Over the last decade, applications of resin-based luting agents for seating restorations and fixed partial dentures have increased substantially. This trend is attributed mainly to development of zirconia ceramic restorative systems as well as varying functional monomers and initiation systems compatible to enamel, dentin, ceramic materials, and casting alloys. This review article takes a general view of currently available luting and bonding systems applicable for cementing restorations and dentures made of ceramics and dental alloys.

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Dental adhesives have rapidly improved since they were introduced more than 50 years ago. Decayed or fractured teeth can be reconstructed minimally, invasively, and nearly invisibly using resin composites. The practice of fixed prosthodontics has changed dramatically with the introduction of innovative adhesive luting agents. Although the bonding mechanism of dental adhesives to tooth tissues is complicated, the fundamental mechanism is essentially based on an exchange process, in which minerals removed from the dental hard tissues are replaced by resin monomers that upon polymerization become micro-mechanically interlocked in the created porosities. In addition to micro-mechanical interlocking through hybridization, the potential benefits of additional chemical interactions between functional monomers/polymers and tooth substrate components have recently regained attention. In this review paper, we focus on the tooth bonding mechanism, especially on how chemical interaction at the biomaterial-hard tissue interface can improve bond durability.

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Post and core restoration can compensate for loss of tooth structure and permits restoration of an abutment tooth into a suitable shape for the attachment of crown-restoration devices. It is therefore a procedure of considerable clinical significance. The most common problem in endodontically treated teeth caused by post and core is tooth loss, followed by secondary caries or root fracture. However, the appropriate use of bonding agents is very effective in preventing such problems. Based on previous clinical studies, we have drawn up clinical guidelines to build-up an abutment for an endodontically treated tooth from the remaining coronal tooth structure, presupposing the use of a bonding agent. These clinical guidelines are classified from I to V, according to the amount of remaining tooth structure. The results indicate the amount of remaining structure necessary for post-hole preparation. They also indicate the usefulness of composite build-up and a fiber post.

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[in Japanese]

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[in Japanese]

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Papers related to the question of "how occlusion and masticatory function contribute to general health and longevity" were reviewed. Longitudinal cohort studies on humans were examined. There are many confirmed factors associated with incidence of fatal diseases or mortality, such as smoking, dietary habits, and socioeconomic factors. Therefore I selected researches of the association between oral health and general health or life expectancy adjusted for these confounding factors by a multivariate analysis.
From the literature survey, it is concluded that (1) the number of teeth is associated with longevity; (2) the pathway for the association should be infection and inflammation resulting from periodontal disease andnutritional change by the decline of oral functions; (3) tooth loss decreases intakes of vegetables, which areimportant for the prevention of cardiovascular diseases; (4) among fully-edentulous patients and partially-edentulous patients with a few teeth, a disuse removable dentures may cause short life expectancy; (5) at the present time, there is little evidence of the association of quality of prostheses or oral function with general health and longevity.

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[in Japanese]

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Purpose: This study was to compare the bonding strength of two kinds of directly built-up resin cores (Clearfil DC Core; Kuraray and Unifil Core EM; GC) that were prepared by the use of various setting times.
Methods: Dentin of bovine teeth roots were used as experimental specimens. The dentin surface was polished smoothly, and an adhesive surface 3 mm in diameter was then lined with masking tape. A translucent acrylic tube 4 mm in diameter was fixed around the adhesive surface. The tube was 5 mm high and shielded around with putty to simulate the root canal. The composite resin was irradiated for 20 s and prepared. The time of tooth preparation was decided as follows: immediately, after the maker's designation time, 30 min, 1 h, 1 day, and 1 week later, and it was not prepared as the control. Six specimens were prepared for each condition, and bonding strength was measured by shear testing. The average measurement datum was calculated and analyzed by using two-way ANOVA and Tukey's test. Furthermore, the fractured section after shear testing was observed by SEM.
Results: For both materials, the time of tooth preparation immediately, after the maker's designation time, and 30 min later showed significantly lower bonding strength (p < 0.05). No significant difference was observed among the conditions of those prepared after 1 h and those not prepared. Regarding the bonding strength between materials, a significant difference was not recognized under all conditions. Observation of the adhesion interface under the condition immediately after treatment showed interfacial failure and cohesive failure within the adhesive, but other conditions showed mostly mixed failure and cohesive failure within the resin.
Conclusion: When building up the resin core in root canal length, we observed more than 5 mm under conditions of this experiment; thus the preparation of teeth should be carried out after 1 h or more.

