SS10H, and NS20H at point-P showed significantly lower values (range: 3.72 +/- 0.44 kPa to 9.10 +/- 0.26 kPa) than those at point-R (range: 13.40 +/- 1.31 kPa to 14.40 +/- 0.98 kPa). Moreover, the data obtained from BSNH, BS05H, BS10H, and BS20H at point-P showed significantly lower values (range: 3.24 +/- 1.96 kPa to 10.20 +/- 1.84 kPa) than those of point-R (range: 11.69 +/- 1.01 kPa to 14.04 +/- 2.08 kPa). CONCLUSION: For making impressions of an edentulous maxilla, the data suggest that a tray with an escape hole 1.0 mm or larger or a spacer thickness of base plate wax (1.40 mm) be used.

Randomized controlled clinical trial on satisfaction with resilient denture liners among edentulous patients.

PURPOSE: The purpose of this study was to measure patients' satisfaction and their preference between mandibular dentures with permanent silicone-based resilient denture liner (SR) and conventional heat-activated acrylic resin (AR), both opposed by acrylic resin-based maxillary complete dentures. MATERIALS AND METHODS: Twenty-eight edentulous patients who had fulfilled selection criteria and provided informed consent were enrolled in this trial. Subjects were allocated randomly to either arm of cross-over groups (AR-SR/SR-AR), stratified by gender, using a random permuted block within the strata method. The AR-SR group received AR denture treatment followed by SR denture treatment. The SR-AR group received treatment in the reverse sequence. The primary outcome was patient satisfaction measured on 100-mm VAS, analyzed by two-way ANOVA and the Bonferroni multiple comparison as a post hoc test. The secondary outcome was patients' preference, evaluated by chi-square goodness-of-fit test. An intention-to-treat analysis was performed. RESULTS: Twenty-five subjects were enrolled in the analysis. There were no significant differences between AR and SR dentures 1, 2, and 3 months after the completion of control. Eighteen of 25 patients preferred SR dentures. CONCLUSION: Although there were no significant differences in patient satisfaction ratings between the two types of dentures, a significant majority of patients preferred those with a resilient denture liner.