This article reviews the findings of the original papers related to complete dentures published in the Journal of the Japan Prosthodontic Society (Nippon Hotetsu Shika Gakkai Zasshi), Vol. 52, 2008. A total of six articles focused on complete dentures or materials related to complete dentures were selected and summarized. A variety of subjects in relation to removable prosthodontics were discussed in the articles, including denture plaque control, resilient denture lining materials or denture adhesives, and assessment and/or anatomical analysis of prognosis of complete dentures.

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Purpose: The existence of a relationship between head posture and mandibular function has been discussed by several authors. However, the relationship between head posture and the cervical spine in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) who are using oral appliances (OAs) remains unknown. The aim of this study was to evaluate the changes in the cervical spine associated with the use of OAs in patients with OSAHS.
Methods: Fifteen patients (4 females and 11 males; mean age, 48 years) diagnosed with OSAHS were randomly selected. An OA was fabricated individually for each patient. Two lateral cephalometric radiographs were taken while the patient was sitting awake in an upright position. The first radiograph was taken in the intercuspal position and the second was taken while the subject was wearing the OA. Analyses based on the sella- nasion (SN) line were performed in the lateral cephalogram. Comparison of craniocervical angles in patients with and without the OA was performed using Wilcoxon's signed-rank test.
Results: Cephalometric analysis showed that the craniocervical angles (CVT-C2V and SN-C4) with OA were higher than those without OA (P < 0.05). It seems that the OA caused a significant flexion of the cranium on the upper cervical spine. A significant increase in the craniocervical angle occurred in the fourth cervical segment.
Conclusion: The changes in forward flexion of the upper cervical spine found in this study imply that changes in the craniocervical relationship should be evaluated periodically after an OA has been inserted.

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Purpose: Several previous reports have described factors that affect masticatory function. However, there are no known predictors that affect the food mixing ability of the masticatory function, and it has been impossible to predict masticatory function in mandibulectomy and/or glossectomy patients. The purpose of the present study was to develop a numerical formula that could predict the food mixing ability of the masticatory function among mandibulectomy and/or glossectomy patients. The null hypothesis of the study was that five predictors, namely mandibulectomy, mandibular continuity, number of residual mandibular teeth, occlusal units and tongue movement score, were unable to account for the mixing ability index (MAI) in mandibulectomy and/or glossectomy patients.
Methods: The subjects were 20 patients who had undergone mandibulectomy and/or glossectomy. The above-described five predictors were assessed. Tongue movement was evaluated with a tongue movement test and the MAI was evaluated with a mixing ability test. Multiple regression analysis was used to examine whether the five predictors affected the MAI after prosthetic treatment.
Results: A regression equation was determined for the five predictors (R² = 0.83; adjusted R² = 0.77; p < 0.001).
Conclusion: The obtained regression equation could successfully account for the MAI in mandibulectomy and/or glossectomy patients.

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Purpose: The purpose of this study was to examine the bond strength between tooth-colored porcelain and sandblasted zirconia framework.
Methods: The surfaces of zirconia specimens that had been cut into a size suitable for a bending test were sandblasted at three different pressures (0.2, 0.4 and 0.6 MPa). The surface roughness of each specimen was measured and then a 3-point bending test was performed. After that, other zirconia specimens simulating a crown framework were fabricated and their surfaces were sandblasted. Three types of tooth-colored porcelain were fired onto the surface of those zirconia specimens, and the tensile bond strength between the two substances was examined.
Results: When the sandblasting pressure was increased, the surface roughness of zirconia specimens tended to become, but the flexural strength remained unchanged. The specimens simulating a zirconia framework had a higher strength of bond when sandblasted at 0.4 or 0.6 MPa than when blasted at 0.2 MPa. The zirconia specimens sandblasted at a pressure of 0.4 MPa had a bond strength to tooth-colored porcelain of 37.7-49.5 MPa.
Conclusion: When sandblasted at a pressure of 0.4 MPa, the zirconia specimens developed a strong bond with the tooth-colored porcelain, regardless of the type of porcelain.

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Purpose: Treatment with an occlusal splint is used for temporomandibular disorders, bruxism, and occlusal disturbance to relieve orofacial symptoms such as myofascial pain and jaw movement restriction. However, the effects of various types of occlusal splints have not been elucidated. We investigated the effects of jaw clenching with soft and hard occlusal splints on the awareness of tiredness, bite force, and EEG activity.
Methods: Six healthy adults were used as subjects, with a visual analogue scale utilized to evaluate the awareness of each patient's tiredness both preceding the session and following the clenching trials. In addition, a Dental Prescale was used to measure bite force and an EEG recording was conducted while performing jaw clenching. The jaw clenching task comprised 1 min of maximal voluntary clenching under 3 kinds of clenching conditions: with natural dentition, and with soft and hard occlusal splints, which were each repeated 5 times.
Results: Jaw clenching with natural dentition and a hard occlusal splint did not cause a significant awareness of tiredness following repetitive jaw clenching, and there was not a significant alteration of EEG spectrum values with those conditions. In contrast, jaw clenching with a soft occlusal splint caused a significant increase in awareness of tiredness, as well as significant decreases in bite force and EEG alpha 2 power spectrum values.
Conclusions: Jaw clenching with a soft resilient occlusal splint causes an awareness of tiredness, which might be accompanied by declines in bite force and EEG spectrum values.

