Purpose: The maxillary unilateral or bilateral molars of rats were extracted, and the influences of the partial loss of occlusal support were evaluated using an 8-arm radial maze and a step-through type passive-avoidance apparatus.
Methods: Rats were randomly allocated to three groups not undergoing molar extraction or undergoing extraction of the maxillary unilateral or bilateral molars. Each group was further divided into two groups for maze or passive-avoidance experiments. Thus, a total of six groups were established. The maze experiment was conducted once daily for 10 days. The number of correct choices, number of errors, and the trial time were recorded. The passive-avoidance experiment consisted of an acquisition trial and retention trial. In the acquisition trial, rats were placed in a light room, and the response latency until their entry into a dark room was measured. After 24 h, a similar procedure was performed as a retention trial.
Results: In the maze experiment, there was no significant difference by all the groups except on the day 1 in the number of correct choices. But bilateral molar loss group, the number of errors were significantly lower than no extraction group on days 1, 2, 3, 4, and 7. In the passive-avoidance experiment, though the response latency in the retention trial was longer than that in the acquisition trial in all three groups, according to the increase in the number of tooth extraction, it became significantly shorter between P1 and P3.
Conclusion: These results suggested that molar loss may be a cause of learning/memory impairment.

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Purpose: The aim of the present study was to clarify the influence of early setting conditions on the properties of self curing addition silicone resilient denture lining materials.
Methods: Four auto-mix types of commercial self curing addition silicone resilient denture lining materials were used. Agar plates containing various concentrations of methyl mercaptan (MMP) were prepared and cylindrical specimens (10 mm in height and 10 mm in diameter) of silicone liners were set on the agar plate. The Shore A hardness of the agar-contacted surface of the specimen was measured at 0, 1, 7 and 28 days after stored in 37 °C water. The viscoelastic properties (instantaneous elastic modulus, coefficient of viscosity and permanent deformation) of two silicone liners, which showed a great decrease in the Shore A hardness by agar contact, were determined by a creep meter.
Results: The Shore A hardness, coefficient of viscosity, and instantaneous elastic modulus deceased when the specimen was set on the MMP containing agar plate, but the permanent deformation of these specimens increased.
Conclusion: The exposure to MMP at the early setting stage influenced the properties of self curing addition silicone resilient denture lining materials.

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Low fusing porcelains demonstrate great variations in bond strength with cpTi, a result directly associated with the performance of their bonding agents. The aim of this study was to investigate the composition of bonding agents used for the production of Ti-ceramic restorations. The powder or paste components of nine commercially available products were imaged under LV-SEM and their elemental composition was determined by energy-dispersive X-ray microanalysis (X-ray EDS). According to the EDS results five bonding agents (Duceratin, Duceratin Plus, Ti-22, TitanKeramik, and Triceram) were mainly composed of Si Sn and Na oxides. TiKrom contained La and Ba, whereas Initial Ti was based on La, B, and Sr formulations. Backscattered electron images revealed that Titankeramik, Triceram paste, Initial Bonder and Aesthetic Universal Bonder consisted of a single-phase material, while Duceratin, Duceratin Plus, Ti-22, Tikrom, and Triceram powders consisted of two-phase materials. The large differences found in elemental compositions of the bonding agents and the development of completely new formulations imply that the relevant technology has not yet attained a standard and thus is a promising field for further research.

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Purpose: The purpose of this study was to determine the effect of wearing a palatal plate on swallowing function.
Methods: The subject group consisted of 10 healthy, fully dentate males. Two experimental palatal plates (EPP) were used in this study: one was 1.4 mm thick (EPP1), and the other was 2.8 mm thick (EPP2). Tongue movements and swallowing sounds were simultaneously recorded. The position of the surface of the tongue was recorded by using ultrasound diagnostic equipment in the sagittal plane. Swallowing tests were performed under three conditions: without EPP (WOE), with EPP1 (WP1), and with EPP2 (WP2). Swallowing index (SI) and tongue contact time (TCT) was calculated.
Results: The value of SI was lowest under WOE, and highest under WP2, with a statistically significant difference. There was no statistical significance, however, between SI under WOE and that under WP1. The value of TCT was longest under WOE, and shortest under WP2, with a statistically significant difference.
Conclusions: This investigation suggests that the thickness of a palatal plate influences SI and TCT, which correlate with swallowing function.

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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 3month 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: ≤31; maxillary: ≤47; mandibular: ≤36) were considered unsatisfied with existing or new dentures. Relative validity of the diagnostic tests was assessed by means of sensitivity, specificity, and likelihood ratios.
Results: Mandibular dentures showed a significant association between baseline and new dentures (coefficient = 0.27, p = 0.01). Results of test measures for overall, maxillary, and mandibular existing dentures were 71%, 38%, and 87% (sensitivity); 62%, 66%, and 49% (specificity); and 1.1, 1.9, and 1.7 (positive likelihood), and 0.5, 1.0, and 0.2 (negative likelihood).
Conclusions: Test performance indicates that the negative (satisfied) result for mandibular existing dentures may be useful to rule out the unsatisfied patients with new mandibular dentures.

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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.

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Purpose: Fiber-reinforced composite (FRC) posts have gained much interest recently and understanding of their viscoelastic properties is important as they can be used in stress-bearing posterior restorations. The aim of this study was to evaluate the creep behavior and the viscoelastic properties of four commercial FRC posts under different temperatures and different storage conditions.
Methods: The FRC posts tested were Glassix, C-Post, Carbonite and Snowlight. For the creep measurements a constant load below the proportional limit of the posts was applied and the angular deformation of the specimens was recorded. The viscoelastic parameters were determined by using dynamic torsional loading under four different conditions.
Results: All materials were susceptible to creep and exhibited linear viscoelastic behavior. Residual strain was observed in all FRC posts. The viscoelastic properties were affected by the increase of temperature and water storage ( p < 0.001) resulting in their decline. Carbon fiber posts exhibited better performance than glass fiber posts.
Conclusions: FRC posts exhibit permanent strains under regular masticatory stresses that can be generated in the oral cavity. Their properties are susceptible to changes in temperature, while direct contact with water also affects them deleteriously.

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Purpose: This study aimed to examine how coverage of the hard palate by an experimental palatal plate influenced thermosensation.
Methods: A total of 20 young adult volunteers were recruited from Osaka University Graduate School of Dentistry. An experimental palatal plate, 1.5 mm in thickness, was made for each subject from acrylic resin. The stimulus water were either warmed to 40, 42, 44, 46, or 48 °C or cooled to 30, 26, 22, 18, or 14 °C in a constant-temperature water bath, and the control water were maintained at 37 °C. Subjects were instructed to retain the control water in their mouths for 5 s, then to spit it out and to repeat with the stimulus water. They then rated the intensity of stimulation of warmth or cold compared to the control water by the magnitude estimation method. Each stimulus was administered three times in random order. Two experimental conditions were set: with and without the experimental palatal plate.
Results: Perceived thermal intensity was measured as the slope of the regression line for each condition (with or without the experimental palatal plate, cold or warmth). There was a significant difference between with and without the experimental palatal plate; the regression slope with the plate was shallower than that without the plate (warmth perception with plate = 0.55 ± 0.21 vs. warmth perception without plate = 0.70 ± 0.23, P < 0.05; cold perception with plate = -0.33 ± 0.14 vs. cold perception without plate = -0.39 ± 0.11, P < 0.05).
Conclusion: The findings suggested that a denture covering the hard palate obstructs thermal perception.

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