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Purpose: To minimize fractures of veneering porcelain, zirconia-based all-ceramic restorations have recently incorporated coping designs with collars, the height of which remains to be determined or ideal mechanical strength. The aim of this study was to learn if collar height influences the fracture strength of veneering porcelain.
Methods: Thirty zirconia copings of uniform size were fabricated using a computer-aided design/computer-aided manufacturing system. These copings comprised 3 different designs (10 copings each): margin without collar (CH0), with a 1-mm-high collar (CH1), and with a 3-mm-high collar (CH3). Using a press-on system, we veneered the copings to a uniform cylindrical shape and quality of veneering porcelain. All veneered crowns were cemented onto metal abutments and loaded, using a universal testing machine on a point 2 mm inside the crown edge. Load until fracture was assessed as fracture strength, and values and images of fractures were compared among the CH0, CH1, and CH3 groups.
Results: Fracture strengths in the CH1 (2,340 ± 189 N, p = 0.048) and CH3 (2,440 ± 210 N, p = 0.004) groups were significantly higher than in the CH0 (2,110 ± 215 N) group. The value was higher, but not significantly so, in the CH3 group than in the CH1 group. Fracture images showed that porcelain veneers, but not zirconia copings, were fractured. In the CH0 and CH1 groups, the coping surfaces were exposed at the top edge, but covered inferiorly by some of the fractured porcelain. In the CH3 group, the copings were mostly exposed from the top edge to the collar.
Conclusion: The use of collars in zirconia copings enhanced the fracture strength of the veneering porcelain. Increasing the collar height rendered insignificant, but additional, strength to the collar.

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Purpose: It is not very rare for institutionalized elderly patients to be unable to adapt to a newly constructed denture prosthesis, especially those who have cognitive disorders or are bedridden. This study investigated the effect of the timing of prosthodontic intervention and cognitive disorders on the rate of denture prosthesis usage.
Methods: Fifty-three subjects were selected from institutionalized edentulous elderly in a long-term care geriatric hospital in Kurashiki, Okayama, Japan. For each of these subjects, data on denture treatment after admission to the hospital, usage of the denture, cognitive function, and independence in activities of daily living were collected and analyzed.
Results: Among bedridden patients, the usage rate of persons who received dentures after hospitalization was 65.6%, whereas all who received dentures before hospitalization continued to use the dentures during hospitalization. Among patients with cognitive disorders, the usage rate among persons who received dentures before hospitalization was 83.3%, but among those who received dentures after hospitalization it was 22.2%.
Conclusion: It was suggested that when a person with usable dentures becomes bedridden, many would continue to use them even after becoming bedridden and/or afflicted with dementia. Furthermore, dentists must carefully examine the timing of denture treatment for the elderly, especially for patients with dementia and those who are bedridden and/or with dementia.

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Purpose: In Japan, sleep apnea syndrome (SAS) has been getting recognition since the superexpress accident caused a drowsy driver in 2003. It is gradually recommended to screen and treat undiagnosed SAS patients in the workforce population. SAS is associated with a wide variety of adverse health outcomes. Although it is considered that there were 2 million SAS patients in Japan, only 130 thousand patients were diagnosed and treated. Because the oral appliance is one of the treatment options for SAS, dentists recently have some chance to see SAS patients in their clinics. However, not enough knowledge about the prevalence of SAS in the dental clinic population is available. The purpose of this questionnaire-based study is to examine the characteristics of SAS in a dental setting.
Methods: The subjects were patients who came to our dental clinic seeking dental treatments. The questionnaire of this study included the Berlin Questionnaire, the Epworth Sleepiness Scale (ESS), and an original questionnaire. We examined the Mallampati Score, which is a useful and practical tool to examine the upper airway constriction in a clinical setting.
Results: A total of 23 patients completed the data collection. Nine were suspected of SAS based on the Berlin Questionnaire. Three exhibited abnormal sleepiness (ESS scores exceeding 10). Eleven scored more than class III in the Mallampati Score, which indicated a narrow upper airway.
Conclusion: From this study, it is revealed that the prevalence of a suspected SAS in dental clinic. Because dentists have frequent opportunities to find high-risk patients from oral examinations, a related questionnaire and examination might be useful to assess the risk of SAS and enlightenment in a dental clinic.