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Purpose: From the standpoint of dental medicine, denture wearing is considered to improve chewing ability, chewing comfort, and quality of life in elderly individuals. We attempted to clarify the effects of prosthodontic treatment on activation of the dorsal prefrontal cortex, which is involved in higher cognitive functions.
Methods: Three partially edentulous patients, one 60-year-old male, and two females, 57 and 64 years old, were enlisted as subjects. For detection of changes in cerebral blood flow, near infrared spectroscopy (NIRS) was used. EMG recording was also conducted to detect bilateral activities of the masseter muscles (Mm).
Results: Significant activation of the dorsal prefrontal cortex in the right and/or left hemisphere was shown while wearing partial denture prosthesis. Furthermore, Mm EMG activity was significantly increased while wearing a partial denture prosthesis.
Conclusions: We concluded that a partial dental prosthesis significantly stimulates both masticatory muscle and dorsal prefrontal cortex activities, which might contribute to the prevention of cognitive impairment in aged individuals.

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Purpose: This study focused on the anti-microbial protein human lactoferrin (hLF) commonly found in saliva, and tried to develop biocompatible dental materials that have higher anti-microbial effects.
Methods: A lyophilized cation exchange resin was added to tissue conditioner at 4 wt% and 8 wt%. The amount of hLF binding to the tissue conditioner and their anti-microbial effect against Candida albicans was investigated. Then their mechanical properties and cytotoxicity were examined.
Results: Tissue conditioner containing cation exchange resin was bound with hLF and had an anti-microbial effect against C. albicans. In addition, their physical properties were sufficient and they were harmless to human fibroblasts.
Conclusion: The clinical application of cation exchange resin for tissue conditioner can be effective for the prevention and treatment of denture stomatitis and systemic opportunistic infections since it is thought that these materials will increase the local concentration of anti-microbial protein in saliva at the lesion site.

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Purpose: The purpose of this study was to clarify whether there was a difference in the masticatory function between two masticatory path patterns: a convex closing path and a concave closing path.
Methods: For 80 healthy subjects, the masticatory function (masticatory muscular activity, mandibular movement, and masticatory performance) when chewing a gummy jelly was recorded. Out of the 160 chewing cases (80 subjects chewing on either side), 65 cases (Group I) in which the incisal point opened in a linear or concave manner toward the working side and closed in a convex manner, and 15 cases (Group II) in which the opening path was the same as that in Group I, but the closing followed a concave path, were selected. For the masticatory function, the integral values per unit time of masseter and temporal muscular activities, the gape and masticatory width, the indicators representing the stability of movement path, and the glucose extraction from chewing gummy jelly were measured and compared between the two groups.
Results: The integral values of muscular activities and the amount of glucose extraction were significantly greater in Group I. The gape and masticatory width were not significantly different between the groups. The values of the indicators representing the stability of path were smaller in Group I than in Group II.
Conclusion: From these results, it was suggested that there was a functional difference between Group I (with a convex closing path) and Group II (with a concave closing path), and that Group I had a superior masticatory function to Group II.

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Patient: Marginal mandibulectomy was performed on a 30-year-old woman with an ameloblastoma in the left side of the mandible. Subsequently, the patient's chief complaints were in regard to the restoration of masticatory function and esthetics. Realizing that a free iliac crest graft and implant were necessary, we made a diagnostic wax-up and surgical template to match the maxillary and mandibular alveolar bone position. The surgical template was used to determine the position of a free iliac crest in the operating room. When the final restoration was finished, good occlusal balance had been achieved.
Discussion: In this case, an oral surgeon as well as a prosthodontist condirmed the graft bone position by using the surgical template in the operating room. Therefore, it was possible to place the graft bone into the preplanned position and carry out the treatment plan smoothly from the first implant operation to the final restoration.
Conclusion: This clinical report describes the importance of free iliac crest graft positions, the surgical template and collaboration between a prosthodontist and oral surgeon in forming the proper treatment plan.

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Purpose: The aim of this study was to develop an ambulatory bruxism recording system capable of sleep-stage analysis.
Methods: A portable EMG system was used to record masseter muscle activity. An EMG sensor was attached onto the masseter muscle belly at either side. EMG data were stored on a notebook type personal computer. A sound level meter was used to assess the sound level of bruxism. Sound level (dB) readings were taken every second and recorded on the same computer. A prototype of sleep sensor, a wristwatch-style biological signal sensor-recorder device, recorded and stored pulse wave, acceleration and temperature on a memory card. All stored data were transferred to a personal computer and analyzed.
Results: The whole system was transportable within a protective case and weighed approximately 5 kg. Raw EMG signals were processed to derive integrated EMG data. TOSHIBA Sleep Analysis Program classified sleep-stages as awake, shallow sleep, deep sleep and REM based on the activity of the autonomic nervous system that was estimated from the fluctuations of pulse intervals. An EMG, sound level and sleep-stage analysis program was developed to analyze all data simultaneously. Using this program, the masseter muscle activity, sound level and sleep-stage could be quantified and correlated.
Conclusion: We developed an ambulatory bruxism recording system that analyzes sleep-stage. We expect that this system will enable us to measure sleep bruxism activity in each sleep-stage on an electromyographical and auditory basis at the subject's home.

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