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Purpose: This study aimed to verify a new method about clinical education and evaluation for preparing a full-veneer crown.
Methods: We made a video recording showing the preparation of a full-veneer crown on the second mandibular premolar by a dental instructor. This recording shows the same area that is seen by the instructor. Ten dental trainees performed the preparation for a full-veneer crown on the same teeth before and after watching the recording. Each of the abutments was evaluated by subjective and objective ways. The measured area between the margin line and the edge of the occlusal surface was used as the objective evaluation. The subjective evaluations by the dental instructor were inspected by comparing them with the results of the objective evaluations.
Results: All abutments prepared by dental trainees who watched the recording were evaluated higher than previous preparations made by those who had not viewed it. Especially, the taper and shape of the abutment had a significant difference comparing before and after the trainees had viewed the recording. The objective evaluations indicated no significant differences. However, the subjective evaluations of the dental instructor were closely correlative with the objective evaluations.
Conclusion: The video recording produced in this study demonstrates the effectiveness for dental trainees to improve the full-veneer crown preparation technique. Measuring the abutment area seems to be useful as an objective evaluation of tooth preparation. It is suggested that an experienced dental instructor can draw an appropriate conclusion from this experience on the evaluation of the abutment for a full-veneer crown.

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Patients: Implant prosthetic treatment was smoothly completed for a patient with adjustment disorder who had previously showed panic syndrome during treatment. It was facilitated by preparing the treatment environment through a sharing of information with the medical department.
Discussion: After maintaining a long-term relationship of mutual trust with the patient, we treated masticatory dysfunction, which was the chief complaint, to recover occlusal support using implants, and a contact condition and an occlusal force equivalent to those of dentulous patients were achieved. Although 3 years have passed since this treatment, a favorable clinical course has been shown without masticatory functional complaints. Therefore, we consider that the treatment for this case was appropriate.
Conclusion: By paying attention to the attitude of a patient with adjustment disorder, we satisfactorily prepared the treatment environment, which smoothly improved masticatory dysfunction.

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Patients: A 76-year-old male presented with a chief complaint of the severe attrition of lower anterior teeth. After examinations, the deep bite and loss of the vertical dimension of occlusion were caused by a defect in the occlusal support as a result of missing upper molars. A cephalometric analysis was employed to obtain objective criteria for the vertical dimension for prosthetic reconstruction. The prognosis was stable after 5 years with the periodic dental follow-ups every 1 to 6 months.
Discussion: Improvements in chewing ability and aesthetics were obtained with the occlusal reconstruction.
Conclusion: In this case of loss of the vertical dimension of occlusion and severe attrition, we believe that the cephalometric analysis was clinically important for determining the adequate vertical dimensions of the occlusion for occlusal reconstruction.

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Patients: The patient was a 69-year-old male who presented with a chief complaint of mastication disorder by pain and unsteadiness of denture. This patient had non-vertical stop occlusion, and masticatory function was recovered by maxillary overdenture. After root coverage with composite resin for the remaining upper teeth, a complete denture was selected for the final prosthesis. As a result of the treatment, improvement of the chief complaint was obtained.
Discussion: In a case with non-vertical stop occlusion, it is difficult to resist the rotational force against dental prostheses. In this case, the overdenture reduced rotational force and led to a positive outcome.
Conclusion: An overdenture resulted in a positive outcome for a case with non vertical stop occlusion.

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Patient: A 65-year-old edentulous male patient in this hospital complained of repeated artificial tooth loss resulting from inserting his dentures. Because of upper- and lower-ridge low-bone resorption, little vertical denture space was available. So it was difficult to save space for an arrangement of artificial tooth and denture bases.
Discussion: It seemed that the main reasons were stress of the denture base by occlusal force and adhesion failure between composite resin teeth and denture base resin. In new dentures, the rigid metal reinforcements applied to denture spaces were designed to ensure rigidity of the denture base, and attention was paid to the choice of artificial teeth.
Conclusion: After new dentures were inserted, they achieved favorable prognosis, and no loss of artificial teeth has occured in 4 years.

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